You can follow the btrfs mailinglists to see the stream of people coming in that hit a case where btrfs can't recover by itself. I've hit one myself that requir

You can follow the btrfs mailinglists to see the stream of people coming in that hit a case where btrfs can't recover by itself. I've hit one myself that required a btrfs-zero-log "fix", but I'm not running Ubuntu. You have been extremely lucky. Keep making backups, though.