server: Add an open_file() function to the object operations.
diff --git a/server/mapping.c b/server/mapping.c
index 566f6dc..7b99134 100644
--- a/server/mapping.c
+++ b/server/mapping.c
@@ -68,6 +68,7 @@
     mapping_get_fd,              /* get_fd */
     mapping_map_access,          /* map_access */
     no_lookup_name,              /* lookup_name */
+    no_open_file,                /* open_file */
     fd_close_handle,             /* close_handle */
     mapping_destroy              /* destroy */
 };