On 8/22/19 5:15 PM, Damien Le Moal wrote:
> Since elevator_init_rq() is called before the device queue is registered
> in sysfs, there is no possible conflict with elevator_switch(). Remove
> the unnecessary locking of q->sysfs_lock mutex.
>
> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
> ---
> block/elevator.c | 12 ++----------
> 1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/block/elevator.c b/block/elevator.c
> index 7fff06751633..6208ddc334ef 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -617,17 +617,12 @@ void elevator_init_mq(struct request_queue *q)
> if (q->nr_hw_queues != 1)
> return;
>
> - /*
> - * q->sysfs_lock must be held to provide mutual exclusion between
> - * elevator_switch() and here.
> - */
> - mutex_lock(&q->sysfs_lock);
> if (unlikely(q->elevator))
> - goto out_unlock;
> + return;
>
> e = elevator_get(q, "mq-deadline", false);
> if (!e)
> - goto out_unlock;
> + return;
>
> err = blk_mq_init_sched(q, e);
> if (err) {
> @@ -635,9 +630,6 @@ void elevator_init_mq(struct request_queue *q)
> "falling back to \"none\"\n", e->elevator_name);
> elevator_put(e);
> }
> -
> -out_unlock:
> - mutex_unlock(&q->sysfs_lock);
> }
Please consider to add a WARN_ON_ONCE() statement that triggers a
warning if this function is called for a request queue that has already
been registered.
Thanks,
Bart.
