cdev.c

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/*
 * 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"

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) {
        ubi_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;
}

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("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;
    loff_t new_offset;

    if (vol->updating) {
        /* Update is in progress, seeking is prohibited */
        ubi_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) {
        ubi_err("bad seek %lld", new_offset);
        return -EINVAL;
    }

    dbg_gen("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 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->f_path.dentry->d_inode;
    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("updating");
        return -EBUSY;
    }
    if (vol->upd_marker) {
        ubi_err("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("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("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("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("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(desc);
        if (err < 0)
            break;

        err = ubi_start_update(ubi, vol, bytes);
        if (bytes == 0)
            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(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;
    }

    default:
        err = -ENOTTY;
        break;
    }
    return err;
}

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("bad volume creation request");
    ubi_dump_mkvol_req(req);
    return err;
}

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 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)
            err = -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("duplicated volume id %d",
                    req->ents[i].vol_id);
                return -EINVAL;
            }
            if (!strcmp(req->ents[i].name, req->ents[n].name)) {
                ubi_err("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_EXCLUSIVE);
        if (IS_ERR(re->desc)) {
            err = PTR_ERR(re->desc);
            ubi_err("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("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,
};