/*
 * fs/sysfs/dir.c - sysfs core and dir operation implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#undef DEBUG

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/idr.h>
#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/hash.h>
#include "sysfs.h"

DEFINE_MUTEX(sysfs_mutex);
DEFINE_SPINLOCK(sysfs_assoc_lock);

#define to_sysfs_dirent(X) rb_entry((X), struct sysfs_dirent, s_rb);

static DEFINE_SPINLOCK(sysfs_ino_lock);
static DEFINE_IDA(sysfs_ino_ida);

static unsigned int sysfs_name_hash(const void *ns, const char *name)
{
	unsigned long hash = init_name_hash();
	unsigned int len = strlen(name);
	while (len--)
		hash = partial_name_hash(*name++, hash);
	hash = ( end_name_hash(hash) ^ hash_ptr( (void *)ns, 31 ) );
	hash &= 0x7fffffffU;
	
	if (hash < 1)
		hash += 2;
	if (hash >= INT_MAX)
		hash = INT_MAX - 1;
	return hash;
}

static int sysfs_name_compare(unsigned int hash, const void *ns,
	const char *name, const struct sysfs_dirent *sd)
{
	if (hash != sd->s_hash)
		return hash - sd->s_hash;
	if (ns != sd->s_ns)
		return ns - sd->s_ns;
	return strcmp(name, sd->s_name);
}

static int sysfs_sd_compare(const struct sysfs_dirent *left,
			    const struct sysfs_dirent *right)
{
	return sysfs_name_compare(left->s_hash, left->s_ns, left->s_name,
				  right);
}

static int sysfs_link_sibling(struct sysfs_dirent *sd)
{
	struct rb_node **node = &sd->s_parent->s_dir.children.rb_node;
	struct rb_node *parent = NULL;

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

	while (*node) {
		struct sysfs_dirent *pos;
		int result;

		pos = to_sysfs_dirent(*node);
		parent = *node;
		result = sysfs_sd_compare(sd, pos);
		if (result < 0)
			node = &pos->s_rb.rb_left;
		else if (result > 0)
			node = &pos->s_rb.rb_right;
		else
			return -EEXIST;
	}
	
	rb_link_node(&sd->s_rb, parent, node);
	rb_insert_color(&sd->s_rb, &sd->s_parent->s_dir.children);
	return 0;
}

static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
{
	if (sysfs_type(sd) == SYSFS_DIR)
		sd->s_parent->s_dir.subdirs--;

	rb_erase(&sd->s_rb, &sd->s_parent->s_dir.children);
}

struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd)
{
	if (unlikely(!sd))
		return NULL;

	while (1) {
		int v, t;

		v = atomic_read(&sd->s_active);
		if (unlikely(v < 0))
			return NULL;

		t = atomic_cmpxchg(&sd->s_active, v, v + 1);
		if (likely(t == v)) {
			rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);
			return sd;
		}
		if (t < 0)
			return NULL;

		cpu_relax();
	}
}

void sysfs_put_active(struct sysfs_dirent *sd)
{
	int v;

	if (unlikely(!sd))
		return;

	rwsem_release(&sd->dep_map, 1, _RET_IP_);
	v = atomic_dec_return(&sd->s_active);
	if (likely(v != SD_DEACTIVATED_BIAS))
		return;

	complete(sd->u.completion);
}

static void sysfs_deactivate(struct sysfs_dirent *sd)
{
	DECLARE_COMPLETION_ONSTACK(wait);
	int v;

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

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

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

	rwsem_acquire(&sd->dep_map, 0, 0, _RET_IP_);
	v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active);

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

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

static int sysfs_alloc_ino(unsigned int *pino)
{
	int ino, rc;

 retry:
	spin_lock(&sysfs_ino_lock);
	rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
	spin_unlock(&sysfs_ino_lock);

	if (rc == -EAGAIN) {
		if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL))
			goto retry;
		rc = -ENOMEM;
	}

	*pino = ino;
	return rc;
}

static void sysfs_free_ino(unsigned int ino)
{
	spin_lock(&sysfs_ino_lock);
	ida_remove(&sysfs_ino_ida, ino);
	spin_unlock(&sysfs_ino_lock);
}

void release_sysfs_dirent(struct sysfs_dirent * sd)
{
	struct sysfs_dirent *parent_sd;

 repeat:
	parent_sd = sd->s_parent;

	if (sysfs_type(sd) == SYSFS_KOBJ_LINK)
		sysfs_put(sd->s_symlink.target_sd);
	if (sysfs_type(sd) & SYSFS_COPY_NAME)
		kfree(sd->s_name);
	if (sd->s_iattr && sd->s_iattr->ia_secdata)
		security_release_secctx(sd->s_iattr->ia_secdata,
					sd->s_iattr->ia_secdata_len);
	kfree(sd->s_iattr);
	sysfs_free_ino(sd->s_ino);
	kmem_cache_free(sysfs_dir_cachep, sd);

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

static int sysfs_dentry_delete(const struct dentry *dentry)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	return !!(sd->s_flags & SYSFS_FLAG_REMOVED);
}

static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	struct sysfs_dirent *sd;
	int is_dir;

	if (nd->flags & LOOKUP_RCU)
		return -ECHILD;

	sd = dentry->d_fsdata;
	mutex_lock(&sysfs_mutex);

	
	if (sd->s_flags & SYSFS_FLAG_REMOVED)
		goto out_bad;

	
	if (dentry->d_parent->d_fsdata != sd->s_parent)
		goto out_bad;

	
	if (strcmp(dentry->d_name.name, sd->s_name) != 0)
		goto out_bad;

	mutex_unlock(&sysfs_mutex);
out_valid:
	return 1;
out_bad:
	is_dir = (sysfs_type(sd) == SYSFS_DIR);
	mutex_unlock(&sysfs_mutex);
	if (is_dir) {
		if (have_submounts(dentry))
			goto out_valid;
		shrink_dcache_parent(dentry);
	}
	d_drop(dentry);
	return 0;
}

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

	sysfs_put(sd);
	iput(inode);
}

static const struct dentry_operations sysfs_dentry_ops = {
	.d_revalidate	= sysfs_dentry_revalidate,
	.d_delete	= sysfs_dentry_delete,
	.d_iput		= sysfs_dentry_iput,
};

struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
{
	char *dup_name = NULL;
	struct sysfs_dirent *sd;

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

	sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
	if (!sd)
		goto err_out1;

	if (sysfs_alloc_ino(&sd->s_ino))
		goto err_out2;

	atomic_set(&sd->s_count, 1);
	atomic_set(&sd->s_active, 0);

	sd->s_name = name;
	sd->s_mode = mode;
	sd->s_flags = type;

	return sd;

 err_out2:
	kmem_cache_free(sysfs_dir_cachep, sd);
 err_out1:
	kfree(dup_name);
	return NULL;
}

void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
		       struct sysfs_dirent *parent_sd)
{
	memset(acxt, 0, sizeof(*acxt));
	acxt->parent_sd = parent_sd;

	mutex_lock(&sysfs_mutex);
}

int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
	struct sysfs_inode_attrs *ps_iattr;
	int ret;

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

	sd->s_hash = sysfs_name_hash(sd->s_ns, sd->s_name);
	sd->s_parent = sysfs_get(acxt->parent_sd);

	ret = sysfs_link_sibling(sd);
	if (ret)
		return ret;

	
	ps_iattr = acxt->parent_sd->s_iattr;
	if (ps_iattr) {
		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
	}

	return 0;
}

static char *sysfs_pathname(struct sysfs_dirent *sd, char *path)
{
	if (sd->s_parent) {
		sysfs_pathname(sd->s_parent, path);
		strlcat(path, "/", PATH_MAX);
	}
	strlcat(path, sd->s_name, PATH_MAX);
	return path;
}

int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
	int ret;

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

	return ret;
}

void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
	struct sysfs_inode_attrs *ps_iattr;

	BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED);

	sysfs_unlink_sibling(sd);

	
	ps_iattr = acxt->parent_sd->s_iattr;
	if (ps_iattr) {
		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
	}

	sd->s_flags |= SYSFS_FLAG_REMOVED;
	sd->u.removed_list = acxt->removed;
	acxt->removed = sd;
}

void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
{
	
	mutex_unlock(&sysfs_mutex);

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

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

		sysfs_deactivate(sd);
		unmap_bin_file(sd);
		sysfs_put(sd);
	}
}

struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
				       const void *ns,
				       const unsigned char *name)
{
	struct rb_node *node = parent_sd->s_dir.children.rb_node;
	unsigned int hash;

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

	hash = sysfs_name_hash(ns, name);
	while (node) {
		struct sysfs_dirent *sd;
		int result;

		sd = to_sysfs_dirent(node);
		result = sysfs_name_compare(hash, ns, name, sd);
		if (result < 0)
			node = node->rb_left;
		else if (result > 0)
			node = node->rb_right;
		else
			return sd;
	}
	return NULL;
}

struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
				      const void *ns,
				      const unsigned char *name)
{
	struct sysfs_dirent *sd;

	mutex_lock(&sysfs_mutex);
	sd = sysfs_find_dirent(parent_sd, ns, name);
	sysfs_get(sd);
	mutex_unlock(&sysfs_mutex);

	return sd;
}
EXPORT_SYMBOL_GPL(sysfs_get_dirent);

static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,
	enum kobj_ns_type type, const void *ns, const char *name,
	struct sysfs_dirent **p_sd)
{
	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
	struct sysfs_addrm_cxt acxt;
	struct sysfs_dirent *sd;
	int rc;

	
	sd = sysfs_new_dirent(name, mode, SYSFS_DIR);
	if (!sd)
		return -ENOMEM;

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

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

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

	return rc;
}

int sysfs_create_subdir(struct kobject *kobj, const char *name,
			struct sysfs_dirent **p_sd)
{
	return create_dir(kobj, kobj->sd,
			  KOBJ_NS_TYPE_NONE, NULL, name, p_sd);
}

static enum kobj_ns_type sysfs_read_ns_type(struct kobject *kobj)
{
	const struct kobj_ns_type_operations *ops;
	enum kobj_ns_type type;

	ops = kobj_child_ns_ops(kobj);
	if (!ops)
		return KOBJ_NS_TYPE_NONE;

	type = ops->type;
	BUG_ON(type <= KOBJ_NS_TYPE_NONE);
	BUG_ON(type >= KOBJ_NS_TYPES);
	BUG_ON(!kobj_ns_type_registered(type));

	return type;
}

int sysfs_create_dir(struct kobject * kobj)
{
	enum kobj_ns_type type;
	struct sysfs_dirent *parent_sd, *sd;
	const void *ns = NULL;
	int error = 0;

	BUG_ON(!kobj);

	if (kobj->parent)
		parent_sd = kobj->parent->sd;
	else
		parent_sd = &sysfs_root;

	if (!parent_sd)
		return -ENOENT;

	if (sysfs_ns_type(parent_sd))
		ns = kobj->ktype->namespace(kobj);
	type = sysfs_read_ns_type(kobj);

	error = create_dir(kobj, parent_sd, type, ns, kobject_name(kobj), &sd);
	if (!error)
		kobj->sd = sd;
	return error;
}

static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
				struct nameidata *nd)
{
	struct dentry *ret = NULL;
	struct dentry *parent = dentry->d_parent;
	struct sysfs_dirent *parent_sd = parent->d_fsdata;
	struct sysfs_dirent *sd;
	struct inode *inode;
	enum kobj_ns_type type;
	const void *ns;

	mutex_lock(&sysfs_mutex);

	type = sysfs_ns_type(parent_sd);
	ns = sysfs_info(dir->i_sb)->ns[type];

	sd = sysfs_find_dirent(parent_sd, ns, dentry->d_name.name);

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

	
	inode = sysfs_get_inode(dir->i_sb, sd);
	if (!inode) {
		ret = ERR_PTR(-ENOMEM);
		goto out_unlock;
	}

	
	ret = d_find_alias(inode);
	if (!ret) {
		d_set_d_op(dentry, &sysfs_dentry_ops);
		dentry->d_fsdata = sysfs_get(sd);
		d_add(dentry, inode);
	} else {
		d_move(ret, dentry);
		iput(inode);
	}

 out_unlock:
	mutex_unlock(&sysfs_mutex);
	return ret;
}

const struct inode_operations sysfs_dir_inode_operations = {
	.lookup		= sysfs_lookup,
	.permission	= sysfs_permission,
	.setattr	= sysfs_setattr,
	.getattr	= sysfs_getattr,
	.setxattr	= sysfs_setxattr,
};

static void remove_dir(struct sysfs_dirent *sd)
{
	struct sysfs_addrm_cxt acxt;

	sysfs_addrm_start(&acxt, sd->s_parent);
	sysfs_remove_one(&acxt, sd);
	sysfs_addrm_finish(&acxt);
}

void sysfs_remove_subdir(struct sysfs_dirent *sd)
{
	remove_dir(sd);
}


static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
{
	struct sysfs_addrm_cxt acxt;
	struct rb_node *pos;

	if (!dir_sd)
		return;

	pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
	sysfs_addrm_start(&acxt, dir_sd);
	pos = rb_first(&dir_sd->s_dir.children);
	while (pos) {
		struct sysfs_dirent *sd = to_sysfs_dirent(pos);
		pos = rb_next(pos);
		if (sysfs_type(sd) != SYSFS_DIR)
			sysfs_remove_one(&acxt, sd);
	}
	sysfs_addrm_finish(&acxt);

	remove_dir(dir_sd);
}


void sysfs_remove_dir(struct kobject * kobj)
{
	struct sysfs_dirent *sd = kobj->sd;

	spin_lock(&sysfs_assoc_lock);
	kobj->sd = NULL;
	spin_unlock(&sysfs_assoc_lock);

	__sysfs_remove_dir(sd);
}

int sysfs_rename(struct sysfs_dirent *sd,
	struct sysfs_dirent *new_parent_sd, const void *new_ns,
	const char *new_name)
{
	const char *dup_name = NULL;
	int error;

	mutex_lock(&sysfs_mutex);

	error = 0;
	if ((sd->s_parent == new_parent_sd) && (sd->s_ns == new_ns) &&
	    (strcmp(sd->s_name, new_name) == 0))
		goto out;	

	error = -EEXIST;
	if (sysfs_find_dirent(new_parent_sd, new_ns, new_name))
		goto out;

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

		dup_name = sd->s_name;
		sd->s_name = new_name;
	}

	
	sysfs_unlink_sibling(sd);
	sysfs_get(new_parent_sd);
	sysfs_put(sd->s_parent);
	sd->s_ns = new_ns;
	sd->s_hash = sysfs_name_hash(sd->s_ns, sd->s_name);
	sd->s_parent = new_parent_sd;
	sysfs_link_sibling(sd);

	error = 0;
 out:
	mutex_unlock(&sysfs_mutex);
	kfree(dup_name);
	return error;
}

int sysfs_rename_dir(struct kobject *kobj, const char *new_name)
{
	struct sysfs_dirent *parent_sd = kobj->sd->s_parent;
	const void *new_ns = NULL;

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

	return sysfs_rename(kobj->sd, parent_sd, new_ns, new_name);
}

int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent_kobj)
{
	struct sysfs_dirent *sd = kobj->sd;
	struct sysfs_dirent *new_parent_sd;
	const void *new_ns = NULL;

	BUG_ON(!sd->s_parent);
	if (sysfs_ns_type(sd->s_parent))
		new_ns = kobj->ktype->namespace(kobj);
	new_parent_sd = new_parent_kobj && new_parent_kobj->sd ?
		new_parent_kobj->sd : &sysfs_root;

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

static inline unsigned char dt_type(struct sysfs_dirent *sd)
{
	return (sd->s_mode >> 12) & 15;
}

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

static struct sysfs_dirent *sysfs_dir_pos(const void *ns,
	struct sysfs_dirent *parent_sd,	loff_t hash, struct sysfs_dirent *pos)
{
	if (pos) {
		int valid = !(pos->s_flags & SYSFS_FLAG_REMOVED) &&
			pos->s_parent == parent_sd &&
			hash == pos->s_hash;
		sysfs_put(pos);
		if (!valid)
			pos = NULL;
	}
	if (!pos && (hash > 1) && (hash < INT_MAX)) {
		struct rb_node *node = parent_sd->s_dir.children.rb_node;
		while (node) {
			pos = to_sysfs_dirent(node);

			if (hash < pos->s_hash)
				node = node->rb_left;
			else if (hash > pos->s_hash)
				node = node->rb_right;
			else
				break;
		}
	}
	
	while (pos && pos->s_ns != ns) {
		struct rb_node *node = rb_next(&pos->s_rb);
		if (!node)
			pos = NULL;
		else
			pos = to_sysfs_dirent(node);
	}
	return pos;
}

static struct sysfs_dirent *sysfs_dir_next_pos(const void *ns,
	struct sysfs_dirent *parent_sd,	ino_t ino, struct sysfs_dirent *pos)
{
	pos = sysfs_dir_pos(ns, parent_sd, ino, pos);
	if (pos) do {
		struct rb_node *node = rb_next(&pos->s_rb);
		if (!node)
			pos = NULL;
		else
			pos = to_sysfs_dirent(node);
	} while (pos && pos->s_ns != ns);
	return pos;
}

static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
	struct dentry *dentry = filp->f_path.dentry;
	struct sysfs_dirent * parent_sd = dentry->d_fsdata;
	struct sysfs_dirent *pos = filp->private_data;
	enum kobj_ns_type type;
	const void *ns;
	ino_t ino;

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

	if (filp->f_pos == 0) {
		ino = parent_sd->s_ino;
		if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)
			filp->f_pos++;
	}
	if (filp->f_pos == 1) {
		if (parent_sd->s_parent)
			ino = parent_sd->s_parent->s_ino;
		else
			ino = parent_sd->s_ino;
		if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)
			filp->f_pos++;
	}
	mutex_lock(&sysfs_mutex);
	for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);
	     pos;
	     pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) {
		const char * name;
		unsigned int type;
		int len, ret;

		name = pos->s_name;
		len = strlen(name);
		ino = pos->s_ino;
		type = dt_type(pos);
		filp->f_pos = pos->s_hash;
		filp->private_data = sysfs_get(pos);

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


const struct file_operations sysfs_dir_operations = {
	.read		= generic_read_dir,
	.readdir	= sysfs_readdir,
	.release	= sysfs_dir_release,
	.llseek		= generic_file_llseek,
};
