drivers/mtd/ubi/cdev.c - fp2-dev/kernel/msm - Gitiles

 /*
  * Copyright (c) International Business Machines Corp., 2006
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
  * the GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  *
  * Author: Artem Bityutskiy (Битюцкий Артём)
  */

 /*
  * This file includes implementation of UBI character device operations.
  *
  * There are two kinds of character devices in UBI: UBI character devices and
  * UBI volume character devices. UBI character devices allow users to
  * manipulate whole volumes: create, remove, and re-size them. Volume character
  * devices provide volume I/O capabilities.
  *
  * Major and minor numbers are assigned dynamically to both UBI and volume
  * character devices.
  */

 #include <linux/module.h>
 #include <linux/stat.h>
 #include <linux/ioctl.h>
 #include <linux/capability.h>
 #include <mtd/ubi-user.h>
 #include <asm/uaccess.h>
 #include <asm/div64.h>
 #include "ubi.h"

 /*
  * Maximum sequence numbers of UBI and volume character device IOCTLs (direct
  * logical eraseblock erase is a debug-only feature).
  */
 #define UBI_CDEV_IOC_MAX_SEQ 2
 #ifndef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
 #define VOL_CDEV_IOC_MAX_SEQ 1
 #else
 #define VOL_CDEV_IOC_MAX_SEQ 2
 #endif

 /**
  * major_to_device - get UBI device object by character device major number.
  * @major: major number
  *
  * This function returns a pointer to the UBI device object.
  */
 static struct ubi_device *major_to_device(int major)
 {
 	int i;

 	for (i = 0; i < ubi_devices_cnt; i++)
 		if (ubi_devices[i] && ubi_devices[i]->major == major)
 			return ubi_devices[i];
 	BUG();
 }

 /**
  * get_exclusive - get exclusive access to an UBI volume.
  * @desc: volume descriptor
  *
  * This function changes UBI volume open mode to "exclusive". Returns previous
  * mode value (positive integer) in case of success and a negative error code
  * in case of failure.
  */
 static int get_exclusive(struct ubi_volume_desc *desc)
 {
 	int users, err;
 	struct ubi_volume *vol = desc->vol;

 	spin_lock(&vol->ubi->volumes_lock);
 	users = vol->readers + vol->writers + vol->exclusive;
 	ubi_assert(users > 0);
 	if (users > 1) {
 		dbg_err("%d users for volume %d", users, vol->vol_id);
 		err = -EBUSY;
 	} else {
 		vol->readers = vol->writers = 0;
 		vol->exclusive = 1;
 		err = desc->mode;
 		desc->mode = UBI_EXCLUSIVE;
 	}
 	spin_unlock(&vol->ubi->volumes_lock);

 	return err;
 }

 /**
  * revoke_exclusive - revoke exclusive mode.
  * @desc: volume descriptor
  * @mode: new mode to switch to
  */
 static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
 {
 	struct ubi_volume *vol = desc->vol;

 	spin_lock(&vol->ubi->volumes_lock);
 	ubi_assert(vol->readers == 0 && vol->writers == 0);
 	ubi_assert(vol->exclusive == 1 && desc->mode == UBI_EXCLUSIVE);
 	vol->exclusive = 0;
 	if (mode == UBI_READONLY)
 		vol->readers = 1;
 	else if (mode == UBI_READWRITE)
 		vol->writers = 1;
 	else
 		vol->exclusive = 1;
 	spin_unlock(&vol->ubi->volumes_lock);

 	desc->mode = mode;
 }

 static int vol_cdev_open(struct inode *inode, struct file *file)
 {
 	struct ubi_volume_desc *desc;
 	const struct ubi_device *ubi = major_to_device(imajor(inode));
 	int vol_id = iminor(inode) - 1;
 	int mode;

 	if (file->f_mode & FMODE_WRITE)
 		mode = UBI_READWRITE;
 	else
 		mode = UBI_READONLY;

 	dbg_msg("open volume %d, mode %d", vol_id, mode);

 	desc = ubi_open_volume(ubi->ubi_num, vol_id, mode);
 	if (IS_ERR(desc))
 		return PTR_ERR(desc);

 	file->private_data = desc;
 	return 0;
 }

 static int vol_cdev_release(struct inode *inode, struct file *file)
 {
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_volume *vol = desc->vol;

 	dbg_msg("release volume %d, mode %d", vol->vol_id, desc->mode);

 	if (vol->updating) {
 		ubi_warn("update of volume %d not finished, volume is damaged",
 			 vol->vol_id);
 		vol->updating = 0;
 		vfree(vol->upd_buf);
 	}

 	ubi_close_volume(desc);
 	return 0;
 }

 static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
 {
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_volume *vol = desc->vol;
 	loff_t new_offset;

 	if (vol->updating) {
 		 /* Update is in progress, seeking is prohibited */
 		dbg_err("updating");
 		return -EBUSY;
 	}

 	switch (origin) {
 	case 0: /* SEEK_SET */
 		new_offset = offset;
 		break;
 	case 1: /* SEEK_CUR */
 		new_offset = file->f_pos + offset;
 		break;
 	case 2: /* SEEK_END */
 		new_offset = vol->used_bytes + offset;
 		break;
 	default:
 		return -EINVAL;
 	}

 	if (new_offset < 0 || new_offset > vol->used_bytes) {
 		dbg_err("bad seek %lld", new_offset);
 		return -EINVAL;
 	}

 	dbg_msg("seek volume %d, offset %lld, origin %d, new offset %lld",
 		vol->vol_id, offset, origin, new_offset);

 	file->f_pos = new_offset;
 	return new_offset;
 }

 static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
 			     loff_t *offp)
 {
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_volume *vol = desc->vol;
 	struct ubi_device *ubi = vol->ubi;
 	int err, lnum, off, len,  vol_id = desc->vol->vol_id, tbuf_size;
 	size_t count_save = count;
 	void *tbuf;
 	uint64_t tmp;

 	dbg_msg("read %zd bytes from offset %lld of volume %d",
 		count, *offp, vol_id);

 	if (vol->updating) {
 		dbg_err("updating");
 		return -EBUSY;
 	}
 	if (vol->upd_marker) {
 		dbg_err("damaged volume, update marker is set");
 		return -EBADF;
 	}
 	if (*offp == vol->used_bytes || count == 0)
 		return 0;

 	if (vol->corrupted)
 		dbg_msg("read from corrupted volume %d", vol_id);

 	if (*offp + count > vol->used_bytes)
 		count_save = count = vol->used_bytes - *offp;

 	tbuf_size = vol->usable_leb_size;
 	if (count < tbuf_size)
 		tbuf_size = ALIGN(count, ubi->min_io_size);
 	tbuf = vmalloc(tbuf_size);
 	if (!tbuf)
 		return -ENOMEM;

 	len = count > tbuf_size ? tbuf_size : count;

 	tmp = *offp;
 	off = do_div(tmp, vol->usable_leb_size);
 	lnum = tmp;

 	do {
 		cond_resched();

 		if (off + len >= vol->usable_leb_size)
 			len = vol->usable_leb_size - off;

 		err = ubi_eba_read_leb(ubi, vol_id, lnum, tbuf, off, len, 0);
 		if (err)
 			break;

 		off += len;
 		if (off == vol->usable_leb_size) {
 			lnum += 1;
 			off -= vol->usable_leb_size;
 		}

 		count -= len;
 		*offp += len;

 		err = copy_to_user(buf, tbuf, len);
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		buf += len;
 		len = count > tbuf_size ? tbuf_size : count;
 	} while (count);

 	vfree(tbuf);
 	return err ? err : count_save - count;
 }

 #ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO

 /*
  * This function allows to directly write to dynamic UBI volumes, without
  * issuing the volume update operation. Available only as a debugging feature.
  * Very useful for testing UBI.
  */
 static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
 				     size_t count, loff_t *offp)
 {
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_volume *vol = desc->vol;
 	struct ubi_device *ubi = vol->ubi;
 	int lnum, off, len, tbuf_size, vol_id = vol->vol_id, err = 0;
 	size_t count_save = count;
 	char *tbuf;
 	uint64_t tmp;

 	dbg_msg("requested: write %zd bytes to offset %lld of volume %u",
 		count, *offp, desc->vol->vol_id);

 	if (vol->vol_type == UBI_STATIC_VOLUME)
 		return -EROFS;

 	tmp = *offp;
 	off = do_div(tmp, vol->usable_leb_size);
 	lnum = tmp;

 	if (off % ubi->min_io_size) {
 		dbg_err("unaligned position");
 		return -EINVAL;
 	}

 	if (*offp + count > vol->used_bytes)
 		count_save = count = vol->used_bytes - *offp;

 	/* We can write only in fractions of the minimum I/O unit */
 	if (count % ubi->min_io_size) {
 		dbg_err("unaligned write length");
 		return -EINVAL;
 	}

 	tbuf_size = vol->usable_leb_size;
 	if (count < tbuf_size)
 		tbuf_size = ALIGN(count, ubi->min_io_size);
 	tbuf = vmalloc(tbuf_size);
 	if (!tbuf)
 		return -ENOMEM;

 	len = count > tbuf_size ? tbuf_size : count;

 	while (count) {
 		cond_resched();

 		if (off + len >= vol->usable_leb_size)
 			len = vol->usable_leb_size - off;

 		err = copy_from_user(tbuf, buf, len);
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		err = ubi_eba_write_leb(ubi, vol_id, lnum, tbuf, off, len,
 					UBI_UNKNOWN);
 		if (err)
 			break;

 		off += len;
 		if (off == vol->usable_leb_size) {
 			lnum += 1;
 			off -= vol->usable_leb_size;
 		}

 		count -= len;
 		*offp += len;
 		buf += len;
 		len = count > tbuf_size ? tbuf_size : count;
 	}

 	vfree(tbuf);
 	return err ? err : count_save - count;
 }

 #else
 #define vol_cdev_direct_write(file, buf, count, offp) -EPERM
 #endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */

 static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
 			      size_t count, loff_t *offp)
 {
 	int err = 0;
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_volume *vol = desc->vol;
 	struct ubi_device *ubi = vol->ubi;

 	if (!vol->updating)
 		return vol_cdev_direct_write(file, buf, count, offp);

 	err = ubi_more_update_data(ubi, vol->vol_id, buf, count);
 	if (err < 0) {
 		ubi_err("cannot write %zd bytes of update data", count);
 		return err;
 	}

 	if (err) {
 		/*
 		 * Update is finished, @err contains number of actually written
 		 * bytes now.
 		 */
 		count = err;

 		err = ubi_check_volume(ubi, vol->vol_id);
 		if (err < 0)
 			return err;

 		if (err) {
 			ubi_warn("volume %d on UBI device %d is corrupted",
 				 vol->vol_id, ubi->ubi_num);
 			vol->corrupted = 1;
 		}
 		vol->checked = 1;
 		ubi_gluebi_updated(vol);
 		revoke_exclusive(desc, UBI_READWRITE);
 	}

 	*offp += count;
 	return count;
 }

 static int vol_cdev_ioctl(struct inode *inode, struct file *file,
 			  unsigned int cmd, unsigned long arg)
 {
 	int err = 0;
 	struct ubi_volume_desc *desc = file->private_data;
 	struct ubi_volume *vol = desc->vol;
 	struct ubi_device *ubi = vol->ubi;
 	void __user *argp = (void __user *)arg;

 	if (_IOC_NR(cmd) > VOL_CDEV_IOC_MAX_SEQ ||
 	    _IOC_TYPE(cmd) != UBI_VOL_IOC_MAGIC)
 		return -ENOTTY;

 	if (_IOC_DIR(cmd) && _IOC_READ)
 		err = !access_ok(VERIFY_WRITE, argp, _IOC_SIZE(cmd));
 	else if (_IOC_DIR(cmd) && _IOC_WRITE)
 		err = !access_ok(VERIFY_READ, argp, _IOC_SIZE(cmd));
 	if (err)
 		return -EFAULT;

 	switch (cmd) {

 	/* Volume update command */
 	case UBI_IOCVOLUP:
 	{
 		int64_t bytes, rsvd_bytes;

 		if (!capable(CAP_SYS_RESOURCE)) {
 			err = -EPERM;
 			break;
 		}

 		err = copy_from_user(&bytes, argp, sizeof(int64_t));
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		if (desc->mode == UBI_READONLY) {
 			err = -EROFS;
 			break;
 		}

 		rsvd_bytes = vol->reserved_pebs * (ubi->leb_size-vol->data_pad);
 		if (bytes < 0 || bytes > rsvd_bytes) {
 			err = -EINVAL;
 			break;
 		}

 		err = get_exclusive(desc);
 		if (err < 0)
 			break;

 		err = ubi_start_update(ubi, vol->vol_id, bytes);
 		if (bytes == 0)
 			revoke_exclusive(desc, UBI_READWRITE);

 		file->f_pos = 0;
 		break;
 	}

 #ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
 	/* Logical eraseblock erasure command */
 	case UBI_IOCEBER:
 	{
 		int32_t lnum;

 		err = __get_user(lnum, (__user int32_t *)argp);
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		if (desc->mode == UBI_READONLY) {
 			err = -EROFS;
 			break;
 		}

 		if (lnum < 0 || lnum >= vol->reserved_pebs) {
 			err = -EINVAL;
 			break;
 		}

 		if (vol->vol_type != UBI_DYNAMIC_VOLUME) {
 			err = -EROFS;
 			break;
 		}

 		dbg_msg("erase LEB %d:%d", vol->vol_id, lnum);
 		err = ubi_eba_unmap_leb(ubi, vol->vol_id, lnum);
 		if (err)
 			break;

 		err = ubi_wl_flush(ubi);
 		break;
 	}
 #endif

 	default:
 		err = -ENOTTY;
 		break;
 	}

 	return err;
 }

 /**
  * verify_mkvol_req - verify volume creation request.
  * @ubi: UBI device description object
  * @req: the request to check
  *
  * This function zero if the request is correct, and %-EINVAL if not.
  */
 static int verify_mkvol_req(const struct ubi_device *ubi,
 			    const struct ubi_mkvol_req *req)
 {
 	int n, err = -EINVAL;

 	if (req->bytes < 0 || req->alignment < 0 || req->vol_type < 0 ||
 	    req->name_len < 0)
 		goto bad;

 	if ((req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots) &&
 	    req->vol_id != UBI_VOL_NUM_AUTO)
 		goto bad;

 	if (req->alignment == 0)
 		goto bad;

 	if (req->bytes == 0)
 		goto bad;

 	if (req->vol_type != UBI_DYNAMIC_VOLUME &&
 	    req->vol_type != UBI_STATIC_VOLUME)
 		goto bad;

 	if (req->alignment > ubi->leb_size)
 		goto bad;

 	n = req->alignment % ubi->min_io_size;
 	if (req->alignment != 1 && n)
 		goto bad;

 	if (req->name_len > UBI_VOL_NAME_MAX) {
 		err = -ENAMETOOLONG;
 		goto bad;
 	}

 	return 0;

 bad:
 	dbg_err("bad volume creation request");
 	ubi_dbg_dump_mkvol_req(req);
 	return err;
 }

 /**
  * verify_rsvol_req - verify volume re-size request.
  * @ubi: UBI device description object
  * @req: the request to check
  *
  * This function returns zero if the request is correct, and %-EINVAL if not.
  */
 static int verify_rsvol_req(const struct ubi_device *ubi,
 			    const struct ubi_rsvol_req *req)
 {
 	if (req->bytes <= 0)
 		return -EINVAL;

 	if (req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots)
 		return -EINVAL;

 	return 0;
 }

 static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
 			  unsigned int cmd, unsigned long arg)
 {
 	int err = 0;
 	struct ubi_device *ubi;
 	struct ubi_volume_desc *desc;
 	void __user *argp = (void __user *)arg;

 	if (_IOC_NR(cmd) > UBI_CDEV_IOC_MAX_SEQ ||
 	    _IOC_TYPE(cmd) != UBI_IOC_MAGIC)
 		return -ENOTTY;

 	if (_IOC_DIR(cmd) && _IOC_READ)
 		err = !access_ok(VERIFY_WRITE, argp, _IOC_SIZE(cmd));
 	else if (_IOC_DIR(cmd) && _IOC_WRITE)
 		err = !access_ok(VERIFY_READ, argp, _IOC_SIZE(cmd));
 	if (err)
 		return -EFAULT;

 	if (!capable(CAP_SYS_RESOURCE))
 		return -EPERM;

 	ubi = major_to_device(imajor(inode));
 	if (IS_ERR(ubi))
 		return PTR_ERR(ubi);

 	switch (cmd) {
 	/* Create volume command */
 	case UBI_IOCMKVOL:
 	{
 		struct ubi_mkvol_req req;

 		dbg_msg("create volume");
 		err = __copy_from_user(&req, argp,
 				       sizeof(struct ubi_mkvol_req));
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		err = verify_mkvol_req(ubi, &req);
 		if (err)
 			break;

 		req.name[req.name_len] = '\0';

 		err = ubi_create_volume(ubi, &req);
 		if (err)
 			break;

 		err = __put_user(req.vol_id, (__user int32_t *)argp);
 		if (err)
 			err = -EFAULT;

 		break;
 	}

 	/* Remove volume command */
 	case UBI_IOCRMVOL:
 	{
 		int vol_id;

 		dbg_msg("remove volume");
 		err = __get_user(vol_id, (__user int32_t *)argp);
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_EXCLUSIVE);
 		if (IS_ERR(desc)) {
 			err = PTR_ERR(desc);
 			break;
 		}

 		err = ubi_remove_volume(desc);
 		if (err)
 			ubi_close_volume(desc);

 		break;
 	}

 	/* Re-size volume command */
 	case UBI_IOCRSVOL:
 	{
 		int pebs;
 		uint64_t tmp;
 		struct ubi_rsvol_req req;

 		dbg_msg("re-size volume");
 		err = __copy_from_user(&req, argp,
 				       sizeof(struct ubi_rsvol_req));
 		if (err) {
 			err = -EFAULT;
 			break;
 		}

 		err = verify_rsvol_req(ubi, &req);
 		if (err)
 			break;

 		desc = ubi_open_volume(ubi->ubi_num, req.vol_id, UBI_EXCLUSIVE);
 		if (IS_ERR(desc)) {
 			err = PTR_ERR(desc);
 			break;
 		}

 		tmp = req.bytes;
 		pebs = !!do_div(tmp, desc->vol->usable_leb_size);
 		pebs += tmp;

 		err = ubi_resize_volume(desc, pebs);
 		ubi_close_volume(desc);
 		break;
 	}

 	default:
 		err = -ENOTTY;
 		break;
 	}

 	return err;
 }

 /* UBI character device operations */
 struct file_operations ubi_cdev_operations = {
 	.owner = THIS_MODULE,
 	.ioctl = ubi_cdev_ioctl,
 	.llseek = no_llseek,
 };

 /* UBI volume character device operations */
 struct file_operations ubi_vol_cdev_operations = {
 	.owner   = THIS_MODULE,
 	.open    = vol_cdev_open,
 	.release = vol_cdev_release,
 	.llseek  = vol_cdev_llseek,
 	.read    = vol_cdev_read,
 	.write   = vol_cdev_write,
 	.ioctl   = vol_cdev_ioctl,
 };
	/*
	* Copyright (c) International Business Machines Corp., 2006
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
	* the GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*
	* Author: Artem Bityutskiy (Битюцкий Артём)
	*/

	/*
	* This file includes implementation of UBI character device operations.
	*
	* There are two kinds of character devices in UBI: UBI character devices and
	* UBI volume character devices. UBI character devices allow users to
	* manipulate whole volumes: create, remove, and re-size them. Volume character
	* devices provide volume I/O capabilities.
	*
	* Major and minor numbers are assigned dynamically to both UBI and volume
	* character devices.
	*/

	#include <linux/module.h>
	#include <linux/stat.h>
	#include <linux/ioctl.h>
	#include <linux/capability.h>
	#include <mtd/ubi-user.h>
	#include <asm/uaccess.h>
	#include <asm/div64.h>
	#include "ubi.h"

	/*
	* Maximum sequence numbers of UBI and volume character device IOCTLs (direct
	* logical eraseblock erase is a debug-only feature).
	*/
	#define UBI_CDEV_IOC_MAX_SEQ 2
	#ifndef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
	#define VOL_CDEV_IOC_MAX_SEQ 1
	#else
	#define VOL_CDEV_IOC_MAX_SEQ 2
	#endif

	/**
	* major_to_device - get UBI device object by character device major number.
	* @major: major number
	*
	* This function returns a pointer to the UBI device object.
	*/
	static struct ubi_device *major_to_device(int major)
	{
	int i;

	for (i = 0; i < ubi_devices_cnt; i++)
	if (ubi_devices[i] && ubi_devices[i]->major == major)
	return ubi_devices[i];
	BUG();
	}

	/**
	* get_exclusive - get exclusive access to an UBI volume.
	* @desc: volume descriptor
	*
	* This function changes UBI volume open mode to "exclusive". Returns previous
	* mode value (positive integer) in case of success and a negative error code
	* in case of failure.
	*/
	static int get_exclusive(struct ubi_volume_desc *desc)
	{
	int users, err;
	struct ubi_volume *vol = desc->vol;

	spin_lock(&vol->ubi->volumes_lock);
	users = vol->readers + vol->writers + vol->exclusive;
	ubi_assert(users > 0);
	if (users > 1) {
	dbg_err("%d users for volume %d", users, vol->vol_id);
	err = -EBUSY;
	} else {
	vol->readers = vol->writers = 0;
	vol->exclusive = 1;
	err = desc->mode;
	desc->mode = UBI_EXCLUSIVE;
	}
	spin_unlock(&vol->ubi->volumes_lock);

	return err;
	}

	/**
	* revoke_exclusive - revoke exclusive mode.
	* @desc: volume descriptor
	* @mode: new mode to switch to
	*/
	static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
	{
	struct ubi_volume *vol = desc->vol;

	spin_lock(&vol->ubi->volumes_lock);
	ubi_assert(vol->readers == 0 && vol->writers == 0);
	ubi_assert(vol->exclusive == 1 && desc->mode == UBI_EXCLUSIVE);
	vol->exclusive = 0;
	if (mode == UBI_READONLY)
	vol->readers = 1;
	else if (mode == UBI_READWRITE)
	vol->writers = 1;
	else
	vol->exclusive = 1;
	spin_unlock(&vol->ubi->volumes_lock);

	desc->mode = mode;
	}

	static int vol_cdev_open(struct inode inode, struct file file)
	{
	struct ubi_volume_desc *desc;
	const struct ubi_device *ubi = major_to_device(imajor(inode));
	int vol_id = iminor(inode) - 1;
	int mode;

	if (file->f_mode & FMODE_WRITE)
	mode = UBI_READWRITE;
	else
	mode = UBI_READONLY;

	dbg_msg("open volume %d, mode %d", vol_id, mode);

	desc = ubi_open_volume(ubi->ubi_num, vol_id, mode);
	if (IS_ERR(desc))
	return PTR_ERR(desc);

	file->private_data = desc;
	return 0;
	}

	static int vol_cdev_release(struct inode inode, struct file file)
	{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;

	dbg_msg("release volume %d, mode %d", vol->vol_id, desc->mode);

	if (vol->updating) {
	ubi_warn("update of volume %d not finished, volume is damaged",
	vol->vol_id);
	vol->updating = 0;
	vfree(vol->upd_buf);
	}

	ubi_close_volume(desc);
	return 0;
	}

	static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
	{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	loff_t new_offset;

	if (vol->updating) {
	/* Update is in progress, seeking is prohibited */
	dbg_err("updating");
	return -EBUSY;
	}

	switch (origin) {
	case 0: /* SEEK_SET */
	new_offset = offset;
	break;
	case 1: /* SEEK_CUR */
	new_offset = file->f_pos + offset;
	break;
	case 2: /* SEEK_END */
	new_offset = vol->used_bytes + offset;
	break;
	default:
	return -EINVAL;
	}

	if (new_offset < 0 \|\| new_offset > vol->used_bytes) {
	dbg_err("bad seek %lld", new_offset);
	return -EINVAL;
	}

	dbg_msg("seek volume %d, offset %lld, origin %d, new offset %lld",
	vol->vol_id, offset, origin, new_offset);

	file->f_pos = new_offset;
	return new_offset;
	}

	static ssize_t vol_cdev_read(struct file file, __user char buf, size_t count,
	loff_t *offp)
	{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int err, lnum, off, len, vol_id = desc->vol->vol_id, tbuf_size;
	size_t count_save = count;
	void *tbuf;
	uint64_t tmp;

	dbg_msg("read %zd bytes from offset %lld of volume %d",
	count, *offp, vol_id);

	if (vol->updating) {
	dbg_err("updating");
	return -EBUSY;
	}
	if (vol->upd_marker) {
	dbg_err("damaged volume, update marker is set");
	return -EBADF;
	}
	if (*offp == vol->used_bytes \|\| count == 0)
	return 0;

	if (vol->corrupted)
	dbg_msg("read from corrupted volume %d", vol_id);

	if (*offp + count > vol->used_bytes)
	count_save = count = vol->used_bytes - *offp;

	tbuf_size = vol->usable_leb_size;
	if (count < tbuf_size)
	tbuf_size = ALIGN(count, ubi->min_io_size);
	tbuf = vmalloc(tbuf_size);
	if (!tbuf)
	return -ENOMEM;

	len = count > tbuf_size ? tbuf_size : count;

	tmp = *offp;
	off = do_div(tmp, vol->usable_leb_size);
	lnum = tmp;

	do {
	cond_resched();

	if (off + len >= vol->usable_leb_size)
	len = vol->usable_leb_size - off;

	err = ubi_eba_read_leb(ubi, vol_id, lnum, tbuf, off, len, 0);
	if (err)
	break;

	off += len;
	if (off == vol->usable_leb_size) {
	lnum += 1;
	off -= vol->usable_leb_size;
	}

	count -= len;
	*offp += len;

	err = copy_to_user(buf, tbuf, len);
	if (err) {
	err = -EFAULT;
	break;
	}

	buf += len;
	len = count > tbuf_size ? tbuf_size : count;
	} while (count);

	vfree(tbuf);
	return err ? err : count_save - count;
	}

	#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO

	/*
	* This function allows to directly write to dynamic UBI volumes, without
	* issuing the volume update operation. Available only as a debugging feature.
	* Very useful for testing UBI.
	*/
	static ssize_t vol_cdev_direct_write(struct file file, const char __user buf,
	size_t count, loff_t *offp)
	{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int lnum, off, len, tbuf_size, vol_id = vol->vol_id, err = 0;
	size_t count_save = count;
	char *tbuf;
	uint64_t tmp;

	dbg_msg("requested: write %zd bytes to offset %lld of volume %u",
	count, *offp, desc->vol->vol_id);

	if (vol->vol_type == UBI_STATIC_VOLUME)
	return -EROFS;

	tmp = *offp;
	off = do_div(tmp, vol->usable_leb_size);
	lnum = tmp;

	if (off % ubi->min_io_size) {
	dbg_err("unaligned position");
	return -EINVAL;
	}

	if (*offp + count > vol->used_bytes)
	count_save = count = vol->used_bytes - *offp;

	/* We can write only in fractions of the minimum I/O unit */
	if (count % ubi->min_io_size) {
	dbg_err("unaligned write length");
	return -EINVAL;
	}

	tbuf_size = vol->usable_leb_size;
	if (count < tbuf_size)
	tbuf_size = ALIGN(count, ubi->min_io_size);
	tbuf = vmalloc(tbuf_size);
	if (!tbuf)
	return -ENOMEM;

	len = count > tbuf_size ? tbuf_size : count;

	while (count) {
	cond_resched();

	if (off + len >= vol->usable_leb_size)
	len = vol->usable_leb_size - off;

	err = copy_from_user(tbuf, buf, len);
	if (err) {
	err = -EFAULT;
	break;
	}

	err = ubi_eba_write_leb(ubi, vol_id, lnum, tbuf, off, len,
	UBI_UNKNOWN);
	if (err)
	break;

	off += len;
	if (off == vol->usable_leb_size) {
	lnum += 1;
	off -= vol->usable_leb_size;
	}

	count -= len;
	*offp += len;
	buf += len;
	len = count > tbuf_size ? tbuf_size : count;
	}

	vfree(tbuf);
	return err ? err : count_save - count;
	}

	#else
	#define vol_cdev_direct_write(file, buf, count, offp) -EPERM
	#endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */

	static ssize_t vol_cdev_write(struct file file, const char __user buf,
	size_t count, loff_t *offp)
	{
	int err = 0;
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;

	if (!vol->updating)
	return vol_cdev_direct_write(file, buf, count, offp);

	err = ubi_more_update_data(ubi, vol->vol_id, buf, count);
	if (err < 0) {
	ubi_err("cannot write %zd bytes of update data", count);
	return err;
	}

	if (err) {
	/*
	* Update is finished, @err contains number of actually written
	* bytes now.
	*/
	count = err;

	err = ubi_check_volume(ubi, vol->vol_id);
	if (err < 0)
	return err;

	if (err) {
	ubi_warn("volume %d on UBI device %d is corrupted",
	vol->vol_id, ubi->ubi_num);
	vol->corrupted = 1;
	}
	vol->checked = 1;
	ubi_gluebi_updated(vol);
	revoke_exclusive(desc, UBI_READWRITE);
	}

	*offp += count;
	return count;
	}

	static int vol_cdev_ioctl(struct inode inode, struct file file,
	unsigned int cmd, unsigned long arg)
	{
	int err = 0;
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	void __user argp = (void __user )arg;

	if (_IOC_NR(cmd) > VOL_CDEV_IOC_MAX_SEQ \|\|
	_IOC_TYPE(cmd) != UBI_VOL_IOC_MAGIC)
	return -ENOTTY;

	if (_IOC_DIR(cmd) && _IOC_READ)
	err = !access_ok(VERIFY_WRITE, argp, _IOC_SIZE(cmd));
	else if (_IOC_DIR(cmd) && _IOC_WRITE)
	err = !access_ok(VERIFY_READ, argp, _IOC_SIZE(cmd));
	if (err)
	return -EFAULT;

	switch (cmd) {

	/* Volume update command */
	case UBI_IOCVOLUP:
	{
	int64_t bytes, rsvd_bytes;

	if (!capable(CAP_SYS_RESOURCE)) {
	err = -EPERM;
	break;
	}

	err = copy_from_user(&bytes, argp, sizeof(int64_t));
	if (err) {
	err = -EFAULT;
	break;
	}

	if (desc->mode == UBI_READONLY) {
	err = -EROFS;
	break;
	}

	rsvd_bytes = vol->reserved_pebs * (ubi->leb_size-vol->data_pad);
	if (bytes < 0 \|\| bytes > rsvd_bytes) {
	err = -EINVAL;
	break;
	}

	err = get_exclusive(desc);
	if (err < 0)
	break;

	err = ubi_start_update(ubi, vol->vol_id, bytes);
	if (bytes == 0)
	revoke_exclusive(desc, UBI_READWRITE);

	file->f_pos = 0;
	break;
	}

	#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
	/* Logical eraseblock erasure command */
	case UBI_IOCEBER:
	{
	int32_t lnum;

	err = __get_user(lnum, (__user int32_t *)argp);
	if (err) {
	err = -EFAULT;
	break;
	}

	if (desc->mode == UBI_READONLY) {
	err = -EROFS;
	break;
	}

	if (lnum < 0 \|\| lnum >= vol->reserved_pebs) {
	err = -EINVAL;
	break;
	}

	if (vol->vol_type != UBI_DYNAMIC_VOLUME) {
	err = -EROFS;
	break;
	}

	dbg_msg("erase LEB %d:%d", vol->vol_id, lnum);
	err = ubi_eba_unmap_leb(ubi, vol->vol_id, lnum);
	if (err)
	break;

	err = ubi_wl_flush(ubi);
	break;
	}
	#endif

	default:
	err = -ENOTTY;
	break;
	}

	return err;
	}

	/**
	* verify_mkvol_req - verify volume creation request.
	* @ubi: UBI device description object
	* @req: the request to check
	*
	* This function zero if the request is correct, and %-EINVAL if not.
	*/
	static int verify_mkvol_req(const struct ubi_device *ubi,
	const struct ubi_mkvol_req *req)
	{
	int n, err = -EINVAL;

	if (req->bytes < 0 \|\| req->alignment < 0 \|\| req->vol_type < 0 \|\|
	req->name_len < 0)
	goto bad;

	if ((req->vol_id < 0 \|\| req->vol_id >= ubi->vtbl_slots) &&
	req->vol_id != UBI_VOL_NUM_AUTO)
	goto bad;

	if (req->alignment == 0)
	goto bad;

	if (req->bytes == 0)
	goto bad;

	if (req->vol_type != UBI_DYNAMIC_VOLUME &&
	req->vol_type != UBI_STATIC_VOLUME)
	goto bad;

	if (req->alignment > ubi->leb_size)
	goto bad;

	n = req->alignment % ubi->min_io_size;
	if (req->alignment != 1 && n)
	goto bad;

	if (req->name_len > UBI_VOL_NAME_MAX) {
	err = -ENAMETOOLONG;
	goto bad;
	}

	return 0;

	bad:
	dbg_err("bad volume creation request");
	ubi_dbg_dump_mkvol_req(req);
	return err;
	}

	/**
	* verify_rsvol_req - verify volume re-size request.
	* @ubi: UBI device description object
	* @req: the request to check
	*
	* This function returns zero if the request is correct, and %-EINVAL if not.
	*/
	static int verify_rsvol_req(const struct ubi_device *ubi,
	const struct ubi_rsvol_req *req)
	{
	if (req->bytes <= 0)
	return -EINVAL;

	if (req->vol_id < 0 \|\| req->vol_id >= ubi->vtbl_slots)
	return -EINVAL;

	return 0;
	}

	static int ubi_cdev_ioctl(struct inode inode, struct file file,
	unsigned int cmd, unsigned long arg)
	{
	int err = 0;
	struct ubi_device *ubi;
	struct ubi_volume_desc *desc;
	void __user argp = (void __user )arg;

	if (_IOC_NR(cmd) > UBI_CDEV_IOC_MAX_SEQ \|\|
	_IOC_TYPE(cmd) != UBI_IOC_MAGIC)
	return -ENOTTY;

	if (_IOC_DIR(cmd) && _IOC_READ)
	err = !access_ok(VERIFY_WRITE, argp, _IOC_SIZE(cmd));
	else if (_IOC_DIR(cmd) && _IOC_WRITE)
	err = !access_ok(VERIFY_READ, argp, _IOC_SIZE(cmd));
	if (err)
	return -EFAULT;

	if (!capable(CAP_SYS_RESOURCE))
	return -EPERM;

	ubi = major_to_device(imajor(inode));
	if (IS_ERR(ubi))
	return PTR_ERR(ubi);

	switch (cmd) {
	/* Create volume command */
	case UBI_IOCMKVOL:
	{
	struct ubi_mkvol_req req;

	dbg_msg("create volume");
	err = __copy_from_user(&req, argp,
	sizeof(struct ubi_mkvol_req));
	if (err) {
	err = -EFAULT;
	break;
	}

	err = verify_mkvol_req(ubi, &req);
	if (err)
	break;

	req.name[req.name_len] = '\0';

	err = ubi_create_volume(ubi, &req);
	if (err)
	break;

	err = __put_user(req.vol_id, (__user int32_t *)argp);
	if (err)
	err = -EFAULT;

	break;
	}

	/* Remove volume command */
	case UBI_IOCRMVOL:
	{
	int vol_id;

	dbg_msg("remove volume");
	err = __get_user(vol_id, (__user int32_t *)argp);
	if (err) {
	err = -EFAULT;
	break;
	}

	desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_EXCLUSIVE);
	if (IS_ERR(desc)) {
	err = PTR_ERR(desc);
	break;
	}

	err = ubi_remove_volume(desc);
	if (err)
	ubi_close_volume(desc);

	break;
	}

	/* Re-size volume command */
	case UBI_IOCRSVOL:
	{
	int pebs;
	uint64_t tmp;
	struct ubi_rsvol_req req;

	dbg_msg("re-size volume");
	err = __copy_from_user(&req, argp,
	sizeof(struct ubi_rsvol_req));
	if (err) {
	err = -EFAULT;
	break;
	}

	err = verify_rsvol_req(ubi, &req);
	if (err)
	break;

	desc = ubi_open_volume(ubi->ubi_num, req.vol_id, UBI_EXCLUSIVE);
	if (IS_ERR(desc)) {
	err = PTR_ERR(desc);
	break;
	}

	tmp = req.bytes;
	pebs = !!do_div(tmp, desc->vol->usable_leb_size);
	pebs += tmp;

	err = ubi_resize_volume(desc, pebs);
	ubi_close_volume(desc);
	break;
	}

	default:
	err = -ENOTTY;
	break;
	}

	return err;
	}

	/* UBI character device operations */
	struct file_operations ubi_cdev_operations = {
	.owner = THIS_MODULE,
	.ioctl = ubi_cdev_ioctl,
	.llseek = no_llseek,
	};

	/* UBI volume character device operations */
	struct file_operations ubi_vol_cdev_operations = {
	.owner = THIS_MODULE,
	.open = vol_cdev_open,
	.release = vol_cdev_release,
	.llseek = vol_cdev_llseek,
	.read = vol_cdev_read,
	.write = vol_cdev_write,
	.ioctl = vol_cdev_ioctl,
	};