block: bfq: fix bfq_set_next_ioprio_data()

For a request that has a priority level equal to or larger than
IOPRIO_BE_NR, bfq_set_next_ioprio_data() prints a critical warning but
defaults to setting the request new_ioprio field to IOPRIO_BE_NR. This
is not consistent with the warning and the allowed values for priority
levels. Fix this by setting the request new_ioprio field to
IOPRIO_BE_NR - 1, the lowest priority level allowed.

Cc: <stable@vger.kernel.org>
Fixes: aee69d78de ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210811033702.368488-2-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-iosched.c

@@ -5296,7 +5296,7 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
 	if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
 		pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
 			bfqq->new_ioprio);
-		bfqq->new_ioprio = IOPRIO_BE_NR;
+		bfqq->new_ioprio = IOPRIO_BE_NR - 1;
 	}
 
 	bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);