netdev - Re: [PATCH v3] net: af_packet: don't call tpacket_destruct

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Message-ID: <AANLkTin71NME-WwD+tjuxFyh_6Ue7gFTXpLwDUVtaLKR@mail.gmail.com>
Date:	Mon, 27 Sep 2010 09:24:02 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>, xiaohui.xin@...el.com
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v3] net: af_packet: don't call tpacket_destruct_skb()
 until the skb is sent out

On Fri, Sep 24, 2010 at 2:36 PM, Jarek Poplawski <jarkao2@...il.com> wrote:
> On 2010-09-23 12:15, Changli Gao wrote:
>> Since skb->destructor() is used to account socket memory, and maybe called
>> before the skb is sent out, a corrupt skb maybe sent out finally.
>>
>> A new destructor is added into structure skb_shared_info(), and it won't
>> be called until the last reference to the data of an skb is put. af_packet
>> uses this destructor instead.
>
> IMHO, we shouldn't allow for fixing the bad design of one protocol at
> the expense of others by adding more and more conditionals. The proper
> way of handling paged skbs (splice compatible) exists. And the current
> patch doesn't even fix the problem completely against things like
> pskb_expand_head or pskb_copy.

pskb_expand_head is handled in my patch, but not pskb_copy().

indeed, there are many issues to fix, and xiaohui's patch may have the
same issues. The proper way may put the destruct handler in pages
instead.

-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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