linux-kernel - Re: [PATCH -mmotm] [BUGFIX] pagemap: fix pfn calculation for hugepage

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Message-ID: <1269449671.3552.173.camel@calx>
Date:	Wed, 24 Mar 2010 11:54:31 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH -mmotm] [BUGFIX] pagemap: fix pfn calculation for
 hugepage

On Wed, 2010-03-24 at 14:42 +0900, Naoya Horiguchi wrote:
> When we look into pagemap using page-types with option -p, the value
> of pfn for hugepages looks wrong (see below.)
> This is because pte was evaluated only once for one vma
> although it should be updated for each hugepage. This patch fixes it.
> 
>   $ page-types -p 3277 -Nl -b huge
>   voffset   offset  len     flags
>   7f21e8a00 11e400  1       ___U___________H_G________________
>   7f21e8a01 11e401  1ff     ________________TG________________
>                ^^^
>   7f21e8c00 11e400  1       ___U___________H_G________________
>   7f21e8c01 11e401  1ff     ________________TG________________
>                ^^^
> 
> One hugepage contains 1 head page and 511 tail pages in x86_64 and
> each two lines represent each hugepage. Voffset and offset mean
> virtual address and physical address in the page unit, respectively.
> The different hugepages should not have the same offset value.
> 
> With this patch applied:
> 
>   $ page-types -p 3386 -Nl -b huge
>   voffset   offset   len    flags
>   7fec7a600 112c00   1      ___UD__________H_G________________
>   7fec7a601 112c01   1ff    ________________TG________________
>                ^^^
>   7fec7a800 113200   1      ___UD__________H_G________________
>   7fec7a801 113201   1ff    ________________TG________________
>                ^^^
>                OK
> 
> Changelog:
>  - add hugetlb entry walker in mm/pagewalk.c
>    (the idea based on Kamezawa-san's patch)
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Looks good to me.

Acked-by: Matt Mackall <mpm@...enic.com>

-- 
http://selenic.com : development and support for Mercurial and Linux


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