[PATCH v4 07/14] blk-mq: make blk_mq_commit_rqs a general function for all commits

Kemeng Shi
2023-01-18T01:39:43Z

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>
---
block/blk-mq.c | 37 +++++++++++++++++++++++--------------
1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5d146ec9f8cb..159d9163c46c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2007,6 +2007,23 @@ 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.
*/
@@ -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,
--
2.30.0