Commit 40ac240c authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jakub Kicinski
Browse files

ipv6: optimise dst refcounting on cork init 



udpv6_sendmsg() doesn't need dst after calling ip6_make_skb(), so
instead of taking an additional reference inside ip6_setup_cork()
and releasing the initial one afterwards, we can hand over a reference
into ip6_make_skb() saving two atomics. The only other user of
ip6_setup_cork() is ip6_append_data() and it requires an extra
dst_hold().

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 5298953e

net/ipv6/ip6_output.c

+9 −4
Original line number Diff line number Diff line
@@ -1356,6 +1356,11 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, 
	unsigned int mtu;

	struct ipv6_txoptions *nopt, *opt = ipc6->opt;



	/* callers pass dst together with a reference, set it first so

	 * ip6_cork_release() can put it down even in case of an error.

	 */

	cork->base.dst = &rt->dst;



	/*

	 * setup for corking

	 */
@@ -1389,8 +1394,6 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, 


		/* need source address above miyazawa*/

	}

	dst_hold(&rt->dst);

	cork->base.dst = &rt->dst;

	v6_cork->hop_limit = ipc6->hlimit;

	v6_cork->tclass = ipc6->tclass;

	if (rt->dst.flags & DST_XFRM_TUNNEL)
@@ -1784,6 +1787,7 @@ int ip6_append_data(struct sock *sk, 
		/*

		 * setup for corking

		 */

		dst_hold(&rt->dst);

		err = ip6_setup_cork(sk, &inet->cork, &np->cork,

				     ipc6, rt);

		if (err)
@@ -1974,15 +1978,16 @@ struct sk_buff *ip6_make_skb(struct sock *sk, 
	int exthdrlen = (ipc6->opt ? ipc6->opt->opt_flen : 0);

	int err;



	if (flags & MSG_PROBE)

	if (flags & MSG_PROBE) {

		dst_release(&rt->dst);

		return NULL;

	}



	__skb_queue_head_init(&queue);



	cork->base.flags = 0;

	cork->base.addr = 0;

	cork->base.opt = NULL;

	cork->base.dst = NULL;

	v6_cork.opt = NULL;

	err = ip6_setup_cork(sk, cork, &v6_cork, ipc6, rt);

	if (err) {

net/ipv6/udp.c

+2 −1
Original line number Diff line number Diff line
@@ -1541,7 +1541,8 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 
		err = PTR_ERR(skb);

		if (!IS_ERR_OR_NULL(skb))

			err = udp_v6_send_skb(skb, fl6, &cork.base);

		goto out;

		/* ip6_make_skb steals dst reference */

		goto out_no_dst;

	}



	lock_sock(sk);