linux-kernel - Re: [RFC][PATCH 1/3] mm/debug-pagealloc.c: Split out page poisoning from debug page

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Date:	Tue, 26 Jan 2016 12:25:44 -0800
From:	Laura Abbott <labbott@...hat.com>
To:	Jianyu Zhan <nasa4836@...il.com>,
	Laura Abbott <labbott@...oraproject.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Michal Hocko <mhocko@...e.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-hardening@...ts.openwall.com,
	Kees Cook <keescook@...omium.org>
Subject: Re: [RFC][PATCH 1/3] mm/debug-pagealloc.c: Split out page poisoning
 from debug page_alloc

On 01/25/2016 10:26 PM, Jianyu Zhan wrote:
> On Tue, Jan 26, 2016 at 12:55 AM, Laura Abbott
> <labbott@...oraproject.org> wrote:
>> +static bool __page_poisoning_enabled __read_mostly;
>> +static bool want_page_poisoning __read_mostly =
>> +       !IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC);
>> +
>
>
> I would say this patch is nice with regard to decoupling
> CONFIG_DEBUG_PAGEALLOC and CONFIG_PAGE_POISONING.
>
> But  since when we enable CONFIG_DEBUG_PAGEALLOC,
> CONFIG_PAGE_POISONING will be selected.
>
> So it would be better to make page_poison.c totally
> CONFIG_DEBUG_PAGEALLOC agnostic,  in case we latter have
> more PAGE_POISONING users(currently only DEBUG_PAGEALLOC ). How about like this:
>
> +static bool want_page_poisoning __read_mostly =
> +       !IS_ENABLED(CONFIG_PAGE_POISONING );
>
> Or just let it default to 'true',  since we only compile this
> page_poison.c when we enable CONFIG_PAGE_POISONING.
>

This patch was just supposed to be the refactor and keep the existing
behavior. There are no Kconfig changes here and the existing behavior
is to poison if !ARCH_SUPPORTS_DEBUG_PAGEALLOC so I think keeping
what I have is appropriate for this particular patch. This can be
updated in another series if appropriate.

Thanks,
Laura
  
>
> Thanks,
> Jianyu Zhan
>