Re: [PATCH v2 1/3] qga: add command guest-get-disks

[Daniel P . Berrangé]

On Tue, Oct 06, 2020 at 03:53:08PM +0200, Tomáš Golembiovský wrote:
> On Tue, Oct 06, 2020 at 09:36:32AM +0100, Daniel P. Berrangé wrote:
> > On Mon, Sep 07, 2020 at 11:14:40AM +0200, Tomáš Golembiovský wrote:
> > > Add API and stubs for new guest-get-disks command.
> > > 
> > > The command guest-get-fsinfo can be used to list information about disks
> > > and partitions but it is limited only to mounted disks with filesystem.
> > > This new command should allow listing information about disks of the VM
> > > regardles whether they are mounted or not. This can be usefull for
> > > management applications for mapping virtualized devices or pass-through
> > > devices to device names in the guest OS.
> > > 
> > > Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
> > > ---
> > >  qga/commands-posix.c |  6 ++++++
> > >  qga/commands-win32.c |  6 ++++++
> > >  qga/qapi-schema.json | 29 +++++++++++++++++++++++++++++
> > >  3 files changed, 41 insertions(+)
> > > 
> > > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > > index 744c2b5a5d..f99731af51 100644
> > > --- a/qga/commands-posix.c
> > > +++ b/qga/commands-posix.c
> > > @@ -3042,3 +3042,9 @@ GuestOSInfo *qmp_guest_get_osinfo(Error **errp)
> > >  
> > >      return info;
> > >  }
> > > +
> > > +GuestDiskInfoList *qmp_guest_get_disks(Error **errp)
> > > +{
> > > +    error_setg(errp, QERR_UNSUPPORTED);
> > > +    return NULL;
> > > +}
> > > diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> > > index aaa71f147b..e9976a0c46 100644
> > > --- a/qga/commands-win32.c
> > > +++ b/qga/commands-win32.c
> > > @@ -2229,3 +2229,9 @@ GuestOSInfo *qmp_guest_get_osinfo(Error **errp)
> > >  
> > >      return info;
> > >  }
> > > +
> > > +GuestDiskInfoList *qmp_guest_get_disks(Error **errp)
> > > +{
> > > +    error_setg(errp, QERR_UNSUPPORTED);
> > > +    return NULL;
> > > +}
> > > diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> > > index 408a662ea5..70b54e0d07 100644
> > > --- a/qga/qapi-schema.json
> > > +++ b/qga/qapi-schema.json
> > > @@ -862,6 +862,35 @@
> > >             'bus': 'int', 'target': 'int', 'unit': 'int',
> > >             '*serial': 'str', '*dev': 'str'} }
> > >  
> > > +##
> > > +# @GuestDiskInfo:
> > > +#
> > > +# @name: device node (Linux) or device UNC (Windows)
> > > +# @partition: whether this is a partition or disk
> > > +# @slaves: list of slave devices (Linux)
> > 
> > What are "slave devices" ?
> 
> That is how Linux calls dependent devices. E.g. PVs in your LVM setup
> are considered "slaves" to your LVs. Or if you have LUKS volume called
> "foo" on your "bar" drive then "bar" would be listed as a "slave" for
> "foo".
> 
> The dependency is in the opposite direction then I have always pictured
> it in my had, but I guess that there are reasons for that.
> 
> > For that matter, please don't use the term "slaves" at all in any
> > new code.
> 
> Fair enough... so how shall we call those devices? Dependents,
> dependencies, parents... ? Ideas welcome.

Sounds like "dependents" sounds like a reasonable term for what
this is expressing.

Giving the LVM VG/PV and LUKS examples in the QAPI docs would be
useful.

Regards,
Daniel
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