gro: Avoid unnecessary comparison after skb_gro_header

For the overwhelming majority of cases, skb_gro_header's return
value cannot be NULL.  Yet we must check it because of its current
form.  This patch splits it up into multiple functions in order
to avoid this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 61f55386a236..b6215be0963f 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -817,13 +817,20 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
         struct sk_buff *p;
         struct ipv6hdr *iph;
         unsigned int nlen;
+        unsigned int hlen;
+        unsigned int off;
         int flush = 1;
         int proto;
         __wsum csum;
 
-        iph = skb_gro_header(skb, sizeof(*iph));
-        if (unlikely(!iph))
-                goto out;
+        off = skb_gro_offset(skb);
+        hlen = off + sizeof(*iph);
+        iph = skb_gro_header_fast(skb, off);
+        if (skb_gro_header_hard(skb, hlen)) {
+                iph = skb_gro_header_slow(skb, hlen, off);
+                if (unlikely(!iph))
+                        goto out;
+        }
 
         skb_gro_pull(skb, sizeof(*iph));
         skb_set_transport_header(skb, skb_gro_offset(skb));