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

[Baolu Lu <baolu.lu@linux.intel.com>]

On 12/5/25 01:39, Samiullah Khawaja wrote:
> On Wed, Dec 3, 2025 at 6:30 PM Baolu Lu<baolu.lu@linux.intel.com> 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!