[PATCH V3] nvme: enable char device per namespace

[Keith Busch]

On Tue, Dec 15, 2020 at 08:55:57PM +0100, javier at javigon.com wrote:
> +static int nvme_alloc_chardev_ns(struct nvme_ctrl *ctrl, struct nvme_ns *ns)
> +{
> +	char cdisk_name[DISK_NAME_LEN];
> +	int ret;
> +
> +	device_initialize(&ns->cdev_device);
> +	ns->cdev_device.devt = MKDEV(MAJOR(nvme_ns_base_chr_devt),
> +				     ns->head->instance);

Ah, I see now. We are making these generic handles for each path, but
the ns->head->instance is the same for all paths to a namespace, so it's
not unique for that. Further, that head->instance is allocated per
subsystem, so it's not unique from namespace heads seen in other
subsystems.

So, I think you need to allocate a new dev_t for each subsystem rather
than the global nvme_ns_base_chr_devt, and I guess we also need a new
nvme_ns instance field assigned from yet another ida?