SP_BACKSP
bp->b_bcount & SP_BACKSP ? "backward" : "forward",
bp->b_bcount & SP_BACKSP ? "backward" : "forward",
#define SPACE_CNT(x) (((x) & SP_BACKSP)? \
#define SPACE_CNT(x) (((x) & SP_BACKSP)? \
#define SPACE(cmd, cnt) ((cnt < 0) ? (SP_BACKSP | (-(cnt)) | cmd) : (cmd | cnt))