linux-kernel - Re: [PATCH] Tight check of pfn_valid on sparsemem

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Message-ID: <AANLkTikMMMWcT5Uvv5+80yeGP-uYbW7awQsHL7A7NXmw@mail.gmail.com>
Date:	Tue, 27 Jul 2010 07:47:26 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-mm <linux-mm@...ck.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] Tight check of pfn_valid on sparsemem - v4

Hi Christoph,

On Tue, Jul 27, 2010 at 1:40 AM, Christoph Lameter
<cl@...ux-foundation.org> wrote:
> On Tue, 27 Jul 2010, Minchan Kim wrote:
>
>> This patch registers address of mem_section to memmap itself's page struct's
>> pg->private field. This means the page is used for memmap of the section.
>> Otherwise, the page is used for other purpose and memmap has a hole.
>
> What if page->private just happens to be the value of the page struct?
> Even if that is not possible today, someday someone may add new
> functionality to the kernel where page->pivage == page is used for some
> reason.

I agree.

>
> Checking for PG_reserved wont work?

Okay. It would be better to consider page point itself with PG_reserved.
I will reflect your opinion next version. :)

Thanks, Christoph.




-- 
Kind regards,
Minchan Kim
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