netdev - Re: [PATCH net] net: Revert "net: avoid one atomic operation in skb

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Date:	Fri, 21 Nov 2014 14:39:34 -0500
From:	Chris Mason <clm@...com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Sabrina Dubroca <sd@...asysnail.net>,
	David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net: Revert "net: avoid one atomic operation in
 skb_clone()"

On Fri, Nov 21, 2014 at 2:29 PM, Eric Dumazet <eric.dumazet@...il.com> 
wrote:
> On Fri, 2014-11-21 at 19:05 +0100, Sabrina Dubroca wrote:
>>  Hello Eric,
>> 
>>  >
>>  > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>>  > index c16615bfb61e..be4c7deed971 100644
>>  > --- a/net/core/skbuff.c
>>  > +++ b/net/core/skbuff.c
>>  > @@ -552,20 +552,13 @@ static void kfree_skbmem(struct sk_buff 
>> *skb)
>>  >  	case SKB_FCLONE_CLONE:
>>  >  		fclones = container_of(skb, struct sk_buff_fclones, skb2);
>>  >
>>  > -		/* Warning : We must perform the atomic_dec_and_test() before
>>  > -		 * setting skb->fclone back to SKB_FCLONE_FREE, otherwise
>>  > -		 * skb_clone() could set clone_ref to 2 before our decrement.
>>  > -		 * Anyway, if we are going to free the structure, no need to
>>  > -		 * rewrite skb->fclone.
>>  > +		/* The clone portion is available for
>>  > +		 * fast-cloning again.
>>  >  		 */
>>  > -		if (atomic_dec_and_test(&fclones->fclone_ref)) {
>>  > +		skb->fclone = SKB_FCLONE_UNAVAILABLE;
>> 
>>  Shouldn't that be SKB_FCLONE_FREE ?
> 
> Absolutely :(
> 
> I'll send a v2, thanks !

v1 made it through the first pass here.  I'll switch to SKB_FCLONE_FREE 
and restart.

-chris



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