[PATCH AUTOSEL 5.14 38/40] block: don't call rq_qos_ops->done_bio if the bio isn't tracked

From: Sasha Levin
Date: Tue Sep 28 2021 - 01:58:47 EST

From: Ming Lei <ming.lei@xxxxxxxxxx>

[ 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

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

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@xxxxxxxxxx>
Cc: tj@xxxxxxxxxx
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210924110704.1541818-1-ming.lei@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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))

- 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)) {