mm/demotion: add hotplug callbacks to handle new numa node onlined

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

[aneesh.kumar@linux.ibm.com: fix kernel error with memory hotplug]
  Link: https://lkml.kernel.org/r/20220825092019.379069-1-aneesh.kumar@linux.ibm.com
Link: https://lkml.kernel.org/r/20220818131042.113280-4-aneesh.kumar@linux.ibm.comSigned-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Wei Xu <weixugc@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hesham Almatary <hesham.almatary@huawei.com>
Cc: Jagdish Gediya <jvgediya.oss@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/memory-tiers.h

@@ -14,6 +14,7 @@
  * the same memory tier.
  */
 #define MEMTIER_ADISTANCE_DRAM	((4 * MEMTIER_CHUNK_SIZE) + (MEMTIER_CHUNK_SIZE >> 1))
+#define MEMTIER_HOTPLUG_PRIO	100
 
 #ifdef CONFIG_NUMA
 #include <linux/types.h>

mm/memory-tiers.c

@@ -5,6 +5,7 @@
 #include <linux/lockdep.h>
 #include <linux/sysfs.h>
 #include <linux/kobject.h>
+#include <linux/memory.h>
 #include <linux/memory-tiers.h>
 
 struct memory_tier {
@@ -105,6 +106,72 @@ static struct memory_tier *set_node_memory_tier(int node)
 	return memtier;
 }
 
+static struct memory_tier *__node_get_memory_tier(int node)
+{
+	struct memory_dev_type *memtype;
+
+	memtype = node_memory_types[node];
+	if (memtype && node_isset(node, memtype->nodes))
+		return memtype->memtier;
+	return NULL;
+}
+
+static void destroy_memory_tier(struct memory_tier *memtier)
+{
+	list_del(&memtier->list);
+	kfree(memtier);
+}
+
+static bool clear_node_memory_tier(int node)
+{
+	bool cleared = false;
+	struct memory_tier *memtier;
+
+	memtier = __node_get_memory_tier(node);
+	if (memtier) {
+		struct memory_dev_type *memtype;
+
+		memtype = node_memory_types[node];
+		node_clear(node, memtype->nodes);
+		if (nodes_empty(memtype->nodes)) {
+			list_del_init(&memtype->tier_sibiling);
+			memtype->memtier = NULL;
+			if (list_empty(&memtier->memory_types))
+				destroy_memory_tier(memtier);
+		}
+		cleared = true;
+	}
+	return cleared;
+}
+
+static int __meminit memtier_hotplug_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:
+		mutex_lock(&memory_tier_lock);
+		clear_node_memory_tier(arg->status_change_nid);
+		mutex_unlock(&memory_tier_lock);
+		break;
+	case MEM_ONLINE:
+		mutex_lock(&memory_tier_lock);
+		set_node_memory_tier(arg->status_change_nid);
+		mutex_unlock(&memory_tier_lock);
+		break;
+	}
+
+	return notifier_from_errno(0);
+}
+
 static int __init memory_tier_init(void)
 {
 	int node;
@@ -126,6 +193,7 @@ static int __init memory_tier_init(void)
 	}
 	mutex_unlock(&memory_tier_lock);
 
+	hotplug_memory_notifier(memtier_hotplug_callback, MEMTIER_HOTPLUG_PRIO);
 	return 0;
 }
 subsys_initcall(memory_tier_init);