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, 14 insertions, 9 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 2e44a049be0f..371ece521e58 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1132,18 +1132,23 @@ static inline void skb_gro_pull(struct sk_buff *skb, unsigned int len)
         NAPI_GRO_CB(skb)->data_offset += len;
 }
 
-static inline void *skb_gro_header(struct sk_buff *skb, unsigned int hlen)
+static inline void *skb_gro_header_fast(struct sk_buff *skb,
+                                        unsigned int offset)
 {
-        unsigned int offset = skb_gro_offset(skb);
+        return NAPI_GRO_CB(skb)->frag0 + offset;
+}
 
-        hlen += offset;
-        if (NAPI_GRO_CB(skb)->frag0_len < hlen) {
-                NAPI_GRO_CB(skb)->frag0 = NULL;
-                NAPI_GRO_CB(skb)->frag0_len = 0;
-                return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
-        }
+static inline int skb_gro_header_hard(struct sk_buff *skb, unsigned int hlen)
+{
+        return NAPI_GRO_CB(skb)->frag0_len < hlen;
+}
 
-        return NAPI_GRO_CB(skb)->frag0 + offset;
+static inline void *skb_gro_header_slow(struct sk_buff *skb, unsigned int hlen,
+                                        unsigned int offset)
+{
+        NAPI_GRO_CB(skb)->frag0 = NULL;
+        NAPI_GRO_CB(skb)->frag0_len = 0;
+        return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
 }
 
 static inline void *skb_gro_mac_header(struct sk_buff *skb)