linux-kernel - [PATCH 04/12] mm: fix handling PTE-mapped THPs in page_idle_clear_pte

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Message-Id: <20170124162824.91275-5-kirill.shutemov@linux.intel.com>
Date:   Tue, 24 Jan 2017 19:28:16 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: [PATCH 04/12] 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_check_walk().

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

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Vladimir Davydov <vdavydov.dev@...il.com>
---
 mm/page_idle.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/mm/page_idle.c b/mm/page_idle.c
index ae11aa914e55..573d217457cb 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -54,27 +54,27 @@ 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_check_walk pcw = {
+		.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);
-	} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
-		referenced = pmdp_clear_young_notify(vma, addr, pmd);
-	} else {
-		/* unexpected pmd-mapped page? */
-		WARN_ON_ONCE(1);
+	while (page_check_walk(&pcw)) {
+		addr = pcw.address;
+		if (pcw.pte) {
+			referenced = ptep_clear_young_notify(vma, addr,
+					pcw.pte);
+		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+			referenced = pmdp_clear_young_notify(vma, addr,
+					pcw.pmd);
+		} else {
+			/* unexpected pmd-mapped page? */
+			WARN_ON_ONCE(1);
+		}
 	}
 
-	spin_unlock(ptl);
-
 	if (referenced) {
 		clear_page_idle(page);
 		/*
-- 
2.11.0