linux-kernel - Re: [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache pages

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Message-ID: <x2i28c262361004222155w354632eq636186639ac445b7@mail.gmail.com>
Date:	Fri, 23 Apr 2010 13:55:19 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache 
	pages

Hi, Christoph.

On Fri, Apr 23, 2010 at 12:14 AM, Christoph Lameter <cl@...ux.com> wrote:
> On Thu, 22 Apr 2010, Minchan Kim wrote:
>
>> For further optimization, we can hold vma->adjust_lock if vma_address
>> returns -EFAULT. But I hope we redesigns it without new locking.
>> But I don't have good idea, now. :(
>
> You could make it atomic through the use of RCU.
>
> Create a new vma entry with the changed parameters and then atomically
> switch to the new vma.
> Problem is that you have some list_heads in there.

That's a good idea if we can do _simply_.
That's because there are many confusion anon_vma and vma handling nowadays.
(http://thread.gmane.org/gmane.linux.kernel/969907)
So I hope we solve the problem without rather complicated rcu locking
if it isn't critical path.

-- 
Kind regards,
Minchan Kim
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