linux-kernel - [PATCH 2/3] block, bfq: convert to use ioc_lookup_icq

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Message-Id: <20250725070547.3953398-3-yukuai1@huaweicloud.com>
Date: Fri, 25 Jul 2025 15:05:46 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: jack@...e.cz,
	dlemoal@...nel.org,
	axboe@...nel.dk
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH 2/3] block, bfq: convert to use ioc_lookup_icq_rcu()

From: Yu Kuai <yukuai3@...wei.com>

ioc_lookup_icq() are all called from IO issue path with queue_lock held,
convert to use ioc_lookup_icq_rcu() to get rid of the disk level spin
lock.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/bfq-iosched.c | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 0cb1e9873aab..b3b9dbbc16d2 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -454,17 +454,13 @@ static struct bfq_io_cq *icq_to_bic(struct io_cq *icq)
  */
 static struct bfq_io_cq *bfq_bic_lookup(struct request_queue *q)
 {
-	struct bfq_io_cq *icq;
-	unsigned long flags;
-
-	if (!current->io_context)
-		return NULL;
+	struct io_cq *icq;
 
-	spin_lock_irqsave(&q->queue_lock, flags);
-	icq = icq_to_bic(ioc_lookup_icq(q));
-	spin_unlock_irqrestore(&q->queue_lock, flags);
+	rcu_read_lock();
+	icq = ioc_lookup_icq_rcu(q);
+	rcu_read_unlock();
 
-	return icq;
+	return icq_to_bic(icq);
 }
 
 /*
@@ -2457,15 +2453,8 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs)
 {
 	struct bfq_data *bfqd = q->elevator->elevator_data;
-	struct request *free = NULL;
-	/*
-	 * bfq_bic_lookup grabs the queue_lock: invoke it now and
-	 * store its return value for later use, to avoid nesting
-	 * queue_lock inside the bfqd->lock. We assume that the bic
-	 * returned by bfq_bic_lookup does not go away before
-	 * bfqd->lock is taken.
-	 */
 	struct bfq_io_cq *bic = bfq_bic_lookup(q);
+	struct request *free = NULL;
 	bool ret;
 
 	spin_lock_irq(&bfqd->lock);
-- 
2.39.2