[PATCH] Do not cross section boundary when moving pages between mobility lists

[PATCH] Do not cross section boundary when moving pages between mobility lists

[Mel Gorman]

move-free-pages-between-lists-on-steal-fix-2.patch fixed an issue with a
BUG_ON() that checked for a page just outside a MAX_ORDER_NR_PAGES boundary. In
fact, the proper place to check it was earlier. A situation can occur on
SPARSEMEM where a section boundary is crossed which will cause problems on some
machines. This patch addresses the problem.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.21-rc5-mm4-clean/mm/page_alloc.c linux-movefree_sparsememfix/mm/page_alloc.c
--- linux-2.6.21-rc5-mm4-clean/mm/page_alloc.c	2007-04-04 17:33:15.000000000 +0100
+++ linux-movefree_sparsememfix/mm/page_alloc.c	2007-04-06 10:06:08.000000000 +0100
@@ -743,10 +743,10 @@ int move_freepages(struct zone *zone,
 	 * Remove at a later date when no bug reports exist related to
 	 * CONFIG_PAGE_GROUP_BY_MOBILITY
 	 */
-	BUG_ON(page_zone(start_page) != page_zone(end_page - 1));
+	BUG_ON(page_zone(start_page) != page_zone(end_page));
 #endif
 
-	for (page = start_page; page < end_page;) {
+	for (page = start_page; page <= end_page;) {
 		if (!pfn_valid_within(page_to_pfn(page))) {
 			page++;
 			continue;
@@ -776,8 +776,8 @@ int move_freepages_block(struct zone *zo
 	start_pfn = page_to_pfn(page);
 	start_pfn = start_pfn & ~(MAX_ORDER_NR_PAGES-1);
 	start_page = pfn_to_page(start_pfn);
-	end_page = start_page + MAX_ORDER_NR_PAGES;
-	end_pfn = start_pfn + MAX_ORDER_NR_PAGES;
+	end_page = start_page + MAX_ORDER_NR_PAGES - 1;
+	end_pfn = start_pfn + MAX_ORDER_NR_PAGES - 1;
 
 	/* Do not cross zone boundaries */
 	if (start_pfn < zone->zone_start_pfn)

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Re: [PATCH] Do not cross section boundary when moving pages between mobility lists

[Yasunori Goto]

> move-free-pages-between-lists-on-steal-fix-2.patch fixed an issue with a
> BUG_ON() that checked for a page just outside a MAX_ORDER_NR_PAGES boundary. In
> fact, the proper place to check it was earlier. A situation can occur on
> SPARSEMEM where a section boundary is crossed which will cause problems on some
> machines. This patch addresses the problem.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>

I reviewed it, looks ok. :-)

Acked-by: Yasunori Goto <y-goto@jp.fujitsu.com>

Thanks.

-- 
Yasunori Goto 


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