jbd2: Drop pointless wakeup from jbd2_journal_stop()

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.
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-16-jack@suse.czSigned-off-by: Theodore Ts'o <tytso@mit.edu>

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_);