gluebi.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), Joern Engel
 */

/*
 * This is a small driver which implements fake MTD devices on top of UBI
 * volumes. This sounds strange, but it is in fact quite useful to make
 * MTD-oriented software (including all the legacy software) work on top of
 * UBI.
 *
 * Gluebi emulates MTD devices of "MTD_UBIVOLUME" type. Their minimal I/O unit
 * size (@mtd->writesize) is equivalent to the UBI minimal I/O unit. The
 * eraseblock size is equivalent to the logical eraseblock size of the volume.
 */

#include <linux/err.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/mtd/ubi.h>
#include <linux/mtd/mtd.h>
#include "ubi-media.h"

#define err_msg(fmt, ...)                                   \
    pr_err("gluebi (pid %d): %s: " fmt "\n",            \
           current->pid, __func__, ##__VA_ARGS__)

struct gluebi_device {
    struct mtd_info mtd;
    int refcnt;
    struct ubi_volume_desc *desc;
    int ubi_num;
    int vol_id;
    struct list_head list;
};

/* List of all gluebi devices */
static LIST_HEAD(gluebi_devices);
static DEFINE_MUTEX(devices_mutex);

static struct gluebi_device *find_gluebi_nolock(int ubi_num, int vol_id)
{
    struct gluebi_device *gluebi;

    list_for_each_entry(gluebi, &gluebi_devices, list)
        if (gluebi->ubi_num == ubi_num && gluebi->vol_id == vol_id)
            return gluebi;
    return NULL;
}

static int gluebi_get_device(struct mtd_info *mtd)
{
    struct gluebi_device *gluebi;
    int ubi_mode = UBI_READONLY;

    if (!try_module_get(THIS_MODULE))
        return -ENODEV;

    if (mtd->flags & MTD_WRITEABLE)
        ubi_mode = UBI_READWRITE;

    gluebi = container_of(mtd, struct gluebi_device, mtd);
    mutex_lock(&devices_mutex);
    if (gluebi->refcnt > 0) {
        /*
         * The MTD device is already referenced and this is just one
         * more reference. MTD allows many users to open the same
         * volume simultaneously and do not distinguish between
         * readers/writers/exclusive openers as UBI does. So we do not
         * open the UBI volume again - just increase the reference
         * counter and return.
         */
        gluebi->refcnt += 1;
        mutex_unlock(&devices_mutex);
        return 0;
    }

    /*
     * This is the first reference to this UBI volume via the MTD device
     * interface. Open the corresponding volume in read-write mode.
     */
    gluebi->desc = ubi_open_volume(gluebi->ubi_num, gluebi->vol_id,
                       ubi_mode);
    if (IS_ERR(gluebi->desc)) {
        mutex_unlock(&devices_mutex);
        module_put(THIS_MODULE);
        return PTR_ERR(gluebi->desc);
    }
    gluebi->refcnt += 1;
    mutex_unlock(&devices_mutex);
    return 0;
}

static void gluebi_put_device(struct mtd_info *mtd)
{
    struct gluebi_device *gluebi;

    gluebi = container_of(mtd, struct gluebi_device, mtd);
    mutex_lock(&devices_mutex);
    gluebi->refcnt -= 1;
    if (gluebi->refcnt == 0)
        ubi_close_volume(gluebi->desc);
    module_put(THIS_MODULE);
    mutex_unlock(&devices_mutex);
}

static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
               size_t *retlen, unsigned char *buf)
{
    int err = 0, lnum, offs, total_read;
    struct gluebi_device *gluebi;

    gluebi = container_of(mtd, struct gluebi_device, mtd);
    lnum = div_u64_rem(from, mtd->erasesize, &offs);
    total_read = len;
    while (total_read) {
        size_t to_read = mtd->erasesize - offs;

        if (to_read > total_read)
            to_read = total_read;

        err = ubi_read(gluebi->desc, lnum, buf, offs, to_read);
        if (err)
            break;

        lnum += 1;
        offs = 0;
        total_read -= to_read;
        buf += to_read;
    }

    *retlen = len - total_read;
    return err;
}

static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
            size_t *retlen, const u_char *buf)
{
    int err = 0, lnum, offs, total_written;
    struct gluebi_device *gluebi;

    gluebi = container_of(mtd, struct gluebi_device, mtd);
    lnum = div_u64_rem(to, mtd->erasesize, &offs);

    if (len % mtd->writesize || offs % mtd->writesize)
        return -EINVAL;

    total_written = len;
    while (total_written) {
        size_t to_write = mtd->erasesize - offs;

        if (to_write > total_written)
            to_write = total_written;

        err = ubi_leb_write(gluebi->desc, lnum, buf, offs, to_write);
        if (err)
            break;

        lnum += 1;
        offs = 0;
        total_written -= to_write;
        buf += to_write;
    }

    *retlen = len - total_written;
    return err;
}

static int gluebi_erase(struct mtd_info *mtd, struct erase_info *instr)
{
    int err, i, lnum, count;
    struct gluebi_device *gluebi;

    if (mtd_mod_by_ws(instr->addr, mtd) || mtd_mod_by_ws(instr->len, mtd))
        return -EINVAL;

    lnum = mtd_div_by_eb(instr->addr, mtd);
    count = mtd_div_by_eb(instr->len, mtd);
    gluebi = container_of(mtd, struct gluebi_device, mtd);

    for (i = 0; i < count - 1; i++) {
        err = ubi_leb_unmap(gluebi->desc, lnum + i);
        if (err)
            goto out_err;
    }
    /*
     * MTD erase operations are synchronous, so we have to make sure the
     * physical eraseblock is wiped out.
     *
     * Thus, perform leb_erase instead of leb_unmap operation - leb_erase
     * will wait for the end of operations
     */
    err = ubi_leb_erase(gluebi->desc, lnum + i);
    if (err)
        goto out_err;

    instr->state = MTD_ERASE_DONE;
    mtd_erase_callback(instr);
    return 0;

out_err:
    instr->state = MTD_ERASE_FAILED;
    instr->fail_addr = (long long)lnum * mtd->erasesize;
    return err;
}

static int gluebi_create(struct ubi_device_info *di,
             struct ubi_volume_info *vi)
{
    struct gluebi_device *gluebi, *g;
    struct mtd_info *mtd;

    gluebi = kzalloc(sizeof(struct gluebi_device), GFP_KERNEL);
    if (!gluebi)
        return -ENOMEM;

    mtd = &gluebi->mtd;
    mtd->name = kmemdup(vi->name, vi->name_len + 1, GFP_KERNEL);
    if (!mtd->name) {
        kfree(gluebi);
        return -ENOMEM;
    }

    gluebi->vol_id = vi->vol_id;
    gluebi->ubi_num = vi->ubi_num;
    mtd->type = MTD_UBIVOLUME;
    if (!di->ro_mode)
        mtd->flags = MTD_WRITEABLE;
    mtd->owner      = THIS_MODULE;
    mtd->writesize  = di->min_io_size;
    mtd->erasesize  = vi->usable_leb_size;
    mtd->_read       = gluebi_read;
    mtd->_write      = gluebi_write;
    mtd->_erase      = gluebi_erase;
    mtd->_get_device = gluebi_get_device;
    mtd->_put_device = gluebi_put_device;

    /*
     * In case of dynamic a volume, MTD device size is just volume size. In
     * case of a static volume the size is equivalent to the amount of data
     * bytes.
     */
    if (vi->vol_type == UBI_DYNAMIC_VOLUME)
        mtd->size = (unsigned long long)vi->usable_leb_size * vi->size;
    else
        mtd->size = vi->used_bytes;

    /* Just a sanity check - make sure this gluebi device does not exist */
    mutex_lock(&devices_mutex);
    g = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
    if (g)
        err_msg("gluebi MTD device %d form UBI device %d volume %d already exists",
            g->mtd.index, vi->ubi_num, vi->vol_id);
    mutex_unlock(&devices_mutex);

    if (mtd_device_register(mtd, NULL, 0)) {
        err_msg("cannot add MTD device");
        kfree(mtd->name);
        kfree(gluebi);
        return -ENFILE;
    }

    mutex_lock(&devices_mutex);
    list_add_tail(&gluebi->list, &gluebi_devices);
    mutex_unlock(&devices_mutex);
    return 0;
}

static int gluebi_remove(struct ubi_volume_info *vi)
{
    int err = 0;
    struct mtd_info *mtd;
    struct gluebi_device *gluebi;

    mutex_lock(&devices_mutex);
    gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
    if (!gluebi) {
        err_msg("got remove notification for unknown UBI device %d volume %d",
            vi->ubi_num, vi->vol_id);
        err = -ENOENT;
    } else if (gluebi->refcnt)
        err = -EBUSY;
    else
        list_del(&gluebi->list);
    mutex_unlock(&devices_mutex);
    if (err)
        return err;

    mtd = &gluebi->mtd;
    err = mtd_device_unregister(mtd);
    if (err) {
        err_msg("cannot remove fake MTD device %d, UBI device %d, volume %d, error %d",
            mtd->index, gluebi->ubi_num, gluebi->vol_id, err);
        mutex_lock(&devices_mutex);
        list_add_tail(&gluebi->list, &gluebi_devices);
        mutex_unlock(&devices_mutex);
        return err;
    }

    kfree(mtd->name);
    kfree(gluebi);
    return 0;
}

static int gluebi_updated(struct ubi_volume_info *vi)
{
    struct gluebi_device *gluebi;

    mutex_lock(&devices_mutex);
    gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
    if (!gluebi) {
        mutex_unlock(&devices_mutex);
        err_msg("got update notification for unknown UBI device %d volume %d",
            vi->ubi_num, vi->vol_id);
        return -ENOENT;
    }

    if (vi->vol_type == UBI_STATIC_VOLUME)
        gluebi->mtd.size = vi->used_bytes;
    mutex_unlock(&devices_mutex);
    return 0;
}

static int gluebi_resized(struct ubi_volume_info *vi)
{
    struct gluebi_device *gluebi;

    mutex_lock(&devices_mutex);
    gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
    if (!gluebi) {
        mutex_unlock(&devices_mutex);
        err_msg("got update notification for unknown UBI device %d volume %d",
            vi->ubi_num, vi->vol_id);
        return -ENOENT;
    }
    gluebi->mtd.size = vi->used_bytes;
    mutex_unlock(&devices_mutex);
    return 0;
}

static int gluebi_notify(struct notifier_block *nb, unsigned long l,
             void *ns_ptr)
{
    struct ubi_notification *nt = ns_ptr;

    switch (l) {
    case UBI_VOLUME_ADDED:
        gluebi_create(&nt->di, &nt->vi);
        break;
    case UBI_VOLUME_REMOVED:
        gluebi_remove(&nt->vi);
        break;
    case UBI_VOLUME_RESIZED:
        gluebi_resized(&nt->vi);
        break;
    case UBI_VOLUME_UPDATED:
        gluebi_updated(&nt->vi);
        break;
    default:
        break;
    }
    return NOTIFY_OK;
}

static struct notifier_block gluebi_notifier = {
    .notifier_call  = gluebi_notify,
};

static int __init ubi_gluebi_init(void)
{
    return ubi_register_volume_notifier(&gluebi_notifier, 0);
}

static void __exit ubi_gluebi_exit(void)
{
    struct gluebi_device *gluebi, *g;

    list_for_each_entry_safe(gluebi, g, &gluebi_devices, list) {
        int err;
        struct mtd_info *mtd = &gluebi->mtd;

        err = mtd_device_unregister(mtd);
        if (err)
            err_msg("error %d while removing gluebi MTD device %d, UBI device %d, volume %d - ignoring",
                err, mtd->index, gluebi->ubi_num,
                gluebi->vol_id);
        kfree(mtd->name);
        kfree(gluebi);
    }
    ubi_unregister_volume_notifier(&gluebi_notifier);
}

module_init(ubi_gluebi_init);
module_exit(ubi_gluebi_exit);
MODULE_DESCRIPTION("MTD emulation layer over UBI volumes");
MODULE_AUTHOR("Artem Bityutskiy, Joern Engel");
MODULE_LICENSE("GPL");