Re: [PATCH v2 2/6] dm rq: add DM_MAPIO_DELAY_REQUEUE to delay requeue of blk-mq requests

Otherwise blk-mq will immediately dispatch requests that are requeued
via a BLK_MQ_RQ_QUEUE_BUSY return from blk_mq_ops .queue_rq.

Delayed requeue is implemented using blk_mq_delay_kick_requeue_list()
with a delay of 5 secs.  In the context of DM multipath (all paths down)
it doesn't make any sense to requeue more quickly.

Signed-off-by: Mike Snitzer <redacted>
---
 drivers/md/dm-rq.c            | 32 ++++++++++++++++++--------------
 include/linux/device-mapper.h |  1 +
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 0d301d5..9eebc8d 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c

@@ -671,7 +673,10 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq,
 		break;
 	case DM_MAPIO_REQUEUE:
 		/* The target wants to requeue the I/O */
-		dm_requeue_original_request(md, tio->orig);
+		break;
+	case DM_MAPIO_DELAY_REQUEUE:
+		/* The target wants to requeue the I/O after a delay */
+		dm_requeue_original_request(md, tio->orig, true);
 		break;
 	default:
 		if (r > 0) {

@@ -681,10 +686,9 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq,
 
 		/* The target wants to complete the I/O */
 		dm_kill_unmapped_request(rq, r);
-		return r;
 	}
 
-	return 0;
+	return r;
 }
 
 static void dm_start_request(struct mapped_device *md, struct request *orig)