Bug#549691: lvm2: can't remove unmounted snapshot volume

[Peter Rajnoha]

On 04/07/2010 03:24 AM, Celejar wrote:
> Eventually, I noticed that after a suspend / resume cycle, mount now shows that
> the snapshot volume is mounted where the original should be:

Not exactly this case, I suppose, but maybe it's worth mentioning because
it's very similar...

There's a flag set by lvm2 automatically for snapshot devices: DM_UDEV_LOW_PRIORITY_FLAG
(which I can't find in Debian version of the udev rules). This gives low
priority to snapshot devices while creating symlinks in /dev/disk/by-uuid.
Since only the FS UUID is used as a name here, we need to determinize the
naming and so we try to give preference to origin devices by setting proper
symlink priorities (symlink creation would be prone to races otherwise).

All these flags and synchronization works only in kernels >= 2.6.31.