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    Subject[PATCH AUTOSEL 5.6 58/79] blk-iocost: Fix error on iocost_ioc_vrate_adj
    Date
    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
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