mm/memory_hotplug: drop valid_start/valid_end from test_pages_in_a_zone()

The callers are only interested in the actual zone, they don't care about
boundaries.  Return the zone instead to simplify.

Link: http://lkml.kernel.org/r/20200110183308.11849-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 1565930..b9f474c 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -376,7 +376,6 @@ static ssize_t valid_zones_show(struct device *dev,
 	struct memory_block *mem = to_memory_block(dev);
 	unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
 	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
-	unsigned long valid_start_pfn, valid_end_pfn;
 	struct zone *default_zone;
 	int nid;
 
@@ -389,11 +388,11 @@ static ssize_t valid_zones_show(struct device *dev,
 		 * The block contains more than one zone can not be offlined.
 		 * This can happen e.g. for ZONE_DMA and ZONE_DMA32
 		 */
-		if (!test_pages_in_a_zone(start_pfn, start_pfn + nr_pages,
-					  &valid_start_pfn, &valid_end_pfn))
+		default_zone = test_pages_in_a_zone(start_pfn,
+						    start_pfn + nr_pages);
+		if (!default_zone)
 			return sprintf(buf, "none\n");
-		start_pfn = valid_start_pfn;
-		strcat(buf, page_zone(pfn_to_page(start_pfn))->name);
+		strcat(buf, default_zone->name);
 		goto out;
 	}