Re: [Qemu-devel] [RFC 0/4] qemu-img: add max-size subcommand

[John Snow]

On 03/03/2017 08:51 AM, Stefan Hajnoczi wrote:
> RFCv1:
>  * Publishing patch series with just raw support, no qcow2 yet.  Please review
>    the command-line interface and let me know if you are happy with this
>    approach.
> 
> Users and management tools sometimes need to know the size required for a new
> disk image so that an LVM volume, SAN LUN, etc can be allocated ahead of time.
> Image formats like qcow2 have non-trivial metadata that makes it hard to
> estimate the exact size without knowledge of file format internals.
> 
> This patch series introduces a new qemu-img subcommand that calculates the
> required size for both image creation and conversion scenarios.
> 
> The conversion scenario is:
> 
>   $ qemu-img max-size -f raw -O qcow2 input.img
>   107374184448
> 
> Here an existing image file is taken and the output includes the space 
> required
> for data from the input image file.
> 
> The creation scenario is:
> 
>   $ qemu-img max-size -O qcow2 --size 5G
>   196688
> 

It looks sane to me, implementation looks clean enough.
Thanks!

> Stefan Hajnoczi (4):
>   block: add bdrv_max_size() API
>   raw-format: add bdrv_max_size() support
>   qemu-img: add max-size subcommand
>   iotests: add test 178 for qemu-img max-size
> 
>  include/block/block.h      |   2 +
>  include/block/block_int.h  |   2 +
>  block.c                    |  37 +++++++++
>  block/raw-format.c         |  16 ++++
>  qemu-img.c                 | 196 
> +++++++++++++++++++++++++++++++++++++++++++++
>  qemu-img-cmds.hx           |   6 ++
>  tests/qemu-iotests/178     |  75 +++++++++++++++++
>  tests/qemu-iotests/178.out |  25 ++++++
>  tests/qemu-iotests/group   |   1 +
>  9 files changed, 360 insertions(+)
>  create mode 100755 tests/qemu-iotests/178
>  create mode 100644 tests/qemu-iotests/178.out
>