linux-kernel - [PATCH AUTOSEL 5.14 38/40] block: don't call rq_qos_ops->done

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Message-Id: <20210928055524.172051-38-sashal@kernel.org>
Date:   Tue, 28 Sep 2021 01:55:22 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ming Lei <ming.lei@...hat.com>, Yu Kuai <yukuai3@...wei.com>,
        tj@...nel.org, Christoph Hellwig <hch@....de>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.14 38/40] block: don't call rq_qos_ops->done_bio if the bio isn't tracked

From: Ming Lei <ming.lei@...hat.com>

[ Upstream commit a647a524a46736786c95cdb553a070322ca096e3 ]

rq_qos framework is only applied on request based driver, so:

1) rq_qos_done_bio() needn't to be called for bio based driver

2) rq_qos_done_bio() needn't to be called for bio which isn't tracked,
such as bios ended from error handling code.

Especially in bio_endio():

1) request queue is referred via bio->bi_bdev->bd_disk->queue, which
may be gone since request queue refcount may not be held in above two
cases

2) q->rq_qos may be freed in blk_cleanup_queue() when calling into
__rq_qos_done_bio()

Fix the potential kernel panic by not calling rq_qos_ops->done_bio if
the bio isn't tracked. This way is safe because both ioc_rqos_done_bio()
and blkcg_iolatency_done_bio() are nop if the bio isn't tracked.

Reported-by: Yu Kuai <yukuai3@...wei.com>
Cc: tj@...nel.org
Signed-off-by: Ming Lei <ming.lei@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Acked-by: Tejun Heo <tj@...nel.org>
Link: https://lore.kernel.org/r/20210924110704.1541818-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 block/bio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index d95e3456ba0c..52548c487883 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1396,7 +1396,7 @@ void bio_endio(struct bio *bio)
 	if (!bio_integrity_endio(bio))
 		return;
 
-	if (bio->bi_bdev)
+	if (bio->bi_bdev && bio_flagged(bio, BIO_TRACKED))
 		rq_qos_done_bio(bio->bi_bdev->bd_disk->queue, bio);
 
 	if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
-- 
2.33.0