On Wed, 2007-10-31 at 16:40 +0100, Kay Sievers wrote:
> On Wed, 2007-10-31 at 10:15 -0500, James Bottomley wrote:
> > On Wed, 2007-10-31 at 07:32 -0700, Greg KH wrote:
> > > Hm, I seem to have missed the part in this thread where someone said
> > > that it was valid to have a parent reference a child device. That's
> > > just wrong and needs to be fixed. Is that in the scsi layer somewhere?
> > > The block layer? It sure isn't in the driver core...
> >
> > This is the piece I'm still not clear on. It's something to do with the
> > gendisk. I'd have to look in block, but I believe the queue takes a ref
> > to the gendisk.
>
> Yes, the queue is a child of the disk.
Right, so this goes gendisk->queue (-> meaning parent of, or takes
reference to)
> > 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
> > and the scsi_disk (in sd) has a
> > ref to both the scsi_device and the gendisk. That means, until sd is
> > unbound and the scsi_disk released, there's an implied unbreakable
> > reference chain.
> >
> > at least, I think that's what the problem is.
>
> 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.
James
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