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-rw-r--r--fs/btrfs/tree-log.c8
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 */