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Date: Tue, 18 Apr 2017 19:56:41 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>, Christoph Lameter <cl@linux.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
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        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@lge.com,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: copy_page() on a kmalloc-ed page with DEBUG_SLAB enabled (was
 "zram: do not use copy_page with non-page alinged address")
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On (04/18/17 09:33), Michal Hocko wrote:
[..]
> > Another approach is the API does normal thing for non-aligned prefix and
> > tail space and fast thing for aligned space.
> > Otherwise, it would be happy if the API has WARN_ON non-page SIZE aligned
> > address.
> 
> copy_page is a performance sensitive function and I believe that we do
> those tricks exactly for this purpose.

a wild thought,

use
	#define copy_page(to,from)	memcpy((to), (from), PAGE_SIZE)

when DEBUG_SLAB is set? so arch copy_page() (if provided by arch)
won't be affected otherwise.

	-ss