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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>
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89b0212697
@ -889,7 +889,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
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struct net_device_stats *stats = &t->dev->stats;
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struct ipv6hdr *ipv6h = ipv6_hdr(skb);
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struct ipv6_tel_txoption opt;
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struct dst_entry *dst;
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struct dst_entry *dst, *ndst = NULL;
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struct net_device *tdev;
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int mtu;
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unsigned int max_headroom = sizeof(struct ipv6hdr);
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@ -897,19 +897,19 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
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int err = -1;
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int pkt_len;
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if ((dst = ip6_tnl_dst_check(t)) != NULL)
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dst_hold(dst);
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else {
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dst = ip6_route_output(net, NULL, fl6);
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dst = ip6_tnl_dst_check(t);
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if (!dst) {
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ndst = ip6_route_output(net, NULL, fl6);
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if (dst->error)
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if (ndst->error)
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goto tx_err_link_failure;
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dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), NULL, 0);
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if (IS_ERR(dst)) {
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err = PTR_ERR(dst);
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dst = NULL;
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ndst = xfrm_lookup(net, ndst, flowi6_to_flowi(fl6), NULL, 0);
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if (IS_ERR(ndst)) {
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err = PTR_ERR(ndst);
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ndst = NULL;
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goto tx_err_link_failure;
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}
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dst = ndst;
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}
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tdev = dst->dev;
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@ -955,7 +955,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
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skb = new_skb;
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}
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skb_dst_drop(skb);
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skb_dst_set(skb, dst_clone(dst));
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skb_dst_set_noref(skb, dst);
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skb->transport_header = skb->network_header;
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@ -987,13 +987,14 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
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stats->tx_errors++;
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stats->tx_aborted_errors++;
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}
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ip6_tnl_dst_store(t, dst);
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if (ndst)
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ip6_tnl_dst_store(t, ndst);
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return 0;
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tx_err_link_failure:
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stats->tx_carrier_errors++;
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dst_link_failure(skb);
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tx_err_dst_release:
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dst_release(dst);
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dst_release(ndst);
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return err;
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}
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