Re: [PATCH] splice: report related fsnotify events

[Amir Goldstein <amir73il@gmail.com>]

On Tue, Apr 4, 2023 at 12:21 PM Jan Kara <jack@suse.cz> wrote:
>
> On Mon 03-04-23 11:23:25, Jens Axboe wrote:
> > On 4/3/23 11:15?AM, Amir Goldstein wrote:
> > >> On 4/3/23 11:00?AM, Amir Goldstein wrote:
> > >> io_uring does do it for non-polled IO, I don't think there's much point
> > >> in adding it to IOPOLL however. Not really seeing any use cases where
> > >> that would make sense.
> > >>
> > >
> > > Users subscribe to fsnotify because they want to be notified of changes/
> > > access to a file.
> > > Why do you think that polled IO should be exempt?
> >
> > Because it's a drastically different use case. If you're doing high
> > performance polled IO, then you'd never rely on something as slow as
> > fsnotify to tell you of any changes that happened to a device or file.
> > That would be counter productive.
>
> Well, I guess Amir wanted to say that the application using fsnotify is not
> necessarily the one doing high performance polled IO. You could have e.g.
> data mirroring application A tracking files that need mirroring to another
> host using fsnotify and if some application B uses high performance polled
> IO to modify a file, application A could miss the modified file.
>
> That being said if I look at exact details, currently I don't see a very
> realistic usecase that would have problems (people don't depend on
> FS_MODIFY or FS_ACCESS events too much, usually they just use FS_OPEN /
> FS_CLOSE), which is likely why nobody reported these issues yet :).
>

I guess so.
Our monitoring application also does not rely on FS_MODIFY/FS_ACCESS
as they could be too noisy.

The thing that I find missing is being able to tell if a file was *actually*
accessed/modified in between open and close.
This information could be provided with FS_CLOSE event

Thanks,
Amir.