On 2019/09/25 15:24, Ming Lei wrote:
> 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.
>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Damien Le Moal <Damien.LeMoal@xxxxxxx>
> Reported-by: syzbot+da3b7677bb913dc1b737@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixed: c48dac137a62 ("block: don't hold q->sysfs_lock in elevator_init_mq")
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> 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 c9d183d6c499..ca22afd47b3d 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -555,8 +555,6 @@ 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 ed347f7a97b1..25773d668ec0 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -194,6 +194,8 @@ 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);
> }
>
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
--
Damien Le Moal
Western Digital Research
