Re: [PATCH 5/8] qio: Let listening sockets remember their owning QIONetListener

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Nov 06, 2025 at 12:35:05PM -0600, Eric Blake wrote:
> On Wed, Nov 05, 2025 at 02:06:06PM -0600, Eric Blake wrote:
> > On Mon, Nov 03, 2025 at 02:10:56PM -0600, Eric Blake wrote:
> > > Make it easier to get from the sioc listening to a single address on
> > > behalf of a NetListener back to its owning object, which will be
> > > beneficial in an upcoming patch that teaches NetListener how to
> > > interact with AioContext.
> > > 
> > > Signed-off-by: Eric Blake <eblake@redhat.com>
> > > ---
> > >  include/io/channel-socket.h | 1 +
> > >  io/channel-socket.c         | 1 +
> > >  io/net-listener.c           | 1 +
> > >  3 files changed, 3 insertions(+)
> > > 
> > > diff --git a/include/io/channel-socket.h b/include/io/channel-socket.h
> > > index a88cf8b3a9f..eee686f3b4d 100644
> > > --- a/include/io/channel-socket.h
> > > +++ b/include/io/channel-socket.h
> > > @@ -49,6 +49,7 @@ struct QIOChannelSocket {
> > >      socklen_t remoteAddrLen;
> > >      ssize_t zero_copy_queued;
> > >      ssize_t zero_copy_sent;
> > > +    struct QIONetListener *listener;
> > 
> > Commenting on my own patch:
> > 
> > After re-reading docs/devel/style.rst, I can see that this particular
> > forward declaration of QIONetListener is not consistent with the
> > guidelines.  I have to have a forward reference, since the style guide
> > also forbids circular inclusion (net-listener.h already includes
> > channel-socket.h, so channel-socket.h cannot include net-listener.h);
> > but it may be better for me to move the forward reference into
> > include/qemu/typedefs.h rather than inlining it how I did here.
> 
> Then again, include/qemu/typedefs.h states "For struct types used in
> only a few headers, judicious use of the struct tag instead of the
> typedef name is commonly preferable."
> 
> So, to keep it simpler, I'll just justify my choice in the commit message.

I would really rather we avoided the bi-directional pointer linkage
entirely. AFAICT, this is only required because the later patch is
passing a QIOChannelSocket as the opaque data parametr for a callback.

It would be preferrable if we would instead pass a standalonme data
struct containing the QIOChannelSocket + QIONetListener, and then
avoid this back-linkage.


With regards,
Daniel
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