Minor comments.
On 12/9/2016 1:43 AM, Jens Axboe wrote:
Takes a list of requests, and dispatches it. Moves any residual
requests to the dispatch list.
Signed-off-by: Jens Axboe <axboe@xxxxxx>
---
block/blk-mq.c | 85 ++++++++++++++++++++++++++++++++--------------------------
block/blk-mq.h | 1 +
2 files changed, 48 insertions(+), 38 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index b216746be9d3..abbf7cca4d0d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -821,41 +821,13 @@ static inline unsigned int queued_to_index(unsigned int queued)
return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
}
-/*
- * Run this hardware queue, pulling any software queues mapped to it in.
- * Note that this function currently has various problems around ordering
- * of IO. In particular, we'd like FIFO behaviour on handling existing
- * items on the hctx->dispatch list. Ignore that for now.
- */
-static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
+bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
{
struct request_queue *q = hctx->queue;
struct request *rq;
- LIST_HEAD(rq_list);
LIST_HEAD(driver_list);
struct list_head *dptr;
- int queued;
-
- if (unlikely(blk_mq_hctx_stopped(hctx)))
- return;
-
- hctx->run++;
-
- /*
- * Touch any software queue that has pending entries.
- */
- flush_busy_ctxs(hctx, &rq_list);
-
- /*
- * If we have previous entries on our dispatch list, grab them
- * and stuff them at the front for more fair dispatch.
- */
- if (!list_empty_careful(&hctx->dispatch)) {
- spin_lock(&hctx->lock);
- if (!list_empty(&hctx->dispatch))
- list_splice_init(&hctx->dispatch, &rq_list);
- spin_unlock(&hctx->lock);
- }
+ int queued, ret = BLK_MQ_RQ_QUEUE_OK;
/*
* Start off with dptr being NULL, so we start the first request
@@ -867,16 +839,15 @@ static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
* Now process all the entries, sending them to the driver.
*/
queued = 0;
- while (!list_empty(&rq_list)) {
+ while (!list_empty(list)) {
struct blk_mq_queue_data bd;
- int ret;
- rq = list_first_entry(&rq_list, struct request, queuelist);
+ rq = list_first_entry(list, struct request, queuelist);
list_del_init(&rq->queuelist);
bd.rq = rq;
bd.list = dptr;
- bd.last = list_empty(&rq_list);
+ bd.last = list_empty(list);
ret = q->mq_ops->queue_rq(hctx, &bd);
switch (ret) {
@@ -884,7 +855,7 @@ static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
queued++;
break;
case BLK_MQ_RQ_QUEUE_BUSY:
- list_add(&rq->queuelist, &rq_list);
+ list_add(&rq->queuelist, list);
__blk_mq_requeue_request(rq);
break;
default:
@@ -902,7 +873,7 @@ static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
* We've done the first request. If we have more than 1
* left in the list, set dptr to defer issue.
*/
- if (!dptr && rq_list.next != rq_list.prev)
+ if (!dptr && list->next != list->prev)
dptr = &driver_list;
}
@@ -912,10 +883,11 @@ static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
* Any items that need requeuing? Stuff them into hctx->dispatch,
* that is where we will continue on next queue run.
*/
- if (!list_empty(&rq_list)) {
+ if (!list_empty(list)) {
spin_lock(&hctx->lock);
- list_splice(&rq_list, &hctx->dispatch);
+ list_splice(list, &hctx->dispatch);
spin_unlock(&hctx->lock);
+
/*
* the queue is expected stopped with BLK_MQ_RQ_QUEUE_BUSY, but
* it's possible the queue is stopped and restarted again
@@ -927,6 +899,43 @@ static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
**/
blk_mq_run_hw_queue(hctx, true);
}
+
+ return ret != BLK_MQ_RQ_QUEUE_BUSY;
+}
+
+/*
+ * Run this hardware queue, pulling any software queues mapped to it in.
+ * Note that this function currently has various problems around ordering
+ * of IO. In particular, we'd like FIFO behaviour on handling existing
+ * items on the hctx->dispatch list. Ignore that for now.
+ */
+static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
+{
+ LIST_HEAD(rq_list);
+ LIST_HEAD(driver_list);
driver_list is not required. since not used in this function anymore.
+
+ if (unlikely(blk_mq_hctx_stopped(hctx)))
+ return;
+
+ hctx->run++;
+
+ /*
+ * Touch any software queue that has pending entries.
+ */
+ flush_busy_ctxs(hctx, &rq_list);
+
+ /*
+ * If we have previous entries on our dispatch list, grab them
+ * and stuff them at the front for more fair dispatch.
+ */
+ if (!list_empty_careful(&hctx->dispatch)) {
+ spin_lock(&hctx->lock);
+ if (!list_empty(&hctx->dispatch))
list_splice_init already checks for list_empty. So this may be
redundant. Please check.
+ list_splice_init(&hctx->dispatch, &rq_list);
+ spin_unlock(&hctx->lock);
+ }
+
+ blk_mq_dispatch_rq_list(hctx, &rq_list);
}
static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
diff --git a/block/blk-mq.h b/block/blk-mq.h
index b444370ae05b..3a54dd32a6fc 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -31,6 +31,7 @@ void blk_mq_freeze_queue(struct request_queue *q);
void blk_mq_free_queue(struct request_queue *q);
int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
void blk_mq_wake_waiters(struct request_queue *q);
+bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *, struct list_head *);
/*
* CPU hotplug helpers
--
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