Kevin Wolf <kw...@redhat.com> writes: > 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. :-) > > 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.
Been there, done that, more than once. > 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.) In this case, probably for the better --- I'd expect documentation of this mess (if any) to be rather losely related to the code.
