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

Jason Wang
2022-07-01T09:09:36Z

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@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@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().