[PATCH 05/17] nvme: wire-up support for async-passthru on char-device.

[Sagi Grimberg]

>>>> I know, and that was my original question, no one cares that this
>>>> interface completely lacks this capability? Maybe it is fine, but
>>>> it is not a trivial assumption given that this is designed to be more
>>>> than an interface to send admin/vs commands to the controller...
>>>
>>> Most people don't really care about or use multipath, so it's not a
>>> primary goal.
>>
>> This statement is generally correct. However what application would be
>> interested in speaking raw nvme to a device and gaining performance that
>> is even higher than the block layer (which is great to begin with)?
> 
> If passthrough is faster than the block I/O path we're doing someting
> wrong.  At best it should be the same performance.

That is not what the changelog says.

> That being said multipathing is an integral part of the nvme driver
> architecture, and the /dev/ngX devices.  If we want to support uring
> async commands on /dev/ngX it will have to support multipath.

Couldn't agree more...