/*
 * 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.
 *
 * Well, there is the third kind of character devices - the UBI control
 * character device, which allows to manipulate by UBI devices - create and
 * delete them. In other words, it is used for attaching and detaching MTD
 * devices.
 */

#include <linux/module.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/capability.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include <linux/math64.h>
#include <mtd/ubi-user.h>
#include "ubi.h"

/**
 * get_exclusive - get exclusive access to an UBI volume.
 * @ubi: UBI device description object
 * @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_device *ubi, 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) {
                ubi_err(ubi, "%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;
        int vol_id = iminor(inode) - 1, mode, ubi_num;

        ubi_num = ubi_major2num(imajor(inode));
        if (ubi_num < 0)
                return ubi_num;

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

        dbg_gen("open device %d, volume %d, mode %d",
                ubi_num, vol_id, mode);

        desc = ubi_open_volume(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_gen("release device %d, volume %d, mode %d",
                vol->ubi->ubi_num, vol->vol_id, desc->mode);

        if (vol->updating) {
                ubi_warn(vol->ubi, "update of volume %d not finished, volume is damaged",
                         vol->vol_id);
                ubi_assert(!vol->changing_leb);
                vol->updating = 0;
                vfree(vol->upd_buf);
        } else if (vol->changing_leb) {
                dbg_gen("only %lld of %lld bytes received for atomic LEB change for volume %d:%d, cancel",
                        vol->upd_received, vol->upd_bytes, vol->ubi->ubi_num,
                        vol->vol_id);
                vol->changing_leb = 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;

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

        return fixed_size_llseek(file, offset, origin, vol->used_bytes);
}

static int vol_cdev_fsync(struct file *file, loff_t start, loff_t end,
                          int datasync)
{
        struct ubi_volume_desc *desc = file->private_data;
        struct ubi_device *ubi = desc->vol->ubi;
        struct inode *inode = file_inode(file);
        int err;
        mutex_lock(&inode->i_mutex);
        err = ubi_sync(ubi->ubi_num);
        mutex_unlock(&inode->i_mutex);
        return err;
}


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,  tbuf_size;
        size_t count_save = count;
        void *tbuf;

        dbg_gen("read %zd bytes from offset %lld of volume %d",
                count, *offp, vol->vol_id);

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

        if (vol->corrupted)
                dbg_gen("read from corrupted volume %d", vol->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;
        lnum = div_u64_rem(*offp, vol->usable_leb_size, &off);

        do {
                cond_resched();

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

                err = ubi_eba_read_leb(ubi, vol, 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;
}

/*
 * This function allows to directly write to dynamic UBI volumes, without
 * issuing the volume update operation.
 */
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, err = 0;
        size_t count_save = count;
        char *tbuf;

        if (!vol->direct_writes)
                return -EPERM;

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

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

        lnum = div_u64_rem(*offp, vol->usable_leb_size, &off);
        if (off & (ubi->min_io_size - 1)) {
                ubi_err(ubi, "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 - 1)) {
                ubi_err(ubi, "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, lnum, tbuf, off, len);
                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;
}

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 && !vol->changing_leb)
                return vol_cdev_direct_write(file, buf, count, offp);

        if (vol->updating)
                err = ubi_more_update_data(ubi, vol, buf, count);
        else
                err = ubi_more_leb_change_data(ubi, vol, buf, count);

        if (err < 0) {
                ubi_err(ubi, "cannot accept more %zd bytes of data, error %d",
                        count, err);
                return err;
        }

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

                if (vol->changing_leb) {
                        revoke_exclusive(desc, UBI_READWRITE);
                        return count;
                }

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

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

        return count;
}

static long vol_cdev_ioctl(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;

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

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

                err = ubi_start_update(ubi, vol, bytes);
                if (bytes == 0) {
                        ubi_volume_notify(ubi, vol, UBI_VOLUME_UPDATED);
                        revoke_exclusive(desc, UBI_READWRITE);
                }
                break;
        }

        /* Atomic logical eraseblock change command */
        case UBI_IOCEBCH:
        {
                struct ubi_leb_change_req req;

                err = copy_from_user(&req, argp,
                                     sizeof(struct ubi_leb_change_req));
                if (err) {
                        err = -EFAULT;
                        break;
                }

                if (desc->mode == UBI_READONLY ||
                    vol->vol_type == UBI_STATIC_VOLUME) {
                        err = -EROFS;
                        break;
                }

                /* Validate the request */
                err = -EINVAL;
                if (req.lnum < 0 || req.lnum >= vol->reserved_pebs ||
                    req.bytes < 0 || req.lnum >= vol->usable_leb_size)
                        break;

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

                err = ubi_start_leb_change(ubi, vol, &req);
                if (req.bytes == 0)
                        revoke_exclusive(desc, UBI_READWRITE);
                break;
        }

        /* 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 ||
                    vol->vol_type == UBI_STATIC_VOLUME) {
                        err = -EROFS;
                        break;
                }

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

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

                err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
                break;
        }

        /* Logical eraseblock map command */
        case UBI_IOCEBMAP:
        {
                struct ubi_map_req req;

                err = copy_from_user(&req, argp, sizeof(struct ubi_map_req));
                if (err) {
                        err = -EFAULT;
                        break;
                }
                err = ubi_leb_map(desc, req.lnum);
                break;
        }

        /* Logical eraseblock un-map command */
        case UBI_IOCEBUNMAP:
        {
                int32_t lnum;

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

        /* Check if logical eraseblock is mapped command */
        case UBI_IOCEBISMAP:
        {
                int32_t lnum;

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

        /* Set volume property command */
        case UBI_IOCSETVOLPROP:
        {
                struct ubi_set_vol_prop_req req;

                err = copy_from_user(&req, argp,
                                     sizeof(struct ubi_set_vol_prop_req));
                if (err) {
                        err = -EFAULT;
                        break;
                }
                switch (req.property) {
                case UBI_VOL_PROP_DIRECT_WRITE:
                        mutex_lock(&ubi->device_mutex);
                        desc->vol->direct_writes = !!req.value;
                        mutex_unlock(&ubi->device_mutex);
                        break;
                default:
                        err = -EINVAL;
                        break;
                }
                break;
        }

        /* Create a R/O block device on top of the UBI volume */
        case UBI_IOCVOLCRBLK:
        {
                struct ubi_volume_info vi;

                ubi_get_volume_info(desc, &vi);
                err = ubiblock_create(&vi);
                break;
        }

        /* Remove the R/O block device */
        case UBI_IOCVOLRMBLK:
        {
                struct ubi_volume_info vi;

                ubi_get_volume_info(desc, &vi);
                err = ubiblock_remove(&vi);
                break;
        }

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

        if (!req->name[0] || !req->name_len)
                goto bad;

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

        n = strnlen(req->name, req->name_len + 1);
        if (n != req->name_len)
                goto bad;

        return 0;

bad:
        ubi_err(ubi, "bad volume creation request");
        ubi_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;
}

/**
 * rename_volumes - rename UBI volumes.
 * @ubi: UBI device description object
 * @req: volumes re-name request
 *
 * This is a helper function for the volume re-name IOCTL which validates the
 * the request, opens the volume and calls corresponding volumes management
 * function. Returns zero in case of success and a negative error code in case
 * of failure.
 */
static int rename_volumes(struct ubi_device *ubi,
                          struct ubi_rnvol_req *req)
{
        int i, n, err;
        struct list_head rename_list;
        struct ubi_rename_entry *re, *re1;

        if (req->count < 0 || req->count > UBI_MAX_RNVOL)
                return -EINVAL;

        if (req->count == 0)
                return 0;

        /* Validate volume IDs and names in the request */
        for (i = 0; i < req->count; i++) {
                if (req->ents[i].vol_id < 0 ||
                    req->ents[i].vol_id >= ubi->vtbl_slots)
                        return -EINVAL;
                if (req->ents[i].name_len < 0)
                        return -EINVAL;
                if (req->ents[i].name_len > UBI_VOL_NAME_MAX)
                        return -ENAMETOOLONG;
                req->ents[i].name[req->ents[i].name_len] = '\0';
                n = strlen(req->ents[i].name);
                if (n != req->ents[i].name_len)
                        return -EINVAL;
        }

        /* Make sure volume IDs and names are unique */
        for (i = 0; i < req->count - 1; i++) {
                for (n = i + 1; n < req->count; n++) {
                        if (req->ents[i].vol_id == req->ents[n].vol_id) {
                                ubi_err(ubi, "duplicated volume id %d",
                                        req->ents[i].vol_id);
                                return -EINVAL;
                        }
                        if (!strcmp(req->ents[i].name, req->ents[n].name)) {
                                ubi_err(ubi, "duplicated volume name \"%s\"",
                                        req->ents[i].name);
                                return -EINVAL;
                        }
                }
        }

        /* Create the re-name list */
        INIT_LIST_HEAD(&rename_list);
        for (i = 0; i < req->count; i++) {
                int vol_id = req->ents[i].vol_id;
                int name_len = req->ents[i].name_len;
                const char *name = req->ents[i].name;

                re = kzalloc(sizeof(struct ubi_rename_entry), GFP_KERNEL);
                if (!re) {
                        err = -ENOMEM;
                        goto out_free;
                }

                re->desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_READWRITE);
                if (IS_ERR(re->desc)) {
                        err = PTR_ERR(re->desc);
                        ubi_err(ubi, "cannot open volume %d, error %d",
                                vol_id, err);
                        kfree(re);
                        goto out_free;
                }

                /* Skip this re-naming if the name does not really change */
                if (re->desc->vol->name_len == name_len &&
                    !memcmp(re->desc->vol->name, name, name_len)) {
                        ubi_close_volume(re->desc);
                        kfree(re);
                        continue;
                }

                re->new_name_len = name_len;
                memcpy(re->new_name, name, name_len);
                list_add_tail(&re->list, &rename_list);
                dbg_gen("will rename volume %d from \"%s\" to \"%s\"",
                        vol_id, re->desc->vol->name, name);
        }

        if (list_empty(&rename_list))
                return 0;

        /* Find out the volumes which have to be removed */
        list_for_each_entry(re, &rename_list, list) {
                struct ubi_volume_desc *desc;
                int no_remove_needed = 0;

                /*
                 * Volume @re->vol_id is going to be re-named to
                 * @re->new_name, while its current name is @name. If a volume
                 * with name @re->new_name currently exists, it has to be
                 * removed, unless it is also re-named in the request (@req).
                 */
                list_for_each_entry(re1, &rename_list, list) {
                        if (re->new_name_len == re1->desc->vol->name_len &&
                            !memcmp(re->new_name, re1->desc->vol->name,
                                    re1->desc->vol->name_len)) {
                                no_remove_needed = 1;
                                break;
                        }
                }

                if (no_remove_needed)
                        continue;

                /*
                 * It seems we need to remove volume with name @re->new_name,
                 * if it exists.
                 */
                desc = ubi_open_volume_nm(ubi->ubi_num, re->new_name,
                                          UBI_EXCLUSIVE);
                if (IS_ERR(desc)) {
                        err = PTR_ERR(desc);
                        if (err == -ENODEV)
                                /* Re-naming into a non-existing volume name */
                                continue;

                        /* The volume exists but busy, or an error occurred */
                        ubi_err(ubi, "cannot open volume \"%s\", error %d",
                                re->new_name, err);
                        goto out_free;
                }

                re1 = kzalloc(sizeof(struct ubi_rename_entry), GFP_KERNEL);
                if (!re1) {
                        err = -ENOMEM;
                        ubi_close_volume(desc);
                        goto out_free;
                }

                re1->remove = 1;
                re1->desc = desc;
                list_add(&re1->list, &rename_list);
                dbg_gen("will remove volume %d, name \"%s\"",
                        re1->desc->vol->vol_id, re1->desc->vol->name);
        }

        mutex_lock(&ubi->device_mutex);
        err = ubi_rename_volumes(ubi, &rename_list);
        mutex_unlock(&ubi->device_mutex);

out_free:
        list_for_each_entry_safe(re, re1, &rename_list, list) {
                ubi_close_volume(re->desc);
                list_del(&re->list);
                kfree(re);
        }
        return err;
}

static long ubi_cdev_ioctl(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 (!capable(CAP_SYS_RESOURCE))
                return -EPERM;

        ubi = ubi_get_by_major(imajor(file->f_mapping->host));
        if (!ubi)
                return -ENODEV;

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

                dbg_gen("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;

                mutex_lock(&ubi->device_mutex);
                err = ubi_create_volume(ubi, &req);
                mutex_unlock(&ubi->device_mutex);
                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_gen("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;
                }

                mutex_lock(&ubi->device_mutex);
                err = ubi_remove_volume(desc, 0);
                mutex_unlock(&ubi->device_mutex);

                /*
                 * The volume is deleted (unless an error occurred), and the
                 * 'struct ubi_volume' object will be freed when
                 * 'ubi_close_volume()' will call 'put_device()'.
                 */
                ubi_close_volume(desc);
                break;
        }

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

                dbg_gen("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;
                }

                pebs = div_u64(req.bytes + desc->vol->usable_leb_size - 1,
                               desc->vol->usable_leb_size);

                mutex_lock(&ubi->device_mutex);
                err = ubi_resize_volume(desc, pebs);
                mutex_unlock(&ubi->device_mutex);
                ubi_close_volume(desc);
                break;
        }

        /* Re-name volumes command */
        case UBI_IOCRNVOL:
        {
                struct ubi_rnvol_req *req;

                dbg_gen("re-name volumes");
                req = kmalloc(sizeof(struct ubi_rnvol_req), GFP_KERNEL);
                if (!req) {
                        err = -ENOMEM;
                        break;
                };

                err = copy_from_user(req, argp, sizeof(struct ubi_rnvol_req));
                if (err) {
                        err = -EFAULT;
                        kfree(req);
                        break;
                }

                err = rename_volumes(ubi, req);
                kfree(req);
                break;
        }

        default:
                err = -ENOTTY;
                break;
        }

        ubi_put_device(ubi);
        return err;
}

static long ctrl_cdev_ioctl(struct file *file, unsigned int cmd,
                            unsigned long arg)
{
        int err = 0;
        void __user *argp = (void __user *)arg;

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

        switch (cmd) {
        /* Attach an MTD device command */
        case UBI_IOCATT:
        {
                struct ubi_attach_req req;
                struct mtd_info *mtd;

                dbg_gen("attach MTD device");
                err = copy_from_user(&req, argp, sizeof(struct ubi_attach_req));
                if (err) {
                        err = -EFAULT;
                        break;
                }

                if (req.mtd_num < 0 ||
                    (req.ubi_num < 0 && req.ubi_num != UBI_DEV_NUM_AUTO)) {
                        err = -EINVAL;
                        break;

                }

                mtd = get_mtd_device(NULL, req.mtd_num);
                if (IS_ERR(mtd)) {
                        err = PTR_ERR(mtd);
                        break;
                }

                /*
                 * Note, further request verification is done by
                 * 'ubi_attach_mtd_dev()'.
                 */
                mutex_lock(&ubi_devices_mutex);
                err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset,
                                         req.max_beb_per1024);
                mutex_unlock(&ubi_devices_mutex);
                if (err < 0)
                        put_mtd_device(mtd);
                else
                        /* @err contains UBI device number */
                        err = put_user(err, (__user int32_t *)argp);

                break;
        }

        /* Detach an MTD device command */
        case UBI_IOCDET:
        {
                int ubi_num;

                dbg_gen("detach MTD device");
                err = get_user(ubi_num, (__user int32_t *)argp);
                if (err) {
                        err = -EFAULT;
                        break;
                }

                mutex_lock(&ubi_devices_mutex);
                err = ubi_detach_mtd_dev(ubi_num, 0);
                mutex_unlock(&ubi_devices_mutex);
                break;
        }

        default:
                err = -ENOTTY;
                break;
        }

        return err;
}

#ifdef CONFIG_COMPAT
static long vol_cdev_compat_ioctl(struct file *file, unsigned int cmd,
                                  unsigned long arg)
{
        unsigned long translated_arg = (unsigned long)compat_ptr(arg);

        return vol_cdev_ioctl(file, cmd, translated_arg);
}

static long ubi_cdev_compat_ioctl(struct file *file, unsigned int cmd,
                                  unsigned long arg)
{
        unsigned long translated_arg = (unsigned long)compat_ptr(arg);

        return ubi_cdev_ioctl(file, cmd, translated_arg);
}

static long ctrl_cdev_compat_ioctl(struct file *file, unsigned int cmd,
                                   unsigned long arg)
{
        unsigned long translated_arg = (unsigned long)compat_ptr(arg);

        return ctrl_cdev_ioctl(file, cmd, translated_arg);
}
#else
#define vol_cdev_compat_ioctl  NULL
#define ubi_cdev_compat_ioctl  NULL
#define ctrl_cdev_compat_ioctl NULL
#endif

/* UBI volume character device operations */
const 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,
        .fsync          = vol_cdev_fsync,
        .unlocked_ioctl = vol_cdev_ioctl,
        .compat_ioctl   = vol_cdev_compat_ioctl,
};

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

/* UBI control character device operations */
const struct file_operations ubi_ctrl_cdev_operations = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = ctrl_cdev_ioctl,
        .compat_ioctl   = ctrl_cdev_compat_ioctl,
        .llseek         = no_llseek,
};