diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2026-03-27 02:13:15 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2026-03-27 23:39:10 -0400 |
| commit | 9ee29d20aab228adfb02ca93f87fb53c56c2f3af (patch) | |
| tree | d23704927b4fb967a47df0403b6f4f01c90c5eea | |
| parent | bb81702370fad22c06ca12b6e1648754dbc37e0f (diff) | |
ext4: always drain queued discard work in ext4_mb_release()
While reviewing recent ext4 patch[1], Sashiko raised the following
concern[2]:
> If the filesystem is initially mounted with the discard option,
> deleting files will populate sbi->s_discard_list and queue
> s_discard_work. If it is then remounted with nodiscard, the
> EXT4_MOUNT_DISCARD flag is cleared, but the pending s_discard_work is
> neither cancelled nor flushed.
[1] https://lore.kernel.org/r/20260319094545.19291-1-qiang.zhang@linux.dev/
[2] https://sashiko.dev/#/patchset/20260319094545.19291-1-qiang.zhang%40linux.dev
The concern was valid, but it had nothing to do with the patch[1].
One of the problems with Sashiko in its current (early) form is that
it will detect pre-existing issues and report it as a problem with the
patch that it is reviewing.
In practice, it would be hard to hit deliberately (unless you are a
malicious syzkaller fuzzer), since it would involve mounting the file
system with -o discard, and then deleting a large number of files,
remounting the file system with -o nodiscard, and then immediately
unmounting the file system before the queued discard work has a change
to drain on its own.
Fix it because it's a real bug, and to avoid Sashiko from raising this
concern when analyzing future patches to mballoc.c.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Fixes: 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex")
Cc: stable@kernel.org
| -rw-r--r-- | fs/ext4/mballoc.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index cb2bd87c355c..bb58eafb87bc 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -3893,13 +3893,11 @@ void ext4_mb_release(struct super_block *sb) struct kmem_cache *cachep = get_groupinfo_cache(sb->s_blocksize_bits); int count; - if (test_opt(sb, DISCARD)) { - /* - * wait the discard work to drain all of ext4_free_data - */ - flush_work(&sbi->s_discard_work); - WARN_ON_ONCE(!list_empty(&sbi->s_discard_list)); - } + /* + * wait the discard work to drain all of ext4_free_data + */ + flush_work(&sbi->s_discard_work); + WARN_ON_ONCE(!list_empty(&sbi->s_discard_list)); group_info = rcu_access_pointer(sbi->s_group_info); if (group_info) { |