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ext4: fix fast commit inode enqueueing during a full journal commit

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When a full journal commit is on-going, any fast commit has to be enqueued
into a different queue: FC_Q_STAGING instead of FC_Q_MAIN.  This enqueueing
is done only once, i.e. if an inode is already queued in a previous fast
commit entry it won't be enqueued again.  However, if a full commit starts
_after_ the inode is enqueued into FC_Q_MAIN, the next fast commit needs to
be done into FC_Q_STAGING.  And this is not being done in function
ext4_fc_track_template().

This patch fixes the issue by re-enqueuing an inode into the STAGING queue
during the fast commit clean-up callback when doing a full commit.  However,
to prevent a race with a fast-commit, the clean-up callback has to be called
with the journal locked.

This bug was found using fstest generic/047.  This test creates several 32k
bytes files, sync'ing each of them after it's creation, and then shutting
down the filesystem.  Some data may be loss in this operation; for example a
file may have it's size truncated to zero.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240717172220.14201-1-luis.henriques@linux.dev
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Luis Henriques (SUSE)
2024-07-17 18:22:20 +01:00
committed by Theodore Ts'o
parent 0ce160c5bd
commit 6db3c1575a
2 changed files with 15 additions and 2 deletions
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15
fs/ext4/fast_commit.c
View File

@@ -1288,8 +1288,21 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
list_del_init(&iter->i_fc_list);
ext4_clear_inode_state(&iter->vfs_inode,
EXT4_STATE_FC_COMMITTING);
if (tid_geq(tid, iter->i_sync_tid))
if (tid_geq(tid, iter->i_sync_tid)) {
ext4_fc_reset_inode(&iter->vfs_inode);
} else if (full) {
/*
* We are called after a full commit, inode has been
* modified while the commit was running. Re-enqueue
* the inode into STAGING, which will then be splice
* back into MAIN. This cannot happen during
* fastcommit because the journal is locked all the
* time in that case (and tid doesn't increase so
* tid check above isn't reliable).
*/
list_add_tail(&EXT4_I(&iter->vfs_inode)->i_fc_list,
&sbi->s_fc_q[FC_Q_STAGING]);
}
/* Make sure EXT4_STATE_FC_COMMITTING bit is clear */
smp_mb();
#if (BITS_PER_LONG < 64)