Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
Am 23.08.2019 um 11:22 hat Vladimir Sementsov-Ogievskiy geschrieben: > 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. A modern client is supposed to be interested in node-names. We basically expect it to manage the whole block graph at a node level, so it should certainly make sure to know the node-name of every node. It will need it to take snapshots, insert filter drivers or anything like this on top of the implicit node. So once we make the option mandatory (which means returning an error for legacy clients that don't do node-level management), I don't see a good reason to ever make it optional again. Kevin -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
On 8/29/19 11:17 AM, Vladimir Sementsov-Ogievskiy wrote: > Aren't you going to deprecate and drop it at some moment? Libvirt's going to keep supporting older versions of QEMU in perpetuity. Apparently, there are still some barriers (SD cards?) to using only blockdev API for new versions, too: >> "Note that even with new qemu, if an SD card is used blockdev will be >> disabled." It sounds like we need to facilitate libvirt's transfer to an all-blockdev API for modern QEMU instances. Once we do that, we can likely add an introspectable feature flag to commands that create formerly-implicit nodes to tip off libvirt as to what behavior it can expect. (In practice, if libvirt sees the new flag, it knows it needs to rely exclusively on blockdev API and that (likely) it should always provide a node-name for the filter.) I think it is reasonably clear that deprecating and re-implementing is not something that will be compatible with libvirt's feature detection, so we shouldn't do it. I'm still not sold that this is worth the effort, but you and Max would know best right now. I'll leave it to you two to sort out. --js -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
29.08.2019 17:44, Peter Krempa wrote:
> On Wed, Aug 28, 2019 at 13:48:10 -0400, John Snow wrote:
>> (Peter: search for "pkrempa" down below.)
>>
>> On 8/28/19 5:20 AM, Vladimir Sementsov-Ogievskiy wrote:
>
> []
>
>
>> So that's a bit of a change, but only visually. The "reality" is still
>> the same, we just report it more "accurately." libvirt MIGHT need a
>> heads up here. I'm looping pkrempa back in for comment.
>>
>>
>> Would libvirt be negatively impacted by the revelation of formerly
>> internal ("implicit") nodes created by mirror and commit via query block
>> commands? At the moment, QEMU hides them from you if you do not name them.
>
> Currently we would not be able to handle that properly at least
> definitely in the pre-blockdev case. In blockdev case I must make sure
> that it will work.
>
> The thing is that I didn't really want to touch the pre-blockdev case
> code any more,
Aren't you going to deprecate and drop it at some moment?
but if you decide that we should do it I'm willing to
> investigate this case also for the old commands.
>
>>
>>
>>> 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
>>>
>>
>> I'm much less certain about what the impact of this would be and would
>> need to audit it (and don't have the time to, personally.)
>>
>> Do you have a POC or RFC patch that demonstrates dropping these special
>> cases? It might be nice to see as proof that it's safe to deprecate.
>>
>>> 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?
>>>
>>
>> I'm not sure if it's worth it yet, what does dropping the implicit field
>> buy us? Conceptually I understand that it's simpler without the notion
>> of implicit fields, but I imagine there's some cleanup in particular
>> that motivated this.
>>
>> I'd say to just change the behavior, we should:
>>
>> - Give a standard three-release warning that the behavior will change in
>> an incompatible way
>> - Demonstrate with an RFC patch that special cases around ->implicit in
>> block.c can be removed and do not make the code more complex,
>> - Get blessings from Peter Krempa.
>>
>> As always: Libvirt is not the end-all be-all of QEMU management, but if
>> libvirt is capable of working around design changes then I believe any
>> project out there today also could, so it's a good litmus test.
>
> For libvirt we really care more whether a node is format/protocol
> related or not rather than whether it's implicit or not.
>
> In this case we could filter it by the known protocol and format driver
> types and filter out the rest in cases when we e.g. detect the node
> names for the pre-blockdev era cases.
>
> (Note that even with new qemu, if an SD card is used blockdev will be
> disabled).
>
--
Best regards,
Vladimir
--
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Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
29.08.2019 18:00, Vladimir Sementsov-Ogievskiy wrote:
> 28.08.2019 20:48, John Snow wrote:
>> (Peter: search for "pkrempa" down below.)
>>
>> On 8/28/19 5:20 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> 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)
>>>
>>
>> It teaches me some fun words!
>>
> 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.
>>>
>>
>> Oh, oh, yes. I see.
>>
>>> 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?
>>>
>>
>> `git grep -E '(->|\.)implicit'` is what I used to find usages.
>>
>>> 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.
>>>
>>
>> So that's a bit of a change, but only visually. The "reality" is still
>> the same, we just report it more "accurately." libvirt MIGHT need a
>> heads up here. I'm looping pkrempa back in for comment.
>>
>>
>> Would libvirt be negatively impacted by the revelation of formerly
>> internal ("implicit") nodes created by mirror and commit via query block
>> commands? At the moment, QEMU hides them from you if you do not name them.
>>
>>
>>> 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
>>>
>>
>> I'm much less certain about what the impact of this would be and would
>> need to audit it (and don't have the time to, personally.)
>>
>> Do you have a POC or RFC patch that demonstrates dropping these special
>> cases? It might be nice to see as proof that it's safe to deprecate.
I faced a problem with some iotest (it's not a surprise of course), but I
think, I'll
come back with and RFC of course.
>>
>>> 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?
>>>
>>
>> I'm not sure if it's worth it yet, what does dropping the implicit field
>> buy us? Conceptually I understand
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
28.08.2019 20:48, John Snow wrote:
> (Peter: search for "pkrempa" down below.)
>
> On 8/28/19 5:20 AM, Vladimir Sementsov-Ogievskiy wrote:
>> 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)
>>
>
> It teaches me some fun words!
>
>>>
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.
>>
>
> Oh, oh, yes. I see.
>
>> 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?
>>
>
> `git grep -E '(->|\.)implicit'` is what I used to find usages.
>
>> 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.
>>
>
> So that's a bit of a change, but only visually. The "reality" is still
> the same, we just report it more "accurately." libvirt MIGHT need a
> heads up here. I'm looping pkrempa back in for comment.
>
>
> Would libvirt be negatively impacted by the revelation of formerly
> internal ("implicit") nodes created by mirror and commit via query block
> commands? At the moment, QEMU hides them from you if you do not name them.
>
>
>> 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
>>
>
> I'm much less certain about what the impact of this would be and would
> need to audit it (and don't have the time to, personally.)
>
> Do you have a POC or RFC patch that demonstrates dropping these special
> cases? It might be nice to see as proof that it's safe to deprecate.
>
>> 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?
>>
>
> I'm not sure if it's worth it yet, what does dropping the implicit field
> buy us? Conceptually I understand that it's simpler without the notion
> of implicit fields, but I imagine there's some cleanup in particular
> that motivated this.
Reviewing Max's "block: Deal with filters" series motivated me.
>
> I'd say to just change the behavior, we should:
>
> - Give a standard three-release warning
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
On Wed, Aug 28, 2019 at 13:48:10 -0400, John Snow wrote:
> (Peter: search for "pkrempa" down below.)
>
> On 8/28/19 5:20 AM, Vladimir Sementsov-Ogievskiy wrote:
[]
> So that's a bit of a change, but only visually. The "reality" is still
> the same, we just report it more "accurately." libvirt MIGHT need a
> heads up here. I'm looping pkrempa back in for comment.
>
>
> Would libvirt be negatively impacted by the revelation of formerly
> internal ("implicit") nodes created by mirror and commit via query block
> commands? At the moment, QEMU hides them from you if you do not name them.
Currently we would not be able to handle that properly at least
definitely in the pre-blockdev case. In blockdev case I must make sure
that it will work.
The thing is that I didn't really want to touch the pre-blockdev case
code any more, but if you decide that we should do it I'm willing to
investigate this case also for the old commands.
>
>
> > 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
> >
>
> I'm much less certain about what the impact of this would be and would
> need to audit it (and don't have the time to, personally.)
>
> Do you have a POC or RFC patch that demonstrates dropping these special
> cases? It might be nice to see as proof that it's safe to deprecate.
>
> > 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?
> >
>
> I'm not sure if it's worth it yet, what does dropping the implicit field
> buy us? Conceptually I understand that it's simpler without the notion
> of implicit fields, but I imagine there's some cleanup in particular
> that motivated this.
>
> I'd say to just change the behavior, we should:
>
> - Give a standard three-release warning that the behavior will change in
> an incompatible way
> - Demonstrate with an RFC patch that special cases around ->implicit in
> block.c can be removed and do not make the code more complex,
> - Get blessings from Peter Krempa.
>
> As always: Libvirt is not the end-all be-all of QEMU management, but if
> libvirt is capable of working around design changes then I believe any
> project out there today also could, so it's a good litmus test.
For libvirt we really care more whether a node is format/protocol
related or not rather than whether it's implicit or not.
In this case we could filter it by the known protocol and format driver
types and filter out the rest in cases when we e.g. detect the node
names for the pre-blockdev era cases.
(Note that even with new qemu, if an SD card is used blockdev will be
disabled).
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Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
(Peter: search for "pkrempa" down below.)
On 8/28/19 5:20 AM, Vladimir Sementsov-Ogievskiy wrote:
> 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)
>
It teaches me some fun words!
>>
>>> 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.
>
Oh, oh, yes. I see.
> 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?
>
`git grep -E '(->|\.)implicit'` is what I used to find usages.
> 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.
>
So that's a bit of a change, but only visually. The "reality" is still
the same, we just report it more "accurately." libvirt MIGHT need a
heads up here. I'm looping pkrempa back in for comment.
Would libvirt be negatively impacted by the revelation of formerly
internal ("implicit") nodes created by mirror and commit via query block
commands? At the moment, QEMU hides them from you if you do not name them.
> 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
>
I'm much less certain about what the impact of this would be and would
need to audit it (and don't have the time to, personally.)
Do you have a POC or RFC patch that demonstrates dropping these special
cases? It might be nice to see as proof that it's safe to deprecate.
> 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?
>
I'm not sure if it's worth it yet, what does dropping the implicit field
buy us? Conceptually I understand that it's simpler without the notion
of implicit fields, but I imagine there's some cleanup in particular
that motivated this.
I'd say to just change the behavior, we should:
- Give a standard three-release warning that the behavior will change in
an incompatible way
- Demonstrate with an RFC patch that special cases around ->implicit in
block.c can be removed and do not make the code more complex,
- Get blessings from Peter Krempa.
As always: Libvirt is not the end-all be-all
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
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 -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
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. > 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? --js -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [PATCH 2/2] qapi: deprecate implicit filters
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.
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
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?
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy
> ---
> qemu-deprecated.texi | 7 +++
> qapi/block-core.json | 6 --
> include/block/block_int.h | 10 +-
> blockdev.c| 10 ++
> 4 files changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> index 2753fafd0b..8222440148 100644
> --- a/qemu-deprecated.texi
> +++ b/qemu-deprecated.texi
> @@ -183,6 +183,13 @@ the 'wait' field, which is only applicable to sockets in
> server mode
>
> Use blockdev-mirror and blockdev-backup instead.
>
> +@subsection implicit filters (since 4.2)
> +
> +Mirror and commit jobs inserts filters, which becomes implicit if user
> +omitted filter-node-name parameter. So omitting it is deprecated, set it
> +always. Note, that drive-mirror don't have this parameter, so it will
> +create implicit filter anyway, but drive-mirror is deprecated itself too.
> +
> @section Human Monitor Protocol (HMP) commands
>
> @subsection The hub_id parameter of 'hostfwd_add' / 'hostfwd_remove' (since
> 3.1)
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 4e35526634..0505ac9d8b 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -1596,7 +1596,8 @@
> # @filter-node-name: the node name that should be assigned to the
> #filter driver that the commit job inserts into the
> graph
> #above @top. If this option is not given, a node name is
> -#autogenerated. (Since: 2.9)
> +#autogenerated. Omitting this option is deprecated, it
> will
> +#be required in future. (Since: 2.9)
> #
> # @auto-finalize: When false, this job will wait in a PENDING state after
> it has
> # finished its work, waiting for @block-job-finalize before
> @@ -2249,7 +2250,8 @@
> # @filter-node-name: the node name that should be assigned to the
> #filter driver that the mirror job inserts into the
> graph
> #above @device. If this option is not given, a node
> name is
> -#autogenerated. (Since: 2.9)
> +#autogenerated. Omitting this option is deprecated, it
> will
> +#be required in future. (Since: 2.9)
> #
> # @copy-mode: when to copy data to the destination; defaults to 'background'
> # (Since: 3.0)
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 3aa1e832a8..624da0b4a2 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -762,7 +762,15 @@ struct BlockDriverState {
> bool sg;/* if true, the device is a /dev/sg* */
> bool probed;/* if true, format was probed rather than specified */
> bool force_share; /* if true, always allow all shared permissions */
> -bool implicit; /* if true, this filter node was automatically inserted
> */
> +
> +/*
> + * @implicit field is deprecated, don't set it to true for new filters.
> + * If true, this filter node was automatically inserted and user don't
> + * know about it and unprepared for any effects of it. So, implicit
> + * filters are workarounded and skipped in many places of the block
> + * layer code.
> + */
> +bool implicit;
>
>
