diff mbox series

[14/22] jbd2: Drop pointless wakeup from jbd2_journal_stop()

Message ID 20191003220613.10791-14-jack@suse.cz
State Superseded
Headers show
Series ext4: Fix transaction overflow due to revoke descriptors | expand

Commit Message

Jan Kara Oct. 3, 2019, 10:06 p.m. UTC 
When we drop last handle from a transaction and journal->j_barrier_count
> 0, jbd2_journal_stop() wakes up journal->j_wait_transaction_locked
wait queue. This looks pointless - wait for outstanding handles always
happens on journal->j_wait_updates waitqueue.
journal->j_wait_transaction_locked is used to wait for transaction state
changes and by start_this_handle() for waiting until
journal->j_barrier_count drops to 0. The first case is clearly
irrelevant here since only jbd2 thread changes transaction state. The
second case looks related but jbd2_journal_unlock_updates() is
responsible for the wakeup in this case. So just drop the wakeup.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/jbd2/transaction.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

Comments

Theodore Ts'o Oct. 21, 2019, 5:34 p.m. UTC | #1 
On Fri, Oct 04, 2019 at 12:06:00AM +0200, Jan Kara wrote:
> When we drop last handle from a transaction and journal->j_barrier_count
> > 0, jbd2_journal_stop() wakes up journal->j_wait_transaction_locked
> wait queue. This looks pointless - wait for outstanding handles always
> happens on journal->j_wait_updates waitqueue.
> journal->j_wait_transaction_locked is used to wait for transaction state
> changes and by start_this_handle() for waiting until
> journal->j_barrier_count drops to 0. The first case is clearly
> irrelevant here since only jbd2 thread changes transaction state. The
> second case looks related but jbd2_journal_unlock_updates() is
> responsible for the wakeup in this case. So just drop the wakeup.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

Looks good; feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
diff mbox series

Patch

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index a160c3f665f9..d648cec3f90f 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1831,11 +1831,8 @@  int jbd2_journal_stop(handle_t *handle)
 	 * once we do this, we must not dereference transaction
 	 * pointer again.
 	 */
-	if (atomic_dec_and_test(&transaction->t_updates)) {
+	if (atomic_dec_and_test(&transaction->t_updates))
 		wake_up(&journal->j_wait_updates);
-		if (journal->j_barrier_count)
-			wake_up(&journal->j_wait_transaction_locked);
-	}
 
 	rwsem_release(&journal->j_trans_commit_map, 1, _THIS_IP_);