---

yaml
---
r: 343307
b: refs/heads/master
c: 78ca0e6
h: refs/heads/master
i:
  343305: cab6458
  343303: 8db2eb2
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 80371957f09814d25c38733d2d08de47f59a13c2
+refs/heads/master: 78ca0e679203bbf74f8febd9725a1c8dd083d073

trunk/mm/huge_memory.c

@@ -160,22 +160,24 @@ static int start_khugepaged(void)
 	return err;
 }
 
-static int __init init_huge_zero_page(void)
+static int init_huge_zero_pfn(void)
 {
 	struct page *hpage;
+	unsigned long pfn;
 
 	hpage = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 			HPAGE_PMD_ORDER);
 	if (!hpage)
 		return -ENOMEM;
-
-	huge_zero_pfn = page_to_pfn(hpage);
+	pfn = page_to_pfn(hpage);
+	if (cmpxchg(&huge_zero_pfn, 0, pfn))
+		__free_page(hpage);
 	return 0;
 }
 
 static inline bool is_huge_zero_pfn(unsigned long pfn)
 {
-	return pfn == huge_zero_pfn;
+	return huge_zero_pfn && pfn == huge_zero_pfn;
 }
 
 static inline bool is_huge_zero_pmd(pmd_t pmd)
@@ -564,10 +566,6 @@ static int __init hugepage_init(void)
 	if (err)
 		return err;
 
-	err = init_huge_zero_page();
-	if (err)
-		goto out;
-
 	err = khugepaged_slab_init();
 	if (err)
 		goto out;
@@ -590,8 +588,6 @@ static int __init hugepage_init(void)
 
 	return 0;
 out:
-	if (huge_zero_pfn)
-		__free_page(pfn_to_page(huge_zero_pfn));
 	hugepage_exit_sysfs(hugepage_kobj);
 	return err;
 }
@@ -735,6 +731,10 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			return VM_FAULT_OOM;
 		if (!(flags & FAULT_FLAG_WRITE)) {
 			pgtable_t pgtable;
+			if (unlikely(!huge_zero_pfn && init_huge_zero_pfn())) {
+				count_vm_event(THP_FAULT_FALLBACK);
+				goto out;
+			}
 			pgtable = pte_alloc_one(mm, haddr);
 			if (unlikely(!pgtable))
 				return VM_FAULT_OOM;