[7/7] block: split elevator_switch

Commit Message

Christoph Hellwig Oct. 30, 2022, 10:07 a.m. UTC

Split an elevator_disable helper from elevator_switch for the case where
we want to switch to no scheduler at all.  This includes removing the
pointless elevator_switch_mq helper and removing the switch to no
schedule logic from blk_mq_init_sched.

Signed-off-by: Christoph Hellwig <[e-mail]>
---
 block/blk-mq-sched.c |  7 ----
 block/blk-mq.c       |  2 +-
 block/blk.h          |  1 +
 block/elevator.c     | 77 ++++++++++++++++++++++----------------------
 4 files changed, 40 insertions(+), 47 deletions(-)

Patch

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 68227240fdea3..23d1a90fec427 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -564,13 +564,6 @@  int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 	unsigned long i;
 	int ret;
 
-	if (!e) {
-		blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
-		q->elevator = NULL;
-		q->nr_requests = q->tag_set->queue_depth;
-		return 0;
-	}
-
 	/*
 	 * Default to double of smaller one between hw queue_depth and 128,
 	 * since we don't split into sync/async like the old code did.
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 4cecf281123f6..1ebb2e68ac66f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4556,7 +4556,7 @@  static bool blk_mq_elv_switch_none(struct list_head *head,
 	__elevator_get(qe->type);
 	qe->type = q->elevator->type;
 	list_add(&qe->node, head);
-	elevator_switch(q, NULL);
+	elevator_disable(q);
 	mutex_unlock(&q->sysfs_lock);
 
 	return true;
diff --git a/block/blk.h b/block/blk.h
index 7f9e089ab1f75..f1398fb96cec9 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -278,6 +278,7 @@  bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
 void blk_insert_flush(struct request *rq);
 
 int elevator_switch(struct request_queue *q, struct elevator_type *new_e);
+void elevator_disable(struct request_queue *q);
 void elevator_exit(struct request_queue *q);
 int elv_register_queue(struct request_queue *q, bool uevent);
 void elv_unregister_queue(struct request_queue *q);
diff --git a/block/elevator.c b/block/elevator.c
index 4042e524333e0..6fdbfca1bc61e 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -548,39 +548,6 @@  void elv_unregister(struct elevator_type *e)
 }
 EXPORT_SYMBOL_GPL(elv_unregister);
 
-static int elevator_switch_mq(struct request_queue *q,
-			      struct elevator_type *new_e)
-{
-	int ret;
-
-	lockdep_assert_held(&q->sysfs_lock);
-
-	if (q->elevator) {
-		elv_unregister_queue(q);
-		elevator_exit(q);
-	}
-
-	ret = blk_mq_init_sched(q, new_e);
-	if (ret)
-		goto out;
-
-	if (new_e) {
-		ret = elv_register_queue(q, true);
-		if (ret) {
-			elevator_exit(q);
-			goto out;
-		}
-	}
-
-	if (new_e)
-		blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
-	else
-		blk_add_trace_msg(q, "elv switch: none");
-
-out:
-	return ret;
-}
-
 static inline bool elv_support_iosched(struct request_queue *q)
 {
 	if (!queue_is_mq(q) ||
@@ -685,19 +652,51 @@  void elevator_init_mq(struct request_queue *q)
  */
 int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 {
-	int err;
+	int ret;
 
 	lockdep_assert_held(&q->sysfs_lock);
 
 	blk_mq_freeze_queue(q);
 	blk_mq_quiesce_queue(q);
 
-	err = elevator_switch_mq(q, new_e);
+	if (q->elevator) {
+		elv_unregister_queue(q);
+		elevator_exit(q);
+	}
 
+	ret = blk_mq_init_sched(q, new_e);
+	if (ret)
+		goto out_unfreeze;
+
+	ret = elv_register_queue(q, true);
+	if (ret) {
+		elevator_exit(q);
+		goto out_unfreeze;
+	}
+	blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
+
+out_unfreeze:
 	blk_mq_unquiesce_queue(q);
 	blk_mq_unfreeze_queue(q);
+	return ret;
+}
+
+void elevator_disable(struct request_queue *q)
+{
+	lockdep_assert_held(&q->sysfs_lock);
 
-	return err;
+	blk_mq_freeze_queue(q);
+	blk_mq_quiesce_queue(q);
+
+	elv_unregister_queue(q);
+	elevator_exit(q);
+	blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
+	q->elevator = NULL;
+	q->nr_requests = q->tag_set->queue_depth;
+	blk_add_trace_msg(q, "elv switch: none");
+
+	blk_mq_unquiesce_queue(q);
+	blk_mq_unfreeze_queue(q);
 }
 
 /*
@@ -716,9 +715,9 @@  static int elevator_change(struct request_queue *q, const char *elevator_name)
 	 * Special case for mq, turn off scheduling
 	 */
 	if (!strncmp(elevator_name, "none", 4)) {
-		if (!q->elevator)
-			return 0;
-		return elevator_switch(q, NULL);
+		if (q->elevator)
+			elevator_disable(q);
+		return 0;
 	}
 
 	if (q->elevator && elevator_match(q->elevator->type, elevator_name))