From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265316AbUAAB2J (ORCPT ); Wed, 31 Dec 2003 20:28:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265317AbUAAB2J (ORCPT ); Wed, 31 Dec 2003 20:28:09 -0500 Received: from gort.metaparadigm.com ([203.117.131.12]:58553 "EHLO gort.metaparadigm.com") by vger.kernel.org with ESMTP id S265316AbUAAB2D (ORCPT ); Wed, 31 Dec 2003 20:28:03 -0500 Message-ID: <3FF377A8.6040302@metaparadigm.com> Date: Thu, 01 Jan 2004 09:28:08 +0800 From: Michael Clark Organization: Metaparadigm Pte Ltd User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20031107 Debian/1.5-3 X-Accept-Language: en MIME-Version: 1.0 To: rudi@lambda-computing.de Cc: ivern@acm.org, linux-kernel@vger.kernel.org Subject: Re: File change notification References: <3FF2FC85.5070906@lambda-computing.de> <3FF31366.30206@acm.org> <3FF31A15.4070307@lambda-computing.de> In-Reply-To: <3FF31A15.4070307@lambda-computing.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 01/01/04 02:48, Rüdiger Klaehn wrote: > Javier Fernandez-Ivern wrote: > >> Rüdiger Klaehn wrote: >> >>> I have been wondering for some time why there is no decent file >>> change notification mechanism in linux. Is there some deep >>> philosophical reason for this, or is it just that nobody has found >>> the time to implement it? If it is the latter, I am willing to >>> implement it as long there is a chance to get this accepted into the >>> mainstream kernel. >> >> >> >> Well, there's fam. But AFAIK that's all done in user space, and your >> approach would be significantly more efficient (as a matter of fact, >> fam could be modified to use your change device as a first level of >> notification.) >> > Fam is a user space library that has some nice features such as network > transparent change notification. It currently uses the dnotify mechanism > if the underlying kernel supports it, but as I mentioned the dnotify > mechanism requires an open file handle and works only for single > directories. If the underlying os does not support dnotify, fam resorts > to polling for file changes (yuk!). Have you had a look at dazuko. It provides a consistent file access notification mechanism (and also intervention for denying access) across linux and freebsd. It is currently being used by various on-access virus scanners. It is under active development and supports 2.6 (and 2.4) http://www.dazuko.org/about.shtml Seems like a good idea. I've always thought it would be nice to use something like this to maintain a dynamic locatedb (among many other potential uses). ~mc