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

From: Simon Horman <[email-masked]>
Date: Thu, 7 Dec 2023 20:59:39 +0000

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 <[email-masked]>
> Signed-off-by: Pedro Tammela <[email-masked]>

Thanks Pedro,

my comment below notwithstanding, this looks good to me.

Reviewed-by: Simon Horman <[email-masked]>

> ---
>  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?

> +		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
>