Comment 9 for bug 282189

I can confirm this bug in Ubuntu 8.04.2 LTS

This bug is nasty, because you wont find this bug report before you figured out the root of the problem yourself. That should be another reason to fix this bug. Since i'm not able to fix it, i will use the following workaround:
* use pvdisplay to determine the number of free logical extents in the first physical volume
* create a logical volume with this size (lvcreate ... -l num_of_extents)
Now the first physical volume should be full, the second one still empty.
* extend the root LV by one extent
Now the root LV uses one extent on the second partition and dmsetup deps returns both major/minor-pairs.
* delete the logical volume created in step 2.

That works but it's awkward.

I hope someone competent will soon recognize how significant this bug is. And it's just 10 lines of code...