在fsync中使用mmap是否安全？ （fsync将使mmap上的某些页面无效吗？）

Question

For example, I use mmap to map a file into the memory as read-only shared mode. And I read some data on the file based on their address in the memory. What if I call write and fsync to update or changes the underlying file after then? Will the data in the memory also change? Or I need to call some other system call to synchronize the mapped memory? I find this question when reading source code of BoltDB.