[PATCH V5 10/25] block: look up the elevator type in elevator_switch

[Ming Lei <ming.lei@xxxxxxxxxx>]

From: Christoph Hellwig <hch@xxxxxx>

That makes the function nicely self-contained and can be used
to avoid code duplication.

Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 block/blk-mq.c   |  2 +-
 block/blk.h      |  2 +-
 block/elevator.c | 18 ++++++++----------
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 240afa4c6ab3..20bf2d797bdf 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -5060,7 +5060,7 @@ static void blk_mq_elv_switch_back(struct list_head *head,
 	kfree(qe);
 
 	mutex_lock(&q->elevator_lock);
-	elevator_switch(q, t);
+	elevator_switch(q, t->elevator_name);
 	/* drop the reference acquired in blk_mq_elv_switch_none */
 	elevator_put(t);
 	mutex_unlock(&q->elevator_lock);
diff --git a/block/blk.h b/block/blk.h
index 328075787814..ac90a8c5a8cf 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -322,7 +322,7 @@ bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
 
 bool blk_insert_flush(struct request *rq);
 
-int elevator_switch(struct request_queue *q, struct elevator_type *new_e);
+int elevator_switch(struct request_queue *q, const char *name);
 void elevator_disable(struct request_queue *q);
 void elevator_exit(struct request_queue *q);
 int elv_register_queue(struct request_queue *q, bool uevent);
diff --git a/block/elevator.c b/block/elevator.c
index 2e18513dcd73..286d240a3aef 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -621,13 +621,18 @@ void elevator_init_mq(struct request_queue *q)
  * If switching fails, we are most likely running out of memory and not able
  * to restore the old io scheduler, so leaving the io scheduler being none.
  */
-int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
+int elevator_switch(struct request_queue *q, const char *name)
 {
+	struct elevator_type *new_e;
 	int ret;
 
 	WARN_ON_ONCE(q->mq_freeze_depth == 0);
 	lockdep_assert_held(&q->elevator_lock);
 
+	new_e = elevator_find_get(name);
+	if (!new_e)
+		return -EINVAL;
+
 	blk_mq_quiesce_queue(q);
 
 	if (q->elevator) {
@@ -654,6 +659,7 @@ int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 			new_e->elevator_name);
 	}
 
+	elevator_put(new_e);
 	return ret;
 }
 
@@ -679,9 +685,6 @@ void elevator_disable(struct request_queue *q)
  */
 static int elevator_change(struct request_queue *q, const char *elevator_name)
 {
-	struct elevator_type *e;
-	int ret;
-
 	/* Make sure queue is not in the middle of being removed */
 	if (!blk_queue_registered(q))
 		return -ENOENT;
@@ -695,12 +698,7 @@ static int elevator_change(struct request_queue *q, const char *elevator_name)
 	if (q->elevator && elevator_match(q->elevator->type, elevator_name))
 		return 0;
 
-	e = elevator_find_get(elevator_name);
-	if (!e)
-		return -EINVAL;
-	ret = elevator_switch(q, e);
-	elevator_put(e);
-	return ret;
+	return elevator_switch(q, elevator_name);
 }
 
 static void elv_iosched_load_module(char *elevator_name)
-- 
2.47.0