-/* non-blocking function to manipulate a lock whose cb_data is being put away.*/
-void ldlm_resource_iterate(struct ldlm_namespace *ns, struct ldlm_res_id *res_id,
+/* non-blocking function to manipulate a lock whose cb_data is being put away.
+ * return 0: find no resource
+ * > 0: must be LDLM_ITER_STOP/LDLM_ITER_CONTINUE.
+ * < 0: errors
+ */
+int ldlm_resource_iterate(struct ldlm_namespace *ns, struct ldlm_res_id *res_id,