[PATCH 5.13 255/300] sch_htb: Fix inconsistency when leaf qdisc creation fails

Greg Kroah-Hartman
2021-09-13T14:17:43Z

From: Maxim Mikityanskiy <maximmi@nvidia.com>

[ Upstream commit ca49bfd90a9dde175d2929dc1544b54841e33804 ]

In HTB offload mode, qdiscs of leaf classes are grafted to netdev
queues. sch_htb expects the dev_queue field of these qdiscs to point to
the corresponding queues. However, qdisc creation may fail, and in that
case noop_qdisc is used instead. Its dev_queue doesn't point to the
right queue, so sch_htb can lose track of used netdev queues, which will
cause internal inconsistencies.

This commit fixes this bug by keeping track of the netdev queue inside
struct htb_class. All reads of cl->leaf.q->dev_queue are replaced by the
new field, the two values are synced on writes, and WARNs are added to
assert equality of the two values.

The driver API has changed: when TC_HTB_LEAF_DEL needs to move a queue,
the driver used to pass the old and new queue IDs to sch_htb. Now that
there is a new field (offload_queue) in struct htb_class that needs to
be updated on this operation, the driver will pass the old class ID to
sch_htb instead (it already knows the new class ID).

Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20210826115425.1744053-1-maximmi@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../net/ethernet/mellanox/mlx5/core/en/qos.c | 15 ++-
.../net/ethernet/mellanox/mlx5/core/en/qos.h | 4 +-
.../net/ethernet/mellanox/mlx5/core/en_main.c | 3 +-
include/net/pkt_cls.h | 3 +-
net/sched/sch_htb.c | 97 ++++++++++++-------
5 files changed, 72 insertions(+), 50 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
index 5efe3278b0f6..1fd8baf19829 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
@@ -733,8 +733,8 @@ static void mlx5e_reset_qdisc(struct net_device *dev, u16 qid)
spin_unlock_bh(qdisc_lock(qdisc));
}

-int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 classid, u16 *old_qid,
- u16 *new_qid, struct netlink_ext_ack *extack)
+int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 *classid,
+ struct netlink_ext_ack *extack)
{
struct mlx5e_qos_node *node;
struct netdev_queue *txq;
@@ -742,11 +742,9 @@ int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 classid, u16 *old_qid,
bool opened;
int err;

- qos_dbg(priv->mdev, "TC_HTB_LEAF_DEL classid %04x\n", classid);
-
- *old_qid = *new_qid = 0;
+ qos_dbg(priv->mdev, "TC_HTB_LEAF_DEL classid %04x\n", *classid);

- node = mlx5e_sw_node_find(priv, classid);
+ node = mlx5e_sw_node_find(priv, *classid);
if (!node)
return -ENOENT;

@@ -764,7 +762,7 @@ int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 classid, u16 *old_qid,
err = mlx5_qos_destroy_node(priv->mdev, node->hw_id);
if (err) /* Not fatal. */
qos_warn(priv->mdev, "Failed to destroy leaf node %u (class %04x), err = %d\n",
- node->hw_id, classid, err);
+ node->hw_id, *classid, err);

mlx5e_sw_node_delete(priv, node);

@@ -826,8 +824,7 @@ int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 classid, u16 *old_qid,
if (opened)
mlx5e_reactivate_qos_sq(priv, moved_qid, txq);

- *old_qid = mlx5e_qid_from_qos(&priv->channels, moved_qid);
- *new_qid = mlx5e_qid_from_qos(&priv->channels, qid);
+ *classid = node->classid;
return 0;
}

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.h b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.h
index 5af7991fcd19..757682b7c0e0 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.h
@@ -34,8 +34,8 @@ int mlx5e_htb_leaf_alloc_queue(struct mlx5e_priv *priv, u16 classid,
struct netlink_ext_ack *extack);
int mlx5e_htb_leaf_to_inner(struct mlx5e_priv *priv, u16 classid, u16 child_classid,
u64 rate, u64 ceil, struct netlink_ext_ack *extack);
-int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 classid, u16 *old_qid,
- u16 *new_qid, struct netlink_ext_ack *extack);
+int mlx5e_htb_leaf_del(struct mlx5e_priv *priv, u16 *classid,
+ struct netlink_ext_ack *extack);
int mlx5e_htb_leaf_del_last(struct mlx5e_priv *priv, u16 classid, bool force,
struct netlink_ext_ack *extack);
int mlx5e_htb_node_modify(struct mlx5e_priv *priv, u16 classid, u64 rate, u64 ceil,
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index b0424c36cf7f..814ff51db1a5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3447,8 +3447,7 @@ static int mlx5e_setup_tc_htb(struct mlx5e_priv *priv, struct tc_htb_qopt_offloa
return mlx5e_htb_leaf_to_inner(priv, htb->parent_classid, htb->classid,
htb->rate, htb->ceil, htb->extack);
case TC_HTB_LEAF_DEL:
- return mlx5e_htb_leaf_del(priv, htb->classid, &htb->moved_qid, &htb->qid,
- htb->extack);
+ return mlx5e_htb_leaf_del(priv, &htb->classid, htb->extack);
case TC_HTB_LEAF_DEL_LAST:
case TC_HTB_LEAF_DEL_LAST_FORCE:
return mlx5e_htb_leaf_del_last(priv, htb->classid,
diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index ec7823921bd2..b420f905f4f6 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -820,10 +820,9 @@ enum tc_htb_command {
struct tc_htb_qopt_offload {
struct netlink_ext_ack *extack;
enum tc_htb_command command;
- u16 classid;
u32 parent_classid;
+ u16 classid;
u16 qid;
- u16 moved_qid;
u64 rate;
u64 ceil;
};
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 8827987ba903..11bc6bf35f84 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -125,6 +125,7 @@ struct htb_class {
struct htb_class_leaf {
int deficit[TC_HTB_MAXDEPTH];
struct Qdisc *q;
+ struct netdev_queue *offload_queue;
} leaf;
struct htb_class_inner {
struct htb_prio clprio[TC_HTB_NUMPRIO];
@@ -1376,24 +1377,47 @@ htb_graft_helper(struct netdev_queue *dev_queue, struct Qdisc *new_q)
return old_q;
}

-static void htb_offload_move_qdisc(struct Qdisc *sch, u16 qid_old, u16 qid_new)
+static struct netdev_queue *htb_offload_get_queue(struct htb_class *cl)
+{
+ struct netdev_queue *queue;
+
+ queue = cl->leaf.offload_queue;
+ if (!(cl->leaf.q->flags & TCQ_F_BUILTIN))
+ WARN_ON(cl->leaf.q->dev_queue != queue);
+
+ return queue;
+}
+
+static void htb_offload_move_qdisc(struct Qdisc *sch, struct htb_class *cl_old,
+ struct htb_class *cl_new, bool destroying)
{
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);
+ queue_old = htb_offload_get_queue(cl_old);
+ queue_new = htb_offload_get_queue(cl_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);
+ if (!destroying) {
+ struct Qdisc *qdisc;

- WARN_ON(!(qdisc->flags & TCQ_F_BUILTIN));
+ if (dev->flags & IFF_UP)
+ dev_deactivate(dev);
+ qdisc = dev_graft_qdisc(queue_old, NULL);
+ WARN_ON(qdisc != cl_old->leaf.q);
+ }
+
+ if (!(cl_old->leaf.q->flags & TCQ_F_BUILTIN))
+ cl_old->leaf.q->dev_queue = queue_new;
+ cl_old->leaf.offload_queue = queue_new;
+
+ if (!destroying) {
+ struct Qdisc *qdisc;
+
+ qdisc = dev_graft_qdisc(queue_new, cl_old->leaf.q);
+ 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,
@@ -1407,10 +1431,8 @@ static int htb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
if (cl->level)
return -EINVAL;

- if (q->offload) {
- dev_queue = new->dev_queue;
- WARN_ON(dev_queue != cl->leaf.q->dev_queue);
- }
+ if (q->offload)
+ dev_queue = htb_offload_get_queue(cl);

if (!new) {
new = qdisc_create_dflt(dev_queue, &pfifo_qdisc_ops,
@@ -1479,6 +1501,8 @@ static void htb_parent_to_leaf(struct Qdisc *sch, struct htb_class *cl,
parent->ctokens = parent->cbuffer;
parent->t_c = ktime_get_ns();
parent->cmode = HTB_CAN_SEND;
+ if (q->offload)
+ parent->leaf.offload_queue = cl->leaf.offload_queue;
}

static void htb_parent_to_leaf_offload(struct Qdisc *sch,
@@ -1499,6 +1523,7 @@ static int htb_destroy_class_offload(struct Qdisc *sch, struct htb_class *cl,
struct netlink_ext_ack *extack)
{
struct tc_htb_qopt_offload offload_opt;
+ struct netdev_queue *dev_queue;
struct Qdisc *q = cl->leaf.q;
struct Qdisc *old = NULL;
int err;
@@ -1507,16 +1532,15 @@ static int htb_destroy_class_offload(struct Qdisc *sch, struct htb_class *cl,
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.
+ dev_queue = htb_offload_get_queue(cl);
+ old = htb_graft_helper(dev_queue, NULL);
+ if (destroying)
+ /* Before HTB is destroyed, the kernel grafts noop_qdisc to
+ * all queues.
*/
- old = htb_graft_helper(q->dev_queue, NULL);
- WARN_ON(!old);
+ WARN_ON(!(old->flags & TCQ_F_BUILTIN));
+ else
WARN_ON(old != q);
- }

if (cl->parent) {
cl->parent->bstats_bias.bytes += q->bstats.bytes;
@@ -1535,18 +1559,17 @@ static int htb_destroy_class_offload(struct Qdisc *sch, struct htb_class *cl,
if (!err || destroying)
qdisc_put(old);
else
- htb_graft_helper(q->dev_queue, old);
+ htb_graft_helper(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);
+ if (!err && offload_opt.classid != TC_H_MIN(cl->common.classid)) {
+ u32 classid = TC_H_MAJ(sch->handle) |
+ TC_H_MIN(offload_opt.classid);
+ struct htb_class *moved_cl = htb_find(classid, sch);
+
+ htb_offload_move_qdisc(sch, moved_cl, cl, destroying);
}

return err;
@@ -1669,9 +1692,11 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg,
}

if (last_child) {
- struct netdev_queue *dev_queue;
+ struct netdev_queue *dev_queue = sch->dev_queue;
+
+ if (q->offload)
+ dev_queue = htb_offload_get_queue(cl);

- 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);
@@ -1843,7 +1868,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
}
dev_queue = netdev_get_tx_queue(dev, offload_opt.qid);
} else { /* First child. */
- dev_queue = parent->leaf.q->dev_queue;
+ dev_queue = htb_offload_get_queue(parent);
old_q = htb_graft_helper(dev_queue, NULL);
WARN_ON(old_q != parent->leaf.q);
offload_opt = (struct tc_htb_qopt_offload) {
@@ -1900,6 +1925,8 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,

/* leaf (we) needs elementary qdisc */
cl->leaf.q = new_q ? new_q : &noop_qdisc;
+ if (q->offload)
+ cl->leaf.offload_queue = dev_queue;

cl->parent = parent;

--
2.30.2