[net-next] net: sched: fallback to qdisc noqueue if default qdisc setup fail

Message ID 158807197021.1980046.17172496536132159811.stgit@firesoul
State New
Headers show
Series
  • [net-next] net: sched: fallback to qdisc noqueue if default qdisc setup fail
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Commit Message

Jesper Dangaard Brouer April 28, 2020, 11:06 a.m.
Currently if the default qdisc setup/init fails, the device ends up with
qdisc "noop", which causes all TX packets to get dropped.

With the introduction of sysctl net/core/default_qdisc it is possible
to change the default qdisc to be more advanced, which opens for the
possibility that Qdisc_ops->init() can fail.

This patch detect these kind of failures, and choose to fallback to
qdisc "noqueue", which is so simple that its init call will not fail.
This allows the interface to continue functioning.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 net/sched/sch_generic.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Patch

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 2efd5b61acef..275b1347265e 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1037,10 +1037,9 @@  static void attach_one_default_qdisc(struct net_device *dev,
 		ops = &pfifo_fast_ops;
 
 	qdisc = qdisc_create_dflt(dev_queue, ops, TC_H_ROOT, NULL);
-	if (!qdisc) {
-		netdev_info(dev, "activation failed\n");
+	if (!qdisc)
 		return;
-	}
+
 	if (!netif_is_multiqueue(dev))
 		qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
 	dev_queue->qdisc_sleeping = qdisc;
@@ -1055,6 +1054,7 @@  static void attach_default_qdiscs(struct net_device *dev)
 
 	if (!netif_is_multiqueue(dev) ||
 	    dev->priv_flags & IFF_NO_QUEUE) {
+init_each_txq:
 		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
 		dev->qdisc = txq->qdisc_sleeping;
 		qdisc_refcount_inc(dev->qdisc);
@@ -1065,6 +1065,15 @@  static void attach_default_qdiscs(struct net_device *dev)
 			qdisc->ops->attach(qdisc);
 		}
 	}
+
+	/* Detect default qdisc setup/init failed and fallback to "noqueue" */
+	if (dev->qdisc == &noop_qdisc) {
+		netdev_warn(dev, "default qdisc (%s) fail, fallback to %s\n",
+			    default_qdisc_ops->id, noqueue_qdisc_ops.id);
+		dev->priv_flags |= IFF_NO_QUEUE;
+		goto init_each_txq;
+	}
+
 #ifdef CONFIG_NET_SCHED
 	if (dev->qdisc != &noop_qdisc)
 		qdisc_hash_add(dev->qdisc, false);