Hello,
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.
I tried to set *underlying to MACH_PORT_NULL, but it (in a quite
expected way) refused to work. I then tried to do
*underlying = underlying_node;
where underlying_node is a port right describing a port to the
underlying node of the unionfs translator. This led to the following
error:
unionfs: /var/tmp/hurd-20090404/./libports/complete-deallocate.c:29:
_ports_complete_deallocate: Assertion `(pi->flags & 0x0001) == 0'
failed.
/hurd/filterfs: Translator startup failure: fsys_startup: (ipc/mig)
server died
(lines wrapped by MUA)
filterfs is the my own libnetfs-based translator which I use for
testing unionmount.
Now the question: can the reason for such failure be the fact that the
port right stored in underlying_node is used both in unionmount and in
the mountee? If so, is there a way to clone the port right?
Regards,
scolobb
