  This note intends to demonstrate how to discuss scalar curvature functions'
admissibility on bundles by directly applying some of the Kazdan--Warner
results. Proofs of the concept include determining which functions are
realizable as scalar curvature functions on the total space of several bundles
over exotic manifolds. In addition, we employ traditional variational methods
to provide reasonable conditions to smooth functions on the total spaces of
some fiber bundles to be realized as scalar curvature functions for some
Riemannian submersions metrics. We apply these last results to bundles over
Calabi--Yau manifolds.
