2 files changed, 64 insertions, 2 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 939eabcaf488..e675bfb856da 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -3021,3 +3021,64 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
 		p += scnprintf(p, buffer + maxlen - p, ":%*pbl",
 			       nodemask_pr_args(&nodes));
 }
+
+bool numa_demotion_enabled = false;
+
+#ifdef CONFIG_SYSFS
+static ssize_t numa_demotion_enabled_show(struct kobject *kobj,
+					  struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n",
+			  numa_demotion_enabled? "true" : "false");
+}
+
+static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
+					   struct kobj_attribute *attr,
+					   const char *buf, size_t count)
+{
+	if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
+		numa_demotion_enabled = true;
+	else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
+		numa_demotion_enabled = false;
+	else
+		return -EINVAL;
+
+	return count;
+}
+
+static struct kobj_attribute numa_demotion_enabled_attr =
+	__ATTR(demotion_enabled, 0644, numa_demotion_enabled_show,
+	       numa_demotion_enabled_store);
+
+static struct attribute *numa_attrs[] = {
+	&numa_demotion_enabled_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group numa_attr_group = {
+	.attrs = numa_attrs,
+};
+
+static int __init numa_init_sysfs(void)
+{
+	int err;
+	struct kobject *numa_kobj;
+
+	numa_kobj = kobject_create_and_add("numa", mm_kobj);
+	if (!numa_kobj) {
+		pr_err("failed to create numa kobject\n");
+		return -ENOMEM;
+	}
+	err = sysfs_create_group(numa_kobj, &numa_attr_group);
+	if (err) {
+		pr_err("failed to register numa group\n");
+		goto delete_obj;
+	}
+	return 0;
+
+delete_obj:
+	kobject_put(numa_kobj);
+	return err;
+}
+subsys_initcall(numa_init_sysfs);
+#endif
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 43289f5f8488..2255025f1891 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -524,6 +524,8 @@ static long add_nr_deferred(long nr, struct shrinker *shrinker,
 
 static bool can_demote(int nid, struct scan_control *sc)
 {
+	if (!numa_demotion_enabled)
+		return false;
 	if (sc) {
 		if (sc->no_demotion)
 			return false;
@@ -534,8 +536,7 @@ static bool can_demote(int nid, struct scan_control *sc)
 	if (next_demotion_node(nid) == NUMA_NO_NODE)
 		return false;
 
-	// FIXME: actually enable this later in the series
-	return false;
+	return true;
 }
 
 static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,