[dm-devel] [PATCH v5 3/3] dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO

[Hannes Reinecke]

On 7/5/21 3:02 PM, Paolo Bonzini wrote:
> On 02/07/21 16:21, Martin Wilck wrote:
>>> SG_IO gives you raw access to the SCSI logic unit, and you get to
>>> keep the pieces if anything goes wrong.
>>
>> That's a very fragile user space API, on the fringe of being useless
>> IMO.
> 
> Indeed.  If SG_IO is for raw access to an ITL nexus, it shouldn't be
> supported at all by mpath devices.  If on the other hand SG_IO is for
> raw access to a LUN, there is no reason for it to not support failover.
> 
Or we look at IO_URING_OP_URING_CMD, to send raw cdbs via io_uring.
And delegate SG_IO to raw access to an ITL nexus.
Doesn't help with existing issues, but should get a clean way forward.

... I think I've even tendered a topic at LSF for this ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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