Re: [PATCH] block: rbd: switch to dynamic root device

[Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>]

On Fri, 2026-04-24 at 12:39 +0200, Johan Hovold wrote:
> Driver core expects devices to be dynamically allocated and will, for
> example, complain loudly when no release function has been provided.
> 
> Use root_device_register() to allocate and register the root device
> instead of open coding using a static device.

I think the approach makes sense. Ilya, what do you think? Do we have any
objection?

> 
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/block/rbd.c | 23 +++++++----------------
>  1 file changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index e7da06200c1e..ffab1b4e7c25 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -580,14 +580,7 @@ static const struct bus_type rbd_bus_type = {
>  	.bus_groups	= rbd_bus_groups,
>  };
>  
> -static void rbd_root_dev_release(struct device *dev)
> -{
> -}
> -
> -static struct device rbd_root_dev = {
> -	.init_name =    "rbd",
> -	.release =      rbd_root_dev_release,
> -};
> +static struct device *rbd_root_dev;
>  
>  static __printf(2, 3)
>  void rbd_warn(struct rbd_device *rbd_dev, const char *fmt, ...)
> @@ -5390,7 +5383,7 @@ static struct rbd_device *__rbd_dev_create(struct rbd_spec *spec)
>  
>  	rbd_dev->dev.bus = &rbd_bus_type;
>  	rbd_dev->dev.type = &rbd_device_type;
> -	rbd_dev->dev.parent = &rbd_root_dev;
> +	rbd_dev->dev.parent = rbd_root_dev;
>  	device_initialize(&rbd_dev->dev);
>  
>  	return rbd_dev;
> @@ -7331,15 +7324,13 @@ static int __init rbd_sysfs_init(void)
>  {
>  	int ret;
>  
> -	ret = device_register(&rbd_root_dev);
> -	if (ret < 0) {
> -		put_device(&rbd_root_dev);
> -		return ret;
> -	}
> +	rbd_root_dev = root_device_register("rbd");
> +	if (IS_ERR(rbd_root_dev))
> +		return PTR_ERR(rbd_root_dev);
>  
>  	ret = bus_register(&rbd_bus_type);
>  	if (ret < 0)
> -		device_unregister(&rbd_root_dev);
> +		root_device_unregister(rbd_root_dev);

I think we need to assign NULL here:

rbd_root_dev = NULL;

>  
>  	return ret;
>  }
> @@ -7347,7 +7338,7 @@ static int __init rbd_sysfs_init(void)
>  static void __exit rbd_sysfs_cleanup(void)
>  {
>  	bus_unregister(&rbd_bus_type);
> -	device_unregister(&rbd_root_dev);
> +	root_device_unregister(rbd_root_dev);

The same issue here:

rbd_root_dev = NULL;

Thanks,
Slava.

>  }
>  
>  static int __init rbd_slab_init(void)