linux-kernel - 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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Message-ID: <alpine.LFD.2.00.1005061905230.901@i5.linux-foundation.org>
Date:	Thu, 6 May 2010 19:12:59 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.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



On Fri, 7 May 2010, KAMEZAWA Hiroyuki wrote:
> 
> IIUC, move_page_tables() may call "page table allocation" and it cannot be
> done under spinlock.

Bah. It only does a "alloc_new_pmd()", and we could easily move that out 
of the loop and pre-allocate the pmd's.

If that's the only reason, then it's a really weak one, methinks.

			Linus
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