Re: [PATCH] root-hopping for pre-2.3.41-3

[Werner Almesberger]

Guest section DW wrote:
> Some Unix flavours allow overmounting, where more than one filesystem
> is mounted on the same path - maybe Linux doesnt allow that today,
> it didnt last time I checked, but still I suppose it would be good
> to define the semantics of pivot_root() in such a case.]

I guess it should move the whole stack if / is overmounted, and
perhaps only the top-level if /new_root is. For /put_old, things
would just be added to the stack. Anyway, details depend on the
overmounting implementation. It should be pretty straightforward
to adapt the dentry juggling.

> Usually in such a situation not many processes will be around, but still..

Typically, if you have a lot of unruly processes, you can't unmount the
old root anyway. So in this case, it's probably better to forget about
pivot_root and to do a simple chroot. Or, if all else fails, reboot.

- Werner

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 / Werner Almesberger, ICA, EPFL, CH       [e-mail] /
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