Re: 2.4.22-pre4: devfs on initrd stays busy after pivot_root

Herbert Pötzl
2003-07-29T14:54:20Z

On Tue, Jul 29, 2003 at 04:08:23PM +0200, Andreas Haumer wrote:
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> Hi!
>
> Marcelo Tosatti wrote:
> > Hi,
> >
> > Here goes -pre4. It contains a lot of updates and fixes.
> >
> > We decided to include this new code quota code which allows usage of
> > quotas with 32bit UID/GIDs.
> >
> > Most Toshibas should work now due to an important ACPI fix.
> >
> > Please help and test.
> >
> Beginning with 2.4.22-pre4 I can't unmount devfs on my
> initial ramdisk anymore because of EBUSY
>
> I use initrd and let the kernel mount devfs on /dev on boot.
> I then set up all the drivers needed to mount the real root
> device, do a "pivot_root" and continue with /sbin/init,
> just like it is described in Documentation/initrd.txt
>
> When the boot process is finished, filesystems are mounted as
> follows:
>
> root@install:~ {520} $ mount
> rootfs on / type rootfs (rw)
> /dev/root on /initrd type romfs (ro)
> none on /initrd/dev type devfs (rw)
> /dev/ide/host0/bus0/target0/lun0/part3 on / type ext2 (rw)
> devfs on /dev type devfs (rw)
> proc on /proc type proc (rw)
>
> I then want to get rid of everything mounted under /initrd
>
> root@install:~ {521} $ umount /initrd/dev
> umount: /initrd/dev: device is busy
>
> This used to work just fine with 2.4.21 and 2.4.22-pre[123]
>
> It does not work with 2.4.22-pre4 and 2.4.22-pre8
> Also, with linux-2.4.21-ac4 unmounting /initrd/dev
> does not work.
>
> I made a diff between pre3 and pre4 and some changes in
> fs/exec.c, fs/binfmt_elf.c and kernel/fork.c (around new
> function "unshare_files()") look suspicious to me. I find
> these changes in both 2.4.21-ac4 and 2.4.22-pre4 patchset
> (but I'm not a kernel hacker, so I might be wrong)
>
> Any idea anyone?

there is an update of devfs available since 2.4.20 or
so, but it hasn't made it in the marcelo tree yet

I don't remember the original path, but it was in
one of Richard Goochs directories on kernel.org,
anyway, you can grab it from the following url:

http://www.13thfloor.at/VServer/patches-2.4.22-p7c17/04_devfs-patch-v199.17.diff.bz2

I don't know if this solves your problems or not, but
I use this patch since it is available, and had no
issues with devfs, so I would suggest you give it a try ...

best,
Herbert

> - - andreas
>
> - --
> Andreas Haumer | mailto:andreas@xss.co.at
> *x Software + Systeme | http://www.xss.co.at/
> Karmarschgasse 51/2/20 | Tel: +43-1-6060114-0
> A-1100 Vienna, Austria | Fax: +43-1-6060114-71
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