netdev - Re: [PATCH net v2] net/sched: act_mirred: Don't zero blockid when net device is being deleted

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Date: Fri, 9 Feb 2024 06:28:01 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Victor Nogueira <victor@...atatu.com>
Cc: xiyou.wangcong@...il.com, jiri@...nulli.us, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	netdev@...r.kernel.org, kernel@...atatu.com, pctammela@...atatu.com
Subject: Re: [PATCH net v2] net/sched: act_mirred: Don't zero blockid when net
 device is being deleted

On Wed, Feb 7, 2024 at 5:29 PM Victor Nogueira <victor@...atatu.com> wrote:
>
> While testing tdc with parallel tests for mirred to block we caught an
> intermittent bug. The blockid was being zeroed out when a net device
> was deleted and, thus, giving us an incorrect blockid value whenever
> we tried to dump the mirred action. Since we don't increment the block
> refcount in the control path (and only use the ID), we don't need to
> zero the blockid field whenever a net device is going down.
>
> Fixes: 42f39036cda8 ("net/sched: act_mirred: Allow mirred to block")
> Signed-off-by: Victor Nogueira <victor@...atatu.com>

Acked-by: Jamal Hadi Salim <jhs@...atatu.com>

cheers,
jamal

> ---
> v1 -> v2:
> - Reword commit message to emphasise the bug is caused when a net
>   device is being deleted
> - Reword subject to emphasise the bug is caused when a net device is
>   being deleted. Original patch subject was:
>   "net/sched: act_mirred: Don't zero blockid when netns is going down"
>
>  net/sched/act_mirred.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> index 93a96e9d8d90..6f4bb1c8ce7b 100644
> --- a/net/sched/act_mirred.c
> +++ b/net/sched/act_mirred.c
> @@ -533,8 +533,6 @@ static int mirred_device_event(struct notifier_block *unused,
>                                  * net_device are already rcu protected.
>                                  */
>                                 RCU_INIT_POINTER(m->tcfm_dev, NULL);
> -                       } else if (m->tcfm_blockid) {
> -                               m->tcfm_blockid = 0;
>                         }
>                         spin_unlock_bh(&m->tcf_lock);
>                 }
> --
> 2.34.1
>