From: Daniel Borkmann <daniel-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
To: Zhiyi Sun <zhiyisun-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: bblanco-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org,
Tariq Toukan <tariqt-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
alexei.starovoitov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Subject: Re: [PATCH] net/mlx4_en: Fix bpf_prog_add ref_cnt in mlx4
Date: Wed, 09 Nov 2016 10:05:31 +0100 [thread overview]
Message-ID: <5822E6DB.40204@iogearbox.net> (raw)
In-Reply-To: <20161109073544.jbufjqn7y7oa6ptg@ubuntu>
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 <zhiyisun-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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);
> }
>
--
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WARNING: multiple messages have this Message-ID (diff)
From: Daniel Borkmann <daniel@iogearbox.net>
To: Zhiyi Sun <zhiyisun@gmail.com>
Cc: bblanco@plumgrid.com, Tariq Toukan <tariqt@mellanox.com>,
Yishai Hadas <yishaih@mellanox.com>,
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
Date: Wed, 09 Nov 2016 10:05:31 +0100 [thread overview]
Message-ID: <5822E6DB.40204@iogearbox.net> (raw)
In-Reply-To: <20161109073544.jbufjqn7y7oa6ptg@ubuntu>
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 <zhiyisun@gmail.com>
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);
> }
>
next prev parent reply other threads:[~2016-11-09 9:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-09 7:35 [PATCH] net/mlx4_en: Fix bpf_prog_add ref_cnt in mlx4 Zhiyi Sun
2016-11-09 9:05 ` Daniel Borkmann [this message]
2016-11-09 9:05 ` Daniel Borkmann
[not found] ` <5822E6DB.40204-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
2016-11-09 9:45 ` Zhiyi Sun
2016-11-09 9:45 ` Zhiyi Sun
2016-11-09 9:57 ` Daniel Borkmann
[not found] ` <5822F30C.1050900-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
2016-11-09 10:58 ` [PATCH net-next 1/2] bpf, mlx4: fix prog refcount in mlx4_en_try_alloc_resources error path kbuild test robot
2016-11-09 10:58 ` kbuild test robot
2016-11-09 11:04 ` Daniel Borkmann
2016-11-09 17:06 ` [PATCH] net/mlx4_en: Fix bpf_prog_add ref_cnt in mlx4 Brenden Blanco
[not found] ` <20161109170615.GB10428-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-11-09 19:05 ` Daniel Borkmann
2016-11-09 19:05 ` Daniel Borkmann
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