Instead of returning -EINVAL if an internal inconsistency is detected,
fall back to a single submission queue. This patch prepares for changing
the return value of the .map_queues() callbacks into void.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <redacted>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/block/null_blk/main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index c451c477978f..535059209693 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c

@@ -1555,7 +1555,9 @@ static int null_map_queues(struct blk_mq_tag_set *set)
 		} else {
 			pr_warn("tag set has unexpected nr_hw_queues: %d\n",
 				set->nr_hw_queues);
-			return -EINVAL;
+			WARN_ON_ONCE(true);
+			submit_queues = 1;
+			poll_queues = 0;
 		}
 	}