Reviewed-by: Sage Weil <sage@xxxxxxxxxxx>
On Thu, 13 Dec 2012, Alex Elder wrote:
> There is no check in rbd_remove() to see if anybody holds open the
> image being removed. That's not cool.
>
> Add a simple open count that goes up and down with opens and closes
> (releases) of the device, and don't allow an rbd image to be removed
> if the count is non-zero.
>
> Protect the updates of the open count value with ctl_mutex to ensure
> the underlying rbd device doesn't get removed while concurrently
> being opened.
>
> Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
> ---
> drivers/block/rbd.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 842caf4..c7bf961 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -235,6 +235,7 @@ struct rbd_device {
>
> /* sysfs related */
> struct device dev;
> + unsigned long open_count;
> };
>
> static DEFINE_MUTEX(ctl_mutex); /* Serialize open/close/setup/teardown */
> @@ -309,8 +310,11 @@ static int rbd_open(struct block_device *bdev,
> fmode_t mode)
> if ((mode & FMODE_WRITE) && rbd_dev->mapping.read_only)
> return -EROFS;
>
> + mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
> rbd_get_dev(rbd_dev);
> set_device_ro(bdev, rbd_dev->mapping.read_only);
> + rbd_dev->open_count++;
> + mutex_unlock(&ctl_mutex);
>
> return 0;
> }
> @@ -319,7 +323,11 @@ static int rbd_release(struct gendisk *disk,
> fmode_t mode)
> {
> struct rbd_device *rbd_dev = disk->private_data;
>
> + mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
> + rbd_assert(rbd_dev->open_count > 0);
> + rbd_dev->open_count--;
> rbd_put_dev(rbd_dev);
> + mutex_unlock(&ctl_mutex);
>
> return 0;
> }
> @@ -3745,6 +3753,11 @@ static ssize_t rbd_remove(struct bus_type *bus,
> goto done;
> }
>
> + if (rbd_dev->open_count) {
> + ret = -EBUSY;
> + goto done;
> + }
> +
> rbd_remove_all_snaps(rbd_dev);
> rbd_bus_del_dev(rbd_dev);
>
> --
> 1.7.9.5
>
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