mm: swap: move sysctl to mm/swap.c

The page-cluster belongs to mm/swap.c, move it to mm/swap.c .
Removes the redundant external variable declaration and unneeded
include(linux/swap.h).

Signed-off-by: Kaixiong Yu <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Signed-off-by: Joel Granados <[email protected]>

Author: yukaixiong

include/linux/mm.h

@@ -76,8 +76,6 @@ static inline void totalram_pages_add(long count)
 }
 
 extern void * high_memory;
-extern int page_cluster;
-extern const int page_cluster_max;
 
 #ifdef CONFIG_SYSCTL
 extern int sysctl_legacy_va_layout;

kernel/sysctl.c

@@ -21,7 +21,6 @@
 
 #include <linux/module.h>
 #include <linux/mm.h>
-#include <linux/swap.h>
 #include <linux/slab.h>
 #include <linux/sysctl.h>
 #include <linux/bitmap.h>
@@ -2044,15 +2043,6 @@ static const struct ctl_table vm_table[] = {
 		.mode		= 0644,
 		.proc_handler	= overcommit_kbytes_handler,
 	},
-	{
-		.procname	= "page-cluster",
-		.data		= &page_cluster,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= (void *)&page_cluster_max,
-	},
 	{
 		.procname	= "dirtytime_expire_seconds",
 		.data		= &dirtytime_expire_interval,

mm/swap.c

@@ -45,7 +45,7 @@
 
 /* How many pages do we try to swap or page in/out together? As a power of 2 */
 int page_cluster;
-const int page_cluster_max = 31;
+static const int page_cluster_max = 31;
 
 struct cpu_fbatches {
 	/*
@@ -1076,6 +1076,18 @@ void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
 	fbatch->nr = j;
 }
 
+static const struct ctl_table swap_sysctl_table[] = {
+	{
+		.procname	= "page-cluster",
+		.data		= &page_cluster,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= (void *)&page_cluster_max,
+	}
+};
+
 /*
  * Perform any setup for the swap system
  */
@@ -1092,4 +1104,6 @@ void __init swap_setup(void)
 	 * Right now other parts of the system means that we
 	 * _really_ don't want to cluster much more
 	 */
+
+	register_sysctl_init("vm", swap_sysctl_table);
 }

mm/swap.h

@@ -3,6 +3,7 @@
 #define _MM_SWAP_H
 
 struct mempolicy;
+extern int page_cluster;
 
 #ifdef CONFIG_SWAP
 #include <linux/swapops.h> /* for swp_offset */