Re: [PATCH v2] block-backend: per-device throttling of BLOCK_IO_ERROR reports

[Kevin Wolf <kwolf@redhat.com>]

Am 09.01.2024 um 14:13 hat Vladimir Sementsov-Ogievskiy geschrieben:
> From: Leonid Kaplan <xeor@yandex-team.ru>
> 
> BLOCK_IO_ERROR events comes from guest, so we must throttle them.
> We still want per-device throttling, so let's use device id as a key.
> 
> Signed-off-by: Leonid Kaplan <xeor@yandex-team.ru>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
> 
> v2: add Note: to QAPI doc
> 
>  monitor/monitor.c    | 10 ++++++++++
>  qapi/block-core.json |  2 ++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/monitor/monitor.c b/monitor/monitor.c
> index 01ede1babd..ad0243e9d7 100644
> --- a/monitor/monitor.c
> +++ b/monitor/monitor.c
> @@ -309,6 +309,7 @@ int error_printf_unless_qmp(const char *fmt, ...)
>  static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
>      /* Limit guest-triggerable events to 1 per second */
>      [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },
> +    [QAPI_EVENT_BLOCK_IO_ERROR]    = { 1000 * SCALE_MS },
>      [QAPI_EVENT_WATCHDOG]          = { 1000 * SCALE_MS },
>      [QAPI_EVENT_BALLOON_CHANGE]    = { 1000 * SCALE_MS },
>      [QAPI_EVENT_QUORUM_REPORT_BAD] = { 1000 * SCALE_MS },
> @@ -498,6 +499,10 @@ static unsigned int qapi_event_throttle_hash(const void *key)
>          hash += g_str_hash(qdict_get_str(evstate->data, "qom-path"));
>      }
>  
> +    if (evstate->event == QAPI_EVENT_BLOCK_IO_ERROR) {
> +        hash += g_str_hash(qdict_get_str(evstate->data, "device"));
> +    }

Using "device" only works with -drive, i.e. when the BlockBackend
actually has a name. In modern configurations with a -blockdev
referenced by -device, the BlockBackend doesn't have a name any more.

Maybe we should be using the qdev id (or more generally, QOM path) here,
but that's something the event doesn't even contain yet.

> +
>      return hash;
>  }
>  
> @@ -525,6 +530,11 @@ static gboolean qapi_event_throttle_equal(const void *a, const void *b)
>                         qdict_get_str(evb->data, "qom-path"));
>      }
>  
> +    if (eva->event == QAPI_EVENT_BLOCK_IO_ERROR) {
> +        return !strcmp(qdict_get_str(eva->data, "device"),
> +                       qdict_get_str(evb->data, "device"));
> +    }
> +
>      return TRUE;
>  }
>  
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index ca390c5700..32c2c2f030 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -5559,6 +5559,8 @@
>  # Note: If action is "stop", a STOP event will eventually follow the
>  #     BLOCK_IO_ERROR event
>  #
> +# Note: This event is rate-limited.
> +#
>  # Since: 0.13
>  #
>  # Example:

Kevin