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

Jens Axboe
2022-03-16T14:35:58Z

On 3/16/22 7:52 AM, Sagi Grimberg wrote:
>
>>>>>>> No one cares that this has no multipathing capabilities what-so-ever?
>>>>>>> despite being issued on the mpath device node?
>>>>>>>
>>>>>>> I know we are not doing multipathing for userspace today, but this
>>>>>>> feels like an alternative I/O interface for nvme, seems a bit cripled
>>>>>>> with zero multipathing capabilities...
>
> [...]
>
>> Got it, thanks. Passthrough (sync or async) just returns the failure
>> to user-space if that fails.
>> No attempt to retry/requeue as the block path does.
>
> 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. For passthrough, most of request types should hit the
exact target, I would suggest that if someone cares about multipath for
specific commands, that they be flagged as such.

--
Jens Axboe