On Tue, Feb 11, 2014 at 03:07:10PM +0800, Hu Tao wrote:
> This adds a preallocation=full mode to qcow2 image creation, which
> creates a non-sparse image file.
Ping.
This is the major part of the patchset that needs review, especially
the calculation of metadata size.
>
> Signed-off-by: Hu Tao <hu...@cn.fujitsu.com>
> ---
> block/qcow2.c | 75
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 72 insertions(+), 3 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index e4bab70..4b113b7 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1456,6 +1456,7 @@ static int qcow2_create2(const char *filename, int64_t
> total_size,
> QEMUOptionParameter *options, int version,
> Error **errp)
> {
> + QEMUOptionParameter *alloc_options = NULL;
> /* Calculate cluster_bits */
> int cluster_bits;
> cluster_bits = ffs(cluster_size) - 1;
> @@ -1485,16 +1486,80 @@ static int qcow2_create2(const char *filename,
> int64_t total_size,
> Error *local_err = NULL;
> int ret;
>
> + if (prealloc == PREALLOC_MODE_FULL) {
> + int64_t meta_size = 0;
> + unsigned nreftablee, nrefblocke, nl1e, nl2e;
> + BlockDriver *drv;
> +
> + total_size = align_offset(total_size, cluster_size);
> +
> + drv = bdrv_find_protocol(filename, true);
> + if (drv == NULL) {
> + error_setg(errp, "Could not find protocol for file '%s'",
> filename);
> + return -ENOENT;
> + }
> +
> + alloc_options = append_option_parameters(alloc_options,
> + drv->create_options);
> + alloc_options = append_option_parameters(alloc_options, options);
> +
> + /* header: 1 cluster */
> + meta_size += cluster_size;
> +
> + /* total size of L2 tables */
> + nl2e = total_size / cluster_size;
> + nl2e = align_offset(nl2e, cluster_size / sizeof(uint64_t));
> + meta_size += nl2e * sizeof(uint64_t);
> +
> + /* total size of L1 tables */
> + nl1e = nl2e * sizeof(uint64_t) / cluster_size;
> + nl1e = align_offset(nl1e, cluster_size / sizeof(uint64_t));
Although not stated in the qcow2 spec, but actually l1 tables are
aligned to cluster too because of the nature of qcow2_alloc_clusters().
Same for refcount tables below.
> + meta_size += nl1e * sizeof(uint64_t);
> +
> + /* total size of refcount blocks
> + *
> + * note: every host cluster is reference-counted, including metadata
> + * (even refcount blocks are recursively included).
> + * Let:
> + * a = total_size (this is the guest disk size)
> + * m = meta size not including refcount blocks and refcount tables
> + * c = cluster size
> + * y1 = number of refcount blocks entries
> + * y2 = meta size including everything
> + * then,
> + * y1 = (y2 + a)/c
> + * y2 = y1 * sizeof(u16) + y1 * sizeof(u16) * sizeof(u64) / c + m
> + * we can get y1:
> + * y1 = (a + m) / (c - sizeof(u16) - sizeof(u16) * sizeof(u64) / c)
> + */
> + nrefblocke = (total_size + meta_size + cluster_size) /
> + (cluster_size - sizeof(uint16_t) -
> + 1.0 * sizeof(uint16_t) * sizeof(uint64_t) / cluster_size);
> + nrefblocke = align_offset(nrefblocke, cluster_size /
> sizeof(uint16_t));
> + meta_size += nrefblocke * sizeof(uint16_t);
> +
> + /* total size of refcount tables */
> + nreftablee = nrefblocke * sizeof(uint16_t) / cluster_size;
> + nreftablee = align_offset(nreftablee, cluster_size /
> sizeof(uint64_t));
> + meta_size += nreftablee * sizeof(uint64_t);
> +
> + set_option_parameter_int(alloc_options, BLOCK_OPT_SIZE,
> + total_size + meta_size);
> + set_option_parameter(alloc_options, BLOCK_OPT_PREALLOC, "full");
> +
> + options = alloc_options;
> + }
> +
> ret = bdrv_create_file(filename, options, &local_err);
> if (ret < 0) {
> error_propagate(errp, local_err);
> - return ret;
> + goto out_options;
> }
>
> ret = bdrv_file_open(&bs, filename, NULL, NULL, BDRV_O_RDWR, &local_err);
> if (ret < 0) {
> error_propagate(errp, local_err);
> - return ret;
> + goto out_options;
> }
>
> /* Write the header */
> @@ -1611,6 +1676,8 @@ static int qcow2_create2(const char *filename, int64_t
> total_size,
> ret = 0;
> out:
> bdrv_unref(bs);
> +out_options:
> + free_option_parameters(alloc_options);
> return ret;
> }
>
> @@ -1646,6 +1713,8 @@ static int qcow2_create(const char *filename,
> QEMUOptionParameter *options,
> prealloc = PREALLOC_MODE_OFF;
> } else if (!strcmp(options->value.s, "metadata")) {
> prealloc = PREALLOC_MODE_METADATA;
> + } else if (!strcmp(options->value.s, "full")) {
> + prealloc = PREALLOC_MODE_FULL;
> } else {
> error_setg(errp, "Invalid preallocation mode: '%s'",
> options->value.s);
> @@ -2211,7 +2280,7 @@ static QEMUOptionParameter qcow2_create_options[] = {
> {
> .name = BLOCK_OPT_PREALLOC,
> .type = OPT_STRING,
> - .help = "Preallocation mode (allowed values: off, metadata)"
> + .help = "Preallocation mode (allowed values: off, metadata, full)"
> },
> {
> .name = BLOCK_OPT_LAZY_REFCOUNTS,
> --
> 1.8.0
>
