Investigate ways to improve performance of `InodeToPathMapper` class

[korydraughn]

Investigation

The InodeToPathMapper class uses a single ReadWriteLock to control access to the mappings. While it works correctly, a lot of performance is likely left on the table because modifying the mappings locks the entire data structure. A better solution would allow multiple readers and writers to access the mappings.

Here are some ideas ...

• Consider using multiple locks to control access to segments of the mappings
• Consider using a ConcurrentHashMap
• Consider using lock-free data structures