From owner-freebsd-stable@FreeBSD.ORG Tue Nov 22 22:33:24 2005 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7F05316A41F for ; Tue, 22 Nov 2005 22:33:24 +0000 (GMT) (envelope-from dwhite@gumbysoft.com) Received: from carver.gumbysoft.com (carver.gumbysoft.com [66.220.23.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 41DE443D46 for ; Tue, 22 Nov 2005 22:33:24 +0000 (GMT) (envelope-from dwhite@gumbysoft.com) Received: by carver.gumbysoft.com (Postfix, from userid 1000) id 2EF4572DD4; Tue, 22 Nov 2005 14:33:24 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by carver.gumbysoft.com (Postfix) with ESMTP id 2951F72DCB; Tue, 22 Nov 2005 14:33:24 -0800 (PST) Date: Tue, 22 Nov 2005 14:33:24 -0800 (PST) From: Doug White To: =?UTF-8?B?VsOhY2xhdiBIYWlzbWFu?= In-Reply-To: Message-ID: <20051122142927.Y24336@carver.gumbysoft.com> References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=X-UNKNOWN Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: freebsd-stable@freebsd.org Subject: Re: Mount related panic with FreeBSD 6? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Nov 2005 22:33:24 -0000 On Sun, 20 Nov 2005, [UTF-8] V=C3=A1clav Haisman wrote: > Hi, > I got this panic on freshly installed FreeBSD 6. I did this df -h and > noticed that /mnt/oldroot/home is somewhat mangled. The /mnt/oldroot is > root of FreeBSD 4.11 system. I successfully copied some settings and all > user accounts from that /mnt/oldroot/home earlier today. This is what I > did before the panic: [...] I discovered this by accident with a CDROM the other day. In 6.0 you can overlay read-only mounts (i.e., mount the same R/O FS on top of itself) but unmounting it will cause GEOM to tear down the underlying device while leaving the first mount behind. Next access to the mountpoint will panic the system. You can't mount a read/write mount on top of itself, or a r/o mount on a r/w mount -- you get an error. A quick discussion with phk points to a faulty or missing access check in GEOM. I'm not familiar with the VFS operations required to mount a filesystem, though, so I'm not sure where to look to put in the fix. In the interim, be careful not to mount a read-only FS multiple times. --=20 Doug White | FreeBSD: The Power to Serve dwhite@gumbysoft.com | www.FreeBSD.org