[PATCH v2 4/5] scsi: core: Only kick the requeue list if necessary

[Bart Van Assche <bvanassche@xxxxxxx>]

Instead of running the request queue of each device associated with a
host every 3 ms (BLK_MQ_RESOURCE_DELAY) while host error handling is in
progress, run the request queue after error handling has finished.

Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: John Garry <john.g.garry@xxxxxxxxxx>
Cc: Mike Christie <michael.christie@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 drivers/scsi/scsi_lib.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e59eb0cbfc83..a34390d35f1d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -122,11 +122,9 @@ static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd, unsigned long msecs)
 		WARN_ON_ONCE(true);
 	}
 
-	if (msecs) {
-		blk_mq_requeue_request(rq, false);
+	blk_mq_requeue_request(rq, false);
+	if (!scsi_host_in_recovery(cmd->device->host))
 		blk_mq_delay_kick_requeue_list(rq->q, msecs);
-	} else
-		blk_mq_requeue_request(rq, true);
 }
 
 /**
@@ -165,7 +163,8 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
 	 */
 	cmd->result = 0;
 
-	blk_mq_requeue_request(scsi_cmd_to_rq(cmd), true);
+	blk_mq_requeue_request(scsi_cmd_to_rq(cmd),
+			       !scsi_host_in_recovery(cmd->device->host));
 }
 
 /**
@@ -462,10 +461,16 @@ void scsi_requeue_run_queue(struct work_struct *work)
 	scsi_run_queue(q);
 }
 
+/*
+ * Transfer requests from the requeue_list to from where these can be dispatched
+ * and run the request queues.
+ */
 void scsi_run_host_queues(struct Scsi_Host *shost)
 {
 	struct scsi_device *sdev;
 
+	shost_for_each_device(sdev, shost)
+		blk_mq_kick_requeue_list(sdev->request_queue);
 	shost_for_each_device(sdev, shost)
 		scsi_run_queue(sdev->request_queue);
 }
@@ -499,6 +504,9 @@ static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
 
 static void scsi_run_queue_async(struct scsi_device *sdev)
 {
+	if (scsi_host_in_recovery(sdev->host))
+		return;
+
 	if (scsi_target(sdev)->single_lun ||
 	    !list_empty(&sdev->host->starved_list)) {
 		kblockd_schedule_work(&sdev->requeue_work);