NFSv4.1/pnfs: Ensure the flexfiles layoutstats timers are consistent

We want to ensure that the stopwatches for the busy timer and the
aggregate timer are consistent. This means that they need to use
the same start/stop times.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -419,42 +419,35 @@ ff_layout_get_lseg_count(struct nfs4_ff_layout_segment *fls)
 }
 
 static void
-nfs4_ff_start_busy_timer(struct nfs4_ff_busy_timer *timer)
+nfs4_ff_start_busy_timer(struct nfs4_ff_busy_timer *timer, ktime_t now)
 {
 	/* first IO request? */
 	if (atomic_inc_return(&timer->n_ops) == 1) {
-		timer->start_time = ktime_get();
+		timer->start_time = now;
 	}
 }
 
 static ktime_t
-nfs4_ff_end_busy_timer(struct nfs4_ff_busy_timer *timer)
+nfs4_ff_end_busy_timer(struct nfs4_ff_busy_timer *timer, ktime_t now)
 {
-	ktime_t start, now;
+	ktime_t start;
 
 	if (atomic_dec_return(&timer->n_ops) < 0)
 		WARN_ON_ONCE(1);
 
-	now = ktime_get();
 	start = timer->start_time;
 	timer->start_time = now;
 	return ktime_sub(now, start);
 }
 
-static ktime_t
-nfs4_ff_layout_calc_completion_time(struct rpc_task *task)
-{
-	return ktime_sub(ktime_get(), task->tk_start);
-}
-
 static bool
 nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_mirror *mirror,
-			    struct nfs4_ff_layoutstat *layoutstat)
+			    struct nfs4_ff_layoutstat *layoutstat,
+			    ktime_t now)
 {
 	static const ktime_t notime = {0};
-	ktime_t now = ktime_get();
 
-	nfs4_ff_start_busy_timer(&layoutstat->busy_timer);
+	nfs4_ff_start_busy_timer(&layoutstat->busy_timer, now);
 	if (ktime_equal(mirror->start_time, notime))
 		mirror->start_time = now;
 	if (ktime_equal(mirror->last_report_time, notime))
@@ -482,30 +475,33 @@ static void
 nfs4_ff_layout_stat_io_update_completed(struct nfs4_ff_layoutstat *layoutstat,
 		__u64 requested,
 		__u64 completed,
-		ktime_t time_completed)
+		ktime_t time_completed,
+		ktime_t time_started)
 {
 	struct nfs4_ff_io_stat *iostat = &layoutstat->io_stat;
+	ktime_t completion_time = ktime_sub(time_completed, time_started);
 	ktime_t timer;
 
 	iostat->ops_completed++;
 	iostat->bytes_completed += completed;
 	iostat->bytes_not_delivered += requested - completed;
 
-	timer = nfs4_ff_end_busy_timer(&layoutstat->busy_timer);
+	timer = nfs4_ff_end_busy_timer(&layoutstat->busy_timer, time_completed);
 	iostat->total_busy_time =
 			ktime_add(iostat->total_busy_time, timer);
 	iostat->aggregate_completion_time =
-			ktime_add(iostat->aggregate_completion_time, time_completed);
+			ktime_add(iostat->aggregate_completion_time,
+					completion_time);
 }
 
 static void
 nfs4_ff_layout_stat_io_start_read(struct nfs4_ff_layout_mirror *mirror,
-		__u64 requested)
+		__u64 requested, ktime_t now)
 {
 	bool report;
 
 	spin_lock(&mirror->lock);
-	report = nfs4_ff_layoutstat_start_io(mirror, &mirror->read_stat);
+	report = nfs4_ff_layoutstat_start_io(mirror, &mirror->read_stat, now);
 	nfs4_ff_layout_stat_io_update_requested(&mirror->read_stat, requested);
 	spin_unlock(&mirror->lock);
 
@@ -523,18 +519,18 @@ nfs4_ff_layout_stat_io_end_read(struct rpc_task *task,
 	spin_lock(&mirror->lock);
 	nfs4_ff_layout_stat_io_update_completed(&mirror->read_stat,
 			requested, completed,
-			nfs4_ff_layout_calc_completion_time(task));
+			ktime_get(), task->tk_start);
 	spin_unlock(&mirror->lock);
 }
 
 static void
 nfs4_ff_layout_stat_io_start_write(struct nfs4_ff_layout_mirror *mirror,
-		__u64 requested)
+		__u64 requested, ktime_t now)
 {
 	bool report;
 
 	spin_lock(&mirror->lock);
-	report = nfs4_ff_layoutstat_start_io(mirror , &mirror->write_stat);
+	report = nfs4_ff_layoutstat_start_io(mirror , &mirror->write_stat, now);
 	nfs4_ff_layout_stat_io_update_requested(&mirror->write_stat, requested);
 	spin_unlock(&mirror->lock);
 
@@ -555,8 +551,7 @@ nfs4_ff_layout_stat_io_end_write(struct rpc_task *task,
 
 	spin_lock(&mirror->lock);
 	nfs4_ff_layout_stat_io_update_completed(&mirror->write_stat,
-			requested, completed,
-			nfs4_ff_layout_calc_completion_time(task));
+			requested, completed, ktime_get(), task->tk_start);
 	spin_unlock(&mirror->lock);
 }
 
@@ -1063,7 +1058,8 @@ static int ff_layout_read_prepare_common(struct rpc_task *task,
 {
 	nfs4_ff_layout_stat_io_start_read(
 			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
-			hdr->args.count);
+			hdr->args.count,
+			task->tk_start);
 
 	if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
 		rpc_exit(task, -EIO);
@@ -1249,7 +1245,8 @@ static int ff_layout_write_prepare_common(struct rpc_task *task,
 {
 	nfs4_ff_layout_stat_io_start_write(
 			FF_LAYOUT_COMP(hdr->lseg, hdr->pgio_mirror_idx),
-			hdr->args.count);
+			hdr->args.count,
+			task->tk_start);
 
 	if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
 		rpc_exit(task, -EIO);
@@ -1330,7 +1327,7 @@ static void ff_layout_commit_prepare_common(struct rpc_task *task,
 {
 	nfs4_ff_layout_stat_io_start_write(
 			FF_LAYOUT_COMP(cdata->lseg, cdata->ds_commit_index),
-			0);
+			0, task->tk_start);
 }
 
 static void ff_layout_commit_prepare_v3(struct rpc_task *task, void *data)