Fanotify

Things that need to be fixed:

• Ignore masks, so that events on files can be ignored until the files are modified.
• Support for access decisions (by privileged processes).
• Per mount point notification (general subtree notification seems too hard).
  • Clarify how mount point marks should propagate to new mounts from parent mounts, when creating a new bind mount, and to existing bind mounts.
• Include uid, not just pid.

Probably for the next round:

• Add a flag to turn off event merging (or make merging less aggressive) so that events will happen "in order"?
• Support non-root processes (will require permission checks).
  • Reliable vs. non-reliable delivery: cannot allow non-privileged processes to have arbitrarily long event queues.
• Support directory events by passing an fd to the directory.
• Think about mark propagation across directories.
• Allow users to get a watch descriptor (as with inotify) instead of a file descriptor if desired. (Controversial.)
• inotify or denotify don't generate events for deleted inodes. Deleted inodes may still be accessed via open file descriptors though, so it may make sense to continue generating fanotify events.