[PATCH] mm: sysctl: fix missing numa_stat when !CONFIG_HUGETLB_PAGE

[Muchun Song]

"numa_stat" should not be included in the scope of CONFIG_HUGETLB_PAGE,
if CONFIG_HUGETLB_PAGE is not configured even if CONFIG_NUMA is configured,
"numa_stat" is missed form /proc.  Remove it out of CONFIG_HUGETLB_PAGE
and move numa_stat sysctl handling to mm/vmstat.c.

Fixes: 4518085e127d ("mm, sysctl: make NUMA stats configurable")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
 include/linux/vmstat.h |  5 -----
 kernel/sysctl.c        |  9 ---------
 mm/vmstat.c            | 52 +++++++++++++++++++++++++-------------------------
 3 files changed, 26 insertions(+), 40 deletions(-)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index bfe38869498d..1297a6b8ba23 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -13,12 +13,7 @@
 extern int sysctl_stat_interval;
 
 #ifdef CONFIG_NUMA
-#define ENABLE_NUMA_STAT   1
-#define DISABLE_NUMA_STAT   0
-extern int sysctl_vm_numa_stat;
 DECLARE_STATIC_KEY_TRUE(vm_numa_stat_key);
-int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
-		void *buffer, size_t *length, loff_t *ppos);
 #endif
 
 struct reclaim_stat {
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e52b6e372c60..3d6f36f230bb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2107,15 +2107,6 @@ static struct ctl_table vm_table[] = {
 		.mode           = 0644,
 		.proc_handler   = &hugetlb_mempolicy_sysctl_handler,
 	},
-	{
-		.procname		= "numa_stat",
-		.data			= &sysctl_vm_numa_stat,
-		.maxlen			= sizeof(int),
-		.mode			= 0644,
-		.proc_handler	= sysctl_vm_numa_stat_handler,
-		.extra1			= SYSCTL_ZERO,
-		.extra2			= SYSCTL_ONE,
-	},
 #endif
 	 {
 		.procname	= "hugetlb_shm_group",
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 373d2730fcf2..e10afbee888e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -33,8 +33,6 @@
 #include "internal.h"
 
 #ifdef CONFIG_NUMA
-int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;
-
 /* zero numa counters within a zone */
 static void zero_zone_numa_counters(struct zone *zone)
 {
@@ -73,35 +71,37 @@ static void invalid_numa_statistics(void)
 	zero_global_numa_counters();
 }
 
-static DEFINE_MUTEX(vm_numa_stat_lock);
-
-int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
-		void *buffer, size_t *length, loff_t *ppos)
+static int sysctl_numa_stat_handler(struct ctl_table *table, int write,
+				    void *buffer, size_t *length, loff_t *ppos)
 {
-	int ret, oldval;
+	int ret;
+	struct static_key *key = table->data;
+	static DEFINE_MUTEX(lock);
 
-	mutex_lock(&vm_numa_stat_lock);
-	if (write)
-		oldval = sysctl_vm_numa_stat;
-	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
-	if (ret || !write)
-		goto out;
-
-	if (oldval == sysctl_vm_numa_stat)
-		goto out;
-	else if (sysctl_vm_numa_stat == ENABLE_NUMA_STAT) {
-		static_branch_enable(&vm_numa_stat_key);
-		pr_info("enable numa statistics\n");
-	} else {
-		static_branch_disable(&vm_numa_stat_key);
+	mutex_lock(&lock);
+	ret = proc_do_static_key(table, write, buffer, length, ppos);
+	if (!ret && write && !static_key_enabled(key))
 		invalid_numa_statistics();
-		pr_info("disable numa statistics, and clear numa counters\n");
-	}
-
-out:
-	mutex_unlock(&vm_numa_stat_lock);
+	mutex_unlock(&lock);
 	return ret;
 }
+
+static struct ctl_table numa_stat_sysctl[] = {
+	{
+		.procname	= "numa_stat",
+		.data		= &vm_numa_stat_key.key,
+		.mode		= 0644,
+		.proc_handler	= sysctl_numa_stat_handler,
+	},
+	{ }
+};
+
+static int __init numa_stat_sysctl_init(void)
+{
+	register_sysctl_init("vm", numa_stat_sysctl);
+	return 0;
+}
+late_initcall(numa_stat_sysctl_init);
 #endif
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
-- 
2.11.0