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Commit 95f38411 authored by Nicolas Dichtel's avatar Nicolas Dichtel Committed by David S. Miller
Browse files

netns: use a spin_lock to protect nsid management 



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: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3138dbf8

net/core/net_namespace.c

+44 −13
Original line number Diff line number Diff line
@@ -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;