Merge branch 'htb-offload'

Maxim Mikityanskiy says:

====================
HTB offload

This series adds support for HTB offload to the HTB qdisc, and adds
usage to mlx5 driver.

The previous RFCs are available at [1], [2].

The feature is intended to solve the performance bottleneck caused by
the single lock of the HTB qdisc, which prevents it from scaling well.
The HTB algorithm itself is offloaded to the device, eliminating the
need to take the root lock of HTB on every packet. Classification part
is done in clsact (still in software) to avoid acquiring the lock, which
imposes a limitation that filters can target only leaf classes.

The speedup on Mellanox ConnectX-6 Dx was 14.2 times in the UDP
multi-stream test, compared to software HTB implementation (more details
in the mlx5 patch).

[1]: https://www.spinics.net/lists/netdev/msg628422.html
[2]: https://www.spinics.net/lists/netdev/msg663548.html

v2 changes:

Fixed sparse and smatch warnings. Formatted HTB patches to 80 chars per
line.

v3 changes:

Fixed the CI failure on parisc with 16-bit xchg by replacing it with
WRITE_ONCE. Fixed the capability bits in mlx5_ifc.h and the value of
MLX5E_QOS_MAX_LEAF_NODES.

v4 changes:

Check if HTB is root when offloading. Add extack for hardware errors.
Rephrase explanations of how it works in the commit message. Remove %hu
from format strings. Add resiliency when leaf_del_last fails to create a
new leaf node.
====================

Link: https://lore.kernel.org/r/20210119120815.463334-1-maximmi@mellanox.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 528 insertions, 29 deletions

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index cd70dbcbd72f..dff3adf5a915 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -114,6 +114,7 @@ struct htb_class {
 	 * Written often fields
 	 */
 	struct gnet_stats_basic_packed bstats;
+	struct gnet_stats_basic_packed bstats_bias;
 	struct tc_htb_xstats	xstats;	/* our special stats */
 
 	/* token bucket parameters */
@@ -174,6 +175,11 @@ struct htb_sched {
 	int			row_mask[TC_HTB_MAXDEPTH];
 
 	struct htb_level	hlevel[TC_HTB_MAXDEPTH];
+
+	struct Qdisc		**direct_qdiscs;
+	unsigned int            num_direct_qdiscs;
+
+	bool			offload;
 };
 
 /* find class in global hash table using given handle */
@@ -957,7 +963,7 @@ static void htb_reset(struct Qdisc *sch)
 			if (cl->level)
 				memset(&cl->inner, 0, sizeof(cl->inner));
 			else {
-				if (cl->leaf.q)
+				if (cl->leaf.q && !q->offload)
 					qdisc_reset(cl->leaf.q);
 			}
 			cl->prio_activity = 0;
@@ -980,6 +986,7 @@ static const struct nla_policy htb_policy[TCA_HTB_MAX + 1] = {
 	[TCA_HTB_DIRECT_QLEN] = { .type = NLA_U32 },
 	[TCA_HTB_RATE64] = { .type = NLA_U64 },
 	[TCA_HTB_CEIL64] = { .type = NLA_U64 },
+	[TCA_HTB_OFFLOAD] = { .type = NLA_FLAG },
 };
 
 static void htb_work_func(struct work_struct *work)
@@ -992,12 +999,27 @@ static void htb_work_func(struct work_struct *work)
 	rcu_read_unlock();
 }
 
+static void htb_set_lockdep_class_child(struct Qdisc *q)
+{
+	static struct lock_class_key child_key;
+
+	lockdep_set_class(qdisc_lock(q), &child_key);
+}
+
+static int htb_offload(struct net_device *dev, struct tc_htb_qopt_offload *opt)
+{
+	return dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_HTB, opt);
+}
+
 static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 		    struct netlink_ext_ack *extack)
 {
+	struct net_device *dev = qdisc_dev(sch);
+	struct tc_htb_qopt_offload offload_opt;
 	struct htb_sched *q = qdisc_priv(sch);
 	struct nlattr *tb[TCA_HTB_MAX + 1];
 	struct tc_htb_glob *gopt;
+	unsigned int ntx;
 	int err;
 
 	qdisc_watchdog_init(&q->watchdog, sch);
@@ -1022,9 +1044,26 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 	if (gopt->version != HTB_VER >> 16)
 		return -EINVAL;
 
+	q->offload = nla_get_flag(tb[TCA_HTB_OFFLOAD]);
+
+	if (q->offload) {
+		if (sch->parent != TC_H_ROOT)
+			return -EOPNOTSUPP;
+
+		if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
+			return -EOPNOTSUPP;
+
+		q->num_direct_qdiscs = dev->real_num_tx_queues;
+		q->direct_qdiscs = kcalloc(q->num_direct_qdiscs,
+					   sizeof(*q->direct_qdiscs),
+					   GFP_KERNEL);
+		if (!q->direct_qdiscs)
+			return -ENOMEM;
+	}
+
 	err = qdisc_class_hash_init(&q->clhash);
 	if (err < 0)
-		return err;
+		goto err_free_direct_qdiscs;
 
 	qdisc_skb_head_init(&q->direct_queue);
 
@@ -1037,7 +1076,107 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt,
 		q->rate2quantum = 1;
 	q->defcls = gopt->defcls;
 
+	if (!q->offload)
+		return 0;
+
+	for (ntx = 0; ntx < q->num_direct_qdiscs; ntx++) {
+		struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, ntx);
+		struct Qdisc *qdisc;
+
+		qdisc = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops,
+					  TC_H_MAKE(sch->handle, 0), extack);
+		if (!qdisc) {
+			err = -ENOMEM;
+			goto err_free_qdiscs;
+		}
+
+		htb_set_lockdep_class_child(qdisc);
+		q->direct_qdiscs[ntx] = qdisc;
+		qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
+	}
+
+	sch->flags |= TCQ_F_MQROOT;
+
+	offload_opt = (struct tc_htb_qopt_offload) {
+		.command = TC_HTB_CREATE,
+		.parent_classid = TC_H_MAJ(sch->handle) >> 16,
+		.classid = TC_H_MIN(q->defcls),
+		.extack = extack,
+	};
+	err = htb_offload(dev, &offload_opt);
+	if (err)
+		goto err_free_qdiscs;
+
 	return 0;
+
+err_free_qdiscs:
+	/* TC_HTB_CREATE call failed, avoid any further calls to the driver. */
+	q->offload = false;
+
+	for (ntx = 0; ntx < q->num_direct_qdiscs && q->direct_qdiscs[ntx];
+	     ntx++)
+		qdisc_put(q->direct_qdiscs[ntx]);
+
+	qdisc_class_hash_destroy(&q->clhash);
+	/* Prevent use-after-free and double-free when htb_destroy gets called.
+	 */
+	q->clhash.hash = NULL;
+	q->clhash.hashsize = 0;
+
+err_free_direct_qdiscs:
+	kfree(q->direct_qdiscs);
+	q->direct_qdiscs = NULL;
+	return err;
+}
+
+static void htb_attach_offload(struct Qdisc *sch)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct htb_sched *q = qdisc_priv(sch);
+	unsigned int ntx;
+
+	for (ntx = 0; ntx < q->num_direct_qdiscs; ntx++) {
+		struct Qdisc *old, *qdisc = q->direct_qdiscs[ntx];
+
+		old = dev_graft_qdisc(qdisc->dev_queue, qdisc);
+		qdisc_put(old);
+		qdisc_hash_add(qdisc, false);
+	}
+	for (ntx = q->num_direct_qdiscs; ntx < dev->num_tx_queues; ntx++) {
+		struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, ntx);
+		struct Qdisc *old = dev_graft_qdisc(dev_queue, NULL);
+
+		qdisc_put(old);
+	}
+
+	kfree(q->direct_qdiscs);
+	q->direct_qdiscs = NULL;
+}
+
+static void htb_attach_software(struct Qdisc *sch)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	unsigned int ntx;
+
+	/* Resemble qdisc_graft behavior. */
+	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
+		struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, ntx);
+		struct Qdisc *old = dev_graft_qdisc(dev_queue, sch);
+
+		qdisc_refcount_inc(sch);
+
+		qdisc_put(old);
+	}
+}
+
+static void htb_attach(struct Qdisc *sch)
+{
+	struct htb_sched *q = qdisc_priv(sch);
+
+	if (q->offload)
+		htb_attach_offload(sch);
+	else
+		htb_attach_software(sch);
 }
 
 static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
@@ -1046,6 +1185,11 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
 	struct nlattr *nest;
 	struct tc_htb_glob gopt;
 
+	if (q->offload)
+		sch->flags |= TCQ_F_OFFLOADED;
+	else
+		sch->flags &= ~TCQ_F_OFFLOADED;
+
 	sch->qstats.overlimits = q->overlimits;
 	/* Its safe to not acquire qdisc lock. As we hold RTNL,
 	 * no change can happen on the qdisc parameters.
@@ -1063,6 +1207,8 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
 	if (nla_put(skb, TCA_HTB_INIT, sizeof(gopt), &gopt) ||
 	    nla_put_u32(skb, TCA_HTB_DIRECT_QLEN, q->direct_qlen))
 		goto nla_put_failure;
+	if (q->offload && nla_put_flag(skb, TCA_HTB_OFFLOAD))
+		goto nla_put_failure;
 
 	return nla_nest_end(skb, nest);
 
@@ -1075,6 +1221,7 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
 			  struct sk_buff *skb, struct tcmsg *tcm)
 {
 	struct htb_class *cl = (struct htb_class *)arg;
+	struct htb_sched *q = qdisc_priv(sch);
 	struct nlattr *nest;
 	struct tc_htb_opt opt;
 
@@ -1101,6 +1248,8 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
 	opt.level = cl->level;
 	if (nla_put(skb, TCA_HTB_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
+	if (q->offload && nla_put_flag(skb, TCA_HTB_OFFLOAD))
+		goto nla_put_failure;
 	if ((cl->rate.rate_bytes_ps >= (1ULL << 32)) &&
 	    nla_put_u64_64bit(skb, TCA_HTB_RATE64, cl->rate.rate_bytes_ps,
 			      TCA_HTB_PAD))
@@ -1117,10 +1266,39 @@ nla_put_failure:
 	return -1;
 }
 
+static void htb_offload_aggregate_stats(struct htb_sched *q,
+					struct htb_class *cl)
+{
+	struct htb_class *c;
+	unsigned int i;
+
+	memset(&cl->bstats, 0, sizeof(cl->bstats));
+
+	for (i = 0; i < q->clhash.hashsize; i++) {
+		hlist_for_each_entry(c, &q->clhash.hash[i], common.hnode) {
+			struct htb_class *p = c;
+
+			while (p && p->level < cl->level)
+				p = p->parent;
+
+			if (p != cl)
+				continue;
+
+			cl->bstats.bytes += c->bstats_bias.bytes;
+			cl->bstats.packets += c->bstats_bias.packets;
+			if (c->level == 0) {
+				cl->bstats.bytes += c->leaf.q->bstats.bytes;
+				cl->bstats.packets += c->leaf.q->bstats.packets;
+			}
+		}
+	}
+}
+
 static int
 htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
 {
 	struct htb_class *cl = (struct htb_class *)arg;
+	struct htb_sched *q = qdisc_priv(sch);
 	struct gnet_stats_queue qs = {
 		.drops = cl->drops,
 		.overlimits = cl->overlimits,
@@ -1135,6 +1313,19 @@ htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
 	cl->xstats.ctokens = clamp_t(s64, PSCHED_NS2TICKS(cl->ctokens),
 				     INT_MIN, INT_MAX);
 
+	if (q->offload) {
+		if (!cl->level) {
+			if (cl->leaf.q)
+				cl->bstats = cl->leaf.q->bstats;
+			else
+				memset(&cl->bstats, 0, sizeof(cl->bstats));
+			cl->bstats.bytes += cl->bstats_bias.bytes;
+			cl->bstats.packets += cl->bstats_bias.packets;
+		} else {
+			htb_offload_aggregate_stats(q, cl);
+		}
+	}
+
 	if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
 				  d, NULL, &cl->bstats) < 0 ||
 	    gnet_stats_copy_rate_est(d, &cl->rate_est) < 0 ||
@@ -1144,19 +1335,97 @@ htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
 	return gnet_stats_copy_app(d, &cl->xstats, sizeof(cl->xstats));
 }
 
+static struct netdev_queue *
+htb_select_queue(struct Qdisc *sch, struct tcmsg *tcm)
+{
+	struct net_device *dev = qdisc_dev(sch);
+	struct tc_htb_qopt_offload offload_opt;
+	int err;
+
+	offload_opt = (struct tc_htb_qopt_offload) {
+		.command = TC_HTB_LEAF_QUERY_QUEUE,
+		.classid = TC_H_MIN(tcm->tcm_parent),
+	};
+	err = htb_offload(dev, &offload_opt);
+	if (err || offload_opt.qid >= dev->num_tx_queues)
+		return NULL;
+	return netdev_get_tx_queue(dev, offload_opt.qid);
+}
+
+static struct Qdisc *
+htb_graft_helper(struct netdev_queue *dev_queue, struct Qdisc *new_q)
+{
+	struct net_device *dev = dev_queue->dev;
+	struct Qdisc *old_q;
+
+	if (dev->flags & IFF_UP)
+		dev_deactivate(dev);
+	old_q = dev_graft_qdisc(dev_queue, new_q);
+	if (new_q)
+		new_q->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
+	if (dev->flags & IFF_UP)
+		dev_activate(dev);
+
+	return old_q;
+}
+
+static void htb_offload_move_qdisc(struct Qdisc *sch, u16 qid_old, u16 qid_new)
+{
+	struct netdev_queue *queue_old, *queue_new;
+	struct net_device *dev = qdisc_dev(sch);
+	struct Qdisc *qdisc;
+
+	queue_old = netdev_get_tx_queue(dev, qid_old);
+	queue_new = netdev_get_tx_queue(dev, qid_new);
+
+	if (dev->flags & IFF_UP)
+		dev_deactivate(dev);
+	qdisc = dev_graft_qdisc(queue_old, NULL);
+	qdisc->dev_queue = queue_new;
+	qdisc = dev_graft_qdisc(queue_new, qdisc);
+	if (dev->flags & IFF_UP)
+		dev_activate(dev);
+
+	WARN_ON(!(qdisc->flags & TCQ_F_BUILTIN));
+}
+
 static int htb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 		     struct Qdisc **old, struct netlink_ext_ack *extack)
 {
+	struct netdev_queue *dev_queue = sch->dev_queue;
 	struct htb_class *cl = (struct htb_class *)arg;
+	struct htb_sched *q = qdisc_priv(sch);
+	struct Qdisc *old_q;
 
 	if (cl->level)
 		return -EINVAL;
-	if (new == NULL &&
-	    (new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
-				     cl->common.classid, extack)) == NULL)
-		return -ENOBUFS;
+
+	if (q->offload) {
+		dev_queue = new->dev_queue;
+		WARN_ON(dev_queue != cl->leaf.q->dev_queue);
+	}
+
+	if (!new) {
+		new = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops,
+					cl->common.classid, extack);
+		if (!new)
+			return -ENOBUFS;
+	}
+
+	if (q->offload) {
+		htb_set_lockdep_class_child(new);
+		/* One ref for cl->leaf.q, the other for dev_queue->qdisc. */
+		qdisc_refcount_inc(new);
+		old_q = htb_graft_helper(dev_queue, new);
+	}
 
 	*old = qdisc_replace(sch, new, &cl->leaf.q);
+
+	if (q->offload) {
+		WARN_ON(old_q != *old);
+		qdisc_put(old_q);
+	}
+
 	return 0;
 }
 
@@ -1184,9 +1453,10 @@ static inline int htb_parent_last_child(struct htb_class *cl)
 	return 1;
 }
 
-static void htb_parent_to_leaf(struct htb_sched *q, struct htb_class *cl,
+static void htb_parent_to_leaf(struct Qdisc *sch, struct htb_class *cl,
 			       struct Qdisc *new_q)
 {
+	struct htb_sched *q = qdisc_priv(sch);
 	struct htb_class *parent = cl->parent;
 
 	WARN_ON(cl->level || !cl->leaf.q || cl->prio_activity);
@@ -1204,6 +1474,76 @@ static void htb_parent_to_leaf(struct htb_sched *q, struct htb_class *cl,
 	parent->cmode = HTB_CAN_SEND;
 }
 
+static void htb_parent_to_leaf_offload(struct Qdisc *sch,
+				       struct netdev_queue *dev_queue,
+				       struct Qdisc *new_q)
+{
+	struct Qdisc *old_q;
+
+	/* One ref for cl->leaf.q, the other for dev_queue->qdisc. */
+	qdisc_refcount_inc(new_q);
+	old_q = htb_graft_helper(dev_queue, new_q);
+	WARN_ON(!(old_q->flags & TCQ_F_BUILTIN));
+}
+
+static int htb_destroy_class_offload(struct Qdisc *sch, struct htb_class *cl,
+				     bool last_child, bool destroying,
+				     struct netlink_ext_ack *extack)
+{
+	struct tc_htb_qopt_offload offload_opt;
+	struct Qdisc *q = cl->leaf.q;
+	struct Qdisc *old = NULL;
+	int err;
+
+	if (cl->level)
+		return -EINVAL;
+
+	WARN_ON(!q);
+	if (!destroying) {
+		/* On destroy of HTB, two cases are possible:
+		 * 1. q is a normal qdisc, but q->dev_queue has noop qdisc.
+		 * 2. q is a noop qdisc (for nodes that were inner),
+		 *    q->dev_queue is noop_netdev_queue.
+		 */
+		old = htb_graft_helper(q->dev_queue, NULL);
+		WARN_ON(!old);
+		WARN_ON(old != q);
+	}
+
+	if (cl->parent) {
+		cl->parent->bstats_bias.bytes += q->bstats.bytes;
+		cl->parent->bstats_bias.packets += q->bstats.packets;
+	}
+
+	offload_opt = (struct tc_htb_qopt_offload) {
+		.command = !last_child ? TC_HTB_LEAF_DEL :
+			   destroying ? TC_HTB_LEAF_DEL_LAST_FORCE :
+			   TC_HTB_LEAF_DEL_LAST,
+		.classid = cl->common.classid,
+		.extack = extack,
+	};
+	err = htb_offload(qdisc_dev(sch), &offload_opt);
+
+	if (!err || destroying)
+		qdisc_put(old);
+	else
+		htb_graft_helper(q->dev_queue, old);
+
+	if (last_child)
+		return err;
+
+	if (!err && offload_opt.moved_qid != 0) {
+		if (destroying)
+			q->dev_queue = netdev_get_tx_queue(qdisc_dev(sch),
+							   offload_opt.qid);
+		else
+			htb_offload_move_qdisc(sch, offload_opt.moved_qid,
+					       offload_opt.qid);
+	}
+
+	return err;
+}
+
 static void htb_destroy_class(struct Qdisc *sch, struct htb_class *cl)
 {
 	if (!cl->level) {
@@ -1217,8 +1557,11 @@ static void htb_destroy_class(struct Qdisc *sch, struct htb_class *cl)
 
 static void htb_destroy(struct Qdisc *sch)
 {
+	struct net_device *dev = qdisc_dev(sch);
+	struct tc_htb_qopt_offload offload_opt;
 	struct htb_sched *q = qdisc_priv(sch);
 	struct hlist_node *next;
+	bool nonempty, changed;
 	struct htb_class *cl;
 	unsigned int i;
 
@@ -1237,21 +1580,68 @@ static void htb_destroy(struct Qdisc *sch)
 			cl->block = NULL;
 		}
 	}
-	for (i = 0; i < q->clhash.hashsize; i++) {
-		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
-					  common.hnode)
-			htb_destroy_class(sch, cl);
-	}
+
+	do {
+		nonempty = false;
+		changed = false;
+		for (i = 0; i < q->clhash.hashsize; i++) {
+			hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
+						  common.hnode) {
+				bool last_child;
+
+				if (!q->offload) {
+					htb_destroy_class(sch, cl);
+					continue;
+				}
+
+				nonempty = true;
+
+				if (cl->level)
+					continue;
+
+				changed = true;
+
+				last_child = htb_parent_last_child(cl);
+				htb_destroy_class_offload(sch, cl, last_child,
+							  true, NULL);
+				qdisc_class_hash_remove(&q->clhash,
+							&cl->common);
+				if (cl->parent)
+					cl->parent->children--;
+				if (last_child)
+					htb_parent_to_leaf(sch, cl, NULL);
+				htb_destroy_class(sch, cl);
+			}
+		}
+	} while (changed);
+	WARN_ON(nonempty);
+
 	qdisc_class_hash_destroy(&q->clhash);
 	__qdisc_reset_queue(&q->direct_queue);
+
+	if (!q->offload)
+		return;
+
+	offload_opt = (struct tc_htb_qopt_offload) {
+		.command = TC_HTB_DESTROY,
+	};
+	htb_offload(dev, &offload_opt);
+
+	if (!q->direct_qdiscs)
+		return;
+	for (i = 0; i < q->num_direct_qdiscs && q->direct_qdiscs[i]; i++)
+		qdisc_put(q->direct_qdiscs[i]);
+	kfree(q->direct_qdiscs);
 }
 
-static int htb_delete(struct Qdisc *sch, unsigned long arg)
+static int htb_delete(struct Qdisc *sch, unsigned long arg,
+		      struct netlink_ext_ack *extack)
 {
 	struct htb_sched *q = qdisc_priv(sch);
 	struct htb_class *cl = (struct htb_class *)arg;
 	struct Qdisc *new_q = NULL;
 	int last_child = 0;
+	int err;
 
 	/* TODO: why don't allow to delete subtree ? references ? does
 	 * tc subsys guarantee us that in htb_destroy it holds no class
@@ -1260,11 +1650,28 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
 	if (cl->children || cl->filter_cnt)
 		return -EBUSY;
 
-	if (!cl->level && htb_parent_last_child(cl)) {
-		new_q = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
+	if (!cl->level && htb_parent_last_child(cl))
+		last_child = 1;
+
+	if (q->offload) {
+		err = htb_destroy_class_offload(sch, cl, last_child, false,
+						extack);
+		if (err)
+			return err;
+	}
+
+	if (last_child) {
+		struct netdev_queue *dev_queue;
+
+		dev_queue = q->offload ? cl->leaf.q->dev_queue : sch->dev_queue;
+		new_q = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops,
 					  cl->parent->common.classid,
 					  NULL);
-		last_child = 1;
+		if (q->offload) {
+			if (new_q)
+				htb_set_lockdep_class_child(new_q);
+			htb_parent_to_leaf_offload(sch, dev_queue, new_q);
+		}
 	}
 
 	sch_tree_lock(sch);
@@ -1285,7 +1692,7 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
 				  &q->hlevel[cl->level].wait_pq);
 
 	if (last_child)
-		htb_parent_to_leaf(q, cl, new_q);
+		htb_parent_to_leaf(sch, cl, new_q);
 
 	sch_tree_unlock(sch);
 
@@ -1300,9 +1707,11 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 	int err = -EINVAL;
 	struct htb_sched *q = qdisc_priv(sch);
 	struct htb_class *cl = (struct htb_class *)*arg, *parent;
+	struct tc_htb_qopt_offload offload_opt;
 	struct nlattr *opt = tca[TCA_OPTIONS];
 	struct nlattr *tb[TCA_HTB_MAX + 1];
 	struct Qdisc *parent_qdisc = NULL;
+	struct netdev_queue *dev_queue;
 	struct tc_htb_opt *hopt;
 	u64 rate64, ceil64;
 	int warn = 0;
@@ -1335,8 +1744,12 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 		qdisc_put_rtab(qdisc_get_rtab(&hopt->ceil, tb[TCA_HTB_CTAB],
 					      NULL));
 
+	rate64 = tb[TCA_HTB_RATE64] ? nla_get_u64(tb[TCA_HTB_RATE64]) : 0;
+	ceil64 = tb[TCA_HTB_CEIL64] ? nla_get_u64(tb[TCA_HTB_CEIL64]) : 0;
+
 	if (!cl) {		/* new class */
-		struct Qdisc *new_q;
+		struct net_device *dev = qdisc_dev(sch);
+		struct Qdisc *new_q, *old_q;
 		int prio;
 		struct {
 			struct nlattr		nla;
@@ -1379,11 +1792,8 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 						NULL,
 						qdisc_root_sleeping_running(sch),
 						tca[TCA_RATE] ? : &est.nla);
-			if (err) {
-				tcf_block_put(cl->block);
-				kfree(cl);
-				goto failure;
-			}
+			if (err)
+				goto err_block_put;
 		}
 
 		cl->children = 0;
@@ -1392,12 +1802,76 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 		for (prio = 0; prio < TC_HTB_NUMPRIO; prio++)
 			RB_CLEAR_NODE(&cl->node[prio]);
 
+		cl->common.classid = classid;
+
+		/* Make sure nothing interrupts us in between of two
+		 * ndo_setup_tc calls.
+		 */
+		ASSERT_RTNL();
+
 		/* create leaf qdisc early because it uses kmalloc(GFP_KERNEL)
 		 * so that can't be used inside of sch_tree_lock
 		 * -- thanks to Karlis Peisenieks
 		 */
-		new_q = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
+		if (!q->offload) {
+			dev_queue = sch->dev_queue;
+		} else if (!(parent && !parent->level)) {
+			/* Assign a dev_queue to this classid. */
+			offload_opt = (struct tc_htb_qopt_offload) {
+				.command = TC_HTB_LEAF_ALLOC_QUEUE,
+				.classid = cl->common.classid,
+				.parent_classid = parent ?
+					TC_H_MIN(parent->common.classid) :
+					TC_HTB_CLASSID_ROOT,
+				.rate = max_t(u64, hopt->rate.rate, rate64),
+				.ceil = max_t(u64, hopt->ceil.rate, ceil64),
+				.extack = extack,
+			};
+			err = htb_offload(dev, &offload_opt);
+			if (err) {
+				pr_err("htb: TC_HTB_LEAF_ALLOC_QUEUE failed with err = %d\n",
+				       err);
+				goto err_kill_estimator;
+			}
+			dev_queue = netdev_get_tx_queue(dev, offload_opt.qid);
+		} else { /* First child. */
+			dev_queue = parent->leaf.q->dev_queue;
+			old_q = htb_graft_helper(dev_queue, NULL);
+			WARN_ON(old_q != parent->leaf.q);
+			offload_opt = (struct tc_htb_qopt_offload) {
+				.command = TC_HTB_LEAF_TO_INNER,
+				.classid = cl->common.classid,
+				.parent_classid =
+					TC_H_MIN(parent->common.classid),
+				.rate = max_t(u64, hopt->rate.rate, rate64),
+				.ceil = max_t(u64, hopt->ceil.rate, ceil64),
+				.extack = extack,
+			};
+			err = htb_offload(dev, &offload_opt);
+			if (err) {
+				pr_err("htb: TC_HTB_LEAF_TO_INNER failed with err = %d\n",
+				       err);
+				htb_graft_helper(dev_queue, old_q);
+				goto err_kill_estimator;
+			}
+			parent->bstats_bias.bytes += old_q->bstats.bytes;
+			parent->bstats_bias.packets += old_q->bstats.packets;
+			qdisc_put(old_q);
+		}
+		new_q = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops,
 					  classid, NULL);
+		if (q->offload) {
+			if (new_q) {
+				htb_set_lockdep_class_child(new_q);
+				/* One ref for cl->leaf.q, the other for
+				 * dev_queue->qdisc.
+				 */
+				qdisc_refcount_inc(new_q);
+			}
+			old_q = htb_graft_helper(dev_queue, new_q);
+			/* No qdisc_put needed. */
+			WARN_ON(!(old_q->flags & TCQ_F_BUILTIN));
+		}
 		sch_tree_lock(sch);
 		if (parent && !parent->level) {
 			/* turn parent into inner node */
@@ -1415,10 +1889,10 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 					 : TC_HTB_MAXDEPTH) - 1;
 			memset(&parent->inner, 0, sizeof(parent->inner));
 		}
+
 		/* leaf (we) needs elementary qdisc */
 		cl->leaf.q = new_q ? new_q : &noop_qdisc;
 
-		cl->common.classid = classid;
 		cl->parent = parent;
 
 		/* set class to be in HTB_CAN_SEND state */
@@ -1444,12 +1918,30 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 			if (err)
 				return err;
 		}
-		sch_tree_lock(sch);
-	}
 
-	rate64 = tb[TCA_HTB_RATE64] ? nla_get_u64(tb[TCA_HTB_RATE64]) : 0;
+		if (q->offload) {
+			struct net_device *dev = qdisc_dev(sch);
+
+			offload_opt = (struct tc_htb_qopt_offload) {
+				.command = TC_HTB_NODE_MODIFY,
+				.classid = cl->common.classid,
+				.rate = max_t(u64, hopt->rate.rate, rate64),
+				.ceil = max_t(u64, hopt->ceil.rate, ceil64),
+				.extack = extack,
+			};
+			err = htb_offload(dev, &offload_opt);
+			if (err)
+				/* Estimator was replaced, and rollback may fail
+				 * as well, so we don't try to recover it, and
+				 * the estimator won't work property with the
+				 * offload anyway, because bstats are updated
+				 * only when the stats are queried.
+				 */
+				return err;
+		}
 
-	ceil64 = tb[TCA_HTB_CEIL64] ? nla_get_u64(tb[TCA_HTB_CEIL64]) : 0;
+		sch_tree_lock(sch);
+	}
 
 	psched_ratecfg_precompute(&cl->rate, &hopt->rate, rate64);
 	psched_ratecfg_precompute(&cl->ceil, &hopt->ceil, ceil64);
@@ -1492,6 +1984,11 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 	*arg = (unsigned long)cl;
 	return 0;
 
+err_kill_estimator:
+	gen_kill_estimator(&cl->rate_est);
+err_block_put:
+	tcf_block_put(cl->block);
+	kfree(cl);
 failure:
 	return err;
 }
@@ -1557,6 +2054,7 @@ static void htb_walk(struct Qdisc *sch, struct qdisc_walker *arg)
 }
 
 static const struct Qdisc_class_ops htb_class_ops = {
+	.select_queue	=	htb_select_queue,
 	.graft		=	htb_graft,
 	.leaf		=	htb_leaf,
 	.qlen_notify	=	htb_qlen_notify,
@@ -1579,6 +2077,7 @@ static struct Qdisc_ops htb_qdisc_ops __read_mostly = {
 	.dequeue	=	htb_dequeue,
 	.peek		=	qdisc_peek_dequeued,
 	.init		=	htb_init,
+	.attach		=	htb_attach,
 	.reset		=	htb_reset,
 	.destroy	=	htb_destroy,
 	.dump		=	htb_dump,