Re: [PATCH rdma-next] IB/IPoIB: Forward MTU change to driver below

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Tue, May 23, 2017 at 11:56:45AM +0300, Yuval Shaia wrote:
> On Tue, May 23, 2017 at 11:42:52AM +0300, Leon Romanovsky wrote:
> > From: Erez Shitrit <erezsh-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >
> > This patch checks if there is a driver below that
>
> Is it "below" or "upper" in the driver hierarchy?

The part which  close to the HW. I called it "below".

>
> > needs to be updated on the new MTU and calls it
> > accordingly.
> >
> > Signed-off-by: Erez Shitrit <erezsh-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > Reviewed by: Alex Vesker <valex-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > Signed-off-by: Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> > ---
> >  drivers/infiniband/ulp/ipoib/ipoib_main.c | 19 +++++++++++++++++--
> >  1 file changed, 17 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> > index 2869d1adb1de..28068140800c 100644
> > --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
> > +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> > @@ -233,6 +233,7 @@ static netdev_features_t ipoib_fix_features(struct net_device *dev, netdev_featu
> >  static int ipoib_change_mtu(struct net_device *dev, int new_mtu)
> >  {
> >  	struct ipoib_dev_priv *priv = ipoib_priv(dev);
> > +	int ret = 0;
> >
> >  	/* dev->mtu > 2K ==> connected mode */
> >  	if (ipoib_cm_admin_enabled(dev)) {
> > @@ -256,9 +257,23 @@ static int ipoib_change_mtu(struct net_device *dev, int new_mtu)
> >  		ipoib_dbg(priv, "MTU must be smaller than the underlying "
> >  				"link layer MTU - 4 (%u)\n", priv->mcast_mtu);
> >
> > -	dev->mtu = min(priv->mcast_mtu, priv->admin_mtu);
> > +	new_mtu = min(priv->mcast_mtu, priv->admin_mtu);
> >
> > -	return 0;
> > +	if (priv->rn_ops->ndo_change_mtu) {
> > +		bool carrier_status = netif_carrier_ok(dev);
> > +
> > +		netif_carrier_off(dev);
> > +
> > +		/* notify lower level on the real mtu */
> > +		ret = priv->rn_ops->ndo_change_mtu(dev, new_mtu);
> > +
> > +		if (carrier_status)
> > +			netif_carrier_on(dev);
> > +	} else {
> > +		dev->mtu = new_mtu;
> > +	}
>
> So we don't want dev->mtu to be updated if driver was registered?

It is updated in ndo_change_mtu call. See nes. cxgb3/4 and mlx4/5 as an
example.

>
> > +
> > +	return ret;
> >  }
> >
> >  /* Called with an RCU read lock taken */
> > --
> > 2.12.2
> >
> > --
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