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Date: Fri, 9 Mar 2001 19:43:05 +0100 (CET)
From: Mike Galbraith <mikeg@wen-online.de>
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To: Alexander Viro <viro@math.psu.edu>
cc: Andries Brouwer <aeb@veritas.com>,
        "Richard B. Johnson" <root@chaos.analogic.com>,
        Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: Ramdisk (and other) problems with 2.4.2
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Message-ID: <Pine.LNX.4.33.0103091929140.532-100000@mikeg.weiden.de>
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On Fri, 9 Mar 2001, Alexander Viro wrote:

> On Fri, 9 Mar 2001, Mike Galbraith wrote:
>
> > I think I've figured it out.. at least I've found a way to reproduce
> > the exact errors to the last detail and some pretty nasty corruption
> > to go with it.  The operator must help though.. a lot ;-)
> >
> > If you do mount -o remount /dev/somedisk / thinking that that will get
> > rid of your /dev/ram0 root, that isn't the case, and you will corrupt
> > the device you remounted (I did it to a scratch monkey) very badly when
> > you write to the still mounted ramdisk.
>
> Ugh. mount -o remount ignores dev_name argument. It will change the

Ah.. didn't know that.

> flags of fs mounted from /dev/ram0 and will not even touch a /dev/somedisk.
> If you write to device you have mounted... Well, don't expect it to be pretty.

I knew the ramdisk would be history :)  It munged the disk though too.

> > You must exec a shell (or something) chrooted to your mounted harddisk
> > to un-busy the old root and then pivot_root/unmount that old root.  I
> > tested this, and all is well.
> >
> > I think this is a consequence of the multiple mount changes.. not sure.
> > (ergo cc to Al Viro.. he knows eeeeverything about mount points)
>
> I _really_ doubt that it has anything to multiple mounts. mount -o remount
> never unmounts anything. Never did. The rest is an obvious result - you
> leave fs mounted, you do direct write to its device, you see it fucked.
> The fact that it is a root doesn't matter. Relevant part of manpage:

I started imagining a possible connection when I saw two root entries
in proc/mounts.

	-Mike

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