api.py 文件源码

def instance_for_image(image, partition):
        """Get a VFS instance for the image

        :param image: instance of nova.virt.image.model.Image
        :param partition: the partition number to access
        """

        LOG.debug("Instance for image image=%(image)s "
                  "partition=%(partition)s",
                  {'image': image, 'partition': partition})

        vfs = None
        try:
            LOG.debug("Using primary VFSGuestFS")
            vfs = importutils.import_object(
                "nova.virt.disk.vfs.guestfs.VFSGuestFS",
                image, partition)
            if not VFS.guestfs_ready:
                # Inspect for capabilities and keep
                # track of the result only if succeeded.
                vfs.inspect_capabilities()
                VFS.guestfs_ready = True
            return vfs
        except exception.NovaException:
            if vfs is not None:
                # We are able to load libguestfs but
                # something wrong happens when trying to
                # check for capabilities.
                raise
            else:
                LOG.info(_LI("Unable to import guestfs, "
                             "falling back to VFSLocalFS"))

        return importutils.import_object(
            "nova.virt.disk.vfs.localfs.VFSLocalFS",
            image, partition)