From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mason <slash.tmp@free.fr>
Subject: Re: [PATCH v8] net: ethernet: add driver for Aurora VLSI NB8800
 Ethernet controller
Date: Wed, 25 Nov 2015 14:00:15 +0100
Message-ID: <5655B0DF.8060000@free.fr>
References: <1447938180-19651-1-git-send-email-mans@mansr.com>
 <5655AB63.40204@free.fr> <yw1x37vuqmcy.fsf@unicorn.mansr.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: netdev@vger.kernel.org, Eric Dumazet <eric.dumazet@gmail.com>
To: Mans Rullgard <mans@mansr.com>,
	Alexander Duyck <alexander.duyck@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from smtp2-g21.free.fr ([212.27.42.2]:3860 "EHLO smtp2-g21.free.fr"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751751AbbKYNAX (ORCPT <rfc822;netdev@vger.kernel.org>);
	Wed, 25 Nov 2015 08:00:23 -0500
In-Reply-To: <yw1x37vuqmcy.fsf@unicorn.mansr.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On 25/11/2015 13:45, M=E5ns Rullg=E5rd wrote:

> Mason wrote:
>=20
>> 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() ?
>=20
> 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

Alexander, does that look correct?

Regards.