[pve-devel] [PATCH v1 storage 1/9] storage: expose find_free_diskname

[Fabian Ebner]

Am 03.08.21 um 16:20 schrieb Aaron Lauterer:
> 
> 
> On 8/2/21 2:56 PM, Fabian Ebner wrote:
>> Am 19.07.21 um 16:52 schrieb Aaron Lauterer:
>>> We do not expose the parameter 'add_fmt_suffix' used by the internal
>>> implemantion of 'find_free_diskname'. This is something only the plugins
>>> themselves know but cannot be determined easily and reliably from an
>>> outside caller.
>>>
>>> This is why the new 'wants_fmt_suffix' method has been introduced. For
>>> most plugins the return value is very clear. For the default
>>> implementation in Plugin.pm we add another check to be on the safe side
>>> and only return true if the '$scfg->{path}' option is present.
>>> It indicates that the volume in question is an actual file which will
>>> need the suffix.
>>>
>>> Signed-off-by: Aaron Lauterer <a.lauterer at proxmox.com>
>>> --- > rfc -> v1:
>>> dropped $add_fmt_suffix parameter and added the "wants_fmt_suffix"
>>> helper method in each plugin.
>>>
>>>   PVE/Storage.pm               | 11 +++++++++++
>>>   PVE/Storage/LVMPlugin.pm     |  5 +++++
>>>   PVE/Storage/Plugin.pm        |  7 +++++++
>>>   PVE/Storage/RBDPlugin.pm     |  5 +++++
>>>   PVE/Storage/ZFSPoolPlugin.pm |  5 +++++
>>>   5 files changed, 33 insertions(+)
>>>
>>> diff --git a/PVE/Storage.pm b/PVE/Storage.pm
>>> index c04b5a2..afeb2e3 100755
>>> --- a/PVE/Storage.pm
>>> +++ b/PVE/Storage.pm
>>> @@ -203,6 +203,17 @@ sub storage_can_replicate {
>>>       return $plugin->storage_can_replicate($scfg, $storeid, $format);
>>>   }
>>> +sub find_free_diskname {
>>> +    my ($cfg, $storeid, $vmid, $fmt) = @_;
>>> +
>>> +    my $scfg = storage_config($cfg, $storeid);
>>> +    my $plugin = PVE::Storage::Plugin->lookup($scfg->{type});
>>> +
>>> +    my $add_fmt_suffix = $plugin->wants_fmt_suffix($scfg);
>>> +
>>> +    return $plugin->find_free_diskname($storeid, $scfg, $vmid, $fmt, 
>>> $add_fmt_suffix);
>>
>> Maybe this should rather be find_free_volname and always return the 
>> full volname (i.e. "<VMID>/vm-<VMID>-disk-<N>.<FMT>" for dir-based 
>> storages) so that it can be parsed with parse_volname later?
>>
>> That would mean something like wants_vmid_prefix() is needed, but I'd 
>> rather extend (and rename) the wants_fmt_suffix method instead.
>>
>> The rationale is: the value returned here is used for the 
>> $target_volname parameter in the next patch, and in case it's a 
>> dir-based storage, passing in an actual volname like 
>> '123/vm-123-disk-0.raw' currently fails (because it actually expects 
>> only the disk name).
> 
> Adding a new "find_free_volname" is probably the cleanest approach. For 
> the default directory implementation we can return it in the full 
> "<VMID>/vm-<VMID>-disk-<N>.<FMT>" format. All other storage plugins 
> would need their own implementation though and for most it will be 
> basically a thin wrapper around "find_free_diskname". Alternatively it 
> might work to check against $scfg->{path} to decide if we should return 
> just what we get from "find_free_diskname" (LVM, RBD, ZFS,...) or add 
> the VMID prefix and FMT suffix (files/directory)?

Yes, that would work too. I'd prefer the latter approach where the 
default implementation simply decides based on the presence of 
$scfg->{path}.

> 
> 
> What do you have in mind regarding "wants_fmt_suffix" exactly? If I am 
> not mistaken, we usually need both (FMT suffix and VMID prefix) as it is 
> usually needed for directory based storages. All other storages (AFAICT) 
> will not have either.
> 

In principle, there might be external plugins using a format suffix, but 
no vmid prefix. Using only one bit of information to decide how the 
volname should be is not enough then. But I suppose one can argue that 
an external plugin could even have a completely different volname 
scheme. Introducing find_free_volname instead would avoid that problem 
altogether.

>>
>>> +}
>>> +
>>>   sub storage_ids {
>>>       my ($cfg) = @_;
>>> diff --git a/PVE/Storage/LVMPlugin.pm b/PVE/Storage/LVMPlugin.pm
>>> index 139d391..3e5b6c8 100644
>>> --- a/PVE/Storage/LVMPlugin.pm
>>> +++ b/PVE/Storage/LVMPlugin.pm
>>> @@ -201,6 +201,11 @@ sub type {
>>>       return 'lvm';
>>>   }
>>> +sub wants_fmt_suffix {
>>> +    my ($class, $scfg) = @_;
>>> +    return 0;
>>> +}
>>> +
>>
>> Nit: since there is no $scfg->{path}, the default implementation would 
>> already return 0. Same for {RBD,ZFSPool}Plugin below, but overwriting 
>> the method doesn't really hurt either of course.
> 
> You're right. I guess it comes down to if we want this to be explicit or 
> implicit. Other opinions?
> 
>>
>>>   sub plugindata {
>>>       return {
>>>       content => [ {images => 1, rootdir => 1}, { images => 1 }],
>>> diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
>>> index b1865cb..5c6c659 100644
>>> --- a/PVE/Storage/Plugin.pm
>>> +++ b/PVE/Storage/Plugin.pm
>>> @@ -191,6 +191,13 @@ sub default_format {
>>>       return wantarray ? ($def_format, $valid_formats) : $def_format;
>>>   }
>>> +sub wants_fmt_suffix {
>>> +    my ($class, $scfg) = @_;
>>> +    return 1 if $scfg->{path};
>>> +    return 0;
>>> +}
>>> +
>>> +
>>>   PVE::JSONSchema::register_format('pve-storage-path', \&verify_path);
>>>   sub verify_path {
>>>       my ($path, $noerr) = @_;
>>> diff --git a/PVE/Storage/RBDPlugin.pm b/PVE/Storage/RBDPlugin.pm
>>> index a8d1243..86ea45a 100644
>>> --- a/PVE/Storage/RBDPlugin.pm
>>> +++ b/PVE/Storage/RBDPlugin.pm
>>> @@ -273,6 +273,11 @@ sub type {
>>>       return 'rbd';
>>>   }
>>> +sub wants_fmt_suffix {
>>> +    my ($class, $scfg) = @_;
>>> +    return 0;
>>> +}
>>> +
>>>   sub plugindata {
>>>       return {
>>>       content => [ {images => 1, rootdir => 1}, { images => 1 }],
>>> diff --git a/PVE/Storage/ZFSPoolPlugin.pm b/PVE/Storage/ZFSPoolPlugin.pm
>>> index c4be70f..85e2211 100644
>>> --- a/PVE/Storage/ZFSPoolPlugin.pm
>>> +++ b/PVE/Storage/ZFSPoolPlugin.pm
>>> @@ -18,6 +18,11 @@ sub type {
>>>       return 'zfspool';
>>>   }
>>> +sub wants_fmt_suffix {
>>> +    my ($class, $scfg) = @_;
>>> +    return 0;
>>> +}
>>> +
>>>   sub plugindata {
>>>       return {
>>>       content => [ {images => 1, rootdir => 1}, {images => 1 , 
>>> rootdir => 1}],
>>>