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

[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.

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