Re: [PATCH 1/2] ublk_drv: move destroying device out of ublk_add_dev

[Ziyang Zhang <ZiyangZhang@linux.alibaba.com>]

On 2022/7/22 10:36, Ming Lei wrote:
> ublk_device is allocated in ublk_ctrl_add_dev(), so code will become more
> readable by just letting ublk_ctrl_add_dev() destroy ublk_device in case
> of ublk_add_dev() failure.
> 
> Meantime ub->mutex is destroyed in __ublk_destroy_dev(), but it may
> not be initialized when ublk_add_dev() fails, so fix it by moving
> mutex_init(ub->mutex) before any failure path.
> 
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/block/ublk_drv.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index f058f40b639c..d03563286c76 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1106,9 +1106,10 @@ static int ublk_add_dev(struct ublk_device *ub)
>  
>  	INIT_WORK(&ub->stop_work, ublk_stop_work_fn);
>  	INIT_DELAYED_WORK(&ub->monitor_work, ublk_daemon_monitor_work);
> +	mutex_init(&ub->mutex);
>  
>  	if (ublk_init_queues(ub))
> -		goto out_destroy_dev;
> +		return err;
>  
>  	ub->tag_set.ops = &ublk_mq_ops;
>  	ub->tag_set.nr_hw_queues = ub->dev_info.nr_hw_queues;
> @@ -1122,7 +1123,6 @@ static int ublk_add_dev(struct ublk_device *ub)
>  		goto out_deinit_queues;
>  
>  	ublk_align_max_io_size(ub);
> -	mutex_init(&ub->mutex);
>  	spin_lock_init(&ub->mm_lock);
>  
>  	/* add char dev so that ublksrv daemon can be setup */
> @@ -1130,8 +1130,6 @@ static int ublk_add_dev(struct ublk_device *ub)
>  
>  out_deinit_queues:
>  	ublk_deinit_queues(ub);
> -out_destroy_dev:
> -	__ublk_destroy_dev(ub);
>  	return err;
>  }
>  
> @@ -1331,8 +1329,10 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
>  	ub->dev_info.dev_id = ub->ub_number;
>  
>  	ret = ublk_add_dev(ub);
> -	if (ret)
> +	if (ret) {
> +		__ublk_destroy_dev(ub);
>  		goto out_unlock;
> +	}

Hi, Ming.

Now, if ublk_add_dev() returns failure, __ublk_destroy_dev() is called anyway.

However, in current ublk_drv:ublk_add_dev():

...
	return ublk_add_chdev(ub);   <---- here
out_deinit_queues:
	ublk_deinit_queues(ub);
out_destroy_dev:
	__ublk_destroy_dev(ub);
	return err;


ublk_add_chdev() returns and the returned value(maybe a failure) directly
pass to ublk_ctrl_add_dev which does NOT call __ublk_destroy_dev()

please check it is correct to call __ublk_destroy_dev() if ublk_add_chdev() fails.


>  
>  	if (copy_to_user(argp, &ub->dev_info, sizeof(info))) {
>  		ublk_remove(ub);