[PATCH 0/2] don't call io scheduler callbacks for passthrough requests

From: Niklas Cassel <Niklas.Cassel@wdc.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Bart Van Assche <bvanassche@acm.org>,
	Damien Le Moal <Damien.LeMoal@wdc.com>,
	Paolo Valente <paolo.valente@linaro.org>,
	Ming Lei <ming.lei@redhat.com>,
	Niklas Cassel <Niklas.Cassel@wdc.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH 0/2] don't call io scheduler callbacks for passthrough requests
Date: Tue, 7 Sep 2021 14:21:54 +0000	[thread overview]
Message-ID: <20210907142145.112096-1-Niklas.Cassel@wdc.com> (raw)

From: Niklas Cassel <niklas.cassel@wdc.com>

Recently, there were some extra "dummy" data added into mq-deadline
rq->elv.priv, that was added for the solve purpose of working around
quirky behavior in blk-mq (which called the scheduler callbacks even
for requests that bypassed the scheduler).

Fix blk-mq to not call the I/O scheduler callbacks for passthrough requests,
since they will later bypass the I/O scheduler anyway.

This way, we can remove unnecessary logic in mq-deadline that was added to
deal with this quirky behavior.

BFQ should be able to perform a similar cleanup, if they wish, and should
then be able to drop this comment from the code:
https://github.com/torvalds/linux/blob/v5.14/block/bfq-iosched.c#L6456-L6462

Considering that I'm quite unfamiliar with the BFQ code, I'd rather
someone who is a bit more familiar with BFQ performs that cleanup.

Kind regards,
Niklas

Niklas Cassel (2):
  blk-mq: don't call callbacks for requests that bypassed the scheduler
  Revert "mq-deadline: Fix request accounting"

 block/blk-mq.c      |  7 ++++++-
 block/mq-deadline.c | 16 +++++-----------
 2 files changed, 11 insertions(+), 12 deletions(-)

-- 
2.31.1