autounmountd: set filter-specific flags for the EVFILT_FS event

[rew]

Summary

Set the filter-specific flags VQ_MOUNT and VQ_UNMOUNT for the
EVFILT_FS event.

[trasz]

Thank you, but why?

This is more about the commit message than the code itself; I don't remember how kevent works for mount/umount events, and it's not documented in the kqueue(2) man page. In particular, does it fix a bug, or is an API-correctness fix that doesn't change semantics?

[trasz]

Looks like related to D28974, in which case it looks fine.

[rew]

In D28975#649731, @trasz wrote:

Looks like related to D28974, in which case it looks fine.

yep, cool - thanks.

D28974 is a bug fix for the EVFILT_FS filter - the bug was that kevents registered for EVFILT_FS were triggered for every EVFILT_FS event, regardless of the fflags specified.

After the fix in D28974, autounmountd wasn't being notified of any kevents (since fflags was 0) - so this review fixes that.

couple other things:

EV_CLEAR could be removed here since it's set by default for EVFILT_FS events - as you know, it doesn't hurt to leave it there though..

noted about the lack of documentation for EVFILT_FS in kqueue(2), will add it to the TODO list..