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) &&