On Fri, Apr 26, 2024 at 2:42 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 26.04.24 05:43, Pasha Tatashin wrote: > > Changelog > > ================================================================ > > v2: Use mapcount instead of refcount > > Synchronized with IOMMU Observability changes. > > ================================================================ > > > > This series frees empty page tables on unmaps. It intends to be a > > low overhead feature. > > > > The read-writer lock is used to synchronize page table, but most of > > time the lock is held is reader. It is held as a writer for short > > period of time when unmapping a page that is bigger than the current > > iova request. For all other cases this lock is read-only. > > > > page->mapcount is used in order to track number of entries at each page > > table. > > I'm wondering if this will conflict with page_type at some point? We're > already converting other page table users to ptdesc. CCing Willy. Hi David, This contradicts with the following comment in mm_types.h: * If your page will not be mapped to userspace, you can also use the four * bytes in the mapcount union, but you must call page_mapcount_reset() * before freeing it. Thank you, Pasha
