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Subject[RFC 06/16] mm/page_alloc: watch out zone range overlap
In the following patches, new zone, ZONE_CMA, will be introduced and
it would be overlapped with other zones. Currently, many places
iterating pfn range doesn't consider possibility of zone overlap and
this would cause a problem such as printing wrong statistics information.
To prevent this situation, this patch add some code to consider zone
overlapping before adding ZONE_CMA.

setup_zone_migrate_reserve() reserve some pages for specific zone so
should consider zone overlap.

Signed-off-by: Joonsoo Kim <>
mm/page_alloc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c784035..1c45934b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4040,8 +4040,8 @@ static void setup_zone_migrate_reserve(struct zone *zone)
page = pfn_to_page(pfn);

- /* Watch out for overlapping nodes */
- if (page_to_nid(page) != zone_to_nid(zone))
+ /* Watch out for overlapping zones */
+ if (page_zone(page) != zone)

block_migratetype = get_pageblock_migratetype(page);

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