From: Matthew Wilcox <email@example.com> To: Amir Goldstein <firstname.lastname@example.org> Cc: Jan Kara <email@example.com>, Mo Re Ra <firstname.lastname@example.org>, linux-fsdevel <email@example.com> Subject: Re: File monitor problem Date: Wed, 4 Dec 2019 11:02:06 -0800 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 <firstname.lastname@example.org> 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 index Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-04 10:02 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 2019-12-07 12:36 ` Mo Re Ra
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