text: /************************************************************/
  /* ../linux-3.17/fs/configfs/inode.c */
  /************************************************************/
  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * inode.c - basic inode and dentry operations.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   *
   * Please see Documentation/filesystems/configfs/configfs.txt for more
   * information.
   */
  
  #undef DEBUG
  
  #include <linux/pagemap.h>
  #include <linux/namei.h>
  #include <linux/backing-dev.h>
  #include <linux/capability.h>
  #include <linux/sched.h>
  #include <linux/lockdep.h>
  #include <linux/slab.h>
  
  #include <linux/configfs.h>
  #include "configfs_internal.h"
  
  #ifdef CONFIG_LOCKDEP
  static struct lock_class_key default_group_class[MAX_LOCK_DEPTH];
  #endif
  
  static const struct address_space_operations configfs_aops = {
  	.readpage	= simple_readpage,
  	.write_begin	= simple_write_begin,
  	.write_end	= simple_write_end,
  };
  
  static struct backing_dev_info configfs_backing_dev_info = {
  	.name		= "configfs",
  	.ra_pages	= 0,	/* No readahead */
  	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
  };
  
  static const struct inode_operations configfs_inode_operations ={
  	.setattr	= configfs_setattr,
  };
  
  int configfs_setattr(struct dentry * dentry, struct iattr * iattr)
  {
  	struct inode * inode = dentry->d_inode;
  	struct configfs_dirent * sd = dentry->d_fsdata;
  	struct iattr * sd_iattr;
  	unsigned int ia_valid = iattr->ia_valid;
  	int error;
  
  	if (!sd)
  		return -EINVAL;
  
  	sd_iattr = sd->s_iattr;
  	if (!sd_iattr) {
  		/* setting attributes for the first time, allocate now */
  		sd_iattr = kzalloc(sizeof(struct iattr), GFP_KERNEL);
  		if (!sd_iattr)
  			return -ENOMEM;
  		/* assign default attributes */
  		sd_iattr->ia_mode = sd->s_mode;
  		sd_iattr->ia_uid = GLOBAL_ROOT_UID;
  		sd_iattr->ia_gid = GLOBAL_ROOT_GID;
  		sd_iattr->ia_atime = sd_iattr->ia_mtime = sd_iattr->ia_ctime = CURRENT_TIME;
  		sd->s_iattr = sd_iattr;
  	}
  	/* attributes were changed atleast once in past */
  
  	error = simple_setattr(dentry, iattr);
  	if (error)
  		return error;
  
  	if (ia_valid & ATTR_UID)
  		sd_iattr->ia_uid = iattr->ia_uid;
  	if (ia_valid & ATTR_GID)
  		sd_iattr->ia_gid = iattr->ia_gid;
  	if (ia_valid & ATTR_ATIME)
  		sd_iattr->ia_atime = timespec_trunc(iattr->ia_atime,
  						inode->i_sb->s_time_gran);
  	if (ia_valid & ATTR_MTIME)
  		sd_iattr->ia_mtime = timespec_trunc(iattr->ia_mtime,
  						inode->i_sb->s_time_gran);
  	if (ia_valid & ATTR_CTIME)
  		sd_iattr->ia_ctime = timespec_trunc(iattr->ia_ctime,
  						inode->i_sb->s_time_gran);
  	if (ia_valid & ATTR_MODE) {
  		umode_t mode = iattr->ia_mode;
  
  		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
  			mode &= ~S_ISGID;
  		sd_iattr->ia_mode = sd->s_mode = mode;
  	}
  
  	return error;
  }
  
  static inline void set_default_inode_attr(struct inode * inode, umode_t mode)
  {
  	inode->i_mode = mode;
  	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  }
  
  static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
  {
  	inode->i_mode = iattr->ia_mode;
  	inode->i_uid = iattr->ia_uid;
  	inode->i_gid = iattr->ia_gid;
  	inode->i_atime = iattr->ia_atime;
  	inode->i_mtime = iattr->ia_mtime;
  	inode->i_ctime = iattr->ia_ctime;
  }
  
  struct inode *configfs_new_inode(umode_t mode, struct configfs_dirent *sd,
  				 struct super_block *s)
  {
  	struct inode * inode = new_inode(s);
  	if (inode) {
  		inode->i_ino = get_next_ino();
  		inode->i_mapping->a_ops = &configfs_aops;
  		inode->i_mapping->backing_dev_info = &configfs_backing_dev_info;
  		inode->i_op = &configfs_inode_operations;
  
  		if (sd->s_iattr) {
  			/* sysfs_dirent has non-default attributes
  			 * get them for the new inode from persistent copy
  			 * in sysfs_dirent
  			 */
  			set_inode_attr(inode, sd->s_iattr);
  		} else
  			set_default_inode_attr(inode, mode);
  	}
  	return inode;
  }
  
  #ifdef CONFIG_LOCKDEP
  
  static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
  					  struct inode *inode)
  {
  	int depth = sd->s_depth;
  
  	if (depth > 0) {
  		if (depth <= ARRAY_SIZE(default_group_class)) {
  			lockdep_set_class(&inode->i_mutex,
  					  &default_group_class[depth - 1]);
  		} else {
  			/*
  			 * In practice the maximum level of locking depth is
  			 * already reached. Just inform about possible reasons.
  			 */
  			pr_info("Too many levels of inodes for the locking correctness validator.\n");
  			pr_info("Spurious warnings may appear.\n");
  		}
  	}
  }
  
  #else /* CONFIG_LOCKDEP */
  
  static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
  					  struct inode *inode)
  {
  }
  
  #endif /* CONFIG_LOCKDEP */
  
  int configfs_create(struct dentry * dentry, umode_t mode, int (*init)(struct inode *))
  {
  	int error = 0;
  	struct inode *inode = NULL;
  	struct configfs_dirent *sd;
  	struct inode *p_inode;
  
  	if (!dentry)
  		return -ENOENT;
  
  	if (dentry->d_inode)
  		return -EEXIST;
  
  	sd = dentry->d_fsdata;
  	inode = configfs_new_inode(mode, sd, dentry->d_sb);
  	if (!inode)
  		return -ENOMEM;
  
  	p_inode = dentry->d_parent->d_inode;
  	p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
  	configfs_set_inode_lock_class(sd, inode);
  
  	if (init) {
  		error = init(inode);
  		if (error) {
  			iput(inode);
  			return error;
  		}
  	}
  	d_instantiate(dentry, inode);
  	if (S_ISDIR(mode) || S_ISLNK(mode))
  		dget(dentry);  /* pin link and directory dentries in core */
  	return error;
  }
  
  /*
   * Get the name for corresponding element represented by the given configfs_dirent
   */
  const unsigned char * configfs_get_name(struct configfs_dirent *sd)
  {
  	struct configfs_attribute *attr;
  
  	BUG_ON(!sd || !sd->s_element);
  
  	/* These always have a dentry, so use that */
  	if (sd->s_type & (CONFIGFS_DIR | CONFIGFS_ITEM_LINK))
  		return sd->s_dentry->d_name.name;
  
  	if (sd->s_type & CONFIGFS_ITEM_ATTR) {
  		attr = sd->s_element;
  		return attr->ca_name;
  	}
  	return NULL;
  }
  
  
  /*
   * Unhashes the dentry corresponding to given configfs_dirent
   * Called with parent inode's i_mutex held.
   */
  void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
  {
  	struct dentry * dentry = sd->s_dentry;
  
  	if (dentry) {
  		spin_lock(&dentry->d_lock);
  		if (!(d_unhashed(dentry) && dentry->d_inode)) {
  			dget_dlock(dentry);
  			__d_drop(dentry);
  			spin_unlock(&dentry->d_lock);
  			simple_unlink(parent->d_inode, dentry);
  		} else
  			spin_unlock(&dentry->d_lock);
  	}
  }
  
  void configfs_hash_and_remove(struct dentry * dir, const char * name)
  {
  	struct configfs_dirent * sd;
  	struct configfs_dirent * parent_sd = dir->d_fsdata;
  
  	if (dir->d_inode == NULL)
  		/* no inode means this hasn't been made visible yet */
  		return;
  
  	mutex_lock(&dir->d_inode->i_mutex);
  	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
  		if (!sd->s_element)
  			continue;
  		if (!strcmp(configfs_get_name(sd), name)) {
  			spin_lock(&configfs_dirent_lock);
  			list_del_init(&sd->s_sibling);
  			spin_unlock(&configfs_dirent_lock);
  			configfs_drop_dentry(sd, dir);
  			configfs_put(sd);
  			break;
  		}
  	}
  	mutex_unlock(&dir->d_inode->i_mutex);
  }
  
  int __init configfs_inode_init(void)
  {
  	return bdi_init(&configfs_backing_dev_info);
  }
  
  void configfs_inode_exit(void)
  {
  	bdi_destroy(&configfs_backing_dev_info);
  }
  /************************************************************/
  /* ../linux-3.17/fs/configfs/file.c */
  /************************************************************/
  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * file.c - operations for regular (text) files.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   */
  
  #include <linux/fs.h>
  #include <linux/module.h>
  // #include <linux/slab.h>
  #include <linux/mutex.h>
  #include <asm/uaccess.h>
  
  // #include <linux/configfs.h>
  // #include "configfs_internal.h"
  
  /*
   * A simple attribute can only be 4096 characters.  Why 4k?  Because the
   * original code limited it to PAGE_SIZE.  That's a bad idea, though,
   * because an attribute of 16k on ia64 won't work on x86.  So we limit to
   * 4k, our minimum common page size.
   */
  #define SIMPLE_ATTR_SIZE 4096
  
  struct configfs_buffer {
  	size_t			count;
  	loff_t			pos;
  	char			* page;
  	struct configfs_item_operations	* ops;
  	struct mutex		mutex;
  	int			needs_read_fill;
  };
  
  
  /**
   *	fill_read_buffer - allocate and fill buffer from item.
   *	@dentry:	dentry pointer.
   *	@buffer:	data buffer for file.
   *
   *	Allocate @buffer->page, if it hasn't been already, then call the
   *	config_item's show() method to fill the buffer with this attribute's
   *	data.
   *	This is called only once, on the file's first read.
   */
  static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
  {
  	struct configfs_attribute * attr = to_attr(dentry);
  	struct config_item * item = to_item(dentry->d_parent);
  	struct configfs_item_operations * ops = buffer->ops;
  	int ret = 0;
  	ssize_t count;
  
  	if (!buffer->page)
  		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
  	if (!buffer->page)
  		return -ENOMEM;
  
  	count = ops->show_attribute(item,attr,buffer->page);
  	buffer->needs_read_fill = 0;
  	BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
  	if (count >= 0)
  		buffer->count = count;
  	else
  		ret = count;
  	return ret;
  }
  
  /**
   *	configfs_read_file - read an attribute.
   *	@file:	file pointer.
   *	@buf:	buffer to fill.
   *	@count:	number of bytes to read.
   *	@ppos:	starting offset in file.
   *
   *	Userspace wants to read an attribute file. The attribute descriptor
   *	is in the file's ->d_fsdata. The target item is in the directory's
   *	->d_fsdata.
   *
   *	We call fill_read_buffer() to allocate and fill the buffer from the
   *	item's show() method exactly once (if the read is happening from
   *	the beginning of the file). That should fill the entire buffer with
   *	all the data the item has to offer for that attribute.
   *	We then call flush_read_buffer() to copy the buffer to userspace
   *	in the increments specified.
   */
  
  static ssize_t
  configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
  {
  	struct configfs_buffer * buffer = file->private_data;
  	ssize_t retval = 0;
  
  	mutex_lock(&buffer->mutex);
  	if (buffer->needs_read_fill) {
  		if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
  			goto out;
  	}
  	pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
  		 __func__, count, *ppos, buffer->page);
  	retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
  					 buffer->count);
  out:
  	mutex_unlock(&buffer->mutex);
  	return retval;
  }
  
  
  /**
   *	fill_write_buffer - copy buffer from userspace.
   *	@buffer:	data buffer for file.
   *	@buf:		data from user.
   *	@count:		number of bytes in @userbuf.
   *
   *	Allocate @buffer->page if it hasn't been already, then
   *	copy the user-supplied buffer into it.
   */
  
  static int
  fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
  {
  	int error;
  
  	if (!buffer->page)
  		buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
  	if (!buffer->page)
  		return -ENOMEM;
  
  	if (count >= SIMPLE_ATTR_SIZE)
  		count = SIMPLE_ATTR_SIZE - 1;
  	error = copy_from_user(buffer->page,buf,count);
  	buffer->needs_read_fill = 1;
  	/* if buf is assumed to contain a string, terminate it by \0,
  	 * so e.g. sscanf() can scan the string easily */
  	buffer->page[count] = 0;
  	return error ? -EFAULT : count;
  }
  
  
  /**
   *	flush_write_buffer - push buffer to config_item.
   *	@dentry:	dentry to the attribute
   *	@buffer:	data buffer for file.
   *	@count:		number of bytes
   *
   *	Get the correct pointers for the config_item and the attribute we're
   *	dealing with, then call the store() method for the attribute,
   *	passing the buffer that we acquired in fill_write_buffer().
   */
  
  static int
  flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
  {
  	struct configfs_attribute * attr = to_attr(dentry);
  	struct config_item * item = to_item(dentry->d_parent);
  	struct configfs_item_operations * ops = buffer->ops;
  
  	return ops->store_attribute(item,attr,buffer->page,count);
  }
  
  
  /**
   *	configfs_write_file - write an attribute.
   *	@file:	file pointer
   *	@buf:	data to write
   *	@count:	number of bytes
   *	@ppos:	starting offset
   *
   *	Similar to configfs_read_file(), though working in the opposite direction.
   *	We allocate and fill the data from the user in fill_write_buffer(),
   *	then push it to the config_item in flush_write_buffer().
   *	There is no easy way for us to know if userspace is only doing a partial
   *	write, so we don't support them. We expect the entire buffer to come
   *	on the first write.
   *	Hint: if you're writing a value, first read the file, modify only the
   *	the value you're changing, then write entire buffer back.
   */
  
  static ssize_t
  configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
  {
  	struct configfs_buffer * buffer = file->private_data;
  	ssize_t len;
  
  	mutex_lock(&buffer->mutex);
  	len = fill_write_buffer(buffer, buf, count);
  	if (len > 0)
  		len = flush_write_buffer(file->f_path.dentry, buffer, len);
  	if (len > 0)
  		*ppos += len;
  	mutex_unlock(&buffer->mutex);
  	return len;
  }
  
  static int check_perm(struct inode * inode, struct file * file)
  {
  	struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
  	struct configfs_attribute * attr = to_attr(file->f_path.dentry);
  	struct configfs_buffer * buffer;
  	struct configfs_item_operations * ops = NULL;
  	int error = 0;
  
  	if (!item || !attr)
  		goto Einval;
  
  	/* Grab the module reference for this attribute if we have one */
  	if (!try_module_get(attr->ca_owner)) {
  		error = -ENODEV;
  		goto Done;
  	}
  
  	if (item->ci_type)
  		ops = item->ci_type->ct_item_ops;
  	else
  		goto Eaccess;
  
  	/* File needs write support.
  	 * The inode's perms must say it's ok,
  	 * and we must have a store method.
  	 */
  	if (file->f_mode & FMODE_WRITE) {
  
  		if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute)
  			goto Eaccess;
  
  	}
  
  	/* File needs read support.
  	 * The inode's perms must say it's ok, and we there
  	 * must be a show method for it.
  	 */
  	if (file->f_mode & FMODE_READ) {
  		if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute)
  			goto Eaccess;
  	}
  
  	/* No error? Great, allocate a buffer for the file, and store it
  	 * it in file->private_data for easy access.
  	 */
  	buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
  	if (!buffer) {
  		error = -ENOMEM;
  		goto Enomem;
  	}
  	mutex_init(&buffer->mutex);
  	buffer->needs_read_fill = 1;
  	buffer->ops = ops;
  	file->private_data = buffer;
  	goto Done;
  
   Einval:
  	error = -EINVAL;
  	goto Done;
   Eaccess:
  	error = -EACCES;
   Enomem:
  	module_put(attr->ca_owner);
   Done:
  	if (error && item)
  		config_item_put(item);
  	return error;
  }
  
  static int configfs_open_file(struct inode * inode, struct file * filp)
  {
  	return check_perm(inode,filp);
  }
  
  static int configfs_release(struct inode * inode, struct file * filp)
  {
  	struct config_item * item = to_item(filp->f_path.dentry->d_parent);
  	struct configfs_attribute * attr = to_attr(filp->f_path.dentry);
  	struct module * owner = attr->ca_owner;
  	struct configfs_buffer * buffer = filp->private_data;
  
  	if (item)
  		config_item_put(item);
  	/* After this point, attr should not be accessed. */
  	module_put(owner);
  
  	if (buffer) {
  		if (buffer->page)
  			free_page((unsigned long)buffer->page);
  		mutex_destroy(&buffer->mutex);
  		kfree(buffer);
  	}
  	return 0;
  }
  
  const struct file_operations configfs_file_operations = {
  	.read		= configfs_read_file,
  	.write		= configfs_write_file,
  	.llseek		= generic_file_llseek,
  	.open		= configfs_open_file,
  	.release	= configfs_release,
  };
  
  
  int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type)
  {
  	struct configfs_dirent * parent_sd = dir->d_fsdata;
  	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
  	int error = 0;
  
  	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_NORMAL);
  	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
  	mutex_unlock(&dir->d_inode->i_mutex);
  
  	return error;
  }
  
  
  /**
   *	configfs_create_file - create an attribute file for an item.
   *	@item:	item we're creating for.
   *	@attr:	atrribute descriptor.
   */
  
  int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
  {
  	BUG_ON(!item || !item->ci_dentry || !attr);
  
  	return configfs_add_file(item->ci_dentry, attr,
  				 CONFIGFS_ITEM_ATTR);
  }
  /************************************************************/
  /* ../linux-3.17/fs/configfs/dir.c */
  /************************************************************/
  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * dir.c - Operations for configfs directories.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   */
  
  #undef DEBUG
  
  // #include <linux/fs.h>
  #include <linux/mount.h>
  // #include <linux/module.h>
  // #include <linux/slab.h>
  #include <linux/err.h>
  
  // #include <linux/configfs.h>
  // #include "configfs_internal.h"
  
  DECLARE_RWSEM(configfs_rename_sem);
  /*
   * Protects mutations of configfs_dirent linkage together with proper i_mutex
   * Also protects mutations of symlinks linkage to target configfs_dirent
   * Mutators of configfs_dirent linkage must *both* have the proper inode locked
   * and configfs_dirent_lock locked, in that order.
   * This allows one to safely traverse configfs_dirent trees and symlinks without
   * having to lock inodes.
   *
   * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
   * unlocked is not reliable unless in detach_groups() called from
   * rmdir()/unregister() and from configfs_attach_group()
   */
  DEFINE_SPINLOCK(configfs_dirent_lock);
  
  static void configfs_d_iput(struct dentry * dentry,
  			    struct inode * inode)
  {
  	struct configfs_dirent *sd = dentry->d_fsdata;
  
  	if (sd) {
  		/* Coordinate with configfs_readdir */
  		spin_lock(&configfs_dirent_lock);
  		/* Coordinate with configfs_attach_attr where will increase
  		 * sd->s_count and update sd->s_dentry to new allocated one.
  		 * Only set sd->dentry to null when this dentry is the only
  		 * sd owner.
  		 * If not do so, configfs_d_iput may run just after
  		 * configfs_attach_attr and set sd->s_dentry to null
  		 * even it's still in use.
  		 */
  		if (atomic_read(&sd->s_count) <= 2)
  			sd->s_dentry = NULL;
  
  		spin_unlock(&configfs_dirent_lock);
  		configfs_put(sd);
  	}
  	iput(inode);
  }
  
  const struct dentry_operations configfs_dentry_ops = {
  	.d_iput		= configfs_d_iput,
  	.d_delete	= always_delete_dentry,
  };
  
  #ifdef CONFIG_LOCKDEP
  
  /*
   * Helpers to make lockdep happy with our recursive locking of default groups'
   * inodes (see configfs_attach_group() and configfs_detach_group()).
   * We put default groups i_mutexes in separate classes according to their depth
   * from the youngest non-default group ancestor.
   *
   * For a non-default group A having default groups A/B, A/C, and A/C/D, default
   * groups A/B and A/C will have their inode's mutex in class
   * default_group_class[0], and default group A/C/D will be in
   * default_group_class[1].
   *
   * The lock classes are declared and assigned in inode.c, according to the
   * s_depth value.
   * The s_depth value is initialized to -1, adjusted to >= 0 when attaching
   * default groups, and reset to -1 when all default groups are attached. During
   * attachment, if configfs_create() sees s_depth > 0, the lock class of the new
   * inode's mutex is set to default_group_class[s_depth - 1].
   */
  
  static void configfs_init_dirent_depth(struct configfs_dirent *sd)
  {
  	sd->s_depth = -1;
  }
  
  static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
  					  struct configfs_dirent *sd)
  {
  	int parent_depth = parent_sd->s_depth;
  
  	if (parent_depth >= 0)
  		sd->s_depth = parent_depth + 1;
  }
  
  static void
  configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
  {
  	/*
  	 * item's i_mutex class is already setup, so s_depth is now only
  	 * used to set new sub-directories s_depth, which is always done
  	 * with item's i_mutex locked.
  	 */
  	/*
  	 *  sd->s_depth == -1 iff we are a non default group.
  	 *  else (we are a default group) sd->s_depth > 0 (see
  	 *  create_dir()).
  	 */
  	if (sd->s_depth == -1)
  		/*
  		 * We are a non default group and we are going to create
  		 * default groups.
  		 */
  		sd->s_depth = 0;
  }
  
  static void
  configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
  {
  	/* We will not create default groups anymore. */
  	sd->s_depth = -1;
  }
  
  #else /* CONFIG_LOCKDEP */
  
  static void configfs_init_dirent_depth(struct configfs_dirent *sd)
  {
  }
  
  static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
  					  struct configfs_dirent *sd)
  {
  }
  
  static void
  configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
  {
  }
  
  static void
  configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
  {
  }
  
  #endif /* CONFIG_LOCKDEP */
  
  /*
   * Allocates a new configfs_dirent and links it to the parent configfs_dirent
   */
  static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
  						   void *element, int type)
  {
  	struct configfs_dirent * sd;
  
  	sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
  	if (!sd)
  		return ERR_PTR(-ENOMEM);
  
  	atomic_set(&sd->s_count, 1);
  	INIT_LIST_HEAD(&sd->s_links);
  	INIT_LIST_HEAD(&sd->s_children);
  	sd->s_element = element;
  	sd->s_type = type;
  	configfs_init_dirent_depth(sd);
  	spin_lock(&configfs_dirent_lock);
  	if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
  		spin_unlock(&configfs_dirent_lock);
  		kmem_cache_free(configfs_dir_cachep, sd);
  		return ERR_PTR(-ENOENT);
  	}
  	list_add(&sd->s_sibling, &parent_sd->s_children);
  	spin_unlock(&configfs_dirent_lock);
  
  	return sd;
  }
  
  /*
   *
   * Return -EEXIST if there is already a configfs element with the same
   * name for the same parent.
   *
   * called with parent inode's i_mutex held
   */
  static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
  				  const unsigned char *new)
  {
  	struct configfs_dirent * sd;
  
  	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
  		if (sd->s_element) {
  			const unsigned char *existing = configfs_get_name(sd);
  			if (strcmp(existing, new))
  				continue;
  			else
  				return -EEXIST;
  		}
  	}
  
  	return 0;
  }
  
  
  int configfs_make_dirent(struct configfs_dirent * parent_sd,
  			 struct dentry * dentry, void * element,
  			 umode_t mode, int type)
  {
  	struct configfs_dirent * sd;
  
  	sd = configfs_new_dirent(parent_sd, element, type);
  	if (IS_ERR(sd))
  		return PTR_ERR(sd);
  
  	sd->s_mode = mode;
  	sd->s_dentry = dentry;
  	if (dentry)
  		dentry->d_fsdata = configfs_get(sd);
  
  	return 0;
  }
  
  static int init_dir(struct inode * inode)
  {
  	inode->i_op = &configfs_dir_inode_operations;
  	inode->i_fop = &configfs_dir_operations;
  
  	/* directory inodes start off with i_nlink == 2 (for "." entry) */
  	inc_nlink(inode);
  	return 0;
  }
  
  static int configfs_init_file(struct inode * inode)
  {
  	inode->i_size = PAGE_SIZE;
  	inode->i_fop = &configfs_file_operations;
  	return 0;
  }
  
  static int init_symlink(struct inode * inode)
  {
  	inode->i_op = &configfs_symlink_inode_operations;
  	return 0;
  }
  
  static int create_dir(struct config_item *k, struct dentry *d)
  {
  	int error;
  	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
  	struct dentry *p = d->d_parent;
  
  	BUG_ON(!k);
  
  	error = configfs_dirent_exists(p->d_fsdata, d->d_name.name);
  	if (!error)
  		error = configfs_make_dirent(p->d_fsdata, d, k, mode,
  					     CONFIGFS_DIR | CONFIGFS_USET_CREATING);
  	if (!error) {
  		configfs_set_dir_dirent_depth(p->d_fsdata, d->d_fsdata);
  		error = configfs_create(d, mode, init_dir);
  		if (!error) {
  			inc_nlink(p->d_inode);
  		} else {
  			struct configfs_dirent *sd = d->d_fsdata;
  			if (sd) {
  				spin_lock(&configfs_dirent_lock);
  				list_del_init(&sd->s_sibling);
  				spin_unlock(&configfs_dirent_lock);
  				configfs_put(sd);
  			}
  		}
  	}
  	return error;
  }
  
  
  /**
   *	configfs_create_dir - create a directory for an config_item.
   *	@item:		config_itemwe're creating directory for.
   *	@dentry:	config_item's dentry.
   *
   *	Note: user-created entries won't be allowed under this new directory
   *	until it is validated by configfs_dir_set_ready()
   */
  
  static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
  {
  	int error = create_dir(item, dentry);
  	if (!error)
  		item->ci_dentry = dentry;
  	return error;
  }
  
  /*
   * Allow userspace to create new entries under a new directory created with
   * configfs_create_dir(), and under all of its chidlren directories recursively.
   * @sd		configfs_dirent of the new directory to validate
   *
   * Caller must hold configfs_dirent_lock.
   */
  static void configfs_dir_set_ready(struct configfs_dirent *sd)
  {
  	struct configfs_dirent *child_sd;
  
  	sd->s_type &= ~CONFIGFS_USET_CREATING;
  	list_for_each_entry(child_sd, &sd->s_children, s_sibling)
  		if (child_sd->s_type & CONFIGFS_USET_CREATING)
  			configfs_dir_set_ready(child_sd);
  }
  
  /*
   * Check that a directory does not belong to a directory hierarchy being
   * attached and not validated yet.
   * @sd		configfs_dirent of the directory to check
   *
   * @return	non-zero iff the directory was validated
   *
   * Note: takes configfs_dirent_lock, so the result may change from false to true
   * in two consecutive calls, but never from true to false.
   */
  int configfs_dirent_is_ready(struct configfs_dirent *sd)
  {
  	int ret;
  
  	spin_lock(&configfs_dirent_lock);
  	ret = !(sd->s_type & CONFIGFS_USET_CREATING);
  	spin_unlock(&configfs_dirent_lock);
  
  	return ret;
  }
  
  int configfs_create_link(struct configfs_symlink *sl,
  			 struct dentry *parent,
  			 struct dentry *dentry)
  {
  	int err = 0;
  	umode_t mode = S_IFLNK | S_IRWXUGO;
  
  	err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
  				   CONFIGFS_ITEM_LINK);
  	if (!err) {
  		err = configfs_create(dentry, mode, init_symlink);
  		if (err) {
  			struct configfs_dirent *sd = dentry->d_fsdata;
  			if (sd) {
  				spin_lock(&configfs_dirent_lock);
  				list_del_init(&sd->s_sibling);
  				spin_unlock(&configfs_dirent_lock);
  				configfs_put(sd);
  			}
  		}
  	}
  	return err;
  }
  
  static void remove_dir(struct dentry * d)
  {
  	struct dentry * parent = dget(d->d_parent);
  	struct configfs_dirent * sd;
  
  	sd = d->d_fsdata;
  	spin_lock(&configfs_dirent_lock);
  	list_del_init(&sd->s_sibling);
  	spin_unlock(&configfs_dirent_lock);
  	configfs_put(sd);
  	if (d->d_inode)
  		simple_rmdir(parent->d_inode,d);
  
  	pr_debug(" o %s removing done (%d)\n",d->d_name.name, d_count(d));
  
  	dput(parent);
  }
  
  /**
   * configfs_remove_dir - remove an config_item's directory.
   * @item:	config_item we're removing.
   *
   * 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 configfs_rmdir() below, instead of calling separately.
   *
   * Caller holds the mutex of the item's inode
   */
  
  static void configfs_remove_dir(struct config_item * item)
  {
  	struct dentry * dentry = dget(item->ci_dentry);
  
  	if (!dentry)
  		return;
  
  	remove_dir(dentry);
  	/**
  	 * Drop reference from dget() on entrance.
  	 */
  	dput(dentry);
  }
  
  
  /* attaches attribute's configfs_dirent to the dentry corresponding to the
   * attribute file
   */
  static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
  {
  	struct configfs_attribute * attr = sd->s_element;
  	int error;
  
  	spin_lock(&configfs_dirent_lock);
  	dentry->d_fsdata = configfs_get(sd);
  	sd->s_dentry = dentry;
  	spin_unlock(&configfs_dirent_lock);
  
  	error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
  				configfs_init_file);
  	if (error) {
  		configfs_put(sd);
  		return error;
  	}
  
  	d_rehash(dentry);
  
  	return 0;
  }
  
  static struct dentry * configfs_lookup(struct inode *dir,
  				       struct dentry *dentry,
  				       unsigned int flags)
  {
  	struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
  	struct configfs_dirent * sd;
  	int found = 0;
  	int err;
  
  	/*
  	 * Fake invisibility if dir belongs to a group/default groups hierarchy
  	 * being attached
  	 *
  	 * This forbids userspace to read/write attributes of items which may
  	 * not complete their initialization, since the dentries of the
  	 * attributes won't be instantiated.
  	 */
  	err = -ENOENT;
  	if (!configfs_dirent_is_ready(parent_sd))
  		goto out;
  
  	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
  		if (sd->s_type & CONFIGFS_NOT_PINNED) {
  			const unsigned char * name = configfs_get_name(sd);
  
  			if (strcmp(name, dentry->d_name.name))
  				continue;
  
  			found = 1;
  			err = configfs_attach_attr(sd, dentry);
  			break;
  		}
  	}
  
  	if (!found) {
  		/*
  		 * If it doesn't exist and it isn't a NOT_PINNED item,
  		 * it must be negative.
  		 */
  		if (dentry->d_name.len > NAME_MAX)
  			return ERR_PTR(-ENAMETOOLONG);
  		d_add(dentry, NULL);
  		return NULL;
  	}
  
  out:
  	return ERR_PTR(err);
  }
  
  /*
   * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
   * attributes and are removed by rmdir().  We recurse, setting
   * CONFIGFS_USET_DROPPING on all children that are candidates for
   * default detach.
   * If there is an error, the caller will reset the flags via
   * configfs_detach_rollback().
   */
  static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex)
  {
  	struct configfs_dirent *parent_sd = dentry->d_fsdata;
  	struct configfs_dirent *sd;
  	int ret;
  
  	/* Mark that we're trying to drop the group */
  	parent_sd->s_type |= CONFIGFS_USET_DROPPING;
  
  	ret = -EBUSY;
  	if (!list_empty(&parent_sd->s_links))
  		goto out;
  
  	ret = 0;
  	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
  		if (!sd->s_element ||
  		    (sd->s_type & CONFIGFS_NOT_PINNED))
  			continue;
  		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
  			/* Abort if racing with mkdir() */
  			if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
  				if (wait_mutex)
  					*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
  				return -EAGAIN;
  			}
  
  			/*
  			 * Yup, recursive.  If there's a problem, blame
  			 * deep nesting of default_groups
  			 */
  			ret = configfs_detach_prep(sd->s_dentry, wait_mutex);
  			if (!ret)
  				continue;
  		} else
  			ret = -ENOTEMPTY;
  
  		break;
  	}
  
  out:
  	return ret;
  }
  
  /*
   * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
   * set.
   */
  static void configfs_detach_rollback(struct dentry *dentry)
  {
  	struct configfs_dirent *parent_sd = dentry->d_fsdata;
  	struct configfs_dirent *sd;
  
  	parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
  
  	list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
  		if (sd->s_type & CONFIGFS_USET_DEFAULT)
  			configfs_detach_rollback(sd->s_dentry);
  }
  
  static void detach_attrs(struct config_item * item)
  {
  	struct dentry * dentry = dget(item->ci_dentry);
  	struct configfs_dirent * parent_sd;
  	struct configfs_dirent * sd, * tmp;
  
  	if (!dentry)
  		return;
  
  	pr_debug("configfs %s: dropping attrs for  dir\n",
  		 dentry->d_name.name);
  
  	parent_sd = dentry->d_fsdata;
  	list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
  		if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
  			continue;
  		spin_lock(&configfs_dirent_lock);
  		list_del_init(&sd->s_sibling);
  		spin_unlock(&configfs_dirent_lock);
  		configfs_drop_dentry(sd, dentry);
  		configfs_put(sd);
  	}
  
  	/**
  	 * Drop reference from dget() on entrance.
  	 */
  	dput(dentry);
  }
  
  static int populate_attrs(struct config_item *item)
  {
  	struct config_item_type *t = item->ci_type;
  	struct configfs_attribute *attr;
  	int error = 0;
  	int i;
  
  	if (!t)
  		return -EINVAL;
  	if (t->ct_attrs) {
  		for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
  			if ((error = configfs_create_file(item, attr)))
  				break;
  		}
  	}
  
  	if (error)
  		detach_attrs(item);
  
  	return error;
  }
  
  static int configfs_attach_group(struct config_item *parent_item,
  				 struct config_item *item,
  				 struct dentry *dentry);
  static void configfs_detach_group(struct config_item *item);
  
  static void detach_groups(struct config_group *group)
  {
  	struct dentry * dentry = dget(group->cg_item.ci_dentry);
  	struct dentry *child;
  	struct configfs_dirent *parent_sd;
  	struct configfs_dirent *sd, *tmp;
  
  	if (!dentry)
  		return;
  
  	parent_sd = dentry->d_fsdata;
  	list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
  		if (!sd->s_element ||
  		    !(sd->s_type & CONFIGFS_USET_DEFAULT))
  			continue;
  
  		child = sd->s_dentry;
  
  		mutex_lock(&child->d_inode->i_mutex);
  
  		configfs_detach_group(sd->s_element);
  		child->d_inode->i_flags |= S_DEAD;
  		dont_mount(child);
  
  		mutex_unlock(&child->d_inode->i_mutex);
  
  		d_delete(child);
  		dput(child);
  	}
  
  	/**
  	 * Drop reference from dget() on entrance.
  	 */
  	dput(dentry);
  }
  
  /*
   * This fakes mkdir(2) on a default_groups[] entry.  It
   * creates a dentry, attachs it, and then does fixup
   * on the sd->s_type.
   *
   * We could, perhaps, tweak our parent's ->mkdir for a minute and
   * try using vfs_mkdir.  Just a thought.
   */
  static int create_default_group(struct config_group *parent_group,
  				struct config_group *group)
  {
  	int ret;
  	struct configfs_dirent *sd;
  	/* We trust the caller holds a reference to parent */
  	struct dentry *child, *parent = parent_group->cg_item.ci_dentry;
  
  	if (!group->cg_item.ci_name)
  		group->cg_item.ci_name = group->cg_item.ci_namebuf;
  
  	ret = -ENOMEM;
  	child = d_alloc_name(parent, group->cg_item.ci_name);
  	if (child) {
  		d_add(child, NULL);
  
  		ret = configfs_attach_group(&parent_group->cg_item,
  					    &group->cg_item, child);
  		if (!ret) {
  			sd = child->d_fsdata;
  			sd->s_type |= CONFIGFS_USET_DEFAULT;
  		} else {
  			BUG_ON(child->d_inode);
  			d_drop(child);
  			dput(child);
  		}
  	}
  
  	return ret;
  }
  
  static int populate_groups(struct config_group *group)
  {
  	struct config_group *new_group;
  	int ret = 0;
  	int i;
  
  	if (group->default_groups) {
  		for (i = 0; group->default_groups[i]; i++) {
  			new_group = group->default_groups[i];
  
  			ret = create_default_group(group, new_group);
  			if (ret) {
  				detach_groups(group);
  				break;
  			}
  		}
  	}
  
  	return ret;
  }
  
  /*
   * All of link_obj/unlink_obj/link_group/unlink_group require that
   * subsys->su_mutex is held.
   */
  
  static void unlink_obj(struct config_item *item)
  {
  	struct config_group *group;
  
  	group = item->ci_group;
  	if (group) {
  		list_del_init(&item->ci_entry);
  
  		item->ci_group = NULL;
  		item->ci_parent = NULL;
  
  		/* Drop the reference for ci_entry */
  		config_item_put(item);
  
  		/* Drop the reference for ci_parent */
  		config_group_put(group);
  	}
  }
  
  static void link_obj(struct config_item *parent_item, struct config_item *item)
  {
  	/*
  	 * Parent seems redundant with group, but it makes certain
  	 * traversals much nicer.
  	 */
  	item->ci_parent = parent_item;
  
  	/*
  	 * We hold a reference on the parent for the child's ci_parent
  	 * link.
  	 */
  	item->ci_group = config_group_get(to_config_group(parent_item));
  	list_add_tail(&item->ci_entry, &item->ci_group->cg_children);
  
  	/*
  	 * We hold a reference on the child for ci_entry on the parent's
  	 * cg_children
  	 */
  	config_item_get(item);
  }
  
  static void unlink_group(struct config_group *group)
  {
  	int i;
  	struct config_group *new_group;
  
  	if (group->default_groups) {
  		for (i = 0; group->default_groups[i]; i++) {
  			new_group = group->default_groups[i];
  			unlink_group(new_group);
  		}
  	}
  
  	group->cg_subsys = NULL;
  	unlink_obj(&group->cg_item);
  }
  
  static void link_group(struct config_group *parent_group, struct config_group *group)
  {
  	int i;
  	struct config_group *new_group;
  	struct configfs_subsystem *subsys = NULL; /* gcc is a turd */
  
  	link_obj(&parent_group->cg_item, &group->cg_item);
  
  	if (parent_group->cg_subsys)
  		subsys = parent_group->cg_subsys;
  	else if (configfs_is_root(&parent_group->cg_item))
  		subsys = to_configfs_subsystem(group);
  	else
  		BUG();
  	group->cg_subsys = subsys;
  
  	if (group->default_groups) {
  		for (i = 0; group->default_groups[i]; i++) {
  			new_group = group->default_groups[i];
  			link_group(group, new_group);
  		}
  	}
  }
  
  /*
   * The goal is that configfs_attach_item() (and
   * configfs_attach_group()) can be called from either the VFS or this
   * module.  That is, they assume that the items have been created,
   * the dentry allocated, and the dcache is all ready to go.
   *
   * If they fail, they must clean up after themselves as if they
   * had never been called.  The caller (VFS or local function) will
   * handle cleaning up the dcache bits.
   *
   * configfs_detach_group() and configfs_detach_item() behave similarly on
   * the way out.  They assume that the proper semaphores are held, they
   * clean up the configfs items, and they expect their callers will
   * handle the dcache bits.
   */
  static int configfs_attach_item(struct config_item *parent_item,
  				struct config_item *item,
  				struct dentry *dentry)
  {
  	int ret;
  
  	ret = configfs_create_dir(item, dentry);
  	if (!ret) {
  		ret = populate_attrs(item);
  		if (ret) {
  			/*
  			 * We are going to remove an inode and its dentry but
  			 * the VFS may already have hit and used them. Thus,
  			 * we must lock them as rmdir() would.
  			 */
  			mutex_lock(&dentry->d_inode->i_mutex);
  			configfs_remove_dir(item);
  			dentry->d_inode->i_flags |= S_DEAD;
  			dont_mount(dentry);
  			mutex_unlock(&dentry->d_inode->i_mutex);
  			d_delete(dentry);
  		}
  	}
  
  	return ret;
  }
  
  /* Caller holds the mutex of the item's inode */
  static void configfs_detach_item(struct config_item *item)
  {
  	detach_attrs(item);
  	configfs_remove_dir(item);
  }
  
  static int configfs_attach_group(struct config_item *parent_item,
  				 struct config_item *item,
  				 struct dentry *dentry)
  {
  	int ret;
  	struct configfs_dirent *sd;
  
  	ret = configfs_attach_item(parent_item, item, dentry);
  	if (!ret) {
  		sd = dentry->d_fsdata;
  		sd->s_type |= CONFIGFS_USET_DIR;
  
  		/*
  		 * FYI, we're faking mkdir in populate_groups()
  		 * We must lock the group's inode to avoid races with the VFS
  		 * which can already hit the inode and try to add/remove entries
  		 * under it.
  		 *
  		 * We must also lock the inode to remove it safely in case of
  		 * error, as rmdir() would.
  		 */
  		mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
  		configfs_adjust_dir_dirent_depth_before_populate(sd);
  		ret = populate_groups(to_config_group(item));
  		if (ret) {
  			configfs_detach_item(item);
  			dentry->d_inode->i_flags |= S_DEAD;
  			dont_mount(dentry);
  		}
  		configfs_adjust_dir_dirent_depth_after_populate(sd);
  		mutex_unlock(&dentry->d_inode->i_mutex);
  		if (ret)
  			d_delete(dentry);
  	}
  
  	return ret;
  }
  
  /* Caller holds the mutex of the group's inode */
  static void configfs_detach_group(struct config_item *item)
  {
  	detach_groups(to_config_group(item));
  	configfs_detach_item(item);
  }
  
  /*
   * After the item has been detached from the filesystem view, we are
   * ready to tear it out of the hierarchy.  Notify the client before
   * we do that so they can perform any cleanup that requires
   * navigating the hierarchy.  A client does not need to provide this
   * callback.  The subsystem semaphore MUST be held by the caller, and
   * references must be valid for both items.  It also assumes the
   * caller has validated ci_type.
   */
  static void client_disconnect_notify(struct config_item *parent_item,
  				     struct config_item *item)
  {
  	struct config_item_type *type;
  
  	type = parent_item->ci_type;
  	BUG_ON(!type);
  
  	if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)
  		type->ct_group_ops->disconnect_notify(to_config_group(parent_item),
  						      item);
  }
  
  /*
   * Drop the initial reference from make_item()/make_group()
   * This function assumes that reference is held on item
   * and that item holds a valid reference to the parent.  Also, it
   * assumes the caller has validated ci_type.
   */
  static void client_drop_item(struct config_item *parent_item,
  			     struct config_item *item)
  {
  	struct config_item_type *type;
  
  	type = parent_item->ci_type;
  	BUG_ON(!type);
  
  	/*
  	 * If ->drop_item() exists, it is responsible for the
  	 * config_item_put().
  	 */
  	if (type->ct_group_ops && type->ct_group_ops->drop_item)
  		type->ct_group_ops->drop_item(to_config_group(parent_item),
  					      item);
  	else
  		config_item_put(item);
  }
  
  #ifdef DEBUG
  static void configfs_dump_one(struct configfs_dirent *sd, int level)
  {
  	pr_info("%*s\"%s\":\n", level, " ", configfs_get_name(sd));
  
  #define type_print(_type) if (sd->s_type & _type) pr_info("%*s %s\n", level, " ", #_type);
  	type_print(CONFIGFS_ROOT);
  	type_print(CONFIGFS_DIR);
  	type_print(CONFIGFS_ITEM_ATTR);
  	type_print(CONFIGFS_ITEM_LINK);
  	type_print(CONFIGFS_USET_DIR);
  	type_print(CONFIGFS_USET_DEFAULT);
  	type_print(CONFIGFS_USET_DROPPING);
  #undef type_print
  }
  
  static int configfs_dump(struct configfs_dirent *sd, int level)
  {
  	struct configfs_dirent *child_sd;
  	int ret = 0;
  
  	configfs_dump_one(sd, level);
  
  	if (!(sd->s_type & (CONFIGFS_DIR|CONFIGFS_ROOT)))
  		return 0;
  
  	list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
  		ret = configfs_dump(child_sd, level + 2);
  		if (ret)
  			break;
  	}
  
  	return ret;
  }
  #endif
  
  
  /*
   * configfs_depend_item() and configfs_undepend_item()
   *
   * WARNING: Do not call these from a configfs callback!
   *
   * This describes these functions and their helpers.
   *
   * Allow another kernel system to depend on a config_item.  If this
   * happens, the item cannot go away until the dependent can live without
   * it.  The idea is to give client modules as simple an interface as
   * possible.  When a system asks them to depend on an item, they just
   * call configfs_depend_item().  If the item is live and the client
   * driver is in good shape, we'll happily do the work for them.
   *
   * Why is the locking complex?  Because configfs uses the VFS to handle
   * all locking, but this function is called outside the normal
   * VFS->configfs path.  So it must take VFS locks to prevent the
   * VFS->configfs stuff (configfs_mkdir(), configfs_rmdir(), etc).  This is
   * why you can't call these functions underneath configfs callbacks.
   *
   * Note, btw, that this can be called at *any* time, even when a configfs
   * subsystem isn't registered, or when configfs is loading or unloading.
   * Just like configfs_register_subsystem().  So we take the same
   * precautions.  We pin the filesystem.  We lock configfs_dirent_lock.
   * If we can find the target item in the
   * configfs tree, it must be part of the subsystem tree as well, so we
   * do not need the subsystem semaphore.  Holding configfs_dirent_lock helps
   * locking out mkdir() and rmdir(), who might be racing us.
   */
  
  /*
   * configfs_depend_prep()
   *
   * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
   * attributes.  This is similar but not the same to configfs_detach_prep().
   * Note that configfs_detach_prep() expects the parent to be locked when it
   * is called, but we lock the parent *inside* configfs_depend_prep().  We
   * do that so we can unlock it if we find nothing.
   *
   * Here we do a depth-first search of the dentry hierarchy looking for
   * our object.
   * We deliberately ignore items tagged as dropping since they are virtually
   * dead, as well as items in the middle of attachment since they virtually
   * do not exist yet. This completes the locking out of racing mkdir() and
   * rmdir().
   * Note: subdirectories in the middle of attachment start with s_type =
   * CONFIGFS_DIR|CONFIGFS_USET_CREATING set by create_dir().  When
   * CONFIGFS_USET_CREATING is set, we ignore the item.  The actual set of
   * s_type is in configfs_new_dirent(), which has configfs_dirent_lock.
   *
   * If the target is not found, -ENOENT is bubbled up.
   *
   * This adds a requirement that all config_items be unique!
   *
   * This is recursive.  There isn't
   * much on the stack, though, so folks that need this function - be careful
   * about your stack!  Patches will be accepted to make it iterative.
   */
  static int configfs_depend_prep(struct dentry *origin,
  				struct config_item *target)
  {
  	struct configfs_dirent *child_sd, *sd;
  	int ret = 0;
  
  	BUG_ON(!origin || !origin->d_fsdata);
  	sd = origin->d_fsdata;
  
  	if (sd->s_element == target)  /* Boo-yah */
  		goto out;
  
  	list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
  		if ((child_sd->s_type & CONFIGFS_DIR) &&
  		    !(child_sd->s_type & CONFIGFS_USET_DROPPING) &&
  		    !(child_sd->s_type & CONFIGFS_USET_CREATING)) {
  			ret = configfs_depend_prep(child_sd->s_dentry,
  						   target);
  			if (!ret)
  				goto out;  /* Child path boo-yah */
  		}
  	}
  
  	/* We looped all our children and didn't find target */
  	ret = -ENOENT;
  
  out:
  	return ret;
  }
  
  int configfs_depend_item(struct configfs_subsystem *subsys,
  			 struct config_item *target)
  {
  	int ret;
  	struct configfs_dirent *p, *root_sd, *subsys_sd = NULL;
  	struct config_item *s_item = &subsys->su_group.cg_item;
  	struct dentry *root;
  
  	/*
  	 * Pin the configfs filesystem.  This means we can safely access
  	 * the root of the configfs filesystem.
  	 */
  	root = configfs_pin_fs();
  	if (IS_ERR(root))
  		return PTR_ERR(root);
  
  	/*
  	 * Next, lock the root directory.  We're going to check that the
  	 * subsystem is really registered, and so we need to lock out
  	 * configfs_[un]register_subsystem().
  	 */
  	mutex_lock(&root->d_inode->i_mutex);
  
  	root_sd = root->d_fsdata;
  
  	list_for_each_entry(p, &root_sd->s_children, s_sibling) {
  		if (p->s_type & CONFIGFS_DIR) {
  			if (p->s_element == s_item) {
  				subsys_sd = p;
  				break;
  			}
  		}
  	}
  
  	if (!subsys_sd) {
  		ret = -ENOENT;
  		goto out_unlock_fs;
  	}
  
  	/* Ok, now we can trust subsys/s_item */
  
  	spin_lock(&configfs_dirent_lock);
  	/* Scan the tree, return 0 if found */
  	ret = configfs_depend_prep(subsys_sd->s_dentry, target);
  	if (ret)
  		goto out_unlock_dirent_lock;
  
  	/*
  	 * We are sure that the item is not about to be removed by rmdir(), and
  	 * not in the middle of attachment by mkdir().
  	 */
  	p = target->ci_dentry->d_fsdata;
  	p->s_dependent_count += 1;
  
  out_unlock_dirent_lock:
  	spin_unlock(&configfs_dirent_lock);
  out_unlock_fs:
  	mutex_unlock(&root->d_inode->i_mutex);
  
  	/*
  	 * If we succeeded, the fs is pinned via other methods.  If not,
  	 * we're done with it anyway.  So release_fs() is always right.
  	 */
  	configfs_release_fs();
  
  	return ret;
  }
  EXPORT_SYMBOL(configfs_depend_item);
  
  /*
   * Release the dependent linkage.  This is much simpler than
   * configfs_depend_item() because we know that that the client driver is
   * pinned, thus the subsystem is pinned, and therefore configfs is pinned.
   */
  void configfs_undepend_item(struct configfs_subsystem *subsys,
  			    struct config_item *target)
  {
  	struct configfs_dirent *sd;
  
  	/*
  	 * Since we can trust everything is pinned, we just need
  	 * configfs_dirent_lock.
  	 */
  	spin_lock(&configfs_dirent_lock);
  
  	sd = target->ci_dentry->d_fsdata;
  	BUG_ON(sd->s_dependent_count < 1);
  
  	sd->s_dependent_count -= 1;
  
  	/*
  	 * After this unlock, we cannot trust the item to stay alive!
  	 * DO NOT REFERENCE item after this unlock.
  	 */
  	spin_unlock(&configfs_dirent_lock);
  }
  EXPORT_SYMBOL(configfs_undepend_item);
  
  static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
  {
  	int ret = 0;
  	int module_got = 0;
  	struct config_group *group = NULL;
  	struct config_item *item = NULL;
  	struct config_item *parent_item;
  	struct configfs_subsystem *subsys;
  	struct configfs_dirent *sd;
  	struct config_item_type *type;
  	struct module *subsys_owner = NULL, *new_item_owner = NULL;
  	char *name;
  
  	sd = dentry->d_parent->d_fsdata;
  
  	/*
  	 * Fake invisibility if dir belongs to a group/default groups hierarchy
  	 * being attached
  	 */
  	if (!configfs_dirent_is_ready(sd)) {
  		ret = -ENOENT;
  		goto out;
  	}
  
  	if (!(sd->s_type & CONFIGFS_USET_DIR)) {
  		ret = -EPERM;
  		goto out;
  	}
  
  	/* Get a working ref for the duration of this function */
  	parent_item = configfs_get_config_item(dentry->d_parent);
  	type = parent_item->ci_type;
  	subsys = to_config_group(parent_item)->cg_subsys;
  	BUG_ON(!subsys);
  
  	if (!type || !type->ct_group_ops ||
  	    (!type->ct_group_ops->make_group &&
  	     !type->ct_group_ops->make_item)) {
  		ret = -EPERM;  /* Lack-of-mkdir returns -EPERM */
  		goto out_put;
  	}
  
  	/*
  	 * The subsystem may belong to a different module than the item
  	 * being created.  We don't want to safely pin the new item but
  	 * fail to pin the subsystem it sits under.
  	 */
  	if (!subsys->su_group.cg_item.ci_type) {
  		ret = -EINVAL;
  		goto out_put;
  	}
  	subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
  	if (!try_module_get(subsys_owner)) {
  		ret = -EINVAL;
  		goto out_put;
  	}
  
  	name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
  	if (!name) {
  		ret = -ENOMEM;
  		goto out_subsys_put;
  	}
  
  	snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
  
  	mutex_lock(&subsys->su_mutex);
  	if (type->ct_group_ops->make_group) {
  		group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
  		if (!group)
  			group = ERR_PTR(-ENOMEM);
  		if (!IS_ERR(group)) {
  			link_group(to_config_group(parent_item), group);
  			item = &group->cg_item;
  		} else
  			ret = PTR_ERR(group);
  	} else {
  		item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
  		if (!item)
  			item = ERR_PTR(-ENOMEM);
  		if (!IS_ERR(item))
  			link_obj(parent_item, item);
  		else
  			ret = PTR_ERR(item);
  	}
  	mutex_unlock(&subsys->su_mutex);
  
  	kfree(name);
  	if (ret) {
  		/*
  		 * If ret != 0, then link_obj() was never called.
  		 * There are no extra references to clean up.
  		 */
  		goto out_subsys_put;
  	}
  
  	/*
  	 * link_obj() has been called (via link_group() for groups).
  	 * From here on out, errors must clean that up.
  	 */
  
  	type = item->ci_type;
  	if (!type) {
  		ret = -EINVAL;
  		goto out_unlink;
  	}
  
  	new_item_owner = type->ct_owner;
  	if (!try_module_get(new_item_owner)) {
  		ret = -EINVAL;
  		goto out_unlink;
  	}
  
  	/*
  	 * I hate doing it this way, but if there is
  	 * an error,  module_put() probably should
  	 * happen after any cleanup.
  	 */
  	module_got = 1;
  
  	/*
  	 * Make racing rmdir() fail if it did not tag parent with
  	 * CONFIGFS_USET_DROPPING
  	 * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
  	 * fail and let rmdir() terminate correctly
  	 */
  	spin_lock(&configfs_dirent_lock);
  	/* This will make configfs_detach_prep() fail */
  	sd->s_type |= CONFIGFS_USET_IN_MKDIR;
  	spin_unlock(&configfs_dirent_lock);
  
  	if (group)
  		ret = configfs_attach_group(parent_item, item, dentry);
  	else
  		ret = configfs_attach_item(parent_item, item, dentry);
  
  	spin_lock(&configfs_dirent_lock);
  	sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
  	if (!ret)
  		configfs_dir_set_ready(dentry->d_fsdata);
  	spin_unlock(&configfs_dirent_lock);
  
  out_unlink:
  	if (ret) {
  		/* Tear down everything we built up */
  		mutex_lock(&subsys->su_mutex);
  
  		client_disconnect_notify(parent_item, item);
  		if (group)
  			unlink_group(group);
  		else
  			unlink_obj(item);
  		client_drop_item(parent_item, item);
  
  		mutex_unlock(&subsys->su_mutex);
  
  		if (module_got)
  			module_put(new_item_owner);
  	}
  
  out_subsys_put:
  	if (ret)
  		module_put(subsys_owner);
  
  out_put:
  	/*
  	 * link_obj()/link_group() took a reference from child->parent,
  	 * so the parent is safely pinned.  We can drop our working
  	 * reference.
  	 */
  	config_item_put(parent_item);
  
  out:
  	return ret;
  }
  
  static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
  {
  	struct config_item *parent_item;
  	struct config_item *item;
  	struct configfs_subsystem *subsys;
  	struct configfs_dirent *sd;
  	struct module *subsys_owner = NULL, *dead_item_owner = NULL;
  	int ret;
  
  	sd = dentry->d_fsdata;
  	if (sd->s_type & CONFIGFS_USET_DEFAULT)
  		return -EPERM;
  
  	/* Get a working ref until we have the child */
  	parent_item = configfs_get_config_item(dentry->d_parent);
  	subsys = to_config_group(parent_item)->cg_subsys;
  	BUG_ON(!subsys);
  
  	if (!parent_item->ci_type) {
  		config_item_put(parent_item);
  		return -EINVAL;
  	}
  
  	/* configfs_mkdir() shouldn't have allowed this */
  	BUG_ON(!subsys->su_group.cg_item.ci_type);
  	subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
  
  	/*
  	 * Ensure that no racing symlink() will make detach_prep() fail while
  	 * the new link is temporarily attached
  	 */
  	do {
  		struct mutex *wait_mutex;
  
  		mutex_lock(&configfs_symlink_mutex);
  		spin_lock(&configfs_dirent_lock);
  		/*
  		 * Here's where we check for dependents.  We're protected by
  		 * configfs_dirent_lock.
  		 * If no dependent, atomically tag the item as dropping.
  		 */
  		ret = sd->s_dependent_count ? -EBUSY : 0;
  		if (!ret) {
  			ret = configfs_detach_prep(dentry, &wait_mutex);
  			if (ret)
  				configfs_detach_rollback(dentry);
  		}
  		spin_unlock(&configfs_dirent_lock);
  		mutex_unlock(&configfs_symlink_mutex);
  
  		if (ret) {
  			if (ret != -EAGAIN) {
  				config_item_put(parent_item);
  				return ret;
  			}
  
  			/* Wait until the racing operation terminates */
  			mutex_lock(wait_mutex);
  			mutex_unlock(wait_mutex);
  		}
  	} while (ret == -EAGAIN);
  
  	/* Get a working ref for the duration of this function */
  	item = configfs_get_config_item(dentry);
  
  	/* Drop reference from above, item already holds one. */
  	config_item_put(parent_item);
  
  	if (item->ci_type)
  		dead_item_owner = item->ci_type->ct_owner;
  
  	if (sd->s_type & CONFIGFS_USET_DIR) {
  		configfs_detach_group(item);
  
  		mutex_lock(&subsys->su_mutex);
  		client_disconnect_notify(parent_item, item);
  		unlink_group(to_config_group(item));
  	} else {
  		configfs_detach_item(item);
  
  		mutex_lock(&subsys->su_mutex);
  		client_disconnect_notify(parent_item, item);
  		unlink_obj(item);
  	}
  
  	client_drop_item(parent_item, item);
  	mutex_unlock(&subsys->su_mutex);
  
  	/* Drop our reference from above */
  	config_item_put(item);
  
  	module_put(dead_item_owner);
  	module_put(subsys_owner);
  
  	return 0;
  }
  
  const struct inode_operations configfs_dir_inode_operations = {
  	.mkdir		= configfs_mkdir,
  	.rmdir		= configfs_rmdir,
  	.symlink	= configfs_symlink,
  	.unlink		= configfs_unlink,
  	.lookup		= configfs_lookup,
  	.setattr	= configfs_setattr,
  };
  
  const struct inode_operations configfs_root_inode_operations = {
  	.lookup		= configfs_lookup,
  	.setattr	= configfs_setattr,
  };
  
  #if 0
  int configfs_rename_dir(struct config_item * item, const char *new_name)
  {
  	int error = 0;
  	struct dentry * new_dentry, * parent;
  
  	if (!strcmp(config_item_name(item), new_name))
  		return -EINVAL;
  
  	if (!item->parent)
  		return -EINVAL;
  
  	down_write(&configfs_rename_sem);
  	parent = item->parent->dentry;
  
  	mutex_lock(&parent->d_inode->i_mutex);
  
  	new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
  	if (!IS_ERR(new_dentry)) {
  		if (!new_dentry->d_inode) {
  			error = config_item_set_name(item, "%s", new_name);
  			if (!error) {
  				d_add(new_dentry, NULL);
  				d_move(item->dentry, new_dentry);
  			}
  			else
  				d_delete(new_dentry);
  		} else
  			error = -EEXIST;
  		dput(new_dentry);
  	}
  	mutex_unlock(&parent->d_inode->i_mutex);
  	up_write(&configfs_rename_sem);
  
  	return error;
  }
  #endif
  
  static int configfs_dir_open(struct inode *inode, struct file *file)
  {
  	struct dentry * dentry = file->f_path.dentry;
  	struct configfs_dirent * parent_sd = dentry->d_fsdata;
  	int err;
  
  	mutex_lock(&dentry->d_inode->i_mutex);
  	/*
  	 * Fake invisibility if dir belongs to a group/default groups hierarchy
  	 * being attached
  	 */
  	err = -ENOENT;
  	if (configfs_dirent_is_ready(parent_sd)) {
  		file->private_data = configfs_new_dirent(parent_sd, NULL, 0);
  		if (IS_ERR(file->private_data))
  			err = PTR_ERR(file->private_data);
  		else
  			err = 0;
  	}
  	mutex_unlock(&dentry->d_inode->i_mutex);
  
  	return err;
  }
  
  static int configfs_dir_close(struct inode *inode, struct file *file)
  {
  	struct dentry * dentry = file->f_path.dentry;
  	struct configfs_dirent * cursor = file->private_data;
  
  	mutex_lock(&dentry->d_inode->i_mutex);
  	spin_lock(&configfs_dirent_lock);
  	list_del_init(&cursor->s_sibling);
  	spin_unlock(&configfs_dirent_lock);
  	mutex_unlock(&dentry->d_inode->i_mutex);
  
  	release_configfs_dirent(cursor);
  
  	return 0;
  }
  
  /* Relationship between s_mode and the DT_xxx types */
  static inline unsigned char dt_type(struct configfs_dirent *sd)
  {
  	return (sd->s_mode >> 12) & 15;
  }
  
  static int configfs_readdir(struct file *file, struct dir_context *ctx)
  {
  	struct dentry *dentry = file->f_path.dentry;
  	struct super_block *sb = dentry->d_sb;
  	struct configfs_dirent * parent_sd = dentry->d_fsdata;
  	struct configfs_dirent *cursor = file->private_data;
  	struct list_head *p, *q = &cursor->s_sibling;
  	ino_t ino = 0;
  
  	if (!dir_emit_dots(file, ctx))
  		return 0;
  	if (ctx->pos == 2) {
  		spin_lock(&configfs_dirent_lock);
  		list_move(q, &parent_sd->s_children);
  		spin_unlock(&configfs_dirent_lock);
  	}
  	for (p = q->next; p != &parent_sd->s_children; p = p->next) {
  		struct configfs_dirent *next;
  		const char *name;
  		int len;
  		struct inode *inode = NULL;
  
  		next = list_entry(p, struct configfs_dirent, s_sibling);
  		if (!next->s_element)
  			continue;
  
  		name = configfs_get_name(next);
  		len = strlen(name);
  
  		/*
  		 * We'll have a dentry and an inode for
  		 * PINNED items and for open attribute
  		 * files.  We lock here to prevent a race
  		 * with configfs_d_iput() clearing
  		 * s_dentry before calling iput().
  		 *
  		 * Why do we go to the trouble?  If
  		 * someone has an attribute file open,
  		 * the inode number should match until
  		 * they close it.  Beyond that, we don't
  		 * care.
  		 */
  		spin_lock(&configfs_dirent_lock);
  		dentry = next->s_dentry;
  		if (dentry)
  			inode = dentry->d_inode;
  		if (inode)
  			ino = inode->i_ino;
  		spin_unlock(&configfs_dirent_lock);
  		if (!inode)
  			ino = iunique(sb, 2);
  
  		if (!dir_emit(ctx, name, len, ino, dt_type(next)))
  			return 0;
  
  		spin_lock(&configfs_dirent_lock);
  		list_move(q, p);
  		spin_unlock(&configfs_dirent_lock);
  		p = q;
  		ctx->pos++;
  	}
  	return 0;
  }
  
  static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence)
  {
  	struct dentry * dentry = file->f_path.dentry;
  
  	mutex_lock(&dentry->d_inode->i_mutex);
  	switch (whence) {
  		case 1:
  			offset += file->f_pos;
  		case 0:
  			if (offset >= 0)
  				break;
  		default:
  			mutex_unlock(&file_inode(file)->i_mutex);
  			return -EINVAL;
  	}
  	if (offset != file->f_pos) {
  		file->f_pos = offset;
  		if (file->f_pos >= 2) {
  			struct configfs_dirent *sd = dentry->d_fsdata;
  			struct configfs_dirent *cursor = file->private_data;
  			struct list_head *p;
  			loff_t n = file->f_pos - 2;
  
  			spin_lock(&configfs_dirent_lock);
  			list_del(&cursor->s_sibling);
  			p = sd->s_children.next;
  			while (n && p != &sd->s_children) {
  				struct configfs_dirent *next;
  				next = list_entry(p, struct configfs_dirent,
  						   s_sibling);
  				if (next->s_element)
  					n--;
  				p = p->next;
  			}
  			list_add_tail(&cursor->s_sibling, p);
  			spin_unlock(&configfs_dirent_lock);
  		}
  	}
  	mutex_unlock(&dentry->d_inode->i_mutex);
  	return offset;
  }
  
  const struct file_operations configfs_dir_operations = {
  	.open		= configfs_dir_open,
  	.release	= configfs_dir_close,
  	.llseek		= configfs_dir_lseek,
  	.read		= generic_read_dir,
  	.iterate	= configfs_readdir,
  };
  
  int configfs_register_subsystem(struct configfs_subsystem *subsys)
  {
  	int err;
  	struct config_group *group = &subsys->su_group;
  	struct dentry *dentry;
  	struct dentry *root;
  	struct configfs_dirent *sd;
  
  	root = configfs_pin_fs();
  	if (IS_ERR(root))
  		return PTR_ERR(root);
  
  	if (!group->cg_item.ci_name)
  		group->cg_item.ci_name = group->cg_item.ci_namebuf;
  
  	sd = root->d_fsdata;
  	link_group(to_config_group(sd->s_element), group);
  
  	mutex_lock_nested(&root->d_inode->i_mutex, I_MUTEX_PARENT);
  
  	err = -ENOMEM;
  	dentry = d_alloc_name(root, group->cg_item.ci_name);
  	if (dentry) {
  		d_add(dentry, NULL);
  
  		err = configfs_attach_group(sd->s_element, &group->cg_item,
  					    dentry);
  		if (err) {
  			BUG_ON(dentry->d_inode);
  			d_drop(dentry);
  			dput(dentry);
  		} else {
  			spin_lock(&configfs_dirent_lock);
  			configfs_dir_set_ready(dentry->d_fsdata);
  			spin_unlock(&configfs_dirent_lock);
  		}
  	}
  
  	mutex_unlock(&root->d_inode->i_mutex);
  
  	if (err) {
  		unlink_group(group);
  		configfs_release_fs();
  	}
  
  	return err;
  }
  
  void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
  {
  	struct config_group *group = &subsys->su_group;
  	struct dentry *dentry = group->cg_item.ci_dentry;
  	struct dentry *root = dentry->d_sb->s_root;
  
  	if (dentry->d_parent != root) {
  		pr_err("Tried to unregister non-subsystem!\n");
  		return;
  	}
  
  	mutex_lock_nested(&root->d_inode->i_mutex,
  			  I_MUTEX_PARENT);
  	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
  	mutex_lock(&configfs_symlink_mutex);
  	spin_lock(&configfs_dirent_lock);
  	if (configfs_detach_prep(dentry, NULL)) {
  		pr_err("Tried to unregister non-empty subsystem!\n");
  	}
  	spin_unlock(&configfs_dirent_lock);
  	mutex_unlock(&configfs_symlink_mutex);
  	configfs_detach_group(&group->cg_item);
  	dentry->d_inode->i_flags |= S_DEAD;
  	dont_mount(dentry);
  	mutex_unlock(&dentry->d_inode->i_mutex);
  
  	d_delete(dentry);
  
  	mutex_unlock(&root->d_inode->i_mutex);
  
  	dput(dentry);
  
  	unlink_group(group);
  	configfs_release_fs();
  }
  
  EXPORT_SYMBOL(configfs_register_subsystem);
  EXPORT_SYMBOL(configfs_unregister_subsystem);
  /************************************************************/
  /* ../linux-3.17/fs/configfs/symlink.c */
  /************************************************************/
  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * symlink.c - operations for configfs symlinks.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   */
  
  // #include <linux/fs.h>
  // #include <linux/module.h>
  // #include <linux/namei.h>
  // #include <linux/slab.h>
  
  // #include <linux/configfs.h>
  // #include "configfs_internal.h"
  
  /* Protects attachments of new symlinks */
  DEFINE_MUTEX(configfs_symlink_mutex);
  
  static int item_depth(struct config_item * item)
  {
  	struct config_item * p = item;
  	int depth = 0;
  	do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
  	return depth;
  }
  
  static int item_path_length(struct config_item * item)
  {
  	struct config_item * p = item;
  	int length = 1;
  	do {
  		length += strlen(config_item_name(p)) + 1;
  		p = p->ci_parent;
  	} while (p && !configfs_is_root(p));
  	return length;
  }
  
  static void fill_item_path(struct config_item * item, char * buffer, int length)
  {
  	struct config_item * p;
  
  	--length;
  	for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
  		int cur = strlen(config_item_name(p));
  
  		/* back up enough to print this bus id with '/' */
  		length -= cur;
  		strncpy(buffer + length,config_item_name(p),cur);
  		*(buffer + --length) = '/';
  	}
  }
  
  static int create_link(struct config_item *parent_item,
  		       struct config_item *item,
  		       struct dentry *dentry)
  {
  	struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
  	struct configfs_symlink *sl;
  	int ret;
  
  	ret = -ENOENT;
  	if (!configfs_dirent_is_ready(target_sd))
  		goto out;
  	ret = -ENOMEM;
  	sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
  	if (sl) {
  		sl->sl_target = config_item_get(item);
  		spin_lock(&configfs_dirent_lock);
  		if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
  			spin_unlock(&configfs_dirent_lock);
  			config_item_put(item);
  			kfree(sl);
  			return -ENOENT;
  		}
  		list_add(&sl->sl_list, &target_sd->s_links);
  		spin_unlock(&configfs_dirent_lock);
  		ret = configfs_create_link(sl, parent_item->ci_dentry,
  					   dentry);
  		if (ret) {
  			spin_lock(&configfs_dirent_lock);
  			list_del_init(&sl->sl_list);
  			spin_unlock(&configfs_dirent_lock);
  			config_item_put(item);
  			kfree(sl);
  		}
  	}
  
  out:
  	return ret;
  }
  
  
  static int get_target(const char *symname, struct path *path,
  		      struct config_item **target, struct super_block *sb)
  {
  	int ret;
  
  	ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
  	if (!ret) {
  		if (path->dentry->d_sb == sb) {
  			*target = configfs_get_config_item(path->dentry);
  			if (!*target) {
  				ret = -ENOENT;
  				path_put(path);
  			}
  		} else {
  			ret = -EPERM;
  			path_put(path);
  		}
  	}
  
  	return ret;
  }
  
  
  int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
  {
  	int ret;
  	struct path path;
  	struct configfs_dirent *sd;
  	struct config_item *parent_item;
  	struct config_item *target_item = NULL;
  	struct config_item_type *type;
  
  	sd = dentry->d_parent->d_fsdata;
  	/*
  	 * Fake invisibility if dir belongs to a group/default groups hierarchy
  	 * being attached
  	 */
  	ret = -ENOENT;
  	if (!configfs_dirent_is_ready(sd))
  		goto out;
  
  	parent_item = configfs_get_config_item(dentry->d_parent);
  	type = parent_item->ci_type;
  
  	ret = -EPERM;
  	if (!type || !type->ct_item_ops ||
  	    !type->ct_item_ops->allow_link)
  		goto out_put;
  
  	ret = get_target(symname, &path, &target_item, dentry->d_sb);
  	if (ret)
  		goto out_put;
  
  	ret = type->ct_item_ops->allow_link(parent_item, target_item);
  	if (!ret) {
  		mutex_lock(&configfs_symlink_mutex);
  		ret = create_link(parent_item, target_item, dentry);
  		mutex_unlock(&configfs_symlink_mutex);
  		if (ret && type->ct_item_ops->drop_link)
  			type->ct_item_ops->drop_link(parent_item,
  						     target_item);
  	}
  
  	config_item_put(target_item);
  	path_put(&path);
  
  out_put:
  	config_item_put(parent_item);
  
  out:
  	return ret;
  }
  
  int configfs_unlink(struct inode *dir, struct dentry *dentry)
  {
  	struct configfs_dirent *sd = dentry->d_fsdata;
  	struct configfs_symlink *sl;
  	struct config_item *parent_item;
  	struct config_item_type *type;
  	int ret;
  
  	ret = -EPERM;  /* What lack-of-symlink returns */
  	if (!(sd->s_type & CONFIGFS_ITEM_LINK))
  		goto out;
  
  	sl = sd->s_element;
  
  	parent_item = configfs_get_config_item(dentry->d_parent);
  	type = parent_item->ci_type;
  
  	spin_lock(&configfs_dirent_lock);
  	list_del_init(&sd->s_sibling);
  	spin_unlock(&configfs_dirent_lock);
  	configfs_drop_dentry(sd, dentry->d_parent);
  	dput(dentry);
  	configfs_put(sd);
  
  	/*
  	 * drop_link() must be called before
  	 * list_del_init(&sl->sl_list), so that the order of
  	 * drop_link(this, target) and drop_item(target) is preserved.
  	 */
  	if (type && type->ct_item_ops &&
  	    type->ct_item_ops->drop_link)
  		type->ct_item_ops->drop_link(parent_item,
  					       sl->sl_target);
  
  	spin_lock(&configfs_dirent_lock);
  	list_del_init(&sl->sl_list);
  	spin_unlock(&configfs_dirent_lock);
  
  	/* Put reference from create_link() */
  	config_item_put(sl->sl_target);
  	kfree(sl);
  
  	config_item_put(parent_item);
  
  	ret = 0;
  
  out:
  	return ret;
  }
  
  static int configfs_get_target_path(struct config_item * item, struct config_item * target,
  				   char *path)
  {
  	char * s;
  	int depth, size;
  
  	depth = item_depth(item);
  	size = item_path_length(target) + depth * 3 - 1;
  	if (size > PATH_MAX)
  		return -ENAMETOOLONG;
  
  	pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
  
  	for (s = path; depth--; s += 3)
  		strcpy(s,"../");
  
  	fill_item_path(target, path, size);
  	pr_debug("%s: path = '%s'\n", __func__, path);
  
  	return 0;
  }
  
  static int configfs_getlink(struct dentry *dentry, char * path)
  {
  	struct config_item *item, *target_item;
  	int error = 0;
  
  	item = configfs_get_config_item(dentry->d_parent);
  	if (!item)
  		return -EINVAL;
  
  	target_item = configfs_get_config_item(dentry);
  	if (!target_item) {
  		config_item_put(item);
  		return -EINVAL;
  	}
  
  	down_read(&configfs_rename_sem);
  	error = configfs_get_target_path(item, target_item, path);
  	up_read(&configfs_rename_sem);
  
  	config_item_put(item);
  	config_item_put(target_item);
  	return error;
  
  }
  
  static void *configfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  {
  	int error = -ENOMEM;
  	unsigned long page = get_zeroed_page(GFP_KERNEL);
  
  	if (page) {
  		error = configfs_getlink(dentry, (char *)page);
  		if (!error) {
  			nd_set_link(nd, (char *)page);
  			return (void *)page;
  		}
  	}
  
  	nd_set_link(nd, ERR_PTR(error));
  	return NULL;
  }
  
  static void configfs_put_link(struct dentry *dentry, struct nameidata *nd,
  			      void *cookie)
  {
  	if (cookie) {
  		unsigned long page = (unsigned long)cookie;
  		free_page(page);
  	}
  }
  
  const struct inode_operations configfs_symlink_inode_operations = {
  	.follow_link = configfs_follow_link,
  	.readlink = generic_readlink,
  	.put_link = configfs_put_link,
  	.setattr = configfs_setattr,
  };
  /************************************************************/
  /* ../linux-3.17/fs/configfs/mount.c */
  /************************************************************/
  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * mount.c - operations for initializing and mounting configfs.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on sysfs:
   * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   */
  
  // #include <linux/fs.h>
  // #include <linux/module.h>
  // #include <linux/mount.h>
  // #include <linux/pagemap.h>
  #include <linux/init.h>
  // #include <linux/slab.h>
  
  // #include <linux/configfs.h>
  // #include "configfs_internal.h"
  
  /* Random magic number */
  #define CONFIGFS_MAGIC 0x62656570
  
  static struct vfsmount *configfs_mount = NULL;
  struct kmem_cache *configfs_dir_cachep;
  static int configfs_mnt_count = 0;
  
  static const struct super_operations configfs_ops = {
  	.statfs		= simple_statfs,
  	.drop_inode	= generic_delete_inode,
  };
  
  static struct config_group configfs_root_group = {
  	.cg_item = {
  		.ci_namebuf	= "root",
  		.ci_name	= configfs_root_group.cg_item.ci_namebuf,
  	},
  };
  
  int configfs_is_root(struct config_item *item)
  {
  	return item == &configfs_root_group.cg_item;
  }
  
  static struct configfs_dirent configfs_root = {
  	.s_sibling	= LIST_HEAD_INIT(configfs_root.s_sibling),
  	.s_children	= LIST_HEAD_INIT(configfs_root.s_children),
  	.s_element	= &configfs_root_group.cg_item,
  	.s_type		= CONFIGFS_ROOT,
  	.s_iattr	= NULL,
  };
  
  static int configfs_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct inode *inode;
  	struct dentry *root;
  
  	sb->s_blocksize = PAGE_CACHE_SIZE;
  	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
  	sb->s_magic = CONFIGFS_MAGIC;
  	sb->s_op = &configfs_ops;
  	sb->s_time_gran = 1;
  
  	inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
  				   &configfs_root, sb);
  	if (inode) {
  		inode->i_op = &configfs_root_inode_operations;
  		inode->i_fop = &configfs_dir_operations;
  		/* directory inodes start off with i_nlink == 2 (for "." entry) */
  		inc_nlink(inode);
  	} else {
  		pr_debug("could not get root inode\n");
  		return -ENOMEM;
  	}
  
  	root = d_make_root(inode);
  	if (!root) {
  		pr_debug("%s: could not get root dentry!\n",__func__);
  		return -ENOMEM;
  	}
  	config_group_init(&configfs_root_group);
  	configfs_root_group.cg_item.ci_dentry = root;
  	root->d_fsdata = &configfs_root;
  	sb->s_root = root;
  	sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
  	return 0;
  }
  
  static struct dentry *configfs_do_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)
  {
  	return mount_single(fs_type, flags, data, configfs_fill_super);
  }
  
  static struct file_system_type configfs_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "configfs",
  	.mount		= configfs_do_mount,
  	.kill_sb	= kill_litter_super,
  };
  MODULE_ALIAS_FS("configfs");
  
  struct dentry *configfs_pin_fs(void)
  {
  	int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
  			     &configfs_mnt_count);
  	return err ? ERR_PTR(err) : configfs_mount->mnt_root;
  }
  
  void configfs_release_fs(void)
  {
  	simple_release_fs(&configfs_mount, &configfs_mnt_count);
  }
  
  
  static struct kobject *config_kobj;
  
  static int __init configfs_init(void)
  {
  	int err = -ENOMEM;
  
  	configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
  						sizeof(struct configfs_dirent),
  						0, 0, NULL);
  	if (!configfs_dir_cachep)
  		goto out;
  
  	config_kobj = kobject_create_and_add("config", kernel_kobj);
  	if (!config_kobj)
  		goto out2;
  
  	err = configfs_inode_init();
  	if (err)
  		goto out3;
  
  	err = register_filesystem(&configfs_fs_type);
  	if (err)
  		goto out4;
  
  	return 0;
  out4:
  	pr_err("Unable to register filesystem!\n");
  	configfs_inode_exit();
  out3:
  	kobject_put(config_kobj);
  out2:
  	kmem_cache_destroy(configfs_dir_cachep);
  	configfs_dir_cachep = NULL;
  out:
  	return err;
  }
  
  static void __exit configfs_exit(void)
  {
  	unregister_filesystem(&configfs_fs_type);
  	kobject_put(config_kobj);
  	kmem_cache_destroy(configfs_dir_cachep);
  	configfs_dir_cachep = NULL;
  	configfs_inode_exit();
  }
  
  MODULE_AUTHOR("Oracle");
  MODULE_LICENSE("GPL");
  MODULE_VERSION("0.0.2");
  MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
  
  module_init(configfs_init);
  module_exit(configfs_exit);
  /************************************************************/
  /* ../linux-3.17/fs/configfs/item.c */
  /************************************************************/
  /* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * item.c - library routines for handling generic config items
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on kobject:
   *	kobject is Copyright (c) 2002-2003 Patrick Mochel
   *
   * configfs Copyright (C) 2005 Oracle.  All rights reserved.
   *
   * Please see the file Documentation/filesystems/configfs/configfs.txt for
   * critical information about using the config_item interface.
   */
  
  #include <linux/string.h>
  // #include <linux/module.h>
  #include <linux/stat.h>
  // #include <linux/slab.h>
  
  // #include <linux/configfs.h>
  
  
  static inline struct config_item *to_item(struct list_head *entry)
  {
  	return container_of(entry, struct config_item, ci_entry);
  }
  
  /* Evil kernel */
  static void config_item_release(struct kref *kref);
  
  /**
   *	config_item_init - initialize item.
   *	@item:	item in question.
   */
  void config_item_init(struct config_item *item)
  {
  	kref_init(&item->ci_kref);
  	INIT_LIST_HEAD(&item->ci_entry);
  }
  EXPORT_SYMBOL(config_item_init);
  
  /**
   *	config_item_set_name - Set the name of an item
   *	@item:	item.
   *	@fmt:  The vsnprintf()'s format string.
   *
   *	If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
   *	dynamically allocated string that @item->ci_name points to.
   *	Otherwise, use the static @item->ci_namebuf array.
   */
  int config_item_set_name(struct config_item *item, const char *fmt, ...)
  {
  	int error = 0;
  	int limit = CONFIGFS_ITEM_NAME_LEN;
  	int need;
  	va_list args;
  	char *name;
  
  	/*
  	 * First, try the static array
  	 */
  	va_start(args, fmt);
  	need = vsnprintf(item->ci_namebuf, limit, fmt, args);
  	va_end(args);
  	if (need < limit)
  		name = item->ci_namebuf;
  	else {
  		/*
  		 * Need more space? Allocate it and try again
  		 */
  		limit = need + 1;
  		name = kmalloc(limit, GFP_KERNEL);
  		if (!name) {
  			error = -ENOMEM;
  			goto Done;
  		}
  		va_start(args, fmt);
  		need = vsnprintf(name, limit, fmt, args);
  		va_end(args);
  
  		/* Still? Give up. */
  		if (need >= limit) {
  			kfree(name);
  			error = -EFAULT;
  			goto Done;
  		}
  	}
  
  	/* Free the old name, if necessary. */
  	if (item->ci_name && item->ci_name != item->ci_namebuf)
  		kfree(item->ci_name);
  
  	/* Now, set the new name */
  	item->ci_name = name;
   Done:
  	return error;
  }
  EXPORT_SYMBOL(config_item_set_name);
  
  void config_item_init_type_name(struct config_item *item,
  				const char *name,
  				struct config_item_type *type)
  {
  	config_item_set_name(item, name);
  	item->ci_type = type;
  	config_item_init(item);
  }
  EXPORT_SYMBOL(config_item_init_type_name);
  
  void config_group_init_type_name(struct config_group *group, const char *name,
  			 struct config_item_type *type)
  {
  	config_item_set_name(&group->cg_item, name);
  	group->cg_item.ci_type = type;
  	config_group_init(group);
  }
  EXPORT_SYMBOL(config_group_init_type_name);
  
  struct config_item *config_item_get(struct config_item *item)
  {
  	if (item)
  		kref_get(&item->ci_kref);
  	return item;
  }
  EXPORT_SYMBOL(config_item_get);
  
  static void config_item_cleanup(struct config_item *item)
  {
  	struct config_item_type *t = item->ci_type;
  	struct config_group *s = item->ci_group;
  	struct config_item *parent = item->ci_parent;
  
  	pr_debug("config_item %s: cleaning up\n", config_item_name(item));
  	if (item->ci_name != item->ci_namebuf)
  		kfree(item->ci_name);
  	item->ci_name = NULL;
  	if (t && t->ct_item_ops && t->ct_item_ops->release)
  		t->ct_item_ops->release(item);
  	if (s)
  		config_group_put(s);
  	if (parent)
  		config_item_put(parent);
  }
  
  static void config_item_release(struct kref *kref)
  {
  	config_item_cleanup(container_of(kref, struct config_item, ci_kref));
  }
  
  /**
   *	config_item_put - decrement refcount for item.
   *	@item:	item.
   *
   *	Decrement the refcount, and if 0, call config_item_cleanup().
   */
  void config_item_put(struct config_item *item)
  {
  	if (item)
  		kref_put(&item->ci_kref, config_item_release);
  }
  EXPORT_SYMBOL(config_item_put);
  
  /**
   *	config_group_init - initialize a group for use
   *	@group:	config_group
   */
  void config_group_init(struct config_group *group)
  {
  	config_item_init(&group->cg_item);
  	INIT_LIST_HEAD(&group->cg_children);
  }
  EXPORT_SYMBOL(config_group_init);
  
  /**
   *	config_group_find_item - search for item in group.
   *	@group:	group we're looking in.
   *	@name:	item's name.
   *
   *	Iterate over @group->cg_list, looking for a matching config_item.
   *	If matching item is found take a reference and return the item.
   *	Caller must have locked group via @group->cg_subsys->su_mtx.
   */
  struct config_item *config_group_find_item(struct config_group *group,
  					   const char *name)
  {
  	struct list_head *entry;
  	struct config_item *ret = NULL;
  
  	list_for_each(entry, &group->cg_children) {
  		struct config_item *item = to_item(entry);
  		if (config_item_name(item) &&
  		    !strcmp(config_item_name(item), name)) {
  			ret = config_item_get(item);
  			break;
  		}
  	}
  	return ret;
  }
  EXPORT_SYMBOL(config_group_find_item);
  