net: sched: introduce and use qdisc tree flush/purge helpers

The same code to flush qdisc tree and purge the qdisc queue
is duplicated in many places and in most cases it does not
respect NOLOCK qdisc: the global backlog len is used and the
per CPU values are ignored.

This change addresses the above, factoring-out the relevant
code and using the helpers introduced by the previous patch
to fetch the correct backlog len.

Fixes: c5ad119 ("net: sched: pfifo_fast use skb_array")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Paolo Abeni

include/net/sch_generic.h

@@ -941,6 +941,23 @@ static inline void qdisc_qstats_qlen_backlog(struct Qdisc *sch,  __u32 *qlen,
 	*backlog = qstats.backlog;
 }
 
+static inline void qdisc_tree_flush_backlog(struct Qdisc *sch)
+{
+	__u32 qlen, backlog;
+
+	qdisc_qstats_qlen_backlog(sch, &qlen, &backlog);
+	qdisc_tree_reduce_backlog(sch, qlen, backlog);
+}
+
+static inline void qdisc_purge_queue(struct Qdisc *sch)
+{
+	__u32 qlen, backlog;
+
+	qdisc_qstats_qlen_backlog(sch, &qlen, &backlog);
+	qdisc_reset(sch);
+	qdisc_tree_reduce_backlog(sch, qlen, backlog);
+}
+
 static inline void qdisc_skb_head_init(struct qdisc_skb_head *qh)
 {
 	qh->head = NULL;
@@ -1124,13 +1141,8 @@ static inline struct Qdisc *qdisc_replace(struct Qdisc *sch, struct Qdisc *new,
 	sch_tree_lock(sch);
 	old = *pold;
 	*pold = new;
-	if (old != NULL) {
-		unsigned int qlen = old->q.qlen;
-		unsigned int backlog = old->qstats.backlog;
-
-		qdisc_reset(old);
-		qdisc_tree_reduce_backlog(old, qlen, backlog);
-	}
+	if (old != NULL)
+		qdisc_tree_flush_backlog(old);
 	sch_tree_unlock(sch);
 
 	return old;

net/sched/sch_cbq.c

@@ -1667,17 +1667,13 @@ static int cbq_delete(struct Qdisc *sch, unsigned long arg)
 {
 	struct cbq_sched_data *q = qdisc_priv(sch);
 	struct cbq_class *cl = (struct cbq_class *)arg;
-	unsigned int qlen, backlog;
 
 	if (cl->filters || cl->children || cl == &q->link)
 		return -EBUSY;
 
 	sch_tree_lock(sch);
 
-	qlen = cl->q->q.qlen;
-	backlog = cl->q->qstats.backlog;
-	qdisc_reset(cl->q);
-	qdisc_tree_reduce_backlog(cl->q, qlen, backlog);
+	qdisc_purge_queue(cl->q);
 
 	if (cl->next_alive)
 		cbq_deactivate_class(cl);

net/sched/sch_drr.c

@@ -50,15 +50,6 @@ static struct drr_class *drr_find_class(struct Qdisc *sch, u32 classid)
 	return container_of(clc, struct drr_class, common);
 }
 
-static void drr_purge_queue(struct drr_class *cl)
-{
-	unsigned int len = cl->qdisc->q.qlen;
-	unsigned int backlog = cl->qdisc->qstats.backlog;
-
-	qdisc_reset(cl->qdisc);
-	qdisc_tree_reduce_backlog(cl->qdisc, len, backlog);
-}
-
 static const struct nla_policy drr_policy[TCA_DRR_MAX + 1] = {
 	[TCA_DRR_QUANTUM]	= { .type = NLA_U32 },
 };
@@ -167,7 +158,7 @@ static int drr_delete_class(struct Qdisc *sch, unsigned long arg)
 
 	sch_tree_lock(sch);
 
-	drr_purge_queue(cl);
+	qdisc_purge_queue(cl->qdisc);
 	qdisc_class_hash_remove(&q->clhash, &cl->common);
 
 	sch_tree_unlock(sch);

net/sched/sch_hfsc.c

@@ -844,16 +844,6 @@ qdisc_peek_len(struct Qdisc *sch)
 	return len;
 }
 
-static void
-hfsc_purge_queue(struct Qdisc *sch, struct hfsc_class *cl)
-{
-	unsigned int len = cl->qdisc->q.qlen;
-	unsigned int backlog = cl->qdisc->qstats.backlog;
-
-	qdisc_reset(cl->qdisc);
-	qdisc_tree_reduce_backlog(cl->qdisc, len, backlog);
-}
-
 static void
 hfsc_adjust_levels(struct hfsc_class *cl)
 {
@@ -1076,7 +1066,7 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 	qdisc_class_hash_insert(&q->clhash, &cl->cl_common);
 	list_add_tail(&cl->siblings, &parent->children);
 	if (parent->level == 0)
-		hfsc_purge_queue(sch, parent);
+		qdisc_purge_queue(parent->qdisc);
 	hfsc_adjust_levels(parent);
 	sch_tree_unlock(sch);
 
@@ -1112,7 +1102,7 @@ hfsc_delete_class(struct Qdisc *sch, unsigned long arg)
 	list_del(&cl->siblings);
 	hfsc_adjust_levels(cl->cl_parent);
 
-	hfsc_purge_queue(sch, cl);
+	qdisc_purge_queue(cl->qdisc);
 	qdisc_class_hash_remove(&q->clhash, &cl->cl_common);
 
 	sch_tree_unlock(sch);

net/sched/sch_htb.c

@@ -1269,13 +1269,8 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
 
 	sch_tree_lock(sch);
 
-	if (!cl->level) {
-		unsigned int qlen = cl->leaf.q->q.qlen;
-		unsigned int backlog = cl->leaf.q->qstats.backlog;
-
-		qdisc_reset(cl->leaf.q);
-		qdisc_tree_reduce_backlog(cl->leaf.q, qlen, backlog);
-	}
+	if (!cl->level)
+		qdisc_purge_queue(cl->leaf.q);
 
 	/* delete from hash and active; remainder in destroy_class */
 	qdisc_class_hash_remove(&q->clhash, &cl->common);
@@ -1403,12 +1398,8 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 					  classid, NULL);
 		sch_tree_lock(sch);
 		if (parent && !parent->level) {
-			unsigned int qlen = parent->leaf.q->q.qlen;
-			unsigned int backlog = parent->leaf.q->qstats.backlog;
-
 			/* turn parent into inner node */
-			qdisc_reset(parent->leaf.q);
-			qdisc_tree_reduce_backlog(parent->leaf.q, qlen, backlog);
+			qdisc_purge_queue(parent->leaf.q);
 			qdisc_put(parent->leaf.q);
 			if (parent->prio_activity)
 				htb_deactivate(q, parent);

net/sched/sch_multiq.c

@@ -201,9 +201,9 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt,
 	for (i = q->bands; i < q->max_bands; i++) {
 		if (q->queues[i] != &noop_qdisc) {
 			struct Qdisc *child = q->queues[i];
+
 			q->queues[i] = &noop_qdisc;
-			qdisc_tree_reduce_backlog(child, child->q.qlen,
-						  child->qstats.backlog);
+			qdisc_tree_flush_backlog(child);
 			qdisc_put(child);
 		}
 	}
@@ -225,9 +225,7 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt,
 					qdisc_hash_add(child, true);
 
 				if (old != &noop_qdisc) {
-					qdisc_tree_reduce_backlog(old,
-								  old->q.qlen,
-								  old->qstats.backlog);
+					qdisc_tree_flush_backlog(old);
 					qdisc_put(old);
 				}
 				sch_tree_unlock(sch);

net/sched/sch_prio.c

@@ -216,12 +216,8 @@ static int prio_tune(struct Qdisc *sch, struct nlattr *opt,
 	q->bands = qopt->bands;
 	memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1);
 
-	for (i = q->bands; i < oldbands; i++) {
-		struct Qdisc *child = q->queues[i];
-
-		qdisc_tree_reduce_backlog(child, child->q.qlen,
-					  child->qstats.backlog);
-	}
+	for (i = q->bands; i < oldbands; i++)
+		qdisc_tree_flush_backlog(q->queues[i]);
 
 	for (i = oldbands; i < q->bands; i++) {
 		q->queues[i] = queues[i];

net/sched/sch_qfq.c

@@ -217,15 +217,6 @@ static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
 	return container_of(clc, struct qfq_class, common);
 }
 
-static void qfq_purge_queue(struct qfq_class *cl)
-{
-	unsigned int len = cl->qdisc->q.qlen;
-	unsigned int backlog = cl->qdisc->qstats.backlog;
-
-	qdisc_reset(cl->qdisc);
-	qdisc_tree_reduce_backlog(cl->qdisc, len, backlog);
-}
-
 static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
 	[TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
 	[TCA_QFQ_LMAX] = { .type = NLA_U32 },
@@ -551,7 +542,7 @@ static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
 
 	sch_tree_lock(sch);
 
-	qfq_purge_queue(cl);
+	qdisc_purge_queue(cl->qdisc);
 	qdisc_class_hash_remove(&q->clhash, &cl->common);
 
 	sch_tree_unlock(sch);

net/sched/sch_red.c

@@ -233,8 +233,7 @@ static int red_change(struct Qdisc *sch, struct nlattr *opt,
 	q->flags = ctl->flags;
 	q->limit = ctl->limit;
 	if (child) {
-		qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
-					  q->qdisc->qstats.backlog);
+		qdisc_tree_flush_backlog(q->qdisc);
 		old_child = q->qdisc;
 		q->qdisc = child;
 	}

net/sched/sch_sfb.c

@@ -521,8 +521,7 @@ static int sfb_change(struct Qdisc *sch, struct nlattr *opt,
 		qdisc_hash_add(child, true);
 	sch_tree_lock(sch);
 
-	qdisc_tree_reduce_backlog(q->qdisc, q->qdisc->q.qlen,
-				  q->qdisc->qstats.backlog);
+	qdisc_tree_flush_backlog(q->qdisc);
 	qdisc_put(q->qdisc);
 	q->qdisc = child;