linux-kernel - Re: [PATCH] mm:add VM_BUG_ON() for page

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Message-ID: <20141208115032.GB28846@node.dhcp.inet.fi>
Date:	Mon, 8 Dec 2014 13:50:32 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Cc:	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'linux-mm@...ck.org'" <linux-mm@...ck.org>,
	"'linux-arm-kernel@...ts.infradead.org'" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'akpm@...ux-foundation.org'" <akpm@...ux-foundation.org>,
	"'riel@...hat.com'" <riel@...hat.com>,
	"'nasa4836@...il.com'" <nasa4836@...il.com>,
	"'sasha.levin@...cle.com'" <sasha.levin@...cle.com>
Subject: Re: [PATCH] mm:add VM_BUG_ON() for page_mapcount()

On Mon, Dec 08, 2014 at 03:47:47PM +0800, Wang, Yalin wrote:
> This patch add VM_BUG_ON() for slab page,
> because _mapcount is an union with slab struct in struct page,
> avoid access _mapcount if this page is a slab page.
> Also remove the unneeded bracket.
> 
> Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>
> ---
>  include/linux/mm.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 11b65cf..34124c4 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -373,7 +373,8 @@ static inline void reset_page_mapcount(struct page *page)
>  
>  static inline int page_mapcount(struct page *page)
>  {
> -	return atomic_read(&(page)->_mapcount) + 1;
> +	VM_BUG_ON(PageSlab(page));

VM_BUG_ON_PAGE(), please.

-- 
 Kirill A. Shutemov
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