From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C14CCA9EA9 for ; Fri, 18 Oct 2019 18:03:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDE0421D7C for ; Fri, 18 Oct 2019 18:03:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="UMvBPf6Z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2505669AbfJRSD5 (ORCPT ); Fri, 18 Oct 2019 14:03:57 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:29880 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727054AbfJRSD5 (ORCPT ); Fri, 18 Oct 2019 14:03:57 -0400 Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id x9II2wBw008978 for ; Fri, 18 Oct 2019 11:03:56 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=C9I2JQCkwhgmNcawYjp9ktOND4N69jgabqizXoyl1NM=; b=UMvBPf6ZOMQ+Dpt3VIm/m96Oaq/2F6zAAXBbRvJsMk0/g/2cGkWfmmPE6rcwAX10HKM6 3LL4UtpA5H7DxM+WEfGC0S4/MXer+TitoyTneCwedZSncePeAl+dB3/NzHRAI8Pqmm4b IPOxj5Ry7kKWJSAg6VAHcOBDPnJYWT3n+Yk= Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 2vqhgjr8g2-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Fri, 18 Oct 2019 11:03:56 -0700 Received: from 2401:db00:30:6007:face:0:1:0 (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::129) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Fri, 18 Oct 2019 11:03:50 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 2CA3962E1ADD; Fri, 18 Oct 2019 11:03:49 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , , CC: , , , , Song Liu , Johannes Weiner , Hugh Dickins Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v3] mm,thp: recheck each page before collapsing file THP Date: Fri, 18 Oct 2019 11:03:45 -0700 Message-ID: <20191018180345.4188310-1-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-18_04:2019-10-18,2019-10-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 phishscore=0 mlxscore=0 impostorscore=0 clxscore=1015 bulkscore=0 mlxlogscore=926 adultscore=0 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1908290000 definitions=main-1910180164 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In collapse_file(), after locking the page, it is necessary to recheck that the page is up-to-date. Add PageUptodate() check for both shmem THP and file THP. Current khugepaged should not try to collapse dirty file THP, because it is limited to read only text. Add a PageDirty check and warning for file THP. This is added after page_mapping() check, because if the page is truncated, it might be dirty. Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Cc: Kirill A. Shutemov Cc: Johannes Weiner Cc: Hugh Dickins Cc: William Kucharski Cc: Andrew Morton Signed-off-by: Song Liu --- Changes v1 => v2: Rearrange the checks per feedback from Johannes, Rik, and Kirill. Changes v2 => v3: Remove redudant checks before trylock_page(). (Johannes) --- mm/khugepaged.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0a1b4b484ac5..e20bb9d3482d 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1601,17 +1601,6 @@ static void collapse_file(struct mm_struct *mm, result = SCAN_FAIL; goto xa_unlocked; } - } else if (!PageUptodate(page)) { - xas_unlock_irq(&xas); - wait_on_page_locked(page); - if (!trylock_page(page)) { - result = SCAN_PAGE_LOCK; - goto xa_unlocked; - } - get_page(page); - } else if (PageDirty(page)) { - result = SCAN_FAIL; - goto xa_locked; } else if (trylock_page(page)) { get_page(page); xas_unlock_irq(&xas); @@ -1626,7 +1615,12 @@ static void collapse_file(struct mm_struct *mm, * without racing with truncate. */ VM_BUG_ON_PAGE(!PageLocked(page), page); - VM_BUG_ON_PAGE(!PageUptodate(page), page); + + /* double check the page is up to date */ + if (unlikely(!PageUptodate(page))) { + result = SCAN_FAIL; + goto out_unlock; + } /* * If file was truncated then extended, or hole-punched, before @@ -1642,6 +1636,15 @@ static void collapse_file(struct mm_struct *mm, goto out_unlock; } + /* + * khugepaged should not try to collapse dirty pages for + * file THP. Show warning if this somehow happens. + */ + if (WARN_ON_ONCE(!is_shmem && PageDirty(page))) { + result = SCAN_FAIL; + goto out_unlock; + } + if (isolate_lru_page(page)) { result = SCAN_DEL_PAGE_LRU; goto out_unlock; -- 2.17.1