[PATCH 3/5] dm-rq: return BLK_STS_* from map_request()

[Ming Lei <ming.lei@xxxxxxxxxx>]

Except for DM_MAPIO_REQUEUE, map_request() handles other dispatch exception
already, so return BLK_STS_* from map_request() directly.

Another change is that if dm_dispatch_clone_request() returns
BLK_STS_DEV_RESOURCE from underlying queue, this status is returned
to blk-mq too, since underlying queue's RESTART can handle dm-rq's
RESTART in this case.

Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Laurence Oberman <loberman@xxxxxxxxxx>
Cc: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 drivers/md/dm-rq.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 1408e6664c16..830e1ccfbb44 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -482,9 +482,10 @@ static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
 
 /*
  * Returns:
- * DM_MAPIO_*       : the request has been processed as indicated
- * DM_MAPIO_REQUEUE : the original request needs to be immediately requeued
- * < 0              : the request was completed due to failure
+ * BLK_STS_OK       : the request has been processed aready, no need to
+ * 		ask block layer to handle it any more
+ * BLK_STS_RESOURCE : the original request needs to be immediately requeued
+ * BLK_STS_DEV_RESOURCE : same with BLK_STS_RESOURCE, but blk-mq need this info
  */
 static int map_request(struct dm_rq_target_io *tio)
 {
@@ -493,7 +494,7 @@ static int map_request(struct dm_rq_target_io *tio)
 	struct mapped_device *md = tio->md;
 	struct request *rq = tio->orig;
 	struct request *clone = NULL;
-	blk_status_t ret;
+	blk_status_t ret, result = BLK_STS_OK;
 
 	r = ti->type->clone_and_map_rq(ti, rq, &tio->info, &clone);
 check_again:
@@ -513,15 +514,16 @@ static int map_request(struct dm_rq_target_io *tio)
 				     blk_rq_pos(rq));
 		ret = dm_dispatch_clone_request(tio, clone, rq);
 		if (dispatch_busy(ret)) {
-			if (!rq->q->mq_ops)
+			if (!rq->q->mq_ops) {
 				r = DM_MAPIO_DELAY_REQUEUE;
-			else
-				r = DM_MAPIO_REQUEUE;
-			goto check_again;
+				goto check_again;
+			}
+			result = ret;
 		}
 		break;
 	case DM_MAPIO_REQUEUE:
 		/* The target wants to requeue the I/O */
+		result = BLK_STS_RESOURCE;
 		break;
 	case DM_MAPIO_DELAY_REQUEUE:
 		/* The target wants to requeue the I/O after a delay */
@@ -536,7 +538,7 @@ static int map_request(struct dm_rq_target_io *tio)
 		BUG();
 	}
 
-	return r;
+	return result;
 }
 
 static void dm_start_request(struct mapped_device *md, struct request *orig)
@@ -599,7 +601,7 @@ static void map_tio_request(struct kthread_work *work)
 {
 	struct dm_rq_target_io *tio = container_of(work, struct dm_rq_target_io, work);
 
-	if (map_request(tio) == DM_MAPIO_REQUEUE)
+	if (dispatch_busy(map_request(tio)))
 		dm_requeue_original_request(tio, false);
 }
 
@@ -754,6 +756,7 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 	struct dm_rq_target_io *tio = blk_mq_rq_to_pdu(rq);
 	struct mapped_device *md = tio->md;
 	struct dm_target *ti = md->immutable_target;
+	blk_status_t ret;
 
 	if (unlikely(!ti)) {
 		int srcu_idx;
@@ -777,14 +780,15 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 	tio->ti = ti;
 
 	/* Direct call is fine since .queue_rq allows allocations */
-	if (map_request(tio) == DM_MAPIO_REQUEUE) {
+	ret = map_request(tio);
+	if (dispatch_busy(ret)) {
 		/* Undo dm_start_request() before requeuing */
 		rq_end_stats(md, rq);
 		rq_completed(md, rq_data_dir(rq), false);
-		return BLK_STS_RESOURCE;
+		return ret;
 	}
 
-	return BLK_STS_OK;
+	return ret;
 }
 
 static const struct blk_mq_ops dm_mq_ops = {
-- 
2.9.5