net/mlx5: Simplify matching group searches

Instead of using two different structs for searching groups with the
same match, use a single struct and thus simplify the code, make it more
readable and smaller size which means less code cache misses.

         text    data     bss     dec     hex
before: 35524    2744       0   38268    957c
after:  35038    2744       0   37782    9396

When testing add 70000 rules, delete all the rules, and repeat three
times taking the average, we get (time in seconds):

Before the change: insert 16.80, delete 11.02
After the change:  insert 16.55, delete 10.95
Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/fs_core.c

@@ -1577,28 +1577,19 @@ struct match_list {
 	struct mlx5_flow_group *g;
 };
 
-struct match_list_head {
-	struct list_head  list;
-	struct match_list first;
-};
-
-static void free_match_list(struct match_list_head *head, bool ft_locked)
+static void free_match_list(struct match_list *head, bool ft_locked)
 {
-	if (!list_empty(&head->list)) {
-		struct match_list *iter, *match_tmp;
+	struct match_list *iter, *match_tmp;
 
-		list_del(&head->first.list);
-		tree_put_node(&head->first.g->node, ft_locked);
-		list_for_each_entry_safe(iter, match_tmp, &head->list,
-					 list) {
-			tree_put_node(&iter->g->node, ft_locked);
-			list_del(&iter->list);
-			kfree(iter);
-		}
+	list_for_each_entry_safe(iter, match_tmp, &head->list,
+				 list) {
+		tree_put_node(&iter->g->node, ft_locked);
+		list_del(&iter->list);
+		kfree(iter);
 	}
 }
 
-static int build_match_list(struct match_list_head *match_head,
+static int build_match_list(struct match_list *match_head,
 			    struct mlx5_flow_table *ft,
 			    const struct mlx5_flow_spec *spec,
 			    bool ft_locked)
@@ -1615,14 +1606,8 @@ static int build_match_list(struct match_list_head *match_head,
 	rhl_for_each_entry_rcu(g, tmp, list, hash) {
 		struct match_list *curr_match;
 
-		if (likely(list_empty(&match_head->list))) {
-			if (!tree_get_node(&g->node))
-				continue;
-			match_head->first.g = g;
-			list_add_tail(&match_head->first.list,
-				      &match_head->list);
+		if (unlikely(!tree_get_node(&g->node)))
 			continue;
-		}
 
 		curr_match = kmalloc(sizeof(*curr_match), GFP_ATOMIC);
 		if (!curr_match) {
@@ -1630,10 +1615,6 @@ static int build_match_list(struct match_list_head *match_head,
 			err = -ENOMEM;
 			goto out;
 		}
-		if (!tree_get_node(&g->node)) {
-			kfree(curr_match);
-			continue;
-		}
 		curr_match->g = g;
 		list_add_tail(&curr_match->list, &match_head->list);
 	}
@@ -1785,9 +1766,9 @@ _mlx5_add_flow_rules(struct mlx5_flow_table *ft,
 
 {
 	struct mlx5_flow_steering *steering = get_steering(&ft->node);
-	struct mlx5_flow_group *g;
 	struct mlx5_flow_handle *rule;
-	struct match_list_head match_head;
+	struct match_list match_head;
+	struct mlx5_flow_group *g;
 	bool take_write = false;
 	struct fs_fte *fte;
 	int version;