linux-kernel - Re: [PATCH] mm: do not inc NR_PAGETABLE if ptlock

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Message-ID: <20151019132053.GI11998@dhcp22.suse.cz>
Date:	Mon, 19 Oct 2015 15:20:53 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: do not inc NR_PAGETABLE if ptlock_init failed

On Mon 19-10-15 15:14:41, Vladimir Davydov wrote:
> If ALLOC_SPLIT_PTLOCKS is defined, ptlock_init may fail, in which case
> we shouldn't increment NR_PAGETABLE.
> 
> Since small allocations, such as ptlock, normally do not fail (currently
> they can fail if kmemcg is used though), this patch does not really fix
> anything and should be considered as a code cleanup.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@...tuozzo.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  include/linux/mm.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 6adf4167d664..30ef3b535444 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1553,8 +1553,10 @@ static inline void pgtable_init(void)
>  
>  static inline bool pgtable_page_ctor(struct page *page)
>  {
> +	if (!ptlock_init(page))
> +		return false;
>  	inc_zone_page_state(page, NR_PAGETABLE);
> -	return ptlock_init(page);
> +	return true;
>  }
>  
>  static inline void pgtable_page_dtor(struct page *page)
> -- 
> 2.1.4
> 
> --
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-- 
Michal Hocko
SUSE Labs
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