nexthop: Introduce to struct nh_grp_entry a per-type union

The values that a next-hop group needs to keep track of depend on the group
type. Introduce a union to separate fields specific to the mpath groups
from fields specific to other group types.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/nexthop.h

@@ -66,7 +66,12 @@ struct nh_info {
 struct nh_grp_entry {
 	struct nexthop	*nh;
 	u8		weight;
+
+	union {
+		struct {
 			atomic_t	upper_bound;
+		} mpath;
+	};
 
 	struct list_head nh_list;
 	struct nexthop	*nh_parent;  /* nexthop of group with this entry */

net/ipv4/nexthop.c

@@ -689,7 +689,7 @@ static struct nexthop *nexthop_select_path_mp(struct nh_group *nhg, int hash)
 		struct nh_grp_entry *nhge = &nhg->nh_entries[i];
 		struct nh_info *nhi;
 
-		if (hash > atomic_read(&nhge->upper_bound))
+		if (hash > atomic_read(&nhge->mpath.upper_bound))
 			continue;
 
 		nhi = rcu_dereference(nhge->nh->nh_info);
@@ -924,7 +924,7 @@ static void nh_group_rebalance(struct nh_group *nhg)
 
 		w += nhge->weight;
 		upper_bound = DIV_ROUND_CLOSEST_ULL((u64)w << 31, total) - 1;
-		atomic_set(&nhge->upper_bound, upper_bound);
+		atomic_set(&nhge->mpath.upper_bound, upper_bound);
 	}
 }