virtio_ring: split: extract the logic of alloc state and extra

Separate the logic of creating desc_state, desc_extra, and subsequent
patches will call it independently.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220801063902.129329-12-xuanzhuo@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_ring.c

@@ -212,6 +212,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 					       bool (*notify)(struct virtqueue *),
 					       void (*callback)(struct virtqueue *),
 					       const char *name);
+static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num);
 
 /*
  * Helpers.
@@ -937,6 +938,32 @@ static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
 	return NULL;
 }
 
+static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_split)
+{
+	struct vring_desc_state_split *state;
+	struct vring_desc_extra *extra;
+	u32 num = vring_split->vring.num;
+
+	state = kmalloc_array(num, sizeof(struct vring_desc_state_split), GFP_KERNEL);
+	if (!state)
+		goto err_state;
+
+	extra = vring_alloc_desc_extra(num);
+	if (!extra)
+		goto err_extra;
+
+	memset(state, 0, num * sizeof(struct vring_desc_state_split));
+
+	vring_split->desc_state = state;
+	vring_split->desc_extra = extra;
+	return 0;
+
+err_extra:
+	kfree(state);
+err_state:
+	return -ENOMEM;
+}
+
 static void vring_free_split(struct vring_virtqueue_split *vring_split,
 			     struct virtio_device *vdev)
 {
@@ -2240,6 +2267,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 					       const char *name)
 {
 	struct vring_virtqueue *vq;
+	int err;
 
 	if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED))
 		return NULL;
@@ -2285,19 +2313,17 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 					vq->split.avail_flags_shadow);
 	}
 
-	vq->split.desc_state = kmalloc_array(vring_split->vring.num,
-			sizeof(struct vring_desc_state_split), GFP_KERNEL);
-	if (!vq->split.desc_state)
-		goto err_state;
-
-	vq->split.desc_extra = vring_alloc_desc_extra(vring_split->vring.num);
-	if (!vq->split.desc_extra)
-		goto err_extra;
+	err = vring_alloc_state_extra_split(vring_split);
+	if (err) {
+		kfree(vq);
+		return NULL;
+	}
 
 	/* Put everything in free lists. */
 	vq->free_head = 0;
-	memset(vq->split.desc_state, 0, vring_split->vring.num *
-			sizeof(struct vring_desc_state_split));
+
+	vq->split.desc_state = vring_split->desc_state;
+	vq->split.desc_extra = vring_split->desc_extra;
 
 	virtqueue_init(vq, vring_split->vring.num);
 
@@ -2305,12 +2331,6 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 	list_add_tail(&vq->vq.list, &vdev->vqs);
 	spin_unlock(&vdev->vqs_list_lock);
 	return &vq->vq;
-
-err_extra:
-	kfree(vq->split.desc_state);
-err_state:
-	kfree(vq);
-	return NULL;
 }
 
 struct virtqueue *vring_create_virtqueue(