vxlan: Fix racy device stats updates.

VXLAN devices update their stats locklessly. Therefore these counters
should either be stored in per-cpu data structures or the updates
should be done using atomic increments.

Since the net_device_core_stats infrastructure is already used in
vxlan_rcv(), use it for the other rx_dropped and tx_dropped counter
updates. Update the other counters atomically using DEV_STATS_INC().

Fixes: d342894 ("vxlan: virtual extensible lan")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Guillaume Nault

drivers/net/vxlan/vxlan_core.c

@@ -1766,8 +1766,8 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
 	skb_reset_network_header(skb);
 
 	if (!vxlan_ecn_decapsulate(vs, oiph, skb)) {
-		++vxlan->dev->stats.rx_frame_errors;
-		++vxlan->dev->stats.rx_errors;
+		DEV_STATS_INC(vxlan->dev, rx_frame_errors);
+		DEV_STATS_INC(vxlan->dev, rx_errors);
 		vxlan_vnifilter_count(vxlan, vni, vninode,
 				      VXLAN_VNI_STATS_RX_ERRORS, 0);
 		goto drop;
@@ -1837,7 +1837,7 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 		goto out;
 
 	if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
-		dev->stats.tx_dropped++;
+		dev_core_stats_tx_dropped_inc(dev);
 		goto out;
 	}
 	parp = arp_hdr(skb);
@@ -1893,7 +1893,7 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 		reply->pkt_type = PACKET_HOST;
 
 		if (netif_rx(reply) == NET_RX_DROP) {
-			dev->stats.rx_dropped++;
+			dev_core_stats_rx_dropped_inc(dev);
 			vxlan_vnifilter_count(vxlan, vni, NULL,
 					      VXLAN_VNI_STATS_RX_DROPS, 0);
 		}
@@ -2052,7 +2052,7 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni)
 			goto out;
 
 		if (netif_rx(reply) == NET_RX_DROP) {
-			dev->stats.rx_dropped++;
+			dev_core_stats_rx_dropped_inc(dev);
 			vxlan_vnifilter_count(vxlan, vni, NULL,
 					      VXLAN_VNI_STATS_RX_DROPS, 0);
 		}
@@ -2263,7 +2263,7 @@ static void vxlan_encap_bypass(struct sk_buff *skb, struct vxlan_dev *src_vxlan,
 				      len);
 	} else {
 drop:
-		dev->stats.rx_dropped++;
+		dev_core_stats_rx_dropped_inc(dev);
 		vxlan_vnifilter_count(dst_vxlan, vni, NULL,
 				      VXLAN_VNI_STATS_RX_DROPS, 0);
 	}
@@ -2295,7 +2295,7 @@ static int encap_bypass_if_local(struct sk_buff *skb, struct net_device *dev,
 					   addr_family, dst_port,
 					   vxlan->cfg.flags);
 		if (!dst_vxlan) {
-			dev->stats.tx_errors++;
+			DEV_STATS_INC(dev, tx_errors);
 			vxlan_vnifilter_count(vxlan, vni, NULL,
 					      VXLAN_VNI_STATS_TX_ERRORS, 0);
 			kfree_skb(skb);
@@ -2559,19 +2559,19 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 	return;
 
 drop:
-	dev->stats.tx_dropped++;
+	dev_core_stats_tx_dropped_inc(dev);
 	vxlan_vnifilter_count(vxlan, vni, NULL, VXLAN_VNI_STATS_TX_DROPS, 0);
 	dev_kfree_skb(skb);
 	return;
 
 tx_error:
 	rcu_read_unlock();
 	if (err == -ELOOP)
-		dev->stats.collisions++;
+		DEV_STATS_INC(dev, collisions);
 	else if (err == -ENETUNREACH)
-		dev->stats.tx_carrier_errors++;
+		DEV_STATS_INC(dev, tx_carrier_errors);
 	dst_release(ndst);
-	dev->stats.tx_errors++;
+	DEV_STATS_INC(dev, tx_errors);
 	vxlan_vnifilter_count(vxlan, vni, NULL, VXLAN_VNI_STATS_TX_ERRORS, 0);
 	kfree_skb(skb);
 }
@@ -2604,7 +2604,7 @@ static void vxlan_xmit_nh(struct sk_buff *skb, struct net_device *dev,
 	return;
 
 drop:
-	dev->stats.tx_dropped++;
+	dev_core_stats_tx_dropped_inc(dev);
 	vxlan_vnifilter_count(netdev_priv(dev), vni, NULL,
 			      VXLAN_VNI_STATS_TX_DROPS, 0);
 	dev_kfree_skb(skb);
@@ -2642,7 +2642,7 @@ static netdev_tx_t vxlan_xmit_nhid(struct sk_buff *skb, struct net_device *dev,
 	return NETDEV_TX_OK;
 
 drop:
-	dev->stats.tx_dropped++;
+	dev_core_stats_tx_dropped_inc(dev);
 	vxlan_vnifilter_count(netdev_priv(dev), vni, NULL,
 			      VXLAN_VNI_STATS_TX_DROPS, 0);
 	dev_kfree_skb(skb);
@@ -2739,7 +2739,7 @@ static netdev_tx_t vxlan_xmit(struct sk_buff *skb, struct net_device *dev)
 			    !is_multicast_ether_addr(eth->h_dest))
 				vxlan_fdb_miss(vxlan, eth->h_dest);
 
-			dev->stats.tx_dropped++;
+			dev_core_stats_tx_dropped_inc(dev);
 			vxlan_vnifilter_count(vxlan, vni, NULL,
 					      VXLAN_VNI_STATS_TX_DROPS, 0);
 			kfree_skb(skb);