6.12-stable review patch. If anyone has any objections, please let me know.
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From: Naohiro Aota naohiro.aota@wdc.com
[ Upstream commit 5a4041f2c47247575a6c2e53ce14f7b0ac946c33 ]
Running generic/751 on the for-next branch often results in a hang like below. They are both stack by locking an extent. This suggests someone forget to unlock an extent.
INFO: task kworker/u128:1:12 blocked for more than 323 seconds. Not tainted 6.13.0-BTRFS-ZNS+ #503 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u128:1 state:D stack:0 pid:12 tgid:12 ppid:2 flags:0x00004000 Workqueue: btrfs-fixup btrfs_work_helper [btrfs] Call Trace: <TASK> __schedule+0x534/0xdd0 schedule+0x39/0x140 __lock_extent+0x31b/0x380 [btrfs] ? __pfx_autoremove_wake_function+0x10/0x10 btrfs_writepage_fixup_worker+0xf1/0x3a0 [btrfs] btrfs_work_helper+0xff/0x480 [btrfs] ? lock_release+0x178/0x2c0 process_one_work+0x1ee/0x570 ? srso_return_thunk+0x5/0x5f worker_thread+0x1d1/0x3b0 ? __pfx_worker_thread+0x10/0x10 kthread+0x10b/0x230 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x30/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> INFO: task kworker/u134:0:184 blocked for more than 323 seconds. Not tainted 6.13.0-BTRFS-ZNS+ #503 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u134:0 state:D stack:0 pid:184 tgid:184 ppid:2 flags:0x00004000 Workqueue: writeback wb_workfn (flush-btrfs-4) Call Trace: <TASK> __schedule+0x534/0xdd0 schedule+0x39/0x140 __lock_extent+0x31b/0x380 [btrfs] ? __pfx_autoremove_wake_function+0x10/0x10 find_lock_delalloc_range+0xdb/0x260 [btrfs] writepage_delalloc+0x12f/0x500 [btrfs] ? srso_return_thunk+0x5/0x5f extent_write_cache_pages+0x232/0x840 [btrfs] btrfs_writepages+0x72/0x130 [btrfs] do_writepages+0xe7/0x260 ? srso_return_thunk+0x5/0x5f ? lock_acquire+0xd2/0x300 ? srso_return_thunk+0x5/0x5f ? find_held_lock+0x2b/0x80 ? wbc_attach_and_unlock_inode.part.0+0x102/0x250 ? wbc_attach_and_unlock_inode.part.0+0x102/0x250 __writeback_single_inode+0x5c/0x4b0 writeback_sb_inodes+0x22d/0x550 __writeback_inodes_wb+0x4c/0xe0 wb_writeback+0x2f6/0x3f0 wb_workfn+0x32a/0x510 process_one_work+0x1ee/0x570 ? srso_return_thunk+0x5/0x5f worker_thread+0x1d1/0x3b0 ? __pfx_worker_thread+0x10/0x10 kthread+0x10b/0x230 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x30/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK>
This happens because we have another success path for the zoned mode. When there is no active zone available, btrfs_reserve_extent() returns -EAGAIN. In this case, we have two reactions.
(1) If the given range is never allocated, we can only wait for someone to finish a zone, so wait on BTRFS_FS_NEED_ZONE_FINISH bit and retry afterward.
(2) Or, if some allocations are already done, we must bail out and let the caller to send IOs for the allocation. This is because these IOs may be necessary to finish a zone.
The commit 06f364284794 ("btrfs: do proper folio cleanup when cow_file_range() failed") moved the unlock code from the inside of the loop to the outside. So, previously, the allocated extents are unlocked just after the allocation and so before returning from the function. However, they are no longer unlocked on the case (2) above. That caused the hang issue.
Fix the issue by modifying the 'end' to the end of the allocated range. Then, we can exit the loop and the same unlock code can properly handle the case.
Reported-by: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com Tested-by: Johannes Thumshirn johannes.thumshirn@wdc.com Fixes: 06f364284794 ("btrfs: do proper folio cleanup when cow_file_range() failed") CC: stable@vger.kernel.org Reviewed-by: Qu Wenruo wqu@suse.com 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 Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/inode.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 2f0b2cb2ae6e8..921ec3802648b 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1463,8 +1463,13 @@ static noinline int cow_file_range(struct btrfs_inode *inode, continue; } if (done_offset) { - *done_offset = start - 1; - return 0; + /* + * Move @end to the end of the processed range, + * and exit the loop to unlock the processed extents. + */ + end = start - 1; + ret = 0; + break; } ret = -ENOSPC; }