net_sched: convert tcf_hashinfo to hlist and use spinlock

So that we don't need to play with singly linked list,
and since the code is not on hot path, we can use spinlock
instead of rwlock.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/act_api.h

@@ -9,7 +9,7 @@
 #include <net/pkt_sched.h>
 
 struct tcf_common {
-	struct tcf_common		*tcfc_next;
+	struct hlist_node		tcfc_head;
 	u32				tcfc_index;
 	int				tcfc_refcnt;
 	int				tcfc_bindcnt;
@@ -22,7 +22,7 @@ struct tcf_common {
 	spinlock_t			tcfc_lock;
 	struct rcu_head			tcfc_rcu;
 };
-#define tcf_next	common.tcfc_next
+#define tcf_head	common.tcfc_head
 #define tcf_index	common.tcfc_index
 #define tcf_refcnt	common.tcfc_refcnt
 #define tcf_bindcnt	common.tcfc_bindcnt
@@ -36,9 +36,9 @@ struct tcf_common {
 #define tcf_rcu		common.tcfc_rcu
 
 struct tcf_hashinfo {
-	struct tcf_common	**htab;
+	struct hlist_head	*htab;
 	unsigned int		hmask;
-	rwlock_t		lock;
+	spinlock_t		lock;
 };
 
 static inline unsigned int tcf_hash(u32 index, unsigned int hmask)
@@ -48,12 +48,16 @@ static inline unsigned int tcf_hash(u32 index, unsigned int hmask)
 
 static inline int tcf_hashinfo_init(struct tcf_hashinfo *hf, unsigned int mask)
 {
-	rwlock_init(&hf->lock);
+	int i;
+
+	spin_lock_init(&hf->lock);
 	hf->hmask = mask;
-	hf->htab = kzalloc((mask + 1) * sizeof(struct tcf_common *),
+	hf->htab = kzalloc((mask + 1) * sizeof(struct hlist_head),
 			   GFP_KERNEL);
 	if (!hf->htab)
 		return -ENOMEM;
+	for (i = 0; i < mask + 1; i++)
+		INIT_HLIST_HEAD(&hf->htab[i]);
 	return 0;
 }
 

net/sched/act_api.c

@@ -29,25 +29,16 @@
 
 void tcf_hash_destroy(struct tcf_common *p, struct tcf_hashinfo *hinfo)
 {
-	unsigned int h = tcf_hash(p->tcfc_index, hinfo->hmask);
-	struct tcf_common **p1p;
-
-	for (p1p = &hinfo->htab[h]; *p1p; p1p = &(*p1p)->tcfc_next) {
-		if (*p1p == p) {
-			write_lock_bh(&hinfo->lock);
-			*p1p = p->tcfc_next;
-			write_unlock_bh(&hinfo->lock);
-			gen_kill_estimator(&p->tcfc_bstats,
-					   &p->tcfc_rate_est);
-			/*
-			 * gen_estimator est_timer() might access p->tcfc_lock
-			 * or bstats, wait a RCU grace period before freeing p
-			 */
-			kfree_rcu(p, tcfc_rcu);
-			return;
-		}
-	}
-	WARN_ON(1);
+	spin_lock_bh(&hinfo->lock);
+	hlist_del(&p->tcfc_head);
+	spin_unlock_bh(&hinfo->lock);
+	gen_kill_estimator(&p->tcfc_bstats,
+			   &p->tcfc_rate_est);
+	/*
+	 * gen_estimator est_timer() might access p->tcfc_lock
+	 * or bstats, wait a RCU grace period before freeing p
+	 */
+	kfree_rcu(p, tcfc_rcu);
 }
 EXPORT_SYMBOL(tcf_hash_destroy);
 
@@ -73,18 +64,19 @@ EXPORT_SYMBOL(tcf_hash_release);
 static int tcf_dump_walker(struct sk_buff *skb, struct netlink_callback *cb,
 			   struct tc_action *a, struct tcf_hashinfo *hinfo)
 {
+	struct hlist_head *head;
 	struct tcf_common *p;
 	int err = 0, index = -1, i = 0, s_i = 0, n_i = 0;
 	struct nlattr *nest;
 
-	read_lock_bh(&hinfo->lock);
+	spin_lock_bh(&hinfo->lock);
 
 	s_i = cb->args[0];
 
 	for (i = 0; i < (hinfo->hmask + 1); i++) {
-		p = hinfo->htab[tcf_hash(i, hinfo->hmask)];
+		head = &hinfo->htab[tcf_hash(i, hinfo->hmask)];
 
-		for (; p; p = p->tcfc_next) {
+		hlist_for_each_entry_rcu(p, head, tcfc_head) {
 			index++;
 			if (index < s_i)
 				continue;
@@ -107,7 +99,7 @@ static int tcf_dump_walker(struct sk_buff *skb, struct netlink_callback *cb,
 		}
 	}
 done:
-	read_unlock_bh(&hinfo->lock);
+	spin_unlock_bh(&hinfo->lock);
 	if (n_i)
 		cb->args[0] += n_i;
 	return n_i;
@@ -120,7 +112,9 @@ static int tcf_dump_walker(struct sk_buff *skb, struct netlink_callback *cb,
 static int tcf_del_walker(struct sk_buff *skb, struct tc_action *a,
 			  struct tcf_hashinfo *hinfo)
 {
-	struct tcf_common *p, *s_p;
+	struct hlist_head *head;
+	struct hlist_node *n;
+	struct tcf_common *p;
 	struct nlattr *nest;
 	int i = 0, n_i = 0;
 
@@ -130,14 +124,11 @@ static int tcf_del_walker(struct sk_buff *skb, struct tc_action *a,
 	if (nla_put_string(skb, TCA_KIND, a->ops->kind))
 		goto nla_put_failure;
 	for (i = 0; i < (hinfo->hmask + 1); i++) {
-		p = hinfo->htab[tcf_hash(i, hinfo->hmask)];
-
-		while (p != NULL) {
-			s_p = p->tcfc_next;
+		head = &hinfo->htab[tcf_hash(i, hinfo->hmask)];
+		hlist_for_each_entry_safe(p, n, head, tcfc_head) {
 			if (ACT_P_DELETED == tcf_hash_release(p, 0, hinfo))
 				module_put(a->ops->owner);
 			n_i++;
-			p = s_p;
 		}
 	}
 	if (nla_put_u32(skb, TCA_FCNT, n_i))
@@ -168,15 +159,15 @@ EXPORT_SYMBOL(tcf_generic_walker);
 
 struct tcf_common *tcf_hash_lookup(u32 index, struct tcf_hashinfo *hinfo)
 {
-	struct tcf_common *p;
+	struct tcf_common *p = NULL;
+	struct hlist_head *head;
 
-	read_lock_bh(&hinfo->lock);
-	for (p = hinfo->htab[tcf_hash(index, hinfo->hmask)]; p;
-	     p = p->tcfc_next) {
+	spin_lock_bh(&hinfo->lock);
+	head = &hinfo->htab[tcf_hash(index, hinfo->hmask)];
+	hlist_for_each_entry_rcu(p, head, tcfc_head)
 		if (p->tcfc_index == index)
 			break;
-	}
-	read_unlock_bh(&hinfo->lock);
+	spin_unlock_bh(&hinfo->lock);
 
 	return p;
 }
@@ -236,6 +227,7 @@ struct tcf_common *tcf_hash_create(u32 index, struct nlattr *est,
 		p->tcfc_bindcnt = 1;
 
 	spin_lock_init(&p->tcfc_lock);
+	INIT_HLIST_NODE(&p->tcfc_head);
 	p->tcfc_index = index ? index : tcf_hash_new_index(idx_gen, hinfo);
 	p->tcfc_tm.install = jiffies;
 	p->tcfc_tm.lastuse = jiffies;
@@ -257,10 +249,9 @@ void tcf_hash_insert(struct tcf_common *p, struct tcf_hashinfo *hinfo)
 {
 	unsigned int h = tcf_hash(p->tcfc_index, hinfo->hmask);
 
-	write_lock_bh(&hinfo->lock);
-	p->tcfc_next = hinfo->htab[h];
-	hinfo->htab[h] = p;
-	write_unlock_bh(&hinfo->lock);
+	spin_lock_bh(&hinfo->lock);
+	hlist_add_head(&p->tcfc_head, &hinfo->htab[h]);
+	spin_unlock_bh(&hinfo->lock);
 }
 EXPORT_SYMBOL(tcf_hash_insert);
 

net/sched/act_police.c

@@ -60,18 +60,19 @@ struct tc_police_compat {
 static int tcf_act_police_walker(struct sk_buff *skb, struct netlink_callback *cb,
 			      int type, struct tc_action *a)
 {
+	struct hlist_head *head;
 	struct tcf_common *p;
 	int err = 0, index = -1, i = 0, s_i = 0, n_i = 0;
 	struct nlattr *nest;
 
-	read_lock_bh(&police_hash_info.lock);
+	spin_lock_bh(&police_hash_info.lock);
 
 	s_i = cb->args[0];
 
 	for (i = 0; i < (POL_TAB_MASK + 1); i++) {
-		p = police_hash_info.htab[tcf_hash(i, POL_TAB_MASK)];
+		head = &police_hash_info.htab[tcf_hash(i, POL_TAB_MASK)];
 
-		for (; p; p = p->tcfc_next) {
+		hlist_for_each_entry_rcu(p, head, tcfc_head) {
 			index++;
 			if (index < s_i)
 				continue;
@@ -94,7 +95,7 @@ static int tcf_act_police_walker(struct sk_buff *skb, struct netlink_callback *c
 		}
 	}
 done:
-	read_unlock_bh(&police_hash_info.lock);
+	spin_unlock_bh(&police_hash_info.lock);
 	if (n_i)
 		cb->args[0] += n_i;
 	return n_i;
@@ -106,25 +107,16 @@ static int tcf_act_police_walker(struct sk_buff *skb, struct netlink_callback *c
 
 static void tcf_police_destroy(struct tcf_police *p)
 {
-	unsigned int h = tcf_hash(p->tcf_index, POL_TAB_MASK);
-	struct tcf_common **p1p;
-
-	for (p1p = &police_hash_info.htab[h]; *p1p; p1p = &(*p1p)->tcfc_next) {
-		if (*p1p == &p->common) {
-			write_lock_bh(&police_hash_info.lock);
-			*p1p = p->tcf_next;
-			write_unlock_bh(&police_hash_info.lock);
-			gen_kill_estimator(&p->tcf_bstats,
-					   &p->tcf_rate_est);
-			/*
-			 * gen_estimator est_timer() might access p->tcf_lock
-			 * or bstats, wait a RCU grace period before freeing p
-			 */
-			kfree_rcu(p, tcf_rcu);
-			return;
-		}
-	}
-	WARN_ON(1);
+	spin_lock_bh(&police_hash_info.lock);
+	hlist_del(&p->tcf_head);
+	spin_unlock_bh(&police_hash_info.lock);
+	gen_kill_estimator(&p->tcf_bstats,
+			   &p->tcf_rate_est);
+	/*
+	 * gen_estimator est_timer() might access p->tcf_lock
+	 * or bstats, wait a RCU grace period before freeing p
+	 */
+	kfree_rcu(p, tcf_rcu);
 }
 
 static const struct nla_policy police_policy[TCA_POLICE_MAX + 1] = {
@@ -259,10 +251,9 @@ static int tcf_act_police_locate(struct net *net, struct nlattr *nla,
 	police->tcf_index = parm->index ? parm->index :
 		tcf_hash_new_index(&police_idx_gen, &police_hash_info);
 	h = tcf_hash(police->tcf_index, POL_TAB_MASK);
-	write_lock_bh(&police_hash_info.lock);
-	police->tcf_next = police_hash_info.htab[h];
-	police_hash_info.htab[h] = &police->common;
-	write_unlock_bh(&police_hash_info.lock);
+	spin_lock_bh(&police_hash_info.lock);
+	hlist_add_head(&police->tcf_head, &police_hash_info.htab[h]);
+	spin_unlock_bh(&police_hash_info.lock);
 
 	a->priv = police;
 	return ret;