From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756080Ab3KHADv (ORCPT ); Thu, 7 Nov 2013 19:03:51 -0500 Received: from dmz-mailsec-scanner-7.mit.edu ([18.7.68.36]:57909 "EHLO dmz-mailsec-scanner-7.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753584Ab3KHADn (ORCPT ); Thu, 7 Nov 2013 19:03:43 -0500 X-AuditID: 12074424-b7f0b8e000004bf2-24-527c2931e2bd Date: Thu, 7 Nov 2013 18:58:40 -0500 From: Greg Price To: "Theodore Ts'o" Cc: linux-kernel@vger.kernel.org Subject: [PATCH 04/11] random: simplify loop in random_read Message-ID: <20131107235839.GG16018@ringworld.MIT.EDU> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrNIsWRmVeSWpSXmKPExsUixG6nrmukWRNk8O8+k8XlXXPYHBg9Pm+S C2CM4rJJSc3JLEst0rdL4MpYPn8qe8F6kYpp6y8zNTA+4u9i5OSQEDCROPX/MROELSZx4d56 ti5GLg4hgdlMEtcOv2SGcDYwSkxctpAFwvnJKLHk9GSwFhYBFYnZGy+zg9hsAgoSP+avYwax RQSUJVbN3ARWwwwU/3VvEyuILSxgLXH9+HGgQRwcvAJmElfeK4OEhQQMJH5Of8sCYvMKCEqc nPmEBaJVS+LGv5dMIOXMAtISy/9xgIQ5BQwl2puvgE0UBbpgysltbBMYBWch6Z6FpHsWQvcC RuZVjLIpuVW6uYmZOcWpybrFyYl5ealFuuZ6uZkleqkppZsYwWHqorKDsfmQ0iFGAQ5GJR7e ggvVQUKsiWXFlbmHGCU5mJREeSeq1wQJ8SXlp1RmJBZnxBeV5qQWH2KU4GBWEuF9pgiU401J rKxKLcqHSUlzsCiJ897isA8SEkhPLEnNTk0tSC2CycpwcChJ8H4AGSpYlJqeWpGWmVOCkGbi 4AQZzgM0/AlIDW9xQWJucWY6RP4Uo6KUOO93kIQASCKjNA+uF5ZGXjGKA70izPsCpIoHmILg ul8BDWYCGhzyqxJkcEkiQkqqgbH/2yRPKx7+BpZrN35YCi58NvW83JHPlxjYw09tNvv9TWfZ 0rU3Chxmbvrx8du+hZWmUZe+GBorpOiF35ymcPtG5MVQ5foi1irpuF7FJSHGuc8zl3BYPzg2 gaH/mGZg+5d+QS7J+dtjw5TmFH6Z82mOwdq1Cm+2XTBYziLUs7hz2mW1npDdOY+UWIozEg21 mIuKEwFaq1Gg/gIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The loop condition never changes until just before a break, so we might as well write it as a constant. Also since v2.6.33-rc7~40^2~2 ("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. The behavior should be identical except that I've changed a debug message. Cc: "Theodore Ts'o" Signed-off-by: Greg Price --- drivers/char/random.c | 68 +++++++++++++++++---------------------------------- 1 file changed, 22 insertions(+), 46 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index d1466c9..85f5fce 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1155,58 +1155,34 @@ 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; - - DEBUG_ENT("reading %zu bits\n", n*8); - - n = extract_entropy_user(&blocking_pool, buf, n); - - if (n < 0) { - retval = n; - break; - } - - DEBUG_ENT("read got %zd bits (%zd still needed)\n", + nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE); + while (1) { + DEBUG_ENT("reading %zu bits\n", nbytes*8); + n = extract_entropy_user(&blocking_pool, buf, nbytes); + if (n < 0) + return n; + DEBUG_ENT("read got %zd bits (%zd short)\n", n*8, (nbytes-n)*8); - - if (n == 0) { - if (file->f_flags & O_NONBLOCK) { - retval = -EAGAIN; - break; - } - - DEBUG_ENT("sleeping?\n"); - - wait_event_interruptible(random_read_wait, - input_pool.entropy_count >= - random_read_wakeup_thresh); - - DEBUG_ENT("awake\n"); - - 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; + + DEBUG_ENT("sleeping?\n"); + wait_event_interruptible(random_read_wait, + input_pool.entropy_count >= + random_read_wakeup_thresh); + DEBUG_ENT("awake\n"); + if (signal_pending(current)) + return -ERESTARTSYS; } - - return (count ? count : retval); } static ssize_t -- 1.8.3.2