Re: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync_one()

[Thomas Gleixner]

Joerg,

On Thu, 18 Jul 2019, Joerg Roedel wrote:
> On Wed, Jul 17, 2019 at 11:43:43PM +0200, Thomas Gleixner wrote:
> > On Wed, 17 Jul 2019, Joerg Roedel wrote:
> > > +
> > > +	if (!pmd_present(*pmd_k))
> > > +		return NULL;
> > >  	else
> > >  		BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
> > 
> > So in case of unmap, this updates only the first entry in the pgd_list
> > because vmalloc_sync_all() will break out of the iteration over pgd_list
> > when NULL is returned from vmalloc_sync_one().
> > 
> > I'm surely missing something, but how is that supposed to sync _all_ page
> > tables on unmap as the changelog claims?
> 
> No, you are right, I missed that. It is a bug in this patch, the code
> that breaks out of the loop in vmalloc_sync_all() needs to be removed as
> well. Will do that in the next version.

I assume that p4d/pud do not need the pmd treatment, but a comment
explaining why would be appreciated.

Thanks,

	tglx