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Thu, 24 Sep 2020 20:29:15 +0000 Date: Thu, 24 Sep 2020 13:29:11 -0700 From: Roman Gushchin To: Johannes Weiner CC: Andrew Morton , Shakeel Butt , Michal Hocko , , , Subject: Re: [PATCH v1 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data Message-ID: <20200924202911.GC1899519@carbon.dhcp.thefacebook.com> References: <20200922203700.2879671-1-guro@fb.com> <20200922203700.2879671-3-guro@fb.com> <20200924195356.GB329853@cmpxchg.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200924195356.GB329853@cmpxchg.org> X-ClientProxiedBy: MWHPR1701CA0006.namprd17.prod.outlook.com (2603:10b6:301:14::16) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.dhcp.thefacebook.com (2620:10d:c090:400::5:a448) by MWHPR1701CA0006.namprd17.prod.outlook.com (2603:10b6:301:14::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3412.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 6c01261e-82d9-4329-0944-08d860c88184 X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4136.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Sep 2020 20:29:15.7563 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: b7Fxt3/zH1edlO2QeYfDLzZX75R8SP3SDCU+2xSV5stZwmuH9WyBjCqMK5raazKi X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2518 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-24_15:2020-09-24,2020-09-24 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 mlxlogscore=999 clxscore=1015 phishscore=0 suspectscore=1 spamscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009240149 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 24, 2020 at 03:53:56PM -0400, Johannes Weiner wrote: > On Tue, Sep 22, 2020 at 01:36:58PM -0700, Roman Gushchin wrote: > > To gather all direct accesses to struct page's memcg_data field > > in one place, let's introduce 4 new helper functions to use in > > the slab accounting code: > > struct obj_cgroup **page_obj_cgroups(struct page *page); > > struct obj_cgroup **page_obj_cgroups_check(struct page *page); > > bool set_page_obj_cgroups(struct page *page, struct obj_cgroup **objcgs); > > void clear_page_obj_cgroups(struct page *page); > > > > They are similar to the corresponding API for generic pages, except > > that the setter can return false, indicating that the value has been > > already set from a different thread. > > > > Signed-off-by: Roman Gushchin > > Reviewed-by: Shakeel Butt > > --- > > include/linux/memcontrol.h | 80 ++++++++++++++++++++++++++++++++++++++ > > mm/memcontrol.c | 4 +- > > mm/slab.h | 27 ++----------- > > 3 files changed, 85 insertions(+), 26 deletions(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index 3313e7c21534..ab3ea3e90583 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -409,6 +409,86 @@ static inline void clear_page_mem_cgroup(struct page *page) > > page->memcg_data = 0; > > } > > > > +#ifdef CONFIG_MEMCG_KMEM > > +/* > > + * page_obj_cgroups - get the object cgroups vector associated with a page > > + * @page: a pointer to the page struct > > + * > > + * Returns a pointer to the object cgroups vector associated with the page, > > + * or NULL. This function assumes that the page is known to have an > > + * associated object cgroups vector. It's not safe to call this function > > + * against pages, which might have an associated memory cgroup: e.g. > > + * kernel stack pages. > > + */ > > +static inline struct obj_cgroup **page_obj_cgroups(struct page *page) > > +{ > > + return (struct obj_cgroup **)(page->memcg_data & ~0x1UL); > > page_mem_cgroup() has a VM_BUG_ON() if the page is in fact a slab > type. Should this also check that if memcg_data is set, it MUST have > the lower bit set? Absolutely, patch 3 does this after the formalization of the bit as a flag. > > In line with page_memcg(), I think page_objcgs() would be nicer. Ok to me. Thanks!