读取python中的Fuse实现未按预期返回，cat：<mountpoint>：错误地址

import os
import errno
import fuse

class MyFS(fuse.Fuse):
    def __init__(self, *args, **kwargs):
        super(MyFS, self).__init__(*args, **kwargs)

    def getattr(self, path, fh=None):
        if path == '/':
            return {'st_mode': (fuse.S_IFDIR | 0o755), 'st_nlink': 2}
        return {'st_mode': (fuse.S_IFREG | 0o644), 'st_nlink': 1, 'st_size': 13}

    def readdir(self, path, fh):
        if path == '/':
            return ['.', '..', 'hello.txt']
        return []

    def read(self, path, size, offset, fh):
        with open(os.path.join(self.root, path.lstrip('/')), 'rb') as f:
            f.seek(offset)
            return f.read(size)

if __name__ == '__main__':
    fuse = MyFS(version="%prog " + fuse.__version__, usage=fuse.Fuse.fusage, dash_s_do='setsingle')
    fuse.parse(errex=1)
    fuse.main()