rtnetlink: remove a level of indentation in rtnl_newlink()

rtnl_newlink() used to create VLAs based on link kind.  Since
commit ccf8dbcd ("rtnetlink: Remove VLA usage") statically
sized array is created on the stack, so there is no more use
for a separate code block that used to be the VLA's live range.

While at it christmas tree the variables.  Note that there is
a goto-based retry so to be on the safe side the variables can
no longer be initialized in place.  It doesn't seem to matter,
logically, but why make the code harder to read..
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2974,17 +2974,22 @@ static int rtnl_group_changelink(const struct sk_buff *skb,
 static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			struct netlink_ext_ack *extack)
 {
+	struct nlattr *slave_attr[RTNL_SLAVE_MAX_TYPE + 1];
+	unsigned char name_assign_type = NET_NAME_USER;
+	struct nlattr *linkinfo[IFLA_INFO_MAX + 1];
+	const struct rtnl_link_ops *m_ops = NULL;
+	struct nlattr *attr[RTNL_MAX_TYPE + 1];
+	struct net_device *master_dev = NULL;
 	struct net *net = sock_net(skb->sk);
 	const struct rtnl_link_ops *ops;
-	const struct rtnl_link_ops *m_ops = NULL;
+	struct nlattr *tb[IFLA_MAX + 1];
+	struct net *dest_net, *link_net;
+	struct nlattr **slave_data;
+	char kind[MODULE_NAME_LEN];
 	struct net_device *dev;
-	struct net_device *master_dev = NULL;
 	struct ifinfomsg *ifm;
-	char kind[MODULE_NAME_LEN];
 	char ifname[IFNAMSIZ];
-	struct nlattr *tb[IFLA_MAX+1];
-	struct nlattr *linkinfo[IFLA_INFO_MAX+1];
-	unsigned char name_assign_type = NET_NAME_USER;
+	struct nlattr **data;
 	int err;
 
 #ifdef CONFIG_MODULES
@@ -3040,195 +3045,185 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		ops = NULL;
 	}
 
-	if (1) {
-		struct nlattr *attr[RTNL_MAX_TYPE + 1];
-		struct nlattr *slave_attr[RTNL_SLAVE_MAX_TYPE + 1];
-		struct nlattr **data = NULL;
-		struct nlattr **slave_data = NULL;
-		struct net *dest_net, *link_net = NULL;
-
-		if (ops) {
-			if (ops->maxtype > RTNL_MAX_TYPE)
-				return -EINVAL;
+	data = NULL;
+	if (ops) {
+		if (ops->maxtype > RTNL_MAX_TYPE)
+			return -EINVAL;
 
-			if (ops->maxtype && linkinfo[IFLA_INFO_DATA]) {
-				err = nla_parse_nested(attr, ops->maxtype,
-						       linkinfo[IFLA_INFO_DATA],
-						       ops->policy, extack);
-				if (err < 0)
-					return err;
-				data = attr;
-			}
-			if (ops->validate) {
-				err = ops->validate(tb, data, extack);
-				if (err < 0)
-					return err;
-			}
+		if (ops->maxtype && linkinfo[IFLA_INFO_DATA]) {
+			err = nla_parse_nested(attr, ops->maxtype,
+					       linkinfo[IFLA_INFO_DATA],
+					       ops->policy, extack);
+			if (err < 0)
+				return err;
+			data = attr;
+		}
+		if (ops->validate) {
+			err = ops->validate(tb, data, extack);
+			if (err < 0)
+				return err;
 		}
+	}
 
-		if (m_ops) {
-			if (m_ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE)
-				return -EINVAL;
+	slave_data = NULL;
+	if (m_ops) {
+		if (m_ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE)
+			return -EINVAL;
 
-			if (m_ops->slave_maxtype &&
-			    linkinfo[IFLA_INFO_SLAVE_DATA]) {
-				err = nla_parse_nested(slave_attr,
-						       m_ops->slave_maxtype,
-						       linkinfo[IFLA_INFO_SLAVE_DATA],
-						       m_ops->slave_policy,
-						       extack);
-				if (err < 0)
-					return err;
-				slave_data = slave_attr;
-			}
+		if (m_ops->slave_maxtype &&
+		    linkinfo[IFLA_INFO_SLAVE_DATA]) {
+			err = nla_parse_nested(slave_attr, m_ops->slave_maxtype,
+					       linkinfo[IFLA_INFO_SLAVE_DATA],
+					       m_ops->slave_policy, extack);
+			if (err < 0)
+				return err;
+			slave_data = slave_attr;
 		}
+	}
 
-		if (dev) {
-			int status = 0;
-
-			if (nlh->nlmsg_flags & NLM_F_EXCL)
-				return -EEXIST;
-			if (nlh->nlmsg_flags & NLM_F_REPLACE)
-				return -EOPNOTSUPP;
+	if (dev) {
+		int status = 0;
 
-			if (linkinfo[IFLA_INFO_DATA]) {
-				if (!ops || ops != dev->rtnl_link_ops ||
-				    !ops->changelink)
-					return -EOPNOTSUPP;
+		if (nlh->nlmsg_flags & NLM_F_EXCL)
+			return -EEXIST;
+		if (nlh->nlmsg_flags & NLM_F_REPLACE)
+			return -EOPNOTSUPP;
 
-				err = ops->changelink(dev, tb, data, extack);
-				if (err < 0)
-					return err;
-				status |= DO_SETLINK_NOTIFY;
-			}
+		if (linkinfo[IFLA_INFO_DATA]) {
+			if (!ops || ops != dev->rtnl_link_ops ||
+			    !ops->changelink)
+				return -EOPNOTSUPP;
 
-			if (linkinfo[IFLA_INFO_SLAVE_DATA]) {
-				if (!m_ops || !m_ops->slave_changelink)
-					return -EOPNOTSUPP;
+			err = ops->changelink(dev, tb, data, extack);
+			if (err < 0)
+				return err;
+			status |= DO_SETLINK_NOTIFY;
+		}
 
-				err = m_ops->slave_changelink(master_dev, dev,
-							      tb, slave_data,
-							      extack);
-				if (err < 0)
-					return err;
-				status |= DO_SETLINK_NOTIFY;
-			}
+		if (linkinfo[IFLA_INFO_SLAVE_DATA]) {
+			if (!m_ops || !m_ops->slave_changelink)
+				return -EOPNOTSUPP;
 
-			return do_setlink(skb, dev, ifm, extack, tb, ifname,
-					  status);
+			err = m_ops->slave_changelink(master_dev, dev, tb,
+						      slave_data, extack);
+			if (err < 0)
+				return err;
+			status |= DO_SETLINK_NOTIFY;
 		}
 
-		if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
-			if (ifm->ifi_index == 0 && tb[IFLA_GROUP])
-				return rtnl_group_changelink(skb, net,
+		return do_setlink(skb, dev, ifm, extack, tb, ifname, status);
+	}
+
+	if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
+		if (ifm->ifi_index == 0 && tb[IFLA_GROUP])
+			return rtnl_group_changelink(skb, net,
 						nla_get_u32(tb[IFLA_GROUP]),
 						ifm, extack, tb);
-			return -ENODEV;
-		}
+		return -ENODEV;
+	}
 
-		if (tb[IFLA_MAP] || tb[IFLA_PROTINFO])
-			return -EOPNOTSUPP;
+	if (tb[IFLA_MAP] || tb[IFLA_PROTINFO])
+		return -EOPNOTSUPP;
 
-		if (!ops) {
+	if (!ops) {
 #ifdef CONFIG_MODULES
-			if (kind[0]) {
-				__rtnl_unlock();
-				request_module("rtnl-link-%s", kind);
-				rtnl_lock();
-				ops = rtnl_link_ops_get(kind);
-				if (ops)
-					goto replay;
-			}
-#endif
-			NL_SET_ERR_MSG(extack, "Unknown device type");
-			return -EOPNOTSUPP;
+		if (kind[0]) {
+			__rtnl_unlock();
+			request_module("rtnl-link-%s", kind);
+			rtnl_lock();
+			ops = rtnl_link_ops_get(kind);
+			if (ops)
+				goto replay;
 		}
+#endif
+		NL_SET_ERR_MSG(extack, "Unknown device type");
+		return -EOPNOTSUPP;
+	}
 
-		if (!ops->setup)
-			return -EOPNOTSUPP;
-
-		if (!ifname[0]) {
-			snprintf(ifname, IFNAMSIZ, "%s%%d", ops->kind);
-			name_assign_type = NET_NAME_ENUM;
-		}
+	if (!ops->setup)
+		return -EOPNOTSUPP;
 
-		dest_net = rtnl_link_get_net_capable(skb, net, tb, CAP_NET_ADMIN);
-		if (IS_ERR(dest_net))
-			return PTR_ERR(dest_net);
+	if (!ifname[0]) {
+		snprintf(ifname, IFNAMSIZ, "%s%%d", ops->kind);
+		name_assign_type = NET_NAME_ENUM;
+	}
 
-		if (tb[IFLA_LINK_NETNSID]) {
-			int id = nla_get_s32(tb[IFLA_LINK_NETNSID]);
+	dest_net = rtnl_link_get_net_capable(skb, net, tb, CAP_NET_ADMIN);
+	if (IS_ERR(dest_net))
+		return PTR_ERR(dest_net);
 
-			link_net = get_net_ns_by_id(dest_net, id);
-			if (!link_net) {
-				NL_SET_ERR_MSG(extack, "Unknown network namespace id");
-				err =  -EINVAL;
-				goto out;
-			}
-			err = -EPERM;
-			if (!netlink_ns_capable(skb, link_net->user_ns, CAP_NET_ADMIN))
-				goto out;
-		}
+	if (tb[IFLA_LINK_NETNSID]) {
+		int id = nla_get_s32(tb[IFLA_LINK_NETNSID]);
 
-		dev = rtnl_create_link(link_net ? : dest_net, ifname,
-				       name_assign_type, ops, tb, extack);
-		if (IS_ERR(dev)) {
-			err = PTR_ERR(dev);
+		link_net = get_net_ns_by_id(dest_net, id);
+		if (!link_net) {
+			NL_SET_ERR_MSG(extack, "Unknown network namespace id");
+			err =  -EINVAL;
 			goto out;
 		}
+		err = -EPERM;
+		if (!netlink_ns_capable(skb, link_net->user_ns, CAP_NET_ADMIN))
+			goto out;
+	} else {
+		link_net = NULL;
+	}
 
-		dev->ifindex = ifm->ifi_index;
+	dev = rtnl_create_link(link_net ? : dest_net, ifname,
+			       name_assign_type, ops, tb, extack);
+	if (IS_ERR(dev)) {
+		err = PTR_ERR(dev);
+		goto out;
+	}
 
-		if (ops->newlink) {
-			err = ops->newlink(link_net ? : net, dev, tb, data,
-					   extack);
-			/* Drivers should call free_netdev() in ->destructor
-			 * and unregister it on failure after registration
-			 * so that device could be finally freed in rtnl_unlock.
-			 */
-			if (err < 0) {
-				/* If device is not registered at all, free it now */
-				if (dev->reg_state == NETREG_UNINITIALIZED)
-					free_netdev(dev);
-				goto out;
-			}
-		} else {
-			err = register_netdevice(dev);
-			if (err < 0) {
+	dev->ifindex = ifm->ifi_index;
+
+	if (ops->newlink) {
+		err = ops->newlink(link_net ? : net, dev, tb, data, extack);
+		/* Drivers should call free_netdev() in ->destructor
+		 * and unregister it on failure after registration
+		 * so that device could be finally freed in rtnl_unlock.
+		 */
+		if (err < 0) {
+			/* If device is not registered at all, free it now */
+			if (dev->reg_state == NETREG_UNINITIALIZED)
 				free_netdev(dev);
-				goto out;
-			}
+			goto out;
+		}
+	} else {
+		err = register_netdevice(dev);
+		if (err < 0) {
+			free_netdev(dev);
+			goto out;
 		}
-		err = rtnl_configure_link(dev, ifm);
+	}
+	err = rtnl_configure_link(dev, ifm);
+	if (err < 0)
+		goto out_unregister;
+	if (link_net) {
+		err = dev_change_net_namespace(dev, dest_net, ifname);
 		if (err < 0)
 			goto out_unregister;
-		if (link_net) {
-			err = dev_change_net_namespace(dev, dest_net, ifname);
-			if (err < 0)
-				goto out_unregister;
-		}
-		if (tb[IFLA_MASTER]) {
-			err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]),
-					    extack);
-			if (err)
-				goto out_unregister;
-		}
+	}
+	if (tb[IFLA_MASTER]) {
+		err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]), extack);
+		if (err)
+			goto out_unregister;
+	}
 out:
-		if (link_net)
-			put_net(link_net);
-		put_net(dest_net);
-		return err;
+	if (link_net)
+		put_net(link_net);
+	put_net(dest_net);
+	return err;
 out_unregister:
-		if (ops->newlink) {
-			LIST_HEAD(list_kill);
+	if (ops->newlink) {
+		LIST_HEAD(list_kill);
 
-			ops->dellink(dev, &list_kill);
-			unregister_netdevice_many(&list_kill);
-		} else {
-			unregister_netdevice(dev);
-		}
-		goto out;
+		ops->dellink(dev, &list_kill);
+		unregister_netdevice_many(&list_kill);
+	} else {
+		unregister_netdevice(dev);
 	}
+	goto out;
 }
 
 static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,