[PATCH AUTOSEL 5.4 41/57] blk-iocost: Fix error on iocost_ioc_vrate_adj

Sasha Levin
2020-04-30T14:02:21Z

From: Waiman Long <longman@redhat.com>

[ Upstream commit d6c8e949a35d6906d6c03a50e9a9cdf4e494528a ]

Systemtap 4.2 is unable to correctly interpret the "u32 (*missed_ppm)[2]"
argument of the iocost_ioc_vrate_adj trace entry defined in
include/trace/events/iocost.h leading to the following error:

/tmp/stapAcz0G0/stap_c89c58b83cea1724e26395efa9ed4939_6321_aux_6.c:78:8:
error: expected ‘;’, ‘,’ or ‘)’ before ‘*’ token
, u32[]* __tracepoint_arg_missed_ppm

That argument type is indeed rather complex and hard to read. Looking
at block/blk-iocost.c. It is just a 2-entry u32 array. By simplifying
the argument to a simple "u32 *missed_ppm" and adjusting the trace
entry accordingly, the compilation error was gone.

Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@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 9a599cc28c290..2dc5dc54e257f 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1594,7 +1594,7 @@ skip_surplus_transfers:
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);

@@ -1603,7 +1603,7 @@ skip_surplus_transfers:
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 7ecaa65b7106e..c2f580fd371b1 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;
--
2.20.1