BFIGNDIRTY
bp->b_flag |= BFIGNDIRTY;
if (!(bp->b_flag & BFIGNDIRTY) && (bp->b_flag & BFCHG) != 0 &&
if ((bp->b_flag & (BFDIRTY | BFIGNDIRTY)) == BFDIRTY) {
bp->b_flag |= BFIGNDIRTY;
bp->b_flag |= BFREADONLY | BFIGNDIRTY;
bp->b_flag &= ~(BFIGNDIRTY | BFDIRTY);