Re: [PATCH block-5.17] fix rq-qos breakage from skipping rq_qos_done_bio()

From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>, Yu Kuai <yukuai3@huawei.com>,
	kernel-team@fb.com,
	Christopher Obbard <chris.obbard@collabora.com>,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	Saravanan D <saravanand@fb.com>
Subject: Re: [PATCH block-5.17] fix rq-qos breakage from skipping rq_qos_done_bio()
Date: Mon, 14 Mar 2022 14:23:57 -0600	[thread overview]
Message-ID: <164728943786.144850.10059816217572335500.b4-ty@kernel.dk> (raw)
In-Reply-To: <Yi7rdrzQEHjJLGKB@slm.duckdns.org>

On Sun, 13 Mar 2022 21:15:02 -1000, Tejun Heo wrote:
> a647a524a467 ("block: don't call rq_qos_ops->done_bio if the bio isn't
> tracked") made bio_endio() skip rq_qos_done_bio() if BIO_TRACKED is not set.
> While this fixed a potential oops, it also broke blk-iocost by skipping the
> done_bio callback for merged bios.
> 
> Before, whether a bio goes through rq_qos_throttle() or rq_qos_merge(),
> rq_qos_done_bio() would be called on the bio on completion with BIO_TRACKED
> distinguishing the former from the latter. rq_qos_done_bio() is not called
> for bios which wenth through rq_qos_merge(). This royally confuses
> blk-iocost as the merged bios never finish and are considered perpetually
> in-flight.
> 
> [...]

Applied, thanks!

[1/1] fix rq-qos breakage from skipping rq_qos_done_bio()
      (no commit info)

Best regards,
-- 
Jens Axboe