linux-kernel - Re: Analyzed/Solved: Booting 2.6.30-rc2-git7 very slow

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Message-ID: <957194.27869.qm@web32605.mail.mud.yahoo.com>
Date:	Wed, 6 May 2009 00:55:34 -0700 (PDT)
From:	Martin Knoblauch <knobi@...bisoft.de>
To:	Mike Galbraith <efault@....de>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	viro@...IV.linux.org.uk, rjw@...k.pl, linux-kernel@...r.kernel.org,
	tigran@...azian.fsnet.co.uk
Subject: Re: Analyzed/Solved: Booting 2.6.30-rc2-git7 very slow


----- Original Message ----

> From: Mike Galbraith <efault@....de>
> To: Andrew Morton <akpm@...ux-foundation.org>
> Cc: viro@...IV.linux.org.uk; knobi@...bisoft.de; rjw@...k.pl; linux-kernel@...r.kernel.org; tigran@...azian.fsnet.co.uk
> Sent: Wednesday, May 6, 2009 6:45:40 AM
> Subject: Re: Analyzed/Solved: Booting 2.6.30-rc2-git7 very slow
> 
> 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 :)
> 

 just to bring this back to my problem :-) Last week I reported that the "new" sysfs entry in /proc/mounts already comes out of initrd. Does this ring a bell?

http://lkml.indiana.edu/hypermail/linux/kernel/0904.3/03048.html

Cheers
Martin

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