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

[Markus Armbruster]

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?

>>
>> >> >
>> >> >> +#
>> >> >> +# @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' } }
>>
>> [...]
>>