virtio_ring: factor out split detaching logic

This patch factors out the split core detaching logic that could be
reused by in order feature into a dedicated function.

Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-19-jasowang@redhat.com>

Author: jasowang

drivers/virtio/virtio_ring.c

@@ -805,8 +805,9 @@ static void detach_indirect_split(struct vring_virtqueue *vq,
 	vq->split.desc_state[head].indir_desc = NULL;
 }
 
-static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
-			     void **ctx)
+static unsigned detach_buf_split_in_order(struct vring_virtqueue *vq,
+					  unsigned int head,
+					  void **ctx)
 {
 	struct vring_desc_extra *extra;
 	unsigned int i;
@@ -826,8 +827,6 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 	}
 
 	vring_unmap_one_split(vq, &extra[i]);
-	extra[i].next = vq->free_head;
-	vq->free_head = head;
 
 	/* Plus final descriptor */
 	vq->vq.num_free++;
@@ -836,6 +835,17 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 		detach_indirect_split(vq, head);
 	else if (ctx)
 		*ctx = vq->split.desc_state[head].indir_desc;
+
+	return i;
+}
+
+static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
+			     void **ctx)
+{
+	unsigned int i = detach_buf_split_in_order(vq, head, ctx);
+
+	vq->split.desc_extra[i].next = vq->free_head;
+	vq->free_head = head;
 }
 
 static bool virtqueue_poll_split(const struct vring_virtqueue *vq,