cgroup: convert cgroup_next_sibling() to cgroup_next_child()

cgroup is transitioning to using css (cgroup_subsys_state) as the main
subsys interface handle instead of cgroup and the iterators will be
updated to use css too.  The iterators need to walk the cgroup
hierarchy and return the css's matching the origin css, which is a bit
cumbersome to open code.

This patch converts cgroup_next_sibling() to cgroup_next_child() so
that it can handle all steps of direct child iteration.  This will be
used to update iterators to take @css instead of @cgrp.  In addition
to the new iteration init handling, cgroup_next_child() is
restructured so that the different branches share the end of iteration
condition check.

This patch doesn't change any behavior.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 0b91436c68ef..5f9ba5881717 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -779,7 +779,7 @@ static inline struct cgroup *cgroup_from_id(struct cgroup_subsys *ss, int id)
 	return idr_find(&ss->root->cgroup_idr, id);
 }
 
-struct cgroup *cgroup_next_sibling(struct cgroup *pos);
+struct cgroup *cgroup_next_child(struct cgroup *pos, struct cgroup *cgrp);
 
 /**
  * cgroup_for_each_child - iterate through children of a cgroup
@@ -802,7 +802,7 @@ struct cgroup *cgroup_next_sibling(struct cgroup *pos);
 #define cgroup_for_each_child(pos, cgrp)				\
 	for ((pos) = list_first_or_null_rcu(&(cgrp)->children,		\
 					    struct cgroup, sibling);	\
-	     (pos); (pos) = cgroup_next_sibling((pos)))
+	     (pos); (pos) = cgroup_next_child((pos), (cgrp)))
 
 struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
 					  struct cgroup *cgroup);