On Thu, Aug 27, 2020 at 09:25:07AM +0200, Hannes Reinecke wrote:

Do you really need the mutex?
Wouldn't xa_store_range() be better and avoid the mutex?

We need the mutex as we need to grab the kobject reference under it.

xa_store_range is only available with a separate config option, and
has really strange calling conventions.  So I'd rather not pull it in
here, especially as most cdev_add callers are for a single minor only
anyway.