[v2,03/13] blk-mq: wait on correct sbitmap_queue in blk_mq_mark_tag_wait

Commit Message

Kemeng Shi Jan. 4, 2023, 2:22 p.m. UTC

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 from which rq from to fix this.

Fixes: f906a6a0f426 ("blk-mq: improve tag waiting setup for non-shared tags")
Signed-off-by: Kemeng Shi <[e-mail]>
---
 block/blk-mq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Jan. 8, 2023, 5:55 p.m. UTC | #1

Looks good:

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 42bb59fa275c..ec958aa044ba 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1820,7 +1820,7 @@  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;
@@ -1843,6 +1843,10 @@  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);