I have a problem when upgrading from 13.10 to 14.04: I have a triple boot (Mac 10.9 + Win 7 + 13.10) on a Macbook with a 120GB SSD. The Ubuntu is on sda6, btrfs, 15GB. GParted says 2,9GB are free, but Baobab sees only around 4GB occupied. Why is there such a huge difference? I do not have any subvolumes, and no snapshots as far as I can see. Any ideas?