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

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Date: Wed, 17 May 2023 11:48:05 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Vlad Buslov <vladbu@...dia.com>
Cc: Peilin Ye <yepeilin.cs@...il.com>, Jiri Pirko <jiri@...nulli.us>,
 "Daniel Borkmann" <daniel@...earbox.net>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, "Jamal Hadi Salim" <jhs@...atatu.com>, Cong Wang
 <xiyou.wangcong@...il.com>, "Peilin Ye" <peilin.ye@...edance.com>, John
 Fastabend <john.fastabend@...il.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 net 6/6] net/sched: qdisc_destroy() old ingress and
 clsact Qdiscs before grafting

On Wed, 17 May 2023 11:49:10 +0300 Vlad Buslov wrote:
> On Tue 16 May 2023 at 17:39, Jakub Kicinski <kuba@...nel.org> wrote:
> > On Tue, 16 May 2023 15:58:46 -0700 Peilin Ye wrote:  
> >> 
> >> Seems like trying to delete an "in-use" cls_u32 filter returns -EBUSY  
> >
> > I meant -EBUSY due to a race (another operation being in flight).
> > I think that's different.  
> 
> I wonder if somehow leveraging existing tc_modify_qdisc() 'replay'
> functionality instead of returning error to the user would be a better
> approach? Currently the function is replayed when qdisc_create() returns
> EAGAIN. It should be trivial to do the same for qdisc_graft() result.

Sounds better than returning -EBUSY to the user and expecting them 
to retry, yes.