#val_type uint64_t
BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR
BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED
BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED
BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS