linux-kernel - Re: [PATCH net] mvpp2: refactor MTU change code

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Date:   Fri, 26 Jul 2019 16:26:37 +0200
From:   Matteo Croce <mcroce@...hat.com>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Stefan Chulski <stefanc@...vell.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] mvpp2: refactor MTU change code

On Fri, Jul 26, 2019 at 2:50 PM Antoine Tenart
<antoine.tenart@...tlin.com> wrote:
>
> Hi Matteo,
>
> On Fri, Jul 26, 2019 at 01:19:31AM +0200, Matteo Croce wrote:
> > The MTU change code can call napi_disable() with the device already down,
> > leading to a deadlock. Also, lot of code is duplicated unnecessarily.
> >
> > Rework mvpp2_change_mtu() to avoid the deadlock and remove duplicated code.
> >
> > Signed-off-by: Matteo Croce <mcroce@...hat.com>
>
> As this is a fix sent to net, you could add a Fixes: tag.
>
> Otherwise this looks good,
> Acked-by: Antoine Tenart <antoine.tenart@...tlin.com>
>
> Thanks!
> Antoine
>
> > ---
> >  .../net/ethernet/marvell/mvpp2/mvpp2_main.c   | 41 ++++++-------------
> >  1 file changed, 13 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > index 2f7286bd203b..60eb98f99571 100644
> > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> > @@ -3612,6 +3612,7 @@ static int mvpp2_set_mac_address(struct net_device *dev, void *p)
> >  static int mvpp2_change_mtu(struct net_device *dev, int mtu)
> >  {
> >       struct mvpp2_port *port = netdev_priv(dev);
> > +     bool running = netif_running(dev);
> >       int err;
> >
> >       if (!IS_ALIGNED(MVPP2_RX_PKT_SIZE(mtu), 8)) {
> > @@ -3620,40 +3621,24 @@ static int mvpp2_change_mtu(struct net_device *dev, int mtu)
> >               mtu = ALIGN(MVPP2_RX_PKT_SIZE(mtu), 8);
> >       }
> >
> > -     if (!netif_running(dev)) {
> > -             err = mvpp2_bm_update_mtu(dev, mtu);
> > -             if (!err) {
> > -                     port->pkt_size =  MVPP2_RX_PKT_SIZE(mtu);
> > -                     return 0;
> > -             }
> > -
> > -             /* Reconfigure BM to the original MTU */
> > -             err = mvpp2_bm_update_mtu(dev, dev->mtu);
> > -             if (err)
> > -                     goto log_error;
> > -     }
> > -
> > -     mvpp2_stop_dev(port);
> > +     if (running)
> > +             mvpp2_stop_dev(port);
> >
> >       err = mvpp2_bm_update_mtu(dev, mtu);
> > -     if (!err) {
> > +     if (err) {
> > +             netdev_err(dev, "failed to change MTU\n");
> > +             /* Reconfigure BM to the original MTU */
> > +             mvpp2_bm_update_mtu(dev, dev->mtu);
> > +     } else {
> >               port->pkt_size =  MVPP2_RX_PKT_SIZE(mtu);
> > -             goto out_start;
> >       }
> >
> > -     /* Reconfigure BM to the original MTU */
> > -     err = mvpp2_bm_update_mtu(dev, dev->mtu);
> > -     if (err)
> > -             goto log_error;
> > -
> > -out_start:
> > -     mvpp2_start_dev(port);
> > -     mvpp2_egress_enable(port);
> > -     mvpp2_ingress_enable(port);
> > +     if (running) {
> > +             mvpp2_start_dev(port);
> > +             mvpp2_egress_enable(port);
> > +             mvpp2_ingress_enable(port);
> > +     }
> >
> > -     return 0;
> > -log_error:
> > -     netdev_err(dev, "failed to change MTU\n");
> >       return err;
> >  }
> >
> > --
> > 2.21.0
> >
>
> --
> Antoine Ténart, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

It seems to me that the fixes tag should refer to the driver inclusion:

Fixes: 3f518509dedc ("ethernet: Add new driver for Marvell Armada 375
network unit")

-- 
Matteo Croce
per aspera ad upstream