Re: [PATCH v3 2/4] qcow2: add configurations for zoned format extension

[Sam Li <faithilikerun@gmail.com>]

Markus Armbruster <armbru@redhat.com> 于2023年9月18日周一 22:46写道：
>
> Sam Li <faithilikerun@gmail.com> writes:
>
> > Markus Armbruster <armbru@redhat.com> 于2023年9月1日周五 19:08写道：
> >>
> >> Sam Li <faithilikerun@gmail.com> writes:
> >>
> >> > To configure the zoned format feature on the qcow2 driver, it
> >> > requires following arguments: the device size, zoned profile,
> >>
> >> "Zoned profile" is gone in v3.
> >>
> >> > zone model, zone size, zone capacity, number of conventional
> >> > zones, limits on zone resources (max append sectors, max open
> >> > zones, and max_active_zones).
> >> >
> >> > To create a qcow2 file with zoned format, use command like this:
> >> > $ qemu-img create -f qcow2 test.qcow2 -o size=768M -o
> >> > zone_size=64M -o zone_capacity=64M -o nr_conv_zones=0 -o
> >> > max_append_sectors=512 -o max_open_zones=0 -o max_active_zones=0
> >> > -o zone_model=1
> >> >
> >> > Signed-off-by: Sam Li <faithilikerun@gmail.com>
> >>
> >> [...]
> >>
> >> > diff --git a/qapi/block-core.json b/qapi/block-core.json
> >> > index 2b1d493d6e..0d8f9e0a88 100644
> >> > --- a/qapi/block-core.json
> >> > +++ b/qapi/block-core.json
> >> > @@ -5021,6 +5021,27 @@
> >> >  # @compression-type: The image cluster compression method
> >> >  #     (default: zlib, since 5.1)
> >> >  #
> >> > +# @zone-model: Zoned device model, 1 for host-managed and 0 for
> >>
> >> Why is this encoded as a number?
> >>
> >> If it's fundamentally a flag, use bool.
> >>
> >> If more models could appear in the future, make it an enum.
> >>
> >
> > Yes, it is an enum.
> >
> > typedef enum BlockZoneModel {
> >     BLK_Z_NONE = 0x0, /* Regular block device */
> >     BLK_Z_HM = 0x1, /* Host-managed zoned block device */
> >     BLK_Z_HA = 0x2, /* Host-aware zoned block device */
> > } BlockZoneModel;
>
> Please make it an enum in the QAPI schema, too.

I see.

>
> >> > +#     non-zoned devices (default: 0, since 8.0)
> >>
> >> Since 8.2.  More of the same below.
> >>
> >> > +#
> >> > +# @zone-size: Total number of logical blocks within zones in bytes
> >> > +#     (since 8.0)
> >> > +#
> >> > +# @zone-capacity: The number of usable logical blocks within zones
> >> > +#     in bytes. A zone capacity is always smaller or equal to the
> >> > +#     zone size. (since 8.0)
> >>
> >> Two spaces between sentences for consistency, please.
> >>
> >> > +#
> >> > +# @nr-conv-zones: The number of conventional zones of the zoned device
> >> > +#     (since 8.0)
> >>
> >> I think @conventional-zones would be more obvious.
> >>
> >> > +#
> >> > +# @max-open-zones: The maximal allowed open zones (since 8.0)
> >>
> >> Maybe "The maximum number of open zones".
> >>
> >> > +#
> >> > +# @max-active-zones: The limit of the zones that have the implicit
> >> > +#     open, explicit open or closed state (since 8.0)
> >>
> >> Maybe "The maximum number of zones in the implicit open, explicit open
> >> or closed state".
> >>
> >> > +#
> >> > +# @max-append-sectors: The maximal data size in sectors of a zone
> >> > +#     append request that can be issued to the device. (since 8.0)
> >>
> >> What's the sector size, and how can the user determine it?  Why can't we
> >> use bytes here?
> >
> > The sector size is 512 bytes.
>
> Needs to be documented.
>
> I believe bytes would be easier to document, which makes me suspect
> they'd be the simpler interface.
>
> >                               It's more for conventional use.
>
> I'm afraid I don't understand this part.  Do I have to?

Not necessarily. I adopt the name from zoned storage part of virtio spec.

+If the VIRTIO_BLK_F_ZONED feature is negotiated, then in
+\field{virtio_blk_zoned_characteristics},
+\begin{itemize}
+\item \field{zone_sectors} value is expressed in 512-byte sectors.
+\item \field{max_append_sectors} value is expressed in 512-byte sectors.
+\item \field{write_granularity} value is expressed in bytes.
+\end{itemize}

>
> >> > +#
> >> >  # Since: 2.12
> >> >  ##
> >> >  { 'struct': 'BlockdevCreateOptionsQcow2',
> >> > @@ -5037,7 +5058,14 @@
> >> >              '*preallocation':   'PreallocMode',
> >> >              '*lazy-refcounts':  'bool',
> >> >              '*refcount-bits':   'int',
> >> > -            '*compression-type':'Qcow2CompressionType' } }
> >> > +            '*compression-type':'Qcow2CompressionType',
> >> > +            '*zone-model':         'uint8',
> >> > +            '*zone-size':          'size',
> >> > +            '*zone-capacity':      'size',
> >> > +            '*nr-conv-zones':      'uint32',
> >> > +            '*max-open-zones':     'uint32',
> >> > +            '*max-active-zones':   'uint32',
> >> > +            '*max-append-sectors': 'uint32' } }
> >> >
> >> >  ##
> >> >  # @BlockdevCreateOptionsQed:
> >>
>