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

[Klaus Jensen <its@irrelevant.dk>]

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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.


Thanks,
Klaus

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