linux-kernel - [PATCH v2] blk-mq: put the reference of the io scheduler module after switching back

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Message-ID: <OS0P286MB0338E8D41770BFDE7B3A4EBBBE229@OS0P286MB0338.JPNP286.PROD.OUTLOOK.COM>
Date:   Wed, 12 Oct 2022 08:35:12 +0800
From:   Jinlong Chen <chenjinlong2016@...look.com>
To:     axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jinlong Chen <chenjinlong2016@...look.com>
Subject: [PATCH v2] blk-mq: put the reference of the io scheduler module after switching back

We got a reference of the io scheduler module in
blk_mq_elv_switch_none to prevent the module from
being removed. We need to put that reference back
once we are done.

Signed-off-by: Jinlong Chen <chenjinlong2016@...look.com>
---
---
Changes in v2:
 - reword the commit message because the patch is for blk-mq precisely 

 block/blk-mq.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8070b6c10e8d..8dfe3bf3e599 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4595,6 +4595,13 @@ static void blk_mq_elv_switch_back(struct list_head *head,
 
 	mutex_lock(&q->sysfs_lock);
 	elevator_switch(q, t);
+	/**
+	 * We got a reference of the io scheduler module in
+	 * blk_mq_elv_switch_none to prevent the module from
+	 * being removed. We need to put that reference back
+	 * once we are done.
+	 */
+	module_put(t->elevator_owner);
 	mutex_unlock(&q->sysfs_lock);
 }
 
-- 
2.34.1