mm: don't drop a partial page in a zone's memory map size

In a zone's present pages number, account for all pages occupied by the
memory map, including a partial.

Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 63835579323a..035300299f94 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3378,7 +3378,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
                  * is used by this zone for memmap. This affects the watermark
                  * and per-cpu initialisations
                  */
-                memmap_pages = (size * sizeof(struct page)) >> PAGE_SHIFT;
+                memmap_pages =
+                        PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
                 if (realsize >= memmap_pages) {
                         realsize -= memmap_pages;
                         printk(KERN_DEBUG