Re: [PATCH v2] nbd/server: Allow MULTI_CONN for shared writable exports

[Eric Blake]

On Wed, Feb 16, 2022 at 02:44:52PM +0100, Markus Armbruster wrote:
> >
> > +##
> > +# @NbdExportMultiConn:
> > +#
> > +# Possible settings for advertising NBD multiple client support.
> > +#
> > +# @off: Do not advertise multiple clients.
> > +#
> > +# @on: Allow multiple clients (for writable clients, this is only safe
> > +#      if the underlying BDS is cache-consistent, such as when backed
> > +#      by the raw file driver); ignored if the NBD server was set up
> > +#      with max-connections of 1.
> > +#
> > +# @auto: Behaves like @off if the export is writable, and @on if the
> > +#        export is read-only.
> > +#
> > +# Since: 7.0
> > +##
> > +{ 'enum': 'NbdExportMultiConn',
> > +  'data': ['off', 'on', 'auto'] }
> 
> Have you considered using OnOffAuto from common.json?

Sounds good to me.

> 
> Duplicating it as NbdExportMultiConn lets you document the values right
> in the enum.  If you reuse it, you have to document them where the enum
> is used, i.e. ...
> 
> > +
> >  ##
> >  # @BlockExportOptionsNbd:
> >  #
> > @@ -95,11 +119,15 @@
> >  #                    the metadata context name "qemu:allocation-depth" to
> >  #                    inspect allocation details. (since 5.2)
> >  #
> > +# @multi-conn: Controls whether multiple client support is advertised, if 
> > the
> > +#              server's max-connections is not 1. (default auto, since 7.0)
> > +#
> 
> ... here.

Yep, that's a good change to make for v3.  I'll do it.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org