1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * Hierarchical Budget Worst-case Fair Weighted Fair Queueing
4  * (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O
9 #include "bfq-iosched.h"
12  * bfq_gt - compare two timestamps.
20 	return (s64)(a - b) > 0;  in bfq_gt()
23 static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree)  in bfq_root_active_entity()  argument
25 	struct rb_node *node = tree->rb_node;  in bfq_root_active_entity()
34 	return bfqq ? bfqq->ioprio_class - 1 :  in bfq_class_idx()
35 		BFQ_DEFAULT_GRP_CLASS - 1;  in bfq_class_idx()
40 	return bfqd->busy_queues[0] + bfqd->busy_queues[1] +  in bfq_tot_busy_queues()
41 		bfqd->busy_queues[2];  in bfq_tot_busy_queues()
50  * bfq_update_next_in_service - update sd->next_in_service
56  *             expiration of the in-service entity
58  * This function is called to update sd->next_in_service, which, in
65  * reposition an entity in its active tree; see comments on
66  * __bfq_activate_entity and __bfq_requeue_entity for details). In
67  * both the last two activation sub-cases, new_entity points to the
70  * Returns true if sd->next_in_service changes in such a way that
71  * entity->parent may become the next_in_service for its parent
78 	struct bfq_entity *next_in_service = sd->next_in_service;  in bfq_update_next_in_service()
85 	 * sd->next_in_service, then a full lookup in the active tree  in bfq_update_next_in_service()
86 	 * can be avoided. In fact, it is enough to check whether the  in bfq_update_next_in_service()
87 	 * just-modified entity has the same priority as  in bfq_update_next_in_service()
88 	 * sd->next_in_service, is eligible and has a lower virtual  in bfq_update_next_in_service()
89 	 * finish time than sd->next_in_service. If this compound  in bfq_update_next_in_service()
93 	if (new_entity && new_entity != sd->next_in_service) {  in bfq_update_next_in_service()
96 		 * sd->next_in_service with new_entity. Tentatively  in bfq_update_next_in_service()
98 		 * sd->next_in_service is NULL.  in bfq_update_next_in_service()
105 		 * to replace sd->service_tree with new_entity.  in bfq_update_next_in_service()
111 				sd->service_tree + new_entity_class_idx;  in bfq_update_next_in_service()
117 				 !bfq_gt(new_entity->start, st->vtime)  in bfq_update_next_in_service()
119 				 bfq_gt(next_in_service->finish,  in bfq_update_next_in_service()
120 					new_entity->finish));  in bfq_update_next_in_service()
134 		parent_sched_may_change = !sd->next_in_service ||  in bfq_update_next_in_service()
138 	sd->next_in_service = next_in_service;  in bfq_update_next_in_service()
146  * Returns true if this budget changes may let next_in_service->parent
156 	group_sd = next_in_service->sched_data;  in bfq_update_parent_budget()
162 	 * as it must never become an in-service entity.  in bfq_update_parent_budget()
164 	bfqg_entity = bfqg->my_entity;  in bfq_update_parent_budget()
166 		if (bfqg_entity->budget > next_in_service->budget)  in bfq_update_parent_budget()
168 		bfqg_entity->budget = next_in_service->budget;  in bfq_update_parent_budget()
177  * next_in_service. In particular, this function is invoked for an
178  * entity that is about to be set in service.
182  * about to become the in-service queue. This function then returns
185  * In contrast, entity could still be a candidate for next service if
186  * it is not a queue, and has more than one active child. In fact,
187  * even if one of its children is about to be set in service, other
190  * non-queue entity is not a candidate for next-service only if it has
192  * function returns true for a non-queue entity.
206 	 * not account for the in-service entity in case the latter is  in bfq_no_longer_next_in_service()
207 	 * removed from its active tree (which may get done after  in bfq_no_longer_next_in_service()
208 	 * invoking the function bfq_no_longer_next_in_service in  in bfq_no_longer_next_in_service()
210 	 * bfq_no_longer_next_in_service is not yet completed in  in bfq_no_longer_next_in_service()
215 	if (bfqg->active_entities == 1)  in bfq_no_longer_next_in_service()
223 	struct bfq_sched_data *sd = entity->sched_data;  in bfq_inc_active_entities()
226 	if (bfqg != bfqg->bfqd->root_group)  in bfq_inc_active_entities()
227 		bfqg->active_entities++;  in bfq_inc_active_entities()
232 	struct bfq_sched_data *sd = entity->sched_data;  in bfq_dec_active_entities()
235 	if (bfqg != bfqg->bfqd->root_group)  in bfq_dec_active_entities()
236 		bfqg->active_entities--;  in bfq_dec_active_entities()
263  * service allowed in one timestamp delta (small shift values increase it),
264  * the maximum total weight that can be used for the queues in the system
274 	if (!entity->my_sched_data)  in bfq_entity_to_bfqq()
282  * bfq_delta - map service into the virtual time domain.
292  * bfq_calc_finish - assign the finish time to an entity.
300 	entity->finish = entity->start +  in bfq_calc_finish()
301 		bfq_delta(service, entity->weight);  in bfq_calc_finish()
304 		bfq_log_bfqq(bfqq->bfqd, bfqq,  in bfq_calc_finish()
306 			service, entity->weight);  in bfq_calc_finish()
307 		bfq_log_bfqq(bfqq->bfqd, bfqq,  in bfq_calc_finish()
309 			entity->start, entity->finish,  in bfq_calc_finish()
310 			bfq_delta(service, entity->weight));  in bfq_calc_finish()
315  * bfq_entity_of - get an entity from a node.
320  * conversion mechanism because, e.g., in the tree walking functions,
334  * bfq_extract - remove an entity from a tree.
335  * @root: the tree root.
340 	entity->tree = NULL;  in bfq_extract()
341 	rb_erase(&entity->rb_node, root);  in bfq_extract()
345  * bfq_idle_extract - extract an entity from the idle tree.
346  * @st: the service tree of the owning @entity.
355 	if (entity == st->first_idle) {  in bfq_idle_extract()
356 		next = rb_next(&entity->rb_node);  in bfq_idle_extract()
357 		st->first_idle = bfq_entity_of(next);  in bfq_idle_extract()
360 	if (entity == st->last_idle) {  in bfq_idle_extract()
361 		next = rb_prev(&entity->rb_node);  in bfq_idle_extract()
362 		st->last_idle = bfq_entity_of(next);  in bfq_idle_extract()
365 	bfq_extract(&st->idle, entity);  in bfq_idle_extract()
368 		list_del(&bfqq->bfqq_list);  in bfq_idle_extract()
372  * bfq_insert - generic tree insertion.
373  * @root: tree root.
376  * This is used for the idle and the active tree, since they are both
382 	struct rb_node **node = &root->rb_node;  in bfq_insert()
389 		if (bfq_gt(entry->finish, entity->finish))  in bfq_insert()
390 			node = &parent->rb_left;  in bfq_insert()
392 			node = &parent->rb_right;  in bfq_insert()
395 	rb_link_node(&entity->rb_node, parent, node);  in bfq_insert()
396 	rb_insert_color(&entity->rb_node, root);  in bfq_insert()
398 	entity->tree = root;  in bfq_insert()
402  * bfq_update_min - update the min_start field of a entity.
407  * min_start due to updates to the active tree.  The function  assumes
417 		if (bfq_gt(entity->min_start, child->min_start))  in bfq_update_min()
418 			entity->min_start = child->min_start;  in bfq_update_min()
423  * bfq_update_active_node - recalculate min_start.
434 	entity->min_start = entity->start;  in bfq_update_active_node()
435 	bfq_update_min(entity, node->rb_right);  in bfq_update_active_node()
436 	bfq_update_min(entity, node->rb_left);  in bfq_update_active_node()
440  * bfq_update_active_tree - update min_start for the whole active tree.
446  * changed in the path to the root.  The only nodes that may have changed
447  * are the ones in the path or their siblings.
460 	if (node == parent->rb_left && parent->rb_right)  in bfq_update_active_tree()
461 		bfq_update_active_node(parent->rb_right);  in bfq_update_active_tree()
462 	else if (parent->rb_left)  in bfq_update_active_tree()
463 		bfq_update_active_node(parent->rb_left);  in bfq_update_active_tree()
470  * bfq_active_insert - insert an entity in the active tree of its
472  * @st: the service tree of the entity.
475  * The active tree is ordered by finish time, but an extra key is kept
478  * the eligible node with the lowest finish time in logarithmic time.
484 	struct rb_node *node = &entity->rb_node;  in bfq_active_insert()
486 	bfq_insert(&st->active, entity);  in bfq_active_insert()
488 	if (node->rb_left)  in bfq_active_insert()
489 		node = node->rb_left;  in bfq_active_insert()
490 	else if (node->rb_right)  in bfq_active_insert()
491 		node = node->rb_right;  in bfq_active_insert()
496 		list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list[bfqq->actuator_idx]);  in bfq_active_insert()
502  * bfq_ioprio_to_weight - calc a weight from an ioprio.
507 	return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;  in bfq_ioprio_to_weight()
511  * bfq_weight_to_ioprio - calc an ioprio from a weight.
514  * To preserve as much as possible the old only-ioprio user interface,
521 		     IOPRIO_NR_LEVELS - weight / BFQ_WEIGHT_CONVERSION_COEFF);  in bfq_weight_to_ioprio()
529 		bfqq->ref++;  in bfq_get_entity()
530 		bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",  in bfq_get_entity()
531 			     bfqq, bfqq->ref);  in bfq_get_entity()
536  * bfq_find_deepest - find the deepest node that an extraction can modify.
539  * Do the first step of an extraction in an rb tree, looking for the
541  * the following modifications to the tree can touch.  If @node is the
542  * last node in the tree return %NULL.
548 	if (!node->rb_right && !node->rb_left)  in bfq_find_deepest()
550 	else if (!node->rb_right)  in bfq_find_deepest()
551 		deepest = node->rb_left;  in bfq_find_deepest()
552 	else if (!node->rb_left)  in bfq_find_deepest()
553 		deepest = node->rb_right;  in bfq_find_deepest()
556 		if (deepest->rb_right)  in bfq_find_deepest()
557 			deepest = deepest->rb_right;  in bfq_find_deepest()
566  * bfq_active_extract - remove an entity from the active tree.
567  * @st: the service_tree containing the tree.
576 	node = bfq_find_deepest(&entity->rb_node);  in bfq_active_extract()
577 	bfq_extract(&st->active, entity);  in bfq_active_extract()
582 		list_del(&bfqq->bfqq_list);  in bfq_active_extract()
588  * bfq_idle_insert - insert an entity into the idle tree.
589  * @st: the service tree containing the tree.
596 	struct bfq_entity *first_idle = st->first_idle;  in bfq_idle_insert()
597 	struct bfq_entity *last_idle = st->last_idle;  in bfq_idle_insert()
599 	if (!first_idle || bfq_gt(first_idle->finish, entity->finish))  in bfq_idle_insert()
600 		st->first_idle = entity;  in bfq_idle_insert()
601 	if (!last_idle || bfq_gt(entity->finish, last_idle->finish))  in bfq_idle_insert()
602 		st->last_idle = entity;  in bfq_idle_insert()
604 	bfq_insert(&st->idle, entity);  in bfq_idle_insert()
607 		list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);  in bfq_idle_insert()
611  * bfq_forget_entity - do not consider entity any longer for scheduling
612  * @st: the service tree.
614  * @is_in_service: true if entity is currently the in-service entity.
616  * Forget everything about @entity. In addition, if entity represents
617  * a queue, and the latter is not in service, then release the service
618  * reference to the queue (the one taken through bfq_get_entity). In
619  * fact, in this case, there is really no more service reference to
620  * the queue, as the latter is also outside any service tree. If,
621  * instead, the queue is in service, then __bfq_bfqd_reset_in_service
631 	entity->on_st_or_in_serv = false;  in bfq_forget_entity()
632 	st->wsum -= entity->weight;  in bfq_forget_entity()
638  * bfq_put_idle_entity - release the idle tree ref of an entity.
639  * @st: service tree for the entity.
646 			  entity == entity->sched_data->in_service_entity);  in bfq_put_idle_entity()
650  * bfq_forget_idle - update the idle tree if necessary.
651  * @st: the service tree to act upon.
654  * as the idle tree will not grow indefinitely this can be done safely.
658 	struct bfq_entity *first_idle = st->first_idle;  in bfq_forget_idle()
659 	struct bfq_entity *last_idle = st->last_idle;  in bfq_forget_idle()
661 	if (RB_EMPTY_ROOT(&st->active) && last_idle &&  in bfq_forget_idle()
662 	    !bfq_gt(last_idle->finish, st->vtime)) {  in bfq_forget_idle()
664 		 * Forget the whole idle tree, increasing the vtime past  in bfq_forget_idle()
667 		st->vtime = last_idle->finish;  in bfq_forget_idle()
670 	if (first_idle && !bfq_gt(first_idle->finish, st->vtime))  in bfq_forget_idle()
676 	struct bfq_sched_data *sched_data = entity->sched_data;  in bfq_entity_service_tree()
679 	return sched_data->service_tree + idx;  in bfq_entity_service_tree()
697  * invoked with update_class_too unset in the points in the code where
698  * entity may happen to be on some tree.
707 	if (entity->prio_changed) {  in __bfq_entity_update_weight_prio()
711 		/* Matches the smp_wmb() in bfq_group_set_weight. */  in __bfq_entity_update_weight_prio()
713 		old_st->wsum -= entity->weight;  in __bfq_entity_update_weight_prio()
715 		if (entity->new_weight != entity->orig_weight) {  in __bfq_entity_update_weight_prio()
716 			if (entity->new_weight < BFQ_MIN_WEIGHT ||  in __bfq_entity_update_weight_prio()
717 			    entity->new_weight > BFQ_MAX_WEIGHT) {  in __bfq_entity_update_weight_prio()
719 					entity->new_weight);  in __bfq_entity_update_weight_prio()
720 				if (entity->new_weight < BFQ_MIN_WEIGHT)  in __bfq_entity_update_weight_prio()
721 					entity->new_weight = BFQ_MIN_WEIGHT;  in __bfq_entity_update_weight_prio()
723 					entity->new_weight = BFQ_MAX_WEIGHT;  in __bfq_entity_update_weight_prio()
725 			entity->orig_weight = entity->new_weight;  in __bfq_entity_update_weight_prio()
727 				bfqq->ioprio =  in __bfq_entity_update_weight_prio()
728 				  bfq_weight_to_ioprio(entity->orig_weight);  in __bfq_entity_update_weight_prio()
732 			bfqq->ioprio_class = bfqq->new_ioprio_class;  in __bfq_entity_update_weight_prio()
738 		if (!bfqq || bfqq->ioprio_class == bfqq->new_ioprio_class)  in __bfq_entity_update_weight_prio()
739 			entity->prio_changed = 0;  in __bfq_entity_update_weight_prio()
746 		 * when entity->finish <= old_st->vtime).  in __bfq_entity_update_weight_prio()
750 		prev_weight = entity->weight;  in __bfq_entity_update_weight_prio()
751 		new_weight = entity->orig_weight *  in __bfq_entity_update_weight_prio()
752 			     (bfqq ? bfqq->wr_coeff : 1);  in __bfq_entity_update_weight_prio()
760 		entity->weight = new_weight;  in __bfq_entity_update_weight_prio()
762 		 * Add the entity, if it is not a weight-raised queue,  in __bfq_entity_update_weight_prio()
765 		if (prev_weight != new_weight && bfqq && bfqq->wr_coeff == 1)  in __bfq_entity_update_weight_prio()
768 		new_st->wsum += entity->weight;  in __bfq_entity_update_weight_prio()
771 			entity->start = new_st->vtime;  in __bfq_entity_update_weight_prio()
778  * bfq_bfqq_served - update the scheduler status after selection for
789 	struct bfq_entity *entity = &bfqq->entity;  in bfq_bfqq_served()
792 	if (!bfqq->service_from_backlogged)  in bfq_bfqq_served()
793 		bfqq->first_IO_time = jiffies;  in bfq_bfqq_served()
795 	if (bfqq->wr_coeff > 1)  in bfq_bfqq_served()
796 		bfqq->service_from_wr += served;  in bfq_bfqq_served()
798 	bfqq->service_from_backlogged += served;  in bfq_bfqq_served()
802 		entity->service += served;  in bfq_bfqq_served()
804 		st->vtime += bfq_delta(served, st->wsum);  in bfq_bfqq_served()
807 	bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served);  in bfq_bfqq_served()
811  * bfq_bfqq_charge_time - charge an amount of service equivalent to the length
812  *			  of the time interval during which bfqq has been in
823  * engine works in the service, and not in the time domain. The trick
830  * distortions in terms of bandwidth distribution, on devices with
840 	struct bfq_entity *entity = &bfqq->entity;  in bfq_bfqq_charge_time()
844 		(bfqd->bfq_max_budget * bounded_time_ms) / timeout_ms;  in bfq_bfqq_charge_time()
845 	int tot_serv_to_charge = max(serv_to_charge_for_time, entity->service);  in bfq_bfqq_charge_time()
848 	if (tot_serv_to_charge > entity->budget)  in bfq_bfqq_charge_time()
849 		entity->budget = tot_serv_to_charge;  in bfq_bfqq_charge_time()
852 			max_t(int, 0, tot_serv_to_charge - entity->service));  in bfq_bfqq_charge_time()
862 	 * When this function is invoked, entity is not in any service  in bfq_update_fin_time_enqueue()
863 	 * tree, then it is safe to invoke next function with the last  in bfq_update_fin_time_enqueue()
867 	bfq_calc_finish(entity, entity->budget);  in bfq_update_fin_time_enqueue()
872 	 * lower than the system virtual time.	In particular, if  in bfq_update_fin_time_enqueue()
877 	 * the system virtual time. In fact, to serve the queues with  in bfq_update_fin_time_enqueue()
879 	 * idle, the system virtual time may be pushed-up to much  in bfq_update_fin_time_enqueue()
894 	 * worst-case fairness guarantees.  in bfq_update_fin_time_enqueue()
896 	 * As a special case, if bfqq is weight-raised, push up  in bfq_update_fin_time_enqueue()
899 	 * weight-raised queues to become higher than the backshifted  in bfq_update_fin_time_enqueue()
900 	 * finish timestamps of non weight-raised queues.  in bfq_update_fin_time_enqueue()
902 	if (backshifted && bfq_gt(st->vtime, entity->finish)) {  in bfq_update_fin_time_enqueue()
903 		unsigned long delta = st->vtime - entity->finish;  in bfq_update_fin_time_enqueue()
906 			delta /= bfqq->wr_coeff;  in bfq_update_fin_time_enqueue()
908 		entity->start += delta;  in bfq_update_fin_time_enqueue()
909 		entity->finish += delta;  in bfq_update_fin_time_enqueue()
916  * __bfq_activate_entity - handle activation of entity.
924  * inserts entity into its active tree, after possibly extracting it
925  * from its idle tree.
935 	if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) {  in __bfq_activate_entity()
937 		min_vstart = entity->finish;  in __bfq_activate_entity()
939 		min_vstart = st->vtime;  in __bfq_activate_entity()
941 	if (entity->tree == &st->idle) {  in __bfq_activate_entity()
943 		 * Must be on the idle tree, bfq_idle_extract() will  in __bfq_activate_entity()
947 		entity->start = bfq_gt(min_vstart, entity->finish) ?  in __bfq_activate_entity()
948 			min_vstart : entity->finish;  in __bfq_activate_entity()
952 		 * it is in the past for sure, otherwise the queue  in __bfq_activate_entity()
953 		 * would have been on the idle tree.  in __bfq_activate_entity()
955 		entity->start = min_vstart;  in __bfq_activate_entity()
956 		st->wsum += entity->weight;  in __bfq_activate_entity()
958 		 * entity is about to be inserted into a service tree,  in __bfq_activate_entity()
959 		 * and then set in service: get a reference to make  in __bfq_activate_entity()
961 		 * longer in service or scheduled for service.  in __bfq_activate_entity()
965 		entity->on_st_or_in_serv = true;  in __bfq_activate_entity()
972  * __bfq_requeue_entity - handle requeueing or repositioning of an entity.
981  * Basically, this function: 1) removes entity from its active tree if
983  * entity back into its active tree (in the new, right position for
988 	struct bfq_sched_data *sd = entity->sched_data;  in __bfq_requeue_entity()
991 	if (entity == sd->in_service_entity) {  in __bfq_requeue_entity()
993 		 * We are requeueing the current in-service entity,  in __bfq_requeue_entity()
996 		 * - entity represents the in-service queue, and the  in __bfq_requeue_entity()
997 		 *   in-service queue is being requeued after an  in __bfq_requeue_entity()
999 		 * - entity represents a group, and its budget has  in __bfq_requeue_entity()
1006 		 * In particular, before requeueing, the start time of  in __bfq_requeue_entity()
1008 		 * service that the entity has received while in  in __bfq_requeue_entity()
1014 		bfq_calc_finish(entity, entity->service);  in __bfq_requeue_entity()
1015 		entity->start = entity->finish;  in __bfq_requeue_entity()
1017 		 * In addition, if the entity had more than one child  in __bfq_requeue_entity()
1018 		 * when set in service, then it was not extracted from  in __bfq_requeue_entity()
1019 		 * the active tree. This implies that the position of  in __bfq_requeue_entity()
1020 		 * the entity in the active tree may need to be  in __bfq_requeue_entity()
1023 		 * time in a moment (the requeueing is then, more  in __bfq_requeue_entity()
1024 		 * precisely, a repositioning in this case). To  in __bfq_requeue_entity()
1029 		if (entity->tree)  in __bfq_requeue_entity()
1031 	} else { /* The entity is already active, and not in service */  in __bfq_requeue_entity()
1033 		 * In this case, this function gets called only if the  in __bfq_requeue_entity()
1039 		 * i.e., the position in the active tree, of this  in __bfq_requeue_entity()
1044 		 * non-extracted-entity sub-case above.  in __bfq_requeue_entity()
1057 	if (entity->sched_data->in_service_entity == entity ||  in __bfq_activate_requeue_entity()
1058 	    entity->tree == &st->active)  in __bfq_activate_requeue_entity()
1060 		  * in service or already queued on the active tree,  in __bfq_activate_requeue_entity()
1066 		 * Not in service and not queued on its active tree:  in __bfq_activate_requeue_entity()
1074  * bfq_activate_requeue_entity - activate or requeue an entity representing a
1083  * @expiration: true if this function is being invoked in the expiration path
1084  *             of the in-service queue
1092 		if (!bfq_update_next_in_service(entity->sched_data, entity,  in bfq_activate_requeue_entity()
1099  * __bfq_deactivate_entity - update sched_data and service trees for
1103  *			idle tree.
1105  * If necessary and allowed, puts entity into the idle tree. NOTE:
1106  * entity may be on no tree if in service.
1110 	struct bfq_sched_data *sd = entity->sched_data;  in __bfq_deactivate_entity()
1114 	if (!entity->on_st_or_in_serv) /*  in __bfq_deactivate_entity()
1124 	 * entity->sched_data has been set, and we can safely use it.  in __bfq_deactivate_entity()
1127 	is_in_service = entity == sd->in_service_entity;  in __bfq_deactivate_entity()
1129 	bfq_calc_finish(entity, entity->service);  in __bfq_deactivate_entity()
1132 		sd->in_service_entity = NULL;  in __bfq_deactivate_entity()
1135 		 * Non in-service entity: nobody will take care of  in __bfq_deactivate_entity()
1139 		entity->service = 0;  in __bfq_deactivate_entity()
1141 	if (entity->tree == &st->active)  in __bfq_deactivate_entity()
1143 	else if (!is_in_service && entity->tree == &st->idle)  in __bfq_deactivate_entity()
1146 	if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime))  in __bfq_deactivate_entity()
1155  * bfq_deactivate_entity - deactivate an entity representing a bfq_queue.
1157  * @ins_into_idle_tree: true if the entity can be put into the idle tree
1158  * @expiration: true if this function is being invoked in the expiration path
1159  *             of the in-service queue
1169 		sd = entity->sched_data;  in bfq_deactivate_entity()
1173 			 * entity is not in any tree any more, so  in bfq_deactivate_entity()
1174 			 * this deactivation is a no-op, and there is  in bfq_deactivate_entity()
1175 			 * nothing to change for upper-level entities  in bfq_deactivate_entity()
1176 			 * (in case of expiration, this can never  in bfq_deactivate_entity()
1182 		if (sd->next_in_service == entity)  in bfq_deactivate_entity()
1190 		if (sd->next_in_service || sd->in_service_entity) {  in bfq_deactivate_entity()
1204 			 * active entity in the parent entity, and 2)  in bfq_deactivate_entity()
1221 		 * Also let parent be queued into the idle tree on  in bfq_deactivate_entity()
1240 		 * already active, to requeue/reposition it in the  in bfq_deactivate_entity()
1241 		 * active tree (because sd->next_in_service has  in bfq_deactivate_entity()
1246 		sd = entity->sched_data;  in bfq_deactivate_entity()
1251 			 * any change in entity->parent->sd, and no  in bfq_deactivate_entity()
1260  * bfq_calc_vtime_jump - compute the value to which the vtime should jump,
1262  * @st: the service tree to act upon.
1268 	struct bfq_entity *root_entity = bfq_root_active_entity(&st->active);  in bfq_calc_vtime_jump()
1270 	if (bfq_gt(root_entity->min_start, st->vtime))  in bfq_calc_vtime_jump()
1271 		return root_entity->min_start;  in bfq_calc_vtime_jump()
1273 	return st->vtime;  in bfq_calc_vtime_jump()
1278 	if (new_value > st->vtime) {  in bfq_update_vtime()
1279 		st->vtime = new_value;  in bfq_update_vtime()
1285  * bfq_first_active_entity - find the eligible entity with
1287  * @st: the service tree to select from.
1291  * root of the tree and going on the left every time on this side there is
1300 	struct rb_node *node = st->active.rb_node;  in bfq_first_active_entity()
1305 		if (!bfq_gt(entry->start, vtime))  in bfq_first_active_entity()
1308 		if (node->rb_left) {  in bfq_first_active_entity()
1309 			entry = rb_entry(node->rb_left,  in bfq_first_active_entity()
1311 			if (!bfq_gt(entry->min_start, vtime)) {  in bfq_first_active_entity()
1312 				node = node->rb_left;  in bfq_first_active_entity()
1318 		node = node->rb_right;  in bfq_first_active_entity()
1325  * __bfq_lookup_next_entity - return the first eligible entity in @st.
1326  * @st: the service tree.
1327  * @in_service: whether or not there is an in-service entity for the sched_data
1328  *	this active tree belongs to.
1330  * If there is no in-service entity for the sched_data st belongs to,
1331  * then return the entity that will be set in service if:
1332  * 1) the parent entity this st belongs to is set in service;
1337  * In this first case, update the virtual time in @st too (see the
1340  * In contrast, if there is an in-service entity, then return the
1341  * entity that would be set in service if not only the above
1343  * in-service entity, on expiration,
1354 	if (RB_EMPTY_ROOT(&st->active))  in __bfq_lookup_next_entity()
1364 	 * If there is no in-service entity for the sched_data this  in __bfq_lookup_next_entity()
1365 	 * active tree belongs to, then push the system virtual time  in __bfq_lookup_next_entity()
1367 	 * eligible. If, instead, there is an in-service entity, then  in __bfq_lookup_next_entity()
1369 	 * eligible entity, namely the in-service one (even if the  in __bfq_lookup_next_entity()
1370 	 * entity is not on st, because it was extracted when set in  in __bfq_lookup_next_entity()
1382  * bfq_lookup_next_entity - return the first eligible entity in @sd.
1384  * @expiration: true if we are on the expiration path of the in-service queue
1386  * This function is invoked when there has been a change in the trees
1393 	struct bfq_service_tree *st = sd->service_tree;  in bfq_lookup_next_entity()
1394 	struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1);  in bfq_lookup_next_entity()
1401 	 * in idle class). This should also mitigate  in bfq_lookup_next_entity()
1402 	 * priority-inversion problems in case a low priority task is  in bfq_lookup_next_entity()
1405 	if (time_is_before_jiffies(sd->bfq_class_idle_last_service +  in bfq_lookup_next_entity()
1407 		if (!RB_EMPTY_ROOT(&idle_class_st->active))  in bfq_lookup_next_entity()
1408 			class_idx = BFQ_IOPRIO_CLASSES - 1;  in bfq_lookup_next_entity()
1410 		sd->bfq_class_idle_last_service = jiffies;  in bfq_lookup_next_entity()
1414 	 * Find the next entity to serve for the highest-priority  in bfq_lookup_next_entity()
1421 		 * of the in-service queue. In this case, even if  in bfq_lookup_next_entity()
1422 		 * sd->in_service_entity is not NULL,  in bfq_lookup_next_entity()
1423 		 * sd->in_service_entity at this point is actually not  in bfq_lookup_next_entity()
1424 		 * in service any more, and, if needed, has already  in bfq_lookup_next_entity()
1426 		 * tree. The reason why sd->in_service_entity is still  in bfq_lookup_next_entity()
1428 		 * sd->in_service_entity is reset as a last step in the  in bfq_lookup_next_entity()
1431 		 * sd->in_service_entity.  in bfq_lookup_next_entity()
1434 						  sd->in_service_entity &&  in bfq_lookup_next_entity()
1446 	struct bfq_sched_data *sd = &bfqd->root_group->sched_data;  in next_queue_may_preempt()
1448 	return sd->next_in_service != sd->in_service_entity;  in next_queue_may_preempt()
1465 	 * serve. Set in service all the entities visited along the  in bfq_get_next_queue()
1468 	sd = &bfqd->root_group->sched_data;  in bfq_get_next_queue()
1469 	for (; sd ; sd = entity->my_sched_data) {  in bfq_get_next_queue()
1471 		 * WARNING. We are about to set the in-service entity  in bfq_get_next_queue()
1472 		 * to sd->next_in_service, i.e., to the (cached) value  in bfq_get_next_queue()
1475 		 * service order in sd changed as a consequence of the  in bfq_get_next_queue()
1476 		 * activation or deactivation of an entity. In this  in bfq_get_next_queue()
1478 		 * in this very moment, it may, although with low  in bfq_get_next_queue()
1480 		 * pointed to by sd->next_in_service. This rare event  in bfq_get_next_queue()
1481 		 * happens in case there was no CLASS_IDLE entity to  in bfq_get_next_queue()
1487 		 * such entity in CLASS_IDLE is postponed until the  in bfq_get_next_queue()
1488 		 * service of the sd->next_in_service entity  in bfq_get_next_queue()
1489 		 * finishes. In fact, when the latter is expired,  in bfq_get_next_queue()
1491 		 * exactly to update sd->next_in_service.  in bfq_get_next_queue()
1495 		entity = sd->next_in_service;  in bfq_get_next_queue()
1496 		sd->in_service_entity = entity;  in bfq_get_next_queue()
1501 		 * tree, so as to make sure that it won't be  in bfq_get_next_queue()
1513 		 * extracted in one of the next iterations of this  in bfq_get_next_queue()
1514 		 * loop. Such an event could cause a change in  in bfq_get_next_queue()
1521 		 * the correct next-to-serve candidate entity for each  in bfq_get_next_queue()
1523 		 * in service. In fact, only after we know which is  in bfq_get_next_queue()
1524 		 * the next-to-serve leaf entity, we can discover  in bfq_get_next_queue()
1526 		 * becomes the next-to-serve, and so on.  in bfq_get_next_queue()
1533 	 * We can finally update all next-to-serve entities along the  in bfq_get_next_queue()
1534 	 * path from the leaf entity just set in service to the root.  in bfq_get_next_queue()
1537 		struct bfq_sched_data *sd = entity->sched_data;  in bfq_get_next_queue()
1546 /* returns true if the in-service queue gets freed */
1549 	struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue;  in __bfq_bfqd_reset_in_service()
1550 	struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity;  in __bfq_bfqd_reset_in_service()
1554 	hrtimer_try_to_cancel(&bfqd->idle_slice_timer);  in __bfq_bfqd_reset_in_service()
1555 	bfqd->in_service_queue = NULL;  in __bfq_bfqd_reset_in_service()
1558 	 * When this function is called, all in-service entities have  in __bfq_bfqd_reset_in_service()
1564 		entity->sched_data->in_service_entity = NULL;  in __bfq_bfqd_reset_in_service()
1567 	 * in_serv_entity is no longer in service, so, if it is in no  in __bfq_bfqd_reset_in_service()
1568 	 * service tree either, then release the service reference to  in __bfq_bfqd_reset_in_service()
1571 	if (!in_serv_entity->on_st_or_in_serv) {  in __bfq_bfqd_reset_in_service()
1578 		int ref = in_serv_bfqq->ref;  in __bfq_bfqd_reset_in_service()
1590 	struct bfq_entity *entity = &bfqq->entity;  in bfq_deactivate_bfqq()
1597 	struct bfq_entity *entity = &bfqq->entity;  in bfq_activate_bfqq()
1607 	struct bfq_entity *entity = &bfqq->entity;  in bfq_requeue_bfqq()
1610 				    bfqq == bfqd->in_service_queue, expiration);  in bfq_requeue_bfqq()
1616 	struct bfq_entity *entity = &bfqq->entity;  in bfq_add_bfqq_in_groups_with_pending_reqs()
1618 	if (!entity->in_groups_with_pending_reqs) {  in bfq_add_bfqq_in_groups_with_pending_reqs()
1619 		entity->in_groups_with_pending_reqs = true;  in bfq_add_bfqq_in_groups_with_pending_reqs()
1620 		if (!(bfqq_group(bfqq)->num_queues_with_pending_reqs++))  in bfq_add_bfqq_in_groups_with_pending_reqs()
1621 			bfqq->bfqd->num_groups_with_pending_reqs++;  in bfq_add_bfqq_in_groups_with_pending_reqs()
1629 	struct bfq_entity *entity = &bfqq->entity;  in bfq_del_bfqq_in_groups_with_pending_reqs()
1631 	if (entity->in_groups_with_pending_reqs) {  in bfq_del_bfqq_in_groups_with_pending_reqs()
1632 		entity->in_groups_with_pending_reqs = false;  in bfq_del_bfqq_in_groups_with_pending_reqs()
1633 		if (!(--bfqq_group(bfqq)->num_queues_with_pending_reqs))  in bfq_del_bfqq_in_groups_with_pending_reqs()
1634 			bfqq->bfqd->num_groups_with_pending_reqs--;  in bfq_del_bfqq_in_groups_with_pending_reqs()
1641  * the service tree. As a special case, it can be invoked during an
1646 	struct bfq_data *bfqd = bfqq->bfqd;  in bfq_del_bfqq_busy()
1652 	bfqd->busy_queues[bfqq->ioprio_class - 1]--;  in bfq_del_bfqq_busy()
1654 	if (bfqq->wr_coeff > 1)  in bfq_del_bfqq_busy()
1655 		bfqd->wr_busy_queues--;  in bfq_del_bfqq_busy()
1661 	if (!bfqq->dispatched) {  in bfq_del_bfqq_busy()
1676 	struct bfq_data *bfqd = bfqq->bfqd;  in bfq_add_bfqq_busy()
1683 	bfqd->busy_queues[bfqq->ioprio_class - 1]++;  in bfq_add_bfqq_busy()
1685 	if (!bfqq->dispatched) {  in bfq_add_bfqq_busy()
1687 		if (bfqq->wr_coeff == 1)  in bfq_add_bfqq_busy()
1691 	if (bfqq->wr_coeff > 1)  in bfq_add_bfqq_busy()
1692 		bfqd->wr_busy_queues++;  in bfq_add_bfqq_busy()
1695 	if (!hlist_unhashed(&bfqq->woken_list_node) &&  in bfq_add_bfqq_busy()
1696 	    &bfqq->woken_list_node != bfqq->waker_bfqq->woken_list.first) {  in bfq_add_bfqq_busy()
1697 		hlist_del_init(&bfqq->woken_list_node);  in bfq_add_bfqq_busy()
1698 		hlist_add_head(&bfqq->woken_list_node,  in bfq_add_bfqq_busy()
1699 			       &bfqq->waker_bfqq->woken_list);  in bfq_add_bfqq_busy()