From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     netdev@vger.kernel.org
Cc:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Jiri Pirko <jiri@resnulli.us>,
        Vinicius Costa Gomes <vinicius.gomes@intel.com>,
        Kurt Kanzenbach <kurt@linutronix.de>,
        Jacob Keller <jacob.e.keller@intel.com>,
        Gerhard Engleder <gerhard@engleder-embedded.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Tony Nguyen <anthony.l.nguyen@intel.com>,
        intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 net-next 01/15] net/sched: taprio: delete peek() implementation
Date:   Tue,  7 Feb 2023 15:54:26 +0200
Message-Id: <20230207135440.1482856-2-vladimir.oltean@nxp.com>
In-Reply-To: <20230207135440.1482856-1-vladimir.oltean@nxp.com>
References: <20230207135440.1482856-1-vladimir.oltean@nxp.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?92202rSHbf+eOf9ecuP/XoUEKURX/NTjGO4O+RqPk6XgAftA+ngI1x+YeiSy?=
 =?us-ascii?Q?1+8P8AmzJrKddWw8blGHZyntVb9MNb7IqP4rMtj20lKQzOdGnfvu73O+4gx5?=
 =?us-ascii?Q?aQ8xMXFPvfB91iaj/IYN+K3FzPLBmy10cn5IXww1DQl5HvQ9LbrcrfqwQ7MN?=
 =?us-ascii?Q?UDgmi3seE94MQK+sQGNMZ892WdNw5VaUdMfh5GqWxgJGOym9YRxWbMx2jq7K?=
 =?us-ascii?Q?7FEYqpCVH3S3Ob1QjG5LWFTsDS/iWRSwPvn8DFcwuiw+sBlCHbOBgyfSM8XT?=
 =?us-ascii?Q?ZStpysRwdOeP4vuH/IzMvVNDOWJY99OYcgA/y3DL3vHArD5ADih7Qf8fNOoi?=
 =?us-ascii?Q?3Yrn/OtStBqvCyfOtcsygJ2vt8xe/hyZigw65oU6RV7bYquqM1exBuylglbE?=
 =?us-ascii?Q?ug/bgxhHuGUs/ssekNmIj3bkl/YYjLtfycbJ4iaMZL4bTOu8r/idKkE15x7B?=
 =?us-ascii?Q?cH6YGsJzJfZL+7r0EblkpRzcP7aeEttoVadBRFrgTMWWAyyR696Qw23bGyvD?=
 =?us-ascii?Q?6dtHV4Mei5t9IHcdARLVH8nepWqkgd1oPTrwNPFqm7UbZuON738Zjj/z6ZXp?=
 =?us-ascii?Q?4pG6SheGYeTTdy64pf5vPpRSIHkLSnt+VVyEMW1ESQ26l3/aKU+oJVn1l0pS?=
 =?us-ascii?Q?mIi6ZdosalQzr4PRwCaOwm4RQpA+zZGYj27JFgPUw/okZf+zgqtCHDVxzAQK?=
 =?us-ascii?Q?U9y2ImCqFWQBeUkI3qHvk6pChIe7FJZyG+2qVqviTuyTa6qHZAstyzk4UYG9?=
 =?us-ascii?Q?BZI1hEBb14+cBVAGg80G0JhSHBIh/Fb2WeuMndlkc+jGSNbkM3N3SPU9S6Th?=
 =?us-ascii?Q?UjbbB278VsM5OV8SUkmQD4SjYQ3SbEq4JAALLhOUDQzkyWwnpGj1D3xM/TB/?=
 =?us-ascii?Q?RXObzz59RRe/317N7/tKvur257bJalYdrfABKHhG7hwpHvhsrX61jb7piB+I?=
 =?us-ascii?Q?1gvvH8tJ5ZzrizPqvtGuoXNKXbaPa37oYx2nffuvQJurclHiXbI/B2pmUbi8?=
 =?us-ascii?Q?k/5wVqtATgEaDFmSUIIBa0FV/YvQ0lMYdq2x+XI7d1bTEHd+FQ37hvdCdy9Q?=
 =?us-ascii?Q?1CHf0hgV715ciblPWR3Tsh8ZxWlJbyALF0VUQDU3xooNI+W6CQQFx0zbZrq+?=
 =?us-ascii?Q?ZsqgkWS0eweqdWZVqq+cBOqWDjkifppMEnkmHmELXT3vjcuj/HSLzx3tmP55?=
 =?us-ascii?Q?vpOHn3WWt/1vCsBSuCQACv2AVNfzgjj8wg3L1Lp6Yb504xnTzbN+PpWuaUZG?=
 =?us-ascii?Q?/LIs+iMmNyJcZ0KK6/a0vDYv9MYqtEzlh6lbFtbQphE+FvBw4hSTDw0utUUx?=
 =?us-ascii?Q?hIYlwYt+MsmkV/x3Hia5UxBxxnSEBUEsCm0jZNezQW4xeeoMSntHZQaBR0/t?=
 =?us-ascii?Q?HqyOTVhFiQwhTklMAXo3BICrqaacUK7JOrKxSC+InnJ6iEOUrQ+hOaAdOLdi?=
 =?us-ascii?Q?e0T2Tu3Vu9z191KfjGxleu356Qk2mKHfmG3BdIpA/mM0Wg8PsBmn2Bj2Lcq7?=
 =?us-ascii?Q?ZwsvAdLxbPAQV88TowLpeV4xUsAB/5Ka6k3+hYk7eGDqvwuFfiKrOY1ulFTu?=
 =?us-ascii?Q?2/W0zNr/nejcDSMpBDSpNMHGs2tjna/Ecq/U24Seua0+g6S4NtCIzPesH38o?=
 =?us-ascii?Q?FQ=3D=3D?=
X-OriginatorOrg: nxp.com
X-MS-Exchange-CrossTenant-Network-Message-Id: f4c3b158-b05a-49d8-9268-08db0912e973
X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5136.eurprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Feb 2023 13:55:04.8626
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: HBP7/2Zvv8G3wGi9XKzDeNrDDFXxAo4DtKRZcPJJEKdYkN4L1WVNFzDqPWdfWspzU9c3kIKGn8kp6MlcpD3HJA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM8PR04MB7299
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

There isn't any code in the network stack which calls taprio_peek().
We only see qdisc->ops->peek() being called on child qdiscs of other
classful qdiscs, never from the generic qdisc code. Whereas taprio is
never a child qdisc, it is always root.

This snippet of a comment from qdisc_peek_dequeued() seems to confirm:

	/* we can reuse ->gso_skb because peek isn't called for root qdiscs */

Since I've been known to be wrong many times though, I'm not completely
removing it, but leaving a stub function in place which emits a warning.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
---
v1->v2: none

 net/sched/sch_taprio.c | 43 +-----------------------------------------
 1 file changed, 1 insertion(+), 42 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 1c95785932b9..d9e26ddaa7f2 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -499,50 +499,9 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	return taprio_enqueue_one(skb, sch, child, to_free);
 }
 
-/* Will not be called in the full offload case, since the TX queues are
- * attached to the Qdisc created using qdisc_create_dflt()
- */
 static struct sk_buff *taprio_peek(struct Qdisc *sch)
 {
-	struct taprio_sched *q = qdisc_priv(sch);
-	struct net_device *dev = qdisc_dev(sch);
-	struct sched_entry *entry;
-	struct sk_buff *skb;
-	u32 gate_mask;
-	int i;
-
-	rcu_read_lock();
-	entry = rcu_dereference(q->current_entry);
-	gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
-	rcu_read_unlock();
-
-	if (!gate_mask)
-		return NULL;
-
-	for (i = 0; i < dev->num_tx_queues; i++) {
-		struct Qdisc *child = q->qdiscs[i];
-		int prio;
-		u8 tc;
-
-		if (unlikely(!child))
-			continue;
-
-		skb = child->ops->peek(child);
-		if (!skb)
-			continue;
-
-		if (TXTIME_ASSIST_IS_ENABLED(q->flags))
-			return skb;
-
-		prio = skb->priority;
-		tc = netdev_get_prio_tc_map(dev, prio);
-
-		if (!(gate_mask & BIT(tc)))
-			continue;
-
-		return skb;
-	}
-
+	WARN_ONCE(1, "taprio only supports operating as root qdisc, peek() not implemented");
 	return NULL;
 }
 
-- 
2.34.1