From: Matthew Wilcox <willy@infradead.org>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jan Kara <jack@suse.cz>, Mo Re Ra <more7.rev@gmail.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: File monitor problem
Date: Wed, 4 Dec 2019 11:02:06 -0800 [thread overview]
Message-ID: <20191204190206.GA8331@bombadil.infradead.org> (raw)
In-Reply-To: <CAOQ4uxjda6iQ1D0QEVB18TcrttVpd7uac++WX0xAyLvxz0x7Ew@mail.gmail.com>
On Wed, Dec 04, 2019 at 08:37:09PM +0200, Amir Goldstein wrote:
> On Wed, Dec 4, 2019 at 7:34 PM Jan Kara <jack@suse.cz> wrote:
> > The problem is there's no better reliable way. For example even if fanotify
> > event provided a name as in the Amir's commit you reference, this name is
> > not very useful. Because by the time your application gets to processing
> > that fanotify event, the file under that name need not exist anymore, or
>
> For DELETE event, file is not expected to exist, the filename in event is
> always "reliable" (i.e. this name was unlinked).
Jan already pointed out that events may be reordered. So a CREATE event
and DELETE event may arrive out of order for the same file. This will
confuse any agent.
> > there may be a different file under that name already. That is my main
> > objection to providing file names with fanotify events - they are not
> > reliable but they are reliable enough that application developers will use
> > them as a reliable thing which then leads to hard to debug bugs. Also
> > fanotify was never designed to guarantee event ordering so it is impossible
> > to reconstruct exact state of a directory in userspace just by knowing some
> > past directory state and then "replaying" changes as reported by fanotify.
next prev parent reply other threads:[~2019-12-04 19:02 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-04 10:02 File monitor problem Mo Re Ra
2019-12-04 12:53 ` Amir Goldstein
2019-12-04 14:24 ` Mo Re Ra
2019-12-04 17:34 ` Jan Kara
2019-12-04 18:37 ` Amir Goldstein
2019-12-04 19:02 ` Matthew Wilcox [this message]
2019-12-04 20:27 ` Amir Goldstein
2019-12-11 10:06 ` Jan Kara
2019-12-11 13:58 ` Amir Goldstein
2019-12-16 15:00 ` Amir Goldstein
2019-12-19 7:33 ` Amir Goldstein
2019-12-23 18:19 ` Jan Kara
2019-12-23 19:14 ` Amir Goldstein
2019-12-24 3:49 ` Amir Goldstein
2019-12-31 11:53 ` Amir Goldstein
2020-01-07 17:10 ` Jan Kara
2020-01-07 18:56 ` Amir Goldstein
2020-01-08 9:04 ` Jan Kara
2020-01-08 10:25 ` Amir Goldstein
2020-01-08 12:04 ` Jan Kara
2019-12-07 12:36 ` Mo Re Ra
2019-12-10 16:55 ` Jan Kara
2019-12-10 20:49 ` Amir Goldstein
2019-12-11 22:06 ` Wez Furlong
2019-12-12 5:56 ` Amir Goldstein
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