From: linzhang <xiaolou4617@gmail.com>
Date: Mon, 17 Jul 2017 17:25:02 +0800
Subject: skbuff: optimize the pull_pages code in __pskb_pull_tail()
Patch-mainline: v4.14-rc1
Git-commit: 3ccc6c6faaa93da70989177b91c7c3ef0df10937
References: bsc#1109837

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/core/skbuff.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1703,6 +1703,8 @@ 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++;
@@ -1710,6 +1712,7 @@ pull_pages:
 	}
 	skb_shinfo(skb)->nr_frags = k;
 
+end:
 	skb->tail     += delta;
 	skb->data_len -= delta;