Re: [Qemu-devel] [RFC v2 5/8] qcow2: add bdrv_measure() support

[Max Reitz]

On 15.03.2017 10:29, Stefan Hajnoczi wrote:
> Use qcow2_calc_prealloc_size() to get the required file size.
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> TODO:
>  * Query block status and only count allocated clusters if in_bs != NULL
>  * Exclude backing file clusters if in_bs != NULL and -o backing_file=
>    is given
> ---
>  block/qcow2.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 19be468..a4caf97 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2940,6 +2940,58 @@ static coroutine_fn int 
> qcow2_co_flush_to_os(BlockDriverState *bs)
>      return 0;
>  }
>  
> +static void qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
> +                          BlockMeasureInfo *info, Error **errp)
> +{
> +    Error *local_err = NULL;
> +    uint64_t allocated_bytes = 0;
> +    uint64_t prealloc_size;
> +    uint64_t size;
> +    uint64_t refcount_bits;
> +    size_t cluster_size;
> +    int version;
> +
> +    size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
> +                    BDRV_SECTOR_SIZE);
> +
> +    cluster_size = qcow2_opt_get_cluster_size_del(opts, &local_err);
> +    if (local_err) {
> +        goto err;
> +    }
> +
> +    version = qcow2_opt_get_version_del(opts, &local_err);
> +    if (local_err) {
> +        goto err;
> +    }
> +
> +    refcount_bits = qcow2_opt_get_refcount_bits_del(opts, version, 
> &local_err);
> +    if (local_err) {
> +        goto err;
> +    }
> +
> +    if (in_bs) {
> +        int64_t ssize = bdrv_getlength(in_bs);
> +        if (ssize < 0) {
> +            error_setg_errno(errp, -ssize, "Unable to get image size");
> +            return;
> +        }
> +
> +        size = ssize;
> +
> +        /* TODO How many clusters are allocated modulo backing file in opts? 
> */
> +    }
> +
> +    prealloc_size = qcow2_calc_prealloc_size(size, cluster_size,
> +                                             ctz32(refcount_bits));
> +    info->required_bytes = prealloc_size - (align_offset(size, cluster_size) 
> -
> +                                            allocated_bytes);

But what if @opts contains a preallocation option?

Max

> +    info->fully_allocated_bytes = prealloc_size;
> +    return;
> +
> +err:
> +    error_propagate(errp, local_err);
> +}
> +
>  static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
>  {
>      BDRVQcow2State *s = bs->opaque;
> @@ -3487,6 +3539,7 @@ BlockDriver bdrv_qcow2 = {
>      .bdrv_snapshot_delete   = qcow2_snapshot_delete,
>      .bdrv_snapshot_list     = qcow2_snapshot_list,
>      .bdrv_snapshot_load_tmp = qcow2_snapshot_load_tmp,
> +    .bdrv_measure           = qcow2_measure,
>      .bdrv_get_info          = qcow2_get_info,
>      .bdrv_get_specific_info = qcow2_get_specific_info,
>  
>

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