thp: change_huge_pmd(): keep huge zero page write-protected

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>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index edc1869c532d8b559394e2bf8e9e42c9fbe02651..12dc04046b9f6f2360893d0da3faacfdb257a335 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1433,6 +1433,8 @@ 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;