mm: compaction: move compaction sysctl to its own file

This moves all compaction sysctls to its own file.

Move sysctl to where the functionality truly belongs to improve
readability, reduce merge conflicts, and facilitate maintenance.

I use x86_defconfig and linux-next-20230327 branch
$ make defconfig;make all -jn
CONFIG_COMPACTION=y

add/remove: 1/0 grow/shrink: 1/1 up/down: 350/-256 (94)
Function                                     old     new   delta
vm_compaction                                  -     320    +320
kcompactd_init                               180     210     +30
vm_table                                    2112    1856    -256
Total: Before=21119987, After=21120081, chg +0.00%

Despite the addition of 94 bytes the patch still seems a worthwile
cleanup.

Link: https://lore.kernel.org/lkml/067f7347-ba10-5405-920c-0f5f985c84f4@suse.cz/
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

3 files changed, 72 insertions, 78 deletions

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 52a9ff65faee..a6e512cfb670 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -81,13 +81,6 @@ static inline unsigned long compact_gap(unsigned int order)
 }
 
 #ifdef CONFIG_COMPACTION
-extern unsigned int sysctl_compaction_proactiveness;
-extern int sysctl_compaction_handler(struct ctl_table *table, int write,
-			void *buffer, size_t *length, loff_t *ppos);
-extern int compaction_proactiveness_sysctl_handler(struct ctl_table *table,
-		int write, void *buffer, size_t *length, loff_t *ppos);
-extern int sysctl_extfrag_threshold;
-extern int sysctl_compact_unevictable_allowed;
 
 extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
 extern int fragmentation_index(struct zone *zone, unsigned int order);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 0a8a3c9c82e4..bfe53e835524 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -42,7 +42,6 @@
 #include <linux/highuid.h>
 #include <linux/writeback.h>
 #include <linux/ratelimit.h>
-#include <linux/compaction.h>
 #include <linux/hugetlb.h>
 #include <linux/initrd.h>
 #include <linux/key.h>
@@ -746,27 +745,6 @@ int proc_dointvec(struct ctl_table *table, int write, void *buffer,
 	return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL);
 }
 
-#ifdef CONFIG_COMPACTION
-static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table,
-		int write, void *buffer, size_t *lenp, loff_t *ppos)
-{
-	int ret, old;
-
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || !write)
-		return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-
-	old = *(int *)table->data;
-	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-	if (ret)
-		return ret;
-	if (old != *(int *)table->data)
-		pr_warn_once("sysctl attribute %s changed by %s[%d]\n",
-			     table->procname, current->comm,
-			     task_pid_nr(current));
-	return ret;
-}
-#endif
-
 /**
  * proc_douintvec - read a vector of unsigned integers
  * @table: the sysctl table
@@ -2157,43 +2135,6 @@ static struct ctl_table vm_table[] = {
 		.extra1		= SYSCTL_ONE,
 		.extra2		= SYSCTL_FOUR,
 	},
-#ifdef CONFIG_COMPACTION
-	{
-		.procname	= "compact_memory",
-		.data		= NULL,
-		.maxlen		= sizeof(int),
-		.mode		= 0200,
-		.proc_handler	= sysctl_compaction_handler,
-	},
-	{
-		.procname	= "compaction_proactiveness",
-		.data		= &sysctl_compaction_proactiveness,
-		.maxlen		= sizeof(sysctl_compaction_proactiveness),
-		.mode		= 0644,
-		.proc_handler	= compaction_proactiveness_sysctl_handler,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE_HUNDRED,
-	},
-	{
-		.procname	= "extfrag_threshold",
-		.data		= &sysctl_extfrag_threshold,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE_THOUSAND,
-	},
-	{
-		.procname	= "compact_unevictable_allowed",
-		.data		= &sysctl_compact_unevictable_allowed,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax_warn_RT_change,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
-
-#endif /* CONFIG_COMPACTION */
 	{
 		.procname	= "min_free_kbytes",
 		.data		= &min_free_kbytes,
diff --git a/mm/compaction.c b/mm/compaction.c
index 5a9501e0ae01..f2ddfb1140e2 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1716,7 +1716,14 @@ typedef enum {
  * Allow userspace to control policy on scanning the unevictable LRU for
  * compactable pages.
  */
-int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT;
+static int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT;
+/*
+ * Tunable for proactive compaction. It determines how
+ * aggressively the kernel should compact memory in the
+ * background. It takes values in the range [0, 100].
+ */
+static unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
+static int sysctl_extfrag_threshold = 500;
 
 static inline void
 update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
@@ -2572,8 +2579,6 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,
 	return ret;
 }
 
-int sysctl_extfrag_threshold = 500;
-
 /**
  * try_to_compact_pages - Direct compact to satisfy a high-order allocation
  * @gfp_mask: The GFP mask of the current allocation
@@ -2730,14 +2735,7 @@ static void compact_nodes(void)
 		compact_node(nid);
 }
 
-/*
- * Tunable for proactive compaction. It determines how
- * aggressively the kernel should compact memory in the
- * background. It takes values in the range [0, 100].
- */
-unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
-
-int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
+static int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
 		void *buffer, size_t *length, loff_t *ppos)
 {
 	int rc, nid;
@@ -2767,7 +2765,7 @@ int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
  * This is the entry point for compacting all nodes via
  * /proc/sys/vm/compact_memory
  */
-int sysctl_compaction_handler(struct ctl_table *table, int write,
+static int sysctl_compaction_handler(struct ctl_table *table, int write,
 			void *buffer, size_t *length, loff_t *ppos)
 {
 	if (write)
@@ -3063,6 +3061,65 @@ static int kcompactd_cpu_online(unsigned int cpu)
 	return 0;
 }
 
+static int proc_dointvec_minmax_warn_RT_change(struct ctl_table *table,
+		int write, void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret, old;
+
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || !write)
+		return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+	old = *(int *)table->data;
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	if (ret)
+		return ret;
+	if (old != *(int *)table->data)
+		pr_warn_once("sysctl attribute %s changed by %s[%d]\n",
+			     table->procname, current->comm,
+			     task_pid_nr(current));
+	return ret;
+}
+
+#ifdef CONFIG_SYSCTL
+static struct ctl_table vm_compaction[] = {
+	{
+		.procname	= "compact_memory",
+		.data		= NULL,
+		.maxlen		= sizeof(int),
+		.mode		= 0200,
+		.proc_handler	= sysctl_compaction_handler,
+	},
+	{
+		.procname	= "compaction_proactiveness",
+		.data		= &sysctl_compaction_proactiveness,
+		.maxlen		= sizeof(sysctl_compaction_proactiveness),
+		.mode		= 0644,
+		.proc_handler	= compaction_proactiveness_sysctl_handler,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE_HUNDRED,
+	},
+	{
+		.procname	= "extfrag_threshold",
+		.data		= &sysctl_extfrag_threshold,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE_THOUSAND,
+	},
+	{
+		.procname	= "compact_unevictable_allowed",
+		.data		= &sysctl_compact_unevictable_allowed,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax_warn_RT_change,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{ }
+};
+#endif
+
 static int __init kcompactd_init(void)
 {
 	int nid;
@@ -3078,6 +3135,9 @@ static int __init kcompactd_init(void)
 
 	for_each_node_state(nid, N_MEMORY)
 		kcompactd_run(nid);
+#ifdef CONFIG_SYSCTL
+	register_sysctl_init("vm", vm_compaction);
+#endif
 	return 0;
 }
 subsys_initcall(kcompactd_init)