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@gmail.com>
Suggested by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index f97306453a0b3454a09c4456e4c48845f6737000..fa15debcc02be1c8fe1d3419d10dd7c5ab0ff968 100644 (file)
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/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"
@@ -1060,37 +1060,6 @@ 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
@@ -1101,7 +1070,7 @@ 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");
@@ -1118,18 +1087,18 @@ 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) {