linux-kernel - Re: [PATCH v14 06/17] Use callback to deal with skb_release

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Message-ID: <1288861465.2659.44.camel@edumazet-laptop>
Date:	Thu, 04 Nov 2010 10:04:25 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	xiaohui.xin@...el.com
Cc:	netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com, mingo@...e.hu,
	davem@...emloft.net, herbert@...dor.apana.org.au,
	jdike@...ux.intel.com
Subject: Re: [PATCH v14 06/17] Use callback to deal with skb_release_data()
 specially.

Le jeudi 04 novembre 2010 à 17:05 +0800, xiaohui.xin@...el.com a écrit :
> From: Xin Xiaohui <xiaohui.xin@...el.com>
> 
> If buffer is external, then use the callback to destruct
> buffers.
> 
> Signed-off-by: Xin Xiaohui <xiaohui.xin@...el.com>
> Signed-off-by: Zhao Yu <yzhao81new@...il.com>
> Reviewed-by: Jeff Dike <jdike@...ux.intel.com>
> ---
>  net/core/skbuff.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index c83b421..5e6d69c 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -210,6 +210,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
>  
>  	/* make sure we initialize shinfo sequentially */
>  	shinfo = skb_shinfo(skb);
> +	shinfo->destructor_arg = NULL;

Hmm, I suggest you read the comment two lines above.

If destructor_arg is now cleared each time we allocate a new skb, then,
please move it before dataref in shinfo structure, so that the following
memset() does the job efficiently...

>  	memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
>  	atomic_set(&shinfo->dataref, 1);
>  
> @@ -343,6 +344,13 @@ static void skb_release_data(struct sk_buff *skb)
>  		if (skb_has_frags(skb))
>  			skb_drop_fraglist(skb);
>  
> +		if (skb->dev && dev_is_mpassthru(skb->dev)) {
> +			struct skb_ext_page *ext_page =
> +				skb_shinfo(skb)->destructor_arg;
> +			if (ext_page && ext_page->dtor)
> +				ext_page->dtor(ext_page);
> +		}
> +
>  		kfree(skb->head);
>  	}
>  }


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