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-rw-r--r--kernel/cgroup.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 65b72d0367c5..7bf3ce09c50c 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 */