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Re: [Qemu-block] [PATCH v3 14/16] block/qcow2: falloc/full preallocating
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH v3 14/16] block/qcow2: falloc/full preallocating growth |
Date: |
Wed, 31 May 2017 11:41:16 +0100 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
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?
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- Re: [Qemu-block] [Qemu-devel] [PATCH v3 09/16] block/qcow2: Generalize preallocate(), (continued)
- [Qemu-block] [PATCH v3 10/16] block/qcow2: Lock s->lock in preallocate(), Max Reitz, 2017/05/26
- [Qemu-block] [PATCH v3 11/16] block/qcow2: Metadata preallocation for truncate, Max Reitz, 2017/05/26
- [Qemu-block] [PATCH v3 12/16] block/qcow2: Add qcow2_refcount_area(), Max Reitz, 2017/05/26
- [Qemu-block] [PATCH v3 13/16] block/qcow2: Rename "fail_block" to just "fail", Max Reitz, 2017/05/26
- [Qemu-block] [PATCH v3 14/16] block/qcow2: falloc/full preallocating growth, Max Reitz, 2017/05/26
- Re: [Qemu-block] [PATCH v3 14/16] block/qcow2: falloc/full preallocating growth,
Stefan Hajnoczi <=
- [Qemu-block] [PATCH v3 15/16] iotests: Add preallocated resize test for raw, Max Reitz, 2017/05/26
- [Qemu-block] [PATCH v3 16/16] iotests: Add preallocated growth test for qcow2, Max Reitz, 2017/05/26