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Commit 89b02126 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ip6tnl: avoid touching dst refcount in ip6_tnl_xmit2() 



Even using percpu stats, we still hit tunnel dst_entry refcount in
ip6_tnl_xmit2()

Since we are in RCU locked section, we can use skb_dst_set_noref() and
avoid these atomic operations, leaving dst shared on cpus.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 897dc80b

net/ipv6/ip6_tunnel.c

+14 −13
Original line number Diff line number Diff line
@@ -889,7 +889,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb, 
	struct net_device_stats *stats = &t->dev->stats;

	struct ipv6hdr *ipv6h = ipv6_hdr(skb);

	struct ipv6_tel_txoption opt;

	struct dst_entry *dst;

	struct dst_entry *dst, *ndst = NULL;

	struct net_device *tdev;

	int mtu;

	unsigned int max_headroom = sizeof(struct ipv6hdr);
@@ -897,19 +897,19 @@ static int ip6_tnl_xmit2(struct sk_buff *skb, 
	int err = -1;

	int pkt_len;



	if ((dst = ip6_tnl_dst_check(t)) != NULL)

		dst_hold(dst);

	else {

		dst = ip6_route_output(net, NULL, fl6);

	dst = ip6_tnl_dst_check(t);

	if (!dst) {

		ndst = ip6_route_output(net, NULL, fl6);



		if (dst->error)

		if (ndst->error)

			goto tx_err_link_failure;

		dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), NULL, 0);

		if (IS_ERR(dst)) {

			err = PTR_ERR(dst);

			dst = NULL;

		ndst = xfrm_lookup(net, ndst, flowi6_to_flowi(fl6), NULL, 0);

		if (IS_ERR(ndst)) {

			err = PTR_ERR(ndst);

			ndst = NULL;

			goto tx_err_link_failure;

		}

		dst = ndst;

	}



	tdev = dst->dev;
@@ -955,7 +955,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb, 
		skb = new_skb;

	}

	skb_dst_drop(skb);

	skb_dst_set(skb, dst_clone(dst));

	skb_dst_set_noref(skb, dst);



	skb->transport_header = skb->network_header;
@@ -987,13 +987,14 @@ static int ip6_tnl_xmit2(struct sk_buff *skb, 
		stats->tx_errors++;

		stats->tx_aborted_errors++;

	}

	ip6_tnl_dst_store(t, dst);

	if (ndst)

		ip6_tnl_dst_store(t, ndst);

	return 0;

tx_err_link_failure:

	stats->tx_carrier_errors++;

	dst_link_failure(skb);

tx_err_dst_release:

	dst_release(dst);

	dst_release(ndst);

	return err;

}