ipv6: addrlabel: rework ip6addrlbl_get()

If we allocate skb before the lookup, we can use RCU
without the need of ip6addrlbl_hold()

This means that the following patch can get rid of refcounting.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/addrlabel.c b/net/ipv6/addrlabel.c
index c6311d7..f314896 100644 (file)
--- a/net/ipv6/addrlabel.c
+++ b/net/ipv6/addrlabel.c
@@ -546,38 +546,28 @@ static int ip6addrlbl_get(struct sk_buff *in_skb, struct nlmsghdr *nlh,
                return -EINVAL;
        addr = nla_data(tb[IFAL_ADDRESS]);
 
-       rcu_read_lock();
-       p = __ipv6_addr_label(net, addr, ipv6_addr_type(addr), ifal->ifal_index);
-       if (p && !ip6addrlbl_hold(p))
-               p = NULL;
-       lseq = net->ipv6.ip6addrlbl_table.seq;
-       rcu_read_unlock();
-
-       if (!p) {
-               err = -ESRCH;
-               goto out;
-       }
-
        skb = nlmsg_new(ip6addrlbl_msgsize(), GFP_KERNEL);
-       if (!skb) {
-               ip6addrlbl_put(p);
+       if (!skb)
                return -ENOBUFS;
-       }
 
-       err = ip6addrlbl_fill(skb, p, lseq,
-                             NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
-                             RTM_NEWADDRLABEL, 0);
+       err = -ESRCH;
 
-       ip6addrlbl_put(p);
+       rcu_read_lock();
+       p = __ipv6_addr_label(net, addr, ipv6_addr_type(addr), ifal->ifal_index);
+       lseq = net->ipv6.ip6addrlbl_table.seq;
+       if (p)
+               err = ip6addrlbl_fill(skb, p, lseq,
+                                     NETLINK_CB(in_skb).portid,
+                                     nlh->nlmsg_seq,
+                                     RTM_NEWADDRLABEL, 0);
+       rcu_read_unlock();
 
        if (err < 0) {
                WARN_ON(err == -EMSGSIZE);
                kfree_skb(skb);
-               goto out;
+       } else {
+               err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
        }
-
-       err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
-out:
        return err;
 }