mmap on file io errors would manifest in Signals (For example SIGBUS or SIGSEGV).

So if you wanted to handle file read/write errors you would need to implement signal handlers.

https://stackoverflow.com/questions/6791415/how-do-memory-ma...

In my experience, having worked with a large system that used almost exclusively mmap for I/O, you don’t. The process segfaults and is restarted. In practice it almost never happened.