From: Zhiyi Sun <zhiyisun-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Daniel Borkmann <daniel-FeC+5ew28dpmcu3hnIyYJQ@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, 9 Nov 2016 17:45:46 +0800 [thread overview]
Message-ID: <20161109094546.jtmzc4xwtaavzcnt@ubuntu> (raw)
In-Reply-To: <5822E6DB.40204-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
On Wed, Nov 09, 2016 at 10:05:31AM +0100, Daniel Borkmann wrote:
> 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 ...
>
Yes, you are correct. My patch is incorrect. It is not a bug.
> 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).
>
I thought mlx4's code is incorrect because in mlx5's driver, function
mlx5e_xdp_set() calls a pair of bpf_prog_add/put, the number of add and
put to the refs are same. I didn't notice that one "add" has been called in its
calller. So, it seems that mlx5's code is incorrect, right?
> > 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);
> > }
> >
>
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2016-11-09 9:45 UTC|newest]
Thread overview: 8+ 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
[not found] ` <5822E6DB.40204-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org>
2016-11-09 9:45 ` Zhiyi Sun [this message]
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 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161109094546.jtmzc4xwtaavzcnt@ubuntu \
--to=zhiyisun-re5jqeeqqe8avxtiumwx3w@public.gmane.org \
--cc=alexei.starovoitov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
--cc=bblanco-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org \
--cc=daniel-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=tariqt-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org \
--cc=yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox