On Wed, Dec 20, 2023 at 11:44:28PM +0100, David Hildenbrand wrote: > hugetlb rmap handling differs quite a lot from "ordinary" rmap code. > For example, hugetlb currently only supports entire mappings, and treats > any mapping as mapped using a single "logical PTE". Let's move it out > of the way so we can overhaul our "ordinary" rmap. > implementation/interface. > > So let's introduce and use hugetlb_try_dup_anon_rmap() to make all > hugetlb handling use dedicated hugetlb_* rmap functions. > > Add sanity checks that we end up with the right folios in the right > functions. > > Note that is_device_private_page() does not apply to hugetlb. > > Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx> > Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > +static inline bool folio_needs_cow_for_dma(struct vm_area_struct *vma, > + struct folio *folio) I particularly like it that you introduced this. > +static inline int hugetlb_try_dup_anon_rmap(struct folio *folio, > + struct vm_area_struct *vma) > +{ > + VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio); > + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); > + > + if (PageAnonExclusive(&folio->page)) { I wonder if we need a folio_test_hugetlb_anon_exclusive() to make this a little more ergonomic? > + if (unlikely(folio_needs_cow_for_dma(vma, folio))) > + return -EBUSY; > + ClearPageAnonExclusive(&folio->page); ... and set/clear variants.