net caif: Register properly as a pernet subsystem.

caif is a subsystem and as such it needs to register with
register_pernet_subsys instead of register_pernet_device.

Among other problems using register_pernet_device was resulting in
net_generic being called before the caif_net structure was allocated.
Which has been causing net_generic to fail with either BUG_ON's or by
return NULL pointers.

A more ugly problem that could be caused is packets in flight why the
subsystem is shutting down.

To remove confusion also remove the cruft cause by inappropriately
trying to fix this bug.

With the aid of the previous patch I have tested this patch and
confirmed that using register_pernet_subsys makes the failure go away as
it should.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index 673728a..82c5706 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c
@@ -59,8 +59,6 @@
 {
 	struct caif_net *caifn;
 	caifn = net_generic(net, caif_net_id);
-	if (!caifn)
-		return NULL;
 	return caifn->cfg;
 }
 EXPORT_SYMBOL(get_cfcnfg);
@@ -69,8 +67,6 @@
 {
 	struct caif_net *caifn;
 	caifn = net_generic(net, caif_net_id);
-	if (!caifn)
-		return NULL;
 	return &caifn->caifdevs;
 }
 
@@ -99,8 +95,6 @@
 	struct caif_device_entry *caifd;
 
 	caifdevs = caif_device_list(dev_net(dev));
-	if (!caifdevs)
-		return NULL;
 
 	caifd = kzalloc(sizeof(*caifd), GFP_KERNEL);
 	if (!caifd)
@@ -120,8 +114,6 @@
 	struct caif_device_entry_list *caifdevs =
 	    caif_device_list(dev_net(dev));
 	struct caif_device_entry *caifd;
-	if (!caifdevs)
-		return NULL;
 
 	list_for_each_entry_rcu(caifd, &caifdevs->list, list) {
 		if (caifd->netdev == dev)
@@ -321,8 +313,6 @@
 	struct caif_device_entry_list *caifdevs;
 
 	caifdevs = caif_device_list(dev_net(dev));
-	if (!cfg || !caifdevs)
-		return;
 	caifd = caif_device_alloc(dev);
 	if (!caifd)
 		return;
@@ -374,8 +364,6 @@
 
 	cfg = get_cfcnfg(dev_net(dev));
 	caifdevs = caif_device_list(dev_net(dev));
-	if (!cfg || !caifdevs)
-		return 0;
 
 	caifd = caif_get(dev);
 	if (caifd == NULL && dev->type != ARPHRD_CAIF)
@@ -507,9 +495,6 @@
 static int caif_init_net(struct net *net)
 {
 	struct caif_net *caifn = net_generic(net, caif_net_id);
-	if (WARN_ON(!caifn))
-		return -EINVAL;
-
 	INIT_LIST_HEAD(&caifn->caifdevs.list);
 	mutex_init(&caifn->caifdevs.lock);
 
@@ -527,9 +512,6 @@
 	    caif_device_list(net);
 	struct cfcnfg *cfg =  get_cfcnfg(net);
 
-	if (!cfg || !caifdevs)
-		return;
-
 	rtnl_lock();
 	mutex_lock(&caifdevs->lock);
 
@@ -569,7 +551,7 @@
 {
 	int result;
 
-	result = register_pernet_device(&caif_net_ops);
+	result = register_pernet_subsys(&caif_net_ops);
 
 	if (result)
 		return result;
@@ -582,7 +564,7 @@
 
 static void __exit caif_device_exit(void)
 {
-	unregister_pernet_device(&caif_net_ops);
+	unregister_pernet_subsys(&caif_net_ops);
 	unregister_netdevice_notifier(&caif_device_notifier);
 	dev_remove_pack(&caif_packet_type);
 }
diff --git a/net/caif/cfcnfg.c b/net/caif/cfcnfg.c
index 598aafb..ba9cfd4 100644
--- a/net/caif/cfcnfg.c
+++ b/net/caif/cfcnfg.c
@@ -309,7 +309,6 @@
 	int err;
 	struct cfctrl_link_param param;
 	struct cfcnfg *cfg = get_cfcnfg(net);
-	caif_assert(cfg != NULL);
 
 	rcu_read_lock();
 	err = caif_connect_req_to_link_param(cfg, conn_req, &param);