Re: [PATCH] block: don't call rq_qos_ops->done_bio if the bio isn't tracked

[Tejun Heo <tj@kernel.org>]

On Fri, Sep 24, 2021 at 07:07:04PM +0800, Ming Lei wrote:
> 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>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun