linux-kernel - Re: [patch v2] hugetlb: correct page offset index for sharing pmd

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Date:	Thu, 16 Aug 2012 20:40:07 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michal Hocko <mhocko@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch v2] hugetlb: correct page offset index for sharing pmd

On Thu, Aug 16, 2012 at 7:03 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:

> Don't be too concerned about the size of a change - it's the end result
> which matters.  If a larger patch results in a better end result, then
> do the larger patch.

Hi Andrew,

This work was triggered by the fact that huge_pmd_share mismatches
unmap_ref_private. But it does match hugetlb_vmtruncate_list.

Plus RADIX_INDEX and HEAP_INDEX are defined, and used when inserting
vma into prio tree.
===
/*
 * The following macros are used for implementing prio_tree for i_mmap
 */

#define RADIX_INDEX(vma)  ((vma)->vm_pgoff)
#define VMA_SIZE(vma)	  (((vma)->vm_end - (vma)->vm_start) >> PAGE_SHIFT)
/* avoid overflow */
#define HEAP_INDEX(vma)	  ((vma)->vm_pgoff + (VMA_SIZE(vma) - 1))
===

Thus it is incorrect to use huge pgoff in searching vma in prio tree, and
I have to withdraw this work.

Thanks,
		Hillf
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