Merge tag 'for-4.19/post-20180822' of git://git.kernel.dk/linux-block

Pull more block updates from Jens Axboe:

 - Set of bcache fixes and changes (Coly)

 - The flush warn fix (me)

 - Small series of BFQ fixes (Paolo)

 - wbt hang fix (Ming)

 - blktrace fix (Steven)

 - blk-mq hardware queue count update fix (Jianchao)

 - Various little fixes

* tag 'for-4.19/post-20180822' of git://git.kernel.dk/linux-block: (31 commits)
  block/DAC960.c: make some arrays static const, shrinks object size
  blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter
  blk-mq: init hctx sched after update ctx and hctx mapping
  block: remove duplicate initialization
  tracing/blktrace: Fix to allow setting same value
  pktcdvd: fix setting of 'ret' error return for a few cases
  block: change return type to bool
  block, bfq: return nbytes and not zero from struct cftype .write() method
  block, bfq: improve code of bfq_bfqq_charge_time
  block, bfq: reduce write overcharge
  block, bfq: always update the budget of an entity when needed
  block, bfq: readd missing reset of parent-entity service
  blk-wbt: fix IO hang in wbt_wait()
  block: don't warn for flush on read-only device
  bcache: add the missing comments for smp_mb()/smp_wmb()
  bcache: remove unnecessary space before ioctl function pointer arguments
  bcache: add missing SPDX header
  bcache: move open brace at end of function definitions to next line
  bcache: add static const prefix to char * array declarations
  bcache: fix code comments style
  ...

1 files changed, 12 insertions, 8 deletions

diff --git a/block/elevator.c b/block/elevator.c
index fa828b5bfd4b..5ea6e7d600e4 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -933,16 +933,13 @@ void elv_unregister(struct elevator_type *e)
 }
 EXPORT_SYMBOL_GPL(elv_unregister);
 
-static int elevator_switch_mq(struct request_queue *q,
+int elevator_switch_mq(struct request_queue *q,
 			      struct elevator_type *new_e)
 {
 	int ret;
 
 	lockdep_assert_held(&q->sysfs_lock);
 
-	blk_mq_freeze_queue(q);
-	blk_mq_quiesce_queue(q);
-
 	if (q->elevator) {
 		if (q->elevator->registered)
 			elv_unregister_queue(q);
@@ -968,8 +965,6 @@ static int elevator_switch_mq(struct request_queue *q,
 		blk_add_trace_msg(q, "elv switch: none");
 
 out:
-	blk_mq_unquiesce_queue(q);
-	blk_mq_unfreeze_queue(q);
 	return ret;
 }
 
@@ -1021,8 +1016,17 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 
 	lockdep_assert_held(&q->sysfs_lock);
 
-	if (q->mq_ops)
-		return elevator_switch_mq(q, new_e);
+	if (q->mq_ops) {
+		blk_mq_freeze_queue(q);
+		blk_mq_quiesce_queue(q);
+
+		err = elevator_switch_mq(q, new_e);
+
+		blk_mq_unquiesce_queue(q);
+		blk_mq_unfreeze_queue(q);
+
+		return err;
+	}
 
 	/*
 	 * Turn on BYPASS and drain all requests w/ elevator private data.