Re: [PATCH] rbd: do not allow remove of mounted-on image

[Josh Durgin <josh.durgin@inktank.com>]

On 11/16/2012 07:43 AM, Alex Elder wrote:
> There is no check in rbd_remove() to see if anybody holds ope 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.  Both functions are protected by the
> bd_mutex so there's no need for any other concurrency protection.
>
> Signed-off-by: Alex Elder <elder@inktank.com>
> ---
>   drivers/block/rbd.c |    9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index fba0822..9d9a2f3 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -255,6 +255,7 @@ struct rbd_device {
>
>   	/* sysfs related */
>   	struct device		dev;
> +	unsigned long		open_count;
>   };
>
>   static DEFINE_MUTEX(ctl_mutex);	  /* Serialize open/close/setup/teardown */
> @@ -358,6 +359,7 @@ static int rbd_open(struct block_device *bdev,
> fmode_t mode)
>
>   	rbd_get_dev(rbd_dev);
>   	set_device_ro(bdev, rbd_dev->mapping.read_only);
> +	rbd_dev->open_count++;
>
>   	return 0;
>   }
> @@ -366,6 +368,8 @@ static int rbd_release(struct gendisk *disk, fmode_t
> mode)
>   {
>   	struct rbd_device *rbd_dev = disk->private_data;
>
> +	rbd_assert(rbd_dev->open_count > 0);
> +	rbd_dev->open_count--;
>   	rbd_put_dev(rbd_dev);
>
>   	return 0;
> @@ -3764,6 +3768,11 @@ static ssize_t rbd_remove(struct bus_type *bus,
>   		goto done;
>   	}
>
> +	if (rbd_dev->open_count) {
> +		ret = -EBUSY;
> +		goto done;
> +	}
> +

Is this protected by bd_mutex?

>   	rbd_remove_all_snaps(rbd_dev);
>   	rbd_bus_del_dev(rbd_dev);
>