linux-kernel - Re: [PATCH 2/8] hugetlb, rmap: add reverse mapping for hugepage

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Message-ID: <20100528144824.GD9774@csn.ul.ie>
Date:	Fri, 28 May 2010 15:48:24 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Larry Woodman <lwoodman@...hat.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>
Subject: Re: [PATCH 2/8] hugetlb, rmap: add reverse mapping for hugepage

On Fri, May 28, 2010 at 09:29:16AM +0900, Naoya Horiguchi wrote:
> This patch adds reverse mapping feature for hugepage by introducing
> mapcount for shared/private-mapped hugepage and anon_vma for
> private-mapped hugepage.
> 
> While hugepage is not currently swappable, reverse mapping can be useful
> for memory error handler.
> 
> Without this patch, memory error handler cannot identify processes
> using the bad hugepage nor unmap it from them. That is:
> - for shared hugepage:
>   we can collect processes using a hugepage through pagecache,
>   but can not unmap the hugepage because of the lack of mapcount.
> - for privately mapped hugepage:
>   we can neither collect processes nor unmap the hugepage.
> This patch solves these problems.
> 
> This patch include the bug fix given by commit 23be7468e8, so reverts it.
> 
> Dependency:
>   "hugetlb: move definition of is_vm_hugetlb_page() to hugepage_inline.h"
> 
> ChangeLog since May 24.
> - create hugetlb_inline.h and move is_vm_hugetlb_index() in it.
> - move functions setting up anon_vma for hugepage into mm/rmap.c.
> 
> ChangeLog since May 13.
> - rebased to 2.6.34
> - fix logic error (in case that private mapping and shared mapping coexist)
> - move is_vm_hugetlb_page() into include/linux/mm.h to use this function
>   from linear_page_index()
> - define and use linear_hugepage_index() instead of compound_order()
> - use page_move_anon_rmap() in hugetlb_cow()
> - copy exclusive switch of __set_page_anon_rmap() into hugepage counterpart.
> - revert commit 24be7468 completely
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Andi Kleen <andi@...stfloor.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Wu Fengguang <fengguang.wu@...el.com>
> Cc: Mel Gorman <mel@....ul.ie>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Larry Woodman <lwoodman@...hat.com>
> Cc: Lee Schermerhorn <Lee.Schermerhorn@...com>

Ok, I could find no other problems with the hugetlb side of things in the
first two patches. I haven't looked at the hwpoison parts but I'm assuming
Andi has looked at those already. Thanks

Acked-by: Mel Gorman <mel@....ul.ie>

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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