Network namespace has two referrence counters:
- count
- use_count.
The namespace is scheduled to destruction automatically when the count
becomes 0.

There are several SLAB objects with a pointer to a namespace on them.
These objects are cleaned up during namespace stop. Some of them
increment use_count, some don't. This set fixes this discrepancy,
i.e. now all such objects increment the use_count.

Though, the use_count itself is used in a very debug manner and checked
only during namespace stop. So, I have placed it under
NETNS_REFCNT_DEBUG definition exactly like this is done for socket
refcounting code to remove extra atomic from any possible fast paths.

Signed-off-by: Denis V. Lunev <den@openvz.org>

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Make release_net/hold_net noop for performance-hungry people. This is a debug
staff and should be used in the debug mode only.

Add check for net != NULL in hold/release calls. This will be required
later on.

Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 include/net/net_namespace.h |   44 +++++++++++++++++++++++++++---------------
 net/core/net_namespace.c    |    4 +++
 2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index e2aee26..269a681 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -21,9 +21,11 @@ struct net_device;
 	atomic_t		count;		/* To decided when the network
 						 *  namespace should be freed.
 						 */
+#ifdef NETNS_REFCNT_DEBUG
 	atomic_t		use_count;	/* To track references we
 						 * destroy on demand
 						 */
+#endif
 	struct list_head	list;		/* list of network namespaces */
 	struct work_struct	work;		/* work struct for freeing */
 
@@ -115,17 +119,6 @@ static inline void put_net(struct net *net)
 		__put_net(net);
 }
 
-static inline struct net *hold_net(struct net *net)
-{
-	atomic_inc(&net->use_count);
-	return net;
-}
-
-static inline void release_net(struct net *net)
-{
-	atomic_dec(&net->use_count);
-}
-
 static inline
 int net_eq(const struct net *net1, const struct net *net2)
 {
@@ -141,27 +134,46 @@ static inline void put_net(struct net *net)
 {
 }
 
+static inline struct net *maybe_get_net(struct net *net)
+{
+	return net;
+}
+
+static inline
+int net_eq(const struct net *net1, const struct net *net2)
+{
+	return 1;
+}
+#endif
+
+
+#ifdef NETNS_REFCNT_DEBUG
 static inline struct net *hold_net(struct net *net)
 {
+	if (net == NULL)
+		return NULL;
+	atomic_inc(&net->use_count);
 	return net;
 }
 
 static inline void release_net(struct net *net)
 {
+	if (net == NULL)
+		return;
+	atomic_dec(&net->use_count);
 }
-
-static inline struct net *maybe_get_net(struct net *net)
+#else
+static inline struct net *hold_net(struct net *net)
 {
 	return net;
 }
 
-static inline
-int net_eq(const struct net *net1, const struct net *net2)
+static inline void release_net(struct net *net)
 {
-	return 1;
 }
 #endif
 
+
 #define for_each_net(VAR)				\
 	list_for_each_entry(VAR, &net_namespace_list, list)
 
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 7b66083..f310ef3 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -30,7 +30,9 @@ static __net_init int setup_net(struct net *net)
 	int error;
 
 	atomic_set(&net->count, 1);
+#ifdef NETNS_REFCNT_DEBUG
 	atomic_set(&net->use_count, 0);
+#endif
 
 	error = 0;
 	list_for_each_entry(ops, &pernet_list, list) {
@@ -70,11 +72,13 @@ static void net_free(struct net *net)
 	if (!net)
 		return;
 
+#ifdef NETNS_REFCNT_DEBUG
 	if (unlikely(atomic_read(&net->use_count) != 0)) {
 		printk(KERN_EMERG "network namespace not free! Usage: %d\n",
 			atomic_read(&net->use_count));
 		return;
 	}
+#endif
 
 	kmem_cache_free(net_cachep, net);
 }
-- 
1.5.3.rc5

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Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 net/ipv6/route.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 6293cb9..210a079 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2622,7 +2622,7 @@ static int ip6_route_net_init(struct net *net)
 					GFP_KERNEL);
 	if (!net->ipv6.ip6_dst_ops)
 		goto out;
-	net->ipv6.ip6_dst_ops->dst_net = net;
+	net->ipv6.ip6_dst_ops->dst_net = hold_net(net);
 
 	net->ipv6.ip6_null_entry = kmemdup(&ip6_null_entry_template,
 					   sizeof(*net->ipv6.ip6_null_entry),
@@ -2669,6 +2669,7 @@ out:
 	return ret;
 
 out_ip6_dst_ops:
+	release_net(net->ipv6.ip6_dst_ops->dst_net);
 	kfree(net->ipv6.ip6_dst_ops);
 	goto out;
 }
@@ -2684,6 +2685,7 @@ static void ip6_route_net_exit(struct net *net)
 	kfree(net->ipv6.ip6_prohibit_entry);
 	kfree(net->ipv6.ip6_blk_hole_entry);
 #endif
+	release_net(net->ipv6.ip6_dst_ops->dst_net);
 	kfree(net->ipv6.ip6_dst_ops);
 }
 
-- 
1.5.3.rc5

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Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 net/ipv4/inet_timewait_sock.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index a741378..ce16e9a 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -57,6 +57,7 @@ void inet_twsk_put(struct inet_timewait_sock *tw)
 		printk(KERN_DEBUG "%s timewait_sock %p released\n",
 		       tw->tw_prot->name, tw);
 #endif
+		release_net(twsk_net(tw));
 		kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
 		module_put(owner);
 	}
@@ -124,7 +125,7 @@ struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int stat
 		tw->tw_hash	    = sk->sk_hash;
 		tw->tw_ipv6only	    = 0;
 		tw->tw_prot	    = sk->sk_prot_creator;
-		twsk_net_set(tw, sock_net(sk));
+		twsk_net_set(tw, hold_net(sock_net(sk)));
 		atomic_set(&tw->tw_refcnt, 1);
 		inet_twsk_dead_node_init(tw);
 		__module_get(tw->tw_prot->owner);
-- 
1.5.3.rc5

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Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 net/ipv4/fib_semantics.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index a13c847..3b83c34 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -152,6 +152,7 @@ void free_fib_info(struct fib_info *fi)
 		nh->nh_dev = NULL;
 	} endfor_nexthops(fi);
 	fib_info_cnt--;
+	release_net(fi->fib_net);
 	kfree(fi);
 }
 
@@ -730,7 +731,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
 		goto failure;
 	fib_info_cnt++;
 
-	fi->fib_net = net;
+	fi->fib_net = hold_net(net);
 	fi->fib_protocol = cfg->fc_protocol;
 	fi->fib_flags = cfg->fc_flags;
 	fi->fib_priority = cfg->fc_priority;
-- 
1.5.3.rc5

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Protocol control sockets and netlink kernel sockets should not prevent the
namespace stop request. They are initialized and disposed in a special way by
sk_change_net/sk_release_kernel.

Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 include/net/sock.h |    2 +-
 net/core/sock.c    |    1 +
 2 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 09255ea..dc42b44 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1314,7 +1314,7 @@ void sock_net_set(struct sock *sk, struct net *net)
 static inline void sk_change_net(struct sock *sk, struct net *net)
 {
 	put_net(sock_net(sk));
-	sock_net_set(sk, net);
+	sock_net_set(sk, hold_net(net));
 }
 
 extern void sock_enable_timestamp(struct sock *sk);
diff --git a/net/core/sock.c b/net/core/sock.c
index f2ccb16..015ec69 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1001,6 +1001,7 @@ void sk_release_kernel(struct sock *sk)
 
 	sock_hold(sk);
 	sock_release(sk->sk_socket);
+	release_net(sock_net(sk));
 	sock_net_set(sk, get_net(&init_net));
 	sock_put(sk);
 }
-- 
1.5.3.rc5

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Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 include/net/fib_rules.h |    1 +
 net/core/fib_rules.c    |    5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index 34349f9..a5c6ccc 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -87,6 +87,7 @@ static inline void fib_rule_get(struct fib_rule *rule)
 static inline void fib_rule_put_rcu(struct rcu_head *head)
 {
 	struct fib_rule *rule = container_of(head, struct fib_rule, rcu);
+	release_net(rule->fr_net);
 	kfree(rule);
 }
 
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 540c072..e3e9ab0 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -29,7 +29,7 @@ int fib_default_rule_add(struct fib_rules_ops *ops,
 	r->pref = pref;
 	r->table = table;
 	r->flags = flags;
-	r->fr_net = ops->fro_net;
+	r->fr_net = hold_net(ops->fro_net);
 
 	/* The lock is not required here, the list in unreacheable
 	 * at the moment this function is called */
@@ -243,7 +243,7 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 		err = -ENOMEM;
 		goto errout;
 	}
-	rule->fr_net = net;
+	rule->fr_net = hold_net(net);
 
 	if (tb[FRA_PRIORITY])
 		rule->pref = nla_get_u32(tb[FRA_PRIORITY]);
@@ -344,6 +344,7 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 	return 0;
 
 errout_free:
+	release_net(rule->fr_net);
 	kfree(rule);
 errout:
 	rules_ops_put(ops);
-- 
1.5.3.rc5

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Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 net/ipv4/inet_hashtables.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 32ca2f8..1612184 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -35,7 +35,7 @@ struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
 	struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);
 
 	if (tb != NULL) {
-		tb->ib_net       = net;
+		tb->ib_net       = hold_net(net);
 		tb->port      = snum;
 		tb->fastreuse = 0;
 		INIT_HLIST_HEAD(&tb->owners);
@@ -51,6 +51,7 @@ void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket
 {
 	if (hlist_empty(&tb->owners)) {
 		__hlist_del(&tb->node);
+		release_net(tb->ib_net);
 		kmem_cache_free(cachep, tb);
 	}
 }
-- 
1.5.3.rc5

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dev_set_net is called for
- just allocated devices
- devices moving from one namespace to another
release_net has proper check inside to distinguish these cases.

Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 include/linux/netdevice.h |    3 ++-
 net/core/dev.c            |    2 ++
 2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8b17ed4..7c1d446 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -758,7 +758,8 @@ static inline
 void dev_net_set(struct net_device *dev, struct net *net)
 {
 #ifdef CONFIG_NET_NS
-	dev->nd_net = net;
+	release_net(dev->nd_net);
+	dev->nd_net = hold_net(net);
 #endif
 }
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 7aa0112..77530e9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4042,6 +4042,8 @@ EXPORT_SYMBOL(alloc_netdev_mq);
  */
 void free_netdev(struct net_device *dev)
 {
+	release_net(dev_net(dev));
+
 	/*  Compatibility with error handling in drivers */
 	if (dev->reg_state == NETREG_UNINITIALIZED) {
 		kfree((char *)dev - dev->padded);
-- 
1.5.3.rc5

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Denis V. Lunev wrote:
> +#ifdef NETNS_REFCNT_DEBUG
>  static inline struct net *hold_net(struct net *net)
>  {
> +	if (net == NULL)
> +		return NULL;
> +	atomic_inc(&net->use_count);
>  	return net;
>  }

This could be shrunk to:

	if (net)
		atomic_inc(&net->use_count);
	return net;

>  static inline void release_net(struct net *net)
>  {
> +	if (net == NULL)
> +		return;
> +	atomic_dec(&net->use_count);
>  }

This one too:

	if (net)
		atomic_dec(&net->use_count);

-Brian
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From: Brian Haley <brian.haley@hp.com>
Date: Tue, 15 Apr 2008 10:55:20 -0400

> Denis V. Lunev wrote:
> > +#ifdef NETNS_REFCNT_DEBUG
> >  static inline struct net *hold_net(struct net *net)
> >  {
> > +	if (net == NULL)
> > +		return NULL;
> > +	atomic_inc(&net->use_count);
> >  	return net;
> >  }
> 
> This could be shrunk to:
 ...
> This one too:

I've checked in Denis's patch with those simplifications added.
Thanks everyone.
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From: "Denis V. Lunev" <den@openvz.org>
Date: Tue, 15 Apr 2008 16:35:59 +0400

> Network namespace has two referrence counters:
> - count
> - use_count.
> The namespace is scheduled to destruction automatically when the count
> becomes 0.
> 
> There are several SLAB objects with a pointer to a namespace on them.
> These objects are cleaned up during namespace stop. Some of them
> increment use_count, some don't. This set fixes this discrepancy,
> i.e. now all such objects increment the use_count.
> 
> Though, the use_count itself is used in a very debug manner and checked
> only during namespace stop. So, I have placed it under
> NETNS_REFCNT_DEBUG definition exactly like this is done for socket
> refcounting code to remove extra atomic from any possible fast paths.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>

This is a notification that the Linux NETDEV Patch Robot has used all
automated tools known to man to validate your patches, and has decided
to apply then to the net-2.6.26 GIT tree.

*beep* *beep*

You may continue hacking.

*beep* *beep*

Have a pleasant day.
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