btrfs crashing at boot

[Chris Murphy]

Ah yes here we go, from today even more info on status of convert.
Gist is that it is broken and it's not certain when it will be fixed,
hopefully for 4.3 kernel and progs (it most likely will take both
since convert is part of btrfs-progs is responsible for reading ext4,
and then the kernel is responsible for writing the data+metadata to
Btrfs).

http://www.spinics.net/lists/linux-btrfs/msg48330.html