Re: [PATCH 11/21] mm: Remove unnecessary vma->vm_ops check

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On Wed, Nov 16, 2016 at 02:29:18PM +0100, Jan Kara wrote:
> On Wed 16-11-16 01:28:19, Kirill A. Shutemov wrote:
> > On Fri, Nov 04, 2016 at 05:25:07AM +0100, Jan Kara wrote:
> > > We don't check whether vma->vm_ops is NULL in do_shared_fault() so
> > > there's hardly any point in checking it in wp_page_shared() or
> > > wp_pfn_shared() which get called only for shared file mappings as well.
> > > 
> > > Signed-off-by: Jan Kara <jack@xxxxxxx>
> > 
> > Well, I'm not sure about this.
> > 
> > do_shared_fault() doesn't have the check since we checked it upper by
> > stack: see vma_is_anonymous() in handle_pte_fault().
> > 
> > In principal, it should be fine. But random crappy driver has potential to
> > blow it up.
> 
> Ok, so do you prefer me to keep this patch or discard it? Either is fine with
> me. It was just a cleanup I wrote when factoring out the functionality.

I would rather drop it.

Eventually, we need to make sure that all file-backed vma has vm_ops.
I tried to do this once, but that back-fired...

-- 
 Kirill A. Shutemov
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