[PATCH v10 16/41] virtio_ring: split: introduce virtqueue_resize_split()

[Xuan Zhuo]

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 8738ec690621..1ba00e73d601 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -210,6 +210,7 @@ struct vring_virtqueue {
 };
 
 static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
+static void vring_free(struct virtqueue *_vq);
 
 /*
  * Helpers.
@@ -1109,6 +1110,37 @@ 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;
+
+	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().
-- 
2.31.0