[PATCH v2] blk-iocost: Simplify parameter type in iocost_ioc_vrate_adj trace entry

[PATCH v2] blk-iocost: Simplify parameter type in iocost_ioc_vrate_adj trace entry

[Waiman Long]

The iocost_ioc_vrate_adj() trace entry in include/trace/events/iocost.h
has one parameter of type "u32 (*missed_ppm)[2]" which is rather ugly
and hard to read. It makes me think for seconds to figure out what
it is and I have to double-check the the caller to confirm that it is
actually a pointer to a 2-entry u32 array.

It also happens that some tools that parse trace entries may not be
able to correctly interpret this parameter type which leads me to take
a look in the first place.

For simplicity sake, it is better to change the parameter type to just
"u32 *" and adjust the trace entry accordingly.

Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Tejun Heo <tj@kernel.org>
---
 block/blk-iocost.c            | 4 ++--
 include/trace/events/iocost.h | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index db35ee682294..3ab0c1c704b6 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1591,7 +1591,7 @@ static void ioc_timer_fn(struct timer_list *timer)
 				      vrate_min, vrate_max);
 		}
 
-		trace_iocost_ioc_vrate_adj(ioc, vrate, &missed_ppm, rq_wait_pct,
+		trace_iocost_ioc_vrate_adj(ioc, vrate, missed_ppm, rq_wait_pct,
 					   nr_lagging, nr_shortages,
 					   nr_surpluses);
 
@@ -1600,7 +1600,7 @@ static void ioc_timer_fn(struct timer_list *timer)
 			ioc->period_us * vrate * INUSE_MARGIN_PCT, 100);
 	} else if (ioc->busy_level != prev_busy_level || nr_lagging) {
 		trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
-					   &missed_ppm, rq_wait_pct, nr_lagging,
+					   missed_ppm, rq_wait_pct, nr_lagging,
 					   nr_shortages, nr_surpluses);
 	}
 
diff --git a/include/trace/events/iocost.h b/include/trace/events/iocost.h
index 7ecaa65b7106..c2f580fd371b 100644
--- a/include/trace/events/iocost.h
+++ b/include/trace/events/iocost.h
@@ -130,7 +130,7 @@ DEFINE_EVENT(iocg_inuse_update, iocost_inuse_reset,
 
 TRACE_EVENT(iocost_ioc_vrate_adj,
 
-	TP_PROTO(struct ioc *ioc, u64 new_vrate, u32 (*missed_ppm)[2],
+	TP_PROTO(struct ioc *ioc, u64 new_vrate, u32 *missed_ppm,
 		u32 rq_wait_pct, int nr_lagging, int nr_shortages,
 		int nr_surpluses),
 
@@ -155,8 +155,8 @@ TRACE_EVENT(iocost_ioc_vrate_adj,
 		__entry->old_vrate = atomic64_read(&ioc->vtime_rate);;
 		__entry->new_vrate = new_vrate;
 		__entry->busy_level = ioc->busy_level;
-		__entry->read_missed_ppm = (*missed_ppm)[READ];
-		__entry->write_missed_ppm = (*missed_ppm)[WRITE];
+		__entry->read_missed_ppm = missed_ppm[READ];
+		__entry->write_missed_ppm = missed_ppm[WRITE];
 		__entry->rq_wait_pct = rq_wait_pct;
 		__entry->nr_lagging = nr_lagging;
 		__entry->nr_shortages = nr_shortages;
-- 
2.18.1