1 files changed, 8 insertions, 2 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 8f23a94dab77..2009cea65d89 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3116,8 +3116,11 @@ out_wake_log_root:
         mutex_unlock(&log_root_tree->log_mutex);
 
         /*
-         * The barrier before waitqueue_active is implied by mutex_unlock
+         * The barrier before waitqueue_active is needed so all the updates
+         * above are seen by the woken threads. It might not be necessary, but
+         * proving that seems to be hard.
          */
+        smp_mb();
         if (waitqueue_active(&log_root_tree->log_commit_wait[index2]))
                 wake_up(&log_root_tree->log_commit_wait[index2]);
 out:
@@ -3128,8 +3131,11 @@ out:
         mutex_unlock(&root->log_mutex);
 
         /*
-         * The barrier before waitqueue_active is implied by mutex_unlock
+         * The barrier before waitqueue_active is needed so all the updates
+         * above are seen by the woken threads. It might not be necessary, but
+         * proving that seems to be hard.
          */
+        smp_mb();
         if (waitqueue_active(&root->log_commit_wait[index1]))
                 wake_up(&root->log_commit_wait[index1]);
         return ret;