B_COWDONE
if (ISSET(bp->b_flags, B_COWDONE)) {
CLR(bp->b_flags, B_COWDONE);
CLR(bp->b_flags, B_COWDONE);
bp->b_vp->v_type == VBLK || ISSET(bp->b_flags, B_COWDONE));
bp->b_flags |= B_COWDONE;
if ((bp->b_flags & B_COWDONE))
bp->b_flags |= B_COWDONE;
bp->b_flags |= B_COWDONE;
bp->b_flags &= ~B_COWDONE; /* we change blkno below */