Re: [PATCH 2/2] mm,migration: Fix race between shift_arg_pages andrmap_walk by guaranteeing rmap_walk finds PTEs created within the temporarystack

[Linus Torvalds]

On Fri, 7 May 2010, Mel Gorman wrote:
> 
> Page migration requires rmap to be able to find all migration ptes
> created by migration. If the second rmap_walk clearing migration PTEs
> misses an entry, it is left dangling causing a BUG_ON to trigger during
> fault. For example;

So I still absolutely detest this patch.

Why didn't the other - much simpler - patch work? The one Rik pointed to:

	http://lkml.org/lkml/2010/4/30/198

and didn't do that _disgusting_ temporary anon_vma?

Alternatively, why don't we just take the anon_vma lock over this region, 
so that rmap can't _walk_ the damn thing?

			Linus
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