linux-kernel - [PATCH v4 03/14] blk-mq: wait on correct sbitmap_queue in blk_mq_mark_tag

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Message-Id: <20230118093726.3939160-3-shikemeng@huaweicloud.com>
Date:   Wed, 18 Jan 2023 17:37:15 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     hch@....de, axboe@...nel.dk, dwagner@...e.de, hare@...e.de,
        ming.lei@...hat.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     john.garry@...wei.com, jack@...e.cz
Subject: [PATCH v4 03/14] blk-mq: wait on correct sbitmap_queue in blk_mq_mark_tag_wait

For shared queues case, we will only wait on bitmap_tags if we fail to get
driver tag. However, rq could be from breserved_tags, then two problems
will occur:
1. io hung if no tag is currently allocated from bitmap_tags.
2. unnecessary wakeup when tag is freed to bitmap_tags while no tag is
freed to breserved_tags.
Wait on the bitmap which rq from to fix this.

Fixes: f906a6a0f426 ("blk-mq: improve tag waiting setup for non-shared tags")
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 block/blk-mq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9c6a6ce9eaf2..943f2ce1e674 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1826,7 +1826,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
 				 struct request *rq)
 {
-	struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags;
+	struct sbitmap_queue *sbq;
 	struct wait_queue_head *wq;
 	wait_queue_entry_t *wait;
 	bool ret;
@@ -1849,6 +1849,10 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
 	if (!list_empty_careful(&wait->entry))
 		return false;
 
+	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag))
+		sbq = &hctx->tags->breserved_tags;
+	else
+		sbq = &hctx->tags->bitmap_tags;
 	wq = &bt_wait_ptr(sbq, hctx)->wait;
 
 	spin_lock_irq(&wq->lock);
-- 
2.30.0