BH_WRITE
if (lg_info != NULL || F_ISSET(bhp, BH_WRITE))
if (F_ISSET(bhp, BH_WRITE)) {
F_CLR(bhp, BH_WRITE);
if (F_ISSET(bhp, BH_WRITE))
F_CLR(bhp, BH_WRITE);
{ BH_WRITE, "write" },
F_SET(bhp, BH_WRITE);
if (F_ISSET(bhp, BH_WRITE))
F_CLR(bhp, BH_WRITE);
F_CLR(bhp, BH_WRITE);