fat_set_start
fat_set_start(&de[0], cluster);
fat_set_start(&de[1], MSDOS_I(dir)->i_logstart);
fat_set_start(raw_entry, MSDOS_I(inode)->i_logstart);
fat_set_start(&de, cluster);
fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
fat_set_start(de, cluster);
fat_set_start(dotdot_de, MSDOS_I(dir)->i_logstart);