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netns: use a spin_lock to protect nsid management

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Before this patch, nsid were protected by the rtnl lock. The goal of this
patch is to be able to find a nsid without needing to hold the rtnl lock.

The next patch will introduce a netlink socket option to listen to all
netns that have a nsid assigned into the netns where the socket is opened.
Thus, it's important to call rtnl_net_notifyid() outside the spinlock, to
avoid a recursive lock (nsid are notified via rtnl). This was the main
reason of the previous patch.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Dichtel 2015-05-07 11:02:51 +02:00 committed by David S. Miller
parent 3138dbf881
commit 95f38411df
1 changed files with 44 additions and 13 deletions
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57
net/core/net_namespace.c
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@ -28,6 +28,7 @@
static LIST_HEAD(pernet_list);
static struct list_head *first_device = &pernet_list;
DEFINE_MUTEX(net_mutex);
static DEFINE_SPINLOCK(nsid_lock);
LIST_HEAD(net_namespace_list);
EXPORT_SYMBOL_GPL(net_namespace_list);
@ -147,18 +148,17 @@ static void ops_free_list(const struct pernet_operations *ops,
}
}
/* should be called with nsid_lock held */
static int alloc_netid(struct net *net, struct net *peer, int reqid)
{
int min = 0, max = 0;
ASSERT_RTNL();
if (reqid >= 0) {
min = reqid;
max = reqid + 1;
}
return idr_alloc(&net->netns_ids, peer, min, max, GFP_KERNEL);
return idr_alloc(&net->netns_ids, peer, min, max, GFP_ATOMIC);
}
/* This function is used by idr_for_each(). If net is equal to peer, the
@ -174,13 +174,15 @@ static int net_eq_idr(int id, void *net, void *peer)
return 0;
}
/* Should be called with nsid_lock held. If a new id is assigned, the bool alloc
* is set to true, thus the caller knows that the new id must be notified via
* rtnl.
*/
static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
{
int id = idr_for_each(&net->netns_ids, net_eq_idr, peer);
bool alloc_it = *alloc;
ASSERT_RTNL();
*alloc = false;
/* Magic value for id 0. */
@ -198,6 +200,7 @@ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
return NETNSA_NSID_NOT_ASSIGNED;
}
/* should be called with nsid_lock held */
static int __peernet2id(struct net *net, struct net *peer)
{
bool no = false;
@ -211,27 +214,46 @@ static void rtnl_net_notifyid(struct net *net, int cmd, int id);
*/
int peernet2id_alloc(struct net *net, struct net *peer)
{
bool alloc = atomic_read(&peer->count) == 0 ? false : true;
unsigned long flags;
bool alloc;
int id;
spin_lock_irqsave(&nsid_lock, flags);
alloc = atomic_read(&peer->count) == 0 ? false : true;
id = __peernet2id_alloc(net, peer, &alloc);
spin_unlock_irqrestore(&nsid_lock, flags);
if (alloc && id >= 0)
rtnl_net_notifyid(net, RTM_NEWNSID, id);
return id;
}
EXPORT_SYMBOL(peernet2id_alloc);
/* This function returns, if assigned, the id of a peer netns. */
static int peernet2id(struct net *net, struct net *peer)
{
unsigned long flags;
int id;
spin_lock_irqsave(&nsid_lock, flags);
id = __peernet2id(net, peer);
spin_unlock_irqrestore(&nsid_lock, flags);
return id;
}
struct net *get_net_ns_by_id(struct net *net, int id)
{
unsigned long flags;
struct net *peer;
if (id < 0)
return NULL;
rcu_read_lock();
spin_lock_irqsave(&nsid_lock, flags);
peer = idr_find(&net->netns_ids, id);
if (peer)
get_net(peer);
spin_unlock_irqrestore(&nsid_lock, flags);
rcu_read_unlock();
return peer;
@ -372,14 +394,19 @@ static void cleanup_net(struct work_struct *work)
list_del_rcu(&net->list);
list_add_tail(&net->exit_list, &net_exit_list);
for_each_net(tmp) {
int id = __peernet2id(tmp, net);
int id;
if (id >= 0) {
rtnl_net_notifyid(tmp, RTM_DELNSID, id);
spin_lock_irq(&nsid_lock);
id = __peernet2id(tmp, net);
if (id >= 0)
idr_remove(&tmp->netns_ids, id);
spin_unlock_irq(&nsid_lock);
if (id >= 0)
rtnl_net_notifyid(tmp, RTM_DELNSID, id);
}
}
spin_lock_irq(&nsid_lock);
idr_destroy(&net->netns_ids);
spin_unlock_irq(&nsid_lock);
}
rtnl_unlock();
@ -507,6 +534,7 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh)
{
struct net *net = sock_net(skb->sk);
struct nlattr *tb[NETNSA_MAX + 1];
unsigned long flags;
struct net *peer;
int nsid, err;
@ -527,12 +555,14 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh)
if (IS_ERR(peer))
return PTR_ERR(peer);
spin_lock_irqsave(&nsid_lock, flags);
if (__peernet2id(net, peer) >= 0) {
err = -EEXIST;
goto out;
}
err = alloc_netid(net, peer, nsid);
spin_unlock_irqrestore(&nsid_lock, flags);
if (err >= 0) {
rtnl_net_notifyid(net, RTM_NEWNSID, err);
err = 0;
@ -601,7 +631,7 @@ static int rtnl_net_getid(struct sk_buff *skb, struct nlmsghdr *nlh)
goto out;
}
id = __peernet2id(net, peer);
id = peernet2id(net, peer);
err = rtnl_net_fill(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0,
RTM_GETNSID, net, id);
if (err < 0)
@ -654,10 +684,11 @@ static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb)
.idx = 0,
.s_idx = cb->args[0],
};
unsigned long flags;
ASSERT_RTNL();
spin_lock_irqsave(&nsid_lock, flags);
idr_for_each(&net->netns_ids, rtnl_net_dumpid_one, &net_cb);
spin_unlock_irqrestore(&nsid_lock, flags);
cb->args[0] = net_cb.idx;
return skb->len;