dnotify semantics

dnotify semantics

[Alex Larsson]

Currently when monitoring a directory using dnotify you get notifications 
whenever some file in the directory changes, or is added/removed. But when 
the directory itself is changed (i.e. chmoded) you don't get any notification.

Reading Documentation/dnotify.txt it does not seem clear what the expected 
behaviour is, it says:

 The intention of directory notification is to allow user applications
 to be notified when a directory, or any of the files in it, are changed.

But then:

        DN_ACCESS       A file in the directory was accessed (read)
        DN_MODIFY       A file in the directory was modified (write,truncate)
        DN_CREATE       A file was created in the directory
        DN_DELETE       A file was unlinked from directory
        DN_RENAME       A file in the directory was renamed
        DN_ATTRIB       A file in the directory had its attributes
                        changed (chmod,chown)

 (i.e. no directory was changed event)

This is somewhat of a problem for me, implementing fam using dnotify. When 
monitoring a directory i need to send events also when the directory 
changes. The only way this can be done with the current semantics would be 
to monitor both the directory and it's parent. Unfortunately this could
create many spurious events/stats, and is not possible to do for the root 
directory.

Is there any chance that we can get a change in semantics so that changes 
to the directory itself also causes a notification?

/ Alex

(Please CC me, I'm not on the linux-kernel list)

Re: dnotify semantics

[Andreas Dilger]

On Oct 26, 2001  11:48 -0400, Alex Larsson wrote:
> Currently when monitoring a directory using dnotify you get notifications 
> whenever some file in the directory changes, or is added/removed. But when 
> the directory itself is changed (i.e. chmoded) you don't get any notification.

So, monitor the parent of the directory in question for attribute changes.

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

Re: dnotify semantics

[Andreas Ferber]

On Fri, Oct 26, 2001 at 12:16:28PM -0600, Andreas Dilger wrote:

> So, monitor the parent of the directory in question for attribute changes.

... which is a little bit difficult if you want to monitor the root
directory.

Andreas
-- 
       Andreas Ferber - dev/consulting GmbH - Bielefeld, FRG
     ---------------------------------------------------------
         +49 521 1365800 - af@devcon.net - www.devcon.net

Re: dnotify semantics

[Alex Larsson]

On Fri, 26 Oct 2001, Andreas Ferber wrote:

> On Fri, Oct 26, 2001 at 12:16:28PM -0600, Andreas Dilger wrote:
> 
> > So, monitor the parent of the directory in question for attribute changes.
> 
> ... which is a little bit difficult if you want to monitor the root
> directory.

Which is what i said in my mail, if you read it.

It also adds a monitor to a possibly busy directory that could cause a lot 
of spurious events and corresponding stats.

/ Alex