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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: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2011-07-28 04:32:25 +00:00 committed by David S. Miller
parent 897dc80b95
commit 89b0212697
1 changed files with 14 additions and 13 deletions
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27
net/ipv6/ip6_tunnel.c
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@ -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;
}