random: simplify loop in random_read

The loop condition never changes until just before a break, so we
might as well write it as a constant.  Also since a996996dd75a
("random: drop weird m_time/a_time manipulation") we don't do anything
after the loop finishes, so the 'break's might as well return
directly.  Some other simplifications.

There should be no change in behavior introduced by this commit.

Signed-off-by: Greg Price <price@mit.edu>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index fcda7d3937e0b508178a9f130e66e3f39c6b30d1..fcc2bff8f887ea2d4f9281f80265786b2f21c1ca 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1285,53 +1285,32 @@ void rand_initialize_disk(struct gendisk *disk)
 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) {
-                       if (file->f_flags & O_NONBLOCK) {
-                               retval = -EAGAIN;
-                               break;
-                       }
-
-                       wait_event_interruptible(random_read_wait,
-                               ENTROPY_BITS(&input_pool) >=
-                               random_read_wakeup_thresh);
-
-                       if (signal_pending(current)) {
-                               retval = -ERESTARTSYS;
-                               break;
-                       }
-
-                       continue;
-               }
-
-               count += n;
-               buf += n;
-               nbytes -= n;
-               break;          /* This break makes the device work */
-                               /* like a named pipe */
+               if (n > 0)
+                       return n;
+               /* Pool is (near) empty.  Maybe wait and retry. */
+
+               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))
+                       return -ERESTARTSYS;
        }
-
-       return (count ? count : retval);
 }
 
 static ssize_t