fs/ubifs/xattr.c - linux - Git at Google

 /*
  * This file is part of UBIFS.
  *
  * Copyright (C) 2006-2008 Nokia Corporation.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 as published by
  * the Free Software Foundation.
  *
  * 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., 51
  * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  *
  * Authors: Artem Bityutskiy (Битюцкий Артём)
  *          Adrian Hunter
  */

 /*
  * This file implements UBIFS extended attributes support.
  *
  * Extended attributes are implemented as regular inodes with attached data,
  * which limits extended attribute size to UBIFS block size (4KiB). Names of
  * extended attributes are described by extended attribute entries (xentries),
  * which are almost identical to directory entries, but have different key type.
  *
  * In other words, the situation with extended attributes is very similar to
  * directories. Indeed, any inode (but of course not xattr inodes) may have a
  * number of associated xentries, just like directory inodes have associated
  * directory entries. Extended attribute entries store the name of the extended
  * attribute, the host inode number, and the extended attribute inode number.
  * Similarly, direntries store the name, the parent and the target inode
  * numbers. Thus, most of the common UBIFS mechanisms may be re-used for
  * extended attributes.
  *
  * The number of extended attributes is not limited, but there is Linux
  * limitation on the maximum possible size of the list of all extended
  * attributes associated with an inode (%XATTR_LIST_MAX), so UBIFS makes sure
  * the sum of all extended attribute names of the inode does not exceed that
  * limit.
  *
  * Extended attributes are synchronous, which means they are written to the
  * flash media synchronously and there is no write-back for extended attribute
  * inodes. The extended attribute values are not stored in compressed form on
  * the media.
  *
  * Since extended attributes are represented by regular inodes, they are cached
  * in the VFS inode cache. The xentries are cached in the LNC cache (see
  * tnc.c).
  *
  * ACL support is not implemented.
  */

 #include "ubifs.h"
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/xattr.h>

 /*
  * Limit the number of extended attributes per inode so that the total size
  * (@xattr_size) is guaranteeded to fit in an 'unsigned int'.
  */
 #define MAX_XATTRS_PER_INODE 65535

 /*
  * Extended attribute type constants.
  *
  * USER_XATTR: user extended attribute ("user.*")
  * TRUSTED_XATTR: trusted extended attribute ("trusted.*)
  * SECURITY_XATTR: security extended attribute ("security.*")
  */
 enum {
 	USER_XATTR,
 	TRUSTED_XATTR,
 	SECURITY_XATTR,
 };

 static const struct inode_operations empty_iops;
 static const struct file_operations empty_fops;

 /**
  * create_xattr - create an extended attribute.
  * @c: UBIFS file-system description object
  * @host: host inode
  * @nm: extended attribute name
  * @value: extended attribute value
  * @size: size of extended attribute value
  *
  * This is a helper function which creates an extended attribute of name @nm
  * and value @value for inode @host. The host inode is also updated on flash
  * because the ctime and extended attribute accounting data changes. This
  * function returns zero in case of success and a negative error code in case
  * of failure.
  */
 static int create_xattr(struct ubifs_info *c, struct inode *host,
 			const struct qstr *nm, const void *value, int size)
 {
 	int err, names_len;
 	struct inode *inode;
 	struct ubifs_inode *ui, *host_ui = ubifs_inode(host);
 	struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
 				.new_ino_d = ALIGN(size, 8), .dirtied_ino = 1,
 				.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };

 	if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE) {
 		ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more",
 			  host->i_ino, host_ui->xattr_cnt);
 		return -ENOSPC;
 	}
 	/*
 	 * Linux limits the maximum size of the extended attribute names list
 	 * to %XATTR_LIST_MAX. This means we should not allow creating more
 	 * extended attributes if the name list becomes larger. This limitation
 	 * is artificial for UBIFS, though.
 	 */
 	names_len = host_ui->xattr_names + host_ui->xattr_cnt + nm->len + 1;
 	if (names_len > XATTR_LIST_MAX) {
 		ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d",
 			  host->i_ino, names_len, XATTR_LIST_MAX);
 		return -ENOSPC;
 	}

 	err = ubifs_budget_space(c, &req);
 	if (err)
 		return err;

 	inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		goto out_budg;
 	}

 	/* Re-define all operations to be "nothing" */
 	inode->i_mapping->a_ops = &empty_aops;
 	inode->i_op = &empty_iops;
 	inode->i_fop = &empty_fops;

 	inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA;
 	ui = ubifs_inode(inode);
 	ui->xattr = 1;
 	ui->flags |= UBIFS_XATTR_FL;
 	ui->data = kmemdup(value, size, GFP_NOFS);
 	if (!ui->data) {
 		err = -ENOMEM;
 		goto out_free;
 	}
 	inode->i_size = ui->ui_size = size;
 	ui->data_len = size;

 	mutex_lock(&host_ui->ui_mutex);
 	host->i_ctime = ubifs_current_time(host);
 	host_ui->xattr_cnt += 1;
 	host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 	host_ui->xattr_size += CALC_XATTR_BYTES(size);
 	host_ui->xattr_names += nm->len;

 	err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
 	if (err)
 		goto out_cancel;
 	mutex_unlock(&host_ui->ui_mutex);

 	ubifs_release_budget(c, &req);
 	insert_inode_hash(inode);
 	iput(inode);
 	return 0;

 out_cancel:
 	host_ui->xattr_cnt -= 1;
 	host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 	host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 	mutex_unlock(&host_ui->ui_mutex);
 out_free:
 	make_bad_inode(inode);
 	iput(inode);
 out_budg:
 	ubifs_release_budget(c, &req);
 	return err;
 }

 /**
  * change_xattr - change an extended attribute.
  * @c: UBIFS file-system description object
  * @host: host inode
  * @inode: extended attribute inode
  * @value: extended attribute value
  * @size: size of extended attribute value
  *
  * This helper function changes the value of extended attribute @inode with new
  * data from @value. Returns zero in case of success and a negative error code
  * in case of failure.
  */
 static int change_xattr(struct ubifs_info *c, struct inode *host,
 			struct inode *inode, const void *value, int size)
 {
 	int err;
 	struct ubifs_inode *host_ui = ubifs_inode(host);
 	struct ubifs_inode *ui = ubifs_inode(inode);
 	void *buf = NULL;
 	struct ubifs_budget_req req = { .dirtied_ino = 2,
 		.dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };

 	ubifs_assert(ui->data_len == inode->i_size);
 	err = ubifs_budget_space(c, &req);
 	if (err)
 		return err;

 	buf = kmemdup(value, size, GFP_NOFS);
 	if (!buf) {
 		err = -ENOMEM;
 		goto out_free;
 	}
 	mutex_lock(&ui->ui_mutex);
 	kfree(ui->data);
 	ui->data = buf;
 	inode->i_size = ui->ui_size = size;
 	ui->data_len = size;
 	mutex_unlock(&ui->ui_mutex);

 	mutex_lock(&host_ui->ui_mutex);
 	host->i_ctime = ubifs_current_time(host);
 	host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 	host_ui->xattr_size += CALC_XATTR_BYTES(size);

 	/*
 	 * It is important to write the host inode after the xattr inode
 	 * because if the host inode gets synchronized (via 'fsync()'), then
 	 * the extended attribute inode gets synchronized, because it goes
 	 * before the host inode in the write-buffer.
 	 */
 	err = ubifs_jnl_change_xattr(c, inode, host);
 	if (err)
 		goto out_cancel;
 	mutex_unlock(&host_ui->ui_mutex);

 	ubifs_release_budget(c, &req);
 	return 0;

 out_cancel:
 	host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 	host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 	mutex_unlock(&host_ui->ui_mutex);
 	make_bad_inode(inode);
 out_free:
 	ubifs_release_budget(c, &req);
 	return err;
 }

 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 {
 	struct inode *inode;

 	inode = ubifs_iget(c->vfs_sb, inum);
 	if (IS_ERR(inode)) {
 		ubifs_err(c, "dead extended attribute entry, error %d",
 			  (int)PTR_ERR(inode));
 		return inode;
 	}
 	if (ubifs_inode(inode)->xattr)
 		return inode;
 	ubifs_err(c, "corrupt extended attribute entry");
 	iput(inode);
 	return ERR_PTR(-EINVAL);
 }

 static int __ubifs_setxattr(struct inode *host, const char *name,
 			    const void *value, size_t size, int flags)
 {
 	struct inode *inode;
 	struct ubifs_info *c = host->i_sb->s_fs_info;
 	struct qstr nm = QSTR_INIT(name, strlen(name));
 	struct ubifs_dent_node *xent;
 	union ubifs_key key;
 	int err;

 	ubifs_assert(inode_is_locked(host));

 	if (size > UBIFS_MAX_INO_DATA)
 		return -ERANGE;

 	if (nm.len > UBIFS_MAX_NLEN)
 		return -ENAMETOOLONG;

 	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 	if (!xent)
 		return -ENOMEM;

 	/*
 	 * The extended attribute entries are stored in LNC, so multiple
 	 * look-ups do not involve reading the flash.
 	 */
 	xent_key_init(c, &key, host->i_ino, &nm);
 	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 	if (err) {
 		if (err != -ENOENT)
 			goto out_free;

 		if (flags & XATTR_REPLACE)
 			/* We are asked not to create the xattr */
 			err = -ENODATA;
 		else
 			err = create_xattr(c, host, &nm, value, size);
 		goto out_free;
 	}

 	if (flags & XATTR_CREATE) {
 		/* We are asked not to replace the xattr */
 		err = -EEXIST;
 		goto out_free;
 	}

 	inode = iget_xattr(c, le64_to_cpu(xent->inum));
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		goto out_free;
 	}

 	err = change_xattr(c, host, inode, value, size);
 	iput(inode);

 out_free:
 	kfree(xent);
 	return err;
 }

 static ssize_t __ubifs_getxattr(struct inode *host, const char *name,
 				void *buf, size_t size)
 {
 	struct inode *inode;
 	struct ubifs_info *c = host->i_sb->s_fs_info;
 	struct qstr nm = QSTR_INIT(name, strlen(name));
 	struct ubifs_inode *ui;
 	struct ubifs_dent_node *xent;
 	union ubifs_key key;
 	int err;

 	if (nm.len > UBIFS_MAX_NLEN)
 		return -ENAMETOOLONG;

 	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 	if (!xent)
 		return -ENOMEM;

 	xent_key_init(c, &key, host->i_ino, &nm);
 	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 	if (err) {
 		if (err == -ENOENT)
 			err = -ENODATA;
 		goto out_unlock;
 	}

 	inode = iget_xattr(c, le64_to_cpu(xent->inum));
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		goto out_unlock;
 	}

 	ui = ubifs_inode(inode);
 	ubifs_assert(inode->i_size == ui->data_len);
 	ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);

 	mutex_lock(&ui->ui_mutex);
 	if (buf) {
 		/* If @buf is %NULL we are supposed to return the length */
 		if (ui->data_len > size) {
 			ubifs_err(c, "buffer size %zd, xattr len %d",
 				  size, ui->data_len);
 			err = -ERANGE;
 			goto out_iput;
 		}

 		memcpy(buf, ui->data, ui->data_len);
 	}
 	err = ui->data_len;

 out_iput:
 	mutex_unlock(&ui->ui_mutex);
 	iput(inode);
 out_unlock:
 	kfree(xent);
 	return err;
 }

 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 {
 	union ubifs_key key;
 	struct inode *host = d_inode(dentry);
 	struct ubifs_info *c = host->i_sb->s_fs_info;
 	struct ubifs_inode *host_ui = ubifs_inode(host);
 	struct ubifs_dent_node *xent, *pxent = NULL;
 	int err, len, written = 0;
 	struct qstr nm = { .name = NULL };

 	dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
 		dentry, size);

 	len = host_ui->xattr_names + host_ui->xattr_cnt;
 	if (!buffer)
 		/*
 		 * We should return the minimum buffer size which will fit a
 		 * null-terminated list of all the extended attribute names.
 		 */
 		return len;

 	if (len > size)
 		return -ERANGE;

 	lowest_xent_key(c, &key, host->i_ino);
 	while (1) {
 		xent = ubifs_tnc_next_ent(c, &key, &nm);
 		if (IS_ERR(xent)) {
 			err = PTR_ERR(xent);
 			break;
 		}

 		nm.name = xent->name;
 		nm.len = le16_to_cpu(xent->nlen);

 		/* Show trusted namespace only for "power" users */
 		if (strncmp(xent->name, XATTR_TRUSTED_PREFIX,
 			    XATTR_TRUSTED_PREFIX_LEN) ||
 		    capable(CAP_SYS_ADMIN)) {
 			memcpy(buffer + written, nm.name, nm.len + 1);
 			written += nm.len + 1;
 		}

 		kfree(pxent);
 		pxent = xent;
 		key_read(c, &xent->key, &key);
 	}

 	kfree(pxent);
 	if (err != -ENOENT) {
 		ubifs_err(c, "cannot find next direntry, error %d", err);
 		return err;
 	}

 	ubifs_assert(written <= size);
 	return written;
 }

 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 			struct inode *inode, const struct qstr *nm)
 {
 	int err;
 	struct ubifs_inode *host_ui = ubifs_inode(host);
 	struct ubifs_inode *ui = ubifs_inode(inode);
 	struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 				.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };

 	ubifs_assert(ui->data_len == inode->i_size);

 	err = ubifs_budget_space(c, &req);
 	if (err)
 		return err;

 	mutex_lock(&host_ui->ui_mutex);
 	host->i_ctime = ubifs_current_time(host);
 	host_ui->xattr_cnt -= 1;
 	host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 	host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 	host_ui->xattr_names -= nm->len;

 	err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 	if (err)
 		goto out_cancel;
 	mutex_unlock(&host_ui->ui_mutex);

 	ubifs_release_budget(c, &req);
 	return 0;

 out_cancel:
 	host_ui->xattr_cnt += 1;
 	host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 	host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 	mutex_unlock(&host_ui->ui_mutex);
 	ubifs_release_budget(c, &req);
 	make_bad_inode(inode);
 	return err;
 }

 static int __ubifs_removexattr(struct inode *host, const char *name)
 {
 	struct inode *inode;
 	struct ubifs_info *c = host->i_sb->s_fs_info;
 	struct qstr nm = QSTR_INIT(name, strlen(name));
 	struct ubifs_dent_node *xent;
 	union ubifs_key key;
 	int err;

 	ubifs_assert(inode_is_locked(host));

 	if (nm.len > UBIFS_MAX_NLEN)
 		return -ENAMETOOLONG;

 	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 	if (!xent)
 		return -ENOMEM;

 	xent_key_init(c, &key, host->i_ino, &nm);
 	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 	if (err) {
 		if (err == -ENOENT)
 			err = -ENODATA;
 		goto out_free;
 	}

 	inode = iget_xattr(c, le64_to_cpu(xent->inum));
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		goto out_free;
 	}

 	ubifs_assert(inode->i_nlink == 1);
 	clear_nlink(inode);
 	err = remove_xattr(c, host, inode, &nm);
 	if (err)
 		set_nlink(inode, 1);

 	/* If @i_nlink is 0, 'iput()' will delete the inode */
 	iput(inode);

 out_free:
 	kfree(xent);
 	return err;
 }

 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
 		      void *fs_info)
 {
 	const struct xattr *xattr;
 	char *name;
 	int err = 0;

 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 		name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 			       strlen(xattr->name) + 1, GFP_NOFS);
 		if (!name) {
 			err = -ENOMEM;
 			break;
 		}
 		strcpy(name, XATTR_SECURITY_PREFIX);
 		strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 		err = __ubifs_setxattr(inode, name, xattr->value, xattr->value_len, 0);
 		kfree(name);
 		if (err < 0)
 			break;
 	}

 	return err;
 }

 int ubifs_init_security(struct inode *dentry, struct inode *inode,
 			const struct qstr *qstr)
 {
 	int err;

 	err = security_inode_init_security(inode, dentry, qstr,
 					   &init_xattrs, 0);
 	if (err) {
 		struct ubifs_info *c = dentry->i_sb->s_fs_info;
 		ubifs_err(c, "cannot initialize security for inode %lu, error %d",
 			  inode->i_ino, err);
 	}
 	return err;
 }

 static int ubifs_xattr_get(const struct xattr_handler *handler,
 			   struct dentry *dentry, struct inode *inode,
 			   const char *name, void *buffer, size_t size)
 {
 	dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
 		inode->i_ino, dentry, size);

 	return  __ubifs_getxattr(inode, name, buffer, size);
 }

 static int ubifs_xattr_set(const struct xattr_handler *handler,
 			   struct dentry *dentry, const char *name,
 			   const void *value, size_t size, int flags)
 {
 	struct inode *inode = d_inode(dentry);

 	dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
 		name, inode->i_ino, dentry, size);

 	if (value)
 		return __ubifs_setxattr(inode, name, value, size, flags);
 	else
 		return __ubifs_removexattr(inode, name);
 }

 const struct xattr_handler ubifs_user_xattr_handler = {
 	.prefix = XATTR_USER_PREFIX,
 	.get = ubifs_xattr_get,
 	.set = ubifs_xattr_set,
 };

 const struct xattr_handler ubifs_trusted_xattr_handler = {
 	.prefix = XATTR_TRUSTED_PREFIX,
 	.get = ubifs_xattr_get,
 	.set = ubifs_xattr_set,
 };

 const struct xattr_handler ubifs_security_xattr_handler = {
 	.prefix = XATTR_SECURITY_PREFIX,
 	.get = ubifs_xattr_get,
 	.set = ubifs_xattr_set,
 };

 const struct xattr_handler *ubifs_xattr_handlers[] = {
 	&ubifs_user_xattr_handler,
 	&ubifs_trusted_xattr_handler,
 	&ubifs_security_xattr_handler,
 	NULL
 };
	/*
	* This file is part of UBIFS.
	*
	* Copyright (C) 2006-2008 Nokia Corporation.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 as published by
	* the Free Software Foundation.
	*
	* 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., 51
	* Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	*
	* Authors: Artem Bityutskiy (Битюцкий Артём)
	* Adrian Hunter
	*/

	/*
	* This file implements UBIFS extended attributes support.
	*
	* Extended attributes are implemented as regular inodes with attached data,
	* which limits extended attribute size to UBIFS block size (4KiB). Names of
	* extended attributes are described by extended attribute entries (xentries),
	* which are almost identical to directory entries, but have different key type.
	*
	* In other words, the situation with extended attributes is very similar to
	* directories. Indeed, any inode (but of course not xattr inodes) may have a
	* number of associated xentries, just like directory inodes have associated
	* directory entries. Extended attribute entries store the name of the extended
	* attribute, the host inode number, and the extended attribute inode number.
	* Similarly, direntries store the name, the parent and the target inode
	* numbers. Thus, most of the common UBIFS mechanisms may be re-used for
	* extended attributes.
	*
	* The number of extended attributes is not limited, but there is Linux
	* limitation on the maximum possible size of the list of all extended
	* attributes associated with an inode (%XATTR_LIST_MAX), so UBIFS makes sure
	* the sum of all extended attribute names of the inode does not exceed that
	* limit.
	*
	* Extended attributes are synchronous, which means they are written to the
	* flash media synchronously and there is no write-back for extended attribute
	* inodes. The extended attribute values are not stored in compressed form on
	* the media.
	*
	* Since extended attributes are represented by regular inodes, they are cached
	* in the VFS inode cache. The xentries are cached in the LNC cache (see
	* tnc.c).
	*
	* ACL support is not implemented.
	*/

	#include "ubifs.h"
	#include <linux/fs.h>
	#include <linux/slab.h>
	#include <linux/xattr.h>

	/*
	* Limit the number of extended attributes per inode so that the total size
	* (@xattr_size) is guaranteeded to fit in an 'unsigned int'.
	*/
	#define MAX_XATTRS_PER_INODE 65535

	/*
	* Extended attribute type constants.
	*
	* USER_XATTR: user extended attribute ("user.*")
	* TRUSTED_XATTR: trusted extended attribute ("trusted.*)
	* SECURITY_XATTR: security extended attribute ("security.*")
	*/
	enum {
	USER_XATTR,
	TRUSTED_XATTR,
	SECURITY_XATTR,
	};

	static const struct inode_operations empty_iops;
	static const struct file_operations empty_fops;

	/**
	* create_xattr - create an extended attribute.
	* @c: UBIFS file-system description object
	* @host: host inode
	* @nm: extended attribute name
	* @value: extended attribute value
	* @size: size of extended attribute value
	*
	* This is a helper function which creates an extended attribute of name @nm
	* and value @value for inode @host. The host inode is also updated on flash
	* because the ctime and extended attribute accounting data changes. This
	* function returns zero in case of success and a negative error code in case
	* of failure.
	*/
	static int create_xattr(struct ubifs_info c, struct inode host,
	const struct qstr nm, const void value, int size)
	{
	int err, names_len;
	struct inode *inode;
	struct ubifs_inode ui, host_ui = ubifs_inode(host);
	struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
	.new_ino_d = ALIGN(size, 8), .dirtied_ino = 1,
	.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };

	if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE) {
	ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more",
	host->i_ino, host_ui->xattr_cnt);
	return -ENOSPC;
	}
	/*
	* Linux limits the maximum size of the extended attribute names list
	* to %XATTR_LIST_MAX. This means we should not allow creating more
	* extended attributes if the name list becomes larger. This limitation
	* is artificial for UBIFS, though.
	*/
	names_len = host_ui->xattr_names + host_ui->xattr_cnt + nm->len + 1;
	if (names_len > XATTR_LIST_MAX) {
	ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d",
	host->i_ino, names_len, XATTR_LIST_MAX);
	return -ENOSPC;
	}

	err = ubifs_budget_space(c, &req);
	if (err)
	return err;

	inode = ubifs_new_inode(c, host, S_IFREG \| S_IRWXUGO);
	if (IS_ERR(inode)) {
	err = PTR_ERR(inode);
	goto out_budg;
	}

	/* Re-define all operations to be "nothing" */
	inode->i_mapping->a_ops = &empty_aops;
	inode->i_op = &empty_iops;
	inode->i_fop = &empty_fops;

	inode->i_flags \|= S_SYNC \| S_NOATIME \| S_NOCMTIME \| S_NOQUOTA;
	ui = ubifs_inode(inode);
	ui->xattr = 1;
	ui->flags \|= UBIFS_XATTR_FL;
	ui->data = kmemdup(value, size, GFP_NOFS);
	if (!ui->data) {
	err = -ENOMEM;
	goto out_free;
	}
	inode->i_size = ui->ui_size = size;
	ui->data_len = size;

	mutex_lock(&host_ui->ui_mutex);
	host->i_ctime = ubifs_current_time(host);
	host_ui->xattr_cnt += 1;
	host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
	host_ui->xattr_size += CALC_XATTR_BYTES(size);
	host_ui->xattr_names += nm->len;

	err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
	if (err)
	goto out_cancel;
	mutex_unlock(&host_ui->ui_mutex);

	ubifs_release_budget(c, &req);
	insert_inode_hash(inode);
	iput(inode);
	return 0;

	out_cancel:
	host_ui->xattr_cnt -= 1;
	host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
	host_ui->xattr_size -= CALC_XATTR_BYTES(size);
	mutex_unlock(&host_ui->ui_mutex);
	out_free:
	make_bad_inode(inode);
	iput(inode);
	out_budg:
	ubifs_release_budget(c, &req);
	return err;
	}

	/**
	* change_xattr - change an extended attribute.
	* @c: UBIFS file-system description object
	* @host: host inode
	* @inode: extended attribute inode
	* @value: extended attribute value
	* @size: size of extended attribute value
	*
	* This helper function changes the value of extended attribute @inode with new
	* data from @value. Returns zero in case of success and a negative error code
	* in case of failure.
	*/
	static int change_xattr(struct ubifs_info c, struct inode host,
	struct inode inode, const void value, int size)
	{
	int err;
	struct ubifs_inode *host_ui = ubifs_inode(host);
	struct ubifs_inode *ui = ubifs_inode(inode);
	void *buf = NULL;
	struct ubifs_budget_req req = { .dirtied_ino = 2,
	.dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };

	ubifs_assert(ui->data_len == inode->i_size);
	err = ubifs_budget_space(c, &req);
	if (err)
	return err;

	buf = kmemdup(value, size, GFP_NOFS);
	if (!buf) {
	err = -ENOMEM;
	goto out_free;
	}
	mutex_lock(&ui->ui_mutex);
	kfree(ui->data);
	ui->data = buf;
	inode->i_size = ui->ui_size = size;
	ui->data_len = size;
	mutex_unlock(&ui->ui_mutex);

	mutex_lock(&host_ui->ui_mutex);
	host->i_ctime = ubifs_current_time(host);
	host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
	host_ui->xattr_size += CALC_XATTR_BYTES(size);

	/*
	* It is important to write the host inode after the xattr inode
	* because if the host inode gets synchronized (via 'fsync()'), then
	* the extended attribute inode gets synchronized, because it goes
	* before the host inode in the write-buffer.
	*/
	err = ubifs_jnl_change_xattr(c, inode, host);
	if (err)
	goto out_cancel;
	mutex_unlock(&host_ui->ui_mutex);

	ubifs_release_budget(c, &req);
	return 0;

	out_cancel:
	host_ui->xattr_size -= CALC_XATTR_BYTES(size);
	host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
	mutex_unlock(&host_ui->ui_mutex);
	make_bad_inode(inode);
	out_free:
	ubifs_release_budget(c, &req);
	return err;
	}

	static struct inode iget_xattr(struct ubifs_info c, ino_t inum)
	{
	struct inode *inode;

	inode = ubifs_iget(c->vfs_sb, inum);
	if (IS_ERR(inode)) {
	ubifs_err(c, "dead extended attribute entry, error %d",
	(int)PTR_ERR(inode));
	return inode;
	}
	if (ubifs_inode(inode)->xattr)
	return inode;
	ubifs_err(c, "corrupt extended attribute entry");
	iput(inode);
	return ERR_PTR(-EINVAL);
	}

	static int __ubifs_setxattr(struct inode host, const char name,
	const void *value, size_t size, int flags)
	{
	struct inode *inode;
	struct ubifs_info *c = host->i_sb->s_fs_info;
	struct qstr nm = QSTR_INIT(name, strlen(name));
	struct ubifs_dent_node *xent;
	union ubifs_key key;
	int err;

	ubifs_assert(inode_is_locked(host));

	if (size > UBIFS_MAX_INO_DATA)
	return -ERANGE;

	if (nm.len > UBIFS_MAX_NLEN)
	return -ENAMETOOLONG;

	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
	if (!xent)
	return -ENOMEM;

	/*
	* The extended attribute entries are stored in LNC, so multiple
	* look-ups do not involve reading the flash.
	*/
	xent_key_init(c, &key, host->i_ino, &nm);
	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
	if (err) {
	if (err != -ENOENT)
	goto out_free;

	if (flags & XATTR_REPLACE)
	/* We are asked not to create the xattr */
	err = -ENODATA;
	else
	err = create_xattr(c, host, &nm, value, size);
	goto out_free;
	}

	if (flags & XATTR_CREATE) {
	/* We are asked not to replace the xattr */
	err = -EEXIST;
	goto out_free;
	}

	inode = iget_xattr(c, le64_to_cpu(xent->inum));
	if (IS_ERR(inode)) {
	err = PTR_ERR(inode);
	goto out_free;
	}

	err = change_xattr(c, host, inode, value, size);
	iput(inode);

	out_free:
	kfree(xent);
	return err;
	}

	static ssize_t __ubifs_getxattr(struct inode host, const char name,
	void *buf, size_t size)
	{
	struct inode *inode;
	struct ubifs_info *c = host->i_sb->s_fs_info;
	struct qstr nm = QSTR_INIT(name, strlen(name));
	struct ubifs_inode *ui;
	struct ubifs_dent_node *xent;
	union ubifs_key key;
	int err;

	if (nm.len > UBIFS_MAX_NLEN)
	return -ENAMETOOLONG;

	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
	if (!xent)
	return -ENOMEM;

	xent_key_init(c, &key, host->i_ino, &nm);
	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
	if (err) {
	if (err == -ENOENT)
	err = -ENODATA;
	goto out_unlock;
	}

	inode = iget_xattr(c, le64_to_cpu(xent->inum));
	if (IS_ERR(inode)) {
	err = PTR_ERR(inode);
	goto out_unlock;
	}

	ui = ubifs_inode(inode);
	ubifs_assert(inode->i_size == ui->data_len);
	ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);

	mutex_lock(&ui->ui_mutex);
	if (buf) {
	/* If @buf is %NULL we are supposed to return the length */
	if (ui->data_len > size) {
	ubifs_err(c, "buffer size %zd, xattr len %d",
	size, ui->data_len);
	err = -ERANGE;
	goto out_iput;
	}

	memcpy(buf, ui->data, ui->data_len);
	}
	err = ui->data_len;

	out_iput:
	mutex_unlock(&ui->ui_mutex);
	iput(inode);
	out_unlock:
	kfree(xent);
	return err;
	}

	ssize_t ubifs_listxattr(struct dentry dentry, char buffer, size_t size)
	{
	union ubifs_key key;
	struct inode *host = d_inode(dentry);
	struct ubifs_info *c = host->i_sb->s_fs_info;
	struct ubifs_inode *host_ui = ubifs_inode(host);
	struct ubifs_dent_node xent, pxent = NULL;
	int err, len, written = 0;
	struct qstr nm = { .name = NULL };

	dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
	dentry, size);

	len = host_ui->xattr_names + host_ui->xattr_cnt;
	if (!buffer)
	/*
	* We should return the minimum buffer size which will fit a
	* null-terminated list of all the extended attribute names.
	*/
	return len;

	if (len > size)
	return -ERANGE;

	lowest_xent_key(c, &key, host->i_ino);
	while (1) {
	xent = ubifs_tnc_next_ent(c, &key, &nm);
	if (IS_ERR(xent)) {
	err = PTR_ERR(xent);
	break;
	}

	nm.name = xent->name;
	nm.len = le16_to_cpu(xent->nlen);

	/* Show trusted namespace only for "power" users */
	if (strncmp(xent->name, XATTR_TRUSTED_PREFIX,
	XATTR_TRUSTED_PREFIX_LEN) \|\|
	capable(CAP_SYS_ADMIN)) {
	memcpy(buffer + written, nm.name, nm.len + 1);
	written += nm.len + 1;
	}

	kfree(pxent);
	pxent = xent;
	key_read(c, &xent->key, &key);
	}

	kfree(pxent);
	if (err != -ENOENT) {
	ubifs_err(c, "cannot find next direntry, error %d", err);
	return err;
	}

	ubifs_assert(written <= size);
	return written;
	}

	static int remove_xattr(struct ubifs_info c, struct inode host,
	struct inode inode, const struct qstr nm)
	{
	int err;
	struct ubifs_inode *host_ui = ubifs_inode(host);
	struct ubifs_inode *ui = ubifs_inode(inode);
	struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
	.dirtied_ino_d = ALIGN(host_ui->data_len, 8) };

	ubifs_assert(ui->data_len == inode->i_size);

	err = ubifs_budget_space(c, &req);
	if (err)
	return err;

	mutex_lock(&host_ui->ui_mutex);
	host->i_ctime = ubifs_current_time(host);
	host_ui->xattr_cnt -= 1;
	host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
	host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
	host_ui->xattr_names -= nm->len;

	err = ubifs_jnl_delete_xattr(c, host, inode, nm);
	if (err)
	goto out_cancel;
	mutex_unlock(&host_ui->ui_mutex);

	ubifs_release_budget(c, &req);
	return 0;

	out_cancel:
	host_ui->xattr_cnt += 1;
	host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
	host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
	mutex_unlock(&host_ui->ui_mutex);
	ubifs_release_budget(c, &req);
	make_bad_inode(inode);
	return err;
	}

	static int __ubifs_removexattr(struct inode host, const char name)
	{
	struct inode *inode;
	struct ubifs_info *c = host->i_sb->s_fs_info;
	struct qstr nm = QSTR_INIT(name, strlen(name));
	struct ubifs_dent_node *xent;
	union ubifs_key key;
	int err;

	ubifs_assert(inode_is_locked(host));

	if (nm.len > UBIFS_MAX_NLEN)
	return -ENAMETOOLONG;

	xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
	if (!xent)
	return -ENOMEM;

	xent_key_init(c, &key, host->i_ino, &nm);
	err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
	if (err) {
	if (err == -ENOENT)
	err = -ENODATA;
	goto out_free;
	}

	inode = iget_xattr(c, le64_to_cpu(xent->inum));
	if (IS_ERR(inode)) {
	err = PTR_ERR(inode);
	goto out_free;
	}

	ubifs_assert(inode->i_nlink == 1);
	clear_nlink(inode);
	err = remove_xattr(c, host, inode, &nm);
	if (err)
	set_nlink(inode, 1);

	/* If @i_nlink is 0, 'iput()' will delete the inode */
	iput(inode);

	out_free:
	kfree(xent);
	return err;
	}

	static int init_xattrs(struct inode inode, const struct xattr xattr_array,
	void *fs_info)
	{
	const struct xattr *xattr;
	char *name;
	int err = 0;

	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
	name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
	strlen(xattr->name) + 1, GFP_NOFS);
	if (!name) {
	err = -ENOMEM;
	break;
	}
	strcpy(name, XATTR_SECURITY_PREFIX);
	strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
	err = __ubifs_setxattr(inode, name, xattr->value, xattr->value_len, 0);
	kfree(name);
	if (err < 0)
	break;
	}

	return err;
	}

	int ubifs_init_security(struct inode dentry, struct inode inode,
	const struct qstr *qstr)
	{
	int err;

	err = security_inode_init_security(inode, dentry, qstr,
	&init_xattrs, 0);
	if (err) {
	struct ubifs_info *c = dentry->i_sb->s_fs_info;
	ubifs_err(c, "cannot initialize security for inode %lu, error %d",
	inode->i_ino, err);
	}
	return err;
	}

	static int ubifs_xattr_get(const struct xattr_handler *handler,
	struct dentry dentry, struct inode inode,
	const char name, void buffer, size_t size)
	{
	dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
	inode->i_ino, dentry, size);

	return __ubifs_getxattr(inode, name, buffer, size);
	}

	static int ubifs_xattr_set(const struct xattr_handler *handler,
	struct dentry dentry, const char name,
	const void *value, size_t size, int flags)
	{
	struct inode *inode = d_inode(dentry);

	dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
	name, inode->i_ino, dentry, size);

	if (value)
	return __ubifs_setxattr(inode, name, value, size, flags);
	else
	return __ubifs_removexattr(inode, name);
	}

	const struct xattr_handler ubifs_user_xattr_handler = {
	.prefix = XATTR_USER_PREFIX,
	.get = ubifs_xattr_get,
	.set = ubifs_xattr_set,
	};

	const struct xattr_handler ubifs_trusted_xattr_handler = {
	.prefix = XATTR_TRUSTED_PREFIX,
	.get = ubifs_xattr_get,
	.set = ubifs_xattr_set,
	};

	const struct xattr_handler ubifs_security_xattr_handler = {
	.prefix = XATTR_SECURITY_PREFIX,
	.get = ubifs_xattr_get,
	.set = ubifs_xattr_set,
	};

	const struct xattr_handler *ubifs_xattr_handlers[] = {
	&ubifs_user_xattr_handler,
	&ubifs_trusted_xattr_handler,
	&ubifs_security_xattr_handler,
	NULL
	};