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

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
...@@ -1356,6 +1356,11 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, ...@@ -1356,6 +1356,11 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
unsigned int mtu; unsigned int mtu;
struct ipv6_txoptions *nopt, *opt = ipc6->opt; 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 * setup for corking
*/ */
...@@ -1389,8 +1394,6 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, ...@@ -1389,8 +1394,6 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
/* need source address above miyazawa*/ /* need source address above miyazawa*/
} }
dst_hold(&rt->dst);
cork->base.dst = &rt->dst;
v6_cork->hop_limit = ipc6->hlimit; v6_cork->hop_limit = ipc6->hlimit;
v6_cork->tclass = ipc6->tclass; v6_cork->tclass = ipc6->tclass;
if (rt->dst.flags & DST_XFRM_TUNNEL) if (rt->dst.flags & DST_XFRM_TUNNEL)
...@@ -1784,6 +1787,7 @@ int ip6_append_data(struct sock *sk, ...@@ -1784,6 +1787,7 @@ int ip6_append_data(struct sock *sk,
/* /*
* setup for corking * setup for corking
*/ */
dst_hold(&rt->dst);
err = ip6_setup_cork(sk, &inet->cork, &np->cork, err = ip6_setup_cork(sk, &inet->cork, &np->cork,
ipc6, rt); ipc6, rt);
if (err) if (err)
...@@ -1974,15 +1978,16 @@ struct sk_buff *ip6_make_skb(struct sock *sk, ...@@ -1974,15 +1978,16 @@ struct sk_buff *ip6_make_skb(struct sock *sk,
int exthdrlen = (ipc6->opt ? ipc6->opt->opt_flen : 0); int exthdrlen = (ipc6->opt ? ipc6->opt->opt_flen : 0);
int err; int err;
if (flags & MSG_PROBE) if (flags & MSG_PROBE) {
dst_release(&rt->dst);
return NULL; return NULL;
}
__skb_queue_head_init(&queue); __skb_queue_head_init(&queue);
cork->base.flags = 0; cork->base.flags = 0;
cork->base.addr = 0; cork->base.addr = 0;
cork->base.opt = NULL; cork->base.opt = NULL;
cork->base.dst = NULL;
v6_cork.opt = NULL; v6_cork.opt = NULL;
err = ip6_setup_cork(sk, cork, &v6_cork, ipc6, rt); err = ip6_setup_cork(sk, cork, &v6_cork, ipc6, rt);
if (err) { if (err) {
......
...@@ -1541,7 +1541,8 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) ...@@ -1541,7 +1541,8 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
err = PTR_ERR(skb); err = PTR_ERR(skb);
if (!IS_ERR_OR_NULL(skb)) if (!IS_ERR_OR_NULL(skb))
err = udp_v6_send_skb(skb, fl6, &cork.base); err = udp_v6_send_skb(skb, fl6, &cork.base);
goto out; /* ip6_make_skb steals dst reference */
goto out_no_dst;
} }
lock_sock(sk); lock_sock(sk);
......
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