FYI: As reported on the btrfs wiki pages, btrfs-progs-4.7 and btrfs-progs-4.7.1 should not be used at all but btrfs-progs-4.7.2 instead due to an urgend fix. https://btrfs.wiki.kernel.org/index.php/Main_Page However, 4.7/4.7.1 are in unstable portage, 4.7.2 is missing. Gentoo should probably hardmask the buggy versions and include the new. Reproducible: Always