Re: [PATCH v2 repost 3/7] mm: add a function to get the max pfn

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 27, 2016 at 09:23:32AM +0800, Liang Li wrote:
> Expose the function to get the max pfn, so it can be used in the
> virtio-balloon device driver.
> 
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Amit Shah <amit.shah@redhat.com>
> ---
>  mm/page_alloc.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 8b3e134..7da61ad 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4517,6 +4517,12 @@ void show_free_areas(unsigned int filter)
>  	show_swap_cache_info();
>  }
>  
> +unsigned long get_max_pfn(void)
> +{
> +	return max_pfn;
> +}
> +EXPORT_SYMBOL(get_max_pfn);
> +


This needs a coment that this can change at any time.
So it's only good as a hint e.g. for sizing data structures.

>  static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
>  {
>  	zoneref->zone = zone;
> -- 
> 1.9.1