On 2017-05-31 12:41, Stefan Hajnoczi wrote:
> On Fri, May 26, 2017 at 06:55:16PM +0200, Max Reitz wrote:
>> @@ -2677,6 +2679,102 @@ static int qcow2_truncate(BlockDriverState *bs,
>> int64_t offset,
>> }
>> break;
>>
>> + case PREALLOC_MODE_FALLOC:
>> + case PREALLOC_MODE_FULL:
>> + {
>> + int64_t allocation_start, host_offset, guest_offset;
>> + int64_t clusters_allocated;
>> + int64_t old_file_size, new_file_size;
>> + uint64_t nb_new_data_clusters, nb_new_l2_tables;
>> +
>> + old_file_size = bdrv_getlength(bs->file->bs);
>> + if (old_file_size < 0) {
>> + error_setg_errno(errp, -old_file_size,
>> + "Failed to inquire current file length");
>> + return ret;
>> + }
>> +
>> + nb_new_data_clusters = DIV_ROUND_UP(offset - old_length,
>> + s->cluster_size);
>> +
>> + /* This is an overestimation; we will not actually allocate space
>> for
>> + * these in the file but just make sure the new refcount structures
>> are
>> + * able to cover them so we will not have to allocate new refblocks
>> + * while entering the data blocks in the potentially new L2 tables.
>> + * (We do not actually care where the L2 tables are placed. Maybe
>> they
>> + * are already allocated or they can be placed somewhere before
>> + * @old_file_size. It does not matter because they will be fully
>> + * allocated automatically, so they do not need to be covered by
>> the
>> + * preallocation. All that matters is that we will not have to
>> allocate
>> + * new refcount structures for them.) */
>> + nb_new_l2_tables = DIV_ROUND_UP(nb_new_data_clusters,
>> + s->cluster_size / sizeof(uint64_t));
>> + /* The cluster range may not be aligned to L2 boundaries, so add
>> one L2
>> + * table for a potential head/tail */
>> + nb_new_l2_tables++;
>> +
>> + allocation_start = qcow2_refcount_area(bs, old_file_size,
>> + nb_new_data_clusters +
>> + nb_new_l2_tables,
>> + true, 0, 0);
>> + if (allocation_start < 0) {
>> + error_setg_errno(errp, -allocation_start,
>> + "Failed to resize refcount structures");
>> + return -allocation_start;
>> + }
>> +
>> + clusters_allocated = qcow2_alloc_clusters_at(bs, allocation_start,
>> + nb_new_data_clusters);
>> + if (clusters_allocated < 0) {
>> + error_setg_errno(errp, -clusters_allocated,
>> + "Failed to allocate data clusters");
>> + return -clusters_allocated;
>> + }
>> +
>> + assert(clusters_allocated == nb_new_data_clusters);
>> +
>> + /* Allocate the data area */
>> + new_file_size = allocation_start +
>> + nb_new_data_clusters * s->cluster_size;
>> + ret = bdrv_truncate(bs->file, new_file_size, prealloc, errp);
>> + if (ret < 0) {
>> + error_prepend(errp, "Failed to resize underlying file: ");
>> + qcow2_free_clusters(bs, allocation_start,
>> + nb_new_data_clusters * s->cluster_size,
>> + QCOW2_DISCARD_OTHER);
>> + return ret;
>> + }
>> +
>> + /* Create the necessary L2 entries */
>> + host_offset = allocation_start;
>> + guest_offset = old_length;
>> + while (nb_new_data_clusters) {
>> + int64_t guest_cluster = guest_offset >> s->cluster_bits;
>> + int64_t nb_clusters = MIN(nb_new_data_clusters,
>> + s->l2_size - guest_cluster %
>> s->l2_size);
>> + QCowL2Meta allocation = {
>> + .offset = guest_offset,
>> + .alloc_offset = host_offset,
>> + .nb_clusters = nb_clusters,
>> + };
>> + qemu_co_queue_init(&allocation.dependent_requests);
>> +
>> + ret = qcow2_alloc_cluster_link_l2(bs, &allocation);
>> + if (ret < 0) {
>> + error_setg_errno(errp, -ret, "Failed to update L2 tables");
>> + qcow2_free_clusters(bs, host_offset,
>> + nb_new_data_clusters * s->cluster_size,
>> + QCOW2_DISCARD_OTHER);
>> + return ret;
>> + }
>> +
>> + guest_offset += nb_clusters * s->cluster_size;
>> + host_offset += nb_clusters * s->cluster_size;
>> + nb_new_data_clusters -= nb_clusters;
>> + }
>> + break;
>> + }
>
> Flush L1/L2 tables?Right. It would be good to actually have the area allocated for sure before writing the new size. :-) The same applies to the metadata-only preallocate(), though. So this should probably be added in patch 11. Thanks for spotting this, and thanks for reviewing! Max
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