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=-14.3 required=3.0 tests=BAYES_00,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=unavailable 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 20519C2D0E2 for ; Tue, 22 Sep 2020 21:02:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C3A823600 for ; Tue, 22 Sep 2020 21:02:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="SxjqcTLZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726686AbgIVVCK (ORCPT ); Tue, 22 Sep 2020 17:02:10 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:14602 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726550AbgIVVCJ (ORCPT ); Tue, 22 Sep 2020 17:02:09 -0400 Received: from pps.filterd (m0089730.ppops.net [127.0.0.1]) by m0089730.ppops.net (8.16.0.42/8.16.0.42) with SMTP id 08MKYnaV016640 for ; Tue, 22 Sep 2020 13:37:27 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=OWbgJScCJjF4/NDWKw0S32FO6Lo1EgQ3Xsl+NSkPRIo=; b=SxjqcTLZqfEwQjEkJs1vmv07QIDmijGLUukfXm6S3ebLowY9/p8zh6P3u1jgjOcChTrQ j7Nx8Icpc8dXrqp84FnQtw/OUcBPDOD8UlcJS5xbExDlKw8Bb5QghKpcl8lEav3ZOgd5 o5VAziIpDIQHjpQjeR5Airn6nz7B2/QHglg= Received: from maileast.thefacebook.com ([163.114.130.16]) by m0089730.ppops.net with ESMTP id 33qn0as92x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 22 Sep 2020 13:37:27 -0700 Received: from intmgw002.41.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Tue, 22 Sep 2020 13:37:26 -0700 Received: by devvm1755.vll0.facebook.com (Postfix, from userid 111017) id D5FB2864B5E; Tue, 22 Sep 2020 13:37:21 -0700 (PDT) From: Roman Gushchin To: Andrew Morton CC: Shakeel Butt , Johannes Weiner , Michal Hocko , , , , Roman Gushchin Subject: [PATCH v1 3/4] mm: introduce page memcg flags Date: Tue, 22 Sep 2020 13:36:59 -0700 Message-ID: <20200922203700.2879671-4-guro@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200922203700.2879671-1-guro@fb.com> References: <20200922203700.2879671-1-guro@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-22_18:2020-09-21,2020-09-22 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 adultscore=0 bulkscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 mlxscore=0 mlxlogscore=266 clxscore=1015 priorityscore=1501 impostorscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009220161 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The lowest bit in page->memcg_data is used to distinguish between struct memory_cgroup pointer and a pointer to a objcgs array. All checks and modifications of this bit are open-coded. Let's formalize it using page memcg flags, defined in page_memcg_flags enum and replace all open-coded accesses with test_bit()/__set_bit(). Few additional flags might be added later. Flags are intended to be mutually exclusive. Signed-off-by: Roman Gushchin --- include/linux/memcontrol.h | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index ab3ea3e90583..9a49f1e1c0c7 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -343,6 +343,11 @@ struct mem_cgroup { =20 extern struct mem_cgroup *root_mem_cgroup; =20 +enum page_memcg_flags { + /* page->memcg_data is a pointer to an objcgs vector */ + PG_MEMCG_OBJ_CGROUPS, +}; + /* * page_mem_cgroup - get the memory cgroup associated with a page * @page: a pointer to the page struct @@ -371,13 +376,7 @@ static inline struct mem_cgroup *page_mem_cgroup_che= ck(struct page *page) { unsigned long memcg_data =3D page->memcg_data; =20 - /* - * The lowest bit set means that memcg isn't a valid - * memcg pointer, but a obj_cgroups pointer. - * In this case the page is shared and doesn't belong - * to any specific memory cgroup. - */ - if (memcg_data & 0x1UL) + if (test_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data)) return NULL; =20 return (struct mem_cgroup *)memcg_data; @@ -422,7 +421,13 @@ static inline void clear_page_mem_cgroup(struct page= *page) */ static inline struct obj_cgroup **page_obj_cgroups(struct page *page) { - return (struct obj_cgroup **)(page->memcg_data & ~0x1UL); + unsigned long memcg_data =3D page->memcg_data; + + VM_BUG_ON_PAGE(memcg_data && !test_bit(PG_MEMCG_OBJ_CGROUPS, + &memcg_data), page); + __clear_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data); + + return (struct obj_cgroup **)memcg_data; } =20 /* @@ -437,7 +442,7 @@ static inline struct obj_cgroup **page_obj_cgroups_ch= eck(struct page *page) { unsigned long memcg_data =3D page->memcg_data; =20 - if (memcg_data && (memcg_data & 0x1UL)) + if (memcg_data && test_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data)) return (struct obj_cgroup **)memcg_data; =20 return NULL; @@ -453,7 +458,11 @@ static inline struct obj_cgroup **page_obj_cgroups_c= heck(struct page *page) static inline bool set_page_obj_cgroups(struct page *page, struct obj_cgroup **objcgs) { - return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL); + unsigned long memcg_data =3D (unsigned long)objcgs; + + __set_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data); + + return !cmpxchg(&page->memcg_data, 0, memcg_data); } =20 /* --=20 2.26.2