Re: [RFC PATCH v2 11/32] iommu/pages: Add APIs to preserve/unpreserve/restore iommu pages

[Baolu Lu]

On 12/5/25 01:39, Samiullah Khawaja wrote:
> On Wed, Dec 3, 2025 at 6:30 PM Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx> wrote:
> > On 12/3/25 07:02, Samiullah Khawaja wrote:
> > > +int iommu_preserve_pages(struct iommu_pages_list *list)
> > > +{
> > > +     struct ioptdesc *iopt;
> > > +     int count = 0;
> > > +     int ret;
> > > +
> > > +     list_for_each_entry(iopt, &list->pages, iopt_freelist_elm) {
> > > +             ret = kho_preserve_folio(ioptdesc_folio(iopt));
> > > +             if (ret) {
> > > +                     iommu_unpreserve_pages(list, count);
> > > +                     return ret;
> > > +             }
> > > +
> > > +             ++count;
> > > +     }
> > > +
> > > +     return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(iommu_preserve_pages);
> > What is the purpose of "count"?
> Thanks for reviewing.
>
> The count is there to unpreserve only the preserved pages if an error
> occurs during preservation. For example if 4 pages (from the start of
> the list) were preserved out of 10 pages in the list, the unpreserve
> function will unpreserve the first 4 pages from the start of the list.
> Please take a look at the implementation of iommu_unpreserve_pages for
> details.

Oh, I see now. Thanks!