Re: [PATCH v7 2/4] qcow2: add configurations for zoned format extension

[Sam Li]

Markus Armbruster <armbru@redhat.com> 于2024年2月19日周一 16:56写道：
>
> Sam Li <faithilikerun@gmail.com> writes:
>
> > Markus Armbruster <armbru@redhat.com> 于2024年2月19日周一 15:40写道：
> >>
> >> Sam Li <faithilikerun@gmail.com> writes:
> >>
> >> > Markus Armbruster <armbru@redhat.com> 于2024年2月19日周一 13:05写道：
> >> >>
> >> >> One more thing...
> >> >>
> >> >> Markus Armbruster <armbru@redhat.com> writes:
> >> >>
> >> >> > I apologize for the delayed review.
> >> >
> >> > No problems. Thanks for reviewing!
> >> >
> >> >> >
> >> >> > Sam Li <faithilikerun@gmail.com> writes:
> >> >> >
> >> >> >> To configure the zoned format feature on the qcow2 driver, it
> >> >> >> requires settings as: the device size, zone model, zone size,
> >> >> >> zone capacity, number of conventional zones, limits on zone
> >> >> >> resources (max append bytes, max open zones, and max_active_zones).
> >> >> >>
> >> >> >> To create a qcow2 image with zoned format feature, use command like
> >> >> >> this:
> >> >> >> qemu-img create -f qcow2 zbc.qcow2 -o size=768M \
> >> >> >> -o zone.size=64M -o zone.capacity=64M -o zone.conventional_zones=0 \
> >> >> >> -o zone.max_append_bytes=4096 -o zone.max_open_zones=6 \
> >> >> >> -o zone.max_active_zones=8 -o zone.mode=host-managed
> >> >> >>
> >> >> >> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> >> >> >
> >> >> > [...]
> >> >> >
> >> >> >> diff --git a/qapi/block-core.json b/qapi/block-core.json
> >> >> >> index ca390c5700..e2e0ec21a5 100644
> >> >> >> --- a/qapi/block-core.json
> >> >> >> +++ b/qapi/block-core.json
> >> >> >> @@ -5038,6 +5038,67 @@
> >> >> >>  { 'enum': 'Qcow2CompressionType',
> >> >> >>    'data': [ 'zlib', { 'name': 'zstd', 'if': 'CONFIG_ZSTD' } ] }
> >> >> >>
> >> >> >> +##
> >> >> >> +# @Qcow2ZoneModel:
> >> >> >> +#
> >> >> >> +# Zoned device model used in qcow2 image file
> >> >> >> +#
> >> >> >> +# @host-managed: The host-managed model only allows sequential 
> >> >> >> write over the
> >> >> >> +#     device zones.
> >> >> >> +#
> >> >> >> +# Since 8.2
> >> >> >> +##
> >> >> >> +{ 'enum': 'Qcow2ZoneModel',
> >> >> >> +  'data': [ 'host-managed'] }
> >> >> >> +
> >> >> >> +##
> >> >> >> +# @Qcow2ZoneHostManaged:
> >> >> >> +#
> >> >> >> +# The host-managed zone model.  It only allows sequential writes.
> >> >> >> +#
> >> >> >> +# @size: Total number of bytes within zones.
> >> >> >
> >> >> > Default?
> >> >
> >> > It should be set by users. No default value provided. If it's unset
> >> > then it is zero and an error will be returned.
> >>
> >> If the user must provide @size, why is it optional then?
> >
> > It is not optional when the zone model is host-managed. If it's
> > non-zoned, then we don't care about zone info. I am not sure how to
> > make it unoptional.
>
> We have:
>
>    blockdev-create argument @options of type BlockdevCreateOptions
>
>    BlockdevCreateOptions union branch @qcow2 of type
>    BlockdevCreateOptionsQcow2, union tag member is @driver
>
>    BlockdevCreateOptionsQcow2 optional member @zone of type
>    Qcow2ZoneCreateOptions, default not zoned
>
>    Qcow2ZoneCreateOptions union branch @host-managed of type
>    Qcow2ZoneHostManaged, union tag member is @mode
>
>    Qcow2ZoneHostManaged optional member @size of type size.
>
> Making this member @size mandatory means we must specify it when
> BlockdevCreateOptionsQcow2 member @zone is present and @zone's member
> @mode is "host-managed".  Feels right to me.  Am I missing anything?

That's right. And the checks when creating such an img can help do
that. It's not specified in the .json file directly.

>
> >>
> >> >> >
> >> >> >> +#
> >> >> >> +# @capacity: The number of usable logical blocks within zones
> >> >> >> +#     in bytes.  A zone capacity is always smaller or equal to the
> >> >> >> +#     zone size.
> >> >> >
> >> >> > Default?
> >> >
> >> > Same.
> >> >
> >> >> >
> >> >> >> +# @max-append-bytes: The maximal number of bytes of a zone
> >> >> >> +#     append request that can be issued to the device.  It must be
> >> >> >> +#     512-byte aligned and less than the zone capacity.
> >> >> >
> >> >> > Default?
> >> >
> >> > Same.
> >> >
> >> > For those values, I guess it could be set when users provide no
> >> > information and still want a workable emulated zoned block device.
> >> >
> >> >> >
> >> >> >> +#
> >> >> >> +# Since 8.2
> >> >> >> +##
> >> >> >> +{ 'struct': 'Qcow2ZoneHostManaged',
> >> >> >> +  'data': { '*size':          'size',
> >> >> >> +            '*capacity':      'size',
> >> >> >> +            '*conventional-zones': 'uint32',
> >> >> >> +            '*max-open-zones':     'uint32',
> >> >> >> +            '*max-active-zones':   'uint32',
> >> >> >> +            '*max-append-bytes':   'size' } }
> >>
> >> [...]
> >>
>