Re: [PATCH v2 0/4] Add full zoned storage emulation to qcow2 driver

[Sam Li]

Klaus Jensen <its@irrelevant.dk> 于2023年8月16日周三 15:37写道：
>
> On Aug 14 16:57, Sam Li wrote:
> > This patch series add a new extension - zoned format - to the
> > qcow2 driver thereby allowing full zoned storage emulation on
> > the qcow2 img file. Users can attach such a qcow2 file to the
> > guest as a zoned device.
> >
> > 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 zone_nr_conv=0 -o
> > max_append_sectors=512 -o max_open_zones=0 -o max_active_zones=0
> > -o zoned_profile=zbc
> >
> > Then add it to the QEMU command line:
> >     -blockdev 
> > node-name=drive1,driver=qcow2,file.driver=file,file.filename=../qemu/test.qcow2
> >  \
> >     -device virtio-blk-pci,drive=drive1 \
> >
> > v1->v2:
> > - add more tests to qemu-io zoned commands
> > - make zone append change state to full when wp reaches end
> > - add documentation to qcow2 zoned extension header
> > - address review comments (Stefan):
> >   * fix zoned_mata allocation size
> >   * use bitwise or than addition
> >   * fix wp index overflow and locking
> >   * cleanups: comments, naming
> >
> > Sam Li (4):
> >   docs/qcow2: add the zoned format feature
> >   qcow2: add configurations for zoned format extension
> >   qcow2: add zoned emulation capability
> >   iotests: test the zoned format feature for qcow2 file
> >
> >  block/qcow2.c                            | 799 ++++++++++++++++++++++-
> >  block/qcow2.h                            |  23 +
> >  docs/interop/qcow2.txt                   |  26 +
> >  docs/system/qemu-block-drivers.rst.inc   |  39 ++
> >  include/block/block-common.h             |   5 +
> >  include/block/block_int-common.h         |  16 +
> >  qapi/block-core.json                     |  46 +-
> >  tests/qemu-iotests/tests/zoned-qcow2     | 135 ++++
> >  tests/qemu-iotests/tests/zoned-qcow2.out | 140 ++++
> >  9 files changed, 1214 insertions(+), 15 deletions(-)
> >  create mode 100755 tests/qemu-iotests/tests/zoned-qcow2
> >  create mode 100644 tests/qemu-iotests/tests/zoned-qcow2.out
> >
>
> Hi Sam,
>
> Thanks for this and for the RFC for hw/nvme - this is an awesome
> improvement.
>
> Can you explain the need for the zoned_profile? I understand that only
> ZNS requires potentially setting zone_capacity and configuring extended
> descriptors. When an image is hooked up to a block emulation device that
> doesnt understand cap < size or extended descriptors, it could just
> would fail on the cap < size and just ignore the extended descriptor
> space. Do we really need to add the complexity of the user explicitly
> having to set the profile? I also think it is fair for the QEMU zoned
> block api to accomodate both variations - if a particular configuration
> is supported or not is up to the emulating device.
>
> Checking the profile from hw/nvme or hw/block/virtio is the same as
> checking if cap < size or possibly the presence of extended descriptors.

Hi Klaus,

Thanks for your feedback.

The zoned_profile is for users to choose the emulating device type,
either zbc or zns. It implies using virtio-blk or nvme pass through.
The zoned block api does accommodate both variations. Since the cap <
size and extended descriptor config can also infer zoned_profile, this
option can be dropped. Then the device type is determined by the
configurations. When cap = size and no extended descriptor, the img
can be used both in virtio-blk and nvme zns depending on the QEMU
command line.


Best regards,
Sam