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From:   Vlad Buslov <vladbu@mellanox.com>
To:     Jiri Pirko <jiri@resnulli.us>
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        coreteam@netfilter.org, kliteyn@mellanox.com
Subject: Re: [PATCH 12/14] net: sched: retry action check-insert on concurrent modification
In-reply-to: <20180516095953.GI1972@nanopsycho>
Date:   Wed, 16 May 2018 14:55:06 +0300
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On Wed 16 May 2018 at 09:59, Jiri Pirko <jiri@resnulli.us> wrote:
> Mon, May 14, 2018 at 04:27:13PM CEST, vladbu@mellanox.com wrote:
>>Retry check-insert sequence in action init functions if action with same
>>index was inserted concurrently.
>>
>>Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
>>---
>> net/sched/act_bpf.c        | 8 +++++++-
>> net/sched/act_connmark.c   | 8 +++++++-
>> net/sched/act_csum.c       | 8 +++++++-
>> net/sched/act_gact.c       | 8 +++++++-
>> net/sched/act_ife.c        | 8 +++++++-
>> net/sched/act_ipt.c        | 8 +++++++-
>> net/sched/act_mirred.c     | 8 +++++++-
>> net/sched/act_nat.c        | 8 +++++++-
>> net/sched/act_pedit.c      | 8 +++++++-
>> net/sched/act_police.c     | 9 ++++++++-
>> net/sched/act_sample.c     | 8 +++++++-
>> net/sched/act_simple.c     | 9 ++++++++-
>> net/sched/act_skbedit.c    | 8 +++++++-
>> net/sched/act_skbmod.c     | 8 +++++++-
>> net/sched/act_tunnel_key.c | 9 ++++++++-
>> net/sched/act_vlan.c       | 9 ++++++++-
>> 16 files changed, 116 insertions(+), 16 deletions(-)
>>
>>diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
>>index 5554bf7..7e20fdc 100644
>>--- a/net/sched/act_bpf.c
>>+++ b/net/sched/act_bpf.c
>>@@ -299,10 +299,16 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
>> 
>> 	parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
>> 
>>+replay:
>> 	if (!tcf_idr_check(tn, parm->index, act, bind)) {
>> 		ret = tcf_idr_create(tn, parm->index, est, act,
>> 				     &act_bpf_ops, bind, true);
>>-		if (ret < 0)
>>+		/* Action with specified index was created concurrently.
>>+		 * Check again.
>>+		 */
>>+		if (parm->index && ret == -ENOSPC)
>>+			goto replay;
>>+		else if (ret)
>
> Hmm, looks like you are doing the same/very similar thing in every act
> code. I think it would make sense to introduce a helper function for
> this purpose.

This code uses goto so it can't be easily refactored into standalone
function. Could you specify which part of this code you suggest to
extract?

>
> [...]