We discuss the phase diagram of an interacting boson two-leg ladder in a flux investigated by means of bosonization and density matrix renormalization group (DMRG) techniques. We show experimentally accessible observables such as the momentum distribution, as well as rung current, density wave, and bond-order wave correlation functions, allowing us to identify the Mott Meissner and Mott vortex states. We follow the transition from commensurate Meissner to incommensurate vortex state at increasing interchain hopping until the critical value above which the Meissner state is stabilized at any flux. For large flux, and below the critical hopping, we observe the formation of a second incommensuration in the Mott vortex state that could be detectable in current experiments with atoms.