[pnfs] [PATCH 05/28] pnfsblock: expose scsi interface

[Jeff Garzik]

Christoph Hellwig wrote:
> On Wed, Mar 12, 2008 at 06:33:34PM +0200, Benny Halevy wrote:
>> This calls for a layering violation.
>>
>> To fill-in more context, here's an excerpt from the next patch,
>> showing how you use shost_class to scan all scsi disks:
> 
> Yes, absolutely.  No one outside of few places in the core scsi code
> should ever iterate over the scsi disks.
> 
>> My question is how should a proper API between the scsi layer and
>> the block layout driver look like?
>>
>> Can you list your requirements, e.g.:
>> - scanning all available devices,
>>
>> - discovering new devices on the fly
>>
>> - getting notified for new devices?
> 
> Neither.  pnfs shouldn't open block devices from kernelspace at all,
> but do it's disovery in userspace.
> 
> Or even better this whole block layout driver crap should go away
> completely and the people who have designed it beaten up until they
> aren't recognizable anymore.

The fact that NFSv4.1 requires SCSI is stupid crap, too.

The _design_ is a layering violation.  I say we just say "no".

NFS _clients_ should not need to know deep device-level details about 
how to store their data, and should not require SCSI in order to store data.

	Jeff