jbd: don't wake kjournald unnecessarily

Don't send an extra wakeup to kjournald in the case where we
already have the proper target in j_commit_request, i.e. that
commit has already been requested for commit.

commit d9b0193 "jbd: fix fsync() tid wraparound bug" changed
the logic leading to a wakeup, but it caused some extra wakeups
which were found to lead to a measurable performance regression.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index a2862339323b..81cc7eaff863 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -446,7 +446,8 @@ int __log_start_commit(journal_t *journal, tid_t target)
          * currently running transaction (if it exists).  Otherwise,
          * the target tid must be an old one.
          */
-        if (journal->j_running_transaction &&
+        if (journal->j_commit_request != target &&
+            journal->j_running_transaction &&
             journal->j_running_transaction->t_tid == target) {
                 /*
                  * We want a new commit: OK, mark the request and wakeup the