#val_type uint64_t
BTRFS_BALANCE_DATA (1ULL << 0)
BTRFS_BALANCE_SYSTEM (1ULL << 1)
BTRFS_BALANCE_METADATA (1ULL << 2)
BTRFS_BALANCE_FORCE (1ULL << 3)
BTRFS_BALANCE_RESUME (1ULL << 4)