Re: [Qemu-devel] [Qemu-block] [PATCH v2] qemu-img: return allocated size for block device with qcow2 format

[Ivan Ren]

>> qemu-img info with a block device which has a qcow2 format always
>> return 0 for disk size, and this can not reflect the qcow2 size
>> and the used space of the block device. This patch return the
>> allocated size of qcow2 as the disk size.
>>
>
>This has hit over a month old; I only skimmed the comments on V1 from
>Max and Eric. Is this something we still want?

Thanks for reply.

I think it's better to return this information instead of 0.

On Wed, Jun 13, 2018 at 2:42 AM John Snow <address@hidden> wrote:

>
>
> On 05/05/2018 03:49 AM, Ivan Ren wrote:
> > qemu-img info with a block device which has a qcow2 format always
> > return 0 for disk size, and this can not reflect the qcow2 size
> > and the used space of the block device. This patch return the
> > allocated size of qcow2 as the disk size.
> >
>
> This has hit over a month old; I only skimmed the comments on V1 from
> Max and Eric. Is this something we still want?
>
> --js
>
> > Signed-off-by: Ivan Ren <address@hidden>
> > ---
> >  block/qcow2.c | 54
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> >
> > This version differs from the previous:
> > (1).Accumulate all non-0 refcount cluster as the allocated size instead
> the
> > highest offset.
> > (2).Simplify the implementation by just check the refcount info.
> >
> > diff --git a/block/qcow2.c b/block/qcow2.c
> > index ef68772..e64469a 100644
> > --- a/block/qcow2.c
> > +++ b/block/qcow2.c
> > @@ -4493,6 +4493,59 @@ static QemuOptsList qcow2_create_opts = {
> >      }
> >  };
> >
> > +/* Get allocated space of qcow2, aligned to cluster_size */
> > +static int64_t qcow2_get_allocated_size(BlockDriverState *bs)
> > +{
> > +    int64_t allocated_cluster_count = 0;
> > +    uint64_t refcount;
> > +    int64_t i, j, begin_index, end_index;
> > +
> > +    BDRVQcow2State *s = bs->opaque;
> > +
> > +    /* Traverse refcount table */
> > +    for (i = 0; i < s->refcount_table_size; i++) {
> > +        if (s->refcount_table[i] & REFT_OFFSET_MASK) {
> > +            begin_index = i * s->refcount_block_size;
> > +            end_index = begin_index + s->refcount_block_size;
> > +            for (j = begin_index; j < end_index; j++) {
> > +                if (qcow2_get_refcount(bs, j, &refcount) < 0) {
> > +                    continue;
> > +                }
> > +                if (refcount > 0) {
> > +                    allocated_cluster_count++;
> > +                }
> > +            }
> > +        }
> > +
> > +    }
> > +
> > +    return allocated_cluster_count * s->cluster_size;
> > +}
> > +
> > +static int64_t qcow2_get_allocated_file_size(BlockDriverState *bs)
> > +{
> > +    int64_t ret = 0;
> > +
> > +    /* Get through bs->file first */
> > +    if (bs->file) {
> > +        ret = bdrv_get_allocated_file_size(bs->file->bs);
> > +    }
> > +
> > +    /*
> > +     * If ret < 0, some error may happen to the underlying media,
> return the
> > +     * error directly.
> > +     * If ret == 0, means length get from bs->file is 0, which is
> impossible
> > +     * for a normal file because of the qcow2 header. In this case, the
> > +     * underlying media may be a block device or anything else that
> can't
> > +     * return a suitable size. So we get the allocated size of qcow2
> instead.
> > +     */
> > +    if (!ret) {
> > +        ret = qcow2_get_allocated_size(bs);
> > +    }
> > +
> > +    return ret;
> > +}
> > +
> >  BlockDriver bdrv_qcow2 = {
> >      .format_name        = "qcow2",
> >      .instance_size      = sizeof(BDRVQcow2State),
> > @@ -4516,6 +4569,7 @@ BlockDriver bdrv_qcow2 = {
> >      .bdrv_co_pwrite_zeroes  = qcow2_co_pwrite_zeroes,
> >      .bdrv_co_pdiscard       = qcow2_co_pdiscard,
> >      .bdrv_truncate          = qcow2_truncate,
> > +    .bdrv_get_allocated_file_size = qcow2_get_allocated_file_size,
> >      .bdrv_co_pwritev_compressed = qcow2_co_pwritev_compressed,
> >      .bdrv_make_empty        = qcow2_make_empty,
> >
> >
>