Re: [RFC 2/6] block: add flag for add_disk() completion notation

[Christoph Hellwig]

>  {
>  	might_sleep();
>  
> +	if (!blk_disk_registered(disk))
> +		return;
> +

Can't say I like this all that much.  Drivers should keep some
basic sanity for their unregister path, and while blk_disk_registered
can be useful, it's uses should be kept at a minimum.