Re: How to clone a port right

[Sergiu Ivanov]

Hello,

On Tue, Jul 07, 2009 at 09:54:51PM +0200, Carl Fredrik Hammar wrote:
> On Tue, Jul 07, 2009 at 09:24:27PM +0300, Sergiu Ivanov wrote:
> > In the latest working design unionmount creates a proxy node (by
> > cloning the netfs_root_node of unionfs translator) and sets the
> > mountee on this proxy.  I'm currently trying to implement cfhammar's
> > idea about having the mountee run in orphan mode.  To achieve this I
> > call only fshelp_start_translator, with no file_set_translator
> > following.  When calling fshelp_start_translator, I have to give a
> > pointer to a function, open_port, which in my case looks like this:
> > 
> >   /* Opens the port on which to set the mountee.  */
> >   error_t
> >     open_port (int flags, mach_port_t * underlying,
> >                mach_msg_type_name_t * underlying_type, task_t task,
> >                void *cookie)
> >   {
> >     err = 0;
> > 
> >     /* Create a port to `np`.  */
> >     newpi = netfs_make_protid
> >       (netfs_make_peropen (np, flags, NULL), user);
> >     if (!newpi)
> >       {
> >         iohelp_free_iouser (user);
> >         return errno;
> >       }
> > 
> >     *underlying = underlying_port = ports_get_send_right (newpi);
> >     *underlying_type = MACH_MSG_TYPE_COPY_SEND;
> > 
> >     ports_port_deref (newpi);
> > 
> >     return err;
> >   }                             /*open_port */
> > 
> > np is the pointer to the proxy node.  If I want to get rid of the
> > proxy node I must somehow avoid keeping references to it.  However, in
> > the above code I clearly add a reference to the proxy node by creating
> > a port which goes to the mountee and thus, does not get destroyed
> > immediately.
> 
> Is there any reason to have a proxy at all now that there's no
> file_set_translator?  Why not simply pass unionfs's underlying node?

My previous mail says that when I simply pass the unionfs's underlying
node I get an error; the error is given in that mail :-) That's why
the question in the subject of the post ;-)

Regards,
scolobb