Re: [Libguestfs] APIs affected by btrfs subvolumes

Here's my suggestion. We add a new type 'Mountable' to the generator. This is the same as a string, so it doesn't change the strict C ABI (nor the semantics -- see below). Certain APIs that take a Device parameter would need to change to take a Mountable instead. Certain APIs that return RString/RStringList won't change their generator types, but what can be in the string may change. A Mountable string is normally just a device name, eg. "/dev/sda1". But for special filesystems it may contain an extended string. I suggest "/dev/sda1:btrfs:<subvolume_name>" for btrfs. Other weird filesystems may need other extensions in future. Inspection APIs take and return a Mountable (so Device "root" becomes Mountable "root"). 'list-filesystems' returns a list of Mountables (actually it still returns an RStringList, but it's a list of Mountables). 'mount' and friends take a Mountable instead of a Device. The generator will need to make a small change in the way it checks the Mountable parameter at runtime (q.v. the way Device is checked now, eg. the macro RESOLVE_DEVICE will need another macro RESOLVE_MOUNTABLE). Obviously the ABI doesn't change, since it's all still strings. But I also claim that the semantics of the API don't change: Any existing program that works now will continue to work unchanged. Only programs that would now fail (eg. they try to inspect btrfs guests) would be affected by this change, and in fact those programs would not need to be modified, they would just start to work correctly. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/