linux-kernel - Re: [PATCH v2, part3 01/12] mm: enhance free_reserved_area() to support poisoning memory with zero

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Message-ID: <5144B05E.9040307@gmail.com>
Date:	Sun, 17 Mar 2013 01:48:14 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	Jianguo Wu <wujianguo@...wei.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2, part3 01/12] mm: enhance free_reserved_area() to support
 poisoning memory with zero

On 03/17/2013 01:37 AM, Geert Uytterhoeven wrote:
> On Sat, Mar 16, 2013 at 6:03 PM, Jiang Liu <liuj97@...il.com> wrote:
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5130,13 +5130,13 @@ unsigned long free_reserved_area(unsigned long start, unsigned long end,
>>         pos = start = PAGE_ALIGN(start);
>>         end &= PAGE_MASK;
>>         for (pages = 0; pos < end; pos += PAGE_SIZE, pages++) {
>> -               if (poison)
>> +               if ((unsigned int)poison <= 0xFF)
> 
> "if (poison >= 0)"? No cast needed.
Hi Geert,
	We constraints valid inputs as [0, UCHAR_MAX], so the code follows the comment as below.
/*
 * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
 * into the buddy system. The freed pages will be poisoned with pattern
 * "poison" if it's within range [0, UCHAR_MAX].
 * Return pages freed into the buddy system.
 */

Regards!
Gerry

> 
>>                         memset((void *)pos, poison, PAGE_SIZE);
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 

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