AHDIMAGIC
bb->bb_magic = (blk == 0) ? NBDAMAGIC : AHDIMAGIC;
(p[0] == AHDIMAGIC && blkno != 0)
(p[0] == AHDIMAGIC && offset != 0) ||
if (bb->bb_magic == NBDAMAGIC || bb->bb_magic == AHDIMAGIC) {
|| (p[0] == AHDIMAGIC && offset != 0)
(offs != 0 && bb.bb_magic != AHDIMAGIC) ||
magic = AHDIMAGIC;
|| (p[0] == AHDIMAGIC && offset != 0)
|| (p[0] == AHDIMAGIC && offset != 0)