We show that for every finite structure B with a conservative Maltsev polymorphism, the constraint satisfaction problem for B can be solved by a symmetric linear Z2-Datalog program, and in particular is in the complexity class parity-L. The proof has two steps: we first present the result for a certain subclass whose polymorphism algebras are hereditarily subdirectly irreducible. We then show that every other structure in our class can be primitively positively constructed from one of the struct...