---

yaml
---
r: 343301
b: refs/heads/master
c: fc9fe82
h: refs/heads/master
i:
  343299: 3c1cb77
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 479f0abbfd253d1117a35c1df12755d27a2a0705
+refs/heads/master: fc9fe822f7112db23e51e2be3b886f5d8f0afdb6

trunk/mm/huge_memory.c

@@ -708,6 +708,18 @@ static inline struct page *alloc_hugepage(int defrag)
 }
 #endif
 
+static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
+		struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd)
+{
+	pmd_t entry;
+	entry = pfn_pmd(huge_zero_pfn, vma->vm_page_prot);
+	entry = pmd_wrprotect(entry);
+	entry = pmd_mkhuge(entry);
+	set_pmd_at(mm, haddr, pmd, entry);
+	pgtable_trans_huge_deposit(mm, pgtable);
+	mm->nr_ptes++;
+}
+
 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			       unsigned long address, pmd_t *pmd,
 			       unsigned int flags)
@@ -785,6 +797,16 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		pte_free(dst_mm, pgtable);
 		goto out_unlock;
 	}
+	/*
+	 * mm->page_table_lock is enough to be sure that huge zero pmd is not
+	 * under splitting since we don't split the page itself, only pmd to
+	 * a page table.
+	 */
+	if (is_huge_zero_pmd(pmd)) {
+		set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd);
+		ret = 0;
+		goto out_unlock;
+	}
 	if (unlikely(pmd_trans_splitting(pmd))) {
 		/* split huge page running from under us */
 		spin_unlock(&src_mm->page_table_lock);