net/sched: taprio: refactor one skb dequeue from TXQ to separate function

Future changes will refactor the TXQ selection procedure, and a lot of
stuff will become messy, the indentation of the bulk of the dequeue
procedure would increase, etc.

Break out the bulk of the function into a new one, which knows the TXQ
(child qdisc) we should perform a dequeue from.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_taprio.c

@@ -512,6 +512,66 @@ static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
 			     atomic64_read(&q->picos_per_byte)));
 }
 
+static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
+					       struct sched_entry *entry,
+					       u32 gate_mask)
+{
+	struct taprio_sched *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+	struct Qdisc *child = q->qdiscs[txq];
+	struct sk_buff *skb;
+	ktime_t guard;
+	int prio;
+	int len;
+	u8 tc;
+
+	if (unlikely(!child))
+		return NULL;
+
+	if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
+		skb = child->ops->dequeue(child);
+		if (!skb)
+			return NULL;
+		goto skb_found;
+	}
+
+	skb = child->ops->peek(child);
+	if (!skb)
+		return NULL;
+
+	prio = skb->priority;
+	tc = netdev_get_prio_tc_map(dev, prio);
+
+	if (!(gate_mask & BIT(tc)))
+		return NULL;
+
+	len = qdisc_pkt_len(skb);
+	guard = ktime_add_ns(taprio_get_time(q), length_to_duration(q, len));
+
+	/* In the case that there's no gate entry, there's no
+	 * guard band ...
+	 */
+	if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
+	    ktime_after(guard, entry->close_time))
+		return NULL;
+
+	/* ... and no budget. */
+	if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
+	    atomic_sub_return(len, &entry->budget) < 0)
+		return NULL;
+
+	skb = child->ops->dequeue(child);
+	if (unlikely(!skb))
+		return NULL;
+
+skb_found:
+	qdisc_bstats_update(sch, skb);
+	qdisc_qstats_backlog_dec(sch, skb);
+	sch->q.qlen--;
+
+	return skb;
+}
+
 /* Will not be called in the full offload case, since the TX queues are
  * attached to the Qdisc created using qdisc_create_dflt()
  */
@@ -537,64 +597,9 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
 		goto done;
 
 	for (i = 0; i < dev->num_tx_queues; i++) {
-		struct Qdisc *child = q->qdiscs[i];
-		ktime_t guard;
-		int prio;
-		int len;
-		u8 tc;
-
-		if (unlikely(!child))
-			continue;
-
-		if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
-			skb = child->ops->dequeue(child);
-			if (!skb)
-				continue;
-			goto skb_found;
-		}
-
-		skb = child->ops->peek(child);
-		if (!skb)
-			continue;
-
-		prio = skb->priority;
-		tc = netdev_get_prio_tc_map(dev, prio);
-
-		if (!(gate_mask & BIT(tc))) {
-			skb = NULL;
-			continue;
-		}
-
-		len = qdisc_pkt_len(skb);
-		guard = ktime_add_ns(taprio_get_time(q),
-				     length_to_duration(q, len));
-
-		/* In the case that there's no gate entry, there's no
-		 * guard band ...
-		 */
-		if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
-		    ktime_after(guard, entry->close_time)) {
-			skb = NULL;
-			continue;
-		}
-
-		/* ... and no budget. */
-		if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
-		    atomic_sub_return(len, &entry->budget) < 0) {
-			skb = NULL;
-			continue;
-		}
-
-		skb = child->ops->dequeue(child);
-		if (unlikely(!skb))
-			continue;
-
-skb_found:
-		qdisc_bstats_update(sch, skb);
-		qdisc_qstats_backlog_dec(sch, skb);
-		sch->q.qlen--;
-
-		goto done;
+		skb = taprio_dequeue_from_txq(sch, i, entry, gate_mask);
+		if (skb)
+			goto done;
 	}
 
 done: