[systemd-devel] tentative state and unmount on mapper

Martin Pitt martin.pitt at ubuntu.com
Tue May 19 01:30:11 PDT 2015

Hello Umut,

Umut Tezduyar Lindskog [2015-05-19  8:23 +0200]:
> On Mon, May 18, 2015 at 11:02 PM, Lennart Poettering <lennart at poettering.net> wrote:
> > The "tentative" state is nothing the system should continously leave
> > devices in. It's a state only used for very short time windows, before
> > udev is up, or when a pseudo device (like a loopback block device) is
> > created and immediately mounted. If you have booted up and see a
> > device in "tentative" state, then something is really *wrong*.

Note that it's a permanent state in containers where you don't
actually have udev. My very first patch avoided creating these device
units at all, to simplify state handling; but Lennart nack'ed this as
we want devices/mounts to exist uniformly on real iron and containers,
which is certainly a valid point. So if we need the .devices at all,
they need to be "tentative", as they can't be "plugged" (not present
in the container /dev) nor "dead" (as that would immediately unmount

> - Isn't there a race in that "short time window" that if one tries to
> unmount stuff, things might go south!

Correct, or a permanent situation in containers (with writable /sys at
least, as a r/o sys is handled in a special case).

Note that I just sent an updated patch for this:
Would be nice if you could give it a try.

> - Seems like poky is enabling udev rules for DM. Maybe we should add
> required switches on README file to make DM work. So far I found
> CONFIG_DM_UEVENT on kernel and some switches on lvm,
> --enable-udev_sync, --enable-udev_rules, --with-udev-prefix=.

That's still a preferable fix for non-containers of course.



Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)
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