ipv6: introduce ip6_rt_put()

As suggested by Eric, we could introduce a helper function
for ipv6 too, to avoid checking if rt is NULL before
dst_release().

Cc: Eric Dumazet <[e-mail]>
Cc: David S. Miller <[e-mail]>
Signed-off-by: Cong Wang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ip6_fib.h

···
 	dst_hold(new);
 }
 
+static inline void ip6_rt_put(struct rt6_info *rt)
+{
+	/* dst_release() accepts a NULL parameter.
+	 * We rely on dst being first structure in struct rt6_info
+	 */
+	BUILD_BUG_ON(offsetof(struct rt6_info, dst) != 0);
+	dst_release(&rt->dst);
+}
+
 struct fib6_walker_t {
 	struct list_head lh;
 	struct fib6_node *root, *node;

net/ipv6/addrconf.c

···
 		pr_warn("Freeing alive inet6 address %p\n", ifp);
 		return;
 	}
-	dst_release(&ifp->rt->dst);
+	ip6_rt_put(ifp->rt);
 
 	kfree_rcu(ifp, rcu);
 }
···
 				rt6_set_expires(rt, expires);
 			}
 		}
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 
 	/* clean up prefsrc entries */
···
 			addrconf_prefix_route(&pinfo->prefix, pinfo->prefix_len,
 					      dev, expires, flags);
 		}
-		if (rt)
-			dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 
 	/* Try to figure out our local address for this prefix */

net/ipv6/anycast.c

···
 		rt = rt6_lookup(net, addr, NULL, 0, 0);
 		if (rt) {
 			dev = rt->dst.dev;
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 		} else if (ishost) {
 			err = -EADDRNOTAVAIL;
 			goto error;

net/ipv6/fib6_rules.c

···
 		goto out;
 	}
 again:
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	rt = NULL;
 	goto out;
 

net/ipv6/ip6_gre.c

···
 					dev->mtu = IPV6_MIN_MTU;
 			}
 		}
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 
 	t->hlen = addend;

net/ipv6/ip6_output.c

···
 		if (err == 0) {
 			IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
 				      IPSTATS_MIB_FRAGOKS);
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 			return 0;
 		}
 
···
 
 		IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
 			      IPSTATS_MIB_FRAGFAILS);
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 		return err;
 
 slow_path_clean:

net/ipv6/ip6_tunnel.c

···
 
 		icmpv6_send(skb2, rel_type, rel_code, rel_info);
 
-		if (rt)
-			dst_release(&rt->dst);
+		ip6_rt_put(rt);
 
 		kfree_skb(skb2);
 	}
···
 			if (dev->mtu < IPV6_MIN_MTU)
 				dev->mtu = IPV6_MIN_MTU;
 		}
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 }
 

net/ipv6/mcast.c

···
 		rt = rt6_lookup(net, addr, NULL, 0, 0);
 		if (rt) {
 			dev = rt->dst.dev;
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 		}
 	} else
 		dev = dev_get_by_index_rcu(net, ifindex);
···
 
 		if (rt) {
 			dev = rt->dst.dev;
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 		}
 	} else
 		dev = dev_get_by_index_rcu(net, ifindex);

net/ipv6/ndisc.c

···
 			ND_PRINTK(0, err,
 				  "RA: %s got default router without neighbour\n",
 				  __func__);
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 			return;
 		}
 	}
···
 			ND_PRINTK(0, err,
 				  "RA: %s got default router without neighbour\n",
 				  __func__);
-			dst_release(&rt->dst);
+			ip6_rt_put(rt);
 			return;
 		}
 		neigh->flags |= NTF_ROUTER;
···
 		ND_PRINTK(2, warn, "RA: invalid RA options\n");
 	}
 out:
-	if (rt)
-		dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	if (neigh)
 		neigh_release(neigh);
 }

net/ipv6/netfilter/ip6t_rpfilter.c

···
 	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
 		ret = true;
  out:
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	return ret;
 }
 

net/ipv6/route.c

···
 		else
 			rt6_set_expires(rt, jiffies + HZ * lifetime);
 
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 	}
 	return 0;
 }
···
 	else
 		goto out2;
 
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	rt = nrt ? : net->ipv6.ip6_null_entry;
 
 	dst_hold(&rt->dst);
···
 	 * Race condition! In the gap, when table->tb6_lock was
 	 * released someone could insert this route.  Relookup.
 	 */
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	goto relookup;
 
 out:
···
 				goto out;
 			if (dev) {
 				if (dev != grt->dst.dev) {
-					dst_release(&grt->dst);
+					ip6_rt_put(grt);
 					goto out;
 				}
 			} else {
···
 			}
 			if (!(grt->rt6i_flags & RTF_GATEWAY))
 				err = 0;
-			dst_release(&grt->dst);
+			ip6_rt_put(grt);
 
 			if (err)
 				goto out;
···
 	write_unlock_bh(&table->tb6_lock);
 
 out:
-	dst_release(&rt->dst);
+	ip6_rt_put(rt);
 	return err;
 }
 
···
 
 	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
 	if (!skb) {
-		dst_release(&rt->dst);
+		ip6_rt_put(rt);
 		err = -ENOBUFS;
 		goto errout;
 	}