From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754540AbZEFEpz (ORCPT ); Wed, 6 May 2009 00:45:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751005AbZEFEpq (ORCPT ); Wed, 6 May 2009 00:45:46 -0400 Received: from mail.gmx.net ([213.165.64.20]:56904 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750770AbZEFEpp (ORCPT ); Wed, 6 May 2009 00:45:45 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+FSxczghOF/1ad7tHm3Kg+6VhZqB4xpDHcWn0FUl 3hkV/NOLw7ne1u Subject: Re: Analyzed/Solved: Booting 2.6.30-rc2-git7 very slow From: Mike Galbraith To: Andrew Morton Cc: viro@ZenIV.linux.org.uk, knobi@knobisoft.de, rjw@sisk.pl, linux-kernel@vger.kernel.org, tigran@aivazian.fsnet.co.uk In-Reply-To: <20090505154911.e0309a4f.akpm@linux-foundation.org> References: <409142.83316.qm@web32605.mail.mud.yahoo.com> <20090428182837.62c51f26.akpm@linux-foundation.org> <1240977096.5478.3.camel@marge.simson.net> <20090429011755.c141c599.akpm@linux-foundation.org> <20090429120827.GI8633@ZenIV.linux.org.uk> <1241014725.15095.19.camel@marge.simson.net> <20090505154911.e0309a4f.akpm@linux-foundation.org> Content-Type: text/plain Date: Wed, 06 May 2009 06:45:40 +0200 Message-Id: <1241585140.5196.28.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 X-FuHaFi: 0.57 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-05-05 at 15:49 -0700, Andrew Morton wrote: > On Wed, 29 Apr 2009 16:18:45 +0200 > Mike Galbraith wrote: > > > On Wed, 2009-04-29 at 13:08 +0100, Al Viro wrote: > > > On Wed, Apr 29, 2009 at 01:17:55AM -0700, Andrew Morton wrote: > > > > > > > > > > Questions remains: was this intentional? It breaks existing userspace and should therefore be considered a regression - right? On the other hand, it will never be a problem for RHEL-4/5 kernels, unless the change in 2.6.29 gets backported. Any ideas? > > > > > > > > > > > > afaik that was unintentional and was probably a mistake. > > > > > > > > > > > > I wonder how we did that. > > > > > > > > > > > > > > > > [hotplug]# grep sysfs /proc/mounts > > > > > > none /sys sysfs rw,relatime 0 0 > > > > > > /sys /sys sysfs rw,relatime 0 0 > > > > > > > > > > ___(I wonder how the heck that is accomplished) > > > > > > > > Beats me. I'm not seeing likely changes in fs/proc/base.c or around > > > > show_mountinfo(). Maybe sysfs broke in an ingenious way. (hopefully > > > > cc's viro). > > > > > > Er... Somebody mounting sysfs twice? From some init script and from > > > /etc/fstab, perhaps? That definitely looks like two mount(2) had to > > > have been done to cause that... > > > > Yeah, but how does one go about doing that? > > > > Using mount -f, I can convince mount to succeed, but I still have only > > one entry in /proc/mounts, despite what my mount binary imagines. > > > > marge:..sys/vm # grep sysfs /proc/mounts > > sysfs /sys sysfs rw,relatime 0 0 > > > > marge:..sys/vm # mount|grep sysfs > > sysfs on /sys type sysfs (rw) > > sys on /sys type sysfs (rw) > > /sys on /sys type sysfs (rw) > > > > So /proc/mounts is OK and /etc/mtab is wrong? > > Obvious next step is to strace `mount -f', see what's happening around > sys_mount(), please. Well, there is no syscall with -f. I was trying various mount options to see if I could find a way to create bogons that could confuse scripts. I could create bogons in /etc/mtab with -f, or bogons in /proc/mounts by using --move. I could re-create the exact reported data with a combination of mount -n and mount --move. I could not get a double /proc/mounts entry without --move, and that seems unlikely to appear in boot scripts. So I still wonder how the heck it was accomplished. I also now wonder why you can --move mounts on top of one another, but beck with it, ignorance conserves braincells I may some day need :) -Mike