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

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Message-ID: <AANLkTikCsGHshU8v86SQiuO+UZBCbdjOKN=GyJFPb7rY@mail.gmail.com>
Date:	Tue, 27 Jul 2010 19:01:14 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Milton Miller <miltonm@....com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <linux@....linux.org.uk>,
	Mel Gorman <mel@....ul.ie>,
	Johannes Weiner <hannes@...xchg.org>,
	Kukjin Kim <kgene.kim@...sung.com>
Subject: Re: [PATCH] Tight check of pfn_valid on sparsemem - v4

Hi, Kame.

On Tue, Jul 27, 2010 at 5:13 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com>
>> Perhaps the mem_section array.  Using a symbol that is part of
>> the model pre-checks can remove a global symbol lookup and has the side
>> effect of making sure our pfn_valid is for the right model.
>>
>
> But yes, maybe it's good to make use of a fixed-(magic)-value.

fixed-magic-value?
Yes. It can be good for some debugging.
But as Christoph pointed out, we need some strict check(ex,
PG_reserved) for preventing unlucky valid using of magic value in
future.
But in fact I have a concern to use PG_reserved since it can be used
afterward pfn_valid normally to check hole in non-hole system. So I
think it's redundant.

Hmm..

-- 
Kind regards,
Minchan Kim
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