Re: [PATCH v2 07/12] qapi/block: Add BLOCK_IO_DONE event

[Markus Armbruster <armbru@redhat.com>]

Hanna Czenczek <hreitz@redhat.com> writes:

> This event is emitted when an operation completes, for which a
> BLOCK_IO_DELAY event has previously been emitted.
>
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
> ---
>  qapi/block.json | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>
> diff --git a/qapi/block.json b/qapi/block.json
> index 5f9f5c28050..38f293dd32d 100644
> --- a/qapi/block.json
> +++ b/qapi/block.json
> @@ -660,6 +660,9 @@
>  # Note that delays deliberately incurred by throttling do count
>  # towards the operation duration.
>  #
> +# This event will only be emitted once per request and action.  When
> +# the operation does finish, a `BLOCK_IO_DONE` event is emitted.

I think the first sentence answers a question I had on the previous
patch.  Move it there?

> +#
>  # @qom-path: path to the block device object in the QOM tree
>  #
>  # @operation: I/O operation
> @@ -686,3 +689,33 @@
>        'action': 'BlockErrorAction',
>        '*offset': 'uint64',
>        'bytes': 'uint64' } }
> +
> +##
> +# @BLOCK_IO_DONE:
> +#
> +# Emitted on completion for disk operations that previously emitted a
> +# `BLOCK_IO_DELAY` event.

Can we have multiple operations in flight that previously emitted
BLOCK_IO_DELAY?

If yes, might a management application need to connect the BLOCK_IO_DONE
back to the BLOCK_IO_DELAY?

If yes, how could it do that?

Please use the revised syntax for introductions:

   ##
   # @BLOCK_IO_DONE: Emitted on completion for disk operations that
   #     previously emitted a `BLOCK_IO_DELAY` event.

> +#
> +# @qom-path: path to the block device object in the QOM tree
> +#
> +# @operation: I/O operation
> +#
> +# @latency-ns: Full duration of the operation (in nanoseconds)
> +#
> +# @offset: Request offset in the guest disk (in bytes), if available

Out of curiosity: when could @offset be unavailable?

> +#
> +# @bytes: Request length
> +#
> +# @failed: If true, this request failed for any reason.  If false, the

Suggest "for some reason".

> +#     request succeeded.
> +#
> +# Since: 11.2
> +##
> +{ 'event': 'BLOCK_IO_DONE',
> +  'data': {
> +      'qom-path': 'str',
> +      'operation': 'IoAccountingOperation',
> +      'latency-ns': 'uint64',
> +      '*offset': 'uint64',
> +      'bytes': 'uint64',
> +      'failed': 'bool' } }