Re: [PATCH v8 1/3] mm/memory hotplug: Fix zone->contiguous always false when hotplug

[Li, Tianyou]

On 1/27/2026 2:53 PM, Mike Rapoport wrote:
> Hi,
>
> On Sat, Jan 24, 2026 at 08:18:39PM +0800, Li, Tianyou wrote:
> > On 1/22/2026 7:16 PM, Mike Rapoport wrote:
> > > On Tue, Jan 20, 2026 at 10:33:44PM +0800, Tianyou Li wrote:
> > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > > > index a63ec679d861..c8f492b5daf0 100644
> > > > --- a/mm/memory_hotplug.c
> > > > +++ b/mm/memory_hotplug.c
> > > > @@ -782,8 +782,6 @@ void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
> > > >    	memmap_init_range(nr_pages, nid, zone_idx(zone), start_pfn, 0,
> > > >    			 MEMINIT_HOTPLUG, altmap, migratetype,
> > > >    			 isolate_pageblock);
> > > > -
> > > > -	set_zone_contiguous(zone);
> > > move_pfn_range_to_zone() is also called from memremap::pagemap_range().
> > > Shouldn't we add set_zone_contiguous() there as well?
> > I did not find the place where the online_pages was invoked along path of
> > the memremap:pagemap_range() function. Would there be other functions to
> > online the pages remapped? Much appreciated for the guidance.
> Currently when we do memremap_pages() we have
>
> 	memremap_pages() ->
> 		pagemap_range() ->
> 			move_pfn_range_to_zone() ->
> 				set_zone_contiguous();
>   
> Once set_zone_contiguous() is moved out from move_pfn_range_to_zone(),
> memremap_pages() path never calls it.
> I'm not sure if the pages added in memremap_pages() are online, but to keep
> it's current behaviour I think it should call set_zone_contiguous()
> explicitly.

Thanks Mike. It's doable for me to add such a line. I am worried about 
place a set_zone_contiguous() will not add any meaningful value. Per my 
understanding, the zone contiguous will remain as false because the page 
is not online.

Regards,

Tianyou