5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
[ Upstream commit ac6f420291b3fee1113f21d612fa88b628afab5b ]
One of the paths quota writeback is called from is:
freeze_super()
sync_filesystem()
ext4_sync_fs()
dquot_writeback_dquots()
Since we currently don't always flush the quota_release_work queue in
this path, we can end up with the following race:
1. dquot are added to releasing_dquots list during regular operations.
2. FS Freeze starts, however, this does not flush the quota_release_work queue.
3. Freeze completes.
4. Kernel eventually tries to flush the workqueue while FS is frozen which
hits a WARN_ON since transaction gets started during frozen state:
ext4_journal_check_start+0x28/0x110 [ext4] (unreliable)
__ext4_journal_start_sb+0x64/0x1c0 [ext4]
ext4_release_dquot+0x90/0x1d0 [ext4]
quota_release_workfn+0x43c/0x4d0
Which is the following line:
WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
Which ultimately results in generic/390 failing due to dmesg
noise. This was detected on powerpc machine 15 cores.
To avoid this, make sure to flush the workqueue during
dquot_writeback_dquots() so we dont have any pending workitems after
freeze.
Reported-by: Disha Goel <disgoel@xxxxxxxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
Fixes: dabc8b207566 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide")
Reviewed-by: Baokun Li <libaokun1@xxxxxxxxxx>
Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Link: https://patch.msgid.link/20241121123855.645335-2-ojaswin@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/quota/dquot.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 3b62fbcefa8c3..5e2cf15b82f4d 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -690,6 +690,8 @@ int dquot_writeback_dquots(struct super_block *sb, int type)
WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount));
+ flush_delayed_work("a_release_work);
+
for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
if (type != -1 && cnt != type)
continue;
--
2.43.0
