arp: RCU change in arp_solicit()

Avoid two atomic ops in arp_solicit()

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index cf78f41..09ead1b 100644 (file)
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -333,11 +333,14 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
        struct net_device *dev = neigh->dev;
        __be32 target = *(__be32*)neigh->primary_key;
        int probes = atomic_read(&neigh->probes);
-       struct in_device *in_dev = in_dev_get(dev);
+       struct in_device *in_dev;
 
-       if (!in_dev)
+       rcu_read_lock();
+       in_dev = __in_dev_get_rcu(dev);
+       if (!in_dev) {
+               rcu_read_unlock();
                return;
-
+       }
        switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
        default:
        case 0:         /* By default announce any local IP */
@@ -358,9 +361,8 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
        case 2:         /* Avoid secondary IPs, get a primary/preferred one */
                break;
        }
+       rcu_read_unlock();
 
-       if (in_dev)
-               in_dev_put(in_dev);
        if (!saddr)
                saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);