netdev - Re: [PATCH net-next v3 5/5] net/sched: cls_api: conditional notification of events

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Date: Fri, 8 Dec 2023 14:48:52 -0300
From: Pedro Tammela <pctammela@...atatu.com>
To: Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, jhs@...atatu.com,
 xiyou.wangcong@...il.com, jiri@...nulli.us, marcelo.leitner@...il.com,
 vladbu@...dia.com, Jiri Pirko <jiri@...dia.com>
Subject: Re: [PATCH net-next v3 5/5] net/sched: cls_api: conditional
 notification of events

On 07/12/2023 17:59, Simon Horman wrote:
> On Wed, Dec 06, 2023 at 01:44:16PM -0300, Pedro Tammela wrote:
>> As of today tc-filter/chain events are unconditionally built and sent to
>> RTNLGRP_TC. As with the introduction of rtnl_notify_needed we can check
>> before-hand if they are really needed. This will help to alleviate
>> system pressure when filters are concurrently added without the rtnl
>> lock as in tc-flower.
>>
>> Reviewed-by: Jiri Pirko <jiri@...dia.com>
>> Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
> 
> Thanks Pedro,
> 
> my comment below notwithstanding, this looks good to me.
> 
> Reviewed-by: Simon Horman <horms@...nel.org>
> 
>> ---
>>   net/sched/cls_api.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>> index 1976bd163986..123185907ebd 100644
>> --- a/net/sched/cls_api.c
>> +++ b/net/sched/cls_api.c
>> @@ -2053,6 +2053,9 @@ static int tfilter_notify(struct net *net, struct sk_buff *oskb,
>>   	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
>>   	int err = 0;
>>   
>> +	if (!unicast && !rtnl_notify_needed(net, n->nlmsg_flags, RTNLGRP_TC))
> 
> I don't feel strongly about this, but
> as the above condition appears 3 times in this patch,
> perhaps it could be a helper?

I noticed that some of these functions will never call with unicast set 
to true (delete routines). So I will append a patch that removes it.
So this pattern will hopefully bet not repeating enough for a macro :)

> 
>> +		return 0;
>> +
>>   	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
>>   	if (!skb)
>>   		return -ENOBUFS;
>> @@ -2082,6 +2085,9 @@ static int tfilter_del_notify(struct net *net, struct sk_buff *oskb,
>>   	u32 portid = oskb ? NETLINK_CB(oskb).portid : 0;
>>   	int err;
>>   
>> +	if (!unicast && !rtnl_notify_needed(net, n->nlmsg_flags, RTNLGRP_TC))
>> +		return tp->ops->delete(tp, fh, last, rtnl_held, extack);
>> +
>>   	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
>>   	if (!skb)
>>   		return -ENOBUFS;
>> @@ -2906,6 +2912,9 @@ static int tc_chain_notify(struct tcf_chain *chain, struct sk_buff *oskb,
>>   	struct sk_buff *skb;
>>   	int err = 0;
>>   
>> +	if (!unicast && !rtnl_notify_needed(net, flags, RTNLGRP_TC))
>> +		return 0;
>> +
>>   	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
>>   	if (!skb)
>>   		return -ENOBUFS;
>> @@ -2935,6 +2944,9 @@ static int tc_chain_notify_delete(const struct tcf_proto_ops *tmplt_ops,
>>   	struct net *net = block->net;
>>   	struct sk_buff *skb;
>>   
>> +	if (!unicast && !rtnl_notify_needed(net, flags, RTNLGRP_TC))
>> +		return 0;
>> +
>>   	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
>>   	if (!skb)
>>   		return -ENOBUFS;
>> -- 
>> 2.40.1
>>