Re: [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands

[John Garry]

> > >
> >
> > FWIW, the only other driver (gdth) which I see uses this API has 
> > this_id = -1 in the scsi host template.
> >
> > > But alright, I'll give it a go; let's see what I'll end up with.
> >
> > note: If we want a fixed scsi_device per host, calling 
> > scsi_mq_setup_tags() -> scsi_get_host_dev() will fail as shost state 
> > is not running. Maybe we need to juggle some things there to provide a 
> > generic solution.
> It might even get worse, as during device setup things like 
> 'slave_alloc' etc is getting called, which has a fair chance of getting 
> confused for non-existing devices.
> Cf qla2xxx:qla2xx_slave_alloc() is calling starget_to_rport(), which 
> will get us a nice oops when accessing a target which is _not_ the child 
> of a fc remote port.

Yes, something similar happens for libsas [hence my hack], where 
sas_alloc_target()->sas_find_dev_by_rphy() fails as it cannot handle 
rphy for scsi host as parent properly.

> And this is why I'm not utterly keen on this approach; auditing all 
> these callbacks is _not_ fun.

Understood. And if you can't test them, then a change like this is too 
risky for those drivers.

Cheers,
John