Re: [Xen-devel] [PATCH net-next v1] xen-netback: implement dynamic multicast control

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Feb 01, 2016 at 02:40:53PM +0000, Paul Durrant wrote:
[...]
> +static int xen_register_mcast_ctrl_watch(struct xenbus_device *dev,
> +                                      struct xenvif *vif)
> +{
> +     int err = 0;
> +     char *node;
> +     unsigned maxlen = strlen(dev->otherend) +
> +             sizeof("/request-multicast-control");
> +
> +     if (vif->mcast_ctrl_watch.node)
> +             return -EADDRINUSE;
> +
> +     node = kmalloc(maxlen, GFP_KERNEL);
> +     if (!node)
> +             return -ENOMEM;

This is one error path that has no logging, so please either add logging
in each error patch ...

> +     snprintf(node, maxlen, "%s/request-multicast-control",
> +              dev->otherend);
> +     vif->mcast_ctrl_watch.node = node;
> +     vif->mcast_ctrl_watch.callback = xen_mcast_ctrl_changed;
> +     err = register_xenbus_watch(&vif->mcast_ctrl_watch);
> +     if (err) {
> +             pr_err("Failed to set watcher %s\n",
> +                    vif->mcast_ctrl_watch.node);
> +             kfree(node);
> +             vif->mcast_ctrl_watch.node = NULL;
> +             vif->mcast_ctrl_watch.callback = NULL;
> +     }
> +     return err;
> +}
> +
> +static void xen_unregister_mcast_ctrl_watch(struct xenvif *vif)
> +{
> +     if (vif->mcast_ctrl_watch.node) {
> +             unregister_xenbus_watch(&vif->mcast_ctrl_watch);
> +             kfree(vif->mcast_ctrl_watch.node);
> +             vif->mcast_ctrl_watch.node = NULL;
> +     }
> +}
> +
> +static void xen_register_watchers(struct xenbus_device *dev,
> +                               struct xenvif *vif)
> +{
> +     xen_register_credit_watch(dev, vif);
> +     xen_register_mcast_ctrl_watch(dev, vif);
> +}
> +
> +static void xen_unregister_watchers(struct xenvif *vif)
> +{
> +     xen_unregister_mcast_ctrl_watch(vif);
> +     xen_unregister_credit_watch(vif);
> +}

... or check if these register/unregister function calls' return value
and log if something fails.

Wei.

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