1 files changed, 19 insertions, 3 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ab79cd4dd23c..ce8cbb29860b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2071,6 +2071,14 @@ follow_huge_pud(struct mm_struct *mm, unsigned long address,
         return NULL;
 }
 
+static int huge_zeropage_ok(pte_t *ptep, int write, int shared)
+{
+        if (!ptep || write || shared)
+                return 0;
+        else
+                return huge_pte_none(huge_ptep_get(ptep));
+}
+
 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         struct page **pages, struct vm_area_struct **vmas,
                         unsigned long *position, int *length, int i,
@@ -2080,6 +2088,8 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
         unsigned long vaddr = *position;
         int remainder = *length;
         struct hstate *h = hstate_vma(vma);
+        int zeropage_ok = 0;
+        int shared = vma->vm_flags & VM_SHARED;
 
         spin_lock(&mm->page_table_lock);
         while (vaddr < vma->vm_end && remainder) {
@@ -2092,8 +2102,11 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                  * first, for the page indexing below to work.
                  */
                 pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
+                if (huge_zeropage_ok(pte, write, shared))
+                        zeropage_ok = 1;
 
-                if (!pte || huge_pte_none(huge_ptep_get(pte)) ||
+                if (!pte ||
+                    (huge_pte_none(huge_ptep_get(pte)) && !zeropage_ok) ||
                     (write && !pte_write(huge_ptep_get(pte)))) {
                         int ret;
 
@@ -2113,8 +2126,11 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 page = pte_page(huge_ptep_get(pte));
 same_page:
                 if (pages) {
-                        get_page(page);
-                        pages[i] = page + pfn_offset;
+                        if (zeropage_ok)
+                                pages[i] = ZERO_PAGE(0);
+                        else
+                                pages[i] = page + pfn_offset;
+                        get_page(pages[i]);
                 }
 
                 if (vmas)