Re: [9fans] Unmount of /mnt directory

[erik quanstrom <quanstro@quanstro.net>]

> it seems I still do not fully understand namespaces.
> But this sequence seems strange to me:
>
> cdfs -d /dev/sdD0
> unmount /mnt/cd
>
> ...everything is OK.
>
> cdfs -d /dev/sdD0
> unmount /mnt
>
> ...I unmounted wrong directory...
>
> cdfs -d /dev/sdD0
> cdfs: openscsi '/dev/sdD0': '/dev/sdD0/raw' device or object already
> in use
>
> ...this situation is persistent.
>
> What happened in the system when I unmounted /mnt directory?

on my system /mnt is constructed like this

	chula# ns | grep '/mnt $'
	bind -c /root/mnt /mnt
	mount -a '#s/factotum' /mnt

if i unmount /mnt i get

	chula# unmount /mnt
	chula#  '/mnt $'

it might be surprising that, e.g.,
	mount -c '#D/ssl/2/data' /mnt/term
is not unmounted, but the mntpt isn't /mnt,
it's /mnt/term.  things below /mnt are not
accessable because we must walk from the
root.

with this knowledge, one can reconstruct
the former namespace and unmount /mnt/cd.

	chula# bind -c /root/mnt /mnt
	chula# mount -a '#s/factotum' /mnt
	chula# unmount /mnt/cd

alternatevely, "slay cdfs | rc" would work,
if you didn't care about that ns being screwy.

- erik