From 6fb255bed1c82a24931595502a8e393200c7dd52 Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@openvz.org>
Date: Sun, 16 Oct 2016 17:18:43 -0700
Subject: [PATCH] [RFC] net: convert net_mutex into a read-write lock
It protects per-namespace lists of operations, which are modified only
when modules are loaded or unloaded.
And the kernel reads these lists to create or destroy a new network
namespace.
Signed-off-by: Andrei Vagin <avagin@openvz.org>
---
include/linux/rtnetlink.h | 2 +-
net/core/net_namespace.c | 32 ++++++++++++++++----------------
net/core/rtnetlink.c | 4 ++--
3 files changed, 19 insertions(+), 19 deletions(-)
@@ -30,7 +30,7 @@ extern int rtnl_trylock(void);
extern int rtnl_is_locked(void);
extern wait_queue_head_t netdev_unregistering_wq;
-extern struct mutex net_mutex;
+extern struct rw_semaphore net_mutex;
#ifdef CONFIG_PROVE_LOCKING
extern bool lockdep_rtnl_is_held(void);
@@ -27,7 +27,7 @@
static LIST_HEAD(pernet_list);
static struct list_head *first_device = &pernet_list;
-DEFINE_MUTEX(net_mutex);
+DECLARE_RWSEM(net_mutex);
LIST_HEAD(net_namespace_list);
EXPORT_SYMBOL_GPL(net_namespace_list);
@@ -59,7 +59,7 @@ static int net_assign_generic(struct net *net, int id, void *data)
{
struct net_generic *ng, *old_ng;
- BUG_ON(!mutex_is_locked(&net_mutex));
+ BUG_ON(!rwsem_is_locked(&net_mutex));
BUG_ON(id == 0);
old_ng = rcu_dereference_protected(net->gen,
@@ -379,7 +379,7 @@ struct net *copy_net_ns(unsigned long flags,
get_user_ns(user_ns);
- mutex_lock(&net_mutex);
+ down_read(&net_mutex);
net->ucounts = ucounts;
rv = setup_net(net, user_ns);
if (rv == 0) {
@@ -387,7 +387,7 @@ struct net *copy_net_ns(unsigned long flags,
list_add_tail_rcu(&net->list, &net_namespace_list);
rtnl_unlock();
}
- mutex_unlock(&net_mutex);
+ up_read(&net_mutex);
if (rv < 0) {
dec_net_namespaces(ucounts);
put_user_ns(user_ns);
@@ -412,7 +412,7 @@ static void cleanup_net(struct work_struct *work)
list_replace_init(&cleanup_list, &net_kill_list);
spin_unlock_irq(&cleanup_list_lock);
- mutex_lock(&net_mutex);
+ down_read(&net_mutex);
/* Don't let anyone else find us. */
rtnl_lock();
@@ -452,7 +452,7 @@ static void cleanup_net(struct work_struct *work)
list_for_each_entry_reverse(ops, &pernet_list, list)
ops_free_list(ops, &net_exit_list);
- mutex_unlock(&net_mutex);
+ up_read(&net_mutex);
/* Ensure there are no outstanding rcu callbacks using this
* network namespace.
@@ -763,7 +763,7 @@ static int __init net_ns_init(void)
rcu_assign_pointer(init_net.gen, ng);
- mutex_lock(&net_mutex);
+ down_read(&net_mutex);
if (setup_net(&init_net, &init_user_ns))
panic("Could not setup the initial network namespace");
@@ -773,7 +773,7 @@ static int __init net_ns_init(void)
list_add_tail_rcu(&init_net.list, &net_namespace_list);
rtnl_unlock();
- mutex_unlock(&net_mutex);
+ up_read(&net_mutex);
register_pernet_subsys(&net_ns_ops);
@@ -912,9 +912,9 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
int register_pernet_subsys(struct pernet_operations *ops)
{
int error;
- mutex_lock(&net_mutex);
+ down_write(&net_mutex);
error = register_pernet_operations(first_device, ops);
- mutex_unlock(&net_mutex);
+ up_write(&net_mutex);
return error;
}
EXPORT_SYMBOL_GPL(register_pernet_subsys);
@@ -930,9 +930,9 @@ EXPORT_SYMBOL_GPL(register_pernet_subsys);
*/
void unregister_pernet_subsys(struct pernet_operations *ops)
{
- mutex_lock(&net_mutex);
+ down_write(&net_mutex);
unregister_pernet_operations(ops);
- mutex_unlock(&net_mutex);
+ up_write(&net_mutex);
}
EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
@@ -958,11 +958,11 @@ EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
int register_pernet_device(struct pernet_operations *ops)
{
int error;
- mutex_lock(&net_mutex);
+ down_write(&net_mutex);
error = register_pernet_operations(&pernet_list, ops);
if (!error && (first_device == &pernet_list))
first_device = &ops->list;
- mutex_unlock(&net_mutex);
+ up_write(&net_mutex);
return error;
}
EXPORT_SYMBOL_GPL(register_pernet_device);
@@ -978,11 +978,11 @@ EXPORT_SYMBOL_GPL(register_pernet_device);
*/
void unregister_pernet_device(struct pernet_operations *ops)
{
- mutex_lock(&net_mutex);
+ down_write(&net_mutex);
if (&ops->list == first_device)
first_device = first_device->next;
unregister_pernet_operations(ops);
- mutex_unlock(&net_mutex);
+ up_write(&net_mutex);
}
EXPORT_SYMBOL_GPL(unregister_pernet_device);
@@ -418,11 +418,11 @@ static void rtnl_lock_unregistering_all(void)
void rtnl_link_unregister(struct rtnl_link_ops *ops)
{
/* Close the race with cleanup_net() */
- mutex_lock(&net_mutex);
+ down_write(&net_mutex);
rtnl_lock_unregistering_all();
__rtnl_link_unregister(ops);
rtnl_unlock();
- mutex_unlock(&net_mutex);
+ up_write(&net_mutex);
}
EXPORT_SYMBOL_GPL(rtnl_link_unregister);
--
2.7.4