mm/rmap.c: don't call mmu_notifier_invalidate_page() during munlock

In its munmap mode, try_to_unmap_one() searches other mlocked vmas, it
never unmaps pages.  There is no reason for invalidation because ptes are
left unchanged.
Signed-off-by: NKonstantin Khlebnikov <koct9i@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/rmap.c

@@ -1252,7 +1252,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 
 out_unmap:
 	pte_unmap_unlock(pte, ptl);
-	if (ret != SWAP_FAIL)
+	if (ret != SWAP_FAIL && TTU_ACTION(flags) != TTU_MUNLOCK)
 		mmu_notifier_invalidate_page(mm, address);
 out:
 	return ret;