kernel/git/stable/linux.git/fs/btrfs, branch linux-6.18.y

btrfs: fix incorrect buffered IO fallback for append direct writes

2026-07-24T14:17:25+00:00

[ Upstream commit ff66fe6662330226b3f486014c375538d91c44aa ] [BUG] With the previous bug of short direct writes fixed, test case generic/362 (*) still fails with the following error with nodatasum mount option: # generic/362 0s ... - output mismatch (see /home/adam/xfstests/results//generic/362.out.bad) # - output mismatch (see /home/adam/xfstests/results//generic/362.out.bad) # --- tests/generic/362.out 2024-08-24 15:31:37.200000000 +0930 # +++ /home/adam/xfstests/results//generic/362.out.bad 2026-05-27 10:13:09.072485767 +0930 # @@ -1,2 +1,3 @@ # QA output created by 362 # +Wrong file size after first write, got 8192 expected 4096 # Silence is golden # ... *: If the test case has been executed before with default data checksum, the failure will not reproduce. Need the following fix to make it reliably reproducible: https://lore.kernel.org/linux-btrfs/20260528111659.87113-1-wqu@suse.com/ [CAUSE] Inside btrfs_dio_iomap_begin() for a direct write, we increase the isize if it's beyond the current isize. But if the direct io finished short, we do not revert the isize to the previous value nor to the short write end. Then if we need to fall back to buffered writes, and the write has IOCB_APPEND flag, then the buffered write will be positioned at the incorrect isize. The call chain looks like this: btrfs_direct_write(pos=0, length=4K) |- __iomap_dio_rw() | |- iomap_iter() | | |- btrfs_dio_iomap_begin() | | |- btrfs_get_blocks_direct_write() | | |- i_size_write() | | Which updates the isize to the write end (4K). | | | |- iomap_dio_iter() | | Failed with -EFAULT on the first page. | | | |- iomap_iter() | | |- btrfs_dio_iomap_end() | | Detects a short write, return -ENOTBLK | |- if (ret == -ENOTBLK) { ret = 0;} | Which resets the return value. | |- ret = iomap_dio_complet() | Which returns 0. | |- btrfs_buffered_write(iocb, from); |- generic_write_checks() |- iocb->ki_pos = i_size_read() Which is still the new size (4K), other than the original isize 0. [FIX] Introduce the following btrfs_dio_data members: - old_isize - updated_isize If the direct write has enlarged the isize. Then if we got a short write, and btrfs_dio_data::updated_isize is set, revert to the correct isize based on old_isize and current file position. And here we call i_size_write() without holding an extent lock, which is a very special case that we're safe to do: - Only a single writer can be enlarging isize Enlarging isize will take the exclusive inode lock. - Buffered readers need to wait for the OE we're holding Buffered readers will lock extent and wait for OE of the folio range. Sometimes we can skip the OE wait, but since all page cache is invalidated, the OE wait can not be skipped. But I do not think this is the most elegant solution, nor covers all cases. E.g. if the bio is submitted but IO failed, we are unable to do the revert. I believe the more elegant one would be extend the EXTENT_DIO_LOCKED lifespan for direct writes, so that we can update the isize when a write beyond EOF finished successfully. However that change is too huge for a small bug fix. So only implement the minimal partial fix for now. [REASON FOR NO FIXES TAG] The bug is again very old, before commit f85781fb505e ("btrfs: switch to iomap for direct IO") we are already increasing isize without a proper rollback for short writes. Thus only a CC to stable. CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Boris Burkov Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: fix false IO failure after falling back to buffered write

2026-07-24T14:17:25+00:00

[ Upstream commit 66ff4d366e7eb4d31813d2acabf3af512ce03aa5 ] [BUG] The test case generic/362 will fail with "nodatasum" mount option (*): MOUNT_OPTIONS -- -o nodatasum /dev/mapper/test-scratch1 /mnt/scratch # generic/362 0s ... - output mismatch (see /home/adam/xfstests/results//generic/362.out.bad) # --- tests/generic/362.out 2024-08-24 15:31:37.200000000 +0930 # +++ /home/adam/xfstests/results//generic/362.out.bad 2026-05-27 10:21:17.574771567 +0930 # @@ -1,2 +1,3 @@ # QA output created by 362 # +First write failed: Input/output error # Silence is golden # ... *: If the test case has been executed before with default data checksum, the failure will not reproduce. Need the following fix to make it reliably reproducible: https://lore.kernel.org/linux-btrfs/20260528111659.87113-1-wqu@suse.com/ [CAUSE] Inside __iomap_dio_rw(), the -EFAULT/-ENOTBLK error is not directly returned. Thus we never got an error pointer from __iomap_dio_rw(). The call chain looks like this: btrfs_direct_write() |- btrfs_dio_write() |- __iomap_dio_rw() | |- iomap_iter() | | |- btrfs_dio_iomap_begin() | | Now an ordered extent is allocated for the 4K write. | | | |- iomi.status = iomap_dio_iter() | | Where iomap_dio_iter() returned -EFAULT. | | | |- ret = iomap_iter() | | |- btrfs_dio_iomap_end() | | | |- btrfs_finish_ordered_extent(uptodate = false) | | | | |- can_finish_ordered_extent() | | | | |- btrfs_mark_ordered_extent_error() | | | | |- mapping_set_error() | | | | Now the address space is marked error. | | | | return -ENOTBLK | | |- return -ENOTBLK | |- if (ret == -ENOTBLK) { ret = 0; } | Now the return value is reset to 0. | Thus no error pointer will be returned. | |- ret = iomap_dio_complete() | Since no byte is submitted, @ret is 0. | |- Fallback to buffered IO | And the buffered write finished without error | |- filemap_fdatawait_range() |- filemap_check_errors() The previous error is recorded, thus an error is returned However the buffered write is properly submitted and finished, the error is from the btrfs_finish_ordered_extent() call with @uptodate = false. [FIX] When a short dio write happened, any range that is submitted will have btrfs_extract_ordered_extent() to be called, thus the submitted range will always have an OE just covering the submitted range. The remaining OE range is never submitted, thus they should be treated as truncated, not an error. So that we can properly reclaim and not insert an unnecessary file extent item, without marking the mapping as error. Extract a helper, btrfs_mark_ordered_extent_truncated(), and utilize that helper to mark the direct IO ordered extent as truncated, so it won't cause failure for the later buffered fallback. [REASON FOR NO FIXES TAG] The bug itself is pretty old, at commit f85781fb505e ("btrfs: switch to iomap for direct IO") we're already passing @uptodate=false finishing the OE. But at that time OE with IOERR won't call mapping_set_error(), so it's not exposed. Later commit d61bec08b904 ("btrfs: mark ordered extent and inode with error if we fail to finish") finally exposed the bug, but that commit is doing a correct job, not the root cause. Anyway the bug is very old, dating back to 5.1x days, thus only CC to stable. CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Boris Burkov Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: remove folio parameter from ordered io related functions

2026-07-24T14:17:25+00:00

[ Upstream commit a11d6912fdd9e57aff889ec97256b1d6b4e5bf06 ] Both functions btrfs_finish_ordered_extent() and btrfs_mark_ordered_io_finished() are accepting an optional folio parameter. That @folio is passed into can_finish_ordered_extent(), which later will test and clear the ordered flag for the involved range. However I do not think there is any other call site that can clear ordered flags of an page cache folio and can affect can_finish_ordered_extent(). There are limited *_clear_ordered() callers out of can_finish_ordered_extent() function: - btrfs_migrate_folio() This is completely unrelated, it's just migrating the ordered flag to the new folio. - btrfs_cleanup_ordered_extents() We manually clean the ordered flags of all involved folios, then call btrfs_mark_ordered_io_finished() without a @folio parameter. So it doesn't need and didn't pass a @folio parameter in the first place. - btrfs_writepage_fixup_worker() This function is going to be removed soon, and we should not hit that function anymore. - btrfs_invalidate_folio() This is the real call site we need to bother with. If we already have a bio running, btrfs_finish_ordered_extent() in end_bbio_data_write() will be executed first, as btrfs_invalidate_folio() will wait for the writeback to finish. Thus if there is a running bio, it will not see the range has ordered flags, and just skip to the next range. If there is no bio running, meaning the ordered extent is created but the folio is not yet submitted. In that case btrfs_invalidate_folio() will manually clear the folio ordered range, but then manually finish the ordered extent with btrfs_dec_test_ordered_pending() without bothering the folio ordered flags. Meaning if the OE range with folio ordered flags will be finished manually without the need to call can_finish_ordered_extent(). This means all can_finish_ordered_extent() call sites should get a range that has folio ordered flag set, thus the old "return false" branch should never be triggered. Now we can: - Remove the @folio parameter from involved functions * btrfs_mark_ordered_io_finished() * btrfs_finish_ordered_extent() For call sites passing a @folio into those functions, let them manually clear the ordered flag of involved folios. - Move btrfs_finish_ordered_extent() out of the loop in end_bbio_data_write() We only need to call btrfs_finish_ordered_extent() once per bbio, not per folio. - Add an ASSERT() to make sure all folio ranges have ordered flags It's only for end_bbio_data_write(). And we already have enough safe nets to catch over-accounting of ordered extents. Reviewed-by: Filipe Manana Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Stable-dep-of: 66ff4d366e7e ("btrfs: fix false IO failure after falling back to buffered write") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: replace for_each_set_bit() with for_each_set_bitmap()

2026-07-24T14:17:25+00:00

[ Upstream commit e6698b34fab33867ef3faeeea6feb165f31aae24 ] Inside extent_io.c, there are several simple call sites doing things like: for_each_set_bit(bit, bitmap, bitmap_size) { /* handle one fs block */ } The workload includes: - set_bit() Inside extent_writepage_io(). This can be replaced with a bitmap_set(). - btrfs_folio_set_lock() - btrfs_mark_ordered_io_finished() Inside writepage_delalloc(). Instead of calling it multiple times, we can pass a range into the function with one call. Reviewed-by: Boris Burkov Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Stable-dep-of: 66ff4d366e7e ("btrfs: fix false IO failure after falling back to buffered write") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: concentrate the error handling of submit_one_sector()

2026-07-24T14:17:25+00:00

[ Upstream commit 44820d80026e0b509007d41c83d42f1213ee8589 ] Currently submit_one_sector() has only one failure path from btrfs_get_extent(). However the error handling is split into two parts, one inside submit_one_sector(), which clears the dirty flag and finishes the writeback for the fs block. The other part is to submit any remaining bio inside bio_ctrl and mark the ordered extent finished for the fs block. There is no special reason that we must split the error handling, let's just concentrate all the error handling into submit_one_sector(). Reviewed-by: Boris Burkov Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Stable-dep-of: 66ff4d366e7e ("btrfs: fix false IO failure after falling back to buffered write") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: fix deadlock cloning inline extent when using flushoncommit

2026-07-24T14:16:06+00:00

[ Upstream commit 532085d00eb54c074bdeae648b194765239f4d11 ] In commit b48c980b6a7e ("btrfs: fix deadlock between reflink and transaction commit when using flushoncommit") a deadlock was fixed between reflinks and transaction commits when the fs is mounted with the flushoncommit option. This happened when we had to copy an inline extent's data to the destination file. However the issue was fixed only for the case where the destination offset is 0, it missed the case when the offset is greater than zero. Fix this by ensuring we get i_size update whenever we copied an inline extent's data into the destination file. Syzbot reported this with the following trace: INFO: task kworker/u8:3:57 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u8:3 state:D stack:21600 pid:57 tgid:57 ppid:2 task_flags:0x4208160 flags:0x00080000 Workqueue: writeback wb_workfn (flush-btrfs-129) Call Trace: context_switch kernel/sched/core.c:5402 [inline] __schedule+0x16f9/0x5500 kernel/sched/core.c:7204 __schedule_loop kernel/sched/core.c:7283 [inline] schedule+0x164/0x360 kernel/sched/core.c:7298 wait_extent_bit fs/btrfs/extent-io-tree.c:905 [inline] btrfs_lock_extent_bits+0x59c/0x700 fs/btrfs/extent-io-tree.c:2008 btrfs_lock_extent fs/btrfs/extent-io-tree.h:152 [inline] btrfs_invalidate_folio+0x440/0xc00 fs/btrfs/inode.c:7718 extent_writepage fs/btrfs/extent_io.c:1848 [inline] extent_write_cache_pages fs/btrfs/extent_io.c:2552 [inline] btrfs_writepages+0x12f3/0x2410 fs/btrfs/extent_io.c:2684 do_writepages+0x32e/0x550 mm/page-writeback.c:2571 __writeback_single_inode+0x133/0x10e0 fs/fs-writeback.c:1764 writeback_sb_inodes+0x97f/0x1980 fs/fs-writeback.c:2056 wb_writeback+0x445/0xb00 fs/fs-writeback.c:2241 wb_do_writeback fs/fs-writeback.c:2388 [inline] wb_workfn+0x3fd/0xf20 fs/fs-writeback.c:2428 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 INFO: task syz.0.145:8523 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.0.145 state:D stack:22752 pid:8523 tgid:8522 ppid:5850 task_flags:0x400140 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5402 [inline] __schedule+0x16f9/0x5500 kernel/sched/core.c:7204 __schedule_loop kernel/sched/core.c:7283 [inline] schedule+0x164/0x360 kernel/sched/core.c:7298 wb_wait_for_completion+0x3e8/0x790 fs/fs-writeback.c:227 __writeback_inodes_sb_nr+0x24c/0x2d0 fs/fs-writeback.c:2847 try_to_writeback_inodes_sb+0x9a/0xc0 fs/fs-writeback.c:2895 btrfs_start_delalloc_flush fs/btrfs/transaction.c:2182 [inline] btrfs_commit_transaction+0x813/0x2fc0 fs/btrfs/transaction.c:2371 btrfs_sync_file+0xdf4/0x1230 fs/btrfs/file.c:1822 generic_write_sync include/linux/fs.h:2663 [inline] btrfs_do_write_iter+0x6a9/0x840 fs/btrfs/file.c:1473 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:688 ksys_write+0x156/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5a0bdece59 RSP: 002b:00007f5a0b446028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f5a0c065fa0 RCX: 00007f5a0bdece59 RDX: 000000000000029f RSI: 0000200000000200 RDI: 0000000000000004 RBP: 00007f5a0be82d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5a0c066038 R14: 00007f5a0c065fa0 R15: 00007ffe149206b8 INFO: task syz.0.145:8539 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.0.145 state:D stack:23704 pid:8539 tgid:8522 ppid:5850 task_flags:0x400140 flags:0x00080002 Call Trace: context_switch kernel/sched/core.c:5402 [inline] __schedule+0x16f9/0x5500 kernel/sched/core.c:7204 __schedule_loop kernel/sched/core.c:7283 [inline] schedule+0x164/0x360 kernel/sched/core.c:7298 wait_current_trans+0x39f/0x590 fs/btrfs/transaction.c:536 start_transaction+0xbd8/0x1820 fs/btrfs/transaction.c:716 clone_copy_inline_extent fs/btrfs/reflink.c:299 [inline] btrfs_clone+0x1316/0x2540 fs/btrfs/reflink.c:574 btrfs_clone_files+0x271/0x3f0 fs/btrfs/reflink.c:795 btrfs_remap_file_range+0x76b/0x1320 fs/btrfs/reflink.c:948 vfs_clone_file_range+0x435/0x7b0 fs/remap_range.c:403 ioctl_file_clone fs/ioctl.c:239 [inline] ioctl_file_clone_range fs/ioctl.c:257 [inline] do_vfs_ioctl+0xe15/0x1540 fs/ioctl.c:544 __do_sys_ioctl fs/ioctl.c:595 [inline] __se_sys_ioctl+0x82/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5a0bdece59 RSP: 002b:00007f5a0b425028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f5a0c066090 RCX: 00007f5a0bdece59 RDX: 00002000000000c0 RSI: 000000004020940d RDI: 0000000000000004 RBP: 00007f5a0be82d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5a0c066128 R14: 00007f5a0c066090 R15: 00007ffe149206b8 Reported-by: syzbot+c7443384724bb0f9e913@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/6a150a09.820a0220.e7972.0006.GAE@google.com/ Fixes: 05a5a7621ce6 ("Btrfs: implement full reflink support for inline extents") Reviewed-by: Boris Burkov Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: annotate lockless read of defrag_bytes in should_nocow()

2026-07-24T14:16:06+00:00

[ Upstream commit 89c0dc3de7a73e8aba5e9bfef543eee047a3d0d2 ] should_nocow() reads inode->defrag_bytes without holding inode->lock, while btrfs_set_delalloc_extent() and btrfs_clear_delalloc_extent() update it under that spinlock. This is a data race. The read is a quick check used to decide whether to fall back to COW for a NOCOW inode: if defrag_bytes is non-zero and the range is tagged EXTENT_DEFRAG, we force COW so that defragmentation can rewrite the extent. Reading a stale value is harmless because: - A missed increment may skip COW once, but the defrag pass will redo the extent later. - A stale non-zero may force an unnecessary COW, which is a minor efficiency loss, not a correctness issue. On 64-bit platforms an aligned u64 load is naturally atomic so tearing cannot happen. On 32-bit platforms u64 may tear, but we only test for zero vs non-zero, so the heuristic stays correct regardless. Use data_race() annotation. Fixes: 47059d930f0e ("Btrfs: make defragment work with nodatacow option") Signed-off-by: Cen Zhang [ Use data_race() instead of READ_ONCXE() ] Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: zoned: always set max_active_zones for zoned devices

2026-07-24T14:16:06+00:00

[ Upstream commit 21a3533b99b8a53a026cc9f5041b10795c1f3ae8 ] When a block device does not report a maximum number of open or active zones, currently assign BTRFS_DEFAULT_MAX_ACTIVE_ZONES (128) to the internal limit, if the device has more than BTRFS_DEFAULT_MAX_ACTIVE_ZONES zones. But if the device has less than BTRFS_DEFAULT_MAX_ACTIVE_ZONES the internal max_active_zones limit will stay at 0, even if the device has zone resource limits. Furthermore, if the device has a total number of zones that is less than BTRFS_DEFAULT_MAX_ACTIVE_ZONE, max_active_zones should be set to at most the number of zones. Also move the max_active_zone calculation and setting into a dedicated helper, to shrink btrfs_get_dev_zone_info(). Fixes: 04147d8394e8 ("btrfs: zoned: limit active zones to max_open_zones") Reviewed-by: Damien Le Moal Signed-off-by: Johannes Thumshirn Signed-off-by: David Sterba Signed-off-by: Sasha Levin

Revert "btrfs: fix the file offset calculation inside btrfs_decompress_buf2page()"

2026-07-24T14:16:06+00:00

[ Upstream commit 0279bed34c22dd5ebff12e5af8ef940de93c5523 ] It seems that af566bdaff54 was tested against a tree which did not contain commit 12851bd921d4 ("fs: Turn page_offset() into a wrapper around folio_pos()). Unfortunately it has a bug of its own; on 32-bit systems, shifting by PAGE_SHIFT will overflow on files larger than 4GiB. Since page_offset() is now fixed, just revert af566bdaff54. Fixes: af566bdaff54 (btrfs: fix the file offset calculation inside btrfs_decompress_buf2page()) Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Qu Wenruo Reviewed-by: Boris Burkov Tested-by: Boris Burkov Signed-off-by: David Sterba Signed-off-by: Sasha Levin

btrfs: zoned: don't account data relocation space-info in statfs free space

2026-07-24T14:16:06+00:00

[ Upstream commit 52416a27aabc43eab3792fd0ca9f5dabeab58f31 ] Don't account the free space in a data relocation space-info sub-group as usable free space in statfs. This is misleading as no user allocations can be made in this space-info sub-group. It is only a target for relocation. Fixes: f92ee31e031c ("btrfs: introduce btrfs_space_info sub-group") Reviewed-by: Boris Burkov Reviewed-by: Naohiro Aota Signed-off-by: Johannes Thumshirn Signed-off-by: David Sterba Signed-off-by: Sasha Levin