Subject: Re: [PATCH v4 08/10] flow_offload: add reoffload process to update hw_count

From: Vlad Buslov <[email-masked]>
Date: Fri, 19 Nov 2021 22:09:12 +0200

On Thu 18 Nov 2021 at 15:08, Simon Horman <[email-masked]> wrote:
> From: Baowen Zheng <[email-masked]>
>
> Add reoffload process to update hw_count when driver
> is inserted or removed.
>
> When reoffloading actions, we still offload the actions
> that are added independent of filters.
>
> Signed-off-by: Baowen Zheng <[email-masked]>
> Signed-off-by: Louis Peens <[email-masked]>
> Signed-off-by: Simon Horman <[email-masked]>
> ---
>  include/net/act_api.h   |  24 +++++
>  net/core/flow_offload.c |   4 +
>  net/sched/act_api.c     | 213 ++++++++++++++++++++++++++++++++++++----
>  3 files changed, 222 insertions(+), 19 deletions(-)
>
> diff --git a/include/net/act_api.h b/include/net/act_api.h
> index 7900598d2dd3..e5e6e58df618 100644
> --- a/include/net/act_api.h
> +++ b/include/net/act_api.h
> @@ -7,6 +7,7 @@
>  */
>  
>  #include <linux/refcount.h>
> +#include <net/flow_offload.h>
>  #include <net/sch_generic.h>
>  #include <net/pkt_sched.h>
>  #include <net/net_namespace.h>
> @@ -243,11 +244,26 @@ static inline void flow_action_hw_count_set(struct tc_action *act,
>  	act->in_hw_count = hw_count;
>  }
>  
> +static inline void flow_action_hw_count_inc(struct tc_action *act,
> +					    u32 hw_count)
> +{
> +	act->in_hw_count += hw_count;
> +}
> +
> +static inline void flow_action_hw_count_dec(struct tc_action *act,
> +					    u32 hw_count)
> +{
> +	act->in_hw_count = act->in_hw_count > hw_count ?
> +			   act->in_hw_count - hw_count : 0;
> +}
> +
>  void tcf_action_update_stats(struct tc_action *a, u64 bytes, u64 packets,
>  			     u64 drops, bool hw);
>  int tcf_action_copy_stats(struct sk_buff *, struct tc_action *, int);
>  
>  int tcf_action_update_hw_stats(struct tc_action *action);
> +int tcf_action_reoffload_cb(flow_indr_block_bind_cb_t *cb,
> +			    void *cb_priv, bool add);
>  int tcf_action_check_ctrlact(int action, struct tcf_proto *tp,
>  			     struct tcf_chain **handle,
>  			     struct netlink_ext_ack *newchain);
> @@ -259,6 +275,14 @@ DECLARE_STATIC_KEY_FALSE(tcf_frag_xmit_count);
>  #endif
>  
>  int tcf_dev_queue_xmit(struct sk_buff *skb, int (*xmit)(struct sk_buff *skb));
> +
> +#else /* !CONFIG_NET_CLS_ACT */
> +
> +static inline int tcf_action_reoffload_cb(flow_indr_block_bind_cb_t *cb,
> +					  void *cb_priv, bool add) {
> +	return 0;
> +}
> +
>  #endif /* CONFIG_NET_CLS_ACT */
>  
>  static inline void tcf_action_stats_update(struct tc_action *a, u64 bytes,
> diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
> index 6676431733ef..92000164ac37 100644
> --- a/net/core/flow_offload.c
> +++ b/net/core/flow_offload.c
> @@ -1,6 +1,7 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
> +#include <net/act_api.h>
>  #include <net/flow_offload.h>
>  #include <linux/rtnetlink.h>
>  #include <linux/mutex.h>
> @@ -418,6 +419,8 @@ int flow_indr_dev_register(flow_indr_block_bind_cb_t *cb, void *cb_priv)
>  	existing_qdiscs_register(cb, cb_priv);
>  	mutex_unlock(&flow_indr_block_lock);
>  
> +	tcf_action_reoffload_cb(cb, cb_priv, true);
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(flow_indr_dev_register);
> @@ -470,6 +473,7 @@ void flow_indr_dev_unregister(flow_indr_block_bind_cb_t *cb, void *cb_priv,
>  	__flow_block_indr_cleanup(release, cb_priv, &cleanup_list);
>  	mutex_unlock(&flow_indr_block_lock);
>  
> +	tcf_action_reoffload_cb(cb, cb_priv, false);
>  	flow_block_indr_notify(&cleanup_list);
>  	kfree(indr_dev);
>  }
> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
> index f5834d47a392..ada51b2df851 100644
> --- a/net/sched/act_api.c
> +++ b/net/sched/act_api.c
> @@ -225,15 +225,11 @@ static int flow_action_init(struct flow_offload_action *fl_action,
>  	return 0;
>  }
>  
> -static int tcf_action_offload_cmd(struct flow_offload_action *fl_act,
> -				  u32 *hw_count,
> -				  struct netlink_ext_ack *extack)
> +static int tcf_action_offload_cmd_ex(struct flow_offload_action *fl_act,
> +				     u32 *hw_count)
>  {
>  	int err;
>  
> -	if (IS_ERR(fl_act))
> -		return PTR_ERR(fl_act);
> -
>  	err = flow_indr_dev_setup_offload(NULL, NULL, TC_SETUP_ACT,
>  					  fl_act, NULL, NULL);
>  	if (err < 0)
> @@ -245,9 +241,41 @@ static int tcf_action_offload_cmd(struct flow_offload_action *fl_act,
>  	return 0;
>  }
>  
> +static int tcf_action_offload_cmd_cb_ex(struct flow_offload_action *fl_act,
> +					u32 *hw_count,
> +					flow_indr_block_bind_cb_t *cb,
> +					void *cb_priv)
> +{
> +	int err;
> +
> +	err = cb(NULL, NULL, cb_priv, TC_SETUP_ACT, NULL, fl_act, NULL);
> +	if (err < 0)
> +		return err;
> +
> +	if (hw_count)
> +		*hw_count = 1;
> +
> +	return 0;
> +}
> +
> +static int tcf_action_offload_cmd(struct flow_offload_action *fl_act,
> +				  u32 *hw_count,
> +				  flow_indr_block_bind_cb_t *cb,
> +				  void *cb_priv)
> +{
> +	if (IS_ERR(fl_act))
> +		return PTR_ERR(fl_act);
> +
> +	return cb ? tcf_action_offload_cmd_cb_ex(fl_act, hw_count,
> +						 cb, cb_priv) :
> +		    tcf_action_offload_cmd_ex(fl_act, hw_count);
> +}
> +
>  /* offload the tc command after inserted */
> -static int tcf_action_offload_add(struct tc_action *action,
> -				  struct netlink_ext_ack *extack)
> +static int tcf_action_offload_add_ex(struct tc_action *action,
> +				     struct netlink_ext_ack *extack,
> +				     flow_indr_block_bind_cb_t *cb,
> +				     void *cb_priv)
>  {
>  	bool skip_sw = tc_act_skip_sw(action->tcfa_flags);
>  	struct tc_action *actions[TCA_ACT_MAX_PRIO] = {
> @@ -275,9 +303,10 @@ static int tcf_action_offload_add(struct tc_action *action,
>  		goto fl_err;
>  	}
>  
> -	err = tcf_action_offload_cmd(fl_action, &in_hw_count, extack);
> +	err = tcf_action_offload_cmd(fl_action, &in_hw_count, cb, cb_priv);
>  	if (!err)
> -		flow_action_hw_count_set(action, in_hw_count);
> +		cb ? flow_action_hw_count_inc(action, in_hw_count) :
> +		     flow_action_hw_count_set(action, in_hw_count);
>  
>  	if (skip_sw && !tc_act_in_hw(action))
>  		err = -EINVAL;
> @@ -290,6 +319,12 @@ static int tcf_action_offload_add(struct tc_action *action,
>  	return err;
>  }
>  
> +static int tcf_action_offload_add(struct tc_action *action,
> +				  struct netlink_ext_ack *extack)
> +{
> +	return tcf_action_offload_add_ex(action, extack, NULL, NULL);
> +}
> +
>  int tcf_action_update_hw_stats(struct tc_action *action)
>  {
>  	struct flow_offload_action fl_act = {};
> @@ -302,7 +337,7 @@ int tcf_action_update_hw_stats(struct tc_action *action)
>  	if (err)
>  		return err;
>  
> -	err = tcf_action_offload_cmd(&fl_act, NULL, NULL);
> +	err = tcf_action_offload_cmd(&fl_act, NULL, NULL, NULL);
>  	if (!err) {
>  		preempt_disable();
>  		tcf_action_stats_update(action, fl_act.stats.bytes,
> @@ -321,7 +356,9 @@ int tcf_action_update_hw_stats(struct tc_action *action)
>  }
>  EXPORT_SYMBOL(tcf_action_update_hw_stats);
>  
> -static int tcf_action_offload_del(struct tc_action *action)
> +static int tcf_action_offload_del_ex(struct tc_action *action,
> +				     flow_indr_block_bind_cb_t *cb,
> +				     void *cb_priv)
>  {
>  	struct flow_offload_action fl_act;
>  	u32 in_hw_count = 0;
> @@ -337,16 +374,25 @@ static int tcf_action_offload_del(struct tc_action *action)
>  	if (err)
>  		return err;
>  
> -	err = tcf_action_offload_cmd(&fl_act, &in_hw_count, NULL);
> -	if (err)
> +	err = tcf_action_offload_cmd(&fl_act, &in_hw_count, cb, cb_priv);
> +	if (err < 0)
>  		return err;
>  
> -	if (action->in_hw_count != in_hw_count)
> +	if (!cb && action->in_hw_count != in_hw_count)
>  		return -EINVAL;
>  
> +	/* do not need to update hw state when deleting action */
> +	if (cb && in_hw_count)
> +		flow_action_hw_count_dec(action, in_hw_count);
> +
>  	return 0;
>  }
>  
> +static int tcf_action_offload_del(struct tc_action *action)
> +{
> +	return tcf_action_offload_del_ex(action, NULL, NULL);
> +}
> +
>  static void tcf_action_cleanup(struct tc_action *p)
>  {
>  	tcf_action_offload_del(p);
> @@ -841,6 +887,59 @@ EXPORT_SYMBOL(tcf_idrinfo_destroy);
>  
>  static LIST_HEAD(act_base);
>  static DEFINE_RWLOCK(act_mod_lock);
> +/* since act ops id is stored in pernet subsystem list,
> + * then there is no way to walk through only all the action
> + * subsystem, so we keep tc action pernet ops id for
> + * reoffload to walk through.
> + */
> +static LIST_HEAD(act_pernet_id_list);
> +static DEFINE_MUTEX(act_id_mutex);
> +struct tc_act_pernet_id {
> +	struct list_head list;
> +	unsigned int id;
> +};
> +
> +static int tcf_pernet_add_id_list(unsigned int id)
> +{
> +	struct tc_act_pernet_id *id_ptr;
> +	int ret = 0;
> +
> +	mutex_lock(&act_id_mutex);
> +	list_for_each_entry(id_ptr, &act_pernet_id_list, list) {
> +		if (id_ptr->id == id) {
> +			ret = -EEXIST;
> +			goto err_out;
> +		}
> +	}
> +
> +	id_ptr = kzalloc(sizeof(*id_ptr), GFP_KERNEL);
> +	if (!id_ptr) {
> +		ret = -ENOMEM;
> +		goto err_out;
> +	}
> +	id_ptr->id = id;
> +
> +	list_add_tail(&id_ptr->list, &act_pernet_id_list);
> +
> +err_out:
> +	mutex_unlock(&act_id_mutex);
> +	return ret;
> +}
> +
> +static void tcf_pernet_del_id_list(unsigned int id)
> +{
> +	struct tc_act_pernet_id *id_ptr;
> +
> +	mutex_lock(&act_id_mutex);
> +	list_for_each_entry(id_ptr, &act_pernet_id_list, list) {
> +		if (id_ptr->id == id) {
> +			list_del(&id_ptr->list);
> +			kfree(id_ptr);
> +			break;
> +		}
> +	}
> +	mutex_unlock(&act_id_mutex);
> +}
>  
>  int tcf_register_action(struct tc_action_ops *act,
>  			struct pernet_operations *ops)
> @@ -859,18 +958,30 @@ int tcf_register_action(struct tc_action_ops *act,
>  	if (ret)
>  		return ret;
>  
> +	if (ops->id) {
> +		ret = tcf_pernet_add_id_list(*ops->id);
> +		if (ret)
> +			goto id_err;
> +	}
> +
>  	write_lock(&act_mod_lock);
>  	list_for_each_entry(a, &act_base, head) {
>  		if (act->id == a->id || (strcmp(act->kind, a->kind) == 0)) {
> -			write_unlock(&act_mod_lock);
> -			unregister_pernet_subsys(ops);
> -			return -EEXIST;
> +			ret = -EEXIST;
> +			goto err_out;
>  		}
>  	}
>  	list_add_tail(&act->head, &act_base);
>  	write_unlock(&act_mod_lock);
>  
>  	return 0;
> +
> +err_out:
> +	write_unlock(&act_mod_lock);
> +	tcf_pernet_del_id_list(*ops->id);
> +id_err:

Rename to 'err_id' to harmonize label naming.

> +	unregister_pernet_subsys(ops);
> +	return ret;
>  }
>  EXPORT_SYMBOL(tcf_register_action);
>  
> @@ -889,12 +1000,76 @@ int tcf_unregister_action(struct tc_action_ops *act,
>  		}
>  	}
>  	write_unlock(&act_mod_lock);
> -	if (!err)
> +	if (!err) {
>  		unregister_pernet_subsys(ops);
> +		if (ops->id)
> +			tcf_pernet_del_id_list(*ops->id);
> +	}
>  	return err;
>  }
>  EXPORT_SYMBOL(tcf_unregister_action);
>  
> +int tcf_action_reoffload_cb(flow_indr_block_bind_cb_t *cb,
> +			    void *cb_priv, bool add)
> +{
> +	struct tc_act_pernet_id *id_ptr;
> +	struct tcf_idrinfo *idrinfo;
> +	struct tc_action_net *tn;
> +	struct tc_action *p;
> +	unsigned int act_id;
> +	unsigned long tmp;
> +	unsigned long id;
> +	struct idr *idr;
> +	struct net *net;
> +	int ret;
> +
> +	if (!cb)
> +		return -EINVAL;
> +
> +	down_read(&net_rwsem);
> +	mutex_lock(&act_id_mutex);
> +
> +	for_each_net(net) {
> +		list_for_each_entry(id_ptr, &act_pernet_id_list, list) {
> +			act_id = id_ptr->id;
> +			tn = net_generic(net, act_id);
> +			if (!tn)
> +				continue;
> +			idrinfo = tn->idrinfo;
> +			if (!idrinfo)
> +				continue;
> +
> +			mutex_lock(&idrinfo->lock);
> +			idr = &idrinfo->action_idr;
> +			idr_for_each_entry_ul(idr, p, tmp, id) {
> +				if (IS_ERR(p) || tc_act_bind(p->tcfa_flags))
> +					continue;
> +				if (add) {
> +					tcf_action_offload_add_ex(p, NULL, cb,
> +								  cb_priv);
> +					continue;
> +				}
> +
> +				/* cb unregister to update hw count */
> +				ret = tcf_action_offload_del_ex(p, cb, cb_priv);
> +				if (ret < 0)
> +					continue;
> +				if (tc_act_skip_sw(p->tcfa_flags) &&
> +				    !tc_act_in_hw(p)) {
> +					ret = tcf_idr_release_unsafe(p);

Deleting skip_sw action that is no longer offloaded to any hardware
device is reasonable, but note that in this case no netlink notification
is ever generated. Don't know if it is a problem, just highlighting the
fact since the whole behavior of implicitly deleting such actions is
completely omitted from the change log.

> +					if (ret == ACT_P_DELETED)
> +						module_put(p->ops->owner);
> +				}
> +			}
> +			mutex_unlock(&idrinfo->lock);
> +		}
> +	}
> +	mutex_unlock(&act_id_mutex);
> +	up_read(&net_rwsem);
> +
> +	return 0;
> +}
> +
>  /* lookup by name */
>  static struct tc_action_ops *tc_lookup_action_n(char *kind)
>  {