From: Chris Taylor <ctaylor@pivot3.com>
Date: Sun, 2 Apr 2017 21:54:02 +0000 (-0600)
Subject: time: fix overflow in timeval_add_msec()
X-Git-Tag: fio-2.19~3
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=d19251c4a191dd024bec82be876f57f7770e32f6;p=fio.git

time: fix overflow in timeval_add_msec()

There is an issue in FIO when using the detailed bandwidth and iops
logging with averaging over a period of time > 1 second.  It seems that
usecs overflows which later causes negative time diff values resulting
in skewed toward 0 results.  I have attached a potential fix that should
prevent usecs from going beyond 1000000.

[Modified by Jens to put the adj_sec in the branch.]

Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/time.c b/time.c
index f5dc0496..f637afb5 100644
--- a/time.c
+++ b/time.c
@@ -8,8 +8,16 @@ static unsigned long ns_granularity;
 
 void timeval_add_msec(struct timeval *tv, unsigned int msec)
 {
-	tv->tv_usec += 1000 * msec;
-	if (tv->tv_usec >= 1000000) {
+	unsigned int adj_usec = 1000 * msec;
+
+	tv->tv_usec += adj_usec;
+	if (adj_usec >= 1000000) {
+		unsigned int adj_sec = adj_usec / 1000000;
+
+		tv->tv_usec -=  adj_sec * 1000000;
+		tv->tv_sec += adj_sec;
+	}
+	if (tv->tv_usec >= 1000000){
 		tv->tv_usec -= 1000000;
 		tv->tv_sec++;
 	}