1#val_type uint64_t 2BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED 3BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED 4BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED 5BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED 6BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED 7