exfat_dentries_to_bytes
es->start_off = exfat_dentries_to_bytes(i) % sb->s_blocksize;
*cpos = exfat_dentries_to_bytes(dentry + 1 + num_ext);
*cpos = exfat_dentries_to_bytes(dentry);
off = exfat_dentries_to_bytes(entry);