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    Subject[PATCH 05/17] blktrans: add proper locking
    Date
    First, use lockless versions of get/put_mtd_device
    We don't care what happened to mtd table, because we have a pointer
    to mtd device. It guaranteed to exist till we do final put_mtd_device

    Also add locking to prevent all kinds or races

    Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
    ---
    drivers/mtd/mtd_blkdevs.c | 82 ++++++++++++++++++++++++++++----------------
    1 files changed, 52 insertions(+), 30 deletions(-)
    diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
    index 9e118cf..841c6ae 100644
    --- a/drivers/mtd/mtd_blkdevs.c
    +++ b/drivers/mtd/mtd_blkdevs.c
    @@ -123,33 +123,33 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode)
    {
    struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
    struct mtd_blktrans_ops *tr = dev->tr;
    - int ret = -ENODEV;
    -
    - if (!get_mtd_device(NULL, dev->mtd->index))
    - goto out;
    + int ret = 0;

    + mutex_lock(&dev->lock);
    if (dev->open++)
    goto out;

    if (dev->deleted)
    goto out;

    + ret = -ENODEV;
    if (!try_module_get(tr->owner))
    - goto out_tr;
    + goto out;

    - /* FIXME: Locking. A hot pluggable device can go away
    - (del_mtd_device can be called for it) without its module
    - being unloaded. */
    - dev->mtd->usecount++;
    + if (__get_mtd_device(dev->mtd)) {
    + module_put(tr->owner);
    + goto out;
    + }

    ret = 0;
    if (tr->open && (ret = tr->open(dev))) {
    - dev->mtd->usecount--;
    - put_mtd_device(dev->mtd);
    - out_tr:
    module_put(tr->owner);
    + __put_mtd_device(dev->mtd);
    + goto out;
    +
    }
    out:
    + mutex_unlock(&dev->lock);
    return ret;
    }

    @@ -159,18 +159,11 @@ static int blktrans_release(struct gendisk *disk, fmode_t mode)
    struct mtd_blktrans_ops *tr = dev->tr;
    int ret = 0;

    + mutex_lock(&dev->lock);
    dev->open--;
    if (dev->open)
    return 0;

    - if (tr->release)
    - ret = tr->release(dev);
    -
    - if (!ret) {
    - dev->mtd->usecount--;
    - put_mtd_device(dev->mtd);
    - module_put(tr->owner);
    - }

    /* Free the private data */
    if (dev->deleted) {
    @@ -180,33 +173,59 @@ static int blktrans_release(struct gendisk *disk, fmode_t mode)
    return 0;
    }

    + ret = tr->release ? tr->release(dev) : 0;
    + module_put(tr->owner);
    +
    + if (dev->mtd)
    + __put_mtd_device(dev->mtd);
    +
    + mutex_unlock(&dev->lock);
    return ret;
    }

    static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
    {
    struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
    + int error;
    +
    + mutex_lock(&dev->lock);

    + error = -ENODEV;
    + if (dev->deleted)
    + goto out;
    +
    + error = -ENOTTY;
    if (dev->tr->getgeo)
    - return dev->tr->getgeo(dev, geo);
    - return -ENOTTY;
    + error = dev->tr->getgeo(dev, geo);
    +out:
    + mutex_unlock(&dev->lock);
    + return error;
    }

    static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
    unsigned int cmd, unsigned long arg)
    {
    struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
    - struct mtd_blktrans_ops *tr = dev->tr;
    + int error = -ENODEV;
    +
    + mutex_lock(&dev->lock);
    +
    + if (dev->deleted)
    + goto out;
    +
    + error = -ENOTTY;

    switch (cmd) {
    case BLKFLSBUF:
    - if (tr->flush)
    - return tr->flush(dev);
    - /* The core code did the work, we had nothing to do. */
    - return 0;
    + if (dev->tr->flush)
    + error = dev->tr->flush(dev);
    + break;
    default:
    - return -ENOTTY;
    + break;
    }
    +out:
    + mutex_unlock(&dev->lock);
    + return error;
    }

    static const struct block_device_operations mtd_blktrans_ops = {
    @@ -354,16 +373,19 @@ int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
    /* Stop the thread */
    kthread_stop(old->thread);

    + /* Tell trans driver to release the device */
    + mutex_lock(&old->lock);
    +
    if (old->open) {
    if (old->tr->release)
    old->tr->release(old);
    - put_mtd_device(old->mtd);
    + __put_mtd_device(old->mtd);
    }

    /* From now on, no calls into trans can be made */
    /* Mtd device will be gone real soon now */
    old->mtd = NULL;
    -
    + mutex_unlock(&old->lock);
    blk_cleanup_queue(old->rq);
    return 0;
    }
    --
    1.6.3.3


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