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

[Markus Armbruster <armbru@redhat.com>]

Kevin Wolf <kwolf@redhat.com> writes:

> 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.

Uh, does the event reliably identify the I/O error's node or not?  If
not, then that's a serious design defect.

There's @node-name.  Several commands use "either @device or @node-name"
to identify a node.  Is that sufficient here?

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