[PATCH] block: Remove redundant hctx pointer dereferencing operation

[PATCH] block: Remove redundant hctx pointer dereferencing operation

[chengkaitao]

From: Chengkaitao <chengkaitao@kylinos.cn>

The {*q = hctx->queue} statement in the dd_insert_requestfunction is
redundant. This patch removes the operation and modifies the function's
formal parameters accordingly. To maintain code formatting consistency,
similar modifications are applied to bfq_insert_request. Changing both
functions' parameters to request_queue also improves logical consistency.

Signed-off-by: Chengkaitao <chengkaitao@kylinos.cn>
---
 block/bfq-iosched.c | 5 ++---
 block/mq-deadline.c | 5 ++---
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 50e51047e1fe..b0e2fe645c3e 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -6233,10 +6233,9 @@ static inline void bfq_update_insert_stats(struct request_queue *q,
 
 static struct bfq_queue *bfq_init_rq(struct request *rq);
 
-static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
+static void bfq_insert_request(struct request_queue *q, struct request *rq,
 			       blk_insert_t flags)
 {
-	struct request_queue *q = hctx->queue;
 	struct bfq_data *bfqd = q->elevator->elevator_data;
 	struct bfq_queue *bfqq;
 	bool idle_timer_disabled = false;
@@ -6298,7 +6297,7 @@ static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
 
 		rq = list_first_entry(list, struct request, queuelist);
 		list_del_init(&rq->queuelist);
-		bfq_insert_request(hctx, rq, flags);
+		bfq_insert_request(hctx->queue, rq, flags);
 	}
 }
 
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index b9b7cdf1d3c9..86b888681552 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -646,10 +646,9 @@ static bool dd_bio_merge(struct request_queue *q, struct bio *bio,
 /*
  * add rq to rbtree and fifo
  */
-static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
+static void dd_insert_request(struct request_queue *q, struct request *rq,
 			      blk_insert_t flags, struct list_head *free)
 {
-	struct request_queue *q = hctx->queue;
 	struct deadline_data *dd = q->elevator->elevator_data;
 	const enum dd_data_dir data_dir = rq_data_dir(rq);
 	u16 ioprio = req_get_ioprio(rq);
@@ -707,7 +706,7 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
 
 		rq = list_first_entry(list, struct request, queuelist);
 		list_del_init(&rq->queuelist);
-		dd_insert_request(hctx, rq, flags, &free);
+		dd_insert_request(q, rq, flags, &free);
 	}
 	spin_unlock(&dd->lock);
 
-- 
2.50.1 (Apple Git-155)

Re: [PATCH] block: Remove redundant hctx pointer dereferencing operation

[Christoph Hellwig]

On Thu, Oct 16, 2025 at 09:16:51PM +0800, chengkaitao wrote:
> From: Chengkaitao <chengkaitao@kylinos.cn>
> 
> The {*q = hctx->queue} statement in the dd_insert_requestfunction is
> redundant. This patch removes the operation and modifies the function's
> formal parameters accordingly.

What formal parameters?

Basically you're passing a pointless extra argument instead of deriving
it locally.  Why would you do that?

Re: [PATCH] block: Remove redundant hctx pointer dereferencing operation

[Tao pilgrim]

On Fri, Oct 17, 2025 at 2:27 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Thu, Oct 16, 2025 at 09:16:51PM +0800, chengkaitao wrote:
> > From: Chengkaitao <chengkaitao@kylinos.cn>
> >
> > The {*q = hctx->queue} statement in the dd_insert_requestfunction is
> > redundant. This patch removes the operation and modifies the function's
> > formal parameters accordingly.
>
> What formal parameters?
>
> Basically you're passing a pointless extra argument instead of deriving
> it locally.  Why would you do that?

The value of 'hctx->queue' is already stored in '*q' within dd_insert_requests,
we can directly reuse the result instead of dereferencing hctx again in the
dd_insert_request function. We can eliminate an LDR instruction.
-- 
Yours,
Kaitao Cheng