[PATCH 2/5] blk-mq: Keep set->nr_hw_queues and set->map[].nr_queues in sync

[Bart Van Assche <bvanassche@acm.org>]

This patch fixes the following kernel warning:

WARNING: CPU: 0 PID: 2501 at include/linux/cpumask.h:137
Call Trace:
 blk_mq_run_hw_queue+0x19d/0x350 block/blk-mq.c:1508
 blk_mq_run_hw_queues+0x112/0x1a0 block/blk-mq.c:1525
 blk_mq_requeue_work+0x502/0x780 block/blk-mq.c:775
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x361/0x430 kernel/kthread.c:255

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jth@kernel.org>
Reported-by: syzbot+d44e1b26ce5c3e77458d@syzkaller.appspotmail.com
Fixes: ed76e329d74a ("blk-mq: abstract out queue map") # v5.0
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-mq.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f298500e6dda..2b9f490f5a64 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3050,6 +3050,16 @@ static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
 	}
 }
 
+static void blk_mq_set_nr_hw_queues(struct blk_mq_tag_set *set,
+				    int new_nr_hw_queues)
+{
+	int i;
+
+	set->nr_hw_queues = new_nr_hw_queues;
+	for (i = 0; i < set->nr_maps; i++)
+		set->map[i].nr_queues = new_nr_hw_queues;
+}
+
 static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
 				  int cur_nr_hw_queues, int new_nr_hw_queues)
 {
@@ -3068,7 +3078,7 @@ static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
 		       sizeof(*set->tags));
 	kfree(set->tags);
 	set->tags = new_tags;
-	set->nr_hw_queues = new_nr_hw_queues;
+	blk_mq_set_nr_hw_queues(set, new_nr_hw_queues);
 
 	return 0;
 }
@@ -3330,7 +3340,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 		goto reregister;
 
 	prev_nr_hw_queues = set->nr_hw_queues;
-	set->nr_hw_queues = nr_hw_queues;
+	blk_mq_set_nr_hw_queues(set, nr_hw_queues);
 	blk_mq_update_queue_map(set);
 fallback:
 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
@@ -3338,7 +3348,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 		if (q->nr_hw_queues != set->nr_hw_queues) {
 			pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
 					nr_hw_queues, prev_nr_hw_queues);
-			set->nr_hw_queues = prev_nr_hw_queues;
+			blk_mq_set_nr_hw_queues(set, prev_nr_hw_queues);
 			blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
 			goto fallback;
 		}