linux-kernel - [PATCH] blk-throtl: avoid double charge of bio IOPS due to split

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Date:   Mon, 10 Jan 2022 16:29:23 +0800
From:   brookxu <brookxu.cn@...il.com>
To:     tj@...nel.org, axboe@...nel.dk
Cc:     ming.lei@...hat.com, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] blk-throtl: avoid double charge of bio IOPS due to split

From: Chunguang Xu <brookxu@...cent.com>

After commit 900e08075202("block: move queue enter logic into
blk_mq_submit_bio()"), submit_bio_checks() moved to __submit_bio_fops()
and blk_mq_submit_bio(). The IOs go through blk_mq_submit_bio()
may be splited before entering blk-throtl, so we need to check
whether the BIO is throttled, and only update the io_split_cnt
for the THROTTLED bio to avoid double charge.

Signed-off-by: Chunguang Xu <brookxu@...cent.com>
---
 block/blk-throttle.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 39bb6e6..2b12fc7 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2049,6 +2049,9 @@ void blk_throtl_charge_bio_split(struct bio *bio)
 	struct throtl_service_queue *parent_sq;
 	bool rw = bio_data_dir(bio);
 
+	if (!bio_flagged(bio, BIO_THROTTLED))
+		return;
+
 	do {
 		if (!parent->has_rules[rw])
 			break;
-- 
1.8.3.1