Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261380AbVDMP73 (ORCPT ); Wed, 13 Apr 2005 11:59:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261379AbVDMP72 (ORCPT ); Wed, 13 Apr 2005 11:59:28 -0400 Received: from mail.shareable.org ([81.29.64.88]:14241 "EHLO mail.shareable.org") by vger.kernel.org with ESMTP id S261378AbVDMP7N (ORCPT ); Wed, 13 Apr 2005 11:59:13 -0400 Date: Wed, 13 Apr 2005 16:58:52 +0100 From: Jamie Lokier To: Jan Hudec Cc: Miklos Szeredi , 7eggert@gmx.de, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, akpm@osdl.org, viro@parcelfarce.linux.theplanet.co.uk Subject: Re: [RFC] FUSE permission modell (Was: fuse review bits) Message-ID: <20050413155852.GB12825@mail.shareable.org> References: <20050412144529.GE10995@mail.shareable.org> <20050412160409.GH10995@mail.shareable.org> <20050412164401.GA14149@mail.shareable.org> <20050412171338.GA14633@mail.shareable.org> <20050413125609.GA9571@vagabond> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050413125609.GA9571@vagabond> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1469 Lines: 33 > > > A nice implemention of it in FUSE could push it along a bit :) > > > > Aren't there some assumptions in VFS that currently make this > > impossible? > > I believe it's OK with VFS, but applications would be confused to death. > Well, there really is one issue -- dentries have exactly one parent, so > what do you do when opening a file with hardlinks as a directory? (In > fact IIRC that is what lead to all the funny talk about mountpoints, > since they don't have this limitation) Hardlinks aren't a problem when entering a file as if it's a directory, provided the directory does not contain any hard links to a parent in the hierarchy. In other words, as long as it's a directed acyclic graph. This is trivially always true for virtual directories such as entering an archive file. And detachable/movable mountpoints are a nice and sensible way to implement it. Some work has actually been done on this. Experiments with the reiserfs file-as-directory extension showed that applications are generally ok with it. It looks like a file, but you can cd into it or follow a path lookup into it. Linus had some good ideas on the exact semantics to implement when doing path lookup on these objects. -- Jamie - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/