Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753182AbcKIJFl (ORCPT ); Wed, 9 Nov 2016 04:05:41 -0500 Received: from www62.your-server.de ([213.133.104.62]:44625 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbcKIJFg (ORCPT ); Wed, 9 Nov 2016 04:05:36 -0500 Message-ID: <5822E6DB.40204@iogearbox.net> Date: Wed, 09 Nov 2016 10:05:31 +0100 From: Daniel Borkmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Zhiyi Sun CC: bblanco@plumgrid.com, Tariq Toukan , Yishai Hadas , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, alexei.starovoitov@gmail.com Subject: Re: [PATCH] net/mlx4_en: Fix bpf_prog_add ref_cnt in mlx4 References: <20161109073544.jbufjqn7y7oa6ptg@ubuntu> In-Reply-To: <20161109073544.jbufjqn7y7oa6ptg@ubuntu> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1677 Lines: 41 On 11/09/2016 08:35 AM, Zhiyi Sun wrote: > There are rx_ring_num queues. Each queue will load xdp prog. So > bpf_prog_add() should add rx_ring_num to ref_cnt. > > Signed-off-by: Zhiyi Sun Your analysis looks incorrect to me. Please elaborate in more detail why you think current code is buggy ... Call path is dev_change_xdp_fd(), which does bpf_prog_get_type() on the fd. This already takes a ref and only drops it in case of error. Thus in mlx4_xdp_set(), you only need priv->rx_ring_num - 1 refs for the rest of the rings, so that dropping refs from old_prog makes sure we release it again. Looks correct to me (maybe a comment would have helped there). > drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c > index 12c99a2..d25e150 100644 > --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c > +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c > @@ -2650,7 +2650,7 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) > */ > if (priv->xdp_ring_num == xdp_ring_num) { > if (prog) { > - prog = bpf_prog_add(prog, priv->rx_ring_num - 1); > + prog = bpf_prog_add(prog, priv->rx_ring_num); > if (IS_ERR(prog)) > return PTR_ERR(prog); > } > @@ -2680,7 +2680,7 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) > } > > if (prog) { > - prog = bpf_prog_add(prog, priv->rx_ring_num - 1); > + prog = bpf_prog_add(prog, priv->rx_ring_num); > if (IS_ERR(prog)) > return PTR_ERR(prog); > } >