netdev - Re: [PATCH v3] net: mv643xx_eth: Fix highmem support in non-TSO egress path

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Date:	Sat, 24 Jan 2015 10:45:29 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	David Miller <davem@...emloft.net>,
	Russell King <linux@....linux.org.uk>
CC:	netdev@...r.kernel.org, B38611@...escale.com,
	fabio.estevam@...escale.com, David.Laight@...LAB.COM
Subject: Re: [PATCH v3] net: mv643xx_eth: Fix highmem support in non-TSO egress
 path

Hi all,

On 01/22/2015 11:33 AM, Ezequiel Garcia wrote:
> Commit 69ad0dd7af22b61d9e0e68e56b6290121618b0fb
> Author: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
> Date:   Mon May 19 13:59:59 2014 -0300
> 
>     net: mv643xx_eth: Use dma_map_single() to map the skb fragments
> 
> caused a nasty regression by removing the support for highmem skb
> fragments. By using page_address() to get the address of a fragment's
> page, we are assuming a lowmem page. However, such assumption is incorrect,
> as fragments can be in highmem pages, resulting in very nasty issues.
> 
> This commit fixes this by using the skb_frag_dma_map() helper,
> which takes care of mapping the skb fragment properly. Additionally,
> the type of mapping is now tracked, so it can be unmapped using
> dma_unmap_page or dma_unmap_single when appropriate.
> 
> This commit also fixes the error path in txq_init() to release the
> resources properly.
> 
> Fixes: 69ad0dd7af22 ("net: mv643xx_eth: Use dma_map_single() to map the skb fragments")
> Reported-by: Russell King <rmk+kernel@....linux.org.uk>

Russell, when you have some time, please test this patch. I think it
solves the regression and it manages to unmap the descriptors properly.

Thanks!
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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