[LTP] [PATCH v2 2/4] syscalls/fanotify15: Add a test case for inode marks

[Jan Kara <jack@suse.cz>]

On Mon 04-05-20 11:51:27, Amir Goldstein wrote:
> On Mon, May 4, 2020 at 11:07 AM Jan Kara <jack@suse.cz> wrote:
> >
> > On Sat 02-05-20 19:27:42, Amir Goldstein wrote:
> > > Test reporting events with fid also with recusrive inode marks:
> > > - Test events "on self" (FAN_DELETE_SELF) on file and dir
> > > - Test events "on child" (FAN_MODIFY) on file
> > >
> > > With recursive inode marks, verify that the FAN_MODIFY event reported
> > > to parent "on child" is merged with the FAN_MODIFY event reported to
> > > child.
> > >
> > > The new test case is a regression test for commit f367a62a7cad:
> > >
> > >     fanotify: merge duplicate events on parent and child
> >
> > The test looks OK but do we want a test for this? I mean: A test like this
> > seems to imply we promise to merge identical events. Although that is a
> > good general guideline, I consider it rather an optimization that may or
> > may not happen but userspace should not rely on it. Thoughts?
> 
> The thing is, those are not really two identical events.
> This is in fact the same event (fsnotify_change() hook was called once).
> The fact that listener process may have an inode watch, parent directory
> watch and a filesystem watch should not affect the number of read events.

Yeah, I agree that in this case we should be merging the event if sanely
possible (which is why I've merged that patch).

> Now it's true that internally, fsnotify_dentry() emits two event flavors to
> parent and to victim. For inotify it even made some sense, because listener
> would read two different event flavors with two different formats.
> With fanotify (either reporting fd or fid) receiving two events makes very
> little sense.
> 
> I agree that the fix (merging those events) is best effort and we cannot
> commit to merging the events, but this isolated regression test does
> check the best effort fix reliably and this is the reason I think it
> should stay.

OK, I'm not too concerned about this test. But still the functionality is
more in the area of "nice to have" than "must have" so in future we may
break this if the implementation would get too hairy. But I guess we can
remove the test in that case.

> Upcoming FAN_REPORT_NAME is about to change the picture a bit
> towards the inotify behavior - victim watch gets event without name,
> parent watch gets event with name, filesystem watch gets both event
> flavors... that is, if you will agree to this behavior, but we shall continue
> this discussion on the fanotiify_name patches....

Yes.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR