static uint64_t alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, int n_start, int n_end, int *num, QCowL2Meta *m) { BDRVQcowState *s = bs->opaque; int l2_index, ret; uint64_t l2_offset, *l2_table, cluster_offset; int nb_clusters, i = 0; ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &l2_index); if (ret == 0) return 0; nb_clusters = size_to_clusters(s, n_end << 9); nb_clusters = MIN(nb_clusters, s->l2_size - l2_index); cluster_offset = be64_to_cpu(l2_table[l2_index]); /* We keep all QCOW_OFLAG_COPIED clusters */ if (cluster_offset & QCOW_OFLAG_COPIED) { nb_clusters = count_contiguous_clusters(nb_clusters, s->cluster_size, &l2_table[l2_index], 0); cluster_offset &= ~QCOW_OFLAG_COPIED; m->nb_clusters = 0; goto out; } /* for the moment, multiple compressed clusters are not managed */ if (cluster_offset & QCOW_OFLAG_COMPRESSED) nb_clusters = 1; /* how many available clusters ? */ while (i < nb_clusters) { i += count_contiguous_clusters(nb_clusters - i, s->cluster_size, &l2_table[l2_index + i], 0); if(be64_to_cpu(l2_table[l2_index + i])) break; i += count_contiguous_free_clusters(nb_clusters - i, &l2_table[l2_index + i]); cluster_offset = be64_to_cpu(l2_table[l2_index + i]); if ((cluster_offset & QCOW_OFLAG_COPIED) || (cluster_offset & QCOW_OFLAG_COMPRESSED)) break; } nb_clusters = i; /* allocate a new cluster */ cluster_offset = alloc_clusters(bs, nb_clusters * s->cluster_size); /* save info needed for meta data update */ m->offset = offset; m->n_start = n_start; m->nb_clusters = nb_clusters; out: m->nb_available = MIN(nb_clusters << (s->cluster_bits - 9), n_end); *num = m->nb_available - n_start; return cluster_offset; }