Comment # 9 on bug 980065 from Stefan Hundhammer

So, this machine has a Btrfs that spans over two partitions (/dev/sda2 and
/dev/sda4), i.e. it uses the volume manager feature of Btrfs. From the y2log:

2016-05-19 14:28:37 <1> (none)(3685) [libstorage] SystemCmd.cc(execute):134
SystemCmd
Executing: "/sbin/btrfs filesystem show

    Label: none  uuid: c5a20327-9e28-48d5-8321-96a35f02df84
        Total devices 2 FS bytes used 18.77GiB
        devid    1 size 19.53GiB used 16.52GiB path /dev/sda4
        devid    2 size 20.47GiB used 10.00GiB path /dev/sda2

    Label: none  uuid: 5b1a3d43-e99e-4f1e-a36c-1b4ee16f234a
        Total devices 1 FS bytes used 17.06GiB
        devid    1 size 40.00GiB used 19.57GiB path /dev/sdb2

    Label: none  uuid: d7c6824d-e107-42cc-b892-591ea0e83a5f
        Total devices 1 FS bytes used 23.58GiB
        devid    1 size 27.94GiB used 27.04GiB path /dev/sdb8


While this is a legitimate setup with Btrfs, this is not a scenario we support
from YaST. We support Btrfs on LVM doing something like this, but not Btrfs
without LVM, but with Btrfs built-in volume management.

So, according to disk_sda.info, those two partitions have the same filesystem
UUID, and that seems to confuse the internal logic of YaST and/or libstorage,
so it seems to be unable to figure out the mount points of either of those two
partitions.