Re: [PATCH 2/2] Revert "mq-deadline: Fix request accounting"

From: Bart Van Assche
Date: Tue Sep 07 2021 - 10:54:18 EST


On 9/7/21 7:21 AM, Niklas Cassel wrote:
From: Niklas Cassel <niklas.cassel@xxxxxxx>

This reverts commit b6d2b054e8baaee53fd2d4854c63cbf0f2c6262a.

blk-mq will no longer call the I/O scheduler .finish_request() callback
for requests that were never inserted to the I/O scheduler.

Therefore, we can remove the logic inside mq-deadline that was added to
workaround the (no longer existing) quirky behavior of blk-mq.

Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
---
block/mq-deadline.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 7f3c3932b723..b2d1e3adcb39 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -678,7 +678,6 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
prio = ioprio_class_to_prio[ioprio_class];
dd_count(dd, inserted, prio);
- rq->elv.priv[0] = (void *)(uintptr_t)1;
if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
blk_mq_free_requests(&free);
@@ -727,10 +726,12 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
spin_unlock(&dd->lock);
}
-/* Callback from inside blk_mq_rq_ctx_init(). */
+/*
+ * Nothing to do here. This is defined only to ensure that .finish_request
+ * method is called upon request completion.
+ */
static void dd_prepare_request(struct request *rq)
{
- rq->elv.priv[0] = NULL;
}

Please take a look at
https://lore.kernel.org/linux-block/18594aff-4a94-8a48-334c-f21ae32120c6@xxxxxxx/
If dd_prepare_request() is removed I will have to reintroduce it.

Thanks,

Bart.