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Date: Mon, 16 May 2011 23:04:54 +0300
Message-ID: <BANLkTimvCVcQX-7teQgG7EQV9eeLgG3JnQ@mail.gmail.com> (sfid-20110516_220504_598521_9CE58F7D)
Subject: Re: several packets in a single buffer in Rx
From: Tomas Winkler <tomasw@gmail.com>
To: Emmanuel Grumbach <egrumbach@gmail.com>
Cc: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirqus@gmail.com>,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	Johannes Berg <johannes@sipsolutions.net>,
	"Guy, Wey-Yi" <wey-yi.w.guy@intel.com>, guy.cohen@intel.com
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Sender: linux-wireless-owner@vger.kernel.org

2011/5/16 Emmanuel Grumbach <egrumbach@gmail.com>:
> 2011/5/16 Michał Mirosław <mirqus@gmail.com>:
>> W dniu 16 maja 2011 14:59 użytkownik Emmanuel Grumbach
>> <egrumbach@gmail.com> napisał:
>>> 2011/5/16 Michał Mirosław <mirqus@gmail.com>:
>>>> 2011/5/16 Emmanuel Grumbach <egrumbach@gmail.com>:
>>>>> I would like to be able to deliver the same page several times to the
>>>>> stack without having the stack consume it before the last time I
>>>>> deliver it.
>>>>> Of course I would like to avoid cloning it.
>>>>
>>>> Just do get_page() on the page having another packet in it before
>>>> passing skb up.
>>>>
>>>
>>> I can see the path:
>>> __kfree_skb -> skb_release_all -> skb_release_data -> put_page
>>> put_page will free the page iff the _count variable reaches 0. Of course,
>>> _count is incremented by get_page.
>>>
>>> I will give it try.
>>>
>>> I understand that this will work regardless the order given to
>>> alloc_pages right ?
>>
>> Yes. Remember that if you put a lot of packets in a big-order page
>> then the memory will be freed only after all packets are freed.
>
> Sure. Thanks for the help.

How it is ensured that skb manipulation won't corrupt another packet
on the same page?

Thanks
Tomas