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Date: Mon, 17 Apr 2006 18:57:40 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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       lee.schermerhorn@hp.com, linux-mm@kvack.org, taka@valinux.co.jp,
       marcelo.tosatti@cyclades.com
Subject: Re: [PATCH 5/5] Swapless V2: Revise main migration logic
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On Tue, 18 Apr 2006, KAMEZAWA Hiroyuki wrote:

> BTW, when copying mm, mm->mmap_sem is held. Is mm->mmap_sem is not held while 
> page migraion now ? I'm sorry I can't catch up all changes.
> or Is this needed for lazy migration (migration-on-fault) ?

mmap_sem must be held during page migration due to the way we retrieve the 
anonymous vma.

I think you would want to get rid of that requirement for the hotplug 
remove. But how do we reliably get to the anon_vma of the page without 
mmap_sem?