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1/*
2 * Hierarchical Budget Worst-case Fair Weighted Fair Queueing
3 * (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O
4 * scheduler schedules generic entities. The latter can represent
5 * either single bfq queues (associated with processes) or groups of
6 * bfq queues (associated with cgroups).
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of the
11 * License, or (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
17 */
18#include "bfq-iosched.h"
19
20/**
21 * bfq_gt - compare two timestamps.
22 * @a: first ts.
23 * @b: second ts.
24 *
25 * Return @a > @b, dealing with wrapping correctly.
26 */
27static int bfq_gt(u64 a, u64 b)
28{
29 return (s64)(a - b) > 0;
30}
31
32static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree)
33{
34 struct rb_node *node = tree->rb_node;
35
36 return rb_entry(node, struct bfq_entity, rb_node);
37}
38
39static unsigned int bfq_class_idx(struct bfq_entity *entity)
40{
41 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
42
43 return bfqq ? bfqq->ioprio_class - 1 :
44 BFQ_DEFAULT_GRP_CLASS - 1;
45}
46
47static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,
48 bool expiration);
49
50static bool bfq_update_parent_budget(struct bfq_entity *next_in_service);
51
52/**
53 * bfq_update_next_in_service - update sd->next_in_service
54 * @sd: sched_data for which to perform the update.
55 * @new_entity: if not NULL, pointer to the entity whose activation,
56 * requeueing or repositionig triggered the invocation of
57 * this function.
58 * @expiration: id true, this function is being invoked after the
59 * expiration of the in-service entity
60 *
61 * This function is called to update sd->next_in_service, which, in
62 * its turn, may change as a consequence of the insertion or
63 * extraction of an entity into/from one of the active trees of
64 * sd. These insertions/extractions occur as a consequence of
65 * activations/deactivations of entities, with some activations being
66 * 'true' activations, and other activations being requeueings (i.e.,
67 * implementing the second, requeueing phase of the mechanism used to
68 * reposition an entity in its active tree; see comments on
69 * __bfq_activate_entity and __bfq_requeue_entity for details). In
70 * both the last two activation sub-cases, new_entity points to the
71 * just activated or requeued entity.
72 *
73 * Returns true if sd->next_in_service changes in such a way that
74 * entity->parent may become the next_in_service for its parent
75 * entity.
76 */
77static bool bfq_update_next_in_service(struct bfq_sched_data *sd,
78 struct bfq_entity *new_entity,
79 bool expiration)
80{
81 struct bfq_entity *next_in_service = sd->next_in_service;
82 bool parent_sched_may_change = false;
83 bool change_without_lookup = false;
84
85 /*
86 * If this update is triggered by the activation, requeueing
87 * or repositiong of an entity that does not coincide with
88 * sd->next_in_service, then a full lookup in the active tree
89 * can be avoided. In fact, it is enough to check whether the
90 * just-modified entity has the same priority as
91 * sd->next_in_service, is eligible and has a lower virtual
92 * finish time than sd->next_in_service. If this compound
93 * condition holds, then the new entity becomes the new
94 * next_in_service. Otherwise no change is needed.
95 */
96 if (new_entity && new_entity != sd->next_in_service) {
97 /*
98 * Flag used to decide whether to replace
99 * sd->next_in_service with new_entity. Tentatively
100 * set to true, and left as true if
101 * sd->next_in_service is NULL.
102 */
103 change_without_lookup = true;
104
105 /*
106 * If there is already a next_in_service candidate
107 * entity, then compare timestamps to decide whether
108 * to replace sd->service_tree with new_entity.
109 */
110 if (next_in_service) {
111 unsigned int new_entity_class_idx =
112 bfq_class_idx(new_entity);
113 struct bfq_service_tree *st =
114 sd->service_tree + new_entity_class_idx;
115
116 change_without_lookup =
117 (new_entity_class_idx ==
118 bfq_class_idx(next_in_service)
119 &&
120 !bfq_gt(new_entity->start, st->vtime)
121 &&
122 bfq_gt(next_in_service->finish,
123 new_entity->finish));
124 }
125
126 if (change_without_lookup)
127 next_in_service = new_entity;
128 }
129
130 if (!change_without_lookup) /* lookup needed */
131 next_in_service = bfq_lookup_next_entity(sd, expiration);
132
133 if (next_in_service)
134 parent_sched_may_change = !sd->next_in_service ||
135 bfq_update_parent_budget(next_in_service);
136
137 sd->next_in_service = next_in_service;
138
139 if (!next_in_service)
140 return parent_sched_may_change;
141
142 return parent_sched_may_change;
143}
144
145#ifdef CONFIG_BFQ_GROUP_IOSCHED
146
147struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
148{
149 struct bfq_entity *group_entity = bfqq->entity.parent;
150
151 if (!group_entity)
152 group_entity = &bfqq->bfqd->root_group->entity;
153
154 return container_of(group_entity, struct bfq_group, entity);
155}
156
157/*
158 * Returns true if this budget changes may let next_in_service->parent
159 * become the next_in_service entity for its parent entity.
160 */
161static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
162{
163 struct bfq_entity *bfqg_entity;
164 struct bfq_group *bfqg;
165 struct bfq_sched_data *group_sd;
166 bool ret = false;
167
168 group_sd = next_in_service->sched_data;
169
170 bfqg = container_of(group_sd, struct bfq_group, sched_data);
171 /*
172 * bfq_group's my_entity field is not NULL only if the group
173 * is not the root group. We must not touch the root entity
174 * as it must never become an in-service entity.
175 */
176 bfqg_entity = bfqg->my_entity;
177 if (bfqg_entity) {
178 if (bfqg_entity->budget > next_in_service->budget)
179 ret = true;
180 bfqg_entity->budget = next_in_service->budget;
181 }
182
183 return ret;
184}
185
186/*
187 * This function tells whether entity stops being a candidate for next
188 * service, according to the restrictive definition of the field
189 * next_in_service. In particular, this function is invoked for an
190 * entity that is about to be set in service.
191 *
192 * If entity is a queue, then the entity is no longer a candidate for
193 * next service according to the that definition, because entity is
194 * about to become the in-service queue. This function then returns
195 * true if entity is a queue.
196 *
197 * In contrast, entity could still be a candidate for next service if
198 * it is not a queue, and has more than one active child. In fact,
199 * even if one of its children is about to be set in service, other
200 * active children may still be the next to serve, for the parent
201 * entity, even according to the above definition. As a consequence, a
202 * non-queue entity is not a candidate for next-service only if it has
203 * only one active child. And only if this condition holds, then this
204 * function returns true for a non-queue entity.
205 */
206static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
207{
208 struct bfq_group *bfqg;
209
210 if (bfq_entity_to_bfqq(entity))
211 return true;
212
213 bfqg = container_of(entity, struct bfq_group, entity);
214
215 /*
216 * The field active_entities does not always contain the
217 * actual number of active children entities: it happens to
218 * not account for the in-service entity in case the latter is
219 * removed from its active tree (which may get done after
220 * invoking the function bfq_no_longer_next_in_service in
221 * bfq_get_next_queue). Fortunately, here, i.e., while
222 * bfq_no_longer_next_in_service is not yet completed in
223 * bfq_get_next_queue, bfq_active_extract has not yet been
224 * invoked, and thus active_entities still coincides with the
225 * actual number of active entities.
226 */
227 if (bfqg->active_entities == 1)
228 return true;
229
230 return false;
231}
232
233#else /* CONFIG_BFQ_GROUP_IOSCHED */
234
235struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
236{
237 return bfqq->bfqd->root_group;
238}
239
240static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
241{
242 return false;
243}
244
245static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
246{
247 return true;
248}
249
250#endif /* CONFIG_BFQ_GROUP_IOSCHED */
251
252/*
253 * Shift for timestamp calculations. This actually limits the maximum
254 * service allowed in one timestamp delta (small shift values increase it),
255 * the maximum total weight that can be used for the queues in the system
256 * (big shift values increase it), and the period of virtual time
257 * wraparounds.
258 */
259#define WFQ_SERVICE_SHIFT 22
260
261struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity)
262{
263 struct bfq_queue *bfqq = NULL;
264
265 if (!entity->my_sched_data)
266 bfqq = container_of(entity, struct bfq_queue, entity);
267
268 return bfqq;
269}
270
271
272/**
273 * bfq_delta - map service into the virtual time domain.
274 * @service: amount of service.
275 * @weight: scale factor (weight of an entity or weight sum).
276 */
277static u64 bfq_delta(unsigned long service, unsigned long weight)
278{
279 u64 d = (u64)service << WFQ_SERVICE_SHIFT;
280
281 do_div(d, weight);
282 return d;
283}
284
285/**
286 * bfq_calc_finish - assign the finish time to an entity.
287 * @entity: the entity to act upon.
288 * @service: the service to be charged to the entity.
289 */
290static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service)
291{
292 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
293
294 entity->finish = entity->start +
295 bfq_delta(service, entity->weight);
296
297 if (bfqq) {
298 bfq_log_bfqq(bfqq->bfqd, bfqq,
299 "calc_finish: serv %lu, w %d",
300 service, entity->weight);
301 bfq_log_bfqq(bfqq->bfqd, bfqq,
302 "calc_finish: start %llu, finish %llu, delta %llu",
303 entity->start, entity->finish,
304 bfq_delta(service, entity->weight));
305 }
306}
307
308/**
309 * bfq_entity_of - get an entity from a node.
310 * @node: the node field of the entity.
311 *
312 * Convert a node pointer to the relative entity. This is used only
313 * to simplify the logic of some functions and not as the generic
314 * conversion mechanism because, e.g., in the tree walking functions,
315 * the check for a %NULL value would be redundant.
316 */
317struct bfq_entity *bfq_entity_of(struct rb_node *node)
318{
319 struct bfq_entity *entity = NULL;
320
321 if (node)
322 entity = rb_entry(node, struct bfq_entity, rb_node);
323
324 return entity;
325}
326
327/**
328 * bfq_extract - remove an entity from a tree.
329 * @root: the tree root.
330 * @entity: the entity to remove.
331 */
332static void bfq_extract(struct rb_root *root, struct bfq_entity *entity)
333{
334 entity->tree = NULL;
335 rb_erase(&entity->rb_node, root);
336}
337
338/**
339 * bfq_idle_extract - extract an entity from the idle tree.
340 * @st: the service tree of the owning @entity.
341 * @entity: the entity being removed.
342 */
343static void bfq_idle_extract(struct bfq_service_tree *st,
344 struct bfq_entity *entity)
345{
346 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
347 struct rb_node *next;
348
349 if (entity == st->first_idle) {
350 next = rb_next(&entity->rb_node);
351 st->first_idle = bfq_entity_of(next);
352 }
353
354 if (entity == st->last_idle) {
355 next = rb_prev(&entity->rb_node);
356 st->last_idle = bfq_entity_of(next);
357 }
358
359 bfq_extract(&st->idle, entity);
360
361 if (bfqq)
362 list_del(&bfqq->bfqq_list);
363}
364
365/**
366 * bfq_insert - generic tree insertion.
367 * @root: tree root.
368 * @entity: entity to insert.
369 *
370 * This is used for the idle and the active tree, since they are both
371 * ordered by finish time.
372 */
373static void bfq_insert(struct rb_root *root, struct bfq_entity *entity)
374{
375 struct bfq_entity *entry;
376 struct rb_node **node = &root->rb_node;
377 struct rb_node *parent = NULL;
378
379 while (*node) {
380 parent = *node;
381 entry = rb_entry(parent, struct bfq_entity, rb_node);
382
383 if (bfq_gt(entry->finish, entity->finish))
384 node = &parent->rb_left;
385 else
386 node = &parent->rb_right;
387 }
388
389 rb_link_node(&entity->rb_node, parent, node);
390 rb_insert_color(&entity->rb_node, root);
391
392 entity->tree = root;
393}
394
395/**
396 * bfq_update_min - update the min_start field of a entity.
397 * @entity: the entity to update.
398 * @node: one of its children.
399 *
400 * This function is called when @entity may store an invalid value for
401 * min_start due to updates to the active tree. The function assumes
402 * that the subtree rooted at @node (which may be its left or its right
403 * child) has a valid min_start value.
404 */
405static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node)
406{
407 struct bfq_entity *child;
408
409 if (node) {
410 child = rb_entry(node, struct bfq_entity, rb_node);
411 if (bfq_gt(entity->min_start, child->min_start))
412 entity->min_start = child->min_start;
413 }
414}
415
416/**
417 * bfq_update_active_node - recalculate min_start.
418 * @node: the node to update.
419 *
420 * @node may have changed position or one of its children may have moved,
421 * this function updates its min_start value. The left and right subtrees
422 * are assumed to hold a correct min_start value.
423 */
424static void bfq_update_active_node(struct rb_node *node)
425{
426 struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node);
427
428 entity->min_start = entity->start;
429 bfq_update_min(entity, node->rb_right);
430 bfq_update_min(entity, node->rb_left);
431}
432
433/**
434 * bfq_update_active_tree - update min_start for the whole active tree.
435 * @node: the starting node.
436 *
437 * @node must be the deepest modified node after an update. This function
438 * updates its min_start using the values held by its children, assuming
439 * that they did not change, and then updates all the nodes that may have
440 * changed in the path to the root. The only nodes that may have changed
441 * are the ones in the path or their siblings.
442 */
443static void bfq_update_active_tree(struct rb_node *node)
444{
445 struct rb_node *parent;
446
447up:
448 bfq_update_active_node(node);
449
450 parent = rb_parent(node);
451 if (!parent)
452 return;
453
454 if (node == parent->rb_left && parent->rb_right)
455 bfq_update_active_node(parent->rb_right);
456 else if (parent->rb_left)
457 bfq_update_active_node(parent->rb_left);
458
459 node = parent;
460 goto up;
461}
462
463/**
464 * bfq_active_insert - insert an entity in the active tree of its
465 * group/device.
466 * @st: the service tree of the entity.
467 * @entity: the entity being inserted.
468 *
469 * The active tree is ordered by finish time, but an extra key is kept
470 * per each node, containing the minimum value for the start times of
471 * its children (and the node itself), so it's possible to search for
472 * the eligible node with the lowest finish time in logarithmic time.
473 */
474static void bfq_active_insert(struct bfq_service_tree *st,
475 struct bfq_entity *entity)
476{
477 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
478 struct rb_node *node = &entity->rb_node;
479#ifdef CONFIG_BFQ_GROUP_IOSCHED
480 struct bfq_sched_data *sd = NULL;
481 struct bfq_group *bfqg = NULL;
482 struct bfq_data *bfqd = NULL;
483#endif
484
485 bfq_insert(&st->active, entity);
486
487 if (node->rb_left)
488 node = node->rb_left;
489 else if (node->rb_right)
490 node = node->rb_right;
491
492 bfq_update_active_tree(node);
493
494#ifdef CONFIG_BFQ_GROUP_IOSCHED
495 sd = entity->sched_data;
496 bfqg = container_of(sd, struct bfq_group, sched_data);
497 bfqd = (struct bfq_data *)bfqg->bfqd;
498#endif
499 if (bfqq)
500 list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list);
501#ifdef CONFIG_BFQ_GROUP_IOSCHED
502 else /* bfq_group */
503 bfq_weights_tree_add(bfqd, entity, &bfqd->group_weights_tree);
504
505 if (bfqg != bfqd->root_group)
506 bfqg->active_entities++;
507#endif
508}
509
510/**
511 * bfq_ioprio_to_weight - calc a weight from an ioprio.
512 * @ioprio: the ioprio value to convert.
513 */
514unsigned short bfq_ioprio_to_weight(int ioprio)
515{
516 return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
517}
518
519/**
520 * bfq_weight_to_ioprio - calc an ioprio from a weight.
521 * @weight: the weight value to convert.
522 *
523 * To preserve as much as possible the old only-ioprio user interface,
524 * 0 is used as an escape ioprio value for weights (numerically) equal or
525 * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
526 */
527static unsigned short bfq_weight_to_ioprio(int weight)
528{
529 return max_t(int, 0,
530 IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
531}
532
533static void bfq_get_entity(struct bfq_entity *entity)
534{
535 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
536
537 if (bfqq) {
538 bfqq->ref++;
539 bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",
540 bfqq, bfqq->ref);
541 }
542}
543
544/**
545 * bfq_find_deepest - find the deepest node that an extraction can modify.
546 * @node: the node being removed.
547 *
548 * Do the first step of an extraction in an rb tree, looking for the
549 * node that will replace @node, and returning the deepest node that
550 * the following modifications to the tree can touch. If @node is the
551 * last node in the tree return %NULL.
552 */
553static struct rb_node *bfq_find_deepest(struct rb_node *node)
554{
555 struct rb_node *deepest;
556
557 if (!node->rb_right && !node->rb_left)
558 deepest = rb_parent(node);
559 else if (!node->rb_right)
560 deepest = node->rb_left;
561 else if (!node->rb_left)
562 deepest = node->rb_right;
563 else {
564 deepest = rb_next(node);
565 if (deepest->rb_right)
566 deepest = deepest->rb_right;
567 else if (rb_parent(deepest) != node)
568 deepest = rb_parent(deepest);
569 }
570
571 return deepest;
572}
573
574/**
575 * bfq_active_extract - remove an entity from the active tree.
576 * @st: the service_tree containing the tree.
577 * @entity: the entity being removed.
578 */
579static void bfq_active_extract(struct bfq_service_tree *st,
580 struct bfq_entity *entity)
581{
582 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
583 struct rb_node *node;
584#ifdef CONFIG_BFQ_GROUP_IOSCHED
585 struct bfq_sched_data *sd = NULL;
586 struct bfq_group *bfqg = NULL;
587 struct bfq_data *bfqd = NULL;
588#endif
589
590 node = bfq_find_deepest(&entity->rb_node);
591 bfq_extract(&st->active, entity);
592
593 if (node)
594 bfq_update_active_tree(node);
595
596#ifdef CONFIG_BFQ_GROUP_IOSCHED
597 sd = entity->sched_data;
598 bfqg = container_of(sd, struct bfq_group, sched_data);
599 bfqd = (struct bfq_data *)bfqg->bfqd;
600#endif
601 if (bfqq)
602 list_del(&bfqq->bfqq_list);
603#ifdef CONFIG_BFQ_GROUP_IOSCHED
604 else /* bfq_group */
605 bfq_weights_tree_remove(bfqd, entity,
606 &bfqd->group_weights_tree);
607
608 if (bfqg != bfqd->root_group)
609 bfqg->active_entities--;
610#endif
611}
612
613/**
614 * bfq_idle_insert - insert an entity into the idle tree.
615 * @st: the service tree containing the tree.
616 * @entity: the entity to insert.
617 */
618static void bfq_idle_insert(struct bfq_service_tree *st,
619 struct bfq_entity *entity)
620{
621 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
622 struct bfq_entity *first_idle = st->first_idle;
623 struct bfq_entity *last_idle = st->last_idle;
624
625 if (!first_idle || bfq_gt(first_idle->finish, entity->finish))
626 st->first_idle = entity;
627 if (!last_idle || bfq_gt(entity->finish, last_idle->finish))
628 st->last_idle = entity;
629
630 bfq_insert(&st->idle, entity);
631
632 if (bfqq)
633 list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);
634}
635
636/**
637 * bfq_forget_entity - do not consider entity any longer for scheduling
638 * @st: the service tree.
639 * @entity: the entity being removed.
640 * @is_in_service: true if entity is currently the in-service entity.
641 *
642 * Forget everything about @entity. In addition, if entity represents
643 * a queue, and the latter is not in service, then release the service
644 * reference to the queue (the one taken through bfq_get_entity). In
645 * fact, in this case, there is really no more service reference to
646 * the queue, as the latter is also outside any service tree. If,
647 * instead, the queue is in service, then __bfq_bfqd_reset_in_service
648 * will take care of putting the reference when the queue finally
649 * stops being served.
650 */
651static void bfq_forget_entity(struct bfq_service_tree *st,
652 struct bfq_entity *entity,
653 bool is_in_service)
654{
655 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
656
657 entity->on_st = false;
658 st->wsum -= entity->weight;
659 if (bfqq && !is_in_service)
660 bfq_put_queue(bfqq);
661}
662
663/**
664 * bfq_put_idle_entity - release the idle tree ref of an entity.
665 * @st: service tree for the entity.
666 * @entity: the entity being released.
667 */
668void bfq_put_idle_entity(struct bfq_service_tree *st, struct bfq_entity *entity)
669{
670 bfq_idle_extract(st, entity);
671 bfq_forget_entity(st, entity,
672 entity == entity->sched_data->in_service_entity);
673}
674
675/**
676 * bfq_forget_idle - update the idle tree if necessary.
677 * @st: the service tree to act upon.
678 *
679 * To preserve the global O(log N) complexity we only remove one entry here;
680 * as the idle tree will not grow indefinitely this can be done safely.
681 */
682static void bfq_forget_idle(struct bfq_service_tree *st)
683{
684 struct bfq_entity *first_idle = st->first_idle;
685 struct bfq_entity *last_idle = st->last_idle;
686
687 if (RB_EMPTY_ROOT(&st->active) && last_idle &&
688 !bfq_gt(last_idle->finish, st->vtime)) {
689 /*
690 * Forget the whole idle tree, increasing the vtime past
691 * the last finish time of idle entities.
692 */
693 st->vtime = last_idle->finish;
694 }
695
696 if (first_idle && !bfq_gt(first_idle->finish, st->vtime))
697 bfq_put_idle_entity(st, first_idle);
698}
699
700struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity)
701{
702 struct bfq_sched_data *sched_data = entity->sched_data;
703 unsigned int idx = bfq_class_idx(entity);
704
705 return sched_data->service_tree + idx;
706}
707
708/*
709 * Update weight and priority of entity. If update_class_too is true,
710 * then update the ioprio_class of entity too.
711 *
712 * The reason why the update of ioprio_class is controlled through the
713 * last parameter is as follows. Changing the ioprio class of an
714 * entity implies changing the destination service trees for that
715 * entity. If such a change occurred when the entity is already on one
716 * of the service trees for its previous class, then the state of the
717 * entity would become more complex: none of the new possible service
718 * trees for the entity, according to bfq_entity_service_tree(), would
719 * match any of the possible service trees on which the entity
720 * is. Complex operations involving these trees, such as entity
721 * activations and deactivations, should take into account this
722 * additional complexity. To avoid this issue, this function is
723 * invoked with update_class_too unset in the points in the code where
724 * entity may happen to be on some tree.
725 */
726struct bfq_service_tree *
727__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
728 struct bfq_entity *entity,
729 bool update_class_too)
730{
731 struct bfq_service_tree *new_st = old_st;
732
733 if (entity->prio_changed) {
734 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
735 unsigned int prev_weight, new_weight;
736 struct bfq_data *bfqd = NULL;
737 struct rb_root *root;
738#ifdef CONFIG_BFQ_GROUP_IOSCHED
739 struct bfq_sched_data *sd;
740 struct bfq_group *bfqg;
741#endif
742
743 if (bfqq)
744 bfqd = bfqq->bfqd;
745#ifdef CONFIG_BFQ_GROUP_IOSCHED
746 else {
747 sd = entity->my_sched_data;
748 bfqg = container_of(sd, struct bfq_group, sched_data);
749 bfqd = (struct bfq_data *)bfqg->bfqd;
750 }
751#endif
752
753 old_st->wsum -= entity->weight;
754
755 if (entity->new_weight != entity->orig_weight) {
756 if (entity->new_weight < BFQ_MIN_WEIGHT ||
757 entity->new_weight > BFQ_MAX_WEIGHT) {
758 pr_crit("update_weight_prio: new_weight %d\n",
759 entity->new_weight);
760 if (entity->new_weight < BFQ_MIN_WEIGHT)
761 entity->new_weight = BFQ_MIN_WEIGHT;
762 else
763 entity->new_weight = BFQ_MAX_WEIGHT;
764 }
765 entity->orig_weight = entity->new_weight;
766 if (bfqq)
767 bfqq->ioprio =
768 bfq_weight_to_ioprio(entity->orig_weight);
769 }
770
771 if (bfqq && update_class_too)
772 bfqq->ioprio_class = bfqq->new_ioprio_class;
773
774 /*
775 * Reset prio_changed only if the ioprio_class change
776 * is not pending any longer.
777 */
778 if (!bfqq || bfqq->ioprio_class == bfqq->new_ioprio_class)
779 entity->prio_changed = 0;
780
781 /*
782 * NOTE: here we may be changing the weight too early,
783 * this will cause unfairness. The correct approach
784 * would have required additional complexity to defer
785 * weight changes to the proper time instants (i.e.,
786 * when entity->finish <= old_st->vtime).
787 */
788 new_st = bfq_entity_service_tree(entity);
789
790 prev_weight = entity->weight;
791 new_weight = entity->orig_weight *
792 (bfqq ? bfqq->wr_coeff : 1);
793 /*
794 * If the weight of the entity changes, remove the entity
795 * from its old weight counter (if there is a counter
796 * associated with the entity), and add it to the counter
797 * associated with its new weight.
798 */
799 if (prev_weight != new_weight) {
800 root = bfqq ? &bfqd->queue_weights_tree :
801 &bfqd->group_weights_tree;
802 bfq_weights_tree_remove(bfqd, entity, root);
803 }
804 entity->weight = new_weight;
805 /*
806 * Add the entity to its weights tree only if it is
807 * not associated with a weight-raised queue.
808 */
809 if (prev_weight != new_weight &&
810 (bfqq ? bfqq->wr_coeff == 1 : 1))
811 /* If we get here, root has been initialized. */
812 bfq_weights_tree_add(bfqd, entity, root);
813
814 new_st->wsum += entity->weight;
815
816 if (new_st != old_st)
817 entity->start = new_st->vtime;
818 }
819
820 return new_st;
821}
822
823/**
824 * bfq_bfqq_served - update the scheduler status after selection for
825 * service.
826 * @bfqq: the queue being served.
827 * @served: bytes to transfer.
828 *
829 * NOTE: this can be optimized, as the timestamps of upper level entities
830 * are synchronized every time a new bfqq is selected for service. By now,
831 * we keep it to better check consistency.
832 */
833void bfq_bfqq_served(struct bfq_queue *bfqq, int served)
834{
835 struct bfq_entity *entity = &bfqq->entity;
836 struct bfq_service_tree *st;
837
838 if (!bfqq->service_from_backlogged)
839 bfqq->first_IO_time = jiffies;
840
841 if (bfqq->wr_coeff > 1)
842 bfqq->service_from_wr += served;
843
844 bfqq->service_from_backlogged += served;
845 for_each_entity(entity) {
846 st = bfq_entity_service_tree(entity);
847
848 entity->service += served;
849
850 st->vtime += bfq_delta(served, st->wsum);
851 bfq_forget_idle(st);
852 }
853 bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served);
854}
855
856/**
857 * bfq_bfqq_charge_time - charge an amount of service equivalent to the length
858 * of the time interval during which bfqq has been in
859 * service.
860 * @bfqd: the device
861 * @bfqq: the queue that needs a service update.
862 * @time_ms: the amount of time during which the queue has received service
863 *
864 * If a queue does not consume its budget fast enough, then providing
865 * the queue with service fairness may impair throughput, more or less
866 * severely. For this reason, queues that consume their budget slowly
867 * are provided with time fairness instead of service fairness. This
868 * goal is achieved through the BFQ scheduling engine, even if such an
869 * engine works in the service, and not in the time domain. The trick
870 * is charging these queues with an inflated amount of service, equal
871 * to the amount of service that they would have received during their
872 * service slot if they had been fast, i.e., if their requests had
873 * been dispatched at a rate equal to the estimated peak rate.
874 *
875 * It is worth noting that time fairness can cause important
876 * distortions in terms of bandwidth distribution, on devices with
877 * internal queueing. The reason is that I/O requests dispatched
878 * during the service slot of a queue may be served after that service
879 * slot is finished, and may have a total processing time loosely
880 * correlated with the duration of the service slot. This is
881 * especially true for short service slots.
882 */
883void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
884 unsigned long time_ms)
885{
886 struct bfq_entity *entity = &bfqq->entity;
887 int tot_serv_to_charge = entity->service;
888 unsigned int timeout_ms = jiffies_to_msecs(bfq_timeout);
889
890 if (time_ms > 0 && time_ms < timeout_ms)
891 tot_serv_to_charge =
892 (bfqd->bfq_max_budget * time_ms) / timeout_ms;
893
894 if (tot_serv_to_charge < entity->service)
895 tot_serv_to_charge = entity->service;
896
897 /* Increase budget to avoid inconsistencies */
898 if (tot_serv_to_charge > entity->budget)
899 entity->budget = tot_serv_to_charge;
900
901 bfq_bfqq_served(bfqq,
902 max_t(int, 0, tot_serv_to_charge - entity->service));
903}
904
905static void bfq_update_fin_time_enqueue(struct bfq_entity *entity,
906 struct bfq_service_tree *st,
907 bool backshifted)
908{
909 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
910
911 /*
912 * When this function is invoked, entity is not in any service
913 * tree, then it is safe to invoke next function with the last
914 * parameter set (see the comments on the function).
915 */
916 st = __bfq_entity_update_weight_prio(st, entity, true);
917 bfq_calc_finish(entity, entity->budget);
918
919 /*
920 * If some queues enjoy backshifting for a while, then their
921 * (virtual) finish timestamps may happen to become lower and
922 * lower than the system virtual time. In particular, if
923 * these queues often happen to be idle for short time
924 * periods, and during such time periods other queues with
925 * higher timestamps happen to be busy, then the backshifted
926 * timestamps of the former queues can become much lower than
927 * the system virtual time. In fact, to serve the queues with
928 * higher timestamps while the ones with lower timestamps are
929 * idle, the system virtual time may be pushed-up to much
930 * higher values than the finish timestamps of the idle
931 * queues. As a consequence, the finish timestamps of all new
932 * or newly activated queues may end up being much larger than
933 * those of lucky queues with backshifted timestamps. The
934 * latter queues may then monopolize the device for a lot of
935 * time. This would simply break service guarantees.
936 *
937 * To reduce this problem, push up a little bit the
938 * backshifted timestamps of the queue associated with this
939 * entity (only a queue can happen to have the backshifted
940 * flag set): just enough to let the finish timestamp of the
941 * queue be equal to the current value of the system virtual
942 * time. This may introduce a little unfairness among queues
943 * with backshifted timestamps, but it does not break
944 * worst-case fairness guarantees.
945 *
946 * As a special case, if bfqq is weight-raised, push up
947 * timestamps much less, to keep very low the probability that
948 * this push up causes the backshifted finish timestamps of
949 * weight-raised queues to become higher than the backshifted
950 * finish timestamps of non weight-raised queues.
951 */
952 if (backshifted && bfq_gt(st->vtime, entity->finish)) {
953 unsigned long delta = st->vtime - entity->finish;
954
955 if (bfqq)
956 delta /= bfqq->wr_coeff;
957
958 entity->start += delta;
959 entity->finish += delta;
960 }
961
962 bfq_active_insert(st, entity);
963}
964
965/**
966 * __bfq_activate_entity - handle activation of entity.
967 * @entity: the entity being activated.
968 * @non_blocking_wait_rq: true if entity was waiting for a request
969 *
970 * Called for a 'true' activation, i.e., if entity is not active and
971 * one of its children receives a new request.
972 *
973 * Basically, this function updates the timestamps of entity and
974 * inserts entity into its active tree, ater possibly extracting it
975 * from its idle tree.
976 */
977static void __bfq_activate_entity(struct bfq_entity *entity,
978 bool non_blocking_wait_rq)
979{
980 struct bfq_service_tree *st = bfq_entity_service_tree(entity);
981 bool backshifted = false;
982 unsigned long long min_vstart;
983
984 /* See comments on bfq_fqq_update_budg_for_activation */
985 if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) {
986 backshifted = true;
987 min_vstart = entity->finish;
988 } else
989 min_vstart = st->vtime;
990
991 if (entity->tree == &st->idle) {
992 /*
993 * Must be on the idle tree, bfq_idle_extract() will
994 * check for that.
995 */
996 bfq_idle_extract(st, entity);
997 entity->start = bfq_gt(min_vstart, entity->finish) ?
998 min_vstart : entity->finish;
999 } else {
1000 /*
1001 * The finish time of the entity may be invalid, and
1002 * it is in the past for sure, otherwise the queue
1003 * would have been on the idle tree.
1004 */
1005 entity->start = min_vstart;
1006 st->wsum += entity->weight;
1007 /*
1008 * entity is about to be inserted into a service tree,
1009 * and then set in service: get a reference to make
1010 * sure entity does not disappear until it is no
1011 * longer in service or scheduled for service.
1012 */
1013 bfq_get_entity(entity);
1014
1015 entity->on_st = true;
1016 }
1017
1018 bfq_update_fin_time_enqueue(entity, st, backshifted);
1019}
1020
1021/**
1022 * __bfq_requeue_entity - handle requeueing or repositioning of an entity.
1023 * @entity: the entity being requeued or repositioned.
1024 *
1025 * Requeueing is needed if this entity stops being served, which
1026 * happens if a leaf descendant entity has expired. On the other hand,
1027 * repositioning is needed if the next_inservice_entity for the child
1028 * entity has changed. See the comments inside the function for
1029 * details.
1030 *
1031 * Basically, this function: 1) removes entity from its active tree if
1032 * present there, 2) updates the timestamps of entity and 3) inserts
1033 * entity back into its active tree (in the new, right position for
1034 * the new values of the timestamps).
1035 */
1036static void __bfq_requeue_entity(struct bfq_entity *entity)
1037{
1038 struct bfq_sched_data *sd = entity->sched_data;
1039 struct bfq_service_tree *st = bfq_entity_service_tree(entity);
1040
1041 if (entity == sd->in_service_entity) {
1042 /*
1043 * We are requeueing the current in-service entity,
1044 * which may have to be done for one of the following
1045 * reasons:
1046 * - entity represents the in-service queue, and the
1047 * in-service queue is being requeued after an
1048 * expiration;
1049 * - entity represents a group, and its budget has
1050 * changed because one of its child entities has
1051 * just been either activated or requeued for some
1052 * reason; the timestamps of the entity need then to
1053 * be updated, and the entity needs to be enqueued
1054 * or repositioned accordingly.
1055 *
1056 * In particular, before requeueing, the start time of
1057 * the entity must be moved forward to account for the
1058 * service that the entity has received while in
1059 * service. This is done by the next instructions. The
1060 * finish time will then be updated according to this
1061 * new value of the start time, and to the budget of
1062 * the entity.
1063 */
1064 bfq_calc_finish(entity, entity->service);
1065 entity->start = entity->finish;
1066 /*
1067 * In addition, if the entity had more than one child
1068 * when set in service, then it was not extracted from
1069 * the active tree. This implies that the position of
1070 * the entity in the active tree may need to be
1071 * changed now, because we have just updated the start
1072 * time of the entity, and we will update its finish
1073 * time in a moment (the requeueing is then, more
1074 * precisely, a repositioning in this case). To
1075 * implement this repositioning, we: 1) dequeue the
1076 * entity here, 2) update the finish time and requeue
1077 * the entity according to the new timestamps below.
1078 */
1079 if (entity->tree)
1080 bfq_active_extract(st, entity);
1081 } else { /* The entity is already active, and not in service */
1082 /*
1083 * In this case, this function gets called only if the
1084 * next_in_service entity below this entity has
1085 * changed, and this change has caused the budget of
1086 * this entity to change, which, finally implies that
1087 * the finish time of this entity must be
1088 * updated. Such an update may cause the scheduling,
1089 * i.e., the position in the active tree, of this
1090 * entity to change. We handle this change by: 1)
1091 * dequeueing the entity here, 2) updating the finish
1092 * time and requeueing the entity according to the new
1093 * timestamps below. This is the same approach as the
1094 * non-extracted-entity sub-case above.
1095 */
1096 bfq_active_extract(st, entity);
1097 }
1098
1099 bfq_update_fin_time_enqueue(entity, st, false);
1100}
1101
1102static void __bfq_activate_requeue_entity(struct bfq_entity *entity,
1103 struct bfq_sched_data *sd,
1104 bool non_blocking_wait_rq)
1105{
1106 struct bfq_service_tree *st = bfq_entity_service_tree(entity);
1107
1108 if (sd->in_service_entity == entity || entity->tree == &st->active)
1109 /*
1110 * in service or already queued on the active tree,
1111 * requeue or reposition
1112 */
1113 __bfq_requeue_entity(entity);
1114 else
1115 /*
1116 * Not in service and not queued on its active tree:
1117 * the activity is idle and this is a true activation.
1118 */
1119 __bfq_activate_entity(entity, non_blocking_wait_rq);
1120}
1121
1122
1123/**
1124 * bfq_activate_requeue_entity - activate or requeue an entity representing a
1125 * bfq_queue, and activate, requeue or reposition
1126 * all ancestors for which such an update becomes
1127 * necessary.
1128 * @entity: the entity to activate.
1129 * @non_blocking_wait_rq: true if this entity was waiting for a request
1130 * @requeue: true if this is a requeue, which implies that bfqq is
1131 * being expired; thus ALL its ancestors stop being served and must
1132 * therefore be requeued
1133 * @expiration: true if this function is being invoked in the expiration path
1134 * of the in-service queue
1135 */
1136static void bfq_activate_requeue_entity(struct bfq_entity *entity,
1137 bool non_blocking_wait_rq,
1138 bool requeue, bool expiration)
1139{
1140 struct bfq_sched_data *sd;
1141
1142 for_each_entity(entity) {
1143 sd = entity->sched_data;
1144 __bfq_activate_requeue_entity(entity, sd, non_blocking_wait_rq);
1145
1146 if (!bfq_update_next_in_service(sd, entity, expiration) &&
1147 !requeue)
1148 break;
1149 }
1150}
1151
1152/**
1153 * __bfq_deactivate_entity - deactivate an entity from its service tree.
1154 * @entity: the entity to deactivate.
1155 * @ins_into_idle_tree: if false, the entity will not be put into the
1156 * idle tree.
1157 *
1158 * Deactivates an entity, independently of its previous state. Must
1159 * be invoked only if entity is on a service tree. Extracts the entity
1160 * from that tree, and if necessary and allowed, puts it into the idle
1161 * tree.
1162 */
1163bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree)
1164{
1165 struct bfq_sched_data *sd = entity->sched_data;
1166 struct bfq_service_tree *st;
1167 bool is_in_service;
1168
1169 if (!entity->on_st) /* entity never activated, or already inactive */
1170 return false;
1171
1172 /*
1173 * If we get here, then entity is active, which implies that
1174 * bfq_group_set_parent has already been invoked for the group
1175 * represented by entity. Therefore, the field
1176 * entity->sched_data has been set, and we can safely use it.
1177 */
1178 st = bfq_entity_service_tree(entity);
1179 is_in_service = entity == sd->in_service_entity;
1180
1181 if (is_in_service) {
1182 bfq_calc_finish(entity, entity->service);
1183 sd->in_service_entity = NULL;
1184 }
1185
1186 if (entity->tree == &st->active)
1187 bfq_active_extract(st, entity);
1188 else if (!is_in_service && entity->tree == &st->idle)
1189 bfq_idle_extract(st, entity);
1190
1191 if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime))
1192 bfq_forget_entity(st, entity, is_in_service);
1193 else
1194 bfq_idle_insert(st, entity);
1195
1196 return true;
1197}
1198
1199/**
1200 * bfq_deactivate_entity - deactivate an entity representing a bfq_queue.
1201 * @entity: the entity to deactivate.
1202 * @ins_into_idle_tree: true if the entity can be put into the idle tree
1203 * @expiration: true if this function is being invoked in the expiration path
1204 * of the in-service queue
1205 */
1206static void bfq_deactivate_entity(struct bfq_entity *entity,
1207 bool ins_into_idle_tree,
1208 bool expiration)
1209{
1210 struct bfq_sched_data *sd;
1211 struct bfq_entity *parent = NULL;
1212
1213 for_each_entity_safe(entity, parent) {
1214 sd = entity->sched_data;
1215
1216 if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) {
1217 /*
1218 * entity is not in any tree any more, so
1219 * this deactivation is a no-op, and there is
1220 * nothing to change for upper-level entities
1221 * (in case of expiration, this can never
1222 * happen).
1223 */
1224 return;
1225 }
1226
1227 if (sd->next_in_service == entity)
1228 /*
1229 * entity was the next_in_service entity,
1230 * then, since entity has just been
1231 * deactivated, a new one must be found.
1232 */
1233 bfq_update_next_in_service(sd, NULL, expiration);
1234
1235 if (sd->next_in_service || sd->in_service_entity) {
1236 /*
1237 * The parent entity is still active, because
1238 * either next_in_service or in_service_entity
1239 * is not NULL. So, no further upwards
1240 * deactivation must be performed. Yet,
1241 * next_in_service has changed. Then the
1242 * schedule does need to be updated upwards.
1243 *
1244 * NOTE If in_service_entity is not NULL, then
1245 * next_in_service may happen to be NULL,
1246 * although the parent entity is evidently
1247 * active. This happens if 1) the entity
1248 * pointed by in_service_entity is the only
1249 * active entity in the parent entity, and 2)
1250 * according to the definition of
1251 * next_in_service, the in_service_entity
1252 * cannot be considered as
1253 * next_in_service. See the comments on the
1254 * definition of next_in_service for details.
1255 */
1256 break;
1257 }
1258
1259 /*
1260 * If we get here, then the parent is no more
1261 * backlogged and we need to propagate the
1262 * deactivation upwards. Thus let the loop go on.
1263 */
1264
1265 /*
1266 * Also let parent be queued into the idle tree on
1267 * deactivation, to preserve service guarantees, and
1268 * assuming that who invoked this function does not
1269 * need parent entities too to be removed completely.
1270 */
1271 ins_into_idle_tree = true;
1272 }
1273
1274 /*
1275 * If the deactivation loop is fully executed, then there are
1276 * no more entities to touch and next loop is not executed at
1277 * all. Otherwise, requeue remaining entities if they are
1278 * about to stop receiving service, or reposition them if this
1279 * is not the case.
1280 */
1281 entity = parent;
1282 for_each_entity(entity) {
1283 /*
1284 * Invoke __bfq_requeue_entity on entity, even if
1285 * already active, to requeue/reposition it in the
1286 * active tree (because sd->next_in_service has
1287 * changed)
1288 */
1289 __bfq_requeue_entity(entity);
1290
1291 sd = entity->sched_data;
1292 if (!bfq_update_next_in_service(sd, entity, expiration) &&
1293 !expiration)
1294 /*
1295 * next_in_service unchanged or not causing
1296 * any change in entity->parent->sd, and no
1297 * requeueing needed for expiration: stop
1298 * here.
1299 */
1300 break;
1301 }
1302}
1303
1304/**
1305 * bfq_calc_vtime_jump - compute the value to which the vtime should jump,
1306 * if needed, to have at least one entity eligible.
1307 * @st: the service tree to act upon.
1308 *
1309 * Assumes that st is not empty.
1310 */
1311static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st)
1312{
1313 struct bfq_entity *root_entity = bfq_root_active_entity(&st->active);
1314
1315 if (bfq_gt(root_entity->min_start, st->vtime))
1316 return root_entity->min_start;
1317
1318 return st->vtime;
1319}
1320
1321static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value)
1322{
1323 if (new_value > st->vtime) {
1324 st->vtime = new_value;
1325 bfq_forget_idle(st);
1326 }
1327}
1328
1329/**
1330 * bfq_first_active_entity - find the eligible entity with
1331 * the smallest finish time
1332 * @st: the service tree to select from.
1333 * @vtime: the system virtual to use as a reference for eligibility
1334 *
1335 * This function searches the first schedulable entity, starting from the
1336 * root of the tree and going on the left every time on this side there is
1337 * a subtree with at least one eligible (start <= vtime) entity. The path on
1338 * the right is followed only if a) the left subtree contains no eligible
1339 * entities and b) no eligible entity has been found yet.
1340 */
1341static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st,
1342 u64 vtime)
1343{
1344 struct bfq_entity *entry, *first = NULL;
1345 struct rb_node *node = st->active.rb_node;
1346
1347 while (node) {
1348 entry = rb_entry(node, struct bfq_entity, rb_node);
1349left:
1350 if (!bfq_gt(entry->start, vtime))
1351 first = entry;
1352
1353 if (node->rb_left) {
1354 entry = rb_entry(node->rb_left,
1355 struct bfq_entity, rb_node);
1356 if (!bfq_gt(entry->min_start, vtime)) {
1357 node = node->rb_left;
1358 goto left;
1359 }
1360 }
1361 if (first)
1362 break;
1363 node = node->rb_right;
1364 }
1365
1366 return first;
1367}
1368
1369/**
1370 * __bfq_lookup_next_entity - return the first eligible entity in @st.
1371 * @st: the service tree.
1372 *
1373 * If there is no in-service entity for the sched_data st belongs to,
1374 * then return the entity that will be set in service if:
1375 * 1) the parent entity this st belongs to is set in service;
1376 * 2) no entity belonging to such parent entity undergoes a state change
1377 * that would influence the timestamps of the entity (e.g., becomes idle,
1378 * becomes backlogged, changes its budget, ...).
1379 *
1380 * In this first case, update the virtual time in @st too (see the
1381 * comments on this update inside the function).
1382 *
1383 * In constrast, if there is an in-service entity, then return the
1384 * entity that would be set in service if not only the above
1385 * conditions, but also the next one held true: the currently
1386 * in-service entity, on expiration,
1387 * 1) gets a finish time equal to the current one, or
1388 * 2) is not eligible any more, or
1389 * 3) is idle.
1390 */
1391static struct bfq_entity *
1392__bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service)
1393{
1394 struct bfq_entity *entity;
1395 u64 new_vtime;
1396
1397 if (RB_EMPTY_ROOT(&st->active))
1398 return NULL;
1399
1400 /*
1401 * Get the value of the system virtual time for which at
1402 * least one entity is eligible.
1403 */
1404 new_vtime = bfq_calc_vtime_jump(st);
1405
1406 /*
1407 * If there is no in-service entity for the sched_data this
1408 * active tree belongs to, then push the system virtual time
1409 * up to the value that guarantees that at least one entity is
1410 * eligible. If, instead, there is an in-service entity, then
1411 * do not make any such update, because there is already an
1412 * eligible entity, namely the in-service one (even if the
1413 * entity is not on st, because it was extracted when set in
1414 * service).
1415 */
1416 if (!in_service)
1417 bfq_update_vtime(st, new_vtime);
1418
1419 entity = bfq_first_active_entity(st, new_vtime);
1420
1421 return entity;
1422}
1423
1424/**
1425 * bfq_lookup_next_entity - return the first eligible entity in @sd.
1426 * @sd: the sched_data.
1427 * @expiration: true if we are on the expiration path of the in-service queue
1428 *
1429 * This function is invoked when there has been a change in the trees
1430 * for sd, and we need to know what is the new next entity to serve
1431 * after this change.
1432 */
1433static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,
1434 bool expiration)
1435{
1436 struct bfq_service_tree *st = sd->service_tree;
1437 struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1);
1438 struct bfq_entity *entity = NULL;
1439 int class_idx = 0;
1440
1441 /*
1442 * Choose from idle class, if needed to guarantee a minimum
1443 * bandwidth to this class (and if there is some active entity
1444 * in idle class). This should also mitigate
1445 * priority-inversion problems in case a low priority task is
1446 * holding file system resources.
1447 */
1448 if (time_is_before_jiffies(sd->bfq_class_idle_last_service +
1449 BFQ_CL_IDLE_TIMEOUT)) {
1450 if (!RB_EMPTY_ROOT(&idle_class_st->active))
1451 class_idx = BFQ_IOPRIO_CLASSES - 1;
1452 /* About to be served if backlogged, or not yet backlogged */
1453 sd->bfq_class_idle_last_service = jiffies;
1454 }
1455
1456 /*
1457 * Find the next entity to serve for the highest-priority
1458 * class, unless the idle class needs to be served.
1459 */
1460 for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) {
1461 /*
1462 * If expiration is true, then bfq_lookup_next_entity
1463 * is being invoked as a part of the expiration path
1464 * of the in-service queue. In this case, even if
1465 * sd->in_service_entity is not NULL,
1466 * sd->in_service_entiy at this point is actually not
1467 * in service any more, and, if needed, has already
1468 * been properly queued or requeued into the right
1469 * tree. The reason why sd->in_service_entity is still
1470 * not NULL here, even if expiration is true, is that
1471 * sd->in_service_entiy is reset as a last step in the
1472 * expiration path. So, if expiration is true, tell
1473 * __bfq_lookup_next_entity that there is no
1474 * sd->in_service_entity.
1475 */
1476 entity = __bfq_lookup_next_entity(st + class_idx,
1477 sd->in_service_entity &&
1478 !expiration);
1479
1480 if (entity)
1481 break;
1482 }
1483
1484 if (!entity)
1485 return NULL;
1486
1487 return entity;
1488}
1489
1490bool next_queue_may_preempt(struct bfq_data *bfqd)
1491{
1492 struct bfq_sched_data *sd = &bfqd->root_group->sched_data;
1493
1494 return sd->next_in_service != sd->in_service_entity;
1495}
1496
1497/*
1498 * Get next queue for service.
1499 */
1500struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
1501{
1502 struct bfq_entity *entity = NULL;
1503 struct bfq_sched_data *sd;
1504 struct bfq_queue *bfqq;
1505
1506 if (bfqd->busy_queues == 0)
1507 return NULL;
1508
1509 /*
1510 * Traverse the path from the root to the leaf entity to
1511 * serve. Set in service all the entities visited along the
1512 * way.
1513 */
1514 sd = &bfqd->root_group->sched_data;
1515 for (; sd ; sd = entity->my_sched_data) {
1516 /*
1517 * WARNING. We are about to set the in-service entity
1518 * to sd->next_in_service, i.e., to the (cached) value
1519 * returned by bfq_lookup_next_entity(sd) the last
1520 * time it was invoked, i.e., the last time when the
1521 * service order in sd changed as a consequence of the
1522 * activation or deactivation of an entity. In this
1523 * respect, if we execute bfq_lookup_next_entity(sd)
1524 * in this very moment, it may, although with low
1525 * probability, yield a different entity than that
1526 * pointed to by sd->next_in_service. This rare event
1527 * happens in case there was no CLASS_IDLE entity to
1528 * serve for sd when bfq_lookup_next_entity(sd) was
1529 * invoked for the last time, while there is now one
1530 * such entity.
1531 *
1532 * If the above event happens, then the scheduling of
1533 * such entity in CLASS_IDLE is postponed until the
1534 * service of the sd->next_in_service entity
1535 * finishes. In fact, when the latter is expired,
1536 * bfq_lookup_next_entity(sd) gets called again,
1537 * exactly to update sd->next_in_service.
1538 */
1539
1540 /* Make next_in_service entity become in_service_entity */
1541 entity = sd->next_in_service;
1542 sd->in_service_entity = entity;
1543
1544 /*
1545 * Reset the accumulator of the amount of service that
1546 * the entity is about to receive.
1547 */
1548 entity->service = 0;
1549
1550 /*
1551 * If entity is no longer a candidate for next
1552 * service, then it must be extracted from its active
1553 * tree, so as to make sure that it won't be
1554 * considered when computing next_in_service. See the
1555 * comments on the function
1556 * bfq_no_longer_next_in_service() for details.
1557 */
1558 if (bfq_no_longer_next_in_service(entity))
1559 bfq_active_extract(bfq_entity_service_tree(entity),
1560 entity);
1561
1562 /*
1563 * Even if entity is not to be extracted according to
1564 * the above check, a descendant entity may get
1565 * extracted in one of the next iterations of this
1566 * loop. Such an event could cause a change in
1567 * next_in_service for the level of the descendant
1568 * entity, and thus possibly back to this level.
1569 *
1570 * However, we cannot perform the resulting needed
1571 * update of next_in_service for this level before the
1572 * end of the whole loop, because, to know which is
1573 * the correct next-to-serve candidate entity for each
1574 * level, we need first to find the leaf entity to set
1575 * in service. In fact, only after we know which is
1576 * the next-to-serve leaf entity, we can discover
1577 * whether the parent entity of the leaf entity
1578 * becomes the next-to-serve, and so on.
1579 */
1580 }
1581
1582 bfqq = bfq_entity_to_bfqq(entity);
1583
1584 /*
1585 * We can finally update all next-to-serve entities along the
1586 * path from the leaf entity just set in service to the root.
1587 */
1588 for_each_entity(entity) {
1589 struct bfq_sched_data *sd = entity->sched_data;
1590
1591 if (!bfq_update_next_in_service(sd, NULL, false))
1592 break;
1593 }
1594
1595 return bfqq;
1596}
1597
1598void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
1599{
1600 struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue;
1601 struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity;
1602 struct bfq_entity *entity = in_serv_entity;
1603
1604 bfq_clear_bfqq_wait_request(in_serv_bfqq);
1605 hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
1606 bfqd->in_service_queue = NULL;
1607
1608 /*
1609 * When this function is called, all in-service entities have
1610 * been properly deactivated or requeued, so we can safely
1611 * execute the final step: reset in_service_entity along the
1612 * path from entity to the root.
1613 */
1614 for_each_entity(entity)
1615 entity->sched_data->in_service_entity = NULL;
1616
1617 /*
1618 * in_serv_entity is no longer in service, so, if it is in no
1619 * service tree either, then release the service reference to
1620 * the queue it represents (taken with bfq_get_entity).
1621 */
1622 if (!in_serv_entity->on_st)
1623 bfq_put_queue(in_serv_bfqq);
1624}
1625
1626void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1627 bool ins_into_idle_tree, bool expiration)
1628{
1629 struct bfq_entity *entity = &bfqq->entity;
1630
1631 bfq_deactivate_entity(entity, ins_into_idle_tree, expiration);
1632}
1633
1634void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
1635{
1636 struct bfq_entity *entity = &bfqq->entity;
1637
1638 bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq),
1639 false, false);
1640 bfq_clear_bfqq_non_blocking_wait_rq(bfqq);
1641}
1642
1643void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1644 bool expiration)
1645{
1646 struct bfq_entity *entity = &bfqq->entity;
1647
1648 bfq_activate_requeue_entity(entity, false,
1649 bfqq == bfqd->in_service_queue, expiration);
1650}
1651
1652/*
1653 * Called when the bfqq no longer has requests pending, remove it from
1654 * the service tree. As a special case, it can be invoked during an
1655 * expiration.
1656 */
1657void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1658 bool expiration)
1659{
1660 bfq_log_bfqq(bfqd, bfqq, "del from busy");
1661
1662 bfq_clear_bfqq_busy(bfqq);
1663
1664 bfqd->busy_queues--;
1665
1666 if (!bfqq->dispatched)
1667 bfq_weights_tree_remove(bfqd, &bfqq->entity,
1668 &bfqd->queue_weights_tree);
1669
1670 if (bfqq->wr_coeff > 1)
1671 bfqd->wr_busy_queues--;
1672
1673 bfqg_stats_update_dequeue(bfqq_group(bfqq));
1674
1675 bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);
1676}
1677
1678/*
1679 * Called when an inactive queue receives a new request.
1680 */
1681void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq)
1682{
1683 bfq_log_bfqq(bfqd, bfqq, "add to busy");
1684
1685 bfq_activate_bfqq(bfqd, bfqq);
1686
1687 bfq_mark_bfqq_busy(bfqq);
1688 bfqd->busy_queues++;
1689
1690 if (!bfqq->dispatched)
1691 if (bfqq->wr_coeff == 1)
1692 bfq_weights_tree_add(bfqd, &bfqq->entity,
1693 &bfqd->queue_weights_tree);
1694
1695 if (bfqq->wr_coeff > 1)
1696 bfqd->wr_busy_queues++;
1697}