[Dwedit]

Using mmap means that you need to be able to handle memory access exceptions when a disk read or write fails. Examples of disk access that fails includes reading from a file on a Wifi network drive, a USB device with a cable that suddenly loses its connection when the cable is jiggled, or even a removable USB drive where all disk reads fail after it sees one bad sector. If you're not prepared to handle a memory access exception when you access the mapped file, don't use mmap.

[justmedep]

You can even mmap a socket on some systems (iOS and macOS via GCD). But doing that is super fragile. Socket errors are swallowed.

My interpretation always was the mmap should only be used for immutable and local files. You may still run into issues with those type of files but it’s very unlikely.

[phoronixrly]

Ah, reminds me of 'Are You Sure You Want to Use MMAP in Your Database Management System? (2022)' https://db.cs.cmu.edu/mmap-cidr2022/