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Date: Fri, 19 Oct 2012 15:57:58 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 25/25] hmp: add NBD server commands
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To: Markus Armbruster <armbru@redhat.com>
Cc: qemu-devel@nongnu.org, lcapitulino@redhat.com

Il 19/10/2012 15:53, Markus Armbruster ha scritto:
> Paolo Bonzini <pbonzini@redhat.com> writes:
> 
>> Il 19/10/2012 14:44, Markus Armbruster ha scritto:
>>> Apropos hotplug.  The only way to unexport a block device is to stop the
>>> NBD server outright.  Once the device backend has been exported,
>>> unplugging the device gets rid of the frontend, but the backend stays
>>> until you stop the NBD server, or you kill the backend with the big
>>> drive_del hammer.
>>
>> Right.  (Though for removable devices you can just eject it, which calls
>> the close notifier).
>>
>>> Makes me wonder whether we need QMP command nbd-server-del.
>>
>> Perhaps yes, but it can be added later.
> 
> Perhaps deleting the backend should automatically unexport it.  I
> suspect that's not the case for the automatic delete on unplug.

No, because we keep a reference via drive_put_ref.  But that's by
design, drive_del exists after all and we can add a more fine-grained
nbd_server_del too.

Paolo