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TOMOYO Linux Cross Reference
Linux/block/bfq-cgroup.c

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  1 /*
  2  * cgroups support for the BFQ I/O scheduler.
  3  *
  4  *  This program is free software; you can redistribute it and/or
  5  *  modify it under the terms of the GNU General Public License as
  6  *  published by the Free Software Foundation; either version 2 of the
  7  *  License, or (at your option) any later version.
  8  *
  9  *  This program is distributed in the hope that it will be useful,
 10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 12  *  General Public License for more details.
 13  */
 14 #include <linux/module.h>
 15 #include <linux/slab.h>
 16 #include <linux/blkdev.h>
 17 #include <linux/cgroup.h>
 18 #include <linux/elevator.h>
 19 #include <linux/ktime.h>
 20 #include <linux/rbtree.h>
 21 #include <linux/ioprio.h>
 22 #include <linux/sbitmap.h>
 23 #include <linux/delay.h>
 24 
 25 #include "bfq-iosched.h"
 26 
 27 #if defined(CONFIG_BFQ_GROUP_IOSCHED) &&  defined(CONFIG_DEBUG_BLK_CGROUP)
 28 
 29 /* bfqg stats flags */
 30 enum bfqg_stats_flags {
 31         BFQG_stats_waiting = 0,
 32         BFQG_stats_idling,
 33         BFQG_stats_empty,
 34 };
 35 
 36 #define BFQG_FLAG_FNS(name)                                             \
 37 static void bfqg_stats_mark_##name(struct bfqg_stats *stats)    \
 38 {                                                                       \
 39         stats->flags |= (1 << BFQG_stats_##name);                       \
 40 }                                                                       \
 41 static void bfqg_stats_clear_##name(struct bfqg_stats *stats)   \
 42 {                                                                       \
 43         stats->flags &= ~(1 << BFQG_stats_##name);                      \
 44 }                                                                       \
 45 static int bfqg_stats_##name(struct bfqg_stats *stats)          \
 46 {                                                                       \
 47         return (stats->flags & (1 << BFQG_stats_##name)) != 0;          \
 48 }                                                                       \
 49 
 50 BFQG_FLAG_FNS(waiting)
 51 BFQG_FLAG_FNS(idling)
 52 BFQG_FLAG_FNS(empty)
 53 #undef BFQG_FLAG_FNS
 54 
 55 /* This should be called with the scheduler lock held. */
 56 static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
 57 {
 58         unsigned long long now;
 59 
 60         if (!bfqg_stats_waiting(stats))
 61                 return;
 62 
 63         now = sched_clock();
 64         if (time_after64(now, stats->start_group_wait_time))
 65                 blkg_stat_add(&stats->group_wait_time,
 66                               now - stats->start_group_wait_time);
 67         bfqg_stats_clear_waiting(stats);
 68 }
 69 
 70 /* This should be called with the scheduler lock held. */
 71 static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
 72                                                  struct bfq_group *curr_bfqg)
 73 {
 74         struct bfqg_stats *stats = &bfqg->stats;
 75 
 76         if (bfqg_stats_waiting(stats))
 77                 return;
 78         if (bfqg == curr_bfqg)
 79                 return;
 80         stats->start_group_wait_time = sched_clock();
 81         bfqg_stats_mark_waiting(stats);
 82 }
 83 
 84 /* This should be called with the scheduler lock held. */
 85 static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
 86 {
 87         unsigned long long now;
 88 
 89         if (!bfqg_stats_empty(stats))
 90                 return;
 91 
 92         now = sched_clock();
 93         if (time_after64(now, stats->start_empty_time))
 94                 blkg_stat_add(&stats->empty_time,
 95                               now - stats->start_empty_time);
 96         bfqg_stats_clear_empty(stats);
 97 }
 98 
 99 void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
100 {
101         blkg_stat_add(&bfqg->stats.dequeue, 1);
102 }
103 
104 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg)
105 {
106         struct bfqg_stats *stats = &bfqg->stats;
107 
108         if (blkg_rwstat_total(&stats->queued))
109                 return;
110 
111         /*
112          * group is already marked empty. This can happen if bfqq got new
113          * request in parent group and moved to this group while being added
114          * to service tree. Just ignore the event and move on.
115          */
116         if (bfqg_stats_empty(stats))
117                 return;
118 
119         stats->start_empty_time = sched_clock();
120         bfqg_stats_mark_empty(stats);
121 }
122 
123 void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
124 {
125         struct bfqg_stats *stats = &bfqg->stats;
126 
127         if (bfqg_stats_idling(stats)) {
128                 unsigned long long now = sched_clock();
129 
130                 if (time_after64(now, stats->start_idle_time))
131                         blkg_stat_add(&stats->idle_time,
132                                       now - stats->start_idle_time);
133                 bfqg_stats_clear_idling(stats);
134         }
135 }
136 
137 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
138 {
139         struct bfqg_stats *stats = &bfqg->stats;
140 
141         stats->start_idle_time = sched_clock();
142         bfqg_stats_mark_idling(stats);
143 }
144 
145 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
146 {
147         struct bfqg_stats *stats = &bfqg->stats;
148 
149         blkg_stat_add(&stats->avg_queue_size_sum,
150                       blkg_rwstat_total(&stats->queued));
151         blkg_stat_add(&stats->avg_queue_size_samples, 1);
152         bfqg_stats_update_group_wait_time(stats);
153 }
154 
155 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
156                               unsigned int op)
157 {
158         blkg_rwstat_add(&bfqg->stats.queued, op, 1);
159         bfqg_stats_end_empty_time(&bfqg->stats);
160         if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
161                 bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
162 }
163 
164 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
165 {
166         blkg_rwstat_add(&bfqg->stats.queued, op, -1);
167 }
168 
169 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
170 {
171         blkg_rwstat_add(&bfqg->stats.merged, op, 1);
172 }
173 
174 void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time,
175                                   uint64_t io_start_time, unsigned int op)
176 {
177         struct bfqg_stats *stats = &bfqg->stats;
178         unsigned long long now = sched_clock();
179 
180         if (time_after64(now, io_start_time))
181                 blkg_rwstat_add(&stats->service_time, op,
182                                 now - io_start_time);
183         if (time_after64(io_start_time, start_time))
184                 blkg_rwstat_add(&stats->wait_time, op,
185                                 io_start_time - start_time);
186 }
187 
188 #else /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
189 
190 void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
191                               unsigned int op) { }
192 void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
193 void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
194 void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time,
195                                   uint64_t io_start_time, unsigned int op) { }
196 void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
197 void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
198 void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
199 void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
200 void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
201 
202 #endif /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
203 
204 #ifdef CONFIG_BFQ_GROUP_IOSCHED
205 
206 /*
207  * blk-cgroup policy-related handlers
208  * The following functions help in converting between blk-cgroup
209  * internal structures and BFQ-specific structures.
210  */
211 
212 static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd)
213 {
214         return pd ? container_of(pd, struct bfq_group, pd) : NULL;
215 }
216 
217 struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg)
218 {
219         return pd_to_blkg(&bfqg->pd);
220 }
221 
222 static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg)
223 {
224         return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq));
225 }
226 
227 /*
228  * bfq_group handlers
229  * The following functions help in navigating the bfq_group hierarchy
230  * by allowing to find the parent of a bfq_group or the bfq_group
231  * associated to a bfq_queue.
232  */
233 
234 static struct bfq_group *bfqg_parent(struct bfq_group *bfqg)
235 {
236         struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent;
237 
238         return pblkg ? blkg_to_bfqg(pblkg) : NULL;
239 }
240 
241 struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
242 {
243         struct bfq_entity *group_entity = bfqq->entity.parent;
244 
245         return group_entity ? container_of(group_entity, struct bfq_group,
246                                            entity) :
247                               bfqq->bfqd->root_group;
248 }
249 
250 /*
251  * The following two functions handle get and put of a bfq_group by
252  * wrapping the related blk-cgroup hooks.
253  */
254 
255 static void bfqg_get(struct bfq_group *bfqg)
256 {
257         bfqg->ref++;
258 }
259 
260 static void bfqg_put(struct bfq_group *bfqg)
261 {
262         bfqg->ref--;
263 
264         if (bfqg->ref == 0)
265                 kfree(bfqg);
266 }
267 
268 static void bfqg_and_blkg_get(struct bfq_group *bfqg)
269 {
270         /* see comments in bfq_bic_update_cgroup for why refcounting bfqg */
271         bfqg_get(bfqg);
272 
273         blkg_get(bfqg_to_blkg(bfqg));
274 }
275 
276 void bfqg_and_blkg_put(struct bfq_group *bfqg)
277 {
278         bfqg_put(bfqg);
279 
280         blkg_put(bfqg_to_blkg(bfqg));
281 }
282 
283 /* @stats = 0 */
284 static void bfqg_stats_reset(struct bfqg_stats *stats)
285 {
286 #ifdef CONFIG_DEBUG_BLK_CGROUP
287         /* queued stats shouldn't be cleared */
288         blkg_rwstat_reset(&stats->merged);
289         blkg_rwstat_reset(&stats->service_time);
290         blkg_rwstat_reset(&stats->wait_time);
291         blkg_stat_reset(&stats->time);
292         blkg_stat_reset(&stats->avg_queue_size_sum);
293         blkg_stat_reset(&stats->avg_queue_size_samples);
294         blkg_stat_reset(&stats->dequeue);
295         blkg_stat_reset(&stats->group_wait_time);
296         blkg_stat_reset(&stats->idle_time);
297         blkg_stat_reset(&stats->empty_time);
298 #endif
299 }
300 
301 /* @to += @from */
302 static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
303 {
304         if (!to || !from)
305                 return;
306 
307 #ifdef CONFIG_DEBUG_BLK_CGROUP
308         /* queued stats shouldn't be cleared */
309         blkg_rwstat_add_aux(&to->merged, &from->merged);
310         blkg_rwstat_add_aux(&to->service_time, &from->service_time);
311         blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
312         blkg_stat_add_aux(&from->time, &from->time);
313         blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
314         blkg_stat_add_aux(&to->avg_queue_size_samples,
315                           &from->avg_queue_size_samples);
316         blkg_stat_add_aux(&to->dequeue, &from->dequeue);
317         blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
318         blkg_stat_add_aux(&to->idle_time, &from->idle_time);
319         blkg_stat_add_aux(&to->empty_time, &from->empty_time);
320 #endif
321 }
322 
323 /*
324  * Transfer @bfqg's stats to its parent's aux counts so that the ancestors'
325  * recursive stats can still account for the amount used by this bfqg after
326  * it's gone.
327  */
328 static void bfqg_stats_xfer_dead(struct bfq_group *bfqg)
329 {
330         struct bfq_group *parent;
331 
332         if (!bfqg) /* root_group */
333                 return;
334 
335         parent = bfqg_parent(bfqg);
336 
337         lockdep_assert_held(bfqg_to_blkg(bfqg)->q->queue_lock);
338 
339         if (unlikely(!parent))
340                 return;
341 
342         bfqg_stats_add_aux(&parent->stats, &bfqg->stats);
343         bfqg_stats_reset(&bfqg->stats);
344 }
345 
346 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
347 {
348         struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
349 
350         entity->weight = entity->new_weight;
351         entity->orig_weight = entity->new_weight;
352         if (bfqq) {
353                 bfqq->ioprio = bfqq->new_ioprio;
354                 bfqq->ioprio_class = bfqq->new_ioprio_class;
355                 /*
356                  * Make sure that bfqg and its associated blkg do not
357                  * disappear before entity.
358                  */
359                 bfqg_and_blkg_get(bfqg);
360         }
361         entity->parent = bfqg->my_entity; /* NULL for root group */
362         entity->sched_data = &bfqg->sched_data;
363 }
364 
365 static void bfqg_stats_exit(struct bfqg_stats *stats)
366 {
367 #ifdef CONFIG_DEBUG_BLK_CGROUP
368         blkg_rwstat_exit(&stats->merged);
369         blkg_rwstat_exit(&stats->service_time);
370         blkg_rwstat_exit(&stats->wait_time);
371         blkg_rwstat_exit(&stats->queued);
372         blkg_stat_exit(&stats->time);
373         blkg_stat_exit(&stats->avg_queue_size_sum);
374         blkg_stat_exit(&stats->avg_queue_size_samples);
375         blkg_stat_exit(&stats->dequeue);
376         blkg_stat_exit(&stats->group_wait_time);
377         blkg_stat_exit(&stats->idle_time);
378         blkg_stat_exit(&stats->empty_time);
379 #endif
380 }
381 
382 static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
383 {
384 #ifdef CONFIG_DEBUG_BLK_CGROUP
385         if (blkg_rwstat_init(&stats->merged, gfp) ||
386             blkg_rwstat_init(&stats->service_time, gfp) ||
387             blkg_rwstat_init(&stats->wait_time, gfp) ||
388             blkg_rwstat_init(&stats->queued, gfp) ||
389             blkg_stat_init(&stats->time, gfp) ||
390             blkg_stat_init(&stats->avg_queue_size_sum, gfp) ||
391             blkg_stat_init(&stats->avg_queue_size_samples, gfp) ||
392             blkg_stat_init(&stats->dequeue, gfp) ||
393             blkg_stat_init(&stats->group_wait_time, gfp) ||
394             blkg_stat_init(&stats->idle_time, gfp) ||
395             blkg_stat_init(&stats->empty_time, gfp)) {
396                 bfqg_stats_exit(stats);
397                 return -ENOMEM;
398         }
399 #endif
400 
401         return 0;
402 }
403 
404 static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)
405 {
406         return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL;
407 }
408 
409 static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg)
410 {
411         return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq));
412 }
413 
414 static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
415 {
416         struct bfq_group_data *bgd;
417 
418         bgd = kzalloc(sizeof(*bgd), gfp);
419         if (!bgd)
420                 return NULL;
421         return &bgd->pd;
422 }
423 
424 static void bfq_cpd_init(struct blkcg_policy_data *cpd)
425 {
426         struct bfq_group_data *d = cpd_to_bfqgd(cpd);
427 
428         d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
429                 CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL;
430 }
431 
432 static void bfq_cpd_free(struct blkcg_policy_data *cpd)
433 {
434         kfree(cpd_to_bfqgd(cpd));
435 }
436 
437 static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, int node)
438 {
439         struct bfq_group *bfqg;
440 
441         bfqg = kzalloc_node(sizeof(*bfqg), gfp, node);
442         if (!bfqg)
443                 return NULL;
444 
445         if (bfqg_stats_init(&bfqg->stats, gfp)) {
446                 kfree(bfqg);
447                 return NULL;
448         }
449 
450         /* see comments in bfq_bic_update_cgroup for why refcounting */
451         bfqg_get(bfqg);
452         return &bfqg->pd;
453 }
454 
455 static void bfq_pd_init(struct blkg_policy_data *pd)
456 {
457         struct blkcg_gq *blkg = pd_to_blkg(pd);
458         struct bfq_group *bfqg = blkg_to_bfqg(blkg);
459         struct bfq_data *bfqd = blkg->q->elevator->elevator_data;
460         struct bfq_entity *entity = &bfqg->entity;
461         struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg);
462 
463         entity->orig_weight = entity->weight = entity->new_weight = d->weight;
464         entity->my_sched_data = &bfqg->sched_data;
465         bfqg->my_entity = entity; /*
466                                    * the root_group's will be set to NULL
467                                    * in bfq_init_queue()
468                                    */
469         bfqg->bfqd = bfqd;
470         bfqg->active_entities = 0;
471         bfqg->rq_pos_tree = RB_ROOT;
472 }
473 
474 static void bfq_pd_free(struct blkg_policy_data *pd)
475 {
476         struct bfq_group *bfqg = pd_to_bfqg(pd);
477 
478         bfqg_stats_exit(&bfqg->stats);
479         bfqg_put(bfqg);
480 }
481 
482 static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
483 {
484         struct bfq_group *bfqg = pd_to_bfqg(pd);
485 
486         bfqg_stats_reset(&bfqg->stats);
487 }
488 
489 static void bfq_group_set_parent(struct bfq_group *bfqg,
490                                         struct bfq_group *parent)
491 {
492         struct bfq_entity *entity;
493 
494         entity = &bfqg->entity;
495         entity->parent = parent->my_entity;
496         entity->sched_data = &parent->sched_data;
497 }
498 
499 static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd,
500                                          struct blkcg *blkcg)
501 {
502         struct blkcg_gq *blkg;
503 
504         blkg = blkg_lookup(blkcg, bfqd->queue);
505         if (likely(blkg))
506                 return blkg_to_bfqg(blkg);
507         return NULL;
508 }
509 
510 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
511                                      struct blkcg *blkcg)
512 {
513         struct bfq_group *bfqg, *parent;
514         struct bfq_entity *entity;
515 
516         bfqg = bfq_lookup_bfqg(bfqd, blkcg);
517 
518         if (unlikely(!bfqg))
519                 return NULL;
520 
521         /*
522          * Update chain of bfq_groups as we might be handling a leaf group
523          * which, along with some of its relatives, has not been hooked yet
524          * to the private hierarchy of BFQ.
525          */
526         entity = &bfqg->entity;
527         for_each_entity(entity) {
528                 bfqg = container_of(entity, struct bfq_group, entity);
529                 if (bfqg != bfqd->root_group) {
530                         parent = bfqg_parent(bfqg);
531                         if (!parent)
532                                 parent = bfqd->root_group;
533                         bfq_group_set_parent(bfqg, parent);
534                 }
535         }
536 
537         return bfqg;
538 }
539 
540 /**
541  * bfq_bfqq_move - migrate @bfqq to @bfqg.
542  * @bfqd: queue descriptor.
543  * @bfqq: the queue to move.
544  * @bfqg: the group to move to.
545  *
546  * Move @bfqq to @bfqg, deactivating it from its old group and reactivating
547  * it on the new one.  Avoid putting the entity on the old group idle tree.
548  *
549  * Must be called under the scheduler lock, to make sure that the blkg
550  * owning @bfqg does not disappear (see comments in
551  * bfq_bic_update_cgroup on guaranteeing the consistency of blkg
552  * objects).
553  */
554 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
555                    struct bfq_group *bfqg)
556 {
557         struct bfq_entity *entity = &bfqq->entity;
558 
559         /* If bfqq is empty, then bfq_bfqq_expire also invokes
560          * bfq_del_bfqq_busy, thereby removing bfqq and its entity
561          * from data structures related to current group. Otherwise we
562          * need to remove bfqq explicitly with bfq_deactivate_bfqq, as
563          * we do below.
564          */
565         if (bfqq == bfqd->in_service_queue)
566                 bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
567                                 false, BFQQE_PREEMPTED);
568 
569         if (bfq_bfqq_busy(bfqq))
570                 bfq_deactivate_bfqq(bfqd, bfqq, false, false);
571         else if (entity->on_st)
572                 bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
573         bfqg_and_blkg_put(bfqq_group(bfqq));
574 
575         entity->parent = bfqg->my_entity;
576         entity->sched_data = &bfqg->sched_data;
577         /* pin down bfqg and its associated blkg  */
578         bfqg_and_blkg_get(bfqg);
579 
580         if (bfq_bfqq_busy(bfqq)) {
581                 bfq_pos_tree_add_move(bfqd, bfqq);
582                 bfq_activate_bfqq(bfqd, bfqq);
583         }
584 
585         if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
586                 bfq_schedule_dispatch(bfqd);
587 }
588 
589 /**
590  * __bfq_bic_change_cgroup - move @bic to @cgroup.
591  * @bfqd: the queue descriptor.
592  * @bic: the bic to move.
593  * @blkcg: the blk-cgroup to move to.
594  *
595  * Move bic to blkcg, assuming that bfqd->lock is held; which makes
596  * sure that the reference to cgroup is valid across the call (see
597  * comments in bfq_bic_update_cgroup on this issue)
598  *
599  * NOTE: an alternative approach might have been to store the current
600  * cgroup in bfqq and getting a reference to it, reducing the lookup
601  * time here, at the price of slightly more complex code.
602  */
603 static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
604                                                 struct bfq_io_cq *bic,
605                                                 struct blkcg *blkcg)
606 {
607         struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
608         struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
609         struct bfq_group *bfqg;
610         struct bfq_entity *entity;
611 
612         bfqg = bfq_find_set_group(bfqd, blkcg);
613 
614         if (unlikely(!bfqg))
615                 bfqg = bfqd->root_group;
616 
617         if (async_bfqq) {
618                 entity = &async_bfqq->entity;
619 
620                 if (entity->sched_data != &bfqg->sched_data) {
621                         bic_set_bfqq(bic, NULL, 0);
622                         bfq_log_bfqq(bfqd, async_bfqq,
623                                      "bic_change_group: %p %d",
624                                      async_bfqq, async_bfqq->ref);
625                         bfq_put_queue(async_bfqq);
626                 }
627         }
628 
629         if (sync_bfqq) {
630                 entity = &sync_bfqq->entity;
631                 if (entity->sched_data != &bfqg->sched_data)
632                         bfq_bfqq_move(bfqd, sync_bfqq, bfqg);
633         }
634 
635         return bfqg;
636 }
637 
638 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
639 {
640         struct bfq_data *bfqd = bic_to_bfqd(bic);
641         struct bfq_group *bfqg = NULL;
642         uint64_t serial_nr;
643 
644         rcu_read_lock();
645         serial_nr = bio_blkcg(bio)->css.serial_nr;
646 
647         /*
648          * Check whether blkcg has changed.  The condition may trigger
649          * spuriously on a newly created cic but there's no harm.
650          */
651         if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr))
652                 goto out;
653 
654         bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio));
655         /*
656          * Update blkg_path for bfq_log_* functions. We cache this
657          * path, and update it here, for the following
658          * reasons. Operations on blkg objects in blk-cgroup are
659          * protected with the request_queue lock, and not with the
660          * lock that protects the instances of this scheduler
661          * (bfqd->lock). This exposes BFQ to the following sort of
662          * race.
663          *
664          * The blkg_lookup performed in bfq_get_queue, protected
665          * through rcu, may happen to return the address of a copy of
666          * the original blkg. If this is the case, then the
667          * bfqg_and_blkg_get performed in bfq_get_queue, to pin down
668          * the blkg, is useless: it does not prevent blk-cgroup code
669          * from destroying both the original blkg and all objects
670          * directly or indirectly referred by the copy of the
671          * blkg.
672          *
673          * On the bright side, destroy operations on a blkg invoke, as
674          * a first step, hooks of the scheduler associated with the
675          * blkg. And these hooks are executed with bfqd->lock held for
676          * BFQ. As a consequence, for any blkg associated with the
677          * request queue this instance of the scheduler is attached
678          * to, we are guaranteed that such a blkg is not destroyed, and
679          * that all the pointers it contains are consistent, while we
680          * are holding bfqd->lock. A blkg_lookup performed with
681          * bfqd->lock held then returns a fully consistent blkg, which
682          * remains consistent until this lock is held.
683          *
684          * Thanks to the last fact, and to the fact that: (1) bfqg has
685          * been obtained through a blkg_lookup in the above
686          * assignment, and (2) bfqd->lock is being held, here we can
687          * safely use the policy data for the involved blkg (i.e., the
688          * field bfqg->pd) to get to the blkg associated with bfqg,
689          * and then we can safely use any field of blkg. After we
690          * release bfqd->lock, even just getting blkg through this
691          * bfqg may cause dangling references to be traversed, as
692          * bfqg->pd may not exist any more.
693          *
694          * In view of the above facts, here we cache, in the bfqg, any
695          * blkg data we may need for this bic, and for its associated
696          * bfq_queue. As of now, we need to cache only the path of the
697          * blkg, which is used in the bfq_log_* functions.
698          *
699          * Finally, note that bfqg itself needs to be protected from
700          * destruction on the blkg_free of the original blkg (which
701          * invokes bfq_pd_free). We use an additional private
702          * refcounter for bfqg, to let it disappear only after no
703          * bfq_queue refers to it any longer.
704          */
705         blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
706         bic->blkcg_serial_nr = serial_nr;
707 out:
708         rcu_read_unlock();
709 }
710 
711 /**
712  * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
713  * @st: the service tree being flushed.
714  */
715 static void bfq_flush_idle_tree(struct bfq_service_tree *st)
716 {
717         struct bfq_entity *entity = st->first_idle;
718 
719         for (; entity ; entity = st->first_idle)
720                 __bfq_deactivate_entity(entity, false);
721 }
722 
723 /**
724  * bfq_reparent_leaf_entity - move leaf entity to the root_group.
725  * @bfqd: the device data structure with the root group.
726  * @entity: the entity to move.
727  */
728 static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
729                                      struct bfq_entity *entity)
730 {
731         struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
732 
733         bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
734 }
735 
736 /**
737  * bfq_reparent_active_entities - move to the root group all active
738  *                                entities.
739  * @bfqd: the device data structure with the root group.
740  * @bfqg: the group to move from.
741  * @st: the service tree with the entities.
742  */
743 static void bfq_reparent_active_entities(struct bfq_data *bfqd,
744                                          struct bfq_group *bfqg,
745                                          struct bfq_service_tree *st)
746 {
747         struct rb_root *active = &st->active;
748         struct bfq_entity *entity = NULL;
749 
750         if (!RB_EMPTY_ROOT(&st->active))
751                 entity = bfq_entity_of(rb_first(active));
752 
753         for (; entity ; entity = bfq_entity_of(rb_first(active)))
754                 bfq_reparent_leaf_entity(bfqd, entity);
755 
756         if (bfqg->sched_data.in_service_entity)
757                 bfq_reparent_leaf_entity(bfqd,
758                         bfqg->sched_data.in_service_entity);
759 }
760 
761 /**
762  * bfq_pd_offline - deactivate the entity associated with @pd,
763  *                  and reparent its children entities.
764  * @pd: descriptor of the policy going offline.
765  *
766  * blkio already grabs the queue_lock for us, so no need to use
767  * RCU-based magic
768  */
769 static void bfq_pd_offline(struct blkg_policy_data *pd)
770 {
771         struct bfq_service_tree *st;
772         struct bfq_group *bfqg = pd_to_bfqg(pd);
773         struct bfq_data *bfqd = bfqg->bfqd;
774         struct bfq_entity *entity = bfqg->my_entity;
775         unsigned long flags;
776         int i;
777 
778         spin_lock_irqsave(&bfqd->lock, flags);
779 
780         if (!entity) /* root group */
781                 goto put_async_queues;
782 
783         /*
784          * Empty all service_trees belonging to this group before
785          * deactivating the group itself.
786          */
787         for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
788                 st = bfqg->sched_data.service_tree + i;
789 
790                 /*
791                  * The idle tree may still contain bfq_queues belonging
792                  * to exited task because they never migrated to a different
793                  * cgroup from the one being destroyed now.
794                  */
795                 bfq_flush_idle_tree(st);
796 
797                 /*
798                  * It may happen that some queues are still active
799                  * (busy) upon group destruction (if the corresponding
800                  * processes have been forced to terminate). We move
801                  * all the leaf entities corresponding to these queues
802                  * to the root_group.
803                  * Also, it may happen that the group has an entity
804                  * in service, which is disconnected from the active
805                  * tree: it must be moved, too.
806                  * There is no need to put the sync queues, as the
807                  * scheduler has taken no reference.
808                  */
809                 bfq_reparent_active_entities(bfqd, bfqg, st);
810         }
811 
812         __bfq_deactivate_entity(entity, false);
813 
814 put_async_queues:
815         bfq_put_async_queues(bfqd, bfqg);
816 
817         spin_unlock_irqrestore(&bfqd->lock, flags);
818         /*
819          * @blkg is going offline and will be ignored by
820          * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
821          * that they don't get lost.  If IOs complete after this point, the
822          * stats for them will be lost.  Oh well...
823          */
824         bfqg_stats_xfer_dead(bfqg);
825 }
826 
827 void bfq_end_wr_async(struct bfq_data *bfqd)
828 {
829         struct blkcg_gq *blkg;
830 
831         list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) {
832                 struct bfq_group *bfqg = blkg_to_bfqg(blkg);
833 
834                 bfq_end_wr_async_queues(bfqd, bfqg);
835         }
836         bfq_end_wr_async_queues(bfqd, bfqd->root_group);
837 }
838 
839 static int bfq_io_show_weight(struct seq_file *sf, void *v)
840 {
841         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
842         struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
843         unsigned int val = 0;
844 
845         if (bfqgd)
846                 val = bfqgd->weight;
847 
848         seq_printf(sf, "%u\n", val);
849 
850         return 0;
851 }
852 
853 static int bfq_io_set_weight_legacy(struct cgroup_subsys_state *css,
854                                     struct cftype *cftype,
855                                     u64 val)
856 {
857         struct blkcg *blkcg = css_to_blkcg(css);
858         struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
859         struct blkcg_gq *blkg;
860         int ret = -ERANGE;
861 
862         if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT)
863                 return ret;
864 
865         ret = 0;
866         spin_lock_irq(&blkcg->lock);
867         bfqgd->weight = (unsigned short)val;
868         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
869                 struct bfq_group *bfqg = blkg_to_bfqg(blkg);
870 
871                 if (!bfqg)
872                         continue;
873                 /*
874                  * Setting the prio_changed flag of the entity
875                  * to 1 with new_weight == weight would re-set
876                  * the value of the weight to its ioprio mapping.
877                  * Set the flag only if necessary.
878                  */
879                 if ((unsigned short)val != bfqg->entity.new_weight) {
880                         bfqg->entity.new_weight = (unsigned short)val;
881                         /*
882                          * Make sure that the above new value has been
883                          * stored in bfqg->entity.new_weight before
884                          * setting the prio_changed flag. In fact,
885                          * this flag may be read asynchronously (in
886                          * critical sections protected by a different
887                          * lock than that held here), and finding this
888                          * flag set may cause the execution of the code
889                          * for updating parameters whose value may
890                          * depend also on bfqg->entity.new_weight (in
891                          * __bfq_entity_update_weight_prio).
892                          * This barrier makes sure that the new value
893                          * of bfqg->entity.new_weight is correctly
894                          * seen in that code.
895                          */
896                         smp_wmb();
897                         bfqg->entity.prio_changed = 1;
898                 }
899         }
900         spin_unlock_irq(&blkcg->lock);
901 
902         return ret;
903 }
904 
905 static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
906                                  char *buf, size_t nbytes,
907                                  loff_t off)
908 {
909         u64 weight;
910         /* First unsigned long found in the file is used */
911         int ret = kstrtoull(strim(buf), 0, &weight);
912 
913         if (ret)
914                 return ret;
915 
916         return bfq_io_set_weight_legacy(of_css(of), NULL, weight);
917 }
918 
919 #ifdef CONFIG_DEBUG_BLK_CGROUP
920 static int bfqg_print_stat(struct seq_file *sf, void *v)
921 {
922         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
923                           &blkcg_policy_bfq, seq_cft(sf)->private, false);
924         return 0;
925 }
926 
927 static int bfqg_print_rwstat(struct seq_file *sf, void *v)
928 {
929         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
930                           &blkcg_policy_bfq, seq_cft(sf)->private, true);
931         return 0;
932 }
933 
934 static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
935                                       struct blkg_policy_data *pd, int off)
936 {
937         u64 sum = blkg_stat_recursive_sum(pd_to_blkg(pd),
938                                           &blkcg_policy_bfq, off);
939         return __blkg_prfill_u64(sf, pd, sum);
940 }
941 
942 static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
943                                         struct blkg_policy_data *pd, int off)
944 {
945         struct blkg_rwstat sum = blkg_rwstat_recursive_sum(pd_to_blkg(pd),
946                                                            &blkcg_policy_bfq,
947                                                            off);
948         return __blkg_prfill_rwstat(sf, pd, &sum);
949 }
950 
951 static int bfqg_print_stat_recursive(struct seq_file *sf, void *v)
952 {
953         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
954                           bfqg_prfill_stat_recursive, &blkcg_policy_bfq,
955                           seq_cft(sf)->private, false);
956         return 0;
957 }
958 
959 static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
960 {
961         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
962                           bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq,
963                           seq_cft(sf)->private, true);
964         return 0;
965 }
966 
967 static u64 bfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
968                                int off)
969 {
970         u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes);
971 
972         return __blkg_prfill_u64(sf, pd, sum >> 9);
973 }
974 
975 static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
976 {
977         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
978                           bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false);
979         return 0;
980 }
981 
982 static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
983                                          struct blkg_policy_data *pd, int off)
984 {
985         struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
986                                         offsetof(struct blkcg_gq, stat_bytes));
987         u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
988                 atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
989 
990         return __blkg_prfill_u64(sf, pd, sum >> 9);
991 }
992 
993 static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
994 {
995         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
996                           bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0,
997                           false);
998         return 0;
999 }
1000 
1001 static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf,
1002                                       struct blkg_policy_data *pd, int off)
1003 {
1004         struct bfq_group *bfqg = pd_to_bfqg(pd);
1005         u64 samples = blkg_stat_read(&bfqg->stats.avg_queue_size_samples);
1006         u64 v = 0;
1007 
1008         if (samples) {
1009                 v = blkg_stat_read(&bfqg->stats.avg_queue_size_sum);
1010                 v = div64_u64(v, samples);
1011         }
1012         __blkg_prfill_u64(sf, pd, v);
1013         return 0;
1014 }
1015 
1016 /* print avg_queue_size */
1017 static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
1018 {
1019         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1020                           bfqg_prfill_avg_queue_size, &blkcg_policy_bfq,
1021                           0, false);
1022         return 0;
1023 }
1024 #endif /* CONFIG_DEBUG_BLK_CGROUP */
1025 
1026 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
1027 {
1028         int ret;
1029 
1030         ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq);
1031         if (ret)
1032                 return NULL;
1033 
1034         return blkg_to_bfqg(bfqd->queue->root_blkg);
1035 }
1036 
1037 struct blkcg_policy blkcg_policy_bfq = {
1038         .dfl_cftypes            = bfq_blkg_files,
1039         .legacy_cftypes         = bfq_blkcg_legacy_files,
1040 
1041         .cpd_alloc_fn           = bfq_cpd_alloc,
1042         .cpd_init_fn            = bfq_cpd_init,
1043         .cpd_bind_fn            = bfq_cpd_init,
1044         .cpd_free_fn            = bfq_cpd_free,
1045 
1046         .pd_alloc_fn            = bfq_pd_alloc,
1047         .pd_init_fn             = bfq_pd_init,
1048         .pd_offline_fn          = bfq_pd_offline,
1049         .pd_free_fn             = bfq_pd_free,
1050         .pd_reset_stats_fn      = bfq_pd_reset_stats,
1051 };
1052 
1053 struct cftype bfq_blkcg_legacy_files[] = {
1054         {
1055                 .name = "bfq.weight",
1056                 .flags = CFTYPE_NOT_ON_ROOT,
1057                 .seq_show = bfq_io_show_weight,
1058                 .write_u64 = bfq_io_set_weight_legacy,
1059         },
1060 
1061         /* statistics, covers only the tasks in the bfqg */
1062         {
1063                 .name = "bfq.io_service_bytes",
1064                 .private = (unsigned long)&blkcg_policy_bfq,
1065                 .seq_show = blkg_print_stat_bytes,
1066         },
1067         {
1068                 .name = "bfq.io_serviced",
1069                 .private = (unsigned long)&blkcg_policy_bfq,
1070                 .seq_show = blkg_print_stat_ios,
1071         },
1072 #ifdef CONFIG_DEBUG_BLK_CGROUP
1073         {
1074                 .name = "bfq.time",
1075                 .private = offsetof(struct bfq_group, stats.time),
1076                 .seq_show = bfqg_print_stat,
1077         },
1078         {
1079                 .name = "bfq.sectors",
1080                 .seq_show = bfqg_print_stat_sectors,
1081         },
1082         {
1083                 .name = "bfq.io_service_time",
1084                 .private = offsetof(struct bfq_group, stats.service_time),
1085                 .seq_show = bfqg_print_rwstat,
1086         },
1087         {
1088                 .name = "bfq.io_wait_time",
1089                 .private = offsetof(struct bfq_group, stats.wait_time),
1090                 .seq_show = bfqg_print_rwstat,
1091         },
1092         {
1093                 .name = "bfq.io_merged",
1094                 .private = offsetof(struct bfq_group, stats.merged),
1095                 .seq_show = bfqg_print_rwstat,
1096         },
1097         {
1098                 .name = "bfq.io_queued",
1099                 .private = offsetof(struct bfq_group, stats.queued),
1100                 .seq_show = bfqg_print_rwstat,
1101         },
1102 #endif /* CONFIG_DEBUG_BLK_CGROUP */
1103 
1104         /* the same statictics which cover the bfqg and its descendants */
1105         {
1106                 .name = "bfq.io_service_bytes_recursive",
1107                 .private = (unsigned long)&blkcg_policy_bfq,
1108                 .seq_show = blkg_print_stat_bytes_recursive,
1109         },
1110         {
1111                 .name = "bfq.io_serviced_recursive",
1112                 .private = (unsigned long)&blkcg_policy_bfq,
1113                 .seq_show = blkg_print_stat_ios_recursive,
1114         },
1115 #ifdef CONFIG_DEBUG_BLK_CGROUP
1116         {
1117                 .name = "bfq.time_recursive",
1118                 .private = offsetof(struct bfq_group, stats.time),
1119                 .seq_show = bfqg_print_stat_recursive,
1120         },
1121         {
1122                 .name = "bfq.sectors_recursive",
1123                 .seq_show = bfqg_print_stat_sectors_recursive,
1124         },
1125         {
1126                 .name = "bfq.io_service_time_recursive",
1127                 .private = offsetof(struct bfq_group, stats.service_time),
1128                 .seq_show = bfqg_print_rwstat_recursive,
1129         },
1130         {
1131                 .name = "bfq.io_wait_time_recursive",
1132                 .private = offsetof(struct bfq_group, stats.wait_time),
1133                 .seq_show = bfqg_print_rwstat_recursive,
1134         },
1135         {
1136                 .name = "bfq.io_merged_recursive",
1137                 .private = offsetof(struct bfq_group, stats.merged),
1138                 .seq_show = bfqg_print_rwstat_recursive,
1139         },
1140         {
1141                 .name = "bfq.io_queued_recursive",
1142                 .private = offsetof(struct bfq_group, stats.queued),
1143                 .seq_show = bfqg_print_rwstat_recursive,
1144         },
1145         {
1146                 .name = "bfq.avg_queue_size",
1147                 .seq_show = bfqg_print_avg_queue_size,
1148         },
1149         {
1150                 .name = "bfq.group_wait_time",
1151                 .private = offsetof(struct bfq_group, stats.group_wait_time),
1152                 .seq_show = bfqg_print_stat,
1153         },
1154         {
1155                 .name = "bfq.idle_time",
1156                 .private = offsetof(struct bfq_group, stats.idle_time),
1157                 .seq_show = bfqg_print_stat,
1158         },
1159         {
1160                 .name = "bfq.empty_time",
1161                 .private = offsetof(struct bfq_group, stats.empty_time),
1162                 .seq_show = bfqg_print_stat,
1163         },
1164         {
1165                 .name = "bfq.dequeue",
1166                 .private = offsetof(struct bfq_group, stats.dequeue),
1167                 .seq_show = bfqg_print_stat,
1168         },
1169 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
1170         { }     /* terminate */
1171 };
1172 
1173 struct cftype bfq_blkg_files[] = {
1174         {
1175                 .name = "bfq.weight",
1176                 .flags = CFTYPE_NOT_ON_ROOT,
1177                 .seq_show = bfq_io_show_weight,
1178                 .write = bfq_io_set_weight,
1179         },
1180         {} /* terminate */
1181 };
1182 
1183 #else   /* CONFIG_BFQ_GROUP_IOSCHED */
1184 
1185 void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
1186                    struct bfq_group *bfqg) {}
1187 
1188 void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
1189 {
1190         struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
1191 
1192         entity->weight = entity->new_weight;
1193         entity->orig_weight = entity->new_weight;
1194         if (bfqq) {
1195                 bfqq->ioprio = bfqq->new_ioprio;
1196                 bfqq->ioprio_class = bfqq->new_ioprio_class;
1197         }
1198         entity->sched_data = &bfqg->sched_data;
1199 }
1200 
1201 void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {}
1202 
1203 void bfq_end_wr_async(struct bfq_data *bfqd)
1204 {
1205         bfq_end_wr_async_queues(bfqd, bfqd->root_group);
1206 }
1207 
1208 struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg)
1209 {
1210         return bfqd->root_group;
1211 }
1212 
1213 struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
1214 {
1215         return bfqq->bfqd->root_group;
1216 }
1217 
1218 struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
1219 {
1220         struct bfq_group *bfqg;
1221         int i;
1222 
1223         bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
1224         if (!bfqg)
1225                 return NULL;
1226 
1227         for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
1228                 bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
1229 
1230         return bfqg;
1231 }
1232 #endif  /* CONFIG_BFQ_GROUP_IOSCHED */
1233 

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