Commit Graph

9959 Commits

Author SHA1 Message Date
Naohiro Aota
544d24f9de btrfs: zoned: enable zone append writing for direct IO
Likewise to buffered IO, enable zone append writing for direct IO when
its used on a zoned block device.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:06 +01:00
Naohiro Aota
d8e3fb106f btrfs: zoned: use ZONE_APPEND write for zoned mode
Enable zone append writing for zoned mode. When using zone append, a
bio is issued to the start of a target zone and the device decides to
place it inside the zone. Upon completion the device reports the actual
written position back to the host.

Three parts are necessary to enable zone append mode. First, modify the
bio to use REQ_OP_ZONE_APPEND in btrfs_submit_bio_hook() and adjust the
bi_sector to point the beginning of the zone.

Second, record the returned physical address (and disk/partno) to the
ordered extent in end_bio_extent_writepage() after the bio has been
completed. We cannot resolve the physical address to the logical address
because we can neither take locks nor allocate a buffer in this end_bio
context. So, we need to record the physical address to resolve it later
in btrfs_finish_ordered_io().

And finally, rewrite the logical addresses of the extent mapping and
checksum data according to the physical address using btrfs_rmap_block.
If the returned address matches the originally allocated address, we can
skip this rewriting process.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:06 +01:00
Johannes Thumshirn
24533f6a9a btrfs: save irq flags when looking up an ordered extent
A following patch will add another caller of
btrfs_lookup_ordered_extent(), but from a bio's endio context.

btrfs_lookup_ordered_extent() uses spin_lock_irq() which unconditionally
disables interrupts. Change this to spin_lock_irqsave() so interrupts
aren't disabled and re-enabled unconditionally.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:06 +01:00
Johannes Thumshirn
08f455593f btrfs: zoned: cache if block group is on a sequential zone
On a zoned filesystem, cache if a block group is on a sequential write
only zone.

On sequential write only zones, we can use REQ_OP_ZONE_APPEND for
writing data, therefore provide btrfs_use_zone_append() to figure out if
IO is targeting a sequential write only zone and we can use
REQ_OP_ZONE_APPEND for data writing.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:05 +01:00
Naohiro Aota
138082f366 btrfs: extend btrfs_rmap_block for specifying a device
btrfs_rmap_block currently reverse-maps the physical addresses on all
devices to the corresponding logical addresses.

Extend the function to match to a specified device. The old functionality
of querying all devices is left intact by specifying NULL as target
device.

A block_device instead of a btrfs_device is passed into btrfs_rmap_block,
as this function is intended to reverse-map the result of a bio, which
only has a block_device.

Also export the function for later use.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:05 +01:00
Johannes Thumshirn
cacb2cea46 btrfs: zoned: check if bio spans across an ordered extent
To ensure that an ordered extent maps to a contiguous region on disk, we
need to maintain a "one bio == one ordered extent" rule.

Ensure that constructing bio does not span more than an ordered extent.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:05 +01:00
Naohiro Aota
d22002fd37 btrfs: zoned: split ordered extent when bio is sent
For a zone append write, the device decides the location the data is being
written to. Therefore we cannot ensure that two bios are written
consecutively on the device. In order to ensure that an ordered extent
maps to a contiguous region on disk, we need to maintain a "one bio ==
one ordered extent" rule.

Implement splitting of an ordered extent and extent map on bio submission
to adhere to the rule.

extract_ordered_extent() hooks into btrfs_submit_data_bio() and splits the
corresponding ordered extent so that the ordered extent's region fits into
one bio and the corresponding device limits.

Several sanity checks need to be done in extract_ordered_extent() e.g.

- We cannot split once end_bio'd ordered extent because we cannot divide
  ordered->bytes_left for the split ones
- We do not expect a compressed ordered extent
- We should not have checksum list because we omit the list splitting.
  Since the function is called before btrfs_wq_submit_bio() or
  btrfs_csum_one_bio(), this should be always ensured.

We also need to split an extent map by creating a new one. If not,
unpin_extent_cache() complains about the difference between the start of
the extent map and the file's logical offset.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:05 +01:00
Naohiro Aota
cfe94440d1 btrfs: zoned: handle REQ_OP_ZONE_APPEND as writing
Zoned filesystems use REQ_OP_ZONE_APPEND bios for writing to actual
devices.

Let btrfs_end_bio() and btrfs_op be aware of it, by mapping
REQ_OP_ZONE_APPEND to BTRFS_MAP_WRITE and using btrfs_op() instead of
bio_op().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:05 +01:00
Naohiro Aota
e1326f0339 btrfs: zoned: use bio_add_zone_append_page
A zoned device has its own hardware restrictions e.g. max_zone_append_size
when using REQ_OP_ZONE_APPEND. To follow these restrictions, use
bio_add_zone_append_page() instead of bio_add_page(). We need target device
to use bio_add_zone_append_page(), so this commit reads the chunk
information to cache the target device to btrfs_io_bio(bio)->device.

Caching only the target device is sufficient here as zoned filesystems
only supports the single profile at the moment. Once more profiles will be
supported btrfs_io_bio can hold an extent_map to be able to check for the
restrictions of all devices the btrfs_bio will be mapped to.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:04 +01:00
Naohiro Aota
953651eb30 btrfs: factor out helper adding a page to bio
Factor out adding a page to a bio from submit_extent_page().  The page
is added only when bio_flags are the same, contiguous and the added page
fits in the same stripe as pages in the bio.

Condition checks are reordered to allow early return to avoid possibly
heavy btrfs_bio_fits_in_stripe() calling.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:04 +01:00
Naohiro Aota
dcba6e48b5 btrfs: zoned: reset zones of unused block groups
We must reset the zones of a deleted unused block group to rewind the
zones' write pointers to the zones' start.

To do this, we can use the DISCARD_SYNC code to do the reset when the
filesystem is running on zoned devices.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:04 +01:00
Naohiro Aota
011b41bffa btrfs: zoned: advance allocation pointer after tree log node
Since the allocation info of a tree log node is not recorded in the extent
tree, calculate_alloc_pointer() cannot detect this node, so the pointer
can be over a tree node.

Replaying the log calls btrfs_remove_free_space() for each node in the
log tree.

So, advance the pointer after the node to not allocate over it.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:04 +01:00
Naohiro Aota
d3575156f6 btrfs: zoned: redirty released extent buffers
Tree manipulating operations like merging nodes often release
once-allocated tree nodes. Such nodes are cleaned so that pages in the
node are not uselessly written out. On zoned volumes, however, such
optimization blocks the following IOs as the cancellation of the write
out of the freed blocks breaks the sequential write sequence expected by
the device.

Introduce a list of clean and unwritten extent buffers that have been
released in a transaction. Redirty the buffers so that
btree_write_cache_pages() can send proper bios to the devices.

Besides it clears the entire content of the extent buffer not to confuse
raw block scanners e.g. 'btrfs check'. By clearing the content,
csum_dirty_buffer() complains about bytenr mismatch, so avoid the
checking and checksum using newly introduced buffer flag
EXTENT_BUFFER_NO_CHECK.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:04 +01:00
Naohiro Aota
2eda57089e btrfs: zoned: implement sequential extent allocation
Implement a sequential extent allocator for zoned filesystems. This
allocator only needs to check if there is enough space in the block group
after the allocation pointer to satisfy the extent allocation request.
Therefore the allocator never manages bitmaps or clusters. Also, add
assertions to the corresponding functions.

As zone append writing is used, it would be unnecessary to track the
allocation offset, as the allocator only needs to check available space.
But by tracking and returning the offset as an allocated region, we can
skip modification of ordered extents and checksum information when there
is no IO reordering.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:03 +01:00
Naohiro Aota
169e0da91a btrfs: zoned: track unusable bytes for zones
In a zoned filesystem a once written then freed region is not usable
until the underlying zone has been reset. So we need to distinguish such
unusable space from usable free space.

Therefore we need to introduce the "zone_unusable" field to the block
group structure, and "bytes_zone_unusable" to the space_info structure
to track the unusable space.

Pinned bytes are always reclaimed to the unusable space. But, when an
allocated region is returned before using e.g., the block group becomes
read-only between allocation time and reservation time, we can safely
return the region to the block group. For the situation, this commit
introduces "btrfs_add_free_space_unused". This behaves the same as
btrfs_add_free_space() on regular filesystem. On zoned filesystems, it
rewinds the allocation offset.

Because the read-only bytes tracks free but unusable bytes when the block
group is read-only, we need to migrate the zone_unusable bytes to
read-only bytes when a block group is marked read-only.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:03 +01:00
Naohiro Aota
a94794d50d btrfs: zoned: calculate allocation offset for conventional zones
Conventional zones do not have a write pointer, so we cannot use it to
determine the allocation offset for sequential allocation if a block
group contains a conventional zone.

But instead, we can consider the end of the highest addressed extent in
the block group for the allocation offset.

For new block group, we cannot calculate the allocation offset by
consulting the extent tree, because it can cause deadlock by taking
extent buffer lock after chunk mutex, which is already taken in
btrfs_make_block_group(). Since it is a new block group anyways, we can
simply set the allocation offset to 0.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:03 +01:00
Naohiro Aota
08e11a3db0 btrfs: zoned: load zone's allocation offset
A zoned filesystem must allocate blocks at the zones' write pointer. The
device's write pointer position can be mapped to a logical address within
a block group. To facilitate this, add an "alloc_offset" to the
block-group to track the logical addresses of the write pointer.

This logical address is populated in btrfs_load_block_group_zone_info()
from the write pointers of corresponding zones.

For now, zoned filesystems the single profile. Supporting non-single
profile with zone append writing is not trivial. For example, in the DUP
profile, we send a zone append writing IO to two zones on a device. The
device reply with written LBAs for the IOs. If the offsets of the
returned addresses from the beginning of the zone are different, then it
results in different logical addresses.

We need fine-grained logical to physical mapping to support such separated
physical address issue. Since it should require additional metadata type,
disable non-single profiles for now.

This commit supports the case all the zones in a block group are
sequential. The next patch will handle the case having a conventional
zone.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:03 +01:00
Naohiro Aota
381a696eb5 btrfs: zoned: verify device extent is aligned to zone
Add a check in verify_one_dev_extent() to ensure that a device extent on
a zoned block device is aligned to the respective zone boundary.

If it isn't, mark the filesystem as unclean.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:03 +01:00
Naohiro Aota
1cd6121f2a btrfs: zoned: implement zoned chunk allocator
Implement a zoned chunk and device extent allocator. One device zone
becomes a device extent so that a zone reset affects only this device
extent and does not change the state of blocks in the neighbor device
extents.

To implement the allocator, we need to extend the following functions for
a zoned filesystem.

- init_alloc_chunk_ctl
- dev_extent_search_start
- dev_extent_hole_check
- decide_stripe_size

init_alloc_chunk_ctl_zoned() is mostly the same as regular one. It always
set the stripe_size to the zone size and aligns the parameters to the zone
size.

dev_extent_search_start() only aligns the start offset to zone boundaries.
We don't care about the first 1MB like in regular filesystem because we
anyway reserve the first two zones for superblock logging.

dev_extent_hole_check_zoned() checks if zones in given hole are either
conventional or empty sequential zones. Also, it skips zones reserved for
superblock logging.

With the change to the hole, the new hole may now contain pending extents.
So, in this case, loop again to check that.

Finally, decide_stripe_size_zoned() should shrink the number of devices
instead of stripe size because we need to honor stripe_size == zone_size.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:46:03 +01:00
Johannes Thumshirn
3c9daa09cc btrfs: zoned: allow zoned filesystems on non-zoned block devices
Run a zoned filesystem on non-zoned devices. This is done by "slicing up"
the block device into static sized chunks and fake a conventional zone on
each of them. The emulated zone size is determined from the size of device
extent.

This is mainly aimed at testing of zoned filesystems, i.e. the zoned
chunk allocator, on regular block devices.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:32:21 +01:00
Naohiro Aota
1cb3dc3f79 btrfs: zoned: disallow fitrim on zoned filesystems
The implementation of fitrim depends on space cache, which is not used
and disabled for zoned extent allocator. So the current code does not
work with zoned filesystem.

In the future, we can implement fitrim for zoned filesystems by enabling
space cache (but, only for fitrim) or scanning the extent tree at fitrim
time.  For now, disallow fitrim on zoned filesystems.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:32:20 +01:00
Johannes Thumshirn
b53429bad3 btrfs: zoned: do not load fs_info::zoned from incompat flag
Don't set the zoned flag in fs_info as soon as we're encountering the
incompat filesystem flag for a zoned filesystem on mount. The zoned flag
in fs_info is in a union together with the zone_size, so setting it too
early will result in setting an incorrect zone_size as well.

Once the correct zone_size is read from the device, we can rely on the
zoned flag in fs_info as well to determine if the filesystem is zoned.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:32:20 +01:00
Johannes Thumshirn
4afd2fe835 btrfs: release path before calling to btrfs_load_block_group_zone_info
Since we have no write pointer in conventional zones, we cannot
determine the allocation offset from it. Instead, we set the allocation
offset after the highest addressed extent. This is done by reading the
extent tree in btrfs_load_block_group_zone_info().

However, this function is called from btrfs_read_block_groups(), so the
read lock for the tree node could be recursively taken.

To avoid this unsafe locking scenario, release the path before reading
the extent tree to get the allocation offset.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:32:20 +01:00
Naohiro Aota
d6639b35da btrfs: zoned: use regular super block location on zone emulation
A zoned filesystem currently has a superblock at the beginning of the
superblock logging zones if the zones are conventional. This difference
in superblock position causes a chicken-and-egg problem for filesystems
with emulated zones. Since the device is a regular (non-zoned) device,
we cannot know if the filesystem is regular or zoned while reading the
superblock. But, to load the superblock, we need to see if it is
emulated zoned or not.

Place the superblocks at the same location as they are on regular
filesystem on regular devices to solve the problem. It is possible
because it's ensured that all the superblock locations are at an
(emulated) conventional zone on regular devices.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:32:19 +01:00
Naohiro Aota
7365104236 btrfs: zoned: defer loading zone info after opening trees
This is a preparation patch to implement zone emulation on a regular
device.

To emulate a zoned filesystem on a regular (non-zoned) device, we need to
decide an emulated zone size. Instead of making it a compile-time static
value, we'll make it configurable at mkfs time. Since we have one zone ==
one device extent restriction, we can determine the emulated zone size
from the size of a device extent. We can extend btrfs_get_dev_zone_info()
to show a regular device filled with conventional zones once the zone size
is decided.

The current call site of btrfs_get_dev_zone_info() during the mount process
is earlier than loading the file system trees so that we don't know the
size of a device extent at this point. Thus we can't slice a regular device
to conventional zones.

This patch introduces btrfs_get_dev_zone_info_all_devices to load the zone
info for all the devices. And, it places this function in open_ctree()
after loading the trees.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09 02:32:16 +01:00
Filipe Manana
72c9925f87 btrfs: fix extent buffer leak on failure to copy root
At btrfs_copy_root(), if the call to btrfs_inc_ref() fails we end up
returning without unlocking and releasing our reference on the extent
buffer named "cow" we previously allocated with btrfs_alloc_tree_block().

So fix that by unlocking the extent buffer and dropping our reference on
it before returning.

Fixes: be20aa9dba ("Btrfs: Add mount option to turn off data cow")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:04 +01:00
Qu Wenruo
2c4d8cb737 btrfs: explain page locking and readahead in read_extent_buffer_pages()
In read_extent_buffer_pages(), if we failed to lock the page atomically,
we just exit with return value 0.

This is counter-intuitive, as normally if we can't lock what we need, we
would return something like EAGAIN.

But that return hides under (wait == WAIT_NONE) branch, which only gets
triggered for readahead.

And for readahead, if we failed to lock the page, it means the extent
buffer is either being read by other thread, or has been read and is
under modification.  Either way the eb will or has been cached, thus
readahead has no need to wait for it.

Add comment on this counter-intuitive behavior.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:04 +01:00
Qu Wenruo
0bb3eb3ee8 btrfs: allow read-only mount of 4K sector size fs on 64K page system
This adds the basic RO mount ability for 4K sector size on 64K page
system.

Currently we only plan to support 4K and 64K page system.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:03 +01:00
Qu Wenruo
92082d4097 btrfs: integrate page status update for data read path into begin/end_page_read
In btrfs data page read path, the page status update are handled in two
different locations:

  btrfs_do_read_page()
  {
	while (cur <= end) {
		/* No need to read from disk */
		if (HOLE/PREALLOC/INLINE){
			memset();
			set_extent_uptodate();
			continue;
		}
		/* Read from disk */
		ret = submit_extent_page(end_bio_extent_readpage);
  }

  end_bio_extent_readpage()
  {
	endio_readpage_uptodate_page_status();
  }

This is fine for sectorsize == PAGE_SIZE case, as for above loop we
should only hit one branch and then exit.

But for subpage, there is more work to be done in page status update:

- Page Unlock condition
  Unlike regular page size == sectorsize case, we can no longer just
  unlock a page.
  Only the last reader of the page can unlock the page.
  This means, we can unlock the page either in the while() loop, or in
  the endio function.

- Page uptodate condition
  Since we have multiple sectors to read for a page, we can only mark
  the full page uptodate if all sectors are uptodate.

To handle both subpage and regular cases, introduce a pair of functions
to help handling page status update:

- begin_page_read()
  For regular case, it does nothing.
  For subpage case, it updates the reader counters so that later
  end_page_read() can know who is the last one to unlock the page.

- end_page_read()
  This is just endio_readpage_uptodate_page_status() renamed.
  The original name is a little too long and too specific for endio.

  The new thing added is the condition for page unlock.
  Now for subpage data, we unlock the page if we're the last reader.

This does not only provide the basis for subpage data read, but also
hide the special handling of page read from the main read loop.

Also, since we're changing how the page lock is handled, there are two
existing error paths where we need to manually unlock the page before
calling begin_page_read().

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:03 +01:00
Qu Wenruo
32443de338 btrfs: introduce btrfs_subpage for data inodes
To support subpage sector size, data also need extra info to make sure
which sectors in a page are uptodate/dirty/...

This patch will make pages for data inodes get btrfs_subpage structure
attached, and detached when the page is freed.

This patch also slightly changes the timing when
set_page_extent_mapped() is called to make sure:

- We have page->mapping set
  page->mapping->host is used to grab btrfs_fs_info, thus we can only
  call this function after page is mapped to an inode.

  One call site attaches pages to inode manually, thus we have to modify
  the timing of set_page_extent_mapped() a bit.

- As soon as possible, before other operations
  Since memory allocation can fail, we have to do extra error handling.
  Calling set_page_extent_mapped() as soon as possible can simply the
  error handling for several call sites.

The idea is pretty much the same as iomap_page, but with more bitmaps
for btrfs specific cases.

Currently the plan is to switch iomap if iomap can provide sector
aligned write back (only write back dirty sectors, but not the full
page, data balance require this feature).

So we will stick to btrfs specific bitmap for now.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:03 +01:00
Qu Wenruo
371cdc0700 btrfs: introduce subpage metadata validation check
For subpage metadata validation check, there are some differences:

- Read must finish in one bvec
  Since we're just reading one subpage range in one page, it should
  never be split into two bios nor two bvecs.

- How to grab the existing eb
  Instead of grabbing eb using page->private, we have to go search radix
  tree as we don't have any direct pointer at hand.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:03 +01:00
Qu Wenruo
4325cb2293 btrfs: support subpage in endio_readpage_update_page_status()
To handle subpage status update, add the following:

- Use btrfs_page_*() subpage-aware helpers to update page status
  Now we can handle both cases well.

- No page unlock for subpage metadata
  Since subpage metadata doesn't utilize page locking at all, skip it.
  For subpage data locking, it's handled in later commits.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:03 +01:00
Qu Wenruo
4012daf769 btrfs: introduce read_extent_buffer_subpage()
Introduce a helper, read_extent_buffer_subpage(), to do the subpage
extent buffer read.

The difference between regular and subpage routines are:

- No page locking
  Here we completely rely on extent locking.
  Page locking can reduce the concurrency greatly, as if we lock one
  page to read one extent buffer, all the other extent buffers in the
  same page will have to wait.

- Extent uptodate condition
  Despite the existing PageUptodate() and EXTENT_BUFFER_UPTODATE check,
  We also need to check btrfs_subpage::uptodate_bitmap.

- No page iteration
  Just one page, no need to loop, this greatly simplified the subpage
  routine.

This patch only implements the bio submit part, no endio support yet.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:03 +01:00
Qu Wenruo
d1e86e3fc3 btrfs: support subpage in try_release_extent_buffer()
Unlike the original try_release_extent_buffer(),
try_release_subpage_extent_buffer() will iterate through all the ebs in
the page, and try to release each.

We can release the full page only after there's no private attached,
which means all ebs of that page have been released as well.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
92d83e9436 btrfs: support subpage in btrfs_clone_extent_buffer
For btrfs_clone_extent_buffer(), it's mostly the same code of
__alloc_dummy_extent_buffer(), except it has extra page copy.

So to make it subpage compatible, we only need to:

- Call set_extent_buffer_uptodate() instead of SetPageUptodate()
  This will set correct uptodate bit for subpage and regular sector size
  cases.

Since we're calling set_extent_buffer_uptodate() which will also set
EXTENT_BUFFER_UPTODATE bit, we don't need to manually set that bit
either.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
251f2acc71 btrfs: support subpage in set/clear_extent_buffer_uptodate()
To support subpage in set_extent_buffer_uptodate and
clear_extent_buffer_uptodate we only need to use the subpage-aware
helpers to update the page bits.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
03a816b32b btrfs: introduce helpers for subpage error status
Introduce the following functions to handle subpage error status:

- btrfs_subpage_set_error()
- btrfs_subpage_clear_error()
- btrfs_subpage_test_error()
  These helpers can only be called when the page has subpage attached
  and the range is ensured to be inside the page.

- btrfs_page_set_error()
- btrfs_page_clear_error()
- btrfs_page_test_error()
  These helpers can handle both regular sector size and subpage without
  problem.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
a1d767c11c btrfs: introduce helpers for subpage uptodate status
Introduce the following functions to handle subpage uptodate status:

- btrfs_subpage_set_uptodate()
- btrfs_subpage_clear_uptodate()
- btrfs_subpage_test_uptodate()
  These helpers can only be called when the page has subpage attached
  and the range is ensured to be inside the page.

- btrfs_page_set_uptodate()
- btrfs_page_clear_uptodate()
- btrfs_page_test_uptodate()
  These helpers can handle both regular sector size and subpage.
  Although caller should still ensure that the range is inside the page.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
09bc1f0fb8 btrfs: attach private to dummy extent buffer pages
There are locations where we allocate dummy extent buffers for temporary
usage, like in tree_mod_log_rewind() or get_old_root().

These dummy extent buffers will be handled by the same eb accessors, and
if they don't have page::private subpage eb accessors could fail.

To address such problems, make __alloc_dummy_extent_buffer() attach
page private for dummy extent buffers too.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
8ff8466d29 btrfs: support subpage for extent buffer page release
In btrfs_release_extent_buffer_pages(), we need to add extra handling
for subpage.

Introduce a helper, detach_extent_buffer_page(), to do different
handling for regular and subpage cases.

For subpage case, handle detaching page private.

For unmapped (dummy or cloned) ebs, we can detach the page private
immediately as the page can only be attached to one unmapped eb.

For mapped ebs, we have to ensure there are no eb in the page range
before we delete it, as page->private is shared between all ebs in the
same page.

But there is a subpage specific race, where we can race with extent
buffer allocation, and clear the page private while new eb is still
being utilized, like this:

  Extent buffer A is the new extent buffer which will be allocated,
  while extent buffer B is the last existing extent buffer of the page.

  		T1 (eb A) 	 |		T2 (eb B)
  -------------------------------+------------------------------
  alloc_extent_buffer()		 | btrfs_release_extent_buffer_pages()
  |- p = find_or_create_page()   | |
  |- attach_extent_buffer_page() | |
  |				 | |- detach_extent_buffer_page()
  |				 |    |- if (!page_range_has_eb())
  |				 |    |  No new eb in the page range yet
  |				 |    |  As new eb A hasn't yet been
  |				 |    |  inserted into radix tree.
  |				 |    |- btrfs_detach_subpage()
  |				 |       |- detach_page_private();
  |- radix_tree_insert()	 |

  Then we have a metadata eb whose page has no private bit.

To avoid such race, we introduce a subpage metadata-specific member,
btrfs_subpage::eb_refs.

In alloc_extent_buffer() we increase eb_refs in the critical section of
private_lock.  Then page_range_has_eb() will return true for
detach_extent_buffer_page(), and will not detach page private.

The section is marked by:

- btrfs_page_inc_eb_refs()
- btrfs_page_dec_eb_refs()

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:02 +01:00
Qu Wenruo
819822107d btrfs: make grab_extent_buffer_from_page() handle subpage case
For subpage case, grab_extent_buffer() can't really get an extent buffer
just from btrfs_subpage.

We have radix tree lock protecting us from inserting the same eb into
the tree.  Thus we don't really need to do the extra hassle, just let
alloc_extent_buffer() handle the existing eb in radix tree.

Now if two ebs are being allocated as the same time, one will fail with
-EEIXST when inserting into the radix tree.

So for grab_extent_buffer(), just always return NULL for subpage case.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Qu Wenruo
760f991f14 btrfs: make attach_extent_buffer_page() handle subpage case
For subpage case, we need to allocate additional memory for each
metadata page.

So we need to:

- Allow attach_extent_buffer_page() to return int to indicate allocation
  failure

- Allow manually pre-allocate subpage memory for alloc_extent_buffer()
  As we don't want to use GFP_ATOMIC under spinlock, we introduce
  btrfs_alloc_subpage() and btrfs_free_subpage() functions for this
  purpose.
  (The simple wrap for btrfs_free_subpage() is for later convert to
   kmem_cache. Already internally tested without problem)

- Preallocate btrfs_subpage structure for alloc_extent_buffer()
  We don't want to call memory allocation with spinlock held, so
  do preallocation before we acquire mapping->private_lock.

- Handle subpage and regular case differently in
  attach_extent_buffer_page()
  For regular case, no change, just do the usual thing.
  For subpage case, allocate new memory or use the preallocated memory.

For future subpage metadata, we will make use of radix tree to grab
extent buffer.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Qu Wenruo
cac06d843f btrfs: introduce the skeleton of btrfs_subpage structure
For sectorsize < page size support, we need a structure to record extra
status info for each sector of a page.

Introduce the skeleton structure, all subpage related code would go to
subpage.[ch].

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Qu Wenruo
62c053fbb2 btrfs: set UNMAPPED bit early in btrfs_clone_extent_buffer() for subpage support
For the incoming subpage support, UNMAPPED extent buffer will have
different behavior in btrfs_release_extent_buffer().

This means we need to set UNMAPPED bit early before calling
btrfs_release_extent_buffer().

Currently there is only one caller which relies on
btrfs_release_extent_buffer() in its error path while set UNMAPPED bit
late:
- btrfs_clone_extent_buffer()

Make it subpage compatible by setting the UNMAPPED bit early, since
we're here, also move the UPTODATE bit early.

There is another caller, __alloc_dummy_extent_buffer(), setting
UNMAPPED bit late, but that function clean up the allocated page
manually, thus no need for any modification.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Qu Wenruo
6869b0a8be btrfs: merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK to PAGE_START_WRITEBACK
PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK are two defines used in
__process_pages_contig(), to let the function know to clear page dirty
bit and then set page writeback.

However page writeback and dirty bits are conflicting (at least for
sector size == PAGE_SIZE case), this means these two have to be always
updated together.

This means we can merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK to
PAGE_START_WRITEBACK.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Filipe Manana
d0c2f4fa55 btrfs: make concurrent fsyncs wait less when waiting for a transaction commit
Often an fsync needs to fallback to a transaction commit for several
reasons (to ensure consistency after a power failure, a new block group
was allocated or a temporary error such as ENOMEM or ENOSPC happened).

In that case the log is marked as needing a full commit and any concurrent
tasks attempting to log inodes or commit the log will also fallback to the
transaction commit. When this happens they all wait for the task that first
started the transaction commit to finish the transaction commit - however
they wait until the full transaction commit happens, which is not needed,
as they only need to wait for the superblocks to be persisted and not for
unpinning all the extents pinned during the transaction's lifetime, which
even for short lived transactions can be a few thousand and take some
significant amount of time to complete - for dbench workloads I have
observed up to 4~5 milliseconds of time spent unpinning extents in the
worst cases, and the number of pinned extents was between 2 to 3 thousand.

So allow fsync tasks to skip waiting for the unpinning of extents when
they call btrfs_commit_transaction() and they were not the task that
started the transaction commit (that one has to do it, the alternative
would be to offload the transaction commit to another task so that it
could avoid waiting for the extent unpinning or offload the extent
unpinning to another task).

This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

After applying the entire patchset, dbench shows improvements in respect
to throughput and latency. The script used to measure it is the following:

  $ cat dbench-test.sh
  #!/bin/bash

  DEV=/dev/sdk
  MNT=/mnt/sdk
  MOUNT_OPTIONS="-o ssd"
  MKFS_OPTIONS="-m single -d single"

  echo "performance" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

  umount $DEV &> /dev/null
  mkfs.btrfs -f $MKFS_OPTIONS $DEV
  mount $MOUNT_OPTIONS $DEV $MNT

  dbench -D $MNT -t 300 64

  umount $MNT

The test was run on a physical machine with 12 cores (Intel corei7), 64G
of ram, using a NVMe device and a non-debug kernel configuration (Debian's
default configuration).

Before applying patchset, 32 clients:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    9627107     0.153    61.938
 Close        7072076     0.001     3.175
 Rename        407633     1.222    44.439
 Unlink       1943895     0.658    44.440
 Deltree          256    17.339   110.891
 Mkdir            128     0.003     0.009
 Qpathinfo    8725406     0.064    17.850
 Qfileinfo    1529516     0.001     2.188
 Qfsinfo      1599884     0.002     1.457
 Sfileinfo     784200     0.005     3.562
 Find         3373513     0.411    30.312
 WriteX       4802132     0.053    29.054
 ReadX       15089959     0.002     5.801
 LockX          31344     0.002     0.425
 UnlockX        31344     0.001     0.173
 Flush         674724     5.952   341.830

Throughput 1008.02 MB/sec  32 clients  32 procs  max_latency=341.833 ms

After applying patchset, 32 clients:

After patchset, with 32 clients:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    9931568     0.111    25.597
 Close        7295730     0.001     2.171
 Rename        420549     0.982    49.714
 Unlink       2005366     0.497    39.015
 Deltree          256    11.149    89.242
 Mkdir            128     0.002     0.014
 Qpathinfo    9001863     0.049    20.761
 Qfileinfo    1577730     0.001     2.546
 Qfsinfo      1650508     0.002     3.531
 Sfileinfo     809031     0.005     5.846
 Find         3480259     0.309    23.977
 WriteX       4952505     0.043    41.283
 ReadX       15568127     0.002     5.476
 LockX          32338     0.002     0.978
 UnlockX        32338     0.001     2.032
 Flush         696017     7.485   228.835

Throughput 1049.91 MB/sec  32 clients  32 procs  max_latency=228.847 ms

 --> +4.1% throughput, -39.6% max latency

Before applying patchset, 64 clients:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    8956748     0.342   108.312
 Close        6579660     0.001     3.823
 Rename        379209     2.396    81.897
 Unlink       1808625     1.108   131.148
 Deltree          256    25.632   172.176
 Mkdir            128     0.003     0.018
 Qpathinfo    8117615     0.131    55.916
 Qfileinfo    1423495     0.001     2.635
 Qfsinfo      1488496     0.002     5.412
 Sfileinfo     729472     0.007     8.643
 Find         3138598     0.855    78.321
 WriteX       4470783     0.102    79.442
 ReadX       14038139     0.002     7.578
 LockX          29158     0.002     0.844
 UnlockX        29158     0.001     0.567
 Flush         627746    14.168   506.151

Throughput 924.738 MB/sec  64 clients  64 procs  max_latency=506.154 ms

After applying patchset, 64 clients:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    9069003     0.303    43.193
 Close        6662328     0.001     3.888
 Rename        383976     2.194    46.418
 Unlink       1831080     1.022    43.873
 Deltree          256    24.037   155.763
 Mkdir            128     0.002     0.005
 Qpathinfo    8219173     0.137    30.233
 Qfileinfo    1441203     0.001     3.204
 Qfsinfo      1507092     0.002     4.055
 Sfileinfo     738775     0.006     5.431
 Find         3177874     0.936    38.170
 WriteX       4526152     0.084    39.518
 ReadX       14213562     0.002    24.760
 LockX          29522     0.002     1.221
 UnlockX        29522     0.001     0.694
 Flush         635652    14.358   422.039

Throughput 990.13 MB/sec  64 clients  64 procs  max_latency=422.043 ms

 --> +6.8% throughput, -18.1% max latency

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Filipe Manana
64d6b281ba btrfs: remove unnecessary check_parent_dirs_for_sync()
Whenever we fsync an inode, if it is a directory, a regular file that was
created in the current transaction or has last_unlink_trans set to the
generation of the current transaction, we check if any of its ancestor
inodes (and the inode itself if it is a directory) can not be logged and
need a fallback to a full transaction commit - if so, we return with a
value of 1 in order to fallback to a transaction commit.

However we often do not need to fallback to a transaction commit because:

1) The ancestor inode is not an immediate parent, and therefore there is
   not an explicit request to log it and it is not needed neither to
   guarantee the consistency of the inode originally asked to be logged
   (fsynced) nor its immediate parent;

2) The ancestor inode was already logged before, in which case any link,
   unlink or rename operation updates the log as needed.

So for these two cases we can avoid an unnecessary transaction commit.
Therefore remove check_parent_dirs_for_sync() and add a check at the top
of btrfs_log_inode() to make us fallback immediately to a transaction
commit when we are logging a directory inode that can not be logged and
needs a full transaction commit. All we need to protect is the case where
after renaming a file someone fsyncs only the old directory, which would
result is losing the renamed file after a log replay.

This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

Performance results, after applying all patches, are mentioned in the
change log of the last patch.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:01 +01:00
Filipe Manana
0e44cb3f94 btrfs: skip logging inodes already logged when logging new entries
When logging new directory entries of a directory, we log the inodes of
new dentries and the inodes of dentries pointing to directories that
may have been created in past transactions. For the case of directories
we log in full mode, which can be particularly expensive for large
directories.

We do use btrfs_inode_in_log() to skip already logged inodes, however for
that helper to return true, it requires that the log transaction used to
log the inode to be already committed. This means that when we have more
than one task using the same log transaction we can end up logging an
inode multiple times, which is a waste of time and not necessary since
the log will be committed by one of the tasks and the others will wait for
the log transaction to be committed before returning to user space.

So simply replace the use of btrfs_inode_in_log() with the new helper
function need_log_inode(), introduced in a previous commit.

This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

Performance results, after applying all patches, are mentioned in the
change log of the last patch.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:00 +01:00
Filipe Manana
3e6a86a193 btrfs: skip logging directories already logged when logging all parents
Some times when we fsync an inode we need to do a full log of all its
ancestors (due to unlink, link or rename operations), which can be an
expensive operation, specially if the directories are large.

However if we find an ancestor directory inode that is already logged in
the current transaction, and has no inserted/updated/deleted xattrs since
it was last logged, we can skip logging the directory again. We are safe
to skip that since we know that for logged directories, any link, unlink
or rename operations that implicate the directory will update the log as
necessary.

So use the helper need_log_dir(), introduced in a previous commit, to
detect already logged directories that can be skipped.

This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

Performance results, after applying all patches, are mentioned in the
change log of the last patch.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:00 +01:00
Filipe Manana
ab12313a9f btrfs: avoid logging new ancestor inodes when logging new inode
When we fsync a new file, created in the current transaction, we check
all its ancestor inodes and always log them if they were created in the
current transaction - even if we have already logged them before, which
is a waste of time.

So avoid logging new ancestor inodes if they were already logged before
and have no xattrs added/updated/removed since they were last logged.

This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

Performance results, after applying all patches, are mentioned in the
change log of the last patch.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:00 +01:00
Filipe Manana
e593e54ed1 btrfs: stop setting nbytes when filling inode item for logging
When we fill an inode item for logging we are setting its nbytes field
with the value returned by inode_get_bytes() (a VFS API), however we do
not need it because it is not used during log replay. In fact, for fast
fsyncs, when we call inode_get_bytes() we may even get an outdated value
for nbytes because the nbytes field of the inode is only updated when
ordered extents complete, and a fast fsync only waits for writeback to
complete, it does not wait for ordered extent completion.

So just remove the setup of nbytes and add an explicit comment mentioning
why we do not set it. This also avoids adding contention on the inode's
i_lock (VFS) with concurrent stat() calls, since that spinlock is used by
inode_get_bytes() which is also called by our stat callback
(btrfs_getattr()).

This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

Performance results, after applying all patches, are mentioned in the
change log of the last patch.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:00 +01:00
Filipe Manana
ddffcf6fb5 btrfs: remove unnecessary directory inode item update when deleting dir entry
When we remove a directory entry, as part of an unlink operation, if the
directory was logged before we must remove the directory index items from
the log. We are also updating the inode item of the directory to update
its i_size, but that is not necessary because during log replay we do not
need it and we correctly adjust the i_size in the inode item of the
subvolume as we process directory index items and replay deletes.

This is not needed since commit d555438b6e ("Btrfs: drop dir i_size
when adding new names on replay"), where we explicitly ignore the i_size
of directory inode items on log replay. Before that we used it but it
was buggy as mentioned in that commit's change log (i_size got a larger
value then it should have).

So stop updating the i_size of the directory inode item in the log, as
that is a waste of time, adds more log contention to the log tree and
often results in COWing more extent buffers for the log tree.

This code path is triggered often during dbench workloads for example.
This patch is part of a patchset comprised of the following patches:

  btrfs: remove unnecessary directory inode item update when deleting dir entry
  btrfs: stop setting nbytes when filling inode item for logging
  btrfs: avoid logging new ancestor inodes when logging new inode
  btrfs: skip logging directories already logged when logging all parents
  btrfs: skip logging inodes already logged when logging new entries
  btrfs: remove unnecessary check_parent_dirs_for_sync()
  btrfs: make concurrent fsyncs wait less when waiting for a transaction commit

Performance results, after applying all patches, are mentioned in the
change log of the last patch.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:00 +01:00
Michal Rostecki
4203431319 btrfs: let callers of btrfs_get_io_geometry pass the em
Before this change, the btrfs_get_io_geometry() function was calling
btrfs_get_chunk_map() to get the extent mapping, necessary for
calculating the I/O geometry. It was using that extent mapping only
internally and freeing the pointer after its execution.

That resulted in calling btrfs_get_chunk_map() de facto twice by the
__btrfs_map_block() function. It was calling btrfs_get_io_geometry()
first and then calling btrfs_get_chunk_map() directly to get the extent
mapping, used by the rest of the function.

Change that to passing the extent mapping to the btrfs_get_io_geometry()
function as an argument.

This could improve performance in some cases.  For very large
filesystems, i.e. several thousands of allocated chunks, not only this
avoids searching two times the rbtree, saving time, it may also help
reducing contention on the lock that protects the tree - thinking of
writeback starting for multiple inodes, other tasks allocating or
removing chunks, and anything else that requires access to the rbtree.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Michal Rostecki <mrostecki@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add Filipe's analysis ]
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:59:00 +01:00
Qu Wenruo
951c80f83d btrfs: fix double accounting of ordered extent for subpage case in btrfs_invalidapge
Commit dbfdb6d1b3 ("Btrfs: Search for all ordered extents that could
span across a page") make btrfs_invalidapage() to search all ordered
extents.

The offending code looks like this:

  again:
	  start = page_start;
	  ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1);
	  if (ordred) {
		  end = min(page_end,
			    ordered->file_offset + ordered->num_bytes - 1);

		  /* Do the cleanup */

		  start = end + 1;
		  if (start < page_end)
			  goto again;
	  }

The behavior is indeed necessary for the incoming subpage support, but
when it iterates through all the ordered extents, it also resets the
search range @start.

This means, for the following cases, we can double account the ordered
extents, causing its bytes_left underflow:

	Page offset
	0		16K		32K
	|<--- OE 1  --->|<--- OE 2 ---->|

As the first iteration will find ordered extent (OE) 1, which doesn't
cover the full page, thus after cleanup code, we need to retry again.
But again label will reset start to page_start, and we got OE 1 again,
which causes double accounting on OE 1, and cause OE 1's byte_left to
underflow.

This problem can only happen for subpage case, as for regular sectorsize
== PAGE_SIZE case, we will always find a OE ends at or after page end,
thus no way to trigger the problem.

Move the again label after start = page_start.  There will be more
comprehensive rework to convert the open coded loop to a proper while
loop for subpage support.

Fixes: dbfdb6d1b3 ("Btrfs: Search for all ordered extents that could span across a page")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Abaci Team
a4559e6f6f btrfs: simplify condition in __btrfs_run_delayed_items
Fix the following coccicheck warnings:

./fs/btrfs/delayed-inode.c:1157:39-41: WARNING !A || A && B is
equivalent to !A || B.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Suggested-by: Jiapeng Zhong <oswb@linux.alibaba.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Abaci Team <abaci-bugfix@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Filipe Manana
2965194b77 btrfs: remove wrong comment for can_nocow_extent()
The comment for can_nocow_extent() says that the function will flush
ordered extents, however that never happens and was never true before the
comment was added in commit e4ecaf90bc ("btrfs: add comments for
btrfs_check_can_nocow() and can_nocow_extent()"). This is true only for
the function btrfs_check_can_nocow(), which after that commit was renamed
to check_can_nocow(). So just remove that part of the comment.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Josef Bacik
e5ad49e215 btrfs: add a trace class for dumping the current ENOSPC state
Often when I'm debugging ENOSPC related issues I have to resort to
printing the entire ENOSPC state with trace_printk() in different spots.
This gets pretty annoying, so add a trace state that does this for us.
Then add a trace point at the end of preemptive flushing so you can see
the state of the space_info when we decide to exit preemptive flushing.
This helped me figure out we weren't kicking in the preemptive flushing
soon enough.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Josef Bacik
4b02b00fe5 btrfs: adjust the flush trace point to include the source
Since we have normal ticketed flushing and preemptive flushing, adjust
the tracepoint so that we know the source of the flushing action to make
it easier to debug problems.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Josef Bacik
88a777a6e5 btrfs: implement space clamping for preemptive flushing
Starting preemptive flushing at 50% of available free space is a good
start, but some workloads are particularly abusive and can quickly
overwhelm the preemptive flushing code and drive us into using tickets.

Handle this by clamping down on our threshold for starting and
continuing to run preemptive flushing.  This is particularly important
for our overcommit case, as we can really drive the file system into
overages and then it's more difficult to pull it back as we start to
actually fill up the file system.

The clamping is essentially 2^CLAMP, but we start at 1 so whatever we
calculate for overcommit is the baseline.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Josef Bacik
2e294c6049 btrfs: simplify the logic in need_preemptive_flushing
A lot of this was added all in one go with no explanation, and is a bit
unwieldy and confusing.  Simplify the logic to start preemptive flushing
if we've reserved more than half of our available free space.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:59 +01:00
Josef Bacik
9f42d37748 btrfs: rework btrfs_calc_reclaim_metadata_size
Currently btrfs_calc_reclaim_metadata_size does two things, it returns
the space currently required for flushing by the tickets, and if there
are no tickets it calculates a value for the preemptive flushing.

However for the normal ticketed flushing we really only care about the
space required for tickets.  We will accidentally come in and flush one
time, but as soon as we see there are no tickets we bail out of our
flushing.

Fix this by making btrfs_calc_reclaim_metadata_size really only tell us
what is required for flushing if we have people waiting on space.  Then
move the preemptive flushing logic into need_preemptive_reclaim().  We
ignore btrfs_calc_reclaim_metadata_size() in need_preemptive_reclaim()
because if we are in this path then we made our reservation and there
are not pending tickets currently, so we do not need to check it, simply
do the fuzzy logic to check if we're getting low on space.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
f205edf773 btrfs: check reclaim_size in need_preemptive_reclaim
If we're flushing space for tickets then we have
space_info->reclaim_size set and we do not need to do background
reclaim.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
ae7913ba52 btrfs: rename need_do_async_reclaim
All of our normal flushing is asynchronous reclaim, so this helper is
poorly named.  This is more checking if we need to preemptively flush
space, so rename it to need_preemptive_reclaim.

Also switch it to bool and make it plain static as followup patches will
move more code here.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
576fa34830 btrfs: improve preemptive background space flushing
Currently if we ever have to flush space because we do not have enough
we allocate a ticket and attach it to the space_info, and then
systematically flush things in the filesystem that hold space
reservations until our space is reclaimed.

However this has a latency cost, we must go to sleep and wait for the
flushing to make progress before we are woken up and allowed to continue
doing our work.

In order to address that we used to kick off the async worker to flush
space preemptively, so that we could be reclaiming space hopefully
before any tasks needed to stop and wait for space to reclaim.

When I introduced the ticketed ENOSPC stuff this broke slightly in the
fact that we were using tickets to indicate if we were done flushing.
No tickets, no more flushing.  However this meant that we essentially
never preemptively flushed.  This caused a write performance regression
that Nikolay noticed in an unrelated patch that removed the committing
of the transaction during btrfs_end_transaction.

The behavior that happened pre that patch was btrfs_end_transaction()
would see that we were low on space, and it would commit the
transaction.  This was bad because in this particular case you could end
up with thousands and thousands of transactions being committed during
the 5 minute reproducer.  With the patch to remove this behavior we got
much more sane transaction commits, but we ended up slower because we
would write for a while, flush, write for a while, flush again.

To address this we need to reinstate a preemptive flushing mechanism.
However it is distinctly different from our ticketing flushing in that
it doesn't have tickets to base it's decisions on.  Instead of bolting
this logic into our existing flushing work, add another worker to handle
this preemptive flushing.  Here we will attempt to be slightly
intelligent about the things that we flushing, attempting to balance
between whichever pool is taking up the most space.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
f00c42dd4c btrfs: introduce a FORCE_COMMIT_TRANS flush operation
Solely for preemptive flushing, we want to be able to force the
transaction commit without any of the ambiguity of
may_commit_transaction().  This is because may_commit_transaction()
checks tickets and such, and in preemptive flushing we already know
it'll be helpful, so use this to keep the code nice and clean and
straightforward.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
5deb17e18e btrfs: track ordered bytes instead of just dio ordered bytes
We track dio_bytes because the shrink delalloc code needs to know if we
have more DIO in flight than we have normal buffered IO.  The reason for
this is because we can't "flush" DIO, we have to just wait on the
ordered extents to finish.

However this is true of all ordered extents.  If we have more ordered
space outstanding than dirty pages we should be waiting on ordered
extents.  We already are ok on this front technically, because we always
do a FLUSH_DELALLOC_WAIT loop, but I want to use the ordered counter in
the preemptive flushing code as well, so change this to count all
ordered bytes instead of just DIO ordered bytes.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
ac1ea10e75 btrfs: add a trace point for reserve tickets
While debugging a ENOSPC related performance problem I needed to see the
time difference between start and end of a reserve ticket, so add a
trace point to report when we handle a reserve ticket.

I opted to spit out start_ns itself without calculating the difference
because there could be a gap between enabling the tracepoint and setting
start_ns.  Doing it this way allows us to filter on 0 start_ns so we
don't get bogus entries, and we can easily calculate the time difference
with bpftrace or something else.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:58 +01:00
Josef Bacik
91e79a83ff btrfs: make flush_space take a enum btrfs_flush_state instead of int
I got a automated message from somebody who runs clang against our
kernels and it's because I used the wrong enum type for what I passed
into flush_space, caught by -Wenum-conversion.  Change the argument to
be explicitly the enum we're expecting to make everything consistent.
Maybe eventually gcc will catch errors like this.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:57 +01:00
Roman Anasal
8898038309 btrfs: send: use struct send_ctx *sctx for btrfs_compare_trees and changed_cb
btrfs_compare_trees and changed_cb use a void *ctx parameter instead of
struct send_ctx *sctx but when used in changed_cb it is immediately
cast to `struct send_ctx *sctx = ctx;`.

changed_cb is only ever called from btrfs_compare_trees and full_send_tree:
- full_send_tree already passes a struct send_ctx *sctx
- btrfs_compare_trees is only called by send_subvol with a struct send_ctx *sctx
- void *ctx in btrfs_compare_trees is only used to be passed to changed_cb

So casting to/from void *ctx seems unnecessary and directly using
struct send_ctx *sctx instead provides better type-safety.

The original reason for using void *ctx in the first place seems to have
been dropped with 1b51d6fce4 ("btrfs: send: remove indirect callback
parameter for changed_cb").

Signed-off-by: Roman Anasal <roman.anasal@bdsu.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:57 +01:00
Josef Bacik
488bc2a2d2 btrfs: run delayed refs less often in commit_cowonly_roots
We love running delayed refs in commit_cowonly_roots, but it is a bit
excessive.  I was seeing cases of running 3 or 4 refs a few times in a
row during this time.  Instead simply:

- update all of the roots first
- then run delayed refs
- then handle the empty block groups case
- and then if we have any more dirty roots do the whole thing again

This allows us to be much more efficient with our delayed ref running,
as we can batch a few more operations at once.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:57 +01:00
Josef Bacik
dac348e925 btrfs: stop running all delayed refs during snapshot
This was added in commit 361048f586 ("Btrfs: fix full backref problem
when inserting shared block reference") to address a problem where we
hit the following BUG_ON() in alloc_reserved_tree_block

        if (node->type == BTRFS_SHARED_BLOCK_REF_KEY) {
                BUG_ON(!(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));

However this BUG_ON() is bogus, and was removed by previous commit:

  btrfs: remove bogus BUG_ON in alloc_reserved_tree_block

We no longer need to run delayed refs because of this, and can remove
this flushing here.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:57 +01:00
Josef Bacik
b7774425e0 btrfs: remove bogus BUG_ON in alloc_reserved_tree_block
The fix 361048f586 ("Btrfs: fix full backref problem when inserting
shared block reference") added a delayed ref flushing at subvolume
creation time in order to avoid hitting this particular BUG_ON().

Before this fix, we were tripping the BUG_ON() by

1. Modify snapshot A, which creates blocks with a normal reference for
   snapshot A, as A is the owner of these blocks.  We now have delayed
   refs for these blocks.
2. Create a snapshot of A named B, which pushes references for the
   children blocks of the root node for the new root B, thus creating
   more delayed refs for newly allocated blocks.
3. A is modified, and because the metadata blocks can now be shared, it
   must push FULL_BACKREF references to the children of any block that A
   COWs down it's path to its target key.
4. Delayed refs are run.  Because these are newly allocated blocks, we
   have ->must_insert_reserved reserved set on the delayed ref head, we
   call into alloc_reserved_tree_block() to add the extent item, and
   then add our ref.  At the time of this fix, we were ordering
   FULL_BACKREF delayed ref operations first, so we'd go to add this
   reference and then BUG_ON() because we didn't have the FULL_BACKREF
   flag set.

The patch fixed this problem by making sure we ran the delayed refs
before we had the chance to modify A.  This meant that any *new* blocks
would have had their extent items created _before_ we would ever
actually COW down and generate FULL_BACKREF entries.  Thus the problem
went away.

However this BUG_ON() is actually completely bogus.  The existence of a
full backref doesn't necessarily mean that FULL_BACKREF must be set on
that block, it must only be set on the actual parent itself.  Consider
the example provided above.  If we COW down one path from A, any nodes
are going to have a FULL_BACKREF ref pushed down to _all_ of their
children, but not all of the children are going to have FULL_BACKREF
set.  It is completely valid to have an extent item with normal and full
backrefs without FULL_BACKREF actually set on the block itself.

As a final note, I have been testing with the patch (applied after this
one)

  btrfs: stop running all delayed refs during snapshot

which removed this flushing.  My test was a torture test which did a lot
of operations while snapshotting and deleting snapshots as well as
relocation, and I never tripped this BUG_ON().  This is actually because
at the time of 361048f586, we ordered SHARED keys _before_ normal
references, and thus they would get run first.  However currently they
are ordered _after_ normal references, so we'd do the initial creation
without having a shared reference, and thus not hit this BUG_ON(), which
explains why I didn't start hitting this problem during my testing with
my other patch applied.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:57 +01:00
Josef Bacik
2a4d84c11a btrfs: move delayed ref flushing for qgroup into qgroup helper
The commit d672633545 ("btrfs: qgroup: Make snapshot accounting work
with new extent-oriented qgroup.") added a flush of the delayed refs
during snapshot creation in order to get the qgroup accounting properly.
However this code has changed and been moved to it's own helper that is
skipped if qgroups are turned off.  Move the flushing to the helper, as
we do not need it when qgroups are turned off.

Also add a comment explaining why it exists, and why it doesn't actually
save us.  This will be helpful later when we try to fix qgroup
accounting properly.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:57 +01:00
Josef Bacik
ad368f3394 btrfs: only run delayed refs once before committing
We try to pre-flush the delayed refs when committing, because we want to
do as little work as possible in the critical section of the transaction
commit.

However doing this twice can lead to very long transaction commit delays
as other threads are allowed to continue to generate more delayed refs,
which potentially delays the commit by multiple minutes in very extreme
cases.

So simply stick to one pre-flush, and then continue the rest of the
transaction commit.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
61a56a992f btrfs: delayed refs pre-flushing should only run the heads we have
Previously our delayed ref running used the total number of items as the
items to run.  However we changed that to number of heads to run with
the delayed_refs_rsv, as generally we want to run all of the operations
for one bytenr.

But with btrfs_run_delayed_refs(trans, 0) we set our count to 2x the
number of items that we have.  This is generally fine, but if we have
some operation generation loads of delayed refs while we're doing this
pre-flushing in the transaction commit, we'll just spin forever doing
delayed refs.

Fix this to simply pick the number of delayed refs we currently have,
that way we do not end up doing a lot of extra work that's being
generated in other threads.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
e19eb11f4f btrfs: only let one thread pre-flush delayed refs in commit
I've been running a stress test that runs 20 workers in their own
subvolume, which are running an fsstress instance with 4 threads per
worker, which is 80 total fsstress threads.  In addition to this I'm
running balance in the background as well as creating and deleting
snapshots.  This test takes around 12 hours to run normally, going
slower and slower as the test goes on.

The reason for this is because fsstress is running fsync sometimes, and
because we're messing with block groups we often fall through to
btrfs_commit_transaction, so will often have 20-30 threads all calling
btrfs_commit_transaction at the same time.

These all get stuck contending on the extent tree while they try to run
delayed refs during the initial part of the commit.

This is suboptimal, really because the extent tree is a single point of
failure we only want one thread acting on that tree at once to reduce
lock contention.

Fix this by making the flushing mechanism a bit operation, to make it
easy to use test_and_set_bit() in order to make sure only one task does
this initial flush.

Once we're into the transaction commit we only have one thread doing
delayed ref running, it's just this initial pre-flush that is
problematic.  With this patch my stress test takes around 90 minutes to
run, instead of 12 hours.

The memory barrier is not necessary for the flushing bit as it's
ordered, unlike plain int. The transaction state accessed in
btrfs_should_end_transaction could be affected by that too as it's not
always used under transaction lock. Upon Nikolay's analysis in [1]
it's not necessary:

  In should_end_transaction it's read without holding any locks. (U)

  It's modified in btrfs_cleanup_transaction without holding the
  fs_info->trans_lock (U), but the STATE_ERROR flag is going to be set.

  set in cleanup_transaction under fs_info->trans_lock (L)
  set in btrfs_commit_trans to COMMIT_START under fs_info->trans_lock.(L)
  set in btrfs_commit_trans to COMMIT_DOING under fs_info->trans_lock.(L)
  set in btrfs_commit_trans to COMMIT_UNBLOCK under
  fs_info->trans_lock.(L)

  set in btrfs_commit_trans to COMMIT_COMPLETED without locks but at this
  point the transaction is finished and fs_info->running_trans is NULL (U
  but irrelevant).

  So by the looks of it we can have a concurrent READ race with a WRITE,
  due to reads not taking a lock. In this case what we want to ensure is
  we either see new or old state. I consulted with Will Deacon and he said
  that in such a case we'd want to annotate the accesses to ->state with
  (READ|WRITE)_ONCE so as to avoid a theoretical tear, in this case I
  don't think this could happen but I imagine at some point KCSAN would
  flag such an access as racy (which it is).

[1] https://lore.kernel.org/linux-btrfs/e1fd5cc1-0f28-f670-69f4-e9958b4964e6@suse.com

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ add comments regarding memory barrier ]
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
ddfd08cb04 btrfs: do not block on deleted bgs mutex in the cleaner
While running some stress tests I started getting hung task messages.
This is because the delete unused block groups code has to take the
delete_unused_bgs_mutex to do it's work, which is taken by balance to
make sure we don't delete block groups while we're balancing.

The problem is that balance can take a while, and so we were getting
hung task warnings.  We don't need to block and run these things, and
the cleaner is needed to do other work, so trylock on this mutex and
just bail if we can't acquire it right away.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
867ed321f9 btrfs: abort the transaction if we fail to inc ref in btrfs_copy_root
While testing my error handling patches, I added a error injection site
at btrfs_inc_extent_ref, to validate the error handling I added was
doing the correct thing.  However I hit a pretty ugly corruption while
doing this check, with the following error injection stack trace:

btrfs_inc_extent_ref
  btrfs_copy_root
    create_reloc_root
      btrfs_init_reloc_root
	btrfs_record_root_in_trans
	  btrfs_start_transaction
	    btrfs_update_inode
	      btrfs_update_time
		touch_atime
		  file_accessed
		    btrfs_file_mmap

This is because we do not catch the error from btrfs_inc_extent_ref,
which in practice would be ENOMEM, which means we lose the extent
references for a root that has already been allocated and inserted,
which is the problem.  Fix this by aborting the transaction if we fail
to do the reference modification.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
eddda68d97 btrfs: add asserts for deleting backref cache nodes
A weird KASAN problem that Zygo reported could have been easily caught
if we checked for basic things in our backref freeing code.  We have two
methods of freeing a backref node

- btrfs_backref_free_node: this just is kfree() essentially.
- btrfs_backref_drop_node: this actually unlinks the node and cleans up
  everything and then calls btrfs_backref_free_node().

We should mostly be using btrfs_backref_drop_node(), to make sure the
node is properly unlinked from the backref cache, and only use
btrfs_backref_free_node() when we know the node isn't actually linked to
the backref cache.  We made a mistake here and thus got the KASAN splat.

Make this style of issue easier to find by adding some ASSERT()'s to
btrfs_backref_free_node() and adjusting our deletion stuff to properly
init the list so we can rely on list_empty() checks working properly.

  BUG: KASAN: use-after-free in btrfs_backref_cleanup_node+0x18a/0x420
  Read of size 8 at addr ffff888112402950 by task btrfs/28836

  CPU: 0 PID: 28836 Comm: btrfs Tainted: G        W         5.10.0-e35f27394290-for-next+ #23
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
  Call Trace:
   dump_stack+0xbc/0xf9
   ? btrfs_backref_cleanup_node+0x18a/0x420
   print_address_description.constprop.8+0x21/0x210
   ? record_print_text.cold.34+0x11/0x11
   ? btrfs_backref_cleanup_node+0x18a/0x420
   ? btrfs_backref_cleanup_node+0x18a/0x420
   kasan_report.cold.10+0x20/0x37
   ? btrfs_backref_cleanup_node+0x18a/0x420
   __asan_load8+0x69/0x90
   btrfs_backref_cleanup_node+0x18a/0x420
   btrfs_backref_release_cache+0x83/0x1b0
   relocate_block_group+0x394/0x780
   ? merge_reloc_roots+0x4a0/0x4a0
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x1900
   ? check_flags.part.50+0x6c/0x1e0
   ? btrfs_relocate_chunk+0x120/0x120
   ? kmem_cache_alloc_trace+0xa06/0xcb0
   ? _copy_from_user+0x83/0xc0
   btrfs_ioctl_balance+0x3a7/0x460
   btrfs_ioctl+0x24c8/0x4360
   ? __kasan_check_read+0x11/0x20
   ? check_chain_key+0x1f4/0x2f0
   ? __asan_loadN+0xf/0x20
   ? btrfs_ioctl_get_supported_features+0x30/0x30
   ? kvm_sched_clock_read+0x18/0x30
   ? check_chain_key+0x1f4/0x2f0
   ? lock_downgrade+0x3f0/0x3f0
   ? handle_mm_fault+0xad6/0x2150
   ? do_vfs_ioctl+0xfc/0x9d0
   ? ioctl_file_clone+0xe0/0xe0
   ? check_flags.part.50+0x6c/0x1e0
   ? check_flags.part.50+0x6c/0x1e0
   ? check_flags+0x26/0x30
   ? lock_is_held_type+0xc3/0xf0
   ? syscall_enter_from_user_mode+0x1b/0x60
   ? do_syscall_64+0x13/0x80
   ? rcu_read_lock_sched_held+0xa1/0xd0
   ? __kasan_check_read+0x11/0x20
   ? __fget_light+0xae/0x110
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f4c4bdfe427
  RSP: 002b:00007fff33ee6df8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
  RAX: ffffffffffffffda RBX: 00007fff33ee6e98 RCX: 00007f4c4bdfe427
  RDX: 00007fff33ee6e98 RSI: 00000000c4009420 RDI: 0000000000000003
  RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000078
  R10: fffffffffffff59d R11: 0000000000000202 R12: 0000000000000001
  R13: 0000000000000000 R14: 00007fff33ee8a34 R15: 0000000000000001

  Allocated by task 28836:
   kasan_save_stack+0x21/0x50
   __kasan_kmalloc.constprop.18+0xbe/0xd0
   kasan_kmalloc+0x9/0x10
   kmem_cache_alloc_trace+0x410/0xcb0
   btrfs_backref_alloc_node+0x46/0xf0
   btrfs_backref_add_tree_node+0x60d/0x11d0
   build_backref_tree+0xc5/0x700
   relocate_tree_blocks+0x2be/0xb90
   relocate_block_group+0x2eb/0x780
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x1900
   btrfs_ioctl_balance+0x3a7/0x460
   btrfs_ioctl+0x24c8/0x4360
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  Freed by task 28836:
   kasan_save_stack+0x21/0x50
   kasan_set_track+0x20/0x30
   kasan_set_free_info+0x1f/0x30
   __kasan_slab_free+0xf3/0x140
   kasan_slab_free+0xe/0x10
   kfree+0xde/0x200
   btrfs_backref_error_cleanup+0x452/0x530
   build_backref_tree+0x1a5/0x700
   relocate_tree_blocks+0x2be/0xb90
   relocate_block_group+0x2eb/0x780
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x1900
   btrfs_ioctl_balance+0x3a7/0x460
   btrfs_ioctl+0x24c8/0x4360
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  The buggy address belongs to the object at ffff888112402900
   which belongs to the cache kmalloc-128 of size 128
  The buggy address is located 80 bytes inside of
   128-byte region [ffff888112402900, ffff888112402980)
  The buggy address belongs to the page:
  page:0000000028b1cd08 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888131c810c0 pfn:0x112402
  flags: 0x17ffe0000000200(slab)
  raw: 017ffe0000000200 ffffea000424f308 ffffea0007d572c8 ffff888100040440
  raw: ffff888131c810c0 ffff888112402000 0000000100000009 0000000000000000
  page dumped because: kasan: bad access detected

  Memory state around the buggy address:
   ffff888112402800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
   ffff888112402880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  >ffff888112402900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                   ^
   ffff888112402980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
   ffff888112402a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Link: https://lore.kernel.org/linux-btrfs/20201208194607.GI31381@hungrycats.org/
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
f78743fbda btrfs: do not warn if we can't find the reloc root when looking up backref
The backref code is looking for a reloc_root that corresponds to the
given fs root.  However any number of things could have gone wrong while
initializing that reloc_root, like ENOMEM while trying to allocate the
root itself, or EIO while trying to write the root item.  This would
result in no corresponding reloc_root being in the reloc root cache, and
thus would return NULL when we do the find_reloc_root() call.

Because of this we do not want to WARN_ON().  This presumably was meant
to catch developer errors, cases where we messed up adding the reloc
root.  However we can easily hit this case with error injection, and
thus should not do a WARN_ON().

CC: stable@vger.kernel.org # 5.10+
Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:56 +01:00
Josef Bacik
938fcbfb0c btrfs: splice remaining dirty_bg's onto the transaction dirty bg list
While doing error injection testing with my relocation patches I hit the
following assert:

  assertion failed: list_empty(&block_group->dirty_list), in fs/btrfs/block-group.c:3356
  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/ctree.h:3357!
  invalid opcode: 0000 [#1] SMP NOPTI
  CPU: 0 PID: 24351 Comm: umount Tainted: G        W         5.10.0-rc3+ #193
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
  RIP: 0010:assertfail.constprop.0+0x18/0x1a
  RSP: 0018:ffffa09b019c7e00 EFLAGS: 00010282
  RAX: 0000000000000056 RBX: ffff8f6492c18000 RCX: 0000000000000000
  RDX: ffff8f64fbc27c60 RSI: ffff8f64fbc19050 RDI: ffff8f64fbc19050
  RBP: ffff8f6483bbdc00 R08: 0000000000000000 R09: 0000000000000000
  R10: ffffa09b019c7c38 R11: ffffffff85d70928 R12: ffff8f6492c18100
  R13: ffff8f6492c18148 R14: ffff8f6483bbdd70 R15: dead000000000100
  FS:  00007fbfda4cdc40(0000) GS:ffff8f64fbc00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007fbfda666fd0 CR3: 000000013cf66002 CR4: 0000000000370ef0
  Call Trace:
   btrfs_free_block_groups.cold+0x55/0x55
   close_ctree+0x2c5/0x306
   ? fsnotify_destroy_marks+0x14/0x100
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20
   deactivate_locked_super+0x36/0xa0
   cleanup_mnt+0x12d/0x190
   task_work_run+0x5c/0xa0
   exit_to_user_mode_prepare+0x1b1/0x1d0
   syscall_exit_to_user_mode+0x54/0x280
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

This happened because I injected an error in btrfs_cow_block() while
running the dirty block groups.  When we run the dirty block groups, we
splice the list onto a local list to process.  However if an error
occurs, we only cleanup the transactions dirty block group list, not any
pending block groups we have on our locally spliced list.

In fact if we fail to allocate a path in this function we'll also fail
to clean up the splice list.

Fix this by splicing the list back onto the transaction dirty block
group list so that the block groups are cleaned up.  Then add a 'out'
label and have the error conditions jump to out so that the errors are
handled properly.  This also has the side-effect of fixing a problem
where we would clear 'ret' on error because we unconditionally ran
btrfs_run_delayed_refs().

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:55 +01:00
Josef Bacik
c78a10aebb btrfs: fix reloc root leak with 0 ref reloc roots on recovery
When recovering a relocation, if we run into a reloc root that has 0
refs we simply add it to the reloc_control->reloc_roots list, and then
clean it up later.  The problem with this is __del_reloc_root() doesn't
do anything if the root isn't in the radix tree, which in this case it
won't be because we never call __add_reloc_root() on the reloc_root.

This exit condition simply isn't correct really.  During normal
operation we can remove ourselves from the rb tree and then we're meant
to clean up later at merge_reloc_roots() time, and this happens
correctly.  During recovery we're depending on free_reloc_roots() to
drop our references, but we're short-circuiting.

Fix this by continuing to check if we're on the list and dropping
ourselves from the reloc_control root list and dropping our reference
appropriately.  Change the corresponding BUG_ON() to an ASSERT() that
does the correct thing if we aren't in the rb tree.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:55 +01:00
Nigel Christian
2e626e5673 btrfs: remove repeated word in struct member comment
Comment for processed extent end of range has an unnecessary "in",
remove it.

Signed-off-by: Nigel Christian <nigel.l.christian@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:55 +01:00
Josef Bacik
81e75ac74e btrfs: account for new extents being deleted in total_bytes_pinned
My recent patch set "A variety of lock contention fixes", found here

https://lore.kernel.org/linux-btrfs/cover.1608319304.git.josef@toxicpanda.com/
(Tracked in https://github.com/btrfs/linux/issues/86)

that reduce lock contention on the extent root by running delayed refs
less often resulted in a regression in generic/371.  This test
fallocate()'s the fs until it's full, deletes all the files, and then
tries to fallocate() until full again.

Before these patches we would run all of the delayed refs during
flushing, and then would commit the transaction because we had plenty of
pinned space to recover in order to allocate.  However my patches made
it so we weren't running the delayed refs as aggressively, which meant
that we appeared to have less pinned space when we were deciding to
commit the transaction.

We use the space_info->total_bytes_pinned to approximate how much space
we have pinned.  It's approximate because if we remove a reference to an
extent we may free it, but there may be more references to it than we
know of at that point, but we account it as pinned at the creation time,
and then it's properly accounted when the delayed ref runs.

The way we account for pinned space is if the
delayed_ref_head->total_ref_mod is < 0, because that is clearly a
freeing option.  However there is another case, and that is where
->total_ref_mod == 0 && ->must_insert_reserved == 1.

When we allocate a new extent, we have ->total_ref_mod == 1 and we have
->must_insert_reserved == 1.  This is used to indicate that it is a
brand new extent and will need to have its extent entry added before we
modify any references on the delayed ref head.  But if we subsequently
remove that extent reference, our ->total_ref_mod will be 0, and that
space will be pinned and freed.  Accounting for this case properly
allows for generic/371 to pass with my delayed refs patches applied.

It's important to note that this problem exists without the referenced
patches, it just was uncovered by them.

CC: stable@vger.kernel.org # 5.10
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:55 +01:00
Josef Bacik
2187374f35 btrfs: handle space_info::total_bytes_pinned inside the delayed ref itself
Currently we pass things around to figure out if we maybe freeing data
based on the state of the delayed refs head.  This makes the accounting
sort of confusing and hard to follow, as it's distinctly separate from
the delayed ref heads stuff, but also depends on it entirely.

Fix this by explicitly adjusting the space_info->total_bytes_pinned in
the delayed refs code.  We now have two places where we modify this
counter, once where we create the delayed and destroy the delayed refs,
and once when we pin and unpin the extents.  This means there is a
slight overlap between delayed refs and the pin/unpin mechanisms, but
this is simply used by the ENOSPC infrastructure to determine if we need
to commit the transaction, so there's no adverse affect from this, we
might simply commit thinking it will give us enough space when it might
not.

CC: stable@vger.kernel.org # 5.10
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:55 +01:00
Nikolay Borisov
e9aa7c285d btrfs: enable W=1 checks for btrfs
Now that the btrfs' codebase is clean of almost all W=1 warnings let's
enable those checks unconditionally for the entire fs/btrfs/ and its
subdirectories to catch potential errors during development.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add some comments ]
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:55 +01:00
Nikolay Borisov
8c31a3dbaa btrfs: zoned: remove unused variable in btrfs_sb_log_location_bdev
This fixes warning:

fs/btrfs/zoned.c:491:6: warning: variable ‘zone_size’ set but not used [-Wunused-but-set-variable]
  491 |  u64 zone_size;

which got introduced in 12659251ca ("btrfs: implement log-structured
superblock for ZONED mode"). We'll enable the warning by default and
want clean build until the relevant zoned patches land.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:54 +01:00
Nikolay Borisov
3bed2da1b0 btrfs: fix parameter description for functions in extent_io.c
This makes the file W=1 clean and fixes the following warnings:

fs/btrfs/extent_io.c:414: warning: Function parameter or member 'tree' not described in '__etree_search'
fs/btrfs/extent_io.c:414: warning: Function parameter or member 'offset' not described in '__etree_search'
fs/btrfs/extent_io.c:414: warning: Function parameter or member 'next_ret' not described in '__etree_search'
fs/btrfs/extent_io.c:414: warning: Function parameter or member 'prev_ret' not described in '__etree_search'
fs/btrfs/extent_io.c:414: warning: Function parameter or member 'p_ret' not described in '__etree_search'
fs/btrfs/extent_io.c:414: warning: Function parameter or member 'parent_ret' not described in '__etree_search'
fs/btrfs/extent_io.c:1607: warning: Function parameter or member 'tree' not described in 'find_contiguous_extent_bit'
fs/btrfs/extent_io.c:1607: warning: Function parameter or member 'start' not described in 'find_contiguous_extent_bit'
fs/btrfs/extent_io.c:1607: warning: Function parameter or member 'start_ret' not described in 'find_contiguous_extent_bit'
fs/btrfs/extent_io.c:1607: warning: Function parameter or member 'end_ret' not described in 'find_contiguous_extent_bit'
fs/btrfs/extent_io.c:1607: warning: Function parameter or member 'bits' not described in 'find_contiguous_extent_bit'
fs/btrfs/extent_io.c:1644: warning: Function parameter or member 'tree' not described in 'find_first_clear_extent_bit'
fs/btrfs/extent_io.c:1644: warning: Function parameter or member 'start' not described in 'find_first_clear_extent_bit'
fs/btrfs/extent_io.c:1644: warning: Function parameter or member 'start_ret' not described in 'find_first_clear_extent_bit'
fs/btrfs/extent_io.c:1644: warning: Function parameter or member 'end_ret' not described in 'find_first_clear_extent_bit'
fs/btrfs/extent_io.c:1644: warning: Function parameter or member 'bits' not described in 'find_first_clear_extent_bit'
fs/btrfs/extent_io.c:4187: warning: Function parameter or member 'epd' not described in 'extent_write_cache_pages'
fs/btrfs/extent_io.c:4187: warning: Excess function parameter 'data' description in 'extent_write_cache_pages'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:54 +01:00
Nikolay Borisov
d98b188ea4 btrfs: fix parameter description in space-info.c
With these fixes space-info.c is clear for W=1 warnings, namely the
following ones are fixed:

fs/btrfs/space-info.c:575: warning: Function parameter or member 'fs_info' not described in 'may_commit_transaction'
fs/btrfs/space-info.c:575: warning: Function parameter or member 'space_info' not described in 'may_commit_transaction'
fs/btrfs/space-info.c:1231: warning: Function parameter or member 'fs_info' not described in 'handle_reserve_ticket'
fs/btrfs/space-info.c:1231: warning: Function parameter or member 'space_info' not described in 'handle_reserve_ticket'
fs/btrfs/space-info.c:1231: warning: Function parameter or member 'ticket' not described in 'handle_reserve_ticket'
fs/btrfs/space-info.c:1231: warning: Function parameter or member 'flush' not described in 'handle_reserve_ticket'
fs/btrfs/space-info.c:1315: warning: Function parameter or member 'fs_info' not described in '__reserve_bytes'
fs/btrfs/space-info.c:1315: warning: Function parameter or member 'space_info' not described in '__reserve_bytes'
fs/btrfs/space-info.c:1315: warning: Function parameter or member 'orig_bytes' not described in '__reserve_bytes'
fs/btrfs/space-info.c:1315: warning: Function parameter or member 'flush' not described in '__reserve_bytes'
fs/btrfs/space-info.c:1427: warning: Function parameter or member 'root' not described in 'btrfs_reserve_metadata_bytes'
fs/btrfs/space-info.c:1427: warning: Function parameter or member 'block_rsv' not described in 'btrfs_reserve_metadata_bytes'
fs/btrfs/space-info.c:1427: warning: Function parameter or member 'orig_bytes' not described in 'btrfs_reserve_metadata_bytes'
fs/btrfs/space-info.c:1427: warning: Function parameter or member 'flush' not described in 'btrfs_reserve_metadata_bytes'
fs/btrfs/space-info.c:1462: warning: Function parameter or member 'fs_info' not described in 'btrfs_reserve_data_bytes'
fs/btrfs/space-info.c:1462: warning: Function parameter or member 'bytes' not described in 'btrfs_reserve_data_bytes'
fs/btrfs/space-info.c:1462: warning: Function parameter or member 'flush' not described in 'btrfs_reserve_data_bytes'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:54 +01:00
Nikolay Borisov
b762d1d08d btrfs: fix parameter description of btrfs_inode_rsv_release/btrfs_delalloc_release_space
Fixes following warnings:

fs/btrfs/delalloc-space.c:205: warning: Function parameter or member 'inode' not described in 'btrfs_inode_rsv_release'
fs/btrfs/delalloc-space.c:205: warning: Function parameter or member 'qgroup_free' not described in 'btrfs_inode_rsv_release'
fs/btrfs/delalloc-space.c:472: warning: Function parameter or member 'reserved' not described in 'btrfs_delalloc_release_space'
fs/btrfs/delalloc-space.c:472: warning: Function parameter or member 'qgroup_free' not described in 'btrfs_delalloc_release_space'
fs/btrfs/delalloc-space.c:472: warning: Excess function parameter 'release_bytes' description in 'btrfs_delalloc_release_space'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:54 +01:00
Nikolay Borisov
6e353e3b3c btrfs: document btrfs_check_shared parameters
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:54 +01:00
Nikolay Borisov
2639631d34 btrfs: fix description format of fs_info of btrfs_wait_on_delayed_iputs
Fixes fs/btrfs/inode.c:3101: warning: Function parameter or member 'fs_info' not described in 'btrfs_wait_on_delayed_iputs'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:54 +01:00
Nikolay Borisov
9ee9b97990 btrfs: document fs_info in btrfs_rmap_block
Fixes fs/btrfs/block-group.c:1570: warning: Function parameter or member 'fs_info' not described in 'btrfs_rmap_block'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Nikolay Borisov
9241969547 btrfs: document now parameter of peek_discard_list
Fixes fs/btrfs/discard.c:203: warning: Function parameter or member 'now' not described in 'peek_discard_list'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Nikolay Borisov
f092cf3cfd btrfs: improve parameter description for __btrfs_write_out_cache
Fixes following W=1 warnings:
fs/btrfs/free-space-cache.c:1317: warning: Function parameter or member 'root' not described in '__btrfs_write_out_cache'
fs/btrfs/free-space-cache.c:1317: warning: Function parameter or member 'inode' not described in '__btrfs_write_out_cache'
fs/btrfs/free-space-cache.c:1317: warning: Function parameter or member 'ctl' not described in '__btrfs_write_out_cache'
fs/btrfs/free-space-cache.c:1317: warning: Function parameter or member 'block_group' not described in '__btrfs_write_out_cache'
fs/btrfs/free-space-cache.c:1317: warning: Function parameter or member 'io_ctl' not described in '__btrfs_write_out_cache'
fs/btrfs/free-space-cache.c:1317: warning: Function parameter or member 'trans' not described in '__btrfs_write_out_cache'

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Nikolay Borisov
696eb22b67 btrfs: fix parameter description in delayed-ref.c functions
This fixes the following warnings:

fs/btrfs/delayed-ref.c:80: warning: Function parameter or member 'fs_info' not described in 'btrfs_delayed_refs_rsv_release'
fs/btrfs/delayed-ref.c:80: warning: Function parameter or member 'nr' not described in 'btrfs_delayed_refs_rsv_release'
fs/btrfs/delayed-ref.c:128: warning: Function parameter or member 'fs_info' not described in 'btrfs_migrate_to_delayed_refs_rsv'
fs/btrfs/delayed-ref.c:128: warning: Function parameter or member 'src' not described in 'btrfs_migrate_to_delayed_refs_rsv'
fs/btrfs/delayed-ref.c:128: warning: Function parameter or member 'num_bytes' not described in 'btrfs_migrate_to_delayed_refs_rsv'
fs/btrfs/delayed-ref.c:174: warning: Function parameter or member 'fs_info' not described in 'btrfs_delayed_refs_rsv_refill'
fs/btrfs/delayed-ref.c:174: warning: Function parameter or member 'flush' not described in 'btrfs_delayed_refs_rsv_refill'

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Nikolay Borisov
ca4207ae13 btrfs: fix function description formats in file-item.c
This fixes following W=1 warnings:

fs/btrfs/file-item.c:27: warning: Cannot understand  * @inode:  the inode we want to update the disk_i_size for
 on line 27 - I thought it was a doc line
fs/btrfs/file-item.c:65: warning: Cannot understand  * @inode - the inode we're modifying
 on line 65 - I thought it was a doc line
fs/btrfs/file-item.c:91: warning: Cannot understand  * @inode - the inode we're modifying
 on line 91 - I thought it was a doc line

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Nikolay Borisov
9ad37bb3ff btrfs: fix parameter description of btrfs_add_extent_mapping
This fixes the following compiler warnings:

fs/btrfs/extent_map.c:601: warning: Function parameter or member 'fs_info' not described in 'btrfs_add_extent_mapping'
fs/btrfs/extent_map.c:601: warning: Function parameter or member 'em_tree' not described in 'btrfs_add_extent_mapping'
fs/btrfs/extent_map.c:601: warning: Function parameter or member 'em_in' not described in 'btrfs_add_extent_mapping'
fs/btrfs/extent_map.c:601: warning: Function parameter or member 'start' not described in 'btrfs_add_extent_mapping'
fs/btrfs/extent_map.c:601: warning: Function parameter or member 'len' not described in 'btrfs_add_extent_mapping'

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Nikolay Borisov
401bd2dd12 btrfs: document modified parameter of add_extent_mapping
Fixes fs/btrfs/extent_map.c:399: warning: Function parameter or member
'modified' not described in 'add_extent_mapping'

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:53 +01:00
Qu Wenruo
3c198fe064 btrfs: rework the order of btrfs_ordered_extent::flags
[BUG]
There is a long existing bug in the last parameter of
btrfs_add_ordered_extent(), in commit 771ed689d2 ("Btrfs: Optimize
compressed writeback and reads") back to 2008.

In that ancient commit btrfs_add_ordered_extent() expects the @type
parameter to be one of the following:

- BTRFS_ORDERED_REGULAR
- BTRFS_ORDERED_NOCOW
- BTRFS_ORDERED_PREALLOC
- BTRFS_ORDERED_COMPRESSED

But we pass 0 in cow_file_range(), which means BTRFS_ORDERED_IO_DONE.

Ironically extra check in __btrfs_add_ordered_extent() won't set the bit
if we see (type == IO_DONE || type == IO_COMPLETE), and avoid any
obvious bug.

But this still leads to regular COW ordered extent having no bit to
indicate its type in various trace events, rendering REGULAR bit
useless.

[FIX]
Change the following aspects to avoid such problem:

- Reorder btrfs_ordered_extent::flags
  Now the type bits go first (REGULAR/NOCOW/PREALLCO/COMPRESSED), then
  DIRECT bit, finally extra status bits like IO_DONE/COMPLETE/IOERR.

- Add extra ASSERT() for btrfs_add_ordered_extent_*()

- Remove @type parameter for btrfs_add_ordered_extent_compress()
  As the only valid @type here is BTRFS_ORDERED_COMPRESSED.

- Remove the unnecessary special check for IO_DONE/COMPLETE in
  __btrfs_add_ordered_extent()
  This is just to make the code work, with extra ASSERT(), there are
  limited values can be passed in.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Yang Li
fe3b7bb085 btrfs: remove redundant NULL check before kvfree
Fix below warnings reported by coccicheck:
./fs/btrfs/raid56.c:237:2-8: WARNING: NULL check before some freeing
functions is not needed.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Yang Li <abaci-bugfix@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Josef Bacik
7e2a870a59 btrfs: do not cleanup upper nodes in btrfs_backref_cleanup_node
Zygo reported the following panic when testing my error handling patches
for relocation:

  kernel BUG at fs/btrfs/backref.c:2545!
  invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 3 PID: 8472 Comm: btrfs Tainted: G        W 14
  Hardware name: QEMU Standard PC (i440FX + PIIX,

  Call Trace:
   btrfs_backref_error_cleanup+0x4df/0x530
   build_backref_tree+0x1a5/0x700
   ? _raw_spin_unlock+0x22/0x30
   ? release_extent_buffer+0x225/0x280
   ? free_extent_buffer.part.52+0xd7/0x140
   relocate_tree_blocks+0x2a6/0xb60
   ? kasan_unpoison_shadow+0x35/0x50
   ? do_relocation+0xc10/0xc10
   ? kasan_kmalloc+0x9/0x10
   ? kmem_cache_alloc_trace+0x6a3/0xcb0
   ? free_extent_buffer.part.52+0xd7/0x140
   ? rb_insert_color+0x342/0x360
   ? add_tree_block.isra.36+0x236/0x2b0
   relocate_block_group+0x2eb/0x780
   ? merge_reloc_roots+0x470/0x470
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x18f0
   ? pvclock_clocksource_read+0xeb/0x190
   ? btrfs_relocate_chunk+0x120/0x120
   ? lock_contended+0x620/0x6e0
   ? do_raw_spin_lock+0x1e0/0x1e0
   ? do_raw_spin_unlock+0xa8/0x140
   btrfs_ioctl_balance+0x1f9/0x460
   btrfs_ioctl+0x24c8/0x4380
   ? __kasan_check_read+0x11/0x20
   ? check_chain_key+0x1f4/0x2f0
   ? __asan_loadN+0xf/0x20
   ? btrfs_ioctl_get_supported_features+0x30/0x30
   ? kvm_sched_clock_read+0x18/0x30
   ? check_chain_key+0x1f4/0x2f0
   ? lock_downgrade+0x3f0/0x3f0
   ? handle_mm_fault+0xad6/0x2150
   ? do_vfs_ioctl+0xfc/0x9d0
   ? ioctl_file_clone+0xe0/0xe0
   ? check_flags.part.50+0x6c/0x1e0
   ? check_flags.part.50+0x6c/0x1e0
   ? check_flags+0x26/0x30
   ? lock_is_held_type+0xc3/0xf0
   ? syscall_enter_from_user_mode+0x1b/0x60
   ? do_syscall_64+0x13/0x80
   ? rcu_read_lock_sched_held+0xa1/0xd0
   ? __kasan_check_read+0x11/0x20
   ? __fget_light+0xae/0x110
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

This occurs because of this check

  if (RB_EMPTY_NODE(&upper->rb_node))
	  BUG_ON(!list_empty(&node->upper));

As we are dropping the backref node, if we discover that our upper node
in the edge we just cleaned up isn't linked into the cache that we are
now done with this node, thus the BUG_ON().

However this is an erroneous assumption, as we will look up all the
references for a node first, and then process the pending edges.  All of
the 'upper' nodes in our pending edges won't be in the cache's rb_tree
yet, because they haven't been processed.  We could very well have many
edges still left to cleanup on this node.

The fact is we simply do not need this check, we can just process all of
the edges only for this node, because below this check we do the
following

  if (list_empty(&upper->lower)) {
	  list_add_tail(&upper->lower, &cache->leaves);
	  upper->lowest = 1;
  }

If the upper node truly isn't used yet, then we add it to the
cache->leaves list to be cleaned up later.  If it is still used then the
last child node that has it linked into its node will add it to the
leaves list and then it will be cleaned up.

Fix this problem by dropping this logic altogether.  With this fix I no
longer see the panic when testing with error injection in the backref
code.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Josef Bacik
f7ba2d3751 btrfs: keep track of the root owner for relocation reads
While testing the error paths in relocation, I hit the following lockdep
splat:

  ======================================================
  WARNING: possible circular locking dependency detected
  5.10.0-rc3+ #206 Not tainted
  ------------------------------------------------------
  btrfs-balance/1571 is trying to acquire lock:
  ffff8cdbcc8f77d0 (&head_ref->mutex){+.+.}-{3:3}, at: btrfs_lookup_extent_info+0x156/0x3b0

  but task is already holding lock:
  ffff8cdbc54adbf8 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_lock+0x27/0x100

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

  -> #2 (btrfs-tree-00){++++}-{3:3}:
	 down_write_nested+0x43/0x80
	 __btrfs_tree_lock+0x27/0x100
	 btrfs_search_slot+0x248/0x890
	 relocate_tree_blocks+0x490/0x650
	 relocate_block_group+0x1ba/0x5d0
	 kretprobe_trampoline+0x0/0x50

  -> #1 (btrfs-csum-01){++++}-{3:3}:
	 down_read_nested+0x43/0x130
	 __btrfs_tree_read_lock+0x27/0x100
	 btrfs_read_lock_root_node+0x31/0x40
	 btrfs_search_slot+0x5ab/0x890
	 btrfs_del_csums+0x10b/0x3c0
	 __btrfs_free_extent+0x49d/0x8e0
	 __btrfs_run_delayed_refs+0x283/0x11f0
	 btrfs_run_delayed_refs+0x86/0x220
	 btrfs_start_dirty_block_groups+0x2ba/0x520
	 kretprobe_trampoline+0x0/0x50

  -> #0 (&head_ref->mutex){+.+.}-{3:3}:
	 __lock_acquire+0x1167/0x2150
	 lock_acquire+0x116/0x3e0
	 __mutex_lock+0x7e/0x7b0
	 btrfs_lookup_extent_info+0x156/0x3b0
	 walk_down_proc+0x1c3/0x280
	 walk_down_tree+0x64/0xe0
	 btrfs_drop_subtree+0x182/0x260
	 do_relocation+0x52e/0x660
	 relocate_tree_blocks+0x2ae/0x650
	 relocate_block_group+0x1ba/0x5d0
	 kretprobe_trampoline+0x0/0x50

  other info that might help us debug this:

  Chain exists of:
    &head_ref->mutex --> btrfs-csum-01 --> btrfs-tree-00

   Possible unsafe locking scenario:

	 CPU0                    CPU1
	 ----                    ----
    lock(btrfs-tree-00);
				 lock(btrfs-csum-01);
				 lock(btrfs-tree-00);
    lock(&head_ref->mutex);

   *** DEADLOCK ***

  5 locks held by btrfs-balance/1571:
   #0: ffff8cdb89749ff8 (&fs_info->delete_unused_bgs_mutex){+.+.}-{3:3}, at: btrfs_balance+0x563/0xf40
   #1: ffff8cdb89748838 (&fs_info->cleaner_mutex){+.+.}-{3:3}, at: btrfs_relocate_block_group+0x156/0x300
   #2: ffff8cdbc2c16650 (sb_internal#2){.+.+}-{0:0}, at: start_transaction+0x413/0x5c0
   #3: ffff8cdbc135f538 (btrfs-treloc-01){+.+.}-{3:3}, at: __btrfs_tree_lock+0x27/0x100
   #4: ffff8cdbc54adbf8 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_lock+0x27/0x100

  stack backtrace:
  CPU: 1 PID: 1571 Comm: btrfs-balance Not tainted 5.10.0-rc3+ #206
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
  Call Trace:
   dump_stack+0x8b/0xb0
   check_noncircular+0xcf/0xf0
   ? trace_call_bpf+0x139/0x260
   __lock_acquire+0x1167/0x2150
   lock_acquire+0x116/0x3e0
   ? btrfs_lookup_extent_info+0x156/0x3b0
   __mutex_lock+0x7e/0x7b0
   ? btrfs_lookup_extent_info+0x156/0x3b0
   ? btrfs_lookup_extent_info+0x156/0x3b0
   ? release_extent_buffer+0x124/0x170
   ? _raw_spin_unlock+0x1f/0x30
   ? release_extent_buffer+0x124/0x170
   btrfs_lookup_extent_info+0x156/0x3b0
   walk_down_proc+0x1c3/0x280
   walk_down_tree+0x64/0xe0
   btrfs_drop_subtree+0x182/0x260
   do_relocation+0x52e/0x660
   relocate_tree_blocks+0x2ae/0x650
   ? add_tree_block+0x149/0x1b0
   relocate_block_group+0x1ba/0x5d0
   elfcorehdr_read+0x40/0x40
   ? elfcorehdr_read+0x40/0x40
   ? btrfs_balance+0x796/0xf40
   ? __kthread_parkme+0x66/0x90
   ? btrfs_balance+0xf40/0xf40
   ? balance_kthread+0x37/0x50
   ? kthread+0x137/0x150
   ? __kthread_bind_mask+0x60/0x60
   ? ret_from_fork+0x1f/0x30

As you can see this is bogus, we never take another tree's lock under
the csum lock.  This happens because sometimes we have to read tree
blocks from disk without knowing which root they belong to during
relocation.  We defaulted to an owner of 0, which translates to an fs
tree.  This is fine as all fs trees have the same class, but obviously
isn't fine if the block belongs to a COW only tree.

Thankfully COW only trees only have their owners root as a reference to
them, and since we already look up the extent information during
relocation, go ahead and check and see if this block might belong to a
COW only tree, and if so save the owner in the tree_block struct.  This
allows us to read_tree_block with the proper owner, which gets rid of
this lockdep splat.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Qu Wenruo
c0f0a9e716 btrfs: introduce helper to grab an existing extent buffer from a page
This patch will extract the code to grab an extent buffer from a page
into a helper, grab_extent_buffer_from_page().

This reduces one indent level, and provides the work place for later
expansion for subapge support.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Qu Wenruo
c0fab48095 btrfs: update comment for btrfs_dirty_pages
The original comment is from the initial merge, which has several
problems:

- No holes check any more
- No inline decision is made

Update the out-of-date comment with more correct one.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Qu Wenruo
6bc5636a67 btrfs: refactor __extent_writepage_io() to improve readability
The refactoring involves the following modifications:

- iosize alignment
  In fact we don't really need to manually do alignment at all.
  All extent maps should already be aligned, thus basic ASSERT() check
  would be enough.

- redundant variables
  We have extra variable like blocksize/pg_offset/end.
  They are all unnecessary.

  @blocksize can be replaced by sectorsize size directly, and it's only
  used to verify the em start/size is aligned.

  @pg_offset can be easily calculated using @cur and page_offset(page).

  @end is just assigned from @page_end and never modified, use
  "start + PAGE_SIZE - 1" directly and remove @page_end.

- remove some BUG_ON()s
  The BUG_ON()s are for extent map, which we have tree-checker to check
  on-disk extent data item and runtime check.
  ASSERT() should be enough.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:52 +01:00
Qu Wenruo
0c64c33c60 btrfs: rename parameter offset to disk_bytenr in submit_extent_page
The parameter offset is confusing, it's supposed to be the disk bytenr
of metadata/data.  Rename it to disk_bytenr and update the comment.

Also rename each offset passed to submit_extent_page() as @disk_bytenr
so they're consistent.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Qu Wenruo
58f74b2203 btrfs: refactor btrfs_dec_test_* functions for ordered extents
The refactoring involves the following modifications:

- Return bool instead of int

- Parameter update for @cached of btrfs_dec_test_first_ordered_pending()
  For btrfs_dec_test_first_ordered_pending(), @cached is only used to
  return the finished ordered extent.
  Rename it to @finished_ret.

- Comment updates

  * Change one stale comment
    Which still refers to btrfs_dec_test_ordered_pending(), but the
    context is calling  btrfs_dec_test_first_ordered_pending().
  * Follow the common comment style for both functions
    Add more detailed descriptions for parameters and the return value
  * Move the reason why test_and_set_bit() is used into the call sites

- Change how the return value is calculated
  The most anti-human part of the return value is:

    if (...)
	ret = 1;
    ...
    return ret == 0;

  This means, when we set ret to 1, the function returns 0.
  Change the local variable name to @finished, and directly return the
  value of it.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Qu Wenruo
523929f1ca btrfs: make btrfs_dio_private::bytes u32
btrfs_dio_private::bytes is only assigned from bio::bi_iter::bi_size,
which is never larger than U32.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Nikolay Borisov
d7830b7155 btrfs: remove always true condition in btrfs_start_delalloc_roots
Following the rework in e076ab2a2c ("btrfs: shrink delalloc pages
instead of full inodes") the nr variable is no longer passed by
reference to start_delalloc_inodes hence it cannot change. Additionally
we are always guaranteed for it to be positive number hence it's
redundant to have it as a condition in the loop. Simply remove that
usage.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Nikolay Borisov
9db4dc241e btrfs: make btrfs_start_delalloc_root's nr argument a long
It's currently u64 which gets instantly translated either to LONG_MAX
(if U64_MAX is passed) or cast to an unsigned long (which is in fact,
wrong because writeback_control::nr_to_write is a signed, long type).

Just convert the function's argument to be long time which obviates the
need to manually convert u64 value to a long. Adjust all call sites
which pass U64_MAX to pass LONG_MAX. Finally ensure that in
shrink_delalloc the u64 is converted to a long without overflowing,
resulting in a negative number.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Filipe Manana
9c4a062a94 btrfs: send: remove stale code when checking for shared extents
After commit 040ee6120c ("Btrfs: send, improve clone range") we do not
use anymore the data_offset field of struct backref_ctx, as after that we
do all the necessary checks for the data offset of file extent items at
clone_range(). Since there are no more users of data_offset from that
structure, remove it.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Nikolay Borisov
7056bf69e5 btrfs: consolidate btrfs_previous_item ret val handling in btrfs_shrink_device
Instead of having three 'if' to handle non-NULL return value consolidate
this in one 'if (ret)'. That way the code is more obvious:

 - Always drop delete_unused_bgs_mutex if ret is not NULL
 - If ret is negative -> goto done
 - If it's 1 -> reset ret to 0, release the path and finish the loop.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:51 +01:00
Josef Bacik
1478143ac8 btrfs: ref-verify: make sure owner is set for all refs
I noticed that shared ref entries in ref-verify didn't have the proper
owner set, which caused me to think there was something seriously wrong.
However the problem is if we have a parent we simply weren't filling out
the owner part of the reference, even though we have it.

Fix this by making sure we set all the proper fields when we modify a
reference, this way we'll have the proper owner if a problem happens and
we don't waste time thinking we're updating the wrong level.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:50 +01:00
Josef Bacik
0d73a11c62 btrfs: ref-verify: pass down tree block level when building refs
I noticed that sometimes I would have the wrong level printed out with
ref-verify while testing some error injection related problems.  This is
because we only get the level from the main extent item, but our
references could go off the current leaf into another, and at that point
we lose our level.

Fix this by keeping track of the last tree block level that we found,
the same way we keep track of our bytenr and num_bytes, in case we
happen to wander into another leaf while still processing the references
for a bytenr.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:50 +01:00
Josef Bacik
1fec12a560 btrfs: noinline btrfs_should_cancel_balance
I was attempting to reproduce a problem that Zygo hit, but my error
injection wasn't firing for a few of the common calls to
btrfs_should_cancel_balance.  This is because the compiler decided to
inline it at these spots.  Keep this from happening by explicitly
marking the function as noinline so that error injection will always
work.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:50 +01:00
Josef Bacik
f75e2b79b5 btrfs: allow error injection for btrfs_search_slot and btrfs_cow_block
The following patches are going to address error handling in relocation,
in order to test those patches I need to be able to inject errors in
btrfs_search_slot and btrfs_cow_block, as we call both of these pretty
often in different cases during relocation.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:50 +01:00
Nikolay Borisov
69948022c9 btrfs: remove new_dirid argument from btrfs_create_subvol_root
It's no longer used. While at it also remove new_dirid in create_subvol
as it's used in a single place and open code it. No functional changes.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:50 +01:00
Nikolay Borisov
23125104d8 btrfs: make btrfs_root::free_objectid hold the next available objectid
Adjust the way free_objectid is being initialized, it now stores
BTRFS_FIRST_FREE_OBJECTID rather than the, somewhat arbitrary,
BTRFS_FIRST_FREE_OBJECTID - 1. This change also has the added benefit
that now it becomes unnecessary to explicitly initialize free_objectid
for a newly create fs root.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:50 +01:00
Nikolay Borisov
6b8fad576a btrfs: rename btrfs_root::highest_objectid to free_objectid
This reflects the true purpose of the member as it's being used solely
in context where a new objectid is being allocated. Future changes will
also change the way it's being used to closely follow this semantics.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:49 +01:00
Nikolay Borisov
543068a217 btrfs: rename btrfs_find_free_objectid to btrfs_get_free_objectid
This better reflects the semantics of the function i.e no search is
performed whatsoever.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:49 +01:00
Nikolay Borisov
453e487386 btrfs: rename btrfs_find_highest_objectid to btrfs_init_root_free_objectid
This function is used to initialize the in-memory
btrfs_root::highest_objectid member, which is used to get an available
objectid. Rename it to better reflect its semantics.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:49 +01:00
Nikolay Borisov
149716570b btrfs: cleanup local variables in btrfs_file_write_iter
First replace all inode instances with a pointer to btrfs_inode. This
removes multiple invocations of the BTRFS_I macro, subsequently remove
2 local variables as they are called only once and simply refer to
them directly.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:49 +01:00
Zhihao Cheng
3cc64e7ebf btrfs: clarify error returns values in __load_free_space_cache
Return value in __load_free_space_cache is not properly set after
(unlikely) memory allocation failures and 0 is returned instead.
This is not a problem for the caller load_free_space_cache because only
value 1 is considered as 'cache loaded' but for clarity it's better
to set the errors accordingly.

Fixes: a67509c300 ("Btrfs: add a io_ctl struct and helpers for dealing with the space cache")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:49 +01:00
Josef Bacik
4f4317c13a btrfs: fix error handling in commit_fs_roots
While doing error injection I would sometimes get a corrupt file system.
This is because I was injecting errors at btrfs_search_slot, but would
only do it one time per stack.  This uncovered a problem in
commit_fs_roots, where if we get an error we would just break.  However
we're in a nested loop, the first loop being a loop to find all the
dirty fs roots, and then subsequent root updates would succeed clearing
the error value.

This isn't likely to happen in real scenarios, however we could
potentially get a random ENOMEM once and then not again, and we'd end up
with a corrupted file system.  Fix this by moving the error checking
around a bit to the main loop, as this is the only place where something
will fail, and return the error as soon as it occurs.

With this patch my reproducer no longer corrupts the file system.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-08 22:58:49 +01:00
Linus Torvalds
c05d51c773 for-5.11-rc5-tag
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Merge tag 'for-5.11-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fixes from David Sterba:
 "A few more fixes for a late rc:

   - fix lockdep complaint on 32bit arches and also remove an unsafe
     memory use due to device vs filesystem lifetime

   - two fixes for free space tree:

      * race during log replay and cache rebuild, now more likely to
        happen due to changes in this dev cycle

      * possible free space tree corruption with online conversion
        during initial tree population"

* tag 'for-5.11-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: fix log replay failure due to race with space cache rebuild
  btrfs: fix lockdep warning due to seqcount_mutex on 32bit arch
  btrfs: fix possible free space tree corruption with online conversion
2021-01-29 13:54:40 -08:00
Christoph Hellwig
616c6a6884 btrfs: use bio_kmalloc in __alloc_device
Use bio_kmalloc instead of open coding it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-27 09:51:48 -07:00
Filipe Manana
9ad6d91f05 btrfs: fix log replay failure due to race with space cache rebuild
After a sudden power failure we may end up with a space cache on disk that
is not valid and needs to be rebuilt from scratch.

If that happens, during log replay when we attempt to pin an extent buffer
from a log tree, at btrfs_pin_extent_for_log_replay(), we do not wait for
the space cache to be rebuilt through the call to:

    btrfs_cache_block_group(cache, 1);

That is because that only waits for the task (work queue job) that loads
the space cache to change the cache state from BTRFS_CACHE_FAST to any
other value. That is ok when the space cache on disk exists and is valid,
but when the cache is not valid and needs to be rebuilt, it ends up
returning as soon as the cache state changes to BTRFS_CACHE_STARTED (done
at caching_thread()).

So this means that we can end up trying to unpin a range which is not yet
marked as free in the block group. This results in the call to
btrfs_remove_free_space() to return -EINVAL to
btrfs_pin_extent_for_log_replay(), which in turn makes the log replay fail
as well as mounting the filesystem. More specifically the -EINVAL comes
from free_space_cache.c:remove_from_bitmap(), because the requested range
is not marked as free space (ones in the bitmap), we have the following
condition triggered:

static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
(...)
       if (ret < 0 || search_start != *offset)
            return -EINVAL;
(...)

It's the "search_start != *offset" that results in the condition being
evaluated to true.

When this happens we got the following in dmesg/syslog:

[72383.415114] BTRFS: device fsid 32b95b69-0ea9-496a-9f02-3f5a56dc9322 devid 1 transid 1432 /dev/sdb scanned by mount (3816007)
[72383.417837] BTRFS info (device sdb): disk space caching is enabled
[72383.418536] BTRFS info (device sdb): has skinny extents
[72383.423846] BTRFS info (device sdb): start tree-log replay
[72383.426416] BTRFS warning (device sdb): block group 30408704 has wrong amount of free space
[72383.427686] BTRFS warning (device sdb): failed to load free space cache for block group 30408704, rebuilding it now
[72383.454291] BTRFS: error (device sdb) in btrfs_recover_log_trees:6203: errno=-22 unknown (Failed to pin buffers while recovering log root tree.)
[72383.456725] BTRFS: error (device sdb) in btrfs_replay_log:2253: errno=-22 unknown (Failed to recover log tree)
[72383.460241] BTRFS error (device sdb): open_ctree failed

We also mark the range for the extent buffer in the excluded extents io
tree. That is fine when the space cache is valid on disk and we can load
it, in which case it causes no problems.

However, for the case where we need to rebuild the space cache, because it
is either invalid or it is missing, having the extent buffer range marked
in the excluded extents io tree leads to a -EINVAL failure from the call
to btrfs_remove_free_space(), resulting in the log replay and mount to
fail. This is because by having the range marked in the excluded extents
io tree, the caching thread ends up never adding the range of the extent
buffer as free space in the block group since the calls to
add_new_free_space(), called from load_extent_tree_free(), filter out any
ranges that are marked as excluded extents.

So fix this by making sure that during log replay we wait for the caching
task to finish completely when we need to rebuild a space cache, and also
drop the need to mark the extent buffer range in the excluded extents io
tree, as well as clearing ranges from that tree at
btrfs_finish_extent_commit().

This started to happen with some frequency on large filesystems having
block groups with a lot of fragmentation since the recent commit
e747853cae ("btrfs: load free space cache asynchronously"), but in
fact the issue has been there for years, it was just much less likely
to happen.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-25 18:44:53 +01:00
Su Yue
c41ec4529d btrfs: fix lockdep warning due to seqcount_mutex on 32bit arch
This effectively reverts commit d5c8238849 ("btrfs: convert
data_seqcount to seqcount_mutex_t").

While running fstests on 32 bits test box, many tests failed because of
warnings in dmesg. One of those warnings (btrfs/003):

  [66.441317] WARNING: CPU: 6 PID: 9251 at include/linux/seqlock.h:279 btrfs_remove_chunk+0x58b/0x7b0 [btrfs]
  [66.441446] CPU: 6 PID: 9251 Comm: btrfs Tainted: G           O      5.11.0-rc4-custom+ #5
  [66.441449] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ArchLinux 1.14.0-1 04/01/2014
  [66.441451] EIP: btrfs_remove_chunk+0x58b/0x7b0 [btrfs]
  [66.441472] EAX: 00000000 EBX: 00000001 ECX: c576070c EDX: c6b15803
  [66.441475] ESI: 10000000 EDI: 00000000 EBP: c56fbcfc ESP: c56fbc70
  [66.441477] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246
  [66.441481] CR0: 80050033 CR2: 05c8da20 CR3: 04b20000 CR4: 00350ed0
  [66.441485] Call Trace:
  [66.441510]  btrfs_relocate_chunk+0xb1/0x100 [btrfs]
  [66.441529]  ? btrfs_lookup_block_group+0x17/0x20 [btrfs]
  [66.441562]  btrfs_balance+0x8ed/0x13b0 [btrfs]
  [66.441586]  ? btrfs_ioctl_balance+0x333/0x3c0 [btrfs]
  [66.441619]  ? __this_cpu_preempt_check+0xf/0x11
  [66.441643]  btrfs_ioctl_balance+0x333/0x3c0 [btrfs]
  [66.441664]  ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs]
  [66.441683]  btrfs_ioctl+0x414/0x2ae0 [btrfs]
  [66.441700]  ? __lock_acquire+0x35f/0x2650
  [66.441717]  ? lockdep_hardirqs_on+0x87/0x120
  [66.441720]  ? lockdep_hardirqs_on_prepare+0xd0/0x1e0
  [66.441724]  ? call_rcu+0x2d3/0x530
  [66.441731]  ? __might_fault+0x41/0x90
  [66.441736]  ? kvm_sched_clock_read+0x15/0x50
  [66.441740]  ? sched_clock+0x8/0x10
  [66.441745]  ? sched_clock_cpu+0x13/0x180
  [66.441750]  ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs]
  [66.441750]  ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs]
  [66.441768]  __ia32_sys_ioctl+0x165/0x8a0
  [66.441773]  ? __this_cpu_preempt_check+0xf/0x11
  [66.441785]  ? __might_fault+0x89/0x90
  [66.441791]  __do_fast_syscall_32+0x54/0x80
  [66.441796]  do_fast_syscall_32+0x32/0x70
  [66.441801]  do_SYSENTER_32+0x15/0x20
  [66.441805]  entry_SYSENTER_32+0x9f/0xf2
  [66.441808] EIP: 0xab7b5549
  [66.441814] EAX: ffffffda EBX: 00000003 ECX: c4009420 EDX: bfa91f5c
  [66.441816] ESI: 00000003 EDI: 00000001 EBP: 00000000 ESP: bfa91e98
  [66.441818] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000292
  [66.441833] irq event stamp: 42579
  [66.441835] hardirqs last  enabled at (42585): [<c60eb065>] console_unlock+0x495/0x590
  [66.441838] hardirqs last disabled at (42590): [<c60eafd5>] console_unlock+0x405/0x590
  [66.441840] softirqs last  enabled at (41698): [<c601b76c>] call_on_stack+0x1c/0x60
  [66.441843] softirqs last disabled at (41681): [<c601b76c>] call_on_stack+0x1c/0x60

  ========================================================================
  btrfs_remove_chunk+0x58b/0x7b0:
  __seqprop_mutex_assert at linux/./include/linux/seqlock.h:279
  (inlined by) btrfs_device_set_bytes_used at linux/fs/btrfs/volumes.h:212
  (inlined by) btrfs_remove_chunk at linux/fs/btrfs/volumes.c:2994
  ========================================================================

The warning is produced by lockdep_assert_held() in
__seqprop_mutex_assert() if CONFIG_LOCKDEP is enabled.
And "olumes.c:2994 is btrfs_device_set_bytes_used() with mutex lock
fs_info->chunk_mutex held already.

After adding some debug prints, the cause was found that many
__alloc_device() are called with NULL @fs_info (during scanning ioctl).
Inside the function, btrfs_device_data_ordered_init() is expanded to
seqcount_mutex_init().  In this scenario, its second
parameter info->chunk_mutex  is &NULL->chunk_mutex which equals
to offsetof(struct btrfs_fs_info, chunk_mutex) unexpectedly. Thus,
seqcount_mutex_init() is called in wrong way. And later
btrfs_device_get/set helpers trigger lockdep warnings.

The device and filesystem object lifetimes are different and we'd have
to synchronize initialization of the btrfs_device::data_seqcount with
the fs_info, possibly using some additional synchronization. It would
still not prevent concurrent access to the seqcount lock when it's used
for read and initialization.

Commit d5c8238849 ("btrfs: convert data_seqcount to seqcount_mutex_t")
does not mention a particular problem being fixed so revert should not
cause any harm and we'll get the lockdep warning fixed.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=210139
Reported-by: Erhard F <erhard_f@mailbox.org>
Fixes: d5c8238849 ("btrfs: convert data_seqcount to seqcount_mutex_t")
CC: stable@vger.kernel.org # 5.10
CC: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Su Yue <l@damenly.su>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-25 18:44:50 +01:00
Josef Bacik
2f96e40212 btrfs: fix possible free space tree corruption with online conversion
While running btrfs/011 in a loop I would often ASSERT() while trying to
add a new free space entry that already existed, or get an EEXIST while
adding a new block to the extent tree, which is another indication of
double allocation.

This occurs because when we do the free space tree population, we create
the new root and then populate the tree and commit the transaction.
The problem is when you create a new root, the root node and commit root
node are the same.  During this initial transaction commit we will run
all of the delayed refs that were paused during the free space tree
generation, and thus begin to cache block groups.  While caching block
groups the caching thread will be reading from the main root for the
free space tree, so as we make allocations we'll be changing the free
space tree, which can cause us to add the same range twice which results
in either the ASSERT(ret != -EEXIST); in __btrfs_add_free_space, or in a
variety of different errors when running delayed refs because of a
double allocation.

Fix this by marking the fs_info as unsafe to load the free space tree,
and fall back on the old slow method.  We could be smarter than this,
for example caching the block group while we're populating the free
space tree, but since this is a serious problem I've opted for the
simplest solution.

CC: stable@vger.kernel.org # 4.9+
Fixes: a5ed918285 ("Btrfs: implement the free space B-tree")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-25 18:44:37 +01:00
Christoph Hellwig
309dca309f block: store a block_device pointer in struct bio
Replace the gendisk pointer in struct bio with a pointer to the newly
improved struct block device.  From that the gendisk can be trivially
accessed with an extra indirection, but it also allows to directly
look up all information related to partition remapping.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-24 18:17:20 -07:00
Christian Brauner
549c729771
fs: make helpers idmap mount aware
Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:20 +01:00
Christian Brauner
ba73d98745
namei: handle idmapped mounts in may_*() helpers
The may_follow_link(), may_linkat(), may_lookup(), may_open(),
may_o_create(), may_create_in_sticky(), may_delete(), and may_create()
helpers determine whether the caller is privileged enough to perform the
associated operations. Let them handle idmapped mounts by mapping the
inode or fsids according to the mount's user namespace. Afterwards the
checks are identical to non-idmapped inodes. The patch takes care to
retrieve the mount's user namespace right before performing permission
checks and passing it down into the fileystem so the user namespace
can't change in between by someone idmapping a mount that is currently
not idmapped. If the initial user namespace is passed nothing changes so
non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-13-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:17 +01:00
Christian Brauner
0d56a4518d
stat: handle idmapped mounts
The generic_fillattr() helper fills in the basic attributes associated
with an inode. Enable it to handle idmapped mounts. If the inode is
accessed through an idmapped mount map it into the mount's user
namespace before we store the uid and gid. If the initial user namespace
is passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-12-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:17 +01:00
Christian Brauner
e65ce2a50c
acl: handle idmapped mounts
The posix acl permission checking helpers determine whether a caller is
privileged over an inode according to the acls associated with the
inode. Add helpers that make it possible to handle acls on idmapped
mounts.

The vfs and the filesystems targeted by this first iteration make use of
posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to
translate basic posix access and default permissions such as the
ACL_USER and ACL_GROUP type according to the initial user namespace (or
the superblock's user namespace) to and from the caller's current user
namespace. Adapt these two helpers to handle idmapped mounts whereby we
either map from or into the mount's user namespace depending on in which
direction we're translating.
Similarly, cap_convert_nscap() is used by the vfs to translate user
namespace and non-user namespace aware filesystem capabilities from the
superblock's user namespace to the caller's user namespace. Enable it to
handle idmapped mounts by accounting for the mount's user namespace.

In addition the fileystems targeted in the first iteration of this patch
series make use of the posix_acl_chmod() and, posix_acl_update_mode()
helpers. Both helpers perform permission checks on the target inode. Let
them handle idmapped mounts. These two helpers are called when posix
acls are set by the respective filesystems to handle this case we extend
the ->set() method to take an additional user namespace argument to pass
the mount's user namespace down.

Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:17 +01:00
Christian Brauner
2f221d6f7b
attr: handle idmapped mounts
When file attributes are changed most filesystems rely on the
setattr_prepare(), setattr_copy(), and notify_change() helpers for
initialization and permission checking. Let them handle idmapped mounts.
If the inode is accessed through an idmapped mount map it into the
mount's user namespace. Afterwards the checks are identical to
non-idmapped mounts. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Helpers that perform checks on the ia_uid and ia_gid fields in struct
iattr assume that ia_uid and ia_gid are intended values and have already
been mapped correctly at the userspace-kernelspace boundary as we
already do today. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Christian Brauner
21cb47be6f
inode: make init and permission helpers idmapped mount aware
The inode_owner_or_capable() helper determines whether the caller is the
owner of the inode or is capable with respect to that inode. Allow it to
handle idmapped mounts. If the inode is accessed through an idmapped
mount it according to the mount's user namespace. Afterwards the checks
are identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Similarly, allow the inode_init_owner() helper to handle idmapped
mounts. It initializes a new inode on idmapped mounts by mapping the
fsuid and fsgid of the caller from the mount's user namespace. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Christian Brauner
47291baa8d
namei: make permission helpers idmapped mount aware
The two helpers inode_permission() and generic_permission() are used by
the vfs to perform basic permission checking by verifying that the
caller is privileged over an inode. In order to handle idmapped mounts
we extend the two helpers with an additional user namespace argument.
On idmapped mounts the two helpers will make sure to map the inode
according to the mount's user namespace and then peform identical
permission checks to inode_permission() and generic_permission(). If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-6-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Christoph Hellwig
2f63296578 iomap: pass a flags argument to iomap_dio_rw
Pass a set of flags to iomap_dio_rw instead of the boolean
wait_for_completion argument.  The IOMAP_DIO_FORCE_WAIT flag
replaces the wait_for_completion, but only needs to be passed
when the iocb isn't synchronous to start with to simplify the
callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
[djwong: rework xfs_file.c so that we can push iomap changes separately]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
2021-01-23 10:06:09 -08:00
Linus Torvalds
9791581c04 for-5.11-rc4-tag
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Merge tag 'for-5.11-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fixes from David Sterba:
 "A few more one line fixes for various bugs, stable material.

   - fix send when emitting clone operation from the same file and root

   - fix double free on error when cleaning backrefs

   - lockdep fix during relocation

   - handle potential error during reloc when starting transaction

   - skip running delayed refs during commit (leftover from code removal
     in this dev cycle)"

* tag 'for-5.11-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: don't clear ret in btrfs_start_dirty_block_groups
  btrfs: fix lockdep splat in btrfs_recover_relocation
  btrfs: do not double free backref nodes on error
  btrfs: don't get an EINTR during drop_snapshot for reloc
  btrfs: send: fix invalid clone operations when cloning from the same file and root
  btrfs: no need to run delayed refs after commit_fs_roots during commit
2021-01-20 14:15:33 -08:00
Josef Bacik
34d1eb0e59 btrfs: don't clear ret in btrfs_start_dirty_block_groups
If we fail to update a block group item in the loop we'll break, however
we'll do btrfs_run_delayed_refs and lose our error value in ret, and
thus not clean up properly.  Fix this by only running the delayed refs
if there was no failure.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-18 16:00:11 +01:00
Josef Bacik
fb28610097 btrfs: fix lockdep splat in btrfs_recover_relocation
While testing the error paths of relocation I hit the following lockdep
splat:

  ======================================================
  WARNING: possible circular locking dependency detected
  5.10.0-rc6+ #217 Not tainted
  ------------------------------------------------------
  mount/779 is trying to acquire lock:
  ffffa0e676945418 (&fs_info->balance_mutex){+.+.}-{3:3}, at: btrfs_recover_balance+0x2f0/0x340

  but task is already holding lock:
  ffffa0e60ee31da8 (btrfs-root-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x27/0x100

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

  -> #2 (btrfs-root-00){++++}-{3:3}:
	 down_read_nested+0x43/0x130
	 __btrfs_tree_read_lock+0x27/0x100
	 btrfs_read_lock_root_node+0x31/0x40
	 btrfs_search_slot+0x462/0x8f0
	 btrfs_update_root+0x55/0x2b0
	 btrfs_drop_snapshot+0x398/0x750
	 clean_dirty_subvols+0xdf/0x120
	 btrfs_recover_relocation+0x534/0x5a0
	 btrfs_start_pre_rw_mount+0xcb/0x170
	 open_ctree+0x151f/0x1726
	 btrfs_mount_root.cold+0x12/0xea
	 legacy_get_tree+0x30/0x50
	 vfs_get_tree+0x28/0xc0
	 vfs_kern_mount.part.0+0x71/0xb0
	 btrfs_mount+0x10d/0x380
	 legacy_get_tree+0x30/0x50
	 vfs_get_tree+0x28/0xc0
	 path_mount+0x433/0xc10
	 __x64_sys_mount+0xe3/0x120
	 do_syscall_64+0x33/0x40
	 entry_SYSCALL_64_after_hwframe+0x44/0xa9

  -> #1 (sb_internal#2){.+.+}-{0:0}:
	 start_transaction+0x444/0x700
	 insert_balance_item.isra.0+0x37/0x320
	 btrfs_balance+0x354/0xf40
	 btrfs_ioctl_balance+0x2cf/0x380
	 __x64_sys_ioctl+0x83/0xb0
	 do_syscall_64+0x33/0x40
	 entry_SYSCALL_64_after_hwframe+0x44/0xa9

  -> #0 (&fs_info->balance_mutex){+.+.}-{3:3}:
	 __lock_acquire+0x1120/0x1e10
	 lock_acquire+0x116/0x370
	 __mutex_lock+0x7e/0x7b0
	 btrfs_recover_balance+0x2f0/0x340
	 open_ctree+0x1095/0x1726
	 btrfs_mount_root.cold+0x12/0xea
	 legacy_get_tree+0x30/0x50
	 vfs_get_tree+0x28/0xc0
	 vfs_kern_mount.part.0+0x71/0xb0
	 btrfs_mount+0x10d/0x380
	 legacy_get_tree+0x30/0x50
	 vfs_get_tree+0x28/0xc0
	 path_mount+0x433/0xc10
	 __x64_sys_mount+0xe3/0x120
	 do_syscall_64+0x33/0x40
	 entry_SYSCALL_64_after_hwframe+0x44/0xa9

  other info that might help us debug this:

  Chain exists of:
    &fs_info->balance_mutex --> sb_internal#2 --> btrfs-root-00

   Possible unsafe locking scenario:

	 CPU0                    CPU1
	 ----                    ----
    lock(btrfs-root-00);
				 lock(sb_internal#2);
				 lock(btrfs-root-00);
    lock(&fs_info->balance_mutex);

   *** DEADLOCK ***

  2 locks held by mount/779:
   #0: ffffa0e60dc040e0 (&type->s_umount_key#47/1){+.+.}-{3:3}, at: alloc_super+0xb5/0x380
   #1: ffffa0e60ee31da8 (btrfs-root-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x27/0x100

  stack backtrace:
  CPU: 0 PID: 779 Comm: mount Not tainted 5.10.0-rc6+ #217
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
  Call Trace:
   dump_stack+0x8b/0xb0
   check_noncircular+0xcf/0xf0
   ? trace_call_bpf+0x139/0x260
   __lock_acquire+0x1120/0x1e10
   lock_acquire+0x116/0x370
   ? btrfs_recover_balance+0x2f0/0x340
   __mutex_lock+0x7e/0x7b0
   ? btrfs_recover_balance+0x2f0/0x340
   ? btrfs_recover_balance+0x2f0/0x340
   ? rcu_read_lock_sched_held+0x3f/0x80
   ? kmem_cache_alloc_trace+0x2c4/0x2f0
   ? btrfs_get_64+0x5e/0x100
   btrfs_recover_balance+0x2f0/0x340
   open_ctree+0x1095/0x1726
   btrfs_mount_root.cold+0x12/0xea
   ? rcu_read_lock_sched_held+0x3f/0x80
   legacy_get_tree+0x30/0x50
   vfs_get_tree+0x28/0xc0
   vfs_kern_mount.part.0+0x71/0xb0
   btrfs_mount+0x10d/0x380
   ? __kmalloc_track_caller+0x2f2/0x320
   legacy_get_tree+0x30/0x50
   vfs_get_tree+0x28/0xc0
   ? capable+0x3a/0x60
   path_mount+0x433/0xc10
   __x64_sys_mount+0xe3/0x120
   do_syscall_64+0x33/0x40
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

This is straightforward to fix, simply release the path before we setup
the balance_ctl.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-18 15:44:59 +01:00
Josef Bacik
49ecc679ab btrfs: do not double free backref nodes on error
Zygo reported the following KASAN splat:

  BUG: KASAN: use-after-free in btrfs_backref_cleanup_node+0x18a/0x420
  Read of size 8 at addr ffff888112402950 by task btrfs/28836

  CPU: 0 PID: 28836 Comm: btrfs Tainted: G        W         5.10.0-e35f27394290-for-next+ #23
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
  Call Trace:
   dump_stack+0xbc/0xf9
   ? btrfs_backref_cleanup_node+0x18a/0x420
   print_address_description.constprop.8+0x21/0x210
   ? record_print_text.cold.34+0x11/0x11
   ? btrfs_backref_cleanup_node+0x18a/0x420
   ? btrfs_backref_cleanup_node+0x18a/0x420
   kasan_report.cold.10+0x20/0x37
   ? btrfs_backref_cleanup_node+0x18a/0x420
   __asan_load8+0x69/0x90
   btrfs_backref_cleanup_node+0x18a/0x420
   btrfs_backref_release_cache+0x83/0x1b0
   relocate_block_group+0x394/0x780
   ? merge_reloc_roots+0x4a0/0x4a0
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x1900
   ? check_flags.part.50+0x6c/0x1e0
   ? btrfs_relocate_chunk+0x120/0x120
   ? kmem_cache_alloc_trace+0xa06/0xcb0
   ? _copy_from_user+0x83/0xc0
   btrfs_ioctl_balance+0x3a7/0x460
   btrfs_ioctl+0x24c8/0x4360
   ? __kasan_check_read+0x11/0x20
   ? check_chain_key+0x1f4/0x2f0
   ? __asan_loadN+0xf/0x20
   ? btrfs_ioctl_get_supported_features+0x30/0x30
   ? kvm_sched_clock_read+0x18/0x30
   ? check_chain_key+0x1f4/0x2f0
   ? lock_downgrade+0x3f0/0x3f0
   ? handle_mm_fault+0xad6/0x2150
   ? do_vfs_ioctl+0xfc/0x9d0
   ? ioctl_file_clone+0xe0/0xe0
   ? check_flags.part.50+0x6c/0x1e0
   ? check_flags.part.50+0x6c/0x1e0
   ? check_flags+0x26/0x30
   ? lock_is_held_type+0xc3/0xf0
   ? syscall_enter_from_user_mode+0x1b/0x60
   ? do_syscall_64+0x13/0x80
   ? rcu_read_lock_sched_held+0xa1/0xd0
   ? __kasan_check_read+0x11/0x20
   ? __fget_light+0xae/0x110
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f4c4bdfe427

  Allocated by task 28836:
   kasan_save_stack+0x21/0x50
   __kasan_kmalloc.constprop.18+0xbe/0xd0
   kasan_kmalloc+0x9/0x10
   kmem_cache_alloc_trace+0x410/0xcb0
   btrfs_backref_alloc_node+0x46/0xf0
   btrfs_backref_add_tree_node+0x60d/0x11d0
   build_backref_tree+0xc5/0x700
   relocate_tree_blocks+0x2be/0xb90
   relocate_block_group+0x2eb/0x780
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x1900
   btrfs_ioctl_balance+0x3a7/0x460
   btrfs_ioctl+0x24c8/0x4360
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  Freed by task 28836:
   kasan_save_stack+0x21/0x50
   kasan_set_track+0x20/0x30
   kasan_set_free_info+0x1f/0x30
   __kasan_slab_free+0xf3/0x140
   kasan_slab_free+0xe/0x10
   kfree+0xde/0x200
   btrfs_backref_error_cleanup+0x452/0x530
   build_backref_tree+0x1a5/0x700
   relocate_tree_blocks+0x2be/0xb90
   relocate_block_group+0x2eb/0x780
   btrfs_relocate_block_group+0x26e/0x4c0
   btrfs_relocate_chunk+0x52/0x120
   btrfs_balance+0xe2e/0x1900
   btrfs_ioctl_balance+0x3a7/0x460
   btrfs_ioctl+0x24c8/0x4360
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

This occurred because we freed our backref node in
btrfs_backref_error_cleanup(), but then tried to free it again in
btrfs_backref_release_cache().  This is because
btrfs_backref_release_cache() will cycle through all of the
cache->leaves nodes and free them up.  However
btrfs_backref_error_cleanup() freed the backref node with
btrfs_backref_free_node(), which simply kfree()d the backref node
without unlinking it from the cache.  Change this to a
btrfs_backref_drop_node(), which does the appropriate cleanup and
removes the node from the cache->leaves list, so when we go to free the
remaining cache we don't trip over items we've already dropped.

Fixes: 75bfb9aff4 ("Btrfs: cleanup error handling in build_backref_tree")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-18 15:44:53 +01:00
Josef Bacik
18d3bff411 btrfs: don't get an EINTR during drop_snapshot for reloc
This was partially fixed by f3e3d9cc35 ("btrfs: avoid possible signal
interruption of btrfs_drop_snapshot() on relocation tree"), however it
missed a spot when we restart a trans handle because we need to end the
transaction.  The fix is the same, simply use btrfs_join_transaction()
instead of btrfs_start_transaction() when deleting reloc roots.

Fixes: f3e3d9cc35 ("btrfs: avoid possible signal interruption of btrfs_drop_snapshot() on relocation tree")
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-18 15:44:47 +01:00
Filipe Manana
518837e650 btrfs: send: fix invalid clone operations when cloning from the same file and root
When an incremental send finds an extent that is shared, it checks which
file extent items in the range refer to that extent, and for those it
emits clone operations, while for others it emits regular write operations
to avoid corruption at the destination (as described and fixed by commit
d906d49fc5 ("Btrfs: send, fix file corruption due to incorrect cloning
operations")).

However when the root we are cloning from is the send root, we are cloning
from the inode currently being processed and the source file range has
several extent items that partially point to the desired extent, with an
offset smaller than the offset in the file extent item for the range we
want to clone into, it can cause the algorithm to issue a clone operation
that starts at the current eof of the file being processed in the receiver
side, in which case the receiver will fail, with EINVAL, when attempting
to execute the clone operation.

Example reproducer:

  $ cat test-send-clone.sh
  #!/bin/bash

  DEV=/dev/sdi
  MNT=/mnt/sdi

  mkfs.btrfs -f $DEV >/dev/null
  mount $DEV $MNT

  # Create our test file with a single and large extent (1M) and with
  # different content for different file ranges that will be reflinked
  # later.
  xfs_io -f \
         -c "pwrite -S 0xab 0 128K" \
         -c "pwrite -S 0xcd 128K 128K" \
         -c "pwrite -S 0xef 256K 256K" \
         -c "pwrite -S 0x1a 512K 512K" \
         $MNT/foobar

  btrfs subvolume snapshot -r $MNT $MNT/snap1
  btrfs send -f /tmp/snap1.send $MNT/snap1

  # Now do a series of changes to our file such that we end up with
  # different parts of the extent reflinked into different file offsets
  # and we overwrite a large part of the extent too, so no file extent
  # items refer to that part that was overwritten. This used to confuse
  # the algorithm used by the kernel to figure out which file ranges to
  # clone, making it attempt to clone from a source range starting at
  # the current eof of the file, resulting in the receiver to fail since
  # it is an invalid clone operation.
  #
  xfs_io -c "reflink $MNT/foobar 64K 1M 960K" \
         -c "reflink $MNT/foobar 0K 512K 256K" \
         -c "reflink $MNT/foobar 512K 128K 256K" \
         -c "pwrite -S 0x73 384K 640K" \
         $MNT/foobar

  btrfs subvolume snapshot -r $MNT $MNT/snap2
  btrfs send -f /tmp/snap2.send -p $MNT/snap1 $MNT/snap2

  echo -e "\nFile digest in the original filesystem:"
  md5sum $MNT/snap2/foobar

  # Now unmount the filesystem, create a new one, mount it and try to
  # apply both send streams to recreate both snapshots.
  umount $DEV

  mkfs.btrfs -f $DEV >/dev/null
  mount $DEV $MNT

  btrfs receive -f /tmp/snap1.send $MNT
  btrfs receive -f /tmp/snap2.send $MNT

  # Must match what we got in the original filesystem of course.
  echo -e "\nFile digest in the new filesystem:"
  md5sum $MNT/snap2/foobar

  umount $MNT

When running the reproducer, the incremental send operation fails due to
an invalid clone operation:

  $ ./test-send-clone.sh
  wrote 131072/131072 bytes at offset 0
  128 KiB, 32 ops; 0.0015 sec (80.906 MiB/sec and 20711.9741 ops/sec)
  wrote 131072/131072 bytes at offset 131072
  128 KiB, 32 ops; 0.0013 sec (90.514 MiB/sec and 23171.6148 ops/sec)
  wrote 262144/262144 bytes at offset 262144
  256 KiB, 64 ops; 0.0025 sec (98.270 MiB/sec and 25157.2327 ops/sec)
  wrote 524288/524288 bytes at offset 524288
  512 KiB, 128 ops; 0.0052 sec (95.730 MiB/sec and 24506.9883 ops/sec)
  Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap1'
  At subvol /mnt/sdi/snap1
  linked 983040/983040 bytes at offset 1048576
  960 KiB, 1 ops; 0.0006 sec (1.419 GiB/sec and 1550.3876 ops/sec)
  linked 262144/262144 bytes at offset 524288
  256 KiB, 1 ops; 0.0020 sec (120.192 MiB/sec and 480.7692 ops/sec)
  linked 262144/262144 bytes at offset 131072
  256 KiB, 1 ops; 0.0018 sec (133.833 MiB/sec and 535.3319 ops/sec)
  wrote 655360/655360 bytes at offset 393216
  640 KiB, 160 ops; 0.0093 sec (66.781 MiB/sec and 17095.8436 ops/sec)
  Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap2'
  At subvol /mnt/sdi/snap2

  File digest in the original filesystem:
  9c13c61cb0b9f5abf45344375cb04dfa  /mnt/sdi/snap2/foobar
  At subvol snap1
  At snapshot snap2
  ERROR: failed to clone extents to foobar: Invalid argument

  File digest in the new filesystem:
  132f0396da8f48d2e667196bff882cfc  /mnt/sdi/snap2/foobar

The clone operation is invalid because its source range starts at the
current eof of the file in the receiver, causing the receiver to get
an EINVAL error from the clone operation when attempting it.

For the example above, what happens is the following:

1) When processing the extent at file offset 1M, the algorithm checks that
   the extent is shared and can be (fully or partially) found at file
   offset 0.

   At this point the file has a size (and eof) of 1M at the receiver;

2) It finds that our extent item at file offset 1M has a data offset of
   64K and, since the file extent item at file offset 0 has a data offset
   of 0, it issues a clone operation, from the same file and root, that
   has a source range offset of 64K, destination offset of 1M and a length
   of 64K, since the extent item at file offset 0 refers only to the first
   128K of the shared extent.

   After this clone operation, the file size (and eof) at the receiver is
   increased from 1M to 1088K (1M + 64K);

3) Now there's still 896K (960K - 64K) of data left to clone or write, so
   it checks for the next file extent item, which starts at file offset
   128K. This file extent item has a data offset of 0 and a length of
   256K, so a clone operation with a source range offset of 256K, a
   destination offset of 1088K (1M + 64K) and length of 128K is issued.

   After this operation the file size (and eof) at the receiver increases
   from 1088K to 1216K (1088K + 128K);

4) Now there's still 768K (896K - 128K) of data left to clone or write, so
   it checks for the next file extent item, located at file offset 384K.
   This file extent item points to a different extent, not the one we want
   to clone, with a length of 640K. So we issue a write operation into the
   file range 1216K (1088K + 128K, end of the last clone operation), with
   a length of 640K and with a data matching the one we can find for that
   range in send root.

   After this operation, the file size (and eof) at the receiver increases
   from 1216K to 1856K (1216K + 640K);

5) Now there's still 128K (768K - 640K) of data left to clone or write, so
   we look into the file extent item, which is for file offset 1M and it
   points to the extent we want to clone, with a data offset of 64K and a
   length of 960K.

   However this matches the file offset we started with, the start of the
   range to clone into. So we can't for sure find any file extent item
   from here onwards with the rest of the data we want to clone, yet we
   proceed and since the file extent item points to the shared extent,
   with a data offset of 64K, we issue a clone operation with a source
   range starting at file offset 1856K, which matches the file extent
   item's offset, 1M, plus the amount of data cloned and written so far,
   which is 64K (step 2) + 128K (step 3) + 640K (step 4). This clone
   operation is invalid since the source range offset matches the current
   eof of the file in the receiver. We should have stopped looking for
   extents to clone at this point and instead fallback to write, which
   would simply the contain the data in the file range from 1856K to
   1856K + 128K.

So fix this by stopping the loop that looks for file ranges to clone at
clone_range() when we reach the current eof of the file being processed,
if we are cloning from the same file and using the send root as the clone
root. This ensures any data not yet cloned will be sent to the receiver
through a write operation.

A test case for fstests will follow soon.

Reported-by: Massimo B. <massimo.b@gmx.net>
Link: https://lore.kernel.org/linux-btrfs/6ae34776e85912960a253a8327068a892998e685.camel@gmx.net/
Fixes: 11f2069c11 ("Btrfs: send, allow clone operations within the same file")
CC: stable@vger.kernel.org # 5.5+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-12 15:35:09 +01:00
David Sterba
14ff8e1970 btrfs: no need to run delayed refs after commit_fs_roots during commit
The inode number cache has been removed in this dev cycle, there's one
more leftover. We don't need to run the delayed refs again after
commit_fs_roots as stated in the comment, because btrfs_save_ino_cache
is no more since 5297199a8b ("btrfs: remove inode number cache
feature").

Nothing else between commit_fs_roots and btrfs_qgroup_account_extents
could create new delayed refs so the qgroup consistency should be safe.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-12 15:35:04 +01:00
Linus Torvalds
6e68b9961f for-5.11-rc3-tag
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Merge tag 'for-5.11-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fixes from David Sterba:
 "More material for stable trees.

   - tree-checker: check item end overflow

   - fix false warning during relocation regarding extent type

   - fix inode flushing logic, caused notable performance regression
     (since 5.10)

   - debugging fixups:
      - print correct offset for reloc tree key
      - pass reliable fs_info pointer to error reporting helper"

* tag 'for-5.11-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: shrink delalloc pages instead of full inodes
  btrfs: reloc: fix wrong file extent type check to avoid false ENOENT
  btrfs: tree-checker: check if chunk item end overflows
  btrfs: prevent NULL pointer dereference in extent_io_tree_panic
  btrfs: print the actual offset in btrfs_root_name
2021-01-11 14:18:56 -08:00
Josef Bacik
e076ab2a2c btrfs: shrink delalloc pages instead of full inodes
Commit 38d715f494 ("btrfs: use btrfs_start_delalloc_roots in
shrink_delalloc") cleaned up how we do delalloc shrinking by utilizing
some infrastructure we have in place to flush inodes that we use for
device replace and snapshot.  However this introduced a pretty serious
performance regression.  To reproduce the user untarred the source
tarball of Firefox (360MiB xz compressed/1.5GiB uncompressed), and would
see it take anywhere from 5 to 20 times as long to untar in 5.10
compared to 5.9. This was observed on fast devices (SSD and better) and
not on HDD.

The root cause is because before we would generally use the normal
writeback path to reclaim delalloc space, and for this we would provide
it with the number of pages we wanted to flush.  The referenced commit
changed this to flush that many inodes, which drastically increased the
amount of space we were flushing in certain cases, which severely
affected performance.

We cannot revert this patch unfortunately because of 3d45f221ce
("btrfs: fix deadlock when cloning inline extent and low on free
metadata space") which requires the ability to skip flushing inodes that
are being cloned in certain scenarios, which means we need to keep using
our flushing infrastructure or risk re-introducing the deadlock.

Instead to fix this problem we can go back to providing
btrfs_start_delalloc_roots with a number of pages to flush, and then set
up a writeback_control and utilize sync_inode() to handle the flushing
for us.  This gives us the same behavior we had prior to the fix, while
still allowing us to avoid the deadlock that was fixed by Filipe.  I
redid the users original test and got the following results on one of
our test machines (256GiB of ram, 56 cores, 2TiB Intel NVMe drive)

  5.9		0m54.258s
  5.10		1m26.212s
  5.10+patch	0m38.800s

5.10+patch is significantly faster than plain 5.9 because of my patch
series "Change data reservations to use the ticketing infra" which
contained the patch that introduced the regression, but generally
improved the overall ENOSPC flushing mechanisms.

Additional testing on consumer-grade SSD (8GiB ram, 8 CPU) confirm
the results:

  5.10.5            4m00s
  5.10.5+patch      1m08s
  5.11-rc2	    5m14s
  5.11-rc2+patch    1m30s

Reported-by: René Rebe <rene@exactcode.de>
Fixes: 38d715f494 ("btrfs: use btrfs_start_delalloc_roots in shrink_delalloc")
CC: stable@vger.kernel.org # 5.10
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Tested-by: David Sterba <dsterba@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add my test results ]
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-08 16:36:44 +01:00
Qu Wenruo
50e31ef486 btrfs: reloc: fix wrong file extent type check to avoid false ENOENT
[BUG]
There are several bug reports about recent kernel unable to relocate
certain data block groups.

Sometimes the error just goes away, but there is one reporter who can
reproduce it reliably.

The dmesg would look like:

  [438.260483] BTRFS info (device dm-10): balance: start -dvrange=34625344765952..34625344765953
  [438.269018] BTRFS info (device dm-10): relocating block group 34625344765952 flags data|raid1
  [450.439609] BTRFS info (device dm-10): found 167 extents, stage: move data extents
  [463.501781] BTRFS info (device dm-10): balance: ended with status: -2

[CAUSE]
The ENOENT error is returned from the following call chain:

  add_data_references()
  |- delete_v1_space_cache();
     |- if (!found)
	   return -ENOENT;

The variable @found is set to true if we find a data extent whose
disk bytenr matches parameter @data_bytes.

With extra debugging, the offending tree block looks like this:

  leaf bytenr = 42676709441536, data_bytenr = 34626327621632

                ctime 1567904822.739884119 (2019-09-08 03:07:02)
                mtime 0.0 (1970-01-01 01:00:00)
                otime 0.0 (1970-01-01 01:00:00)
        item 27 key (51933 EXTENT_DATA 0) itemoff 9854 itemsize 53
                generation 1517381 type 2 (prealloc)
                prealloc data disk byte 34626327621632 nr 262144 <<<
                prealloc data offset 0 nr 262144
        item 28 key (52262 ROOT_ITEM 0) itemoff 9415 itemsize 439
                generation 2618893 root_dirid 256 bytenr 42677048360960 level 3 refs 1
                lastsnap 2618893 byte_limit 0 bytes_used 5557338112 flags 0x0(none)
                uuid d0d4361f-d231-6d40-8901-fe506e4b2b53

Although item 27 has disk bytenr 34626327621632, which matches the
data_bytenr, its type is prealloc, not reg.
This makes the existing code skip that item, and return ENOENT.

[FIX]
The code is modified in commit 19b546d7a1 ("btrfs: relocation: Use
btrfs_find_all_leafs to locate data extent parent tree leaves"), before
that commit, we use something like

  "if (type == BTRFS_FILE_EXTENT_INLINE) continue;"

But in that offending commit, we use (type == BTRFS_FILE_EXTENT_REG),
ignoring BTRFS_FILE_EXTENT_PREALLOC.

Fix it by also checking BTRFS_FILE_EXTENT_PREALLOC.

Reported-by: Stéphane Lesimple <stephane_btrfs2@lesimple.fr>
Link: https://lore.kernel.org/linux-btrfs/505cabfa88575ed6dbe7cb922d8914fb@lesimple.fr
Fixes: 19b546d7a1 ("btrfs: relocation: Use btrfs_find_all_leafs to locate data extent parent tree leaves")
CC: stable@vger.kernel.org # 5.6+
Tested-By: Stéphane Lesimple <stephane_btrfs2@lesimple.fr>
Reviewed-by: Su Yue <l@damenly.su>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-07 17:25:05 +01:00
Su Yue
347fb0cfc9 btrfs: tree-checker: check if chunk item end overflows
While mounting a crafted image provided by user, kernel panics due to
the invalid chunk item whose end is less than start.

  [66.387422] loop: module loaded
  [66.389773] loop0: detected capacity change from 262144 to 0
  [66.427708] BTRFS: device fsid a62e00e8-e94e-4200-8217-12444de93c2e devid 1 transid 12 /dev/loop0 scanned by mount (613)
  [66.431061] BTRFS info (device loop0): disk space caching is enabled
  [66.431078] BTRFS info (device loop0): has skinny extents
  [66.437101] BTRFS error: insert state: end < start 29360127 37748736
  [66.437136] ------------[ cut here ]------------
  [66.437140] WARNING: CPU: 16 PID: 613 at fs/btrfs/extent_io.c:557 insert_state.cold+0x1a/0x46 [btrfs]
  [66.437369] CPU: 16 PID: 613 Comm: mount Tainted: G           O      5.11.0-rc1-custom #45
  [66.437374] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ArchLinux 1.14.0-1 04/01/2014
  [66.437378] RIP: 0010:insert_state.cold+0x1a/0x46 [btrfs]
  [66.437420] RSP: 0018:ffff93e5414c3908 EFLAGS: 00010286
  [66.437427] RAX: 0000000000000000 RBX: 0000000001bfffff RCX: 0000000000000000
  [66.437431] RDX: 0000000000000000 RSI: ffffffffb90d4660 RDI: 00000000ffffffff
  [66.437434] RBP: ffff93e5414c3938 R08: 0000000000000001 R09: 0000000000000001
  [66.437438] R10: ffff93e5414c3658 R11: 0000000000000000 R12: ffff8ec782d72aa0
  [66.437441] R13: ffff8ec78bc71628 R14: 0000000000000000 R15: 0000000002400000
  [66.437447] FS:  00007f01386a8580(0000) GS:ffff8ec809000000(0000) knlGS:0000000000000000
  [66.437451] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [66.437455] CR2: 00007f01382fa000 CR3: 0000000109a34000 CR4: 0000000000750ee0
  [66.437460] PKRU: 55555554
  [66.437464] Call Trace:
  [66.437475]  set_extent_bit+0x652/0x740 [btrfs]
  [66.437539]  set_extent_bits_nowait+0x1d/0x20 [btrfs]
  [66.437576]  add_extent_mapping+0x1e0/0x2f0 [btrfs]
  [66.437621]  read_one_chunk+0x33c/0x420 [btrfs]
  [66.437674]  btrfs_read_chunk_tree+0x6a4/0x870 [btrfs]
  [66.437708]  ? kvm_sched_clock_read+0x18/0x40
  [66.437739]  open_ctree+0xb32/0x1734 [btrfs]
  [66.437781]  ? bdi_register_va+0x1b/0x20
  [66.437788]  ? super_setup_bdi_name+0x79/0xd0
  [66.437810]  btrfs_mount_root.cold+0x12/0xeb [btrfs]
  [66.437854]  ? __kmalloc_track_caller+0x217/0x3b0
  [66.437873]  legacy_get_tree+0x34/0x60
  [66.437880]  vfs_get_tree+0x2d/0xc0
  [66.437888]  vfs_kern_mount.part.0+0x78/0xc0
  [66.437897]  vfs_kern_mount+0x13/0x20
  [66.437902]  btrfs_mount+0x11f/0x3c0 [btrfs]
  [66.437940]  ? kfree+0x5ff/0x670
  [66.437944]  ? __kmalloc_track_caller+0x217/0x3b0
  [66.437962]  legacy_get_tree+0x34/0x60
  [66.437974]  vfs_get_tree+0x2d/0xc0
  [66.437983]  path_mount+0x48c/0xd30
  [66.437998]  __x64_sys_mount+0x108/0x140
  [66.438011]  do_syscall_64+0x38/0x50
  [66.438018]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [66.438023] RIP: 0033:0x7f0138827f6e
  [66.438033] RSP: 002b:00007ffecd79edf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
  [66.438040] RAX: ffffffffffffffda RBX: 00007f013894c264 RCX: 00007f0138827f6e
  [66.438044] RDX: 00005593a4a41360 RSI: 00005593a4a33690 RDI: 00005593a4a3a6c0
  [66.438047] RBP: 00005593a4a33440 R08: 0000000000000000 R09: 0000000000000001
  [66.438050] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
  [66.438054] R13: 00005593a4a3a6c0 R14: 00005593a4a41360 R15: 00005593a4a33440
  [66.438078] irq event stamp: 18169
  [66.438082] hardirqs last  enabled at (18175): [<ffffffffb81154bf>] console_unlock+0x4ff/0x5f0
  [66.438088] hardirqs last disabled at (18180): [<ffffffffb8115427>] console_unlock+0x467/0x5f0
  [66.438092] softirqs last  enabled at (16910): [<ffffffffb8a00fe2>] asm_call_irq_on_stack+0x12/0x20
  [66.438097] softirqs last disabled at (16905): [<ffffffffb8a00fe2>] asm_call_irq_on_stack+0x12/0x20
  [66.438103] ---[ end trace e114b111db64298b ]---
  [66.438107] BTRFS error: found node 12582912 29360127 on insert of 37748736 29360127
  [66.438127] BTRFS critical: panic in extent_io_tree_panic:679: locking error: extent tree was modified by another thread while locked (errno=-17 Object already exists)
  [66.441069] ------------[ cut here ]------------
  [66.441072] kernel BUG at fs/btrfs/extent_io.c:679!
  [66.442064] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
  [66.443018] CPU: 16 PID: 613 Comm: mount Tainted: G        W  O      5.11.0-rc1-custom #45
  [66.444538] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ArchLinux 1.14.0-1 04/01/2014
  [66.446223] RIP: 0010:extent_io_tree_panic.isra.0+0x23/0x25 [btrfs]
  [66.450878] RSP: 0018:ffff93e5414c3948 EFLAGS: 00010246
  [66.451840] RAX: 0000000000000000 RBX: 0000000001bfffff RCX: 0000000000000000
  [66.453141] RDX: 0000000000000000 RSI: ffffffffb90d4660 RDI: 00000000ffffffff
  [66.454445] RBP: ffff93e5414c3948 R08: 0000000000000001 R09: 0000000000000001
  [66.455743] R10: ffff93e5414c3658 R11: 0000000000000000 R12: ffff8ec782d728c0
  [66.457055] R13: ffff8ec78bc71628 R14: ffff8ec782d72aa0 R15: 0000000002400000
  [66.458356] FS:  00007f01386a8580(0000) GS:ffff8ec809000000(0000) knlGS:0000000000000000
  [66.459841] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [66.460895] CR2: 00007f01382fa000 CR3: 0000000109a34000 CR4: 0000000000750ee0
  [66.462196] PKRU: 55555554
  [66.462692] Call Trace:
  [66.463139]  set_extent_bit.cold+0x30/0x98 [btrfs]
  [66.464049]  set_extent_bits_nowait+0x1d/0x20 [btrfs]
  [66.490466]  add_extent_mapping+0x1e0/0x2f0 [btrfs]
  [66.514097]  read_one_chunk+0x33c/0x420 [btrfs]
  [66.534976]  btrfs_read_chunk_tree+0x6a4/0x870 [btrfs]
  [66.555718]  ? kvm_sched_clock_read+0x18/0x40
  [66.575758]  open_ctree+0xb32/0x1734 [btrfs]
  [66.595272]  ? bdi_register_va+0x1b/0x20
  [66.614638]  ? super_setup_bdi_name+0x79/0xd0
  [66.633809]  btrfs_mount_root.cold+0x12/0xeb [btrfs]
  [66.652938]  ? __kmalloc_track_caller+0x217/0x3b0
  [66.671925]  legacy_get_tree+0x34/0x60
  [66.690300]  vfs_get_tree+0x2d/0xc0
  [66.708221]  vfs_kern_mount.part.0+0x78/0xc0
  [66.725808]  vfs_kern_mount+0x13/0x20
  [66.742730]  btrfs_mount+0x11f/0x3c0 [btrfs]
  [66.759350]  ? kfree+0x5ff/0x670
  [66.775441]  ? __kmalloc_track_caller+0x217/0x3b0
  [66.791750]  legacy_get_tree+0x34/0x60
  [66.807494]  vfs_get_tree+0x2d/0xc0
  [66.823349]  path_mount+0x48c/0xd30
  [66.838753]  __x64_sys_mount+0x108/0x140
  [66.854412]  do_syscall_64+0x38/0x50
  [66.869673]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [66.885093] RIP: 0033:0x7f0138827f6e
  [66.945613] RSP: 002b:00007ffecd79edf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
  [66.977214] RAX: ffffffffffffffda RBX: 00007f013894c264 RCX: 00007f0138827f6e
  [66.994266] RDX: 00005593a4a41360 RSI: 00005593a4a33690 RDI: 00005593a4a3a6c0
  [67.011544] RBP: 00005593a4a33440 R08: 0000000000000000 R09: 0000000000000001
  [67.028836] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
  [67.045812] R13: 00005593a4a3a6c0 R14: 00005593a4a41360 R15: 00005593a4a33440
  [67.216138] ---[ end trace e114b111db64298c ]---
  [67.237089] RIP: 0010:extent_io_tree_panic.isra.0+0x23/0x25 [btrfs]
  [67.325317] RSP: 0018:ffff93e5414c3948 EFLAGS: 00010246
  [67.347946] RAX: 0000000000000000 RBX: 0000000001bfffff RCX: 0000000000000000
  [67.371343] RDX: 0000000000000000 RSI: ffffffffb90d4660 RDI: 00000000ffffffff
  [67.394757] RBP: ffff93e5414c3948 R08: 0000000000000001 R09: 0000000000000001
  [67.418409] R10: ffff93e5414c3658 R11: 0000000000000000 R12: ffff8ec782d728c0
  [67.441906] R13: ffff8ec78bc71628 R14: ffff8ec782d72aa0 R15: 0000000002400000
  [67.465436] FS:  00007f01386a8580(0000) GS:ffff8ec809000000(0000) knlGS:0000000000000000
  [67.511660] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [67.535047] CR2: 00007f01382fa000 CR3: 0000000109a34000 CR4: 0000000000750ee0
  [67.558449] PKRU: 55555554
  [67.581146] note: mount[613] exited with preempt_count 2

The image has a chunk item which has a logical start 37748736 and length
18446744073701163008 (-8M). The calculated end 29360127 overflows.
EEXIST was caught by insert_state() because of the duplicate end and
extent_io_tree_panic() was called.

Add overflow check of chunk item end to tree checker so it can be
detected early at mount time.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=208929
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Su Yue <l@damenly.su>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-07 17:25:05 +01:00
Su Yue
29b665cc51 btrfs: prevent NULL pointer dereference in extent_io_tree_panic
Some extent io trees are initialized with NULL private member (e.g.
btrfs_device::alloc_state and btrfs_fs_info::excluded_extents).
Dereference of a NULL tree->private as inode pointer will cause panic.

Pass tree->fs_info as it's known to be valid in all cases.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=208929
Fixes: 05912a3c04 ("btrfs: drop extent_io_ops::tree_fs_info callback")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Su Yue <l@damenly.su>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-07 17:25:05 +01:00
Josef Bacik
71008734d2 btrfs: print the actual offset in btrfs_root_name
We're supposed to print the root_key.offset in btrfs_root_name in the
case of a reloc root, not the objectid.  Fix this helper to take the key
so we have access to the offset when we need it.

Fixes: 457f1864b5 ("btrfs: pretty print leaked root name")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-01-07 17:25:05 +01:00
Linus Torvalds
71c061d244 for-5.11-rc2-tag
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Merge tag 'for-5.11-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fixes from David Sterba:
 "A few more fixes that arrived before the end of the year:

   - a bunch of fixes related to transaction handle lifetime wrt various
     operations (umount, remount, qgroup scan, orphan cleanup)

   - async discard scheduling fixes

   - fix item size calculation when item keys collide for extend refs
     (hardlinks)

   - fix qgroup flushing from running transaction

   - fix send, wrong file path when there is an inode with a pending
     rmdir

   - fix deadlock when cloning inline extent and low on free metadata
     space"

* tag 'for-5.11-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: run delayed iputs when remounting RO to avoid leaking them
  btrfs: add assertion for empty list of transactions at late stage of umount
  btrfs: fix race between RO remount and the cleaner task
  btrfs: fix transaction leak and crash after cleaning up orphans on RO mount
  btrfs: fix transaction leak and crash after RO remount caused by qgroup rescan
  btrfs: merge critical sections of discard lock in workfn
  btrfs: fix racy access to discard_ctl data
  btrfs: fix async discard stall
  btrfs: tests: initialize test inodes location
  btrfs: send: fix wrong file path when there is an inode with a pending rmdir
  btrfs: qgroup: don't try to wait flushing if we're already holding a transaction
  btrfs: correctly calculate item size used when item key collision happens
  btrfs: fix deadlock when cloning inline extent and low on free metadata space
2021-01-06 11:19:08 -08:00
Filipe Manana
a8cc263eb5 btrfs: run delayed iputs when remounting RO to avoid leaking them
When remounting RO, after setting the superblock with the RO flag, the
cleaner task will start sleeping and do nothing, since the call to
btrfs_need_cleaner_sleep() keeps returning 'true'. However, when the
cleaner task goes to sleep, the list of delayed iputs may not be empty.

As long as we are in RO mode, the cleaner task will keep sleeping and
never run the delayed iputs. This means that if a filesystem unmount
is started, we get into close_ctree() with a non-empty list of delayed
iputs, and because the filesystem is in RO mode and is not in an error
state (or a transaction aborted), btrfs_error_commit_super() and
btrfs_commit_super(), which run the delayed iputs, are never called,
and later we fail the assertion that checks if the delayed iputs list
is empty:

  assertion failed: list_empty(&fs_info->delayed_iputs), in fs/btrfs/disk-io.c:4049
  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/ctree.h:3153!
  invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
  CPU: 1 PID: 3780621 Comm: umount Tainted: G             L    5.6.0-rc2-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
  RIP: 0010:assertfail.constprop.0+0x18/0x26 [btrfs]
  Code: 8b 7b 58 48 85 ff 74 (...)
  RSP: 0018:ffffb748c89bbdf8 EFLAGS: 00010246
  RAX: 0000000000000051 RBX: ffff9608f2584000 RCX: 0000000000000000
  RDX: 0000000000000000 RSI: ffffffff91998988 RDI: 00000000ffffffff
  RBP: ffff9608f25870d8 R08: 0000000000000000 R09: 0000000000000001
  R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffc0cbc500
  R13: ffffffff92411750 R14: 0000000000000000 R15: ffff9608f2aab250
  FS:  00007fcbfaa66c80(0000) GS:ffff960936c80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007fffc2c2dd38 CR3: 0000000235e54002 CR4: 00000000003606e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   close_ctree+0x1a2/0x2e6 [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x93/0xc0
   exit_to_usermode_loop+0xf9/0x100
   do_syscall_64+0x20d/0x260
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7fcbfaca6307
  Code: eb 0b 00 f7 d8 64 89 (...)
  RSP: 002b:00007fffc2c2ed68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 0000558203b559b0 RCX: 00007fcbfaca6307
  RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000558203b55bc0
  RBP: 0000000000000000 R08: 0000000000000001 R09: 00007fffc2c2dad0
  R10: 0000558203b55bf0 R11: 0000000000000246 R12: 0000558203b55bc0
  R13: 00007fcbfadcc204 R14: 0000558203b55aa8 R15: 0000000000000000
  Modules linked in: btrfs dm_flakey dm_log_writes (...)
  ---[ end trace d44d303790049ef6 ]---

So fix this by making the remount RO path run any remaining delayed iputs
after waiting for the cleaner to become inactive.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 15:00:08 +01:00
Filipe Manana
0a31daa4b6 btrfs: add assertion for empty list of transactions at late stage of umount
Add an assertion to close_ctree(), after destroying all the work queues,
to verify we do not have any transaction still open or committing at that
at that point. If we have any, it means something is seriously wrong and
that can cause memory leaks and use-after-free problems. This is motivated
by the previous patches that fixed bugs where we ended up leaking an open
transaction after unmounting the filesystem.

Tested-by: Fabian Vogt <fvogt@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 15:00:06 +01:00
Filipe Manana
a0a1db70df btrfs: fix race between RO remount and the cleaner task
When we are remounting a filesystem in RO mode we can race with the cleaner
task and result in leaking a transaction if the filesystem is unmounted
shortly after, before the transaction kthread had a chance to commit that
transaction. That also results in a crash during unmount, due to a
use-after-free, if hardware acceleration is not available for crc32c.

The following sequence of steps explains how the race happens.

1) The filesystem is mounted in RW mode and the cleaner task is running.
   This means that currently BTRFS_FS_CLEANER_RUNNING is set at
   fs_info->flags;

2) The cleaner task is currently running delayed iputs for example;

3) A filesystem RO remount operation starts;

4) The RO remount task calls btrfs_commit_super(), which commits any
   currently open transaction, and it finishes;

5) At this point the cleaner task is still running and it creates a new
   transaction by doing one of the following things:

   * When running the delayed iput() for an inode with a 0 link count,
     in which case at btrfs_evict_inode() we start a transaction through
     the call to evict_refill_and_join(), use it and then release its
     handle through btrfs_end_transaction();

   * When deleting a dead root through btrfs_clean_one_deleted_snapshot(),
     a transaction is started at btrfs_drop_snapshot() and then its handle
     is released through a call to btrfs_end_transaction_throttle();

   * When the remount task was still running, and before the remount task
     called btrfs_delete_unused_bgs(), the cleaner task also called
     btrfs_delete_unused_bgs() and it picked and removed one block group
     from the list of unused block groups. Before the cleaner task started
     a transaction, through btrfs_start_trans_remove_block_group() at
     btrfs_delete_unused_bgs(), the remount task had already called
     btrfs_commit_super();

6) So at this point the filesystem is in RO mode and we have an open
   transaction that was started by the cleaner task;

7) Shortly after a filesystem unmount operation starts. At close_ctree()
   we stop the transaction kthread before it had a chance to commit the
   transaction, since less than 30 seconds (the default commit interval)
   have elapsed since the last transaction was committed;

8) We end up calling iput() against the btree inode at close_ctree() while
   there is an open transaction, and since that transaction was used to
   update btrees by the cleaner, we have dirty pages in the btree inode
   due to COW operations on metadata extents, and therefore writeback is
   triggered for the btree inode.

   So btree_write_cache_pages() is invoked to flush those dirty pages
   during the final iput() on the btree inode. This results in creating a
   bio and submitting it, which makes us end up at
   btrfs_submit_metadata_bio();

9) At btrfs_submit_metadata_bio() we end up at the if-then-else branch
   that calls btrfs_wq_submit_bio(), because check_async_write() returned
   a value of 1. This value of 1 is because we did not have hardware
   acceleration available for crc32c, so BTRFS_FS_CSUM_IMPL_FAST was not
   set in fs_info->flags;

10) Then at btrfs_wq_submit_bio() we call btrfs_queue_work() against the
    workqueue at fs_info->workers, which was already freed before by the
    call to btrfs_stop_all_workers() at close_ctree(). This results in an
    invalid memory access due to a use-after-free, leading to a crash.

When this happens, before the crash there are several warnings triggered,
since we have reserved metadata space in a block group, the delayed refs
reservation, etc:

  ------------[ cut here ]------------
  WARNING: CPU: 4 PID: 1729896 at fs/btrfs/block-group.c:125 btrfs_put_block_group+0x63/0xa0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 4 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_put_block_group+0x63/0xa0 [btrfs]
  Code: f0 01 00 00 48 39 c2 75 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 0000000000000001 RBX: ffff947ed73e4000 RCX: ffff947ebc8b29c8
  RDX: 0000000000000001 RSI: ffffffffc0b150a0 RDI: ffff947ebc8b2800
  RBP: ffff947ebc8b2800 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e4160 R14: ffff947ebc8b2988 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f37e2893320 CR3: 0000000138f68001 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x17f/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 48 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c6 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-rsv.c:459 btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 2 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Code: 48 83 bb b0 03 00 00 00 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 000000000033c000 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffffffffc0b0d8c1 RDI: 00000000ffffffff
  RBP: ffff947ebc8b7000 R08: 0000000000000001 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481aca00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000561a79f76e20 CR3: 0000000138f68006 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x24c/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c7 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-group.c:3377 btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 5 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Code: ad de 49 be 22 01 00 (...)
  RSP: 0018:ffffb270826bbde8 EFLAGS: 00010206
  RAX: ffff947ebeae1d08 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff947e9d823ae8 RDI: 0000000000000246
  RBP: ffff947ebeae1d08 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ebeae1c00
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad200000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1475d98ea8 CR3: 0000000138f68005 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c8 ]---
  BTRFS info (device sdc): space_info 4 has 268238848 free, is not full
  BTRFS info (device sdc): space_info total=268435456, used=114688, pinned=0, reserved=16384, may_use=0, readonly=65536
  BTRFS info (device sdc): global_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): trans_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): chunk_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_refs_rsv: size 524288 reserved 0

And the crash, which only happens when we do not have crc32c hardware
acceleration, produces the following trace immediately after those
warnings:

  stack segment: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
  CPU: 2 PID: 1749129 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_queue_work+0x36/0x190 [btrfs]
  Code: 54 55 53 48 89 f3 (...)
  RSP: 0018:ffffb27082443ae8 EFLAGS: 00010282
  RAX: 0000000000000004 RBX: ffff94810ee9ad90 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff94810ee9ad90 RDI: ffff947ed8ee75a0
  RBP: a56b6b6b6b6b6b6b R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000007 R11: 0000000000000001 R12: ffff947fa9b435a8
  R13: ffff94810ee9ad90 R14: 0000000000000000 R15: ffff947e93dc0000
  FS:  00007f3cfe974840(0000) GS:ffff9481ac600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1b42995a70 CR3: 0000000127638003 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_wq_submit_bio+0xb3/0xd0 [btrfs]
   btrfs_submit_metadata_bio+0x44/0xc0 [btrfs]
   submit_one_bio+0x61/0x70 [btrfs]
   btree_write_cache_pages+0x414/0x450 [btrfs]
   ? kobject_put+0x9a/0x1d0
   ? trace_hardirqs_on+0x1b/0xf0
   ? _raw_spin_unlock_irqrestore+0x3c/0x60
   ? free_debug_processing+0x1e1/0x2b0
   do_writepages+0x43/0xe0
   ? lock_acquired+0x199/0x490
   __writeback_single_inode+0x59/0x650
   writeback_single_inode+0xaf/0x120
   write_inode_now+0x94/0xd0
   iput+0x187/0x2b0
   close_ctree+0x2c6/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f3cfebabee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffc9c9a05f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f3cfecd1264 RCX: 00007f3cfebabee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 0000562b6b478000
  RBP: 0000562b6b473a30 R08: 0000000000000000 R09: 00007f3cfec6cbe0
  R10: 0000562b6b479fe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 0000562b6b478000 R14: 0000562b6b473b40 R15: 0000562b6b473c60
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  ---[ end trace dd74718fef1ed5cc ]---

Finally when we remove the btrfs module (rmmod btrfs), there are several
warnings about objects that were allocated from our slabs but were never
freed, consequence of the transaction that was never committed and got
leaked:

  =============================================================================
  BUG btrfs_delayed_ref_head (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_ref_head on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000094c2ae56 objects=24 used=2 fp=0x000000002bfa2521 flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x0000000050cbdd61 @offset=12104
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1894 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
        btrfs_free_tree_block+0x128/0x360 [btrfs]
        __btrfs_cow_block+0x489/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=4292 cpu=2 pid=1729526
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        sync_filesystem+0x74/0x90
        generic_shutdown_super+0x22/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x0000000086e9b0ff @offset=12776
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1900 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
        btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=3141 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        btrfs_write_dirty_block_groups+0x17d/0x3d0 [btrfs]
        commit_cowonly_roots+0x248/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_ref_head: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 0b (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_tree_ref (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_tree_ref on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000011f78dc0 objects=37 used=2 fp=0x0000000032d55d91 flags=0x17fffc000010200
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000001a340018 @offset=4408
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1917 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
        btrfs_free_tree_block+0x128/0x360 [btrfs]
        __btrfs_cow_block+0x489/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=4167 cpu=4 pid=1729795
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        btrfs_commit_transaction+0x60/0xc40 [btrfs]
        create_subvol+0x56a/0x990 [btrfs]
        btrfs_mksubvol+0x3fb/0x4a0 [btrfs]
        __btrfs_ioctl_snap_create+0x119/0x1a0 [btrfs]
        btrfs_ioctl_snap_create+0x58/0x80 [btrfs]
        btrfs_ioctl+0x1a92/0x36f0 [btrfs]
        __x64_sys_ioctl+0x83/0xb0
        do_syscall_64+0x33/0x80
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x000000002b46292a @offset=13648
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1923 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
        btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=3164 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_tree_ref: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_extent_op (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_extent_op on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------
  INFO: Slab 0x00000000f145ce2f objects=22 used=1 fp=0x00000000af0f92cf flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? __mutex_unlock_slowpath+0x45/0x2a0
   kmem_cache_destroy+0x55/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000004cf95ea8 @offset=6264
  INFO: Allocated in btrfs_alloc_tree_block+0x1e0/0x360 [btrfs] age=1931 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_alloc_tree_block+0x1e0/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs] age=3173 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_extent_op: Slab cache still has objects
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  BTRFS: state leak: start 30408704 end 30425087 state 1 in tree 1 refs 1

So fix this by making the remount path to wait for the cleaner task before
calling btrfs_commit_super(). The remount path now waits for the bit
BTRFS_FS_CLEANER_RUNNING to be cleared from fs_info->flags before calling
btrfs_commit_super() and this ensures the cleaner can not start a
transaction after that, because it sleeps when the filesystem is in RO
mode and we have already flagged the filesystem as RO before waiting for
BTRFS_FS_CLEANER_RUNNING to be cleared.

This also introduces a new flag BTRFS_FS_STATE_RO to be used for
fs_info->fs_state when the filesystem is in RO mode. This is because we
were doing the RO check using the flags of the superblock and setting the
RO mode simply by ORing into the superblock's flags - those operations are
not atomic and could result in the cleaner not seeing the update from the
remount task after it clears BTRFS_FS_CLEANER_RUNNING.

Tested-by: Fabian Vogt <fvogt@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 15:00:02 +01:00
Filipe Manana
638331fa56 btrfs: fix transaction leak and crash after cleaning up orphans on RO mount
When we delete a root (subvolume or snapshot), at the very end of the
operation, we attempt to remove the root's orphan item from the root tree,
at btrfs_drop_snapshot(), by calling btrfs_del_orphan_item(). We ignore any
error from btrfs_del_orphan_item() since it is not a serious problem and
the next time the filesystem is mounted we remove such stray orphan items
at btrfs_find_orphan_roots().

However if the filesystem is mounted RO and we have stray orphan items for
any previously deleted root, we can end up leaking a transaction and other
data structures when unmounting the filesystem, as well as crashing if we
do not have hardware acceleration for crc32c available.

The steps that lead to the transaction leak are the following:

1) The filesystem is mounted in RW mode;

2) A subvolume is deleted;

3) When the cleaner kthread runs btrfs_drop_snapshot() to delete the root,
   it gets a failure at btrfs_del_orphan_item(), which is ignored, due to
   an ENOMEM when allocating a path for example. So the orphan item for
   the root remains in the root tree;

4) The filesystem is unmounted;

5) The filesystem is mounted RO (-o ro). During the mount path we call
   btrfs_find_orphan_roots(), which iterates the root tree searching for
   orphan items. It finds the orphan item for our deleted root, and since
   it can not find the root, it starts a transaction to delete the orphan
   item (by calling btrfs_del_orphan_item());

6) The RO mount completes;

7) Before the transaction kthread commits the transaction created for
   deleting the orphan item (i.e. less than 30 seconds elapsed since the
   mount, the default commit interval), a filesystem unmount operation is
   started;

8) At close_ctree(), we stop the transaction kthread, but we still have a
   transaction open with at least one dirty extent buffer, a leaf for the
   tree root which was COWed when deleting the orphan item;

9) We then proceed to destroy the work queues, free the roots and block
   groups, etc. After that we drop the last reference on the btree inode by
   calling iput() on it. Since there are dirty pages for the btree inode,
   corresponding to the COWed extent buffer, btree_write_cache_pages() is
   invoked to flush those dirty pages. This results in creating a bio and
   submitting it, which makes us end up at btrfs_submit_metadata_bio();

10) At btrfs_submit_metadata_bio() we end up at the if-then-else branch
    that calls btrfs_wq_submit_bio(), because check_async_write() returned
    a value of 1. This value of 1 is because we did not have hardware
    acceleration available for crc32c, so BTRFS_FS_CSUM_IMPL_FAST was not
    set in fs_info->flags;

11) Then at btrfs_wq_submit_bio() we call btrfs_queue_work() against the
    workqueue at fs_info->workers, which was already freed before by the
    call to btrfs_stop_all_workers() at close_ctree(). This results in an
    invalid memory access due to a use-after-free, leading to a crash.

When this happens, before the crash there are several warnings triggered,
since we have reserved metadata space in a block group, the delayed refs
reservation, etc:

 ------------[ cut here ]------------
 WARNING: CPU: 4 PID: 1729896 at fs/btrfs/block-group.c:125 btrfs_put_block_group+0x63/0xa0 [btrfs]
 Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
 CPU: 4 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:btrfs_put_block_group+0x63/0xa0 [btrfs]
 Code: f0 01 00 00 48 39 c2 75 (...)
 RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
 RAX: 0000000000000001 RBX: ffff947ed73e4000 RCX: ffff947ebc8b29c8
 RDX: 0000000000000001 RSI: ffffffffc0b150a0 RDI: ffff947ebc8b2800
 RBP: ffff947ebc8b2800 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
 R13: ffff947ed73e4160 R14: ffff947ebc8b2988 R15: dead000000000100
 FS:  00007f15edfea840(0000) GS:ffff9481ad600000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f37e2893320 CR3: 0000000138f68001 CR4: 00000000003706e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  btrfs_free_block_groups+0x17f/0x2f0 [btrfs]
  close_ctree+0x2ba/0x2fa [btrfs]
  generic_shutdown_super+0x6c/0x100
  kill_anon_super+0x14/0x30
  btrfs_kill_super+0x12/0x20 [btrfs]
  deactivate_locked_super+0x31/0x70
  cleanup_mnt+0x100/0x160
  task_work_run+0x68/0xb0
  exit_to_user_mode_prepare+0x1bb/0x1c0
  syscall_exit_to_user_mode+0x4b/0x260
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f15ee221ee7
 Code: ff 0b 00 f7 d8 64 89 01 48 (...)
 RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
 RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
 RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
 RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
 R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
 R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
 irq event stamp: 0
 hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
 softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
 softirqs last disabled at (0): [<0000000000000000>] 0x0
 ---[ end trace dd74718fef1ed5c6 ]---
 ------------[ cut here ]------------
 WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-rsv.c:459 btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
 Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
 CPU: 2 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
 Code: 48 83 bb b0 03 00 00 00 (...)
 RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
 RAX: 000000000033c000 RBX: ffff947ed73e4000 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: ffffffffc0b0d8c1 RDI: 00000000ffffffff
 RBP: ffff947ebc8b7000 R08: 0000000000000001 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
 R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
 FS:  00007f15edfea840(0000) GS:ffff9481aca00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000561a79f76e20 CR3: 0000000138f68006 CR4: 00000000003706e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  btrfs_free_block_groups+0x24c/0x2f0 [btrfs]
  close_ctree+0x2ba/0x2fa [btrfs]
  generic_shutdown_super+0x6c/0x100
  kill_anon_super+0x14/0x30
  btrfs_kill_super+0x12/0x20 [btrfs]
  deactivate_locked_super+0x31/0x70
  cleanup_mnt+0x100/0x160
  task_work_run+0x68/0xb0
  exit_to_user_mode_prepare+0x1bb/0x1c0
  syscall_exit_to_user_mode+0x4b/0x260
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f15ee221ee7
 Code: ff 0b 00 f7 d8 64 89 01 (...)
 RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
 RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
 RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
 RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
 R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
 R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
 irq event stamp: 0
 hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
 softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
 softirqs last disabled at (0): [<0000000000000000>] 0x0
 ---[ end trace dd74718fef1ed5c7 ]---
 ------------[ cut here ]------------
 WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-group.c:3377 btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
 Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
 CPU: 5 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
 Code: ad de 49 be 22 01 00 (...)
 RSP: 0018:ffffb270826bbde8 EFLAGS: 00010206
 RAX: ffff947ebeae1d08 RBX: ffff947ed73e4000 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: ffff947e9d823ae8 RDI: 0000000000000246
 RBP: ffff947ebeae1d08 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ebeae1c00
 R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
 FS:  00007f15edfea840(0000) GS:ffff9481ad200000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f1475d98ea8 CR3: 0000000138f68005 CR4: 00000000003706e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  close_ctree+0x2ba/0x2fa [btrfs]
  generic_shutdown_super+0x6c/0x100
  kill_anon_super+0x14/0x30
  btrfs_kill_super+0x12/0x20 [btrfs]
  deactivate_locked_super+0x31/0x70
  cleanup_mnt+0x100/0x160
  task_work_run+0x68/0xb0
  exit_to_user_mode_prepare+0x1bb/0x1c0
  syscall_exit_to_user_mode+0x4b/0x260
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f15ee221ee7
 Code: ff 0b 00 f7 d8 64 89 (...)
 RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
 RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
 RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
 RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
 R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
 R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
 irq event stamp: 0
 hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
 softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
 softirqs last disabled at (0): [<0000000000000000>] 0x0
 ---[ end trace dd74718fef1ed5c8 ]---
 BTRFS info (device sdc): space_info 4 has 268238848 free, is not full
 BTRFS info (device sdc): space_info total=268435456, used=114688, pinned=0, reserved=16384, may_use=0, readonly=65536
 BTRFS info (device sdc): global_block_rsv: size 0 reserved 0
 BTRFS info (device sdc): trans_block_rsv: size 0 reserved 0
 BTRFS info (device sdc): chunk_block_rsv: size 0 reserved 0
 BTRFS info (device sdc): delayed_block_rsv: size 0 reserved 0
 BTRFS info (device sdc): delayed_refs_rsv: size 524288 reserved 0

And the crash, which only happens when we do not have crc32c hardware
acceleration, produces the following trace immediately after those
warnings:

 stack segment: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
 CPU: 2 PID: 1749129 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:btrfs_queue_work+0x36/0x190 [btrfs]
 Code: 54 55 53 48 89 f3 (...)
 RSP: 0018:ffffb27082443ae8 EFLAGS: 00010282
 RAX: 0000000000000004 RBX: ffff94810ee9ad90 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: ffff94810ee9ad90 RDI: ffff947ed8ee75a0
 RBP: a56b6b6b6b6b6b6b R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000007 R11: 0000000000000001 R12: ffff947fa9b435a8
 R13: ffff94810ee9ad90 R14: 0000000000000000 R15: ffff947e93dc0000
 FS:  00007f3cfe974840(0000) GS:ffff9481ac600000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f1b42995a70 CR3: 0000000127638003 CR4: 00000000003706e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  btrfs_wq_submit_bio+0xb3/0xd0 [btrfs]
  btrfs_submit_metadata_bio+0x44/0xc0 [btrfs]
  submit_one_bio+0x61/0x70 [btrfs]
  btree_write_cache_pages+0x414/0x450 [btrfs]
  ? kobject_put+0x9a/0x1d0
  ? trace_hardirqs_on+0x1b/0xf0
  ? _raw_spin_unlock_irqrestore+0x3c/0x60
  ? free_debug_processing+0x1e1/0x2b0
  do_writepages+0x43/0xe0
  ? lock_acquired+0x199/0x490
  __writeback_single_inode+0x59/0x650
  writeback_single_inode+0xaf/0x120
  write_inode_now+0x94/0xd0
  iput+0x187/0x2b0
  close_ctree+0x2c6/0x2fa [btrfs]
  generic_shutdown_super+0x6c/0x100
  kill_anon_super+0x14/0x30
  btrfs_kill_super+0x12/0x20 [btrfs]
  deactivate_locked_super+0x31/0x70
  cleanup_mnt+0x100/0x160
  task_work_run+0x68/0xb0
  exit_to_user_mode_prepare+0x1bb/0x1c0
  syscall_exit_to_user_mode+0x4b/0x260
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f3cfebabee7
 Code: ff 0b 00 f7 d8 64 89 01 (...)
 RSP: 002b:00007ffc9c9a05f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
 RAX: 0000000000000000 RBX: 00007f3cfecd1264 RCX: 00007f3cfebabee7
 RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 0000562b6b478000
 RBP: 0000562b6b473a30 R08: 0000000000000000 R09: 00007f3cfec6cbe0
 R10: 0000562b6b479fe0 R11: 0000000000000246 R12: 0000000000000000
 R13: 0000562b6b478000 R14: 0000562b6b473b40 R15: 0000562b6b473c60
 Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
 ---[ end trace dd74718fef1ed5cc ]---

Finally when we remove the btrfs module (rmmod btrfs), there are several
warnings about objects that were allocated from our slabs but were never
freed, consequence of the transaction that was never committed and got
leaked:
 =============================================================================
 BUG btrfs_delayed_ref_head (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_ref_head on __kmem_cache_shutdown()
 -----------------------------------------------------------------------------

 INFO: Slab 0x0000000094c2ae56 objects=24 used=2 fp=0x000000002bfa2521 flags=0x17fffc000010200
 CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack+0x8d/0xb5
  slab_err+0xb7/0xdc
  ? lock_acquired+0x199/0x490
  __kmem_cache_shutdown+0x1ac/0x3c0
  ? lock_release+0x20e/0x4c0
  kmem_cache_destroy+0x55/0x120
  btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
  exit_btrfs_fs+0xa/0x59 [btrfs]
  __x64_sys_delete_module+0x194/0x260
  ? fpregs_assert_state_consistent+0x1e/0x40
  ? exit_to_user_mode_prepare+0x55/0x1c0
  ? trace_hardirqs_on+0x1b/0xf0
  do_syscall_64+0x33/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f693e305897
 Code: 73 01 c3 48 8b 0d f9 f5 (...)
 RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
 RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
 RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
 R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
 R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
 INFO: Object 0x0000000050cbdd61 @offset=12104
 INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1894 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
        btrfs_free_tree_block+0x128/0x360 [btrfs]
        __btrfs_cow_block+0x489/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
 INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=4292 cpu=2 pid=1729526
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        sync_filesystem+0x74/0x90
        generic_shutdown_super+0x22/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
 INFO: Object 0x0000000086e9b0ff @offset=12776
 INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1900 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
        btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
 INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=3141 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        btrfs_write_dirty_block_groups+0x17d/0x3d0 [btrfs]
        commit_cowonly_roots+0x248/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
 kmem_cache_destroy btrfs_delayed_ref_head: Slab cache still has objects
 CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack+0x8d/0xb5
  kmem_cache_destroy+0x119/0x120
  btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
  exit_btrfs_fs+0xa/0x59 [btrfs]
  __x64_sys_delete_module+0x194/0x260
  ? fpregs_assert_state_consistent+0x1e/0x40
  ? exit_to_user_mode_prepare+0x55/0x1c0
  ? trace_hardirqs_on+0x1b/0xf0
  do_syscall_64+0x33/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f693e305897
 Code: 73 01 c3 48 8b 0d f9 f5 0b (...)
 RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
 RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
 RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
 R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
 R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
 =============================================================================
 BUG btrfs_delayed_tree_ref (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_tree_ref on __kmem_cache_shutdown()
 -----------------------------------------------------------------------------

 INFO: Slab 0x0000000011f78dc0 objects=37 used=2 fp=0x0000000032d55d91 flags=0x17fffc000010200
 CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack+0x8d/0xb5
  slab_err+0xb7/0xdc
  ? lock_acquired+0x199/0x490
  __kmem_cache_shutdown+0x1ac/0x3c0
  ? lock_release+0x20e/0x4c0
  kmem_cache_destroy+0x55/0x120
  btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
  exit_btrfs_fs+0xa/0x59 [btrfs]
  __x64_sys_delete_module+0x194/0x260
  ? fpregs_assert_state_consistent+0x1e/0x40
  ? exit_to_user_mode_prepare+0x55/0x1c0
  ? trace_hardirqs_on+0x1b/0xf0
  do_syscall_64+0x33/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f693e305897
 Code: 73 01 c3 48 8b 0d f9 f5 (...)
 RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
 RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
 RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
 R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
 R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
 INFO: Object 0x000000001a340018 @offset=4408
 INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1917 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
        btrfs_free_tree_block+0x128/0x360 [btrfs]
        __btrfs_cow_block+0x489/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
 INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=4167 cpu=4 pid=1729795
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        btrfs_commit_transaction+0x60/0xc40 [btrfs]
        create_subvol+0x56a/0x990 [btrfs]
        btrfs_mksubvol+0x3fb/0x4a0 [btrfs]
        __btrfs_ioctl_snap_create+0x119/0x1a0 [btrfs]
        btrfs_ioctl_snap_create+0x58/0x80 [btrfs]
        btrfs_ioctl+0x1a92/0x36f0 [btrfs]
        __x64_sys_ioctl+0x83/0xb0
        do_syscall_64+0x33/0x80
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
 INFO: Object 0x000000002b46292a @offset=13648
 INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1923 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
        btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
 INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=3164 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
 kmem_cache_destroy btrfs_delayed_tree_ref: Slab cache still has objects
 CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack+0x8d/0xb5
  kmem_cache_destroy+0x119/0x120
  btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
  exit_btrfs_fs+0xa/0x59 [btrfs]
  __x64_sys_delete_module+0x194/0x260
  ? fpregs_assert_state_consistent+0x1e/0x40
  ? exit_to_user_mode_prepare+0x55/0x1c0
  ? trace_hardirqs_on+0x1b/0xf0
  do_syscall_64+0x33/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f693e305897
 Code: 73 01 c3 48 8b 0d f9 f5 (...)
 RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
 RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
 RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
 R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
 R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
 =============================================================================
 BUG btrfs_delayed_extent_op (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_extent_op on __kmem_cache_shutdown()
 -----------------------------------------------------------------------------

 INFO: Slab 0x00000000f145ce2f objects=22 used=1 fp=0x00000000af0f92cf flags=0x17fffc000010200
 CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack+0x8d/0xb5
  slab_err+0xb7/0xdc
  ? lock_acquired+0x199/0x490
  __kmem_cache_shutdown+0x1ac/0x3c0
  ? __mutex_unlock_slowpath+0x45/0x2a0
  kmem_cache_destroy+0x55/0x120
  exit_btrfs_fs+0xa/0x59 [btrfs]
  __x64_sys_delete_module+0x194/0x260
  ? fpregs_assert_state_consistent+0x1e/0x40
  ? exit_to_user_mode_prepare+0x55/0x1c0
  ? trace_hardirqs_on+0x1b/0xf0
  do_syscall_64+0x33/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f693e305897
 Code: 73 01 c3 48 8b 0d f9 f5 (...)
 RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
 RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
 RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
 R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
 R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
 INFO: Object 0x000000004cf95ea8 @offset=6264
 INFO: Allocated in btrfs_alloc_tree_block+0x1e0/0x360 [btrfs] age=1931 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_alloc_tree_block+0x1e0/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
 INFO: Freed in __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs] age=3173 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
 kmem_cache_destroy btrfs_delayed_extent_op: Slab cache still has objects
 CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack+0x8d/0xb5
  kmem_cache_destroy+0x119/0x120
  exit_btrfs_fs+0xa/0x59 [btrfs]
  __x64_sys_delete_module+0x194/0x260
  ? fpregs_assert_state_consistent+0x1e/0x40
  ? exit_to_user_mode_prepare+0x55/0x1c0
  ? trace_hardirqs_on+0x1b/0xf0
  do_syscall_64+0x33/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f693e305897
 Code: 73 01 c3 48 8b 0d f9 (...)
 RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
 RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
 RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
 R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
 R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
 BTRFS: state leak: start 30408704 end 30425087 state 1 in tree 1 refs 1

So fix this by calling btrfs_find_orphan_roots() in the mount path only if
we are mounting the filesystem in RW mode. It's pointless to have it called
for RO mounts anyway, since despite adding any deleted roots to the list of
dead roots, we will never have the roots deleted until the filesystem is
remounted in RW mode, as the cleaner kthread does nothing when we are
mounted in RO - btrfs_need_cleaner_sleep() always returns true and the
cleaner spends all time sleeping, never cleaning dead roots.

This is accomplished by moving the call to btrfs_find_orphan_roots() from
open_ctree() to btrfs_start_pre_rw_mount(), which also guarantees that
if later the filesystem is remounted RW, we populate the list of dead
roots and have the cleaner task delete the dead roots.

Tested-by: Fabian Vogt <fvogt@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:59:59 +01:00
Filipe Manana
cb13eea3b4 btrfs: fix transaction leak and crash after RO remount caused by qgroup rescan
If we remount a filesystem in RO mode while the qgroup rescan worker is
running, we can end up having it still running after the remount is done,
and at unmount time we may end up with an open transaction that ends up
never getting committed. If that happens we end up with several memory
leaks and can crash when hardware acceleration is unavailable for crc32c.
Possibly it can lead to other nasty surprises too, due to use-after-free
issues.

The following steps explain how the problem happens.

1) We have a filesystem mounted in RW mode and the qgroup rescan worker is
   running;

2) We remount the filesystem in RO mode, and never stop/pause the rescan
   worker, so after the remount the rescan worker is still running. The
   important detail here is that the rescan task is still running after
   the remount operation committed any ongoing transaction through its
   call to btrfs_commit_super();

3) The rescan is still running, and after the remount completed, the
   rescan worker started a transaction, after it finished iterating all
   leaves of the extent tree, to update the qgroup status item in the
   quotas tree. It does not commit the transaction, it only releases its
   handle on the transaction;

4) A filesystem unmount operation starts shortly after;

5) The unmount task, at close_ctree(), stops the transaction kthread,
   which had not had a chance to commit the open transaction since it was
   sleeping and the commit interval (default of 30 seconds) has not yet
   elapsed since the last time it committed a transaction;

6) So after stopping the transaction kthread we still have the transaction
   used to update the qgroup status item open. At close_ctree(), when the
   filesystem is in RO mode and no transaction abort happened (or the
   filesystem is in error mode), we do not expect to have any transaction
   open, so we do not call btrfs_commit_super();

7) We then proceed to destroy the work queues, free the roots and block
   groups, etc. After that we drop the last reference on the btree inode
   by calling iput() on it. Since there are dirty pages for the btree
   inode, corresponding to the COWed extent buffer for the quotas btree,
   btree_write_cache_pages() is invoked to flush those dirty pages. This
   results in creating a bio and submitting it, which makes us end up at
   btrfs_submit_metadata_bio();

8) At btrfs_submit_metadata_bio() we end up at the if-then-else branch
   that calls btrfs_wq_submit_bio(), because check_async_write() returned
   a value of 1. This value of 1 is because we did not have hardware
   acceleration available for crc32c, so BTRFS_FS_CSUM_IMPL_FAST was not
   set in fs_info->flags;

9) Then at btrfs_wq_submit_bio() we call btrfs_queue_work() against the
   workqueue at fs_info->workers, which was already freed before by the
   call to btrfs_stop_all_workers() at close_ctree(). This results in an
   invalid memory access due to a use-after-free, leading to a crash.

When this happens, before the crash there are several warnings triggered,
since we have reserved metadata space in a block group, the delayed refs
reservation, etc:

  ------------[ cut here ]------------
  WARNING: CPU: 4 PID: 1729896 at fs/btrfs/block-group.c:125 btrfs_put_block_group+0x63/0xa0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 4 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_put_block_group+0x63/0xa0 [btrfs]
  Code: f0 01 00 00 48 39 c2 75 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 0000000000000001 RBX: ffff947ed73e4000 RCX: ffff947ebc8b29c8
  RDX: 0000000000000001 RSI: ffffffffc0b150a0 RDI: ffff947ebc8b2800
  RBP: ffff947ebc8b2800 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e4160 R14: ffff947ebc8b2988 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f37e2893320 CR3: 0000000138f68001 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x17f/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 48 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c6 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-rsv.c:459 btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 2 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Code: 48 83 bb b0 03 00 00 00 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 000000000033c000 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffffffffc0b0d8c1 RDI: 00000000ffffffff
  RBP: ffff947ebc8b7000 R08: 0000000000000001 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481aca00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000561a79f76e20 CR3: 0000000138f68006 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x24c/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c7 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-group.c:3377 btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 5 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Code: ad de 49 be 22 01 00 (...)
  RSP: 0018:ffffb270826bbde8 EFLAGS: 00010206
  RAX: ffff947ebeae1d08 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff947e9d823ae8 RDI: 0000000000000246
  RBP: ffff947ebeae1d08 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ebeae1c00
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad200000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1475d98ea8 CR3: 0000000138f68005 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c8 ]---
  BTRFS info (device sdc): space_info 4 has 268238848 free, is not full
  BTRFS info (device sdc): space_info total=268435456, used=114688, pinned=0, reserved=16384, may_use=0, readonly=65536
  BTRFS info (device sdc): global_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): trans_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): chunk_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_refs_rsv: size 524288 reserved 0

And the crash, which only happens when we do not have crc32c hardware
acceleration, produces the following trace immediately after those
warnings:

  stack segment: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
  CPU: 2 PID: 1749129 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_queue_work+0x36/0x190 [btrfs]
  Code: 54 55 53 48 89 f3 (...)
  RSP: 0018:ffffb27082443ae8 EFLAGS: 00010282
  RAX: 0000000000000004 RBX: ffff94810ee9ad90 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff94810ee9ad90 RDI: ffff947ed8ee75a0
  RBP: a56b6b6b6b6b6b6b R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000007 R11: 0000000000000001 R12: ffff947fa9b435a8
  R13: ffff94810ee9ad90 R14: 0000000000000000 R15: ffff947e93dc0000
  FS:  00007f3cfe974840(0000) GS:ffff9481ac600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1b42995a70 CR3: 0000000127638003 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_wq_submit_bio+0xb3/0xd0 [btrfs]
   btrfs_submit_metadata_bio+0x44/0xc0 [btrfs]
   submit_one_bio+0x61/0x70 [btrfs]
   btree_write_cache_pages+0x414/0x450 [btrfs]
   ? kobject_put+0x9a/0x1d0
   ? trace_hardirqs_on+0x1b/0xf0
   ? _raw_spin_unlock_irqrestore+0x3c/0x60
   ? free_debug_processing+0x1e1/0x2b0
   do_writepages+0x43/0xe0
   ? lock_acquired+0x199/0x490
   __writeback_single_inode+0x59/0x650
   writeback_single_inode+0xaf/0x120
   write_inode_now+0x94/0xd0
   iput+0x187/0x2b0
   close_ctree+0x2c6/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f3cfebabee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffc9c9a05f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f3cfecd1264 RCX: 00007f3cfebabee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 0000562b6b478000
  RBP: 0000562b6b473a30 R08: 0000000000000000 R09: 00007f3cfec6cbe0
  R10: 0000562b6b479fe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 0000562b6b478000 R14: 0000562b6b473b40 R15: 0000562b6b473c60
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  ---[ end trace dd74718fef1ed5cc ]---

Finally when we remove the btrfs module (rmmod btrfs), there are several
warnings about objects that were allocated from our slabs but were never
freed, consequence of the transaction that was never committed and got
leaked:

  =============================================================================
  BUG btrfs_delayed_ref_head (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_ref_head on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000094c2ae56 objects=24 used=2 fp=0x000000002bfa2521 flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x0000000050cbdd61 @offset=12104
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1894 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
	btrfs_free_tree_block+0x128/0x360 [btrfs]
	__btrfs_cow_block+0x489/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
	btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=4292 cpu=2 pid=1729526
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	commit_cowonly_roots+0xfb/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	sync_filesystem+0x74/0x90
	generic_shutdown_super+0x22/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x0000000086e9b0ff @offset=12776
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1900 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
	btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
	alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
	__btrfs_cow_block+0x12d/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=3141 cpu=6 pid=1729803
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	btrfs_write_dirty_block_groups+0x17d/0x3d0 [btrfs]
	commit_cowonly_roots+0x248/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	close_ctree+0x113/0x2fa [btrfs]
	generic_shutdown_super+0x6c/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_ref_head: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 0b (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_tree_ref (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_tree_ref on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000011f78dc0 objects=37 used=2 fp=0x0000000032d55d91 flags=0x17fffc000010200
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000001a340018 @offset=4408
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1917 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
	btrfs_free_tree_block+0x128/0x360 [btrfs]
	__btrfs_cow_block+0x489/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
	btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=4167 cpu=4 pid=1729795
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	btrfs_commit_transaction+0x60/0xc40 [btrfs]
	create_subvol+0x56a/0x990 [btrfs]
	btrfs_mksubvol+0x3fb/0x4a0 [btrfs]
	__btrfs_ioctl_snap_create+0x119/0x1a0 [btrfs]
	btrfs_ioctl_snap_create+0x58/0x80 [btrfs]
	btrfs_ioctl+0x1a92/0x36f0 [btrfs]
	__x64_sys_ioctl+0x83/0xb0
	do_syscall_64+0x33/0x80
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x000000002b46292a @offset=13648
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1923 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
	btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
	alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
	__btrfs_cow_block+0x12d/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=3164 cpu=6 pid=1729803
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	commit_cowonly_roots+0xfb/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	close_ctree+0x113/0x2fa [btrfs]
	generic_shutdown_super+0x6c/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_tree_ref: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_extent_op (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_extent_op on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x00000000f145ce2f objects=22 used=1 fp=0x00000000af0f92cf flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? __mutex_unlock_slowpath+0x45/0x2a0
   kmem_cache_destroy+0x55/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000004cf95ea8 @offset=6264
  INFO: Allocated in btrfs_alloc_tree_block+0x1e0/0x360 [btrfs] age=1931 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_alloc_tree_block+0x1e0/0x360 [btrfs]
	alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
	__btrfs_cow_block+0x12d/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
	btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs] age=3173 cpu=6 pid=1729803
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0xabd/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	commit_cowonly_roots+0xfb/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	close_ctree+0x113/0x2fa [btrfs]
	generic_shutdown_super+0x6c/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_extent_op: Slab cache still has objects
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  BTRFS: state leak: start 30408704 end 30425087 state 1 in tree 1 refs 1

Fix this issue by having the remount path stop the qgroup rescan worker
when we are remounting RO and teach the rescan worker to stop when a
remount is in progress. If later a remount in RW mode happens, we are
already resuming the qgroup rescan worker through the call to
btrfs_qgroup_rescan_resume(), so we do not need to worry about that.

Tested-by: Fabian Vogt <fvogt@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:59:57 +01:00
Pavel Begunkov
8fc058597a btrfs: merge critical sections of discard lock in workfn
btrfs_discard_workfn() drops discard_ctl->lock just to take it again in
a moment in btrfs_discard_schedule_work(). Avoid that and also reuse
ktime.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:59:54 +01:00
Pavel Begunkov
1ea2872fc6 btrfs: fix racy access to discard_ctl data
Because only one discard worker may be running at any given point, it
could have been safe to modify ->prev_discard, etc. without
synchronization, if not for @override flag in
btrfs_discard_schedule_work() and delayed_work_pending() returning false
while workfn is running.

That may lead to torn reads of u64 for some architectures, but that's
not a big problem as only slightly affects the discard rate.

Suggested-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:59:53 +01:00
Pavel Begunkov
ea9ed87c73 btrfs: fix async discard stall
Might happen that bg->discard_eligible_time was changed without
rescheduling, so btrfs_discard_workfn() wakes up earlier than that new
time, peek_discard_list() returns NULL, and all work halts and goes to
sleep without further rescheduling even there are block groups to
discard.

It happens pretty often, but not so visible from the userspace because
after some time it usually will be kicked off anyway by someone else
calling btrfs_discard_reschedule_work().

Fix it by continue rescheduling if block group discard lists are not
empty.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:59:51 +01:00
Josef Bacik
675a4fc8f3 btrfs: tests: initialize test inodes location
I noticed that sometimes the module failed to load because the self
tests failed like this:

  BTRFS: selftest: fs/btrfs/tests/inode-tests.c:963 miscount, wanted 1, got 0

This turned out to be because sometimes the btrfs ino would be the btree
inode number, and thus we'd skip calling the set extent delalloc bit
helper, and thus not adjust ->outstanding_extents.

Fix this by making sure we initialize test inodes with a valid inode
number so that we don't get random failures during self tests.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:59:49 +01:00
Filipe Manana
0b3f407e67 btrfs: send: fix wrong file path when there is an inode with a pending rmdir
When doing an incremental send, if we have a new inode that happens to
have the same number that an old directory inode had in the base snapshot
and that old directory has a pending rmdir operation, we end up computing
a wrong path for the new inode, causing the receiver to fail.

Example reproducer:

  $ cat test-send-rmdir.sh
  #!/bin/bash

  DEV=/dev/sdi
  MNT=/mnt/sdi

  mkfs.btrfs -f $DEV >/dev/null
  mount $DEV $MNT

  mkdir $MNT/dir
  touch $MNT/dir/file1
  touch $MNT/dir/file2
  touch $MNT/dir/file3

  # Filesystem looks like:
  #
  # .                                     (ino 256)
  # |----- dir/                           (ino 257)
  #         |----- file1                  (ino 258)
  #         |----- file2                  (ino 259)
  #         |----- file3                  (ino 260)
  #

  btrfs subvolume snapshot -r $MNT $MNT/snap1
  btrfs send -f /tmp/snap1.send $MNT/snap1

  # Now remove our directory and all its files.
  rm -fr $MNT/dir

  # Unmount the filesystem and mount it again. This is to ensure that
  # the next inode that is created ends up with the same inode number
  # that our directory "dir" had, 257, which is the first free "objectid"
  # available after mounting again the filesystem.
  umount $MNT
  mount $DEV $MNT

  # Now create a new file (it could be a directory as well).
  touch $MNT/newfile

  # Filesystem now looks like:
  #
  # .                                     (ino 256)
  # |----- newfile                        (ino 257)
  #

  btrfs subvolume snapshot -r $MNT $MNT/snap2
  btrfs send -f /tmp/snap2.send -p $MNT/snap1 $MNT/snap2

  # Now unmount the filesystem, create a new one, mount it and try to apply
  # both send streams to recreate both snapshots.
  umount $DEV

  mkfs.btrfs -f $DEV >/dev/null

  mount $DEV $MNT

  btrfs receive -f /tmp/snap1.send $MNT
  btrfs receive -f /tmp/snap2.send $MNT

  umount $MNT

When running the test, the receive operation for the incremental stream
fails:

  $ ./test-send-rmdir.sh
  Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap1'
  At subvol /mnt/sdi/snap1
  Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap2'
  At subvol /mnt/sdi/snap2
  At subvol snap1
  At snapshot snap2
  ERROR: chown o257-9-0 failed: No such file or directory

So fix this by tracking directories that have a pending rmdir by inode
number and generation number, instead of only inode number.

A test case for fstests follows soon.

Reported-by: Massimo B. <massimo.b@gmx.net>
Tested-by: Massimo B. <massimo.b@gmx.net>
Link: https://lore.kernel.org/linux-btrfs/6ae34776e85912960a253a8327068a892998e685.camel@gmx.net/
CC: stable@vger.kernel.org # 4.19+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:50:16 +01:00
Qu Wenruo
ae5e070eac btrfs: qgroup: don't try to wait flushing if we're already holding a transaction
There is a chance of racing for qgroup flushing which may lead to
deadlock:

	Thread A		|	Thread B
   (not holding trans handle)	|  (holding a trans handle)
--------------------------------+--------------------------------
__btrfs_qgroup_reserve_meta()   | __btrfs_qgroup_reserve_meta()
|- try_flush_qgroup()		| |- try_flush_qgroup()
   |- QGROUP_FLUSHING bit set   |    |
   |				|    |- test_and_set_bit()
   |				|    |- wait_event()
   |- btrfs_join_transaction()	|
   |- btrfs_commit_transaction()|

			!!! DEAD LOCK !!!

Since thread A wants to commit transaction, but thread B is holding a
transaction handle, blocking the commit.
At the same time, thread B is waiting for thread A to finish its commit.

This is just a hot fix, and would lead to more EDQUOT when we're near
the qgroup limit.

The proper fix would be to make all metadata/data reservations happen
without holding a transaction handle.

CC: stable@vger.kernel.org # 5.9+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:50:07 +01:00
ethanwu
9a66497156 btrfs: correctly calculate item size used when item key collision happens
Item key collision is allowed for some item types, like dir item and
inode refs, but the overall item size is limited by the nodesize.

item size(ins_len) passed from btrfs_insert_empty_items to
btrfs_search_slot already contains size of btrfs_item.

When btrfs_search_slot reaches leaf, we'll see if we need to split leaf.
The check incorrectly reports that split leaf is required, because
it treats the space required by the newly inserted item as
btrfs_item + item data. But in item key collision case, only item data
is actually needed, the newly inserted item could merge into the existing
one. No new btrfs_item will be inserted.

And split_leaf return EOVERFLOW from following code:

  if (extend && data_size + btrfs_item_size_nr(l, slot) +
      sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(fs_info))
      return -EOVERFLOW;

In most cases, when callers receive EOVERFLOW, they either return
this error or handle in different ways. For example, in normal dir item
creation the userspace will get errno EOVERFLOW; in inode ref case
INODE_EXTREF is used instead.

However, this is not the case for rename. To avoid the unrecoverable
situation in rename, btrfs_check_dir_item_collision is called in
early phase of rename. In this function, when item key collision is
detected leaf space is checked:

  data_size = sizeof(*di) + name_len;
  if (data_size + btrfs_item_size_nr(leaf, slot) +
      sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root->fs_info))

the sizeof(struct btrfs_item) + btrfs_item_size_nr(leaf, slot) here
refers to existing item size, the condition here correctly calculates
the needed size for collision case rather than the wrong case above.

The consequence of inconsistent condition check between
btrfs_check_dir_item_collision and btrfs_search_slot when item key
collision happens is that we might pass check here but fail
later at btrfs_search_slot. Rename fails and volume is forced readonly

  [436149.586170] ------------[ cut here ]------------
  [436149.586173] BTRFS: Transaction aborted (error -75)
  [436149.586196] WARNING: CPU: 0 PID: 16733 at fs/btrfs/inode.c:9870 btrfs_rename2+0x1938/0x1b70 [btrfs]
  [436149.586227] CPU: 0 PID: 16733 Comm: python Tainted: G      D           4.18.0-rc5+ #1
  [436149.586228] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/05/2016
  [436149.586238] RIP: 0010:btrfs_rename2+0x1938/0x1b70 [btrfs]
  [436149.586254] RSP: 0018:ffffa327043a7ce0 EFLAGS: 00010286
  [436149.586255] RAX: 0000000000000000 RBX: ffff8d8a17d13340 RCX: 0000000000000006
  [436149.586256] RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff8d8a7fc164b0
  [436149.586257] RBP: ffffa327043a7da0 R08: 0000000000000560 R09: 7265282064657472
  [436149.586258] R10: 0000000000000000 R11: 6361736e61725420 R12: ffff8d8a0d4c8b08
  [436149.586258] R13: ffff8d8a17d13340 R14: ffff8d8a33e0a540 R15: 00000000000001fe
  [436149.586260] FS:  00007fa313933740(0000) GS:ffff8d8a7fc00000(0000) knlGS:0000000000000000
  [436149.586261] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [436149.586262] CR2: 000055d8d9c9a720 CR3: 000000007aae0003 CR4: 00000000003606f0
  [436149.586295] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  [436149.586296] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  [436149.586296] Call Trace:
  [436149.586311]  vfs_rename+0x383/0x920
  [436149.586313]  ? vfs_rename+0x383/0x920
  [436149.586315]  do_renameat2+0x4ca/0x590
  [436149.586317]  __x64_sys_rename+0x20/0x30
  [436149.586324]  do_syscall_64+0x5a/0x120
  [436149.586330]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [436149.586332] RIP: 0033:0x7fa3133b1d37
  [436149.586348] RSP: 002b:00007fffd3e43908 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
  [436149.586349] RAX: ffffffffffffffda RBX: 00007fa3133b1d30 RCX: 00007fa3133b1d37
  [436149.586350] RDX: 000055d8da06b5e0 RSI: 000055d8da225d60 RDI: 000055d8da2c4da0
  [436149.586351] RBP: 000055d8da2252f0 R08: 00007fa313782000 R09: 00000000000177e0
  [436149.586351] R10: 000055d8da010680 R11: 0000000000000246 R12: 00007fa313840b00

Thanks to Hans van Kranenburg for information about crc32 hash collision
tools, I was able to reproduce the dir item collision with following
python script.
https://github.com/wutzuchieh/misc_tools/blob/master/crc32_forge.py Run
it under a btrfs volume will trigger the abort transaction.  It simply
creates files and rename them to forged names that leads to
hash collision.

There are two ways to fix this. One is to simply revert the patch
878f2d2cb3 ("Btrfs: fix max dir item size calculation") to make the
condition consistent although that patch is correct about the size.

The other way is to handle the leaf space check correctly when
collision happens. I prefer the second one since it correct leaf
space check in collision case. This fix will not account
sizeof(struct btrfs_item) when the item already exists.
There are two places where ins_len doesn't contain
sizeof(struct btrfs_item), however.

  1. extent-tree.c: lookup_inline_extent_backref
  2. file-item.c: btrfs_csum_file_blocks

to make the logic of btrfs_search_slot more clear, we add a flag
search_for_extension in btrfs_path.

This flag indicates that ins_len passed to btrfs_search_slot doesn't
contain sizeof(struct btrfs_item). When key exists, btrfs_search_slot
will use the actual size needed to calculate the required leaf space.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: ethanwu <ethanwu@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:50:00 +01:00
Filipe Manana
3d45f221ce btrfs: fix deadlock when cloning inline extent and low on free metadata space
When cloning an inline extent there are cases where we can not just copy
the inline extent from the source range to the target range (e.g. when the
target range starts at an offset greater than zero). In such cases we copy
the inline extent's data into a page of the destination inode and then
dirty that page. However, after that we will need to start a transaction
for each processed extent and, if we are ever low on available metadata
space, we may need to flush existing delalloc for all dirty inodes in an
attempt to release metadata space - if that happens we may deadlock:

* the async reclaim task queued a delalloc work to flush delalloc for
  the destination inode of the clone operation;

* the task executing that delalloc work gets blocked waiting for the
  range with the dirty page to be unlocked, which is currently locked
  by the task doing the clone operation;

* the async reclaim task blocks waiting for the delalloc work to complete;

* the cloning task is waiting on the waitqueue of its reservation ticket
  while holding the range with the dirty page locked in the inode's
  io_tree;

* if metadata space is not released by some other task (like delalloc for
  some other inode completing for example), the clone task waits forever
  and as a consequence the delalloc work and async reclaim tasks will hang
  forever as well. Releasing more space on the other hand may require
  starting a transaction, which will hang as well when trying to reserve
  metadata space, resulting in a deadlock between all these tasks.

When this happens, traces like the following show up in dmesg/syslog:

  [87452.323003] INFO: task kworker/u16:11:1810830 blocked for more than 120 seconds.
  [87452.323644]       Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  [87452.324248] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [87452.324852] task:kworker/u16:11  state:D stack:    0 pid:1810830 ppid:     2 flags:0x00004000
  [87452.325520] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]
  [87452.326136] Call Trace:
  [87452.326737]  __schedule+0x5d1/0xcf0
  [87452.327390]  schedule+0x45/0xe0
  [87452.328174]  lock_extent_bits+0x1e6/0x2d0 [btrfs]
  [87452.328894]  ? finish_wait+0x90/0x90
  [87452.329474]  btrfs_invalidatepage+0x32c/0x390 [btrfs]
  [87452.330133]  ? __mod_memcg_state+0x8e/0x160
  [87452.330738]  __extent_writepage+0x2d4/0x400 [btrfs]
  [87452.331405]  extent_write_cache_pages+0x2b2/0x500 [btrfs]
  [87452.332007]  ? lock_release+0x20e/0x4c0
  [87452.332557]  ? trace_hardirqs_on+0x1b/0xf0
  [87452.333127]  extent_writepages+0x43/0x90 [btrfs]
  [87452.333653]  ? lock_acquire+0x1a3/0x490
  [87452.334177]  do_writepages+0x43/0xe0
  [87452.334699]  ? __filemap_fdatawrite_range+0xa4/0x100
  [87452.335720]  __filemap_fdatawrite_range+0xc5/0x100
  [87452.336500]  btrfs_run_delalloc_work+0x17/0x40 [btrfs]
  [87452.337216]  btrfs_work_helper+0xf1/0x600 [btrfs]
  [87452.337838]  process_one_work+0x24e/0x5e0
  [87452.338437]  worker_thread+0x50/0x3b0
  [87452.339137]  ? process_one_work+0x5e0/0x5e0
  [87452.339884]  kthread+0x153/0x170
  [87452.340507]  ? kthread_mod_delayed_work+0xc0/0xc0
  [87452.341153]  ret_from_fork+0x22/0x30
  [87452.341806] INFO: task kworker/u16:1:2426217 blocked for more than 120 seconds.
  [87452.342487]       Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  [87452.343274] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [87452.344049] task:kworker/u16:1   state:D stack:    0 pid:2426217 ppid:     2 flags:0x00004000
  [87452.344974] Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs]
  [87452.345655] Call Trace:
  [87452.346305]  __schedule+0x5d1/0xcf0
  [87452.346947]  ? kvm_clock_read+0x14/0x30
  [87452.347676]  ? wait_for_completion+0x81/0x110
  [87452.348389]  schedule+0x45/0xe0
  [87452.349077]  schedule_timeout+0x30c/0x580
  [87452.349718]  ? _raw_spin_unlock_irqrestore+0x3c/0x60
  [87452.350340]  ? lock_acquire+0x1a3/0x490
  [87452.351006]  ? try_to_wake_up+0x7a/0xa20
  [87452.351541]  ? lock_release+0x20e/0x4c0
  [87452.352040]  ? lock_acquired+0x199/0x490
  [87452.352517]  ? wait_for_completion+0x81/0x110
  [87452.353000]  wait_for_completion+0xab/0x110
  [87452.353490]  start_delalloc_inodes+0x2af/0x390 [btrfs]
  [87452.353973]  btrfs_start_delalloc_roots+0x12d/0x250 [btrfs]
  [87452.354455]  flush_space+0x24f/0x660 [btrfs]
  [87452.355063]  btrfs_async_reclaim_metadata_space+0x1bb/0x480 [btrfs]
  [87452.355565]  process_one_work+0x24e/0x5e0
  [87452.356024]  worker_thread+0x20f/0x3b0
  [87452.356487]  ? process_one_work+0x5e0/0x5e0
  [87452.356973]  kthread+0x153/0x170
  [87452.357434]  ? kthread_mod_delayed_work+0xc0/0xc0
  [87452.357880]  ret_from_fork+0x22/0x30
  (...)
  < stack traces of several tasks waiting for the locks of the inodes of the
    clone operation >
  (...)
  [92867.444138] RSP: 002b:00007ffc3371bbe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
  [92867.444624] RAX: ffffffffffffffda RBX: 00007ffc3371bea0 RCX: 00007f61efe73f97
  [92867.445116] RDX: 0000000000000000 RSI: 0000560fbd5d7a40 RDI: 0000560fbd5d8960
  [92867.445595] RBP: 00007ffc3371beb0 R08: 0000000000000001 R09: 0000000000000003
  [92867.446070] R10: 00007ffc3371b996 R11: 0000000000000246 R12: 0000000000000000
  [92867.446820] R13: 000000000000001f R14: 00007ffc3371bea0 R15: 00007ffc3371beb0
  [92867.447361] task:fsstress        state:D stack:    0 pid:2508238 ppid:2508153 flags:0x00004000
  [92867.447920] Call Trace:
  [92867.448435]  __schedule+0x5d1/0xcf0
  [92867.448934]  ? _raw_spin_unlock_irqrestore+0x3c/0x60
  [92867.449423]  schedule+0x45/0xe0
  [92867.449916]  __reserve_bytes+0x4a4/0xb10 [btrfs]
  [92867.450576]  ? finish_wait+0x90/0x90
  [92867.451202]  btrfs_reserve_metadata_bytes+0x29/0x190 [btrfs]
  [92867.451815]  btrfs_block_rsv_add+0x1f/0x50 [btrfs]
  [92867.452412]  start_transaction+0x2d1/0x760 [btrfs]
  [92867.453216]  clone_copy_inline_extent+0x333/0x490 [btrfs]
  [92867.453848]  ? lock_release+0x20e/0x4c0
  [92867.454539]  ? btrfs_search_slot+0x9a7/0xc30 [btrfs]
  [92867.455218]  btrfs_clone+0x569/0x7e0 [btrfs]
  [92867.455952]  btrfs_clone_files+0xf6/0x150 [btrfs]
  [92867.456588]  btrfs_remap_file_range+0x324/0x3d0 [btrfs]
  [92867.457213]  do_clone_file_range+0xd4/0x1f0
  [92867.457828]  vfs_clone_file_range+0x4d/0x230
  [92867.458355]  ? lock_release+0x20e/0x4c0
  [92867.458890]  ioctl_file_clone+0x8f/0xc0
  [92867.459377]  do_vfs_ioctl+0x342/0x750
  [92867.459913]  __x64_sys_ioctl+0x62/0xb0
  [92867.460377]  do_syscall_64+0x33/0x80
  [92867.460842]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
  (...)
  < stack traces of more tasks blocked on metadata reservation like the clone
    task above, because the async reclaim task has deadlocked >
  (...)

Another thing to notice is that the worker task that is deadlocked when
trying to flush the destination inode of the clone operation is at
btrfs_invalidatepage(). This is simply because the clone operation has a
destination offset greater than the i_size and we only update the i_size
of the destination file after cloning an extent (just like we do in the
buffered write path).

Since the async reclaim path uses btrfs_start_delalloc_roots() to trigger
the flushing of delalloc for all inodes that have delalloc, add a runtime
flag to an inode to signal it should not be flushed, and for inodes with
that flag set, start_delalloc_inodes() will simply skip them. When the
cloning code needs to dirty a page to copy an inline extent, set that flag
on the inode and then clear it when the clone operation finishes.

This could be sporadically triggered with test case generic/269 from
fstests, which exercises many fsstress processes running in parallel with
several dd processes filling up the entire filesystem.

CC: stable@vger.kernel.org # 5.9+
Fixes: 05a5a7621c ("Btrfs: implement full reflink support for inline extents")
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-18 14:49:50 +01:00
Linus Torvalds
ac7ac4618c for-5.11/block-2020-12-14
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Merge tag 'for-5.11/block-2020-12-14' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:
 "Another series of killing more code than what is being added, again
  thanks to Christoph's relentless cleanups and tech debt tackling.

  This contains:

   - blk-iocost improvements (Baolin Wang)

   - part0 iostat fix (Jeffle Xu)

   - Disable iopoll for split bios (Jeffle Xu)

   - block tracepoint cleanups (Christoph Hellwig)

   - Merging of struct block_device and hd_struct (Christoph Hellwig)

   - Rework/cleanup of how block device sizes are updated (Christoph
     Hellwig)

   - Simplification of gendisk lookup and removal of block device
     aliasing (Christoph Hellwig)

   - Block device ioctl cleanups (Christoph Hellwig)

   - Removal of bdget()/blkdev_get() as exported API (Christoph Hellwig)

   - Disk change rework, avoid ->revalidate_disk() (Christoph Hellwig)

   - sbitmap improvements (Pavel Begunkov)

   - Hybrid polling fix (Pavel Begunkov)

   - bvec iteration improvements (Pavel Begunkov)

   - Zone revalidation fixes (Damien Le Moal)

   - blk-throttle limit fix (Yu Kuai)

   - Various little fixes"

* tag 'for-5.11/block-2020-12-14' of git://git.kernel.dk/linux-block: (126 commits)
  blk-mq: fix msec comment from micro to milli seconds
  blk-mq: update arg in comment of blk_mq_map_queue
  blk-mq: add helper allocating tagset->tags
  Revert "block: Fix a lockdep complaint triggered by request queue flushing"
  nvme-loop: use blk_mq_hctx_set_fq_lock_class to set loop's lock class
  blk-mq: add new API of blk_mq_hctx_set_fq_lock_class
  block: disable iopoll for split bio
  block: Improve blk_revalidate_disk_zones() checks
  sbitmap: simplify wrap check
  sbitmap: replace CAS with atomic and
  sbitmap: remove swap_lock
  sbitmap: optimise sbitmap_deferred_clear()
  blk-mq: skip hybrid polling if iopoll doesn't spin
  blk-iocost: Factor out the base vrate change into a separate function
  blk-iocost: Factor out the active iocgs' state check into a separate function
  blk-iocost: Move the usage ratio calculation to the correct place
  blk-iocost: Remove unnecessary advance declaration
  blk-iocost: Fix some typos in comments
  blktrace: fix up a kerneldoc comment
  block: remove the request_queue to argument request based tracepoints
  ...
2020-12-16 12:57:51 -08:00
Linus Torvalds
f1ee3b8829 for-5.11-tag
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Merge tag 'for-5.11-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs updates from David Sterba:
 "We have a mix of all kinds of changes, feature updates, core stuff,
  performance improvements and lots of cleanups and preparatory changes.

  User visible:

   - export filesystem generation in sysfs

   - new features for mount option 'rescue':
       - what's currently supported is exported in sysfs
       - 'ignorebadroots'/'ibadroots' - continue even if some essential
         tree roots are not usable (extent, uuid, data reloc, device,
         csum, free space)
       - 'ignoredatacsums'/'idatacsums' - skip checksum verification on
         data
       - 'all' - now enables 'ignorebadroots' + 'ignoredatacsums' +
         'nologreplay'

   - export read mirror policy settings to sysfs, new policies will be
     added in the future

   - remove inode number cache feature (mount -o inode_cache), obsoleted
     in 5.9

  User visible fixes:

   - async discard scheduling fixes on high loads

   - update inode byte counter atomically so stat() does not report
     wrong value in some cases

   - free space tree fixes:
       - correctly report status of v2 after remount
       - clear v1 cache inodes when v2 is newly enabled after remount

  Core:

   - switch own tree lock implementation to standard rw semaphore:
       - one-level lock nesting is not required anymore, the last use of
         this was in free space that's now loaded asynchronously
       - own implementation of adaptive spinning before taking mutex has
         been part of rwsem
       - performance seems to be better in general, much better (+tens
         of percents) for some workloads
       - lockdep does not complain

   - finish direct IO conversion to iomap infrastructure, remove
     temporary workaround for DSYNC after iomap API updates

   - preparatory work to support data and metadata blocks smaller than
     page:
       - generalize code that assumes sectorsize == PAGE_SIZE, lots of
         refactoring
       - planned namely for 64K pages (eg. arm64, ppc64)
       - scrub read-only support

   - preparatory work for zoned allocation mode (SMR/ZBC/ZNS friendly):
       - disable incompatible features
       - round-robin superblock write

   - free space cache (v1) is loaded asynchronously, remove tree path
     recursion

   - slightly improved time tacking for transaction kthread wake ups

  Performance improvements (note that the numbers depend on load type or
  other features and weren't run on the same machine):

   - skip unnecessary work:
       - do not start readahead for csum tree when scrubbing non-data
         block groups
       - do not start and wait for delalloc on snapshot roots on
         transaction commit
       - fix race when defragmenting leads to unnecessary IO

   - dbench speedups (+throughput%/-max latency%):
       - skip unnecessary searches for xattrs when logging an inode
         (+10.8/-8.2)
       - stop incrementing log batch when joining log transaction (1-2)
       - unlock path before checking if extent is shared during nocow
         writeback (+5.0/-20.5), on fio load +9.7% throughput/-9.8%
         runtime
       - several tree log improvements, eg. removing unnecessary
         operations, fixing races that lead to additional work
         (+12.7/-8.2)

   - tree-checker error branches annotated with unlikely() (+3%
     throughput)

  Other:

   - cleanups

   - lockdep fixes

   - more btrfs_inode conversions

   - error variable cleanups"

* tag 'for-5.11-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (198 commits)
  btrfs: scrub: allow scrub to work with subpage sectorsize
  btrfs: scrub: support subpage data scrub
  btrfs: scrub: support subpage tree block scrub
  btrfs: scrub: always allocate one full page for one sector for RAID56
  btrfs: scrub: reduce width of extent_len/stripe_len from 64 to 32 bits
  btrfs: refactor btrfs_lookup_bio_sums to handle out-of-order bvecs
  btrfs: remove btrfs_find_ordered_sum call from btrfs_lookup_bio_sums
  btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors
  btrfs: update num_extent_pages to support subpage sized extent buffer
  btrfs: don't allow tree block to cross page boundary for subpage support
  btrfs: calculate inline extent buffer page size based on page size
  btrfs: factor out btree page submission code to a helper
  btrfs: make btrfs_verify_data_csum follow sector size
  btrfs: pass bio_offset to check_data_csum() directly
  btrfs: rename bio_offset of extent_submit_bio_start_t to dio_file_offset
  btrfs: fix lockdep warning when creating free space tree
  btrfs: skip space_cache v1 setup when not using it
  btrfs: remove free space items when disabling space cache v1
  btrfs: warn when remount will not change the free space tree
  btrfs: use superblock state to print space_cache mount option
  ...
2020-12-15 18:40:42 -08:00
Linus Torvalds
edd7ab7684 The new preemtible kmap_local() implementation:
- Consolidate all kmap_atomic() internals into a generic implementation
     which builds the base for the kmap_local() API and make the
     kmap_atomic() interface wrappers which handle the disabling/enabling of
     preemption and pagefaults.
 
   - Switch the storage from per-CPU to per task and provide scheduler
     support for clearing mapping when scheduling out and restoring them
     when scheduling back in.
 
   - Merge the migrate_disable/enable() code, which is also part of the
     scheduler pull request. This was required to make the kmap_local()
     interface available which does not disable preemption when a mapping
     is established. It has to disable migration instead to guarantee that
     the virtual address of the mapped slot is the same accross preemption.
 
   - Provide better debug facilities: guard pages and enforced utilization
     of the mapping mechanics on 64bit systems when the architecture allows
     it.
 
   - Provide the new kmap_local() API which can now be used to cleanup the
     kmap_atomic() usage sites all over the place. Most of the usage sites
     do not require the implicit disabling of preemption and pagefaults so
     the penalty on 64bit and 32bit non-highmem systems is removed and quite
     some of the code can be simplified. A wholesale conversion is not
     possible because some usage depends on the implicit side effects and
     some need to be cleaned up because they work around these side effects.
 
     The migrate disable side effect is only effective on highmem systems
     and when enforced debugging is enabled. On 64bit and 32bit non-highmem
     systems the overhead is completely avoided.
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Merge tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull kmap updates from Thomas Gleixner:
 "The new preemtible kmap_local() implementation:

   - Consolidate all kmap_atomic() internals into a generic
     implementation which builds the base for the kmap_local() API and
     make the kmap_atomic() interface wrappers which handle the
     disabling/enabling of preemption and pagefaults.

   - Switch the storage from per-CPU to per task and provide scheduler
     support for clearing mapping when scheduling out and restoring them
     when scheduling back in.

   - Merge the migrate_disable/enable() code, which is also part of the
     scheduler pull request. This was required to make the kmap_local()
     interface available which does not disable preemption when a
     mapping is established. It has to disable migration instead to
     guarantee that the virtual address of the mapped slot is the same
     across preemption.

   - Provide better debug facilities: guard pages and enforced
     utilization of the mapping mechanics on 64bit systems when the
     architecture allows it.

   - Provide the new kmap_local() API which can now be used to cleanup
     the kmap_atomic() usage sites all over the place. Most of the usage
     sites do not require the implicit disabling of preemption and
     pagefaults so the penalty on 64bit and 32bit non-highmem systems is
     removed and quite some of the code can be simplified. A wholesale
     conversion is not possible because some usage depends on the
     implicit side effects and some need to be cleaned up because they
     work around these side effects.

     The migrate disable side effect is only effective on highmem
     systems and when enforced debugging is enabled. On 64bit and 32bit
     non-highmem systems the overhead is completely avoided"

* tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
  ARM: highmem: Fix cache_is_vivt() reference
  x86/crashdump/32: Simplify copy_oldmem_page()
  io-mapping: Provide iomap_local variant
  mm/highmem: Provide kmap_local*
  sched: highmem: Store local kmaps in task struct
  x86: Support kmap_local() forced debugging
  mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
  mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL
  microblaze/mm/highmem: Add dropped #ifdef back
  xtensa/mm/highmem: Make generic kmap_atomic() work correctly
  mm/highmem: Take kmap_high_get() properly into account
  highmem: High implementation details and document API
  Documentation/io-mapping: Remove outdated blurb
  io-mapping: Cleanup atomic iomap
  mm/highmem: Remove the old kmap_atomic cruft
  highmem: Get rid of kmap_types.h
  xtensa/mm/highmem: Switch to generic kmap atomic
  sparc/mm/highmem: Switch to generic kmap atomic
  powerpc/mm/highmem: Switch to generic kmap atomic
  nds32/mm/highmem: Switch to generic kmap atomic
  ...
2020-12-14 18:35:53 -08:00
Qu Wenruo
b42fe98c92 btrfs: scrub: allow scrub to work with subpage sectorsize
Since btrfs scrub is utilizing its own infrastructure to submit
read/write, scrub is independent from all other routines.

This brings one very neat feature, allow us to read 4K data into offset
0 of a 64K page.  So is the writeback routine.

This makes scrub on subpage sector size much easier to implement, and
thanks to previous commits which just changed the implementation to
always do scrub based on sector size, now scrub can handle subpage
filesystem without any problem.

This patch will just remove the restriction on
(sectorsize != PAGE_SIZE), to make scrub finally work on subpage
filesystems.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:11 +01:00
Qu Wenruo
b29dca44ab btrfs: scrub: support subpage data scrub
Btrfs scrub is more flexible than buffered data write path, as we can
read an unaligned subpage data into page offset 0.

This ability makes subpage support much easier, we just need to check
each scrub_page::page_len and ensure we only calculate hash for [0,
page_len) of a page.

There is a small thing to notice: for subpage case, we still do sector
by sector scrub.  This means we will submit a read bio for each sector
to scrub, resulting in the same amount of read bios, just like on the 4K
page systems.

This behavior can be considered as a good thing, if we want everything
to be the same as 4K page systems.  But this also means, we're wasting
the possibility to submit larger bio using 64K page size.  This is
another problem to consider in the future.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:11 +01:00
Qu Wenruo
53f3251d3b btrfs: scrub: support subpage tree block scrub
To support subpage tree block scrub, scrub_checksum_tree_block() only
needs to learn 2 new tricks:

- Follow sector size
  Now scrub_page only represents one sector, we need to follow it
  properly.

- Run checksum on all sectors
  Since scrub_page only represents one sector, we need to run checksum
  on all sectors, not only (nodesize >> PAGE_SIZE).

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:11 +01:00
Qu Wenruo
d0a7a9c050 btrfs: scrub: always allocate one full page for one sector for RAID56
For scrub_pages() and scrub_pages_for_parity(), we currently allocate
one scrub_page structure for one page.

This is fine if we only read/write one sector one time.  But for cases
like scrubbing RAID56, we need to read/write the full stripe, which is
in 64K size for now.

For subpage size, we will submit the read in just one page, which is
normally a good thing, but for RAID56 case, it only expects to see one
sector, not the full stripe in its endio function.
This could lead to wrong parity checksum for RAID56 on subpage.

To make the existing code work well for subpage case, here we take a
shortcut by always allocating a full page for one sector.

This should provide the base to make RAID56 work for subpage case.

The cost is pretty obvious now, for one RAID56 stripe now we always need
16 pages. For support subpage situation (64K page size, 4K sector size),
this means we need full one megabyte to scrub just one RAID56 stripe.

And for data scrub, each 4K sector will also need one 64K page.

This is mostly just a workaround, the proper fix for this is a much
larger project, using scrub_block to replace scrub_page, and allow
scrub_block to handle multi pages, csums, and csum_bitmap to avoid
allocating one page for each sector.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:11 +01:00
Qu Wenruo
fa485d21a7 btrfs: scrub: reduce width of extent_len/stripe_len from 64 to 32 bits
Btrfs on-disk format chose to use u64 for almost everything, but there
are a other restrictions that won't let us use more than u32 for things
like extent length (the maximum length is 128MiB for non-hole extents),
or stripe length (we have device number limit).

This means if we don't have extra handling to convert u64 to u32, we
will always have some questionable operations like
"u32 = u64 >> sectorsize_bits" in the code.

This patch will try to address the problem by reducing the width for the
following members/parameters:

- scrub_parity::stripe_len
- @len of scrub_pages()
- @extent_len of scrub_remap_extent()
- @len of scrub_parity_mark_sectors_error()
- @len of scrub_parity_mark_sectors_data()
- @len of scrub_extent()
- @len of scrub_pages_for_parity()
- @len of scrub_extent_for_parity()

For members extracted from on-disk structure, like map->stripe_len, they
will be kept as is. Since that modification would require on-disk format
change.

There will be cases like "u32 = u64 - u64" or "u32 = u64", for such call
sites, extra ASSERT() is added to be extra safe for debug builds.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:11 +01:00
Qu Wenruo
6275193ef1 btrfs: refactor btrfs_lookup_bio_sums to handle out-of-order bvecs
Refactor btrfs_lookup_bio_sums() by:

- Remove the @file_offset parameter
  There are two factors making the @file_offset parameter useless:

  * For csum lookup in csum tree, file offset makes no sense
    We only need disk_bytenr, which is unrelated to file_offset

  * page_offset (file offset) of each bvec is not contiguous.
    Pages can be added to the same bio as long as their on-disk bytenr
    is contiguous, meaning we could have pages at different file offsets
    in the same bio.

  Thus passing file_offset makes no sense any more.
  The only user of file_offset is for data reloc inode, we will use
  a new function, search_file_offset_in_bio(), to handle it.

- Extract the csum tree lookup into search_csum_tree()
  The new function will handle the csum search in csum tree.
  The return value is the same as btrfs_find_ordered_sum(), returning
  the number of found sectors which have checksum.

- Change how we do the main loop
  The only needed info from bio is:
  * the on-disk bytenr
  * the length

  After extracting the above info, we can do the search without bio
  at all, which makes the main loop much simpler:

	for (cur_disk_bytenr = orig_disk_bytenr;
	     cur_disk_bytenr < orig_disk_bytenr + orig_len;
	     cur_disk_bytenr += count * sectorsize) {

		/* Lookup csum tree */
		count = search_csum_tree(fs_info, path, cur_disk_bytenr,
					 search_len, csum_dst);
		if (!count) {
			/* Csum hole handling */
		}
	}

- Use single variable as the source to calculate all other offsets
  Instead of all different type of variables, we use only one main
  variable, cur_disk_bytenr, which represents the current disk bytenr.

  All involved values can be calculated from that variable, and
  all those variable will only be visible in the inner loop.

The above refactoring makes btrfs_lookup_bio_sums() way more robust than
it used to be, especially related to the file offset lookup.  Now
file_offset lookup is only related to data reloc inode, otherwise we
don't need to bother file_offset at all.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:11 +01:00
Qu Wenruo
9e46458a7c btrfs: remove btrfs_find_ordered_sum call from btrfs_lookup_bio_sums
The function btrfs_lookup_bio_sums() is only called for read bios.
While btrfs_find_ordered_sum() is to search ordered extent sums, which
is only for write path.

This means to read a page we either:

- Submit read bio if it's not uptodate
  This means we only need to search csum tree for checksums.

- The page is already uptodate
  It can be marked uptodate for previous read, or being marked dirty.
  As we always mark page uptodate for dirty page.
  In that case, we don't need to submit read bio at all, thus no need
  to search any checksums.

Remove the btrfs_find_ordered_sum() call in btrfs_lookup_bio_sums().
And since btrfs_lookup_bio_sums() is the only caller for
btrfs_find_ordered_sum(), also remove the implementation.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:10 +01:00
Qu Wenruo
884b07d0f4 btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors
To support sectorsize < PAGE_SIZE case, we need to take extra care of
extent buffer accessors.

Since sectorsize is smaller than PAGE_SIZE, one page can contain
multiple tree blocks, we must use eb->start to determine the real offset
to read/write for extent buffer accessors.

This patch introduces two helpers to do this:

- get_eb_page_index()
  This is to calculate the index to access extent_buffer::pages.
  It's just a simple wrapper around "start >> PAGE_SHIFT".

  For sectorsize == PAGE_SIZE case, nothing is changed.
  For sectorsize < PAGE_SIZE case, we always get index as 0, and
  the existing page shift also works.

- get_eb_offset_in_page()
  This is to calculate the offset to access extent_buffer::pages.
  This needs to take extent_buffer::start into consideration.

  For sectorsize == PAGE_SIZE case, extent_buffer::start is always
  aligned to PAGE_SIZE, thus adding extent_buffer::start to
  offset_in_page() won't change the result.
  For sectorsize < PAGE_SIZE case, adding extent_buffer::start gives
  us the correct offset to access.

This patch will touch the following parts to cover all extent buffer
accessors:

- BTRFS_SETGET_HEADER_FUNCS()
- read_extent_buffer()
- read_extent_buffer_to_user()
- memcmp_extent_buffer()
- write_extent_buffer_chunk_tree_uuid()
- write_extent_buffer_fsid()
- write_extent_buffer()
- memzero_extent_buffer()
- copy_extent_buffer_full()
- copy_extent_buffer()
- memcpy_extent_buffer()
- memmove_extent_buffer()
- btrfs_get_token_##bits()
- btrfs_get_##bits()
- btrfs_set_token_##bits()
- btrfs_set_##bits()
- generic_bin_search()

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:10 +01:00
Qu Wenruo
4a3dc93843 btrfs: update num_extent_pages to support subpage sized extent buffer
For subpage sized extent buffer, we have ensured no extent buffer will
cross page boundary, thus we would only need one page for any extent
buffer.

Update function num_extent_pages to handle such case.  Now
num_extent_pages() returns 1 for subpage sized extent buffer.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:10 +01:00
Qu Wenruo
1aaac38c83 btrfs: don't allow tree block to cross page boundary for subpage support
As a preparation for subpage sector size support (allowing filesystem
with sector size smaller than page size to be mounted) if the sector
size is smaller than page size, we don't allow tree block to be read if
it crosses 64K(*) boundary.

The 64K is selected because:

- we are only going to support 64K page size for subpage for now
- 64K is also the maximum supported node size

This ensures that tree blocks are always contained in one page for a
system with 64K page size, which can greatly simplify the handling.

Otherwise we would have to do complex multi-page handling of tree
blocks.  Currently there is no way to create such tree blocks.

In kernel we have avoided such tree blocks allocation even on 4K page
size, as it can lead to RAID56 stripe scrubbing.

While btrfs-progs have fixed its chunk allocator since 2016 for convert,
and has extra checks to do the same behavior as the kernel.

Just add such graceful checks in case of an ancient filesystem.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:10 +01:00
Qu Wenruo
deb6789553 btrfs: calculate inline extent buffer page size based on page size
Btrfs only support 64K as maximum node size, thus for 4K page system, we
would have at most 16 pages for one extent buffer.

For a system using 64K page size, we would really have just one page.

While we always use 16 pages for extent_buffer::pages, this means for
systems using 64K pages, we are wasting memory for 15 page pointers
which will never be used.

Calculate the array size based on page size and the node size maximum.

- for systems using 4K page size, it will stay 16 pages
- for systems using 64K page size, it will be 1 page

Move the definition of BTRFS_MAX_METADATA_BLOCKSIZE to btrfs_tree.h, to
avoid circular inclusion of ctree.h.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:10 +01:00
Qu Wenruo
f91e0d0c4c btrfs: factor out btree page submission code to a helper
In btree_write_cache_pages() we have a btree page submission routine
buried deeply in a nested loop.

This patch will extract that part of code into a helper function,
submit_eb_page(), to do the same work.

Since submit_eb_page() now can return >0 for successful extent
buffer submission, remove the "ASSERT(ret <= 0);" line.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:10 +01:00
Qu Wenruo
f44cf41075 btrfs: make btrfs_verify_data_csum follow sector size
Currently btrfs_verify_data_csum() just passes the whole page to
check_data_csum(), which is fine since we only support sectorsize ==
PAGE_SIZE.

To support subpage, we need to properly honor per-sector
checksum verification, just like what we did in dio read path.

This patch will do the csum verification in a for loop, starts with
pg_off == start - page_offset(page), with sectorsize increase for
each loop.

For sectorsize == PAGE_SIZE case, the pg_off will always be 0, and we
will only loop once.

For subpage case, we do the iterate over each sector and if we found any
error, we return error.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:09 +01:00
Qu Wenruo
7ffd27e378 btrfs: pass bio_offset to check_data_csum() directly
Parameter icsum for check_data_csum() is a little hard to understand.
So is the phy_offset for btrfs_verify_data_csum().

Both parameters are calculated values for csum lookup.

Instead of some calculated value, just pass bio_offset and let the
final and only user, check_data_csum(), calculate whatever it needs.

Since we are here, also make the bio_offset parameter and some related
variables to be u32 (unsigned int).
As bio size is limited by its bi_size, which is unsigned int, and has
extra size limit check during various bio operations.
Thus we are ensured that bio_offset won't overflow u32.

Thus for all involved functions, not only rename the parameter from
@phy_offset to @bio_offset, but also reduce its width to u32, so we
won't have suspicious "u32 = u64 >> sector_bits;" lines anymore.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:09 +01:00
Qu Wenruo
1941b64b08 btrfs: rename bio_offset of extent_submit_bio_start_t to dio_file_offset
The parameter bio_offset of extent_submit_bio_start_t is very confusing.
If it's really bio_offset (offset to bio), then it should be u32.  But
in fact, it's only utilized by dio read, and that member is used as file
offset, which must be u64.

Rename it to dio_file_offset since the only user uses it as file offset,
and add comment for who is using it.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:09 +01:00
Boris Burkov
8a6a87cd44 btrfs: fix lockdep warning when creating free space tree
A lock dependency loop exists between the root tree lock, the extent tree
lock, and the free space tree lock.

The root tree lock depends on the free space tree lock because
btrfs_create_tree holds the new tree's lock while adding it to the root
tree.

The extent tree lock depends on the root tree lock because during
umount, we write out space cache v1, which writes inodes in the root
tree, which results in holding the root tree lock while doing a lookup
in the extent tree.

Finally, the free space tree depends on the extent tree because
populate_free_space_tree holds a locked path in the extent tree and then
does a lookup in the free space tree to add the new item.

The simplest of the three to break is the one during tree creation: we
unlock the leaf before inserting the tree node into the root tree, which
fixes the lockdep warning.

  [30.480136] ======================================================
  [30.480830] WARNING: possible circular locking dependency detected
  [30.481457] 5.9.0-rc8+ #76 Not tainted
  [30.481897] ------------------------------------------------------
  [30.482500] mount/520 is trying to acquire lock:
  [30.483064] ffff9babebe03908 (btrfs-free-space-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x39/0x180
  [30.484054]
	      but task is already holding lock:
  [30.484637] ffff9babebe24468 (btrfs-extent-01#2){++++}-{3:3}, at: __btrfs_tree_read_lock+0x39/0x180
  [30.485581]
	      which lock already depends on the new lock.

  [30.486397]
	      the existing dependency chain (in reverse order) is:
  [30.487205]
	      -> #2 (btrfs-extent-01#2){++++}-{3:3}:
  [30.487825]        down_read_nested+0x43/0x150
  [30.488306]        __btrfs_tree_read_lock+0x39/0x180
  [30.488868]        __btrfs_read_lock_root_node+0x3a/0x50
  [30.489477]        btrfs_search_slot+0x464/0x9b0
  [30.490009]        check_committed_ref+0x59/0x1d0
  [30.490603]        btrfs_cross_ref_exist+0x65/0xb0
  [30.491108]        run_delalloc_nocow+0x405/0x930
  [30.491651]        btrfs_run_delalloc_range+0x60/0x6b0
  [30.492203]        writepage_delalloc+0xd4/0x150
  [30.492688]        __extent_writepage+0x18d/0x3a0
  [30.493199]        extent_write_cache_pages+0x2af/0x450
  [30.493743]        extent_writepages+0x34/0x70
  [30.494231]        do_writepages+0x31/0xd0
  [30.494642]        __filemap_fdatawrite_range+0xad/0xe0
  [30.495194]        btrfs_fdatawrite_range+0x1b/0x50
  [30.495677]        __btrfs_write_out_cache+0x40d/0x460
  [30.496227]        btrfs_write_out_cache+0x8b/0x110
  [30.496716]        btrfs_start_dirty_block_groups+0x211/0x4e0
  [30.497317]        btrfs_commit_transaction+0xc0/0xba0
  [30.497861]        sync_filesystem+0x71/0x90
  [30.498303]        btrfs_remount+0x81/0x433
  [30.498767]        reconfigure_super+0x9f/0x210
  [30.499261]        path_mount+0x9d1/0xa30
  [30.499722]        do_mount+0x55/0x70
  [30.500158]        __x64_sys_mount+0xc4/0xe0
  [30.500616]        do_syscall_64+0x33/0x40
  [30.501091]        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [30.501629]
	      -> #1 (btrfs-root-00){++++}-{3:3}:
  [30.502241]        down_read_nested+0x43/0x150
  [30.502727]        __btrfs_tree_read_lock+0x39/0x180
  [30.503291]        __btrfs_read_lock_root_node+0x3a/0x50
  [30.503903]        btrfs_search_slot+0x464/0x9b0
  [30.504405]        btrfs_insert_empty_items+0x60/0xa0
  [30.504973]        btrfs_insert_item+0x60/0xd0
  [30.505412]        btrfs_create_tree+0x1b6/0x210
  [30.505913]        btrfs_create_free_space_tree+0x54/0x110
  [30.506460]        btrfs_mount_rw+0x15d/0x20f
  [30.506937]        btrfs_remount+0x356/0x433
  [30.507369]        reconfigure_super+0x9f/0x210
  [30.507868]        path_mount+0x9d1/0xa30
  [30.508264]        do_mount+0x55/0x70
  [30.508668]        __x64_sys_mount+0xc4/0xe0
  [30.509186]        do_syscall_64+0x33/0x40
  [30.509652]        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [30.510271]
	      -> #0 (btrfs-free-space-00){++++}-{3:3}:
  [30.510972]        __lock_acquire+0x11ad/0x1b60
  [30.511432]        lock_acquire+0xa2/0x360
  [30.511917]        down_read_nested+0x43/0x150
  [30.512383]        __btrfs_tree_read_lock+0x39/0x180
  [30.512947]        __btrfs_read_lock_root_node+0x3a/0x50
  [30.513455]        btrfs_search_slot+0x464/0x9b0
  [30.513947]        search_free_space_info+0x45/0x90
  [30.514465]        __add_to_free_space_tree+0x92/0x39d
  [30.515010]        btrfs_create_free_space_tree.cold.22+0x1ee/0x45d
  [30.515639]        btrfs_mount_rw+0x15d/0x20f
  [30.516142]        btrfs_remount+0x356/0x433
  [30.516538]        reconfigure_super+0x9f/0x210
  [30.517065]        path_mount+0x9d1/0xa30
  [30.517438]        do_mount+0x55/0x70
  [30.517824]        __x64_sys_mount+0xc4/0xe0
  [30.518293]        do_syscall_64+0x33/0x40
  [30.518776]        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [30.519335]
	      other info that might help us debug this:

  [30.520210] Chain exists of:
		btrfs-free-space-00 --> btrfs-root-00 --> btrfs-extent-01#2

  [30.521407]  Possible unsafe locking scenario:

  [30.522037]        CPU0                    CPU1
  [30.522456]        ----                    ----
  [30.522941]   lock(btrfs-extent-01#2);
  [30.523311]                                lock(btrfs-root-00);
  [30.523952]                                lock(btrfs-extent-01#2);
  [30.524620]   lock(btrfs-free-space-00);
  [30.525068]
	       *** DEADLOCK ***

  [30.525669] 5 locks held by mount/520:
  [30.526116]  #0: ffff9babebc520e0 (&type->s_umount_key#37){+.+.}-{3:3}, at: path_mount+0x7ef/0xa30
  [30.527056]  #1: ffff9babebc52640 (sb_internal#2){.+.+}-{0:0}, at: start_transaction+0x3d5/0x5c0
  [30.527960]  #2: ffff9babeae8f2e8 (&cache->free_space_lock#2){+.+.}-{3:3}, at: btrfs_create_free_space_tree.cold.22+0x101/0x45d
  [30.529118]  #3: ffff9babebe24468 (btrfs-extent-01#2){++++}-{3:3}, at: __btrfs_tree_read_lock+0x39/0x180
  [30.530113]  #4: ffff9babebd52eb8 (btrfs-extent-00){++++}-{3:3}, at: btrfs_try_tree_read_lock+0x16/0x100
  [30.531124]
	      stack backtrace:
  [30.531528] CPU: 0 PID: 520 Comm: mount Not tainted 5.9.0-rc8+ #76
  [30.532166] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-4.module_el8.1.0+248+298dec18 04/01/2014
  [30.533215] Call Trace:
  [30.533452]  dump_stack+0x8d/0xc0
  [30.533797]  check_noncircular+0x13c/0x150
  [30.534233]  __lock_acquire+0x11ad/0x1b60
  [30.534667]  lock_acquire+0xa2/0x360
  [30.535063]  ? __btrfs_tree_read_lock+0x39/0x180
  [30.535525]  down_read_nested+0x43/0x150
  [30.535939]  ? __btrfs_tree_read_lock+0x39/0x180
  [30.536400]  __btrfs_tree_read_lock+0x39/0x180
  [30.536862]  __btrfs_read_lock_root_node+0x3a/0x50
  [30.537304]  btrfs_search_slot+0x464/0x9b0
  [30.537713]  ? trace_hardirqs_on+0x1c/0xf0
  [30.538148]  search_free_space_info+0x45/0x90
  [30.538572]  __add_to_free_space_tree+0x92/0x39d
  [30.539071]  ? printk+0x48/0x4a
  [30.539367]  btrfs_create_free_space_tree.cold.22+0x1ee/0x45d
  [30.539972]  btrfs_mount_rw+0x15d/0x20f
  [30.540350]  btrfs_remount+0x356/0x433
  [30.540773]  ? shrink_dcache_sb+0xd9/0x100
  [30.541203]  reconfigure_super+0x9f/0x210
  [30.541642]  path_mount+0x9d1/0xa30
  [30.542040]  do_mount+0x55/0x70
  [30.542366]  __x64_sys_mount+0xc4/0xe0
  [30.542822]  do_syscall_64+0x33/0x40
  [30.543197]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
  [30.543691] RIP: 0033:0x7f109f7ab93a
  [30.546042] RSP: 002b:00007ffc47c4f858 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
  [30.546770] RAX: ffffffffffffffda RBX: 00007f109f8cf264 RCX: 00007f109f7ab93a
  [30.547485] RDX: 0000557e6fc10770 RSI: 0000557e6fc19cf0 RDI: 0000557e6fc19cd0
  [30.548185] RBP: 0000557e6fc10520 R08: 0000557e6fc18e30 R09: 0000557e6fc18cb0
  [30.548911] R10: 0000000000200020 R11: 0000000000000246 R12: 0000000000000000
  [30.549606] R13: 0000557e6fc19cd0 R14: 0000557e6fc10770 R15: 0000557e6fc10520

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:09 +01:00
Boris Burkov
af456a2c0a btrfs: skip space_cache v1 setup when not using it
If we are not using space cache v1, we should not create the free space
object or free space inodes. This comes up when we delete the existing
free space objects/inodes when migrating to v2, only to see them get
recreated for every dirtied block group.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:09 +01:00
Boris Burkov
36b216c85e btrfs: remove free space items when disabling space cache v1
When the filesystem transitions from space cache v1 to v2 or to
nospace_cache, it removes the old cached data, but does not remove
the FREE_SPACE items nor the free space inodes they point to. This
doesn't cause any issues besides being a bit inefficient, since these
items no longer do anything useful.

To fix it, when we are mounting, and plan to disable the space cache,
destroy each block group's free space item and free space inode.
The code to remove the items is lifted from the existing use case of
removing the block group, with a light adaptation to handle whether or
not we have already looked up the free space inode.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:09 +01:00
Boris Burkov
2838d255cb btrfs: warn when remount will not change the free space tree
If the remount is ro->ro, rw->ro, or rw->rw, we will not create or
clear the free space tree. This can be surprising, so print a warning
to dmesg to make the failure more visible. It is also important to
ensure that the space cache options (SPACE_CACHE, FREE_SPACE_TREE) are
consistent, so ensure those are set to properly match the current on
disk state (which won't be changing).

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:08 +01:00
Boris Burkov
04c4155969 btrfs: use superblock state to print space_cache mount option
To make the contents of /proc/mounts better match the actual state of
the filesystem, base the display of the space cache mount options off
the contents of the super block rather than the last mount options
passed in. Since there are many scenarios where the mount will ignore a
space cache option, simply showing the passed in option is misleading.

For example, if we mount with -o remount,space_cache=v2 on a read-write
file system without an existing free space tree, we won't build a free
space tree, but /proc/mounts will read space_cache=v2 (until we mount
again and it goes away)

cache_generation is set iff space_cache=v1, FREE_SPACE_TREE is set iff
space_cache=v2, and if neither is the case, we print nospace_cache.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:08 +01:00
Boris Burkov
9484622945 btrfs: keep sb cache_generation consistent with space_cache
When mounting, btrfs uses the cache_generation in the super block to
determine if space cache v1 is in use. However, by mounting with
nospace_cache or space_cache=v2, it is possible to disable space cache
v1, which does not result in un-setting cache_generation back to 0.

In order to base some logic, like mount option printing in /proc/mounts,
on the current state of the space cache rather than just the values of
the mount option, keep the value of cache_generation consistent with the
status of space cache v1.

We ensure that cache_generation > 0 iff the file system is using
space_cache v1. This requires committing a transaction on any mount
which changes whether we are using v1. (v1->nospace_cache, v1->v2,
nospace_cache->v1, v2->v1).

Since the mechanism for writing out the cache generation is transaction
commit, but we want some finer grained control over when we un-set it,
we can't just rely on the SPACE_CACHE mount option, and introduce an
fs_info flag that mount can use when it wants to unset the generation.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:08 +01:00
Boris Burkov
8b228324a8 btrfs: clear free space tree on ro->rw remount
A user might want to revert to v1 or nospace_cache on a root filesystem,
and much like turning on the free space tree, that can only be done
remounting from ro->rw. Support clearing the free space tree on such
mounts by moving it into the shared remount logic.

Since the CLEAR_CACHE option sticks around across remounts, this change
would result in clearing the tree for ever on every remount, which is
not desirable. To fix that, add CLEAR_CACHE to the oneshot options we
clear at mount end, which has the other bonus of not cluttering the
/proc/mounts output with clear_cache.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:08 +01:00
Boris Burkov
8cd2908846 btrfs: clear oneshot options on mount and remount
Some options only apply during mount time and are cleared at the end
of mount. For now, the example is USEBACKUPROOT, but CLEAR_CACHE also
fits the bill, and this is a preparation patch for also clearing that
option.

One subtlety is that the current code only resets USEBACKUPROOT on rw
mounts, but the option is meaningfully "consumed" by a ro mount, so it
feels appropriate to clear in that case as well. A subsequent read-write
remount would not go through open_ctree, which is the only place that
checks the option, so the change should be benign.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:08 +01:00
Boris Burkov
5011139a47 btrfs: create free space tree on ro->rw remount
When a user attempts to remount a btrfs filesystem with
'mount -o remount,space_cache=v2', that operation silently succeeds.
Unfortunately, this is misleading, because the remount does not create
the free space tree. /proc/mounts will incorrectly show space_cache=v2,
but on the next mount, the file system will revert to the old
space_cache.

For now, we handle only the easier case, where the existing mount is
read-only and the new mount is read-write. In that case, we can create
the free space tree without contending with the block groups changing
as we go.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:07 +01:00
Boris Burkov
997e3e2e71 btrfs: only mark bg->needs_free_space if free space tree is on
If we attempt to create a free space tree while any block groups have
needs_free_space set, we will double add the new free space item
and hit EEXIST. Previously, we only created the free space tree on a new
mount, so we never hit the case, but if we try to create it on a
remount, such block groups could exist and trip us up.

We don't do anything with this field unless the free space tree is
enabled, so there is no harm in not setting it.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:07 +01:00
Boris Burkov
8f1c21d749 btrfs: start orphan cleanup on ro->rw remount
When we mount a rw filesystem, we start the orphan cleanup process in
tree root and filesystem tree. However, when we remount a ro file system
rw, we only clean the former. Move the calls to btrfs_orphan_cleanup()
on tree_root and fs_root to the shared rw mount routine to effectively
add them on ro->rw remount.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:07 +01:00
Boris Burkov
44c0ca211a btrfs: lift read-write mount setup from mount and remount
Mounting rw and remounting from ro to rw naturally share invariants and
functionality which result in a correctly setup rw filesystem. Luckily,
there is even a strong unity in the code which implements them. In
mount's open_ctree, these operations mostly happen after an early return
for ro file systems, and in remount, they happen in a section devoted to
remounting ro->rw, after some remount specific validation passes.

However, there are unfortunately a few differences. There are small
deviations in the order of some of the operations, remount does not
start orphan cleanup in root_tree or fs_tree, remount does not create
the free space tree, and remount does not handle "one-shot" mount
options like clear_cache and uuid tree rescan.

Since we want to add building the free space tree to remount, and also
to start the same orphan cleanup process on a filesystem mounted as ro
then remounted rw, we would benefit from unifying the logic between the
two code paths.

This patch only lifts the existing common functionality, and leaves a
natural path for fixing the discrepancies.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:07 +01:00
Filipe Manana
47876f7cef btrfs: do not block inode logging for so long during transaction commit
Early on during a transaction commit we acquire the tree_log_mutex and
hold it until after we write the super blocks. But before writing the
extent buffers dirtied by the transaction and the super blocks we unblock
the transaction by setting its state to TRANS_STATE_UNBLOCKED and setting
fs_info->running_transaction to NULL.

This means that after that and before writing the super blocks, new
transactions can start. However if any transaction wants to log an inode,
it will block waiting for the transaction commit to write its dirty
extent buffers and the super blocks because the tree_log_mutex is only
released after those operations are complete, and starting a new log
transaction blocks on that mutex (at start_log_trans()).

Writing the dirty extent buffers and the super blocks can take a very
significant amount of time to complete, but we could allow the tasks
wanting to log an inode to proceed with most of their steps:

1) create the log trees
2) log metadata in the trees
3) write their dirty extent buffers

They only need to wait for the previous transaction commit to complete
(write its super blocks) before they attempt to write their super blocks,
otherwise we could end up with a corrupt filesystem after a crash.

So change start_log_trans() to use the root tree's log_mutex to serialize
for the creation of the log root tree instead of using the tree_log_mutex,
and make btrfs_sync_log() acquire the tree_log_mutex before writing the
super blocks. This allows for inode logging to wait much less time when
there is a previous transaction that is still committing, often not having
to wait at all, as by the time when we try to sync the log the previous
transaction already wrote its super blocks.

This patch belongs to a patch set that is comprised of the following
patches:

  btrfs: fix race causing unnecessary inode logging during link and rename
  btrfs: fix race that results in logging old extents during a fast fsync
  btrfs: fix race that causes unnecessary logging of ancestor inodes
  btrfs: fix race that makes inode logging fallback to transaction commit
  btrfs: fix race leading to unnecessary transaction commit when logging inode
  btrfs: do not block inode logging for so long during transaction commit

The following script that uses dbench was used to measure the impact of
the whole patchset:

  $ cat test-dbench.sh
  #!/bin/bash

  DEV=/dev/nvme0n1
  MNT=/mnt/btrfs
  MOUNT_OPTIONS="-o ssd"

  echo "performance" | \
      tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

  mkfs.btrfs -f -m single -d single $DEV
  mount $MOUNT_OPTIONS $DEV $MNT

  dbench -D $MNT -t 300 64

  umount $MNT

The test was run on a machine with 12 cores, 64G of ram, using a NVMe
device and a non-debug kernel configuration (Debian's default).

Before patch set:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    11277211    0.250    85.340
 Close        8283172     0.002     6.479
 Rename        477515     1.935    86.026
 Unlink       2277936     0.770    87.071
 Deltree          256    15.732    81.379
 Mkdir            128     0.003     0.009
 Qpathinfo    10221180    0.056    44.404
 Qfileinfo    1789967     0.002     4.066
 Qfsinfo      1874399     0.003     9.176
 Sfileinfo     918589     0.061    10.247
 Find         3951758     0.341    54.040
 WriteX       5616547     0.047    85.079
 ReadX        17676028    0.005     9.704
 LockX          36704     0.003     1.800
 UnlockX        36704     0.002     0.687
 Flush         790541    14.115   676.236

Throughput 1179.19 MB/sec  64 clients  64 procs  max_latency=676.240 ms

After patch set:

Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    12687926    0.171    86.526
 Close        9320780     0.002     8.063
 Rename        537253     1.444    78.576
 Unlink       2561827     0.559    87.228
 Deltree          374    11.499    73.549
 Mkdir            187     0.003     0.005
 Qpathinfo    11500300    0.061    36.801
 Qfileinfo    2017118     0.002     7.189
 Qfsinfo      2108641     0.003     4.825
 Sfileinfo    1033574     0.008     8.065
 Find         4446553     0.408    47.835
 WriteX       6335667     0.045    84.388
 ReadX        19887312    0.003     9.215
 LockX          41312     0.003     1.394
 UnlockX        41312     0.002     1.425
 Flush         889233    13.014   623.259

Throughput 1339.32 MB/sec  64 clients  64 procs  max_latency=623.265 ms

+12.7% throughput, -8.2% max latency

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:07 +01:00
Filipe Manana
639bd575b7 btrfs: fix race leading to unnecessary transaction commit when logging inode
When logging an inode we may often have to fallback to a full transaction
commit, either because a new block group was allocated, there is some case
we can not deal with without a transaction commit or some error like an
ENOMEM happened. However after we fallback to a transaction commit, we
have a time window where we can make the next attempt to log any inode
commit the next transaction unnecessarily, adding additional overhead and
increasing latency.

A sequence of steps that leads to this issue is the following:

1) The current open transaction has a generation of 1000;

2) A new block group is allocated, and as a consequence we must make sure
   any attempts to commit a log fallback to a transaction commit, so
   btrfs_set_log_full_commit() is called from btrfs_make_block_group().
   This sets fs_info->last_trans_log_full_commit to 1000;

3) Task A is holding a handle on transaction 1000 and tries to log inode X.
   Once it gets to start_log_trans(), it calls btrfs_need_log_full_commit()
   which returns true, since fs_info->last_trans_log_full_commit has a
   value of 1000. So we end up returning EAGAIN and propagating it up to
   btrfs_sync_file(), where we commit transaction 1000;

4) The transaction commit task (task A) sets the transaction state to
   unblocked (TRANS_STATE_UNBLOCKED);

5) Some other task, task B, starts a new transaction with a generation of
   1001;

6) Some stuff is done with transaction 1001, some btree blocks COWed, etc;

7) Transaction 1000 has not fully committed yet, we are still writing all
   the extent buffers it created;

8) Some new task, task C, starts an fsync of inode Y, gets a handle for
   transaction 1001, and it gets to btrfs_log_inode_parent() which does
   the following check:

     if (fs_info->last_trans_log_full_commit > last_committed) {
         ret = 1;
         goto end_no_trans;
     }

   At that point last_trans_log_full_commit has a value of 1000 and
   last_committed (value of fs_info->last_trans_committed) has a value of
   999, since transaction 1000 has not yet committed - it is either still
   writing out dirty extent buffers, its super blocks or unpinning
   extents.

   As a consequence we return 1, which gets propagated up to
   btrfs_sync_file(), which will then call btrfs_commit_transaction()
   for transaction 1001.

   As a consequence we have an unnecessary second transaction commit, we
   previously committed transaction 1000 and now commit transaction 1001
   as well, resulting in more overhead and increased latency.

So fix this double transaction commit issue simply by removing that check,
because all we need to do is wait for the previous transaction to finish
its commit, which we already do later when starting the log transaction at
start_log_trans(), because there we acquire the tree_log_mutex lock, which
is held by a transaction commit and only released after the transaction
commits its super blocks.

Another issue that check has is that it reads last_trans_log_full_commit
without using READ_ONCE(), which is incorrect since that member of
struct btrfs_fs_info is always updated with WRITE_ONCE() through the
helper btrfs_set_log_full_commit().

This double transaction commit issue can actually be triggered quite often
in long runs of dbench, since besides the creation of new block groups
that force inode logging to fallback to a transaction commit, there are
cases where dbench asks to fsync a directory which had files in it that
were previously renamed or subdirectories that were removed, resulting in
the inode logging to fallback to a full transaction commit.

This patch belongs to a patch set that is comprised of the following
patches:

  btrfs: fix race causing unnecessary inode logging during link and rename
  btrfs: fix race that results in logging old extents during a fast fsync
  btrfs: fix race that causes unnecessary logging of ancestor inodes
  btrfs: fix race that makes inode logging fallback to transaction commit
  btrfs: fix race leading to unnecessary transaction commit when logging inode
  btrfs: do not block inode logging for so long during transaction commit

Performance results are mentioned in the change log of the last patch.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:07 +01:00
Filipe Manana
47d3db41e1 btrfs: fix race that makes inode logging fallback to transaction commit
When logging an inode and the previous transaction is still committing, we
have a time window where we can end up incorrectly think an inode has its
last_unlink_trans field with a value greater than the last transaction
committed, which results in the logging to fallback to a full transaction
commit, which is usually much more expensive than doing a log commit.

The race is described by the following steps:

1) We are at transaction 1000;

2) We modify an inode X (a directory) using transaction 1000 and set its
   last_unlink_trans field to 1000, because for example we removed one
   of its subdirectories;

3) We create a new inode Y with a dentry in inode X using transaction 1000,
   so its generation field is set to 1000;

4) The commit for transaction 1000 is started by task A;

5) The task committing transaction 1000 sets the transaction state to
   unblocked, writes the dirty extent buffers and the super blocks, then
   unlocks tree_log_mutex;

6) Some task starts a new transaction with a generation of 1001;

7) We do some modification to inode Y (using transaction 1001);

8) The transaction 1000 commit starts unpinning extents. At this point
   fs_info->last_trans_committed still has a value of 999;

9) Task B starts an fsync on inode Y, and gets a handle for transaction
   1001. When it gets to check_parent_dirs_for_sync() it does the checking
   of the ancestor dentries because the following check does not evaluate
   to true:

       if (S_ISREG(inode->vfs_inode.i_mode) &&
           inode->generation <= last_committed &&
           inode->last_unlink_trans <= last_committed)
               goto out;

   The generation value for inode Y is 1000 and last_committed, which has
   the value read from fs_info->last_trans_committed, has a value of 999,
   so that check evaluates to false and we proceed to check the ancestor
   inodes.

   Once we get to the first ancestor, inode X, we call
   btrfs_must_commit_transaction() on it, which evaluates to true:

   static bool btrfs_must_commit_transaction(...)
   {
       struct btrfs_fs_info *fs_info = inode->root->fs_info;
       bool ret = false;

       mutex_lock(&inode->log_mutex);
       if (inode->last_unlink_trans > fs_info->last_trans_committed) {
           /*
            * Make sure any commits to the log are forced to be full
            * commits.
            */
            btrfs_set_log_full_commit(trans);
            ret = true;
       }
    (...)

    because inode's X last_unlink_trans has a value of 1000 and
    fs_info->last_trans_committed still has a value of 999, it returns
    true to check_parent_dirs_for_sync(), making it return 1 which is
    propagated up to btrfs_sync_file(), causing it to fallback to a full
    transaction commit of transaction 1001.

    We should have not fallen back to commit transaction 1001, since inode
    X had last_unlink_trans set to 1000 and the super blocks for
    transaction 1000 were already written. So while not resulting in a
    functional problem, it leads to a lot more work and higher latencies
    for a fsync since committing a transaction is usually more expensive
    than committing a log (if other filesystem changes happened under that
    transaction).

Similar problem happens when logging directories, for the same reason as
btrfs_must_commit_transaction() returns true on an inode with its
last_unlink_trans having the generation of the previous transaction and
that transaction is still committing, unpinning its freed extents.

So fix this by comparing last_unlink_trans with the id of the current
transaction instead of fs_info->last_trans_committed.

This case is often hit when running dbench for a long enough duration, as
it does lots of rename and rmdir operations (both update the field
last_unlink_trans of an inode) and fsyncs of files and directories.

This patch belongs to a patch set that is comprised of the following
patches:

  btrfs: fix race causing unnecessary inode logging during link and rename
  btrfs: fix race that results in logging old extents during a fast fsync
  btrfs: fix race that causes unnecessary logging of ancestor inodes
  btrfs: fix race that makes inode logging fallback to transaction commit
  btrfs: fix race leading to unnecessary transaction commit when logging inode
  btrfs: do not block inode logging for so long during transaction commit

Performance results are mentioned in the change log of the last patch.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:06 +01:00
Filipe Manana
4d6221d7d8 btrfs: fix race that causes unnecessary logging of ancestor inodes
When logging an inode and we are checking if we need to log ancestors that
are new, if the previous transaction is still committing we have a time
window where we can unnecessarily log ancestor inodes that were created in
the previous transaction.

The race is described by the following steps:

1) We are at transaction 1000;

2) Directory inode X is created, its generation is set to 1000;

3) The commit for transaction 1000 is started by task A;

4) The task committing transaction 1000 sets the transaction state to
   unblocked, writes the dirty extent buffers and the super blocks, then
   unlocks tree_log_mutex;

5) Inode Y, a regular file, is created under directory inode X, this
   results in starting a new transaction with a generation of 1001;

6) The transaction 1000 commit is unpinning extents. At this point
   fs_info->last_trans_committed still has a value of 999;

7) Task B calls fsync on inode Y and gets a handle for transaction 1001;

8) Task B ends up at log_all_new_ancestors() and then because inode Y has
   only one hard link, ends up at log_new_ancestors_fast(). There it reads
   a value of 999 from fs_info->last_trans_committed, and sees that the
   parent inode X has a generation of 1000, so we end up logging inode X:

     if (inode->generation > fs_info->last_trans_committed) {
         ret = btrfs_log_inode(trans, root, inode,
                               LOG_INODE_EXISTS, ctx);
         (...)

   which is not necessary since it was created in the past transaction,
   with a generation of 1000, and that transaction has already committed
   its super blocks - it's still unpinning extents so it has not yet
   updated fs_info->last_trans_committed from 999 to 1000.

   So this just causes us to spend more time logging and allocating and
   writing more tree blocks for the log tree.

So fix this by comparing an inode's generation with the generation of the
transaction our transaction handle refers to - if the inode's generation
matches the generation of the current transaction than we know it is a
new inode we need to log, otherwise don't log it.

This case is often hit when running dbench for a long enough duration.

This patch belongs to a patch set that is comprised of the following
patches:

  btrfs: fix race causing unnecessary inode logging during link and rename
  btrfs: fix race that results in logging old extents during a fast fsync
  btrfs: fix race that causes unnecessary logging of ancestor inodes
  btrfs: fix race that makes inode logging fallback to transaction commit
  btrfs: fix race leading to unnecessary transaction commit when logging inode
  btrfs: do not block inode logging for so long during transaction commit

Performance results are mentioned in the change log of the last patch.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:06 +01:00
Filipe Manana
5f96bfb763 btrfs: fix race that results in logging old extents during a fast fsync
When logging the extents of an inode during a fast fsync, we have a time
window where we can log extents that are from the previous transaction and
already persisted. This only makes us waste time unnecessarily.

The following sequence of steps shows how this can happen:

1) We are at transaction 1000;

2) An ordered extent E from inode I completes, that is it has gone through
   btrfs_finish_ordered_io(), and it set the extent maps' generation to
   1000 when we unpin the extent, which is the generation of the current
   transaction;

3) The commit for transaction 1000 starts by task A;

4) The task committing transaction 1000 sets the transaction state to
   unblocked, writes the dirty extent buffers and the super blocks, then
   unlocks tree_log_mutex;

5) Some change is made to inode I, resulting in creation of a new
   transaction with a generation of 1001;

6) The transaction 1000 commit starts unpinning extents. At this point
   fs_info->last_trans_committed still has a value of 999;

7) Task B starts an fsync on inode I, and when it gets to
   btrfs_log_changed_extents() sees the extent map for extent E in the
   list of modified extents. It sees the extent map has a generation of
   1000 and fs_info->last_trans_committed has a value of 999, so it
   proceeds to logging the respective file extent item and all the
   checksums covering its range.

   So we end up wasting time since the extent was already persisted and
   is reachable through the trees pointed to by the super block committed
   by transaction 1000.

So just fix this by comparing the extent maps generation against the
generation of the transaction handle - if it is smaller then the id in the
handle, we know the extent was already persisted and we do not need to log
it.

This patch belongs to a patch set that is comprised of the following
patches:

  btrfs: fix race causing unnecessary inode logging during link and rename
  btrfs: fix race that results in logging old extents during a fast fsync
  btrfs: fix race that causes unnecessary logging of ancestor inodes
  btrfs: fix race that makes inode logging fallback to transaction commit
  btrfs: fix race leading to unnecessary transaction commit when logging inode
  btrfs: do not block inode logging for so long during transaction commit

Performance results are mentioned in the change log of the last patch.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:06 +01:00
Filipe Manana
de53d892e5 btrfs: fix race causing unnecessary inode logging during link and rename
When we are doing a rename or a link operation for an inode that was logged
in the previous transaction and that transaction is still committing, we
have a time window where we incorrectly consider that the inode was logged
previously in the current transaction and therefore decide to log it to
update it in the log. The following steps give an example on how this
happens during a link operation:

1) Inode X is logged in transaction 1000, so its logged_trans field is set
   to 1000;

2) Task A starts to commit transaction 1000;

3) The state of transaction 1000 is changed to TRANS_STATE_UNBLOCKED;

4) Task B starts a link operation for inode X, and as a consequence it
   starts transaction 1001;

5) Task A is still committing transaction 1000, therefore the value stored
   at fs_info->last_trans_committed is still 999;

6) Task B calls btrfs_log_new_name(), it reads a value of 999 from
   fs_info->last_trans_committed and because the logged_trans field of
   inode X has a value of 1000, the function does not return immediately,
   instead it proceeds to logging the inode, which should not happen
   because the inode was logged in the previous transaction (1000) and
   not in the current one (1001).

This is not a functional problem, just wasted time and space logging an
inode that does not need to be logged, contributing to higher latency
for link and rename operations.

So fix this by comparing the inodes' logged_trans field with the
generation of the current transaction instead of comparing with the value
stored in fs_info->last_trans_committed.

This case is often hit when running dbench for a long enough duration, as
it does lots of rename operations.

This patch belongs to a patch set that is comprised of the following
patches:

  btrfs: fix race causing unnecessary inode logging during link and rename
  btrfs: fix race that results in logging old extents during a fast fsync
  btrfs: fix race that causes unnecessary logging of ancestor inodes
  btrfs: fix race that makes inode logging fallback to transaction commit
  btrfs: fix race leading to unnecessary transaction commit when logging inode
  btrfs: do not block inode logging for so long during transaction commit

Performance results are mentioned in the change log of the last patch.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:06 +01:00
David Sterba
fa598b0696 btrfs: remove recalc_thresholds from free space ops
After removing the inode number cache that was using the free space
cache code, we can remove at least the recalc_thresholds callback from
the ops. Both code and tests use the same callback function. It's moved
before its first use.

The use_bitmaps callback is still needed by tests to create some
extents/bitmap setup.

Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:06 +01:00
Nikolay Borisov
f0d1219def btrfs: always set NODATASUM/NODATACOW in __create_free_space_inode
Since it's being used solely for the freespace cache unconditionally
set the flags required for it.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:06 +01:00
Nikolay Borisov
7dbdb443a7 btrfs: remove crc_check logic from free space
Following removal of the ino cache io_ctl_init will be called only on
behalf of the freespace inode. In this case we always want to check
CRCs so conditional code that depended on io_ctl::check_crc can be
removed.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:05 +01:00
Nikolay Borisov
5297199a8b btrfs: remove inode number cache feature
It's been deprecated since commit b547a88ea5 ("btrfs: start
deprecation of mount option inode_cache") which enumerates the reasons.

A filesystem that uses the feature (mount -o inode_cache) tracks the
inode numbers in bitmaps, that data stay on the filesystem after this
patch. The size is roughly 5MiB for 1M inodes [1], which is considered
small enough to be left there. Removal of the change can be implemented
in btrfs-progs if needed.

[1] https://lore.kernel.org/linux-btrfs/20201127145836.GZ6430@twin.jikos.cz/

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:05 +01:00
Nikolay Borisov
abadc1fcd7 btrfs: replace calls to btrfs_find_free_ino with btrfs_find_free_objectid
The former is going away as part of the inode map removal so switch
callers to btrfs_find_free_objectid. No functional changes since with
INODE_MAP disabled (default) find_free_objectid was called anyway.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:05 +01:00
Nikolay Borisov
ec7d6dfd73 btrfs: move btrfs_find_highest_objectid/btrfs_find_free_objectid to disk-io.c
Those functions are going to be used even after inode cache is removed
so moved them to a more appropriate place.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:05 +01:00
David Sterba
1201b58b67 btrfs: drop casts of bio bi_sector
Since commit 72deb455b5 ("block: remove CONFIG_LBDAF") (5.2) the
sector_t type is u64 on all arches and configs so we don't need to
typecast it.  It used to be unsigned long and the result of sector size
shifts were not guaranteed to fit in the type.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:05 +01:00
Naohiro Aota
12659251ca btrfs: implement log-structured superblock for ZONED mode
Superblock (and its copies) is the only data structure in btrfs which
has a fixed location on a device. Since we cannot overwrite in a
sequential write required zone, we cannot place superblock in the zone.
One easy solution is limiting superblock and copies to be placed only in
conventional zones.  However, this method has two downsides: one is
reduced number of superblock copies. The location of the second copy of
superblock is 256GB, which is in a sequential write required zone on
typical devices in the market today.  So, the number of superblock and
copies is limited to be two.  Second downside is that we cannot support
devices which have no conventional zones at all.

To solve these two problems, we employ superblock log writing. It uses
two adjacent zones as a circular buffer to write updated superblocks.
Once the first zone is filled up, start writing into the second one.
Then, when both zones are filled up and before starting to write to the
first zone again, it reset the first zone.

We can determine the position of the latest superblock by reading write
pointer information from a device. One corner case is when both zones
are full. For this situation, we read out the last superblock of each
zone, and compare them to determine which zone is older.

The following zones are reserved as the circular buffer on ZONED btrfs.

- The primary superblock: zones 0 and 1
- The first copy: zones 16 and 17
- The second copy: zones 1024 or zone at 256GB which is minimum, and
  next to it

If these reserved zones are conventional, superblock is written fixed at
the start of the zone without logging.

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:04 +01:00
Naohiro Aota
a589dde0bc btrfs: disallow mixed-bg in ZONED mode
Placing both data and metadata in a block group is impossible in ZONED
mode. For data, we can allocate a space for it and write it immediately
after the allocation. For metadata, however, we cannot do that, because
the logical addresses are recorded in other metadata buffers to build up
the trees. As a result, a data buffer can be placed after a metadata
buffer, which is not written yet. Writing out the data buffer will break
the sequential write rule.

Check and disallow MIXED_BG with ZONED mode.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:04 +01:00
Naohiro Aota
f1569c4c10 btrfs: disable fallocate in ZONED mode
fallocate() is implemented by reserving actual extent instead of
reservations. This can result in exposing the sequential write
constraint of host-managed zoned block devices to the application, which
would break the POSIX semantic for the fallocated file.  To avoid this,
report fallocate() as not supported when in ZONED mode for now.

In the future, we may be able to implement "in-memory" fallocate() in
ZONED mode by utilizing space_info->bytes_may_use or similar, so this
returns EOPNOTSUPP.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:04 +01:00
Naohiro Aota
d206e9c9c5 btrfs: disallow NODATACOW in ZONED mode
NODATACOW implies overwriting the file data on a device, which is
impossible in sequential required zones. Disable NODATACOW globally with
mount option and per-file NODATACOW attribute by masking FS_NOCOW_FL.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:04 +01:00
Naohiro Aota
5d1ab66c56 btrfs: disallow space_cache in ZONED mode
As updates to the space cache v1 are in-place, the space cache cannot be
located over sequential zones and there is no guarantees that the device
will have enough conventional zones to store this cache. Resolve this
problem by disabling completely the space cache v1.  This does not
introduce any problems with sequential block groups: all the free space
is located after the allocation pointer and no free space before the
pointer.  There is no need to have such cache.

Note: we can technically use free-space-tree (space cache v2) on ZONED
mode. But, since ZONED mode now always allocates extents in a block
group sequentially regardless of underlying device zone type, it's no
use to enable and maintain the tree.

For the same reason, NODATACOW is also disabled.

In summary, ZONED will disable:

| Disabled features | Reason                                              |
|-------------------+-----------------------------------------------------|
| RAID/DUP          | Cannot handle two zone append writes to different   |
|                   | zones                                               |
|-------------------+-----------------------------------------------------|
| space_cache (v1)  | In-place updating                                   |
| NODATACOW         | In-place updating                                   |
|-------------------+-----------------------------------------------------|
| fallocate         | Reserved extent will be a write hole                |
|-------------------+-----------------------------------------------------|
| MIXED_BG          | Allocated metadata region will be write holes for   |
|                   | data writes                                         |

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:04 +01:00
Naohiro Aota
862931c763 btrfs: introduce max_zone_append_size
The zone append write command has a maximum IO size restriction it
accepts. This is because a zone append write command cannot be split, as
we ask the device to place the data into a specific target zone and the
device responds with the actual written location of the data.

Introduce max_zone_append_size to zone_info and fs_info to track the
value, so we can limit all I/O to a zoned block device that we want to
write using the zone append command to the device's limits.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:04 +01:00
Naohiro Aota
b70f509774 btrfs: check and enable ZONED mode
Introduce function btrfs_check_zoned_mode() to check if ZONED flag is
enabled on the file system and if the file system consists of zoned
devices with equal zone size.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:16:03 +01:00
Naohiro Aota
5b31646898 btrfs: get zone information of zoned block devices
If a zoned block device is found, get its zone information (number of
zones and zone size).  To avoid costly run-time zone report
commands to test the device zones type during block allocation, attach
the seq_zones bitmap to the device structure to indicate if a zone is
sequential or accept random writes. Also it attaches the empty_zones
bitmap to indicate if a zone is empty or not.

This patch also introduces the helper function btrfs_dev_is_sequential()
to test if the zone storing a block is a sequential write required zone
and btrfs_dev_is_empty_zone() to test if the zone is a empty zone.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-09 19:15:57 +01:00
Naohiro Aota
7b3d5a90cb btrfs: introduce ZONED feature flag
This patch introduces the ZONED incompat flag. The flag indicates that
the volume management will satisfy the constraints imposed by
host-managed zoned block devices (aligned chunk allocation, append-only
updates, reset zone after filled).

As the zoned support will happen incrementally due to enhancing some
core infrastructure like super block writes, tree-log, raid support, the
feature will appear in sysfs only on debug builds. It will be enabled
once the support is feature complete and applications can reliably check
whether zoned support is present or not.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:16 +01:00
Nikolay Borisov
a2633b6a29 btrfs: return bool from btrfs_should_end_transaction
Results in slightly smaller code.

add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-11 (-11)
Function                                     old     new   delta
btrfs_should_end_transaction                  96      85     -11
Total: Before=20070, After=20059, chg -0.05%

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:16 +01:00
Nikolay Borisov
8a8f4deaba btrfs: return bool from should_end_transaction
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:15 +01:00
Nikolay Borisov
8df01fddb7 btrfs: remove err variable from do_relocation
It simply gets assigned to 'ret' in case of errors. The flow of the
while loop is not changed by this commit since the few call sites
that 'goto next' will simply break from the loop.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:15 +01:00
Nikolay Borisov
c6a592f2e2 btrfs: eliminate err variable from merge_reloc_root
In most cases when an error is returned from a function 'ret' is simply
assigned to 'err'. There is only one case where walk_up_reloc_tree can
return a positive value - in this case the code breaks from the loop and
ret is going to get its return value from btrfs_cow_block - either 0 or
negative. This retains the old logic of how 'err' used to be set at
this call site.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:15 +01:00
Nikolay Borisov
ee0d904fd9 btrfs: remove err variable from btrfs_delete_subvolume
Use only a single 'ret' to control whether we should abort the
transaction or not. That's fine, because if we abort a transaction then
btrfs_end_transaction will return the same value as passed to
btrfs_abort_transaction. No semantic changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:15 +01:00
Filipe Manana
c65ca98f9e btrfs: unlock path before checking if extent is shared during nocow writeback
When we are attempting to start writeback for an existing extent in NOCOW
mode, at run_delalloc_nocow(), we must check if the extent is shared, and
if it is, fallback to a COW write. However we do such check while still
holding a read lock on the leaf that contains the file extent item, and
that check, the call to btrfs_cross_ref_exist(), can take some time
because:

1) It needs to do a search on the extent tree, which obviously takes some
   time, specially if delayed references are being run at the moment, as
   we can block when trying to lock currently write locked btree nodes;

2) It needs to check the delayed references for any existing reference
   for our data extent, this requires acquiring the delayed references'
   spinlock and maybe block on the mutex of a delayed reference head in the
   case where there is a delayed reference for our data extent, in the
   worst case it makes us release the path on the extent tree and retry
   the whole process again (going back to step 1).

There are other operations we do while holding the leaf locked that can
take some significant time as well (specially all together):

* btrfs_extent_readonly() - to check if the block group containing the
  extent is currently in RO mode. This requires taking a spinlock and
  searching for the block group in a rbtree that can be big on large
  filesystems;

* csum_exist_in_range() - to search if there are any checksums in the
  csum tree for the extent. Like before, this can take some time if we are
  in a filesystem that has both COW and NOCOW files, in which case the
  csum tree is not empty;

* btrfs_inc_nocow_writers() - increment the number of nocow writers in the
  block group that contains the data extent. Needs to acquire a spinlock
  and search for the block group in a rbtree that can be big on large
  filesystems.

So just unlock the leaf (release the path) before doing all those checks,
since we do not need it anymore. In case we can not do a NOCOW write for
the extent, due to any of those checks failing, and the writeback range
goes beyond that extents' length, we will do another btree search for the
next file extent item.

The following script that calls dbench was used to measure the impact of
this change on a VM with 8 CPUs, 16Gb of ram, using a raw NVMe device
directly (no intermediary filesystem on the host) and using a non-debug
kernel (default configuration on Debian):

  $ cat test-dbench.sh
  #!/bin/bash

  DEV=/dev/sdk
  MNT=/mnt/sdk
  MOUNT_OPTIONS="-o ssd -o nodatacow"
  MKFS_OPTIONS="-m single -d single"

  mkfs.btrfs -f $MKFS_OPTIONS $DEV
  mount $MOUNT_OPTIONS $DEV $MNT

  dbench -D $MNT -t 300 64

  umount $MNT

Before this change:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    9326331     0.317   399.957
 Close        6851198     0.002     6.402
 Rename        394894     2.621   402.819
 Unlink       1883131     0.931   398.082
 Deltree          256    19.160   303.580
 Mkdir            128     0.003     0.016
 Qpathinfo    8452314     0.068   116.133
 Qfileinfo    1481921     0.001     5.081
 Qfsinfo      1549963     0.002     4.444
 Sfileinfo     759679     0.084    17.079
 Find         3268168     0.396   118.196
 WriteX       4653310     0.056   110.993
 ReadX        14618818     0.005    23.314
 LockX          30364     0.003     0.497
 UnlockX        30364     0.002     1.720
 Flush         653619    16.954   569.299

Throughput 966.651 MB/sec  64 clients  64 procs  max_latency=569.377 ms

After this change:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    9710433     0.302   232.449
 Close        7132948     0.002    11.496
 Rename        411144     2.452   131.805
 Unlink       1960961     0.893   230.383
 Deltree          256    14.858   198.646
 Mkdir            128     0.002     0.005
 Qpathinfo    8800890     0.066   111.588
 Qfileinfo    1542556     0.001     3.852
 Qfsinfo      1613835     0.002     5.483
 Sfileinfo     790871     0.081    19.492
 Find         3402743     0.386   120.185
 WriteX       4842918     0.054   179.312
 ReadX        15220407     0.005    32.435
 LockX          31612     0.003     1.533
 UnlockX        31612     0.002     1.047
 Flush         680567    16.320   463.323

Throughput 1016.59 MB/sec  64 clients  64 procs  max_latency=463.327 ms

+5.0% throughput, -20.5% max latency

Also, the following test using fio was run:

  $ cat test-fio.sh
  #!/bin/bash

  DEV=/dev/sdk
  MNT=/mnt/sdk
  MOUNT_OPTIONS="-o ssd -o nodatacow"
  MKFS_OPTIONS="-d single -m single"

  if [ $# -ne 4 ]; then
      echo "Use $0 NUM_JOBS FILE_SIZE FSYNC_FREQ BLOCK_SIZE"
      exit 1
  fi

  NUM_JOBS=$1
  FILE_SIZE=$2
  FSYNC_FREQ=$3
  BLOCK_SIZE=$4

  cat <<EOF > /tmp/fio-job.ini
  [writers]
  rw=randwrite
  fsync=$FSYNC_FREQ
  fallocate=none
  group_reporting=1
  direct=0
  bs=$BLOCK_SIZE
  ioengine=sync
  size=$FILE_SIZE
  directory=$MNT
  numjobs=$NUM_JOBS
  EOF

  echo
  echo "Using fio config:"
  echo
  cat /tmp/fio-job.ini
  echo
  echo "mount options: $MOUNT_OPTIONS"
  echo

  mkfs.btrfs -f $MKFS_OPTIONS $DEV > /dev/null
  mount $MOUNT_OPTIONS $DEV $MNT

  echo "Creating nodatacow files before fio runs..."
  for ((i = 0; i < $NUM_JOBS; i++)); do
      xfs_io -f -c "pwrite -b 128M 0 $FILE_SIZE" "$MNT/writers.$i.0"
  done
  sync

  fio /tmp/fio-job.ini
  umount $MNT

Before this change:

$ ./test-fio.sh 16 512M 2 4K
(...)
WRITE: bw=28.3MiB/s (29.6MB/s), 28.3MiB/s-28.3MiB/s (29.6MB/s-29.6MB/s), io=8192MiB (8590MB), run=289800-289800msec

After this change:

$ ./test-fio.sh 16 512M 2 4K
(...)
WRITE: bw=31.2MiB/s (32.7MB/s), 31.2MiB/s-31.2MiB/s (32.7MB/s-32.7MB/s), io=8192MiB (8590MB), run=262845-262845msec

+9.7% throughput, -9.8% runtime

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:15 +01:00
David Sterba
c7c01a4a25 btrfs: tree-checker: annotate all error branches as unlikely
The tree checker is called many times as it verifies metadata at
read/write time. The checks follow a simple pattern:

  if (error_condition) {
	  report_error();
	  return -EUCLEAN;
  }

All the error reporting functions are annotated as __cold that is
supposed to hint the compiler to move the statement block out of the hot
path. This does not seem to happen that often.

As the error condition is expected to be false almost always, we can
annotate it with 'unlikely' as this satisfies one of the few use cases
for the annotation. The expected outcome is a stronger hint to compiler
to reorder the checks

  test
  jump to exit
  test
  jump to exit
  ...

which can be observed in asm of eg. check_dir_item,
btrfs_check_chunk_valid, check_root_item or check_leaf.

There's a measurable run time improvement reported by Josef, the testing
workload went from 655 MiB/s to 677 MiB/s, which is about +3%.

There should be no functional changes but some of the conditions have
been rewritten to produce more readable result, some lines are longer
than 80, for the sake of readability.

Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:15 +01:00
David Sterba
a0f6d924ca btrfs: remove stub device info from messages when we have no fs_info
Without a NULL fs_info the helpers will print something like

	BTRFS error (device <unknown>): ...

This can happen in contexts where fs_info is not available at all or
it's potentially unsafe due to object lifetime. The <unknown> stub does
not bring much information and with the prefix makes the message
unnecessarily longer.

Remove it for the NULL fs_info case.

	BTRFS error: ...

Callers can add the device information to the message itself if needed.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:14 +01:00
Qu Wenruo
fb22e9c4cd btrfs: use detach_page_private() in alloc_extent_buffer()
In alloc_extent_buffer(), after we got a page from btree inode, we check
if that page has private pointer attached.

If attached, we check if the existing extent buffer has proper refs.
If not (the eb is being freed), we will detach that private eb pointer.

The point here is, we are detaching that eb pointer by calling:
- ClearPagePrivate()
- put_page()

The put_page() here is especially confusing, as it's decreasing the ref
from attach_page_private().  Without knowing that, it looks like the
put_page() is for the find_or_create_page() call, confusing the reader.

Since we're always modifying page private with attach_page_private() and
detach_page_private(), the only open-coded detach_page_private() here is
really confusing.

Fix it by calling detach_page_private().

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:14 +01:00
Qu Wenruo
35478d053a btrfs: use nodesize to determine if we need readahead in btrfs_lookup_bio_sums
In btrfs_lookup_bio_sums() if the bio is pretty large, we want to
start readahead in the csum tree.

However the threshold is an immediate number, (PAGE_SIZE * 8), from the
initial btrfs merge.

The meaning of the value is pretty hard to guess, especially when the
immediate number is from the times when 4K sectorsize was the default
and only CRC32C was supported.

For the most common btrfs setup, CRC32 csum and 4K sectorsize,
it means just 32K read would kick readahead, while the csum itself is
only 32 bytes in size.

Now let's be more reasonable by taking both csum size and node size into
consideration.

If the csum size for the bio is larger than one leaf, then we kick the
readahead.  This means for current default btrfs, the threshold will be
16M.

This change should not change performance observably, thus this is
mostly a readability enhancement.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:14 +01:00
Qu Wenruo
829ddec922 btrfs: only clear EXTENT_LOCK bit in extent_invalidatepage
extent_invalidatepage() will try to clear all possible bits since it's
calling clear_extent_bit() with delete == 1.

This is currently fine, since for btree io tree, it only utilizes
EXTENT_LOCK bit.  But this could be a problem for later subpage support,
which will utilize extra io tree bit to represent additional info.

This patch will just convert that clear_extent_bit() to
unlock_extent_cached().

For current code since only EXTENT_LOCKED bit is utilized, this doesn't
change the behavior, but provides a much cleaner basis for incoming
subpage support.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:14 +01:00
Qu Wenruo
8e1dc982ed btrfs: remove unused parameter phy_offset from btrfs_validate_metadata_buffer
Parameter @phy_offset is the offset against the bio->bi_iter.bi_sector.
@phy_offset is mostly for data io to lookup the csum in btrfs_io_bio.

But for metadata, it's completely useless as metadata stores their own
csum in its header, so we can remove it.

Note: parameters @start and @end, they are not utilized at all for
current sectorsize == PAGE_SIZE case, as we can grab eb directly from
page.

But those two parameters are very important for later subpage support,
thus @start/@len are not touched here.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:14 +01:00
Qu Wenruo
2c36395430 btrfs: scrub: remove the anonymous structure from scrub_page
That anonymous structure serve no special purpose, just replace it with
regular members.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:14 +01:00
Qu Wenruo
f97e27e91d btrfs: use fixed width int type for extent_state::state
Currently the type is unsigned int which could change its width
depending on the architecture. We need up to 32 bits so make it
explicit.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:13 +01:00
Qu Wenruo
e09caaf913 btrfs: introduce helper to handle page status update in end_bio_extent_readpage()
Introduce a new helper to handle update page status in
end_bio_extent_readpage(). This will be later used for subpage support
where the page status update can be more complex than now.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:13 +01:00
Qu Wenruo
94e8c95ccb btrfs: add structure to keep track of extent range in end_bio_extent_readpage
In end_bio_extent_readpage() we had a strange dance around
extent_start/extent_len.

Hidden behind the strange dance is, it's just calling
endio_readpage_release_extent() on each bvec range.

Here is an example to explain the original work flow:

  Bio is for inode 257, containing 2 pages, for range [1M, 1M+8K)

  end_bio_extent_extent_readpage() entered
  |- extent_start = 0;
  |- extent_end = 0;
  |- bio_for_each_segment_all() {
  |  |- /* Got the 1st bvec */
  |  |- start = SZ_1M;
  |  |- end = SZ_1M + SZ_4K - 1;
  |  |- update = 1;
  |  |- if (extent_len == 0) {
  |  |  |- extent_start = start; /* SZ_1M */
  |  |  |- extent_len = end + 1 - start; /* SZ_1M */
  |  |  }
  |  |
  |  |- /* Got the 2nd bvec */
  |  |- start = SZ_1M + 4K;
  |  |- end = SZ_1M + 4K - 1;
  |  |- update = 1;
  |  |- if (extent_start + extent_len == start) {
  |  |  |- extent_len += end + 1 - start; /* SZ_8K */
  |  |  }
  |  } /* All bio vec iterated */
  |
  |- if (extent_len) {
     |- endio_readpage_release_extent(tree, extent_start, extent_len,
				      update);
	/* extent_start == SZ_1M, extent_len == SZ_8K, uptodate = 1 */

As the above flow shows, the existing code in end_bio_extent_readpage()
is accumulates extent_start/extent_len, and when the contiguous range
stops, calls endio_readpage_release_extent() for the range.

However current behavior has something not really considered:

- The inode can change
  For bio, its pages don't need to have contiguous page_offset.
  This means, even pages from different inodes can be packed into one
  bio.

- bvec cross page boundary
  There is a feature called multi-page bvec, where bvec->bv_len can go
  beyond bvec->bv_page boundary.

- Poor readability

This patch will address the problem:

- Introduce a proper structure, processed_extent, to record processed
  extent range

- Integrate inode/start/end/uptodate check into
  endio_readpage_release_extent()

- Add more comment on each step.
  This should greatly improve the readability, now in
  end_bio_extent_readpage() there are only two
  endio_readpage_release_extent() calls.

- Add inode check for contiguity
  Now we also ensure the inode is the same one before checking if the
  range is contiguous.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:13 +01:00
Qu Wenruo
b1d51f67c9 btrfs: tests: remove invalid extent-io test
In extent-io-test, there are two invalid tests:

- Invalid nodesize for test_eb_bitmaps()
  Instead of the sectorsize and nodesize combination passed in, we're
  always using hand-crafted nodesize, e.g:

	len = (sectorsize < BTRFS_MAX_METADATA_BLOCKSIZE)
		? sectorsize * 4 : sectorsize;

  In above case, if we have 32K page size, then we will get a length of
  128K, which is beyond max node size, and obviously invalid.

  The common page size goes up to 64K so we haven't hit that

- Invalid extent buffer bytenr
  For 64K page size, the only combination we're going to test is
  sectorsize = nodesize = 64K.
  However, in that case we will try to test an eb which bytenr is not
  sectorsize aligned:

	/* Do it over again with an extent buffer which isn't page-aligned. */
	eb = __alloc_dummy_extent_buffer(fs_info, nodesize / 2, len);

  Sector alignment is a hard requirement for any sector size.
  The only exception is superblock. But anything else should follow
  sector size alignment.

  This is definitely an invalid test case.

This patch will fix both problems by:

- Honor the sectorsize/nodesize combination
  Now we won't bother to hand-craft the length and use it as nodesize.

- Use sectorsize as the 2nd run extent buffer start
  This would test the case where extent buffer is aligned to sectorsize
  but not always aligned to nodesize.

Please note that, later subpage related cleanup will reduce
extent_buffer::pages[] to exactly what we need, making the sector
unaligned extent buffer operations cause problems.

Since only extent_io self tests utilize this, this patch is required for
all later cleanup/refactoring.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:13 +01:00
Tom Rix
445d8ab53f btrfs: sysfs: remove unneeded semicolon
A semicolon is not needed after a switch statement.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:13 +01:00
Nikolay Borisov
95b982de37 btrfs: simplify return values in setup_nodes_for_search
The function is needlessly convoluted. Fix that by:

* removing redundant sret variable definition in both if arms

* replace the again/done labels with direct return statements, the
  function is short enough and doesn't do anything special upon exit

* remove BUG_ON on split_node returning a positive number - it can't
  happen as split_node returns either 0 or a negative error code.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:13 +01:00
Nikolay Borisov
d5286a92ea btrfs: remove useless return value statement in split_node
At the point when we set 'ret = 0' it's guaranteed that the function is
going to return 0 so directly return 0. No functional changes.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Filipe Manana
f30bed8342 btrfs: remove unnecessary attempt to drop extent maps after adding inline extent
At inode.c:cow_file_range_inline(), after we insert the inline extent
in the fs/subvolume btree, we call btrfs_drop_extent_cache() to drop
all extent maps in the file range, however that is not necessary because
we have already done it in the call to btrfs_drop_extents(), which calls
btrfs_drop_extent_cache() for us, and since at this point we have the file
range locked in the inode's iotree (we are in the writeback path), we know
no other task can come in and read stale file extent items or find none
and therefore create either stale extent maps or an extent map that
represents a hole.

So just remove that unnecessary call to btrfs_drop_extent_cache(), as it's
doing nothing and only wasting time. This call has been around since 2008,
introduced in commit c8b978188c ("Btrfs: Add zlib compression support"),
but even back then it seems it was not necessary, since we had the range
locked in the inode's iotree and the call to btrfs_drop_extents() already
used to always call btrfs_drop_extent_cache().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Filipe Manana
bc5b5b1e51 btrfs: stop incrementing log batch when joining log transaction
When joining a log transaction we acquire the root's log mutex, then
increment the root's log batch and log writers counters while holding
the mutex. However we don't need to increment the log batch there,
because we are holding the mutex and incremented the log writers counter
as well, so any other task trying to sync log will wait for the current
task to finish its logging and still achieve the desired log batching.

Since the log batch counter is an atomic counter and is incremented twice
at the very beginning of the fsync callback (btrfs_sync_file()), once
before flushing delalloc and once again after waiting for writeback to
complete, eliminating its increment when joining the log transaction
may provide some performance gains in case we have multiple concurrent
tasks doing fsyncs against different files in the same subvolume, as it
reduces contention on the atomic (locking the cacheline and bouncing it).

When testing fio with 32 jobs, on a 8 cores VM, doing fsyncs against
different files of the same subvolume, on top of a zram device, I could
consistently see gains (higher throughput) between 1% to 2%, which is a
very low value and possibly hard to be observed with a real device (I
couldn't observe consistent gains with my low/mid end NVMe device).
So this change is mostly motivated to just simplify the logic, as updating
the log batch counter is only relevant when an fsync starts and while not
holding the root's log mutex.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Filipe Manana
f2f121ab50 btrfs: skip unnecessary searches for xattrs when logging an inode
Every time we log an inode we lookup in the fs/subvol tree for xattrs and
if we have any, log them into the log tree. However it is very common to
have inodes without any xattrs, so doing the search wastes times, but more
importantly it adds contention on the fs/subvol tree locks, either making
the logging code block and wait for tree locks or making the logging code
making other concurrent operations block and wait.

The most typical use cases where xattrs are used are when capabilities or
ACLs are defined for an inode, or when SELinux is enabled.

This change makes the logging code detect when an inode does not have
xattrs and skip the xattrs search the next time the inode is logged,
unless the inode is evicted and loaded again or a xattr is added to the
inode. Therefore skipping the search for xattrs on inodes that don't ever
have xattrs and are fsynced with some frequency.

The following script that calls dbench was used to measure the impact of
this change on a VM with 8 CPUs, 16Gb of ram, using a raw NVMe device
directly (no intermediary filesystem on the host) and using a non-debug
kernel (default configuration on Debian distributions):

  $ cat test.sh
  #!/bin/bash

  DEV=/dev/sdk
  MNT=/mnt/sdk
  MOUNT_OPTIONS="-o ssd"

  mkfs.btrfs -f -m single -d single $DEV
  mount $MOUNT_OPTIONS $DEV $MNT

  dbench -D $MNT -t 200 40

  umount $MNT

The results before this change:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    5761605     0.172   312.057
 Close        4232452     0.002    10.927
 Rename        243937     1.406   277.344
 Unlink       1163456     0.631   298.402
 Deltree          160    11.581   221.107
 Mkdir             80     0.003     0.005
 Qpathinfo    5221410     0.065   122.309
 Qfileinfo     915432     0.001     3.333
 Qfsinfo       957555     0.003     3.992
 Sfileinfo     469244     0.023    20.494
 Find         2018865     0.448   123.659
 WriteX       2874851     0.049   118.529
 ReadX        9030579     0.004    21.654
 LockX          18754     0.003     4.423
 UnlockX        18754     0.002     0.331
 Flush         403792    10.944   359.494

Throughput 908.444 MB/sec  40 clients  40 procs  max_latency=359.500 ms

The results after this change:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    6442521     0.159   230.693
 Close        4732357     0.002    10.972
 Rename        272809     1.293   227.398
 Unlink       1301059     0.563   218.500
 Deltree          160     7.796    54.887
 Mkdir             80     0.008     0.478
 Qpathinfo    5839452     0.047   124.330
 Qfileinfo    1023199     0.001     4.996
 Qfsinfo      1070760     0.003     5.709
 Sfileinfo     524790     0.033    21.765
 Find         2257658     0.314   125.611
 WriteX       3211520     0.040   232.135
 ReadX        10098969     0.004    25.340
 LockX          20974     0.003     1.569
 UnlockX        20974     0.002     3.475
 Flush         451553    10.287   331.037

Throughput 1011.77 MB/sec  40 clients  40 procs  max_latency=331.045 ms

+10.8% throughput, -8.2% max latency

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Nikolay Borisov
1cab5e7283 btrfs: merge __set_extent_bit and set_extent_bit
There are only 2 direct calls to set_extent_bit outside of extent-io -
in btrfs_find_new_delalloc_bytes and btrfs_truncate_block, the rest are
thin wrappers around __set_extent_bit. This adds unnecessary indirection
and just makes it more annoying when looking at the various extent bit
manipulation functions.  This patch renames __set_extent_bit to
set_extent_bit effectively removing a level of indirection. No
functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ reformat and remove __must_check ]
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Nikolay Borisov
729f796172 btrfs: make btrfs_update_inode_fallback take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Nikolay Borisov
b06359a325 btrfs: make btrfs_cont_expand take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00
Nikolay Borisov
217f42eb3d btrfs: make btrfs_truncate_block take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:11 +01:00
Nikolay Borisov
03fcb1ab6f btrfs: make btrfs_insert_replace_extent take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:11 +01:00
Nikolay Borisov
dea46d84a3 btrfs: make find_first_non_hole take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:11 +01:00
Nikolay Borisov
a4ba6cc03e btrfs: make maybe_insert_hole take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:11 +01:00
Nikolay Borisov
9a56fcd15a btrfs: make btrfs_update_inode take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:11 +01:00
Nikolay Borisov
dfeb9e7cc3 btrfs: make btrfs_update_inode_item take btrfs_inode
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:11 +01:00