1 files changed, 6 insertions, 2 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index de729acee738..3fc8d854d7fb 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3110,6 +3110,12 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
         log->log_transid = root->log_transid;
         root->log_start_pid = 0;
         /*
+         * Update or create log root item under the root's log_mutex to prevent
+         * races with concurrent log syncs that can lead to failure to update
+         * log root item because it was not created yet.
+         */
+        ret = update_log_root(trans, log);
+        /*
          * IO has been started, blocks of the log tree have WRITTEN flag set
          * in their headers. new modifications of the log will be written to
          * new positions. so it's safe to allow log writers to go in.
@@ -3128,8 +3134,6 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 
         mutex_unlock(&log_root_tree->log_mutex);
 
-        ret = update_log_root(trans, log);
-
         mutex_lock(&log_root_tree->log_mutex);
         if (atomic_dec_and_test(&log_root_tree->log_writers)) {
                 /* atomic_dec_and_test implies a barrier */