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. 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.) Kevin
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