Re: [Qemu-devel] [PATCH 04/21] block: Add bdrv_close_all() handlers

[Max Reitz]

On 2015-01-26 at 16:10, Paolo Bonzini wrote:
> On 26/01/2015 21:43, Max Reitz wrote:
> > > If the NBD server is attached to the BDS, it should keep serving the BDS.
> > The problem is that it is no longer attached to the BDS, but to the BB.
> That's not necessarily a problem. :)  It is the cause of the problem though.
>
> Is it possible to attach two BBs to the same BDS?
>
> Because part of the solution could be to introduce a new blockdev-serve
> command that takes a BDS, creates a BB and exports that BB.
>
> > I think to retain compatibility we could either just do what we always
> > did (although I find it wrong), or we could simply set up an eject
> > blocker when attaching an NBD server to a BB. What do you think?
> An eject blocker would also break backwards-compatibility though.  What
> about an eject notifier?  Would that concept make sense?

It does make sense (in that it is the way I would implement "just do 
what we always did"), but I just don't like it for the fact that it 
makes NBD a special snowflake. I can live with it, though.

Max