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, 2 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index bdb1a738193d..f9d90c56b6f0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2510,7 +2510,8 @@ void skb_gro_reset_offset(struct sk_buff *skb)
         NAPI_GRO_CB(skb)->data_offset = 0;
         NAPI_GRO_CB(skb)->frag0 = NULL;
 
-        if (!skb_headlen(skb) && !PageHighMem(skb_shinfo(skb)->frags[0].page))
+        if (skb->mac_header == skb->tail &&
+            !PageHighMem(skb_shinfo(skb)->frags[0].page))
                 NAPI_GRO_CB(skb)->frag0 =
                         page_address(skb_shinfo(skb)->frags[0].page) +
                         skb_shinfo(skb)->frags[0].page_offset;