[patch net-next] net: sched: choke: remove dead filter classify code

[patch net-next] net: sched: choke: remove dead filter classify code

[Jiri Pirko]

From: Jiri Pirko <jiri@mellanox.com>

sch_choke is classless qdisc so it does not define cl_ops. Therefore
filter_list cannot be ever changed, being NULL all the time.
Reason is this check in tc_ctl_tfilter:

	/* Is it classful? */
	cops = q->ops->cl_ops;
	if (!cops)
		return -EINVAL;

So remove this dead code.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
---
 net/sched/sch_choke.c | 51 ---------------------------------------------------
 1 file changed, 51 deletions(-)

diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
index 3b86a97..03ce895 100644
--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c
@@ -58,7 +58,6 @@ struct choke_sched_data {
 
 /* Variables */
 	struct red_vars  vars;
-	struct tcf_proto __rcu *filter_list;
 	struct {
 		u32	prob_drop;	/* Early probability drops */
 		u32	prob_mark;	/* Early probability marks */
@@ -152,11 +151,6 @@ static inline void choke_set_classid(struct sk_buff *skb, u16 classid)
 	choke_skb_cb(skb)->classid = classid;
 }
 
-static u16 choke_get_classid(const struct sk_buff *skb)
-{
-	return choke_skb_cb(skb)->classid;
-}
-
 /*
  * Compare flow of two packets
  *  Returns true only if source and destination address and port match.
@@ -188,40 +182,6 @@ static bool choke_match_flow(struct sk_buff *skb1,
 }
 
 /*
- * Classify flow using either:
- *  1. pre-existing classification result in skb
- *  2. fast internal classification
- *  3. use TC filter based classification
- */
-static bool choke_classify(struct sk_buff *skb,
-			   struct Qdisc *sch, int *qerr)
-
-{
-	struct choke_sched_data *q = qdisc_priv(sch);
-	struct tcf_result res;
-	struct tcf_proto *fl;
-	int result;
-
-	fl = rcu_dereference_bh(q->filter_list);
-	result = tc_classify(skb, fl, &res, false);
-	if (result >= 0) {
-#ifdef CONFIG_NET_CLS_ACT
-		switch (result) {
-		case TC_ACT_STOLEN:
-		case TC_ACT_QUEUED:
-			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
-		case TC_ACT_SHOT:
-			return false;
-		}
-#endif
-		choke_set_classid(skb, TC_H_MIN(res.classid));
-		return true;
-	}
-
-	return false;
-}
-
-/*
  * Select a packet at random from queue
  * HACK: since queue can have holes from previous deletion; retry several
  *   times to find a random skb but then just give up and return the head
@@ -257,9 +217,6 @@ static bool choke_match_random(const struct choke_sched_data *q,
 		return false;
 
 	oskb = choke_peek_random(q, pidx);
-	if (rcu_access_pointer(q->filter_list))
-		return choke_get_classid(nskb) == choke_get_classid(oskb);
-
 	return choke_match_flow(oskb, nskb);
 }
 
@@ -270,12 +227,6 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	struct choke_sched_data *q = qdisc_priv(sch);
 	const struct red_parms *p = &q->parms;
 
-	if (rcu_access_pointer(q->filter_list)) {
-		/* If using external classifiers, get result and record it. */
-		if (!choke_classify(skb, sch, &ret))
-			goto other_drop;	/* Packet was eaten by filter */
-	}
-
 	choke_skb_cb(skb)->keys_valid = 0;
 	/* Compute average queue usage (see RED) */
 	q->vars.qavg = red_calc_qavg(p, &q->vars, sch->q.qlen);
@@ -340,7 +291,6 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	qdisc_drop(skb, sch, to_free);
 	return NET_XMIT_CN;
 
-other_drop:
 	if (ret & __NET_XMIT_BYPASS)
 		qdisc_qstats_drop(sch);
 	__qdisc_drop(skb, to_free);
@@ -538,7 +488,6 @@ static void choke_destroy(struct Qdisc *sch)
 {
 	struct choke_sched_data *q = qdisc_priv(sch);
 
-	tcf_destroy_chain(&q->filter_list);
 	choke_free(q->tab);
 }
 
-- 
2.7.4

Re: [patch net-next] net: sched: choke: remove dead filter classify code

[Cong Wang]

On Thu, Mar 23, 2017 at 9:02 AM, Jiri Pirko <jiri@resnulli.us> wrote:
> From: Jiri Pirko <jiri@mellanox.com>
>
> sch_choke is classless qdisc so it does not define cl_ops. Therefore
> filter_list cannot be ever changed, being NULL all the time.
> Reason is this check in tc_ctl_tfilter:

Are you sure? According to the definition in comments:

   CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for
   unresponsive flows) is a variant of RED that penalizes misbehaving flows but
   maintains no flow state. The difference from RED is an additional step
   during the enqueuing process. If average queue size is over the
   low threshold (qmin), a packet is chosen at random from the queue.
   If both the new and chosen packet are from the same flow, both
   are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it
   needs to access packets in queue randomly. It has a minimal class
   interface to allow overriding the builtin flow classifier with
   filters.

It should implement filters otherwise how to classify flows in
its definition?

Re: [patch net-next] net: sched: choke: remove dead filter classify code

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Fri, 24 Mar 2017 10:59:15 -0700

> On Thu, Mar 23, 2017 at 9:02 AM, Jiri Pirko <jiri@resnulli.us> wrote:
>> From: Jiri Pirko <jiri@mellanox.com>
>>
>> sch_choke is classless qdisc so it does not define cl_ops. Therefore
>> filter_list cannot be ever changed, being NULL all the time.
>> Reason is this check in tc_ctl_tfilter:
> 
> Are you sure? According to the definition in comments:
> 
>    CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for
>    unresponsive flows) is a variant of RED that penalizes misbehaving flows but
>    maintains no flow state. The difference from RED is an additional step
>    during the enqueuing process. If average queue size is over the
>    low threshold (qmin), a packet is chosen at random from the queue.
>    If both the new and chosen packet are from the same flow, both
>    are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it
>    needs to access packets in queue randomly. It has a minimal class
>    interface to allow overriding the builtin flow classifier with
>    filters.
> 
> It should implement filters otherwise how to classify flows in
> its definition?

The flows are matched by hand using the flow dissector.

Jiri is right, this is all dead code and should be removed.

Re: [patch net-next] net: sched: choke: remove dead filter classify code

[David Miller]

From: Jiri Pirko <jiri@resnulli.us>
Date: Thu, 23 Mar 2017 17:02:16 +0100

> From: Jiri Pirko <jiri@mellanox.com>
> 
> sch_choke is classless qdisc so it does not define cl_ops. Therefore
> filter_list cannot be ever changed, being NULL all the time.
> Reason is this check in tc_ctl_tfilter:
> 
> 	/* Is it classful? */
> 	cops = q->ops->cl_ops;
> 	if (!cops)
> 		return -EINVAL;
> 
> So remove this dead code.
> 
> Signed-off-by: Jiri Pirko <jiri@mellanox.com>

Applied, thanks Jiri.

Re: [patch net-next] net: sched: choke: remove dead filter classify code

[Cong Wang]

On Fri, Mar 24, 2017 at 12:46 PM, David Miller <davem@davemloft.net> wrote:
> From: Cong Wang <xiyou.wangcong@gmail.com>
> Date: Fri, 24 Mar 2017 10:59:15 -0700
>
>> On Thu, Mar 23, 2017 at 9:02 AM, Jiri Pirko <jiri@resnulli.us> wrote:
>>> From: Jiri Pirko <jiri@mellanox.com>
>>>
>>> sch_choke is classless qdisc so it does not define cl_ops. Therefore
>>> filter_list cannot be ever changed, being NULL all the time.
>>> Reason is this check in tc_ctl_tfilter:
>>
>> Are you sure? According to the definition in comments:
>>
>>    CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for
>>    unresponsive flows) is a variant of RED that penalizes misbehaving flows but
>>    maintains no flow state. The difference from RED is an additional step
>>    during the enqueuing process. If average queue size is over the
>>    low threshold (qmin), a packet is chosen at random from the queue.
>>    If both the new and chosen packet are from the same flow, both
>>    are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it
>>    needs to access packets in queue randomly. It has a minimal class
>>    interface to allow overriding the builtin flow classifier with
>>    filters.
>>
>> It should implement filters otherwise how to classify flows in
>> its definition?
>
> The flows are matched by hand using the flow dissector.
>
> Jiri is right, this is all dead code and should be removed.

Hmm, sch_choke has a (kinda) built-in cls_flower...