netdev - Re: [PATCH RFC] net: add alloc_skb_mustcopy() to make clone copy

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Date:	Tue, 20 Oct 2009 00:52:47 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jeremy@...p.org
Cc:	herbert@...dor.apana.org.au, netdev@...r.kernel.org
Subject: Re: [PATCH RFC] net: add alloc_skb_mustcopy() to make clone copy

From: Jeremy Fitzhardinge <jeremy@...p.org>
Date: Tue, 20 Oct 2009 15:19:18 +0900

> When doing network IO on behalf of guests, a Xen dom0 kernel gets granted
> pages from guests.  These pages cannot be released normally, so we must
> handle releasing them specially, which can do with a skb_destructor.
> 
> This is complicated by the fact that the lifetime of an skb's
> frags can be extended via cloning.  To address this, this patch adds
> alloc_skb_mustcopy() which allocates an skb with fclone==SKB_MUST_COPY.
> If skb_clone() sees an skb with this set, it simply calls skb_copy
> instead so that there are no aliases to the granted pages.
> 
> /* Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com> */

This looks perfectly fine to me.

Let me know if it actually works out for you and we can merge
this.
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