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

[Yuval Shaia <yuval.shaia-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

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?

> 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?

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