  We present a graph manifold analog of the Jankins-Neumann classification of
Seifert fibered spaces over $S^2$ admitting taut foliations, providing a finite
recursive formula to compute the L-space Dehn-filling interval for any graph
manifold with torus boundary. As an application of a generalization of this
result to Floer simple manifolds, we compute the L-space interval for any cable
of a Floer simple knot complement in a closed three-manifold in terms of the
original L-space interval, recovering a result of Hedden and Hom as a special
case.
