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net: add exit_batch_rtnl() method

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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>
This commit is contained in:
Eric Dumazet 2024-02-06 14:42:57 +00:00 committed by Jakub Kicinski
parent a1e55f5103
commit fd4f101edb
2 changed files with 33 additions and 1 deletions
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3
include/net/net_namespace.h
View File

@ -448,6 +448,9 @@ 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;
};

31
net/core/net_namespace.c
View File

@ -318,8 +318,9 @@ 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->ns.count, 1);
ref_tracker_dir_init(&net->refcnt_tracker, 128, "net refcnt");
@ -357,6 +358,15 @@ 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);
@ -573,6 +583,7 @@ 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);
@ -613,6 +624,14 @@ 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);
@ -1193,7 +1212,17 @@ 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);
}