complete boot failure in 4.5-rc1 caused by nvme: make SG_IO support optional

[Christoph Hellwig]

On Mon, Feb 08, 2016 at 12:01:16PM +0200, Sagi Grimberg wrote:
>
>> Do we have defined sysfs attributes for NVMe devices nowadays?
>
> /sys/block/nvme0n1/uuid

That's only supported for NVMe 1.1 and higher devices, and optional.
For older or stupid devices we need to support the algorithm based
on the serial attribute from nvme_fill_device_id_scsi_string() in
drivers/nvme/host/scsi.c.

Which btw is іncorrect as it doesn't identify namespaces properly,
and thus the associatation of 0 is an actively harmful lie.