random: simplify loop in random_read

static ssize_t

random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)

{

	ssize_t n, retval = 0, count = 0;

	ssize_t n;

	if (nbytes == 0)

		return 0;

	while (nbytes > 0) {

		n = nbytes;

		if (n > SEC_XFER_SIZE)

			n = SEC_XFER_SIZE;

		n = extract_entropy_user(&blocking_pool, buf, n);

		if (n < 0) {

			retval = n;

			break;

		}

	nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);

	while (1) {

		n = extract_entropy_user(&blocking_pool, buf, nbytes);

		if (n < 0)

			return n;

		trace_random_read(n*8, (nbytes-n)*8,

				  ENTROPY_BITS(&blocking_pool),

				  ENTROPY_BITS(&input_pool));

		if (n > 0)

			return n;

		/* Pool is (near) empty.  Maybe wait and retry. */

		if (n == 0) {

			if (file->f_flags & O_NONBLOCK) {

				retval = -EAGAIN;

				break;

			}

		if (file->f_flags & O_NONBLOCK)

			return -EAGAIN;

		wait_event_interruptible(random_read_wait,

			ENTROPY_BITS(&input_pool) >=

			random_read_wakeup_thresh);

			if (signal_pending(current)) {

				retval = -ERESTARTSYS;

				break;

			}

			continue;

		if (signal_pending(current))

			return -ERESTARTSYS;

	}

		count += n;

		buf += n;

		nbytes -= n;

		break;		/* This break makes the device work */

				/* like a named pipe */

	}

	return (count ? count : retval);

}

static ssize_t