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* [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear()
@ 2020-08-10 12:28 Miaohe Lin
  2020-08-10 13:56 ` Florian Westphal
  2020-08-10 15:06 ` Eric Dumazet
  0 siblings, 2 replies; 6+ messages in thread
From: Miaohe Lin @ 2020-08-10 12:28 UTC (permalink / raw)
  To: davem, kuba, pshelar, martin.varghese, fw, dcaratti, edumazet,
	steffen.klassert, pabeni, shmulik, kyk.segfault
  Cc: netdev, linux-kernel, linmiaohe

The skb_shared_info part of the data is assigned in the following loop. It
is meaningless to do a memcpy here.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 net/core/skbuff.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7e2e502ef519..5b983c9472f5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5952,9 +5952,6 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
 
 	size = SKB_WITH_OVERHEAD(ksize(data));
 
-	memcpy((struct skb_shared_info *)(data + size),
-	       skb_shinfo(skb), offsetof(struct skb_shared_info,
-					 frags[skb_shinfo(skb)->nr_frags]));
 	if (skb_orphan_frags(skb, gfp_mask)) {
 		kfree(data);
 		return -ENOMEM;
-- 
2.19.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear()
  2020-08-10 12:28 [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear() Miaohe Lin
@ 2020-08-10 13:56 ` Florian Westphal
  2020-08-10 15:06 ` Eric Dumazet
  1 sibling, 0 replies; 6+ messages in thread
From: Florian Westphal @ 2020-08-10 13:56 UTC (permalink / raw)
  To: Miaohe Lin
  Cc: davem, kuba, pshelar, martin.varghese, fw, dcaratti, edumazet,
	steffen.klassert, pabeni, shmulik, kyk.segfault, netdev,
	linux-kernel

Miaohe Lin <linmiaohe@huawei.com> wrote:
> The skb_shared_info part of the data is assigned in the following loop.

Where?

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear()
  2020-08-10 12:28 [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear() Miaohe Lin
  2020-08-10 13:56 ` Florian Westphal
@ 2020-08-10 15:06 ` Eric Dumazet
  1 sibling, 0 replies; 6+ messages in thread
From: Eric Dumazet @ 2020-08-10 15:06 UTC (permalink / raw)
  To: Miaohe Lin, davem, kuba, pshelar, martin.varghese, fw, dcaratti,
	edumazet, steffen.klassert, pabeni, shmulik, kyk.segfault
  Cc: netdev, linux-kernel



On 8/10/20 5:28 AM, Miaohe Lin wrote:
> The skb_shared_info part of the data is assigned in the following loop. It
> is meaningless to do a memcpy here.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  net/core/skbuff.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 7e2e502ef519..5b983c9472f5 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5952,9 +5952,6 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
>  
>  	size = SKB_WITH_OVERHEAD(ksize(data));
>  
> -	memcpy((struct skb_shared_info *)(data + size),
> -	       skb_shinfo(skb), offsetof(struct skb_shared_info,
> -					 frags[skb_shinfo(skb)->nr_frags]));
>  	if (skb_orphan_frags(skb, gfp_mask)) {
>  		kfree(data);
>  		return -ENOMEM;
> 

Reminder : net-next is CLOSED.

This is not correct. We still have to copy _something_

Something like :

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2828f6d5ba898a5e50ccce45589bf1370e474b0f..1c0519426c7ba4b04377fc8054c4223c135879ab 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5953,8 +5953,8 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
        size = SKB_WITH_OVERHEAD(ksize(data));
 
        memcpy((struct skb_shared_info *)(data + size),
-              skb_shinfo(skb), offsetof(struct skb_shared_info,
-                                        frags[skb_shinfo(skb)->nr_frags]));
+              skb_shinfo(skb), offsetof(struct skb_shared_info, frags[0]));
+
        if (skb_orphan_frags(skb, gfp_mask)) {
                kfree(data);
                return -ENOMEM;

^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear()
  2020-08-11 12:10 linmiaohe
@ 2020-08-11 15:35 ` Eric Dumazet
  0 siblings, 0 replies; 6+ messages in thread
From: Eric Dumazet @ 2020-08-11 15:35 UTC (permalink / raw)
  To: linmiaohe, Eric Dumazet
  Cc: davem, kuba, pshelar, martin.varghese, fw, dcaratti, edumazet,
	steffen.klassert, pabeni, shmulik, kyk.segfault, netdev,
	linux-kernel



On 8/11/20 5:10 AM, linmiaohe wrote:
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> On 8/10/20 5:28 AM, Miaohe Lin wrote:
>>> The skb_shared_info part of the data is assigned in the following 
>>> loop. It is meaningless to do a memcpy here.
>>>
>>
>> Reminder : net-next is CLOSED.
>>
> 
> Thanks for your remind. I would wait for it open.
> 
>> This is not correct. We still have to copy _something_
>>
>> Something like :
>>
>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 2828f6d5ba898a5e50ccce45589bf1370e474b0f..1c0519426c7ba4b04377fc8054c4223c135879ab 100644
>> --- a/net/core/skbuff.c
>> +++ b/net/core/skbuff.c
>> @@ -5953,8 +5953,8 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
>>        size = SKB_WITH_OVERHEAD(ksize(data));
>>
>>        memcpy((struct skb_shared_info *)(data + size),
>> -              skb_shinfo(skb), offsetof(struct skb_shared_info,
>> -                                        frags[skb_shinfo(skb)->nr_frags]));
>> +              skb_shinfo(skb), offsetof(struct skb_shared_info, 
>> + frags[0]));
>> +
>>        if (skb_orphan_frags(skb, gfp_mask)) {
>>                kfree(data);
>>                return -ENOMEM;
>>
> 
> This looks good. Will send a patch v2 soon. May I add a suggested-by tag of you ?

I would advise not using Suggested-by, as this would imply I suggested the idea of changing
this function in the first place.

I will add a Reviewed-by:  eventually if your v2 submission looks fine to me.

Thanks.


> Many thanks.
> 

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear()
@ 2020-08-11 12:10 linmiaohe
  2020-08-11 15:35 ` Eric Dumazet
  0 siblings, 1 reply; 6+ messages in thread
From: linmiaohe @ 2020-08-11 12:10 UTC (permalink / raw)
  To: Eric Dumazet
  Cc: davem, kuba, pshelar, martin.varghese, fw, dcaratti, edumazet,
	steffen.klassert, pabeni, shmulik, kyk.segfault, netdev,
	linux-kernel

Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On 8/10/20 5:28 AM, Miaohe Lin wrote:
>> The skb_shared_info part of the data is assigned in the following 
>> loop. It is meaningless to do a memcpy here.
>> 
>
>Reminder : net-next is CLOSED.
>

Thanks for your remind. I would wait for it open.

>This is not correct. We still have to copy _something_
>
>Something like :
>
>diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 2828f6d5ba898a5e50ccce45589bf1370e474b0f..1c0519426c7ba4b04377fc8054c4223c135879ab 100644
>--- a/net/core/skbuff.c
>+++ b/net/core/skbuff.c
>@@ -5953,8 +5953,8 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
>        size = SKB_WITH_OVERHEAD(ksize(data));
> 
>        memcpy((struct skb_shared_info *)(data + size),
>-              skb_shinfo(skb), offsetof(struct skb_shared_info,
>-                                        frags[skb_shinfo(skb)->nr_frags]));
>+              skb_shinfo(skb), offsetof(struct skb_shared_info, 
>+ frags[0]));
>+
>        if (skb_orphan_frags(skb, gfp_mask)) {
>                kfree(data);
>                return -ENOMEM;
>

This looks good. Will send a patch v2 soon. May I add a suggested-by tag of you ?
Many thanks.


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear()
@ 2020-08-11 11:54 linmiaohe
  0 siblings, 0 replies; 6+ messages in thread
From: linmiaohe @ 2020-08-11 11:54 UTC (permalink / raw)
  To: Florian Westphal
  Cc: davem, kuba, pshelar, martin.varghese, dcaratti, edumazet,
	steffen.klassert, pabeni, shmulik, kyk.segfault, netdev,
	linux-kernel

Florian Westphal <fw@strlen.de> wrote:
>Miaohe Lin <linmiaohe@huawei.com> wrote:
>> The skb_shared_info part of the data is assigned in the following loop.
>
>Where?
>

It's at the below for (i = 0; i < nfrags; i++) loop. But I missed something as Eric Dumazet pointed out.
Sorry about it.


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2020-08-11 15:35 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-08-10 12:28 [PATCH] net: eliminate meaningless memcpy to data in pskb_carve_inside_nonlinear() Miaohe Lin
2020-08-10 13:56 ` Florian Westphal
2020-08-10 15:06 ` Eric Dumazet
2020-08-11 11:54 linmiaohe
2020-08-11 12:10 linmiaohe
2020-08-11 15:35 ` Eric Dumazet

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