http://repo.or.cz/w/btrfs-progs-unstable/devel.git/shortlog/refs/heads/integration-20141030-2: # btrfsck --repair /dev/sdb2 enabling repair mode Fixed 0 roots. Checking filesystem on /dev/sdb2 UUID: 9e12d35c-87ab-47e3-aecb-01f7c09e3c96 checking extents cmds-check.c:2645: check_owner_ref: Assertion `rec->is_root` failed. btrfs check[0x41d3c9] btrfs check[0x409df3] btrfs check[0x40ac29] btrfs check[0x41f6ef] btrfs check[0x40bdb2] /lib64/libc.so.6(__libc_start_main+0xf5)[0x7f5cbbfebb05] btrfs check[0x40beb4]