IB/mad: Don't send response for failed MADs

Commit 0b30704 ("IB/mad: Return error response for unsupported
MADs") does not failed MADs (eg those that return
IB_MAD_RESULT_FAILURE) properly -- these MADs should be silently
discarded. (We should not force the lower-layer drivers to return
SUCCESS | CONSUMED in this case, since the MAD is NOT successful).
Unsupported MADs are not failures -- they return SUCCESS, but with an
"unsupported error" status value inside the response MAD.

Reviewed-by: Hal Rosenstock <hal@mellanox.com>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/mad.c

@@ -1871,6 +1871,7 @@ static void ib_mad_recv_done_handler(struct ib_mad_port_private *port_priv,
 	struct ib_mad_list_head *mad_list;
 	struct ib_mad_agent_private *mad_agent;
 	int port_num;
+	int ret = IB_MAD_RESULT_SUCCESS;
 
 	mad_list = (struct ib_mad_list_head *)(unsigned long)wc->wr_id;
 	qp_info = mad_list->mad_queue->qp_info;
@@ -1954,8 +1955,6 @@ static void ib_mad_recv_done_handler(struct ib_mad_port_private *port_priv,
 local:
 	/* Give driver "right of first refusal" on incoming MAD */
 	if (port_priv->device->process_mad) {
-		int ret;
-
 		ret = port_priv->device->process_mad(port_priv->device, 0,
 						     port_priv->port_num,
 						     wc, &recv->grh,
@@ -1983,7 +1982,8 @@ static void ib_mad_recv_done_handler(struct ib_mad_port_private *port_priv,
 		 * or via recv_handler in ib_mad_complete_recv()
 		 */
 		recv = NULL;
-	} else if (generate_unmatched_resp(recv, response)) {
+	} else if ((ret & IB_MAD_RESULT_SUCCESS) &&
+		   generate_unmatched_resp(recv, response)) {
 		agent_send_response(&response->mad.mad, &recv->grh, wc,
 				    port_priv->device, port_num, qp_info->qp->qp_num);
 	}