From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754248AbdKFSbE (ORCPT ); Mon, 6 Nov 2017 13:31:04 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:37130 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752825AbdKFSa6 (ORCPT ); Mon, 6 Nov 2017 13:30:58 -0500 From: Roman Gushchin To: Tejun Heo CC: , , , Roman Gushchin Subject: [PATCH v2 2/2] cgroup: export list of cgroups v2 features using sysfs Date: Mon, 6 Nov 2017 13:30:29 -0500 Message-ID: <20171106183029.21297-2-guro@fb.com> X-Mailer: git-send-email 2.13.6 In-Reply-To: <20171106183029.21297-1-guro@fb.com> References: <20171106173854.GE3252168@devbig577.frc2.facebook.com> <20171106183029.21297-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [2620:10d:c091:200::2:f826] X-ClientProxiedBy: CY4PR01CA0005.prod.exchangelabs.com (2603:10b6:903:1f::15) To CO1PR15MB1079.namprd15.prod.outlook.com (2a01:111:e400:7b66::9) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8d8d49cd-8cd8-4d9a-61b0-08d52544839d X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(22001)(4534020)(4602075)(4627115)(201703031133081)(201702281549075)(2017052603199);SRVR:CO1PR15MB1079; 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It's handy to know from userspace, which cgroup v2 features are supported without calculating it based on the kernel version. So, let's export the list of such features using /sys/kernel/cgroup/features pseudo-file. The list is hardcoded and has to be extended when new functionality is added. Each feature is printed on a new line. Example: $ cat /sys/kernel/cgroup/features nsdelegate Signed-off-by: Roman Gushchin Cc: Tejun Heo Cc: kernel-team@fb.com --- kernel/cgroup/cgroup.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index eed92ed624e5..69e65d28fe98 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5877,8 +5877,16 @@ static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr, } static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate); +static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr, + char *buf) +{ + return snprintf(buf, PAGE_SIZE, "nsdelegate\n"); +} +static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features); + static struct attribute *cgroup_sysfs_attrs[] = { &cgroup_delegate_attr.attr, + &cgroup_features_attr.attr, NULL, }; -- 2.13.6