Move to monotonic clock for time

Problem:
`posix_janitor_task()` was using `time()` to get the time which is
wall-clock time. Because of this the janitor task is not firing
periodically as it is supposed to, when ntp is disabled.

Fix:
Use monotonic_raw clock variant to get the time now.

Fixes: #3932
Change-Id: I13e48381495c97cd818161067ba43fe702318416
Signed-off-by: Pranith Kumar Karampuri <pranith.karampuri@phonepe.com>

Author: pranithk

libglusterfs/src/glusterfs/timespec.h

@@ -23,6 +23,8 @@ timespec_now(struct timespec *ts);
 void
 timespec_now_realtime(struct timespec *ts);
 void
+timespec_now_monotonic_raw(struct timespec *ts);
+void
 timespec_adjust_delta(struct timespec *ts, struct timespec delta);
 void
 timespec_sub(const struct timespec *begin, const struct timespec *end,

libglusterfs/src/libglusterfs.sym

@@ -1060,6 +1060,7 @@ tbf_init
 tbf_throttle
 timespec_now
 timespec_now_realtime
+timespec_now_monotonic_raw
 timespec_sub
 timespec_adjust_delta
 timespec_cmp

libglusterfs/src/timespec.c

@@ -91,6 +91,18 @@ timespec_now_realtime(struct timespec *ts)
     return;
 }
 
+void
+timespec_now_monotonic_raw(struct timespec *ts)
+{
+#if defined GF_LINUX_HOST_OS
+    if (0 == clock_gettime(CLOCK_MONOTONIC_RAW, ts)) {
+        return;
+    }
+#endif
+    // fallback to monotonic if monotonic_raw is not available
+    timespec_now(ts);
+}
+
 void
 timespec_adjust_delta(struct timespec *ts, struct timespec delta)
 {

xlators/storage/posix/src/posix-helpers.c

@@ -1474,8 +1474,6 @@ posix_janitor_task(void *data)
     struct posix_private *priv = NULL;
     xlator_t *old_this = NULL;
 
-    time_t now;
-
     this = data;
     priv = this->private;
     /* We need THIS to be set for janitor_walker */
@@ -1485,7 +1483,9 @@ posix_janitor_task(void *data)
     if (!priv)
         goto out;
 
-    now = gf_time();
+    struct timespec ts = {0};
+    timespec_now_monotonic_raw(&ts);
+    time_t now = ts.tv_sec;
     if ((now - priv->last_landfill_check) > priv->janitor_sleep_duration) {
         if (priv->disable_landfill_purge) {
             gf_msg_debug(this->name, 0,