Recent advances in storage hardware have resulted in massive improvements in both I/O latency and throughput. However, existing storage virtualization tools either depend on a heavy and inefficient I/O stack that is not optimized for parallelism, or require a separate API that is difficult to manage and monitor. In this work, we introduce NVMetro, a solution based on the NVMe protocol that proposes a flexible choice between multiple I/O paths to ease the development of adaptive and performant virtual storage. NVMetro provides two components: (1) an intelligent I/O classification and routing framework powered by eBPF; and (2) an easy-to-use and performant API to assist the creation of userspace I/O functions within our framework. We demonstrate the benefits of NVMetro by implementing two virtual storage functions, and we evaluate them using various benchmarks. The obtained results show that NVMetro achieves a performance and scalability comparable to bleeding-edge, kernel-bypass technologies while retaining the flexibility of traditional OS-based storage APIs.