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Subject[PATCH net-next] skbuff: remove some unnecessary operation in skb_segment_list()
Date
From: Yunsheng Lin <linyunsheng@huawei.com>

gro list uses skb_shinfo(skb)->frag_list to link two skb together,
and NAPI_GRO_CB(p)->last->next is used when there are more skb,
see skb_gro_receive_list(). gso expects that each segmented skb is
linked together using skb->next, so only the first skb->next need
to set to skb_shinfo(skb)-> frag_list when doing gso list segment.

It is the same reason that nskb->next does not need to be set to
list_skb before goto the error handling, because nskb->next already
pointers to list_skb.

And nskb is also the last skb at the end of loop, so remove tail
variable and use nskb instead.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
---
net/core/skbuff.c | 15 +++------------
1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c421c8f..e8320b5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3732,13 +3732,13 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
unsigned int tnl_hlen = skb_tnl_header_len(skb);
unsigned int delta_truesize = 0;
unsigned int delta_len = 0;
- struct sk_buff *tail = NULL;
struct sk_buff *nskb, *tmp;
int err;

skb_push(skb, -skb_network_offset(skb) + offset);

skb_shinfo(skb)->frag_list = NULL;
+ skb->next = list_skb;

do {
nskb = list_skb;
@@ -3756,17 +3756,8 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
}
}

- if (!tail)
- skb->next = nskb;
- else
- tail->next = nskb;
-
- if (unlikely(err)) {
- nskb->next = list_skb;
+ if (unlikely(err))
goto err_linearize;
- }
-
- tail = nskb;

delta_len += nskb->len;
delta_truesize += nskb->truesize;
@@ -3793,7 +3784,7 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,

skb_gso_reset(skb);

- skb->prev = tail;
+ skb->prev = nskb;

if (skb_needs_linearize(skb, features) &&
__skb_linearize(skb))
--
2.7.4
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