From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [PATCH 6/7] get rid of tc_u_common ->rcu
Date: Fri, 7 Sep 2018 05:28:56 +0100
Message-ID: <20180907042856.GB19965@ZenIV.linux.org.uk>
References: <20180905190134.GQ19965@ZenIV.linux.org.uk>
 <20180905190414.5477-1-viro@ZenIV.linux.org.uk>
 <20180905190414.5477-6-viro@ZenIV.linux.org.uk>
 <CAM_iQpWnydTkLYwmZq2gQPnNBTS6E0iNNgy1zsmYFcXkKJAnTw@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Jiri Pirko <jiri@resnulli.us>
To: Cong Wang <xiyou.wangcong@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from zeniv.linux.org.uk ([195.92.253.2]:46268 "EHLO
        ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1726447AbeIGJH7 (ORCPT
        <rfc822;netdev@vger.kernel.org>); Fri, 7 Sep 2018 05:07:59 -0400
Content-Disposition: inline
In-Reply-To: <CAM_iQpWnydTkLYwmZq2gQPnNBTS6E0iNNgy1zsmYFcXkKJAnTw@mail.gmail.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Thu, Sep 06, 2018 at 09:18:47PM -0700, Cong Wang wrote:
> On Wed, Sep 5, 2018 at 12:04 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > From: Al Viro <viro@zeniv.linux.org.uk>
> >
> > unused
> >
> > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> > ---
> >  net/sched/cls_u32.c | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> > index 8a1a573487bd..be9240ae1417 100644
> > --- a/net/sched/cls_u32.c
> > +++ b/net/sched/cls_u32.c
> > @@ -98,7 +98,6 @@ struct tc_u_common {
> >         int                     refcnt;
> >         struct idr              handle_idr;
> >         struct hlist_node       hnode;
> > -       struct rcu_head         rcu;
> >  };
> 
> Just FYI:
> 
> This was added when RCU was introduced to u32 fast path,
> it looks like on fast path we never touch tc_u_common, we
> only use tp->root, all the rest are slow paths with RTNL lock,
> so it is probably fine to just remove it rather than converting
> that kfree() to kfree_rcu().

*nod*

In any case, if u32_classify() grows that dereference, we can always
re-add ->rcu at the same time.