decnet: RCU conversion and get rid of dev_base_lock

While tracking dev_base_lock users, I found decnet used it in
dnet_select_source(), but for a wrong purpose:

Writers only hold RTNL, not dev_base_lock, so readers must use RCU if
they cannot use RTNL.

Adds an rcu_head in struct dn_ifaddr and handle proper RCU management.

Adds __rcu annotation in dn_route as well.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 59 insertions, 41 deletions

diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c
index 4c409b46aa3..0ba15633c41 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -267,7 +267,7 @@ static int dn_forwarding_proc(ctl_table *table, int write,
 	if (table->extra1 == NULL)
 		return -EINVAL;
 
-	dn_db = dev->dn_ptr;
+	dn_db = rcu_dereference_raw(dev->dn_ptr);
 	old = dn_db->parms.forwarding;
 
 	err = proc_dointvec(table, write, buffer, lenp, ppos);
@@ -332,14 +332,19 @@ static struct dn_ifaddr *dn_dev_alloc_ifa(void)
 	return ifa;
 }
 
-static __inline__ void dn_dev_free_ifa(struct dn_ifaddr *ifa)
+static void dn_dev_free_ifa_rcu(struct rcu_head *head)
 {
-	kfree(ifa);
+	kfree(container_of(head, struct dn_ifaddr, rcu));
 }
 
-static void dn_dev_del_ifa(struct dn_dev *dn_db, struct dn_ifaddr **ifap, int destroy)
+static void dn_dev_free_ifa(struct dn_ifaddr *ifa)
 {
-	struct dn_ifaddr *ifa1 = *ifap;
+	call_rcu(&ifa->rcu, dn_dev_free_ifa_rcu);
+}
+
+static void dn_dev_del_ifa(struct dn_dev *dn_db, struct dn_ifaddr __rcu **ifap, int destroy)
+{
+	struct dn_ifaddr *ifa1 = rtnl_dereference(*ifap);
 	unsigned char mac_addr[6];
 	struct net_device *dev = dn_db->dev;
 
@@ -373,7 +378,9 @@ static int dn_dev_insert_ifa(struct dn_dev *dn_db, struct dn_ifaddr *ifa)
 	ASSERT_RTNL();
 
 	/* Check for duplicates */
-	for(ifa1 = dn_db->ifa_list; ifa1; ifa1 = ifa1->ifa_next) {
+	for (ifa1 = rtnl_dereference(dn_db->ifa_list);
+	     ifa1 != NULL;
+	     ifa1 = rtnl_dereference(ifa1->ifa_next)) {
 		if (ifa1->ifa_local == ifa->ifa_local)
 			return -EEXIST;
 	}
@@ -386,7 +393,7 @@ static int dn_dev_insert_ifa(struct dn_dev *dn_db, struct dn_ifaddr *ifa)
 	}
 
 	ifa->ifa_next = dn_db->ifa_list;
-	dn_db->ifa_list = ifa;
+	rcu_assign_pointer(dn_db->ifa_list, ifa);
 
 	dn_ifaddr_notify(RTM_NEWADDR, ifa);
 	blocking_notifier_call_chain(&dnaddr_chain, NETDEV_UP, ifa);
@@ -396,7 +403,7 @@ static int dn_dev_insert_ifa(struct dn_dev *dn_db, struct dn_ifaddr *ifa)
 
 static int dn_dev_set_ifa(struct net_device *dev, struct dn_ifaddr *ifa)
 {
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
 	int rv;
 
 	if (dn_db == NULL) {
@@ -425,7 +432,8 @@ int dn_dev_ioctl(unsigned int cmd, void __user *arg)
 	struct sockaddr_dn *sdn = (struct sockaddr_dn *)&ifr->ifr_addr;
 	struct dn_dev *dn_db;
 	struct net_device *dev;
-	struct dn_ifaddr *ifa = NULL, **ifap = NULL;
+	struct dn_ifaddr *ifa = NULL;
+	struct dn_ifaddr __rcu **ifap = NULL;
 	int ret = 0;
 
 	if (copy_from_user(ifr, arg, DN_IFREQ_SIZE))
@@ -454,8 +462,10 @@ int dn_dev_ioctl(unsigned int cmd, void __user *arg)
 		goto done;
 	}
 
-	if ((dn_db = dev->dn_ptr) != NULL) {
-		for (ifap = &dn_db->ifa_list; (ifa=*ifap) != NULL; ifap = &ifa->ifa_next)
+	if ((dn_db = rtnl_dereference(dev->dn_ptr)) != NULL) {
+		for (ifap = &dn_db->ifa_list;
+		     (ifa = rtnl_dereference(*ifap)) != NULL;
+		     ifap = &ifa->ifa_next)
 			if (strcmp(ifr->ifr_name, ifa->ifa_label) == 0)
 				break;
 	}
@@ -558,7 +568,7 @@ static struct dn_dev *dn_dev_by_index(int ifindex)
 
 	dev = __dev_get_by_index(&init_net, ifindex);
 	if (dev)
-		dn_dev = dev->dn_ptr;
+		dn_dev = rtnl_dereference(dev->dn_ptr);
 
 	return dn_dev;
 }
@@ -576,7 +586,8 @@ static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	struct nlattr *tb[IFA_MAX+1];
 	struct dn_dev *dn_db;
 	struct ifaddrmsg *ifm;
-	struct dn_ifaddr *ifa, **ifap;
+	struct dn_ifaddr *ifa;
+	struct dn_ifaddr __rcu **ifap;
 	int err = -EINVAL;
 
 	if (!net_eq(net, &init_net))
@@ -592,7 +603,9 @@ static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 		goto errout;
 
 	err = -EADDRNOTAVAIL;
-	for (ifap = &dn_db->ifa_list; (ifa = *ifap); ifap = &ifa->ifa_next) {
+	for (ifap = &dn_db->ifa_list;
+	     (ifa = rtnl_dereference(*ifap)) != NULL;
+	     ifap = &ifa->ifa_next) {
 		if (tb[IFA_LOCAL] &&
 		    nla_memcmp(tb[IFA_LOCAL], &ifa->ifa_local, 2))
 			continue;
@@ -632,7 +645,7 @@ static int dn_nl_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	if ((dev = __dev_get_by_index(&init_net, ifm->ifa_index)) == NULL)
 		return -ENODEV;
 
-	if ((dn_db = dev->dn_ptr) == NULL) {
+	if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL) {
 		dn_db = dn_dev_create(dev, &err);
 		if (!dn_db)
 			return err;
@@ -748,11 +761,11 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
 			skip_naddr = 0;
 		}
 
-		if ((dn_db = dev->dn_ptr) == NULL)
+		if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL)
 			goto cont;
 
-		for (ifa = dn_db->ifa_list, dn_idx = 0; ifa;
-		     ifa = ifa->ifa_next, dn_idx++) {
+		for (ifa = rtnl_dereference(dn_db->ifa_list), dn_idx = 0; ifa;
+		     ifa = rtnl_dereference(ifa->ifa_next), dn_idx++) {
 			if (dn_idx < skip_naddr)
 				continue;
 
@@ -773,21 +786,22 @@ done:
 
 static int dn_dev_get_first(struct net_device *dev, __le16 *addr)
 {
-	struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+	struct dn_dev *dn_db;
 	struct dn_ifaddr *ifa;
 	int rv = -ENODEV;
 
+	rcu_read_lock();
+	dn_db = rcu_dereference(dev->dn_ptr);
 	if (dn_db == NULL)
 		goto out;
 
-	rtnl_lock();
-	ifa = dn_db->ifa_list;
+	ifa = rcu_dereference(dn_db->ifa_list);
 	if (ifa != NULL) {
 		*addr = ifa->ifa_local;
 		rv = 0;
 	}
-	rtnl_unlock();
 out:
+	rcu_read_unlock();
 	return rv;
 }
 
@@ -823,7 +837,7 @@ static void dn_send_endnode_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 	struct endnode_hello_message *msg;
 	struct sk_buff *skb = NULL;
 	__le16 *pktlen;
-	struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+	struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
 	if ((skb = dn_alloc_skb(NULL, sizeof(*msg), GFP_ATOMIC)) == NULL)
 		return;
@@ -889,7 +903,7 @@ static int dn_am_i_a_router(struct dn_neigh *dn, struct dn_dev *dn_db, struct dn
 static void dn_send_router_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 {
 	int n;
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 	struct dn_neigh *dn = (struct dn_neigh *)dn_db->router;
 	struct sk_buff *skb;
 	size_t size;
@@ -960,7 +974,7 @@ static void dn_send_router_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 
 static void dn_send_brd_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 {
-	struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+	struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
 	if (dn_db->parms.forwarding == 0)
 		dn_send_endnode_hello(dev, ifa);
@@ -998,7 +1012,7 @@ static void dn_send_ptp_hello(struct net_device *dev, struct dn_ifaddr *ifa)
 
 static int dn_eth_up(struct net_device *dev)
 {
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
 	if (dn_db->parms.forwarding == 0)
 		dev_mc_add(dev, dn_rt_all_end_mcast);
@@ -1012,7 +1026,7 @@ static int dn_eth_up(struct net_device *dev)
 
 static void dn_eth_down(struct net_device *dev)
 {
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
 	if (dn_db->parms.forwarding == 0)
 		dev_mc_del(dev, dn_rt_all_end_mcast);
@@ -1025,12 +1039,16 @@ static void dn_dev_set_timer(struct net_device *dev);
 static void dn_dev_timer_func(unsigned long arg)
 {
 	struct net_device *dev = (struct net_device *)arg;
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db;
 	struct dn_ifaddr *ifa;
 
+	rcu_read_lock();
+	dn_db = rcu_dereference(dev->dn_ptr);
 	if (dn_db->t3 <= dn_db->parms.t2) {
 		if (dn_db->parms.timer3) {
-			for(ifa = dn_db->ifa_list; ifa; ifa = ifa->ifa_next) {
+			for (ifa = rcu_dereference(dn_db->ifa_list);
+			     ifa;
+			     ifa = rcu_dereference(ifa->ifa_next)) {
 				if (!(ifa->ifa_flags & IFA_F_SECONDARY))
 					dn_db->parms.timer3(dev, ifa);
 			}
@@ -1039,13 +1057,13 @@ static void dn_dev_timer_func(unsigned long arg)
 	} else {
 		dn_db->t3 -= dn_db->parms.t2;
 	}
-
+	rcu_read_unlock();
 	dn_dev_set_timer(dev);
 }
 
 static void dn_dev_set_timer(struct net_device *dev)
 {
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rcu_dereference_raw(dev->dn_ptr);
 
 	if (dn_db->parms.t2 > dn_db->parms.t3)
 		dn_db->parms.t2 = dn_db->parms.t3;
@@ -1077,8 +1095,8 @@ static struct dn_dev *dn_dev_create(struct net_device *dev, int *err)
 		return NULL;
 
 	memcpy(&dn_db->parms, p, sizeof(struct dn_dev_parms));
-	smp_wmb();
-	dev->dn_ptr = dn_db;
+
+	rcu_assign_pointer(dev->dn_ptr, dn_db);
 	dn_db->dev = dev;
 	init_timer(&dn_db->timer);
 
@@ -1086,7 +1104,7 @@ static struct dn_dev *dn_dev_create(struct net_device *dev, int *err)
 
 	dn_db->neigh_parms = neigh_parms_alloc(dev, &dn_neigh_table);
 	if (!dn_db->neigh_parms) {
-		dev->dn_ptr = NULL;
+		rcu_assign_pointer(dev->dn_ptr, NULL);
 		kfree(dn_db);
 		return NULL;
 	}
@@ -1125,7 +1143,7 @@ void dn_dev_up(struct net_device *dev)
 	struct dn_ifaddr *ifa;
 	__le16 addr = decnet_address;
 	int maybe_default = 0;
-	struct dn_dev *dn_db = (struct dn_dev *)dev->dn_ptr;
+	struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
 
 	if ((dev->type != ARPHRD_ETHER) && (dev->type != ARPHRD_LOOPBACK))
 		return;
@@ -1176,7 +1194,7 @@ void dn_dev_up(struct net_device *dev)
 
 static void dn_dev_delete(struct net_device *dev)
 {
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
 
 	if (dn_db == NULL)
 		return;
@@ -1204,13 +1222,13 @@ static void dn_dev_delete(struct net_device *dev)
 
 void dn_dev_down(struct net_device *dev)
 {
-	struct dn_dev *dn_db = dev->dn_ptr;
+	struct dn_dev *dn_db = rtnl_dereference(dev->dn_ptr);
 	struct dn_ifaddr *ifa;
 
 	if (dn_db == NULL)
 		return;
 
-	while((ifa = dn_db->ifa_list) != NULL) {
+	while ((ifa = rtnl_dereference(dn_db->ifa_list)) != NULL) {
 		dn_dev_del_ifa(dn_db, &dn_db->ifa_list, 0);
 		dn_dev_free_ifa(ifa);
 	}
@@ -1270,7 +1288,7 @@ static inline int is_dn_dev(struct net_device *dev)
 }
 
 static void *dn_dev_seq_start(struct seq_file *seq, loff_t *pos)
-	__acquires(rcu)
+	__acquires(RCU)
 {
 	int i;
 	struct net_device *dev;
@@ -1313,7 +1331,7 @@ static void *dn_dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void dn_dev_seq_stop(struct seq_file *seq, void *v)
-	__releases(rcu)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
@@ -1340,7 +1358,7 @@ static int dn_dev_seq_show(struct seq_file *seq, void *v)
 		struct net_device *dev = v;
 		char peer_buf[DN_ASCBUF_LEN];
 		char router_buf[DN_ASCBUF_LEN];
-		struct dn_dev *dn_db = dev->dn_ptr;
+		struct dn_dev *dn_db = rcu_dereference(dev->dn_ptr);
 
 		seq_printf(seq, "%-8s %1s     %04u %04u   %04lu %04lu"
 				"   %04hu    %03d %02x    %-10s %-7s %-7s\n",