linux-kernel - [PATCH AUTOSEL 5.5 40/56] blk-mq: Keep set->nr_hw_queues and set->map[].nr

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Date:   Thu,  9 Apr 2020 23:47:44 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Bart Van Assche <bvanassche@....org>,
        syzbot+d44e1b26ce5c3e77458d@...kaller.appspotmail.com,
        Ming Lei <ming.lei@...hat.com>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Johannes Thumshirn <jth@...nel.org>,
        Hannes Reinecke <hare@...e.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.5 40/56] blk-mq: Keep set->nr_hw_queues and set->map[].nr_queues in sync

From: Bart Van Assche <bvanassche@....org>

[ Upstream commit 6e66b49392419f3fe134e1be583323ef75da1e4b ]

blk_mq_map_queues() and multiple .map_queues() implementations expect that
set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the number of hardware
queues. Hence set .nr_queues before calling these functions. 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

Fixes: ed76e329d74a ("blk-mq: abstract out queue map") # v5.0
Reported-by: syzbot+d44e1b26ce5c3e77458d@...kaller.appspotmail.com
Signed-off-by: Bart Van Assche <bvanassche@....org>
Reviewed-by: Ming Lei <ming.lei@...hat.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Cc: Johannes Thumshirn <jth@...nel.org>
Cc: Hannes Reinecke <hare@...e.com>
Cc: Ming Lei <ming.lei@...hat.com>
Cc: Christoph Hellwig <hch@...radead.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 block/blk-mq.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 51ff4852d34bc..8391e8e2a5044 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2964,6 +2964,14 @@ static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 
 static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
 {
+	/*
+	 * blk_mq_map_queues() and multiple .map_queues() implementations
+	 * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
+	 * number of hardware queues.
+	 */
+	if (set->nr_maps == 1)
+		set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;
+
 	if (set->ops->map_queues && !is_kdump_kernel()) {
 		int i;
 
-- 
2.20.1