ROUND_UP
*data_offset_out = ROUND_UP(*data_offset_out, align);
*bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
*bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
*bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);