RE: [PATCH v2 net-next 4/5] net: fec: add change_mtu to support dynamic buffer allocation

[Wei Fang]

> > > +static int fec_change_mtu(struct net_device *ndev, int new_mtu) {
> > > +	struct fec_enet_private *fep = netdev_priv(ndev);
> > > +	int order, done;
> > > +	bool running;
> > > +
> > > +	order = get_order(new_mtu + ETH_HLEN + ETH_FCS_LEN);
> > > +	if (fep->pagepool_order == order) {
> > > +		WRITE_ONCE(ndev->mtu, new_mtu);
> >
> > No need to write ndev->mtu, same below, because __netif_set_mtu() will
> > help update it.
> 
> It will only update the ndev->mtu if the driver doesn't have its own chang_mtu
> handler.
> 
> int __netif_set_mtu(struct net_device *dev, int new_mtu) {
> 	const struct net_device_ops *ops = dev->netdev_ops;
> 
> 	if (ops->ndo_change_mtu)
> 		return ops->ndo_change_mtu(dev, new_mtu);
> 
> 	/* Pairs with all the lockless reads of dev->mtu in the stack */
> 	WRITE_ONCE(dev->mtu, new_mtu);
> 	return 0;
> }

Oh, I misread the code, so sorry.