fs/sysfs/dir.c - fp2-dev/kernel/msm - Gitiles

 /*
  * dir.c - Operations for sysfs directories.
  */

 #undef DEBUG

 #include <linux/fs.h>
 #include <linux/mount.h>
 #include <linux/module.h>
 #include <linux/kobject.h>
 #include <linux/namei.h>
 #include <asm/semaphore.h>
 #include "sysfs.h"

 DECLARE_RWSEM(sysfs_rename_sem);
 spinlock_t sysfs_lock = SPIN_LOCK_UNLOCKED;

 static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
 {
 	struct sysfs_dirent * sd = dentry->d_fsdata;

 	if (sd) {
 		/* sd->s_dentry is protected with sysfs_lock.  This
 		 * allows sysfs_drop_dentry() to dereference it.
 		 */
 		spin_lock(&sysfs_lock);

 		/* The dentry might have been deleted or another
 		 * lookup could have happened updating sd->s_dentry to
 		 * point the new dentry.  Ignore if it isn't pointing
 		 * to this dentry.
 		 */
 		if (sd->s_dentry == dentry)
 			sd->s_dentry = NULL;
 		spin_unlock(&sysfs_lock);
 		sysfs_put(sd);
 	}
 	iput(inode);
 }

 static struct dentry_operations sysfs_dentry_ops = {
 	.d_iput		= sysfs_d_iput,
 };

 static unsigned int sysfs_inode_counter;
 ino_t sysfs_get_inum(void)
 {
 	if (unlikely(sysfs_inode_counter < 3))
 		sysfs_inode_counter = 3;
 	return sysfs_inode_counter++;
 }

 /*
  * Allocates a new sysfs_dirent and links it to the parent sysfs_dirent
  */
 static struct sysfs_dirent * __sysfs_new_dirent(void * element)
 {
 	struct sysfs_dirent * sd;

 	sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
 	if (!sd)
 		return NULL;

 	sd->s_ino = sysfs_get_inum();
 	atomic_set(&sd->s_count, 1);
 	atomic_set(&sd->s_event, 1);
 	INIT_LIST_HEAD(&sd->s_children);
 	INIT_LIST_HEAD(&sd->s_sibling);
 	sd->s_element = element;

 	return sd;
 }

 static void __sysfs_list_dirent(struct sysfs_dirent *parent_sd,
 			      struct sysfs_dirent *sd)
 {
 	if (sd)
 		list_add(&sd->s_sibling, &parent_sd->s_children);
 }

 static struct sysfs_dirent * sysfs_new_dirent(struct sysfs_dirent *parent_sd,
 						void * element)
 {
 	struct sysfs_dirent *sd;
 	sd = __sysfs_new_dirent(element);
 	__sysfs_list_dirent(parent_sd, sd);
 	return sd;
 }

 /*
  *
  * Return -EEXIST if there is already a sysfs element with the same name for
  * the same parent.
  *
  * called with parent inode's i_mutex held
  */
 int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
 			  const unsigned char *new)
 {
 	struct sysfs_dirent * sd;

 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_element) {
 			const unsigned char *existing = sysfs_get_name(sd);
 			if (strcmp(existing, new))
 				continue;
 			else
 				return -EEXIST;
 		}
 	}

 	return 0;
 }


 static struct sysfs_dirent *
 __sysfs_make_dirent(struct dentry *dentry, void *element, mode_t mode, int type)
 {
 	struct sysfs_dirent * sd;

 	sd = __sysfs_new_dirent(element);
 	if (!sd)
 		goto out;

 	sd->s_mode = mode;
 	sd->s_type = type;
 	sd->s_dentry = dentry;
 	if (dentry) {
 		dentry->d_fsdata = sysfs_get(sd);
 		dentry->d_op = &sysfs_dentry_ops;
 	}

 out:
 	return sd;
 }

 int sysfs_make_dirent(struct sysfs_dirent * parent_sd, struct dentry * dentry,
 			void * element, umode_t mode, int type)
 {
 	struct sysfs_dirent *sd;

 	sd = __sysfs_make_dirent(dentry, element, mode, type);
 	__sysfs_list_dirent(parent_sd, sd);

 	return sd ? 0 : -ENOMEM;
 }

 static int init_dir(struct inode * inode)
 {
 	inode->i_op = &sysfs_dir_inode_operations;
 	inode->i_fop = &sysfs_dir_operations;

 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
 	return 0;
 }

 static int init_file(struct inode * inode)
 {
 	inode->i_size = PAGE_SIZE;
 	inode->i_fop = &sysfs_file_operations;
 	return 0;
 }

 static int init_symlink(struct inode * inode)
 {
 	inode->i_op = &sysfs_symlink_inode_operations;
 	return 0;
 }

 static int create_dir(struct kobject * k, struct dentry * p,
 		      const char * n, struct dentry ** d)
 {
 	int error;
 	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;

 	mutex_lock(&p->d_inode->i_mutex);
 	*d = lookup_one_len(n, p, strlen(n));
 	if (!IS_ERR(*d)) {
  		if (sysfs_dirent_exist(p->d_fsdata, n))
   			error = -EEXIST;
   		else
 			error = sysfs_make_dirent(p->d_fsdata, *d, k, mode,
 								SYSFS_DIR);
 		if (!error) {
 			error = sysfs_create(*d, mode, init_dir);
 			if (!error) {
 				inc_nlink(p->d_inode);
 				(*d)->d_op = &sysfs_dentry_ops;
 				d_rehash(*d);
 			}
 		}
 		if (error && (error != -EEXIST)) {
 			struct sysfs_dirent *sd = (*d)->d_fsdata;
 			if (sd) {
  				list_del_init(&sd->s_sibling);
 				sysfs_put(sd);
 			}
 			d_drop(*d);
 		}
 		dput(*d);
 	} else
 		error = PTR_ERR(*d);
 	mutex_unlock(&p->d_inode->i_mutex);
 	return error;
 }


 int sysfs_create_subdir(struct kobject * k, const char * n, struct dentry ** d)
 {
 	return create_dir(k,k->dentry,n,d);
 }

 /**
  *	sysfs_create_dir - create a directory for an object.
  *	@kobj:		object we're creating directory for.
  *	@shadow_parent:	parent parent object.
  */

 int sysfs_create_dir(struct kobject * kobj, struct dentry *shadow_parent)
 {
 	struct dentry * dentry = NULL;
 	struct dentry * parent;
 	int error = 0;

 	BUG_ON(!kobj);

 	if (shadow_parent)
 		parent = shadow_parent;
 	else if (kobj->parent)
 		parent = kobj->parent->dentry;
 	else if (sysfs_mount && sysfs_mount->mnt_sb)
 		parent = sysfs_mount->mnt_sb->s_root;
 	else
 		return -EFAULT;

 	error = create_dir(kobj,parent,kobject_name(kobj),&dentry);
 	if (!error)
 		kobj->dentry = dentry;
 	return error;
 }

 /* attaches attribute's sysfs_dirent to the dentry corresponding to the
  * attribute file
  */
 static int sysfs_attach_attr(struct sysfs_dirent * sd, struct dentry * dentry)
 {
 	struct attribute * attr = NULL;
 	struct bin_attribute * bin_attr = NULL;
 	int (* init) (struct inode *) = NULL;
 	int error = 0;

         if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
                 bin_attr = sd->s_element;
                 attr = &bin_attr->attr;
         } else {
                 attr = sd->s_element;
                 init = init_file;
         }

 	dentry->d_fsdata = sysfs_get(sd);
 	/* protect sd->s_dentry against sysfs_d_iput */
 	spin_lock(&sysfs_lock);
 	sd->s_dentry = dentry;
 	spin_unlock(&sysfs_lock);
 	error = sysfs_create(dentry, (attr->mode & S_IALLUGO) | S_IFREG, init);
 	if (error) {
 		sysfs_put(sd);
 		return error;
 	}

         if (bin_attr) {
 		dentry->d_inode->i_size = bin_attr->size;
 		dentry->d_inode->i_fop = &bin_fops;
 	}
 	dentry->d_op = &sysfs_dentry_ops;
 	d_rehash(dentry);

 	return 0;
 }

 static int sysfs_attach_link(struct sysfs_dirent * sd, struct dentry * dentry)
 {
 	int err = 0;

 	dentry->d_fsdata = sysfs_get(sd);
 	/* protect sd->s_dentry against sysfs_d_iput */
 	spin_lock(&sysfs_lock);
 	sd->s_dentry = dentry;
 	spin_unlock(&sysfs_lock);
 	err = sysfs_create(dentry, S_IFLNK|S_IRWXUGO, init_symlink);
 	if (!err) {
 		dentry->d_op = &sysfs_dentry_ops;
 		d_rehash(dentry);
 	} else
 		sysfs_put(sd);

 	return err;
 }

 static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
 				struct nameidata *nd)
 {
 	struct sysfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 	struct sysfs_dirent * sd;
 	int err = 0;

 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_type & SYSFS_NOT_PINNED) {
 			const unsigned char * name = sysfs_get_name(sd);

 			if (strcmp(name, dentry->d_name.name))
 				continue;

 			if (sd->s_type & SYSFS_KOBJ_LINK)
 				err = sysfs_attach_link(sd, dentry);
 			else
 				err = sysfs_attach_attr(sd, dentry);
 			break;
 		}
 	}

 	return ERR_PTR(err);
 }

 const struct inode_operations sysfs_dir_inode_operations = {
 	.lookup		= sysfs_lookup,
 	.setattr	= sysfs_setattr,
 };

 static void remove_dir(struct dentry * d)
 {
 	struct dentry * parent = dget(d->d_parent);
 	struct sysfs_dirent * sd;

 	mutex_lock(&parent->d_inode->i_mutex);
 	d_delete(d);
 	sd = d->d_fsdata;
  	list_del_init(&sd->s_sibling);
 	sysfs_put(sd);
 	if (d->d_inode)
 		simple_rmdir(parent->d_inode,d);

 	pr_debug(" o %s removing done (%d)\n",d->d_name.name,
 		 atomic_read(&d->d_count));

 	mutex_unlock(&parent->d_inode->i_mutex);
 	dput(parent);
 }

 void sysfs_remove_subdir(struct dentry * d)
 {
 	remove_dir(d);
 }


 static void __sysfs_remove_dir(struct dentry *dentry)
 {
 	struct sysfs_dirent * parent_sd;
 	struct sysfs_dirent * sd, * tmp;

 	dget(dentry);
 	if (!dentry)
 		return;

 	pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
 	mutex_lock(&dentry->d_inode->i_mutex);
 	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 & SYSFS_NOT_PINNED))
 			continue;
 		list_del_init(&sd->s_sibling);
 		sysfs_drop_dentry(sd, dentry);
 		sysfs_put(sd);
 	}
 	mutex_unlock(&dentry->d_inode->i_mutex);

 	remove_dir(dentry);
 	/**
 	 * Drop reference from dget() on entrance.
 	 */
 	dput(dentry);
 }

 /**
  *	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)
 {
 	__sysfs_remove_dir(kobj->dentry);
 	kobj->dentry = NULL;
 }

 int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent,
 		     const char *new_name)
 {
 	int error = 0;
 	struct dentry * new_dentry;

 	if (!new_parent)
 		return -EFAULT;

 	down_write(&sysfs_rename_sem);
 	mutex_lock(&new_parent->d_inode->i_mutex);

 	new_dentry = lookup_one_len(new_name, new_parent, strlen(new_name));
 	if (!IS_ERR(new_dentry)) {
 		/* By allowing two different directories with the
 		 * same d_parent we allow this routine to move
 		 * between different shadows of the same directory
 		 */
 		if (kobj->dentry->d_parent->d_inode != new_parent->d_inode)
 			return -EINVAL;
 		else if (new_dentry->d_parent->d_inode != new_parent->d_inode)
 			error = -EINVAL;
 		else if (new_dentry == kobj->dentry)
 			error = -EINVAL;
 		else if (!new_dentry->d_inode) {
 			error = kobject_set_name(kobj, "%s", new_name);
 			if (!error) {
 				struct sysfs_dirent *sd, *parent_sd;

 				d_add(new_dentry, NULL);
 				d_move(kobj->dentry, new_dentry);

 				sd = kobj->dentry->d_fsdata;
 				parent_sd = new_parent->d_fsdata;

 				list_del_init(&sd->s_sibling);
 				list_add(&sd->s_sibling, &parent_sd->s_children);
 			}
 			else
 				d_drop(new_dentry);
 		} else
 			error = -EEXIST;
 		dput(new_dentry);
 	}
 	mutex_unlock(&new_parent->d_inode->i_mutex);
 	up_write(&sysfs_rename_sem);

 	return error;
 }

 int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent)
 {
 	struct dentry *old_parent_dentry, *new_parent_dentry, *new_dentry;
 	struct sysfs_dirent *new_parent_sd, *sd;
 	int error;

 	old_parent_dentry = kobj->parent ?
 		kobj->parent->dentry : sysfs_mount->mnt_sb->s_root;
 	new_parent_dentry = new_parent ?
 		new_parent->dentry : sysfs_mount->mnt_sb->s_root;

 	if (old_parent_dentry->d_inode == new_parent_dentry->d_inode)
 		return 0;	/* nothing to move */
 again:
 	mutex_lock(&old_parent_dentry->d_inode->i_mutex);
 	if (!mutex_trylock(&new_parent_dentry->d_inode->i_mutex)) {
 		mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 		goto again;
 	}

 	new_parent_sd = new_parent_dentry->d_fsdata;
 	sd = kobj->dentry->d_fsdata;

 	new_dentry = lookup_one_len(kobj->name, new_parent_dentry,
 				    strlen(kobj->name));
 	if (IS_ERR(new_dentry)) {
 		error = PTR_ERR(new_dentry);
 		goto out;
 	} else
 		error = 0;
 	d_add(new_dentry, NULL);
 	d_move(kobj->dentry, new_dentry);
 	dput(new_dentry);

 	/* Remove from old parent's list and insert into new parent's list. */
 	list_del_init(&sd->s_sibling);
 	list_add(&sd->s_sibling, &new_parent_sd->s_children);

 out:
 	mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
 	mutex_unlock(&old_parent_dentry->d_inode->i_mutex);

 	return error;
 }

 static int sysfs_dir_open(struct inode *inode, struct file *file)
 {
 	struct dentry * dentry = file->f_path.dentry;
 	struct sysfs_dirent * parent_sd = dentry->d_fsdata;

 	mutex_lock(&dentry->d_inode->i_mutex);
 	file->private_data = sysfs_new_dirent(parent_sd, NULL);
 	mutex_unlock(&dentry->d_inode->i_mutex);

 	return file->private_data ? 0 : -ENOMEM;

 }

 static int sysfs_dir_close(struct inode *inode, struct file *file)
 {
 	struct dentry * dentry = file->f_path.dentry;
 	struct sysfs_dirent * cursor = file->private_data;

 	mutex_lock(&dentry->d_inode->i_mutex);
 	list_del_init(&cursor->s_sibling);
 	mutex_unlock(&dentry->d_inode->i_mutex);

 	release_sysfs_dirent(cursor);

 	return 0;
 }

 /* 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_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 *cursor = filp->private_data;
 	struct list_head *p, *q = &cursor->s_sibling;
 	ino_t ino;
 	int i = filp->f_pos;

 	switch (i) {
 		case 0:
 			ino = parent_sd->s_ino;
 			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 				break;
 			filp->f_pos++;
 			i++;
 			/* fallthrough */
 		case 1:
 			ino = parent_ino(dentry);
 			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 				break;
 			filp->f_pos++;
 			i++;
 			/* fallthrough */
 		default:
 			if (filp->f_pos == 2)
 				list_move(q, &parent_sd->s_children);

 			for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
 				struct sysfs_dirent *next;
 				const char * name;
 				int len;

 				next = list_entry(p, struct sysfs_dirent,
 						   s_sibling);
 				if (!next->s_element)
 					continue;

 				name = sysfs_get_name(next);
 				len = strlen(name);
 				ino = next->s_ino;

 				if (filldir(dirent, name, len, filp->f_pos, ino,
 						 dt_type(next)) < 0)
 					return 0;

 				list_move(q, p);
 				p = q;
 				filp->f_pos++;
 			}
 	}
 	return 0;
 }

 static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
 {
 	struct dentry * dentry = file->f_path.dentry;

 	mutex_lock(&dentry->d_inode->i_mutex);
 	switch (origin) {
 		case 1:
 			offset += file->f_pos;
 		case 0:
 			if (offset >= 0)
 				break;
 		default:
 			mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 			return -EINVAL;
 	}
 	if (offset != file->f_pos) {
 		file->f_pos = offset;
 		if (file->f_pos >= 2) {
 			struct sysfs_dirent *sd = dentry->d_fsdata;
 			struct sysfs_dirent *cursor = file->private_data;
 			struct list_head *p;
 			loff_t n = file->f_pos - 2;

 			list_del(&cursor->s_sibling);
 			p = sd->s_children.next;
 			while (n && p != &sd->s_children) {
 				struct sysfs_dirent *next;
 				next = list_entry(p, struct sysfs_dirent,
 						   s_sibling);
 				if (next->s_element)
 					n--;
 				p = p->next;
 			}
 			list_add_tail(&cursor->s_sibling, p);
 		}
 	}
 	mutex_unlock(&dentry->d_inode->i_mutex);
 	return offset;
 }


 /**
  *	sysfs_make_shadowed_dir - Setup so a directory can be shadowed
  *	@kobj:	object we're creating shadow of.
  */

 int sysfs_make_shadowed_dir(struct kobject *kobj,
 	void * (*follow_link)(struct dentry *, struct nameidata *))
 {
 	struct inode *inode;
 	struct inode_operations *i_op;

 	inode = kobj->dentry->d_inode;
 	if (inode->i_op != &sysfs_dir_inode_operations)
 		return -EINVAL;

 	i_op = kmalloc(sizeof(*i_op), GFP_KERNEL);
 	if (!i_op)
 		return -ENOMEM;

 	memcpy(i_op, &sysfs_dir_inode_operations, sizeof(*i_op));
 	i_op->follow_link = follow_link;

 	/* Locking of inode->i_op?
 	 * Since setting i_op is a single word write and they
 	 * are atomic we should be ok here.
 	 */
 	inode->i_op = i_op;
 	return 0;
 }

 /**
  *	sysfs_create_shadow_dir - create a shadow directory for an object.
  *	@kobj:	object we're creating directory for.
  *
  *	sysfs_make_shadowed_dir must already have been called on this
  *	directory.
  */

 struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
 {
 	struct sysfs_dirent *sd;
 	struct dentry *parent, *dir, *shadow;
 	struct inode *inode;

 	dir = kobj->dentry;
 	inode = dir->d_inode;
 	parent = dir->d_parent;
 	shadow = ERR_PTR(-EINVAL);
 	if (!sysfs_is_shadowed_inode(inode))
 		goto out;

 	shadow = d_alloc(parent, &dir->d_name);
 	if (!shadow)
 		goto nomem;

 	sd = __sysfs_make_dirent(shadow, kobj, inode->i_mode, SYSFS_DIR);
 	if (!sd)
 		goto nomem;

 	d_instantiate(shadow, igrab(inode));
 	inc_nlink(inode);
 	inc_nlink(parent->d_inode);
 	shadow->d_op = &sysfs_dentry_ops;

 	dget(shadow);		/* Extra count - pin the dentry in core */

 out:
 	return shadow;
 nomem:
 	dput(shadow);
 	shadow = ERR_PTR(-ENOMEM);
 	goto out;
 }

 /**
  *	sysfs_remove_shadow_dir - remove an object's directory.
  *	@shadow: dentry of shadow directory
  *
  *	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_shadow_dir(struct dentry *shadow)
 {
 	__sysfs_remove_dir(shadow);
 }

 const struct file_operations sysfs_dir_operations = {
 	.open		= sysfs_dir_open,
 	.release	= sysfs_dir_close,
 	.llseek		= sysfs_dir_lseek,
 	.read		= generic_read_dir,
 	.readdir	= sysfs_readdir,
 };
	/*
	* dir.c - Operations for sysfs directories.
	*/

	#undef DEBUG

	#include <linux/fs.h>
	#include <linux/mount.h>
	#include <linux/module.h>
	#include <linux/kobject.h>
	#include <linux/namei.h>
	#include <asm/semaphore.h>
	#include "sysfs.h"

	DECLARE_RWSEM(sysfs_rename_sem);
	spinlock_t sysfs_lock = SPIN_LOCK_UNLOCKED;

	static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
	{
	struct sysfs_dirent * sd = dentry->d_fsdata;

	if (sd) {
	/* sd->s_dentry is protected with sysfs_lock. This
	* allows sysfs_drop_dentry() to dereference it.
	*/
	spin_lock(&sysfs_lock);

	/* The dentry might have been deleted or another
	* lookup could have happened updating sd->s_dentry to
	* point the new dentry. Ignore if it isn't pointing
	* to this dentry.
	*/
	if (sd->s_dentry == dentry)
	sd->s_dentry = NULL;
	spin_unlock(&sysfs_lock);
	sysfs_put(sd);
	}
	iput(inode);
	}

	static struct dentry_operations sysfs_dentry_ops = {
	.d_iput = sysfs_d_iput,
	};

	static unsigned int sysfs_inode_counter;
	ino_t sysfs_get_inum(void)
	{
	if (unlikely(sysfs_inode_counter < 3))
	sysfs_inode_counter = 3;
	return sysfs_inode_counter++;
	}

	/*
	* Allocates a new sysfs_dirent and links it to the parent sysfs_dirent
	*/
	static struct sysfs_dirent * __sysfs_new_dirent(void * element)
	{
	struct sysfs_dirent * sd;

	sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
	if (!sd)
	return NULL;

	sd->s_ino = sysfs_get_inum();
	atomic_set(&sd->s_count, 1);
	atomic_set(&sd->s_event, 1);
	INIT_LIST_HEAD(&sd->s_children);
	INIT_LIST_HEAD(&sd->s_sibling);
	sd->s_element = element;

	return sd;
	}

	static void __sysfs_list_dirent(struct sysfs_dirent *parent_sd,
	struct sysfs_dirent *sd)
	{
	if (sd)
	list_add(&sd->s_sibling, &parent_sd->s_children);
	}

	static struct sysfs_dirent * sysfs_new_dirent(struct sysfs_dirent *parent_sd,
	void * element)
	{
	struct sysfs_dirent *sd;
	sd = __sysfs_new_dirent(element);
	__sysfs_list_dirent(parent_sd, sd);
	return sd;
	}

	/*
	*
	* Return -EEXIST if there is already a sysfs element with the same name for
	* the same parent.
	*
	* called with parent inode's i_mutex held
	*/
	int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
	const unsigned char *new)
	{
	struct sysfs_dirent * sd;

	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
	if (sd->s_element) {
	const unsigned char *existing = sysfs_get_name(sd);
	if (strcmp(existing, new))
	continue;
	else
	return -EEXIST;
	}
	}

	return 0;
	}


	static struct sysfs_dirent *
	__sysfs_make_dirent(struct dentry dentry, void element, mode_t mode, int type)
	{
	struct sysfs_dirent * sd;

	sd = __sysfs_new_dirent(element);
	if (!sd)
	goto out;

	sd->s_mode = mode;
	sd->s_type = type;
	sd->s_dentry = dentry;
	if (dentry) {
	dentry->d_fsdata = sysfs_get(sd);
	dentry->d_op = &sysfs_dentry_ops;
	}

	out:
	return sd;
	}

	int sysfs_make_dirent(struct sysfs_dirent * parent_sd, struct dentry * dentry,
	void * element, umode_t mode, int type)
	{
	struct sysfs_dirent *sd;

	sd = __sysfs_make_dirent(dentry, element, mode, type);
	__sysfs_list_dirent(parent_sd, sd);

	return sd ? 0 : -ENOMEM;
	}

	static int init_dir(struct inode * inode)
	{
	inode->i_op = &sysfs_dir_inode_operations;
	inode->i_fop = &sysfs_dir_operations;

	/* directory inodes start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
	return 0;
	}

	static int init_file(struct inode * inode)
	{
	inode->i_size = PAGE_SIZE;
	inode->i_fop = &sysfs_file_operations;
	return 0;
	}

	static int init_symlink(struct inode * inode)
	{
	inode->i_op = &sysfs_symlink_inode_operations;
	return 0;
	}

	static int create_dir(struct kobject * k, struct dentry * p,
	const char * n, struct dentry ** d)
	{
	int error;
	umode_t mode = S_IFDIR\| S_IRWXU \| S_IRUGO \| S_IXUGO;

	mutex_lock(&p->d_inode->i_mutex);
	*d = lookup_one_len(n, p, strlen(n));
	if (!IS_ERR(*d)) {
	if (sysfs_dirent_exist(p->d_fsdata, n))
	error = -EEXIST;
	else
	error = sysfs_make_dirent(p->d_fsdata, *d, k, mode,
	SYSFS_DIR);
	if (!error) {
	error = sysfs_create(*d, mode, init_dir);
	if (!error) {
	inc_nlink(p->d_inode);
	(*d)->d_op = &sysfs_dentry_ops;
	d_rehash(*d);
	}
	}
	if (error && (error != -EEXIST)) {
	struct sysfs_dirent sd = (d)->d_fsdata;
	if (sd) {
	list_del_init(&sd->s_sibling);
	sysfs_put(sd);
	}
	d_drop(*d);
	}
	dput(*d);
	} else
	error = PTR_ERR(*d);
	mutex_unlock(&p->d_inode->i_mutex);
	return error;
	}


	int sysfs_create_subdir(struct kobject * k, const char * n, struct dentry ** d)
	{
	return create_dir(k,k->dentry,n,d);
	}

	/**
	* sysfs_create_dir - create a directory for an object.
	* @kobj: object we're creating directory for.
	* @shadow_parent: parent parent object.
	*/

	int sysfs_create_dir(struct kobject * kobj, struct dentry *shadow_parent)
	{
	struct dentry * dentry = NULL;
	struct dentry * parent;
	int error = 0;

	BUG_ON(!kobj);

	if (shadow_parent)
	parent = shadow_parent;
	else if (kobj->parent)
	parent = kobj->parent->dentry;
	else if (sysfs_mount && sysfs_mount->mnt_sb)
	parent = sysfs_mount->mnt_sb->s_root;
	else
	return -EFAULT;

	error = create_dir(kobj,parent,kobject_name(kobj),&dentry);
	if (!error)
	kobj->dentry = dentry;
	return error;
	}

	/* attaches attribute's sysfs_dirent to the dentry corresponding to the
	* attribute file
	*/
	static int sysfs_attach_attr(struct sysfs_dirent * sd, struct dentry * dentry)
	{
	struct attribute * attr = NULL;
	struct bin_attribute * bin_attr = NULL;
	int (* init) (struct inode *) = NULL;
	int error = 0;

	if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
	bin_attr = sd->s_element;
	attr = &bin_attr->attr;
	} else {
	attr = sd->s_element;
	init = init_file;
	}

	dentry->d_fsdata = sysfs_get(sd);
	/* protect sd->s_dentry against sysfs_d_iput */
	spin_lock(&sysfs_lock);
	sd->s_dentry = dentry;
	spin_unlock(&sysfs_lock);
	error = sysfs_create(dentry, (attr->mode & S_IALLUGO) \| S_IFREG, init);
	if (error) {
	sysfs_put(sd);
	return error;
	}

	if (bin_attr) {
	dentry->d_inode->i_size = bin_attr->size;
	dentry->d_inode->i_fop = &bin_fops;
	}
	dentry->d_op = &sysfs_dentry_ops;
	d_rehash(dentry);

	return 0;
	}

	static int sysfs_attach_link(struct sysfs_dirent * sd, struct dentry * dentry)
	{
	int err = 0;

	dentry->d_fsdata = sysfs_get(sd);
	/* protect sd->s_dentry against sysfs_d_iput */
	spin_lock(&sysfs_lock);
	sd->s_dentry = dentry;
	spin_unlock(&sysfs_lock);
	err = sysfs_create(dentry, S_IFLNK\|S_IRWXUGO, init_symlink);
	if (!err) {
	dentry->d_op = &sysfs_dentry_ops;
	d_rehash(dentry);
	} else
	sysfs_put(sd);

	return err;
	}

	static struct dentry * sysfs_lookup(struct inode dir, struct dentry dentry,
	struct nameidata *nd)
	{
	struct sysfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
	struct sysfs_dirent * sd;
	int err = 0;

	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
	if (sd->s_type & SYSFS_NOT_PINNED) {
	const unsigned char * name = sysfs_get_name(sd);

	if (strcmp(name, dentry->d_name.name))
	continue;

	if (sd->s_type & SYSFS_KOBJ_LINK)
	err = sysfs_attach_link(sd, dentry);
	else
	err = sysfs_attach_attr(sd, dentry);
	break;
	}
	}

	return ERR_PTR(err);
	}

	const struct inode_operations sysfs_dir_inode_operations = {
	.lookup = sysfs_lookup,
	.setattr = sysfs_setattr,
	};

	static void remove_dir(struct dentry * d)
	{
	struct dentry * parent = dget(d->d_parent);
	struct sysfs_dirent * sd;

	mutex_lock(&parent->d_inode->i_mutex);
	d_delete(d);
	sd = d->d_fsdata;
	list_del_init(&sd->s_sibling);
	sysfs_put(sd);
	if (d->d_inode)
	simple_rmdir(parent->d_inode,d);

	pr_debug(" o %s removing done (%d)\n",d->d_name.name,
	atomic_read(&d->d_count));

	mutex_unlock(&parent->d_inode->i_mutex);
	dput(parent);
	}

	void sysfs_remove_subdir(struct dentry * d)
	{
	remove_dir(d);
	}


	static void __sysfs_remove_dir(struct dentry *dentry)
	{
	struct sysfs_dirent * parent_sd;
	struct sysfs_dirent * sd, * tmp;

	dget(dentry);
	if (!dentry)
	return;

	pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
	mutex_lock(&dentry->d_inode->i_mutex);
	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 & SYSFS_NOT_PINNED))
	continue;
	list_del_init(&sd->s_sibling);
	sysfs_drop_dentry(sd, dentry);
	sysfs_put(sd);
	}
	mutex_unlock(&dentry->d_inode->i_mutex);

	remove_dir(dentry);
	/**
	* Drop reference from dget() on entrance.
	*/
	dput(dentry);
	}

	/**
	* 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)
	{
	__sysfs_remove_dir(kobj->dentry);
	kobj->dentry = NULL;
	}

	int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent,
	const char *new_name)
	{
	int error = 0;
	struct dentry * new_dentry;

	if (!new_parent)
	return -EFAULT;

	down_write(&sysfs_rename_sem);
	mutex_lock(&new_parent->d_inode->i_mutex);

	new_dentry = lookup_one_len(new_name, new_parent, strlen(new_name));
	if (!IS_ERR(new_dentry)) {
	/* By allowing two different directories with the
	* same d_parent we allow this routine to move
	* between different shadows of the same directory
	*/
	if (kobj->dentry->d_parent->d_inode != new_parent->d_inode)
	return -EINVAL;
	else if (new_dentry->d_parent->d_inode != new_parent->d_inode)
	error = -EINVAL;
	else if (new_dentry == kobj->dentry)
	error = -EINVAL;
	else if (!new_dentry->d_inode) {
	error = kobject_set_name(kobj, "%s", new_name);
	if (!error) {
	struct sysfs_dirent sd, parent_sd;

	d_add(new_dentry, NULL);
	d_move(kobj->dentry, new_dentry);

	sd = kobj->dentry->d_fsdata;
	parent_sd = new_parent->d_fsdata;

	list_del_init(&sd->s_sibling);
	list_add(&sd->s_sibling, &parent_sd->s_children);
	}
	else
	d_drop(new_dentry);
	} else
	error = -EEXIST;
	dput(new_dentry);
	}
	mutex_unlock(&new_parent->d_inode->i_mutex);
	up_write(&sysfs_rename_sem);

	return error;
	}

	int sysfs_move_dir(struct kobject kobj, struct kobject new_parent)
	{
	struct dentry old_parent_dentry, new_parent_dentry, *new_dentry;
	struct sysfs_dirent new_parent_sd, sd;
	int error;

	old_parent_dentry = kobj->parent ?
	kobj->parent->dentry : sysfs_mount->mnt_sb->s_root;
	new_parent_dentry = new_parent ?
	new_parent->dentry : sysfs_mount->mnt_sb->s_root;

	if (old_parent_dentry->d_inode == new_parent_dentry->d_inode)
	return 0; /* nothing to move */
	again:
	mutex_lock(&old_parent_dentry->d_inode->i_mutex);
	if (!mutex_trylock(&new_parent_dentry->d_inode->i_mutex)) {
	mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
	goto again;
	}

	new_parent_sd = new_parent_dentry->d_fsdata;
	sd = kobj->dentry->d_fsdata;

	new_dentry = lookup_one_len(kobj->name, new_parent_dentry,
	strlen(kobj->name));
	if (IS_ERR(new_dentry)) {
	error = PTR_ERR(new_dentry);
	goto out;
	} else
	error = 0;
	d_add(new_dentry, NULL);
	d_move(kobj->dentry, new_dentry);
	dput(new_dentry);

	/* Remove from old parent's list and insert into new parent's list. */
	list_del_init(&sd->s_sibling);
	list_add(&sd->s_sibling, &new_parent_sd->s_children);

	out:
	mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
	mutex_unlock(&old_parent_dentry->d_inode->i_mutex);

	return error;
	}

	static int sysfs_dir_open(struct inode inode, struct file file)
	{
	struct dentry * dentry = file->f_path.dentry;
	struct sysfs_dirent * parent_sd = dentry->d_fsdata;

	mutex_lock(&dentry->d_inode->i_mutex);
	file->private_data = sysfs_new_dirent(parent_sd, NULL);
	mutex_unlock(&dentry->d_inode->i_mutex);

	return file->private_data ? 0 : -ENOMEM;

	}

	static int sysfs_dir_close(struct inode inode, struct file file)
	{
	struct dentry * dentry = file->f_path.dentry;
	struct sysfs_dirent * cursor = file->private_data;

	mutex_lock(&dentry->d_inode->i_mutex);
	list_del_init(&cursor->s_sibling);
	mutex_unlock(&dentry->d_inode->i_mutex);

	release_sysfs_dirent(cursor);

	return 0;
	}

	/* 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_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 *cursor = filp->private_data;
	struct list_head p, q = &cursor->s_sibling;
	ino_t ino;
	int i = filp->f_pos;

	switch (i) {
	case 0:
	ino = parent_sd->s_ino;
	if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
	break;
	filp->f_pos++;
	i++;
	/* fallthrough */
	case 1:
	ino = parent_ino(dentry);
	if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
	break;
	filp->f_pos++;
	i++;
	/* fallthrough */
	default:
	if (filp->f_pos == 2)
	list_move(q, &parent_sd->s_children);

	for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
	struct sysfs_dirent *next;
	const char * name;
	int len;

	next = list_entry(p, struct sysfs_dirent,
	s_sibling);
	if (!next->s_element)
	continue;

	name = sysfs_get_name(next);
	len = strlen(name);
	ino = next->s_ino;

	if (filldir(dirent, name, len, filp->f_pos, ino,
	dt_type(next)) < 0)
	return 0;

	list_move(q, p);
	p = q;
	filp->f_pos++;
	}
	}
	return 0;
	}

	static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
	{
	struct dentry * dentry = file->f_path.dentry;

	mutex_lock(&dentry->d_inode->i_mutex);
	switch (origin) {
	case 1:
	offset += file->f_pos;
	case 0:
	if (offset >= 0)
	break;
	default:
	mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
	return -EINVAL;
	}
	if (offset != file->f_pos) {
	file->f_pos = offset;
	if (file->f_pos >= 2) {
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct sysfs_dirent *cursor = file->private_data;
	struct list_head *p;
	loff_t n = file->f_pos - 2;

	list_del(&cursor->s_sibling);
	p = sd->s_children.next;
	while (n && p != &sd->s_children) {
	struct sysfs_dirent *next;
	next = list_entry(p, struct sysfs_dirent,
	s_sibling);
	if (next->s_element)
	n--;
	p = p->next;
	}
	list_add_tail(&cursor->s_sibling, p);
	}
	}
	mutex_unlock(&dentry->d_inode->i_mutex);
	return offset;
	}


	/**
	* sysfs_make_shadowed_dir - Setup so a directory can be shadowed
	* @kobj: object we're creating shadow of.
	*/

	int sysfs_make_shadowed_dir(struct kobject *kobj,
	void * (follow_link)(struct dentry , struct nameidata *))
	{
	struct inode *inode;
	struct inode_operations *i_op;

	inode = kobj->dentry->d_inode;
	if (inode->i_op != &sysfs_dir_inode_operations)
	return -EINVAL;

	i_op = kmalloc(sizeof(*i_op), GFP_KERNEL);
	if (!i_op)
	return -ENOMEM;

	memcpy(i_op, &sysfs_dir_inode_operations, sizeof(*i_op));
	i_op->follow_link = follow_link;

	/* Locking of inode->i_op?
	* Since setting i_op is a single word write and they
	* are atomic we should be ok here.
	*/
	inode->i_op = i_op;
	return 0;
	}

	/**
	* sysfs_create_shadow_dir - create a shadow directory for an object.
	* @kobj: object we're creating directory for.
	*
	* sysfs_make_shadowed_dir must already have been called on this
	* directory.
	*/

	struct dentry sysfs_create_shadow_dir(struct kobject kobj)
	{
	struct sysfs_dirent *sd;
	struct dentry parent, dir, *shadow;
	struct inode *inode;

	dir = kobj->dentry;
	inode = dir->d_inode;
	parent = dir->d_parent;
	shadow = ERR_PTR(-EINVAL);
	if (!sysfs_is_shadowed_inode(inode))
	goto out;

	shadow = d_alloc(parent, &dir->d_name);
	if (!shadow)
	goto nomem;

	sd = __sysfs_make_dirent(shadow, kobj, inode->i_mode, SYSFS_DIR);
	if (!sd)
	goto nomem;

	d_instantiate(shadow, igrab(inode));
	inc_nlink(inode);
	inc_nlink(parent->d_inode);
	shadow->d_op = &sysfs_dentry_ops;

	dget(shadow); /* Extra count - pin the dentry in core */

	out:
	return shadow;
	nomem:
	dput(shadow);
	shadow = ERR_PTR(-ENOMEM);
	goto out;
	}

	/**
	* sysfs_remove_shadow_dir - remove an object's directory.
	* @shadow: dentry of shadow directory
	*
	* 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_shadow_dir(struct dentry *shadow)
	{
	__sysfs_remove_dir(shadow);
	}

	const struct file_operations sysfs_dir_operations = {
	.open = sysfs_dir_open,
	.release = sysfs_dir_close,
	.llseek = sysfs_dir_lseek,
	.read = generic_read_dir,
	.readdir = sysfs_readdir,
	};