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

[Aaron Lauterer <a.lauterer@proxmox.com>]

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@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)?


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.

> 
>> +}
>> +
>>   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}],
>>