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Date: Tue, 5 Dec 2000 21:27:58 +0000 (GMT)
From: Tigran Aivazian <tigran@veritas.com>
To: linux-kernel@vger.kernel.org
Subject: [FALSE ALLERT]Re: [bug] vfsmount->count accounting broken again?
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Ok, more info on the "kernel bug" -- the /boot filesystem was busy to
begin with so no wonder it remained busy afterwards....

So, there was only one bug for certain and that's the userspace one but
looks like Andries has taken care of that one already.



On Tue, 5 Dec 2000, Tigran Aivazian wrote:

> Hi,
> 
> Imagine two ext2 filesystems
> 
> /dev/hda1 mounted rw on /boot
> /dev/hda3 mounted rw on /usr/src
> 
> now mount /dev/hda3 also on /boot
> 
> mount -t ext2 /dev/hda3 /boot
> 
> this succeeds, which is expected. Now umount it.
> 
> umount /boot
> 
> this also succeeds, which is expected. Now do df(1) and notice that
> /etc/mtab is corrupted and no longer shows the old /boot filesystem even
> though we know (from /proc/mounts) that it is mounted. This is a bug but a
> userspace one (should mail Andries later, probably util-linux). Now, the
> interesting bit, i.e. the kernel bug:
> 
> umount /boot
> 
> this fails with EBUSY. So, I think the reference count has gone wrong
> somewhere -- I will put debugging code in do_umount() and see, but
> everyone is welcome to fix it before I do so...
> 
> Regards,
> Tigran
> 
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