Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264942AbUAMSre (ORCPT ); Tue, 13 Jan 2004 13:47:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264954AbUAMSre (ORCPT ); Tue, 13 Jan 2004 13:47:34 -0500 Received: from nwkea-mail-2.sun.com ([192.18.42.14]:26362 "EHLO nwkea-mail-2.sun.com") by vger.kernel.org with ESMTP id S264942AbUAMSrQ (ORCPT ); Tue, 13 Jan 2004 13:47:16 -0500 Date: Tue, 13 Jan 2004 13:46:49 -0500 From: Mike Waychison Subject: Re: [autofs] [RFC] Towards a Modern Autofs In-reply-to: To: raven@themaw.net Cc: autofs mailing list , Kernel Mailing List Message-id: <40043D19.3010608@sun.com> MIME-version: 1.0 Content-type: multipart/signed; boundary=------------enig5E7A436193FFFE5FA916DA2B; protocol="application/pgp-signature"; micalg=pgp-sha1 X-Accept-Language: en User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20031107 Debian/1.5-3 X-Enigmail-Version: 0.82.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime References: <40029C19.409@sun.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3341 Lines: 105 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig5E7A436193FFFE5FA916DA2B Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit raven@themaw.net wrote: >On Mon, 12 Jan 2004, Mike Waychison wrote: > > > >>>Transparency of an autofs filesystem (as I'm calling it) is the situation >>>where, given a map >>> >>>/usr /man1 server:/usr/man1 >>> /man2 server:/usr/man2 >>> >>>where the filesystem /usr contains, say a directory lib, that needs to be >>>available while also seeing the automounted directories. >>> >>> >>> >>> >>> >>I see. This requires direct mount triggers to do properly. Trying to >>do it with some sort of passthrough to the underlying filesystem is a >>nightmare waiting to happen.. >> >> >> > >So what are we saying here? > >We install triggers at /usr/man1 and /usr/man2. >Then suppose the map had a nobrowse option. > > This is a direct map. The browse / nobrowse options do not apply to direct maps. >Does the trigger also take care of hiding man1 and man2? > > > No. man1 and man2 appear as directories to anyone doing an lstat on them. Traversing *into* them will cause filesystems to be mounted on them. This appears to be similar to browsing of an indirect map at first, however it is a different beast. With indirect maps, we are given the right to cover up /usr to help us detects stats and traversals into its sub-directories. With direct entries, we don't have these leisure. Everything in /usr most be accessible at all times. Your need for 'transparency' comes from the fact that you convert direct maps into indirect maps, which require the covering of /usr. >Is there some definition of these triggers? > > > This question is up in the air. I propose using a magic filesystem, whose root dentry has a follow_link callback defined. When somebody walks into the filesystem, the follow_link is called, which does the mount onto a different dentry, and then forwards the original caller to the new vfsmount/dentry pair. HPA and Viro believe this is better done in the VFS layer directly by using special vfsmounts without super_blocks. The path walking code would be modified to know of these 'traps' or 'triggers' natively. Which solution is best is left as an exercise. -- Mike Waychison Sun Microsystems, Inc. 1 (650) 352-5299 voice 1 (416) 202-8336 voice mailto: Michael.Waychison@Sun.COM http://www.sun.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NOTICE: The opinions expressed in this email are held by me, and may not represent the views of Sun Microsystems, Inc. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ --------------enig5E7A436193FFFE5FA916DA2B Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2 (GNU/Linux) Comment: Using GnuPG with Debian - http://enigmail.mozdev.org iD8DBQFABD0cdQs4kOxk3/MRAl02AJ9DeLf53/wgbXORk2P/11UkCKKRHgCfYQ4j Jsl0hzwGpzEN0Cyy26d8+oc= =6X1I -----END PGP SIGNATURE----- --------------enig5E7A436193FFFE5FA916DA2B-- - 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/