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From: Anisse Astier <anisse@astier.eu>
Date: Wed, 20 May 2015 14:27:37 +0200
Message-ID: <CALUN=qJdiWn9BSYRq9HgXhGDaBKzApVG=JqFVb1B34Ut8U0k1w@mail.gmail.com>
Subject: Re: [PATCH v4 2/3] mm/page_alloc.c: add config option to sanitize
 freed pages
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To: yalin wang <yalin.wang2010@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>, Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, David Rientjes <rientjes@google.com>, Alan Cox <gnomes@lxorguk.ukuu.org.uk>, Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, PaX Team <pageexec@freemail.hu>, Brad Spengler <spender@grsecurity.net>, Kees Cook <keescook@chromium.org>, Andi Kleen <andi@firstfloor.org>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Len Brown <len.brown@intel.com>, linux-mm@kvack.org, Linux PM list <linux-pm@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Tue, May 19, 2015 at 3:58 AM, yalin wang <yalin.wang2010@gmail.com> wrote:
> 2015-05-18 21:04 GMT+08:00 Anisse Astier <anisse@astier.eu>:
>> On Mon, May 18, 2015 at 3:02 PM, Pavel Machek <pavel@ucw.cz> wrote:
>>>
>>> Ok. So there is class of errors where this helps, but you are not
>>> aware of any such errors in kernel, so you can't fix them... Right?
>>
>> Correct.
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>> Please read the FAQ at  http://www.tux.org/lkml/
> i feel your patch is the same as CONFIG_DEBUG_PAGEALLOC ,
> the difference is that CONFIG_DEBUG_PAGEALLOC  will clear
> page to a magic number, while your patch will
> clear to zero,
> do we really need this duplicated function ?

It's different because DEBUG_PAGEALLOC will only use page poisoning on
certain architectures, and clearing a page to a magic number doesn't
allow to optimize alloc with _GFP_ZERO.

Regards,

Anisse

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