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authorTejun Heo <tj@kernel.org>2013-08-08 20:11:23 -0400
committerTejun Heo <tj@kernel.org>2013-08-08 20:11:23 -0400
commit6387698699afd72d6304566fb6ccf84bffe07c56 (patch)
tree9440e96fa8e5adce62409a5b0e40984dfedaada3 /block
parenta7c6d554aa01236ac2a9f851ab0f75704f76dfa2 (diff)
downloadlinux-linaro-stable-6387698699afd72d6304566fb6ccf84bffe07c56.tar.gz
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 'block')
-rw-r--r--block/blk-cgroup.h4
1 files changed, 1 insertions, 3 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 8e5863e900bf..b6802c46d68f 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -209,9 +209,7 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
*/
static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
{
- struct cgroup *pcg = blkcg->css.cgroup->parent;
-
- return pcg ? cgroup_to_blkcg(pcg) : NULL;
+ return css_to_blkcg(css_parent(&blkcg->css));
}
/**