linux-kernel - [BUGFIX][PATCH] Fix usemap initialization v3

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Date:	Wed, 23 Apr 2008 13:46:21 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	akpm@...ux-foundation.org, Hugh Dickins <hugh@...itas.com>,
	Mel Gorman <mel@....ul.ie>, Shi Weihua <shiwh@...fujitsu.com>,
	balbir@...ux.vnet.ibm.com, xemul@...nvz.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [BUGFIX][PATCH] Fix usemap initialization v3

fixed typos.
==
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.

Changelog.
v2->v3
 - Fixed typos.
v1->v2
 - Fixed boundary check.
 - Move calculation of pointer for zone struct to out of loop.


Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

---
 mm/page_alloc.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

Index: linux-2.6.25/mm/page_alloc.c
===================================================================
--- linux-2.6.25.orig/mm/page_alloc.c
+++ linux-2.6.25/mm/page_alloc.c
@@ -2518,7 +2518,9 @@ void __meminit memmap_init_zone(unsigned
 	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
@@ -2536,7 +2538,6 @@ void __meminit memmap_init_zone(unsigned
 		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
@@ -2545,8 +2546,15 @@ void __meminit memmap_init_zone(unsigned
 		 * kernel allocations are made. Later some blocks near
 		 * the start are marked MIGRATE_RESERVE by
 		 * setup_zone_migrate_reserve()
+		 *
+		 * 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 ((pfn & (pageblock_nr_pages-1)))
+		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);
@@ -4460,6 +4468,8 @@ void set_pageblock_flags_group(struct pa
 	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)

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