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 4c409b46aa35..0ba15633c418 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",