mm: fix usemap initialization

usemap must be initialized only when pfn is within zone.  If not, it corrupts
memory.

And this patch also reduces the number of calls to set_pageblock_migratetype()
from
	(pfn & (pageblock_nr_pages -1)
to
	!(pfn & (pageblock_nr_pages-1)
it should be called once per pageblock.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Shi Weihua <shiwh@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -2524,7 +2524,9 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 	struct page *page;
 	unsigned long end_pfn = start_pfn + size;
 	unsigned long pfn;
+	struct zone *z;
 
+	z = &NODE_DATA(nid)->node_zones[zone];
 	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
 		/*
 		 * There can be holes in boot-time mem_map[]s
@@ -2542,7 +2544,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 		init_page_count(page);
 		reset_page_mapcount(page);
 		SetPageReserved(page);
-
 		/*
 		 * Mark the block movable so that blocks are reserved for
 		 * movable at startup. This will force kernel allocations
@@ -2551,8 +2552,15 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 		 * kernel allocations are made. Later some blocks near
 		 * the start are marked MIGRATE_RESERVE by
 		 * setup_zone_migrate_reserve()
-		 */
-		if ((pfn & (pageblock_nr_pages-1)))
+		 *
+		 * bitmap is created for zone's valid pfn range. but memmap
+		 * can be created for invalid pages (for alignment)
+		 * check here not to call set_pageblock_migratetype() against
+		 * pfn out of zone.
+		 */
+		if ((z->zone_start_pfn <= pfn)
+		    && (pfn < z->zone_start_pfn + z->spanned_pages)
+		    && !(pfn & (pageblock_nr_pages - 1)))
 			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
 
 		INIT_LIST_HEAD(&page->lru);
@@ -4464,6 +4472,8 @@ void set_pageblock_flags_group(struct page *page, unsigned long flags,
 	pfn = page_to_pfn(page);
 	bitmap = get_pageblock_bitmap(zone, pfn);
 	bitidx = pfn_to_bitidx(zone, pfn);
+	VM_BUG_ON(pfn < zone->zone_start_pfn);
+	VM_BUG_ON(pfn >= zone->zone_start_pfn + zone->spanned_pages);
 
 	for (; start_bitidx <= end_bitidx; start_bitidx++, value <<= 1)
 		if (flags & value)