skbuff: optimize the pull_pages code in __pskb_pull_tail()

In the pull_pages code block, if the first frag size > eat,
we can end the loop in advance to avoid extra copy.

Signed-off-by: Lin Zhang <xiaolou4617@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8b11341ed69ad97d34dd3e9b73c8c44ef7c452ff..b352c6bcfb31b6ddbf12666d71cb2eca101c65d6 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1719,6 +1719,8 @@ pull_pages:
                        if (eat) {
                                skb_shinfo(skb)->frags[k].page_offset += eat;
                                skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
+                               if (!i)
+                                       goto end;
                                eat = 0;
                        }
                        k++;
@@ -1726,6 +1728,7 @@ pull_pages:
        }
        skb_shinfo(skb)->nr_frags = k;
 
+end:
        skb->tail     += delta;
        skb->data_len -= delta;