linux-kernel - Re: [PATCH] mm/highmem: simplify is

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Message-ID: <CAPcyv4gqKZUh8_oE=J2xv2ZX78v3PKdHa1qmQP-FDMbt1iEAZQ@mail.gmail.com>
Date:	Tue, 29 Mar 2016 23:34:14 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Chanho Min <chanho.min@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Vlastimil Babka <vbabka@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Zhang Zhen <zhenzhang.zhang@...wei.com>,
	Linux MM <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Gunho Lee <gunho.lee@....com>
Subject: Re: [PATCH] mm/highmem: simplify is_highmem()

On Tue, Mar 29, 2016 at 9:43 PM, Chanho Min <chanho.min@....com> wrote:
> The is_highmem() is can be simplified by use of is_highmem_idx().
> This patch removes redundant code and will make it easier to maintain
> if the zone policy is changed or a new zone is added.
>
> Signed-off-by: Chanho Min <chanho.min@....com>
> ---
>  include/linux/mmzone.h |    5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index e23a9e7..9ac90c3 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -817,10 +817,7 @@ static inline int is_highmem_idx(enum zone_type idx)
>  static inline int is_highmem(struct zone *zone)
>  {
>  #ifdef CONFIG_HIGHMEM
> -       int zone_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;
> -       return zone_off == ZONE_HIGHMEM * sizeof(*zone) ||
> -              (zone_off == ZONE_MOVABLE * sizeof(*zone) &&
> -               zone_movable_is_highmem());
> +       return is_highmem_idx(zone_idx(zone));
>  #else
>         return 0;
>  #endif

Yup, looks like a straightforward replacement of open coded versions
of the same routines.

Reviewed-by: Dan Williams <dan.j.williams@...el.com>