linux-kernel - Re: [RFC PATCH 5/6] ARM, mm: change meaning of max_low

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Message-ID: <20130325094816.GO4977@n2100.arm.linux.org.uk>
Date:	Mon, 25 Mar 2013 09:48:16 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Nicolas Pitre <nico@...aro.org>
Subject: Re: [RFC PATCH 5/6] ARM, mm: change meaning of max_low_pfn to
	maximum pfn for nobootmem

On Mon, Mar 25, 2013 at 01:11:13PM +0900, Joonsoo Kim wrote:
> nobootmem use max_low_pfn for computing boundary in free_all_bootmem()
> So we need proper value to max_low_pfn.
> 
> But, there is some difficulty related to max_low_pfn. max_low_pfn is used
> for two meanings in various architectures. One is for number of pages
> in lowmem and the other is for maximum lowmem pfn. Now, in ARM, it is used
> as number of pages in lowmem. You can get more information in below link.
> http://lwn.net/Articles/543408/
> http://lwn.net/Articles/543424/
> 
> As I investigated, architectures which use max_low_pfn as maximum pfn are
> more than others, so to change meaning of max_low_pfn to maximum pfn
> is preferable solution to me. This patch change max_low_pfn as maximum
> lowmem pfn in ARM. In addition, min_low_pfn, max_pfn is assigned according
> to this criteria.
> 
> There is no real user for max_low_pfn except block/blk-setting.c and
> blk-setting.c assume that max_low_pfn is maximum lowmem pfn,
> so this patch may not harm anything.

This will need some very rigorous testing before it can go into mainline.
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