net: provide dev_lstats_add() helper

Many network drivers need it and hand-coded the same function.

In order to ease u64_stats_t adoption, it is time to factorize.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/loopback.c

@@ -68,7 +68,6 @@ EXPORT_SYMBOL(blackhole_netdev);
 static netdev_tx_t loopback_xmit(struct sk_buff *skb,
 				 struct net_device *dev)
 {
-	struct pcpu_lstats *lb_stats;
 	int len;
 
 	skb_tx_timestamp(skb);
@@ -85,16 +84,9 @@ static netdev_tx_t loopback_xmit(struct sk_buff *skb,
 
 	skb->protocol = eth_type_trans(skb, dev);
 
-	/* it's OK to use per_cpu_ptr() because BHs are off */
-	lb_stats = this_cpu_ptr(dev->lstats);
-
 	len = skb->len;
-	if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
-		u64_stats_update_begin(&lb_stats->syncp);
-		lb_stats->bytes += len;
-		lb_stats->packets++;
-		u64_stats_update_end(&lb_stats->syncp);
-	}
+	if (likely(netif_rx(skb) == NET_RX_SUCCESS))
+		dev_lstats_add(dev, len);
 
 	return NETDEV_TX_OK;
 }

include/linux/netdevice.h

@@ -2403,6 +2403,16 @@ struct pcpu_lstats {
 
 void dev_lstats_read(struct net_device *dev, u64 *packets, u64 *bytes);
 
+static inline void dev_lstats_add(struct net_device *dev, unsigned int len)
+{
+	struct pcpu_lstats *lstats = this_cpu_ptr(dev->lstats);
+
+	u64_stats_update_begin(&lstats->syncp);
+	lstats->bytes += len;
+	lstats->packets++;
+	u64_stats_update_end(&lstats->syncp);
+}
+
 #define __netdev_alloc_pcpu_stats(type, gfp)				\
 ({									\
 	typeof(type) __percpu *pcpu_stats = alloc_percpu_gfp(type, gfp);\