Re: [PATCH resubmit] do_mount: reduce stack consumption

From: Al Viro
Date: Fri Nov 04 2005 - 09:06:57 EST


On Fri, Nov 04, 2005 at 01:57:05PM +0100, Heiko Carstens wrote:
> > > This is a resubmit of Andreas' patch that reduces stackframe usage in
> > > do_mount. Problem is that without this patch we get a kernel stack
> > > overflow if we run with 4k stacks (s390 31 bit mode).
> > > See original stack back trace below and Andreas' patch and analysis
> > > here:
> > > http://www.ussg.iu.edu/hypermail/linux/kernel/0410.3/1844.html
> >
> > NAK. Rationale: too ugly.
>
> Ok, since I can only guess what you don't like: here is an updated patch
> that probably addresses a few things.
> If you don't like this one too, could you please explain what should be
> changed?

Depth analysis. E.g. do_move_mount() change is simply nonsense - _this_
is not going to overflow, no matter what. And do_add_mount() change
is also very suspicious - looks like you are attacking the wrong place
in call chain.
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