From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752071AbdLACGC (ORCPT <rfc822;w@1wt.eu>);
        Thu, 30 Nov 2017 21:06:02 -0500
Received: from mail-pf0-f195.google.com ([209.85.192.195]:36187 "EHLO
        mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750735AbdLACGA (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 30 Nov 2017 21:06:00 -0500
X-Google-Smtp-Source: AGs4zMa+iJKFtO6598OTk2/Fg1hEaL1Vu5TCU56b7xxxixcMKMeqmZt9ynyEacP1uLvdLk/ronf6mg==
Date: Thu, 30 Nov 2017 18:05:56 -0800
From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        oss-drivers@netronome.com, alexei.starovoitov@gmail.com,
        daniel@iogearbox.net, "Eric W . Biederman" <ebiederm@xmission.com>
Subject: Re: [RFC] bpf: offload: report device information for offloaded
 programs
Message-ID: <20171130180556.2913ecdb@cakuba.netronome.com>
In-Reply-To: <85513945-bcd2-b2b4-24e7-5fbb3e695419@virtuozzo.com>
References: <20171130002251.30498-1-jakub.kicinski@netronome.com>
        <85513945-bcd2-b2b4-24e7-5fbb3e695419@virtuozzo.com>
Organization: Netronome Systems, Ltd.
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Kirill,

On Thu, 30 Nov 2017 16:19:13 +0300, Kirill Tkhai wrote:
> > @@ -164,6 +166,38 @@ int bpf_prog_offload_compile(struct bpf_prog *prog)
> >  	return bpf_prog_offload_translate(prog);
> >  }
> >  
> > +int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
> > +			       struct bpf_prog *prog)
> > +{
> > +	struct bpf_dev_offload *offload = prog->aux->offload;
> > +	struct inode *ns_inode;
> > +	struct path ns_path;
> > +	struct net *net;
> > +	int ret = 0;
> > +	void *ptr;
> > +
> > +	info->dev_bound = 1;
> > +
> > +	rtnl_lock();  
> 
> rtnl_lock() is too big lock and it is already overused in kernel.
> Can't we use smaller lock in this driver to protect bpf_prog_offload_devs?
> I suppose rwlock would be appropriate for that.
> 
> (Then, we may completely remove rtnl_lock() from bpf_prog_offload_init()
> and use readlocked dev_base_lock for __dev_get_by_index() instead and
> the new small_rwlock to link in the list.
> 
> Not sure about bpf_prog_offload_verifier_prep() and bpf_prog_offload_translate()
> and which context expect net_device_ops->ndo_bpf users. Either they need rtnl
> or not).

Thanks for the comments, removing the use of rtnl_lock is definitely on
my todo list!