In a filesystem-track session at the 2026 Linux Storage, Filesystem, Memory Management, and BPF Summit, Amir Goldstein updated attendees on the fanotify filesystem-event monitoring subsystem. He wanted to describe changes that had come in the last year or so, as well as upcoming features and some remaining challenges in his efforts to use fanotify for hierarchical storage management (HSM). Fanotify is the user-space API for monitoring files, directories, and filesystems for events of various sorts (e.g. opening or deleting a file).