[PATCH 1/8] cgroup: implement cgroup_is_ancestor()

Li Zefan
2013-04-08T08:21:53Z

This will be used as a replacement for css_is_ancestor().

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
include/linux/cgroup.h | 3 +++
kernel/cgroup.c | 21 +++++++++++++++++++++
2 files changed, 24 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 2eaedc1..96072e4 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -177,6 +177,7 @@ struct cgroup {
atomic_t count;

int id; /* ida allocated in-hierarchy ID */
+ int depth; /* the depth of the cgroup */

/*
* We link our 'sibling' struct into our parent's 'children'.
@@ -730,6 +731,8 @@ unsigned short css_id(struct cgroup_subsys_state *css);
unsigned short css_depth(struct cgroup_subsys_state *css);
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);

+bool cgroup_is_ancestor(struct cgroup *child, struct cgroup *root);
+
#else /* !CONFIG_CGROUPS */

static inline int cgroup_init_early(void) { return 0; }
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7ee3bdf..e87872c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4133,6 +4133,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
cgrp->dentry = dentry;

cgrp->parent = parent;
+ cgrp->depth = parent->depth + 1;
cgrp->root = parent->root;
cgrp->top_cgroup = parent->top_cgroup;

@@ -5299,6 +5300,26 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
return css ? css : ERR_PTR(-ENOENT);
}

+/**
+ * cgroup_is_ancestor - test "root" cgroup is an ancestor of "child"
+ * @child: the cgroup to be tested.
+ * @root: the cgroup supposed to be an ancestor of the child.
+ *
+ * Returns true if "root" is an ancestor of "child" in its hierarchy.
+ */
+bool cgroup_is_ancestor(struct cgroup *child, struct cgroup *root)
+{
+ int depth = child->depth;
+
+ if (depth < root->depth)
+ return false;
+
+ while (depth-- != root->depth)
+ child = child->parent;
+
+ return (child == root);
+}
+
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
{
--
1.8.0.2