mtd_blkdevs.c

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/*
 * Interface to Linux block layer for MTD 'translation layers'.
 *
 * Copyright © 2003-2010 David Woodhouse <[email protected]>
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/fs.h>
#include <linux/mtd/blktrans.h>
#include <linux/mtd/mtd.h>
#include <linux/blkdev.h>
#include <linux/blkpg.h>
#include <linux/spinlock.h>
#include <linux/hdreg.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/kthread.h>
#include <asm/uaccess.h>

#include "mtdcore.h"

static LIST_HEAD(blktrans_majors);
static DEFINE_MUTEX(blktrans_ref_mutex);

static void blktrans_dev_release(struct kref *kref)
{
    struct mtd_blktrans_dev *dev =
        container_of(kref, struct mtd_blktrans_dev, ref);

    dev->disk->private_data = NULL;
    blk_cleanup_queue(dev->rq);
    put_disk(dev->disk);
    list_del(&dev->list);
    kfree(dev);
}

static struct mtd_blktrans_dev *blktrans_dev_get(struct gendisk *disk)
{
    struct mtd_blktrans_dev *dev;

    mutex_lock(&blktrans_ref_mutex);
    dev = disk->private_data;

    if (!dev)
        goto unlock;
    kref_get(&dev->ref);
unlock:
    mutex_unlock(&blktrans_ref_mutex);
    return dev;
}

static void blktrans_dev_put(struct mtd_blktrans_dev *dev)
{
    mutex_lock(&blktrans_ref_mutex);
    kref_put(&dev->ref, blktrans_dev_release);
    mutex_unlock(&blktrans_ref_mutex);
}


static int do_blktrans_request(struct mtd_blktrans_ops *tr,
                   struct mtd_blktrans_dev *dev,
                   struct request *req)
{
    unsigned long block, nsect;
    char *buf;

    block = blk_rq_pos(req) << 9 >> tr->blkshift;
    nsect = blk_rq_cur_bytes(req) >> tr->blkshift;

    buf = req->buffer;

    if (req->cmd_type != REQ_TYPE_FS)
        return -EIO;

    if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
        get_capacity(req->rq_disk))
        return -EIO;

    if (req->cmd_flags & REQ_DISCARD)
        return tr->discard(dev, block, nsect);

    switch(rq_data_dir(req)) {
    case READ:
        for (; nsect > 0; nsect--, block++, buf += tr->blksize)
            if (tr->readsect(dev, block, buf))
                return -EIO;
        rq_flush_dcache_pages(req);
        return 0;
    case WRITE:
        if (!tr->writesect)
            return -EIO;

        rq_flush_dcache_pages(req);
        for (; nsect > 0; nsect--, block++, buf += tr->blksize)
            if (tr->writesect(dev, block, buf))
                return -EIO;
        return 0;
    default:
        printk(KERN_NOTICE "Unknown request %u\n", rq_data_dir(req));
        return -EIO;
    }
}

int mtd_blktrans_cease_background(struct mtd_blktrans_dev *dev)
{
    if (kthread_should_stop())
        return 1;

    return dev->bg_stop;
}
EXPORT_SYMBOL_GPL(mtd_blktrans_cease_background);

static int mtd_blktrans_thread(void *arg)
{
    struct mtd_blktrans_dev *dev = arg;
    struct mtd_blktrans_ops *tr = dev->tr;
    struct request_queue *rq = dev->rq;
    struct request *req = NULL;
    int background_done = 0;

    spin_lock_irq(rq->queue_lock);

    while (!kthread_should_stop()) {
        int res;

        dev->bg_stop = false;
        if (!req && !(req = blk_fetch_request(rq))) {
            if (tr->background && !background_done) {
                spin_unlock_irq(rq->queue_lock);
                mutex_lock(&dev->lock);
                tr->background(dev);
                mutex_unlock(&dev->lock);
                spin_lock_irq(rq->queue_lock);
                /*
                 * Do background processing just once per idle
                 * period.
                 */
                background_done = !dev->bg_stop;
                continue;
            }
            set_current_state(TASK_INTERRUPTIBLE);

            if (kthread_should_stop())
                set_current_state(TASK_RUNNING);

            spin_unlock_irq(rq->queue_lock);
            schedule();
            spin_lock_irq(rq->queue_lock);
            continue;
        }

        spin_unlock_irq(rq->queue_lock);

        mutex_lock(&dev->lock);
        res = do_blktrans_request(dev->tr, dev, req);
        mutex_unlock(&dev->lock);

        spin_lock_irq(rq->queue_lock);

        if (!__blk_end_request_cur(req, res))
            req = NULL;

        background_done = 0;
    }

    if (req)
        __blk_end_request_all(req, -EIO);

    spin_unlock_irq(rq->queue_lock);

    return 0;
}

static void mtd_blktrans_request(struct request_queue *rq)
{
    struct mtd_blktrans_dev *dev;
    struct request *req = NULL;

    dev = rq->queuedata;

    if (!dev)
        while ((req = blk_fetch_request(rq)) != NULL)
            __blk_end_request_all(req, -ENODEV);
    else {
        dev->bg_stop = true;
        wake_up_process(dev->thread);
    }
}

static int blktrans_open(struct block_device *bdev, fmode_t mode)
{
    struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
    int ret = 0;

    if (!dev)
        return -ERESTARTSYS; /* FIXME: busy loop! -arnd*/

    mutex_lock(&dev->lock);

    if (dev->open)
        goto unlock;

    kref_get(&dev->ref);
    __module_get(dev->tr->owner);

    if (!dev->mtd)
        goto unlock;

    if (dev->tr->open) {
        ret = dev->tr->open(dev);
        if (ret)
            goto error_put;
    }

    ret = __get_mtd_device(dev->mtd);
    if (ret)
        goto error_release;
    dev->file_mode = mode;

unlock:
    dev->open++;
    mutex_unlock(&dev->lock);
    blktrans_dev_put(dev);
    return ret;

error_release:
    if (dev->tr->release)
        dev->tr->release(dev);
error_put:
    module_put(dev->tr->owner);
    kref_put(&dev->ref, blktrans_dev_release);
    mutex_unlock(&dev->lock);
    blktrans_dev_put(dev);
    return ret;
}

static int blktrans_release(struct gendisk *disk, fmode_t mode)
{
    struct mtd_blktrans_dev *dev = blktrans_dev_get(disk);
    int ret = 0;

    if (!dev)
        return ret;

    mutex_lock(&dev->lock);

    if (--dev->open)
        goto unlock;

    kref_put(&dev->ref, blktrans_dev_release);
    module_put(dev->tr->owner);

    if (dev->mtd) {
        ret = dev->tr->release ? dev->tr->release(dev) : 0;
        __put_mtd_device(dev->mtd);
    }
unlock:
    mutex_unlock(&dev->lock);
    blktrans_dev_put(dev);
    return ret;
}

static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
    struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
    int ret = -ENXIO;

    if (!dev)
        return ret;

    mutex_lock(&dev->lock);

    if (!dev->mtd)
        goto unlock;

    ret = dev->tr->getgeo ? dev->tr->getgeo(dev, geo) : 0;
unlock:
    mutex_unlock(&dev->lock);
    blktrans_dev_put(dev);
    return ret;
}

static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
                  unsigned int cmd, unsigned long arg)
{
    struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
    int ret = -ENXIO;

    if (!dev)
        return ret;

    mutex_lock(&dev->lock);

    if (!dev->mtd)
        goto unlock;

    switch (cmd) {
    case BLKFLSBUF:
        ret = dev->tr->flush ? dev->tr->flush(dev) : 0;
        break;
    default:
        ret = -ENOTTY;
    }
unlock:
    mutex_unlock(&dev->lock);
    blktrans_dev_put(dev);
    return ret;
}

static const struct block_device_operations mtd_blktrans_ops = {
    .owner      = THIS_MODULE,
    .open       = blktrans_open,
    .release    = blktrans_release,
    .ioctl      = blktrans_ioctl,
    .getgeo     = blktrans_getgeo,
};

int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
{
    struct mtd_blktrans_ops *tr = new->tr;
    struct mtd_blktrans_dev *d;
    int last_devnum = -1;
    struct gendisk *gd;
    int ret;

    if (mutex_trylock(&mtd_table_mutex)) {
        mutex_unlock(&mtd_table_mutex);
        BUG();
    }

    mutex_lock(&blktrans_ref_mutex);
    list_for_each_entry(d, &tr->devs, list) {
        if (new->devnum == -1) {
            /* Use first free number */
            if (d->devnum != last_devnum+1) {
                /* Found a free devnum. Plug it in here */
                new->devnum = last_devnum+1;
                list_add_tail(&new->list, &d->list);
                goto added;
            }
        } else if (d->devnum == new->devnum) {
            /* Required number taken */
            mutex_unlock(&blktrans_ref_mutex);
            return -EBUSY;
        } else if (d->devnum > new->devnum) {
            /* Required number was free */
            list_add_tail(&new->list, &d->list);
            goto added;
        }
        last_devnum = d->devnum;
    }

    ret = -EBUSY;
    if (new->devnum == -1)
        new->devnum = last_devnum+1;

    /* Check that the device and any partitions will get valid
     * minor numbers and that the disk naming code below can cope
     * with this number. */
    if (new->devnum > (MINORMASK >> tr->part_bits) ||
        (tr->part_bits && new->devnum >= 27 * 26)) {
        mutex_unlock(&blktrans_ref_mutex);
        goto error1;
    }

    list_add_tail(&new->list, &tr->devs);
 added:
    mutex_unlock(&blktrans_ref_mutex);

    mutex_init(&new->lock);
    kref_init(&new->ref);
    if (!tr->writesect)
        new->readonly = 1;

    /* Create gendisk */
    ret = -ENOMEM;
    gd = alloc_disk(1 << tr->part_bits);

    if (!gd)
        goto error2;

    new->disk = gd;
    gd->private_data = new;
    gd->major = tr->major;
    gd->first_minor = (new->devnum) << tr->part_bits;
    gd->fops = &mtd_blktrans_ops;

    if (tr->part_bits)
        if (new->devnum < 26)
            snprintf(gd->disk_name, sizeof(gd->disk_name),
                 "%s%c", tr->name, 'a' + new->devnum);
        else
            snprintf(gd->disk_name, sizeof(gd->disk_name),
                 "%s%c%c", tr->name,
                 'a' - 1 + new->devnum / 26,
                 'a' + new->devnum % 26);
    else
        snprintf(gd->disk_name, sizeof(gd->disk_name),
             "%s%d", tr->name, new->devnum);

    set_capacity(gd, (new->size * tr->blksize) >> 9);

    /* Create the request queue */
    spin_lock_init(&new->queue_lock);
    new->rq = blk_init_queue(mtd_blktrans_request, &new->queue_lock);

    if (!new->rq)
        goto error3;

    new->rq->queuedata = new;
    blk_queue_logical_block_size(new->rq, tr->blksize);

    queue_flag_set_unlocked(QUEUE_FLAG_NONROT, new->rq);

    if (tr->discard) {
        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, new->rq);
        new->rq->limits.max_discard_sectors = UINT_MAX;
    }

    gd->queue = new->rq;

    /* Create processing thread */
    /* TODO: workqueue ? */
    new->thread = kthread_run(mtd_blktrans_thread, new,
            "%s%d", tr->name, new->mtd->index);
    if (IS_ERR(new->thread)) {
        ret = PTR_ERR(new->thread);
        goto error4;
    }
    gd->driverfs_dev = &new->mtd->dev;

    if (new->readonly)
        set_disk_ro(gd, 1);

    add_disk(gd);

    if (new->disk_attributes) {
        ret = sysfs_create_group(&disk_to_dev(gd)->kobj,
                    new->disk_attributes);
        WARN_ON(ret);
    }
    return 0;
error4:
    blk_cleanup_queue(new->rq);
error3:
    put_disk(new->disk);
error2:
    list_del(&new->list);
error1:
    return ret;
}

int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
{
    unsigned long flags;

    if (mutex_trylock(&mtd_table_mutex)) {
        mutex_unlock(&mtd_table_mutex);
        BUG();
    }

    if (old->disk_attributes)
        sysfs_remove_group(&disk_to_dev(old->disk)->kobj,
                        old->disk_attributes);

    /* Stop new requests to arrive */
    del_gendisk(old->disk);


    /* Stop the thread */
    kthread_stop(old->thread);

    /* Kill current requests */
    spin_lock_irqsave(&old->queue_lock, flags);
    old->rq->queuedata = NULL;
    blk_start_queue(old->rq);
    spin_unlock_irqrestore(&old->queue_lock, flags);

    /* If the device is currently open, tell trans driver to close it,
        then put mtd device, and don't touch it again */
    mutex_lock(&old->lock);
    if (old->open) {
        if (old->tr->release)
            old->tr->release(old);
        __put_mtd_device(old->mtd);
    }

    old->mtd = NULL;

    mutex_unlock(&old->lock);
    blktrans_dev_put(old);
    return 0;
}

static void blktrans_notify_remove(struct mtd_info *mtd)
{
    struct mtd_blktrans_ops *tr;
    struct mtd_blktrans_dev *dev, *next;

    list_for_each_entry(tr, &blktrans_majors, list)
        list_for_each_entry_safe(dev, next, &tr->devs, list)
            if (dev->mtd == mtd)
                tr->remove_dev(dev);
}

static void blktrans_notify_add(struct mtd_info *mtd)
{
    struct mtd_blktrans_ops *tr;

    if (mtd->type == MTD_ABSENT)
        return;

    list_for_each_entry(tr, &blktrans_majors, list)
        tr->add_mtd(tr, mtd);
}

static struct mtd_notifier blktrans_notifier = {
    .add = blktrans_notify_add,
    .remove = blktrans_notify_remove,
};

int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
{
    struct mtd_info *mtd;
    int ret;

    /* Register the notifier if/when the first device type is
       registered, to prevent the link/init ordering from fucking
       us over. */
    if (!blktrans_notifier.list.next)
        register_mtd_user(&blktrans_notifier);


    mutex_lock(&mtd_table_mutex);

    ret = register_blkdev(tr->major, tr->name);
    if (ret < 0) {
        printk(KERN_WARNING "Unable to register %s block device on major %d: %d\n",
               tr->name, tr->major, ret);
        mutex_unlock(&mtd_table_mutex);
        return ret;
    }

    if (ret)
        tr->major = ret;

    tr->blkshift = ffs(tr->blksize) - 1;

    INIT_LIST_HEAD(&tr->devs);
    list_add(&tr->list, &blktrans_majors);

    mtd_for_each_device(mtd)
        if (mtd->type != MTD_ABSENT)
            tr->add_mtd(tr, mtd);

    mutex_unlock(&mtd_table_mutex);
    return 0;
}

int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
{
    struct mtd_blktrans_dev *dev, *next;

    mutex_lock(&mtd_table_mutex);

    /* Remove it from the list of active majors */
    list_del(&tr->list);

    list_for_each_entry_safe(dev, next, &tr->devs, list)
        tr->remove_dev(dev);

    unregister_blkdev(tr->major, tr->name);
    mutex_unlock(&mtd_table_mutex);

    BUG_ON(!list_empty(&tr->devs));
    return 0;
}

static void __exit mtd_blktrans_exit(void)
{
    /* No race here -- if someone's currently in register_mtd_blktrans
       we're screwed anyway. */
    if (blktrans_notifier.list.next)
        unregister_mtd_user(&blktrans_notifier);
}

module_exit(mtd_blktrans_exit);

EXPORT_SYMBOL_GPL(register_mtd_blktrans);
EXPORT_SYMBOL_GPL(deregister_mtd_blktrans);
EXPORT_SYMBOL_GPL(add_mtd_blktrans_dev);
EXPORT_SYMBOL_GPL(del_mtd_blktrans_dev);

MODULE_AUTHOR("David Woodhouse <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Common interface to block layer for MTD 'translation layers'");