Re: [PATCH 2/2] mm/memory_hotplug: remove duplicate call for set_page_links

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 16 Jun 2017 17:23:35 +0800 Wei Yang <richard.weiyang@gmail.com> wrote:

> In function move_pfn_range_to_zone(), memmap_init_zone() will call
> set_page_links for each page.

Well, no.  There are several types of pfn's for which
memmap_init_zone() will not call
__init_single_page()->set_page_links().  Probably the code is OK, as
those are pretty screwy pfn types.  But I'd like to see some
confirmation that this patch is OK for all such pfns, now and in the
future?

> This means we don't need to call it on each
> page explicitly.
> 
> This patch just removes the loop.
> 
> ...
>
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -914,10 +914,6 @@ void __ref move_pfn_range_to_zone(struct zone *zone,
>  	 * are reserved so nobody should be touching them so we should be safe
>  	 */
>  	memmap_init_zone(nr_pages, nid, zone_idx(zone), start_pfn, MEMMAP_HOTPLUG);
> -	for (i = 0; i < nr_pages; i++) {
> -		unsigned long pfn = start_pfn + i;
> -		set_page_links(pfn_to_page(pfn), zone_idx(zone), nid, pfn);
> -	}
>  
>  	set_zone_contiguous(zone);
>  }

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