[Stgt-devel] [PATCH] Move device type to LUN

[FUJITA Tomonori]

From: Hannes Reinecke <hare at suse.de>
Subject: Re: [Stgt-devel] [PATCH] Move device type to LUN
Date: Mon, 11 Jun 2007 17:15:19 +0200

> Pete Wyckoff wrote:
> > hare at suse.de wrote on Tue, 05 Jun 2007 15:38 +0200:
> >> This patch moves the device type down to the LUN structure.
> >> And in doing so we now also have the proper peripheral device
> >> type and peripheral device qualifier attributes for the INQUIRY
> >> data.
> > 
> > Makes sense to me too.
> > 
> >> One thing puzzles me, though: do we support commands with no
> >> LUN attached to it? IE is it valid to have 'cmd->dev == NULL'?
> >> If so: where is the point here? If that's our handling of a
> >> non-existing LUN 0 we should rather add a proper LUN 0 and
> >> treat cmd->dev == NULL as an error case ...
> > 
> > In the SCSI model, every device must have at least one LUN for
> > handling REPORT LUNS and a couple other commands.  It is addressed
> > as LUN 0 or using the "well-known" LUN for the command.  In the stgt
> > abstraction, though, there is no magic LUN like this.  Instead
> > things like spc_inqury use cmd->dev == NULL to handle this case.
> > 
> Ah. Hence.
> 
> > Perhaps it is reasonable to create a special device for these
> > commands.  Up in target.c, you could assign cmd->dev to target->dev,
> > where that is the special device, paralleling the way that
> > target->cmd_queue is used.  As a side effect, lots of "if (cmd->dev)
> > ... else ILLEGAL_REQUEST" clauses can be removed from device code
> > too.
> > 
> Well, I actually thought of creating a proper LUN 0 with type 0xc.

We still need to handle cmd->dev == NULL case though probably we can
remove cmd->dev == NULL case in device type code.

I don't have storage systems that work in your way. Is it common?


> This would be automagically created whenever a target is created.
> And we could hook some management facilities to that one.
> Maybe even turn it into a proper remote management :-)
> 
> But then, for this we definitely need to move the type to the LUN.
> 
> Tomo, what are you're thoughts on that one?
> 
> Cheers,
> 
> Hannes
> -- 
> Dr. Hannes Reinecke		      zSeries & Storage
> hare at suse.de			      +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg
> GF: Markus Rex, HRB 16746 (AG N?rnberg)
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