diff options
| author | Li Zefan <lizefan@huawei.com> | 2013-04-08 19:00:38 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2013-04-10 11:07:08 -0700 |
| commit | 78574cf981cd3d9ae9f6adbd466a772310ec24ff (patch) | |
| tree | 50e9da6e2e201663a22e02240d927592e893780d | |
| parent | 415cf07a1c1c65249773330434878ae7bcd92d0f (diff) | |
cgroup: implement cgroup_is_descendant()
A couple controllers want to determine whether two cgroups are in
ancestor/descendant relationship. As it's more likely that the
descendant is the primary subject of interest and there are other
operations focusing on the descendants, let's ask is_descendent rather
than is_ancestor.
Implementation is trivial as the previous patch guarantees that all
ancestors of a cgroup stay accessible as long as the cgroup is
accessible.
tj: Removed depth optimization, renamed from cgroup_is_ancestor(),
rewrote descriptions.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | include/linux/cgroup.h | 1 | ||||
| -rw-r--r-- | kernel/cgroup.c | 20 |
2 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 92acf8601ae..a2b9d4b1336 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -439,6 +439,7 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); int cgroup_is_removed(const struct cgroup *cgrp); +bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor); int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 65b72d0367c..7bf3ce09c50 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -276,6 +276,26 @@ inline int cgroup_is_removed(const struct cgroup *cgrp) return test_bit(CGRP_REMOVED, &cgrp->flags); } +/** + * cgroup_is_descendant - test ancestry + * @cgrp: the cgroup to be tested + * @ancestor: possible ancestor of @cgrp + * + * Test whether @cgrp is a descendant of @ancestor. It also returns %true + * if @cgrp == @ancestor. This function is safe to call as long as @cgrp + * and @ancestor are accessible. + */ +bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor) +{ + while (cgrp) { + if (cgrp == ancestor) + return true; + cgrp = cgrp->parent; + } + return false; +} +EXPORT_SYMBOL_GPL(cgroup_is_descendant); + /* bits in struct cgroupfs_root flags field */ enum { ROOT_NOPREFIX, /* mounted subsystems have no named prefix */ |