[PATCH -mmotm] mm/memory_hotplug: fix for CONFIG_ZONE_DEVICE not enabled

[Randy Dunlap]

From: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>

Fix memory_hotplug.c when CONFIG_ZONE_DEVICE is not enabled.

Fixes this build error:

../mm/memory_hotplug.c: In function ‘move_pfn_range_to_zone’:
../mm/memory_hotplug.c:772:24: error: ‘ZONE_DEVICE’ undeclared (first use in this function); did you mean ‘ZONE_MOVABLE’?
  if (zone_idx(zone) == ZONE_DEVICE) {

Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 mm/memory_hotplug.c |    2 ++
 1 file changed, 2 insertions(+)

--- mmotm-2021-0119-1336.orig/mm/memory_hotplug.c
+++ mmotm-2021-0119-1336/mm/memory_hotplug.c
@@ -769,12 +769,14 @@ void __ref move_pfn_range_to_zone(struct
 	 * ZONE_DEVICE pages in an otherwise  ZONE_{NORMAL,MOVABLE}
 	 * section.
 	 */
+#ifdef CONFIG_ZONE_DEVICE
 	if (zone_idx(zone) == ZONE_DEVICE) {
 		if (!IS_ALIGNED(start_pfn, PAGES_PER_SECTION))
 			section_taint_zone_device(start_pfn);
 		if (!IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION))
 			section_taint_zone_device(start_pfn + nr_pages);
 	}
+#endif
 
 	/*
 	 * TODO now we have a visible range of pages which are not associated