mm/sparse.c: don't manually decrement num_poisoned_pages

Use the function written to do it instead.

Link: http://lkml.kernel.org/r/20190827053656.32191-2-alastair@au1.ibm.com
Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/sparse.c

@@ -11,6 +11,8 @@
 #include <linux/export.h>
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
 
 #include "internal.h"
 #include <asm/dma.h>
@@ -908,7 +910,7 @@ static void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 
 	for (i = 0; i < nr_pages; i++) {
 		if (PageHWPoison(&memmap[i])) {
-			atomic_long_sub(1, &num_poisoned_pages);
+			num_poisoned_pages_dec();
 			ClearPageHWPoison(&memmap[i]);
 		}
 	}