Re: [rfc][patch] mm: dirty page accounting race fix

[Jeremy Fitzhardinge]

Hugh Dickins wrote:
> I realized that was the intended optimization, what I'd missed is that
> dirty_accountable can only be true there if (vma->vm_flags & VM_WRITE):
> that's checked in vma_wants_writenotify(), which is how dirty_accountable
> gets to be set.
>
> So those lines are okay, panic over, phew.
>   

I got bitten by precisely the same train of thought.  I think that code 
officially Non Obvious (or at least Not Immediately Obvious, which is 
bad in security-sensitive code).

   J
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