5.15-stable review patch. If anyone has any objections, please let me know.
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From: Luis Henriques (SUSE) luis.henriques@linux.dev
commit 6db3c1575a750fd417a70e0178bdf6efa0dd5037 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/fast_commit.c | 15 ++++++++++++++- fs/jbd2/journal.c | 2 +- 2 files changed, 15 insertions(+), 2 deletions(-)
--- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -1278,8 +1278,21 @@ static void ext4_fc_cleanup(journal_t *j 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) --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -770,9 +770,9 @@ 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)