static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
    uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset,
    int flags)
{
    BDRVQcowState *s = bs->opaque;
    uint64_t *l2_table, l2_entry;
    uint64_t next_contiguous_offset = 0;
    int i, l2_size, nb_csectors;

    /* Read L2 table from disk */
    l2_size = s->l2_size * sizeof(uint64_t);
    l2_table = g_malloc(l2_size);

    if (bdrv_pread(bs->file, l2_offset, l2_table, l2_size) != l2_size)
        goto fail;

    /* Do the actual checks */
    for(i = 0; i < s->l2_size; i++) {
        l2_entry = be64_to_cpu(l2_table[i]);

        switch (qcow2_get_cluster_type(l2_entry)) {
        case QCOW2_CLUSTER_COMPRESSED:
            /* Compressed clusters don't have QCOW_OFLAG_COPIED */
            if (l2_entry & QCOW_OFLAG_COPIED) {
                fprintf(stderr, "ERROR: cluster %" PRId64 ": "
                    "copied flag must never be set for compressed "
                    "clusters\n", l2_entry >> s->cluster_bits);
                l2_entry &= ~QCOW_OFLAG_COPIED;
                res->corruptions++;
            }

            /* Mark cluster as used */
            nb_csectors = ((l2_entry >> s->csize_shift) &
                           s->csize_mask) + 1;
            l2_entry &= s->cluster_offset_mask;
            inc_refcounts(bs, res, refcount_table, refcount_table_size,
                l2_entry & ~511, nb_csectors * 512);

            if (flags & CHECK_FRAG_INFO) {
                res->bfi.allocated_clusters++;
                res->bfi.compressed_clusters++;

                /* Compressed clusters are fragmented by nature.  Since they
                 * take up sub-sector space but we only have sector granularity
                 * I/O we need to re-read the same sectors even for adjacent
                 * compressed clusters.
                 */
                res->bfi.fragmented_clusters++;
            }
            break;

        case QCOW2_CLUSTER_ZERO:
            if ((l2_entry & L2E_OFFSET_MASK) == 0) {
                break;
            }
            /* fall through */

        case QCOW2_CLUSTER_NORMAL:
        {
            uint64_t offset = l2_entry & L2E_OFFSET_MASK;

            if (flags & CHECK_FRAG_INFO) {
                res->bfi.allocated_clusters++;
                if (next_contiguous_offset &&
                    offset != next_contiguous_offset) {
                    res->bfi.fragmented_clusters++;
                }
                next_contiguous_offset = offset + s->cluster_size;
            }

            /* Mark cluster as used */
            inc_refcounts(bs, res, refcount_table,refcount_table_size,
                offset, s->cluster_size);

            /* Correct offsets are cluster aligned */
            if (offset_into_cluster(s, offset)) {
                fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
                    "properly aligned; L2 entry corrupted.\n", offset);
                res->corruptions++;
            }
            break;
        }

        case QCOW2_CLUSTER_UNALLOCATED:
            break;

        default:
            abort();
        }
    }

    g_free(l2_table);
    return 0;

fail:
    fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n");
    g_free(l2_table);
    return -EIO;
}