Possible partial miss in pages needed for zone's memory map?

[Johannes Weiner <hannes@saeurebad.de>]

Hi,

I stumbled over the following in the zone initialization code.  Please
let me know if I overlooked something here.

---

From: Johannes Weiner <hannes@saeurebad.de>
Subject: [PATCH] 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>
---

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3378,7 +3378,8 @@ static void __paginginit free_area_init_
 		 * 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