From: Adam Litke <agl@us.ibm.com>
Date: Tue, 2 Sep 2008 21:35:38 +0000 (-0700)
Subject: mm: make setup_zone_migrate_reserve() aware of overlapping nodes
X-Git-Tag: v2.6.27-rc6~74
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=344c790e3821dac37eb742ddd0b611a300f78b9a;p=linux-2.6

mm: make setup_zone_migrate_reserve() aware of overlapping nodes

I have gotten to the root cause of the hugetlb badness I reported back on
August 15th.  My system has the following memory topology (note the
overlapping node):

            Node 0 Memory: 0x8000000-0x44000000
            Node 1 Memory: 0x0-0x8000000 0x44000000-0x80000000

setup_zone_migrate_reserve() scans the address range 0x0-0x8000000 looking
for a pageblock to move onto the MIGRATE_RESERVE list.  Finding no
candidates, it happily continues the scan into 0x8000000-0x44000000.  When
a pageblock is found, the pages are moved to the MIGRATE_RESERVE list on
the wrong zone.  Oops.

setup_zone_migrate_reserve() should skip pageblocks in overlapping nodes.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: <stable@kernel.org>		[2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index af982f7cdb..feb791648a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -694,6 +694,9 @@ static int move_freepages(struct zone *zone,
 #endif
 
 	for (page = start_page; page <= end_page;) {
+		/* Make sure we are not inadvertently changing nodes */
+		VM_BUG_ON(page_to_nid(page) != zone_to_nid(zone));
+
 		if (!pfn_valid_within(page_to_pfn(page))) {
 			page++;
 			continue;
@@ -2516,6 +2519,10 @@ static void setup_zone_migrate_reserve(struct zone *zone)
 			continue;
 		page = pfn_to_page(pfn);
 
+		/* Watch out for overlapping nodes */
+		if (page_to_nid(page) != zone_to_nid(zone))
+			continue;
+
 		/* Blocks with reserved pages will never free, skip them. */
 		if (PageReserved(page))
 			continue;