2.4.22-pre4: devfs on initrd stays busy after pivot_root

[Andreas Haumer <andreas@xss.co.at>]

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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?

- - 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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