Function virtqueue_detach_unused

dpdk/drivers/net/virtio/virtqueue.c:22–60

* Two types of mbuf to be cleaned: * 1) mbuf that has been consumed by backend but not used by virtio. * 2) mbuf that hasn't been consumed by backend. */

 * 2) mbuf that hasn't been consumed by backend.
 */
struct rte_mbuf *
virtqueue_detach_unused(struct virtqueue *vq)
{
	struct rte_mbuf *cookie;
	struct virtio_hw *hw;
	uint16_t start, end;
	int type, idx;

	if (vq == NULL)
		return NULL;

	hw = vq->hw;
	type = virtio_get_queue_type(hw, vq->vq_queue_index);
	start = vq->vq_avail_idx & (vq->vq_nentries - 1);
	end = (vq->vq_avail_idx + vq->vq_free_cnt) & (vq->vq_nentries - 1);

	for (idx = 0; idx < vq->vq_nentries; idx++) {
		if (hw->use_vec_rx && !virtio_with_packed_queue(hw) &&
		    type == VTNET_RQ) {
			if (start <= end && idx >= start && idx < end)
				continue;
			if (start > end && (idx >= start || idx < end))
				continue;
			cookie = vq->rxq.sw_ring[idx];
			if (cookie != NULL) {
				vq->rxq.sw_ring[idx] = NULL;
				return cookie;
			}
		} else {
			cookie = vq->vq_descx[idx].cookie;
			if (cookie != NULL) {
				vq->vq_descx[idx].cookie = NULL;
				return cookie;
			}
		}
	}

	return NULL;
}

/* Flush used descs */
static void