Re: [PATCH v2] ravb: add support for changing MTU

On 02/16/2018 08:10 AM, Niklas Söderlund wrote:

Allow for changing the MTU within the limit of the maximum size of a
descriptor (2048 bytes). Add the callback to change MTU from user-space
and take the configurable MTU into account when configuring the
hardware.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
---

 
+static int ravb_change_mtu(struct net_device *ndev, int new_mtu)
+{
+	if (netif_running(ndev))
+		return -EBUSY;
+
+	ndev->mtu = new_mtu;
+	netdev_update_features(ndev);

Don't you somehow need to quiesce the RX DMA and make sure you that you
re-allocate all RX buffers within priv->rx_skb[q][entry] such that they
will be able to accept a larger buffer size?

If we put the ravb interface under high RX load and we change the MTU on
the fly, can we crash the kernel?
-- 
Florian