[07/11] block: factor out requeue handling from dispatch code

Commit Message

Johannes Thumshirn March 10, 2020, 9:46 a.m. UTC

Factor out the requeue handling from the dispatch code, this will make
subsequent addition of different requeueing schemes easier.

Signed-off-by: Johannes Thumshirn <[e-mail]>
---
 block/blk-mq.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

Comments

Christoph Hellwig March 10, 2020, 4:44 p.m. UTC | #1

On Tue, Mar 10, 2020 at 06:46:49PM +0900, Johannes Thumshirn wrote:
> Factor out the requeue handling from the dispatch code, this will make
> subsequent addition of different requeueing schemes easier.

This should go first in the series, as it is useful even without the
rest of the series.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d92088dec6c3..f7ab75ef4d0e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1178,6 +1178,23 @@  static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
 
 #define BLK_MQ_RESOURCE_DELAY	3		/* ms units */
 
+static void blk_mq_handle_dev_resource(struct request *rq,
+				       struct list_head *list)
+{
+	struct request *next =
+		list_first_entry_or_null(list, struct request, queuelist);
+
+	/*
+	 * If an I/O scheduler has been configured and we got a driver tag for
+	 * the next request already, free it.
+	 */
+	if (next)
+		blk_mq_put_driver_tag(next);
+
+	list_add(&rq->queuelist, list);
+	__blk_mq_requeue_request(rq);
+}
+
 /*
  * Returns true if we did some work AND can potentially do more.
  */
@@ -1245,17 +1262,7 @@  bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
 
 		ret = q->mq_ops->queue_rq(hctx, &bd);
 		if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
-			/*
-			 * If an I/O scheduler has been configured and we got a
-			 * driver tag for the next request already, free it
-			 * again.
-			 */
-			if (!list_empty(list)) {
-				nxt = list_first_entry(list, struct request, queuelist);
-				blk_mq_put_driver_tag(nxt);
-			}
-			list_add(&rq->queuelist, list);
-			__blk_mq_requeue_request(rq);
+			blk_mq_handle_dev_resource(rq, list);
 			break;
 		}