  As the current nuclear PDF analyses are mainly constrained by fixed-target
Drell-Yan and deeply inelastic scattering data only the quark nuclear
modifications at fairly large $x$ values are in a good control. Inclusive pion
production in d+Au collisions at RHIC provides some constraints for gluons but
due to the limited kinematic reach of the data the gluon modifications remain
uncertain especially at small values of $x$. In this talk, we discuss how the
existing data from p+Pb collisions at the LHC can improve the nuclear PDF fits
and which measurements would be sensitive to the small-$x$ gluons. In
particular, we consider inclusive hadron production, compare this to direct
photons, and show estimates of the effect of CMS dijet measurements to the
uncertainty of nuclear gluon distributions.
