This is a note to let you know that I've just added the patch titled
blk-mq: wait on correct sbitmap_queue in blk_mq_mark_tag_wait
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
blk-mq-wait-on-correct-sbitmap_queue-in-blk_mq_mark_.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 748d32e1d793e736693bc5afd2dbff0e5aa1ef6a
Author: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Date: Wed Jan 18 17:37:15 2023 +0800
blk-mq: wait on correct sbitmap_queue in blk_mq_mark_tag_wait
[ Upstream commit 98b99e9412d0cde8c7b442bf5efb09528a2ede8b ]
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@xxxxxx>
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 84798d09ca464..325a5944b4cb2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1112,7 +1112,7 @@ 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;
@@ -1135,6 +1135,10 @@ 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);
