SMAL
#define SETSMAL(x) ((struct lblk *)((long)(x) | SMAL))
#define CLRSMAL(x) ((struct lblk *)((long)(x) & ~SMAL))
#define TESTSMAL(x) ((long)(x) & SMAL)
#define SETALL(x) ((long)(x) | (SMAL | BUSY))
#define CLRALL(x) ((long)(x) & ~(SMAL | BUSY))
(4 | SMAL)) == 0);