Move code for handling partial dispatch into one helper, so that
blk_mq_dispatch_rq_list gets a bit simpified, and easier to read.
No functional change.
Cc: Sagi Grimberg <sagi@xxxxxxxxxxx>
Cc: Baolin Wang <baolin.wang7@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq.c | 126 ++++++++++++++++++++++++++-----------------------
1 file changed, 66 insertions(+), 60 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 34fd09adb7fc..86beb8c66868 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1231,6 +1231,71 @@ static blk_status_t blk_mq_dispatch_rq(struct request *rq, bool is_last)
return rq->q->mq_ops->queue_rq(rq->mq_hctx, &bd);
}
+static void blk_mq_handle_partial_dispatch(struct blk_mq_hw_ctx *hctx,
+ struct list_head *list, enum prep_dispatch prep,
+ blk_status_t ret, bool queued)
+{
+ struct request_queue *q = hctx->queue;
+ bool needs_restart;
+ bool no_tag = false;
+ bool no_budget_avail = false;
+
+ /*
+ * For non-shared tags, the RESTART check
+ * will suffice.
+ */
+ if (prep == PREP_DISPATCH_NO_TAG &&
+ (hctx->flags & BLK_MQ_F_TAG_SHARED))
+ no_tag = true;
+ if (prep == PREP_DISPATCH_NO_BUDGET)
+ no_budget_avail = true;
+
+ /*
+ * If we didn't flush the entire list, we could have told
+ * the driver there was more coming, but that turned out to
+ * be a lie.
+ */
+ if (q->mq_ops->commit_rqs && queued)
+ q->mq_ops->commit_rqs(hctx);
+
+ spin_lock(&hctx->lock);
+ list_splice_tail_init(list, &hctx->dispatch);
+ spin_unlock(&hctx->lock);
+
+ /*
+ * If SCHED_RESTART was set by the caller of this function and
+ * it is no longer set that means that it was cleared by another
+ * thread and hence that a queue rerun is needed.
+ *
+ * If 'no_tag' is set, that means that we failed getting
+ * a driver tag with an I/O scheduler attached. If our dispatch
+ * waitqueue is no longer active, ensure that we run the queue
+ * AFTER adding our entries back to the list.
+ *
+ * If no I/O scheduler has been configured it is possible that
+ * the hardware queue got stopped and restarted before requests
+ * were pushed back onto the dispatch list. Rerun the queue to
+ * avoid starvation. Notes:
+ * - blk_mq_run_hw_queue() checks whether or not a queue has
+ * been stopped before rerunning a queue.
+ * - Some but not all block drivers stop a queue before
+ * returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
+ * and dm-rq.
+ *
+ * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
+ * bit is set, run queue after a delay to avoid IO stalls
+ * that could otherwise occur if the queue is idle. We'll do
+ * similar if we couldn't get budget and SCHED_RESTART is set.
+ */
+ needs_restart = blk_mq_sched_needs_restart(hctx);
+ if (!needs_restart ||
+ (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
+ blk_mq_run_hw_queue(hctx, true);
+ else if (needs_restart && (ret == BLK_STS_RESOURCE ||
+ no_budget_avail))
+ blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
+}
+
/*
* Returns true if we did some work AND can potentially do more.
*/
@@ -1238,7 +1303,6 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
bool got_budget)
{
enum prep_dispatch prep;
- struct request_queue *q = hctx->queue;
struct request *rq;
int errors, queued;
blk_status_t ret = BLK_STS_OK;
@@ -1296,65 +1360,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
* that is where we will continue on next queue run.
*/
if (!list_empty(list)) {
- bool needs_restart;
- bool no_tag = false;
- bool no_budget_avail = false;
-
- /*
- * For non-shared tags, the RESTART check
- * will suffice.
- */
- if (prep == PREP_DISPATCH_NO_TAG &&
- (hctx->flags & BLK_MQ_F_TAG_SHARED))
- no_tag = true;
- if (prep == PREP_DISPATCH_NO_BUDGET)
- no_budget_avail = true;
-
- /*
- * If we didn't flush the entire list, we could have told
- * the driver there was more coming, but that turned out to
- * be a lie.
- */
- if (q->mq_ops->commit_rqs && queued)
- q->mq_ops->commit_rqs(hctx);
-
- spin_lock(&hctx->lock);
- list_splice_tail_init(list, &hctx->dispatch);
- spin_unlock(&hctx->lock);
-
- /*
- * If SCHED_RESTART was set by the caller of this function and
- * it is no longer set that means that it was cleared by another
- * thread and hence that a queue rerun is needed.
- *
- * If 'no_tag' is set, that means that we failed getting
- * a driver tag with an I/O scheduler attached. If our dispatch
- * waitqueue is no longer active, ensure that we run the queue
- * AFTER adding our entries back to the list.
- *
- * If no I/O scheduler has been configured it is possible that
- * the hardware queue got stopped and restarted before requests
- * were pushed back onto the dispatch list. Rerun the queue to
- * avoid starvation. Notes:
- * - blk_mq_run_hw_queue() checks whether or not a queue has
- * been stopped before rerunning a queue.
- * - Some but not all block drivers stop a queue before
- * returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
- * and dm-rq.
- *
- * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
- * bit is set, run queue after a delay to avoid IO stalls
- * that could otherwise occur if the queue is idle. We'll do
- * similar if we couldn't get budget and SCHED_RESTART is set.
- */
- needs_restart = blk_mq_sched_needs_restart(hctx);
- if (!needs_restart ||
- (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
- blk_mq_run_hw_queue(hctx, true);
- else if (needs_restart && (ret == BLK_STS_RESOURCE ||
- no_budget_avail))
- blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
-
+ blk_mq_handle_partial_dispatch(hctx, list, prep, ret, !!queued);
blk_mq_update_dispatch_busy(hctx, true);
return false;
} else
--
2.25.2
