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

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Message-ID: <20160728010729-mutt-send-email-mst@kernel.org>
Date:	Thu, 28 Jul 2016 01:08:05 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Liang Li <liang.z.li@...el.com>
Cc:	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
	virtio-dev@...ts.oasis-open.org, kvm@...r.kernel.org,
	qemu-devel@...gnu.org, dgilbert@...hat.com, quintela@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH v2 repost 3/7] mm: add a function to get the max pfn

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@...el.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Cornelia Huck <cornelia.huck@...ibm.com>
> Cc: Amit Shah <amit.shah@...hat.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