diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 12c57abd..46f3bb7 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -575,3 +575,6 @@
 
 	Old method is only used if the new one is absent; eventually it will
 	be removed.  Switch while you still can; the old one won't stay.
+--
+[mandatory]
+	->atomic_open() calls without O_CREAT may happen in parallel.