1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * cgroups support for the BFQ I/O scheduler.
5 #include <linux/module.h>
6 #include <linux/slab.h>
7 #include <linux/blkdev.h>
8 #include <linux/cgroup.h>
9 #include <linux/elevator.h>
10 #include <linux/ktime.h>
11 #include <linux/rbtree.h>
12 #include <linux/ioprio.h>
13 #include <linux/sbitmap.h>
14 #include <linux/delay.h>
16 #include "bfq-iosched.h"
18 #ifdef CONFIG_BFQ_CGROUP_DEBUG
19 static int bfq_stat_init(struct bfq_stat *stat, gfp_t gfp)
23 ret = percpu_counter_init(&stat->cpu_cnt, 0, gfp);
27 atomic64_set(&stat->aux_cnt, 0);
31 static void bfq_stat_exit(struct bfq_stat *stat)
33 percpu_counter_destroy(&stat->cpu_cnt);
37 * bfq_stat_add - add a value to a bfq_stat
38 * @stat: target bfq_stat
41 * Add @val to @stat. The caller must ensure that IRQ on the same CPU
42 * don't re-enter this function for the same counter.
44 static inline void bfq_stat_add(struct bfq_stat *stat, uint64_t val)
46 percpu_counter_add_batch(&stat->cpu_cnt, val, BLKG_STAT_CPU_BATCH);
50 * bfq_stat_read - read the current value of a bfq_stat
51 * @stat: bfq_stat to read
53 static inline uint64_t bfq_stat_read(struct bfq_stat *stat)
55 return percpu_counter_sum_positive(&stat->cpu_cnt);
59 * bfq_stat_reset - reset a bfq_stat
60 * @stat: bfq_stat to reset
62 static inline void bfq_stat_reset(struct bfq_stat *stat)
64 percpu_counter_set(&stat->cpu_cnt, 0);
65 atomic64_set(&stat->aux_cnt, 0);
69 * bfq_stat_add_aux - add a bfq_stat into another's aux count
70 * @to: the destination bfq_stat
73 * Add @from's count including the aux one to @to's aux count.
75 static inline void bfq_stat_add_aux(struct bfq_stat *to,
76 struct bfq_stat *from)
78 atomic64_add(bfq_stat_read(from) + atomic64_read(&from->aux_cnt),
83 * blkg_prfill_stat - prfill callback for bfq_stat
84 * @sf: seq_file to print to
85 * @pd: policy private data of interest
86 * @off: offset to the bfq_stat in @pd
88 * prfill callback for printing a bfq_stat.
90 static u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd,
93 return __blkg_prfill_u64(sf, pd, bfq_stat_read((void *)pd + off));
96 /* bfqg stats flags */
97 enum bfqg_stats_flags {
98 BFQG_stats_waiting = 0,
103 #define BFQG_FLAG_FNS(name) \
104 static void bfqg_stats_mark_##name(struct bfqg_stats *stats) \
106 stats->flags |= (1 << BFQG_stats_##name); \
108 static void bfqg_stats_clear_##name(struct bfqg_stats *stats) \
110 stats->flags &= ~(1 << BFQG_stats_##name); \
112 static int bfqg_stats_##name(struct bfqg_stats *stats) \
114 return (stats->flags & (1 << BFQG_stats_##name)) != 0; \
117 BFQG_FLAG_FNS(waiting)
118 BFQG_FLAG_FNS(idling)
122 /* This should be called with the scheduler lock held. */
123 static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
127 if (!bfqg_stats_waiting(stats))
130 now = ktime_get_ns();
131 if (now > stats->start_group_wait_time)
132 bfq_stat_add(&stats->group_wait_time,
133 now - stats->start_group_wait_time);
134 bfqg_stats_clear_waiting(stats);
137 /* This should be called with the scheduler lock held. */
138 static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
139 struct bfq_group *curr_bfqg)
141 struct bfqg_stats *stats = &bfqg->stats;
143 if (bfqg_stats_waiting(stats))
145 if (bfqg == curr_bfqg)
147 stats->start_group_wait_time = ktime_get_ns();
148 bfqg_stats_mark_waiting(stats);
151 /* This should be called with the scheduler lock held. */
152 static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
156 if (!bfqg_stats_empty(stats))
159 now = ktime_get_ns();
160 if (now > stats->start_empty_time)
161 bfq_stat_add(&stats->empty_time,
162 now - stats->start_empty_time);
163 bfqg_stats_clear_empty(stats);
166 void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
168 bfq_stat_add(&bfqg->stats.dequeue, 1);
171 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg)
173 struct bfqg_stats *stats = &bfqg->stats;
175 if (blkg_rwstat_total(&stats->queued))
179 * group is already marked empty. This can happen if bfqq got new
180 * request in parent group and moved to this group while being added
181 * to service tree. Just ignore the event and move on.
183 if (bfqg_stats_empty(stats))
186 stats->start_empty_time = ktime_get_ns();
187 bfqg_stats_mark_empty(stats);
190 void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
192 struct bfqg_stats *stats = &bfqg->stats;
194 if (bfqg_stats_idling(stats)) {
195 u64 now = ktime_get_ns();
197 if (now > stats->start_idle_time)
198 bfq_stat_add(&stats->idle_time,
199 now - stats->start_idle_time);
200 bfqg_stats_clear_idling(stats);
204 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
206 struct bfqg_stats *stats = &bfqg->stats;
208 stats->start_idle_time = ktime_get_ns();
209 bfqg_stats_mark_idling(stats);
212 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
214 struct bfqg_stats *stats = &bfqg->stats;
216 bfq_stat_add(&stats->avg_queue_size_sum,
217 blkg_rwstat_total(&stats->queued));
218 bfq_stat_add(&stats->avg_queue_size_samples, 1);
219 bfqg_stats_update_group_wait_time(stats);
222 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
225 blkg_rwstat_add(&bfqg->stats.queued, op, 1);
226 bfqg_stats_end_empty_time(&bfqg->stats);
227 if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
228 bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
231 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
233 blkg_rwstat_add(&bfqg->stats.queued, op, -1);
236 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
238 blkg_rwstat_add(&bfqg->stats.merged, op, 1);
241 void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
242 u64 io_start_time_ns, unsigned int op)
244 struct bfqg_stats *stats = &bfqg->stats;
245 u64 now = ktime_get_ns();
247 if (now > io_start_time_ns)
248 blkg_rwstat_add(&stats->service_time, op,
249 now - io_start_time_ns);
250 if (io_start_time_ns > start_time_ns)
251 blkg_rwstat_add(&stats->wait_time, op,
252 io_start_time_ns - start_time_ns);
255 #else /* CONFIG_BFQ_CGROUP_DEBUG */
257 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
259 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
260 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
261 void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
262 u64 io_start_time_ns, unsigned int op) { }
263 void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
264 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
265 void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
266 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
267 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
269 #endif /* CONFIG_BFQ_CGROUP_DEBUG */
271 #ifdef CONFIG_BFQ_GROUP_IOSCHED
274 * blk-cgroup policy-related handlers
275 * The following functions help in converting between blk-cgroup
276 * internal structures and BFQ-specific structures.
279 static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd)
281 return pd ? container_of(pd, struct bfq_group, pd) : NULL;
284 struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg)
286 return pd_to_blkg(&bfqg->pd);
289 static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg)
291 return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq));
296 * The following functions help in navigating the bfq_group hierarchy
297 * by allowing to find the parent of a bfq_group or the bfq_group
298 * associated to a bfq_queue.
301 static struct bfq_group *bfqg_parent(struct bfq_group *bfqg)
303 struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent;
305 return pblkg ? blkg_to_bfqg(pblkg) : NULL;
308 struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
310 struct bfq_entity *group_entity = bfqq->entity.parent;
312 return group_entity ? container_of(group_entity, struct bfq_group,
314 bfqq->bfqd->root_group;
318 * The following two functions handle get and put of a bfq_group by
319 * wrapping the related blk-cgroup hooks.
322 static void bfqg_get(struct bfq_group *bfqg)
327 static void bfqg_put(struct bfq_group *bfqg)
335 static void bfqg_and_blkg_get(struct bfq_group *bfqg)
337 /* see comments in bfq_bic_update_cgroup for why refcounting bfqg */
340 blkg_get(bfqg_to_blkg(bfqg));
343 void bfqg_and_blkg_put(struct bfq_group *bfqg)
345 blkg_put(bfqg_to_blkg(bfqg));
350 void bfqg_stats_update_legacy_io(struct request_queue *q, struct request *rq)
352 struct bfq_group *bfqg = blkg_to_bfqg(rq->bio->bi_blkg);
357 blkg_rwstat_add(&bfqg->stats.bytes, rq->cmd_flags, blk_rq_bytes(rq));
358 blkg_rwstat_add(&bfqg->stats.ios, rq->cmd_flags, 1);
362 static void bfqg_stats_reset(struct bfqg_stats *stats)
364 #ifdef CONFIG_BFQ_CGROUP_DEBUG
365 /* queued stats shouldn't be cleared */
366 blkg_rwstat_reset(&stats->merged);
367 blkg_rwstat_reset(&stats->service_time);
368 blkg_rwstat_reset(&stats->wait_time);
369 bfq_stat_reset(&stats->time);
370 bfq_stat_reset(&stats->avg_queue_size_sum);
371 bfq_stat_reset(&stats->avg_queue_size_samples);
372 bfq_stat_reset(&stats->dequeue);
373 bfq_stat_reset(&stats->group_wait_time);
374 bfq_stat_reset(&stats->idle_time);
375 bfq_stat_reset(&stats->empty_time);
380 static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
385 #ifdef CONFIG_BFQ_CGROUP_DEBUG
386 /* queued stats shouldn't be cleared */
387 blkg_rwstat_add_aux(&to->merged, &from->merged);
388 blkg_rwstat_add_aux(&to->service_time, &from->service_time);
389 blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
390 bfq_stat_add_aux(&from->time, &from->time);
391 bfq_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
392 bfq_stat_add_aux(&to->avg_queue_size_samples,
393 &from->avg_queue_size_samples);
394 bfq_stat_add_aux(&to->dequeue, &from->dequeue);
395 bfq_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
396 bfq_stat_add_aux(&to->idle_time, &from->idle_time);
397 bfq_stat_add_aux(&to->empty_time, &from->empty_time);
402 * Transfer @bfqg's stats to its parent's aux counts so that the ancestors'
403 * recursive stats can still account for the amount used by this bfqg after
406 static void bfqg_stats_xfer_dead(struct bfq_group *bfqg)
408 struct bfq_group *parent;
410 if (!bfqg) /* root_group */
413 parent = bfqg_parent(bfqg);
415 lockdep_assert_held(&bfqg_to_blkg(bfqg)->q->queue_lock);
417 if (unlikely(!parent))
420 bfqg_stats_add_aux(&parent->stats, &bfqg->stats);
421 bfqg_stats_reset(&bfqg->stats);
424 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
426 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
428 entity->weight = entity->new_weight;
429 entity->orig_weight = entity->new_weight;
431 bfqq->ioprio = bfqq->new_ioprio;
432 bfqq->ioprio_class = bfqq->new_ioprio_class;
434 * Make sure that bfqg and its associated blkg do not
435 * disappear before entity.
437 bfqg_and_blkg_get(bfqg);
439 entity->parent = bfqg->my_entity; /* NULL for root group */
440 entity->sched_data = &bfqg->sched_data;
443 static void bfqg_stats_exit(struct bfqg_stats *stats)
445 blkg_rwstat_exit(&stats->bytes);
446 blkg_rwstat_exit(&stats->ios);
447 #ifdef CONFIG_BFQ_CGROUP_DEBUG
448 blkg_rwstat_exit(&stats->merged);
449 blkg_rwstat_exit(&stats->service_time);
450 blkg_rwstat_exit(&stats->wait_time);
451 blkg_rwstat_exit(&stats->queued);
452 bfq_stat_exit(&stats->time);
453 bfq_stat_exit(&stats->avg_queue_size_sum);
454 bfq_stat_exit(&stats->avg_queue_size_samples);
455 bfq_stat_exit(&stats->dequeue);
456 bfq_stat_exit(&stats->group_wait_time);
457 bfq_stat_exit(&stats->idle_time);
458 bfq_stat_exit(&stats->empty_time);
462 static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
464 if (blkg_rwstat_init(&stats->bytes, gfp) ||
465 blkg_rwstat_init(&stats->ios, gfp))
468 #ifdef CONFIG_BFQ_CGROUP_DEBUG
469 if (blkg_rwstat_init(&stats->merged, gfp) ||
470 blkg_rwstat_init(&stats->service_time, gfp) ||
471 blkg_rwstat_init(&stats->wait_time, gfp) ||
472 blkg_rwstat_init(&stats->queued, gfp) ||
473 bfq_stat_init(&stats->time, gfp) ||
474 bfq_stat_init(&stats->avg_queue_size_sum, gfp) ||
475 bfq_stat_init(&stats->avg_queue_size_samples, gfp) ||
476 bfq_stat_init(&stats->dequeue, gfp) ||
477 bfq_stat_init(&stats->group_wait_time, gfp) ||
478 bfq_stat_init(&stats->idle_time, gfp) ||
479 bfq_stat_init(&stats->empty_time, gfp)) {
480 bfqg_stats_exit(stats);
488 static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)
490 return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL;
493 static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg)
495 return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq));
498 static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
500 struct bfq_group_data *bgd;
502 bgd = kzalloc(sizeof(*bgd), gfp);
508 static void bfq_cpd_init(struct blkcg_policy_data *cpd)
510 struct bfq_group_data *d = cpd_to_bfqgd(cpd);
512 d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
513 CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL;
516 static void bfq_cpd_free(struct blkcg_policy_data *cpd)
518 kfree(cpd_to_bfqgd(cpd));
521 static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, struct request_queue *q,
524 struct bfq_group *bfqg;
526 bfqg = kzalloc_node(sizeof(*bfqg), gfp, q->node);
530 if (bfqg_stats_init(&bfqg->stats, gfp)) {
535 /* see comments in bfq_bic_update_cgroup for why refcounting */
540 static void bfq_pd_init(struct blkg_policy_data *pd)
542 struct blkcg_gq *blkg = pd_to_blkg(pd);
543 struct bfq_group *bfqg = blkg_to_bfqg(blkg);
544 struct bfq_data *bfqd = blkg->q->elevator->elevator_data;
545 struct bfq_entity *entity = &bfqg->entity;
546 struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg);
548 entity->orig_weight = entity->weight = entity->new_weight = d->weight;
549 entity->my_sched_data = &bfqg->sched_data;
550 bfqg->my_entity = entity; /*
551 * the root_group's will be set to NULL
552 * in bfq_init_queue()
555 bfqg->active_entities = 0;
556 bfqg->rq_pos_tree = RB_ROOT;
559 static void bfq_pd_free(struct blkg_policy_data *pd)
561 struct bfq_group *bfqg = pd_to_bfqg(pd);
563 bfqg_stats_exit(&bfqg->stats);
567 static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
569 struct bfq_group *bfqg = pd_to_bfqg(pd);
571 bfqg_stats_reset(&bfqg->stats);
574 static void bfq_group_set_parent(struct bfq_group *bfqg,
575 struct bfq_group *parent)
577 struct bfq_entity *entity;
579 entity = &bfqg->entity;
580 entity->parent = parent->my_entity;
581 entity->sched_data = &parent->sched_data;
584 static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd,
587 struct blkcg_gq *blkg;
589 blkg = blkg_lookup(blkcg, bfqd->queue);
591 return blkg_to_bfqg(blkg);
595 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
598 struct bfq_group *bfqg, *parent;
599 struct bfq_entity *entity;
601 bfqg = bfq_lookup_bfqg(bfqd, blkcg);
607 * Update chain of bfq_groups as we might be handling a leaf group
608 * which, along with some of its relatives, has not been hooked yet
609 * to the private hierarchy of BFQ.
611 entity = &bfqg->entity;
612 for_each_entity(entity) {
613 struct bfq_group *curr_bfqg = container_of(entity,
614 struct bfq_group, entity);
615 if (curr_bfqg != bfqd->root_group) {
616 parent = bfqg_parent(curr_bfqg);
618 parent = bfqd->root_group;
619 bfq_group_set_parent(curr_bfqg, parent);
627 * bfq_bfqq_move - migrate @bfqq to @bfqg.
628 * @bfqd: queue descriptor.
629 * @bfqq: the queue to move.
630 * @bfqg: the group to move to.
632 * Move @bfqq to @bfqg, deactivating it from its old group and reactivating
633 * it on the new one. Avoid putting the entity on the old group idle tree.
635 * Must be called under the scheduler lock, to make sure that the blkg
636 * owning @bfqg does not disappear (see comments in
637 * bfq_bic_update_cgroup on guaranteeing the consistency of blkg
640 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
641 struct bfq_group *bfqg)
643 struct bfq_entity *entity = &bfqq->entity;
646 * Get extra reference to prevent bfqq from being freed in
647 * next possible expire or deactivate.
651 /* If bfqq is empty, then bfq_bfqq_expire also invokes
652 * bfq_del_bfqq_busy, thereby removing bfqq and its entity
653 * from data structures related to current group. Otherwise we
654 * need to remove bfqq explicitly with bfq_deactivate_bfqq, as
657 if (bfqq == bfqd->in_service_queue)
658 bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
659 false, BFQQE_PREEMPTED);
661 if (bfq_bfqq_busy(bfqq))
662 bfq_deactivate_bfqq(bfqd, bfqq, false, false);
663 else if (entity->on_st_or_in_serv)
664 bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
665 bfqg_and_blkg_put(bfqq_group(bfqq));
667 entity->parent = bfqg->my_entity;
668 entity->sched_data = &bfqg->sched_data;
669 /* pin down bfqg and its associated blkg */
670 bfqg_and_blkg_get(bfqg);
672 if (bfq_bfqq_busy(bfqq)) {
673 if (unlikely(!bfqd->nonrot_with_queueing))
674 bfq_pos_tree_add_move(bfqd, bfqq);
675 bfq_activate_bfqq(bfqd, bfqq);
678 if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
679 bfq_schedule_dispatch(bfqd);
680 /* release extra ref taken above, bfqq may happen to be freed now */
685 * __bfq_bic_change_cgroup - move @bic to @cgroup.
686 * @bfqd: the queue descriptor.
687 * @bic: the bic to move.
688 * @blkcg: the blk-cgroup to move to.
690 * Move bic to blkcg, assuming that bfqd->lock is held; which makes
691 * sure that the reference to cgroup is valid across the call (see
692 * comments in bfq_bic_update_cgroup on this issue)
694 * NOTE: an alternative approach might have been to store the current
695 * cgroup in bfqq and getting a reference to it, reducing the lookup
696 * time here, at the price of slightly more complex code.
698 static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
699 struct bfq_io_cq *bic,
702 struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
703 struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
704 struct bfq_group *bfqg;
705 struct bfq_entity *entity;
707 bfqg = bfq_find_set_group(bfqd, blkcg);
710 bfqg = bfqd->root_group;
713 entity = &async_bfqq->entity;
715 if (entity->sched_data != &bfqg->sched_data) {
716 bic_set_bfqq(bic, NULL, 0);
717 bfq_release_process_ref(bfqd, async_bfqq);
722 entity = &sync_bfqq->entity;
723 if (entity->sched_data != &bfqg->sched_data)
724 bfq_bfqq_move(bfqd, sync_bfqq, bfqg);
730 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
732 struct bfq_data *bfqd = bic_to_bfqd(bic);
733 struct bfq_group *bfqg = NULL;
737 serial_nr = __bio_blkcg(bio)->css.serial_nr;
740 * Check whether blkcg has changed. The condition may trigger
741 * spuriously on a newly created cic but there's no harm.
743 if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr))
746 bfqg = __bfq_bic_change_cgroup(bfqd, bic, __bio_blkcg(bio));
748 * Update blkg_path for bfq_log_* functions. We cache this
749 * path, and update it here, for the following
750 * reasons. Operations on blkg objects in blk-cgroup are
751 * protected with the request_queue lock, and not with the
752 * lock that protects the instances of this scheduler
753 * (bfqd->lock). This exposes BFQ to the following sort of
756 * The blkg_lookup performed in bfq_get_queue, protected
757 * through rcu, may happen to return the address of a copy of
758 * the original blkg. If this is the case, then the
759 * bfqg_and_blkg_get performed in bfq_get_queue, to pin down
760 * the blkg, is useless: it does not prevent blk-cgroup code
761 * from destroying both the original blkg and all objects
762 * directly or indirectly referred by the copy of the
765 * On the bright side, destroy operations on a blkg invoke, as
766 * a first step, hooks of the scheduler associated with the
767 * blkg. And these hooks are executed with bfqd->lock held for
768 * BFQ. As a consequence, for any blkg associated with the
769 * request queue this instance of the scheduler is attached
770 * to, we are guaranteed that such a blkg is not destroyed, and
771 * that all the pointers it contains are consistent, while we
772 * are holding bfqd->lock. A blkg_lookup performed with
773 * bfqd->lock held then returns a fully consistent blkg, which
774 * remains consistent until this lock is held.
776 * Thanks to the last fact, and to the fact that: (1) bfqg has
777 * been obtained through a blkg_lookup in the above
778 * assignment, and (2) bfqd->lock is being held, here we can
779 * safely use the policy data for the involved blkg (i.e., the
780 * field bfqg->pd) to get to the blkg associated with bfqg,
781 * and then we can safely use any field of blkg. After we
782 * release bfqd->lock, even just getting blkg through this
783 * bfqg may cause dangling references to be traversed, as
784 * bfqg->pd may not exist any more.
786 * In view of the above facts, here we cache, in the bfqg, any
787 * blkg data we may need for this bic, and for its associated
788 * bfq_queue. As of now, we need to cache only the path of the
789 * blkg, which is used in the bfq_log_* functions.
791 * Finally, note that bfqg itself needs to be protected from
792 * destruction on the blkg_free of the original blkg (which
793 * invokes bfq_pd_free). We use an additional private
794 * refcounter for bfqg, to let it disappear only after no
795 * bfq_queue refers to it any longer.
797 blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
798 bic->blkcg_serial_nr = serial_nr;
804 * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
805 * @st: the service tree being flushed.
807 static void bfq_flush_idle_tree(struct bfq_service_tree *st)
809 struct bfq_entity *entity = st->first_idle;
811 for (; entity ; entity = st->first_idle)
812 __bfq_deactivate_entity(entity, false);
816 * bfq_reparent_leaf_entity - move leaf entity to the root_group.
817 * @bfqd: the device data structure with the root group.
818 * @entity: the entity to move, if entity is a leaf; or the parent entity
819 * of an active leaf entity to move, if entity is not a leaf.
821 static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
822 struct bfq_entity *entity,
825 struct bfq_queue *bfqq;
826 struct bfq_entity *child_entity = entity;
828 while (child_entity->my_sched_data) { /* leaf not reached yet */
829 struct bfq_sched_data *child_sd = child_entity->my_sched_data;
830 struct bfq_service_tree *child_st = child_sd->service_tree +
832 struct rb_root *child_active = &child_st->active;
834 child_entity = bfq_entity_of(rb_first(child_active));
837 child_entity = child_sd->in_service_entity;
840 bfqq = bfq_entity_to_bfqq(child_entity);
841 bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
845 * bfq_reparent_active_queues - move to the root group all active queues.
846 * @bfqd: the device data structure with the root group.
847 * @bfqg: the group to move from.
848 * @st: the service tree to start the search from.
850 static void bfq_reparent_active_queues(struct bfq_data *bfqd,
851 struct bfq_group *bfqg,
852 struct bfq_service_tree *st,
855 struct rb_root *active = &st->active;
856 struct bfq_entity *entity;
858 while ((entity = bfq_entity_of(rb_first(active))))
859 bfq_reparent_leaf_entity(bfqd, entity, ioprio_class);
861 if (bfqg->sched_data.in_service_entity)
862 bfq_reparent_leaf_entity(bfqd,
863 bfqg->sched_data.in_service_entity,
868 * bfq_pd_offline - deactivate the entity associated with @pd,
869 * and reparent its children entities.
870 * @pd: descriptor of the policy going offline.
872 * blkio already grabs the queue_lock for us, so no need to use
875 static void bfq_pd_offline(struct blkg_policy_data *pd)
877 struct bfq_service_tree *st;
878 struct bfq_group *bfqg = pd_to_bfqg(pd);
879 struct bfq_data *bfqd = bfqg->bfqd;
880 struct bfq_entity *entity = bfqg->my_entity;
884 spin_lock_irqsave(&bfqd->lock, flags);
886 if (!entity) /* root group */
887 goto put_async_queues;
890 * Empty all service_trees belonging to this group before
891 * deactivating the group itself.
893 for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
894 st = bfqg->sched_data.service_tree + i;
897 * It may happen that some queues are still active
898 * (busy) upon group destruction (if the corresponding
899 * processes have been forced to terminate). We move
900 * all the leaf entities corresponding to these queues
902 * Also, it may happen that the group has an entity
903 * in service, which is disconnected from the active
904 * tree: it must be moved, too.
905 * There is no need to put the sync queues, as the
906 * scheduler has taken no reference.
908 bfq_reparent_active_queues(bfqd, bfqg, st, i);
911 * The idle tree may still contain bfq_queues
912 * belonging to exited task because they never
913 * migrated to a different cgroup from the one being
914 * destroyed now. In addition, even
915 * bfq_reparent_active_queues() may happen to add some
916 * entities to the idle tree. It happens if, in some
917 * of the calls to bfq_bfqq_move() performed by
918 * bfq_reparent_active_queues(), the queue to move is
919 * empty and gets expired.
921 bfq_flush_idle_tree(st);
924 __bfq_deactivate_entity(entity, false);
927 bfq_put_async_queues(bfqd, bfqg);
929 spin_unlock_irqrestore(&bfqd->lock, flags);
931 * @blkg is going offline and will be ignored by
932 * blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so
933 * that they don't get lost. If IOs complete after this point, the
934 * stats for them will be lost. Oh well...
936 bfqg_stats_xfer_dead(bfqg);
939 void bfq_end_wr_async(struct bfq_data *bfqd)
941 struct blkcg_gq *blkg;
943 list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) {
944 struct bfq_group *bfqg = blkg_to_bfqg(blkg);
946 bfq_end_wr_async_queues(bfqd, bfqg);
948 bfq_end_wr_async_queues(bfqd, bfqd->root_group);
951 static int bfq_io_show_weight_legacy(struct seq_file *sf, void *v)
953 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
954 struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
955 unsigned int val = 0;
960 seq_printf(sf, "%u\n", val);
965 static u64 bfqg_prfill_weight_device(struct seq_file *sf,
966 struct blkg_policy_data *pd, int off)
968 struct bfq_group *bfqg = pd_to_bfqg(pd);
970 if (!bfqg->entity.dev_weight)
972 return __blkg_prfill_u64(sf, pd, bfqg->entity.dev_weight);
975 static int bfq_io_show_weight(struct seq_file *sf, void *v)
977 struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
978 struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
980 seq_printf(sf, "default %u\n", bfqgd->weight);
981 blkcg_print_blkgs(sf, blkcg, bfqg_prfill_weight_device,
982 &blkcg_policy_bfq, 0, false);
986 static void bfq_group_set_weight(struct bfq_group *bfqg, u64 weight, u64 dev_weight)
988 weight = dev_weight ?: weight;
990 bfqg->entity.dev_weight = dev_weight;
992 * Setting the prio_changed flag of the entity
993 * to 1 with new_weight == weight would re-set
994 * the value of the weight to its ioprio mapping.
995 * Set the flag only if necessary.
997 if ((unsigned short)weight != bfqg->entity.new_weight) {
998 bfqg->entity.new_weight = (unsigned short)weight;
1000 * Make sure that the above new value has been
1001 * stored in bfqg->entity.new_weight before
1002 * setting the prio_changed flag. In fact,
1003 * this flag may be read asynchronously (in
1004 * critical sections protected by a different
1005 * lock than that held here), and finding this
1006 * flag set may cause the execution of the code
1007 * for updating parameters whose value may
1008 * depend also on bfqg->entity.new_weight (in
1009 * __bfq_entity_update_weight_prio).
1010 * This barrier makes sure that the new value
1011 * of bfqg->entity.new_weight is correctly
1012 * seen in that code.
1015 bfqg->entity.prio_changed = 1;
1019 static int bfq_io_set_weight_legacy(struct cgroup_subsys_state *css,
1020 struct cftype *cftype,
1023 struct blkcg *blkcg = css_to_blkcg(css);
1024 struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
1025 struct blkcg_gq *blkg;
1028 if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT)
1032 spin_lock_irq(&blkcg->lock);
1033 bfqgd->weight = (unsigned short)val;
1034 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
1035 struct bfq_group *bfqg = blkg_to_bfqg(blkg);
1038 bfq_group_set_weight(bfqg, val, 0);
1040 spin_unlock_irq(&blkcg->lock);
1045 static ssize_t bfq_io_set_device_weight(struct kernfs_open_file *of,
1046 char *buf, size_t nbytes,
1050 struct blkg_conf_ctx ctx;
1051 struct blkcg *blkcg = css_to_blkcg(of_css(of));
1052 struct bfq_group *bfqg;
1055 ret = blkg_conf_prep(blkcg, &blkcg_policy_bfq, buf, &ctx);
1059 if (sscanf(ctx.body, "%llu", &v) == 1) {
1060 /* require "default" on dfl */
1064 } else if (!strcmp(strim(ctx.body), "default")) {
1071 bfqg = blkg_to_bfqg(ctx.blkg);
1074 if (!v || (v >= BFQ_MIN_WEIGHT && v <= BFQ_MAX_WEIGHT)) {
1075 bfq_group_set_weight(bfqg, bfqg->entity.weight, v);
1079 blkg_conf_finish(&ctx);
1080 return ret ?: nbytes;
1083 static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
1084 char *buf, size_t nbytes,
1093 /* "WEIGHT" or "default WEIGHT" sets the default weight */
1094 v = simple_strtoull(buf, &endp, 0);
1095 if (*endp == '\0' || sscanf(buf, "default %llu", &v) == 1) {
1096 ret = bfq_io_set_weight_legacy(of_css(of), NULL, v);
1097 return ret ?: nbytes;
1100 return bfq_io_set_device_weight(of, buf, nbytes, off);
1103 static int bfqg_print_rwstat(struct seq_file *sf, void *v)
1105 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
1106 &blkcg_policy_bfq, seq_cft(sf)->private, true);
1110 static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
1111 struct blkg_policy_data *pd, int off)
1113 struct blkg_rwstat_sample sum;
1115 blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off, &sum);
1116 return __blkg_prfill_rwstat(sf, pd, &sum);
1119 static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
1121 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1122 bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq,
1123 seq_cft(sf)->private, true);
1127 #ifdef CONFIG_BFQ_CGROUP_DEBUG
1128 static int bfqg_print_stat(struct seq_file *sf, void *v)
1130 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
1131 &blkcg_policy_bfq, seq_cft(sf)->private, false);
1135 static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
1136 struct blkg_policy_data *pd, int off)
1138 struct blkcg_gq *blkg = pd_to_blkg(pd);
1139 struct blkcg_gq *pos_blkg;
1140 struct cgroup_subsys_state *pos_css;
1143 lockdep_assert_held(&blkg->q->queue_lock);
1146 blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
1147 struct bfq_stat *stat;
1149 if (!pos_blkg->online)
1152 stat = (void *)blkg_to_pd(pos_blkg, &blkcg_policy_bfq) + off;
1153 sum += bfq_stat_read(stat) + atomic64_read(&stat->aux_cnt);
1157 return __blkg_prfill_u64(sf, pd, sum);
1160 static int bfqg_print_stat_recursive(struct seq_file *sf, void *v)
1162 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1163 bfqg_prfill_stat_recursive, &blkcg_policy_bfq,
1164 seq_cft(sf)->private, false);
1168 static u64 bfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
1171 struct bfq_group *bfqg = blkg_to_bfqg(pd->blkg);
1172 u64 sum = blkg_rwstat_total(&bfqg->stats.bytes);
1174 return __blkg_prfill_u64(sf, pd, sum >> 9);
1177 static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
1179 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1180 bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false);
1184 static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
1185 struct blkg_policy_data *pd, int off)
1187 struct blkg_rwstat_sample tmp;
1189 blkg_rwstat_recursive_sum(pd->blkg, &blkcg_policy_bfq,
1190 offsetof(struct bfq_group, stats.bytes), &tmp);
1192 return __blkg_prfill_u64(sf, pd,
1193 (tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE]) >> 9);
1196 static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
1198 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1199 bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0,
1204 static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf,
1205 struct blkg_policy_data *pd, int off)
1207 struct bfq_group *bfqg = pd_to_bfqg(pd);
1208 u64 samples = bfq_stat_read(&bfqg->stats.avg_queue_size_samples);
1212 v = bfq_stat_read(&bfqg->stats.avg_queue_size_sum);
1213 v = div64_u64(v, samples);
1215 __blkg_prfill_u64(sf, pd, v);
1219 /* print avg_queue_size */
1220 static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
1222 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1223 bfqg_prfill_avg_queue_size, &blkcg_policy_bfq,
1227 #endif /* CONFIG_BFQ_CGROUP_DEBUG */
1229 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
1233 ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq);
1237 return blkg_to_bfqg(bfqd->queue->root_blkg);
1240 struct blkcg_policy blkcg_policy_bfq = {
1241 .dfl_cftypes = bfq_blkg_files,
1242 .legacy_cftypes = bfq_blkcg_legacy_files,
1244 .cpd_alloc_fn = bfq_cpd_alloc,
1245 .cpd_init_fn = bfq_cpd_init,
1246 .cpd_bind_fn = bfq_cpd_init,
1247 .cpd_free_fn = bfq_cpd_free,
1249 .pd_alloc_fn = bfq_pd_alloc,
1250 .pd_init_fn = bfq_pd_init,
1251 .pd_offline_fn = bfq_pd_offline,
1252 .pd_free_fn = bfq_pd_free,
1253 .pd_reset_stats_fn = bfq_pd_reset_stats,
1256 struct cftype bfq_blkcg_legacy_files[] = {
1258 .name = "bfq.weight",
1259 .flags = CFTYPE_NOT_ON_ROOT,
1260 .seq_show = bfq_io_show_weight_legacy,
1261 .write_u64 = bfq_io_set_weight_legacy,
1264 .name = "bfq.weight_device",
1265 .flags = CFTYPE_NOT_ON_ROOT,
1266 .seq_show = bfq_io_show_weight,
1267 .write = bfq_io_set_weight,
1270 /* statistics, covers only the tasks in the bfqg */
1272 .name = "bfq.io_service_bytes",
1273 .private = offsetof(struct bfq_group, stats.bytes),
1274 .seq_show = bfqg_print_rwstat,
1277 .name = "bfq.io_serviced",
1278 .private = offsetof(struct bfq_group, stats.ios),
1279 .seq_show = bfqg_print_rwstat,
1281 #ifdef CONFIG_BFQ_CGROUP_DEBUG
1284 .private = offsetof(struct bfq_group, stats.time),
1285 .seq_show = bfqg_print_stat,
1288 .name = "bfq.sectors",
1289 .seq_show = bfqg_print_stat_sectors,
1292 .name = "bfq.io_service_time",
1293 .private = offsetof(struct bfq_group, stats.service_time),
1294 .seq_show = bfqg_print_rwstat,
1297 .name = "bfq.io_wait_time",
1298 .private = offsetof(struct bfq_group, stats.wait_time),
1299 .seq_show = bfqg_print_rwstat,
1302 .name = "bfq.io_merged",
1303 .private = offsetof(struct bfq_group, stats.merged),
1304 .seq_show = bfqg_print_rwstat,
1307 .name = "bfq.io_queued",
1308 .private = offsetof(struct bfq_group, stats.queued),
1309 .seq_show = bfqg_print_rwstat,
1311 #endif /* CONFIG_BFQ_CGROUP_DEBUG */
1313 /* the same statistics which cover the bfqg and its descendants */
1315 .name = "bfq.io_service_bytes_recursive",
1316 .private = offsetof(struct bfq_group, stats.bytes),
1317 .seq_show = bfqg_print_rwstat_recursive,
1320 .name = "bfq.io_serviced_recursive",
1321 .private = offsetof(struct bfq_group, stats.ios),
1322 .seq_show = bfqg_print_rwstat_recursive,
1324 #ifdef CONFIG_BFQ_CGROUP_DEBUG
1326 .name = "bfq.time_recursive",
1327 .private = offsetof(struct bfq_group, stats.time),
1328 .seq_show = bfqg_print_stat_recursive,
1331 .name = "bfq.sectors_recursive",
1332 .seq_show = bfqg_print_stat_sectors_recursive,
1335 .name = "bfq.io_service_time_recursive",
1336 .private = offsetof(struct bfq_group, stats.service_time),
1337 .seq_show = bfqg_print_rwstat_recursive,
1340 .name = "bfq.io_wait_time_recursive",
1341 .private = offsetof(struct bfq_group, stats.wait_time),
1342 .seq_show = bfqg_print_rwstat_recursive,
1345 .name = "bfq.io_merged_recursive",
1346 .private = offsetof(struct bfq_group, stats.merged),
1347 .seq_show = bfqg_print_rwstat_recursive,
1350 .name = "bfq.io_queued_recursive",
1351 .private = offsetof(struct bfq_group, stats.queued),
1352 .seq_show = bfqg_print_rwstat_recursive,
1355 .name = "bfq.avg_queue_size",
1356 .seq_show = bfqg_print_avg_queue_size,
1359 .name = "bfq.group_wait_time",
1360 .private = offsetof(struct bfq_group, stats.group_wait_time),
1361 .seq_show = bfqg_print_stat,
1364 .name = "bfq.idle_time",
1365 .private = offsetof(struct bfq_group, stats.idle_time),
1366 .seq_show = bfqg_print_stat,
1369 .name = "bfq.empty_time",
1370 .private = offsetof(struct bfq_group, stats.empty_time),
1371 .seq_show = bfqg_print_stat,
1374 .name = "bfq.dequeue",
1375 .private = offsetof(struct bfq_group, stats.dequeue),
1376 .seq_show = bfqg_print_stat,
1378 #endif /* CONFIG_BFQ_CGROUP_DEBUG */
1382 struct cftype bfq_blkg_files[] = {
1384 .name = "bfq.weight",
1385 .flags = CFTYPE_NOT_ON_ROOT,
1386 .seq_show = bfq_io_show_weight,
1387 .write = bfq_io_set_weight,
1392 #else /* CONFIG_BFQ_GROUP_IOSCHED */
1394 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1395 struct bfq_group *bfqg) {}
1397 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
1399 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
1401 entity->weight = entity->new_weight;
1402 entity->orig_weight = entity->new_weight;
1404 bfqq->ioprio = bfqq->new_ioprio;
1405 bfqq->ioprio_class = bfqq->new_ioprio_class;
1407 entity->sched_data = &bfqg->sched_data;
1410 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {}
1412 void bfq_end_wr_async(struct bfq_data *bfqd)
1414 bfq_end_wr_async_queues(bfqd, bfqd->root_group);
1417 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg)
1419 return bfqd->root_group;
1422 struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
1424 return bfqq->bfqd->root_group;
1427 void bfqg_and_blkg_get(struct bfq_group *bfqg) {}
1429 void bfqg_and_blkg_put(struct bfq_group *bfqg) {}
1431 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
1433 struct bfq_group *bfqg;
1436 bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
1440 for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
1441 bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
1445 #endif /* CONFIG_BFQ_GROUP_IOSCHED */