From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S271717AbTHDMrR (ORCPT ); Mon, 4 Aug 2003 08:47:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S271720AbTHDMrR (ORCPT ); Mon, 4 Aug 2003 08:47:17 -0400 Received: from thebsh.namesys.com ([212.16.7.65]:19911 "HELO thebsh.namesys.com") by vger.kernel.org with SMTP id S271717AbTHDMrQ (ORCPT ); Mon, 4 Aug 2003 08:47:16 -0400 From: Nikita Danilov MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16174.21970.527300.160659@laputa.namesys.com> Date: Mon, 4 Aug 2003 16:47:14 +0400 To: Stephan von Krawczynski Cc: linux-kernel Subject: Re: FS: hardlinks on directories In-Reply-To: <20030804141548.5060b9db.skraw@ithnet.com> References: <20030804141548.5060b9db.skraw@ithnet.com> X-Mailer: ed | telnet under Fuzzball OS, emulated on Emacs 21.5 (beta14) "cassava" XEmacs Lucid Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Stephan von Krawczynski writes: > Hello all, > > although it is very likely I am entering (again :-) an ancient discussion I > would like to ask why hardlinks on directories are not allowed/no supported fs > action these days. I can't think of a good reason for this, but can think of > many good reasons why one would like to have such a function, amongst those: > > - restructuring of the fs to meet different sorting criterias (kind of a > database view onto the fs) > - relinking of the fs for export to other hosts via nfs or the like (enhanced > security through artificially constructed, exported trees) > > Would a feature like that be seen as "big action" or rather small enhancement > to the fs-layer? > Are there any supporters for this feature out there? Hard links on directories are hard to do in the UNIX file system model. Where ".." should point? How to implement rmdir? You can think about UNIX unlink as some form of reference counter based garbage collector---when last (persistent) reference to the object is removed it is safe to recycle it. It is well-known that reference counting GC cannot cope with cyclical references. Usually this is not a problem for the file system because all cyclical references are very well known---they always involve "." and "..". But as one allows hard links on directories, file system is no longer tree, but generic directed graph and reference counting GC wouldn't work. > > Regards, > Stephan Nikita.