linux-kernel - [PATCH 4.18 017/145] block: Introduce blk_exit

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Message-Id: <20180907210904.966396533@linuxfoundation.org>
Date:   Fri,  7 Sep 2018 23:08:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bart Van Assche <bart.vanassche@....com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Christoph Hellwig <hch@....de>, Ming Lei <ming.lei@...hat.com>,
        Omar Sandoval <osandov@...com>,
        Alexandru Moise <00moses.alexander00@...il.com>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.18 017/145] block: Introduce blk_exit_queue()

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@....com>

commit 4cf6324b17e96b7b7ab4021c6929500934d46750 upstream.

This patch does not change any functionality.

Signed-off-by: Bart Van Assche <bart.vanassche@....com>
Reviewed-by: Johannes Thumshirn <jthumshirn@...e.de>
Cc: Christoph Hellwig <hch@....de>
Cc: Ming Lei <ming.lei@...hat.com>
Cc: Omar Sandoval <osandov@...com>
Cc: Alexandru Moise <00moses.alexander00@...il.com>
Cc: Joseph Qi <joseph.qi@...ux.alibaba.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-core.c |   54 ++++++++++++++++++++++++++++++------------------------
 block/blk.h      |    1 +
 2 files changed, 31 insertions(+), 24 deletions(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -715,6 +715,35 @@ void blk_set_queue_dying(struct request_
 }
 EXPORT_SYMBOL_GPL(blk_set_queue_dying);
 
+/* Unconfigure the I/O scheduler and dissociate from the cgroup controller. */
+void blk_exit_queue(struct request_queue *q)
+{
+	/*
+	 * Since the I/O scheduler exit code may access cgroup information,
+	 * perform I/O scheduler exit before disassociating from the block
+	 * cgroup controller.
+	 */
+	if (q->elevator) {
+		ioc_clear_queue(q);
+		elevator_exit(q, q->elevator);
+		q->elevator = NULL;
+	}
+
+	/*
+	 * Remove all references to @q from the block cgroup controller before
+	 * restoring @q->queue_lock to avoid that restoring this pointer causes
+	 * e.g. blkcg_print_blkgs() to crash.
+	 */
+	blkcg_exit_queue(q);
+
+	/*
+	 * Since the cgroup code may dereference the @q->backing_dev_info
+	 * pointer, only decrease its reference count after having removed the
+	 * association with the block cgroup controller.
+	 */
+	bdi_put(q->backing_dev_info);
+}
+
 /**
  * blk_cleanup_queue - shutdown a request queue
  * @q: request queue to shutdown
@@ -780,30 +809,7 @@ void blk_cleanup_queue(struct request_qu
 	 */
 	WARN_ON_ONCE(q->kobj.state_in_sysfs);
 
-	/*
-	 * Since the I/O scheduler exit code may access cgroup information,
-	 * perform I/O scheduler exit before disassociating from the block
-	 * cgroup controller.
-	 */
-	if (q->elevator) {
-		ioc_clear_queue(q);
-		elevator_exit(q, q->elevator);
-		q->elevator = NULL;
-	}
-
-	/*
-	 * Remove all references to @q from the block cgroup controller before
-	 * restoring @q->queue_lock to avoid that restoring this pointer causes
-	 * e.g. blkcg_print_blkgs() to crash.
-	 */
-	blkcg_exit_queue(q);
-
-	/*
-	 * Since the cgroup code may dereference the @q->backing_dev_info
-	 * pointer, only decrease its reference count after having removed the
-	 * association with the block cgroup controller.
-	 */
-	bdi_put(q->backing_dev_info);
+	blk_exit_queue(q);
 
 	if (q->mq_ops)
 		blk_mq_free_queue(q);
--- a/block/blk.h
+++ b/block/blk.h
@@ -130,6 +130,7 @@ void blk_free_flush_queue(struct blk_flu
 int blk_init_rl(struct request_list *rl, struct request_queue *q,
 		gfp_t gfp_mask);
 void blk_exit_rl(struct request_queue *q, struct request_list *rl);
+void blk_exit_queue(struct request_queue *q);
 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 			struct bio *bio);
 void blk_queue_bypass_start(struct request_queue *q);