jbd2: protect all log tail updates with j_checkpoint_mutex

commit a78bb11d7acd525623c6a0c2ff4e213d527573fa upstream.

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 jbd2_journal_commit_transaction() and jbd2_journal_flush() can
really race with other log tail updates (e.g. someone doing
jbd2_journal_flush() with someone running jbd2_cleanup_journal_tail()). So
protect all log tail updates with j_checkpoint_mutex.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[bwh: Backported to 3.2:
 - Adjust context
 - Add unlock on the error path in jbd2_journal_flush()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Bartosz Kwitniewski <zerg2000@astral.org.pl>

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index bccb605..b6c3c14 100644 (file)
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -340,6 +340,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
        /* Do we need to erase the effects of a prior jbd2_journal_flush? */
        if (journal->j_flags & JBD2_FLUSHED) {
                jbd_debug(3, "super block updated\n");
+               mutex_lock(&journal->j_checkpoint_mutex);
                /*
                 * We hold j_checkpoint_mutex so tail cannot change under us.
                 * We don't need any special data guarantees for writing sb
@@ -350,6 +351,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
                                                journal->j_tail_sequence,
                                                journal->j_tail,
                                                WRITE_SYNC);
+               mutex_unlock(&journal->j_checkpoint_mutex);
        } else {
                jbd_debug(3, "superblock not updated\n");
        }

diff --cc fs/jbd2/journal.c
Simple merge