[PATCH] blk-mq: fix queue reference leak on blk_mq_alloc_disk_for_queue failure

[Christoph Hellwig <hch@xxxxxx>]

Drop the disk reference just acquired when __alloc_disk_node failed.

Fixes: 6f8191fdf41d ("block: simplify disk shutdown")
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 block/blk-mq.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a3a5fb4d4ef667..02a1f6e501ea8d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4108,9 +4108,14 @@ EXPORT_SYMBOL(__blk_mq_alloc_disk);
 struct gendisk *blk_mq_alloc_disk_for_queue(struct request_queue *q,
 		struct lock_class_key *lkclass)
 {
+	struct gendisk *disk;
+
 	if (!blk_get_queue(q))
 		return NULL;
-	return __alloc_disk_node(q, NUMA_NO_NODE, lkclass);
+	disk = __alloc_disk_node(q, NUMA_NO_NODE, lkclass);
+	if (!disk)
+		blk_put_queue(q);
+	return disk;
 }
 EXPORT_SYMBOL(blk_mq_alloc_disk_for_queue);
 
-- 
2.30.2