Re: [PATCH -alternative] mm: hugetlbfs: Close race during teardownof hugetlbfs shared page tables V2 (resend)

[Michal Hocko]

On Wed 01-08-12 10:20:36, Michal Hocko wrote:
> On Tue 31-07-12 22:45:43, Larry Woodman wrote:
> > On 07/31/2012 04:06 PM, Michal Hocko wrote:
> > >On Tue 31-07-12 13:49:21, Larry Woodman wrote:
> > >>On 07/31/2012 08:46 AM, Mel Gorman wrote:
> > >>>Fundamentally I think the problem is that we are not correctly detecting
> > >>>that page table sharing took place during huge_pte_alloc(). This patch is
> > >>>longer and makes an API change but if I'm right, it addresses the underlying
> > >>>problem. The first VM_MAYSHARE patch is still necessary but would you mind
> > >>>testing this on top please?
> > >>Hi Mel, yes this does work just fine.  It ran for hours without a panic so
> > >>I'll Ack this one if you send it to the list.
> > >Hi Larry, thanks for testing! I have a different patch which tries to
> > >address this very same issue. I am not saying it is better or that it
> > >should be merged instead of Mel's one but I would be really happy if you
> > >could give it a try. We can discuss (dis)advantages of both approaches
> > >later.
> > >
> > >Thanks!
> > 
> > Hi Michal, the system hung when I tested this patch on top of the
> > latest 3.5 kernel.  I wont have AltSysrq access to the system until
> > tomorrow AM.  
> 
> Please hold on. The patch is crap. I forgot about 
> if (!vma_shareable(vma, addr))
> 	return;
> 
> case so somebody got an uninitialized pmd. The patch bellow handles
> that.
> 

I am really lame :/. The previous patch is wrong as well for goto out
branch. The updated patch as follows:
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