Subject: clear compound mapping

From: Andrea Arcangeli <aarcange@redhat.com>

Clear compound mapping for anonymous compound pages like it already happens for
regular anonymous pages.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
---

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -609,6 +609,8 @@ static void __free_pages_ok(struct page 
 	trace_mm_page_free_direct(page, order);
 	kmemcheck_free_shadow(page, order);
 
+	if (PageAnon(page))
+		page->mapping = NULL;
 	for (i = 0 ; i < (1 << order) ; ++i)
 		bad += free_pages_check(page + i);
 	if (bad)