linux-kernel - Re: [PATCH] mm: Remove zone_id() and make use of zone_idx() in is_dev

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Date:   Mon, 30 Jul 2018 16:00:59 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     osalvador@...hadventures.net
Cc:     akpm@...ux-foundation.org, vbabka@...e.cz, sfr@...b.auug.org.au,
        rientjes@...gle.com, pasha.tatashin@...cle.com,
        kemi.wang@...el.com, jia.he@...-semitech.com, ptesarik@...e.com,
        aryabinin@...tuozzo.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, dan.j.williams@...el.com,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH] mm: Remove zone_id() and make use of zone_idx() in
 is_dev_zone()

On Mon 30-07-18 15:37:18, osalvador@...hadventures.net wrote:
> From: Oscar Salvador <osalvador@...e.de>
> 
> is_dev_zone() is using zone_id() to check if the zone is ZONE_DEVICE.
> zone_id() looks pretty much the same as zone_idx(), and while the use of
> zone_idx() is quite spread in the kernel, zone_id() is only being
> used by is_dev_zone().
> 
> This patch removes zone_id() and makes is_dev_zone() use zone_idx()
> to check the zone, so we do not have two things with the same
> functionality around.

Yes this looks like a pointless code duplication. I guess Dan just
wasn't aware of zone_idx() macro.

> Signed-off-by: Oscar Salvador <osalvador@...e.de>

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

> ---
>  include/linux/mmzone.h | 31 ++++++++++++-------------------
>  1 file changed, 12 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 83b1d11e90eb..dbe7635c33dd 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -755,25 +755,6 @@ static inline bool pgdat_is_empty(pg_data_t *pgdat)
>  	return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
>  }
>  
> -static inline int zone_id(const struct zone *zone)
> -{
> -	struct pglist_data *pgdat = zone->zone_pgdat;
> -
> -	return zone - pgdat->node_zones;
> -}
> -
> -#ifdef CONFIG_ZONE_DEVICE
> -static inline bool is_dev_zone(const struct zone *zone)
> -{
> -	return zone_id(zone) == ZONE_DEVICE;
> -}
> -#else
> -static inline bool is_dev_zone(const struct zone *zone)
> -{
> -	return false;
> -}
> -#endif
> -
>  #include <linux/memory_hotplug.h>
>  
>  void build_all_zonelists(pg_data_t *pgdat);
> @@ -824,6 +805,18 @@ static inline int local_memory_node(int node_id) { return node_id; };
>   */
>  #define zone_idx(zone)		((zone) - (zone)->zone_pgdat->node_zones)
>  
> +#ifdef CONFIG_ZONE_DEVICE
> +static inline bool is_dev_zone(const struct zone *zone)
> +{
> +	return zone_idx(zone) == ZONE_DEVICE;
> +}
> +#else
> +static inline bool is_dev_zone(const struct zone *zone)
> +{
> +	return false;
> +}
> +#endif
> +
>  /*
>   * Returns true if a zone has pages managed by the buddy allocator.
>   * All the reclaim decisions have to use this function rather than
> -- 
> 2.13.6
> 

-- 
Michal Hocko
SUSE Labs