Virtualization - Jul 2021 - [PATCH v9 16/17] vduse: Introduce VDUSE - vDPA Device in Userspace

On Tue, Jul 13, 2021 at 04:46:55PM +0800, Xie Yongji
wrote:
> +static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *name)
> +{
> +	struct vduse_vdpa *vdev;
> +	int ret;
> +
> +	if (dev->vdev)
> +		return -EEXIST;
> +
> +	vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
> +				 &vduse_vdpa_config_ops, name, true);
> +	if (!vdev)
> +		return -ENOMEM;
This should be an IS_ERR() check instead of a NULL check.

The vdpa_alloc_device() macro is doing something very complicated but
I'm not sure what.  It calls container_of() and that looks buggy until
you spot the BUILD_BUG_ON_ZERO() compile time assert which ensures that
the container_of() is a no-op.

Only one of the callers checks for error pointers correctly so maybe
it's too complicated or maybe there should be better documentation.

regards,
dan carpenter

? 2021/7/13 ??9:27, Dan Carpenter ??:
> On Tue, Jul 13, 2021 at 04:46:55PM +0800, Xie Yongji wrote:
>> +static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char
*name)
>> +{
>> +	struct vduse_vdpa *vdev;
>> +	int ret;
>> +
>> +	if (dev->vdev)
>> +		return -EEXIST;
>> +
>> +	vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
>> +				 &vduse_vdpa_config_ops, name, true);
>> +	if (!vdev)
>> +		return -ENOMEM;
> This should be an IS_ERR() check instead of a NULL check.

Yes.

>
> The vdpa_alloc_device() macro is doing something very complicated but
> I'm not sure what.  It calls container_of() and that looks buggy until
> you spot the BUILD_BUG_ON_ZERO() compile time assert which ensures that
> the container_of() is a no-op.
>
> Only one of the callers checks for error pointers correctly so maybe
> it's too complicated or maybe there should be better documentation.

We need better documentation for this macro and fix all the buggy callers.

Yong Ji, want to do that?

Thanks

>
> regards,
> dan carpenter
>