On 6/8/21 12:19 AM, Ming Lei wrote:
> static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos)
> {
> + /*
> + * No IO can be in-flight when adding rqos, so freeze queue, which
> + * is fine since we only support rq_qos for blk-mq queue
> + */
> + blk_mq_freeze_queue(q);
> rqos->next = q->rq_qos;
> q->rq_qos = rqos;
> + blk_mq_unfreeze_queue(q);
>
> if (rqos->ops->debugfs_attrs)
> blk_mq_debugfs_register_rqos(rqos);
> @@ -110,12 +117,18 @@ static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
> {
> struct rq_qos **cur;
>
> + /*
> + * No IO can be in-flight when removing rqos, so freeze queue,
> + * which is fine since we only support rq_qos for blk-mq queue
> + */
> + blk_mq_freeze_queue(q);
> for (cur = &q->rq_qos; *cur; cur = &(*cur)->next) {
> if (*cur == rqos) {
> *cur = rqos->next;
> break;
> }
> }
> + blk_mq_unfreeze_queue(q);
>
> blk_mq_debugfs_unregister_rqos(rqos);
> }
Although this patch looks like an improvement to me, I think we also
need protection against concurrent rq_qos_add() and rq_qos_del() calls,
e.g. via a mutex.
Thanks,
Bart.
