net: introduce NAPI_POLL_WEIGHT

Some drivers use a too big NAPI poll weight.

This patch adds a NAPI_POLL_WEIGHT default value
and issues an error message if a driver attempts
to use a bigger weight.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1475,6 +1475,11 @@ static inline void *netdev_priv(const struct net_device *dev)
  */
 #define SET_NETDEV_DEVTYPE(net, devtype)	((net)->dev.type = (devtype))
 
+/* Default NAPI poll() weight
+ * Device drivers are strongly advised to not use bigger value
+ */
+#define NAPI_POLL_WEIGHT 64
+
 /**
  *	netif_napi_add - initialize a napi context
  *	@dev:  network device

net/core/dev.c

@@ -4057,6 +4057,9 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
 	napi->gro_list = NULL;
 	napi->skb = NULL;
 	napi->poll = poll;
+	if (weight > NAPI_POLL_WEIGHT)
+		pr_err_once("netif_napi_add() called with weight %d on device %s\n",
+			    weight, dev->name);
 	napi->weight = weight;
 	list_add(&napi->dev_list, &dev->napi_list);
 	napi->dev = dev;