Re: [PATCH] fix quadratic behavior of shrink_dcache_parent()

Andrew Morton
2007-02-10T00:40:35Z

On Fri, 9 Feb 2007 19:23:31 -0500
"Russ Cox" <rsc@swtch.com> wrote:

> > "The file system mounted on /tmp/z in the example contains 2^50
> > directories". heh.
> >
> > I do wonder how realistic this problem is in real life.
>
> That's a fair concern, although I was trying this as part
> of evaluating how much someone could hose a system
> if we let them mount arbitrary FUSE servers. And the
> answer is: they could make it completely unusable,
> requiring reboot.
>
> I ran a later test that printed how deep it got into
> the file tree and it was only a few hundred thousand
> if I recall correctly. A determined attacker might even
> manage to do this in a normal file system.
>
> But sure, it's not a common case. ;-)

Well that's a good point - sometimes people do crazy things on purpose. We
were all University students once ;)

The patches look nice and as I said, potentially of some use for memory
reclaim. But I hope that someone who has worked on dcache.c more recently
than I has time to apply a toothcomb to this work.