Re: pivot_root solved by patch to 2.4.22-pre7

From: Herbert Pötzl (herbert@13thfloor.at)
Date: Wed Aug 06 2003 - 14:51:01 EST


On Wed, Aug 06, 2003 at 04:33:52PM -0300, Marcelo Tosatti wrote:
>
> What is your problem with pivot_root?
>
> Sorry but I've searched the list archives and found nothing but this email
> and this patch, which seems a bit hackish.

 Jul 21 Rene Mayrhofer 82 pivot_root seems to be broken in 2.4.21-a1716
 Jul 22 Denis Vlasenko 103 >
 Jul 22 Rene Mayrhofer 54 >
 Jul 22 Jason Baron 18 >
 Jul 22 Alan Cox 22 >
 Jul 22 Rene Mayrhofer 25 >
 Jul 22 Alan Cox 17 >
 Jul 22 Rene Mayrhofer 154 >
 Jul 23 Mika Penttilä 40 >
 Jul 22 Mika Penttilä 41 >

HTH,
Herbert

> On Wed, 6 Aug 2003, Rene Mayrhofer wrote:
>
> > Hi all,
> >
> > The problem with pivot_root that appeared in 2.4.21-ac4 and the
> > 2.4.22-pre kernels is now solved (at least for my case) by applying the
> > trvial patch sent by Jason Baron.
> >
> > Jason Baron wrote:
> > > right. so the semantics of how file tables are shared has changed a bit. I
> > > would think that for at least 'init', it'd be nice to preserve the
> > > original behavior, for situations such as you described. Something like
> > > the following would probably work, although i havent' tried the test
> > > script.
> > >
> > > --- linux/kernel/fork.c.orig 2003-07-23 21:34:59.000000000 -0400
> > > +++ linux/kernel/fork.c 2003-07-23 21:35:45.000000000 -0400
> > > @@ -558,7 +558,7 @@ int unshare_files(void)
> > >
> > > /* This can race but the race causes us to copy when we don't
> > > need to and drop the copy */
> > > - if(atomic_read(&files->count) == 1)
> > > + if(atomic_read(&files->count) == 1 || (current->pid == 1))
> > > {
> > > atomic_inc(&files->count);
> > > return 0;
> > >
> >
> >
> >
> > I tried that on my system and it works as expected. The kernel processes
> > close their fds and the old root fs can thus be unmounted after
> > pivot_root. Thanks for the hint !
> > So the problem is solved for me and it would be wonderful to get it into
> > 2.4.22.
> >
> > best regards,
> > Rene
> >
> > -
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