Subject: Re: Change in alloc_skb() behavior in 3.2+ kernels?

From: Grant Edwards <[email-masked]>
Date: Thu, 7 Jun 2012 13:23:55 +0000 (UTC)

On 2012-06-06, David Miller <[email-masked]> wrote:
> From: Grant Edwards <[email-masked]>
> Date: Wed, 6 Jun 2012 18:59:19 +0000 (UTC)
>
>> At the time it was written (probably 10+ years ago) it was relying on
>> the documented API for alloc_skb() that stated alloc_skb() either
>> returned an sk_buff of the requested size or it failed.
>
> It was never a formal API that we would only allocate 'size'
> amount of tailroom.

How can you say that?

>>From skbuff.c:

    /**
    *__alloc_skb-allocate a network buffer
    *@size: size to allocate
    *@gfp_mask: allocation mask
    *@fclone: allocate from fclone cache instead of head cache
    *and allocate a cloned (child) skb
    *@node: numa node to allocate memory on
    *
>>> *Allocate a new &sk_buff. The returned buffer has no headroom and a
>>> *tail room of size bytes. The object has a reference count of one.
    *The return is the buffer. On a failure the return is %NULL.
    *
    *Buffers may only be allocated from interrupts using a @gfp_mask of
    *%GFP_ATOMIC.
    */

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