netdev - Re: [PATCH net-next v2 1/1] driver: ipvlan: Free ipvl_port directly with kfree instead of kfree

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Message-ID: <1481037510.18162.583.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 06 Dec 2016 07:18:30 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     fgao@...ai8.com
Cc:     davem@...emloft.net, maheshb@...gle.com, edumazet@...gle.com,
        netdev@...r.kernel.org, gfree.wind@...il.com
Subject: Re: [PATCH net-next v2 1/1] driver: ipvlan: Free ipvl_port directly
 with kfree instead of kfree_rcu

On Tue, 2016-12-06 at 21:54 +0800, fgao@...ai8.com wrote:
> From: Gao Feng <gfree.wind@...il.com>
> 
> There is no one which may reference the ipvlan port when free it in
> ipvlan_port_create and ipvlan_port_destroy. So it is unnecessary to
> use kfree_rcu.

You did not really explain _why_ it was safe/unnecessary.
Why should anyone trust you ?

The reason an RCU grace period is not needed is that
netdev_rx_handler_unregister() already enforces a grace period.

My guess is ipvlan copied code in macvlan.

At the time macvlan was written, commit
00cfec37484761a44 ("net: add a synchronize_net() in
netdev_rx_handler_unregister()") was not there yet.

macvlan could be changed the same way.