Re: BUG in: Driver core: convert block from raw kobjects to core devices (fwd)

[James Bottomley <James.Bottomley@SteelEye.com>]

On Wed, 2007-10-31 at 12:04 -0400, Alan Stern wrote:
> On Wed, 31 Oct 2007, James Bottomley wrote:
> 
> > > Yes, the queue is a child of the disk.
> > 
> > Right, so this goes gendisk->queue (-> meaning parent of, or takes
> > reference to)
> 
> No, no!  The _child_ takes an implicit reference to the _parent_, not 
> the other way around.
> 
> > > > The scsi_device has a ref to the queue
> > > 
> > > Yeah, while the queue is a grandchild of the scsi_device with the
> > > unified sysfs layout.
> > 
> > No, the scsi_device is a direct parent of the queue, so we have
> > 
> > scsi_device->queue
> 
> Wrong -- the gendisk is the direct parent of the queue.  The relevant 
> line is in ll_rw_blk.c:blk_register_queue():
> 
> 	q->kobj.parent = kobject_get(&disk->dev.kobj);
> 
> > > Yes, sounds right. We need to break that deleted-but-wait-for-cleanup at
> > > least at one of the devices involved.
> > 
> > But it's broken when the driver is unbound.  Diagrammatically it's:
> > 
> > scsi_disk -> scsi_device -> queue
> >           -> gendisk     ->
> > 
> > It's not circular, it's released when scsi_disk is released.  It can
> > become circular if there's some hidden dependency between any of the
> > components ... but I don't think there is.
> 
> Forget about the scsi_disk.  It isn't part of the problem.  Just 
> concentrate on the scsi_device, the gendisk, and the queue.  We have:
> 
> 	scsi_device <- gendisk <- queue <- scsi_device,

OK, so where does the gendisk get a reference to the scsi device?

James