int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset, int *num, uint64_t *cluster_offset) { BDRVQcowState *s = bs->opaque; unsigned int l2_index; uint64_t l1_index, l2_offset, *l2_table; int l1_bits, c; unsigned int index_in_cluster, nb_clusters; uint64_t nb_available, nb_needed; int ret; index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1); nb_needed = *num + index_in_cluster; l1_bits = s->l2_bits + s->cluster_bits; /* compute how many bytes there are between the offset and * the end of the l1 entry */ nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1)); /* compute the number of available sectors */ nb_available = (nb_available >> 9) + index_in_cluster; if (nb_needed > nb_available) { nb_needed = nb_available; } *cluster_offset = 0; /* seek the the l2 offset in the l1 table */ l1_index = offset >> l1_bits; if (l1_index >= s->l1_size) { ret = QCOW2_CLUSTER_UNALLOCATED; goto out; } l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; if (!l2_offset) { ret = QCOW2_CLUSTER_UNALLOCATED; goto out; } /* load the l2 table in memory */ ret = l2_load(bs, l2_offset, &l2_table); if (ret < 0) { return ret; } /* find the cluster offset for the given disk offset */ l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1); *cluster_offset = be64_to_cpu(l2_table[l2_index]); nb_clusters = size_to_clusters(s, nb_needed << 9); ret = qcow2_get_cluster_type(*cluster_offset); switch (ret) { case QCOW2_CLUSTER_COMPRESSED: /* Compressed clusters can only be processed one by one */ c = 1; *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK; break; case QCOW2_CLUSTER_ZERO: if (s->qcow_version < 3) { qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); return -EIO; } c = count_contiguous_clusters(nb_clusters, s->cluster_size, &l2_table[l2_index], QCOW_OFLAG_ZERO); *cluster_offset = 0; break; case QCOW2_CLUSTER_UNALLOCATED: /* how many empty clusters ? */ c = count_contiguous_free_clusters(nb_clusters, &l2_table[l2_index]); *cluster_offset = 0; break; case QCOW2_CLUSTER_NORMAL: /* how many allocated clusters ? */ c = count_contiguous_clusters(nb_clusters, s->cluster_size, &l2_table[l2_index], QCOW_OFLAG_ZERO); *cluster_offset &= L2E_OFFSET_MASK; break; default: abort(); } qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); nb_available = (c * s->cluster_sectors); out: if (nb_available > nb_needed) nb_available = nb_needed; *num = nb_available - index_in_cluster; return ret; }