linux-kernel - Re: [PATCH] slab: fix generic PAGE_POISONING conflict with SLAB_RED

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Date:	Fri, 22 May 2009 11:02:52 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Ron <ron@...ian.org>
Cc:	cl@...ux-foundation.org, mpm@...enic.com, linux-mm@...ck.org,
	akinobu.mita@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] slab: fix generic PAGE_POISONING conflict with
 SLAB_RED_ZONE

On Fri, 2009-05-22 at 04:58 +0930, Ron wrote:
> A generic page poisoning mechanism was added with commit:
>  6a11f75b6a17b5d9ac5025f8d048382fd1f47377
> which destructively poisons full pages with a bitpattern.
> 
> On arches where PAGE_POISONING is used, this conflicts with the slab
> redzone checking enabled by DEBUG_SLAB, scribbling bits all over its
> magic words and making it complain about that quite emphatically.
> 
> On x86 (and I presume at present all the other arches which set
> ARCH_SUPPORTS_DEBUG_PAGEALLOC too), the kernel_map_pages() operation
> is non destructive so it can coexist with the other DEBUG_SLAB
> mechanisms just fine.
> 
> This patch favours the expensive full page destruction test for
> cases where there is a collision and it is explicitly selected.
> 
> Signed-off-by: Ron Lee <ron@...ian.org>

Applied, thanks!

			Pekka

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