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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Christoph Hellwig <hch@lst.de>
Cc: Jerome Glisse <jglisse@redhat.com>,
	Ralph Campbell <rcampbell@nvidia.com>,
	Felix.Kuehling@amd.com, linux-mm@kvack.org,
	John Hubbard <jhubbard@nvidia.com>,
	dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
	Philip Yang <Philip.Yang@amd.com>
Subject: Re: [PATCH v2 hmm 7/9] mm/hmm: do not unconditionally set pfns when returning EBUSY
Date: Tue, 24 Mar 2020 12:47:08 -0300	[thread overview]
Message-ID: <20200324154708.GA14119@ziepe.ca> (raw)
In-Reply-To: <20200324073746.GF23447@lst.de>

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


  reply	other threads:[~2020-03-24 15:47 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24  1:14 [PATCH v2 hmm 0/9] Small hmm_range_fault() cleanups Jason Gunthorpe
2020-03-24  1:14 ` [PATCH v2 hmm 1/9] mm/hmm: remove pgmap checking for devmap pages Jason Gunthorpe
2020-03-24  1:14 ` [PATCH v2 hmm 2/9] mm/hmm: return the fault type from hmm_pte_need_fault() Jason Gunthorpe
2020-03-24  7:27   ` Christoph Hellwig
2020-03-24 18:58     ` Jason Gunthorpe
2020-03-24  1:14 ` [PATCH v2 hmm 3/9] mm/hmm: remove unused code and tidy comments Jason Gunthorpe
2020-03-24  7:27   ` Christoph Hellwig
2020-03-24  1:14 ` [PATCH v2 hmm 4/9] mm/hmm: remove HMM_FAULT_SNAPSHOT Jason Gunthorpe
2020-03-24  7:33   ` Christoph Hellwig
2020-03-24 19:31     ` Jason Gunthorpe
2020-03-24  1:14 ` [PATCH v2 hmm 5/9] mm/hmm: remove the CONFIG_TRANSPARENT_HUGEPAGE #ifdef Jason Gunthorpe
2020-03-24  7:33   ` Christoph Hellwig
2020-03-24  1:14 ` [PATCH v2 hmm 6/9] mm/hmm: use device_private_entry_to_pfn() Jason Gunthorpe
2020-03-24  7:34   ` Christoph Hellwig
2020-03-24  1:14 ` [PATCH v2 hmm 7/9] mm/hmm: do not unconditionally set pfns when returning EBUSY Jason Gunthorpe
2020-03-24  7:37   ` Christoph Hellwig
2020-03-24 15:47     ` Jason Gunthorpe [this message]
2020-03-24  1:14 ` [PATCH v2 hmm 8/9] mm/hmm: do not set pfns when returning an error code Jason Gunthorpe
2020-03-24  7:38   ` Christoph Hellwig
2020-03-24  1:14 ` [PATCH v2 hmm 9/9] mm/hmm: return error for non-vma snapshots Jason Gunthorpe
2020-03-24  7:45   ` Christoph Hellwig
2020-03-26 21:21 ` [PATCH v2 hmm 0/9] Small hmm_range_fault() cleanups Ralph Campbell
2020-03-27 20:00 [PATCH v3 " Jason Gunthorpe
2020-03-27 20:00 ` [PATCH v2 hmm 7/9] mm/hmm: do not unconditionally set pfns when returning EBUSY Jason Gunthorpe

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