Re: [PATCH v9 1/3] madvise: use zap_page_range_single for madvise dontneed

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On 12.11.22 00:26, Mike Kravetz wrote:
Expose the routine zap_page_range_single to zap a range within a single
vma.  The madvise routine madvise_dontneed_single_vma can use this
routine as it explicitly operates on a single vma.  Also, update the mmu
notification range in zap_page_range_single to take hugetlb pmd sharing
into account.  This is required as MADV_DONTNEED supports hugetlb vmas.

Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings")
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Reported-by: Wei Chen <harperchen1110@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>


[...]

-/*
- * Parameter block passed down to zap_pte_range in exceptional cases.
- */
-struct zap_details {
-	struct folio *single_folio;	/* Locked folio to be unmapped */
-	bool even_cows;			/* Zap COWed private pages too? */
-	zap_flags_t zap_flags;		/* Extra flags for zapping */
-};
-
  /* Whether we should zap all COWed (private) pages too */
  static inline bool should_zap_cows(struct zap_details *details)
  {
@@ -1736,19 +1727,27 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
   *
   * The range must fit into one VMA.
   */
-static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
+void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
  		unsigned long size, struct zap_details *details)
  {
+	unsigned long end = address + size;

Could make that const.

  	struct mmu_notifier_range range;
  	struct mmu_gather tlb;
lru_add_drain();
  	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
-				address, address + size);
+				address, end);
+	if (is_vm_hugetlb_page(vma))
+		adjust_range_if_pmd_sharing_possible(vma, &range.start,
+						     &range.end);
  	tlb_gather_mmu(&tlb, vma->vm_mm);
  	update_hiwater_rss(vma->vm_mm);
  	mmu_notifier_invalidate_range_start(&range);
-	unmap_single_vma(&tlb, vma, address, range.end, details);
+	/*
+	 * unmap 'address-end' not 'range.start-range.end' as range
+	 * could have been expanded for hugetlb pmd sharing.
+	 */
+	unmap_single_vma(&tlb, vma, address, end, details);
  	mmu_notifier_invalidate_range_end(&range);
  	tlb_finish_mmu(&tlb);
  }


Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Thanks,

David / dhildenb




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