netdev - Re: [PATCH v8] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

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Message-ID: <yw1xy4dmp6vo.fsf@unicorn.mansr.com>
Date:	Wed, 25 Nov 2015 13:04:43 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Mason <slash.tmp@...e.fr>
Cc:	Alexander Duyck <alexander.duyck@...il.com>,
	netdev@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v8] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

Mason <slash.tmp@...e.fr> writes:

> On 25/11/2015 13:45, Måns Rullgård wrote:
>
>> Mason wrote:
>> 
>>> On 19/11/2015 14:02, Mans Rullgard wrote:
>>>
>>>> +	if (dma_mapping_error(&dev->dev, dma_addr)) {
>>>> +		skb_free_frag(data);
>>>> +		return -ENOMEM;
>>>> +	}
>>>
>>> I'm back-porting this driver to 4.1
>>>
>>> skb_free_frag() was introduced in 4.2 by 181edb2bfa22b IIUC.
>>>
>>> +static inline void skb_free_frag(void *addr)
>>> +{
>>> +       __free_page_frag(addr);
>>> +}
>>>
>>> Should I just copy the definition of __free_page_frag() ?
>> 
>> Looks like it ought to work.  Try and find out.  Not that you'll ever
>> hit that error condition unless you fake it.
>
> Turns out __free_pages_ok() is static and I'd rather not touch
> mm/page_alloc.c in my back-port.
>
> Since you say the error condition is rare, I think I'll go with
> the code that 181edb2bfa22b replaced (put_page, IIUC).
>
> #include <linux/version.h>
> #if LINUX_VERSION_CODE < KERNEL_VERSION(4,2,0)
> #define skb_free_frag(data) put_page(virt_to_head_page(data))
> #else
> #error DELETE ME NOW (see commit 181edb2bfa22b)
> #endif

You can simply put_page(page) instead since we already have the
virt_to_head_page() a few lines up.

-- 
Måns Rullgård
mans@...sr.com
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