[deliverable/linux.git] / fs / kernfs / inode.c

/*
 * fs/kernfs/inode.c - kernfs inode implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
 *
 * This file is released under the GPLv2.
 */

#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/security.h>

#include "kernfs-internal.h"

static const struct address_space_operations sysfs_aops = {
	.readpage	= simple_readpage,
	.write_begin	= simple_write_begin,
	.write_end	= simple_write_end,
};

static struct backing_dev_info sysfs_backing_dev_info = {
	.name		= "sysfs",
	.ra_pages	= 0,	/* No readahead */
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
};

static const struct inode_operations sysfs_inode_operations = {
	.permission	= sysfs_permission,
	.setattr	= sysfs_setattr,
	.getattr	= sysfs_getattr,
	.setxattr	= sysfs_setxattr,
	.removexattr	= sysfs_removexattr,
	.getxattr	= sysfs_getxattr,
	.listxattr	= sysfs_listxattr,
};

void __init sysfs_inode_init(void)
{
	if (bdi_init(&sysfs_backing_dev_info))
		panic("failed to init sysfs_backing_dev_info");
}

static struct sysfs_inode_attrs *sysfs_inode_attrs(struct sysfs_dirent *sd)
{
	struct iattr *iattrs;

	if (sd->s_iattr)
		return sd->s_iattr;

	sd->s_iattr = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
	if (!sd->s_iattr)
		return NULL;
	iattrs = &sd->s_iattr->ia_iattr;

	/* assign default attributes */
	iattrs->ia_mode = sd->s_mode;
	iattrs->ia_uid = GLOBAL_ROOT_UID;
	iattrs->ia_gid = GLOBAL_ROOT_GID;
	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;

	simple_xattrs_init(&sd->s_iattr->xattrs);

	return sd->s_iattr;
}

static int __kernfs_setattr(struct sysfs_dirent *sd, const struct iattr *iattr)
{
	struct sysfs_inode_attrs *attrs;
	struct iattr *iattrs;
	unsigned int ia_valid = iattr->ia_valid;

	attrs = sysfs_inode_attrs(sd);
	if (!attrs)
		return -ENOMEM;

	iattrs = &attrs->ia_iattr;

	if (ia_valid & ATTR_UID)
		iattrs->ia_uid = iattr->ia_uid;
	if (ia_valid & ATTR_GID)
		iattrs->ia_gid = iattr->ia_gid;
	if (ia_valid & ATTR_ATIME)
		iattrs->ia_atime = iattr->ia_atime;
	if (ia_valid & ATTR_MTIME)
		iattrs->ia_mtime = iattr->ia_mtime;
	if (ia_valid & ATTR_CTIME)
		iattrs->ia_ctime = iattr->ia_ctime;
	if (ia_valid & ATTR_MODE) {
		umode_t mode = iattr->ia_mode;
		iattrs->ia_mode = sd->s_mode = mode;
	}
	return 0;
}

/**
 * kernfs_setattr - set iattr on a node
 * @sd: target node
 * @iattr: iattr to set
 *
 * Returns 0 on success, -errno on failure.
 */
int kernfs_setattr(struct sysfs_dirent *sd, const struct iattr *iattr)
{
	int ret;

	mutex_lock(&sysfs_mutex);
	ret = __kernfs_setattr(sd, iattr);
	mutex_unlock(&sysfs_mutex);
	return ret;
}

int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
	struct inode *inode = dentry->d_inode;
	struct sysfs_dirent *sd = dentry->d_fsdata;
	int error;

	if (!sd)
		return -EINVAL;

	mutex_lock(&sysfs_mutex);
	error = inode_change_ok(inode, iattr);
	if (error)
		goto out;

	error = __kernfs_setattr(sd, iattr);
	if (error)
		goto out;

	/* this ignores size changes */
	setattr_copy(inode, iattr);

out:
	mutex_unlock(&sysfs_mutex);
	return error;
}

static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata,
			       u32 *secdata_len)
{
	struct sysfs_inode_attrs *attrs;
	void *old_secdata;
	size_t old_secdata_len;

	attrs = sysfs_inode_attrs(sd);
	if (!attrs)
		return -ENOMEM;

	old_secdata = attrs->ia_secdata;
	old_secdata_len = attrs->ia_secdata_len;

	attrs->ia_secdata = *secdata;
	attrs->ia_secdata_len = *secdata_len;

	*secdata = old_secdata;
	*secdata_len = old_secdata_len;
	return 0;
}

int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
		size_t size, int flags)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct sysfs_inode_attrs *attrs;
	void *secdata;
	int error;
	u32 secdata_len = 0;

	attrs = sysfs_inode_attrs(sd);
	if (!attrs)
		return -ENOMEM;

	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
		error = security_inode_setsecurity(dentry->d_inode, suffix,
						value, size, flags);
		if (error)
			return error;
		error = security_inode_getsecctx(dentry->d_inode,
						&secdata, &secdata_len);
		if (error)
			return error;

		mutex_lock(&sysfs_mutex);
		error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
		mutex_unlock(&sysfs_mutex);

		if (secdata)
			security_release_secctx(secdata, secdata_len);
		return error;
	} else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
		return simple_xattr_set(&attrs->xattrs, name, value, size,
					flags);
	}

	return -EINVAL;
}

int sysfs_removexattr(struct dentry *dentry, const char *name)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct sysfs_inode_attrs *attrs;

	attrs = sysfs_inode_attrs(sd);
	if (!attrs)
		return -ENOMEM;

	return simple_xattr_remove(&attrs->xattrs, name);
}

ssize_t sysfs_getxattr(struct dentry *dentry, const char *name, void *buf,
		       size_t size)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct sysfs_inode_attrs *attrs;

	attrs = sysfs_inode_attrs(sd);
	if (!attrs)
		return -ENOMEM;

	return simple_xattr_get(&attrs->xattrs, name, buf, size);
}

ssize_t sysfs_listxattr(struct dentry *dentry, char *buf, size_t size)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct sysfs_inode_attrs *attrs;

	attrs = sysfs_inode_attrs(sd);
	if (!attrs)
		return -ENOMEM;

	return simple_xattr_list(&attrs->xattrs, buf, size);
}

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_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;
}

static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
{
	struct sysfs_inode_attrs *attrs = sd->s_iattr;

	inode->i_mode = sd->s_mode;
	if (attrs) {
		/* sysfs_dirent has non-default attributes
		 * get them from persistent copy in sysfs_dirent
		 */
		set_inode_attr(inode, &attrs->ia_iattr);
		security_inode_notifysecctx(inode, attrs->ia_secdata,
					    attrs->ia_secdata_len);
	}

	if (sysfs_type(sd) == SYSFS_DIR)
		set_nlink(inode, sd->s_dir.subdirs + 2);
}

int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
		  struct kstat *stat)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct inode *inode = dentry->d_inode;

	mutex_lock(&sysfs_mutex);
	sysfs_refresh_inode(sd, inode);
	mutex_unlock(&sysfs_mutex);

	generic_fillattr(inode, stat);
	return 0;
}

static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
{
	kernfs_get(sd);
	inode->i_private = sd;
	inode->i_mapping->a_ops = &sysfs_aops;
	inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
	inode->i_op = &sysfs_inode_operations;

	set_default_inode_attr(inode, sd->s_mode);
	sysfs_refresh_inode(sd, inode);

	/* initialize inode according to type */
	switch (sysfs_type(sd)) {
	case SYSFS_DIR:
		inode->i_op = &sysfs_dir_inode_operations;
		inode->i_fop = &sysfs_dir_operations;
		break;
	case SYSFS_KOBJ_ATTR:
		inode->i_size = sd->s_attr.size;
		inode->i_fop = &kernfs_file_operations;
		break;
	case SYSFS_KOBJ_LINK:
		inode->i_op = &sysfs_symlink_inode_operations;
		break;
	default:
		BUG();
	}

	unlock_new_inode(inode);
}

/**
 *	sysfs_get_inode - get inode for sysfs_dirent
 *	@sb: super block
 *	@sd: sysfs_dirent to allocate inode for
 *
 *	Get inode for @sd.  If such inode doesn't exist, a new inode
 *	is allocated and basics are initialized.  New inode is
 *	returned locked.
 *
 *	LOCKING:
 *	Kernel thread context (may sleep).
 *
 *	RETURNS:
 *	Pointer to allocated inode on success, NULL on failure.
 */
struct inode *sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)
{
	struct inode *inode;

	inode = iget_locked(sb, sd->s_ino);
	if (inode && (inode->i_state & I_NEW))
		sysfs_init_inode(sd, inode);

	return inode;
}

/*
 * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 * To prevent the sysfs inode numbers from being freed prematurely we take a
 * reference to sysfs_dirent from the sysfs inode.  A
 * super_operations.evict_inode() implementation is needed to drop that
 * reference upon inode destruction.
 */
void sysfs_evict_inode(struct inode *inode)
{
	struct sysfs_dirent *sd  = inode->i_private;

	truncate_inode_pages(&inode->i_data, 0);
	clear_inode(inode);
	kernfs_put(sd);
}

int sysfs_permission(struct inode *inode, int mask)
{
	struct sysfs_dirent *sd;

	if (mask & MAY_NOT_BLOCK)
		return -ECHILD;

	sd = inode->i_private;

	mutex_lock(&sysfs_mutex);
	sysfs_refresh_inode(sd, inode);
	mutex_unlock(&sysfs_mutex);

	return generic_permission(inode, mask);
}
Commit	Line	Data
b8441ed2 TH	1	/*
	2	* fs/kernfs/inode.c - kernfs inode implementation
	3	*
	4	* Copyright (c) 2001-3 Patrick Mochel
	5	* Copyright (c) 2007 SUSE Linux Products GmbH
	6	* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
	7	*
	8	* This file is released under the GPLv2.
	9	*/
ffed24e2 TH	10
	11	#include <linux/pagemap.h>
	12	#include <linux/backing-dev.h>
	13	#include <linux/capability.h>
	14	#include <linux/errno.h>
	15	#include <linux/slab.h>
	16	#include <linux/xattr.h>
	17	#include <linux/security.h>
	18
	19	#include "kernfs-internal.h"
	20
	21	static const struct address_space_operations sysfs_aops = {
	22	.readpage = simple_readpage,
	23	.write_begin = simple_write_begin,
	24	.write_end = simple_write_end,
	25	};
	26
	27	static struct backing_dev_info sysfs_backing_dev_info = {
	28	.name = "sysfs",
	29	.ra_pages = 0, /* No readahead */
	30	.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
	31	};
	32
	33	static const struct inode_operations sysfs_inode_operations = {
	34	.permission = sysfs_permission,
	35	.setattr = sysfs_setattr,
	36	.getattr = sysfs_getattr,
	37	.setxattr = sysfs_setxattr,
2322392b TH	38	.removexattr = sysfs_removexattr,
	39	.getxattr = sysfs_getxattr,
	40	.listxattr = sysfs_listxattr,
ffed24e2 TH	41	};
ffed24e2 TH	42
4b93dc9b	43	void __init sysfs_inode_init(void)
ffed24e2	44	{
4b93dc9b TH	45	if (bdi_init(&sysfs_backing_dev_info))
4b93dc9b TH	46	panic("failed to init sysfs_backing_dev_info");
ffed24e2 TH	47	}
ffed24e2 TH	48
9a8049af	49	static struct sysfs_inode_attrs sysfs_inode_attrs(struct sysfs_dirent sd)
ffed24e2	50	{
ffed24e2 TH	51	struct iattr *iattrs;
ffed24e2 TH	52
9a8049af TH	53	if (sd->s_iattr)
	54	return sd->s_iattr;
	55
	56	sd->s_iattr = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
	57	if (!sd->s_iattr)
ffed24e2	58	return NULL;
9a8049af	59	iattrs = &sd->s_iattr->ia_iattr;
ffed24e2 TH	60
	61	/* assign default attributes */
	62	iattrs->ia_mode = sd->s_mode;
	63	iattrs->ia_uid = GLOBAL_ROOT_UID;
	64	iattrs->ia_gid = GLOBAL_ROOT_GID;
	65	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
	66
2322392b TH	67	simple_xattrs_init(&sd->s_iattr->xattrs);
2322392b TH	68
9a8049af	69	return sd->s_iattr;
ffed24e2 TH	70	}
	71
	72	static int __kernfs_setattr(struct sysfs_dirent sd, const struct iattr iattr)
	73	{
9a8049af	74	struct sysfs_inode_attrs *attrs;
ffed24e2 TH	75	struct iattr *iattrs;
	76	unsigned int ia_valid = iattr->ia_valid;
	77
9a8049af TH	78	attrs = sysfs_inode_attrs(sd);
	79	if (!attrs)
	80	return -ENOMEM;
ffed24e2	81
9a8049af	82	iattrs = &attrs->ia_iattr;
ffed24e2 TH	83
	84	if (ia_valid & ATTR_UID)
	85	iattrs->ia_uid = iattr->ia_uid;
	86	if (ia_valid & ATTR_GID)
	87	iattrs->ia_gid = iattr->ia_gid;
	88	if (ia_valid & ATTR_ATIME)
	89	iattrs->ia_atime = iattr->ia_atime;
	90	if (ia_valid & ATTR_MTIME)
	91	iattrs->ia_mtime = iattr->ia_mtime;
	92	if (ia_valid & ATTR_CTIME)
	93	iattrs->ia_ctime = iattr->ia_ctime;
	94	if (ia_valid & ATTR_MODE) {
	95	umode_t mode = iattr->ia_mode;
	96	iattrs->ia_mode = sd->s_mode = mode;
	97	}
	98	return 0;
	99	}
	100
	101	/**
	102	* kernfs_setattr - set iattr on a node
	103	* @sd: target node
	104	* @iattr: iattr to set
	105	*
	106	* Returns 0 on success, -errno on failure.
	107	*/
	108	int kernfs_setattr(struct sysfs_dirent sd, const struct iattr iattr)
	109	{
	110	int ret;
	111
	112	mutex_lock(&sysfs_mutex);
	113	ret = __kernfs_setattr(sd, iattr);
	114	mutex_unlock(&sysfs_mutex);
	115	return ret;
	116	}
	117
	118	int sysfs_setattr(struct dentry dentry, struct iattr iattr)
	119	{
	120	struct inode *inode = dentry->d_inode;
	121	struct sysfs_dirent *sd = dentry->d_fsdata;
	122	int error;
	123
	124	if (!sd)
	125	return -EINVAL;
	126
	127	mutex_lock(&sysfs_mutex);
	128	error = inode_change_ok(inode, iattr);
	129	if (error)
	130	goto out;
	131
	132	error = __kernfs_setattr(sd, iattr);
	133	if (error)
	134	goto out;
	135
	136	/* this ignores size changes */
	137	setattr_copy(inode, iattr);
	138
	139	out:
	140	mutex_unlock(&sysfs_mutex);
	141	return error;
	142	}
	143
	144	static int sysfs_sd_setsecdata(struct sysfs_dirent sd, void *secdata,
	145	u32 *secdata_len)
	146	{
9a8049af	147	struct sysfs_inode_attrs *attrs;
ffed24e2 TH	148	void *old_secdata;
	149	size_t old_secdata_len;
	150
9a8049af TH	151	attrs = sysfs_inode_attrs(sd);
	152	if (!attrs)
	153	return -ENOMEM;
ffed24e2	154
9a8049af TH	155	old_secdata = attrs->ia_secdata;
9a8049af TH	156	old_secdata_len = attrs->ia_secdata_len;
ffed24e2	157
9a8049af TH	158	attrs->ia_secdata = *secdata;
9a8049af TH	159	attrs->ia_secdata_len = *secdata_len;
ffed24e2 TH	160
	161	*secdata = old_secdata;
	162	*secdata_len = old_secdata_len;
	163	return 0;
	164	}
	165
	166	int sysfs_setxattr(struct dentry dentry, const char name, const void *value,
	167	size_t size, int flags)
	168	{
	169	struct sysfs_dirent *sd = dentry->d_fsdata;
2322392b	170	struct sysfs_inode_attrs *attrs;
ffed24e2 TH	171	void *secdata;
	172	int error;
	173	u32 secdata_len = 0;
	174
2322392b TH	175	attrs = sysfs_inode_attrs(sd);
	176	if (!attrs)
	177	return -ENOMEM;
ffed24e2 TH	178
	179	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
	180	const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
	181	error = security_inode_setsecurity(dentry->d_inode, suffix,
	182	value, size, flags);
	183	if (error)
2322392b	184	return error;
ffed24e2 TH	185	error = security_inode_getsecctx(dentry->d_inode,
	186	&secdata, &secdata_len);
	187	if (error)
2322392b	188	return error;
ffed24e2 TH	189
	190	mutex_lock(&sysfs_mutex);
	191	error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
	192	mutex_unlock(&sysfs_mutex);
	193
	194	if (secdata)
	195	security_release_secctx(secdata, secdata_len);
2322392b TH	196	return error;
	197	} else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
	198	return simple_xattr_set(&attrs->xattrs, name, value, size,
	199	flags);
	200	}
	201
	202	return -EINVAL;
	203	}
	204
	205	int sysfs_removexattr(struct dentry dentry, const char name)
	206	{
	207	struct sysfs_dirent *sd = dentry->d_fsdata;
	208	struct sysfs_inode_attrs *attrs;
	209
	210	attrs = sysfs_inode_attrs(sd);
	211	if (!attrs)
	212	return -ENOMEM;
	213
	214	return simple_xattr_remove(&attrs->xattrs, name);
	215	}
	216
	217	ssize_t sysfs_getxattr(struct dentry dentry, const char name, void *buf,
	218	size_t size)
	219	{
	220	struct sysfs_dirent *sd = dentry->d_fsdata;
	221	struct sysfs_inode_attrs *attrs;
	222
	223	attrs = sysfs_inode_attrs(sd);
	224	if (!attrs)
	225	return -ENOMEM;
	226
	227	return simple_xattr_get(&attrs->xattrs, name, buf, size);
	228	}
	229
	230	ssize_t sysfs_listxattr(struct dentry dentry, char buf, size_t size)
	231	{
	232	struct sysfs_dirent *sd = dentry->d_fsdata;
	233	struct sysfs_inode_attrs *attrs;
	234
	235	attrs = sysfs_inode_attrs(sd);
	236	if (!attrs)
	237	return -ENOMEM;
	238
	239	return simple_xattr_list(&attrs->xattrs, buf, size);
ffed24e2 TH	240	}
	241
	242	static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
	243	{
	244	inode->i_mode = mode;
	245	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	246	}
	247
	248	static inline void set_inode_attr(struct inode inode, struct iattr iattr)
	249	{
	250	inode->i_uid = iattr->ia_uid;
	251	inode->i_gid = iattr->ia_gid;
	252	inode->i_atime = iattr->ia_atime;
	253	inode->i_mtime = iattr->ia_mtime;
	254	inode->i_ctime = iattr->ia_ctime;
	255	}
	256
	257	static void sysfs_refresh_inode(struct sysfs_dirent sd, struct inode inode)
	258	{
9a8049af	259	struct sysfs_inode_attrs *attrs = sd->s_iattr;
ffed24e2 TH	260
ffed24e2 TH	261	inode->i_mode = sd->s_mode;
9a8049af	262	if (attrs) {
ffed24e2 TH	263	/* sysfs_dirent has non-default attributes
	264	* get them from persistent copy in sysfs_dirent
	265	*/
9a8049af TH	266	set_inode_attr(inode, &attrs->ia_iattr);
	267	security_inode_notifysecctx(inode, attrs->ia_secdata,
	268	attrs->ia_secdata_len);
ffed24e2 TH	269	}
	270
	271	if (sysfs_type(sd) == SYSFS_DIR)
	272	set_nlink(inode, sd->s_dir.subdirs + 2);
	273	}
	274
	275	int sysfs_getattr(struct vfsmount mnt, struct dentry dentry,
	276	struct kstat *stat)
	277	{
	278	struct sysfs_dirent *sd = dentry->d_fsdata;
	279	struct inode *inode = dentry->d_inode;
	280
	281	mutex_lock(&sysfs_mutex);
	282	sysfs_refresh_inode(sd, inode);
	283	mutex_unlock(&sysfs_mutex);
	284
	285	generic_fillattr(inode, stat);
	286	return 0;
	287	}
	288
	289	static void sysfs_init_inode(struct sysfs_dirent sd, struct inode inode)
	290	{
	291	kernfs_get(sd);
	292	inode->i_private = sd;
	293	inode->i_mapping->a_ops = &sysfs_aops;
	294	inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
	295	inode->i_op = &sysfs_inode_operations;
	296
	297	set_default_inode_attr(inode, sd->s_mode);
	298	sysfs_refresh_inode(sd, inode);
	299
	300	/* initialize inode according to type */
	301	switch (sysfs_type(sd)) {
	302	case SYSFS_DIR:
	303	inode->i_op = &sysfs_dir_inode_operations;
	304	inode->i_fop = &sysfs_dir_operations;
	305	break;
	306	case SYSFS_KOBJ_ATTR:
	307	inode->i_size = sd->s_attr.size;
	308	inode->i_fop = &kernfs_file_operations;
	309	break;
	310	case SYSFS_KOBJ_LINK:
	311	inode->i_op = &sysfs_symlink_inode_operations;
	312	break;
	313	default:
	314	BUG();
	315	}
	316
	317	unlock_new_inode(inode);
	318	}
	319
	320	/**
	321	* sysfs_get_inode - get inode for sysfs_dirent
	322	* @sb: super block
	323	* @sd: sysfs_dirent to allocate inode for
	324	*
	325	* Get inode for @sd. If such inode doesn't exist, a new inode
	326	* is allocated and basics are initialized. New inode is
	327	* returned locked.
	328	*
	329	* LOCKING:
	330	* Kernel thread context (may sleep).
	331	*
	332	* RETURNS:
333	* Pointer to allocated inode on success, NULL on failure.
334	*/
335	struct inode sysfs_get_inode(struct super_block sb, struct sysfs_dirent *sd)
336	{
337	struct inode *inode;
338
339	inode = iget_locked(sb, sd->s_ino);
340	if (inode && (inode->i_state & I_NEW))
341	sysfs_init_inode(sd, inode);
342
343	return inode;
344	}
345
346	/*
347	* The sysfs_dirent serves as both an inode and a directory entry for sysfs.
348	* To prevent the sysfs inode numbers from being freed prematurely we take a
349	* reference to sysfs_dirent from the sysfs inode. A
350	* super_operations.evict_inode() implementation is needed to drop that
351	* reference upon inode destruction.
352	*/
353	void sysfs_evict_inode(struct inode *inode)
354	{
355	struct sysfs_dirent *sd = inode->i_private;
356
357	truncate_inode_pages(&inode->i_data, 0);
358	clear_inode(inode);
359	kernfs_put(sd);
360	}
361
362	int sysfs_permission(struct inode *inode, int mask)
363	{
364	struct sysfs_dirent *sd;
365
366	if (mask & MAY_NOT_BLOCK)
367	return -ECHILD;
368
369	sd = inode->i_private;
370
371	mutex_lock(&sysfs_mutex);
372	sysfs_refresh_inode(sd, inode);
373	mutex_unlock(&sysfs_mutex);
374
375	return generic_permission(inode, mask);
376	}