net: Add support for batching network namespace cleanups

- Add exit_list to struct net to support building lists of network
  namespaces to cleanup.

- Add exit_batch to pernet_operations to allow running operations only
  once during a network namespace exit.  Instead of once per network
  namespace.

- Factor opt ops_exit_list and ops_exit_free so the logic with cleanup
  up a network namespace does not need to be duplicated.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 63 insertions, 61 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 24a8c5591f63..f307e133d14c 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -43,6 +43,7 @@ struct net {
 #endif
         struct list_head        list;           /* list of network namespaces */
         struct list_head        cleanup_list;   /* namespaces on death row */
+        struct list_head        exit_list;      /* Use only net_mutex */
 
         struct proc_dir_entry   *proc_net;
         struct proc_dir_entry   *proc_net_stat;
@@ -236,6 +237,7 @@ struct pernet_operations {
         struct list_head list;
         int (*init)(struct net *net);
         void (*exit)(struct net *net);
+        void (*exit_batch)(struct list_head *net_exit_list);
         int *id;
         size_t size;
 };
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 9679ad292da9..6c7f6e04dbbf 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -70,6 +70,36 @@ static void ops_free(const struct pernet_operations *ops, struct net *net)
         }
 }
 
+static void ops_exit_list(const struct pernet_operations *ops,
+                          struct list_head *net_exit_list)
+{
+        struct net *net;
+        if (ops->exit) {
+                list_for_each_entry(net, net_exit_list, exit_list)
+                        ops->exit(net);
+        }
+        if (&ops->list == first_device) {
+                LIST_HEAD(dev_kill_list);
+                rtnl_lock();
+                list_for_each_entry(net, net_exit_list, exit_list)
+                        unregister_netdevices(net, &dev_kill_list);
+                unregister_netdevice_many(&dev_kill_list);
+                rtnl_unlock();
+        }
+        if (ops->exit_batch)
+                ops->exit_batch(net_exit_list);
+}
+
+static void ops_free_list(const struct pernet_operations *ops,
+                          struct list_head *net_exit_list)
+{
+        struct net *net;
+        if (ops->size && ops->id) {
+                list_for_each_entry(net, net_exit_list, exit_list)
+                        ops_free(ops, net);
+        }
+}
+
 /*
  * setup_net runs the initializers for the network namespace object.
  */
@@ -78,6 +108,7 @@ static __net_init int setup_net(struct net *net)
         /* Must be called with net_mutex held */
         const struct pernet_operations *ops, *saved_ops;
         int error = 0;
+        LIST_HEAD(net_exit_list);
 
         atomic_set(&net->count, 1);
 
@@ -97,21 +128,14 @@ out_undo:
         /* Walk through the list backwards calling the exit functions
          * for the pernet modules whose init functions did not fail.
          */
+        list_add(&net->exit_list, &net_exit_list);
         saved_ops = ops;
-        list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
-                if (ops->exit)
-                        ops->exit(net);
-                if (&ops->list == first_device) {
-                        LIST_HEAD(dev_kill_list);
-                        rtnl_lock();
-                        unregister_netdevices(net, &dev_kill_list);
-                        unregister_netdevice_many(&dev_kill_list);
-                        rtnl_unlock();
-                }
-        }
+        list_for_each_entry_continue_reverse(ops, &pernet_list, list)
+                ops_exit_list(ops, &net_exit_list);
+
         ops = saved_ops;
         list_for_each_entry_continue_reverse(ops, &pernet_list, list)
-                ops_free(ops, net);
+                ops_free_list(ops, &net_exit_list);
 
         rcu_barrier();
         goto out;
@@ -207,6 +231,7 @@ static void cleanup_net(struct work_struct *work)
         const struct pernet_operations *ops;
         struct net *net, *tmp;
         LIST_HEAD(net_kill_list);
+        LIST_HEAD(net_exit_list);
 
         /* Atomically snapshot the list of namespaces to cleanup */
         spin_lock_irq(&cleanup_list_lock);
@@ -217,8 +242,10 @@ static void cleanup_net(struct work_struct *work)
 
         /* Don't let anyone else find us. */
         rtnl_lock();
-        list_for_each_entry(net, &net_kill_list, cleanup_list)
+        list_for_each_entry(net, &net_kill_list, cleanup_list) {
                 list_del_rcu(&net->list);
+                list_add_tail(&net->exit_list, &net_exit_list);
+        }
         rtnl_unlock();
 
         /*
@@ -229,27 +256,12 @@ static void cleanup_net(struct work_struct *work)
         synchronize_rcu();
 
         /* Run all of the network namespace exit methods */
-        list_for_each_entry_reverse(ops, &pernet_list, list) {
-                if (ops->exit) {
-                        list_for_each_entry(net, &net_kill_list, cleanup_list)
-                                ops->exit(net);
-                }
-                if (&ops->list == first_device) {
-                        LIST_HEAD(dev_kill_list);
-                        rtnl_lock();
-                        list_for_each_entry(net, &net_kill_list, cleanup_list)
-                                unregister_netdevices(net, &dev_kill_list);
-                        unregister_netdevice_many(&dev_kill_list);
-                        rtnl_unlock();
-                }
-        }
+        list_for_each_entry_reverse(ops, &pernet_list, list)
+                ops_exit_list(ops, &net_exit_list);
+
         /* Free the net generic variables */
-        list_for_each_entry_reverse(ops, &pernet_list, list) {
-                if (ops->size && ops->id) {
-                        list_for_each_entry(net, &net_kill_list, cleanup_list)
-                                ops_free(ops, net);
-                }
-        }
+        list_for_each_entry_reverse(ops, &pernet_list, list)
+                ops_free_list(ops, &net_exit_list);
 
         mutex_unlock(&net_mutex);
 
@@ -259,8 +271,8 @@ static void cleanup_net(struct work_struct *work)
         rcu_barrier();
 
         /* Finally it is safe to free my network namespace structure */
-        list_for_each_entry_safe(net, tmp, &net_kill_list, cleanup_list) {
-                list_del_init(&net->cleanup_list);
+        list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
+                list_del_init(&net->exit_list);
                 net_free(net);
         }
 }
@@ -348,8 +360,9 @@ pure_initcall(net_ns_init);
 static int __register_pernet_operations(struct list_head *list,
                                         struct pernet_operations *ops)
 {
-        struct net *net, *undo_net;
+        struct net *net;
         int error;
+        LIST_HEAD(net_exit_list);
 
         list_add_tail(&ops->list, list);
         if (ops->init || (ops->id && ops->size)) {
@@ -357,6 +370,7 @@ static int __register_pernet_operations(struct list_head *list,
                         error = ops_init(ops, net);
                         if (error)
                                 goto out_undo;
+                        list_add_tail(&net->exit_list, &net_exit_list);
                 }
         }
         return 0;
@@ -364,36 +378,21 @@ static int __register_pernet_operations(struct list_head *list,
 out_undo:
         /* If I have an error cleanup all namespaces I initialized */
         list_del(&ops->list);
-        if (ops->exit) {
-                for_each_net(undo_net) {
-                        if (net_eq(undo_net, net))
-                                goto undone;
-                        ops->exit(undo_net);
-                }
-        }
-undone:
-        if (ops->size && ops->id) {
-                for_each_net(undo_net) {
-                        if (net_eq(undo_net, net))
-                                goto freed;
-                        ops_free(ops, undo_net);
-                }
-        }
-freed:
+        ops_exit_list(ops, &net_exit_list);
+        ops_free_list(ops, &net_exit_list);
         return error;
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
         struct net *net;
+        LIST_HEAD(net_exit_list);
 
         list_del(&ops->list);
-        if (ops->exit)
-                for_each_net(net)
-                        ops->exit(net);
-        if (ops->id && ops->size)
-                for_each_net(net)
-                        ops_free(ops, net);
+        for_each_net(net)
+                list_add_tail(&net->exit_list, &net_exit_list);
+        ops_exit_list(ops, &net_exit_list);
+        ops_free_list(ops, &net_exit_list);
 }
 
 #else
@@ -411,9 +410,10 @@ static int __register_pernet_operations(struct list_head *list,
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-        if (ops->exit)
-                ops->exit(&init_net);
-        ops_free(ops, &init_net);
+        LIST_HEAD(net_exit_list);
+        list_add(&init_net.exit_list, &net_exit_list);
+        ops_exit_list(ops, &net_exit_list);
+        ops_free_list(ops, &net_exit_list);
 }
 
 #endif /* CONFIG_NET_NS */