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>

1 files changed, 19 insertions, 4 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index cd29e613bc5a..ed4550fd9ece 100644
--- 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: