netdev - Re: [PATCH net-next v2 7/8] netdevsim: add SR-IOV functionality

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Date:   Fri, 1 Dec 2017 14:43:06 +0100
From:   Phil Sutter <phil@....cc>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, daniel@...earbox.net,
        alexei.starovoitov@...il.com, jiri@...nulli.us,
        oss-drivers@...ronome.com, Sabrina Dubroca <sd@...asysnail.net>
Subject: Re: [PATCH net-next v2 7/8] netdevsim: add SR-IOV functionality

On Thu, Nov 30, 2017 at 05:35:39PM -0800, Jakub Kicinski wrote:
[...]
> +static int nsim_vfs_enable(struct netdevsim *ns, unsigned int num_vfs)
> +{
> +	ns->vfconfigs = kcalloc(num_vfs, sizeof(struct nsim_vf_config),
> +				GFP_KERNEL);
> +	if (!ns->vfconfigs)
> +		return -ENOMEM;
> +	ns->num_vfs = num_vfs;
> +
> +	return 0;
> +}
> +
> +static void nsim_vfs_disable(struct netdevsim *ns)
> +{
> +	kfree(ns->vfconfigs);
> +	ns->vfconfigs = NULL;
> +	ns->num_vfs = 0;
> +}

Why not something like:

| static int nsim_vfs_set(struct netdevsim *ns, unsigned int num_vfs)
| {
| 	void *ptr = krealloc(ns->vfconfigs,
| 			     num_vfs * sizeof(struct nsim_vf_config),
| 			     GFP_KERNEL);
| 
| 	if (!ptr)
| 		return -ENOMEM;
| 
| 	ns->vfconfigs = ptr;
| 	ns->num_vfs = num_vfs;
| 	return 0;
| }

> +static ssize_t
> +nsim_numvfs_store(struct device *dev, struct device_attribute *attr,
> +		  const char *buf, size_t count)
> +{
> +	struct netdevsim *ns = to_nsim(dev);
> +	unsigned int num_vfs;
> +	int ret;
> +
> +	ret = kstrtouint(buf, 0, &num_vfs);
> +	if (ret)
> +		return ret;
> +
> +	rtnl_lock();
> +	if (ns->num_vfs == num_vfs)
> +		goto exit_good;

Then replace this:

> +	if (ns->num_vfs && num_vfs) {
> +		ret = -EBUSY;
> +		goto exit_unlock;
> +	}
> +
> +	if (num_vfs) {
> +		ret = nsim_vfs_enable(ns, num_vfs);
> +		if (ret)
> +			goto exit_unlock;
> +	} else {
> +		nsim_vfs_disable(ns);
> +	}

with just:

|	nsim_vfs_set(ns, num_vfs);

> +exit_good:
> +	ret = count;
> +exit_unlock:
> +	rtnl_unlock();
> +
> +	return ret;
> +}

[...]

> +static void nsim_free(struct net_device *dev)
> +{
> +	struct netdevsim *ns = netdev_priv(dev);
> +
> +	device_unregister(&ns->dev);
>  }

Shouldn't this also kfree(ns->vfconfigs)?

Cheers, Phil