blk-mq: make blk_mq_commit_rqs a general function for all commits

1. move blk_mq_commit_rqs forward before functions need commits.
2. add queued check and only commits request if any request was queued
in blk_mq_commit_rqs to keep commit behavior consistent and remove
unnecessary commit.
3. split the queued clearing from blk_mq_plug_commit_rqs as it is
not wanted general.
4. sync current caller of blk_mq_commit_rqs with new general
blk_mq_commit_rqs.
5. document rule for unusual cases which need explicit commit_rqs.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e356379..99d4343 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2008,6 +2008,23 @@ static void blk_mq_release_budgets(struct request_queue *q,
 }
 
 /*
+ * blk_mq_commit_rqs will notify driver using bd->last that there is no
+ * more requests. (See comment in struct blk_mq_ops for commit_rqs for
+ * details)
+ * Attention, we should explicitly call this in unusual cases:
+ *  1) did not queue everything initially scheduled to queue
+ *  2) the last attempt to queue a request failed
+ */
+static void blk_mq_commit_rqs(struct blk_mq_hw_ctx *hctx, int queued,
+                             bool from_schedule)
+{
+       if (hctx->queue->mq_ops->commit_rqs && queued) {
+               trace_block_unplug(hctx->queue, queued, !from_schedule);
+               hctx->queue->mq_ops->commit_rqs(hctx);
+       }
+}
+
+/*
  * Returns true if we did some work AND can potentially do more.
  */
 bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
@@ -2555,16 +2572,6 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
        spin_unlock(&ctx->lock);
 }
 
-static void blk_mq_commit_rqs(struct blk_mq_hw_ctx *hctx, int *queued,
-                             bool from_schedule)
-{
-       if (hctx->queue->mq_ops->commit_rqs) {
-               trace_block_unplug(hctx->queue, *queued, !from_schedule);
-               hctx->queue->mq_ops->commit_rqs(hctx);
-       }
-       *queued = 0;
-}
-
 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
                unsigned int nr_segs)
 {
@@ -2700,8 +2707,10 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug)
                blk_status_t ret;
 
                if (hctx != rq->mq_hctx) {
-                       if (hctx)
-                               blk_mq_commit_rqs(hctx, &queued, false);
+                       if (hctx) {
+                               blk_mq_commit_rqs(hctx, queued, false);
+                               queued = 0;
+                       }
                        hctx = rq->mq_hctx;
                }
 
@@ -2713,7 +2722,7 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug)
                case BLK_STS_RESOURCE:
                case BLK_STS_DEV_RESOURCE:
                        blk_mq_request_bypass_insert(rq, false, true);
-                       blk_mq_commit_rqs(hctx, &queued, false);
+                       blk_mq_commit_rqs(hctx, queued, false);
                        return;
                default:
                        blk_mq_end_request(rq, ret);
@@ -2727,7 +2736,7 @@ static void blk_mq_plug_issue_direct(struct blk_plug *plug)
         * there was more coming, but that turned out to be a lie.
         */
        if (errors)
-               blk_mq_commit_rqs(hctx, &queued, false);
+               blk_mq_commit_rqs(hctx, queued, false);
 }
 
 static void __blk_mq_flush_plug_list(struct request_queue *q,