page_pool: introduce page_pool_free and use in mlx5

In case driver fails to register the page_pool with XDP return API (via
xdp_rxq_info_reg_mem_model()), then the driver can free the page_pool
resources more directly than calling page_pool_destroy(), which does a
unnecessarily RCU free procedure.

This patch is preparing for removing page_pool_destroy(), from driver
invocation.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -545,8 +545,10 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
 	}
 	err = xdp_rxq_info_reg_mem_model(&rq->xdp_rxq,
 					 MEM_TYPE_PAGE_POOL, rq->page_pool);
-	if (err)
+	if (err) {
+		page_pool_free(rq->page_pool);
 		goto err_free;
+	}
 
 	for (i = 0; i < wq_sz; i++) {
 		if (rq->wq_type == MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ) {
@@ -611,8 +613,6 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
 	if (rq->xdp_prog)
 		bpf_prog_put(rq->xdp_prog);
 	xdp_rxq_info_unreg(&rq->xdp_rxq);
-	if (rq->page_pool)
-		page_pool_destroy(rq->page_pool);
 	mlx5_wq_destroy(&rq->wq_ctrl);
 
 	return err;

include/net/page_pool.h

@@ -111,6 +111,17 @@ struct page_pool *page_pool_create(const struct page_pool_params *params);
 
 void page_pool_destroy(struct page_pool *pool);
 
+void __page_pool_free(struct page_pool *pool);
+static inline void page_pool_free(struct page_pool *pool)
+{
+	/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
+	 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
+	 */
+#ifdef CONFIG_PAGE_POOL
+	__page_pool_free(pool);
+#endif
+}
+
 /* Never call this directly, use helpers below */
 void __page_pool_put_page(struct page_pool *pool,
 			  struct page *page, bool allow_direct);

net/core/page_pool.c

@@ -292,17 +292,24 @@ static void __page_pool_empty_ring(struct page_pool *pool)
 	}
 }
 
+void __page_pool_free(struct page_pool *pool)
+{
+	WARN(pool->alloc.count, "API usage violation");
+	WARN(!ptr_ring_empty(&pool->ring), "ptr_ring is not empty");
+
+	ptr_ring_cleanup(&pool->ring, NULL);
+	kfree(pool);
+}
+EXPORT_SYMBOL(__page_pool_free);
+
 static void __page_pool_destroy_rcu(struct rcu_head *rcu)
 {
 	struct page_pool *pool;
 
 	pool = container_of(rcu, struct page_pool, rcu);
 
-	WARN(pool->alloc.count, "API usage violation");
-
 	__page_pool_empty_ring(pool);
-	ptr_ring_cleanup(&pool->ring, NULL);
-	kfree(pool);
+	__page_pool_free(pool);
 }
 
 /* Cleanup and release resources */