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authorTejun Heo <tj@kernel.org>2013-08-13 17:01:54 +0200
committerTejun Heo <tj@kernel.org>2013-08-13 17:01:54 +0200
commit0ae78e0bf10ac38ab53548e18383afc9997eca22 (patch)
tree8f3e828b1751966af779becd60a0ff432cfefc8d /kernel/cgroup.c
parentcgroup: rename cgroup_subsys_state->dput_work and its callback function (diff)
downloadlinux-0ae78e0bf10ac38ab53548e18383afc9997eca22.tar.xz
linux-0ae78e0bf10ac38ab53548e18383afc9997eca22.zip
cgroup: add cgroup_subsys_state->parent
With the planned unified hierarchy, css's (cgroup_subsys_state) will be RCU protected and allowed to be attached and detached dynamically over the course of a cgroup's lifetime. This means that css's will stay accessible after being detached from its cgroup - the matching pointer in cgroup->subsys[] cleared - for ref draining and RCU grace period. cgroup core still wants to guarantee that the parent css is never destroyed before its children and css_parent() always returns the parent regardless of the state of the child css as long as it's accessible. This patch makes css's hold onto their parents and adds css->parent so that the parent css is never detroyed before its children and can be determined without consulting the cgroups. cgroup->dummy_css is also updated to point to the parent dummy_css; however, it doesn't need to worry about object lifetime as the parent cgroup is already pinned by the child. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0b280978f097..5c6dd7ed26a7 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4264,6 +4264,9 @@ static void css_free_work_fn(struct work_struct *work)
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
+ if (css->parent)
+ css_put(css->parent);
+
cgroup_dput(css->cgroup);
}
@@ -4290,8 +4293,12 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
css->ss = ss;
css->flags = 0;
css->id = NULL;
- if (cgrp == cgroup_dummy_top)
+
+ if (cgrp->parent)
+ css->parent = cgroup_css(cgrp->parent, ss->subsys_id);
+ else
css->flags |= CSS_ROOT;
+
BUG_ON(cgroup_css(cgrp, ss->subsys_id));
cgrp->subsys[ss->subsys_id] = css;
}
@@ -4388,6 +4395,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
cgrp->dentry = dentry;
cgrp->parent = parent;
+ cgrp->dummy_css.parent = &parent->dummy_css;
cgrp->root = parent->root;
if (notify_on_release(parent))
@@ -4436,9 +4444,13 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
root->number_of_cgroups++;
- /* each css holds a ref to the cgroup's dentry */
- for_each_root_subsys(root, ss)
+ /* each css holds a ref to the cgroup's dentry and the parent css */
+ for_each_root_subsys(root, ss) {
+ struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+
dget(dentry);
+ percpu_ref_get(&css->parent->refcnt);
+ }
/* hold a ref to the parent's dentry */
dget(parent->dentry);