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