Merge branch 'pernet-all-async'

Kirill Tkhai says:

====================
Make pernet_operations always read locked

All the pernet_operations are converted, and the last one
is in this patchset (nfsd_net_ops acked by J. Bruce Fields).
So, it's the time to kill pernet_operations::async field,
and make setup_net() and cleanup_net() always require
the rwsem only read locked.

All further pernet_operations have to be developed to fit
this rule. Some of previous patches added a comment to
struct pernet_operations about that.

Also, this patchset renames net_sem to pernet_ops_rwsem
to make the target area of the rwsem is more clear visible,
and adds more comments.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

10 files changed, 26 insertions, 69 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 97a96df4b6da..e13807b5c84d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8883,7 +8883,6 @@ static void __net_exit netdev_exit(struct net *net)
 static struct pernet_operations __net_initdata netdev_net_ops = {
 	.init = netdev_init,
 	.exit = netdev_exit,
-	.async = true,
 };
 
 static void __net_exit default_device_exit(struct net *net)
@@ -8984,7 +8983,6 @@ static void __net_exit default_device_exit_batch(struct list_head *net_list)
 static struct pernet_operations __net_initdata default_device_ops = {
 	.exit = default_device_exit,
 	.exit_batch = default_device_exit_batch,
-	.async = true,
 };
 
 /*
diff --git a/net/core/fib_notifier.c b/net/core/fib_notifier.c
index 5ace0705a3f9..0c048bdeb016 100644
--- a/net/core/fib_notifier.c
+++ b/net/core/fib_notifier.c
@@ -171,7 +171,6 @@ static void __net_exit fib_notifier_net_exit(struct net *net)
 static struct pernet_operations fib_notifier_net_ops = {
 	.init = fib_notifier_net_init,
 	.exit = fib_notifier_net_exit,
-	.async = true,
 };
 
 static int __init fib_notifier_init(void)
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index f6f04fc0f629..9d87ce868402 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -1130,7 +1130,6 @@ static void __net_exit fib_rules_net_exit(struct net *net)
 static struct pernet_operations fib_rules_net_ops = {
 	.init = fib_rules_net_init,
 	.exit = fib_rules_net_exit,
-	.async = true,
 };
 
 static int __init fib_rules_init(void)
diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
index dd6ae431d038..9737302907b1 100644
--- a/net/core/net-procfs.c
+++ b/net/core/net-procfs.c
@@ -349,7 +349,6 @@ static void __net_exit dev_proc_net_exit(struct net *net)
 static struct pernet_operations __net_initdata dev_proc_ops = {
 	.init = dev_proc_net_init,
 	.exit = dev_proc_net_exit,
-	.async = true,
 };
 
 static int dev_mc_seq_show(struct seq_file *seq, void *v)
@@ -406,7 +405,6 @@ static void __net_exit dev_mc_net_exit(struct net *net)
 static struct pernet_operations __net_initdata dev_mc_net_ops = {
 	.init = dev_mc_net_init,
 	.exit = dev_mc_net_exit,
-	.async = true,
 };
 
 int __init dev_proc_init(void)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 95ba2c53bd9a..b5796d17a302 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -40,12 +40,13 @@ struct net init_net = {
 EXPORT_SYMBOL(init_net);
 
 static bool init_net_initialized;
-static unsigned nr_sync_pernet_ops;
 /*
- * net_sem: protects: pernet_list, net_generic_ids, nr_sync_pernet_ops,
+ * pernet_ops_rwsem: protects: pernet_list, net_generic_ids,
  * init_net_initialized and first_device pointer.
+ * This is internal net namespace object. Please, don't use it
+ * outside.
  */
-DECLARE_RWSEM(net_sem);
+DECLARE_RWSEM(pernet_ops_rwsem);
 
 #define MIN_PERNET_OPS_ID	\
 	((sizeof(struct net_generic) + sizeof(void *) - 1) / sizeof(void *))
@@ -73,7 +74,7 @@ static int net_assign_generic(struct net *net, unsigned int id, void *data)
 	BUG_ON(id < MIN_PERNET_OPS_ID);
 
 	old_ng = rcu_dereference_protected(net->gen,
-					   lockdep_is_held(&net_sem));
+					   lockdep_is_held(&pernet_ops_rwsem));
 	if (old_ng->s.len > id) {
 		old_ng->ptr[id] = data;
 		return 0;
@@ -290,7 +291,7 @@ struct net *get_net_ns_by_id(struct net *net, int id)
  */
 static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 {
-	/* Must be called with net_sem held */
+	/* Must be called with pernet_ops_rwsem held */
 	const struct pernet_operations *ops, *saved_ops;
 	int error = 0;
 	LIST_HEAD(net_exit_list);
@@ -339,7 +340,6 @@ static int __net_init net_defaults_init_net(struct net *net)
 
 static struct pernet_operations net_defaults_ops = {
 	.init = net_defaults_init_net,
-	.async = true,
 };
 
 static __init int net_defaults_init(void)
@@ -406,7 +406,6 @@ struct net *copy_net_ns(unsigned long flags,
 {
 	struct ucounts *ucounts;
 	struct net *net;
-	unsigned write;
 	int rv;
 
 	if (!(flags & CLONE_NEWNET))
@@ -424,25 +423,14 @@ struct net *copy_net_ns(unsigned long flags,
 	refcount_set(&net->passive, 1);
 	net->ucounts = ucounts;
 	get_user_ns(user_ns);
-again:
-	write = READ_ONCE(nr_sync_pernet_ops);
-	if (write)
-		rv = down_write_killable(&net_sem);
-	else
-		rv = down_read_killable(&net_sem);
+
+	rv = down_read_killable(&pernet_ops_rwsem);
 	if (rv < 0)
 		goto put_userns;
 
-	if (!write && unlikely(READ_ONCE(nr_sync_pernet_ops))) {
-		up_read(&net_sem);
-		goto again;
-	}
 	rv = setup_net(net, user_ns);
 
-	if (write)
-		up_write(&net_sem);
-	else
-		up_read(&net_sem);
+	up_read(&pernet_ops_rwsem);
 
 	if (rv < 0) {
 put_userns:
@@ -490,21 +478,11 @@ static void cleanup_net(struct work_struct *work)
 	struct net *net, *tmp, *last;
 	struct llist_node *net_kill_list;
 	LIST_HEAD(net_exit_list);
-	unsigned write;
 
 	/* Atomically snapshot the list of namespaces to cleanup */
 	net_kill_list = llist_del_all(&cleanup_list);
-again:
-	write = READ_ONCE(nr_sync_pernet_ops);
-	if (write)
-		down_write(&net_sem);
-	else
-		down_read(&net_sem);
 
-	if (!write && unlikely(READ_ONCE(nr_sync_pernet_ops))) {
-		up_read(&net_sem);
-		goto again;
-	}
+	down_read(&pernet_ops_rwsem);
 
 	/* Don't let anyone else find us. */
 	rtnl_lock();
@@ -543,10 +521,7 @@ again:
 	list_for_each_entry_reverse(ops, &pernet_list, list)
 		ops_free_list(ops, &net_exit_list);
 
-	if (write)
-		up_write(&net_sem);
-	else
-		up_read(&net_sem);
+	up_read(&pernet_ops_rwsem);
 
 	/* Ensure there are no outstanding rcu callbacks using this
 	 * network namespace.
@@ -573,8 +548,8 @@ again:
  */
 void net_ns_barrier(void)
 {
-	down_write(&net_sem);
-	up_write(&net_sem);
+	down_write(&pernet_ops_rwsem);
+	up_write(&pernet_ops_rwsem);
 }
 EXPORT_SYMBOL(net_ns_barrier);
 
@@ -654,7 +629,6 @@ static __net_exit void net_ns_net_exit(struct net *net)
 static struct pernet_operations __net_initdata net_ns_ops = {
 	.init = net_ns_net_init,
 	.exit = net_ns_net_exit,
-	.async = true,
 };
 
 static const struct nla_policy rtnl_net_policy[NETNSA_MAX + 1] = {
@@ -897,12 +871,12 @@ static int __init net_ns_init(void)
 
 	rcu_assign_pointer(init_net.gen, ng);
 
-	down_write(&net_sem);
+	down_write(&pernet_ops_rwsem);
 	if (setup_net(&init_net, &init_user_ns))
 		panic("Could not setup the initial network namespace");
 
 	init_net_initialized = true;
-	up_write(&net_sem);
+	up_write(&pernet_ops_rwsem);
 
 	register_pernet_subsys(&net_ns_ops);
 
@@ -1006,9 +980,6 @@ again:
 		rcu_barrier();
 		if (ops->id)
 			ida_remove(&net_generic_ids, *ops->id);
-	} else if (!ops->async) {
-		pr_info_once("Pernet operations %ps are sync.\n", ops);
-		nr_sync_pernet_ops++;
 	}
 
 	return error;
@@ -1016,8 +987,6 @@ again:
 
 static void unregister_pernet_operations(struct pernet_operations *ops)
 {
-	if (!ops->async)
-		BUG_ON(nr_sync_pernet_ops-- == 0);
 	__unregister_pernet_operations(ops);
 	rcu_barrier();
 	if (ops->id)
@@ -1046,9 +1015,9 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
 int register_pernet_subsys(struct pernet_operations *ops)
 {
 	int error;
-	down_write(&net_sem);
+	down_write(&pernet_ops_rwsem);
 	error =  register_pernet_operations(first_device, ops);
-	up_write(&net_sem);
+	up_write(&pernet_ops_rwsem);
 	return error;
 }
 EXPORT_SYMBOL_GPL(register_pernet_subsys);
@@ -1064,9 +1033,9 @@ EXPORT_SYMBOL_GPL(register_pernet_subsys);
  */
 void unregister_pernet_subsys(struct pernet_operations *ops)
 {
-	down_write(&net_sem);
+	down_write(&pernet_ops_rwsem);
 	unregister_pernet_operations(ops);
-	up_write(&net_sem);
+	up_write(&pernet_ops_rwsem);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
 
@@ -1092,11 +1061,11 @@ EXPORT_SYMBOL_GPL(unregister_pernet_subsys);
 int register_pernet_device(struct pernet_operations *ops)
 {
 	int error;
-	down_write(&net_sem);
+	down_write(&pernet_ops_rwsem);
 	error = register_pernet_operations(&pernet_list, ops);
 	if (!error && (first_device == &pernet_list))
 		first_device = &ops->list;
-	up_write(&net_sem);
+	up_write(&pernet_ops_rwsem);
 	return error;
 }
 EXPORT_SYMBOL_GPL(register_pernet_device);
@@ -1112,11 +1081,11 @@ EXPORT_SYMBOL_GPL(register_pernet_device);
  */
 void unregister_pernet_device(struct pernet_operations *ops)
 {
-	down_write(&net_sem);
+	down_write(&pernet_ops_rwsem);
 	if (&ops->list == first_device)
 		first_device = first_device->next;
 	unregister_pernet_operations(ops);
-	up_write(&net_sem);
+	up_write(&pernet_ops_rwsem);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_device);
 
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 545cf08cd558..7e4ede34cc52 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3852,7 +3852,6 @@ static struct pernet_operations pg_net_ops = {
 	.exit = pg_net_exit,
 	.id   = &pg_net_id,
 	.size = sizeof(struct pktgen_net),
-	.async = true,
 };
 
 static int __init pg_init(void)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 87079eaa871b..2d3949789cef 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -459,12 +459,12 @@ static void rtnl_lock_unregistering_all(void)
  */
 void rtnl_link_unregister(struct rtnl_link_ops *ops)
 {
-	/* Close the race with cleanup_net() */
-	down_write(&net_sem);
+	/* Close the race with setup_net() and cleanup_net() */
+	down_write(&pernet_ops_rwsem);
 	rtnl_lock_unregistering_all();
 	__rtnl_link_unregister(ops);
 	rtnl_unlock();
-	up_write(&net_sem);
+	up_write(&pernet_ops_rwsem);
 }
 EXPORT_SYMBOL_GPL(rtnl_link_unregister);
 
@@ -4730,7 +4730,6 @@ static void __net_exit rtnetlink_net_exit(struct net *net)
 static struct pernet_operations rtnetlink_net_ops = {
 	.init = rtnetlink_net_init,
 	.exit = rtnetlink_net_exit,
-	.async = true,
 };
 
 void __init rtnetlink_init(void)
diff --git a/net/core/sock.c b/net/core/sock.c
index 8cee2920a47f..6444525f610c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3175,7 +3175,6 @@ static void __net_exit sock_inuse_exit_net(struct net *net)
 static struct pernet_operations net_inuse_ops = {
 	.init = sock_inuse_init_net,
 	.exit = sock_inuse_exit_net,
-	.async = true,
 };
 
 static __init int net_inuse_init(void)
@@ -3470,7 +3469,6 @@ static __net_exit void proto_exit_net(struct net *net)
 static __net_initdata struct pernet_operations proto_net_ops = {
 	.init = proto_init_net,
 	.exit = proto_exit_net,
-	.async = true,
 };
 
 static int __init proto_init(void)
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index a3392a8f9276..c37b5be7c5e4 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c
@@ -324,7 +324,6 @@ static void __net_exit diag_net_exit(struct net *net)
 static struct pernet_operations diag_net_ops = {
 	.init = diag_net_init,
 	.exit = diag_net_exit,
-	.async = true,
 };
 
 static int __init sock_diag_init(void)
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 4f47f92459cc..b3b609f0eeb5 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -584,7 +584,6 @@ static __net_exit void sysctl_core_net_exit(struct net *net)
 static __net_initdata struct pernet_operations sysctl_core_ops = {
 	.init = sysctl_core_net_init,
 	.exit = sysctl_core_net_exit,
-	.async = true,
 };
 
 static __init int sysctl_core_init(void)