virtio_ring: split: extract the logic of alloc queue

Separate the logic of split to create vring queue.

This feature is required for subsequent virtuqueue reset vring.
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220801063902.129329-11-xuanzhuo@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_ring.c

@@ -948,29 +948,19 @@ static void vring_free_split(struct vring_virtqueue_split *vring_split,
 	kfree(vring_split->desc_extra);
 }
 
-static struct virtqueue *vring_create_virtqueue_split(
-	unsigned int index,
-	unsigned int num,
-	unsigned int vring_align,
-	struct virtio_device *vdev,
-	bool weak_barriers,
-	bool may_reduce_num,
-	bool context,
-	bool (*notify)(struct virtqueue *),
-	void (*callback)(struct virtqueue *),
-	const char *name)
+static int vring_alloc_queue_split(struct vring_virtqueue_split *vring_split,
+				   struct virtio_device *vdev,
+				   u32 num,
+				   unsigned int vring_align,
+				   bool may_reduce_num)
 {
-	struct vring_virtqueue_split vring_split = {};
-	struct virtqueue *vq;
 	void *queue = NULL;
 	dma_addr_t dma_addr;
-	size_t queue_size_in_bytes;
-	struct vring vring;
 
 	/* We assume num is a power of 2. */
 	if (num & (num - 1)) {
 		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
-		return NULL;
+		return -EINVAL;
 	}
 
 	/* TODO: allocate each queue chunk individually */
@@ -981,11 +971,11 @@ static struct virtqueue *vring_create_virtqueue_split(
 		if (queue)
 			break;
 		if (!may_reduce_num)
-			return NULL;
+			return -ENOMEM;
 	}
 
 	if (!num)
-		return NULL;
+		return -ENOMEM;
 
 	if (!queue) {
 		/* Try to get a single page. You are my only hope! */
@@ -993,21 +983,46 @@ static struct virtqueue *vring_create_virtqueue_split(
 					  &dma_addr, GFP_KERNEL|__GFP_ZERO);
 	}
 	if (!queue)
-		return NULL;
+		return -ENOMEM;
+
+	vring_init(&vring_split->vring, num, queue, vring_align);
 
-	queue_size_in_bytes = vring_size(num, vring_align);
-	vring_init(&vring_split.vring, num, queue, vring_align);
+	vring_split->queue_dma_addr = dma_addr;
+	vring_split->queue_size_in_bytes = vring_size(num, vring_align);
+
+	return 0;
+}
+
+static struct virtqueue *vring_create_virtqueue_split(
+	unsigned int index,
+	unsigned int num,
+	unsigned int vring_align,
+	struct virtio_device *vdev,
+	bool weak_barriers,
+	bool may_reduce_num,
+	bool context,
+	bool (*notify)(struct virtqueue *),
+	void (*callback)(struct virtqueue *),
+	const char *name)
+{
+	struct vring_virtqueue_split vring_split = {};
+	struct virtqueue *vq;
+	int err;
+
+	err = vring_alloc_queue_split(&vring_split, vdev, num, vring_align,
+				      may_reduce_num);
+	if (err)
+		return NULL;
 
 	vq = __vring_new_virtqueue(index, &vring_split, vdev, weak_barriers,
 				   context, notify, callback, name);
 	if (!vq) {
-		vring_free_queue(vdev, queue_size_in_bytes, queue,
-				 dma_addr);
+		vring_free_split(&vring_split, vdev);
 		return NULL;
 	}
 
-	to_vvq(vq)->split.queue_dma_addr = dma_addr;
-	to_vvq(vq)->split.queue_size_in_bytes = queue_size_in_bytes;
+	to_vvq(vq)->split.queue_dma_addr = vring_split.queue_dma_addr;
+	to_vvq(vq)->split.queue_size_in_bytes = vring_split.queue_size_in_bytes;
 	to_vvq(vq)->we_own_ring = true;
 
 	return vq;