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

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Date:	Wed, 28 Jul 2010 07:33:07 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Milton Miller <miltonm@....com>, 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

On Tue, Jul 27, 2010 at 11:34 PM, Christoph Lameter
<cl@...ux-foundation.org> wrote:
> On Tue, 27 Jul 2010, Minchan Kim wrote:
>
>> 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.

Ignore me. I got confused.

>
> PG_reserved is already used to mark pages not handled by the page
> allocator (see mmap_init_zone).


I will resend below approach.

static inline int memmap_valid(unsigned long pfn)
{
       struct page *page = pfn_to_page(pfn);
       struct page *__pg = virt_to_page(page);
       return page_private(__pg) == MAGIC_MEMMAP && PageReserved(__pg);
}

Thanks, all.


-- 
Kind regards,
Minchan Kim
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