code: public Optional<LockResource> tryLockInode(Long inodeId, LockMode mode) {
      return mInodeLocks.tryGet(inodeId, mode);
    }
docs: Attempts to acquire an inode lock.
  
  @param inodeId the inode id to try locking
  @param mode the mode to lock in
  @return either an empty optional, or a lock resource which must be closed to release the lock