[BUG] [PATCH v2] Make setup_zone_migrate_reserve() aware of overlapping nodes

Adam Litke
2008-08-20T19:55:54Z

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.

(Andrew: once the proper fix is agreed upon, this should also be a
candidate for -stable.)

setup_zone_migrate_reserve() should skip pageblocks in overlapping nodes.

Signed-off-by: Adam Litke <agl@us.ibm.com>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index af982f7..feb7916 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;

--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center