From 89b0212697e92bc59a021a2338cd8c09f919325c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 28 Jul 2011 04:32:25 +0000 Subject: 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 Signed-off-by: David S. Miller --- net/ipv6/ip6_tunnel.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) (limited to 'net') diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index 0bc98886c383..6fb1fb3624bf 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -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; } -- cgit v1.2.3-59-g8ed1b