HDR_BLKS
loop_end = ud_part->udp_nblocks + HDR_BLKS;
for (bno = loop_begin + HDR_BLKS; bno + blkcount < loop_end; ) {
*start_blkno = bno - HDR_BLKS;
bno + temp - HDR_BLKS;
old_loc = bno - HDR_BLKS;
loop_end = loop_begin + HDR_BLKS;
start += HDR_BLKS;
beginblk += HDR_BLKS;