static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,

                          int remaining_sectors, QEMUIOVector *qiov)

{

    BDRVQcowState *s = bs->opaque;

    int index_in_cluster, n1;

    int ret;

    int cur_nr_sectors; /* number of sectors in current iteration */

    uint64_t cluster_offset = 0;

    uint64_t bytes_done = 0;

    QEMUIOVector hd_qiov;

    uint8_t *cluster_data = NULL;



    qemu_iovec_init(&hd_qiov, qiov->niov);



    qemu_co_mutex_lock(&s->lock);



    while (remaining_sectors != 0) {



        /* prepare next request */

        cur_nr_sectors = remaining_sectors;

        if (s->crypt_method) {

            cur_nr_sectors = MIN(cur_nr_sectors,

                QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);

        }



        ret = qcow2_get_cluster_offset(bs, sector_num << 9,

            &cur_nr_sectors, &cluster_offset);

        if (ret < 0) {

            goto fail;

        }



        index_in_cluster = sector_num & (s->cluster_sectors - 1);



        qemu_iovec_reset(&hd_qiov);

        qemu_iovec_concat(&hd_qiov, qiov, bytes_done,

            cur_nr_sectors * 512);



        switch (ret) {

        case QCOW2_CLUSTER_UNALLOCATED:



            if (bs->backing_hd) {

                /* read from the base image */

                n1 = qcow2_backing_read1(bs->backing_hd, &hd_qiov,

                    sector_num, cur_nr_sectors);

                if (n1 > 0) {

                    BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);

                    qemu_co_mutex_unlock(&s->lock);

                    ret = bdrv_co_readv(bs->backing_hd, sector_num,

                                        n1, &hd_qiov);

                    qemu_co_mutex_lock(&s->lock);

                    if (ret < 0) {

                        goto fail;

                    }

                }

            } else {

                /* Note: in this case, no need to wait */

                qemu_iovec_memset(&hd_qiov, 0, 0, 512 * cur_nr_sectors);

            }

            break;



        case QCOW2_CLUSTER_ZERO:

            if (s->qcow_version < 3) {

                ret = -EIO;

                goto fail;

            }

            qemu_iovec_memset(&hd_qiov, 0, 0, 512 * cur_nr_sectors);

            break;



        case QCOW2_CLUSTER_COMPRESSED:

            /* add AIO support for compressed blocks ? */

            ret = qcow2_decompress_cluster(bs, cluster_offset);

            if (ret < 0) {

                goto fail;

            }



            qemu_iovec_from_buf(&hd_qiov, 0,

                s->cluster_cache + index_in_cluster * 512,

                512 * cur_nr_sectors);

            break;



        case QCOW2_CLUSTER_NORMAL:

            if ((cluster_offset & 511) != 0) {

                ret = -EIO;

                goto fail;

            }



            if (s->crypt_method) {

                /*

                 * For encrypted images, read everything into a temporary

                 * contiguous buffer on which the AES functions can work.

                 */

                if (!cluster_data) {

                    cluster_data =

                        qemu_blockalign(bs, QCOW_MAX_CRYPT_CLUSTERS * s->cluster_size);

                }



                assert(cur_nr_sectors <=

                    QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors);

                qemu_iovec_reset(&hd_qiov);

                qemu_iovec_add(&hd_qiov, cluster_data,

                    512 * cur_nr_sectors);

            }



            BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);

            qemu_co_mutex_unlock(&s->lock);

            ret = bdrv_co_readv(bs->file,

                                (cluster_offset >> 9) + index_in_cluster,

                                cur_nr_sectors, &hd_qiov);

            qemu_co_mutex_lock(&s->lock);

            if (ret < 0) {

                goto fail;

            }

            if (s->crypt_method) {

                qcow2_encrypt_sectors(s, sector_num,  cluster_data,

                    cluster_data, cur_nr_sectors, 0, &s->aes_decrypt_key);

                qemu_iovec_from_buf(qiov, bytes_done,

                    cluster_data, 512 * cur_nr_sectors);

            }

            break;



        default:

            g_assert_not_reached();

            ret = -EIO;

            goto fail;

        }



        remaining_sectors -= cur_nr_sectors;

        sector_num += cur_nr_sectors;

        bytes_done += cur_nr_sectors * 512;

    }

    ret = 0;



fail:

    qemu_co_mutex_unlock(&s->lock);



    qemu_iovec_destroy(&hd_qiov);

    qemu_vfree(cluster_data);



    return ret;

}
