Re: [PATCH V5 6/9] iommufd: pfn reader for file mappings

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Oct 23, 2024 at 07:40:34AM +0000, Tian, Kevin wrote:

> > +	for (i = 0; i < nfolios; i++) {
> > +		struct folio *folio = user->ufolios[i];
> > +		unsigned long nr = folio_nr_pages(folio);
> > +		unsigned long npin = min(nr - offset, npages);
> > +
> > +		npages -= npin;
> > +		npages_out += npin;
> > +
> > +		if (upages) {
> > +			if (npin == 1) {
> > +				*upages++ = folio_page(folio, offset);
> > +			} else {
> > +				int rc = folio_add_pins(folio, npin - 1);
> > +
> > +				if (rc)
> > +					return rc;
> > +
> > +				while (npin--)
> > +					*upages++ = folio_page(folio,
> > offset++);
> > +			}
> > +		}
> 
> dead code as user->upages is NULL for memfd (echoed below)?

It can be non-null if we go down the iopt_pages_fill() call chain. In
that case it will hold the output array for the access's page list for
mdev type drivers.

Jason