From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH 2/6] cgroup, memcg: allocate cgroup ID from 1 Date: Thu, 24 Apr 2014 17:02:09 -0400 Message-ID: <1398373333-1521-3-git-send-email-tj@kernel.org> References: <1398373333-1521-1-git-send-email-tj@kernel.org> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=NS7b9GReK4W0w4B7KTY8c5W986Q2j2YWJgjUpO7QIps=; b=nDqBe0mPGPVJqCoParjWGiCsh7qRTSH/noa9wANssOpYul7czmoYPg4172YUQjiirp Wb4vjr6swwho8VK/ysS+r77lJInfRhVf4cMR6mjh3cC8epNYAfsaJpnNA7mPFOCtONHa telb6M5IoG/OsMGI6CsfFkJp3Ad4wGEqinOLRPu6RsMhKpob3GtsG6SzzK1Q/ZvEPrvY 4mcQyF+zIEkTzTAh4aY/aLKL0EiYHvGHwOlbM5ii956TShT97dfS3YtWD8RidN9ErZ4/ QqeqjYAqhX2RgRqvchnQx+4G5lL5ZQp4AWUbTZDPSVx124kQKST0xluQ+0ovAYOR3W7Z iSkQ== In-Reply-To: <1398373333-1521-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lizefan@huawei.com Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, hannes@cmpxchg.org, mhocko@suse.cz, nasa4836@gmail.com, Tejun Heo Currently, cgroup->id is allocated from 0, which is always assigned to the root cgroup; unfortunately, memcg wants to use ID 0 to indicate invalid IDs and ends up incrementing all IDs by one. It's reasonable to reserve 0 for special purposes. This patch updates cgroup core so that ID 0 is not used and the root cgroups get ID 1. The ID incrementing is removed form memcg. Signed-off-by: Tejun Heo Cc: Johannes Weiner Cc: Michal Hocko --- include/linux/cgroup.h | 4 ++-- kernel/cgroup.c | 4 ++-- mm/memcontrol.c | 8 ++------ 3 files changed, 6 insertions(+), 10 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c6c703f..793f70a 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -144,8 +144,8 @@ struct cgroup { /* * idr allocated in-hierarchy ID. * - * The ID of the root cgroup is always 0, and a new cgroup - * will be assigned with a smallest available ID. + * ID 0 is not used, the ID of the root cgroup is always 1, and a + * new cgroup will be assigned with a smallest available ID. * * Allocating/Removing ID must be protected by cgroup_mutex. */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 21667f3..3fa0463 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1531,7 +1531,7 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask) lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); - ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL); + ret = idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_KERNEL); if (ret < 0) goto out; root_cgrp->id = ret; @@ -4225,7 +4225,7 @@ static long cgroup_create(struct cgroup *parent, const char *name, * Temporarily set the pointer to NULL, so idr_find() won't return * a half-baked cgroup. */ - cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL); + cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_KERNEL); if (cgrp->id < 0) { err = -ENOMEM; goto err_unlock; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 29501f0..1d0b297 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -527,18 +527,14 @@ static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg) static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg) { - /* - * The ID of the root cgroup is 0, but memcg treat 0 as an - * invalid ID, so we return (cgroup_id + 1). - */ - return memcg->css.cgroup->id + 1; + return memcg->css.cgroup->id; } static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id) { struct cgroup_subsys_state *css; - css = css_from_id(id - 1, &memory_cgrp_subsys); + css = css_from_id(id, &memory_cgrp_subsys); return mem_cgroup_from_css(css); } -- 1.9.0