nvme reservation commands during controller reset

[Sagi Grimberg]

>> We saw that in case of path error, nvme reservation cmds does not get error handling.
>> This is true via the blk layer as well as nvme-cli.
>>
>> We are working on implementing nvmeof stack and
>> this current behavior is blocking our host from running nvme reservation cmds during path error.
> 
> What's blocking you from retrying this command in your host software?
> 
> If we truly want to provide a way to hide intermittent errors on
> passthrough commands via automatic retry, it may be a little longer
> before such an interface hits a released kernel.

I think we need to keep the passthru commands as they are, but
reservations coming from the pr_ops maybe we can failover these
in nvme_pr_command?

What is the semantics in scsi btw? Didn't see any failover functionality
for pr_ops...