Re: RFC: sort out get_gendisk abuses

[Tejun Heo]

Hello, Christoph.

On Fri, Sep 25, 2020 at 06:14:45PM +0200, Christoph Hellwig wrote:
> this series tries to remove two abuses of the get_gendisk API.
> The first one is fairly straigt forward and switched the blk-cgroup
> configuration API to properly open the block device, but I'd love to see
> it reviewed and tested by the cgroup maintainers, as I don't really know
> how this code is actually used.

I'm a bit worried that requiring fully opening the device for configuration
can lead to surprising behaviors. A now-unlikely but still possible case
would be trying to configure IO parameters for a device w/ removeable media.
All that the user is trying to do is configuring a bunch of parameters but
the kernel would try to spin up the media and fail configuration and so on.

The use case of needing to access the associated data structures without
fully activating the IO device seems valid to me. Whether that interface is
blkdev_get() or something better abstracted, I don't really care.

Thanks.

-- 
tejun