From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752554AbeBITMP (ORCPT ); Fri, 9 Feb 2018 14:12:15 -0500 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:57203 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752110AbeBITMN (ORCPT ); Fri, 9 Feb 2018 14:12:13 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R291e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04452;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0SxxDJg-_1518203521; From: Yang Shi To: kirill.shutemov@linux.intel.com, gavin.dg@linux.alibaba.com, akpm@linux-foundation.org Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one() Date: Sat, 10 Feb 2018 03:12:01 +0800 Message-Id: <1518203521-81173-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For PTE-mapped THP, the compound THP has not been split to normal 4K pages yet, the whole THP is considered referenced if any one of sub page is referenced. When walking PTE-mapped THP by pvmw, all relevant PTEs will be checked to retrieve referenced bit. But, the current code just returns the result of the last PTE. If the last PTE has not referenced, the referenced flag will be cleared. Just did logical OR for referenced to get the correct result. Reported-by: Gang Deng Suggested-by: Kirill A. Shutemov Signed-off-by: Yang Shi --- v2: adopted the suggestion from Kirill. Not use "||=" style to keep checkpatch quiet, otherwise it reports ERROR: spaces required around that '||' mm/page_idle.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/page_idle.c b/mm/page_idle.c index 0a49374..a4baec9 100644 --- a/mm/page_idle.c +++ b/mm/page_idle.c @@ -65,11 +65,15 @@ static bool page_idle_clear_pte_refs_one(struct page *page, while (page_vma_mapped_walk(&pvmw)) { addr = pvmw.address; if (pvmw.pte) { - referenced = ptep_clear_young_notify(vma, addr, - pvmw.pte); + /* + * For PTE-mapped THP, one sub page is referenced, + * the whole THP is referenced. + */ + referenced = referenced || ptep_clear_young_notify(vma, + addr, pvmw.pte); } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { - referenced = pmdp_clear_young_notify(vma, addr, - pvmw.pmd); + referenced = referenced || pmdp_clear_young_notify(vma, + addr, pvmw.pmd); } else { /* unexpected pmd-mapped page? */ WARN_ON_ONCE(1); -- 1.8.3.1