netdev - Re: [PATCH 1/4] net: add support for per-paged-fragment destructors

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Date:	Wed, 9 Nov 2011 16:33:00 +0100
From:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:	Ian Campbell <ian.campbell@...rix.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH 1/4] net: add support for per-paged-fragment destructors

On Wed, Nov 09, 2011 at 03:02:04PM +0000, Ian Campbell wrote:
> Entities which care about the complete lifecycle of pages which they inject
> into the network stack via an skb paged fragment can choose to set this
> destructor in order to receive a callback when the stack is really finished
> with a page (including all clones, retransmits, pull-ups etc etc).
[...]
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -139,9 +139,16 @@ struct sk_buff;
>  
>  typedef struct skb_frag_struct skb_frag_t;
>  
> +struct skb_frag_destructor {
> +	atomic_t ref;
> +	int (*destroy)(void *data);
> +	void *data;
> +};
> +
>  struct skb_frag_struct {
>  	struct {
>  		struct page *p;
> +		struct skb_frag_destructor *destructor;
>  	} page;

You can get rid of the data field of skb_frag_destructor: if destroy() gets
pointer to the destroyed struct skb_frag_set_destructor, its users can
get at containing struct via container_of() if needed and the memory
pointed to by data won't have to be managed separately.

Nice work, BTW!

Best Regards,
Michał Mirosław
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