[PATCH net-next] net: sched: revert tx_queue_len on partial qdisc resize failure

[Adriano Cordova]

Pass the old length to dev_qdisc_change_tx_queue_len() and, when a queue
fails to resize, use it to restore the queues already handled.

Fixes: 48bfd55e7e41 ("net_sched: plug in qdisc ops change_tx_queue_len")
Signed-off-by: Adriano Cordova <adrianox@xxxxxxxxx>
---
 include/net/sch_generic.h |  2 +-
 net/core/dev.c            |  2 +-
 net/sched/sch_generic.c   | 15 +++++++++------
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index f35bd06a6bad..0ce97b4b2da1 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -720,7 +720,7 @@ void qdisc_class_hash_remove(struct Qdisc_class_hash *,
 void qdisc_class_hash_grow(struct Qdisc *, struct Qdisc_class_hash *);
 void qdisc_class_hash_destroy(struct Qdisc_class_hash *);
 
-int dev_qdisc_change_tx_queue_len(struct net_device *dev);
+int dev_qdisc_change_tx_queue_len(struct net_device *dev, unsigned int old_len);
 void dev_qdisc_change_real_num_tx(struct net_device *dev,
 				  unsigned int new_real_tx);
 void dev_init_scheduler(struct net_device *dev);
diff --git a/net/core/dev.c b/net/core/dev.c
index f660fccfc0db..57e1fa320d53 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10002,7 +10002,7 @@ int netif_change_tx_queue_len(struct net_device *dev, unsigned long new_len)
 		res = notifier_to_errno(res);
 		if (res)
 			goto err_rollback;
-		res = dev_qdisc_change_tx_queue_len(dev);
+		res = dev_qdisc_change_tx_queue_len(dev, orig_len);
 		if (res)
 			goto err_rollback;
 	}
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 6f6a6f0d5eb0..8fd0fce23cc4 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1422,13 +1422,14 @@ void dev_deactivate(struct net_device *dev, bool reset_needed)
 EXPORT_SYMBOL(dev_deactivate);
 
 static int qdisc_change_tx_queue_len(struct net_device *dev,
-				     struct netdev_queue *dev_queue)
+				     struct netdev_queue *dev_queue,
+				     unsigned int len)
 {
 	struct Qdisc *qdisc = rtnl_dereference(dev_queue->qdisc_sleeping);
 	const struct Qdisc_ops *ops = qdisc->ops;
 
 	if (ops->change_tx_queue_len)
-		return ops->change_tx_queue_len(qdisc, dev->tx_queue_len);
+		return ops->change_tx_queue_len(qdisc, len);
 	return 0;
 }
 
@@ -1465,7 +1466,7 @@ void mq_change_real_num_tx(struct Qdisc *sch, unsigned int new_real_tx)
 }
 EXPORT_SYMBOL(mq_change_real_num_tx);
 
-int dev_qdisc_change_tx_queue_len(struct net_device *dev)
+int dev_qdisc_change_tx_queue_len(struct net_device *dev, unsigned int old_len)
 {
 	bool up = dev->flags & IFF_UP;
 	unsigned int i;
@@ -1475,13 +1476,15 @@ int dev_qdisc_change_tx_queue_len(struct net_device *dev)
 		dev_deactivate(dev, false);
 
 	for (i = 0; i < dev->num_tx_queues; i++) {
-		ret = qdisc_change_tx_queue_len(dev, &dev->_tx[i]);
-
-		/* TODO: revert changes on a partial failure */
+		ret = qdisc_change_tx_queue_len(dev, &dev->_tx[i],
+						dev->tx_queue_len);
 		if (ret)
 			break;
 	}
 
+	while (ret && i--)
+		qdisc_change_tx_queue_len(dev, &dev->_tx[i], old_len);
+
 	if (up)
 		dev_activate(dev);
 	return ret;
-- 
2.51.0