[PATCH net-next v6 11/11] net: sched: change action API to use array of pointers to actions

[Vlad Buslov <vladbu@mellanox.com>]

Act API used linked list to pass set of actions to functions. It is
intrusive data structure that stores list nodes inside action structure
itself, which means it is not safe to modify such list concurrently.
However, action API doesn't use any linked list specific operations on this
set of actions, so it can be safely refactored into plain pointer array.

Refactor action API to use array of pointers to tc_actions instead of
linked list. Change argument 'actions' type of exported action init,
destroy and dump functions.

Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
---
Changes from V5 to V6:
- When action is deleted, set pointer in actions array to NULL to
  prevent double freeing.

Changes from V4 to V5:
- Change action delete API to track actions that were deleted, to
  prevent releasing them on error.

Changes from V3 to V4:
- Reduce actions array size in tcf_action_init_1.

 include/net/act_api.h |  7 ++--
 net/sched/act_api.c   | 89 +++++++++++++++++++++++++++++----------------------
 net/sched/cls_api.c   | 21 ++++--------
 3 files changed, 60 insertions(+), 57 deletions(-)

diff --git a/include/net/act_api.h b/include/net/act_api.h
index 8090de2edab7..683ce41053d9 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -168,19 +168,20 @@ static inline int tcf_idr_release(struct tc_action *a, bool bind)
 int tcf_register_action(struct tc_action_ops *a, struct pernet_operations *ops);
 int tcf_unregister_action(struct tc_action_ops *a,
 			  struct pernet_operations *ops);
-int tcf_action_destroy(struct list_head *actions, int bind);
+int tcf_action_destroy(struct tc_action *actions[], int bind);
 int tcf_action_exec(struct sk_buff *skb, struct tc_action **actions,
 		    int nr_actions, struct tcf_result *res);
 int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
 		    struct nlattr *est, char *name, int ovr, int bind,
-		    struct list_head *actions, size_t *attr_size,
+		    struct tc_action *actions[], size_t *attr_size,
 		    bool rtnl_held, struct netlink_ext_ack *extack);
 struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
 				    struct nlattr *nla, struct nlattr *est,
 				    char *name, int ovr, int bind,
 				    bool rtnl_held,
 				    struct netlink_ext_ack *extack);
-int tcf_action_dump(struct sk_buff *skb, struct list_head *, int, int);
+int tcf_action_dump(struct sk_buff *skb, struct tc_action *actions[], int bind,
+		    int ref);
 int tcf_action_dump_old(struct sk_buff *skb, struct tc_action *a, int, int);
 int tcf_action_dump_1(struct sk_buff *skb, struct tc_action *a, int, int);
 int tcf_action_copy_stats(struct sk_buff *, struct tc_action *, int);
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 9511502e1cbb..bf1c35f3deb6 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -657,13 +657,15 @@ int tcf_action_exec(struct sk_buff *skb, struct tc_action **actions,
 }
 EXPORT_SYMBOL(tcf_action_exec);
 
-int tcf_action_destroy(struct list_head *actions, int bind)
+int tcf_action_destroy(struct tc_action *actions[], int bind)
 {
 	const struct tc_action_ops *ops;
-	struct tc_action *a, *tmp;
-	int ret = 0;
+	struct tc_action *a;
+	int ret = 0, i;
 
-	list_for_each_entry_safe(a, tmp, actions, list) {
+	for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
+		a = actions[i];
+		actions[i] = NULL;
 		ops = a->ops;
 		ret = __tcf_idr_release(a, bind, true);
 		if (ret == ACT_P_DELETED)
@@ -679,11 +681,12 @@ static int tcf_action_put(struct tc_action *p)
 	return __tcf_action_put(p, false);
 }
 
-static void tcf_action_put_lst(struct list_head *actions)
+static void tcf_action_put_many(struct tc_action *actions[])
 {
-	struct tc_action *a, *tmp;
+	int i;
 
-	list_for_each_entry_safe(a, tmp, actions, list) {
+	for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
+		struct tc_action *a = actions[i];
 		const struct tc_action_ops *ops = a->ops;
 
 		if (tcf_action_put(a))
@@ -735,14 +738,15 @@ tcf_action_dump_1(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
 }
 EXPORT_SYMBOL(tcf_action_dump_1);
 
-int tcf_action_dump(struct sk_buff *skb, struct list_head *actions,
+int tcf_action_dump(struct sk_buff *skb, struct tc_action *actions[],
 		    int bind, int ref)
 {
 	struct tc_action *a;
-	int err = -EINVAL;
+	int err = -EINVAL, i;
 	struct nlattr *nest;
 
-	list_for_each_entry(a, actions, list) {
+	for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
+		a = actions[i];
 		nest = nla_nest_start(skb, a->order);
 		if (nest == NULL)
 			goto nla_put_failure;
@@ -878,10 +882,9 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
 	if (TC_ACT_EXT_CMP(a->tcfa_action, TC_ACT_GOTO_CHAIN)) {
 		err = tcf_action_goto_chain_init(a, tp);
 		if (err) {
-			LIST_HEAD(actions);
+			struct tc_action *actions[] = { a, NULL };
 
-			list_add_tail(&a->list, &actions);
-			tcf_action_destroy(&actions, bind);
+			tcf_action_destroy(actions, bind);
 			NL_SET_ERR_MSG(extack, "Failed to init TC action chain");
 			return ERR_PTR(err);
 		}
@@ -899,9 +902,11 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
 	return ERR_PTR(err);
 }
 
+/* Returns numbers of initialized actions or negative error. */
+
 int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
 		    struct nlattr *est, char *name, int ovr, int bind,
-		    struct list_head *actions, size_t *attr_size,
+		    struct tc_action *actions[], size_t *attr_size,
 		    bool rtnl_held, struct netlink_ext_ack *extack)
 {
 	struct nlattr *tb[TCA_ACT_MAX_PRIO + 1];
@@ -923,11 +928,12 @@ int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
 		}
 		act->order = i;
 		sz += tcf_action_fill_size(act);
-		list_add_tail(&act->list, actions);
+		/* Start from index 0 */
+		actions[i - 1] = act;
 	}
 
 	*attr_size = tcf_action_full_attrs_size(sz);
-	return 0;
+	return i - 1;
 
 err:
 	tcf_action_destroy(actions, bind);
@@ -978,7 +984,7 @@ int tcf_action_copy_stats(struct sk_buff *skb, struct tc_action *p,
 	return -1;
 }
 
-static int tca_get_fill(struct sk_buff *skb, struct list_head *actions,
+static int tca_get_fill(struct sk_buff *skb, struct tc_action *actions[],
 			u32 portid, u32 seq, u16 flags, int event, int bind,
 			int ref)
 {
@@ -1014,7 +1020,7 @@ static int tca_get_fill(struct sk_buff *skb, struct list_head *actions,
 
 static int
 tcf_get_notify(struct net *net, u32 portid, struct nlmsghdr *n,
-	       struct list_head *actions, int event,
+	       struct tc_action *actions[], int event,
 	       struct netlink_ext_ack *extack)
 {
 	struct sk_buff *skb;
@@ -1150,14 +1156,14 @@ static int tca_action_flush(struct net *net, struct nlattr *nla,
 	return err;
 }
 
-static int tcf_action_delete(struct net *net, struct list_head *actions,
-			     struct netlink_ext_ack *extack)
+static int tcf_action_delete(struct net *net, struct tc_action *actions[],
+			     int *acts_deleted, struct netlink_ext_ack *extack)
 {
-	struct tc_action *a, *tmp;
 	u32 act_index;
-	int ret;
+	int ret, i;
 
-	list_for_each_entry_safe(a, tmp, actions, list) {
+	for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
+		struct tc_action *a = actions[i];
 		const struct tc_action_ops *ops = a->ops;
 
 		/* Actions can be deleted concurrently so we must save their
@@ -1165,23 +1171,26 @@ static int tcf_action_delete(struct net *net, struct list_head *actions,
 		 */
 		act_index = a->tcfa_index;
 
-		list_del(&a->list);
 		if (tcf_action_put(a)) {
 			/* last reference, action was deleted concurrently */
 			module_put(ops->owner);
 		} else  {
 			/* now do the delete */
 			ret = ops->delete(net, act_index);
-			if (ret < 0)
+			if (ret < 0) {
+				*acts_deleted = i + 1;
 				return ret;
+			}
 		}
 	}
+	*acts_deleted = i;
 	return 0;
 }
 
 static int
-tcf_del_notify(struct net *net, struct nlmsghdr *n, struct list_head *actions,
-	       u32 portid, size_t attr_size, struct netlink_ext_ack *extack)
+tcf_del_notify(struct net *net, struct nlmsghdr *n, struct tc_action *actions[],
+	       int *acts_deleted, u32 portid, size_t attr_size,
+	       struct netlink_ext_ack *extack)
 {
 	int ret;
 	struct sk_buff *skb;
@@ -1199,7 +1208,7 @@ tcf_del_notify(struct net *net, struct nlmsghdr *n, struct list_head *actions,
 	}
 
 	/* now do the delete */
-	ret = tcf_action_delete(net, actions, extack);
+	ret = tcf_action_delete(net, actions, acts_deleted, extack);
 	if (ret < 0) {
 		NL_SET_ERR_MSG(extack, "Failed to delete TC action");
 		kfree_skb(skb);
@@ -1221,7 +1230,8 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n,
 	struct nlattr *tb[TCA_ACT_MAX_PRIO + 1];
 	struct tc_action *act;
 	size_t attr_size = 0;
-	LIST_HEAD(actions);
+	struct tc_action *actions[TCA_ACT_MAX_PRIO + 1] = {};
+	int acts_deleted = 0;
 
 	ret = nla_parse_nested(tb, TCA_ACT_MAX_PRIO, nla, NULL, extack);
 	if (ret < 0)
@@ -1243,26 +1253,27 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n,
 		}
 		act->order = i;
 		attr_size += tcf_action_fill_size(act);
-		list_add_tail(&act->list, &actions);
+		actions[i - 1] = act;
 	}
 
 	attr_size = tcf_action_full_attrs_size(attr_size);
 
 	if (event == RTM_GETACTION)
-		ret = tcf_get_notify(net, portid, n, &actions, event, extack);
+		ret = tcf_get_notify(net, portid, n, actions, event, extack);
 	else { /* delete */
-		ret = tcf_del_notify(net, n, &actions, portid, attr_size, extack);
+		ret = tcf_del_notify(net, n, actions, &acts_deleted, portid,
+				     attr_size, extack);
 		if (ret)
 			goto err;
 		return ret;
 	}
 err:
-	tcf_action_put_lst(&actions);
+	tcf_action_put_many(&actions[acts_deleted]);
 	return ret;
 }
 
 static int
-tcf_add_notify(struct net *net, struct nlmsghdr *n, struct list_head *actions,
+tcf_add_notify(struct net *net, struct nlmsghdr *n, struct tc_action *actions[],
 	       u32 portid, size_t attr_size, struct netlink_ext_ack *extack)
 {
 	struct sk_buff *skb;
@@ -1293,15 +1304,15 @@ static int tcf_action_add(struct net *net, struct nlattr *nla,
 {
 	size_t attr_size = 0;
 	int ret = 0;
-	LIST_HEAD(actions);
+	struct tc_action *actions[TCA_ACT_MAX_PRIO] = {};
 
-	ret = tcf_action_init(net, NULL, nla, NULL, NULL, ovr, 0, &actions,
+	ret = tcf_action_init(net, NULL, nla, NULL, NULL, ovr, 0, actions,
 			      &attr_size, true, extack);
-	if (ret)
+	if (ret < 0)
 		return ret;
-	ret = tcf_add_notify(net, n, &actions, portid, attr_size, extack);
+	ret = tcf_add_notify(net, n, actions, portid, attr_size, extack);
 	if (ovr)
-		tcf_action_put_lst(&actions);
+		tcf_action_put_many(actions);
 
 	return ret;
 }
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 9041f0e43e9a..73d9967c3739 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1609,10 +1609,7 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
 void tcf_exts_destroy(struct tcf_exts *exts)
 {
 #ifdef CONFIG_NET_CLS_ACT
-	LIST_HEAD(actions);
-
-	tcf_exts_to_list(exts, &actions);
-	tcf_action_destroy(&actions, TCA_ACT_UNBIND);
+	tcf_action_destroy(exts->actions, TCA_ACT_UNBIND);
 	kfree(exts->actions);
 	exts->nr_actions = 0;
 #endif
@@ -1639,18 +1636,15 @@ int tcf_exts_validate(struct net *net, struct tcf_proto *tp, struct nlattr **tb,
 			exts->actions[0] = act;
 			exts->nr_actions = 1;
 		} else if (exts->action && tb[exts->action]) {
-			LIST_HEAD(actions);
-			int err, i = 0;
+			int err;
 
 			err = tcf_action_init(net, tp, tb[exts->action],
 					      rate_tlv, NULL, ovr, TCA_ACT_BIND,
-					      &actions, &attr_size, true,
+					      exts->actions, &attr_size, true,
 					      extack);
-			if (err)
+			if (err < 0)
 				return err;
-			list_for_each_entry(act, &actions, list)
-				exts->actions[i++] = act;
-			exts->nr_actions = i;
+			exts->nr_actions = err;
 		}
 		exts->net = net;
 	}
@@ -1699,14 +1693,11 @@ int tcf_exts_dump(struct sk_buff *skb, struct tcf_exts *exts)
 		 * tc data even if iproute2  was newer - jhs
 		 */
 		if (exts->type != TCA_OLD_COMPAT) {
-			LIST_HEAD(actions);
-
 			nest = nla_nest_start(skb, exts->action);
 			if (nest == NULL)
 				goto nla_put_failure;
 
-			tcf_exts_to_list(exts, &actions);
-			if (tcf_action_dump(skb, &actions, 0, 0) < 0)
+			if (tcf_action_dump(skb, exts->actions, 0, 0) < 0)
 				goto nla_put_failure;
 			nla_nest_end(skb, nest);
 		} else if (exts->police) {
-- 
2.7.5