Re: [v4,net-next 2/4] net: schedule: add action gate offloading

[Vlad Buslov <vlad@buslov.dev>]

On Tue 28 Apr 2020 at 06:34, Po Liu <Po.Liu@nxp.com> wrote:
> Add the gate action to the flow action entry. Add the gate parameters to
> the tc_setup_flow_action() queueing to the entries of flow_action_entry
> array provide to the driver.
>
> Signed-off-by: Po Liu <Po.Liu@nxp.com>
> ---
>  include/net/flow_offload.h   |  10 ++++
>  include/net/tc_act/tc_gate.h | 113 +++++++++++++++++++++++++++++++++++
>  net/sched/cls_api.c          |  33 ++++++++++
>  3 files changed, 156 insertions(+)
>
> diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
> index 3619c6acf60f..94a30fe02e6d 100644
> --- a/include/net/flow_offload.h
> +++ b/include/net/flow_offload.h
> @@ -147,6 +147,7 @@ enum flow_action_id {
>  	FLOW_ACTION_MPLS_PUSH,
>  	FLOW_ACTION_MPLS_POP,
>  	FLOW_ACTION_MPLS_MANGLE,
> +	FLOW_ACTION_GATE,
>  	NUM_FLOW_ACTIONS,
>  };
>  
> @@ -255,6 +256,15 @@ struct flow_action_entry {
>  			u8		bos;
>  			u8		ttl;
>  		} mpls_mangle;
> +		struct {
> +			u32		index;
> +			s32		prio;
> +			u64		basetime;
> +			u64		cycletime;
> +			u64		cycletimeext;
> +			u32		num_entries;
> +			struct action_gate_entry *entries;
> +		} gate;
>  	};
>  	struct flow_action_cookie *cookie; /* user defined action cookie */
>  };
> diff --git a/include/net/tc_act/tc_gate.h b/include/net/tc_act/tc_gate.h
> index 330ad8b02495..9e698c7d64cd 100644
> --- a/include/net/tc_act/tc_gate.h
> +++ b/include/net/tc_act/tc_gate.h
> @@ -7,6 +7,13 @@
>  #include <net/act_api.h>
>  #include <linux/tc_act/tc_gate.h>
>  
> +struct action_gate_entry {
> +	u8			gate_state;
> +	u32			interval;
> +	s32			ipv;
> +	s32			maxoctets;
> +};
> +
>  struct tcfg_gate_entry {
>  	int			index;
>  	u8			gate_state;
> @@ -44,4 +51,110 @@ struct tcf_gate {
>  
>  #define to_gate(a) ((struct tcf_gate *)a)
>  
> +static inline bool is_tcf_gate(const struct tc_action *a)
> +{
> +#ifdef CONFIG_NET_CLS_ACT
> +	if (a->ops && a->ops->id == TCA_ID_GATE)
> +		return true;
> +#endif
> +	return false;
> +}
> +
> +static inline u32 tcf_gate_index(const struct tc_action *a)
> +{
> +	return a->tcfa_index;
> +}
> +
> +static inline s32 tcf_gate_prio(const struct tc_action *a)
> +{
> +	s32 tcfg_prio;
> +
> +	rcu_read_lock();

This action no longer uses rcu, so you don't need protect with
rcu_read_lock() in all these helpers.

> +	tcfg_prio = to_gate(a)->param.tcfg_priority;
> +	rcu_read_unlock();
> +
> +	return tcfg_prio;
> +}
> +
> +static inline u64 tcf_gate_basetime(const struct tc_action *a)
> +{
> +	u64 tcfg_basetime;
> +
> +	rcu_read_lock();
> +	tcfg_basetime = to_gate(a)->param.tcfg_basetime;
> +	rcu_read_unlock();
> +
> +	return tcfg_basetime;
> +}
> +
> +static inline u64 tcf_gate_cycletime(const struct tc_action *a)
> +{
> +	u64 tcfg_cycletime;
> +
> +	rcu_read_lock();
> +	tcfg_cycletime = to_gate(a)->param.tcfg_cycletime;
> +	rcu_read_unlock();
> +
> +	return tcfg_cycletime;
> +}
> +
> +static inline u64 tcf_gate_cycletimeext(const struct tc_action *a)
> +{
> +	u64 tcfg_cycletimeext;
> +
> +	rcu_read_lock();
> +	tcfg_cycletimeext = to_gate(a)->param.tcfg_cycletime_ext;
> +	rcu_read_unlock();
> +
> +	return tcfg_cycletimeext;
> +}
> +
> +static inline u32 tcf_gate_num_entries(const struct tc_action *a)
> +{
> +	u32 num_entries;
> +
> +	rcu_read_lock();
> +	num_entries = to_gate(a)->param.num_entries;
> +	rcu_read_unlock();
> +
> +	return num_entries;
> +}
> +
> +static inline struct action_gate_entry
> +			*tcf_gate_get_list(const struct tc_action *a)
> +{
> +	struct action_gate_entry *oe;
> +	struct tcf_gate_params *p;
> +	struct tcfg_gate_entry *entry;
> +	u32 num_entries;
> +	int i = 0;
> +
> +	rcu_read_lock();
> +
> +	p = &to_gate(a)->param;
> +	num_entries = p->num_entries;
> +
> +	list_for_each_entry(entry, &p->entries, list)
> +		i++;
> +
> +	if (i != num_entries)
> +		return NULL;
> +
> +	oe = kzalloc(sizeof(*oe) * num_entries, GFP_KERNEL);

Can't allocate with GFP_KERNEL flag in rcu read blocks, but you don't
need the rcu read lock here anyway. However, tc_setup_flow_action()
calls this function while holding tcfa_lock spinlock, which also
precludes allocating memory with that flag. You can test for such
problems by enabling CONFIG_DEBUG_ATOMIC_SLEEP. To help uncover such
errors all new act APIs and action implementations are usually
accompanied by tdc tests. If you chose to implement such tests you can
look at 6e52fca36c67 ("tc-tests: Add tc action ct tests") for recent
example.

> +	if (!oe)
> +		return NULL;

This returns without releasing rcu read lock, but as I said before you
probably don't need rcu protection here anyway.

> +
> +	i = 0;
> +	list_for_each_entry(entry, &p->entries, list) {
> +		oe[i].gate_state = entry->gate_state;
> +		oe[i].interval = entry->interval;
> +		oe[i].ipv = entry->ipv;
> +		oe[i].maxoctets = entry->maxoctets;
> +		i++;
> +	}
> +
> +	rcu_read_unlock();
> +
> +	return oe;
> +}
>  #endif
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 11b683c45c28..7e85c91d0752 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -39,6 +39,7 @@
>  #include <net/tc_act/tc_skbedit.h>
>  #include <net/tc_act/tc_ct.h>
>  #include <net/tc_act/tc_mpls.h>
> +#include <net/tc_act/tc_gate.h>
>  #include <net/flow_offload.h>
>  
>  extern const struct nla_policy rtm_tca_policy[TCA_MAX + 1];
> @@ -3526,6 +3527,27 @@ static void tcf_sample_get_group(struct flow_action_entry *entry,
>  #endif
>  }
>  
> +static void tcf_gate_entry_destructor(void *priv)
> +{
> +	struct action_gate_entry *oe = priv;
> +
> +	kfree(oe);
> +}
> +
> +static int tcf_gate_get_entries(struct flow_action_entry *entry,
> +				const struct tc_action *act)
> +{
> +	entry->gate.entries = tcf_gate_get_list(act);
> +
> +	if (!entry->gate.entries)
> +		return -EINVAL;
> +
> +	entry->destructor = tcf_gate_entry_destructor;
> +	entry->destructor_priv = entry->gate.entries;
> +
> +	return 0;
> +}
> +
>  int tc_setup_flow_action(struct flow_action *flow_action,
>  			 const struct tcf_exts *exts)
>  {
> @@ -3672,6 +3694,17 @@ int tc_setup_flow_action(struct flow_action *flow_action,
>  		} else if (is_tcf_skbedit_priority(act)) {
>  			entry->id = FLOW_ACTION_PRIORITY;
>  			entry->priority = tcf_skbedit_priority(act);
> +		} else if (is_tcf_gate(act)) {
> +			entry->id = FLOW_ACTION_GATE;
> +			entry->gate.index = tcf_gate_index(act);
> +			entry->gate.prio = tcf_gate_prio(act);
> +			entry->gate.basetime = tcf_gate_basetime(act);
> +			entry->gate.cycletime = tcf_gate_cycletime(act);
> +			entry->gate.cycletimeext = tcf_gate_cycletimeext(act);
> +			entry->gate.num_entries = tcf_gate_num_entries(act);
> +			err = tcf_gate_get_entries(entry, act);
> +			if (err)
> +				goto err_out;
>  		} else {
>  			err = -EOPNOTSUPP;
>  			goto err_out_locked;