[PATCH v2 3/5] blk-mq: Introduce blk_mq_ops.restart_hctx

[Bart Van Assche <bart.vanassche@sandisk.com>]

If a tag set is shared among multiple hardware queues, leave
it to the block driver to rerun hardware queues. Hence remove
QUEUE_FLAG_RESTART and introduce blk_mq_ops.restart_hctx.
Remove blk_mq_sched_mark_restart_queue() because this
function has no callers.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 block/blk-mq-sched.c   | 15 ++++-----------
 block/blk-mq-sched.h   | 14 --------------
 include/linux/blk-mq.h |  7 +++++++
 include/linux/blkdev.h |  1 -
 4 files changed, 11 insertions(+), 26 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 414ed4b3d266..f0c691a3ef9e 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -328,18 +328,11 @@ EXPORT_SYMBOL(blk_mq_sched_restart_hctx);
 void blk_mq_sched_restart_queues(struct blk_mq_hw_ctx *hctx)
 {
 	struct request_queue *q = hctx->queue;
-	unsigned int i;
-
-	if (test_bit(QUEUE_FLAG_RESTART, &q->queue_flags)) {
-		if (test_and_clear_bit(QUEUE_FLAG_RESTART, &q->queue_flags)) {
-			queue_for_each_hw_ctx(q, hctx, i)
-				if (test_bit(BLK_MQ_S_SCHED_RESTART,
-					     &hctx->state))
-					blk_mq_sched_restart_hctx(hctx);
-		}
-	} else if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) {
+
+	if (q->mq_ops->restart_hctx)
+		q->mq_ops->restart_hctx(q, hctx);
+	else if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
 		blk_mq_sched_restart_hctx(hctx);
-	}
 }
 
 /*
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index a75b16b123f7..fe62b1eccf4c 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -131,20 +131,6 @@ static inline void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
 		set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
 }
 
-/*
- * Mark a hardware queue and the request queue it belongs to as needing a
- * restart.
- */
-static inline void blk_mq_sched_mark_restart_queue(struct blk_mq_hw_ctx *hctx)
-{
-	struct request_queue *q = hctx->queue;
-
-	if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
-		set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
-	if (!test_bit(QUEUE_FLAG_RESTART, &q->queue_flags))
-		set_bit(QUEUE_FLAG_RESTART, &q->queue_flags);
-}
-
 static inline bool blk_mq_sched_needs_restart(struct blk_mq_hw_ctx *hctx)
 {
 	return test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f62f3ce2dc65..ebeea36ff9cd 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -86,6 +86,7 @@ struct blk_mq_queue_data {
 };
 
 typedef int (queue_rq_fn)(struct blk_mq_hw_ctx *, const struct blk_mq_queue_data *);
+typedef void (restart_fn)(struct request_queue *q, struct blk_mq_hw_ctx *hctx);
 typedef enum blk_eh_timer_return (timeout_fn)(struct request *, bool);
 typedef int (init_hctx_fn)(struct blk_mq_hw_ctx *, void *, unsigned int);
 typedef void (exit_hctx_fn)(struct blk_mq_hw_ctx *, unsigned int);
@@ -109,6 +110,12 @@ struct blk_mq_ops {
 	queue_rq_fn		*queue_rq;
 
 	/*
+	 * Called upon request completion to rerun all hctxs that share a tag
+	 * set with the hctx for which a request finished.
+	 */
+	restart_fn		*restart_hctx;
+
+	/*
 	 * Called on request timeout
 	 */
 	timeout_fn		*timeout;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a2dc6b390d48..a80543ec8be7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -615,7 +615,6 @@ struct request_queue {
 #define QUEUE_FLAG_FLUSH_NQ    25	/* flush not queueuable */
 #define QUEUE_FLAG_DAX         26	/* device supports DAX */
 #define QUEUE_FLAG_STATS       27	/* track rq completion times */
-#define QUEUE_FLAG_RESTART     28	/* queue needs restart at completion */
 #define QUEUE_FLAG_POLL_STATS  29	/* collecting stats for hybrid polling */
 #define QUEUE_FLAG_REGISTERED  30	/* queue has been registered to a disk */
 
-- 
2.12.0