Re: [PATCH v3] mm/memory hotplug/unplug: Optimize zone contiguous check when changing pfn range

[Wei Yang]

On Tue, Apr 07, 2026 at 11:16:15PM -0400, Yuan Liu wrote:
[...]
> 
> /*
>@@ -956,9 +957,22 @@ static void __init memmap_init_zone_range(struct zone *zone,
> 	memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn,
> 			  zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE,
> 			  false);
>+	zone->pages_with_online_memmap += end_pfn - start_pfn;
> 
>-	if (*hole_pfn < start_pfn)
>-		init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid);
>+	if (*hole_pfn < start_pfn) {
>+		unsigned long pgcnt;
>+
>+		if (*hole_pfn < zone_start_pfn) {
>+			init_unavailable_range(*hole_pfn, zone_start_pfn,
>+					       zone_id, nid);

One question here:

init_unavailable_range(zone_id)
  __init_single_page(zone_id)
    set_page_links(zone_id)
      set_page_zone(page, zone_id)

[hole_pfn, zone_start_pfn) doesn't belong to this zone. Would this be
a problem?

But it seems we have already done this for a long time.
  
>+			pgcnt = init_unavailable_range(zone_start_pfn,
>+					start_pfn, zone_id, nid);
>+		} else {
>+			pgcnt = init_unavailable_range(*hole_pfn, start_pfn,
>+					zone_id, nid);
>+		}
>+		zone->pages_with_online_memmap += pgcnt;
>+	}
> 
> 	*hole_pfn = end_pfn;
> }

-- 
Wei Yang
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