[PATCH] block: blk-mq: fix ws_active refcount leak in blk_mq_mark_tag_wait()

[Wentao Liang <vulab@iscas.ac.cn>]

blk_mq_mark_tag_wait() calls sbitmap_queue_get() which increments
sbq->ws_active. On the error path where the waitqueue_active() check
fails and the function returns early, sbq->ws_active is not decremented,
leaking the reference.

Fix this by calling sbitmap_queue_clear() to properly release the
ws_active reference before returning on the error path.

Fixes: c27d53fb445f ("blk-mq: Reduce the number of if-statements in blk_mq_mark_tag_wait()")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
 block/blk-mq.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d0c37daf568f..e1c2ac416693 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1952,6 +1952,8 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
 	spin_lock_irq(&wq->lock);
 	spin_lock(&hctx->dispatch_wait_lock);
 	if (!list_empty(&wait->entry)) {
+		list_del_init(&wait->entry);
+		atomic_dec(&sbq->ws_active);
 		spin_unlock(&hctx->dispatch_wait_lock);
 		spin_unlock_irq(&wq->lock);
 		return false;
-- 
2.34.1