[PATCH v9 11/32] virtio_ring: split: introduce virtqueue_resize_split()

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

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, the caller must
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 | 47 ++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 3dc6ace2ba7a..33864134a744 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -139,6 +139,12 @@ struct vring_virtqueue {
 			/* DMA address and size information */
 			dma_addr_t queue_dma_addr;
 			size_t queue_size_in_bytes;
+
+			/* The parameters for creating vrings are reserved for
+			 * creating new vring.
+			 */
+			u32 vring_align;
+			bool may_reduce_num;
 		} split;
 
 		/* Available for packed ring */
@@ -199,6 +205,7 @@ struct vring_virtqueue {
 };
 
 static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
+static void vring_free(struct virtqueue *_vq);
 
 /*
  * Helpers.
@@ -1088,6 +1095,8 @@ static struct virtqueue *vring_create_virtqueue_split(
 		return NULL;
 	}
 
+	to_vvq(vq)->split.vring_align = vring_align;
+	to_vvq(vq)->split.may_reduce_num = may_reduce_num;
 	to_vvq(vq)->split.queue_dma_addr = dma_addr;
 	to_vvq(vq)->split.queue_size_in_bytes = queue_size_in_bytes;
 	to_vvq(vq)->we_own_ring = true;
@@ -1095,6 +1104,44 @@ 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 virtio_device *vdev = _vq->vdev;
+	struct vring_desc_state_split *state;
+	struct vring_desc_extra *extra;
+	size_t queue_size_in_bytes;
+	dma_addr_t dma_addr;
+	struct vring vring;
+	int err = -ENOMEM;
+	void *queue;
+
+	queue = vring_alloc_queue_split(vdev, &dma_addr, &num,
+					vq->split.vring_align,
+					vq->weak_barriers,
+					vq->split.may_reduce_num);
+	if (!queue)
+		return -ENOMEM;
+
+	queue_size_in_bytes = vring_size(num, vq->split.vring_align);
+
+	err = vring_alloc_state_extra_split(num, &state, &extra);
+	if (err) {
+		vring_free_queue(vdev, queue_size_in_bytes, queue, dma_addr);
+		return -ENOMEM;
+	}
+
+	vring_free(&vq->vq);
+
+	vring_init(&vring, num, queue, vq->split.vring_align);
+	vring_virtqueue_attach_split(vq, vring, state, extra);
+	vq->split.queue_dma_addr = dma_addr;
+	vq->split.queue_size_in_bytes = queue_size_in_bytes;
+
+	vring_virtqueue_init_split(vq, vdev, true);
+	return 0;
+}
+
 
 /*
  * Packed ring specific functions - *_packed().
-- 
2.31.0

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