From 31cfd7b786682261f58439117e9286cceaa8104a Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Sat, 18 Oct 2008 20:27:10 -0700
Subject: [PATCH] --- yaml --- r: 115871 b: refs/heads/master c:
 4b2e38ad703541f7845c2d766426148b8d1aa329 h: refs/heads/master i:   115869:
 f586b47ef511d0bc452fb79ded7c71a2d94c82fe   115867:
 5b56cc90a1475c7508ee956fd9ca7d746b050961   115863:
 54c5a8d9ab98119f58baf274e773bd89345ebb6d   115855:
 caddaf0535f334df44e62b84bddff523ce404667   115839:
 6c0a54656ba0b036e542d8b4240675fc99e506dd v: v3

---
 [refs]             |  2 +-
 trunk/mm/hugetlb.c | 22 +++++++++++++++++++---
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index aecde45d3b99..23aee5614bf8 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e575f111dc0f27044e170580e7de50985ab3e011
+refs/heads/master: 4b2e38ad703541f7845c2d766426148b8d1aa329
diff --git a/trunk/mm/hugetlb.c b/trunk/mm/hugetlb.c
index ab79cd4dd23c..ce8cbb29860b 100644
--- a/trunk/mm/hugetlb.c
+++ b/trunk/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)