jbd2: cleanup journal tail after transaction commit

Normally, we have to issue a cache flush before we can update journal tail in
journal superblock, effectively wiping out old transactions from the journal.
So use the fact that during transaction commit we issue cache flush anyway and
opportunistically push journal tail as far as we can. Since update of journal
superblock is still costly (we have to use WRITE_FUA), we update log tail only
if we can free significant amount of space.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index c5ff177..bda564f 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -821,6 +821,19 @@ void __jbd2_update_log_tail(journal_t *journal, tid_t tid, unsigned long block)
 	write_unlock(&journal->j_state_lock);
 }
 
+/*
+ * This is a variaon of __jbd2_update_log_tail which checks for validity of
+ * provided log tail and locks j_checkpoint_mutex. So it is safe against races
+ * with other threads updating log tail.
+ */
+void jbd2_update_log_tail(journal_t *journal, tid_t tid, unsigned long block)
+{
+	mutex_lock(&journal->j_checkpoint_mutex);
+	if (tid_gt(tid, journal->j_tail_sequence))
+		__jbd2_update_log_tail(journal, tid, block);
+	mutex_unlock(&journal->j_checkpoint_mutex);
+}
+
 struct jbd2_stats_proc_session {
 	journal_t *journal;
 	struct transaction_stats_s *stats;