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

From: Martin Knoblauch
Date: Wed Apr 29 2009 - 13:28:35 EST



----- Original Message ----

> From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> To: Mike Galbraith <efault@xxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; Martin Knoblauch <knobi@xxxxxxxxxxxx>; Rafael J. Wysocki <rjw@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; tigran aivazian <tigran@xxxxxxxxxxxxxxxxxxxx>
> Sent: Wednesday, April 29, 2009 4:34:03 PM
> Subject: Re: Analyzed/Solved: Booting 2.6.30-rc2-git7 very slow
>
> On Wed, Apr 29, 2009 at 04:18:45PM +0200, Mike Galbraith wrote:
> > > /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.
>
> Huh?
> -f Causes everything to be done except for the actual system call;
> if it's not obvious, this ``fakes'' mounting the file system.
> This option is useful in conjunction with the -v flag to deter-
> mine what the mount command is trying to do. It can also be used
> to add entries for devices that were mounted earlier with the -n
>
> What are you talking about?
>
> The interesting part is why mount(2) doesn't fail with -EBUSY on that
> overmounting. Is there anything else mounted on /sys? That, or any
> interesting patches applied to the tree (fs/sysfs/mount.c, fs/namespace.c)

In my 2.6.30-rc3-git2 there is definitely nothing interesting, just my NFS readahead patch. But that touches nothing near sysfs. And my 2.6.29 test-boot was from a plain build.

Cheers
Martin

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