In the release notes for upgrading from 13.2:
2.2 Btrfs: Disk Space Leak after System Rollbacks #](https://doc.opensuse.org/release-notes/x86_64/openSUSE/Leap/42.1/#idm140289651642016)
openSUSE 13.2 used a Btrfs partition layout that allowed for disk space to become permanently occupied with stale, inaccessible contents after the first system rollback was executed. This layout issue has been fixed in openSUSE Leap 42.1. However, the fix can only be applied to newly installed systems.
If you are upgrading from openSUSE 13.2, you cannot convert the to the new layout, but you can reclaim the lost disk space.
Mount the initial root filesystem:
mount /dev/<ROOT_FILE_SYSTEM> -o subvolid=5 /mnt
Remove all files below /mnt that are not in a subvolume:
find /mnt -xdev -delete
Umount the filesystem again:
When is this meant to be done? Before upgrading? Are we meant to start from a boot CD/DVD emergency recovery console to run the script?