Re: [Intel-wired-lan] [PATCH net-next 1/5] net/sched: taprio: don't overwrite "sch" variable in taprio_dump_class_stats()

From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
To: Vladimir Oltean <vladimir.oltean@nxp.com>, netdev@vger.kernel.org
Cc: Andrew Lunn <andrew@lunn.ch>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Ferenc Fejes <ferenc.fejes@ericsson.com>,
	Kurt Kanzenbach <kurt@linutronix.de>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Eric Dumazet <edumazet@google.com>,
	Tony Nguyen <anthony.l.nguyen@intel.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Gerhard Engleder <gerhard@engleder-embedded.com>,
	UNGLinuxDriver@microchip.com,
	Horatiu Vultur <horatiu.vultur@microchip.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Xiaoliang Yang <xiaoliang.yang_1@nxp.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>,
	intel-wired-lan@lists.osuosl.org,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Pranavi Somisetty <pranavi.somisetty@amd.com>,
	Jiri Pirko <jiri@resnulli.us>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	Roger Quadros <rogerq@kernel.org>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Michael Sit Wei Hong <michael.wei.hong.sit@intel.com>,
	Harini Katakam <harini.katakam@amd.com>,
	linux-kernel@vger.kernel.org, Jose Abreu <joabreu@synopsys.com>,
	Oleksij Rempel <linux@rempel-privat.de>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [Intel-wired-lan] [PATCH net-next 1/5] net/sched: taprio: don't overwrite "sch" variable in taprio_dump_class_stats()
Date: Tue, 30 May 2023 14:14:17 -0700	[thread overview]
Message-ID: <87edmxv7x2.fsf@intel.com> (raw)
In-Reply-To: <20230530091948.1408477-2-vladimir.oltean@nxp.com>

Hi,

Vladimir Oltean <vladimir.oltean@nxp.com> writes:

> In taprio_dump_class_stats() we don't need a reference to the root Qdisc
> once we get the reference to the child corresponding to this traffic
> class, so it's okay to overwrite "sch". But in a future patch we will
> need the root Qdisc too, so create a dedicated "child" pointer variable
> to hold the child reference. This also makes the code adhere to a more
> conventional coding style.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---

The patch looks good:

Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>

But I have a suggestion, this "taprio_queue_get() ->
dev_queue->qdisc_sleeping()" dance should have the same result as
calling 'taprio_leaf()'.

I am thinking of using taprio_leaf() here and in taprio_dump_class().
Could be a separate commit.

>  net/sched/sch_taprio.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index 76db9a10ef50..d29e6785854d 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -2388,10 +2388,10 @@ static int taprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
>  	__acquires(d->lock)
>  {
>  	struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);
> +	struct Qdisc *child = dev_queue->qdisc_sleeping;
>  
> -	sch = dev_queue->qdisc_sleeping;
> -	if (gnet_stats_copy_basic(d, NULL, &sch->bstats, true) < 0 ||
> -	    qdisc_qstats_copy(d, sch) < 0)
> +	if (gnet_stats_copy_basic(d, NULL, &child->bstats, true) < 0 ||
> +	    qdisc_qstats_copy(d, child) < 0)
>  		return -1;
>  	return 0;
>  }
> -- 
> 2.34.1
>

-- 
Vinicius
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