linux-kernel - Re: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin

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Message-ID: <YsWvqvlsccxmuhkv@Asurada-Nvidia>
Date:   Wed, 6 Jul 2022 08:52:10 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Christoph Hellwig <hch@...radead.org>
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Subject: Re: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin_pages() return void

On Tue, Jul 05, 2022 at 11:54:50PM -0700, Christoph Hellwig wrote:
> > +void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> > +		      int npage)
> >  {
> >  	struct vfio_container *container;
> >  	struct vfio_iommu_driver *driver;
> > -	int ret;
> >  
> > -	if (!user_pfn || !npage || !vfio_assert_device_open(device))
> > -		return -EINVAL;
> > +	if (WARN_ON_ONCE(!user_pfn || !npage || !vfio_assert_device_open(device)))
> 
> This adds an overly long line.  Note that I think in general it is
> better to have an individual WARN_ON per condition anyway, as that
> allows to directly pinpoint what went wrong when it triggers.

Following patches are touching this line too. And it'll be shrunk
to a shorter line eventually by the end of PATCH-9.

Yet, I can separate them as you pointed out.

> > +	if (WARN_ON_ONCE(unlikely(!driver || !driver->ops->unpin_pages)))
> > +		return;
> 
> I'd just skip this check an let it crash.  If someone calls unpin
> on something totally random that wasn't even pinned we don't need to
> handle that gracefully.

Makes sense. I can drop that in next version.

> Reviewed-by: Christoph Hellwig <hch@....de>

Will add to v3. Thanks for the review!