Merge branch 'sch_cake-leaf-qdisc-fixes'

Toke Høiland-Jørgensen says:

====================
sched: Fix qdisc interactions exposed by using sch_cake as a leaf qdisc

This series fixes a couple of issues exposed by running sch_cake as a
leaf qdisc in an HFSC tree, which were discovered and reported by Pete
Heist. The interaction between CAKE's GSO splitting and the parent
qdisc's notion of its own queue length could cause queue stalls. While
investigating the report, I also noticed that several qdiscs would
dereference the skb pointer after dequeue, which is potentially
problematic since the GSO splitting code also frees the original skb.

See the individual patches in the series for details.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_cake.c

@@ -1667,7 +1667,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	if (skb_is_gso(skb) && q->rate_flags & CAKE_FLAG_SPLIT_GSO) {
 		struct sk_buff *segs, *nskb;
 		netdev_features_t features = netif_skb_features(skb);
-		unsigned int slen = 0;
+		unsigned int slen = 0, numsegs = 0;
 
 		segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
 		if (IS_ERR_OR_NULL(segs))
@@ -1683,6 +1683,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 			flow_queue_add(flow, segs);
 
 			sch->q.qlen++;
+			numsegs++;
 			slen += segs->len;
 			q->buffer_used += segs->truesize;
 			b->packets++;
@@ -1696,7 +1697,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		sch->qstats.backlog += slen;
 		q->avg_window_bytes += slen;
 
-		qdisc_tree_reduce_backlog(sch, 1, len);
+		qdisc_tree_reduce_backlog(sch, 1-numsegs, len-slen);
 		consume_skb(skb);
 	} else {
 		/* not splitting */

net/sched/sch_cbs.c

@@ -88,13 +88,14 @@ static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 			     struct Qdisc *child,
 			     struct sk_buff **to_free)
 {
+	unsigned int len = qdisc_pkt_len(skb);
 	int err;
 
 	err = child->ops->enqueue(skb, child, to_free);
 	if (err != NET_XMIT_SUCCESS)
 		return err;
 
-	qdisc_qstats_backlog_inc(sch, skb);
+	sch->qstats.backlog += len;
 	sch->q.qlen++;
 
 	return NET_XMIT_SUCCESS;

net/sched/sch_drr.c

@@ -350,9 +350,11 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
 static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		       struct sk_buff **to_free)
 {
+	unsigned int len = qdisc_pkt_len(skb);
 	struct drr_sched *q = qdisc_priv(sch);
 	struct drr_class *cl;
 	int err = 0;
+	bool first;
 
 	cl = drr_classify(skb, sch, &err);
 	if (cl == NULL) {
@@ -362,6 +364,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		return err;
 	}
 
+	first = !cl->qdisc->q.qlen;
 	err = qdisc_enqueue(skb, cl->qdisc, to_free);
 	if (unlikely(err != NET_XMIT_SUCCESS)) {
 		if (net_xmit_drop_count(err)) {
@@ -371,12 +374,12 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		return err;
 	}
 
-	if (cl->qdisc->q.qlen == 1) {
+	if (first) {
 		list_add_tail(&cl->alist, &q->active);
 		cl->deficit = cl->quantum;
 	}
 
-	qdisc_qstats_backlog_inc(sch, skb);
+	sch->qstats.backlog += len;
 	sch->q.qlen++;
 	return err;
 }

net/sched/sch_dsmark.c

@@ -199,6 +199,7 @@ static struct tcf_block *dsmark_tcf_block(struct Qdisc *sch, unsigned long cl,
 static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 			  struct sk_buff **to_free)
 {
+	unsigned int len = qdisc_pkt_len(skb);
 	struct dsmark_qdisc_data *p = qdisc_priv(sch);
 	int err;
 
@@ -271,7 +272,7 @@ static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		return err;
 	}
 
-	qdisc_qstats_backlog_inc(sch, skb);
+	sch->qstats.backlog += len;
 	sch->q.qlen++;
 
 	return NET_XMIT_SUCCESS;

net/sched/sch_hfsc.c

@@ -1539,8 +1539,10 @@ hfsc_dump_qdisc(struct Qdisc *sch, struct sk_buff *skb)
 static int
 hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 {
+	unsigned int len = qdisc_pkt_len(skb);
 	struct hfsc_class *cl;
 	int uninitialized_var(err);
+	bool first;
 
 	cl = hfsc_classify(skb, sch, &err);
 	if (cl == NULL) {
@@ -1550,6 +1552,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 		return err;
 	}
 
+	first = !cl->qdisc->q.qlen;
 	err = qdisc_enqueue(skb, cl->qdisc, to_free);
 	if (unlikely(err != NET_XMIT_SUCCESS)) {
 		if (net_xmit_drop_count(err)) {
@@ -1559,9 +1562,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 		return err;
 	}
 
-	if (cl->qdisc->q.qlen == 1) {
-		unsigned int len = qdisc_pkt_len(skb);
-
+	if (first) {
 		if (cl->cl_flags & HFSC_RSC)
 			init_ed(cl, len);
 		if (cl->cl_flags & HFSC_FSC)
@@ -1576,7 +1577,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 
 	}
 
-	qdisc_qstats_backlog_inc(sch, skb);
+	sch->qstats.backlog += len;
 	sch->q.qlen++;
 
 	return NET_XMIT_SUCCESS;

net/sched/sch_htb.c

@@ -581,6 +581,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		       struct sk_buff **to_free)
 {
 	int uninitialized_var(ret);
+	unsigned int len = qdisc_pkt_len(skb);
 	struct htb_sched *q = qdisc_priv(sch);
 	struct htb_class *cl = htb_classify(skb, sch, &ret);
 
@@ -610,7 +611,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		htb_activate(q, cl);
 	}
 
-	qdisc_qstats_backlog_inc(sch, skb);
+	sch->qstats.backlog += len;
 	sch->q.qlen++;
 	return NET_XMIT_SUCCESS;
 }

net/sched/sch_prio.c

@@ -72,6 +72,7 @@ prio_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
 static int
 prio_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 {
+	unsigned int len = qdisc_pkt_len(skb);
 	struct Qdisc *qdisc;
 	int ret;
 
@@ -88,7 +89,7 @@ prio_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 
 	ret = qdisc_enqueue(skb, qdisc, to_free);
 	if (ret == NET_XMIT_SUCCESS) {
-		qdisc_qstats_backlog_inc(sch, skb);
+		sch->qstats.backlog += len;
 		sch->q.qlen++;
 		return NET_XMIT_SUCCESS;
 	}

net/sched/sch_qfq.c

@@ -1210,10 +1210,12 @@ static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *q)
 static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		       struct sk_buff **to_free)
 {
+	unsigned int len = qdisc_pkt_len(skb), gso_segs;
 	struct qfq_sched *q = qdisc_priv(sch);
 	struct qfq_class *cl;
 	struct qfq_aggregate *agg;
 	int err = 0;
+	bool first;
 
 	cl = qfq_classify(skb, sch, &err);
 	if (cl == NULL) {
@@ -1224,17 +1226,18 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	}
 	pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
 
-	if (unlikely(cl->agg->lmax < qdisc_pkt_len(skb))) {
+	if (unlikely(cl->agg->lmax < len)) {
 		pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
-			 cl->agg->lmax, qdisc_pkt_len(skb), cl->common.classid);
-		err = qfq_change_agg(sch, cl, cl->agg->class_weight,
-				     qdisc_pkt_len(skb));
+			 cl->agg->lmax, len, cl->common.classid);
+		err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
 		if (err) {
 			cl->qstats.drops++;
 			return qdisc_drop(skb, sch, to_free);
 		}
 	}
 
+	gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
+	first = !cl->qdisc->q.qlen;
 	err = qdisc_enqueue(skb, cl->qdisc, to_free);
 	if (unlikely(err != NET_XMIT_SUCCESS)) {
 		pr_debug("qfq_enqueue: enqueue failed %d\n", err);
@@ -1245,16 +1248,17 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		return err;
 	}
 
-	bstats_update(&cl->bstats, skb);
-	qdisc_qstats_backlog_inc(sch, skb);
+	cl->bstats.bytes += len;
+	cl->bstats.packets += gso_segs;
+	sch->qstats.backlog += len;
 	++sch->q.qlen;
 
 	agg = cl->agg;
 	/* if the queue was not empty, then done here */
-	if (cl->qdisc->q.qlen != 1) {
+	if (!first) {
 		if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
 		    list_first_entry(&agg->active, struct qfq_class, alist)
-		    == cl && cl->deficit < qdisc_pkt_len(skb))
+		    == cl && cl->deficit < len)
 			list_move_tail(&cl->alist, &agg->active);
 
 		return err;

net/sched/sch_tbf.c

@@ -185,6 +185,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		       struct sk_buff **to_free)
 {
 	struct tbf_sched_data *q = qdisc_priv(sch);
+	unsigned int len = qdisc_pkt_len(skb);
 	int ret;
 
 	if (qdisc_pkt_len(skb) > q->max_size) {
@@ -200,7 +201,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		return ret;
 	}
 
-	qdisc_qstats_backlog_inc(sch, skb);
+	sch->qstats.backlog += len;
 	sch->q.qlen++;
 	return NET_XMIT_SUCCESS;
 }