[PATCH v11 14/40] virtio_ring: split: introduce virtqueue_resize_split()

[Jason Wang]

在 2022/6/29 14:56, Xuan Zhuo 写道:
> virtio ring split supports resize.
>
> Only after the new vring is successfully allocated based on the new num,
> we will release the old vring. In any case, an error is returned,
> indicating that the vring still points to the old vring.
>
> In the case of an error, re-initialize(virtqueue_reinit_split()) the
> virtqueue to ensure that the vring can be used.
>
> In addition, vring_align, may_reduce_num are necessary for reallocating
> vring, so they are retained for creating vq.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
> ---
>   drivers/virtio/virtio_ring.c | 32 ++++++++++++++++++++++++++++++++
>   1 file changed, 32 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 9c83c5e6d5a9..1aaa1e5f9991 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -212,6 +212,7 @@ struct vring_virtqueue {
>   };
>   
>   static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
> +static void vring_free(struct virtqueue *_vq);
>   
>   /*
>    * Helpers.
> @@ -1114,6 +1115,37 @@ static struct virtqueue *vring_create_virtqueue_split(
>   	return vq;
>   }
>   
> +static int virtqueue_resize_split(struct virtqueue *_vq, u32 num)
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +	struct vring_virtqueue_split vring = {};
> +	struct virtio_device *vdev = _vq->vdev;
> +	int err;
> +
> +	err = vring_alloc_queue_split(&vring, vdev, num, vq->split.vring_align,
> +				      vq->split.may_reduce_num);
> +	if (err)
> +		goto err;


It's better to have decouple the allocation future more to avoid any 
rewind here in the future.

But the patch should be fine.

So

Acked-by: Jason Wang <jasowang at redhat.com>


> +
> +	err = vring_alloc_state_extra_split(&vring);
> +	if (err) {
> +		vring_free_split(&vring, vdev);
> +		goto err;
> +	}
> +
> +	vring_free(&vq->vq);
> +
> +	virtqueue_init(vq, vring.vring.num);
> +	virtqueue_vring_attach_split(vq, &vring);
> +	virtqueue_vring_init_split(vq);
> +
> +	return 0;
> +
> +err:
> +	virtqueue_reinit_split(vq);
> +	return -ENOMEM;
> +}
> +
>   
>   /*
>    * Packed ring specific functions - *_packed().