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* [PATCH net-next V2] net: sched: fallback to qdisc noqueue if default qdisc setup fail
@ 2020-04-30 11:42 Jesper Dangaard Brouer
  2020-04-30 19:45 ` Jakub Kicinski
  2020-05-04 18:51 ` David Miller
  0 siblings, 2 replies; 5+ messages in thread
From: Jesper Dangaard Brouer @ 2020-04-30 11:42 UTC (permalink / raw)
  To: netdev
  Cc: Jesper Dangaard Brouer, Jakub Kicinski, Stephen Hemminger,
	David Ahern

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.

V2:
As this also captures memory failures, which are transient, the
device is not kept in IFF_NO_QUEUE state.  This allows the net_device
to retry to default qdisc assignment.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 net/sched/sch_generic.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 2efd5b61acef..ad24fa1a51e6 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;
@@ -1065,6 +1064,18 @@ 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;
+		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
+		dev->qdisc = txq->qdisc_sleeping;
+		qdisc_refcount_inc(dev->qdisc);
+		dev->priv_flags ^= IFF_NO_QUEUE;
+	}
+
 #ifdef CONFIG_NET_SCHED
 	if (dev->qdisc != &noop_qdisc)
 		qdisc_hash_add(dev->qdisc, false);



^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-05-04 18:51 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-04-30 11:42 [PATCH net-next V2] net: sched: fallback to qdisc noqueue if default qdisc setup fail Jesper Dangaard Brouer
2020-04-30 19:45 ` Jakub Kicinski
2020-05-01 11:56   ` Jesper Dangaard Brouer
2020-05-01 19:01     ` Jakub Kicinski
2020-05-04 18:51 ` David Miller

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