On 22/01/2024 19:41, David Hildenbrand wrote: > Let's prepare for further changes. > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx> > --- > mm/memory.c | 60 ++++++++++++++++++++++++++++------------------------- > 1 file changed, 32 insertions(+), 28 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 7e1f4849463aa..2aa2051ee51d3 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -930,6 +930,29 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma > return 0; > } > > +static inline void __copy_present_pte(struct vm_area_struct *dst_vma, > + struct vm_area_struct *src_vma, pte_t *dst_pte, pte_t *src_pte, > + pte_t pte, unsigned long addr) > +{ > + struct mm_struct *src_mm = src_vma->vm_mm; > + > + /* If it's a COW mapping, write protect it both processes. */ > + if (is_cow_mapping(src_vma->vm_flags) && pte_write(pte)) { > + ptep_set_wrprotect(src_mm, addr, src_pte); > + pte = pte_wrprotect(pte); > + } > + > + /* If it's a shared mapping, mark it clean in the child. */ > + if (src_vma->vm_flags & VM_SHARED) > + pte = pte_mkclean(pte); > + pte = pte_mkold(pte); > + > + if (!userfaultfd_wp(dst_vma)) > + pte = pte_clear_uffd_wp(pte); > + > + set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte); > +} > + > /* > * Copy one pte. Returns 0 if succeeded, or -EAGAIN if one preallocated page > * is required to copy this pte. > @@ -939,16 +962,16 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, > struct folio **prealloc) > { > - struct mm_struct *src_mm = src_vma->vm_mm; > - unsigned long vm_flags = src_vma->vm_flags; > pte_t pte = ptep_get(src_pte); > struct page *page; > struct folio *folio; > > page = vm_normal_page(src_vma, addr, pte); > - if (page) > - folio = page_folio(page); > - if (page && folio_test_anon(folio)) { > + if (unlikely(!page)) > + goto copy_pte; > + > + folio = page_folio(page); > + if (folio_test_anon(folio)) { > /* > * If this page may have been pinned by the parent process, > * copy the page immediately for the child so that we'll always > @@ -963,34 +986,15 @@ copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, > addr, rss, prealloc, page); > } > rss[MM_ANONPAGES]++; > - } else if (page) { > + VM_WARN_ON_FOLIO(PageAnonExclusive(page), folio); > + } else { > folio_get(folio); > folio_dup_file_rmap_pte(folio, page); > rss[mm_counter_file(page)]++; > } > > - /* > - * If it's a COW mapping, write protect it both > - * in the parent and the child > - */ > - if (is_cow_mapping(vm_flags) && pte_write(pte)) { > - ptep_set_wrprotect(src_mm, addr, src_pte); > - pte = pte_wrprotect(pte); > - } > - VM_BUG_ON(page && folio_test_anon(folio) && PageAnonExclusive(page)); > - > - /* > - * If it's a shared mapping, mark it clean in > - * the child > - */ > - if (vm_flags & VM_SHARED) > - pte = pte_mkclean(pte); > - pte = pte_mkold(pte); > - > - if (!userfaultfd_wp(dst_vma)) > - pte = pte_clear_uffd_wp(pte); > - > - set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte); > +copy_pte: > + __copy_present_pte(dst_vma, src_vma, dst_pte, src_pte, pte, addr); > return 0; > } >