[PATCH] blk-cgroup: don't account iostat for root cgroup

[Boris Burkov]

This data is never flushed by rstat, so it is never used. We shouldn't
bother collecting it. We can access global disk stats to compute io
statistics for the root cgroup.

Signed-off-by: Boris Burkov <boris@xxxxxx>
---
 include/linux/blk-cgroup.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index a57ebe2f00ab..e9de4ec07182 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -591,7 +591,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,
 
 	throtl = blk_throtl_bio(q, blkg, bio);
 
-	if (!throtl) {
+	if (blkg->parent && !throtl) {
 		struct blkg_iostat_set *bis;
 		int rwd, cpu;
 
-- 
2.24.1