Re: [PATCH] splice: report related fsnotify events

[Jan Kara <jack@suse.cz>]

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 :).

								Honza


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