1 files changed, 79 insertions, 0 deletions
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
new file mode 100644
index 000000000..1c6ac6fce
--- /dev/null
+++ b/fs/sysfs/mount.c
@@ -0,0 +1,79 @@
+/*
+ * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
+ */
+
+#define DEBUG
+
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/user_namespace.h>
+
+#include "sysfs.h"
+
+static struct kernfs_root *sysfs_root;
+struct kernfs_node *sysfs_root_kn;
+
+static struct dentry *sysfs_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
+{
+	struct dentry *root;
+	void *ns;
+	bool new_sb;
+
+	if (!(flags & MS_KERNMOUNT)) {
+		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
+			return ERR_PTR(-EPERM);
+	}
+
+	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	root = kernfs_mount_ns(fs_type, flags, sysfs_root,
+				SYSFS_MAGIC, &new_sb, ns);
+	if (IS_ERR(root) || !new_sb)
+		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
+	return root;
+}
+
+static void sysfs_kill_sb(struct super_block *sb)
+{
+	void *ns = (void *)kernfs_super_ns(sb);
+
+	kernfs_kill_sb(sb);
+	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
+}
+
+static struct file_system_type sysfs_fs_type = {
+	.name		= "sysfs",
+	.mount		= sysfs_mount,
+	.kill_sb	= sysfs_kill_sb,
+	.fs_flags	= FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
+};
+
+int __init sysfs_init(void)
+{
+	int err;
+
+	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
+					NULL);
+	if (IS_ERR(sysfs_root))
+		return PTR_ERR(sysfs_root);
+
+	sysfs_root_kn = sysfs_root->kn;
+
+	err = register_filesystem(&sysfs_fs_type);
+	if (err) {
+		kernfs_destroy_root(sysfs_root);
+		return err;
+	}
+
+	return 0;
+}