de_cn2doff
error = bread(DETOV(dep), de_cn2doff(pmp, cn),
de_cn2doff(pmp, frcn),
loffset = de_cn2doff(pmp, cn);
off_t raoffset = de_cn2doff(pmp, rablock);
bp = getblk(thisvp, de_cn2doff(pmp, cn),
error = bread(thisvp, de_cn2doff(pmp, cn),