linux-kernel - Re: [PATCH v2 net 6/6] net/sched: qdisc_destroy() old ingress and clsact Qdiscs before grafting

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Message-ID: <ZG0LgCGLAKOV82YN@C02FL77VMD6R.googleapis.com>
Date:   Tue, 23 May 2023 11:52:48 -0700
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Vlad Buslov <vladbu@...dia.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Peilin Ye <peilin.ye@...edance.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Vlad Buslov <vladbu@...lanox.com>,
        Pedro Tammela <pctammela@...atatu.com>,
        Hillf Danton <hdanton@...a.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Cong Wang <cong.wang@...edance.com>
Subject: Re: [PATCH v2 net 6/6] net/sched: qdisc_destroy() old ingress and
 clsact Qdiscs before grafting

Hi Vlad,

On Tue, May 23, 2023 at 05:04:40PM +0300, Vlad Buslov wrote:
> > @@ -1458,6 +1472,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
> >     struct Qdisc *p = NULL;
> >     int err;
> >
> > +replay:
>
> Perhaps also set q and p to NULL here? Even though on cursory look you
> should get the same lookup result since the function is called under
> rtnl_lock, tc_modify_qdisc() does this on replay ("Reinit, just in case
> something touches this.") and tc_new_tfilter() got some non-obvious bugs
> after I introduced replay there without re-setting some of the required
> variables.

Sure, I'll reinitialize tcm, q and p after "replay:" in next version, just
like tc_modify_qdisc().  Thanks for the suggestion!

Peilin Ye