Revert "ipv6: Factorise ip6_route_multipath_add()."

Commit 71c0efb ("ipv6: Factorise ip6_route_multipath_add().") split
a loop in ip6_route_multipath_add() so that we can put rcu_read_lock()
between ip6_route_info_create() and ip6_route_info_create_nh().

We no longer need to do so as ip6_route_info_create_nh() does not require
RCU now.

Let's revert the commit to simplify the code.

Signed-off-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: q2ven

net/ipv6/route.c

@@ -5335,131 +5335,29 @@ struct rt6_nh {
 	struct fib6_info *fib6_info;
 	struct fib6_config r_cfg;
 	struct list_head list;
-	int weight;
 };
 
-static void ip6_route_mpath_info_cleanup(struct list_head *rt6_nh_list)
+static int ip6_route_info_append(struct list_head *rt6_nh_list,
+				 struct fib6_info *rt,
+				 struct fib6_config *r_cfg)
 {
-	struct rt6_nh *nh, *nh_next;
+	struct rt6_nh *nh;
 
-	list_for_each_entry_safe(nh, nh_next, rt6_nh_list, list) {
-		struct fib6_info *rt = nh->fib6_info;
-
-		if (rt) {
-			free_percpu(rt->fib6_nh->nh_common.nhc_pcpu_rth_output);
-			free_percpu(rt->fib6_nh->rt6i_pcpu);
-			ip_fib_metrics_put(rt->fib6_metrics);
-			kfree(rt);
-		}
-
-		list_del(&nh->list);
-		kfree(nh);
+	list_for_each_entry(nh, rt6_nh_list, list) {
+		/* check if fib6_info already exists */
+		if (rt6_duplicate_nexthop(nh->fib6_info, rt))
+			return -EEXIST;
 	}
-}
-
-static int ip6_route_mpath_info_create(struct list_head *rt6_nh_list,
-				       struct fib6_config *cfg,
-				       struct netlink_ext_ack *extack)
-{
-	struct rtnexthop *rtnh;
-	int remaining;
-	int err;
-
-	remaining = cfg->fc_mp_len;
-	rtnh = (struct rtnexthop *)cfg->fc_mp;
-
-	/* Parse a Multipath Entry and build a list (rt6_nh_list) of
-	 * fib6_info structs per nexthop
-	 */
-	while (rtnh_ok(rtnh, remaining)) {
-		struct fib6_config r_cfg;
-		struct fib6_info *rt;
-		struct rt6_nh *nh;
-		int attrlen;
-
-		nh = kzalloc(sizeof(*nh), GFP_KERNEL);
-		if (!nh) {
-			err = -ENOMEM;
-			goto err;
-		}
 
-		list_add_tail(&nh->list, rt6_nh_list);
-
-		memcpy(&r_cfg, cfg, sizeof(*cfg));
-		if (rtnh->rtnh_ifindex)
-			r_cfg.fc_ifindex = rtnh->rtnh_ifindex;
-
-		attrlen = rtnh_attrlen(rtnh);
-		if (attrlen > 0) {
-			struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
-
-			nla = nla_find(attrs, attrlen, RTA_GATEWAY);
-			if (nla) {
-				r_cfg.fc_gateway = nla_get_in6_addr(nla);
-				r_cfg.fc_flags |= RTF_GATEWAY;
-			}
-
-			r_cfg.fc_encap = nla_find(attrs, attrlen, RTA_ENCAP);
-			nla = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);
-			if (nla)
-				r_cfg.fc_encap_type = nla_get_u16(nla);
-		}
-
-		r_cfg.fc_flags |= (rtnh->rtnh_flags & RTNH_F_ONLINK);
-
-		rt = ip6_route_info_create(&r_cfg, GFP_KERNEL, extack);
-		if (IS_ERR(rt)) {
-			err = PTR_ERR(rt);
-			goto err;
-		}
-
-		nh->fib6_info = rt;
-		nh->weight = rtnh->rtnh_hops + 1;
-		memcpy(&nh->r_cfg, &r_cfg, sizeof(r_cfg));
+	nh = kzalloc(sizeof(*nh), GFP_KERNEL);
+	if (!nh)
+		return -ENOMEM;
 
-		rtnh = rtnh_next(rtnh, &remaining);
-	}
+	nh->fib6_info = rt;
+	memcpy(&nh->r_cfg, r_cfg, sizeof(*r_cfg));
+	list_add_tail(&nh->list, rt6_nh_list);
 
 	return 0;
-err:
-	ip6_route_mpath_info_cleanup(rt6_nh_list);
-	return err;
-}
-
-static int ip6_route_mpath_info_create_nh(struct list_head *rt6_nh_list,
-					  struct netlink_ext_ack *extack)
-{
-	struct rt6_nh *nh, *nh_next, *nh_tmp;
-	LIST_HEAD(tmp);
-	int err;
-
-	list_for_each_entry_safe(nh, nh_next, rt6_nh_list, list) {
-		struct fib6_info *rt = nh->fib6_info;
-
-		err = ip6_route_info_create_nh(rt, &nh->r_cfg, extack);
-		if (err) {
-			nh->fib6_info = NULL;
-			goto err;
-		}
-
-		rt->fib6_nh->fib_nh_weight = nh->weight;
-
-		list_move_tail(&nh->list, &tmp);
-
-		list_for_each_entry(nh_tmp, rt6_nh_list, list) {
-			/* check if fib6_info already exists */
-			if (rt6_duplicate_nexthop(nh_tmp->fib6_info, rt)) {
-				err = -EEXIST;
-				goto err;
-			}
-		}
-	}
-out:
-	list_splice(&tmp, rt6_nh_list);
-	return err;
-err:
-	ip6_route_mpath_info_cleanup(rt6_nh_list);
-	goto out;
 }
 
 static void ip6_route_mpath_notify(struct fib6_info *rt,
@@ -5519,11 +5417,16 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
 	struct fib6_info *rt_notif = NULL, *rt_last = NULL;
 	struct nl_info *info = &cfg->fc_nlinfo;
 	struct rt6_nh *nh, *nh_safe;
+	struct fib6_config r_cfg;
+	struct rtnexthop *rtnh;
 	LIST_HEAD(rt6_nh_list);
 	struct rt6_nh *err_nh;
+	struct fib6_info *rt;
 	__u16 nlflags;
-	int nhn = 0;
+	int remaining;
+	int attrlen;
 	int replace;
+	int nhn = 0;
 	int err;
 
 	replace = (cfg->fc_nlinfo.nlh &&
@@ -5533,13 +5436,57 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
 	if (info->nlh && info->nlh->nlmsg_flags & NLM_F_APPEND)
 		nlflags |= NLM_F_APPEND;
 
-	err = ip6_route_mpath_info_create(&rt6_nh_list, cfg, extack);
-	if (err)
-		return err;
+	remaining = cfg->fc_mp_len;
+	rtnh = (struct rtnexthop *)cfg->fc_mp;
 
-	err = ip6_route_mpath_info_create_nh(&rt6_nh_list, extack);
-	if (err)
-		goto cleanup;
+	/* Parse a Multipath Entry and build a list (rt6_nh_list) of
+	 * fib6_info structs per nexthop
+	 */
+	while (rtnh_ok(rtnh, remaining)) {
+		memcpy(&r_cfg, cfg, sizeof(*cfg));
+		if (rtnh->rtnh_ifindex)
+			r_cfg.fc_ifindex = rtnh->rtnh_ifindex;
+
+		attrlen = rtnh_attrlen(rtnh);
+		if (attrlen > 0) {
+			struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
+
+			nla = nla_find(attrs, attrlen, RTA_GATEWAY);
+			if (nla) {
+				r_cfg.fc_gateway = nla_get_in6_addr(nla);
+				r_cfg.fc_flags |= RTF_GATEWAY;
+			}
+
+			r_cfg.fc_encap = nla_find(attrs, attrlen, RTA_ENCAP);
+			nla = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);
+			if (nla)
+				r_cfg.fc_encap_type = nla_get_u16(nla);
+		}
+
+		r_cfg.fc_flags |= (rtnh->rtnh_flags & RTNH_F_ONLINK);
+		rt = ip6_route_info_create(&r_cfg, GFP_KERNEL, extack);
+		if (IS_ERR(rt)) {
+			err = PTR_ERR(rt);
+			rt = NULL;
+			goto cleanup;
+		}
+
+		err = ip6_route_info_create_nh(rt, &r_cfg, extack);
+		if (err) {
+			rt = NULL;
+			goto cleanup;
+		}
+
+		rt->fib6_nh->fib_nh_weight = rtnh->rtnh_hops + 1;
+
+		err = ip6_route_info_append(&rt6_nh_list, rt, &r_cfg);
+		if (err) {
+			fib6_info_release(rt);
+			goto cleanup;
+		}
+
+		rtnh = rtnh_next(rtnh, &remaining);
+	}
 
 	/* for add and replace send one notification with all nexthops.
 	 * Skip the notification in fib6_add_rt2node and send one with