From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: John Snow <jsnow@redhat.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>
Cc: "kwolf@redhat.com" <kwolf@redhat.com>,
Denis Lunev <den@virtuozzo.com>,
"libvir-list@redhat.com" <libvir-list@redhat.com>,
"armbru@redhat.com" <armbru@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"mreitz@redhat.com" <mreitz@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/2] qapi: deprecate implicit filters
Date: Wed, 28 Aug 2019 09:20:51 +0000 [thread overview]
Message-ID: <ba0e7e98-d02f-3514-b435-71923a483c6e@virtuozzo.com> (raw)
In-Reply-To: <d2bf50f1-e441-4cdb-291f-119a3ed93f51@redhat.com>
27.08.2019 23:12, John Snow wrote:
>
>
> On 8/23/19 5:22 AM, Vladimir Sementsov-Ogievskiy wrote:
>> 14.08.2019 13:07, Vladimir Sementsov-Ogievskiy wrote:
>>> To get rid of implicit filters related workarounds in future let's
>>> deprecate them now.
>>
>> Interesting, could we deprecate implicit filter without deprecation of unnecessity of
>> parameter? As actually, it's good when this parameter is not necessary, in most cases
>> user is not interested in node-name.
>>
>
> https://en.wiktionary.org/wiki/unnecessity -- I am surprised to learn
> that this a real word in the language I speak. :)
>
> I assume you're referring to making the optional argument mandatory.
exactly, it's my a bit "google-translate-driven" English)
>
>> Obviously we can do the following:
>>
>> 1. In 4.2 we deprecate unnecessity, which implies deprecation of implicit filters
>> 2. After some releases in 4.x we can drop deprecated functionality, so we drop it together with
>> implicit filters. And, in same release 4.x we return it back (as it's compatible change :)
>> but without implicit filters (so, if filter-node-name not specified, we just create
>> explicit filter with autogenerated node-name)
>>
>> So, effectively we just drop "deprecation mark" together with implicit filters, which is nice
>> but actually confusing.
>>
>> Instead, we may do
>> 1. In 4.2 deprecate
>> 2. In 4.x drop optionality together with implicit filters
>> 3. In 4.y (y > x of course) return optionality back
>>
>
> Ah, I see what you're digging at here now...
>
>> It's a bit safer, but for users who miss releases [4.x, 4.y) it's no difference..
>>
>> Or we just write in spec, that implicit filters are deprecated? But we have nothing about implicit
>> filters in spec. More over, we directly write that we have filter, and if parameter is omitted
>> it's node-name is autogenerated. So actually, the fact the filter is hidden when filter-node-name is
>> unspecified is _undocumented_.
>>
>> So, finally, it looks like nothing to deprecated in specification, we can just drop implicit filters :)
>>
>> What do you think?
>>
>
> What exactly _IS_ an implicit filter? How does it differ today from an
> explicit filter? I assumed the only difference was if it was named or
> not; but I think I must be mistaken now if you're proposing leaving the
> interface alone entirely.
>
> Are they instantiated differently?
>
As I understand, the only difference is their BlockDriverState.impicit field, and several places in code
where we skip implicit filter when trying to find something in a chain starting from a device.
Hmm, OK, let's see:
1. the only implicit filters are commit_top and mirror_top if user don't specify filter-node-name.
Where it make sense, i.e., where implicit field used?
2. bdrv_query_info, bdrv_query_bds_stats, bdrv_block_device_info(only when called from bdrv_query_info), they'll
report filter as top node if we don't mark it implicit.
3. bdrv_refresh_filename, bdrv_reopen_parse_backing, bdrv_drop_intermediate:
I think it's not a problem, just drop special case for implicit fitlers
So, seems the only real change is query-block and query-blockstats output when mirror or commit is started
without specifying filter-node-name (filter would be on top)
So, how should we deprecate this, or can we just change it?
--
Best regards,
Vladimir
next prev parent reply other threads:[~2019-08-28 9:22 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 10:07 [Qemu-devel] [PATCH 0/2] Deprecate implicit filters Vladimir Sementsov-Ogievskiy
2019-08-14 10:07 ` [Qemu-devel] [PATCH 1/2] qapi: deprecate drive-mirror and drive-backup Vladimir Sementsov-Ogievskiy
2019-08-14 19:22 ` John Snow
2019-08-15 7:44 ` [Qemu-devel] [libvirt] " Peter Krempa
2019-08-15 21:24 ` John Snow
2019-08-14 10:07 ` [Qemu-devel] [PATCH 2/2] qapi: deprecate implicit filters Vladimir Sementsov-Ogievskiy
2019-08-14 19:27 ` John Snow
2019-08-14 20:34 ` [Qemu-devel] [Qemu-block] " Maxim Levitsky
2019-08-15 10:49 ` [Qemu-devel] " Kevin Wolf
2019-08-15 11:45 ` [Qemu-devel] [libvirt] " Peter Krempa
2019-08-15 14:04 ` Markus Armbruster
2019-08-29 16:45 ` Christophe de Dinechin
2019-08-29 17:57 ` John Snow
2019-08-30 10:07 ` Christophe de Dinechin
2019-08-30 18:11 ` John Snow
2019-09-02 12:04 ` Kevin Wolf
2019-11-22 8:41 ` Markus Armbruster
2019-11-22 11:32 ` Christophe de Dinechin
2019-08-15 16:07 ` [Qemu-devel] " John Snow
2019-08-15 16:48 ` Kevin Wolf
2019-08-15 17:33 ` John Snow
2019-08-15 19:24 ` Markus Armbruster
2019-08-16 8:20 ` Kevin Wolf
2019-08-16 12:33 ` Markus Armbruster
2019-08-16 12:58 ` Vladimir Sementsov-Ogievskiy
2019-08-15 14:16 ` [Qemu-devel] Exposing feature deprecation to machine clients (was: [PATCH 2/2] qapi: deprecate implicit filters) Markus Armbruster
2019-08-15 17:40 ` John Snow
2019-11-07 18:52 ` [Qemu-devel] Exposing feature deprecation to machine clients Philippe Mathieu-Daudé
2019-11-07 19:13 ` Vladimir Sementsov-Ogievskiy
2019-11-08 6:41 ` Deprecating stuff for 4.2 (was: [Qemu-devel] Exposing feature deprecation to machine clients) Markus Armbruster
2019-11-08 9:36 ` Deprecating stuff for 4.2 Vladimir Sementsov-Ogievskiy
2019-11-08 8:35 ` [Qemu-devel] Exposing feature deprecation to machine clients Max Reitz
2019-08-29 15:59 ` [Qemu-devel] [PATCH 2/2] qapi: deprecate implicit filters Christophe de Dinechin
2019-08-29 17:18 ` [Qemu-devel] [Qemu-block] " John Snow
2019-08-23 9:22 ` [Qemu-devel] " Vladimir Sementsov-Ogievskiy
2019-08-27 20:12 ` John Snow
2019-08-28 9:20 ` Vladimir Sementsov-Ogievskiy [this message]
2019-08-28 17:48 ` John Snow
2019-08-29 14:44 ` Peter Krempa
2019-08-29 15:17 ` Vladimir Sementsov-Ogievskiy
2019-08-29 17:50 ` John Snow
2019-08-29 15:00 ` Vladimir Sementsov-Ogievskiy
2019-08-29 15:16 ` Vladimir Sementsov-Ogievskiy
2019-09-02 12:14 ` Kevin Wolf
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