net: add exit_batch_rtnl() method

[ Upstream commit fd4f101edbd9f99567ab2adb1f2169579ede7c13 ]

Many (struct pernet_operations)->exit_batch() methods have
to acquire rtnl.

In presence of rtnl mutex pressure, this makes cleanup_net()
very slow.

This patch adds a new exit_batch_rtnl() method to reduce
number of rtnl acquisitions from cleanup_net().

exit_batch_rtnl() handlers are called while rtnl is locked,
and devices to be killed can be queued in a list provided
as their second argument.

A single unregister_netdevice_many() is called right
before rtnl is released.

exit_batch_rtnl() handlers are called before ->exit() and
->exit_batch() handlers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://lore.kernel.org/r/20240206144313.2050392-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 46841c7053e6 ("gtp: Use for_each_netdev_rcu() in gtp_genl_dump_pdp().")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index eb0e7731f3b1c8c0e288d5963e8339a8dfa9ddf4..c41e922fdd97e2cae7757cae97af6695b22b55d1 100644 (file)
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -393,6 +393,9 @@ struct pernet_operations {
        void (*pre_exit)(struct net *net);
        void (*exit)(struct net *net);
        void (*exit_batch)(struct list_head *net_exit_list);
+       /* Following method is called with RTNL held. */
+       void (*exit_batch_rtnl)(struct list_head *net_exit_list,
+                               struct list_head *dev_kill_list);
        unsigned int *id;
        size_t size;
 };

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index ef19a0eaa55aa30912bee791d1f58677640f2e2b..bcf3533cb8ff1b2c4f41bb40ec69bb010b1359a4 100644 (file)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -331,8 +331,9 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 {
        /* Must be called with pernet_ops_rwsem held */
        const struct pernet_operations *ops, *saved_ops;
-       int error = 0;
        LIST_HEAD(net_exit_list);
+       LIST_HEAD(dev_kill_list);
+       int error = 0;
 
        refcount_set(&net->count, 1);
        refcount_set(&net->passive, 1);
@@ -365,6 +366,15 @@ out_undo:
 
        synchronize_rcu();
 
+       ops = saved_ops;
+       rtnl_lock();
+       list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
+               if (ops->exit_batch_rtnl)
+                       ops->exit_batch_rtnl(&net_exit_list, &dev_kill_list);
+       }
+       unregister_netdevice_many(&dev_kill_list);
+       rtnl_unlock();
+
        ops = saved_ops;
        list_for_each_entry_continue_reverse(ops, &pernet_list, list)
                ops_exit_list(ops, &net_exit_list);
@@ -569,6 +579,7 @@ static void cleanup_net(struct work_struct *work)
        struct net *net, *tmp, *last;
        struct llist_node *net_kill_list;
        LIST_HEAD(net_exit_list);
+       LIST_HEAD(dev_kill_list);
 
        /* Atomically snapshot the list of namespaces to cleanup */
        net_kill_list = llist_del_all(&cleanup_list);
@@ -609,6 +620,14 @@ static void cleanup_net(struct work_struct *work)
         */
        synchronize_rcu();
 
+       rtnl_lock();
+       list_for_each_entry_reverse(ops, &pernet_list, list) {
+               if (ops->exit_batch_rtnl)
+                       ops->exit_batch_rtnl(&net_exit_list, &dev_kill_list);
+       }
+       unregister_netdevice_many(&dev_kill_list);
+       rtnl_unlock();
+
        /* Run all of the network namespace exit methods */
        list_for_each_entry_reverse(ops, &pernet_list, list)
                ops_exit_list(ops, &net_exit_list);
@@ -1160,7 +1179,17 @@ static void free_exit_list(struct pernet_operations *ops, struct list_head *net_
 {
        ops_pre_exit_list(ops, net_exit_list);
        synchronize_rcu();
+
+       if (ops->exit_batch_rtnl) {
+               LIST_HEAD(dev_kill_list);
+
+               rtnl_lock();
+               ops->exit_batch_rtnl(net_exit_list, &dev_kill_list);
+               unregister_netdevice_many(&dev_kill_list);
+               rtnl_unlock();
+       }
        ops_exit_list(ops, net_exit_list);
+
        ops_free_list(ops, net_exit_list);
 }