From owner-freebsd-hackers Tue Jan 29 19:20:21 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from habanero.hesketh.net (habanero.hesketh.net [66.45.6.196]) by hub.freebsd.org (Postfix) with ESMTP id 1A64337B404 for ; Tue, 29 Jan 2002 19:20:18 -0800 (PST) Received: from mutt.rcfile.org (root@rdu57-26-120.nc.rr.com [66.57.26.120]) by habanero.hesketh.net (8.11.6/8.11.1) with ESMTP id g0U3KBJ06057 for ; Tue, 29 Jan 2002 22:20:11 -0500 X-Received-From: brent@mutt.rcfile.org X-Delivered-To: X-Spam-Filter: check_local@habanero.hesketh.net by digitalanswers.org X-More-Information: http://spamfighter.hesketh.net Received: (from brent@localhost) by mutt.rcfile.org (8.11.6/8.11.6) id g0U3KKN05509 for freebsd-hackers@freebsd.org; Tue, 29 Jan 2002 22:20:20 -0500 (EST) (envelope-from brent) Date: Tue, 29 Jan 2002 22:20:20 -0500 From: Brent Verner To: freebsd-hackers@freebsd.org Subject: multiple mounts of single device Message-ID: <20020130032020.GA5077@rcfile.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.27i X-muttrc: $Id: .muttrc,v 1.9 2002/01/02 07:04:49 brent Exp $ X-uname: FreeBSD 4.5-STABLE #12: Mon Jan 28 03:27:36 EST 2002 brent@mutt.rcfile.org:/usr/obj/usr/src/sys/MUTT Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Hi, I've been searching for info regarding mounting the same device to multiple locations in the filesystem, i.e... # mount /dev/ad0s1e /usr # mount -r /dev/ad0s1e /var/jail/AAAA/usr # mount -r /dev/ad0s1e /var/jail/BBBB/usr [Warning: I /know/ I know next-to-nothing about filesystems... but] I recall seeing some traffic (IIRC, from early 2001) about this ability being in -current, but looking at HEAD:/usr/sys/ufs/ffs/ffs_vfsops.c, I still see around line 571 that EBUSY is still being returned if the device is already mounted. Not being familiar with the fbsd code... Am I even in the correct ballpark? Or is this functionality already present in -current? If it is already in -current, where would I start digging around if I felt like (breaking a perfectly good 4.5 install and) trying to integrate the -current code into 4.5? I'd especially appreciate any two minute (or less) response to any of the following questions -- I'm perfectly comfortable being told "go away and read," if I have some idea of what to read. 0) Is this multiple mount point functionality even necessary, or is there a better/existing mechanism to achieve the same goal (aside from local nfs mount). 1) What is the danger of not failing with EBUSY if the device is already mounted? 2) Would supporting multiple mounts require modifying any code outside the filesystem (/usr/sys/src/ufs/ffs)? If so, how much and where? thanks. brent -- "Develop your talent, man, and leave the world something. Records are really gifts from people. To think that an artist would love you enough to share his music with anyone is a beautiful thing." -- Duane Allman To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message