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- Convert flexible array members, fix -Wstringop-overflow warnings,
and fix KCFI function type mismatches that went ignored by
maintainers (Gustavo A. R. Silva, Nathan Chancellor, Kees Cook).
- Remove the remaining side-effect users of ksize() by converting
dma-buf, btrfs, and coredump to using kmalloc_size_roundup(),
add more __alloc_size attributes, and introduce full testing
of all allocator functions. Finally remove the ksize() side-effect
so that each allocation-aware checker can finally behave without
exceptions.
- Introduce oops_limit (default 10,000) and warn_limit (default off)
to provide greater granularity of control for panic_on_oops and
panic_on_warn (Jann Horn, Kees Cook).
- Introduce overflows_type() and castable_to_type() helpers for
cleaner overflow checking.
- Improve code generation for strscpy() and update str*() kern-doc.
- Convert strscpy and sigphash tests to KUnit, and expand memcpy
tests.
- Always use a non-NULL argument for prepare_kernel_cred().
- Disable structleak plugin in FORTIFY KUnit test (Anders Roxell).
- Adjust orphan linker section checking to respect CONFIG_WERROR
(Xin Li).
- Make sure siginfo is cleared for forced SIGKILL (haifeng.xu).
- Fix um vs FORTIFY warnings for always-NULL arguments.
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Merge tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull kernel hardening updates from Kees Cook:
- Convert flexible array members, fix -Wstringop-overflow warnings, and
fix KCFI function type mismatches that went ignored by maintainers
(Gustavo A. R. Silva, Nathan Chancellor, Kees Cook)
- Remove the remaining side-effect users of ksize() by converting
dma-buf, btrfs, and coredump to using kmalloc_size_roundup(), add
more __alloc_size attributes, and introduce full testing of all
allocator functions. Finally remove the ksize() side-effect so that
each allocation-aware checker can finally behave without exceptions
- Introduce oops_limit (default 10,000) and warn_limit (default off) to
provide greater granularity of control for panic_on_oops and
panic_on_warn (Jann Horn, Kees Cook)
- Introduce overflows_type() and castable_to_type() helpers for cleaner
overflow checking
- Improve code generation for strscpy() and update str*() kern-doc
- Convert strscpy and sigphash tests to KUnit, and expand memcpy tests
- Always use a non-NULL argument for prepare_kernel_cred()
- Disable structleak plugin in FORTIFY KUnit test (Anders Roxell)
- Adjust orphan linker section checking to respect CONFIG_WERROR (Xin
Li)
- Make sure siginfo is cleared for forced SIGKILL (haifeng.xu)
- Fix um vs FORTIFY warnings for always-NULL arguments
* tag 'hardening-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (31 commits)
ksmbd: replace one-element arrays with flexible-array members
hpet: Replace one-element array with flexible-array member
um: virt-pci: Avoid GCC non-NULL warning
signal: Initialize the info in ksignal
lib: fortify_kunit: build without structleak plugin
panic: Expose "warn_count" to sysfs
panic: Introduce warn_limit
panic: Consolidate open-coded panic_on_warn checks
exit: Allow oops_limit to be disabled
exit: Expose "oops_count" to sysfs
exit: Put an upper limit on how often we can oops
panic: Separate sysctl logic from CONFIG_SMP
mm/pgtable: Fix multiple -Wstringop-overflow warnings
mm: Make ksize() a reporting-only function
kunit/fortify: Validate __alloc_size attribute results
drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid()
drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid()
driver core: Add __alloc_size hint to devm allocators
overflow: Introduce overflows_type() and castable_to_type()
coredump: Proactively round up to kmalloc bucket size
...
After the previous patchset which is comprised of the following patches:
01/17 btrfs: fix inode list leak during backref walking at resolve_indirect_refs()
02/17 btrfs: fix inode list leak during backref walking at find_parent_nodes()
03/17 btrfs: fix ulist leaks in error paths of qgroup self tests
04/17 btrfs: remove pointless and double ulist frees in error paths of qgroup tests
05/17 btrfs: send: avoid unnecessary path allocations when finding extent clone
06/17 btrfs: send: update comment at find_extent_clone()
07/17 btrfs: send: drop unnecessary backref context field initializations
08/17 btrfs: send: avoid unnecessary backref lookups when finding clone source
09/17 btrfs: send: optimize clone detection to increase extent sharing
10/17 btrfs: use a single argument for extent offset in backref walking functions
11/17 btrfs: use a structure to pass arguments to backref walking functions
12/17 btrfs: reuse roots ulist on each leaf iteration for iterate_extent_inodes()
13/17 btrfs: constify ulist parameter of ulist_next()
14/17 btrfs: send: cache leaf to roots mapping during backref walking
15/17 btrfs: send: skip unnecessary backref iterations
16/17 btrfs: send: avoid double extent tree search when finding clone source
17/17 btrfs: send: skip resolution of our own backref when finding clone source
we have now much better performance when doing backref walking in the send
code, so we can increase the current limit from 64 to 1024 references.
This limit is still a bit conservative because there are still edge cases
where backref walking will be too slow and spend a lot of cpu time, some IO
reading b+tree nodes/leaves and memory. The goal is to eventually get rid
of any limit, but for now bump it as it benefits users with extents shared
more than 64 times and up to 1024 times, allowing for more deduplication
at the destination without having to run a dedupe tool after a receive.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When doing backref walking to determine a source range to clone from, it
is worthless to collect and resolve our own data backref, as we can't
obviously use it as a clone source and it represents the range we want to
clone into. Collecting the backref implies doing the extra work to resolve
it, doing the search for a file extent item in a subvolume tree, etc.
Skipping the data backref is valid as long as we only have the send root
as the single clone root, otherwise the leaf with the file extent item may
be accessible from another clone root due to shared subtrees created by
snapshots, and therefore we have to collect the backref and resolve it.
So add a callback to the backref walking code to guide it to skip data
backrefs.
This change is part of a patchset comprised of the following patches:
01/17 btrfs: fix inode list leak during backref walking at resolve_indirect_refs()
02/17 btrfs: fix inode list leak during backref walking at find_parent_nodes()
03/17 btrfs: fix ulist leaks in error paths of qgroup self tests
04/17 btrfs: remove pointless and double ulist frees in error paths of qgroup tests
05/17 btrfs: send: avoid unnecessary path allocations when finding extent clone
06/17 btrfs: send: update comment at find_extent_clone()
07/17 btrfs: send: drop unnecessary backref context field initializations
08/17 btrfs: send: avoid unnecessary backref lookups when finding clone source
09/17 btrfs: send: optimize clone detection to increase extent sharing
10/17 btrfs: use a single argument for extent offset in backref walking functions
11/17 btrfs: use a structure to pass arguments to backref walking functions
12/17 btrfs: reuse roots ulist on each leaf iteration for iterate_extent_inodes()
13/17 btrfs: constify ulist parameter of ulist_next()
14/17 btrfs: send: cache leaf to roots mapping during backref walking
15/17 btrfs: send: skip unnecessary backref iterations
16/17 btrfs: send: avoid double extent tree search when finding clone source
17/17 btrfs: send: skip resolution of our own backref when finding clone source
The following test was run on non-debug kernel (Debian's default kernel
config) before and after applying the patchset:
$ cat test-send-many-shared-extents.sh
#!/bin/bash
DEV=/dev/sdh
MNT=/mnt/sdh
umount $DEV &> /dev/null
mkfs.btrfs -f $DEV
mount $DEV $MNT
num_files=50000
num_clones_per_file=50
for ((i = 1; i <= $num_files; i++)); do
xfs_io -f -c "pwrite 0 64K" $MNT/file_$i > /dev/null
echo -ne "\r$i files created..."
done
echo
btrfs subvolume snapshot -r $MNT $MNT/snap1
cloned=0
for ((i = 1; i <= $num_clones_per_file; i++)); do
for ((j = 1; j <= $num_files; j++)); do
cp --reflink=always $MNT/file_$j $MNT/file_${j}_clone_${i}
cloned=$((cloned + 1))
echo -ne "\r$cloned / $((num_files * num_clones_per_file)) clone operations"
done
done
echo
btrfs subvolume snapshot -r $MNT $MNT/snap2
# Unmount and mount again to clear all cached metadata (and data).
umount $DEV
mount $DEV $MNT
start=$(date +%s%N)
btrfs send $MNT/snap2 > /dev/null
end=$(date +%s%N)
dur=$(( (end - start) / 1000000000 ))
echo -e "\nFull send took $dur seconds"
# Unmount and mount again to clear all cached metadata (and data).
umount $DEV
mount $DEV $MNT
start=$(date +%s%N)
btrfs send -p $MNT/snap1 $MNT/snap2 > /dev/null
end=$(date +%s%N)
dur=$(( (end - start) / 1000000000 ))
echo -e "\nIncremental send took $dur seconds"
umount $MNT
Before applying the patchset:
(...)
Full send took 1108 seconds
(...)
Incremental send took 1135 seconds
After applying the whole patchset:
(...)
Full send took 268 seconds (-75.8%)
(...)
Incremental send took 316 seconds (-72.2%)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At find_extent_clone() we search twice for the extent item corresponding
to the data extent that the current file extent items points to:
1) Once with a call to extent_from_logical();
2) Once again during backref walking, through iterate_extent_inodes()
which eventually leads to find_parent_nodes() where we will search
again the extent tree for the same extent item.
The extent tree can be huge, so doing this one extra search for every
extent we want to send adds up and it's expensive.
The first call is there since the send code was introduced and it
accomplishes two things:
1) Check that the extent is flagged as a data extent in the extent tree.
But it can not be anything else, otherwise we wouldn't have a file
extent item in the send root pointing to it.
This was probably added to catch bugs in the early days where send was
yet too young and the interaction with everything else was far from
perfect;
2) Check how many direct references there are on the extent, and if
there's too many (more than SEND_MAX_EXTENT_REFS), avoid doing the
backred walking as it may take too long and slowdown send.
So improve on this by having a callback in the backref walking code that
is called when it finds the extent item in the extent tree, and have those
checks done in the callback. When the callback returns anything different
from 0, it stops the backref walking code. This way we do a single search
on the extent tree for the extent item of our data extent.
Also, before this change we were only checking the number of references on
the data extent against SEND_MAX_EXTENT_REFS, but after starting backref
walking we will end up resolving backrefs for extent buffers in the path
from a leaf having a file extent item pointing to our data extent, up to
roots of trees from which the extent buffer is accessible from, due to
shared subtrees resulting from snapshoting. We were therefore allowing for
the possibility for send taking too long due to some node in the path from
the leaf to a root node being shared too many times. After this change we
check for reference counts being greater than SEND_MAX_EXTENT_REFS for
both data extents and metadata extents.
This change is part of a patchset comprised of the following patches:
01/17 btrfs: fix inode list leak during backref walking at resolve_indirect_refs()
02/17 btrfs: fix inode list leak during backref walking at find_parent_nodes()
03/17 btrfs: fix ulist leaks in error paths of qgroup self tests
04/17 btrfs: remove pointless and double ulist frees in error paths of qgroup tests
05/17 btrfs: send: avoid unnecessary path allocations when finding extent clone
06/17 btrfs: send: update comment at find_extent_clone()
07/17 btrfs: send: drop unnecessary backref context field initializations
08/17 btrfs: send: avoid unnecessary backref lookups when finding clone source
09/17 btrfs: send: optimize clone detection to increase extent sharing
10/17 btrfs: use a single argument for extent offset in backref walking functions
11/17 btrfs: use a structure to pass arguments to backref walking functions
12/17 btrfs: reuse roots ulist on each leaf iteration for iterate_extent_inodes()
13/17 btrfs: constify ulist parameter of ulist_next()
14/17 btrfs: send: cache leaf to roots mapping during backref walking
15/17 btrfs: send: skip unnecessary backref iterations
16/17 btrfs: send: avoid double extent tree search when finding clone source
17/17 btrfs: send: skip resolution of our own backref when finding clone source
Performance test results are in the changelog of patch 17/17.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When looking for a clone source for an extent, we are iterating over all
the backreferences for an extent. This is often a waste of time, because
once we find a good clone source we could stop immediately instead of
continuing backref walking, which is expensive.
Basically what happens currently is this:
1) Call iterate_extent_inodes() to iterate over all the backreferences;
2) It calls btrfs_find_all_leafs() which in turn calls the main function
to walk over backrefs and collect them - find_parent_nodes();
3) Then we collect all the references for our target data extent from the
extent tree (and delayed refs if any), add them to the rb trees,
resolve all the indirect backreferences and search for all the file
extent items in fs trees, building a list of inodes for each one of
them (struct extent_inode_elem);
4) Then back at iterate_extent_inodes() we find all the roots associated
to each found leaf, and call the callback __iterate_backrefs defined
at send.c for each inode in the inode list associated to each leaf.
Some times one the first backreferences we find in a fs tree is optimal
to satisfy the clone operation that send wants to perform, and in that
case we could stop immediately and avoid resolving all the remaining
indirect backreferences (search fs trees for the respective file extent
items, etc). This possibly if when we find a fs tree leaf with a file
extent item we are able to know what are all the roots that can lead to
the leaf - this is now possible after the previous patch in the series
that adds a cache that maps leaves to a list of roots. So we can now
shortcircuit backref walking during send, by having the callback we
pass to iterate_extent_inodes() to be called when we find a file extent
item for an indirect backreference, and have it return a special value
when it found a suitable backreference and it does not need to look for
more backreferences. This change does that.
This change is part of a patchset comprised of the following patches:
01/17 btrfs: fix inode list leak during backref walking at resolve_indirect_refs()
02/17 btrfs: fix inode list leak during backref walking at find_parent_nodes()
03/17 btrfs: fix ulist leaks in error paths of qgroup self tests
04/17 btrfs: remove pointless and double ulist frees in error paths of qgroup tests
05/17 btrfs: send: avoid unnecessary path allocations when finding extent clone
06/17 btrfs: send: update comment at find_extent_clone()
07/17 btrfs: send: drop unnecessary backref context field initializations
08/17 btrfs: send: avoid unnecessary backref lookups when finding clone source
09/17 btrfs: send: optimize clone detection to increase extent sharing
10/17 btrfs: use a single argument for extent offset in backref walking functions
11/17 btrfs: use a structure to pass arguments to backref walking functions
12/17 btrfs: reuse roots ulist on each leaf iteration for iterate_extent_inodes()
13/17 btrfs: constify ulist parameter of ulist_next()
14/17 btrfs: send: cache leaf to roots mapping during backref walking
15/17 btrfs: send: skip unnecessary backref iterations
16/17 btrfs: send: avoid double extent tree search when finding clone source
17/17 btrfs: send: skip resolution of our own backref when finding clone source
Performance test results are in the changelog of patch 17/17.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
During a send operation, when doing backref walking to determine which
inodes/offsets/roots we can clone from, the most repetitive and expensive
step is to map each leaf that has file extent items pointing to the target
data extent to the IDs of the roots from which the leaves are accessible,
which happens at iterate_extent_inodes(). That step requires finding every
parent node of a leaf, then the parent of each parent, and so on until we
reach a root node. So it's a naturally expensive operation, and repetitive
because each leaf can have hundreds of file extent items (for a nodesize
of 16K, that can be slightly over 200 file extent items). There's also
temporal locality, as we process all file extent items from a leave before
moving the next leaf.
This change caches the mapping of leaves to root IDs, to avoid repeating
those computations over and over again. The cache is limited to a maximum
of 128 entries, with each entry being a struct with a size of 128 bytes,
so the maximum cache size is 16K plus any nodes internally allocated by
the maple tree that is used to index pointers to those structs. The cache
is invalidated whenever we detect relocation happened since we started
filling the cache, because if relocation happened then extent buffers for
leaves and nodes of the trees used by a send operation may have been
reallocated.
This cache also allows for another important optimization that is
introduced in the next patch in the series.
This change is part of a patchset comprised of the following patches:
01/17 btrfs: fix inode list leak during backref walking at resolve_indirect_refs()
02/17 btrfs: fix inode list leak during backref walking at find_parent_nodes()
03/17 btrfs: fix ulist leaks in error paths of qgroup self tests
04/17 btrfs: remove pointless and double ulist frees in error paths of qgroup tests
05/17 btrfs: send: avoid unnecessary path allocations when finding extent clone
06/17 btrfs: send: update comment at find_extent_clone()
07/17 btrfs: send: drop unnecessary backref context field initializations
08/17 btrfs: send: avoid unnecessary backref lookups when finding clone source
09/17 btrfs: send: optimize clone detection to increase extent sharing
10/17 btrfs: use a single argument for extent offset in backref walking functions
11/17 btrfs: use a structure to pass arguments to backref walking functions
12/17 btrfs: reuse roots ulist on each leaf iteration for iterate_extent_inodes()
13/17 btrfs: constify ulist parameter of ulist_next()
14/17 btrfs: send: cache leaf to roots mapping during backref walking
15/17 btrfs: send: skip unnecessary backref iterations
16/17 btrfs: send: avoid double extent tree search when finding clone source
17/17 btrfs: send: skip resolution of our own backref when finding clone source
Performance test results are in the changelog of patch 17/17.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The public backref walking functions have quite a lot of arguments that
are passed down the call stack to find_parent_nodes(), the core function
of the backref walking code.
The next patches in series will need to add even arguments to these
functions that should be passed not only to find_parent_nodes(), but also
to other functions used by the later (directly or even lower in the call
stack).
So create a structure to hold all these arguments and state used by the
main backref walking function, find_parent_nodes(), and use it as the
argument for the public backref walking functions iterate_extent_inodes(),
btrfs_find_all_leafs() and btrfs_find_all_roots().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The interface for find_parent_nodes() has two extent offset related
arguments:
1) One u64 pointer argument for the extent offset;
2) One boolean argument to tell if the extent offset should be ignored or
not.
These are confusing, becase the extent offset pointer can be NULL and in
some cases callers pass a NULL value as a way to tell the backref walking
code to ignore offsets in file extent items (and simply consider all file
extent items that point to the target data extent).
The boolean argument was added in commit c995ab3cda3f ("btrfs: add a flag
to iterate_inodes_from_logical to find all extent refs for uncompressed
extents"), but it was never really necessary, it was enough if it could
find a way to get a NULL value passed to the "extent_item_pos" argument of
find_parent_nodes(). The arguments are also passed to functions called
by find_parent_nodes() and respective helper functions, which further
makes everything more complicated than needed.
Then we have several backref walking related functions that end up calling
find_parent_nodes(), either directly or through some other function that
they call, and for many we have to use an "extent_item_pos" (u64) argument
and a boolean "ignore_offset" argument too.
This is confusing and not really necessary. So use a single argument to
specify the extent offset, as a simple u64 and not as a pointer, but
using a special value of (u64)-1, defined as a documented constant, to
indicate when the extent offset should be ignored.
This is also preparation work for the upcoming patches in the series that
add other arguments to find_parent_nodes() and other related functions
that use it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently send does not do the best decisions when it comes to decide
between multiple clone sources, which results in clone operations for
partial extent ranges, which has the following disadvantages:
1) We get less shared extents at the destination;
2) We have to read more data during the send operation and emit more
write commands.
Besides not being optimal behaviour, it also breaks user expectations and
is often reported by users, with a recent example in the Link tag at the
bottom of this change log.
Part of the reason for this non-optimal behaviour is that the backref
walking code does not provide information about the length of the file
extent items that were found for each backref, so send is blind about
which backref is the best to chose as a cloning source.
The other existing reasons are just silliness, namely always prefering
the inode with the lowest number when multiple are found for the same
root and when we can clone from multiple roots, always prefer the send
root over any of the other clone roots. This does not make any sense
since any inode or root is fine and as good as any other inode/root.
Fix this by making backref walking pass information about the number of
bytes referenced by each file extent item and then have send's backref
callback pick the inode with the highest number of bytes for each root.
Finally select the root from which we can clone more bytes from.
Example reproducer:
$ cat test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV
mount $DEV $MNT
xfs_io -f -c "pwrite -S 0xab -b 2M 0 2M" $MNT/foo
cp --reflink=always $MNT/foo $MNT/bar
cp --reflink=always $MNT/foo $MNT/baz
sync
# Overwrite the second half of file foo.
xfs_io -c "pwrite -S 0xcd -b 1M 1M 1M" $MNT/foo
sync
echo
echo "*** fiemap in the original filesystem ***"
echo
xfs_io -c "fiemap -v" $MNT/foo
xfs_io -c "fiemap -v" $MNT/bar
xfs_io -c "fiemap -v" $MNT/baz
echo
btrfs filesystem du $MNT
btrfs subvolume snapshot -r $MNT $MNT/snap
btrfs send -f /tmp/send_stream $MNT/snap
umount $MNT
mkfs.btrfs -f $DEV &> /dev/null
mount $DEV $MNT
btrfs receive -f /tmp/send_stream $MNT
echo
echo "*** fiemap in the new filesystem ***"
echo
xfs_io -r -c "fiemap -v" $MNT/snap/foo
xfs_io -r -c "fiemap -v" $MNT/snap/bar
xfs_io -r -c "fiemap -v" $MNT/snap/baz
echo
btrfs filesystem du $MNT
rm -f /tmp/send_stream
rm -f /tmp/snap.fssum
umount $MNT
Before this change:
$ ./test.sh
(...)
*** fiemap in the original filesystem ***
/mnt/sdi/foo:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2047]: 26624..28671 2048 0x2000
1: [2048..4095]: 30720..32767 2048 0x1
/mnt/sdi/bar:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..4095]: 26624..30719 4096 0x2001
/mnt/sdi/baz:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..4095]: 26624..30719 4096 0x2001
Total Exclusive Set shared Filename
2.00MiB 1.00MiB - /mnt/sdi/foo
2.00MiB 0.00B - /mnt/sdi/bar
2.00MiB 0.00B - /mnt/sdi/baz
6.00MiB 1.00MiB 2.00MiB /mnt/sdi
Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap'
At subvol /mnt/sdi/snap
At subvol snap
*** fiemap in the new filesystem ***
/mnt/sdi/snap/foo:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..4095]: 26624..30719 4096 0x2001
/mnt/sdi/snap/bar:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2047]: 26624..28671 2048 0x2000
1: [2048..4095]: 30720..32767 2048 0x1
/mnt/sdi/snap/baz:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2047]: 26624..28671 2048 0x2000
1: [2048..4095]: 32768..34815 2048 0x1
Total Exclusive Set shared Filename
2.00MiB 0.00B - /mnt/sdi/snap/foo
2.00MiB 1.00MiB - /mnt/sdi/snap/bar
2.00MiB 1.00MiB - /mnt/sdi/snap/baz
6.00MiB 2.00MiB - /mnt/sdi/snap
6.00MiB 2.00MiB 2.00MiB /mnt/sdi
We end up with two 1M extents that are not shared for files bar and baz.
After this change:
$ ./test.sh
(...)
*** fiemap in the original filesystem ***
/mnt/sdi/foo:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2047]: 26624..28671 2048 0x2000
1: [2048..4095]: 30720..32767 2048 0x1
/mnt/sdi/bar:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..4095]: 26624..30719 4096 0x2001
/mnt/sdi/baz:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..4095]: 26624..30719 4096 0x2001
Total Exclusive Set shared Filename
2.00MiB 1.00MiB - /mnt/sdi/foo
2.00MiB 0.00B - /mnt/sdi/bar
2.00MiB 0.00B - /mnt/sdi/baz
6.00MiB 1.00MiB 2.00MiB /mnt/sdi
Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap'
At subvol /mnt/sdi/snap
At subvol snap
*** fiemap in the new filesystem ***
/mnt/sdi/snap/foo:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..4095]: 26624..30719 4096 0x2001
/mnt/sdi/snap/bar:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2047]: 26624..28671 2048 0x2000
1: [2048..4095]: 30720..32767 2048 0x2001
/mnt/sdi/snap/baz:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..2047]: 26624..28671 2048 0x2000
1: [2048..4095]: 30720..32767 2048 0x2001
Total Exclusive Set shared Filename
2.00MiB 0.00B - /mnt/sdi/snap/foo
2.00MiB 0.00B - /mnt/sdi/snap/bar
2.00MiB 0.00B - /mnt/sdi/snap/baz
6.00MiB 0.00B - /mnt/sdi/snap
6.00MiB 0.00B 3.00MiB /mnt/sdi
Now there's a much better sharing, files bar and baz share 1M of the
extent of file foo and the second extent of files bar and baz is shared
between themselves.
This will later be turned into a test case for fstests.
Link: https://lore.kernel.org/linux-btrfs/20221008005704.795b44b0@crass-HP-ZBook-15-G2/
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At find_extent_clone(), unless we are given an inline extent, a file
extent item that represents hole or an extent that starts beyond the
i_size, we always do backref walking to look for clone sources, unless
if we have more than SEND_MAX_EXTENT_REFS (64) known references on the
extent.
However if we know we only have one reference in the extent item and only
one clone source (the send root), then it's pointless to do the backref
walking to search for clone sources, as we can't clone from any other
root. So skip the backref walking in that case.
The following test was run on a non-debug kernel (Debian's default kernel
config):
$ cat test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV
mount $DEV $MNT
# Create an extent tree that's not too small and none of the
# extents is shared.
for ((i = 1; i <= 50000; i++)); do
xfs_io -f -c "pwrite 0 4K" $MNT/file_$i > /dev/null
echo -ne "\r$i files created..."
done
echo
btrfs subvolume snapshot -r $MNT $MNT/snap
start=$(date +%s%N)
btrfs send $MNT/snap > /dev/null
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo -e "\nsend took $dur milliseconds"
umount $MNT
Before this change:
send took 5389 milliseconds
After this change:
send took 4519 milliseconds (-16.1%)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At find_extent_clone() we are initializing to zero the 'found_itself' and
'found' fields of the backref context before we use it but we have already
initialized the structure to zeroes when we declared it on stack, so it's
pointless to initialize those fields and they are unnecessarily increasing
the object text size with two "mov" instructions (x86_64).
Similarly make the 'extent_len' initialization more clear by using an if-
-then-else instead of a double assignment to it in case the extent's end
crosses the i_size boundary.
Before this change:
$ size fs/btrfs/send.o
text data bss dec hex filename
68694 4252 16 72962 11d02 fs/btrfs/send.o
After this change:
$ size fs/btrfs/send.o
text data bss dec hex filename
68678 4252 16 72946 11cf2 fs/btrfs/send.o
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have this unclear comment at find_extent_clone() about extents starting
at a file offset greater than or equals to the i_size of the inode. It's
not really informative and it's misleading, since it mentions the author
found such extents with snapshots and large files.
Such extents are a result of fallocate with FALLOC_FL_KEEP_SIZE and there
is no relation to snapshots or large files (all write paths update the
i_size before inserting a new file extent item). So update the comment to
be precise about it and why we don't bother looking for clone sources in
that case.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When looking for an extent clone, at find_extent_clone(), we start by
allocating a path and then check for cases where we can't have clones
and exit immediately in those cases. It's a waste of time to allocate
the path before those cases, so reorder the logic so that we check for
those cases before allocating the path.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Move these out of ctree.h into verity.h to cut down on code in ctree.h.
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>
Move these out of ctree.h into ioctl.h to cut down on code in ctree.h.
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>
Move these prototypes out of ctree.h and into file-item.h.
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>
Move these prototypes out of ctree.h and into their own header file.
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>
For directories with encrypted files/filenames, we need to store a flag
indicating this fact. There's no room in other fields, so we'll need to
borrow a bit from dir_type. Since it's now a combination of type and
flags, we rename it to dir_flags to reflect its new usage.
The new flag, FT_ENCRYPTED, indicates a directory containing encrypted
data, which is orthogonal to file type; therefore, add the new
flag, and make conversion from directory type to file type strip the
flag.
As the file types almost never change we can afford to use the bits.
Actual usage will be guarded behind an incompat bit, this patch only
adds the support for later use by fscrypt.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While struct qstr is more natural without fscrypt, since it's provided
by dentries, struct fscrypt_str is provided by the fscrypt handlers
processing dentries, and is thus more natural in the fscrypt world.
Replace all of the struct qstr uses with struct fscrypt_str.
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Many functions throughout btrfs take name buffer and name length
arguments. Most of these functions at the highest level are usually
called with these arguments extracted from a supplied dentry's name.
But the entire name can be passed instead, making each function a little
more elegant.
Each function whose arguments are currently the name and length
extracted from a dentry is herein converted to instead take a pointer to
the name in the dentry. The couple of calls to these calls without a
struct dentry are converted to create an appropriate qstr to pass in.
Additionally, every function which is only called with a name/len
extracted directly from a qstr is also converted.
This change has positive effect on stack consumption, frame of many
functions is reduced but this will be used in the future for fscrypt
related structures.
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This is a large patch, but because they're all macros it's impossible to
split up. Simply copy all of the item accessors in ctree.h and paste
them in accessors.h, and then update any files to include the header so
everything compiles.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ reformat comments, style fixups ]
Signed-off-by: David Sterba <dsterba@suse.com>
Add a define for the data buffer size (though the maximum size is not
limited by it) BTRFS_SEND_BUF_SIZE_V2 so it's more visible.
Signed-off-by: Wang Yugui <wangyugui@e16-tech.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When trying to see if we can clone a file range, there are cases where we
end up sending two write operations in case the inode from the source root
has an i_size that is not sector size aligned and the length from the
current offset to its i_size is less than the remaining length we are
trying to clone.
Issuing two write operations when we could instead issue a single write
operation is not incorrect. However it is not optimal, specially if the
extents are compressed and the flag BTRFS_SEND_FLAG_COMPRESSED was passed
to the send ioctl. In that case we can end up sending an encoded write
with an offset that is not sector size aligned, which makes the receiver
fallback to decompressing the data and writing it using regular buffered
IO (so re-compressing the data in case the fs is mounted with compression
enabled), because encoded writes fail with -EINVAL when an offset is not
sector size aligned.
The following example, which triggered a bug in the receiver code for the
fallback logic of decompressing + regular buffer IO and is fixed by the
patchset referred in a Link at the bottom of this changelog, is an example
where we have the non-optimal behaviour due to an unaligned encoded write:
$ cat test.sh
#!/bin/bash
DEV=/dev/sdj
MNT=/mnt/sdj
mkfs.btrfs -f $DEV > /dev/null
mount -o compress $DEV $MNT
# File foo has a size of 33K, not aligned to the sector size.
xfs_io -f -c "pwrite -S 0xab 0 33K" $MNT/foo
xfs_io -f -c "pwrite -S 0xcd 0 64K" $MNT/bar
# Now clone the first 32K of file bar into foo at offset 0.
xfs_io -c "reflink $MNT/bar 0 0 32K" $MNT/foo
# Snapshot the default subvolume and create a full send stream (v2).
btrfs subvolume snapshot -r $MNT $MNT/snap
btrfs send --compressed-data -f /tmp/test.send $MNT/snap
echo -e "\nFile bar in the original filesystem:"
od -A d -t x1 $MNT/snap/bar
umount $MNT
mkfs.btrfs -f $DEV > /dev/null
mount $DEV $MNT
echo -e "\nReceiving stream in a new filesystem..."
btrfs receive -f /tmp/test.send $MNT
echo -e "\nFile bar in the new filesystem:"
od -A d -t x1 $MNT/snap/bar
umount $MNT
Before this patch, the send stream included one regular write and one
encoded write for file 'bar', with the later being not sector size aligned
and causing the receiver to fallback to decompression + buffered writes.
The output of the btrfs receive command in verbose mode (-vvv):
(...)
mkfile o258-7-0
rename o258-7-0 -> bar
utimes
clone bar - source=foo source offset=0 offset=0 length=32768
write bar - offset=32768 length=1024
encoded_write bar - offset=33792, len=4096, unencoded_offset=33792, unencoded_file_len=31744, unencoded_len=65536, compression=1, encryption=0
encoded_write bar - falling back to decompress and write due to errno 22 ("Invalid argument")
(...)
This patch avoids the regular write followed by an unaligned encoded write
so that we end up sending a single encoded write that is aligned. So after
this patch the stream content is (output of btrfs receive -vvv):
(...)
mkfile o258-7-0
rename o258-7-0 -> bar
utimes
clone bar - source=foo source offset=0 offset=0 length=32768
encoded_write bar - offset=32768, len=4096, unencoded_offset=32768, unencoded_file_len=32768, unencoded_len=65536, compression=1, encryption=0
(...)
So we get more optimal behaviour and avoid the silent data loss bug in
versions of btrfs-progs affected by the bug referred by the Link tag
below (btrfs-progs v5.19, v5.19.1, v6.0 and v6.0.1).
Link: https://lore.kernel.org/linux-btrfs/cover.1668529099.git.fdmanana@suse.com/
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit 9ed0a72e5b35 ("btrfs: send: fix failures when processing inodes with
no links") tries to fix all incremental send cases of orphan inodes the
send operation will meet. However, there's still a bug causing the corner
subcase fails with a ENOENT error.
Here's shortened steps of that subcase:
$ btrfs subvolume create vol
$ touch vol/foo
$ btrfs subvolume snapshot -r vol snap1
$ btrfs subvolume snapshot -r vol snap2
# Turn the second snapshot to RW mode and delete the file while
# holding an open file descriptor on it
$ btrfs property set snap2 ro false
$ exec 73<snap2/foo
$ rm snap2/foo
# Set the second snapshot back to RO mode and do an incremental send
# with an unusal reverse order
$ btrfs property set snap2 ro true
$ btrfs send -p snap2 snap1 > /dev/null
At subvol snap1
ERROR: send ioctl failed with -2: No such file or directory
It's subcase 3 of BTRFS_COMPARE_TREE_CHANGED in the commit 9ed0a72e5b35
("btrfs: send: fix failures when processing inodes with no links"). And
it's not a common case. We still have not met it in the real world.
Theoretically, this case can happen in a batch cascading snapshot backup.
In cascading backups, the receive operation in the middle may cause orphan
inodes to appear because of the open file descriptors on the snapshot files
during receiving. And if we don't do the batch snapshot backups in their
creation order, then we can have an inode, which is an orphan in the parent
snapshot but refers to a file in the send snapshot. Since an orphan inode
has no paths, the send operation will fail with a ENOENT error if it
tries to generate a path for it.
In that patch, this subcase will be treated as an inode with a new
generation. However, when the routine tries to delete the old paths in
the parent snapshot, the function process_all_refs() doesn't check whether
there are paths recorded or not before it calls the function
process_recorded_refs(). And the function process_recorded_refs() try
to get the first path in the parent snapshot in the beginning. Since it has
no paths in the parent snapshot, the send operation fails.
To fix this, we can easily put a link count check to avoid entering the
deletion routine like what we do a link count check to avoid creating a
new one. Moreover, we can assume that the function process_all_refs()
can always collect references to process because we know it has a
positive link count.
Fixes: 9ed0a72e5b35 ("btrfs: send: fix failures when processing inodes with no links")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: BingJing Chang <bingjingc@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For a protocol and command compatibility we have a helper that hasn't
been updated for v3 yet. We use it for verity so update where necessary.
Fixes: 38622010a6de ("btrfs: send: add support for fs-verity")
Signed-off-by: David Sterba <dsterba@suse.com>
We haven't finalized send stream v3 yet, so gate the send stream version
behind CONFIG_BTRFS_DEBUG as we want some way to test it.
The original verity send did not check the protocol version, so add that
actual protection as well.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a bug causing send failures when processing an orphan directory
with no links. In commit 46b2f4590aab ("Btrfs: fix send failure when
root has deleted files still open")', the orphan inode issue was
addressed. The send operation fails with a ENOENT error because of any
attempts to generate a path for the inode with a link count of zero.
Therefore, in that patch, sctx->ignore_cur_inode was introduced to be
set if the current inode has a link count of zero for bypassing some
unnecessary steps. And a helper function btrfs_unlink_all_paths() was
introduced and called to clean up old paths found in the parent
snapshot. However, not only regular files but also directories can be
orphan inodes. So if the send operation meets an orphan directory, it
will issue a wrong unlink command for that directory now. Soon the
receive operation fails with a EISDIR error. Besides, the send operation
also fails with a ENOENT error later when it tries to generate a path of
it.
Similar example but making an orphan dir for an incremental send:
$ btrfs subvolume create vol
$ mkdir vol/dir
$ touch vol/dir/foo
$ btrfs subvolume snapshot -r vol snap1
$ btrfs subvolume snapshot -r vol snap2
# Turn the second snapshot to RW mode and delete the whole dir while
# holding an open file descriptor on it.
$ btrfs property set snap2 ro false
$ exec 73<snap2/dir
$ rm -rf snap2/dir
# Set the second snapshot back to RO mode and do an incremental send.
$ btrfs property set snap2 ro true
$ mkdir receive_dir
$ btrfs send snap2 -p snap1 | btrfs receive receive_dir/
At subvol snap2
At snapshot snap2
ERROR: send ioctl failed with -2: No such file or directory
ERROR: unlink dir failed. Is a directory
Actually, orphan inodes are more common use cases in cascading backups.
(Please see the illustration below.) In a cascading backup, a user wants
to replicate a couple of snapshots from Machine A to Machine B and from
Machine B to Machine C. Machine B doesn't take any RO snapshots for
sending. All a receiver does is create an RW snapshot of its parent
snapshot, apply the send stream and turn it into RO mode at the end.
Even if all paths of some inodes are deleted in applying the send
stream, these inodes would not be deleted and become orphans after
changing the subvolume from RW to RO. Moreover, orphan inodes can occur
not only in send snapshots but also in parent snapshots because Machine
B may do a batch replication of a couple of snapshots.
An illustration for cascading backups:
Machine A (snapshot {1..n}) --> Machine B --> Machine C
The idea to solve the problem is to delete all the items of orphan
inodes before using these snapshots for sending. I used to think that
the reasonable timing for doing that is during the ioctl of changing the
subvolume from RW to RO because it sounds good that we will not modify
the fs tree of a RO snapshot anymore. However, attempting to do the
orphan cleanup in the ioctl would be pointless. Because if someone is
holding an open file descriptor on the inode, the reference count of the
inode will never drop to 0. Then iput() cannot trigger eviction, which
finally deletes all the items of it. So we try to extend the original
patch to handle orphans in send/parent snapshots. Here are several cases
that need to be considered:
Case 1: BTRFS_COMPARE_TREE_NEW
| send snapshot | action
--------------------------------
nlink | 0 | ignore
In case 1, when we get a BTRFS_COMPARE_TREE_NEW tree comparison result,
it means that a new inode is found in the send snapshot and it doesn't
appear in the parent snapshot. Since this inode has a link count of zero
(It's an orphan and there're no paths for it.), we can leverage
sctx->ignore_cur_inode in the original patch to prevent it from being
created.
Case 2: BTRFS_COMPARE_TREE_DELETED
| parent snapshot | action
----------------------------------
nlink | 0 | as usual
In case 2, when we get a BTRFS_COMPARE_TREE_DELETED tree comparison
result, it means that the inode only appears in the parent snapshot.
As usual, the send operation will try to delete all its paths. However,
this inode has a link count of zero, so no paths of it will be found. No
deletion operations will be issued. We don't need to change any logic.
Case 3: BTRFS_COMPARE_TREE_CHANGED
| | parent snapshot | send snapshot | action
-----------------------------------------------------------------------
subcase 1 | nlink | 0 | 0 | ignore
subcase 2 | nlink | >0 | 0 | new_gen(deletion)
subcase 3 | nlink | 0 | >0 | new_gen(creation)
In case 3, when we get a BTRFS_COMPARE_TREE_CHANGED tree comparison result,
it means that the inode appears in both snapshots. Here are 3 subcases.
First, when the inode has link counts of zero in both snapshots. Since
there are no paths for this inode in (source/destination) parent
snapshots and we don't care about whether there is also an orphan inode
in destination or not, we can set sctx->ignore_cur_inode on to prevent
it from being created.
For the second and the third subcases, if there are paths in one
snapshot and there're no paths in the other snapshot for this inode. We
can treat this inode as a new generation. We can also leverage the logic
handling a new generation of an inode with small adjustments. Then it
will delete all old paths and create a new inode with new attributes and
paths only when there's a positive link count in the send snapshot.
In subcase 2, the send operation only needs to delete all old paths as
in the parent snapshot. But it may require more operations for a
directory to remove its old paths. If a not-empty directory is going to
be deleted (because it has a link count of zero in the send snapshot)
but there are files/directories with bigger inode numbers under it, the
send operation will need to rename it to its orphan name first. After
processing and deleting the last item under this directory, the send
operation will check this directory, aka the parent directory of the
last item, again and issue a rmdir operation to remove it finally.
Therefore, we also need to treat inodes with a link count of zero as if
they didn't exist in get_cur_inode_state(), which is used in
process_recorded_refs(). By doing this, when checking a directory with
orphan names after the last item under it has been deleted, the send
operation now can properly issue a rmdir operation. Otherwise, without
doing this, the orphan directory with an orphan name would be kept here
at the end due to the existing inode with a link count of zero being
found.
In subcase 3, as in case 2, no old paths would be found, so no deletion
operations will be issued. The send operation will only create a new one
for that inode.
Note that subcase 3 is not common. That's because it's easy to reduce
the hard links of an inode, but once all valid paths are removed,
there are no valid paths for creating other hard links. The only way to
do that is trying to send an older snapshot after a newer snapshot has
been sent.
Reviewed-by: Robbie Ko <robbieko@synology.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: BingJing Chang <bingjingc@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Refactor get_inode_info() to populate all wanted fields on an output
structure. Besides, also introduce a helper function called
get_inode_gen(), which is commonly used.
Reviewed-by: Robbie Ko <robbieko@synology.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: BingJing Chang <bingjingc@synology.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Preserve the fs-verity status of a btrfs file across send/recv.
There is no facility for installing the Merkle tree contents directly on
the receiving filesystem, so we package up the parameters used to enable
verity found in the verity descriptor. This gives the receive side
enough information to properly enable verity again. Note that this means
that receive will have to re-compute the whole Merkle tree, similar to
how compression worked before encoded_write.
Since the file becomes read-only after verity is enabled, it is
important that verity is added to the send stream after any file writes.
Therefore, when we process a verity item, merely note that it happened,
then actually create the command in the send stream during
'finish_inode_if_needed'.
This also creates V3 of the send stream format, without any format
changes besides adding the new commands and attributes.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
After the patch "btrfs: send: fix sending link commands for existing file
paths", we now have two infrastructures to detect and eliminate duplicated
inode references (due to names that got removed and re-added between the
send and parent snapshots):
1) One that works on a single inode ref/extref item;
2) A new one that works acrosss all ref/extref items for an inode, and
it's also more efficient because even in the single ref/extref item
case, it does not do a linear search for all the names encoded in the
ref/extref item, it uses red black trees to speedup up the search.
There's no good reason to keep both infrastructures, we can use the new
one everywhere, and it's always more efficient.
So remove the old infrastructure and change all sites that are using it
to use the new one.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a bug sending link commands for existing file paths. When we're
processing an inode, we go over all references. All the new file paths are
added to the "new_refs" list. And all the deleted file paths are added to
the "deleted_refs" list. In the end, when we finish processing the inode,
we iterate over all the items in the "new_refs" list and send link commands
for those file paths. After that, we go over all the items in the
"deleted_refs" list and send unlink commands for them. If there are
duplicated file paths in both lists, we will try to create them before we
remove them. Then the receiver gets an -EEXIST error when trying the link
operations.
Example for having duplicated file paths in both list:
$ btrfs subvolume create vol
# create a file and 2000 hard links to the same inode
$ touch vol/foo
$ for i in {1..2000}; do link vol/foo vol/$i ; done
# take a snapshot for a parent snapshot
$ btrfs subvolume snapshot -r vol snap1
# remove 2000 hard links and re-create the last 1000 links
$ for i in {1..2000}; do rm vol/$i; done;
$ for i in {1001..2000}; do link vol/foo vol/$i; done
# take another one for a send snapshot
$ btrfs subvolume snapshot -r vol snap2
$ mkdir receive_dir
$ btrfs send snap2 -p snap1 | btrfs receive receive_dir/
At subvol snap2
link 1238 -> foo
ERROR: link 1238 -> foo failed: File exists
In this case, we will have the same file paths added to both lists. In the
parent snapshot, reference paths {1..1237} are stored in inode references,
but reference paths {1238..2000} are stored in inode extended references.
In the send snapshot, all reference paths {1001..2000} are stored in inode
references. During the incremental send, we process their inode references
first. In record_changed_ref(), we iterate all its inode references in the
send/parent snapshot. For every inode reference, we also use find_iref() to
check whether the same file path also appears in the parent/send snapshot
or not. Inode references {1238..2000} which appear in the send snapshot but
not in the parent snapshot are added to the "new_refs" list. On the other
hand, Inode references {1..1000} which appear in the parent snapshot but
not in the send snapshot are added to the "deleted_refs" list. Next, when
we process their inode extended references, reference paths {1238..2000}
are added to the "deleted_refs" list because all of them only appear in the
parent snapshot. Now two lists contain items as below:
"new_refs" list: {1238..2000}
"deleted_refs" list: {1..1000}, {1238..2000}
Reference paths {1238..2000} appear in both lists. And as the processing
order mentioned about before, the receiver gets an -EEXIST error when trying
the link operations.
To fix the bug, the idea is to process the "deleted_refs" list before
the "new_refs" list. However, it's not easy to reshuffle the processing
order. For one reason, if we do so, we may unlink all the existing paths
first, there's no valid path anymore for links. And it's inefficient
because we do a bunch of unlinks followed by links for the same paths.
Moreover, it makes less sense to have duplications in both lists. A
reference path cannot not only be regarded as new but also has been seen in
the past, or we won't call it a new path. However, it's also not a good
idea to make find_iref() check a reference against all inode references
and all inode extended references because it may result in large disk
reads.
So we introduce two rbtrees to make the references easier for lookups.
And we also introduce record_new_ref_if_needed() and
record_deleted_ref_if_needed() for changed_ref() to check and remove
duplicated references early.
Reviewed-by: Robbie Ko <robbieko@synology.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: BingJing Chang <bingjingc@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Introduce wrappers to allocate and free recorded_ref structures.
Reviewed-by: Robbie Ko <robbieko@synology.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: BingJing Chang <bingjingc@synology.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are file attributes inherited from previous ext2 SETFLAGS/GETFLAGS
and later from XFLAGS interfaces, now commonly found under the
'fileattr' API. This corresponds to the individual inode bits and that's
part of the on-disk format, so this is suitable for the protocol. The
other interfaces contain a lot of cruft or bits that btrfs does not
support yet.
Currently the value is u64 and matches btrfs_inode_item. Not all the
bits can be set by ioctls (like NODATASUM or READONLY), but we can send
them over the protocol and leave it up to the receiving side what and
how to apply.
As some of the flags, eg. IMMUTABLE, can prevent any further changes,
the receiving side needs to understand that and apply the changes in the
right order, or possibly with some intermediate steps. This should be
easier, future proof and simpler on the protocol layer than implementing
in kernel.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When send v1 was introduced the otime (inode creation time) was not
available, however the attribute in btrfs send protocol exists. Though
it would be possible to add it for v1 too as the attribute would be
ignored by v1 receive, let's not change the layout of v1 and only add
that to v2+. The otime cannot be changed and is only informative.
Signed-off-by: David Sterba <dsterba@suse.com>
The whole send operation is restartable and handling properly a buffer
write may not be easy. We can't know what caused that and if a short
delay and retry will fix it or how many retries should be performed in
case it's a temporary condition.
The error value is returned to the ioctl caller so in case it's
transient problem, the user would be notified about the reason. Remove
the TODO note as there's no plan to handle ERESTARTSYS.
Signed-off-by: David Sterba <dsterba@suse.com>
Now that the new support is implemented, allow the ioctl to accept v2
and the compressed flag, and update the version in sysfs.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that all of the pieces are in place, we can use the ENCODED_WRITE
command to send compressed extents when appropriate.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For encoded writes in send v2, we will get the encoded data with
btrfs_encoded_read_regular_fill_pages(), which expects a list of raw
pages. To avoid extra buffers and copies, we should read directly into
the send buffer. Therefore, we need the raw pages for the send buffer.
We currently allocate the send buffer with kvmalloc(), which may return
a kmalloc'd buffer or a vmalloc'd buffer. For vmalloc, we can get the
pages with vmalloc_to_page(). For kmalloc, we could use virt_to_page().
However, the buffer size we use (144K) is not a power of two, which in
theory is not guaranteed to return a page-aligned buffer, and in
practice would waste a lot of memory due to rounding up to the next
power of two. 144K is large enough that it usually gets allocated with
vmalloc(), anyways. So, for send v2, replace kvmalloc() with vmalloc()
and save the pages in an array.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The length field of the send stream TLV header is 16 bits. This means
that the maximum amount of data that can be sent for one write is 64K
minus one. However, encoded writes must be able to send the maximum
compressed extent (128K) in one command, or more. To support this, send
stream version 2 encodes the DATA attribute differently: it has no
length field, and the length is implicitly up to the end of containing
command (which has a 32bit length field). Although this is necessary
for encoded writes, normal writes can benefit from it, too.
Also add a check to enforce that the DATA attribute is last. It is only
strictly necessary for v2, but we might as well make v1 consistent with
it.
For v2, let's bump up the send buffer to the maximum compressed extent
size plus 16K for the other metadata (144K total). Since this will most
likely be vmalloc'd (and always will be after the next commit), we round
it up to the next page since we might as well use the rest of the page
on systems with >16K pages.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This adds the definitions of the new commands for send stream version 2
and their respective attributes: fallocate, FS_IOC_SETFLAGS (a.k.a.
chattr), and encoded writes. It also documents two changes to the send
stream format in v2: the receiver shouldn't assume a maximum command
size, and the DATA attribute is encoded differently to allow for writes
larger than 64k. These will be implemented in subsequent changes, and
then the ioctl will accept the new version and flag.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit e77fbf990316 ("btrfs: send: prepare for v2 protocol") added
_BTRFS_SEND_C_MAX_V* macros equal to the maximum command number for the
version plus 1, but as written this creates gaps in the number space.
The maximum command number is currently 22, and __BTRFS_SEND_C_MAX_V1 is
accordingly 23. But then __BTRFS_SEND_C_MAX_V2 is 24, suggesting that v2
has a command numbered 23, and __BTRFS_SEND_C_MAX is 25, suggesting that
23 and 24 are valid commands.
Instead, let's explicitly number all of the commands, attributes, and
sentinel MAX constants.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We collect these statistics but have never exposed them in any way. I
also didn't find any patches that ever attempted to make use of them.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Merge tag 'for-5.19-rc7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs reverts from David Sterba:
"Due to a recent report [1] we need to revert the radix tree to xarray
conversion patches.
There's a problem with sleeping under spinlock, when xa_insert could
allocate memory under pressure. We use GFP_NOFS so this is a real
problem that we unfortunately did not discover during review.
I'm sorry to do such change at rc6 time but the revert is IMO the
safer option, there are patches to use mutex instead of the spin locks
but that would need more testing. The revert branch has been tested on
a few setups, all seem ok.
The conversion to xarray will be revisited in the future"
Link: https://lore.kernel.org/linux-btrfs/cover.1657097693.git.fdmanana@suse.com/ [1]
* tag 'for-5.19-rc7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
Revert "btrfs: turn delayed_nodes_tree into an XArray"
Revert "btrfs: turn name_cache radix tree into XArray in send_ctx"
Revert "btrfs: turn fs_info member buffer_radix into XArray"
Revert "btrfs: turn fs_roots_radix in btrfs_fs_info into an XArray"
This reverts commit 4076942021fe14efecae33bf98566df6dd5ae6f7.
Revert the xarray conversion, there's a problem with potential
sleep-inside-spinlock [1] when calling xa_insert that triggers GFP_NOFS
allocation. The radix tree used the preloading mechanism to avoid
sleeping but this is not available in xarray.
Conversion from spin lock to mutex is possible but at time of rc6 is
riskier than a clean revert.
[1] https://lore.kernel.org/linux-btrfs/cover.1657097693.git.fdmanana@suse.com/
Reported-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
- Appoint myself page cache maintainer
- Fix how scsicam uses the page cache
- Use the memalloc_nofs_save() API to replace AOP_FLAG_NOFS
- Remove the AOP flags entirely
- Remove pagecache_write_begin() and pagecache_write_end()
- Documentation updates
- Convert several address_space operations to use folios:
- is_dirty_writeback
- readpage becomes read_folio
- releasepage becomes release_folio
- freepage becomes free_folio
- Change filler_t to require a struct file pointer be the first argument
like ->read_folio
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Merge tag 'folio-5.19' of git://git.infradead.org/users/willy/pagecache
Pull page cache updates from Matthew Wilcox:
- Appoint myself page cache maintainer
- Fix how scsicam uses the page cache
- Use the memalloc_nofs_save() API to replace AOP_FLAG_NOFS
- Remove the AOP flags entirely
- Remove pagecache_write_begin() and pagecache_write_end()
- Documentation updates
- Convert several address_space operations to use folios:
- is_dirty_writeback
- readpage becomes read_folio
- releasepage becomes release_folio
- freepage becomes free_folio
- Change filler_t to require a struct file pointer be the first
argument like ->read_folio
* tag 'folio-5.19' of git://git.infradead.org/users/willy/pagecache: (107 commits)
nilfs2: Fix some kernel-doc comments
Appoint myself page cache maintainer
fs: Remove aops->freepage
secretmem: Convert to free_folio
nfs: Convert to free_folio
orangefs: Convert to free_folio
fs: Add free_folio address space operation
fs: Convert drop_buffers() to use a folio
fs: Change try_to_free_buffers() to take a folio
jbd2: Convert release_buffer_page() to use a folio
jbd2: Convert jbd2_journal_try_to_free_buffers to take a folio
reiserfs: Convert release_buffer_page() to use a folio
fs: Remove last vestiges of releasepage
ubifs: Convert to release_folio
reiserfs: Convert to release_folio
orangefs: Convert to release_folio
ocfs2: Convert to release_folio
nilfs2: Remove comment about releasepage
nfs: Convert to release_folio
jfs: Convert to release_folio
...
A send operation reads extent data using the buffered IO path for getting
extent data to send in write commands and this is both because it's simple
and to make use of the generic readahead infrastructure, which results in
a massive speedup.
However this fills the page cache with data that, most of the time, is
really only used by the send operation - once the write commands are sent,
it's not useful to have the data in the page cache anymore. For large
snapshots, bringing all data into the page cache eventually leads to the
need to evict other data from the page cache that may be more useful for
applications (and kernel subsystems).
Even if extents are shared with the subvolume on which a snapshot is based
on and the data is currently on the page cache due to being read through
the subvolume, attempting to read the data through the snapshot will
always result in bringing a new copy of the data into another location in
the page cache (there's currently no shared memory for shared extents).
So make send evict the data it has read before if when it first opened
the inode, its mapping had no pages currently loaded: when
inode->i_mapping->nr_pages has a value of 0. Do this instead of deciding
based on the return value of filemap_range_has_page() before reading an
extent because the generic readahead mechanism may read pages beyond the
range we request (and it very often does it), which means a call to
filemap_range_has_page() will return true due to the readahead that was
triggered when processing a previous extent - we don't have a simple way
to distinguish this case from the case where the data was brought into
the page cache through someone else. So checking for the mapping number
of pages being 0 when we first open the inode is simple, cheap and it
generally accomplishes the goal of not trashing the page cache - the
only exception is if part of data was previously loaded into the page
cache through the snapshot by some other process, in that case we end
up not evicting any data send brings into the page cache, just like
before this change - but that however is not the common case.
Example scenario, on a box with 32G of RAM:
$ btrfs subvolume create /mnt/sv1
$ xfs_io -f -c "pwrite 0 4G" /mnt/sv1/file1
$ btrfs subvolume snapshot -r /mnt/sv1 /mnt/snap1
$ free -m
total used free shared buff/cache available
Mem: 31937 186 26866 0 4883 31297
Swap: 8188 0 8188
# After this we get less 4G of free memory.
$ btrfs send /mnt/snap1 >/dev/null
$ free -m
total used free shared buff/cache available
Mem: 31937 186 22814 0 8935 31297
Swap: 8188 0 8188
The same, obviously, applies to an incremental send.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Every time we send a write command, we open the inode, read some data to
a buffer and then close the inode. The amount of data we read for each
write command is at most 48K, returned by max_send_read_size(), and that
corresponds to: BTRFS_SEND_BUF_SIZE - 16K = 48K. In practice this does
not add any significant overhead, because the time elapsed between every
close (iput()) and open (btrfs_iget()) is very short, so the inode is kept
in the VFS's cache after the iput() and it's still there by the time we
do the next btrfs_iget().
As between processing extents of the current inode we don't do anything
else, it makes sense to keep the inode open after we process its first
extent that needs to be sent and keep it open until we start processing
the next inode. This serves to facilitate the next change, which aims
to avoid having send operations trash the page cache with data extents.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
