[NET]: Stop polling when napi_disable() is pending.

This finally adds the code in net_rx_action() to break out of the
->poll()'ing loop when a napi_disable() is found to be pending.

Now, even if a device is being flooded with packets it can be cleanly
brought down.

Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -2207,8 +2207,12 @@ static void net_rx_action(struct softirq_action *h)
 		 * still "owns" the NAPI instance and therefore can
 		 * move the instance around on the list at-will.
 		 */
-		if (unlikely(work == weight))
-			list_move_tail(&n->poll_list, list);
+		if (unlikely(work == weight)) {
+			if (unlikely(napi_disable_pending(n)))
+				__napi_complete(n);
+			else
+				list_move_tail(&n->poll_list, list);
+		}
 
 		netpoll_poll_unlock(have);
 	}