Re: [PATCH v2 hmm 7/9] mm/hmm: do not unconditionally set pfns when returning EBUSY

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Mar 24, 2020 at 08:37:46AM +0100, Christoph Hellwig wrote:
> On Mon, Mar 23, 2020 at 10:14:55PM -0300, Jason Gunthorpe wrote:
> >  	if (pte_none(pte)) {
> >  		required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
> >  		if (required_fault)
> >  			goto fault;
> > +		*pfn = range->values[HMM_PFN_NONE];
> >  		return 0;
> >  	}
> >  
> > @@ -274,8 +274,10 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> >  		}
> >  
> >  		required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
> > -		if (!required_fault)
> > +		if (!required_fault) {
> > +			*pfn = range->values[HMM_PFN_NONE];
> >  			return 0;
> > +		}
> 
> Maybe throw in a goto hole to consolidaste the set PFN and return
> 0 cases?

Then we have goto fault and goto none both ending in returns. I
generally prefer the goto labels to have a single return

The pte_unmap() before faulting makes this routine twisty and I
haven't thought of a good way to untwist it

Thanks,
Jason
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