On Thu, Jan 25, 2018 at 06:26:23PM -0800, Cong Wang wrote:
> Introduce a new qdisc ops ->change_tx_queue_len() so that
> each qdisc could decide how to implement this if it wants.
> Previously we simply read dev->tx_queue_len, after pfifo_fast
> switches to skb array, we need this API to resize the skb array
> when we change dev->tx_queue_len.
>
> To avoid handling race conditions with TX BH, we need to
> deactivate all TX queues before change the value and bring them
> back after we are done, this also makes implementation easier.
>
> Cc: John Fastabend <john.fastab...@gmail.com>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
> ---
> include/net/sch_generic.h | 2 ++
> net/core/dev.c | 1 +
> net/sched/sch_generic.c | 33 +++++++++++++++++++++++++++++++++
> 3 files changed, 36 insertions(+)
>
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index eac43e8ca96d..e2ab13687fb9 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -200,6 +200,7 @@ struct Qdisc_ops {
> struct nlattr *arg,
> struct netlink_ext_ack *extack);
> void (*attach)(struct Qdisc *sch);
> + int (*change_tx_queue_len)(struct Qdisc *, unsigned
> int);
>
> int (*dump)(struct Qdisc *, struct sk_buff *);
> int (*dump_stats)(struct Qdisc *, struct gnet_dump
> *);
> @@ -489,6 +490,7 @@ 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);
> void dev_init_scheduler(struct net_device *dev);
> void dev_shutdown(struct net_device *dev);
> void dev_activate(struct net_device *dev);
> diff --git a/net/core/dev.c b/net/core/dev.c
> index e0b0c2784070..c8443cfaa17a 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -7070,6 +7070,7 @@ int dev_change_tx_queue_len(struct net_device *dev,
> unsigned long new_len)
> dev->tx_queue_len = orig_len;
> return res;
> }
> + return dev_qdisc_change_tx_queue_len(dev);
> }
>
> return 0;
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index 1816bde47256..08f9fa27e06e 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -1178,6 +1178,39 @@ void dev_deactivate(struct net_device *dev)
> }
> EXPORT_SYMBOL(dev_deactivate);
>
> +static int qdisc_change_tx_queue_len(struct net_device *dev,
> + struct netdev_queue *dev_queue)
> +{
> + struct Qdisc *qdisc = 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 0;
> +}
> +
> +int dev_qdisc_change_tx_queue_len(struct net_device *dev)
> +{
> + bool up = dev->flags & IFF_UP;
> + unsigned int i;
> + int ret = 0;
> +
> + if (up)
> + dev_deactivate(dev);
This drops all packets in the queue. I don't think tweaking the queue
length did this previously - did it?
If not this change might surprise some people.
> +
> + 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 */
> + if (ret)
> + break;
> + }
> +
> + if (up)
> + dev_activate(dev);
> + return ret;
> +}
> +
> static void dev_init_scheduler_queue(struct net_device *dev,
> struct netdev_queue *dev_queue,
> void *_qdisc)
> --
> 2.13.0
