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-rw-r--r--block/blk-cgroup.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 4c94a6560f62..9ac1efb053e0 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -2001,6 +2001,10 @@ void blk_cgroup_bio_start(struct bio *bio)
struct blkg_iostat_set *bis;
unsigned long flags;
+ /* Root-level stats are sourced from system-wide IO stats */
+ if (!cgroup_parent(blkcg->css.cgroup))
+ return;
+
cpu = get_cpu();
bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
flags = u64_stats_update_begin_irqsave(&bis->sync);