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This adds support for nocow mode, where we do writes in-place when
possible. Patch components:
- New boolean filesystem and inode option, nocow: note that when nocow
is enabled, data checksumming and compression are implicitly disabled
- To prevent in-place writes from racing with data moves
(data_update.c) or bucket reuse (i.e. a bucket being reused and
re-allocated while a nocow write is in flight, we have a new locking
mechanism.
Buckets can be locked for either data update or data move, using a
fixed size hash table of two_state_shared locks. We don't have any
chaining, meaning updates and moves to different buckets that hash to
the same lock will wait unnecessarily - we'll want to watch for this
becoming an issue.
- The allocator path also needs to check for in-place writes in flight
to a given bucket before giving it out: thus we add another counter
to bucket_alloc_state so we can track this.
- Fsync now may need to issue cache flushes to block devices instead of
flushing the journal. We add a device bitmask to bch_inode_info,
ei_devs_need_flush, which tracks devices that need to have flushes
issued - note that this will lead to unnecessary flushes when other
codepaths have already issued flushes, we may want to replace this with
a sequence number.
- New nocow write path: look up extents, and if they're writable write
to them - otherwise fall back to the normal COW write path.
XXX: switch to sequence numbers instead of bitmask for devs needing
journal flush
XXX: ei_quota_lock being a mutex means bch2_nocow_write_done() needs to
run in process context - see if we can improve this
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This factors out part of __bchfs_fallocate() in fs-io.c into an new,
lower level io.c helper, which creates a single extent reservation.
This is prep work for nocow support - the new helper will shortly gain
the ability to create unwritten extents.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
The extend update path had an optimization to avoid updating the inode
if we knew we were definitely not extending the file. But now that we're
updating inodes on every extent update - for fsync - that code can be
deleted.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
BCH_WRITE_FLUSH is a write flag that causes a journal flush. It's only
used in the direct IO path, and this will allow for some consolidation
with the regular fsync path, which will help with the upcoming nocow
mode.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This adds a new flag for the write path, BCH_WRITE_SYNC, and switches
the O_DIRECT write path to use it when we're not running asynchronously.
It runs the btree update after the write in the original thread's
context instead of a kworker, cutting context switches in half.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
In the write path, after the write to the block device(s) complete we
have to punt to process context to do the btree update.
Instead of using the work item embedded in op->cl, this patch switches
to a per write-point work item. This helps with two different issues:
- lock contention: btree updates to the same writepoint will (usually)
be updating the same alloc keys
- context switch overhead: when we're bottlenecked on btree updates,
having a thread (running out of a work item) checking the write point
for completed ops is cheaper than queueing up a new work item and
waking up a kworker.
In an arbitrary benchmark, 4k random writes with fio running inside a
VM, this patch resulted in a 10% improvement in total iops.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Now that we're recording in each inode the journal sequence number of
the most recent update, fsync becomes a lot simpler and we can delete
all the plumbing for ei_journal_seq.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This plumbs around the subvolume ID as was done previously for other
filesystem code, but now for the IO paths - the control flow in the IO
paths is trickier so the changes in this patch are more involved.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This deletes bch_write_op.index_update_fn: indirect function calls have
gotten considerably more expensive post spectre/meltdown, and we only
have two different index_update_fns - this patch adds a flag to specify
which one to use (normal vs. data move path).
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Also, clean up workqueue usage - we shouldn't be using system
workqueues, pretty much everything we do needs to be on our own
WQ_MEM_RECLAIM workqueues.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Buffered writes may have to increase their disk reservation at btree
update time, due to compression and erasure coding being unpredictable:
O_DIRECT writes should be checking for -ENOSPC, but buffered writes have
already been accepted and should not.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
In the read path, for retry of indirect extents to work we need to
differentiate between the location in the btree the read was for, vs.
the location where we found the data. This patch adds that plumbing to
bch_read_bio.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
With various newer key types - stripe keys, inline data extents - the
old approach of calculating the maximum size of the value is becoming
more and more error prone. Better to switch to bkey_on_stack, which can
dynamically allocate if necessary to handle any size bkey.
In particular we also want to get rid of BKEY_EXTENT_VAL_U64s_MAX.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Originally, we'd check for -ENOSPC when getting a disk reservation
whenever the new extent took up more space on disk than the old extent.
Erasure coding screwed this up, because with erasure coding writes are
initially replicated, and then in the background the extra replicas are
dropped when the stripe is created. This means that with erasure coding
enabled, writes will always take up more space on disk than the data
they're overwriting - but, according to posix, overwrites aren't
supposed to return ENOSPC.
So, in this patch we fudge things: if the new extent has more replicas
than the _effective_ replicas of the old extent, or if the old extent is
compressed and the new one isn't, we check for ENOSPC when getting the
disk reservation - otherwise, we don't.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
With the btree key cache code, we don't need to update the alloc btree
lazily - and this will mean we can remove the bch2_alloc_write() call in
the shutdown path.
Future work: we really need to expend the bucket IO clocks from 16 to 64
bits, so that we don't have to rescale them.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
We define our own BLK_STS_REMOVED, so we need our own to_str helper too.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This fixes a bug where the BCH_WRITE_SKIP_CLOSURE_PUT was set
incorrectly, causing the completion to be delivered multiple times.
oops.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
When a bkey_on_stack is passed to bch_read_indirect_extent, there is no
guarantee that it will be big enough to hold the bkey. And
bch_read_indirect_extent is not aware of bkey_on_stack to call realloc
on it. This cause a stack corruption.
This commit makes bch_read_indirect_extent aware of bkey_on_stack so it
can call realloc when appropriate.
Tested-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
writes running out of a workqueue (via dio path) could block and prevent
other writes from calling bch2_write_index() and completing.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Regression from "bcachefs: Track incompressible data"
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This implements extents that have their data inline, in the value,
instead of the bkey value being pointers to the data - and the read and
write paths are updated to read from these new extent types and write
them out, when the write size is small enough.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This adds some horrible hacks, but the atomic ops for closures were
getting to be a pretty expensive part of the write path. We don't want
to rip out closures entirely from the write path, because they're used
for e.g. waiting on the allocator, or waiting on the journal flush, and
that stuff would get really ugly without closures.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
The generic IO path now handles inode updates for i_size and i_sectors -
this means we can drop a fair amount of code from fs-io.c.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
The next few patches are going to be more moving the logic around
i_size/i_sectors updates to io.c, and better separating the Linux VFS
specific code from core bcachefs code, to better support the fuse port.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
With reflink, we'll no longer be able to calculate the offset of the
data we want into the extent we're reading from from the extent pos and
the iter pos - we'll have to pass it in separately.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Switch to always using bio_add_page(), which merges contiguous pages now
that we have multipage bvecs.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
bch2_alloc_sectors_start() was a nightmare to work with - it's got some
tricky stuff to do, since it wants to use the buckets the writepoint
already has, unless they're not in the target it wants to write to,
unless it can't allocate from any other devices in which case it will
use those buckets if it has to - et cetera.
This restructures the code to start with a new empty list of open
buckets we're going to use for the new allocation, pulling buckets from
the write point's list as we decide that we really are going to use
them - making the code somewhat more functional and drastically easier
to understand.
Also fixes a bug where we could end up waiting on c->freelist_wait
(because allocating from one device failed) but return success from
bch2_bucket_alloc(), because allocating from a different device
succeeded.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Initially forked from drivers/md/bcache, bcachefs is a new copy-on-write
filesystem with every feature you could possibly want.
Website: https://bcachefs.org
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
