[RFC PATCH v2 08/25] page_alloc: in move_freepages(), skip pages instead of VM_BUG on node differences.

From: Cody P Schafer
Date: Thu Apr 11 2013 - 21:14:33 EST


With dynamic numa, pages are going to be gradully moved from one node to
another, causing the page ranges that move_freepages() examines to
contain pages that actually belong to another node.

When dynamic numa is enabled, we skip these pages instead of VM_BUGing
out on them.

This additionally moves the VM_BUG_ON() (which detects a change in node)
so that it follows the pfn_valid_within() check.

Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1fbf5f2..75192eb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -957,6 +957,7 @@ int move_freepages(struct zone *zone,
struct page *page;
unsigned long order;
int pages_moved = 0;
+ int zone_nid = zone_to_nid(zone);

#ifndef CONFIG_HOLES_IN_ZONE
/*
@@ -970,14 +971,24 @@ 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;
}

+ if (page_to_nid(page) != zone_nid) {
+#ifndef CONFIG_DYNAMIC_NUMA
+ /*
+ * In the normal case (without Dynamic NUMA), all pages
+ * in a pageblock should belong to the same zone (and
+ * as a result all have the same nid).
+ */
+ VM_BUG_ON(page_to_nid(page) != zone_nid);
+#endif
+ page++;
+ continue;
+ }
+
if (!PageBuddy(page)) {
page++;
continue;
--
1.8.2.1

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