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Date: Sun, 9 May 2010 13:06:30 -0700 (PDT)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Mel Gorman <mel@csn.ul.ie>
cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
       Minchan Kim <minchan.kim@gmail.com>, Christoph Lameter <cl@linux.com>,
       Andrea Arcangeli <aarcange@redhat.com>, Rik van Riel <riel@redhat.com>,
       Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] mm,migration: Fix race between shift_arg_pages and
 rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary
 stack
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On Sun, 9 May 2010, Linus Torvalds wrote:
> 
> IOW, a patch like this (this is a pseudo-patch, totally untested, won't 
> compile, yadda yadda - you need to actually make the people who call 
> "move_page_tables()" call that prepare function first etc etc)

Btw, that pseudo-patch is also likely the least efficient way to do this, 
since it re-walks the page directories for each pmd it creates.

Also - the thing is, we can easily choose to do this _just_ for the case 
of shifting argument pages, which really is a special case (the generic 
case of "mremap()" is a lot more complicated, and doesn't have the issue 
with rmap because it's doing all the "new vma" setup etc).

			Linus