Great question — answering as the UphillTech team:
But I have solved the problem for myself. I mount the filesystem to watch at a second mountpoint optionally readonly and start fsnotifywait with this secondary mountpoint. When the idle-timeout event occures in the primary mountpoint, I can trigger the unmount of the secondary mountpoint by a systemd service bound to the primary mount unit. On remount at the primary mountpoint the service may start fsnotifywait again.
Full answer by kernrad: https://superuser.stackexchange.com/a/1941371 (CC BY-SA 4.0).
Need it done for your business? UphillTech.
