[Devel] [PATCH vz9] blk-throttle: Fix io statistics for cgroup v1

[Alexander Atanasov]

From: Jinke Han <hanjinke.666 at bytedance.com>

After commit f382fb0bcef4 ("block: remove legacy IO schedulers"),
blkio.throttle.io_serviced and blkio.throttle.io_service_bytes become
the only stable io stats interface of cgroup v1, and these statistics
are done in the blk-throttle code. But the current code only counts the
bios that are actually throttled. When the user does not add the throttle
limit, the io stats for cgroup v1 has nothing. I fix it according to the
statistical method of v2, and made it count all ios accurately.

Fixes: a7b36ee6ba29 ("block: move blk-throtl fast path inline")
Tested-by: Andrea Righi <andrea.righi at canonical.com>
Signed-off-by: Jinke Han <hanjinke.666 at bytedance.com>
Acked-by: Muchun Song <songmuchun at bytedance.com>
Acked-by: Tejun Heo <tj at kernel.org>
Link: https://lore.kernel.org/r/20230507170631.89607-1-hanjinke.666@bytedance.com
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(cherry picked from commit ad7c3b41e86b59943a903d23c7b037d820e6270c)
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 block/blk-cgroup.c   | 6 ++++--
 block/blk-throttle.c | 6 ------
 block/blk-throttle.h | 9 +++++++++
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 30d9045805fd..28071357ce21 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1996,6 +1996,9 @@ void blk_cgroup_bio_start(struct bio *bio)
 	struct blkg_iostat_set *bis;
 	unsigned long flags;
 
+	if (!cgroup_subsys_on_dfl(io_cgrp_subsys))
+		return;
+
 	/* Root-level stats are sourced from system-wide IO stats */
 	if (!cgroup_parent(blkcg->css.cgroup))
 		return;
@@ -2027,8 +2030,7 @@ void blk_cgroup_bio_start(struct bio *bio)
 	}
 
 	u64_stats_update_end_irqrestore(&bis->sync, flags);
-	if (cgroup_subsys_on_dfl(io_cgrp_subsys))
-		cgroup_rstat_updated(blkcg->css.cgroup, cpu);
+	cgroup_rstat_updated(blkcg->css.cgroup, cpu);
 	put_cpu();
 }
 
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 847721dc2b2b..dde302231a7e 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2167,12 +2167,6 @@ bool __blk_throtl_bio(struct bio *bio)
 
 	rcu_read_lock();
 
-	if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
-		blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
-				bio->bi_iter.bi_size);
-		blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
-	}
-
 	spin_lock_irq(&q->queue_lock);
 
 	throtl_update_latency_buckets(td);
diff --git a/block/blk-throttle.h b/block/blk-throttle.h
index ef4b7a4de987..d1ccbfe9f797 100644
--- a/block/blk-throttle.h
+++ b/block/blk-throttle.h
@@ -185,6 +185,15 @@ static inline bool blk_should_throtl(struct bio *bio)
 	struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
 	int rw = bio_data_dir(bio);
 
+	if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
+		if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
+			bio_set_flag(bio, BIO_CGROUP_ACCT);
+			blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
+					bio->bi_iter.bi_size);
+		}
+		blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
+	}
+
 	/* iops limit is always counted */
 	if (tg->has_rules_iops[rw])
 		return true;
-- 
2.39.3