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Re: [Qemu-devel] [PATCH 1/1] qemu-nbd: add the option to use pre-created
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH 1/1] qemu-nbd: add the option to use pre-created server socket |
Date: |
Thu, 29 Sep 2016 12:13:18 +0100 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Thu, Sep 29, 2016 at 02:02:15PM +0300, Denis V. Lunev wrote:
> From: Denis Plotnikov <address@hidden>
>
> Originally NBD server socket was created by qemu-nbd code. This leads to
> the race when the management layer starts qemu-nbd server and allows a
> client to connect to the server. In this case there is a possibility that
> qemu-nbd does not open listening server socket yet. Creating listening
> socket before starting of qemu-ndb and passing socket fd via command line
> solves this issue completely.
FWIW, this could be solved in qemu-nbd itself if we had a general
ability to request "daemon" mode - currently it only daemonizes
if attaching to a nbd block device.
The key would be that qemu-nbd would open the listening socket
before daemonizing. Thus when the mgmt application spawned
qemu-nbd in daemon mode, it can be sure that the listener
socket is present when waitpid() completes.
Regards,
Daniel
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