/*

   * 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 (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
  			return ERR_PTR(-EPERM);

  		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_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;

  }