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    Subject[PATCH 5.14 37/48] block: dont call rq_qos_ops->done_bio if the bio isnt tracked
    Date
    From: Ming Lei <ming.lei@redhat.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@huawei.com>
    Cc: tj@kernel.org
    Signed-off-by: Ming Lei <ming.lei@redhat.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Acked-by: Tejun Heo <tj@kernel.org>
    Link: https://lore.kernel.org/r/20210924110704.1541818-1-ming.lei@redhat.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.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 @@ again:
    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


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