lockdrive
int lockdrive(struct drive *drive, char *, int);
int lockdrive(struct drive *drive);
#define LOCKDRIVE(d) lockdrive (d, __FILE__, __LINE__)
#define LOCKDRIVE(d) lockdrive (d)
wakeup(&lockdrive);
lockdrive(struct drive *drive)
if ((error = tsleep(&lockdrive, 0, "vindrv", 0)) != 0)