Commit 6db3c157 authored by Luis Henriques (SUSE)'s avatar Luis Henriques (SUSE) Committed by Theodore Ts'o
Browse files

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



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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarLuis Henriques (SUSE) <luis.henriques@linux.dev>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240717172220.14201-1-luis.henriques@linux.dev


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
parent 0ce160c5

fs/ext4/fast_commit.c

+14 −1
Original line number Diff line number Diff line
@@ -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)

fs/jbd2/journal.c

+1 −1
Original line number Diff line number Diff line
@@ -740,9 +740,9 @@ EXPORT_SYMBOL(jbd2_fc_begin_commit); 
 */

static int __jbd2_fc_end_commit(journal_t *journal, tid_t tid, bool fallback)

{

	jbd2_journal_unlock_updates(journal);

	if (journal->j_fc_cleanup_callback)

		journal->j_fc_cleanup_callback(journal, 0, tid);

	jbd2_journal_unlock_updates(journal);

	write_lock(&journal->j_state_lock);

	journal->j_flags &= ~JBD2_FAST_COMMIT_ONGOING;

	if (fallback)