jbd: protect all log tail updates with j_checkpoint_mutex

There are some log tail updates that are not protected by j_checkpoint_mutex.
Some of these are harmless because they happen during startup or shutdown but
updates in journal_commit_transaction() and journal_flush() can really race
with other log tail updates (e.g. someone doing journal_flush() with someone
running cleanup_journal_tail()). So protect all log tail updates with
j_checkpoint_mutex.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index dba9cfd75f1a..1b27f46e6108 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -308,7 +308,9 @@ void journal_commit_transaction(journal_t *journal)
         /* Do we need to erase the effects of a prior journal_flush? */
         if (journal->j_flags & JFS_FLUSHED) {
                 jbd_debug(3, "super block updated\n");
+                mutex_lock(&journal->j_checkpoint_mutex);
                 journal_update_sb_log_tail(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
         } else {
                 jbd_debug(3, "superblock not updated\n");
         }