Re: [PATCH v4 3/4] qcow2: add zoned emulation capability

[Eric Blake]

On Mon, Sep 18, 2023 at 05:53:12PM +0800, Sam Li wrote:
> By adding zone operations and zoned metadata, the zoned emulation
> capability enables full emulation support of zoned device using
> a qcow2 file. The zoned device metadata includes zone type,
> zoned device state and write pointer of each zone, which is stored
> to an array of unsigned integers.
> 
> Each zone of a zoned device makes state transitions following
> the zone state machine. The zone state machine mainly describes
> five states, IMPLICIT OPEN, EXPLICIT OPEN, FULL, EMPTY and CLOSED.
> READ ONLY and OFFLINE states will generally be affected by device
> internal events. The operations on zones cause corresponding state
> changing.
> 
> Zoned devices have a limit on zone resources, which puts constraints on
> write operations into zones.
> 
> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> ---
>  block/qcow2.c          | 709 ++++++++++++++++++++++++++++++++++++++++-
>  block/qcow2.h          |   2 +
>  block/trace-events     |   2 +
>  docs/interop/qcow2.txt |   6 +
>  4 files changed, 717 insertions(+), 2 deletions(-)

You may want to look at scripts/git.orderfile; putting spec changes
(docs/*) first in your output before implementation is generally
beneficial to reviewers.

> +++ b/docs/interop/qcow2.txt
> @@ -367,6 +367,12 @@ The fields of the zoned extension are:
>                      The maximal number of 512-byte sectors of a zone
>                      append request that can be issued to the device.
>  
> +          36 - 43:  zonedmeta_offset
> +                    The offset of zoned metadata structure in the file in 
> bytes.

For the spec to be useful, you also need to add a section describing
the layout of the zoned metadata structure actually is.

> +
> +          44 - 51:  zonedmeta_size
> +                    The size of zoned metadata in bytes.
> +

Can the zoned metadata structure ever occupy more than 4G, or can this
field be sized at 4 bytes instead of 8?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org