VisitEachMountedPartition
BPartition *VisitEachMountedPartition(BDiskDeviceVisitor *visitor);
bool VisitEachMountedPartition(
fDDRoster.VisitEachMountedPartition(&srcVisitor, &device, &partition);
if (VisitEachMountedPartition(&visitor, device, _partition))
BDiskDeviceRoster().VisitEachMountedPartition(&visitor);