netdev - [PATCH net-next v2 08/17] net: sched: introduce reference counting for tcf proto

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Date:   Tue, 11 Dec 2018 12:11:51 +0200
From:   Vlad Buslov <vladbu@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, ast@...nel.org, daniel@...earbox.net,
        Vlad Buslov <vladbu@...lanox.com>
Subject: [PATCH net-next v2 08/17] net: sched: introduce reference counting for tcf proto

Add reference counter to tcf proto. Use it to manage tcf proto life cycle
in cls API.

Implement helper get/put functions for tcf proto and use them to modify cls
API to always take reference to tcf proto while using it. This change
allows to concurrently modify proto, instead of relying on rtnl lock for
protection.

Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
---
 include/net/sch_generic.h |  1 +
 net/sched/cls_api.c       | 44 +++++++++++++++++++++++++++++++++++++-------
 2 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 03c0f8325091..a6dade2c22c8 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -327,6 +327,7 @@ struct tcf_proto {
 	void			*data;
 	const struct tcf_proto_ops	*ops;
 	struct tcf_chain	*chain;
+	refcount_t		refcnt;
 	struct rcu_head		rcu;
 	struct work_struct	work;
 };
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 9a77ef0c18fa..9a09926538ef 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -198,6 +198,7 @@ static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
 	tp->prio = prio;
 	tp->chain = chain;
 	INIT_WORK(&tp->work, tcf_proto_destroy_work);
+	refcount_set(&tp->refcnt, 1);
 
 	err = tp->ops->init(tp);
 	if (err) {
@@ -211,12 +212,24 @@ static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
 	return ERR_PTR(err);
 }
 
+static void tcf_proto_get(struct tcf_proto *tp)
+{
+	refcount_inc(&tp->refcnt);
+}
+
 static void tcf_proto_destroy(struct tcf_proto *tp,
 			      struct netlink_ext_ack *extack)
 {
 	tc_queue_proto_work(&tp->work);
 }
 
+static void tcf_proto_put(struct tcf_proto *tp,
+			  struct netlink_ext_ack *extack)
+{
+	if (refcount_dec_and_test(&tp->refcnt))
+		tcf_proto_destroy(tp, extack);
+}
+
 #define ASSERT_BLOCK_LOCKED(block)					\
 	lockdep_assert_held(&(block)->lock)
 
@@ -458,13 +471,13 @@ static void tcf_chain_flush(struct tcf_chain *chain)
 
 	spin_lock(&chain->filter_chain_lock);
 	tp = tcf_chain_dereference(chain->filter_chain, chain);
+	RCU_INIT_POINTER(chain->filter_chain, NULL);
 	tcf_chain0_head_change(chain, NULL);
 	spin_unlock(&chain->filter_chain_lock);
 
 	while (tp) {
-		RCU_INIT_POINTER(chain->filter_chain, tp->next);
-		tcf_proto_destroy(tp, NULL);
-		tp = rtnl_dereference(chain->filter_chain);
+		tcf_proto_put(tp, NULL);
+		tp = tp->next;
 	}
 }
 
@@ -1532,9 +1545,9 @@ static void tcf_chain_tp_insert(struct tcf_chain *chain,
 {
 	if (*chain_info->pprev == chain->filter_chain)
 		tcf_chain0_head_change(chain, tp);
+	tcf_proto_get(tp);
 	RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain, chain_info));
 	rcu_assign_pointer(*chain_info->pprev, tp);
-	tcf_chain_hold(chain);
 }
 
 static void tcf_chain_tp_remove(struct tcf_chain *chain,
@@ -1572,7 +1585,12 @@ static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,
 		}
 	}
 	chain_info->pprev = pprev;
-	chain_info->next = tp ? tp->next : NULL;
+	if (tp) {
+		chain_info->next = tp->next;
+		tcf_proto_get(tp);
+	} else {
+		chain_info->next = NULL;
+	}
 	return tp;
 }
 
@@ -1847,6 +1865,12 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 errout:
 	if (chain)
 		tcf_chain_put(chain);
+	if (chain) {
+		if (tp && !IS_ERR(tp))
+			tcf_proto_put(tp, NULL);
+		if (!tp_created)
+			tcf_chain_put(chain);
+	}
 	tcf_block_release(q, block);
 	if (err == -EAGAIN)
 		/* Replay the request. */
@@ -1977,8 +2001,11 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	}
 
 errout:
-	if (chain)
+	if (chain) {
+		if (tp && !IS_ERR(tp))
+			tcf_proto_put(tp, NULL);
 		tcf_chain_put(chain);
+	}
 	tcf_block_release(q, block);
 	return err;
 
@@ -2069,8 +2096,11 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	}
 
 errout:
-	if (chain)
+	if (chain) {
+		if (tp && !IS_ERR(tp))
+			tcf_proto_put(tp, NULL);
 		tcf_chain_put(chain);
+	}
 	tcf_block_release(q, block);
 	return err;
 }
-- 
2.7.5