[$] Change notifications for network filesystems

Steve French led a discussion on change notifications for network
filesystems in a session at the
2022 Linux Storage,
Filesystem, Memory-management and BPF Summit (LSFMM). He is part of
the Samba team and noted that both Windows and macOS clients get notified
of new and changed files in
a shared directory immediately, while on Linux that does not happen. He
wanted to explore what it would take to add that functionality.