Here is my counter proposal that requeues via two lists and a work struct
in the request_queue. I've also tested it with scsi-mq.
>From 95f15eda9a87d8545e1dff1b996d9227dfca1129 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Wed, 21 May 2014 19:37:11 +0200
Subject: blk-mq: add helper to insert requests from irq context
---
block/blk-flush.c | 16 ++++----------
block/blk-mq.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++-
include/linux/blk-mq.h | 3 +++
include/linux/blkdev.h | 6 +++++-
4 files changed, 65 insertions(+), 14 deletions(-)
diff --git a/block/blk-flush.c b/block/blk-flush.c
index ec7a224..ef608b3 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -130,21 +130,13 @@ static void blk_flush_restore_request(struct request *rq)
blk_clear_rq_complete(rq);
}
-static void mq_flush_run(struct work_struct *work)
-{
- struct request *rq;
-
- rq = container_of(work, struct request, requeue_work);
-
- memset(&rq->csd, 0, sizeof(rq->csd));
- blk_mq_insert_request(rq, false, true, false);
-}
-
static bool blk_flush_queue_rq(struct request *rq, bool add_front)
{
if (rq->q->mq_ops) {
- INIT_WORK(&rq->requeue_work, mq_flush_run);
- kblockd_schedule_work(&rq->requeue_work);
+ struct request_queue *q = rq->q;
+
+ blk_mq_add_to_requeue_list(rq, add_front);
+ blk_mq_kick_requeue_list(q);
return false;
} else {
if (add_front)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 62082c5..926d844 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -510,10 +510,57 @@ void blk_mq_requeue_request(struct request *rq)
blk_clear_rq_complete(rq);
BUG_ON(blk_queued_rq(rq));
- blk_mq_insert_request(rq, true, true, false);
+ blk_mq_add_to_requeue_list(rq, true);
}
EXPORT_SYMBOL(blk_mq_requeue_request);
+static void blk_mq_requeue_work(struct work_struct *work)
+{
+ struct request_queue *q =
+ container_of(work, struct request_queue, requeue_work);
+ LIST_HEAD(head_list);
+ LIST_HEAD(tail_list);
+ struct request *rq;
+ unsigned long flags;
+
+ spin_lock_irqsave(&q->requeue_lock, flags);
+ list_splice_init(&q->requeue_head_list, &head_list);
+ list_splice_init(&q->requeue_list, &tail_list);
+ spin_unlock_irqrestore(&q->requeue_lock, flags);
+
+ while (!list_empty(&head_list)) {
+ rq = list_entry(head_list.next, struct request, queuelist);
+ blk_mq_insert_request(rq, true, false, false);
+ }
+
+ while (!list_empty(&tail_list)) {
+ rq = list_entry(tail_list.next, struct request, queuelist);
+ blk_mq_insert_request(rq, false, false, false);
+ }
+
+ blk_mq_run_queues(q, false);
+}
+
+void blk_mq_add_to_requeue_list(struct request *rq, bool at_head)
+{
+ struct request_queue *q = rq->q;
+ unsigned long flags;
+
+ spin_lock_irqsave(&q->requeue_lock, flags);
+ if (at_head)
+ list_add(&rq->queuelist, &q->requeue_head_list);
+ else
+ list_add_tail(&rq->queuelist, &q->requeue_list);
+ spin_unlock_irqrestore(&q->requeue_lock, flags);
+}
+EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
+
+void blk_mq_kick_requeue_list(struct request_queue *q)
+{
+ kblockd_schedule_work(&q->requeue_work);
+}
+EXPORT_SYMBOL(blk_mq_kick_requeue_list);
+
struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
{
return tags->rqs[tag];
@@ -1777,6 +1824,11 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
q->sg_reserved_size = INT_MAX;
+ INIT_WORK(&q->requeue_work, blk_mq_requeue_work);
+ INIT_LIST_HEAD(&q->requeue_head_list);
+ INIT_LIST_HEAD(&q->requeue_list);
+ spin_lock_init(&q->requeue_lock);
+
if (q->nr_hw_queues > 1)
blk_queue_make_request(q, blk_mq_make_request);
else
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f76bb18..81bb7f1 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -173,6 +173,9 @@ void __blk_mq_end_io(struct request *rq, int error);
void blk_mq_requeue_request(struct request *rq);
+void blk_mq_add_to_requeue_list(struct request *rq, bool at_head);
+void blk_mq_kick_requeue_list(struct request_queue *q);
+
void blk_mq_complete_request(struct request *rq);
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index b0104ba..e137348 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -99,7 +99,6 @@ struct request {
struct list_head queuelist;
union {
struct call_single_data csd;
- struct work_struct requeue_work;
unsigned long fifo_time;
};
@@ -463,6 +462,11 @@ struct request_queue {
struct request *flush_rq;
spinlock_t mq_flush_lock;
+ struct list_head requeue_list;
+ struct list_head requeue_head_list;
+ spinlock_t requeue_lock;
+ struct work_struct requeue_work;
+
struct mutex sysfs_lock;
int bypass_depth;
--
1.7.10.4