net/mlx5: Add new list to store deleted flow counters

In order to prevent flow counters stats work function from traversing whole
flow counters tree while searching for deleted flow counters, new list to
store deleted flow counters is added to struct mlx5_fc_stats. Lockless
NULL-terminated single linked list data type is used due to following
reasons:
 - This use case only needs to add single element to list and
 remove/iterate whole list. Lockless list doesn't require any additional
 synchronization for these operations.
 - First cache line of flow counter data structure only has space to store
 single additional pointer, which precludes usage of double linked list.

Remove flow counter 'deleted' flag that is no longer needed.
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Amir Vadai <amir@vadai.me>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -141,6 +141,7 @@ struct mlx5_fc_cache {
 struct mlx5_fc {
 	struct rb_node node;
 	struct llist_node addlist;
+	struct llist_node dellist;
 
 	/* last{packets,bytes} members are used when calculating the delta since
 	 * last reading
@@ -149,7 +150,6 @@ struct mlx5_fc {
 	u64 lastbytes;
 
 	u32 id;
-	bool deleted;
 	bool aging;
 
 	struct mlx5_fc_cache cache ____cacheline_aligned_in_smp;

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

@@ -58,7 +58,7 @@
  *   - spawn thread to do the actual destroy
  *
  * - destroy (user context)
- *   - mark a counter as deleted
+ *   - add a counter to lockless dellist
  *   - spawn thread to do the actual del
  *
  * - dump (user context)
@@ -171,9 +171,8 @@ static void mlx5_fc_stats_work(struct work_struct *work)
 						 priv.fc_stats.work.work);
 	struct mlx5_fc_stats *fc_stats = &dev->priv.fc_stats;
 	struct llist_node *tmplist = llist_del_all(&fc_stats->addlist);
+	struct mlx5_fc *counter = NULL, *last = NULL, *tmp;
 	unsigned long now = jiffies;
-	struct mlx5_fc *counter = NULL;
-	struct mlx5_fc *last = NULL;
 	struct rb_node *node;
 
 	if (tmplist || !RB_EMPTY_ROOT(&fc_stats->counters))
@@ -183,26 +182,17 @@ static void mlx5_fc_stats_work(struct work_struct *work)
 	llist_for_each_entry(counter, tmplist, addlist)
 		mlx5_fc_stats_insert(&fc_stats->counters, counter);
 
-	node = rb_first(&fc_stats->counters);
-	while (node) {
-		counter = rb_entry(node, struct mlx5_fc, node);
-
-		node = rb_next(node);
-
-		if (counter->deleted) {
+	tmplist = llist_del_all(&fc_stats->dellist);
+	llist_for_each_entry_safe(counter, tmp, tmplist, dellist) {
 		rb_erase(&counter->node, &fc_stats->counters);
 
-			mlx5_cmd_fc_free(dev, counter->id);
-
-			kfree(counter);
-			continue;
-		}
-
-		last = counter;
+		mlx5_free_fc(dev, counter);
 	}
 
-	if (time_before(now, fc_stats->next_query) || !last)
+	node = rb_last(&fc_stats->counters);
+	if (time_before(now, fc_stats->next_query) || !node)
 		return;
+	last = rb_entry(node, struct mlx5_fc, node);
 
 	node = rb_first(&fc_stats->counters);
 	while (node) {
@@ -254,13 +244,12 @@ void mlx5_fc_destroy(struct mlx5_core_dev *dev, struct mlx5_fc *counter)
 		return;
 
 	if (counter->aging) {
-		counter->deleted = true;
+		llist_add(&counter->dellist, &fc_stats->dellist);
 		mod_delayed_work(fc_stats->wq, &fc_stats->work, 0);
 		return;
 	}
 
-	mlx5_cmd_fc_free(dev, counter->id);
-	kfree(counter);
+	mlx5_free_fc(dev, counter);
 }
 EXPORT_SYMBOL(mlx5_fc_destroy);
 
@@ -270,6 +259,7 @@ int mlx5_init_fc_stats(struct mlx5_core_dev *dev)
 
 	fc_stats->counters = RB_ROOT;
 	init_llist_head(&fc_stats->addlist);
+	init_llist_head(&fc_stats->dellist);
 
 	fc_stats->wq = create_singlethread_workqueue("mlx5_fc");
 	if (!fc_stats->wq)

include/linux/mlx5/driver.h

@@ -585,6 +585,7 @@ struct mlx5_irq_info {
 struct mlx5_fc_stats {
 	struct rb_root counters;
 	struct llist_head addlist;
+	struct llist_head dellist;
 
 	struct workqueue_struct *wq;
 	struct delayed_work work;