[PATCH v10 3/8] mm/demotion: Add hotplug callbacks to handle new numa node onlined

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

If the new NUMA node onlined doesn't have a performance level assigned,
the kernel adds the NUMA node to default memory tier.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 include/linux/memory-tiers.h |  1 +
 mm/memory-tiers.c            | 75 ++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index ef380a39db3a..3d5f14d57ae6 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -14,6 +14,7 @@
 #define MEMTIER_PERF_LEVEL_DRAM	(1 << (MEMTIER_CHUNK_BITS + 2))
 /* leave one tier below this slow pmem */
 #define MEMTIER_PERF_LEVEL_PMEM	(1 << MEMTIER_CHUNK_BITS)
+#define MEMTIER_HOTPLUG_PRIO	100
 
 extern bool numa_demotion_enabled;
 
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 41a21cc5ae55..cc3a47ec18e4 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -5,6 +5,7 @@
 #include <linux/lockdep.h>
 #include <linux/moduleparam.h>
 #include <linux/node.h>
+#include <linux/memory.h>
 #include <linux/memory-tiers.h>
 
 struct memory_tier {
@@ -64,6 +65,78 @@ static struct memory_tier *find_create_memory_tier(unsigned int perf_level)
 	return new_memtier;
 }
 
+static struct memory_tier *__node_get_memory_tier(int node)
+{
+	struct memory_tier *memtier;
+
+	list_for_each_entry(memtier, &memory_tiers, list) {
+		if (node_isset(node, memtier->nodelist))
+			return memtier;
+	}
+	return NULL;
+}
+
+static void init_node_memory_tier(int node)
+{
+	int perf_level;
+	struct memory_tier *memtier;
+
+	mutex_lock(&memory_tier_lock);
+
+	memtier = __node_get_memory_tier(node);
+	if (!memtier) {
+		perf_level = node_devices[node]->perf_level;
+		memtier = find_create_memory_tier(perf_level);
+		node_set(node, memtier->nodelist);
+	}
+	mutex_unlock(&memory_tier_lock);
+}
+
+static void clear_node_memory_tier(int node)
+{
+	struct memory_tier *memtier;
+
+	mutex_lock(&memory_tier_lock);
+	memtier = __node_get_memory_tier(node);
+	if (memtier)
+		node_clear(node, memtier->nodelist);
+	mutex_unlock(&memory_tier_lock);
+}
+
+/*
+ * This runs whether reclaim-based migration is enabled or not,
+ * which ensures that the user can turn reclaim-based migration
+ * at any time without needing to recalculate migration targets.
+ */
+static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
+						 unsigned long action, void *_arg)
+{
+	struct memory_notify *arg = _arg;
+
+	/*
+	 * Only update the node migration order when a node is
+	 * changing status, like online->offline.
+	 */
+	if (arg->status_change_nid < 0)
+		return notifier_from_errno(0);
+
+	switch (action) {
+	case MEM_OFFLINE:
+		clear_node_memory_tier(arg->status_change_nid);
+		break;
+	case MEM_ONLINE:
+		init_node_memory_tier(arg->status_change_nid);
+		break;
+	}
+
+	return notifier_from_errno(0);
+}
+
+static void __init migrate_on_reclaim_init(void)
+{
+	hotplug_memory_notifier(migrate_on_reclaim_callback, MEMTIER_HOTPLUG_PRIO);
+}
+
 static int __init memory_tier_init(void)
 {
 	int node;
@@ -96,6 +169,8 @@ static int __init memory_tier_init(void)
 			node_property->perf_level = default_memtier_perf_level;
 	}
 	mutex_unlock(&memory_tier_lock);
+
+	migrate_on_reclaim_init();
 	return 0;
 }
 subsys_initcall(memory_tier_init);
-- 
2.36.1