Re: [Qemu-devel] [PATCH 1/3] block: detach devices from DriveInfo at unrealize time

[Paolo Bonzini <pbonzini@redhat.com>]

On 23/03/2016 09:35, Markus Armbruster wrote:
>> by that time you don't have anymore a QOM path to include in the event.
>
> I see.  To delay DEVICE_DELETED, we'd have to save the QOM path, and
> that would be bothersome.

Not just that, the QOM path goes away at the time we currently raise
DEVICE_DELETED.  If we delay it to finalization, it might even have been
reused.

> Still, copying code from property to devices with that property is
> undesirable.  It's not that bad in this patch, because we copy only to
> the devices that do warty backend deletion, and that's just the two
> places where we call blockdev_mark_auto_del() now.  However, it gets
> worse if we decide to extend warty backend deletion to *all* devices:
> more places, and a new need to consistently copy it to every new user of
> the drive property.
> 
> When you find yourself copying code from a property callback into every
> device using it, the real problem might be you're missing a callback.
> In this case, one that runs at unrealize time.  The existing release()
> runs at finalize time.

That's certainly a good thing to do if we decide to extend autodeletion
to the NVMe and SD devices.

Paolo