[9fans] namec() dislikes #M - why?

[Steve Simon]

Why can I not re-bind #M?

        /sys/src/9/port/chan.c:1374

I want to use auth/newns to flush out my namespace
then build a new one including some bits of devcons.

Is this a security issue for cpu servers? I cannot see
what it is protecting me from.

Also, why is this done here and not in fsattach() of devcons
(with a refcount)?

-Steve