First of all, thank you for your answer and suggestions. My root partition has 40 Gb and the btrfsmaintenance was installed, although I had not done any changes in any configuration tool. I will try to study more about btrfs. It seems it is useful for a server which is maintained and updated in an unattended way through cron. But I think this is a very serious bug. If anyone does not tweak and do "regular semi-cummulative updates" (I still have to find out how to do it) on his desktop or laptop computer, will it run out of space in some months? I have installed opensuse 13.2 on some computers of friends and colleagues of mine, and now I am afraid they will suffer this problem soon. On my own personal computer I did an upgrade from 13.1 and my root partition is still ext4, so I cannot check how btrfs works on a laptop computer with KDE. Let's keep opensuse as a linux for open minds, not only for geeks ;-) Thank you for your effort!