Subject: Re: [net-next PATCH 2/4] net: sched: implement qstat helper routines

From: John Fastabend <[email-masked]>
Date: Fri, 26 Sep 2014 11:41:56 -0700

On 09/26/2014 11:36 AM, Eric Dumazet wrote:
> On Fri, 2014-09-26 at 11:14 -0700, John Fastabend wrote:
>> This adds helpers to manipulate qstats logic and replaces locations
>> that touch the counters directly. This simplifies future patches
>> to push qstats onto per cpu counters.
>>
>> Signed-off-by: John Fastabend <[email-masked]>
>> ---
>>  include/net/sch_generic.h |   43 +++++++++++++++++++++++++++++++++++--------
>>  net/sched/sch_api.c       |    2 +-
>>  net/sched/sch_atm.c       |    2 +-
>>  net/sched/sch_cbq.c       |   10 +++++-----
>>  net/sched/sch_choke.c     |   14 +++++++-------
>>  net/sched/sch_codel.c     |    2 +-
>>  net/sched/sch_drr.c       |    4 ++--
>>  net/sched/sch_dsmark.c    |    2 +-
>>  net/sched/sch_fifo.c      |    2 +-
>>  net/sched/sch_fq.c        |    4 ++--
>>  net/sched/sch_fq_codel.c  |    8 ++++----
>>  net/sched/sch_gred.c      |    4 ++--
>>  net/sched/sch_hfsc.c      |    8 ++++----
>>  net/sched/sch_hhf.c       |    8 ++++----
>>  net/sched/sch_htb.c       |    6 +++---
>>  net/sched/sch_ingress.c   |    2 +-
>>  net/sched/sch_multiq.c    |    4 ++--
>>  net/sched/sch_netem.c     |   15 +++++++--------
>>  net/sched/sch_pie.c       |    2 +-
>>  net/sched/sch_prio.c      |    4 ++--
>>  net/sched/sch_qfq.c       |    4 ++--
>>  net/sched/sch_red.c       |    8 ++++----
>>  net/sched/sch_sfb.c       |   10 +++++-----
>>  net/sched/sch_sfq.c       |   17 +++++++++--------
>>  net/sched/sch_tbf.c       |    8 ++++----
>>  25 files changed, 110 insertions(+), 83 deletions(-)
>>
>> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
>> index 4b93511..5609844 100644
>> --- a/include/net/sch_generic.h
>> +++ b/include/net/sch_generic.h
>> @@ -521,11 +521,39 @@ static inline void qdisc_bstats_update(struct Qdisc *sch,
>>  	bstats_update(&sch->bstats, skb);
>>  }
>>  
>> +static inline void qdisc_qstats_backlog(struct Qdisc *sch,
>> +				       const struct sk_buff *skb)
> 
> qdisc_qstats_backlog_dec() to be consistent with
> qdisc_qstats_backlog_dec() ?
> 
>> +{
>> +	sch->qstats.backlog -= qdisc_pkt_len(skb);
>> +}
>> +
>> +static inline void qdisc_qstats_backlog_inc(struct Qdisc *sch,
>> +					    const struct sk_buff *skb)
>> +{
>> +
>> +	sch->qstats.backlog += qdisc_pkt_len(skb);
>> +}
>> +
>> +static inline void __qdisc_qstats_drop(struct Qdisc *sch, int count)
>> +{
>> +	sch->qstats.drops += count;
>> +}
>> +
>> +static inline void qdisc_qstats_drop(struct Qdisc *sch)
>> +{
>> +	sch->qstats.drops++;
>> +}
>> +
>> +static inline void qdisc_qstats_overlimit(struct Qdisc *sch)
>> +{
>> +	sch->qstats.overlimits++;
>> +}
>> +
>>  static inline int __qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch,
>>  				       struct sk_buff_head *list)
>>  {
>>  	__skb_queue_tail(list, skb);
>> -	sch->qstats.backlog += qdisc_pkt_len(skb);
>> +	qdisc_qstats_backlog_inc(sch, skb);
>>  
>>  	return NET_XMIT_SUCCESS;
>>  }
>> @@ -541,7 +569,7 @@ static inline struct sk_buff *__qdisc_dequeue_head(struct Qdisc *sch,
>>  	struct sk_buff *skb = __skb_dequeue(list);
>>  
>>  	if (likely(skb != NULL)) {
>> -		sch->qstats.backlog -= qdisc_pkt_len(skb);
>> +		qdisc_qstats_backlog(sch, skb);
>>  		qdisc_bstats_update(sch, skb);
>>  	}
>>  
>> @@ -559,10 +587,9 @@ static inline unsigned int __qdisc_queue_drop_head(struct Qdisc *sch,
>>  	struct sk_buff *skb = __skb_dequeue(list);
>>  
>>  	if (likely(skb != NULL)) {
>> -		unsigned int len = qdisc_pkt_len(skb);
>> -		sch->qstats.backlog -= len;
>> +		qdisc_qstats_backlog(sch, skb);
>>  		kfree_skb(skb);
>> -		return len;
>> +		return qdisc_pkt_len(skb);
> 
> Well, you just added a use after free.

hmm should have held off on the v2 I guess. I'll fix this
and add a test for the only drop_head consumer pfifo_head_drop.

Thanks!

> 
>>  	}
>>  
>>  	return 0;
>> @@ -579,7 +606,7 @@ static inline struct sk_buff *__qdisc_dequeue_tail(struct Qdisc *sch,
>>  	struct sk_buff *skb = __skb_dequeue_tail(list);
>>  
>>  	if (likely(skb != NULL))
> 
> 
> Rest of the patch seems fine, thanks !
> 
> 
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