[NET]: Rework dev_base via list_head (v3)

Cleanup of dev_base list use, with the aim to simplify making device
list per-namespace. In almost every occasion, use of dev_base variable
and dev->next pointer could be easily replaced by for_each_netdev
loop. A few most complicated places were converted to using
first_netdev()/next_netdev().

Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Acked-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 45 insertions, 51 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index c305819b7266..f27d4ab181e6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -156,13 +156,13 @@ static spinlock_t net_dma_event_lock;
 #endif
 
 /*
- * The @dev_base list is protected by @dev_base_lock and the rtnl
+ * The @dev_base_head list is protected by @dev_base_lock and the rtnl
  * semaphore.
  *
  * Pure readers hold dev_base_lock for reading.
  *
  * Writers must hold the rtnl semaphore while they loop through the
- * dev_base list, and hold dev_base_lock for writing when they do the
+ * dev_base_head list, and hold dev_base_lock for writing when they do the
  * actual updates.  This allows pure readers to access the list even
  * while a writer is preparing to update it.
  *
@@ -174,11 +174,10 @@ static spinlock_t net_dma_event_lock;
  * unregister_netdevice(), which must be called with the rtnl
  * semaphore held.
  */
-struct net_device *dev_base;
-static struct net_device **dev_tail = &dev_base;
+LIST_HEAD(dev_base_head);
 DEFINE_RWLOCK(dev_base_lock);
 
-EXPORT_SYMBOL(dev_base);
+EXPORT_SYMBOL(dev_base_head);
 EXPORT_SYMBOL(dev_base_lock);
 
 #define NETDEV_HASHBITS 8
@@ -567,11 +566,12 @@ struct net_device *dev_getbyhwaddr(unsigned short type, char *ha)
 
         ASSERT_RTNL();
 
-        for (dev = dev_base; dev; dev = dev->next)
+        for_each_netdev(dev)
                 if (dev->type == type &&
                     !memcmp(dev->dev_addr, ha, dev->addr_len))
-                        break;
-        return dev;
+                        return dev;
+
+        return NULL;
 }
 
 EXPORT_SYMBOL(dev_getbyhwaddr);
@@ -581,11 +581,11 @@ struct net_device *__dev_getfirstbyhwtype(unsigned short type)
         struct net_device *dev;
 
         ASSERT_RTNL();
-        for (dev = dev_base; dev; dev = dev->next) {
+        for_each_netdev(dev)
                 if (dev->type == type)
-                        break;
-        }
-        return dev;
+                        return dev;
+
+        return NULL;
 }
 
 EXPORT_SYMBOL(__dev_getfirstbyhwtype);
@@ -617,17 +617,19 @@ EXPORT_SYMBOL(dev_getfirstbyhwtype);
 
 struct net_device * dev_get_by_flags(unsigned short if_flags, unsigned short mask)
 {
-        struct net_device *dev;
+        struct net_device *dev, *ret;
 
+        ret = NULL;
         read_lock(&dev_base_lock);
-        for (dev = dev_base; dev != NULL; dev = dev->next) {
+        for_each_netdev(dev) {
                 if (((dev->flags ^ if_flags) & mask) == 0) {
                         dev_hold(dev);
+                        ret = dev;
                         break;
                 }
         }
         read_unlock(&dev_base_lock);
-        return dev;
+        return ret;
 }
 
 /**
@@ -693,7 +695,7 @@ int dev_alloc_name(struct net_device *dev, const char *name)
                 if (!inuse)
                         return -ENOMEM;
 
-                for (d = dev_base; d; d = d->next) {
+                for_each_netdev(d) {
                         if (!sscanf(d->name, name, &i))
                                 continue;
                         if (i < 0 || i >= max_netdevices)
@@ -975,7 +977,7 @@ int register_netdevice_notifier(struct notifier_block *nb)
         rtnl_lock();
         err = raw_notifier_chain_register(&netdev_chain, nb);
         if (!err) {
-                for (dev = dev_base; dev; dev = dev->next) {
+                for_each_netdev(dev) {
                         nb->notifier_call(nb, NETDEV_REGISTER, dev);
 
                         if (dev->flags & IFF_UP)
@@ -2049,7 +2051,7 @@ static int dev_ifconf(char __user *arg)
          */
 
         total = 0;
-        for (dev = dev_base; dev; dev = dev->next) {
+        for_each_netdev(dev) {
                 for (i = 0; i < NPROTO; i++) {
                         if (gifconf_list[i]) {
                                 int done;
@@ -2081,26 +2083,28 @@ static int dev_ifconf(char __user *arg)
  *      This is invoked by the /proc filesystem handler to display a device
  *      in detail.
  */
-static struct net_device *dev_get_idx(loff_t pos)
+void *dev_seq_start(struct seq_file *seq, loff_t *pos)
 {
+        loff_t off;
         struct net_device *dev;
-        loff_t i;
 
-        for (i = 0, dev = dev_base; dev && i < pos; ++i, dev = dev->next);
+        read_lock(&dev_base_lock);
+        if (!*pos)
+                return SEQ_START_TOKEN;
 
-        return i == pos ? dev : NULL;
-}
+        off = 1;
+        for_each_netdev(dev)
+                if (off++ == *pos)
+                        return dev;
 
-void *dev_seq_start(struct seq_file *seq, loff_t *pos)
-{
-        read_lock(&dev_base_lock);
-        return *pos ? dev_get_idx(*pos - 1) : SEQ_START_TOKEN;
+        return NULL;
 }
 
 void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
         ++*pos;
-        return v == SEQ_START_TOKEN ? dev_base : ((struct net_device *)v)->next;
+        return v == SEQ_START_TOKEN ?
+                first_net_device() : next_net_device((struct net_device *)v);
 }
 
 void dev_seq_stop(struct seq_file *seq, void *v)
@@ -3082,11 +3086,9 @@ int register_netdevice(struct net_device *dev)
 
         set_bit(__LINK_STATE_PRESENT, &dev->state);
 
-        dev->next = NULL;
         dev_init_scheduler(dev);
         write_lock_bh(&dev_base_lock);
-        *dev_tail = dev;
-        dev_tail = &dev->next;
+        list_add_tail(&dev->dev_list, &dev_base_head);
         hlist_add_head(&dev->name_hlist, head);
         hlist_add_head(&dev->index_hlist, dev_index_hash(dev->ifindex));
         dev_hold(dev);
@@ -3360,8 +3362,6 @@ void synchronize_net(void)
 
 void unregister_netdevice(struct net_device *dev)
 {
-        struct net_device *d, **dp;
-
         BUG_ON(dev_boot_phase);
         ASSERT_RTNL();
 
@@ -3381,19 +3381,11 @@ void unregister_netdevice(struct net_device *dev)
                 dev_close(dev);
 
         /* And unlink it from device chain. */
-        for (dp = &dev_base; (d = *dp) != NULL; dp = &d->next) {
-                if (d == dev) {
-                        write_lock_bh(&dev_base_lock);
-                        hlist_del(&dev->name_hlist);
-                        hlist_del(&dev->index_hlist);
-                        if (dev_tail == &dev->next)
-                                dev_tail = dp;
-                        *dp = d->next;
-                        write_unlock_bh(&dev_base_lock);
-                        break;
-                }
-        }
-        BUG_ON(!d);
+        write_lock_bh(&dev_base_lock);
+        list_del(&dev->dev_list);
+        hlist_del(&dev->name_hlist);
+        hlist_del(&dev->index_hlist);
+        write_unlock_bh(&dev_base_lock);
 
         dev->reg_state = NETREG_UNREGISTERING;
 
diff --git a/net/core/dev_mcast.c b/net/core/dev_mcast.c
index 7d57bf77f3a3..5a54053386c8 100644
--- a/net/core/dev_mcast.c
+++ b/net/core/dev_mcast.c
@@ -223,7 +223,7 @@ static void *dev_mc_seq_start(struct seq_file *seq, loff_t *pos)
         loff_t off = 0;
 
         read_lock(&dev_base_lock);
-        for (dev = dev_base; dev; dev = dev->next) {
+        for_each_netdev(dev) {
                 if (off++ == *pos)
                         return dev;
         }
@@ -232,9 +232,8 @@ static void *dev_mc_seq_start(struct seq_file *seq, loff_t *pos)
 
 static void *dev_mc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-        struct net_device *dev = v;
         ++*pos;
-        return dev->next;
+        return next_net_device((struct net_device *)v);
 }
 
 static void dev_mc_seq_stop(struct seq_file *seq, void *v)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index cec111109155..8c971a2efe2a 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -539,13 +539,16 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
         int s_idx = cb->args[0];
         struct net_device *dev;
 
-        for (dev=dev_base, idx=0; dev; dev = dev->next, idx++) {
+        idx = 0;
+        for_each_netdev(dev) {
                 if (idx < s_idx)
-                        continue;
+                        goto cont;
                 if (rtnl_fill_ifinfo(skb, dev, NULL, 0, RTM_NEWLINK,
                                      NETLINK_CB(cb->skb).pid,
                                      cb->nlh->nlmsg_seq, 0, NLM_F_MULTI) <= 0)
                         break;
+cont:
+                idx++;
         }
         cb->args[0] = idx;