[PATCH 6.4 650/800] md/raid10: fix the condition to call bio_end_io_acct()

Greg Kroah-Hartman
2023-07-16T20:23:16Z

From: Li Nan <linan122@huawei.com>

[ Upstream commit 125bfc7cd750e68c99f1d446e2c22abea08c237f ]

/sys/block/[device]/queue/iostats is used to control whether to count io
stat. Write 0 to it will clear queue_flags QUEUE_FLAG_IO_STAT which means
iostats is disabled. If we disable iostats and later endable it, the io
issued during this period will be counted incorrectly, inflight will be
decreased to -1.

//T1 set iostats
echo 0 > /sys/block/md0/queue/iostats
clear QUEUE_FLAG_IO_STAT

//T2 issue io
if (QUEUE_FLAG_IO_STAT) -> false
bio_start_io_acct
inflight++

echo 1 > /sys/block/md0/queue/iostats
set QUEUE_FLAG_IO_STAT

//T3 io end
if (QUEUE_FLAG_IO_STAT) -> true
bio_end_io_acct
inflight-- -> -1

Also, if iostats is enabled while issuing io but disabled while io end,
inflight will never be decreased.

Fix it by checking start_time when io end. If start_time is not 0, call
bio_end_io_acct().

Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
Signed-off-by: Li Nan <linan122@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230609094320.2397604-1-linan666@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/raid10.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 9d11a52367d17..9d23963496194 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -325,7 +325,7 @@ static void raid_end_bio_io(struct r10bio *r10_bio)
if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
bio->bi_status = BLK_STS_IOERR;

- if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
+ if (r10_bio->start_time)
bio_end_io_acct(bio, r10_bio->start_time);
bio_endio(bio);
/*
--
2.39.2