code: public void lockInode(Inode inode, LockMode mode) {
      Preconditions.checkState(mLockMode == LockMode.READ);
  
      lockInodeInternal(inode, mode);
      mLockMode = mode;
    }
docs: Locks the given inode and adds it to the lock list. This method does *not* check that the inode
  is still a child of the previous inode, or that the inode still exists. This method should only
  be called when the edge leading to the inode is locked.
  
  @param inode the inode to lock
  @param mode the mode to lock in