netdev - Re: [net 05/11] net/mlx5e: Hold reference on mirred devices while accessing them

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Message-ID: <20200705071911.GA148399@mtl-vdi-166.wap.labs.mlnx>
Date:   Sun, 5 Jul 2020 10:19:11 +0300
From:   Eli Cohen <eli@...lanox.com>
To:     Or Gerlitz <gerlitz.or@...il.com>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Vlad Buslov <vladbu@...lanox.com>
Subject: Re: [net 05/11] net/mlx5e: Hold reference on mirred devices while
 accessing them

On Fri, Jul 03, 2020 at 12:33:58PM +0300, Or Gerlitz wrote:
> On Fri, Jul 3, 2020 at 1:24 AM Saeed Mahameed <saeedm@...lanox.com> wrote:
> > From: Eli Cohen <eli@...lanox.com>
> >
> > Net devices might be removed. For example, a vxlan device could be
> > deleted and its ifnidex would become invalid. Use dev_get_by_index()
> > instead of __dev_get_by_index() to hold reference on the device while
> > accessing it and release after done.
> 
> So if user space app installed a tc rule and then crashed or just
> exited without
> uninstalling the rule, the mirred (vxlan, vf rep, etc) device could
> never be removed?

Why do you think so? I decrease ref count, unconditionally, right after
returning from mlx5e_attach_encap().