Commit f0b07bb1 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by David S. Miller

net: Introduce net_rwsem to protect net_namespace_list

rtnl_lock() is used everywhere, and contention is very high.
When someone wants to iterate over alive net namespaces,
he/she has no a possibility to do that without exclusive lock.
But the exclusive rtnl_lock() in such places is overkill,
and it just increases the contention. Yes, there is already
for_each_net_rcu() in kernel, but it requires rcu_read_lock(),
and this can't be sleepable. Also, sometimes it may be need
really prevent net_namespace_list growth, so for_each_net_rcu()
is not fit there.

This patch introduces new rw_semaphore, which will be used
instead of rtnl_mutex to protect net_namespace_list. It is
sleepable and allows not-exclusive iterations over net
namespaces list. It allows to stop using rtnl_lock()
in several places (what is made in next patches) and makes
less the time, we keep rtnl_mutex. Here we just add new lock,
while the explanation of we can remove rtnl_lock() there are
in next patches.

Fine grained locks generally are better, then one big lock,
so let's do that with net_namespace_list, while the situation
allows that.
Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 906edee9
......@@ -403,10 +403,12 @@ static void enum_all_gids_of_dev_cb(struct ib_device *ib_dev,
* our feet
*/
rtnl_lock();
down_read(&net_rwsem);
for_each_net(net)
for_each_netdev(net, ndev)
if (is_eth_port_of_netdev(ib_dev, port, rdma_ndev, ndev))
add_netdev_ips(ib_dev, port, rdma_ndev, ndev);
up_read(&net_rwsem);
rtnl_unlock();
}
......
......@@ -37,6 +37,7 @@ extern int rtnl_lock_killable(void);
extern wait_queue_head_t netdev_unregistering_wq;
extern struct rw_semaphore pernet_ops_rwsem;
extern struct rw_semaphore net_rwsem;
#ifdef CONFIG_PROVE_LOCKING
extern bool lockdep_rtnl_is_held(void);
......
......@@ -291,6 +291,7 @@ static inline struct net *read_pnet(const possible_net_t *pnet)
#endif
}
/* Protected by net_rwsem */
#define for_each_net(VAR) \
list_for_each_entry(VAR, &net_namespace_list, list)
......
......@@ -1629,6 +1629,7 @@ int register_netdevice_notifier(struct notifier_block *nb)
goto unlock;
if (dev_boot_phase)
goto unlock;
down_read(&net_rwsem);
for_each_net(net) {
for_each_netdev(net, dev) {
err = call_netdevice_notifier(nb, NETDEV_REGISTER, dev);
......@@ -1642,6 +1643,7 @@ int register_netdevice_notifier(struct notifier_block *nb)
call_netdevice_notifier(nb, NETDEV_UP, dev);
}
}
up_read(&net_rwsem);
unlock:
rtnl_unlock();
......@@ -1664,6 +1666,7 @@ int register_netdevice_notifier(struct notifier_block *nb)
}
outroll:
up_read(&net_rwsem);
raw_notifier_chain_unregister(&netdev_chain, nb);
goto unlock;
}
......@@ -1694,6 +1697,7 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
if (err)
goto unlock;
down_read(&net_rwsem);
for_each_net(net) {
for_each_netdev(net, dev) {
if (dev->flags & IFF_UP) {
......@@ -1704,6 +1708,7 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
call_netdevice_notifier(nb, NETDEV_UNREGISTER, dev);
}
}
up_read(&net_rwsem);
unlock:
rtnl_unlock();
return err;
......
......@@ -33,6 +33,7 @@ static unsigned int fib_seq_sum(void)
struct net *net;
rtnl_lock();
down_read(&net_rwsem);
for_each_net(net) {
rcu_read_lock();
list_for_each_entry_rcu(ops, &net->fib_notifier_ops, list) {
......@@ -43,6 +44,7 @@ static unsigned int fib_seq_sum(void)
}
rcu_read_unlock();
}
up_read(&net_rwsem);
rtnl_unlock();
return fib_seq;
......
......@@ -33,6 +33,10 @@ static struct list_head *first_device = &pernet_list;
LIST_HEAD(net_namespace_list);
EXPORT_SYMBOL_GPL(net_namespace_list);
/* Protects net_namespace_list. Nests iside rtnl_lock() */
DECLARE_RWSEM(net_rwsem);
EXPORT_SYMBOL_GPL(net_rwsem);
struct net init_net = {
.count = REFCOUNT_INIT(1),
.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
......@@ -309,9 +313,9 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
if (error < 0)
goto out_undo;
}
rtnl_lock();
down_write(&net_rwsem);
list_add_tail_rcu(&net->list, &net_namespace_list);
rtnl_unlock();
up_write(&net_rwsem);
out:
return error;
......@@ -450,7 +454,7 @@ static void unhash_nsid(struct net *net, struct net *last)
* and this work is the only process, that may delete
* a net from net_namespace_list. So, when the below
* is executing, the list may only grow. Thus, we do not
* use for_each_net_rcu() or rtnl_lock().
* use for_each_net_rcu() or net_rwsem.
*/
for_each_net(tmp) {
int id;
......@@ -485,7 +489,7 @@ static void cleanup_net(struct work_struct *work)
down_read(&pernet_ops_rwsem);
/* Don't let anyone else find us. */
rtnl_lock();
down_write(&net_rwsem);
llist_for_each_entry(net, net_kill_list, cleanup_list)
list_del_rcu(&net->list);
/* Cache last net. After we unlock rtnl, no one new net
......@@ -499,7 +503,7 @@ static void cleanup_net(struct work_struct *work)
* useless anyway, as netns_ids are destroyed there.
*/
last = list_last_entry(&net_namespace_list, struct net, list);
rtnl_unlock();
up_write(&net_rwsem);
llist_for_each_entry(net, net_kill_list, cleanup_list) {
unhash_nsid(net, last);
......@@ -900,6 +904,9 @@ static int __register_pernet_operations(struct list_head *list,
list_add_tail(&ops->list, list);
if (ops->init || (ops->id && ops->size)) {
/* We held write locked pernet_ops_rwsem, and parallel
* setup_net() and cleanup_net() are not possible.
*/
for_each_net(net) {
error = ops_init(ops, net);
if (error)
......@@ -923,6 +930,7 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
LIST_HEAD(net_exit_list);
list_del(&ops->list);
/* See comment in __register_pernet_operations() */
for_each_net(net)
list_add_tail(&net->exit_list, &net_exit_list);
ops_exit_list(ops, &net_exit_list);
......
......@@ -418,9 +418,11 @@ void __rtnl_link_unregister(struct rtnl_link_ops *ops)
{
struct net *net;
down_read(&net_rwsem);
for_each_net(net) {
__rtnl_kill_links(net, ops);
}
up_read(&net_rwsem);
list_del(&ops->list);
}
EXPORT_SYMBOL_GPL(__rtnl_link_unregister);
......@@ -438,6 +440,9 @@ static void rtnl_lock_unregistering_all(void)
for (;;) {
unregistering = false;
rtnl_lock();
/* We held write locked pernet_ops_rwsem, and parallel
* setup_net() and cleanup_net() are not possible.
*/
for_each_net(net) {
if (net->dev_unreg_count > 0) {
unregistering = true;
......
......@@ -1764,12 +1764,14 @@ nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data)
struct net *net;
rtnl_lock();
down_read(&net_rwsem);
for_each_net(net) {
if (atomic_read(&net->ct.count) == 0)
continue;
__nf_ct_unconfirmed_destroy(net);
nf_queue_nf_hook_drop(net);
}
up_read(&net_rwsem);
rtnl_unlock();
/* Need to wait for netns cleanup worker to finish, if its
......
......@@ -2364,8 +2364,10 @@ static void __net_exit ovs_exit_net(struct net *dnet)
__dp_destroy(dp);
rtnl_lock();
down_read(&net_rwsem);
for_each_net(net)
list_vports_from_net(net, dnet, &head);
up_read(&net_rwsem);
rtnl_unlock();
/* Detach all vports from given namespace. */
......
......@@ -349,11 +349,13 @@ void wireless_nlevent_flush(void)
ASSERT_RTNL();
down_read(&net_rwsem);
for_each_net(net) {
while ((skb = skb_dequeue(&net->wext_nlevents)))
rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL,
GFP_KERNEL);
}
up_read(&net_rwsem);
}
EXPORT_SYMBOL_GPL(wireless_nlevent_flush);
......
......@@ -48,8 +48,10 @@ static inline void selinux_xfrm_notify_policyload(void)
struct net *net;
rtnl_lock();
down_read(&net_rwsem);
for_each_net(net)
rt_genid_bump_all(net);
up_read(&net_rwsem);
rtnl_unlock();
}
#else
......
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