userfaultfd: move unprivileged_userfaultfd sysctl to its own file

The sysctl_unprivileged_userfaultfd is part of userfaultfd, move it to
its own file.
Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

fs/userfaultfd.c

@@ -32,7 +32,22 @@
 #include <linux/swapops.h>
 #include <linux/miscdevice.h>
 
-int sysctl_unprivileged_userfaultfd __read_mostly;
+static int sysctl_unprivileged_userfaultfd __read_mostly;
+
+#ifdef CONFIG_SYSCTL
+static struct ctl_table vm_userfaultfd_table[] = {
+	{
+		.procname	= "unprivileged_userfaultfd",
+		.data		= &sysctl_unprivileged_userfaultfd,
+		.maxlen		= sizeof(sysctl_unprivileged_userfaultfd),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{ }
+};
+#endif
 
 static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
 
@@ -2178,6 +2193,9 @@ static int __init userfaultfd_init(void)
 						0,
 						SLAB_HWCACHE_ALIGN|SLAB_PANIC,
 						init_once_userfaultfd_ctx);
+#ifdef CONFIG_SYSCTL
+	register_sysctl_init("vm", vm_userfaultfd_table);
+#endif
 	return 0;
 }
 __initcall(userfaultfd_init);

include/linux/userfaultfd_k.h

@@ -36,8 +36,6 @@
 #define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
 #define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS)
 
-extern int sysctl_unprivileged_userfaultfd;
-
 extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
 
 /*

kernel/sysctl.c

@@ -2438,17 +2438,6 @@ static struct ctl_table vm_table[] = {
 		.extra1		= (void *)&mmap_rnd_compat_bits_min,
 		.extra2		= (void *)&mmap_rnd_compat_bits_max,
 	},
-#endif
-#ifdef CONFIG_USERFAULTFD
-	{
-		.procname	= "unprivileged_userfaultfd",
-		.data		= &sysctl_unprivileged_userfaultfd,
-		.maxlen		= sizeof(sysctl_unprivileged_userfaultfd),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
 #endif
 	{ }
 };