[PATCH v2 4/5] btrfs: check for exit condition after waking in wait_log_commit()

From: Filipe Manana <[email protected]>

We check for the exit condition after we add ourselves to the wait queue
and before we unlock the root's log_mutex, sleep and lock again log_mutex.
This is not incorrect, but it's not optimal since in the first iteration
this is pointless because we already know that root->log_commit[index] is
not zero, so we should check the exit condition only after unlocking
log_mutex, sleeping, waking up and locking again the log_mutex.

So move the check for the exit condition to bottom of the loop, after we
were woken and locked log_mutex again.

Signed-off-by: Filipe Manana <[email protected]>
---
 fs/btrfs/tree-log.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index b6ed6671ee26..fe96810d3363 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3182,13 +3182,13 @@ static bool wait_log_commit(struct btrfs_root *root, int transid)
 		prepare_to_wait(&root->log_commit_wait[index],
 				&wait, TASK_UNINTERRUPTIBLE);
 
-		if (!(root->log_transid_committed < transid &&
-		      atomic_read(&root->log_commit[index])))
-			break;
-
 		mutex_unlock(&root->log_mutex);
 		schedule();
 		mutex_lock(&root->log_mutex);
+
+		if (!(root->log_transid_committed < transid &&
+		      atomic_read(&root->log_commit[index]) != 0))
+			break;
 	}
 	finish_wait(&root->log_commit_wait[index], &wait);
 
-- 
2.47.2