Subject: Re: [PATCH net-next v4 3/8] net_sched: mirred: remove action when the target device is gone

From: Jamal Hadi Salim <[email-masked]>
Date: Wed, 18 Dec 2013 09:31:13 -0500

On 12/15/13 23:15, Cong Wang wrote:
> When the target device is removed, the mirred action is
> still there but with the dev pointer setting to NULL.
> This makes the output from 'tc filter' ugly. There is no
> reason to keep it.
>

Sorry - this one i have problems with.
actions may be referenced from multiple filters,
you cant just delete it (that would leave other users
pointing to it dangling). Destroying would eventually
delete it when the refcount goes to 0.
[And when we delete actions we send netlink events to announce
that]. The proper solution would require i.e tag it as to be
deleted and implement some form of garbage collection.
Do you mind leaving this one out for this series?

cheers,
jamal

> Cc: Jamal Hadi Salim <[email-masked]>
> Cc: David S. Miller <[email-masked]>
> Signed-off-by: Cong Wang <[email-masked]>
> ---
>   include/net/tc_act/tc_mirred.h |  4 +++-
>   net/sched/act_mirred.c         | 15 +++++++--------
>   2 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/include/net/tc_act/tc_mirred.h b/include/net/tc_act/tc_mirred.h
> index cfe2943..2026cf6 100644
> --- a/include/net/tc_act/tc_mirred.h
> +++ b/include/net/tc_act/tc_mirred.h
> @@ -7,9 +7,11 @@ struct tcf_mirred {
>   	struct tcf_common	common;
>   	int			tcfm_eaction;
>   	int			tcfm_ifindex;
> -	int			tcfm_ok_push;
> +	unsigned int		tcfm_ok_push:1;
> +	unsigned int		tcfm_bind:1;
>   	struct net_device	*tcfm_dev;
>   	struct list_head	tcfm_list;
> +	struct tc_action	*tcfm_act;
>   };
>   #define to_mirred(pc) \
>   	container_of(pc, struct tcf_mirred, common)
> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> index 2523781..c26bfe5 100644
> --- a/net/sched/act_mirred.c
> +++ b/net/sched/act_mirred.c
> @@ -136,6 +136,8 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
>   		dev_hold(dev);
>   		m->tcfm_dev = dev;
>   		m->tcfm_ok_push = ok_push;
> +		m->tcfm_bind = bind;
> +		m->tcfm_act = a;
>   	}
>   	spin_unlock_bh(&m->tcf_lock);
>   	if (ret == ACT_P_CREATED) {
> @@ -169,10 +171,6 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
>   	bstats_update(&m->tcf_bstats, skb);
>
>   	dev = m->tcfm_dev;
> -	if (!dev) {
> -		printk_once(KERN_NOTICE "tc mirred: target device is gone\n");
> -		goto out;
> -	}
>
>   	if (!(dev->flags & IFF_UP)) {
>   		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
> @@ -244,13 +242,14 @@ static int mirred_device_event(struct notifier_block *unused,
>   			       unsigned long event, void *ptr)
>   {
>   	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> -	struct tcf_mirred *m;
> +	struct tcf_mirred *m, *tmp;
>
>   	if (event == NETDEV_UNREGISTER)
> -		list_for_each_entry(m, &mirred_list, tcfm_list) {
> +		list_for_each_entry_safe(m, tmp, &mirred_list, tcfm_list) {
>   			if (m->tcfm_dev == dev) {
> -				dev_put(dev);
> -				m->tcfm_dev = NULL;
> +				list_del(&m->tcfm_act->list);
> +				tcf_mirred_cleanup(m->tcfm_act, m->tcfm_bind);
> +				kfree(m->tcfm_act);
>   			}
>   		}
>
>