akpm at linux-foundation.org
2015-Aug-21 21:41 UTC
[Ocfs2-devel] [patch 16/24] ocfs2: use 64bit variables to track heartbeat time
From: Tina Ruchandani <ruchandani.tina at gmail.com>
Subject: ocfs2: use 64bit variables to track heartbeat time
o2hb_elapsed_msecs computes the time taken for a disk heartbeat. 'struct
timeval' variables are used to store start and end times. On 32-bit
systems, the 'tv_sec' component of 'struct timeval' will
overflow in year
2038 and beyond.
This patch solves the overflow with the following:
1. Replace o2hb_elapsed_msecs using 'ktime_t' values to measure start
and end time, and built-in function 'ktime_ms_delta' to compute the
elapsed time. ktime_get_real() is used since the code prints out the
wallclock time.
2. Changes format string to print time as a single 64-bit nanoseconds
value ("%lld") instead of seconds and microseconds. This
simplifies
the code since converting ktime_t to that format would need expensive
computation. However, the debug log string is less readable than the
previous format.
Signed-off-by: Tina Ruchandani <ruchandani.tina at gmail.com>
Suggested by: Arnd Bergmann <arnd at arndb.de>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
fs/ocfs2/cluster/heartbeat.c | 49 ++++++---------------------------
1 file changed, 9 insertions(+), 40 deletions(-)
diff -puN
fs/ocfs2/cluster/heartbeat.c~ocfs2-use-64bit-variables-to-track-heartbeat-time
fs/ocfs2/cluster/heartbeat.c
---
a/fs/ocfs2/cluster/heartbeat.c~ocfs2-use-64bit-variables-to-track-heartbeat-time
+++ a/fs/ocfs2/cluster/heartbeat.c
@@ -36,7 +36,7 @@
#include <linux/debugfs.h>
#include <linux/slab.h>
#include <linux/bitmap.h>
-
+#include <linux/ktime.h>
#include "heartbeat.h"
#include "tcp.h"
#include "nodemanager.h"
@@ -1061,37 +1061,6 @@ bail:
return ret;
}
-/* Subtract b from a, storing the result in a. a *must* have a larger
- * value than b. */
-static void o2hb_tv_subtract(struct timeval *a,
- struct timeval *b)
-{
- /* just return 0 when a is after b */
- if (a->tv_sec < b->tv_sec ||
- (a->tv_sec == b->tv_sec && a->tv_usec <
b->tv_usec)) {
- a->tv_sec = 0;
- a->tv_usec = 0;
- return;
- }
-
- a->tv_sec -= b->tv_sec;
- a->tv_usec -= b->tv_usec;
- while ( a->tv_usec < 0 ) {
- a->tv_sec--;
- a->tv_usec += 1000000;
- }
-}
-
-static unsigned int o2hb_elapsed_msecs(struct timeval *start,
- struct timeval *end)
-{
- struct timeval res = *end;
-
- o2hb_tv_subtract(&res, start);
-
- return res.tv_sec * 1000 + res.tv_usec / 1000;
-}
-
/*
* we ride the region ref that the region dir holds. before the region
* dir is removed and drops it ref it will wait to tear down this
@@ -1102,7 +1071,7 @@ static int o2hb_thread(void *data)
int i, ret;
struct o2hb_region *reg = data;
struct o2hb_bio_wait_ctxt write_wc;
- struct timeval before_hb, after_hb;
+ ktime_t before_hb, after_hb;
unsigned int elapsed_msec;
mlog(ML_HEARTBEAT|ML_KTHREAD, "hb thread running\n");
@@ -1119,18 +1088,18 @@ static int o2hb_thread(void *data)
* hr_timeout_ms between disk writes. On busy systems
* this should result in a heartbeat which is less
* likely to time itself out. */
- do_gettimeofday(&before_hb);
+ before_hb = ktime_get_real();
ret = o2hb_do_disk_heartbeat(reg);
- do_gettimeofday(&after_hb);
- elapsed_msec = o2hb_elapsed_msecs(&before_hb, &after_hb);
+ after_hb = ktime_get_real();
+
+ elapsed_msec = (unsigned int)
+ ktime_ms_delta(after_hb, before_hb);
mlog(ML_HEARTBEAT,
- "start = %lu.%lu, end = %lu.%lu, msec = %u, ret = %d\n",
- before_hb.tv_sec, (unsigned long) before_hb.tv_usec,
- after_hb.tv_sec, (unsigned long) after_hb.tv_usec,
- elapsed_msec, ret);
+ "start = %lld, end = %lld, msec = %u, ret = %d\n",
+ before_hb.tv64, after_hb.tv64, elapsed_msec, ret);
if (!kthread_should_stop() &&
elapsed_msec < reg->hr_timeout_ms) {
_