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>
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 0bc9888..6fb1fb3 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -889,7 +889,7 @@
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 @@
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 @@
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 @@
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;
}