gro: Open-code final pskb_may_pull

As we know the only packets which need the final pskb_may_pull
are completely non-linear, and have all the required bits in
frag0, we can perform a straight memcpy instead of going through
pskb_may_pull and doing skb_copy_bits.

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

diff --git a/net/core/dev.c b/net/core/dev.c
index cd29e613bc5a5a864c47bcfa95b8b9c0d7172132..ed4550fd9ececf4cda75057208eab97590be6cd9 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2452,10 +2452,25 @@ int dev_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
        ret = GRO_HELD;
 
 pull:
-       if (unlikely(!pskb_may_pull(skb, skb_gro_offset(skb)))) {
-               if (napi->gro_list == skb)
-                       napi->gro_list = skb->next;
-               ret = GRO_DROP;
+       if (skb_headlen(skb) < skb_gro_offset(skb)) {
+               int grow = skb_gro_offset(skb) - skb_headlen(skb);
+
+               BUG_ON(skb->end - skb->tail < grow);
+
+               memcpy(skb_tail_pointer(skb), NAPI_GRO_CB(skb)->frag0, grow);
+
+               skb->tail += grow;
+               skb->data_len -= grow;
+
+               skb_shinfo(skb)->frags[0].page_offset += grow;
+               skb_shinfo(skb)->frags[0].size -= grow;
+
+               if (unlikely(!skb_shinfo(skb)->frags[0].size)) {
+                       put_page(skb_shinfo(skb)->frags[0].page);
+                       memmove(skb_shinfo(skb)->frags,
+                               skb_shinfo(skb)->frags + 1,
+                               --skb_shinfo(skb)->nr_frags);
+               }
        }
 
 ok: