int qcow2_update_header(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; QCowHeader *header; char *buf; size_t buflen = s->cluster_size; int ret; uint64_t total_size; uint32_t refcount_table_clusters; size_t header_length; Qcow2UnknownHeaderExtension *uext; buf = qemu_blockalign(bs, buflen); /* Header structure */ header = (QCowHeader*) buf; if (buflen < sizeof(*header)) { ret = -ENOSPC; goto fail; } header_length = sizeof(*header) + s->unknown_header_fields_size; total_size = bs->total_sectors * BDRV_SECTOR_SIZE; refcount_table_clusters = s->refcount_table_size >> (s->cluster_bits - 3); *header = (QCowHeader) { /* Version 2 fields */ .magic = cpu_to_be32(QCOW_MAGIC), .version = cpu_to_be32(s->qcow_version), .backing_file_offset = 0, .backing_file_size = 0, .cluster_bits = cpu_to_be32(s->cluster_bits), .size = cpu_to_be64(total_size), .crypt_method = cpu_to_be32(s->crypt_method_header), .l1_size = cpu_to_be32(s->l1_size), .l1_table_offset = cpu_to_be64(s->l1_table_offset), .refcount_table_offset = cpu_to_be64(s->refcount_table_offset), .refcount_table_clusters = cpu_to_be32(refcount_table_clusters), .nb_snapshots = cpu_to_be32(s->nb_snapshots), .snapshots_offset = cpu_to_be64(s->snapshots_offset), /* Version 3 fields */ .incompatible_features = cpu_to_be64(s->incompatible_features), .compatible_features = cpu_to_be64(s->compatible_features), .autoclear_features = cpu_to_be64(s->autoclear_features), .refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT), .header_length = cpu_to_be32(header_length), }; /* For older versions, write a shorter header */ switch (s->qcow_version) { case 2: ret = offsetof(QCowHeader, incompatible_features); break; case 3: ret = sizeof(*header); break; default: return -EINVAL; } buf += ret; buflen -= ret; memset(buf, 0, buflen); /* Preserve any unknown field in the header */ if (s->unknown_header_fields_size) { if (buflen < s->unknown_header_fields_size) { ret = -ENOSPC; goto fail; } memcpy(buf, s->unknown_header_fields, s->unknown_header_fields_size); buf += s->unknown_header_fields_size; buflen -= s->unknown_header_fields_size; } /* Backing file format header extension */ if (*bs->backing_format) { ret = header_ext_add(buf, QCOW2_EXT_MAGIC_BACKING_FORMAT, bs->backing_format, strlen(bs->backing_format), buflen); if (ret < 0) { goto fail; } buf += ret; buflen -= ret; } /* Feature table */ Qcow2Feature features[] = { /* no feature defined yet */ }; ret = header_ext_add(buf, QCOW2_EXT_MAGIC_FEATURE_TABLE, features, sizeof(features), buflen); if (ret < 0) { goto fail; } buf += ret; buflen -= ret; /* Keep unknown header extensions */ QLIST_FOREACH(uext, &s->unknown_header_ext, next) { ret = header_ext_add(buf, uext->magic, uext->data, uext->len, buflen); if (ret < 0) { goto fail; } buf += ret; buflen -= ret; } /* End of header extensions */ ret = header_ext_add(buf, QCOW2_EXT_MAGIC_END, NULL, 0, buflen); if (ret < 0) { goto fail; } buf += ret; buflen -= ret; /* Backing file name */ if (*bs->backing_file) { size_t backing_file_len = strlen(bs->backing_file); if (buflen < backing_file_len) { ret = -ENOSPC; goto fail; } strncpy(buf, bs->backing_file, buflen); header->backing_file_offset = cpu_to_be64(buf - ((char*) header)); header->backing_file_size = cpu_to_be32(backing_file_len); } /* Write the new header */ ret = bdrv_pwrite(bs->file, 0, header, s->cluster_size); if (ret < 0) { goto fail; } ret = 0; fail: qemu_vfree(header); return ret; }