cgroup/rstat: check updated_next only for root
After commit dc26532aed0a ("cgroup: rstat: punt root-level optimization to
individual controllers"), each rstat on updated_children list has its
->updated_next not NULL.
This means we can remove the check on ->updated_next, if we make sure
the subtree from @root is on list, which could be done by checking
updated_next for root.
tj: Coding style fixes.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index bc69932..9d331ba 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -88,6 +88,7 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
struct cgroup *root, int cpu)
{
struct cgroup_rstat_cpu *rstatc;
+ struct cgroup *parent;
if (pos == root)
return NULL;
@@ -96,10 +97,14 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
* We're gonna walk down to the first leaf and visit/remove it. We
* can pick whatever unvisited node as the starting point.
*/
- if (!pos)
+ if (!pos) {
pos = root;
- else
+ /* return NULL if this subtree is not on-list */
+ if (!cgroup_rstat_cpu(pos, cpu)->updated_next)
+ return NULL;
+ } else {
pos = cgroup_parent(pos);
+ }
/* walk down to the first leaf */
while (true) {
@@ -115,31 +120,25 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
* However, due to the way we traverse, @pos will be the first
* child in most cases. The only exception is @root.
*/
- if (rstatc->updated_next) {
- struct cgroup *parent = cgroup_parent(pos);
+ parent = cgroup_parent(pos);
+ if (parent) {
+ struct cgroup_rstat_cpu *prstatc;
+ struct cgroup **nextp;
- if (parent) {
- struct cgroup_rstat_cpu *prstatc;
- struct cgroup **nextp;
+ prstatc = cgroup_rstat_cpu(parent, cpu);
+ nextp = &prstatc->updated_children;
+ while (*nextp != pos) {
+ struct cgroup_rstat_cpu *nrstatc;
- prstatc = cgroup_rstat_cpu(parent, cpu);
- nextp = &prstatc->updated_children;
- while (*nextp != pos) {
- struct cgroup_rstat_cpu *nrstatc;
-
- nrstatc = cgroup_rstat_cpu(*nextp, cpu);
- WARN_ON_ONCE(*nextp == parent);
- nextp = &nrstatc->updated_next;
- }
- *nextp = rstatc->updated_next;
+ nrstatc = cgroup_rstat_cpu(*nextp, cpu);
+ WARN_ON_ONCE(*nextp == parent);
+ nextp = &nrstatc->updated_next;
}
-
- rstatc->updated_next = NULL;
- return pos;
+ *nextp = rstatc->updated_next;
}
- /* only happens for @root */
- return NULL;
+ rstatc->updated_next = NULL;
+ return pos;
}
/* see cgroup_rstat_flush() */