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

Kemeng Shi
2023-01-18T01:39:11Z

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@lst.de>
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.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