linux-kernel - Re: [PATCH 12/14] net: sched: retry action check-insert on concurrent modification

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Date:   Wed, 16 May 2018 11:59:53 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
        xiyou.wangcong@...il.com, pablo@...filter.org,
        kadlec@...ckhole.kfki.hu, fw@...len.de, ast@...nel.org,
        daniel@...earbox.net, edumazet@...gle.com, keescook@...omium.org,
        linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, kliteyn@...lanox.com
Subject: Re: [PATCH 12/14] net: sched: retry action check-insert on
 concurrent modification

Mon, May 14, 2018 at 04:27:13PM CEST, vladbu@...lanox.com wrote:
>Retry check-insert sequence in action init functions if action with same
>index was inserted concurrently.
>
>Signed-off-by: Vlad Buslov <vladbu@...lanox.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.

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