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ipv6: hand away dst refs to cork setup

PATCH New Pavel Begunkov 1 participant 1 message Jan 11, 2022 1 message not in the archive

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A message that is not in the archive (sent off-list or not yet received): [email protected]

Pavel Begunkov

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PATCH 9/14 ipv6: hand away dst refs to cork setup

udpv6_sendmsg() doesn't need dst after calling into ip6_make_skb(), however it still retains a ref and ip6_make_skb() has to do an addition get/put pair. Hand over dst with the reference from ip6_sk_dst_lookup_flow() to avoid two atomics.

Signed-off-by Pavel Begunkov <[email protected]>
---
 net/ipv6/ip6_output.c | 9 ++++++---
 net/ipv6/udp.c        | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)
net/ipv6/ip6_output.c +6 -3
index 0cc490f2cfbf..6a7bba4dd04d 100644
@@ -1356,6 +1356,8 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
 	unsigned int mtu;
 	struct ipv6_txoptions *nopt, *opt = ipc6->opt;
 
+	cork->base.dst = &rt->dst;
+
 	/*
 	 * setup for corking
 	 */

@@ -1389,8 +1391,6 @@ 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 +1784,7 @@ 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)

@@ -1974,8 +1975,10 @@ 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);
net/ipv6/udp.c +2 -1
index eec83e34ae27..3039dff7fe64 100644
@@ -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);
Signature · 1 line
2.34.1