[BUG] Make setup_zone_migrate_reserve() aware of overlapping nodes

Adam Litke
2008-08-20T17:08:54Z

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):

i>>?Node 0 Memory: 0x8000000-0x44000000
i>>?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..f297a9b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2512,6 +2512,10 @@ static void setup_zone_migrate_reserve(struct zone *zone)
pageblock_order;

for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
+ /* Watch out for overlapping nodes */
+ if (!early_pfn_in_nid(pfn, zone->node))
+ continue;
+
if (!pfn_valid(pfn))
continue;
page = pfn_to_page(pfn);

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