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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Hierarchical Budget Worst-case Fair Weighted Fair Queueing4 * (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O5 * scheduler schedules generic entities. The latter can represent6 * either single bfq queues (associated with processes) or groups of7 * bfq queues (associated with cgroups).8 */9#include "bfq-iosched.h"10 11/**12 * bfq_gt - compare two timestamps.13 * @a: first ts.14 * @b: second ts.15 *16 * Return @a > @b, dealing with wrapping correctly.17 */18static int bfq_gt(u64 a, u64 b)19{20 return (s64)(a - b) > 0;21}22 23static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree)24{25 struct rb_node *node = tree->rb_node;26 27 return rb_entry(node, struct bfq_entity, rb_node);28}29 30static unsigned int bfq_class_idx(struct bfq_entity *entity)31{32 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);33 34 return bfqq ? bfqq->ioprio_class - 1 :35 BFQ_DEFAULT_GRP_CLASS - 1;36}37 38unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd)39{40 return bfqd->busy_queues[0] + bfqd->busy_queues[1] +41 bfqd->busy_queues[2];42}43 44static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,45 bool expiration);46 47static bool bfq_update_parent_budget(struct bfq_entity *next_in_service);48 49/**50 * bfq_update_next_in_service - update sd->next_in_service51 * @sd: sched_data for which to perform the update.52 * @new_entity: if not NULL, pointer to the entity whose activation,53 * requeueing or repositioning triggered the invocation of54 * this function.55 * @expiration: id true, this function is being invoked after the56 * expiration of the in-service entity57 *58 * This function is called to update sd->next_in_service, which, in59 * its turn, may change as a consequence of the insertion or60 * extraction of an entity into/from one of the active trees of61 * sd. These insertions/extractions occur as a consequence of62 * activations/deactivations of entities, with some activations being63 * 'true' activations, and other activations being requeueings (i.e.,64 * implementing the second, requeueing phase of the mechanism used to65 * reposition an entity in its active tree; see comments on66 * __bfq_activate_entity and __bfq_requeue_entity for details). In67 * both the last two activation sub-cases, new_entity points to the68 * just activated or requeued entity.69 *70 * Returns true if sd->next_in_service changes in such a way that71 * entity->parent may become the next_in_service for its parent72 * entity.73 */74static bool bfq_update_next_in_service(struct bfq_sched_data *sd,75 struct bfq_entity *new_entity,76 bool expiration)77{78 struct bfq_entity *next_in_service = sd->next_in_service;79 bool parent_sched_may_change = false;80 bool change_without_lookup = false;81 82 /*83 * If this update is triggered by the activation, requeueing84 * or repositioning of an entity that does not coincide with85 * sd->next_in_service, then a full lookup in the active tree86 * can be avoided. In fact, it is enough to check whether the87 * just-modified entity has the same priority as88 * sd->next_in_service, is eligible and has a lower virtual89 * finish time than sd->next_in_service. If this compound90 * condition holds, then the new entity becomes the new91 * next_in_service. Otherwise no change is needed.92 */93 if (new_entity && new_entity != sd->next_in_service) {94 /*95 * Flag used to decide whether to replace96 * sd->next_in_service with new_entity. Tentatively97 * set to true, and left as true if98 * sd->next_in_service is NULL.99 */100 change_without_lookup = true;101 102 /*103 * If there is already a next_in_service candidate104 * entity, then compare timestamps to decide whether105 * to replace sd->service_tree with new_entity.106 */107 if (next_in_service) {108 unsigned int new_entity_class_idx =109 bfq_class_idx(new_entity);110 struct bfq_service_tree *st =111 sd->service_tree + new_entity_class_idx;112 113 change_without_lookup =114 (new_entity_class_idx ==115 bfq_class_idx(next_in_service)116 &&117 !bfq_gt(new_entity->start, st->vtime)118 &&119 bfq_gt(next_in_service->finish,120 new_entity->finish));121 }122 123 if (change_without_lookup)124 next_in_service = new_entity;125 }126 127 if (!change_without_lookup) /* lookup needed */128 next_in_service = bfq_lookup_next_entity(sd, expiration);129 130 if (next_in_service) {131 bool new_budget_triggers_change =132 bfq_update_parent_budget(next_in_service);133 134 parent_sched_may_change = !sd->next_in_service ||135 new_budget_triggers_change;136 }137 138 sd->next_in_service = next_in_service;139 140 return parent_sched_may_change;141}142 143#ifdef CONFIG_BFQ_GROUP_IOSCHED144 145/*146 * Returns true if this budget changes may let next_in_service->parent147 * become the next_in_service entity for its parent entity.148 */149static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)150{151 struct bfq_entity *bfqg_entity;152 struct bfq_group *bfqg;153 struct bfq_sched_data *group_sd;154 bool ret = false;155 156 group_sd = next_in_service->sched_data;157 158 bfqg = container_of(group_sd, struct bfq_group, sched_data);159 /*160 * bfq_group's my_entity field is not NULL only if the group161 * is not the root group. We must not touch the root entity162 * as it must never become an in-service entity.163 */164 bfqg_entity = bfqg->my_entity;165 if (bfqg_entity) {166 if (bfqg_entity->budget > next_in_service->budget)167 ret = true;168 bfqg_entity->budget = next_in_service->budget;169 }170 171 return ret;172}173 174/*175 * This function tells whether entity stops being a candidate for next176 * service, according to the restrictive definition of the field177 * next_in_service. In particular, this function is invoked for an178 * entity that is about to be set in service.179 *180 * If entity is a queue, then the entity is no longer a candidate for181 * next service according to the that definition, because entity is182 * about to become the in-service queue. This function then returns183 * true if entity is a queue.184 *185 * In contrast, entity could still be a candidate for next service if186 * 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, other188 * active children may still be the next to serve, for the parent189 * entity, even according to the above definition. As a consequence, a190 * non-queue entity is not a candidate for next-service only if it has191 * only one active child. And only if this condition holds, then this192 * function returns true for a non-queue entity.193 */194static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)195{196 struct bfq_group *bfqg;197 198 if (bfq_entity_to_bfqq(entity))199 return true;200 201 bfqg = container_of(entity, struct bfq_group, entity);202 203 /*204 * The field active_entities does not always contain the205 * actual number of active children entities: it happens to206 * not account for the in-service entity in case the latter is207 * removed from its active tree (which may get done after208 * invoking the function bfq_no_longer_next_in_service in209 * bfq_get_next_queue). Fortunately, here, i.e., while210 * bfq_no_longer_next_in_service is not yet completed in211 * bfq_get_next_queue, bfq_active_extract has not yet been212 * invoked, and thus active_entities still coincides with the213 * actual number of active entities.214 */215 if (bfqg->active_entities == 1)216 return true;217 218 return false;219}220 221static void bfq_inc_active_entities(struct bfq_entity *entity)222{223 struct bfq_sched_data *sd = entity->sched_data;224 struct bfq_group *bfqg = container_of(sd, struct bfq_group, sched_data);225 226 if (bfqg != bfqg->bfqd->root_group)227 bfqg->active_entities++;228}229 230static void bfq_dec_active_entities(struct bfq_entity *entity)231{232 struct bfq_sched_data *sd = entity->sched_data;233 struct bfq_group *bfqg = container_of(sd, struct bfq_group, sched_data);234 235 if (bfqg != bfqg->bfqd->root_group)236 bfqg->active_entities--;237}238 239#else /* CONFIG_BFQ_GROUP_IOSCHED */240 241static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)242{243 return false;244}245 246static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)247{248 return true;249}250 251static void bfq_inc_active_entities(struct bfq_entity *entity)252{253}254 255static void bfq_dec_active_entities(struct bfq_entity *entity)256{257}258 259#endif /* CONFIG_BFQ_GROUP_IOSCHED */260 261/*262 * Shift for timestamp calculations. This actually limits the maximum263 * 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 system265 * (big shift values increase it), and the period of virtual time266 * wraparounds.267 */268#define WFQ_SERVICE_SHIFT 22269 270struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity)271{272 struct bfq_queue *bfqq = NULL;273 274 if (!entity->my_sched_data)275 bfqq = container_of(entity, struct bfq_queue, entity);276 277 return bfqq;278}279 280 281/**282 * bfq_delta - map service into the virtual time domain.283 * @service: amount of service.284 * @weight: scale factor (weight of an entity or weight sum).285 */286static u64 bfq_delta(unsigned long service, unsigned long weight)287{288 return div64_ul((u64)service << WFQ_SERVICE_SHIFT, weight);289}290 291/**292 * bfq_calc_finish - assign the finish time to an entity.293 * @entity: the entity to act upon.294 * @service: the service to be charged to the entity.295 */296static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service)297{298 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);299 300 entity->finish = entity->start +301 bfq_delta(service, entity->weight);302 303 if (bfqq) {304 bfq_log_bfqq(bfqq->bfqd, bfqq,305 "calc_finish: serv %lu, w %d",306 service, entity->weight);307 bfq_log_bfqq(bfqq->bfqd, bfqq,308 "calc_finish: start %llu, finish %llu, delta %llu",309 entity->start, entity->finish,310 bfq_delta(service, entity->weight));311 }312}313 314/**315 * bfq_entity_of - get an entity from a node.316 * @node: the node field of the entity.317 *318 * Convert a node pointer to the relative entity. This is used only319 * to simplify the logic of some functions and not as the generic320 * conversion mechanism because, e.g., in the tree walking functions,321 * the check for a %NULL value would be redundant.322 */323struct bfq_entity *bfq_entity_of(struct rb_node *node)324{325 struct bfq_entity *entity = NULL;326 327 if (node)328 entity = rb_entry(node, struct bfq_entity, rb_node);329 330 return entity;331}332 333/**334 * bfq_extract - remove an entity from a tree.335 * @root: the tree root.336 * @entity: the entity to remove.337 */338static void bfq_extract(struct rb_root *root, struct bfq_entity *entity)339{340 entity->tree = NULL;341 rb_erase(&entity->rb_node, root);342}343 344/**345 * bfq_idle_extract - extract an entity from the idle tree.346 * @st: the service tree of the owning @entity.347 * @entity: the entity being removed.348 */349static void bfq_idle_extract(struct bfq_service_tree *st,350 struct bfq_entity *entity)351{352 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);353 struct rb_node *next;354 355 if (entity == st->first_idle) {356 next = rb_next(&entity->rb_node);357 st->first_idle = bfq_entity_of(next);358 }359 360 if (entity == st->last_idle) {361 next = rb_prev(&entity->rb_node);362 st->last_idle = bfq_entity_of(next);363 }364 365 bfq_extract(&st->idle, entity);366 367 if (bfqq)368 list_del(&bfqq->bfqq_list);369}370 371/**372 * bfq_insert - generic tree insertion.373 * @root: tree root.374 * @entity: entity to insert.375 *376 * This is used for the idle and the active tree, since they are both377 * ordered by finish time.378 */379static void bfq_insert(struct rb_root *root, struct bfq_entity *entity)380{381 struct bfq_entity *entry;382 struct rb_node **node = &root->rb_node;383 struct rb_node *parent = NULL;384 385 while (*node) {386 parent = *node;387 entry = rb_entry(parent, struct bfq_entity, rb_node);388 389 if (bfq_gt(entry->finish, entity->finish))390 node = &parent->rb_left;391 else392 node = &parent->rb_right;393 }394 395 rb_link_node(&entity->rb_node, parent, node);396 rb_insert_color(&entity->rb_node, root);397 398 entity->tree = root;399}400 401/**402 * bfq_update_min - update the min_start field of a entity.403 * @entity: the entity to update.404 * @node: one of its children.405 *406 * This function is called when @entity may store an invalid value for407 * min_start due to updates to the active tree. The function assumes408 * that the subtree rooted at @node (which may be its left or its right409 * child) has a valid min_start value.410 */411static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node)412{413 struct bfq_entity *child;414 415 if (node) {416 child = rb_entry(node, struct bfq_entity, rb_node);417 if (bfq_gt(entity->min_start, child->min_start))418 entity->min_start = child->min_start;419 }420}421 422/**423 * bfq_update_active_node - recalculate min_start.424 * @node: the node to update.425 *426 * @node may have changed position or one of its children may have moved,427 * this function updates its min_start value. The left and right subtrees428 * are assumed to hold a correct min_start value.429 */430static void bfq_update_active_node(struct rb_node *node)431{432 struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node);433 434 entity->min_start = entity->start;435 bfq_update_min(entity, node->rb_right);436 bfq_update_min(entity, node->rb_left);437}438 439/**440 * bfq_update_active_tree - update min_start for the whole active tree.441 * @node: the starting node.442 *443 * @node must be the deepest modified node after an update. This function444 * updates its min_start using the values held by its children, assuming445 * that they did not change, and then updates all the nodes that may have446 * changed in the path to the root. The only nodes that may have changed447 * are the ones in the path or their siblings.448 */449static void bfq_update_active_tree(struct rb_node *node)450{451 struct rb_node *parent;452 453up:454 bfq_update_active_node(node);455 456 parent = rb_parent(node);457 if (!parent)458 return;459 460 if (node == parent->rb_left && parent->rb_right)461 bfq_update_active_node(parent->rb_right);462 else if (parent->rb_left)463 bfq_update_active_node(parent->rb_left);464 465 node = parent;466 goto up;467}468 469/**470 * bfq_active_insert - insert an entity in the active tree of its471 * group/device.472 * @st: the service tree of the entity.473 * @entity: the entity being inserted.474 *475 * The active tree is ordered by finish time, but an extra key is kept476 * per each node, containing the minimum value for the start times of477 * its children (and the node itself), so it's possible to search for478 * the eligible node with the lowest finish time in logarithmic time.479 */480static void bfq_active_insert(struct bfq_service_tree *st,481 struct bfq_entity *entity)482{483 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);484 struct rb_node *node = &entity->rb_node;485 486 bfq_insert(&st->active, entity);487 488 if (node->rb_left)489 node = node->rb_left;490 else if (node->rb_right)491 node = node->rb_right;492 493 bfq_update_active_tree(node);494 495 if (bfqq)496 list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list[bfqq->actuator_idx]);497 498 bfq_inc_active_entities(entity);499}500 501/**502 * bfq_ioprio_to_weight - calc a weight from an ioprio.503 * @ioprio: the ioprio value to convert.504 */505unsigned short bfq_ioprio_to_weight(int ioprio)506{507 return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;508}509 510/**511 * bfq_weight_to_ioprio - calc an ioprio from a weight.512 * @weight: the weight value to convert.513 *514 * To preserve as much as possible the old only-ioprio user interface,515 * 0 is used as an escape ioprio value for weights (numerically) equal or516 * larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.517 */518static unsigned short bfq_weight_to_ioprio(int weight)519{520 return max_t(int, 0,521 IOPRIO_NR_LEVELS - weight / BFQ_WEIGHT_CONVERSION_COEFF);522}523 524static void bfq_get_entity(struct bfq_entity *entity)525{526 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);527 528 if (bfqq) {529 bfqq->ref++;530 bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",531 bfqq, bfqq->ref);532 }533}534 535/**536 * bfq_find_deepest - find the deepest node that an extraction can modify.537 * @node: the node being removed.538 *539 * Do the first step of an extraction in an rb tree, looking for the540 * node that will replace @node, and returning the deepest node that541 * the following modifications to the tree can touch. If @node is the542 * last node in the tree return %NULL.543 */544static struct rb_node *bfq_find_deepest(struct rb_node *node)545{546 struct rb_node *deepest;547 548 if (!node->rb_right && !node->rb_left)549 deepest = rb_parent(node);550 else if (!node->rb_right)551 deepest = node->rb_left;552 else if (!node->rb_left)553 deepest = node->rb_right;554 else {555 deepest = rb_next(node);556 if (deepest->rb_right)557 deepest = deepest->rb_right;558 else if (rb_parent(deepest) != node)559 deepest = rb_parent(deepest);560 }561 562 return deepest;563}564 565/**566 * bfq_active_extract - remove an entity from the active tree.567 * @st: the service_tree containing the tree.568 * @entity: the entity being removed.569 */570static void bfq_active_extract(struct bfq_service_tree *st,571 struct bfq_entity *entity)572{573 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);574 struct rb_node *node;575 576 node = bfq_find_deepest(&entity->rb_node);577 bfq_extract(&st->active, entity);578 579 if (node)580 bfq_update_active_tree(node);581 if (bfqq)582 list_del(&bfqq->bfqq_list);583 584 bfq_dec_active_entities(entity);585}586 587/**588 * bfq_idle_insert - insert an entity into the idle tree.589 * @st: the service tree containing the tree.590 * @entity: the entity to insert.591 */592static void bfq_idle_insert(struct bfq_service_tree *st,593 struct bfq_entity *entity)594{595 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);596 struct bfq_entity *first_idle = st->first_idle;597 struct bfq_entity *last_idle = st->last_idle;598 599 if (!first_idle || bfq_gt(first_idle->finish, entity->finish))600 st->first_idle = entity;601 if (!last_idle || bfq_gt(entity->finish, last_idle->finish))602 st->last_idle = entity;603 604 bfq_insert(&st->idle, entity);605 606 if (bfqq)607 list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);608}609 610/**611 * bfq_forget_entity - do not consider entity any longer for scheduling612 * @st: the service tree.613 * @entity: the entity being removed.614 * @is_in_service: true if entity is currently the in-service entity.615 *616 * Forget everything about @entity. In addition, if entity represents617 * a queue, and the latter is not in service, then release the service618 * reference to the queue (the one taken through bfq_get_entity). In619 * fact, in this case, there is really no more service reference to620 * the queue, as the latter is also outside any service tree. If,621 * instead, the queue is in service, then __bfq_bfqd_reset_in_service622 * will take care of putting the reference when the queue finally623 * stops being served.624 */625static void bfq_forget_entity(struct bfq_service_tree *st,626 struct bfq_entity *entity,627 bool is_in_service)628{629 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);630 631 entity->on_st_or_in_serv = false;632 st->wsum -= entity->weight;633 if (bfqq && !is_in_service)634 bfq_put_queue(bfqq);635}636 637/**638 * bfq_put_idle_entity - release the idle tree ref of an entity.639 * @st: service tree for the entity.640 * @entity: the entity being released.641 */642void bfq_put_idle_entity(struct bfq_service_tree *st, struct bfq_entity *entity)643{644 bfq_idle_extract(st, entity);645 bfq_forget_entity(st, entity,646 entity == entity->sched_data->in_service_entity);647}648 649/**650 * bfq_forget_idle - update the idle tree if necessary.651 * @st: the service tree to act upon.652 *653 * To preserve the global O(log N) complexity we only remove one entry here;654 * as the idle tree will not grow indefinitely this can be done safely.655 */656static void bfq_forget_idle(struct bfq_service_tree *st)657{658 struct bfq_entity *first_idle = st->first_idle;659 struct bfq_entity *last_idle = st->last_idle;660 661 if (RB_EMPTY_ROOT(&st->active) && last_idle &&662 !bfq_gt(last_idle->finish, st->vtime)) {663 /*664 * Forget the whole idle tree, increasing the vtime past665 * the last finish time of idle entities.666 */667 st->vtime = last_idle->finish;668 }669 670 if (first_idle && !bfq_gt(first_idle->finish, st->vtime))671 bfq_put_idle_entity(st, first_idle);672}673 674struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity)675{676 struct bfq_sched_data *sched_data = entity->sched_data;677 unsigned int idx = bfq_class_idx(entity);678 679 return sched_data->service_tree + idx;680}681 682/*683 * Update weight and priority of entity. If update_class_too is true,684 * then update the ioprio_class of entity too.685 *686 * The reason why the update of ioprio_class is controlled through the687 * last parameter is as follows. Changing the ioprio class of an688 * entity implies changing the destination service trees for that689 * entity. If such a change occurred when the entity is already on one690 * of the service trees for its previous class, then the state of the691 * entity would become more complex: none of the new possible service692 * trees for the entity, according to bfq_entity_service_tree(), would693 * match any of the possible service trees on which the entity694 * is. Complex operations involving these trees, such as entity695 * activations and deactivations, should take into account this696 * additional complexity. To avoid this issue, this function is697 * invoked with update_class_too unset in the points in the code where698 * entity may happen to be on some tree.699 */700struct bfq_service_tree *701__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,702 struct bfq_entity *entity,703 bool update_class_too)704{705 struct bfq_service_tree *new_st = old_st;706 707 if (entity->prio_changed) {708 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);709 unsigned int prev_weight, new_weight;710 711 /* Matches the smp_wmb() in bfq_group_set_weight. */712 smp_rmb();713 old_st->wsum -= entity->weight;714 715 if (entity->new_weight != entity->orig_weight) {716 if (entity->new_weight < BFQ_MIN_WEIGHT ||717 entity->new_weight > BFQ_MAX_WEIGHT) {718 pr_crit("update_weight_prio: new_weight %d\n",719 entity->new_weight);720 if (entity->new_weight < BFQ_MIN_WEIGHT)721 entity->new_weight = BFQ_MIN_WEIGHT;722 else723 entity->new_weight = BFQ_MAX_WEIGHT;724 }725 entity->orig_weight = entity->new_weight;726 if (bfqq)727 bfqq->ioprio =728 bfq_weight_to_ioprio(entity->orig_weight);729 }730 731 if (bfqq && update_class_too)732 bfqq->ioprio_class = bfqq->new_ioprio_class;733 734 /*735 * Reset prio_changed only if the ioprio_class change736 * is not pending any longer.737 */738 if (!bfqq || bfqq->ioprio_class == bfqq->new_ioprio_class)739 entity->prio_changed = 0;740 741 /*742 * NOTE: here we may be changing the weight too early,743 * this will cause unfairness. The correct approach744 * would have required additional complexity to defer745 * weight changes to the proper time instants (i.e.,746 * when entity->finish <= old_st->vtime).747 */748 new_st = bfq_entity_service_tree(entity);749 750 prev_weight = entity->weight;751 new_weight = entity->orig_weight *752 (bfqq ? bfqq->wr_coeff : 1);753 /*754 * If the weight of the entity changes, and the entity is a755 * queue, remove the entity from its old weight counter (if756 * there is a counter associated with the entity).757 */758 if (prev_weight != new_weight && bfqq)759 bfq_weights_tree_remove(bfqq);760 entity->weight = new_weight;761 /*762 * Add the entity, if it is not a weight-raised queue,763 * to the counter associated with its new weight.764 */765 if (prev_weight != new_weight && bfqq && bfqq->wr_coeff == 1)766 bfq_weights_tree_add(bfqq);767 768 new_st->wsum += entity->weight;769 770 if (new_st != old_st)771 entity->start = new_st->vtime;772 }773 774 return new_st;775}776 777/**778 * bfq_bfqq_served - update the scheduler status after selection for779 * service.780 * @bfqq: the queue being served.781 * @served: bytes to transfer.782 *783 * NOTE: this can be optimized, as the timestamps of upper level entities784 * are synchronized every time a new bfqq is selected for service. By now,785 * we keep it to better check consistency.786 */787void bfq_bfqq_served(struct bfq_queue *bfqq, int served)788{789 struct bfq_entity *entity = &bfqq->entity;790 struct bfq_service_tree *st;791 792 if (!bfqq->service_from_backlogged)793 bfqq->first_IO_time = jiffies;794 795 if (bfqq->wr_coeff > 1)796 bfqq->service_from_wr += served;797 798 bfqq->service_from_backlogged += served;799 for_each_entity(entity) {800 st = bfq_entity_service_tree(entity);801 802 entity->service += served;803 804 st->vtime += bfq_delta(served, st->wsum);805 bfq_forget_idle(st);806 }807 bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served);808}809 810/**811 * bfq_bfqq_charge_time - charge an amount of service equivalent to the length812 * of the time interval during which bfqq has been in813 * service.814 * @bfqd: the device815 * @bfqq: the queue that needs a service update.816 * @time_ms: the amount of time during which the queue has received service817 *818 * If a queue does not consume its budget fast enough, then providing819 * the queue with service fairness may impair throughput, more or less820 * severely. For this reason, queues that consume their budget slowly821 * are provided with time fairness instead of service fairness. This822 * goal is achieved through the BFQ scheduling engine, even if such an823 * engine works in the service, and not in the time domain. The trick824 * is charging these queues with an inflated amount of service, equal825 * to the amount of service that they would have received during their826 * service slot if they had been fast, i.e., if their requests had827 * been dispatched at a rate equal to the estimated peak rate.828 *829 * It is worth noting that time fairness can cause important830 * distortions in terms of bandwidth distribution, on devices with831 * internal queueing. The reason is that I/O requests dispatched832 * during the service slot of a queue may be served after that service833 * slot is finished, and may have a total processing time loosely834 * correlated with the duration of the service slot. This is835 * especially true for short service slots.836 */837void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,838 unsigned long time_ms)839{840 struct bfq_entity *entity = &bfqq->entity;841 unsigned long timeout_ms = jiffies_to_msecs(bfq_timeout);842 unsigned long bounded_time_ms = min(time_ms, timeout_ms);843 int serv_to_charge_for_time =844 (bfqd->bfq_max_budget * bounded_time_ms) / timeout_ms;845 int tot_serv_to_charge = max(serv_to_charge_for_time, entity->service);846 847 /* Increase budget to avoid inconsistencies */848 if (tot_serv_to_charge > entity->budget)849 entity->budget = tot_serv_to_charge;850 851 bfq_bfqq_served(bfqq,852 max_t(int, 0, tot_serv_to_charge - entity->service));853}854 855static void bfq_update_fin_time_enqueue(struct bfq_entity *entity,856 struct bfq_service_tree *st,857 bool backshifted)858{859 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);860 861 /*862 * When this function is invoked, entity is not in any service863 * tree, then it is safe to invoke next function with the last864 * parameter set (see the comments on the function).865 */866 st = __bfq_entity_update_weight_prio(st, entity, true);867 bfq_calc_finish(entity, entity->budget);868 869 /*870 * If some queues enjoy backshifting for a while, then their871 * (virtual) finish timestamps may happen to become lower and872 * lower than the system virtual time. In particular, if873 * these queues often happen to be idle for short time874 * periods, and during such time periods other queues with875 * higher timestamps happen to be busy, then the backshifted876 * timestamps of the former queues can become much lower than877 * the system virtual time. In fact, to serve the queues with878 * higher timestamps while the ones with lower timestamps are879 * idle, the system virtual time may be pushed-up to much880 * higher values than the finish timestamps of the idle881 * queues. As a consequence, the finish timestamps of all new882 * or newly activated queues may end up being much larger than883 * those of lucky queues with backshifted timestamps. The884 * latter queues may then monopolize the device for a lot of885 * time. This would simply break service guarantees.886 *887 * To reduce this problem, push up a little bit the888 * backshifted timestamps of the queue associated with this889 * entity (only a queue can happen to have the backshifted890 * flag set): just enough to let the finish timestamp of the891 * queue be equal to the current value of the system virtual892 * time. This may introduce a little unfairness among queues893 * with backshifted timestamps, but it does not break894 * worst-case fairness guarantees.895 *896 * As a special case, if bfqq is weight-raised, push up897 * timestamps much less, to keep very low the probability that898 * this push up causes the backshifted finish timestamps of899 * weight-raised queues to become higher than the backshifted900 * finish timestamps of non weight-raised queues.901 */902 if (backshifted && bfq_gt(st->vtime, entity->finish)) {903 unsigned long delta = st->vtime - entity->finish;904 905 if (bfqq)906 delta /= bfqq->wr_coeff;907 908 entity->start += delta;909 entity->finish += delta;910 }911 912 bfq_active_insert(st, entity);913}914 915/**916 * __bfq_activate_entity - handle activation of entity.917 * @entity: the entity being activated.918 * @non_blocking_wait_rq: true if entity was waiting for a request919 *920 * Called for a 'true' activation, i.e., if entity is not active and921 * one of its children receives a new request.922 *923 * Basically, this function updates the timestamps of entity and924 * inserts entity into its active tree, after possibly extracting it925 * from its idle tree.926 */927static void __bfq_activate_entity(struct bfq_entity *entity,928 bool non_blocking_wait_rq)929{930 struct bfq_service_tree *st = bfq_entity_service_tree(entity);931 bool backshifted = false;932 unsigned long long min_vstart;933 934 /* See comments on bfq_fqq_update_budg_for_activation */935 if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) {936 backshifted = true;937 min_vstart = entity->finish;938 } else939 min_vstart = st->vtime;940 941 if (entity->tree == &st->idle) {942 /*943 * Must be on the idle tree, bfq_idle_extract() will944 * check for that.945 */946 bfq_idle_extract(st, entity);947 entity->start = bfq_gt(min_vstart, entity->finish) ?948 min_vstart : entity->finish;949 } else {950 /*951 * The finish time of the entity may be invalid, and952 * it is in the past for sure, otherwise the queue953 * would have been on the idle tree.954 */955 entity->start = min_vstart;956 st->wsum += entity->weight;957 /*958 * entity is about to be inserted into a service tree,959 * and then set in service: get a reference to make960 * sure entity does not disappear until it is no961 * longer in service or scheduled for service.962 */963 bfq_get_entity(entity);964 965 entity->on_st_or_in_serv = true;966 }967 968 bfq_update_fin_time_enqueue(entity, st, backshifted);969}970 971/**972 * __bfq_requeue_entity - handle requeueing or repositioning of an entity.973 * @entity: the entity being requeued or repositioned.974 *975 * Requeueing is needed if this entity stops being served, which976 * happens if a leaf descendant entity has expired. On the other hand,977 * repositioning is needed if the next_inservice_entity for the child978 * entity has changed. See the comments inside the function for979 * details.980 *981 * Basically, this function: 1) removes entity from its active tree if982 * present there, 2) updates the timestamps of entity and 3) inserts983 * entity back into its active tree (in the new, right position for984 * the new values of the timestamps).985 */986static void __bfq_requeue_entity(struct bfq_entity *entity)987{988 struct bfq_sched_data *sd = entity->sched_data;989 struct bfq_service_tree *st = bfq_entity_service_tree(entity);990 991 if (entity == sd->in_service_entity) {992 /*993 * We are requeueing the current in-service entity,994 * which may have to be done for one of the following995 * reasons:996 * - entity represents the in-service queue, and the997 * in-service queue is being requeued after an998 * expiration;999 * - entity represents a group, and its budget has1000 * changed because one of its child entities has1001 * just been either activated or requeued for some1002 * reason; the timestamps of the entity need then to1003 * be updated, and the entity needs to be enqueued1004 * or repositioned accordingly.1005 *1006 * In particular, before requeueing, the start time of1007 * the entity must be moved forward to account for the1008 * service that the entity has received while in1009 * service. This is done by the next instructions. The1010 * finish time will then be updated according to this1011 * new value of the start time, and to the budget of1012 * the entity.1013 */1014 bfq_calc_finish(entity, entity->service);1015 entity->start = entity->finish;1016 /*1017 * In addition, if the entity had more than one child1018 * when set in service, then it was not extracted from1019 * the active tree. This implies that the position of1020 * the entity in the active tree may need to be1021 * changed now, because we have just updated the start1022 * time of the entity, and we will update its finish1023 * time in a moment (the requeueing is then, more1024 * precisely, a repositioning in this case). To1025 * implement this repositioning, we: 1) dequeue the1026 * entity here, 2) update the finish time and requeue1027 * the entity according to the new timestamps below.1028 */1029 if (entity->tree)1030 bfq_active_extract(st, entity);1031 } else { /* The entity is already active, and not in service */1032 /*1033 * In this case, this function gets called only if the1034 * next_in_service entity below this entity has1035 * changed, and this change has caused the budget of1036 * this entity to change, which, finally implies that1037 * the finish time of this entity must be1038 * updated. Such an update may cause the scheduling,1039 * i.e., the position in the active tree, of this1040 * entity to change. We handle this change by: 1)1041 * dequeueing the entity here, 2) updating the finish1042 * time and requeueing the entity according to the new1043 * timestamps below. This is the same approach as the1044 * non-extracted-entity sub-case above.1045 */1046 bfq_active_extract(st, entity);1047 }1048 1049 bfq_update_fin_time_enqueue(entity, st, false);1050}1051 1052static void __bfq_activate_requeue_entity(struct bfq_entity *entity,1053 bool non_blocking_wait_rq)1054{1055 struct bfq_service_tree *st = bfq_entity_service_tree(entity);1056 1057 if (entity->sched_data->in_service_entity == entity ||1058 entity->tree == &st->active)1059 /*1060 * in service or already queued on the active tree,1061 * requeue or reposition1062 */1063 __bfq_requeue_entity(entity);1064 else1065 /*1066 * Not in service and not queued on its active tree:1067 * the activity is idle and this is a true activation.1068 */1069 __bfq_activate_entity(entity, non_blocking_wait_rq);1070}1071 1072 1073/**1074 * bfq_activate_requeue_entity - activate or requeue an entity representing a1075 * bfq_queue, and activate, requeue or reposition1076 * all ancestors for which such an update becomes1077 * necessary.1078 * @entity: the entity to activate.1079 * @non_blocking_wait_rq: true if this entity was waiting for a request1080 * @requeue: true if this is a requeue, which implies that bfqq is1081 * being expired; thus ALL its ancestors stop being served and must1082 * therefore be requeued1083 * @expiration: true if this function is being invoked in the expiration path1084 * of the in-service queue1085 */1086static void bfq_activate_requeue_entity(struct bfq_entity *entity,1087 bool non_blocking_wait_rq,1088 bool requeue, bool expiration)1089{1090 for_each_entity(entity) {1091 __bfq_activate_requeue_entity(entity, non_blocking_wait_rq);1092 if (!bfq_update_next_in_service(entity->sched_data, entity,1093 expiration) && !requeue)1094 break;1095 }1096}1097 1098/**1099 * __bfq_deactivate_entity - update sched_data and service trees for1100 * entity, so as to represent entity as inactive1101 * @entity: the entity being deactivated.1102 * @ins_into_idle_tree: if false, the entity will not be put into the1103 * idle tree.1104 *1105 * If necessary and allowed, puts entity into the idle tree. NOTE:1106 * entity may be on no tree if in service.1107 */1108bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree)1109{1110 struct bfq_sched_data *sd = entity->sched_data;1111 struct bfq_service_tree *st;1112 bool is_in_service;1113 1114 if (!entity->on_st_or_in_serv) /*1115 * entity never activated, or1116 * already inactive1117 */1118 return false;1119 1120 /*1121 * If we get here, then entity is active, which implies that1122 * bfq_group_set_parent has already been invoked for the group1123 * represented by entity. Therefore, the field1124 * entity->sched_data has been set, and we can safely use it.1125 */1126 st = bfq_entity_service_tree(entity);1127 is_in_service = entity == sd->in_service_entity;1128 1129 bfq_calc_finish(entity, entity->service);1130 1131 if (is_in_service)1132 sd->in_service_entity = NULL;1133 else1134 /*1135 * Non in-service entity: nobody will take care of1136 * resetting its service counter on expiration. Do it1137 * now.1138 */1139 entity->service = 0;1140 1141 if (entity->tree == &st->active)1142 bfq_active_extract(st, entity);1143 else if (!is_in_service && entity->tree == &st->idle)1144 bfq_idle_extract(st, entity);1145 1146 if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime))1147 bfq_forget_entity(st, entity, is_in_service);1148 else1149 bfq_idle_insert(st, entity);1150 1151 return true;1152}1153 1154/**1155 * bfq_deactivate_entity - deactivate an entity representing a bfq_queue.1156 * @entity: the entity to deactivate.1157 * @ins_into_idle_tree: true if the entity can be put into the idle tree1158 * @expiration: true if this function is being invoked in the expiration path1159 * of the in-service queue1160 */1161static void bfq_deactivate_entity(struct bfq_entity *entity,1162 bool ins_into_idle_tree,1163 bool expiration)1164{1165 struct bfq_sched_data *sd;1166 struct bfq_entity *parent = NULL;1167 1168 for_each_entity_safe(entity, parent) {1169 sd = entity->sched_data;1170 1171 if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) {1172 /*1173 * entity is not in any tree any more, so1174 * this deactivation is a no-op, and there is1175 * nothing to change for upper-level entities1176 * (in case of expiration, this can never1177 * happen).1178 */1179 return;1180 }1181 1182 if (sd->next_in_service == entity)1183 /*1184 * entity was the next_in_service entity,1185 * then, since entity has just been1186 * deactivated, a new one must be found.1187 */1188 bfq_update_next_in_service(sd, NULL, expiration);1189 1190 if (sd->next_in_service || sd->in_service_entity) {1191 /*1192 * The parent entity is still active, because1193 * either next_in_service or in_service_entity1194 * is not NULL. So, no further upwards1195 * deactivation must be performed. Yet,1196 * next_in_service has changed. Then the1197 * schedule does need to be updated upwards.1198 *1199 * NOTE If in_service_entity is not NULL, then1200 * next_in_service may happen to be NULL,1201 * although the parent entity is evidently1202 * active. This happens if 1) the entity1203 * pointed by in_service_entity is the only1204 * active entity in the parent entity, and 2)1205 * according to the definition of1206 * next_in_service, the in_service_entity1207 * cannot be considered as1208 * next_in_service. See the comments on the1209 * definition of next_in_service for details.1210 */1211 break;1212 }1213 1214 /*1215 * If we get here, then the parent is no more1216 * backlogged and we need to propagate the1217 * deactivation upwards. Thus let the loop go on.1218 */1219 1220 /*1221 * Also let parent be queued into the idle tree on1222 * deactivation, to preserve service guarantees, and1223 * assuming that who invoked this function does not1224 * need parent entities too to be removed completely.1225 */1226 ins_into_idle_tree = true;1227 }1228 1229 /*1230 * If the deactivation loop is fully executed, then there are1231 * no more entities to touch and next loop is not executed at1232 * all. Otherwise, requeue remaining entities if they are1233 * about to stop receiving service, or reposition them if this1234 * is not the case.1235 */1236 entity = parent;1237 for_each_entity(entity) {1238 /*1239 * Invoke __bfq_requeue_entity on entity, even if1240 * already active, to requeue/reposition it in the1241 * active tree (because sd->next_in_service has1242 * changed)1243 */1244 __bfq_requeue_entity(entity);1245 1246 sd = entity->sched_data;1247 if (!bfq_update_next_in_service(sd, entity, expiration) &&1248 !expiration)1249 /*1250 * next_in_service unchanged or not causing1251 * any change in entity->parent->sd, and no1252 * requeueing needed for expiration: stop1253 * here.1254 */1255 break;1256 }1257}1258 1259/**1260 * bfq_calc_vtime_jump - compute the value to which the vtime should jump,1261 * if needed, to have at least one entity eligible.1262 * @st: the service tree to act upon.1263 *1264 * Assumes that st is not empty.1265 */1266static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st)1267{1268 struct bfq_entity *root_entity = bfq_root_active_entity(&st->active);1269 1270 if (bfq_gt(root_entity->min_start, st->vtime))1271 return root_entity->min_start;1272 1273 return st->vtime;1274}1275 1276static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value)1277{1278 if (new_value > st->vtime) {1279 st->vtime = new_value;1280 bfq_forget_idle(st);1281 }1282}1283 1284/**1285 * bfq_first_active_entity - find the eligible entity with1286 * the smallest finish time1287 * @st: the service tree to select from.1288 * @vtime: the system virtual to use as a reference for eligibility1289 *1290 * This function searches the first schedulable entity, starting from the1291 * root of the tree and going on the left every time on this side there is1292 * a subtree with at least one eligible (start <= vtime) entity. The path on1293 * the right is followed only if a) the left subtree contains no eligible1294 * entities and b) no eligible entity has been found yet.1295 */1296static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st,1297 u64 vtime)1298{1299 struct bfq_entity *entry, *first = NULL;1300 struct rb_node *node = st->active.rb_node;1301 1302 while (node) {1303 entry = rb_entry(node, struct bfq_entity, rb_node);1304left:1305 if (!bfq_gt(entry->start, vtime))1306 first = entry;1307 1308 if (node->rb_left) {1309 entry = rb_entry(node->rb_left,1310 struct bfq_entity, rb_node);1311 if (!bfq_gt(entry->min_start, vtime)) {1312 node = node->rb_left;1313 goto left;1314 }1315 }1316 if (first)1317 break;1318 node = node->rb_right;1319 }1320 1321 return first;1322}1323 1324/**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_data1328 * this active tree belongs to.1329 *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;1333 * 2) no entity belonging to such parent entity undergoes a state change1334 * that would influence the timestamps of the entity (e.g., becomes idle,1335 * becomes backlogged, changes its budget, ...).1336 *1337 * In this first case, update the virtual time in @st too (see the1338 * comments on this update inside the function).1339 *1340 * In contrast, if there is an in-service entity, then return the1341 * entity that would be set in service if not only the above1342 * conditions, but also the next one held true: the currently1343 * in-service entity, on expiration,1344 * 1) gets a finish time equal to the current one, or1345 * 2) is not eligible any more, or1346 * 3) is idle.1347 */1348static struct bfq_entity *1349__bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service)1350{1351 struct bfq_entity *entity;1352 u64 new_vtime;1353 1354 if (RB_EMPTY_ROOT(&st->active))1355 return NULL;1356 1357 /*1358 * Get the value of the system virtual time for which at1359 * least one entity is eligible.1360 */1361 new_vtime = bfq_calc_vtime_jump(st);1362 1363 /*1364 * If there is no in-service entity for the sched_data this1365 * active tree belongs to, then push the system virtual time1366 * up to the value that guarantees that at least one entity is1367 * eligible. If, instead, there is an in-service entity, then1368 * do not make any such update, because there is already an1369 * eligible entity, namely the in-service one (even if the1370 * entity is not on st, because it was extracted when set in1371 * service).1372 */1373 if (!in_service)1374 bfq_update_vtime(st, new_vtime);1375 1376 entity = bfq_first_active_entity(st, new_vtime);1377 1378 return entity;1379}1380 1381/**1382 * bfq_lookup_next_entity - return the first eligible entity in @sd.1383 * @sd: the sched_data.1384 * @expiration: true if we are on the expiration path of the in-service queue1385 *1386 * This function is invoked when there has been a change in the trees1387 * for sd, and we need to know what is the new next entity to serve1388 * after this change.1389 */1390static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,1391 bool expiration)1392{1393 struct bfq_service_tree *st = sd->service_tree;1394 struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1);1395 struct bfq_entity *entity = NULL;1396 int class_idx = 0;1397 1398 /*1399 * Choose from idle class, if needed to guarantee a minimum1400 * bandwidth to this class (and if there is some active entity1401 * in idle class). This should also mitigate1402 * priority-inversion problems in case a low priority task is1403 * holding file system resources.1404 */1405 if (time_is_before_jiffies(sd->bfq_class_idle_last_service +1406 BFQ_CL_IDLE_TIMEOUT)) {1407 if (!RB_EMPTY_ROOT(&idle_class_st->active))1408 class_idx = BFQ_IOPRIO_CLASSES - 1;1409 /* About to be served if backlogged, or not yet backlogged */1410 sd->bfq_class_idle_last_service = jiffies;1411 }1412 1413 /*1414 * Find the next entity to serve for the highest-priority1415 * class, unless the idle class needs to be served.1416 */1417 for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) {1418 /*1419 * If expiration is true, then bfq_lookup_next_entity1420 * is being invoked as a part of the expiration path1421 * of the in-service queue. In this case, even if1422 * sd->in_service_entity is not NULL,1423 * sd->in_service_entity at this point is actually not1424 * in service any more, and, if needed, has already1425 * been properly queued or requeued into the right1426 * tree. The reason why sd->in_service_entity is still1427 * not NULL here, even if expiration is true, is that1428 * sd->in_service_entity is reset as a last step in the1429 * expiration path. So, if expiration is true, tell1430 * __bfq_lookup_next_entity that there is no1431 * sd->in_service_entity.1432 */1433 entity = __bfq_lookup_next_entity(st + class_idx,1434 sd->in_service_entity &&1435 !expiration);1436 1437 if (entity)1438 break;1439 }1440 1441 return entity;1442}1443 1444bool next_queue_may_preempt(struct bfq_data *bfqd)1445{1446 struct bfq_sched_data *sd = &bfqd->root_group->sched_data;1447 1448 return sd->next_in_service != sd->in_service_entity;1449}1450 1451/*1452 * Get next queue for service.1453 */1454struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)1455{1456 struct bfq_entity *entity = NULL;1457 struct bfq_sched_data *sd;1458 struct bfq_queue *bfqq;1459 1460 if (bfq_tot_busy_queues(bfqd) == 0)1461 return NULL;1462 1463 /*1464 * Traverse the path from the root to the leaf entity to1465 * serve. Set in service all the entities visited along the1466 * way.1467 */1468 sd = &bfqd->root_group->sched_data;1469 for (; sd ; sd = entity->my_sched_data) {1470 /*1471 * WARNING. We are about to set the in-service entity1472 * to sd->next_in_service, i.e., to the (cached) value1473 * returned by bfq_lookup_next_entity(sd) the last1474 * time it was invoked, i.e., the last time when the1475 * service order in sd changed as a consequence of the1476 * activation or deactivation of an entity. In this1477 * respect, if we execute bfq_lookup_next_entity(sd)1478 * in this very moment, it may, although with low1479 * probability, yield a different entity than that1480 * pointed to by sd->next_in_service. This rare event1481 * happens in case there was no CLASS_IDLE entity to1482 * serve for sd when bfq_lookup_next_entity(sd) was1483 * invoked for the last time, while there is now one1484 * such entity.1485 *1486 * If the above event happens, then the scheduling of1487 * such entity in CLASS_IDLE is postponed until the1488 * service of the sd->next_in_service entity1489 * finishes. In fact, when the latter is expired,1490 * bfq_lookup_next_entity(sd) gets called again,1491 * exactly to update sd->next_in_service.1492 */1493 1494 /* Make next_in_service entity become in_service_entity */1495 entity = sd->next_in_service;1496 sd->in_service_entity = entity;1497 1498 /*1499 * If entity is no longer a candidate for next1500 * service, then it must be extracted from its active1501 * tree, so as to make sure that it won't be1502 * considered when computing next_in_service. See the1503 * comments on the function1504 * bfq_no_longer_next_in_service() for details.1505 */1506 if (bfq_no_longer_next_in_service(entity))1507 bfq_active_extract(bfq_entity_service_tree(entity),1508 entity);1509 1510 /*1511 * Even if entity is not to be extracted according to1512 * the above check, a descendant entity may get1513 * extracted in one of the next iterations of this1514 * loop. Such an event could cause a change in1515 * next_in_service for the level of the descendant1516 * entity, and thus possibly back to this level.1517 *1518 * However, we cannot perform the resulting needed1519 * update of next_in_service for this level before the1520 * end of the whole loop, because, to know which is1521 * the correct next-to-serve candidate entity for each1522 * level, we need first to find the leaf entity to set1523 * in service. In fact, only after we know which is1524 * the next-to-serve leaf entity, we can discover1525 * whether the parent entity of the leaf entity1526 * becomes the next-to-serve, and so on.1527 */1528 }1529 1530 bfqq = bfq_entity_to_bfqq(entity);1531 1532 /*1533 * We can finally update all next-to-serve entities along the1534 * path from the leaf entity just set in service to the root.1535 */1536 for_each_entity(entity) {1537 struct bfq_sched_data *sd = entity->sched_data;1538 1539 if (!bfq_update_next_in_service(sd, NULL, false))1540 break;1541 }1542 1543 return bfqq;1544}1545 1546/* returns true if the in-service queue gets freed */1547bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)1548{1549 struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue;1550 struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity;1551 struct bfq_entity *entity = in_serv_entity;1552 1553 bfq_clear_bfqq_wait_request(in_serv_bfqq);1554 hrtimer_try_to_cancel(&bfqd->idle_slice_timer);1555 bfqd->in_service_queue = NULL;1556 1557 /*1558 * When this function is called, all in-service entities have1559 * been properly deactivated or requeued, so we can safely1560 * execute the final step: reset in_service_entity along the1561 * path from entity to the root.1562 */1563 for_each_entity(entity)1564 entity->sched_data->in_service_entity = NULL;1565 1566 /*1567 * in_serv_entity is no longer in service, so, if it is in no1568 * service tree either, then release the service reference to1569 * the queue it represents (taken with bfq_get_entity).1570 */1571 if (!in_serv_entity->on_st_or_in_serv) {1572 /*1573 * If no process is referencing in_serv_bfqq any1574 * longer, then the service reference may be the only1575 * reference to the queue. If this is the case, then1576 * bfqq gets freed here.1577 */1578 int ref = in_serv_bfqq->ref;1579 bfq_put_queue(in_serv_bfqq);1580 if (ref == 1)1581 return true;1582 }1583 1584 return false;1585}1586 1587void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,1588 bool ins_into_idle_tree, bool expiration)1589{1590 struct bfq_entity *entity = &bfqq->entity;1591 1592 bfq_deactivate_entity(entity, ins_into_idle_tree, expiration);1593}1594 1595void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)1596{1597 struct bfq_entity *entity = &bfqq->entity;1598 1599 bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq),1600 false, false);1601 bfq_clear_bfqq_non_blocking_wait_rq(bfqq);1602}1603 1604void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,1605 bool expiration)1606{1607 struct bfq_entity *entity = &bfqq->entity;1608 1609 bfq_activate_requeue_entity(entity, false,1610 bfqq == bfqd->in_service_queue, expiration);1611}1612 1613void bfq_add_bfqq_in_groups_with_pending_reqs(struct bfq_queue *bfqq)1614{1615#ifdef CONFIG_BFQ_GROUP_IOSCHED1616 struct bfq_entity *entity = &bfqq->entity;1617 1618 if (!entity->in_groups_with_pending_reqs) {1619 entity->in_groups_with_pending_reqs = true;1620 if (!(bfqq_group(bfqq)->num_queues_with_pending_reqs++))1621 bfqq->bfqd->num_groups_with_pending_reqs++;1622 }1623#endif1624}1625 1626void bfq_del_bfqq_in_groups_with_pending_reqs(struct bfq_queue *bfqq)1627{1628#ifdef CONFIG_BFQ_GROUP_IOSCHED1629 struct bfq_entity *entity = &bfqq->entity;1630 1631 if (entity->in_groups_with_pending_reqs) {1632 entity->in_groups_with_pending_reqs = false;1633 if (!(--bfqq_group(bfqq)->num_queues_with_pending_reqs))1634 bfqq->bfqd->num_groups_with_pending_reqs--;1635 }1636#endif1637}1638 1639/*1640 * Called when the bfqq no longer has requests pending, remove it from1641 * the service tree. As a special case, it can be invoked during an1642 * expiration.1643 */1644void bfq_del_bfqq_busy(struct bfq_queue *bfqq, bool expiration)1645{1646 struct bfq_data *bfqd = bfqq->bfqd;1647 1648 bfq_log_bfqq(bfqd, bfqq, "del from busy");1649 1650 bfq_clear_bfqq_busy(bfqq);1651 1652 bfqd->busy_queues[bfqq->ioprio_class - 1]--;1653 1654 if (bfqq->wr_coeff > 1)1655 bfqd->wr_busy_queues--;1656 1657 bfqg_stats_update_dequeue(bfqq_group(bfqq));1658 1659 bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);1660 1661 if (!bfqq->dispatched) {1662 bfq_del_bfqq_in_groups_with_pending_reqs(bfqq);1663 /*1664 * Next function is invoked last, because it causes bfqq to be1665 * freed. DO NOT use bfqq after the next function invocation.1666 */1667 bfq_weights_tree_remove(bfqq);1668 }1669}1670 1671/*1672 * Called when an inactive queue receives a new request.1673 */1674void bfq_add_bfqq_busy(struct bfq_queue *bfqq)1675{1676 struct bfq_data *bfqd = bfqq->bfqd;1677 1678 bfq_log_bfqq(bfqd, bfqq, "add to busy");1679 1680 bfq_activate_bfqq(bfqd, bfqq);1681 1682 bfq_mark_bfqq_busy(bfqq);1683 bfqd->busy_queues[bfqq->ioprio_class - 1]++;1684 1685 if (!bfqq->dispatched) {1686 bfq_add_bfqq_in_groups_with_pending_reqs(bfqq);1687 if (bfqq->wr_coeff == 1)1688 bfq_weights_tree_add(bfqq);1689 }1690 1691 if (bfqq->wr_coeff > 1)1692 bfqd->wr_busy_queues++;1693 1694 /* Move bfqq to the head of the woken list of its waker */1695 if (!hlist_unhashed(&bfqq->woken_list_node) &&1696 &bfqq->woken_list_node != bfqq->waker_bfqq->woken_list.first) {1697 hlist_del_init(&bfqq->woken_list_node);1698 hlist_add_head(&bfqq->woken_list_node,1699 &bfqq->waker_bfqq->woken_list);1700 }1701}1702