mm: fix handling PTE-mapped THPs in page_idle_clear_pte_refs()

For PTE-mapped THP page_check_address_transhuge() is not adequate: it
cannot find all relevant PTEs, only the first one.i

Let's switch it to page_vma_mapped_walk().

I don't think it's subject for stable@: it's not fatal.

Link: http://lkml.kernel.org/r/20170129173858.45174-5-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_idle.c

@@ -54,26 +54,26 @@ static int page_idle_clear_pte_refs_one(struct page *page,
 					struct vm_area_struct *vma,
 					unsigned long addr, void *arg)
 {
-	struct mm_struct *mm = vma->vm_mm;
-	pmd_t *pmd;
-	pte_t *pte;
-	spinlock_t *ptl;
+	struct page_vma_mapped_walk pvmw = {
+		.page = page,
+		.vma = vma,
+		.address = addr,
+	};
 	bool referenced = false;
 
-	if (!page_check_address_transhuge(page, mm, addr, &pmd, &pte, &ptl))
-		return SWAP_AGAIN;
-
-	if (pte) {
-		referenced = ptep_clear_young_notify(vma, addr, pte);
-		pte_unmap(pte);
+	while (page_vma_mapped_walk(&pvmw)) {
+		addr = pvmw.address;
+		if (pvmw.pte) {
+			referenced = ptep_clear_young_notify(vma, addr,
+					pvmw.pte);
 		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
-		referenced = pmdp_clear_young_notify(vma, addr, pmd);
+			referenced = pmdp_clear_young_notify(vma, addr,
+					pvmw.pmd);
 		} else {
 			/* unexpected pmd-mapped page? */
 			WARN_ON_ONCE(1);
 		}
-
-	spin_unlock(ptl);
+	}
 
 	if (referenced) {
 		clear_page_idle(page);