gro: Only use skb_gro_header for completely non-linear packets

Currently skb_gro_header is used for packets which put the hardware
header in skb->data with the rest in frags.  Since the drivers that
need this optimisation all provide completely non-linear packets,
we can gain extra optimisations by only performing the frag0
optimisation for completely non-linear packets.

In particular, we can simply test frag0 (instead of skb_headlen)
to see whether the optimisation is in force.

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

1 files changed, 6 insertions, 5 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 61890ed0bcf2..d1afc3b64854 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1135,22 +1135,23 @@ static inline void *skb_gro_header(struct sk_buff *skb, unsigned int hlen)
 
         hlen += offset;
         if (!NAPI_GRO_CB(skb)->frag0 ||
-            unlikely(skb_shinfo(skb)->frags[0].size + skb_headlen(skb) < hlen))
+            unlikely(skb_shinfo(skb)->frags[0].size < hlen)) {
+                NAPI_GRO_CB(skb)->frag0 = NULL;
                 return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
+        }
 
         return NAPI_GRO_CB(skb)->frag0 + offset;
 }
 
 static inline void *skb_gro_mac_header(struct sk_buff *skb)
 {
-        return skb_headlen(skb) ? skb_mac_header(skb) :
-               NAPI_GRO_CB(skb)->frag0;
+        return NAPI_GRO_CB(skb)->frag0 ?: skb_mac_header(skb);
 }
 
 static inline void *skb_gro_network_header(struct sk_buff *skb)
 {
-        return skb_headlen(skb) ? skb_network_header(skb) :
-               NAPI_GRO_CB(skb)->frag0 + skb_network_offset(skb);
+        return (NAPI_GRO_CB(skb)->frag0 ?: skb->data) +
+               skb_network_offset(skb);
 }
 
 static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,