Merge branch 'ipv6-sr-perf-improvements'

David Lebrun says:

====================
Performances improvement for IPv6 Segment Routing

This patch series improves the performances of IPv6 SR by optimizing skb head
reallocation and extending the use of dst_cache. The overall performances improve
by 35%.

Before patch series (SRH encap):
Result: OK: 7348320(c7347271+d1048) usec, 5000000 (1000byte,0frags)
  680427pps 5443Mb/sec (5443416000bps) errors: 0

After patch series (SRH encap):
Result: OK: 4774543(c4774084+d459) usec, 5000000 (1000byte,0frags)
  1047220pps 8377Mb/sec (8377760000bps) errors: 0

Baseline for plain IPv6 forwarding:
Result: OK: 4244144(c4243722+d422) usec, 5000000 (1000byte,0frags)
  1178093pps 9424Mb/sec (9424744000bps) errors: 0
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/seg6_iptunnel.c

@@ -105,7 +105,7 @@ static int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
 	hdrlen = (osrh->hdrlen + 1) << 3;
 	tot_len = hdrlen + sizeof(*hdr);
 
-	err = pskb_expand_head(skb, tot_len, 0, GFP_ATOMIC);
+	err = skb_cow_head(skb, tot_len);
 	if (unlikely(err))
 		return err;
 
@@ -156,7 +156,7 @@ static int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
 
 	hdrlen = (osrh->hdrlen + 1) << 3;
 
-	err = pskb_expand_head(skb, hdrlen, 0, GFP_ATOMIC);
+	err = skb_cow_head(skb, hdrlen);
 	if (unlikely(err))
 		return err;
 
@@ -237,6 +237,9 @@ static int seg6_do_srh(struct sk_buff *skb)
 
 static int seg6_input(struct sk_buff *skb)
 {
+	struct dst_entry *orig_dst = skb_dst(skb);
+	struct dst_entry *dst = NULL;
+	struct seg6_lwt *slwt;
 	int err;
 
 	err = seg6_do_srh(skb);
@@ -245,8 +248,30 @@ static int seg6_input(struct sk_buff *skb)
 		return err;
 	}
 
+	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
+
+#ifdef CONFIG_DST_CACHE
+	preempt_disable();
+	dst = dst_cache_get(&slwt->cache);
+	preempt_enable();
+#endif
+
 	skb_dst_drop(skb);
-	ip6_route_input(skb);
+
+	if (!dst) {
+		ip6_route_input(skb);
+#ifdef CONFIG_DST_CACHE
+		dst = skb_dst(skb);
+		if (!dst->error) {
+			preempt_disable();
+			dst_cache_set_ip6(&slwt->cache, dst,
+					  &ipv6_hdr(skb)->saddr);
+			preempt_enable();
+		}
+#endif
+	} else {
+		skb_dst_set(skb, dst);
+	}
 
 	return dst_input(skb);
 }