linux-kernel - [PATCH AUTOSEL 5.2 48/63] blk-mq: move lockdep_assert_held() into elevator

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Message-Id: <20191001164125.15398-48-sashal@kernel.org>
Date:   Tue,  1 Oct 2019 12:41:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ming Lei <ming.lei@...hat.com>,
        syzbot+da3b7677bb913dc1b737@...kaller.appspotmail.com,
        Bart Van Assche <bvanassche@....org>,
        Damien Le Moal <damien.lemoal@....com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.2 48/63] blk-mq: move lockdep_assert_held() into elevator_exit

From: Ming Lei <ming.lei@...hat.com>

[ Upstream commit 284b94be1925dbe035ce5218d8b5c197321262c7 ]

Commit c48dac137a62 ("block: don't hold q->sysfs_lock in elevator_init_mq")
removes q->sysfs_lock from elevator_init_mq(), but forgot to deal with
lockdep_assert_held() called in blk_mq_sched_free_requests() which is
run in failure path of elevator_init_mq().

blk_mq_sched_free_requests() is called in the following 3 functions:

	elevator_init_mq()
	elevator_exit()
	blk_cleanup_queue()

In blk_cleanup_queue(), blk_mq_sched_free_requests() is followed exactly
by 'mutex_lock(&q->sysfs_lock)'.

So moving the lockdep_assert_held() from blk_mq_sched_free_requests()
into elevator_exit() for fixing the report by syzbot.

Reported-by: syzbot+da3b7677bb913dc1b737@...kaller.appspotmail.com
Fixed: c48dac137a62 ("block: don't hold q->sysfs_lock in elevator_init_mq")
Reviewed-by: Bart Van Assche <bvanassche@....org>
Reviewed-by: Damien Le Moal <damien.lemoal@....com>
Signed-off-by: Ming Lei <ming.lei@...hat.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 block/blk-mq-sched.c | 2 --
 block/blk.h          | 2 ++
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 2766066a15dbf..3cf555f127006 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -554,8 +554,6 @@ void blk_mq_sched_free_requests(struct request_queue *q)
 	struct blk_mq_hw_ctx *hctx;
 	int i;
 
-	lockdep_assert_held(&q->sysfs_lock);
-
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (hctx->sched_tags)
 			blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i);
diff --git a/block/blk.h b/block/blk.h
index 7814aa207153c..38938125ab729 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -184,6 +184,8 @@ void elv_unregister_queue(struct request_queue *q);
 static inline void elevator_exit(struct request_queue *q,
 		struct elevator_queue *e)
 {
+	lockdep_assert_held(&q->sysfs_lock);
+
 	blk_mq_sched_free_requests(q);
 	__elevator_exit(q, e);
 }
-- 
2.20.1