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Date:   Mon, 28 May 2018 18:37:53 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     jiri@...nulli.us, netdev@...r.kernel.org, jhs@...atatu.com,
        xiyou.wangcong@...il.com, davem@...emloft.net, ast@...nel.org,
        daniel@...earbox.net, kliteyn@...lanox.com,
        Jiri Pirko <jiri@...lanox.com>
Subject: Re: [PATCH v3 02/11] net: sched: change type of reference and bind
 counters

On Mon, May 28, 2018 at 12:17:20AM +0300, Vlad Buslov wrote:
> Change type of action reference counter to refcount_t.
> 
> Change type of action bind counter to atomic_t.
> This type is used to allow decrementing bind counter without testing
> for 0 result.
> 
> Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
> Signed-off-by: Jiri Pirko <jiri@...lanox.com>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

> ---
>  include/net/act_api.h      |  5 +++--
>  net/sched/act_api.c        | 32 ++++++++++++++++++++++----------
>  net/sched/act_bpf.c        |  4 ++--
>  net/sched/act_connmark.c   |  4 ++--
>  net/sched/act_csum.c       |  4 ++--
>  net/sched/act_gact.c       |  4 ++--
>  net/sched/act_ife.c        |  4 ++--
>  net/sched/act_ipt.c        |  4 ++--
>  net/sched/act_mirred.c     |  4 ++--
>  net/sched/act_nat.c        |  4 ++--
>  net/sched/act_pedit.c      |  4 ++--
>  net/sched/act_police.c     |  4 ++--
>  net/sched/act_sample.c     |  4 ++--
>  net/sched/act_simple.c     |  4 ++--
>  net/sched/act_skbedit.c    |  4 ++--
>  net/sched/act_skbmod.c     |  4 ++--
>  net/sched/act_tunnel_key.c |  4 ++--
>  net/sched/act_vlan.c       |  4 ++--
>  18 files changed, 57 insertions(+), 44 deletions(-)
> 
> diff --git a/include/net/act_api.h b/include/net/act_api.h
> index f7b59ef7303d..e634014605cb 100644
> --- a/include/net/act_api.h
> +++ b/include/net/act_api.h
> @@ -6,6 +6,7 @@
>   * Public action API for classifiers/qdiscs
>  */
>  
> +#include <linux/refcount.h>
>  #include <net/sch_generic.h>
>  #include <net/pkt_sched.h>
>  #include <net/net_namespace.h>
> @@ -26,8 +27,8 @@ struct tc_action {
>  	struct tcf_idrinfo		*idrinfo;
>  
>  	u32				tcfa_index;
> -	int				tcfa_refcnt;
> -	int				tcfa_bindcnt;
> +	refcount_t			tcfa_refcnt;
> +	atomic_t			tcfa_bindcnt;
>  	u32				tcfa_capab;
>  	int				tcfa_action;
>  	struct tcf_t			tcfa_tm;
> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
> index 02670c7489e3..4f064ecab882 100644
> --- a/net/sched/act_api.c
> +++ b/net/sched/act_api.c
> @@ -105,14 +105,26 @@ int __tcf_idr_release(struct tc_action *p, bool bind, bool strict)
>  
>  	ASSERT_RTNL();
>  
> +	/* Release with strict==1 and bind==0 is only called through act API
> +	 * interface (classifiers always bind). Only case when action with
> +	 * positive reference count and zero bind count can exist is when it was
> +	 * also created with act API (unbinding last classifier will destroy the
> +	 * action if it was created by classifier). So only case when bind count
> +	 * can be changed after initial check is when unbound action is
> +	 * destroyed by act API while classifier binds to action with same id
> +	 * concurrently. This result either creation of new action(same behavior
> +	 * as before), or reusing existing action if concurrent process
> +	 * increments reference count before action is deleted. Both scenarios
> +	 * are acceptable.
> +	 */
>  	if (p) {
>  		if (bind)
> -			p->tcfa_bindcnt--;
> -		else if (strict && p->tcfa_bindcnt > 0)
> +			atomic_dec(&p->tcfa_bindcnt);
> +		else if (strict && atomic_read(&p->tcfa_bindcnt) > 0)
>  			return -EPERM;
>  
> -		p->tcfa_refcnt--;
> -		if (p->tcfa_bindcnt <= 0 && p->tcfa_refcnt <= 0) {
> +		if (atomic_read(&p->tcfa_bindcnt) <= 0 &&
> +		    refcount_dec_and_test(&p->tcfa_refcnt)) {
>  			if (p->ops->cleanup)
>  				p->ops->cleanup(p);
>  			tcf_idr_remove(p->idrinfo, p);
> @@ -304,8 +316,8 @@ bool tcf_idr_check(struct tc_action_net *tn, u32 index, struct tc_action **a,
>  
>  	if (index && p) {
>  		if (bind)
> -			p->tcfa_bindcnt++;
> -		p->tcfa_refcnt++;
> +			atomic_inc(&p->tcfa_bindcnt);
> +		refcount_inc(&p->tcfa_refcnt);
>  		*a = p;
>  		return true;
>  	}
> @@ -324,9 +336,9 @@ int tcf_idr_create(struct tc_action_net *tn, u32 index, struct nlattr *est,
>  
>  	if (unlikely(!p))
>  		return -ENOMEM;
> -	p->tcfa_refcnt = 1;
> +	refcount_set(&p->tcfa_refcnt, 1);
>  	if (bind)
> -		p->tcfa_bindcnt = 1;
> +		atomic_set(&p->tcfa_bindcnt, 1);
>  
>  	if (cpustats) {
>  		p->cpu_bstats = netdev_alloc_pcpu_stats(struct gnet_stats_basic_cpu);
> @@ -782,7 +794,7 @@ static void cleanup_a(struct list_head *actions, int ovr)
>  		return;
>  
>  	list_for_each_entry(a, actions, list)
> -		a->tcfa_refcnt--;
> +		refcount_dec(&a->tcfa_refcnt);
>  }
>  
>  int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
> @@ -810,7 +822,7 @@ int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
>  		act->order = i;
>  		sz += tcf_action_fill_size(act);
>  		if (ovr)
> -			act->tcfa_refcnt++;
> +			refcount_inc(&act->tcfa_refcnt);
>  		list_add_tail(&act->list, actions);
>  	}
>  
> diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
> index 18089c02e557..15a2a53cbde1 100644
> --- a/net/sched/act_bpf.c
> +++ b/net/sched/act_bpf.c
> @@ -141,8 +141,8 @@ static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
>  	struct tcf_bpf *prog = to_bpf(act);
>  	struct tc_act_bpf opt = {
>  		.index   = prog->tcf_index,
> -		.refcnt  = prog->tcf_refcnt - ref,
> -		.bindcnt = prog->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&prog->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&prog->tcf_bindcnt) - bind,
>  		.action  = prog->tcf_action,
>  	};
>  	struct tcf_t tm;
> diff --git a/net/sched/act_connmark.c b/net/sched/act_connmark.c
> index e4b880fa51fe..188865034f9a 100644
> --- a/net/sched/act_connmark.c
> +++ b/net/sched/act_connmark.c
> @@ -154,8 +154,8 @@ static inline int tcf_connmark_dump(struct sk_buff *skb, struct tc_action *a,
>  
>  	struct tc_connmark opt = {
>  		.index   = ci->tcf_index,
> -		.refcnt  = ci->tcf_refcnt - ref,
> -		.bindcnt = ci->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&ci->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&ci->tcf_bindcnt) - bind,
>  		.action  = ci->tcf_action,
>  		.zone   = ci->zone,
>  	};
> diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
> index 526a8e491626..da865f7b390a 100644
> --- a/net/sched/act_csum.c
> +++ b/net/sched/act_csum.c
> @@ -597,8 +597,8 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
>  	struct tcf_csum_params *params;
>  	struct tc_csum opt = {
>  		.index   = p->tcf_index,
> -		.refcnt  = p->tcf_refcnt - ref,
> -		.bindcnt = p->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&p->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&p->tcf_bindcnt) - bind,
>  	};
>  	struct tcf_t t;
>  
> diff --git a/net/sched/act_gact.c b/net/sched/act_gact.c
> index 4dc4f153cad8..ca83debd5a70 100644
> --- a/net/sched/act_gact.c
> +++ b/net/sched/act_gact.c
> @@ -169,8 +169,8 @@ static int tcf_gact_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tcf_gact *gact = to_gact(a);
>  	struct tc_gact opt = {
>  		.index   = gact->tcf_index,
> -		.refcnt  = gact->tcf_refcnt - ref,
> -		.bindcnt = gact->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&gact->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&gact->tcf_bindcnt) - bind,
>  		.action  = gact->tcf_action,
>  	};
>  	struct tcf_t t;
> diff --git a/net/sched/act_ife.c b/net/sched/act_ife.c
> index 8527cfdc446d..706e84d6f912 100644
> --- a/net/sched/act_ife.c
> +++ b/net/sched/act_ife.c
> @@ -598,8 +598,8 @@ static int tcf_ife_dump(struct sk_buff *skb, struct tc_action *a, int bind,
>  	struct tcf_ife_params *p = rtnl_dereference(ife->params);
>  	struct tc_ife opt = {
>  		.index = ife->tcf_index,
> -		.refcnt = ife->tcf_refcnt - ref,
> -		.bindcnt = ife->tcf_bindcnt - bind,
> +		.refcnt = refcount_read(&ife->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&ife->tcf_bindcnt) - bind,
>  		.action = ife->tcf_action,
>  		.flags = p->flags,
>  	};
> diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c
> index 14c312d7908f..7bce88dc11c9 100644
> --- a/net/sched/act_ipt.c
> +++ b/net/sched/act_ipt.c
> @@ -280,8 +280,8 @@ static int tcf_ipt_dump(struct sk_buff *skb, struct tc_action *a, int bind,
>  	if (unlikely(!t))
>  		goto nla_put_failure;
>  
> -	c.bindcnt = ipt->tcf_bindcnt - bind;
> -	c.refcnt = ipt->tcf_refcnt - ref;
> +	c.bindcnt = atomic_read(&ipt->tcf_bindcnt) - bind;
> +	c.refcnt = refcount_read(&ipt->tcf_refcnt) - ref;
>  	strcpy(t->u.user.name, ipt->tcfi_t->u.kernel.target->name);
>  
>  	if (nla_put(skb, TCA_IPT_TARG, ipt->tcfi_t->u.user.target_size, t) ||
> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> index fd34015331ab..82a8bdd67c47 100644
> --- a/net/sched/act_mirred.c
> +++ b/net/sched/act_mirred.c
> @@ -250,8 +250,8 @@ static int tcf_mirred_dump(struct sk_buff *skb, struct tc_action *a, int bind,
>  	struct tc_mirred opt = {
>  		.index   = m->tcf_index,
>  		.action  = m->tcf_action,
> -		.refcnt  = m->tcf_refcnt - ref,
> -		.bindcnt = m->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&m->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&m->tcf_bindcnt) - bind,
>  		.eaction = m->tcfm_eaction,
>  		.ifindex = dev ? dev->ifindex : 0,
>  	};
> diff --git a/net/sched/act_nat.c b/net/sched/act_nat.c
> index 4b5848b6c252..457c2ae3de46 100644
> --- a/net/sched/act_nat.c
> +++ b/net/sched/act_nat.c
> @@ -257,8 +257,8 @@ static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
>  
>  		.index    = p->tcf_index,
>  		.action   = p->tcf_action,
> -		.refcnt   = p->tcf_refcnt - ref,
> -		.bindcnt  = p->tcf_bindcnt - bind,
> +		.refcnt   = refcount_read(&p->tcf_refcnt) - ref,
> +		.bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
>  	};
>  	struct tcf_t t;
>  
> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
> index 8a925c72db5f..0102b2935fdb 100644
> --- a/net/sched/act_pedit.c
> +++ b/net/sched/act_pedit.c
> @@ -391,8 +391,8 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a,
>  	opt->nkeys = p->tcfp_nkeys;
>  	opt->flags = p->tcfp_flags;
>  	opt->action = p->tcf_action;
> -	opt->refcnt = p->tcf_refcnt - ref;
> -	opt->bindcnt = p->tcf_bindcnt - bind;
> +	opt->refcnt = refcount_read(&p->tcf_refcnt) - ref;
> +	opt->bindcnt = atomic_read(&p->tcf_bindcnt) - bind;
>  
>  	if (p->tcfp_keys_ex) {
>  		tcf_pedit_key_ex_dump(skb, p->tcfp_keys_ex, p->tcfp_nkeys);
> diff --git a/net/sched/act_police.c b/net/sched/act_police.c
> index 4e72bc2a0dfb..a789b8060968 100644
> --- a/net/sched/act_police.c
> +++ b/net/sched/act_police.c
> @@ -274,8 +274,8 @@ static int tcf_act_police_dump(struct sk_buff *skb, struct tc_action *a,
>  		.action = police->tcf_action,
>  		.mtu = police->tcfp_mtu,
>  		.burst = PSCHED_NS2TICKS(police->tcfp_burst),
> -		.refcnt = police->tcf_refcnt - ref,
> -		.bindcnt = police->tcf_bindcnt - bind,
> +		.refcnt = refcount_read(&police->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&police->tcf_bindcnt) - bind,
>  	};
>  	struct tcf_t t;
>  
> diff --git a/net/sched/act_sample.c b/net/sched/act_sample.c
> index 5db358497c9e..4a46978db092 100644
> --- a/net/sched/act_sample.c
> +++ b/net/sched/act_sample.c
> @@ -173,8 +173,8 @@ static int tcf_sample_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tc_sample opt = {
>  		.index      = s->tcf_index,
>  		.action     = s->tcf_action,
> -		.refcnt     = s->tcf_refcnt - ref,
> -		.bindcnt    = s->tcf_bindcnt - bind,
> +		.refcnt     = refcount_read(&s->tcf_refcnt) - ref,
> +		.bindcnt    = atomic_read(&s->tcf_bindcnt) - bind,
>  	};
>  	struct tcf_t t;
>  
> diff --git a/net/sched/act_simple.c b/net/sched/act_simple.c
> index 9618b4a83cee..95d5985b8d67 100644
> --- a/net/sched/act_simple.c
> +++ b/net/sched/act_simple.c
> @@ -148,8 +148,8 @@ static int tcf_simp_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tcf_defact *d = to_defact(a);
>  	struct tc_defact opt = {
>  		.index   = d->tcf_index,
> -		.refcnt  = d->tcf_refcnt - ref,
> -		.bindcnt = d->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&d->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
>  		.action  = d->tcf_action,
>  	};
>  	struct tcf_t t;
> diff --git a/net/sched/act_skbedit.c b/net/sched/act_skbedit.c
> index 6138d1d71900..d418ec3b0ab9 100644
> --- a/net/sched/act_skbedit.c
> +++ b/net/sched/act_skbedit.c
> @@ -173,8 +173,8 @@ static int tcf_skbedit_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tcf_skbedit *d = to_skbedit(a);
>  	struct tc_skbedit opt = {
>  		.index   = d->tcf_index,
> -		.refcnt  = d->tcf_refcnt - ref,
> -		.bindcnt = d->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&d->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
>  		.action  = d->tcf_action,
>  	};
>  	struct tcf_t t;
> diff --git a/net/sched/act_skbmod.c b/net/sched/act_skbmod.c
> index ad050d7d4b46..ff90d720eda3 100644
> --- a/net/sched/act_skbmod.c
> +++ b/net/sched/act_skbmod.c
> @@ -205,8 +205,8 @@ static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tcf_skbmod_params  *p = rtnl_dereference(d->skbmod_p);
>  	struct tc_skbmod opt = {
>  		.index   = d->tcf_index,
> -		.refcnt  = d->tcf_refcnt - ref,
> -		.bindcnt = d->tcf_bindcnt - bind,
> +		.refcnt  = refcount_read(&d->tcf_refcnt) - ref,
> +		.bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
>  		.action  = d->tcf_action,
>  	};
>  	struct tcf_t t;
> diff --git a/net/sched/act_tunnel_key.c b/net/sched/act_tunnel_key.c
> index 626dac81a48a..c6e50695414b 100644
> --- a/net/sched/act_tunnel_key.c
> +++ b/net/sched/act_tunnel_key.c
> @@ -252,8 +252,8 @@ static int tunnel_key_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tcf_tunnel_key_params *params;
>  	struct tc_tunnel_key opt = {
>  		.index    = t->tcf_index,
> -		.refcnt   = t->tcf_refcnt - ref,
> -		.bindcnt  = t->tcf_bindcnt - bind,
> +		.refcnt   = refcount_read(&t->tcf_refcnt) - ref,
> +		.bindcnt  = atomic_read(&t->tcf_bindcnt) - bind,
>  	};
>  	struct tcf_t tm;
>  
> diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c
> index 853604685965..8dda78473004 100644
> --- a/net/sched/act_vlan.c
> +++ b/net/sched/act_vlan.c
> @@ -237,8 +237,8 @@ static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
>  	struct tcf_vlan_params *p = rtnl_dereference(v->vlan_p);
>  	struct tc_vlan opt = {
>  		.index    = v->tcf_index,
> -		.refcnt   = v->tcf_refcnt - ref,
> -		.bindcnt  = v->tcf_bindcnt - bind,
> +		.refcnt   = refcount_read(&v->tcf_refcnt) - ref,
> +		.bindcnt  = atomic_read(&v->tcf_bindcnt) - bind,
>  		.action   = v->tcf_action,
>  		.v_action = p->tcfv_action,
>  	};
> -- 
> 2.7.5
> 

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