/*

   * fs/sysfs/dir.c - sysfs core and dir operation implementation
   *
   * 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.

   */
  
  #undef DEBUG
  
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/module.h>
  #include <linux/kobject.h>

  #include <linux/namei.h>

  #include <linux/idr.h>

  #include <linux/completion.h>

  #include <linux/mutex.h>

  #include <linux/slab.h>

  #include <linux/security.h>

  #include "sysfs.h"

  DEFINE_MUTEX(sysfs_mutex);

  DEFINE_SPINLOCK(sysfs_assoc_lock);

  static DEFINE_SPINLOCK(sysfs_ino_lock);

  static DEFINE_IDA(sysfs_ino_ida);

  /**

   *	sysfs_link_sibling - link sysfs_dirent into sibling list
   *	@sd: sysfs_dirent of interest
   *
   *	Link @sd into its sibling list which starts from

   *	sd->s_parent->s_dir.children.

   *
   *	Locking:

   *	mutex_lock(sysfs_mutex)

   */

  static void sysfs_link_sibling(struct sysfs_dirent *sd)

  {
  	struct sysfs_dirent *parent_sd = sd->s_parent;

  	struct rb_node **p;
  	struct rb_node *parent;

  	if (sysfs_type(sd) == SYSFS_DIR)
  		parent_sd->s_dir.subdirs++;

  	p = &parent_sd->s_dir.inode_tree.rb_node;
  	parent = NULL;
  	while (*p) {
  		parent = *p;
  #define node	rb_entry(parent, struct sysfs_dirent, inode_node)
  		if (sd->s_ino < node->s_ino) {
  			p = &node->inode_node.rb_left;
  		} else if (sd->s_ino > node->s_ino) {
  			p = &node->inode_node.rb_right;
  		} else {

  			printk(KERN_CRIT "sysfs: inserting duplicate inode '%lx'
  ",
  			       (unsigned long) sd->s_ino);

  			BUG();
  		}
  #undef node

  	}

  	rb_link_node(&sd->inode_node, parent, p);
  	rb_insert_color(&sd->inode_node, &parent_sd->s_dir.inode_tree);

  
  	p = &parent_sd->s_dir.name_tree.rb_node;
  	parent = NULL;
  	while (*p) {
  		int c;
  		parent = *p;
  #define node	rb_entry(parent, struct sysfs_dirent, name_node)
  		c = strcmp(sd->s_name, node->s_name);
  		if (c < 0) {
  			p = &node->name_node.rb_left;
  		} else {
  			p = &node->name_node.rb_right;
  		}
  #undef node
  	}
  	rb_link_node(&sd->name_node, parent, p);
  	rb_insert_color(&sd->name_node, &parent_sd->s_dir.name_tree);

  }
  
  /**
   *	sysfs_unlink_sibling - unlink sysfs_dirent from sibling list
   *	@sd: sysfs_dirent of interest
   *
   *	Unlink @sd from its sibling list which starts from

   *	sd->s_parent->s_dir.children.

   *
   *	Locking:

   *	mutex_lock(sysfs_mutex)

   */

  static void sysfs_unlink_sibling(struct sysfs_dirent *sd)

  {

  	if (sysfs_type(sd) == SYSFS_DIR)
  		sd->s_parent->s_dir.subdirs--;

  	rb_erase(&sd->inode_node, &sd->s_parent->s_dir.inode_tree);

  	rb_erase(&sd->name_node, &sd->s_parent->s_dir.name_tree);

  }
  
  /**

   *	sysfs_get_active - get an active reference to sysfs_dirent
   *	@sd: sysfs_dirent to get an active reference to
   *
   *	Get an active reference of @sd.  This function is noop if @sd
   *	is NULL.
   *
   *	RETURNS:
   *	Pointer to @sd on success, NULL on failure.
   */

  struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd)

  {

  	if (unlikely(!sd))
  		return NULL;
  
  	while (1) {
  		int v, t;
  
  		v = atomic_read(&sd->s_active);
  		if (unlikely(v < 0))
  			return NULL;
  
  		t = atomic_cmpxchg(&sd->s_active, v, v + 1);

  		if (likely(t == v)) {
  			rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);

  			return sd;

  		}

  		if (t < 0)
  			return NULL;
  
  		cpu_relax();

  	}

  }
  
  /**
   *	sysfs_put_active - put an active reference to sysfs_dirent
   *	@sd: sysfs_dirent to put an active reference to
   *
   *	Put an active reference to @sd.  This function is noop if @sd
   *	is NULL.
   */

  void sysfs_put_active(struct sysfs_dirent *sd)

  {

  	int v;
  
  	if (unlikely(!sd))
  		return;

  	rwsem_release(&sd->dep_map, 1, _RET_IP_);

  	v = atomic_dec_return(&sd->s_active);
  	if (likely(v != SD_DEACTIVATED_BIAS))
  		return;
  
  	/* atomic_dec_return() is a mb(), we'll always see the updated

  	 * sd->u.completion.

  	 */

  	complete(sd->u.completion);

  }
  
  /**

   *	sysfs_deactivate - deactivate sysfs_dirent
   *	@sd: sysfs_dirent to deactivate
   *

   *	Deny new active references and drain existing ones.

   */

  static void sysfs_deactivate(struct sysfs_dirent *sd)

  {

  	DECLARE_COMPLETION_ONSTACK(wait);
  	int v;

  	BUG_ON(!(sd->s_flags & SYSFS_FLAG_REMOVED));

  
  	if (!(sysfs_type(sd) & SYSFS_ACTIVE_REF))
  		return;

  	sd->u.completion = (void *)&wait;

  	rwsem_acquire(&sd->dep_map, 0, 0, _RET_IP_);

  	/* atomic_add_return() is a mb(), put_active() will always see

  	 * the updated sd->u.completion.

  	 */

  	v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active);

  	if (v != SD_DEACTIVATED_BIAS) {
  		lock_contended(&sd->dep_map, _RET_IP_);

  		wait_for_completion(&wait);

  	}

  	lock_acquired(&sd->dep_map, _RET_IP_);
  	rwsem_release(&sd->dep_map, 1, _RET_IP_);

  }

  static int sysfs_alloc_ino(ino_t *pino)

  {
  	int ino, rc;
  
   retry:
  	spin_lock(&sysfs_ino_lock);
  	rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
  	spin_unlock(&sysfs_ino_lock);
  
  	if (rc == -EAGAIN) {
  		if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL))
  			goto retry;
  		rc = -ENOMEM;
  	}
  
  	*pino = ino;
  	return rc;
  }
  
  static void sysfs_free_ino(ino_t ino)
  {
  	spin_lock(&sysfs_ino_lock);
  	ida_remove(&sysfs_ino_ida, ino);
  	spin_unlock(&sysfs_ino_lock);
  }

  void release_sysfs_dirent(struct sysfs_dirent * sd)
  {

  	struct sysfs_dirent *parent_sd;
  
   repeat:

  	/* Moving/renaming is always done while holding reference.
  	 * sd->s_parent won't change beneath us.
  	 */

  	parent_sd = sd->s_parent;

  	if (sysfs_type(sd) == SYSFS_KOBJ_LINK)

  		sysfs_put(sd->s_symlink.target_sd);

  	if (sysfs_type(sd) & SYSFS_COPY_NAME)

  		kfree(sd->s_name);

  	if (sd->s_iattr && sd->s_iattr->ia_secdata)
  		security_release_secctx(sd->s_iattr->ia_secdata,
  					sd->s_iattr->ia_secdata_len);

  	kfree(sd->s_iattr);

  	sysfs_free_ino(sd->s_ino);

  	kmem_cache_free(sysfs_dir_cachep, sd);

  
  	sd = parent_sd;
  	if (sd && atomic_dec_and_test(&sd->s_count))
  		goto repeat;

  }

  static int sysfs_dentry_delete(const struct dentry *dentry)

  {
  	struct sysfs_dirent *sd = dentry->d_fsdata;
  	return !!(sd->s_flags & SYSFS_FLAG_REMOVED);
  }
  
  static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
  {

  	struct sysfs_dirent *sd;

  	int is_dir;

  	if (nd->flags & LOOKUP_RCU)
  		return -ECHILD;
  
  	sd = dentry->d_fsdata;

  	mutex_lock(&sysfs_mutex);
  
  	/* The sysfs dirent has been deleted */
  	if (sd->s_flags & SYSFS_FLAG_REMOVED)
  		goto out_bad;

  	/* The sysfs dirent has been moved? */
  	if (dentry->d_parent->d_fsdata != sd->s_parent)
  		goto out_bad;
  
  	/* The sysfs dirent has been renamed */
  	if (strcmp(dentry->d_name.name, sd->s_name) != 0)
  		goto out_bad;

  	mutex_unlock(&sysfs_mutex);
  out_valid:
  	return 1;
  out_bad:
  	/* Remove the dentry from the dcache hashes.
  	 * If this is a deleted dentry we use d_drop instead of d_delete
  	 * so sysfs doesn't need to cope with negative dentries.

  	 *
  	 * If this is a dentry that has simply been renamed we
  	 * use d_drop to remove it from the dcache lookup on its
  	 * old parent.  If this dentry persists later when a lookup
  	 * is performed at its new name the dentry will be readded
  	 * to the dcache hashes.

  	 */
  	is_dir = (sysfs_type(sd) == SYSFS_DIR);
  	mutex_unlock(&sysfs_mutex);
  	if (is_dir) {
  		/* If we have submounts we must allow the vfs caches
  		 * to lie about the state of the filesystem to prevent
  		 * leaks and other nasty things.
  		 */
  		if (have_submounts(dentry))
  			goto out_valid;
  		shrink_dcache_parent(dentry);
  	}
  	d_drop(dentry);
  	return 0;
  }

  static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode)

  {
  	struct sysfs_dirent * sd = dentry->d_fsdata;

  	sysfs_put(sd);

  	iput(inode);
  }

  static const struct dentry_operations sysfs_dentry_ops = {

  	.d_revalidate	= sysfs_dentry_revalidate,
  	.d_delete	= sysfs_dentry_delete,

  	.d_iput		= sysfs_dentry_iput,

  };

  struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)

  {

  	char *dup_name = NULL;

  	struct sysfs_dirent *sd;

  
  	if (type & SYSFS_COPY_NAME) {
  		name = dup_name = kstrdup(name, GFP_KERNEL);
  		if (!name)

  			return NULL;

  	}

  	sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);

  	if (!sd)

  		goto err_out1;

  	if (sysfs_alloc_ino(&sd->s_ino))

  		goto err_out2;

  	atomic_set(&sd->s_count, 1);

  	atomic_set(&sd->s_active, 0);

  	sd->s_name = name;

  	sd->s_mode = mode;

  	sd->s_flags = type;

  
  	return sd;

   err_out2:

  	kmem_cache_free(sysfs_dir_cachep, sd);

   err_out1:
  	kfree(dup_name);

  	return NULL;

  }

  /**

   *	sysfs_addrm_start - prepare for sysfs_dirent add/remove
   *	@acxt: pointer to sysfs_addrm_cxt to be used
   *	@parent_sd: parent sysfs_dirent

   *

   *	This function is called when the caller is about to add or
   *	remove sysfs_dirent under @parent_sd.  This function acquires

   *	sysfs_mutex.  @acxt is used to keep and pass context to

   *	other addrm functions.

   *
   *	LOCKING:

   *	Kernel thread context (may sleep).  sysfs_mutex is locked on

   *	return.

   */

  void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
  		       struct sysfs_dirent *parent_sd)

  {

  	memset(acxt, 0, sizeof(*acxt));
  	acxt->parent_sd = parent_sd;

  	mutex_lock(&sysfs_mutex);

  }
  
  /**

   *	__sysfs_add_one - add sysfs_dirent to parent without warning

   *	@acxt: addrm context to use
   *	@sd: sysfs_dirent to be added
   *
   *	Get @acxt->parent_sd and set sd->s_parent to it and increment

   *	nlink of parent inode if @sd is a directory and link into the
   *	children list of the parent.

   *
   *	This function should be called between calls to
   *	sysfs_addrm_start() and sysfs_addrm_finish() and should be
   *	passed the same @acxt as passed to sysfs_addrm_start().
   *
   *	LOCKING:
   *	Determined by sysfs_addrm_start().

   *
   *	RETURNS:
   *	0 on success, -EEXIST if entry with the given name already
   *	exists.

   */

  int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)

  {

  	struct sysfs_inode_attrs *ps_iattr;

  	if (!!sysfs_ns_type(acxt->parent_sd) != !!sd->s_ns) {
  		WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'
  ",
  			sysfs_ns_type(acxt->parent_sd)? "required": "invalid",
  			acxt->parent_sd->s_name, sd->s_name);
  		return -EINVAL;
  	}

  	if (sysfs_find_dirent(acxt->parent_sd, sd->s_ns, sd->s_name))

  		return -EEXIST;

  	sd->s_parent = sysfs_get(acxt->parent_sd);

  	sysfs_link_sibling(sd);

  	/* Update timestamps on the parent */
  	ps_iattr = acxt->parent_sd->s_iattr;
  	if (ps_iattr) {
  		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
  		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
  	}

  	return 0;

  }
  
  /**

   *	sysfs_pathname - return full path to sysfs dirent
   *	@sd: sysfs_dirent whose path we want
   *	@path: caller allocated buffer
   *
   *	Gives the name "/" to the sysfs_root entry; any path returned
   *	is relative to wherever sysfs is mounted.
   *
   *	XXX: does no error checking on @path size
   */
  static char *sysfs_pathname(struct sysfs_dirent *sd, char *path)
  {
  	if (sd->s_parent) {
  		sysfs_pathname(sd->s_parent, path);
  		strcat(path, "/");
  	}
  	strcat(path, sd->s_name);
  	return path;
  }
  
  /**

   *	sysfs_add_one - add sysfs_dirent to parent
   *	@acxt: addrm context to use
   *	@sd: sysfs_dirent to be added
   *
   *	Get @acxt->parent_sd and set sd->s_parent to it and increment
   *	nlink of parent inode if @sd is a directory and link into the
   *	children list of the parent.
   *
   *	This function should be called between calls to
   *	sysfs_addrm_start() and sysfs_addrm_finish() and should be
   *	passed the same @acxt as passed to sysfs_addrm_start().
   *
   *	LOCKING:
   *	Determined by sysfs_addrm_start().
   *
   *	RETURNS:
   *	0 on success, -EEXIST if entry with the given name already
   *	exists.
   */
  int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
  {
  	int ret;
  
  	ret = __sysfs_add_one(acxt, sd);

  	if (ret == -EEXIST) {
  		char *path = kzalloc(PATH_MAX, GFP_KERNEL);
  		WARN(1, KERN_WARNING
  		     "sysfs: cannot create duplicate filename '%s'
  ",
  		     (path == NULL) ? sd->s_name :
  		     strcat(strcat(sysfs_pathname(acxt->parent_sd, path), "/"),
  		            sd->s_name));
  		kfree(path);
  	}

  	return ret;
  }
  
  /**

   *	sysfs_remove_one - remove sysfs_dirent from parent
   *	@acxt: addrm context to use

   *	@sd: sysfs_dirent to be removed

   *
   *	Mark @sd removed and drop nlink of parent inode if @sd is a

   *	directory.  @sd is unlinked from the children list.

   *
   *	This function should be called between calls to
   *	sysfs_addrm_start() and sysfs_addrm_finish() and should be
   *	passed the same @acxt as passed to sysfs_addrm_start().
   *
   *	LOCKING:
   *	Determined by sysfs_addrm_start().
   */
  void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
  {

  	struct sysfs_inode_attrs *ps_iattr;

  	BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED);
  
  	sysfs_unlink_sibling(sd);

  	/* Update timestamps on the parent */
  	ps_iattr = acxt->parent_sd->s_iattr;
  	if (ps_iattr) {
  		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
  		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
  	}

  	sd->s_flags |= SYSFS_FLAG_REMOVED;

  	sd->u.removed_list = acxt->removed;

  	acxt->removed = sd;

  }
  
  /**

   *	sysfs_addrm_finish - finish up sysfs_dirent add/remove
   *	@acxt: addrm context to finish up
   *
   *	Finish up sysfs_dirent add/remove.  Resources acquired by
   *	sysfs_addrm_start() are released and removed sysfs_dirents are

   *	cleaned up.

   *
   *	LOCKING:

   *	sysfs_mutex is released.

   */

  void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)

  {
  	/* release resources acquired by sysfs_addrm_start() */
  	mutex_unlock(&sysfs_mutex);

  
  	/* kill removed sysfs_dirents */
  	while (acxt->removed) {
  		struct sysfs_dirent *sd = acxt->removed;

  		acxt->removed = sd->u.removed_list;

  		sysfs_deactivate(sd);

  		unmap_bin_file(sd);

  		sysfs_put(sd);

  	}

  }

  /**
   *	sysfs_find_dirent - find sysfs_dirent with the given name
   *	@parent_sd: sysfs_dirent to search under
   *	@name: name to look for
   *
   *	Look for sysfs_dirent with name @name under @parent_sd.

   *

   *	LOCKING:

   *	mutex_lock(sysfs_mutex)

   *

   *	RETURNS:
   *	Pointer to sysfs_dirent if found, NULL if not.

   */

  struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,

  				       const void *ns,

  				       const unsigned char *name)

  {

  	struct rb_node *p = parent_sd->s_dir.name_tree.rb_node;
  	struct sysfs_dirent *found = NULL;

  	if (!!sysfs_ns_type(parent_sd) != !!ns) {
  		WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'
  ",
  			sysfs_ns_type(parent_sd)? "required": "invalid",
  			parent_sd->s_name, name);
  		return NULL;
  	}

  	while (p) {
  		int c;
  #define node	rb_entry(p, struct sysfs_dirent, name_node)
  		c = strcmp(name, node->s_name);
  		if (c < 0) {
  			p = node->name_node.rb_left;
  		} else if (c > 0) {
  			p = node->name_node.rb_right;
  		} else {
  			found = node;
  			p = node->name_node.rb_left;
  		}
  #undef node
  	}

  	if (found) {
  		while (found->s_ns != ns) {

  			p = rb_next(&found->name_node);
  			if (!p)
  				return NULL;
  			found = rb_entry(p, struct sysfs_dirent, name_node);
  			if (strcmp(name, found->s_name))
  				return NULL;
  		}

  	}

  
  	return found;

  }

  /**
   *	sysfs_get_dirent - find and get sysfs_dirent with the given name
   *	@parent_sd: sysfs_dirent to search under
   *	@name: name to look for
   *
   *	Look for sysfs_dirent with name @name under @parent_sd and get
   *	it if found.
   *
   *	LOCKING:

   *	Kernel thread context (may sleep).  Grabs sysfs_mutex.

   *
   *	RETURNS:
   *	Pointer to sysfs_dirent if found, NULL if not.
   */
  struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,

  				      const void *ns,

  				      const unsigned char *name)
  {
  	struct sysfs_dirent *sd;

  	mutex_lock(&sysfs_mutex);

  	sd = sysfs_find_dirent(parent_sd, ns, name);

  	sysfs_get(sd);

  	mutex_unlock(&sysfs_mutex);

  
  	return sd;

  }

  EXPORT_SYMBOL_GPL(sysfs_get_dirent);

  static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,

  	enum kobj_ns_type type, const void *ns, const char *name,
  	struct sysfs_dirent **p_sd)

  {

  	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;

  	struct sysfs_addrm_cxt acxt;

  	struct sysfs_dirent *sd;

  	int rc;

  	/* allocate */

  	sd = sysfs_new_dirent(name, mode, SYSFS_DIR);

  	if (!sd)

  		return -ENOMEM;

  
  	sd->s_flags |= (type << SYSFS_NS_TYPE_SHIFT);
  	sd->s_ns = ns;

  	sd->s_dir.kobj = kobj;

  	/* link in */

  	sysfs_addrm_start(&acxt, parent_sd);

  	rc = sysfs_add_one(&acxt, sd);
  	sysfs_addrm_finish(&acxt);

  	if (rc == 0)
  		*p_sd = sd;
  	else

  		sysfs_put(sd);

  	return rc;

  }

  int sysfs_create_subdir(struct kobject *kobj, const char *name,
  			struct sysfs_dirent **p_sd)

  {

  	return create_dir(kobj, kobj->sd,
  			  KOBJ_NS_TYPE_NONE, NULL, name, p_sd);
  }

  /**
   *	sysfs_read_ns_type: return associated ns_type
   *	@kobj: the kobject being queried
   *
   *	Each kobject can be tagged with exactly one namespace type
   *	(i.e. network or user).  Return the ns_type associated with
   *	this object if any
   */

  static enum kobj_ns_type sysfs_read_ns_type(struct kobject *kobj)
  {
  	const struct kobj_ns_type_operations *ops;
  	enum kobj_ns_type type;
  
  	ops = kobj_child_ns_ops(kobj);
  	if (!ops)
  		return KOBJ_NS_TYPE_NONE;
  
  	type = ops->type;
  	BUG_ON(type <= KOBJ_NS_TYPE_NONE);
  	BUG_ON(type >= KOBJ_NS_TYPES);
  	BUG_ON(!kobj_ns_type_registered(type));
  
  	return type;

  }
  
  /**
   *	sysfs_create_dir - create a directory for an object.

   *	@kobj:		object we're creating directory for. 
   */

  int sysfs_create_dir(struct kobject * kobj)

  {

  	enum kobj_ns_type type;

  	struct sysfs_dirent *parent_sd, *sd;

  	const void *ns = NULL;

  	int error = 0;
  
  	BUG_ON(!kobj);

  	if (kobj->parent)

  		parent_sd = kobj->parent->sd;

  	else

  		parent_sd = &sysfs_root;

  	if (sysfs_ns_type(parent_sd))
  		ns = kobj->ktype->namespace(kobj);
  	type = sysfs_read_ns_type(kobj);
  
  	error = create_dir(kobj, parent_sd, type, ns, kobject_name(kobj), &sd);

  	if (!error)

  		kobj->sd = sd;

  	return error;
  }

  static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
  				struct nameidata *nd)
  {

  	struct dentry *ret = NULL;

  	struct dentry *parent = dentry->d_parent;
  	struct sysfs_dirent *parent_sd = parent->d_fsdata;

  	struct sysfs_dirent *sd;

  	struct inode *inode;

  	enum kobj_ns_type type;
  	const void *ns;

  	mutex_lock(&sysfs_mutex);

  	type = sysfs_ns_type(parent_sd);
  	ns = sysfs_info(dir->i_sb)->ns[type];
  
  	sd = sysfs_find_dirent(parent_sd, ns, dentry->d_name.name);

  	/* no such entry */

  	if (!sd) {
  		ret = ERR_PTR(-ENOENT);

  		goto out_unlock;

  	}

  
  	/* attach dentry and inode */

  	inode = sysfs_get_inode(dir->i_sb, sd);

  	if (!inode) {
  		ret = ERR_PTR(-ENOMEM);
  		goto out_unlock;
  	}

  	/* instantiate and hash dentry */

  	ret = d_find_alias(inode);
  	if (!ret) {

  		d_set_d_op(dentry, &sysfs_dentry_ops);

  		dentry->d_fsdata = sysfs_get(sd);
  		d_add(dentry, inode);
  	} else {
  		d_move(ret, dentry);
  		iput(inode);
  	}

   out_unlock:

  	mutex_unlock(&sysfs_mutex);

  	return ret;

  }

  const struct inode_operations sysfs_dir_inode_operations = {

  	.lookup		= sysfs_lookup,

  	.permission	= sysfs_permission,

  	.setattr	= sysfs_setattr,

  	.getattr	= sysfs_getattr,

  	.setxattr	= sysfs_setxattr,

  };

  static void remove_dir(struct sysfs_dirent *sd)

  {

  	struct sysfs_addrm_cxt acxt;

  	sysfs_addrm_start(&acxt, sd->s_parent);

  	sysfs_remove_one(&acxt, sd);
  	sysfs_addrm_finish(&acxt);

  }

  void sysfs_remove_subdir(struct sysfs_dirent *sd)

  {

  	remove_dir(sd);

  }

  static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)

  {

  	struct sysfs_addrm_cxt acxt;

  	struct rb_node *pos;

  	if (!dir_sd)

  		return;

  	pr_debug("sysfs %s: removing dir
  ", dir_sd->s_name);

  	sysfs_addrm_start(&acxt, dir_sd);

  	pos = rb_first(&dir_sd->s_dir.inode_tree);
  	while (pos) {
  		struct sysfs_dirent *sd = rb_entry(pos, struct sysfs_dirent, inode_node);
  		pos = rb_next(pos);

  		if (sysfs_type(sd) != SYSFS_DIR)

  			sysfs_remove_one(&acxt, sd);

  	}

  	sysfs_addrm_finish(&acxt);

  	remove_dir(dir_sd);

  }
  
  /**
   *	sysfs_remove_dir - remove an object's directory.
   *	@kobj:	object.
   *
   *	The only thing special about this is that we remove any files in
   *	the directory before we remove the directory, and we've inlined
   *	what used to be sysfs_rmdir() below, instead of calling separately.
   */
  
  void sysfs_remove_dir(struct kobject * kobj)
  {

  	struct sysfs_dirent *sd = kobj->sd;

  	spin_lock(&sysfs_assoc_lock);

  	kobj->sd = NULL;

  	spin_unlock(&sysfs_assoc_lock);

  	__sysfs_remove_dir(sd);

  }

  int sysfs_rename(struct sysfs_dirent *sd,

  	struct sysfs_dirent *new_parent_sd, const void *new_ns,
  	const char *new_name)

  {

  	const char *dup_name = NULL;

  	int error;

  	mutex_lock(&sysfs_mutex);

  	error = 0;

  	if ((sd->s_parent == new_parent_sd) && (sd->s_ns == new_ns) &&

  	    (strcmp(sd->s_name, new_name) == 0))

  		goto out;	/* nothing to rename */

  	error = -EEXIST;

  	if (sysfs_find_dirent(new_parent_sd, new_ns, new_name))

  		goto out;

  	/* rename sysfs_dirent */

  	if (strcmp(sd->s_name, new_name) != 0) {
  		error = -ENOMEM;
  		new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
  		if (!new_name)
  			goto out;
  
  		dup_name = sd->s_name;
  		sd->s_name = new_name;
  	}

  	/* Move to the appropriate place in the appropriate directories rbtree. */
  	sysfs_unlink_sibling(sd);
  	sysfs_get(new_parent_sd);
  	sysfs_put(sd->s_parent);

  	sd->s_ns = new_ns;

  	sd->s_parent = new_parent_sd;
  	sysfs_link_sibling(sd);

  	error = 0;

   out:

  	mutex_unlock(&sysfs_mutex);

  	kfree(dup_name);

  	return error;
  }

  int sysfs_rename_dir(struct kobject *kobj, const char *new_name)
  {

  	struct sysfs_dirent *parent_sd = kobj->sd->s_parent;
  	const void *new_ns = NULL;
  
  	if (sysfs_ns_type(parent_sd))
  		new_ns = kobj->ktype->namespace(kobj);
  
  	return sysfs_rename(kobj->sd, parent_sd, new_ns, new_name);

  }

  int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent_kobj)

  {

  	struct sysfs_dirent *sd = kobj->sd;
  	struct sysfs_dirent *new_parent_sd;

  	const void *new_ns = NULL;

  	BUG_ON(!sd->s_parent);

  	if (sysfs_ns_type(sd->s_parent))
  		new_ns = kobj->ktype->namespace(kobj);

  	new_parent_sd = new_parent_kobj && new_parent_kobj->sd ?

  		new_parent_kobj->sd : &sysfs_root;

  	return sysfs_rename(sd, new_parent_sd, new_ns, sd->s_name);

  }

  /* Relationship between s_mode and the DT_xxx types */
  static inline unsigned char dt_type(struct sysfs_dirent *sd)
  {
  	return (sd->s_mode >> 12) & 15;
  }

  static int sysfs_dir_release(struct inode *inode, struct file *filp)
  {
  	sysfs_put(filp->private_data);
  	return 0;
  }

  static struct sysfs_dirent *sysfs_dir_pos(const void *ns,
  	struct sysfs_dirent *parent_sd,	ino_t ino, struct sysfs_dirent *pos)

  {
  	if (pos) {
  		int valid = !(pos->s_flags & SYSFS_FLAG_REMOVED) &&
  			pos->s_parent == parent_sd &&
  			ino == pos->s_ino;
  		sysfs_put(pos);

  		if (!valid)
  			pos = NULL;

  	}

  	if (!pos && (ino > 1) && (ino < INT_MAX)) {

  		struct rb_node *p = parent_sd->s_dir.inode_tree.rb_node;
  		while (p) {
  #define node	rb_entry(p, struct sysfs_dirent, inode_node)
  			if (ino < node->s_ino) {
  				pos = node;
  				p = node->inode_node.rb_left;
  			} else if (ino > node->s_ino) {
  				p = node->inode_node.rb_right;
  			} else {
  				pos = node;
  				break;
  			}
  #undef node
  		}
  	}

  	while (pos && pos->s_ns != ns) {

  		struct rb_node *p = rb_next(&pos->inode_node);
  		if (!p)
  			pos = NULL;
  		else
  			pos = rb_entry(p, struct sysfs_dirent, inode_node);

  	}
  	return pos;
  }

  static struct sysfs_dirent *sysfs_dir_next_pos(const void *ns,
  	struct sysfs_dirent *parent_sd,	ino_t ino, struct sysfs_dirent *pos)

  {

  	pos = sysfs_dir_pos(ns, parent_sd, ino, pos);

  	if (pos) do {
  		struct rb_node *p = rb_next(&pos->inode_node);
  		if (!p)
  			pos = NULL;
  		else
  			pos = rb_entry(p, struct sysfs_dirent, inode_node);

  	} while (pos && pos->s_ns != ns);

  	return pos;
  }

  static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
  {

  	struct dentry *dentry = filp->f_path.dentry;

  	struct sysfs_dirent * parent_sd = dentry->d_fsdata;

  	struct sysfs_dirent *pos = filp->private_data;

  	enum kobj_ns_type type;
  	const void *ns;

  	ino_t ino;

  	type = sysfs_ns_type(parent_sd);
  	ns = sysfs_info(dentry->d_sb)->ns[type];

  	if (filp->f_pos == 0) {
  		ino = parent_sd->s_ino;
  		if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)

  			filp->f_pos++;

  	}
  	if (filp->f_pos == 1) {
  		if (parent_sd->s_parent)
  			ino = parent_sd->s_parent->s_ino;
  		else
  			ino = parent_sd->s_ino;
  		if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)

  			filp->f_pos++;

  	}

  	mutex_lock(&sysfs_mutex);

  	for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);

  	     pos;

  	     pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) {

  		const char * name;
  		unsigned int type;
  		int len, ret;
  
  		name = pos->s_name;
  		len = strlen(name);
  		ino = pos->s_ino;
  		type = dt_type(pos);
  		filp->f_pos = ino;
  		filp->private_data = sysfs_get(pos);

  		mutex_unlock(&sysfs_mutex);

  		ret = filldir(dirent, name, len, filp->f_pos, ino, type);
  		mutex_lock(&sysfs_mutex);
  		if (ret < 0)
  			break;
  	}
  	mutex_unlock(&sysfs_mutex);
  	if ((filp->f_pos > 1) && !pos) { /* EOF */
  		filp->f_pos = INT_MAX;
  		filp->private_data = NULL;

  	}

  	return 0;

  }

  const struct file_operations sysfs_dir_operations = {

  	.read		= generic_read_dir,
  	.readdir	= sysfs_readdir,

  	.release	= sysfs_dir_release,

  	.llseek		= generic_file_llseek,

  };