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Message-ID: <ZXx2Ml5m4I4v4J33@nanopsycho>
Date: Fri, 15 Dec 2023 16:52:18 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jamal Hadi Salim <hadi@...atatu.com>
Cc: Victor Nogueira <victor@...atatu.com>, jhs@...atatu.com,
davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, xiyou.wangcong@...il.com, mleitner@...hat.com,
vladbu@...dia.com, paulb@...dia.com, pctammela@...atatu.com,
netdev@...r.kernel.org, kernel@...atatu.com
Subject: Re: [PATCH net-next v7 1/3] net/sched: Introduce tc block netdev
tracking infra
Fri, Dec 15, 2023 at 03:35:01PM CET, hadi@...atatu.com wrote:
>On Fri, Dec 15, 2023 at 8:31 AM Jiri Pirko <jiri@...nulli.us> wrote:
>>
>> Fri, Dec 15, 2023 at 12:10:48PM CET, victor@...atatu.com wrote:
>> >This commit makes tc blocks track which ports have been added to them.
>> >And, with that, we'll be able to use this new information to send
>> >packets to the block's ports. Which will be done in the patch #3 of this
>> >series.
>> >
>> >Suggested-by: Jiri Pirko <jiri@...dia.com>
>> >Co-developed-by: Jamal Hadi Salim <jhs@...atatu.com>
>> >Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
>> >Co-developed-by: Pedro Tammela <pctammela@...atatu.com>
>> >Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
>> >Signed-off-by: Victor Nogueira <victor@...atatu.com>
>> >---
>> > include/net/sch_generic.h | 4 +++
>> > net/sched/cls_api.c | 2 ++
>> > net/sched/sch_api.c | 55 +++++++++++++++++++++++++++++++++++++++
>> > net/sched/sch_generic.c | 31 ++++++++++++++++++++--
>> > 4 files changed, 90 insertions(+), 2 deletions(-)
>> >
>> >diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
>> >index dcb9160e6467..cefca55dd4f9 100644
>> >--- a/include/net/sch_generic.h
>> >+++ b/include/net/sch_generic.h
>> >@@ -19,6 +19,7 @@
>> > #include <net/gen_stats.h>
>> > #include <net/rtnetlink.h>
>> > #include <net/flow_offload.h>
>> >+#include <linux/xarray.h>
>> >
>> > struct Qdisc_ops;
>> > struct qdisc_walker;
>> >@@ -126,6 +127,8 @@ struct Qdisc {
>> >
>> > struct rcu_head rcu;
>> > netdevice_tracker dev_tracker;
>> >+ netdevice_tracker in_block_tracker;
>> >+ netdevice_tracker eg_block_tracker;
>> > /* private data */
>> > long privdata[] ____cacheline_aligned;
>> > };
>> >@@ -457,6 +460,7 @@ struct tcf_chain {
>> > };
>> >
>> > struct tcf_block {
>> >+ struct xarray ports; /* datapath accessible */
>> > /* Lock protects tcf_block and lifetime-management data of chains
>> > * attached to the block (refcnt, action_refcnt, explicitly_created).
>> > */
>> >diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>> >index dc1c19a25882..6020a32ecff2 100644
>> >--- a/net/sched/cls_api.c
>> >+++ b/net/sched/cls_api.c
>> >@@ -531,6 +531,7 @@ static void tcf_block_destroy(struct tcf_block *block)
>> > {
>> > mutex_destroy(&block->lock);
>> > mutex_destroy(&block->proto_destroy_lock);
>> >+ xa_destroy(&block->ports);
>> > kfree_rcu(block, rcu);
>> > }
>> >
>> >@@ -1002,6 +1003,7 @@ static struct tcf_block *tcf_block_create(struct net *net, struct Qdisc *q,
>> > refcount_set(&block->refcnt, 1);
>> > block->net = net;
>> > block->index = block_index;
>> >+ xa_init(&block->ports);
>> >
>> > /* Don't store q pointer for blocks which are shared */
>> > if (!tcf_block_shared(block))
>> >diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
>> >index e9eaf637220e..09ec64f2f463 100644
>> >--- a/net/sched/sch_api.c
>> >+++ b/net/sched/sch_api.c
>> >@@ -1180,6 +1180,57 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
>> > return 0;
>> > }
>> >
>> >+static int qdisc_block_add_dev(struct Qdisc *sch, struct net_device *dev,
>> >+ struct nlattr **tca,
>> >+ struct netlink_ext_ack *extack)
>> >+{
>> >+ const struct Qdisc_class_ops *cl_ops = sch->ops->cl_ops;
>> >+ struct tcf_block *in_block = NULL;
>> >+ struct tcf_block *eg_block = NULL;
>>
>> No need to null.
>>
>> Can't you just have:
>> struct tcf_block *block;
>>
>> And use it in both ifs? You can easily obtain the block again on
>> the error path.
>>
>
>It's just easier to read.
Hmm.
>
>> >+ int err;
>> >+
>> >+ if (tca[TCA_INGRESS_BLOCK]) {
>> >+ /* works for both ingress and clsact */
>> >+ in_block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
>> >+ if (!in_block) {
>>
>> I don't see how this could happen. In fact, why exactly do you check
>> tca[TCA_INGRESS_BLOCK]?
>>
>
>It's lazy but what is wrong with doing that?
It's not needed, that's wrong.
>
>> At this time, the clsact/ingress init() function was already called, you
>> can just do:
>>
>> block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
>> if (block) {
>> err = xa_insert(&block->ports, dev->ifindex, dev, GFP_KERNEL);
>> if (err) {
>> NL_SET_ERR_MSG(extack, "Ingress block dev insert failed");
>> return err;
>> }
>> netdev_hold(dev, &sch->in_block_tracker, GFP_KERNEL);
>> }
>> block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
>> if (block) {
>> err = xa_insert(&block->ports, dev->ifindex, dev, GFP_KERNEL);
>> if (err) {
>> NL_SET_ERR_MSG(extack, "Egress block dev insert failed");
>> goto err_out;
>> }
>> netdev_hold(dev, &sch->eg_block_tracker, GFP_KERNEL);
>> }
>> return 0;
>>
>> err_out:
>> block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
>> if (block) {
>> xa_erase(&block->ports, dev->ifindex);
>> netdev_put(dev, &sch->in_block_tracker);
>> }
>> return err;
>>
>> >+ NL_SET_ERR_MSG(extack, "Shared ingress block missing");
>> >+ return -EINVAL;
>> >+ }
>> >+
>> >+ err = xa_insert(&in_block->ports, dev->ifindex, dev, GFP_KERNEL);
>> >+ if (err) {
>> >+ NL_SET_ERR_MSG(extack, "Ingress block dev insert failed");
>> >+ return err;
>> >+ }
>> >+
>
>How about a middle ground:
> in_block = cl_ops->tcf_block(sch, TC_H_MIN_INGRESS, NULL);
> if (in_block) {
> err = xa_insert(&in_block->ports, dev->ifindex, dev,
>GFP_KERNEL);
> if (err) {
> NL_SET_ERR_MSG(extack, "ingress block dev
>insert failed");
> return err;
> }
> netdev_hold(dev, &sch->in_block_tracker, GFP_KERNEL)
> }
> eg_block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
> if (eg_block) {
> err = xa_insert(&eg_block->ports, dev->ifindex, dev,
>GFP_KERNEL);
> if (err) {
> netdev_put(dev, &sch->eg_block_tracker);
> NL_SET_ERR_MSG(extack, "Egress block dev
>insert failed");
> xa_erase(&in_block->ports, dev->ifindex);
> netdev_put(dev, &sch->in_block_tracker);
> return err;
> }
> netdev_hold(dev, &sch->eg_block_tracker, GFP_KERNEL);
> }
> return 0;
>
>> >+ netdev_hold(dev, &sch->in_block_tracker, GFP_KERNEL);
>>
>> Why exactly do you need an extra reference of netdev? Qdisc is already
>> having one.
>
>More fine grained tracking.
Again, good for what exactly?
>
>>
>> >+ }
>> >+
>> >+ if (tca[TCA_EGRESS_BLOCK]) {
>> >+ eg_block = cl_ops->tcf_block(sch, TC_H_MIN_EGRESS, NULL);
>> >+ if (!eg_block) {
>> >+ NL_SET_ERR_MSG(extack, "Shared egress block missing");
>> >+ err = -EINVAL;
>> >+ goto err_out;
>> >+ }
>> >+
>> >+ err = xa_insert(&eg_block->ports, dev->ifindex, dev, GFP_KERNEL);
>> >+ if (err) {
>> >+ NL_SET_ERR_MSG(extack, "Egress block dev insert failed");
>> >+ goto err_out;
>> >+ }
>> >+ netdev_hold(dev, &sch->eg_block_tracker, GFP_KERNEL);
>> >+ }
>> >+
>> >+ return 0;
>> >+err_out:
>> >+ if (in_block) {
>> >+ xa_erase(&in_block->ports, dev->ifindex);
>> >+ netdev_put(dev, &sch->in_block_tracker);
>> >+ }
>> >+ return err;
>> >+}
>> >+
>> > static int qdisc_block_indexes_set(struct Qdisc *sch, struct nlattr **tca,
>> > struct netlink_ext_ack *extack)
>> > {
>> >@@ -1350,6 +1401,10 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
>> > qdisc_hash_add(sch, false);
>> > trace_qdisc_create(ops, dev, parent);
>> >
>> >+ err = qdisc_block_add_dev(sch, dev, tca, extack);
>> >+ if (err)
>> >+ goto err_out4;
>> >+
>> > return sch;
>> >
>> > err_out4:
>> >diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
>> >index 8dd0e5925342..32bed60dea9f 100644
>> >--- a/net/sched/sch_generic.c
>> >+++ b/net/sched/sch_generic.c
>> >@@ -1050,7 +1050,11 @@ static void qdisc_free_cb(struct rcu_head *head)
>> >
>> > static void __qdisc_destroy(struct Qdisc *qdisc)
>> > {
>> >- const struct Qdisc_ops *ops = qdisc->ops;
>> >+ struct net_device *dev = qdisc_dev(qdisc);
>> >+ const struct Qdisc_ops *ops = qdisc->ops;
>> >+ const struct Qdisc_class_ops *cops;
>> >+ struct tcf_block *block;
>> >+ u32 block_index;
>> >
>> > #ifdef CONFIG_NET_SCHED
>> > qdisc_hash_del(qdisc);
>> >@@ -1061,11 +1065,34 @@ static void __qdisc_destroy(struct Qdisc *qdisc)
>> >
>> > qdisc_reset(qdisc);
>> >
>> >+ cops = ops->cl_ops;
>> >+ if (ops->ingress_block_get) {
>> >+ block_index = ops->ingress_block_get(qdisc);
>> >+ if (block_index) {
>>
>> I don't follow. What you need block_index for? Why can't you just call:
>> block = cops->tcf_block(qdisc, TC_H_MIN_INGRESS, NULL);
>> right away?
>
>Good point.
>
>cheers,
>jamal
>
>>
>> >+ block = cops->tcf_block(qdisc, TC_H_MIN_INGRESS, NULL);
>> >+ if (block) {
>> >+ if (xa_erase(&block->ports, dev->ifindex))
>> >+ netdev_put(dev, &qdisc->in_block_tracker);
>> >+ }
>> >+ }
>> >+ }
>> >+
>> >+ if (ops->egress_block_get) {
>> >+ block_index = ops->egress_block_get(qdisc);
>> >+ if (block_index) {
>> >+ block = cops->tcf_block(qdisc, TC_H_MIN_EGRESS, NULL);
>> >+ if (block) {
>> >+ if (xa_erase(&block->ports, dev->ifindex))
>> >+ netdev_put(dev, &qdisc->eg_block_tracker);
>> >+ }
>> >+ }
>> >+ }
>> >+
>> > if (ops->destroy)
>> > ops->destroy(qdisc);
>> >
>> > module_put(ops->owner);
>> >- netdev_put(qdisc_dev(qdisc), &qdisc->dev_tracker);
>> >+ netdev_put(dev, &qdisc->dev_tracker);
>> >
>> > trace_qdisc_destroy(qdisc);
>> >
>> >--
>> >2.25.1
>> >
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