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

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Date:	Mon, 26 Jan 2015 23:11:49 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Cc:	David Miller <davem@...emloft.net>, 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

On Sat, Jan 24, 2015 at 10:45:29AM -0300, Ezequiel Garcia wrote:
> 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.

Yes, this seems to work as well, thanks.

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