1 files changed, 39 insertions, 3 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index eb477809a5c0..1e79fac3186b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1362,11 +1362,21 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 	}
 
 	/*
-	 * We have to assume the worse case ie pmd for invalidation. Note that
-	 * the page can not be free in this function as call of try_to_unmap()
-	 * must hold a reference on the page.
+	 * For THP, we have to assume the worse case ie pmd for invalidation.
+	 * For hugetlb, it could be much worse if we need to do pud
+	 * invalidation in the case of pmd sharing.
+	 *
+	 * Note that the page can not be free in this function as call of
+	 * try_to_unmap() must hold a reference on the page.
 	 */
 	end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
+	if (PageHuge(page)) {
+		/*
+		 * If sharing is possible, start and end will be adjusted
+		 * accordingly.
+		 */
+		adjust_range_if_pmd_sharing_possible(vma, &start, &end);
+	}
 	mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
 
 	while (page_vma_mapped_walk(&pvmw)) {
@@ -1409,6 +1419,32 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 		subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
 		address = pvmw.address;
 
+		if (PageHuge(page)) {
+			if (huge_pmd_unshare(mm, &address, pvmw.pte)) {
+				/*
+				 * huge_pmd_unshare unmapped an entire PMD
+				 * page.  There is no way of knowing exactly
+				 * which PMDs may be cached for this mm, so
+				 * we must flush them all.  start/end were
+				 * already adjusted above to cover this range.
+				 */
+				flush_cache_range(vma, start, end);
+				flush_tlb_range(vma, start, end);
+				mmu_notifier_invalidate_range(mm, start, end);
+
+				/*
+				 * The ref count of the PMD page was dropped
+				 * which is part of the way map counting
+				 * is done for shared PMDs.  Return 'true'
+				 * here.  When there is no other sharing,
+				 * huge_pmd_unshare returns false and we will
+				 * unmap the actual page and drop map count
+				 * to zero.
+				 */
+				page_vma_mapped_walk_done(&pvmw);
+				break;
+			}
+		}
 
 		if (IS_ENABLED(CONFIG_MIGRATION) &&
 		    (flags & TTU_MIGRATION) &&