ipv6: use RCU to walk list of network devices

No longer need read_lock(&dev_base_lock), use RCU instead.
We also can avoid taking references on inet6_dev structs.

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

3 files changed, 47 insertions, 43 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8b266390b9e2..61425d0c6123 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1114,6 +1114,16 @@ static inline struct net_device *next_net_device(struct net_device *dev)
         return lh == &net->dev_base_head ? NULL : net_device_entry(lh);
 }
 
+static inline struct net_device *next_net_device_rcu(struct net_device *dev)
+{
+        struct list_head *lh;
+        struct net *net;
+
+        net = dev_net(dev);
+        lh = rcu_dereference(dev->dev_list.next);
+        return lh == &net->dev_base_head ? NULL : net_device_entry(lh);
+}
+
 static inline struct net_device *first_net_device(struct net *net)
 {
         return list_empty(&net->dev_base_head) ? NULL :
diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 2f00ca83f049..f1c74c8ef9de 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -431,9 +431,9 @@ static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
         struct net *net = seq_file_net(seq);
 
         state->idev = NULL;
-        for_each_netdev(net, state->dev) {
+        for_each_netdev_rcu(net, state->dev) {
                 struct inet6_dev *idev;
-                idev = in6_dev_get(state->dev);
+                idev = __in6_dev_get(state->dev);
                 if (!idev)
                         continue;
                 read_lock_bh(&idev->lock);
@@ -443,7 +443,6 @@ static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
                         break;
                 }
                 read_unlock_bh(&idev->lock);
-                in6_dev_put(idev);
         }
         return im;
 }
@@ -454,16 +453,15 @@ static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im
 
         im = im->aca_next;
         while (!im) {
-                if (likely(state->idev != NULL)) {
+                if (likely(state->idev != NULL))
                         read_unlock_bh(&state->idev->lock);
-                        in6_dev_put(state->idev);
-                }
-                state->dev = next_net_device(state->dev);
+
+                state->dev = next_net_device_rcu(state->dev);
                 if (!state->dev) {
                         state->idev = NULL;
                         break;
                 }
-                state->idev = in6_dev_get(state->dev);
+                state->idev = __in6_dev_get(state->dev);
                 if (!state->idev)
                         continue;
                 read_lock_bh(&state->idev->lock);
@@ -482,29 +480,30 @@ static struct ifacaddr6 *ac6_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *ac6_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(dev_base_lock)
+        __acquires(RCU)
 {
-        read_lock(&dev_base_lock);
+        rcu_read_lock();
         return ac6_get_idx(seq, *pos);
 }
 
 static void *ac6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-        struct ifacaddr6 *im;
-        im = ac6_get_next(seq, v);
+        struct ifacaddr6 *im = ac6_get_next(seq, v);
+
         ++*pos;
         return im;
 }
 
 static void ac6_seq_stop(struct seq_file *seq, void *v)
-        __releases(dev_base_lock)
+        __releases(RCU)
 {
         struct ac6_iter_state *state = ac6_seq_private(seq);
+
         if (likely(state->idev != NULL)) {
                 read_unlock_bh(&state->idev->lock);
-                in6_dev_put(state->idev);
+                state->idev = NULL;
         }
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 }
 
 static int ac6_seq_show(struct seq_file *seq, void *v)
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index f9fcf690bd5d..1f9c44442e65 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -2375,9 +2375,9 @@ static inline struct ifmcaddr6 *igmp6_mc_get_first(struct seq_file *seq)
         struct net *net = seq_file_net(seq);
 
         state->idev = NULL;
-        for_each_netdev(net, state->dev) {
+        for_each_netdev_rcu(net, state->dev) {
                 struct inet6_dev *idev;
-                idev = in6_dev_get(state->dev);
+                idev = __in6_dev_get(state->dev);
                 if (!idev)
                         continue;
                 read_lock_bh(&idev->lock);
@@ -2387,7 +2387,6 @@ static inline struct ifmcaddr6 *igmp6_mc_get_first(struct seq_file *seq)
                         break;
                 }
                 read_unlock_bh(&idev->lock);
-                in6_dev_put(idev);
         }
         return im;
 }
@@ -2398,16 +2397,15 @@ static struct ifmcaddr6 *igmp6_mc_get_next(struct seq_file *seq, struct ifmcaddr
 
         im = im->next;
         while (!im) {
-                if (likely(state->idev != NULL)) {
+                if (likely(state->idev != NULL))
                         read_unlock_bh(&state->idev->lock);
-                        in6_dev_put(state->idev);
-                }
-                state->dev = next_net_device(state->dev);
+
+                state->dev = next_net_device_rcu(state->dev);
                 if (!state->dev) {
                         state->idev = NULL;
                         break;
                 }
-                state->idev = in6_dev_get(state->dev);
+                state->idev = __in6_dev_get(state->dev);
                 if (!state->idev)
                         continue;
                 read_lock_bh(&state->idev->lock);
@@ -2426,31 +2424,31 @@ static struct ifmcaddr6 *igmp6_mc_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *igmp6_mc_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(dev_base_lock)
+        __acquires(RCU)
 {
-        read_lock(&dev_base_lock);
+        rcu_read_lock();
         return igmp6_mc_get_idx(seq, *pos);
 }
 
 static void *igmp6_mc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-        struct ifmcaddr6 *im;
-        im = igmp6_mc_get_next(seq, v);
+        struct ifmcaddr6 *im = igmp6_mc_get_next(seq, v);
+
         ++*pos;
         return im;
 }
 
 static void igmp6_mc_seq_stop(struct seq_file *seq, void *v)
-        __releases(dev_base_lock)
+        __releases(RCU)
 {
         struct igmp6_mc_iter_state *state = igmp6_mc_seq_private(seq);
+
         if (likely(state->idev != NULL)) {
                 read_unlock_bh(&state->idev->lock);
-                in6_dev_put(state->idev);
                 state->idev = NULL;
         }
         state->dev = NULL;
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 }
 
 static int igmp6_mc_seq_show(struct seq_file *seq, void *v)
@@ -2507,9 +2505,9 @@ static inline struct ip6_sf_list *igmp6_mcf_get_first(struct seq_file *seq)
 
         state->idev = NULL;
         state->im = NULL;
-        for_each_netdev(net, state->dev) {
+        for_each_netdev_rcu(net, state->dev) {
                 struct inet6_dev *idev;
-                idev = in6_dev_get(state->dev);
+                idev = __in6_dev_get(state->dev);
                 if (unlikely(idev == NULL))
                         continue;
                 read_lock_bh(&idev->lock);
@@ -2525,7 +2523,6 @@ static inline struct ip6_sf_list *igmp6_mcf_get_first(struct seq_file *seq)
                         spin_unlock_bh(&im->mca_lock);
                 }
                 read_unlock_bh(&idev->lock);
-                in6_dev_put(idev);
         }
         return psf;
 }
@@ -2539,16 +2536,15 @@ static struct ip6_sf_list *igmp6_mcf_get_next(struct seq_file *seq, struct ip6_s
                 spin_unlock_bh(&state->im->mca_lock);
                 state->im = state->im->next;
                 while (!state->im) {
-                        if (likely(state->idev != NULL)) {
+                        if (likely(state->idev != NULL))
                                 read_unlock_bh(&state->idev->lock);
-                                in6_dev_put(state->idev);
-                        }
-                        state->dev = next_net_device(state->dev);
+
+                        state->dev = next_net_device_rcu(state->dev);
                         if (!state->dev) {
                                 state->idev = NULL;
                                 goto out;
                         }
-                        state->idev = in6_dev_get(state->dev);
+                        state->idev = __in6_dev_get(state->dev);
                         if (!state->idev)
                                 continue;
                         read_lock_bh(&state->idev->lock);
@@ -2573,9 +2569,9 @@ static struct ip6_sf_list *igmp6_mcf_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *igmp6_mcf_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(dev_base_lock)
+        __acquires(RCU)
 {
-        read_lock(&dev_base_lock);
+        rcu_read_lock();
         return *pos ? igmp6_mcf_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
 }
 
@@ -2591,7 +2587,7 @@ static void *igmp6_mcf_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void igmp6_mcf_seq_stop(struct seq_file *seq, void *v)
-        __releases(dev_base_lock)
+        __releases(RCU)
 {
         struct igmp6_mcf_iter_state *state = igmp6_mcf_seq_private(seq);
         if (likely(state->im != NULL)) {
@@ -2600,11 +2596,10 @@ static void igmp6_mcf_seq_stop(struct seq_file *seq, void *v)
         }
         if (likely(state->idev != NULL)) {
                 read_unlock_bh(&state->idev->lock);
-                in6_dev_put(state->idev);
                 state->idev = NULL;
         }
         state->dev = NULL;
-        read_unlock(&dev_base_lock);
+        rcu_read_unlock();
 }
 
 static int igmp6_mcf_seq_show(struct seq_file *seq, void *v)