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authorTejun Heo <tj@kernel.org>2013-08-09 04:11:23 +0400
committerTejun Heo <tj@kernel.org>2013-08-09 04:11:23 +0400
commit6387698699afd72d6304566fb6ccf84bffe07c56 (patch)
tree9440e96fa8e5adce62409a5b0e40984dfedaada3 /include/linux/cgroup.h
parenta7c6d554aa01236ac2a9f851ab0f75704f76dfa2 (diff)
downloadlinux-6387698699afd72d6304566fb6ccf84bffe07c56.tar.xz
cgroup: add css_parent()
Currently, controllers have to explicitly follow the cgroup hierarchy to find the parent of a given css. cgroup is moving towards using cgroup_subsys_state as the main controller interface construct, so let's provide a way to climb the hierarchy using just csses. This patch implements css_parent() which, given a css, returns its parent. The function is guarnateed to valid non-NULL parent css as long as the target css is not at the top of the hierarchy. freezer, cpuset, cpu, cpuacct, hugetlb, memory, net_cls and devices are converted to use css_parent() instead of accessing cgroup->parent directly. * __parent_ca() is dropped from cpuacct and its usage is replaced with parent_ca(). The only difference between the two was NULL test on cgroup->parent which is now embedded in css_parent() making the distinction moot. Note that eventually a css->parent field will be added to css and the NULL check in css_parent() will go away. This patch shouldn't cause any behavior differences. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'include/linux/cgroup.h')
-rw-r--r--include/linux/cgroup.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 821678aae4db..18112a3bb12b 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -647,6 +647,21 @@ struct cgroup_subsys {
#undef SUBSYS
/**
+ * css_parent - find the parent css
+ * @css: the target cgroup_subsys_state
+ *
+ * Return the parent css of @css. This function is guaranteed to return
+ * non-NULL parent as long as @css isn't the root.
+ */
+static inline
+struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
+{
+ struct cgroup *parent_cgrp = css->cgroup->parent;
+
+ return parent_cgrp ? parent_cgrp->subsys[css->ss->subsys_id] : NULL;
+}
+
+/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
* @subsys_id: the subsystem of interest