On Tue, Jun 08, 2021 at 08:04:00AM -0700, Bart Van Assche wrote:
> 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.
Fine, one spinlock should be enough, will do it in V3.
Thanks,
Ming
