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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fix from David Sterba:
"One regression fix.
The rewrite of scrub code in 6.4 broke device replace in zoned mode,
some of the writes could happen out of order so this had to be
adjusted for all cases"
* tag 'for-6.4-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: zoned: fix dev-replace after the scrub rework
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[BUG]
After commit e02ee89baa66 ("btrfs: scrub: switch scrub_simple_mirror()
to scrub_stripe infrastructure"), scrub no longer works for zoned device
at all.
Even an empty zoned btrfs cannot be replaced:
# mkfs.btrfs -f /dev/nvme0n1
# mount /dev/nvme0n1 /mnt/btrfs
# btrfs replace start -Bf 1 /dev/nvme0n2 /mnt/btrfs
Resetting device zones /dev/nvme1n1 (160 zones) ...
ERROR: ioctl(DEV_REPLACE_START) failed on "/mnt/btrfs/": Input/output error
And we can hit kernel crash related to that:
BTRFS info (device nvme1n1): host-managed zoned block device /dev/nvme3n1, 160 zones of 134217728 bytes
BTRFS info (device nvme1n1): dev_replace from /dev/nvme2n1 (devid 2) to /dev/nvme3n1 started
nvme3n1: Zone Management Append(0x7d) @ LBA 65536, 4 blocks, Zone Is Full (sct 0x1 / sc 0xb9) DNR
I/O error, dev nvme3n1, sector 786432 op 0xd:(ZONE_APPEND) flags 0x4000 phys_seg 3 prio class 2
BTRFS error (device nvme1n1): bdev /dev/nvme3n1 errs: wr 1, rd 0, flush 0, corrupt 0, gen 0
BUG: kernel NULL pointer dereference, address: 00000000000000a8
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
RIP: 0010:_raw_spin_lock_irqsave+0x1e/0x40
Call Trace:
<IRQ>
btrfs_lookup_ordered_extent+0x31/0x190
btrfs_record_physical_zoned+0x18/0x40
btrfs_simple_end_io+0xaf/0xc0
blk_update_request+0x153/0x4c0
blk_mq_end_request+0x15/0xd0
nvme_poll_cq+0x1d3/0x360
nvme_irq+0x39/0x80
__handle_irq_event_percpu+0x3b/0x190
handle_irq_event+0x2f/0x70
handle_edge_irq+0x7c/0x210
__common_interrupt+0x34/0xa0
common_interrupt+0x7d/0xa0
</IRQ>
<TASK>
asm_common_interrupt+0x22/0x40
[CAUSE]
Dev-replace reuses scrub code to iterate all extents and write the
existing content back to the new device.
And for zoned devices, we call fill_writer_pointer_gap() to make sure
all the writes into the zoned device is sequential, even if there may be
some gaps between the writes.
However we have several different bugs all related to zoned dev-replace:
- We are using ZONE_APPEND operation for metadata style write back
For zoned devices, btrfs has two ways to write data:
* ZONE_APPEND for data
This allows higher queue depth, but will not be able to know where
the write would land.
Thus needs to grab the real on-disk physical location in it's endio.
* WRITE for metadata
This requires single queue depth (new writes can only be submitted
after previous one finished), and all writes must be sequential.
For scrub, we go single queue depth, but still goes with ZONE_APPEND,
which requires btrfs_bio::inode being populated.
This is the cause of that crash.
- No correct tracing of write_pointer
After a write finished, we should forward sctx->write_pointer, or
fill_writer_pointer_gap() would not work properly and cause more
than necessary zero out, and fill the whole zone prematurely.
- Incorrect physical bytenr passed to fill_writer_pointer_gap()
In scrub_write_sectors(), one call site passes logical address, which
is completely wrong.
The other call site passes physical address of current sector, but
we should pass the physical address of the btrfs_bio we're submitting.
This is the cause of the -EIO errors.
[FIX]
- Do not use ZONE_APPEND for btrfs_submit_repair_write().
- Manually forward sctx->write_pointer after successful writeback
- Use the physical address of the to-be-submitted btrfs_bio for
fill_writer_pointer_gap()
Now zoned device replace would work as expected.
Reported-by: Christoph Hellwig <hch@lst.de>
Fixes: e02ee89baa66 ("btrfs: scrub: switch scrub_simple_mirror() to scrub_stripe infrastructure")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
"One bug fix and two build warning fixes:
- call proper end bio callback for metadata RAID0 in a rare case of
an unaligned block
- fix uninitialized variable (reported by gcc 10.2)
- fix warning about potential access beyond array bounds on mips64
with 64k pages (runtime check would not allow that)"
* tag 'for-6.4-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: fix csum_tree_block page iteration to avoid tripping on -Werror=array-bounds
btrfs: fix an uninitialized variable warning in btrfs_log_inode
btrfs: call btrfs_orig_bbio_end_io in btrfs_end_bio_work
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-Werror=array-bounds
When compiling on a MIPS 64-bit machine we get these warnings:
In file included from ./arch/mips/include/asm/cacheflush.h:13,
from ./include/linux/cacheflush.h:5,
from ./include/linux/highmem.h:8,
from ./include/linux/bvec.h:10,
from ./include/linux/blk_types.h:10,
from ./include/linux/blkdev.h:9,
from fs/btrfs/disk-io.c:7:
fs/btrfs/disk-io.c: In function ‘csum_tree_block’:
fs/btrfs/disk-io.c:100:34: error: array subscript 1 is above array bounds of ‘struct page *[1]’ [-Werror=array-bounds]
100 | kaddr = page_address(buf->pages[i]);
| ~~~~~~~~~~^~~
./include/linux/mm.h:2135:48: note: in definition of macro ‘page_address’
2135 | #define page_address(page) lowmem_page_address(page)
| ^~~~
cc1: all warnings being treated as errors
We can check if i overflows to solve the problem. However, this doesn't make
much sense, since i == 1 and num_pages == 1 doesn't execute the body of the loop.
In addition, i < num_pages can also ensure that buf->pages[i] will not cross
the boundary. Unfortunately, this doesn't help with the problem observed here:
gcc still complains.
To fix this add a compile-time condition for the extent buffer page
array size limit, which would eventually lead to eliminating the whole
for loop.
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: pengfuyuan <pengfuyuan@kylinos.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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This fixes the following warning reported by gcc 10.2.1 under x86_64:
../fs/btrfs/tree-log.c: In function ‘btrfs_log_inode’:
../fs/btrfs/tree-log.c:6211:9: error: ‘last_range_start’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
6211 | ret = insert_dir_log_key(trans, log, path, key.objectid,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6212 | first_dir_index, last_dir_index);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../fs/btrfs/tree-log.c:6161:6: note: ‘last_range_start’ was declared here
6161 | u64 last_range_start;
| ^~~~~~~~~~~~~~~~
This might be a false positive fixed in later compiler versions but we
want to have it fixed.
Reported-by: k2ci <kernel-bot@kylinos.cn>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Shida Zhang <zhangshida@kylinos.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When I implemented the storage layer bio splitting, I was under the
assumption that we'll never split metadata bios. But Qu reminded me that
this can actually happen with very old file systems with unaligned
metadata chunks and RAID0.
I still haven't seen such a case in practice, but we better handled this
case, especially as it is fairly easily to do not calling the ->end_іo
method directly in btrfs_end_io_work, and using the proper
btrfs_orig_bbio_end_io helper instead.
In addition to the old file system with unaligned metadata chunks case
documented in the commit log, the combination of the new scrub code
with Johannes pending raid-stripe-tree also triggers this case. We
spent some time debugging it and found that this patch solves
the problem.
Fixes: 103c19723c80 ("btrfs: split the bio submission path into a separate file")
CC: stable@vger.kernel.org # 6.3+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
- handle memory allocation error in checksumming helper (reported by
syzbot)
- fix lockdep splat when aborting a transaction, add NOFS protection
around invalidate_inode_pages2 that could allocate with GFP_KERNEL
- reduce chances to hit an ENOSPC during scrub with RAID56 profiles
* tag 'for-6.4-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: use nofs when cleaning up aborted transactions
btrfs: handle memory allocation failure in btrfs_csum_one_bio
btrfs: scrub: try harder to mark RAID56 block groups read-only
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Our CI system caught a lockdep splat:
======================================================
WARNING: possible circular locking dependency detected
6.3.0-rc7+ #1167 Not tainted
------------------------------------------------------
kswapd0/46 is trying to acquire lock:
ffff8c6543abd650 (sb_internal#2){++++}-{0:0}, at: btrfs_commit_inode_delayed_inode+0x5f/0x120
but task is already holding lock:
ffffffffabe61b40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x4aa/0x7a0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (fs_reclaim){+.+.}-{0:0}:
fs_reclaim_acquire+0xa5/0xe0
kmem_cache_alloc+0x31/0x2c0
alloc_extent_state+0x1d/0xd0
__clear_extent_bit+0x2e0/0x4f0
try_release_extent_mapping+0x216/0x280
btrfs_release_folio+0x2e/0x90
invalidate_inode_pages2_range+0x397/0x470
btrfs_cleanup_dirty_bgs+0x9e/0x210
btrfs_cleanup_one_transaction+0x22/0x760
btrfs_commit_transaction+0x3b7/0x13a0
create_subvol+0x59b/0x970
btrfs_mksubvol+0x435/0x4f0
__btrfs_ioctl_snap_create+0x11e/0x1b0
btrfs_ioctl_snap_create_v2+0xbf/0x140
btrfs_ioctl+0xa45/0x28f0
__x64_sys_ioctl+0x88/0xc0
do_syscall_64+0x38/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
-> #0 (sb_internal#2){++++}-{0:0}:
__lock_acquire+0x1435/0x21a0
lock_acquire+0xc2/0x2b0
start_transaction+0x401/0x730
btrfs_commit_inode_delayed_inode+0x5f/0x120
btrfs_evict_inode+0x292/0x3d0
evict+0xcc/0x1d0
inode_lru_isolate+0x14d/0x1e0
__list_lru_walk_one+0xbe/0x1c0
list_lru_walk_one+0x58/0x80
prune_icache_sb+0x39/0x60
super_cache_scan+0x161/0x1f0
do_shrink_slab+0x163/0x340
shrink_slab+0x1d3/0x290
shrink_node+0x300/0x720
balance_pgdat+0x35c/0x7a0
kswapd+0x205/0x410
kthread+0xf0/0x120
ret_from_fork+0x29/0x50
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(sb_internal#2);
lock(fs_reclaim);
lock(sb_internal#2);
*** DEADLOCK ***
3 locks held by kswapd0/46:
#0: ffffffffabe61b40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x4aa/0x7a0
#1: ffffffffabe50270 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x113/0x290
#2: ffff8c6543abd0e0 (&type->s_umount_key#44){++++}-{3:3}, at: super_cache_scan+0x38/0x1f0
stack backtrace:
CPU: 0 PID: 46 Comm: kswapd0 Not tainted 6.3.0-rc7+ #1167
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x58/0x90
check_noncircular+0xd6/0x100
? save_trace+0x3f/0x310
? add_lock_to_list+0x97/0x120
__lock_acquire+0x1435/0x21a0
lock_acquire+0xc2/0x2b0
? btrfs_commit_inode_delayed_inode+0x5f/0x120
start_transaction+0x401/0x730
? btrfs_commit_inode_delayed_inode+0x5f/0x120
btrfs_commit_inode_delayed_inode+0x5f/0x120
btrfs_evict_inode+0x292/0x3d0
? lock_release+0x134/0x270
? __pfx_wake_bit_function+0x10/0x10
evict+0xcc/0x1d0
inode_lru_isolate+0x14d/0x1e0
__list_lru_walk_one+0xbe/0x1c0
? __pfx_inode_lru_isolate+0x10/0x10
? __pfx_inode_lru_isolate+0x10/0x10
list_lru_walk_one+0x58/0x80
prune_icache_sb+0x39/0x60
super_cache_scan+0x161/0x1f0
do_shrink_slab+0x163/0x340
shrink_slab+0x1d3/0x290
shrink_node+0x300/0x720
balance_pgdat+0x35c/0x7a0
kswapd+0x205/0x410
? __pfx_autoremove_wake_function+0x10/0x10
? __pfx_kswapd+0x10/0x10
kthread+0xf0/0x120
? __pfx_kthread+0x10/0x10
ret_from_fork+0x29/0x50
</TASK>
This happens because when we abort the transaction in the transaction
commit path we call invalidate_inode_pages2_range on our block group
cache inodes (if we have space cache v1) and any delalloc inodes we may
have. The plain invalidate_inode_pages2_range() call passes through
GFP_KERNEL, which makes sense in most cases, but not here. Wrap these
two invalidate callees with memalloc_nofs_save/memalloc_nofs_restore to
make sure we don't end up with the fs reclaim dependency under the
transaction dependency.
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Since f8a53bb58ec7 ("btrfs: handle checksum generation in the storage
layer") the failures of btrfs_csum_one_bio() are handled via
bio_end_io().
This means, we can return BLK_STS_RESOURCE from btrfs_csum_one_bio() in
case the allocation of the ordered sums fails.
This also fixes a syzkaller report, where injecting a failure into the
kvzalloc() call results in a BUG_ON().
Reported-by: syzbot+d8941552e21eac774778@syzkaller.appspotmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anand Jain <anand.jain@oracle.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>
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Currently we allow a block group not to be marked read-only for scrub.
But for RAID56 block groups if we require the block group to be
read-only, then we're allowed to use cached content from scrub stripe to
reduce unnecessary RAID56 reads.
So this patch would:
- Make btrfs_inc_block_group_ro() try harder
During my tests, for cases like btrfs/061 and btrfs/064, we can hit
ENOSPC from btrfs_inc_block_group_ro() calls during scrub.
The reason is if we only have one single data chunk, and trying to
scrub it, we won't have any space left for any newer data writes.
But this check should be done by the caller, especially for scrub
cases we only temporarily mark the chunk read-only.
And newer data writes would always try to allocate a new data chunk
when needed.
- Return error for scrub if we failed to mark a RAID56 chunk read-only
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull more btrfs fixes from David Sterba:
- fix incorrect number of bitmap entries for space cache if loading is
interrupted by some error
- fix backref walking, this breaks a mode of LOGICAL_INO_V2 ioctl that
is used in deduplication tools
- zoned mode fixes:
- properly finish zone reserved for relocation
- correctly calculate super block zone end on ZNS
- properly initialize new extent buffer for redirty
- make mount option clear_cache work with block-group-tree, to rebuild
free-space-tree instead of temporarily disabling it that would lead
to a forced read-only mount
- fix alignment check for offset when printing extent item
* tag 'for-6.4-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: make clear_cache mount option to rebuild FST without disabling it
btrfs: zero the buffer before marking it dirty in btrfs_redirty_list_add
btrfs: zoned: fix full zone super block reading on ZNS
btrfs: zoned: zone finish data relocation BG with last IO
btrfs: fix backref walking not returning all inode refs
btrfs: fix space cache inconsistency after error loading it from disk
btrfs: print-tree: parent bytenr must be aligned to sector size
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Previously clear_cache mount option would simply disable free-space-tree
feature temporarily then re-enable it to rebuild the whole free space
tree.
But this is problematic for block-group-tree feature, as we have an
artificial dependency on free-space-tree feature.
If we go the existing method, after clearing the free-space-tree
feature, we would flip the filesystem to read-only mode, as we detect a
super block write with block-group-tree but no free-space-tree feature.
This patch would change the behavior by properly rebuilding the free
space tree without disabling this feature, thus allowing clear_cache
mount option to work with block group tree.
Now we can mount a filesystem with block-group-tree feature and
clear_mount option:
$ mkfs.btrfs -O block-group-tree /dev/test/scratch1 -f
$ sudo mount /dev/test/scratch1 /mnt/btrfs -o clear_cache
$ sudo dmesg -t | head -n 5
BTRFS info (device dm-1): force clearing of disk cache
BTRFS info (device dm-1): using free space tree
BTRFS info (device dm-1): auto enabling async discard
BTRFS info (device dm-1): rebuilding free space tree
BTRFS info (device dm-1): checking UUID tree
CC: stable@vger.kernel.org # 6.1+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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btrfs_redirty_list_add zeroes the buffer data and sets the
EXTENT_BUFFER_NO_CHECK to make sure writeback is fine with a bogus
header. But it does that after already marking the buffer dirty, which
means that writeback could already be looking at the buffer.
Switch the order of operations around so that the buffer is only marked
dirty when we're ready to write it.
Fixes: d3575156f662 ("btrfs: zoned: redirty released extent buffers")
CC: stable@vger.kernel.org # 5.15+
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When both of the superblock zones are full, we need to check which
superblock is newer. The calculation of last superblock position is wrong
as it does not consider zone_capacity and uses the length.
Fixes: 9658b72ef300 ("btrfs: zoned: locate superblock position using zone capacity")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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For data block groups, we zone finish a zone (or, just deactivate it) when
seeing the last IO in btrfs_finish_ordered_io(). That is only called for
IOs using ZONE_APPEND, but we use a regular WRITE command for data
relocation IOs. Detect it and call btrfs_zone_finish_endio() properly.
Fixes: be1a1d7a5d24 ("btrfs: zoned: finish fully written block group")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When using the logical to ino ioctl v2, if the flag to ignore offsets of
file extent items (BTRFS_LOGICAL_INO_ARGS_IGNORE_OFFSET) is given, the
backref walking code ends up not returning references for all file offsets
of an inode that point to the given logical bytenr. This happens since
kernel 6.2, commit 6ce6ba534418 ("btrfs: use a single argument for extent
offset in backref walking functions") because:
1) It mistakenly skipped the search for file extent items in a leaf that
point to the target extent if that flag is given. Instead it should
only skip the filtering done by check_extent_in_eb() - that is, it
should not avoid the calls to that function (or find_extent_in_eb(),
which uses it).
2) It was also not building a list of inode extent elements (struct
extent_inode_elem) if we have multiple inode references for an extent
when the ignore offset flag is given to the logical to ino ioctl - it
would leave a single element, only the last one that was found.
These stem from the confusing old interface for backref walking functions
where we had an extent item offset argument that was a pointer to a u64
and another boolean argument that indicated if the offset should be
ignored, but the pointer could be NULL. That NULL case is used by
relocation, qgroup extent accounting and fiemap, simply to avoid building
the inode extent list for each reference, as it's not necessary for those
use cases and therefore avoids memory allocations and some computations.
Fix this by adding a boolean argument to the backref walk context
structure to indicate that the inode extent list should not be built,
make relocation set that argument to true and fix the backref walking
logic to skip the calls to check_extent_in_eb() and find_extent_in_eb()
only if this new argument is true, instead of 'ignore_extent_item_pos'
being true.
A test case for fstests will be added soon, to provide cover not only
for these cases but to the logical to ino ioctl in general as well, as
currently we do not have a test case for it.
Reported-by: Vladimir Panteleev <git@vladimir.panteleev.md>
Link: https://lore.kernel.org/linux-btrfs/CAHhfkvwo=nmzrJSqZ2qMfF-rZB-ab6ahHnCD_sq9h4o8v+M7QQ@mail.gmail.com/
Fixes: 6ce6ba534418 ("btrfs: use a single argument for extent offset in backref walking functions")
CC: stable@vger.kernel.org # 6.2+
Tested-by: Vladimir Panteleev <git@vladimir.panteleev.md>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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When loading a free space cache from disk, at __load_free_space_cache(),
if we fail to insert a bitmap entry, we still increment the number of
total bitmaps in the btrfs_free_space_ctl structure, which is incorrect
since we failed to add the bitmap entry. On error we then empty the
cache by calling __btrfs_remove_free_space_cache(), which will result
in getting the total bitmaps counter set to 1.
A failure to load a free space cache is not critical, so if a failure
happens we just rebuild the cache by scanning the extent tree, which
happens at block-group.c:caching_thread(). Yet the failure will result
in having the total bitmaps of the btrfs_free_space_ctl always bigger
by 1 then the number of bitmap entries we have. So fix this by having
the total bitmaps counter be incremented only if we successfully added
the bitmap entry.
Fixes: a67509c30079 ("Btrfs: add a io_ctl struct and helpers for dealing with the space cache")
Reviewed-by: Anand Jain <anand.jain@oracle.com>
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>
|
|
Check nodesize to sectorsize in alignment check in print_extent_item.
The comment states that and this is correct, similar check is done
elsewhere in the functions.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: ea57788eb76d ("btrfs: require only sector size alignment for parent eb bytenr")
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Anastasia Belova <abelova@astralinux.ru>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
Pull btrfs fixes from David Sterba:
- fix backward leaf iteration which could possibly return the same key
- fix assertion when device add and balance race for exclusive
operation
- fix regression when freeing device, state tree would leak after
device replace
- fix attempt to clear space cache v1 when block-group-tree is enabled
- fix potential i_size corruption when encoded write races with send v2
and enabled no-holes (the race is hard to hit though, the window is a
few instructions wide)
- fix wrong bitmap API use when checking empty zones, parameters were
swapped but not causing a bug due to other code
- prevent potential qgroup leak if subvolume create does not commit
transaction (which is pending in the development queue)
- error handling and reporting:
- abort transaction when sibling keys check fails for leaves
- print extent buffers when sibling keys check fails
* tag 'for-6.4-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: don't free qgroup space unless specified
btrfs: fix encoded write i_size corruption with no-holes
btrfs: zoned: fix wrong use of bitops API in btrfs_ensure_empty_zones
btrfs: properly reject clear_cache and v1 cache for block-group-tree
btrfs: print extent buffers when sibling keys check fails
btrfs: abort transaction when sibling keys check fails for leaves
btrfs: fix leak of source device allocation state after device replace
btrfs: fix assertion of exclop condition when starting balance
btrfs: fix btrfs_prev_leaf() to not return the same key twice
|
|
Boris noticed in his simple quotas testing that he was getting a leak
with Sweet Tea's change to subvol create that stopped doing a
transaction commit. This was just a side effect of that change.
In the delayed inode code we have an optimization that will free extra
reservations if we think we can pack a dir item into an already modified
leaf. Previously this wouldn't be triggered in the subvolume create
case because we'd commit the transaction, it was still possible but
much harder to trigger. It could actually be triggered if we did a
mkdir && subvol create with qgroups enabled.
This occurs because in btrfs_insert_delayed_dir_index(), which gets
called when we're adding the dir item, we do the following:
btrfs_block_rsv_release(fs_info, trans->block_rsv, bytes, NULL);
if we're able to skip reserving space.
The problem here is that trans->block_rsv points at the temporary block
rsv for the subvolume create, which has qgroup reservations in the block
rsv.
This is a problem because btrfs_block_rsv_release() will do the
following:
if (block_rsv->qgroup_rsv_reserved >= block_rsv->qgroup_rsv_size) {
qgroup_to_release = block_rsv->qgroup_rsv_reserved -
block_rsv->qgroup_rsv_size;
block_rsv->qgroup_rsv_reserved = block_rsv->qgroup_rsv_size;
}
The temporary block rsv just has ->qgroup_rsv_reserved set,
->qgroup_rsv_size == 0. The optimization in
btrfs_insert_delayed_dir_index() sets ->qgroup_rsv_reserved = 0. Then
later on when we call btrfs_subvolume_release_metadata() which has
btrfs_block_rsv_release(fs_info, rsv, (u64)-1, &qgroup_to_release);
btrfs_qgroup_convert_reserved_meta(root, qgroup_to_release);
qgroup_to_release is set to 0, and we do not convert the reserved
metadata space.
The problem here is that the block rsv code has been unconditionally
messing with ->qgroup_rsv_reserved, because the main place this is used
is delalloc, and any time we call btrfs_block_rsv_release() we do it
with qgroup_to_release set, and thus do the proper accounting.
The subvolume code is the only other code that uses the qgroup
reservation stuff, but it's intermingled with the above optimization,
and thus was getting its reservation freed out from underneath it and
thus leaking the reserved space.
The solution is to simply not mess with the qgroup reservations if we
don't have qgroup_to_release set. This works with the existing code as
anything that messes with the delalloc reservations always have
qgroup_to_release set. This fixes the leak that Boris was observing.
Reviewed-by: Qu Wenruo <wqu@suse.com>
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
We have observed a btrfs filesystem corruption on workloads using
no-holes and encoded writes via send stream v2. The symptom is that a
file appears to be truncated to the end of its last aligned extent, even
though the final unaligned extent and even the file extent and otherwise
correctly updated inode item have been written.
So if we were writing out a 1MiB+X file via 8 128K extents and one
extent of length X, i_size would be set to 1MiB, but the ninth extent,
nbyte, etc. would all appear correct otherwise.
The source of the race is a narrow (one line of code) window in which a
no-holes fs has read in an updated i_size, but has not yet set a shared
disk_i_size variable to write. Therefore, if two ordered extents run in
parallel (par for the course for receive workloads), the following
sequence can play out: (following "threads" a bit loosely, since there
are callbacks involved for endio but extra threads aren't needed to
cause the issue)
ENC-WR1 (second to last) ENC-WR2 (last)
------- -------
btrfs_do_encoded_write
set i_size = 1M
submit bio B1 ending at 1M
endio B1
btrfs_inode_safe_disk_i_size_write
local i_size = 1M
falls off a cliff for some reason
btrfs_do_encoded_write
set i_size = 1M+X
submit bio B2 ending at 1M+X
endio B2
btrfs_inode_safe_disk_i_size_write
local i_size = 1M+X
disk_i_size = 1M+X
disk_i_size = 1M
btrfs_delayed_update_inode
btrfs_delayed_update_inode
And the delayed inode ends up filled with nbytes=1M+X and isize=1M, and
writes respect i_size and present a corrupted file missing its last
extents.
Fix this by holding the inode lock in the no-holes case so that a thread
can't sneak in a write to disk_i_size that gets overwritten with an out
of date i_size.
Fixes: 41a2ee75aab0 ("btrfs: introduce per-inode file extent tree")
CC: stable@vger.kernel.org # 5.10+
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>
|
|
find_next_bit and find_next_zero_bit take @size as the second parameter and
@offset as the third parameter. They are specified opposite in
btrfs_ensure_empty_zones(). Thanks to the later loop, it never failed to
detect the empty zones. Fix them and (maybe) return the result a bit
faster.
Note: the naming is a bit confusing, size has two meanings here, bitmap
and our range size.
Fixes: 1cd6121f2a38 ("btrfs: zoned: implement zoned chunk allocator")
CC: stable@vger.kernel.org # 5.15+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
[BUG]
With block-group-tree feature enabled, mounting it with clear_cache
would cause the following transaction abort at mount or remount:
BTRFS info (device dm-4): force clearing of disk cache
BTRFS info (device dm-4): using free space tree
BTRFS info (device dm-4): auto enabling async discard
BTRFS info (device dm-4): clearing free space tree
BTRFS info (device dm-4): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1)
BTRFS info (device dm-4): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2)
BTRFS error (device dm-4): block-group-tree feature requires fres-space-tree and no-holes
BTRFS error (device dm-4): super block corruption detected before writing it to disk
BTRFS: error (device dm-4) in write_all_supers:4288: errno=-117 Filesystem corrupted (unexpected superblock corruption detected)
BTRFS warning (device dm-4: state E): Skipping commit of aborted transaction.
[CAUSE]
For block-group-tree feature, we have an artificial dependency on
free-space-tree.
This means if we detect block-group-tree without v2 cache, we consider
it a corruption and cause the problem.
For clear_cache mount option, it would temporary disable v2 cache, then
re-enable it.
But unfortunately for that temporary v2 cache disabled status, we refuse
to write a superblock with bg tree only flag, thus leads to the above
transaction abortion.
[FIX]
For now, just reject clear_cache and v1 cache mount option for block
group tree. So now we got a graceful rejection other than a transaction
abort:
BTRFS info (device dm-4): force clearing of disk cache
BTRFS error (device dm-4): cannot disable free space tree with block-group-tree feature
BTRFS error (device dm-4): open_ctree failed
CC: stable@vger.kernel.org # 6.1+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When trying to move keys from one node/leaf to another sibling node/leaf,
if the sibling keys check fails we just print an error message with the
last key of the left sibling and the first key of the right sibling.
However it's also useful to print all the keys of each sibling, as it
may provide some clues to what went wrong, which code path may be
inserting keys in an incorrect order. So just do that, print the siblings
with btrfs_print_tree(), as it works for both leaves and nodes.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
If the sibling keys check fails before we move keys from one sibling
leaf to another, we are not aborting the transaction - we leave that to
some higher level caller of btrfs_search_slot() (or anything else that
uses it to insert items into a b+tree).
This means that the transaction abort will provide a stack trace that
omits the b+tree modification call chain. So change this to immediately
abort the transaction and therefore get a more useful stack trace that
shows us the call chain in the bt+tree modification code.
It's also important to immediately abort the transaction just in case
some higher level caller is not doing it, as this indicates a very
serious corruption and we should stop the possibility of doing further
damage.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
When a device replace finishes, the source device is freed by calling
btrfs_free_device() at btrfs_rm_dev_replace_free_srcdev(), but the
allocation state, tracked in the device's alloc_state io tree, is never
freed.
This is a regression recently introduced by commit f0bb5474cff0 ("btrfs:
remove redundant release of btrfs_device::alloc_state"), which removed a
call to extent_io_tree_release() from btrfs_free_device(), with the
rationale that btrfs_close_one_device() already releases the allocation
state from a device and btrfs_close_one_device() is always called before
a device is freed with btrfs_free_device(). However that is not true for
the device replace case, as btrfs_free_device() is called without any
previous call to btrfs_close_one_device().
The issue is trivial to reproduce, for example, by running test btrfs/027
from fstests:
$ ./check btrfs/027
$ rmmod btrfs
$ dmesg
(...)
[84519.395485] BTRFS info (device sdc): dev_replace from <missing disk> (devid 2) to /dev/sdg started
[84519.466224] BTRFS info (device sdc): dev_replace from <missing disk> (devid 2) to /dev/sdg finished
[84519.552251] BTRFS info (device sdc): scrub: started on devid 1
[84519.552277] BTRFS info (device sdc): scrub: started on devid 2
[84519.552332] BTRFS info (device sdc): scrub: started on devid 3
[84519.552705] BTRFS info (device sdc): scrub: started on devid 4
[84519.604261] BTRFS info (device sdc): scrub: finished on devid 4 with status: 0
[84519.609374] BTRFS info (device sdc): scrub: finished on devid 3 with status: 0
[84519.610818] BTRFS info (device sdc): scrub: finished on devid 1 with status: 0
[84519.610927] BTRFS info (device sdc): scrub: finished on devid 2 with status: 0
[84559.503795] BTRFS: state leak: start 1048576 end 1351614463 state 1 in tree 1 refs 1
[84559.506764] BTRFS: state leak: start 1048576 end 1347420159 state 1 in tree 1 refs 1
[84559.510294] BTRFS: state leak: start 1048576 end 1351614463 state 1 in tree 1 refs 1
So fix this by adding back the call to extent_io_tree_release() at
btrfs_free_device().
Fixes: f0bb5474cff0 ("btrfs: remove redundant release of btrfs_device::alloc_state")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
Balance as exclusive state is compatible with paused balance and device
add, which makes some things more complicated. The assertion of valid
states when starting from paused balance needs to take into account two
more states, the combinations can be hit when there are several threads
racing to start balance and device add. This won't typically happen when
the commands are started from command line.
Scenario 1: With exclusive_operation state == BTRFS_EXCLOP_NONE.
Concurrently adding multiple devices to the same mount point and
btrfs_exclop_finish executed finishes before assertion in
btrfs_exclop_balance, exclusive_operation will changed to
BTRFS_EXCLOP_NONE state which lead to assertion failed:
fs_info->exclusive_operation == BTRFS_EXCLOP_BALANCE ||
fs_info->exclusive_operation == BTRFS_EXCLOP_DEV_ADD,
in fs/btrfs/ioctl.c:456
Call Trace:
<TASK>
btrfs_exclop_balance+0x13c/0x310
? memdup_user+0xab/0xc0
? PTR_ERR+0x17/0x20
btrfs_ioctl_add_dev+0x2ee/0x320
btrfs_ioctl+0x9d5/0x10d0
? btrfs_ioctl_encoded_write+0xb80/0xb80
__x64_sys_ioctl+0x197/0x210
do_syscall_64+0x3c/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Scenario 2: With exclusive_operation state == BTRFS_EXCLOP_BALANCE_PAUSED.
Concurrently adding multiple devices to the same mount point and
btrfs_exclop_balance executed finish before the latter thread execute
assertion in btrfs_exclop_balance, exclusive_operation will changed to
BTRFS_EXCLOP_BALANCE_PAUSED state which lead to assertion failed:
fs_info->exclusive_operation == BTRFS_EXCLOP_BALANCE ||
fs_info->exclusive_operation == BTRFS_EXCLOP_DEV_ADD ||
fs_info->exclusive_operation == BTRFS_EXCLOP_NONE,
fs/btrfs/ioctl.c:458
Call Trace:
<TASK>
btrfs_exclop_balance+0x240/0x410
? memdup_user+0xab/0xc0
? PTR_ERR+0x17/0x20
btrfs_ioctl_add_dev+0x2ee/0x320
btrfs_ioctl+0x9d5/0x10d0
? btrfs_ioctl_encoded_write+0xb80/0xb80
__x64_sys_ioctl+0x197/0x210
do_syscall_64+0x3c/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd
An example of the failed assertion is below, which shows that the
paused balance is also needed to be checked.
root@syzkaller:/home/xsk# ./repro
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
[ 416.611428][ T7970] BTRFS info (device loop0): fs_info exclusive_operation: 0
Failed to add device /dev/vda, errno 14
[ 416.613973][ T7971] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.615456][ T7972] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.617528][ T7973] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.618359][ T7974] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.622589][ T7975] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.624034][ T7976] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.626420][ T7977] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.627643][ T7978] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.629006][ T7979] BTRFS info (device loop0): fs_info exclusive_operation: 3
[ 416.630298][ T7980] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
Failed to add device /dev/vda, errno 14
[ 416.632787][ T7981] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.634282][ T7982] BTRFS info (device loop0): fs_info exclusive_operation: 3
Failed to add device /dev/vda, errno 14
[ 416.636202][ T7983] BTRFS info (device loop0): fs_info exclusive_operation: 3
[ 416.637012][ T7984] BTRFS info (device loop0): fs_info exclusive_operation: 1
Failed to add device /dev/vda, errno 14
[ 416.637759][ T7984] assertion failed: fs_info->exclusive_operation ==
BTRFS_EXCLOP_BALANCE || fs_info->exclusive_operation ==
BTRFS_EXCLOP_DEV_ADD || fs_info->exclusive_operation ==
BTRFS_EXCLOP_NONE, in fs/btrfs/ioctl.c:458
[ 416.639845][ T7984] invalid opcode: 0000 [#1] PREEMPT SMP KASAN
[ 416.640485][ T7984] CPU: 0 PID: 7984 Comm: repro Not tainted 6.2.0 #7
[ 416.641172][ T7984] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[ 416.642090][ T7984] RIP: 0010:btrfs_assertfail+0x2c/0x2e
[ 416.644423][ T7984] RSP: 0018:ffffc90003ea7e28 EFLAGS: 00010282
[ 416.645018][ T7984] RAX: 00000000000000cc RBX: 0000000000000000 RCX: 0000000000000000
[ 416.645763][ T7984] RDX: ffff88801d030000 RSI: ffffffff81637e7c RDI: fffff520007d4fb7
[ 416.646554][ T7984] RBP: ffffffff8a533de0 R08: 00000000000000cc R09: 0000000000000000
[ 416.647299][ T7984] R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff8a533da0
[ 416.648041][ T7984] R13: 00000000000001ca R14: 000000005000940a R15: 0000000000000000
[ 416.648785][ T7984] FS: 00007fa2985d4640(0000) GS:ffff88802cc00000(0000) knlGS:0000000000000000
[ 416.649616][ T7984] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 416.650238][ T7984] CR2: 0000000000000000 CR3: 0000000018e5e000 CR4: 0000000000750ef0
[ 416.650980][ T7984] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 416.651725][ T7984] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 416.652502][ T7984] PKRU: 55555554
[ 416.652888][ T7984] Call Trace:
[ 416.653241][ T7984] <TASK>
[ 416.653527][ T7984] btrfs_exclop_balance+0x240/0x410
[ 416.654036][ T7984] ? memdup_user+0xab/0xc0
[ 416.654465][ T7984] ? PTR_ERR+0x17/0x20
[ 416.654874][ T7984] btrfs_ioctl_add_dev+0x2ee/0x320
[ 416.655380][ T7984] btrfs_ioctl+0x9d5/0x10d0
[ 416.655822][ T7984] ? btrfs_ioctl_encoded_write+0xb80/0xb80
[ 416.656400][ T7984] __x64_sys_ioctl+0x197/0x210
[ 416.656874][ T7984] do_syscall_64+0x3c/0xb0
[ 416.657346][ T7984] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 416.657922][ T7984] RIP: 0033:0x4546af
[ 416.660170][ T7984] RSP: 002b:00007fa2985d4150 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 416.660972][ T7984] RAX: ffffffffffffffda RBX: 00007fa2985d4640 RCX: 00000000004546af
[ 416.661714][ T7984] RDX: 0000000000000000 RSI: 000000005000940a RDI: 0000000000000003
[ 416.662449][ T7984] RBP: 00007fa2985d41d0 R08: 0000000000000000 R09: 00007ffee37a4c4f
[ 416.663195][ T7984] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa2985d4640
[ 416.663951][ T7984] R13: 0000000000000009 R14: 000000000041b320 R15: 00007fa297dd4000
[ 416.664703][ T7984] </TASK>
[ 416.665040][ T7984] Modules linked in:
[ 416.665590][ T7984] ---[ end trace 0000000000000000 ]---
[ 416.666176][ T7984] RIP: 0010:btrfs_assertfail+0x2c/0x2e
[ 416.668775][ T7984] RSP: 0018:ffffc90003ea7e28 EFLAGS: 00010282
[ 416.669425][ T7984] RAX: 00000000000000cc RBX: 0000000000000000 RCX: 0000000000000000
[ 416.670235][ T7984] RDX: ffff88801d030000 RSI: ffffffff81637e7c RDI: fffff520007d4fb7
[ 416.671050][ T7984] RBP: ffffffff8a533de0 R08: 00000000000000cc R09: 0000000000000000
[ 416.671867][ T7984] R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff8a533da0
[ 416.672685][ T7984] R13: 00000000000001ca R14: 000000005000940a R15: 0000000000000000
[ 416.673501][ T7984] FS: 00007fa2985d4640(0000) GS:ffff88802cc00000(0000) knlGS:0000000000000000
[ 416.674425][ T7984] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 416.675114][ T7984] CR2: 0000000000000000 CR3: 0000000018e5e000 CR4: 0000000000750ef0
[ 416.675933][ T7984] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 416.676760][ T7984] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Link: https://lore.kernel.org/linux-btrfs/20230324031611.98986-1-xiaoshoukui@gmail.com/
CC: stable@vger.kernel.org # 6.1+
Signed-off-by: xiaoshoukui <xiaoshoukui@ruijie.com.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
|
|
A call to btrfs_prev_leaf() may end up returning a path that points to the
same item (key) again. This happens if while btrfs_prev_leaf(), after we
release the path, a concurrent insertion happens, which moves items off
from a sibling into the front of the previous leaf, and an item with the
computed previous key does not exists.
For example, suppose we have the two following leaves:
Leaf A
-------------------------------------------------------------
| ... key (300 96 10) key (300 96 15) key (300 96 16) |
-------------------------------------------------------------
slot 20 slot 21 slot 22
Leaf B
-------------------------------------------------------------
| key (300 96 20) key (300 96 21) key (300 96 22) ... |
-------------------------------------------------------------
slot 0 slot 1 slot 2
If we call btrfs_prev_leaf(), from btrfs_previous_item() for example, with
a path pointing to leaf B and slot 0 and the following happens:
1) At btrfs_prev_leaf() we compute the previous key to search as:
(300 96 19), which is a key that does not exists in the tree;
2) Then we call btrfs_release_path() at btrfs_prev_leaf();
3) Some other task inserts a key at leaf A, that sorts before the key at
slot 20, for example it has an objectid of 299. In order to make room
for the new key, the key at slot 22 is moved to the front of leaf B.
This happens at push_leaf_right(), called from split_leaf().
After this leaf B now looks like:
--------------------------------------------------------------------------------
| key (300 96 16) key (300 96 20) key (300 96 21) key (300 96 22) ... |
--------------------------------------------------------------------------------
slot 0 slot 1 slot 2 slot 3
4) At btrfs_prev_leaf() we call btrfs_search_slot() for the computed
previous key: (300 96 19). Since the key does not exists,
btrfs_search_slot() returns 1 and with a path pointing to leaf B
and slot 1, the item with key (300 96 20);
5) This makes btrfs_prev_leaf() return a path that points to slot 1 of
leaf B, the same key as before it was called, since the key at slot 0
of leaf B (300 96 16) is less than the computed previous key, which is
(300 96 19);
6) As a consequence btrfs_previous_item() returns a path that points again
to the item with key (300 96 20).
For some users of btrfs_prev_leaf() or btrfs_previous_item() this may not
be functional a problem, d |
