gro: Nasty optimisations for page frags in skb_gro_receive
This patch reverses the direction of the frags array copy in
skb_gro_receive in order simplify the loop conditional. It
also avoids touching the first element of the original frags
array.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 168e949..19afb18 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2676,22 +2676,27 @@
goto merge;
else if (headlen <= offset) {
skb_frag_t *frag;
- int i;
+ skb_frag_t *frag2;
+ int i = skb_shinfo(skb)->nr_frags;
+ int nr_frags = skb_shinfo(p)->nr_frags + i;
- if (skb_shinfo(p)->nr_frags + skb_shinfo(skb)->nr_frags >
- MAX_SKB_FRAGS)
+ offset -= headlen;
+
+ if (nr_frags > MAX_SKB_FRAGS)
return -E2BIG;
- skb_shinfo(skb)->frags[0].page_offset += offset - headlen;
- skb_shinfo(skb)->frags[0].size -= offset - headlen;
-
- frag = skb_shinfo(p)->frags + skb_shinfo(p)->nr_frags;
- for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
- *frag++ = skb_shinfo(skb)->frags[i];
-
- skb_shinfo(p)->nr_frags += skb_shinfo(skb)->nr_frags;
+ skb_shinfo(p)->nr_frags = nr_frags;
skb_shinfo(skb)->nr_frags = 0;
+ frag = skb_shinfo(p)->frags + nr_frags;
+ frag2 = skb_shinfo(skb)->frags + i;
+ do {
+ *--frag = *--frag2;
+ } while (--i);
+
+ frag->page_offset += offset;
+ frag->size -= offset;
+
skb->truesize -= skb->data_len;
skb->len -= skb->data_len;
skb->data_len = 0;