Am 09.01.2019 um 17:27 hat Max Reitz geschrieben: > On 09.01.19 16:13, Kevin Wolf wrote: > > Am 09.01.2019 um 15:54 hat Max Reitz geschrieben: > >> On 09.01.19 15:48, Kevin Wolf wrote: > >>> Am 09.01.2019 um 15:27 hat Max Reitz geschrieben: > >>>> On 09.01.19 15:21, Kevin Wolf wrote: > >>>>> Am 09.01.2019 um 15:10 hat Max Reitz geschrieben: > >>>>>> On 06.09.18 13:11, Daniel Henrique Barboza wrote: > >>>>>>> changes in v2: > >>>>>>> - removed the "RFC" marker; > >>>>>>> - added a new patch (patch 2) that removes > >>>>>>> bdrv_snapshot_delete_by_id_or_name from the code; > >>>>>>> - made changes in patch 1 as suggested by Murilo; > >>>>>>> - previous patch set link: > >>>>>>> https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg04658.html > >>>>>>> > >>>>>>> > >>>>>>> It is not uncommon to see bugs being opened by testers that attempt to > >>>>>>> create VM snapshots using HMP. It turns out that "0" and "1" are quite > >>>>>>> common snapshot names and they trigger a lot of bugs. I gave an > >>>>>>> example > >>>>>>> in the commit message of patch 1, but to sum up here: QEMU treats the > >>>>>>> input of savevm/loadvm/delvm sometimes as 'ID', sometimes as 'name'. > >>>>>>> It > >>>>>>> is documented as such, but this can lead to strange situations. > >>>>>>> > >>>>>>> Given that it is strange for an API to consider a parameter to be 2 > >>>>>>> fields > >>>>>>> at the same time, and inadvently treating them as one or the other, > >>>>>>> and > >>>>>>> that removing the ID field is too drastic, my idea here is to keep the > >>>>>>> ID field for internal control, but do not let the user set it. > >>>>>>> > >>>>>>> I guess there's room for discussion about considering this change an > >>>>>>> API > >>>>>>> change or not. It doesn't affect users of HMP and it doesn't affect > >>>>>>> Libvirt, > >>>>>>> but simplifying the meaning of the parameters of savevm/loadvm/delvm. > >>>>>> > >>>>>> (Yes, very late reply, I'm sorry...) > >>>>>> > >>>>>> I do think it affects users of HMP, because right now you can delete > >>>>>> snapshots with their ID, and after this series you cannot. > >>>>> > >>>>> Can there be snapshots that can't be identified by a snapshot name, but > >>>>> only by their ID? > >>>> > >>>> I don't know, but what I meant is that if you have scripts to do all > >>>> this, you might have to adjust them with this change. > >>> > >>> That's what the H in HMP means. > >>> > >>>>>> I think we had a short discussion about just disallowing numeric > >>>>>> snapshot names. How bad would that be? > >>>>> > >>>>> It would be incompatible with existing images and result in a more > >>>>> complex snapshot identifier resolution. Why would it be any better? > >>>> > >>>> It wouldn't be incompatible with existing images if we'd just disallow > >>>> creating such snapshots. I don't see how the identifier resolution > >>>> would be more complex. > >>>> > >>>> I don't know if it'd be better. I'd just find it simpler (for us, that > >>>> is -- for users, I'm not sure). > >>> > >>> Identifier resolution A: > >>> - Find a snapshot that has the given identifier as a name > >>> - If no such snapshot exists, it is an error > >>> > >>> Identifier resolution B: > >>> - If the identifier is a number, find a snapshot that has the given > >>> identifier as its ID > >>> - If the identifier is not a number, find a snapshot that has the given > >>> identifier as a name > >>> - If no such snapshot exists, it is an error > >> > >> No, my idea was to keep the resolution the same as it is; just to forbid > >> creating new snapshots with numeric names. This would prevent users > >> from getting into the whole situation. > > > > That's the version with an even more complex resolution method C. :-) > > How so if the resolution method stays the same? Because it already is > too complex? > > If so, yes, that is an argument. I was arguing for the simplest patch > instead of the simplest code, true.
Yes, because it already is too complex. Not even necessarily the code (even though that's true as well), but most importantly the interface. > > I actually think the current behaviour is more confusing than helpful. > > Without looking into the code or trying it out, I couldn't even tell > > whether ID or name takes precedence if there is a matching snapshot for > > both. Considering your proposal, it's probably the ID, but how should a > > user know that? (If against all expectations documentation exists, it > > doesn't count because nobody reads that.) > > It isn't more confusing than it is right now. With my proposal, all > current images are simply as confusing as they are right now (I think ID > takes precedence, yes), but if you create new snapshots, it's clear, > since you simply cannot create names that could be IDs. I agree. But wasn't the goal of the patch to make it less confusing than it is right now? Kevin
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