linux-kernel - [BUG] Make setup_zone_migrate_reserve() aware of overlapping nodes

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Date:	Wed, 20 Aug 2008 12:08:54 -0500
From:	Adam Litke <agl@...ibm.com>
To:	linux-mm <linux-mm@...ck.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	nacc <nacc@...ux.vnet.ibm.com>, mel@....ul.ie,
	apw <apw@...dowen.org>, agl <agl@...ux.vnet.ibm.com>
Subject: [BUG] 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.

(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@...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

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