Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755152AbcCBSHS (ORCPT ); Wed, 2 Mar 2016 13:07:18 -0500 Received: from mail-yw0-f172.google.com ([209.85.161.172]:36013 "EHLO mail-yw0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751793AbcCBSHP (ORCPT ); Wed, 2 Mar 2016 13:07:15 -0500 Date: Wed, 2 Mar 2016 13:07:12 -0500 From: Tejun Heo To: Li Zefan , Johannes Weiner Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [cgroup/for-4.6 1/2] cgroup: re-hash init_css_set after subsystems are initialized Message-ID: <20160302180712.GA11029@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1903 Lines: 55 css_sets are hashed by their subsys[] contents and in cgroup_init() init_css_set is hashed early, before subsystem inits, when all entries in its subsys[] are NULL, so that cgroup_dfl_root initialization can find and link to it. As subsystems are initialized, init_css_set.subsys[] is filled up but the hashing is never updated making init_css_set hashed in the wrong place. While incorrect, this doesn't cause a critical failure as css_set management code would create an identical css_set dynamically. Fix it by rehashing init_css_set after subsystems are initialized. While at it, drop unnecessary @key local variable. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5263,7 +5263,6 @@ static u16 cgroup_disable_mask __initdat int __init cgroup_init(void) { struct cgroup_subsys *ss; - unsigned long key; int ssid; BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16); @@ -5273,9 +5272,12 @@ int __init cgroup_init(void) mutex_lock(&cgroup_mutex); - /* Add init_css_set to the hash table */ - key = css_set_hash(init_css_set.subsys); - hash_add(css_set_table, &init_css_set.hlist, key); + /* + * Add init_css_set to the hash table so that dfl_root can link to + * it during init. + */ + hash_add(css_set_table, &init_css_set.hlist, + css_set_hash(init_css_set.subsys)); BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0)); @@ -5328,6 +5330,11 @@ int __init cgroup_init(void) ss->bind(init_css_set.subsys[ssid]); } + /* init_css_set.subsys[] has been updated, re-hash */ + hash_del(&init_css_set.hlist); + hash_add(css_set_table, &init_css_set.hlist, + css_set_hash(init_css_set.subsys)); + WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup")); WARN_ON(register_filesystem(&cgroup_fs_type)); WARN_ON(register_filesystem(&cgroup2_fs_type));