[PATCH v2 1/7] memory-hotplug: add zone_for_memory() for selecting zone for new memory

Wang Nan wangnan0 at huawei.com
Mon Jul 21 13:46:36 EST 2014

This patch introduces a zone_for_memory function in arch independent
code for arch_add_memory() using.

Many arch_add_memory() function simply selects ZONE_HIGHMEM or
ZONE_NORMAL and add new memory into it. However, with the existance of
ZONE_MOVABLE, the selection method should be carefully considered: if
new, higher memory is added after ZONE_MOVABLE is setup, the default
zone and ZONE_MOVABLE may overlap each other.

should_add_memory_movable() checks the status of ZONE_MOVABLE. If it has
already contain memory, compare the address of new memory and movable
memory. If new memory is higher than movable, it should be added into
ZONE_MOVABLE instead of default zone.

Signed-off-by: Wang Nan <wangnan0 at huawei.com>
Cc: Zhang Yanfei <zhangyanfei at cn.fujitsu.com>
Cc: Dave Hansen <dave.hansen at intel.com>
 include/linux/memory_hotplug.h |  1 +
 mm/memory_hotplug.c            | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 010d125..3de3d02 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -258,6 +258,7 @@ static inline void remove_memory(int nid, u64 start, u64 size) {}
 extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
 		void *arg, int (*func)(struct memory_block *, void *));
 extern int add_memory(int nid, u64 start, u64 size);
+extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern bool is_memblock_offlined(struct memory_block *mem);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 469bbf5..348fda7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1156,6 +1156,34 @@ static int check_hotplug_memory_range(u64 start, u64 size)
 	return 0;
+ * If movable zone has already been setup, newly added memory should be check.
+ * If its address is higher than movable zone, it should be added as movable.
+ * Without this check, movable zone may overlap with other zone.
+ */
+static int should_add_memory_movable(int nid, u64 start, u64 size)
+	unsigned long start_pfn = start >> PAGE_SHIFT;
+	pg_data_t *pgdat = NODE_DATA(nid);
+	struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
+	if (zone_is_empty(movable_zone))
+		return 0;
+	if (movable_zone->zone_start_pfn <= start_pfn)
+		return 1;
+	return 0;
+int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
+	if (should_add_memory_movable(nid, start, size))
+		return ZONE_MOVABLE;
+	return zone_default;
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
 int __ref add_memory(int nid, u64 start, u64 size)

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