[PATCH v3 05/10] thp: change_huge_pmd(): keep huge zero page write-protected

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

We want to get page fault on write attempt to huge zero page, so let's
keep it write-protected.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
---
 mm/huge_memory.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f30f39d..d864cd4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1249,6 +1249,8 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		pmd_t entry;
 		entry = pmdp_get_and_clear(mm, addr, pmd);
 		entry = pmd_modify(entry, newprot);
+		if (is_huge_zero_pmd(entry))
+			entry = pmd_wrprotect(entry);
 		set_pmd_at(mm, addr, pmd, entry);
 		spin_unlock(&vma->vm_mm->page_table_lock);
 		ret = 1;
-- 
1.7.7.6

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