Bug 557065

This bug mainly is the result of a long long long debugging session to hunt down bug 551790.

The problem is triggered by partitions on dmraid sets being activated with kpartx now a days as that can handle gpt partition tables, which dmraid itself cannot.

When anaconda runs from the livecd environment the dmraid set and its
partitions mappings are already setup by dmraid + kpartx. In the normal
install environment this is not the case, so anaconda tries to activate the
sets itself using python-pyblock (which uses libdmraid + libparted + devicemapper for this).

This is not a problem as python-pyblock contains code to detect if it is trying to add an already existing mapping (like in the livecd case), and in that case does nothing.

Things get troublesome however when there are logical partitions on the disk. The problem is that kpartx creates linear mappings of the extended partition for these instead of creating linear mappings directly of the disk. python-pyblock however does create linear mappings directly of the disk for the logical partitions. So the is this mapping already present check fails, after
which the map creation fails and anaconda aborts.

My first reaction when I finally figured this out was to modify python-pyblock to match kpartx behavior. But then I realized other tools might be bitten by the too, and indeed they are:

parted:
Cannot change the partition mappings of a dmraid device with logical partitions activated with kpartx, as it expects logical partitions to be linear mappings
of the disk (not the extended partitions), and thus fails to remove the old
mappings when trying to re-create the mappings to match changes made to the disk. So even if the entire raidset is not mounted / used in anyway a reboot
is required to get the kernel to see the new partition table.

python-pyblock:
See above

dmraid:
Cannot stop a raid set (dmraid -an) with logical partitions, even if it
is not gpt, as it too expects linear mappings directly of the disk.


So I've come to the conclusion that it is not python-pyblock which needs to change, but kpartx as that is the only one handling mapping of logical
partitions in this way.