1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Common Block IO controller cgroup interface 4 * 5 * Based on ideas and code from CFQ, CFS and BFQ: 6 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk> 7 * 8 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it> 9 * Paolo Valente <paolo.valente@unimore.it> 10 * 11 * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com> 12 * Nauman Rafique <nauman@google.com> 13 * 14 * For policy-specific per-blkcg data: 15 * Copyright (C) 2015 Paolo Valente <paolo.valente@unimore.it> 16 * Arianna Avanzini <avanzini.arianna@gmail.com> 17 */ 18#include <linux/ioprio.h> 19#include <linux/kdev_t.h> 20#include <linux/module.h> 21#include <linux/sched/signal.h> 22#include <linux/err.h> 23#include <linux/blkdev.h> 24#include <linux/backing-dev.h> 25#include <linux/slab.h> 26#include <linux/delay.h> 27#include <linux/atomic.h> 28#include <linux/ctype.h> 29#include <linux/resume_user_mode.h> 30#include <linux/psi.h> 31#include <linux/part_stat.h> 32#include "blk.h" 33#include "blk-cgroup.h" 34#include "blk-ioprio.h" 35#include "blk-throttle.h" 36 37static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu); 38 39/* 40 * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation. 41 * blkcg_pol_register_mutex nests outside of it and synchronizes entire 42 * policy [un]register operations including cgroup file additions / 43 * removals. Putting cgroup file registration outside blkcg_pol_mutex 44 * allows grabbing it from cgroup callbacks. 45 */ 46static DEFINE_MUTEX(blkcg_pol_register_mutex); 47static DEFINE_MUTEX(blkcg_pol_mutex); 48 49struct blkcg blkcg_root; 50EXPORT_SYMBOL_GPL(blkcg_root); 51 52struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css; 53EXPORT_SYMBOL_GPL(blkcg_root_css); 54 55static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS]; 56 57static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */ 58 59bool blkcg_debug_stats = false; 60 61static DEFINE_RAW_SPINLOCK(blkg_stat_lock); 62 63#define BLKG_DESTROY_BATCH_SIZE 64 64 65/* 66 * Lockless lists for tracking IO stats update 67 * 68 * New IO stats are stored in the percpu iostat_cpu within blkcg_gq (blkg). 69 * There are multiple blkg's (one for each block device) attached to each 70 * blkcg. The rstat code keeps track of which cpu has IO stats updated, 71 * but it doesn't know which blkg has the updated stats. If there are many 72 * block devices in a system, the cost of iterating all the blkg's to flush 73 * out the IO stats can be high. To reduce such overhead, a set of percpu 74 * lockless lists (lhead) per blkcg are used to track the set of recently 75 * updated iostat_cpu's since the last flush. An iostat_cpu will be put 76 * onto the lockless list on the update side [blk_cgroup_bio_start()] if 77 * not there yet and then removed when being flushed [blkcg_rstat_flush()]. 78 * References to blkg are gotten and then put back in the process to 79 * protect against blkg removal. 80 * 81 * Return: 0 if successful or -ENOMEM if allocation fails. 82 */ 83static int init_blkcg_llists(struct blkcg *blkcg) 84{ 85 int cpu; 86 87 blkcg->lhead = alloc_percpu_gfp(struct llist_head, GFP_KERNEL); 88 if (!blkcg->lhead) 89 return -ENOMEM; 90 91 for_each_possible_cpu(cpu) 92 init_llist_head(per_cpu_ptr(blkcg->lhead, cpu)); 93 return 0; 94} 95 96/** 97 * blkcg_css - find the current css 98 * 99 * Find the css associated with either the kthread or the current task. 100 * This may return a dying css, so it is up to the caller to use tryget logic 101 * to confirm it is alive and well. 102 */ 103static struct cgroup_subsys_state *blkcg_css(void) 104{ 105 struct cgroup_subsys_state *css; 106 107 css = kthread_blkcg(); 108 if (css) 109 return css; 110 return task_css(current, io_cgrp_id); 111} 112 113static bool blkcg_policy_enabled(struct request_queue *q, 114 const struct blkcg_policy *pol) 115{ 116 return pol && test_bit(pol->plid, q->blkcg_pols); 117} 118 119static void blkg_free_workfn(struct work_struct *work) 120{ 121 struct blkcg_gq *blkg = container_of(work, struct blkcg_gq, 122 free_work); 123 struct request_queue *q = blkg->q; 124 int i; 125 126 /* 127 * pd_free_fn() can also be called from blkcg_deactivate_policy(), 128 * in order to make sure pd_free_fn() is called in order, the deletion 129 * of the list blkg->q_node is delayed to here from blkg_destroy(), and 130 * blkcg_mutex is used to synchronize blkg_free_workfn() and 131 * blkcg_deactivate_policy(). 132 */ 133 mutex_lock(&q->blkcg_mutex); 134 for (i = 0; i < BLKCG_MAX_POLS; i++) 135 if (blkg->pd[i]) 136 blkcg_policy[i]->pd_free_fn(blkg->pd[i]); 137 if (blkg->parent) 138 blkg_put(blkg->parent); 139 spin_lock_irq(&q->queue_lock); 140 list_del_init(&blkg->q_node); 141 spin_unlock_irq(&q->queue_lock); 142 mutex_unlock(&q->blkcg_mutex); 143 144 blk_put_queue(q); 145 free_percpu(blkg->iostat_cpu); 146 percpu_ref_exit(&blkg->refcnt); 147 kfree(blkg); 148} 149 150/** 151 * blkg_free - free a blkg 152 * @blkg: blkg to free 153 * 154 * Free @blkg which may be partially allocated. 155 */ 156static void blkg_free(struct blkcg_gq *blkg) 157{ 158 if (!blkg) 159 return; 160 161 /* 162 * Both ->pd_free_fn() and request queue's release handler may 163 * sleep, so free us by scheduling one work func 164 */ 165 INIT_WORK(&blkg->free_work, blkg_free_workfn); 166 schedule_work(&blkg->free_work); 167} 168 169static void __blkg_release(struct rcu_head *rcu) 170{ 171 struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head); 172 struct blkcg *blkcg = blkg->blkcg; 173 int cpu; 174 175#ifdef CONFIG_BLK_CGROUP_PUNT_BIO 176 WARN_ON(!bio_list_empty(&blkg->async_bios)); 177#endif 178 /* 179 * Flush all the non-empty percpu lockless lists before releasing 180 * us, given these stat belongs to us. 181 * 182 * blkg_stat_lock is for serializing blkg stat update 183 */ 184 for_each_possible_cpu(cpu) 185 __blkcg_rstat_flush(blkcg, cpu); 186 187 /* release the blkcg and parent blkg refs this blkg has been holding */ 188 css_put(&blkg->blkcg->css); 189 blkg_free(blkg); 190} 191 192/* 193 * A group is RCU protected, but having an rcu lock does not mean that one 194 * can access all the fields of blkg and assume these are valid. For 195 * example, don't try to follow throtl_data and request queue links. 196 * 197 * Having a reference to blkg under an rcu allows accesses to only values 198 * local to groups like group stats and group rate limits. 199 */ 200static void blkg_release(struct percpu_ref *ref) 201{ 202 struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt); 203 204 call_rcu(&blkg->rcu_head, __blkg_release); 205} 206 207#ifdef CONFIG_BLK_CGROUP_PUNT_BIO 208static struct workqueue_struct *blkcg_punt_bio_wq; 209 210static void blkg_async_bio_workfn(struct work_struct *work) 211{ 212 struct blkcg_gq *blkg = container_of(work, struct blkcg_gq, 213 async_bio_work); 214 struct bio_list bios = BIO_EMPTY_LIST; 215 struct bio *bio; 216 struct blk_plug plug; 217 bool need_plug = false; 218 219 /* as long as there are pending bios, @blkg can't go away */ 220 spin_lock(&blkg->async_bio_lock); 221 bio_list_merge(&bios, &blkg->async_bios); 222 bio_list_init(&blkg->async_bios); 223 spin_unlock(&blkg->async_bio_lock); 224 225 /* start plug only when bio_list contains at least 2 bios */ 226 if (bios.head && bios.head->bi_next) { 227 need_plug = true; 228 blk_start_plug(&plug); 229 } 230 while ((bio = bio_list_pop(&bios))) 231 submit_bio(bio); 232 if (need_plug) 233 blk_finish_plug(&plug); 234} 235 236/* 237 * When a shared kthread issues a bio for a cgroup, doing so synchronously can 238 * lead to priority inversions as the kthread can be trapped waiting for that 239 * cgroup. Use this helper instead of submit_bio to punt the actual issuing to 240 * a dedicated per-blkcg work item to avoid such priority inversions. 241 */ 242void blkcg_punt_bio_submit(struct bio *bio) 243{ 244 struct blkcg_gq *blkg = bio->bi_blkg; 245 246 if (blkg->parent) { 247 spin_lock(&blkg->async_bio_lock); 248 bio_list_add(&blkg->async_bios, bio); 249 spin_unlock(&blkg->async_bio_lock); 250 queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work); 251 } else { 252 /* never bounce for the root cgroup */ 253 submit_bio(bio); 254 } 255} 256EXPORT_SYMBOL_GPL(blkcg_punt_bio_submit); 257 258static int __init blkcg_punt_bio_init(void) 259{ 260 blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio", 261 WQ_MEM_RECLAIM | WQ_FREEZABLE | 262 WQ_UNBOUND | WQ_SYSFS, 0); 263 if (!blkcg_punt_bio_wq) 264 return -ENOMEM; 265 return 0; 266} 267subsys_initcall(blkcg_punt_bio_init); 268#endif /* CONFIG_BLK_CGROUP_PUNT_BIO */ 269 270/** 271 * bio_blkcg_css - return the blkcg CSS associated with a bio 272 * @bio: target bio 273 * 274 * This returns the CSS for the blkcg associated with a bio, or %NULL if not 275 * associated. Callers are expected to either handle %NULL or know association 276 * has been done prior to calling this. 277 */ 278struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio) 279{ 280 if (!bio || !bio->bi_blkg) 281 return NULL; 282 return &bio->bi_blkg->blkcg->css; 283} 284EXPORT_SYMBOL_GPL(bio_blkcg_css); 285 286/** 287 * blkcg_parent - get the parent of a blkcg 288 * @blkcg: blkcg of interest 289 * 290 * Return the parent blkcg of @blkcg. Can be called anytime. 291 */ 292static inline struct blkcg *blkcg_parent(struct blkcg *blkcg) 293{ 294 return css_to_blkcg(blkcg->css.parent); 295} 296 297/** 298 * blkg_alloc - allocate a blkg 299 * @blkcg: block cgroup the new blkg is associated with 300 * @disk: gendisk the new blkg is associated with 301 * @gfp_mask: allocation mask to use 302 * 303 * Allocate a new blkg associating @blkcg and @disk. 304 */ 305static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct gendisk *disk, 306 gfp_t gfp_mask) 307{ 308 struct blkcg_gq *blkg; 309 int i, cpu; 310 311 /* alloc and init base part */ 312 blkg = kzalloc_node(sizeof(*blkg), gfp_mask, disk->queue->node); 313 if (!blkg) 314 return NULL; 315 if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask)) 316 goto out_free_blkg; 317 blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask); 318 if (!blkg->iostat_cpu) 319 goto out_exit_refcnt; 320 if (!blk_get_queue(disk->queue)) 321 goto out_free_iostat; 322 323 blkg->q = disk->queue; 324 INIT_LIST_HEAD(&blkg->q_node); 325 blkg->blkcg = blkcg; 326#ifdef CONFIG_BLK_CGROUP_PUNT_BIO 327 spin_lock_init(&blkg->async_bio_lock); 328 bio_list_init(&blkg->async_bios); 329 INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn); 330#endif 331 332 u64_stats_init(&blkg->iostat.sync); 333 for_each_possible_cpu(cpu) { 334 u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync); 335 per_cpu_ptr(blkg->iostat_cpu, cpu)->blkg = blkg; 336 } 337 338 for (i = 0; i < BLKCG_MAX_POLS; i++) { 339 struct blkcg_policy *pol = blkcg_policy[i]; 340 struct blkg_policy_data *pd; 341 342 if (!blkcg_policy_enabled(disk->queue, pol)) 343 continue; 344 345 /* alloc per-policy data and attach it to blkg */ 346 pd = pol->pd_alloc_fn(disk, blkcg, gfp_mask); 347 if (!pd) 348 goto out_free_pds; 349 blkg->pd[i] = pd; 350 pd->blkg = blkg; 351 pd->plid = i; 352 pd->online = false; 353 } 354 355 return blkg; 356 357out_free_pds: 358 while (--i >= 0) 359 if (blkg->pd[i]) 360 blkcg_policy[i]->pd_free_fn(blkg->pd[i]); 361 blk_put_queue(disk->queue); 362out_free_iostat: 363 free_percpu(blkg->iostat_cpu); 364out_exit_refcnt: 365 percpu_ref_exit(&blkg->refcnt); 366out_free_blkg: 367 kfree(blkg); 368 return NULL; 369} 370 371/* 372 * If @new_blkg is %NULL, this function tries to allocate a new one as 373 * necessary using %GFP_NOWAIT. @new_blkg is always consumed on return. 374 */ 375static struct blkcg_gq *blkg_create(struct blkcg *blkcg, struct gendisk *disk, 376 struct blkcg_gq *new_blkg) 377{ 378 struct blkcg_gq *blkg; 379 int i, ret; 380 381 lockdep_assert_held(&disk->queue->queue_lock); 382 383 /* request_queue is dying, do not create/recreate a blkg */ 384 if (blk_queue_dying(disk->queue)) { 385 ret = -ENODEV; 386 goto err_free_blkg; 387 } 388 389 /* blkg holds a reference to blkcg */ 390 if (!css_tryget_online(&blkcg->css)) { 391 ret = -ENODEV; 392 goto err_free_blkg; 393 } 394 395 /* allocate */ 396 if (!new_blkg) { 397 new_blkg = blkg_alloc(blkcg, disk, GFP_NOWAIT | __GFP_NOWARN); 398 if (unlikely(!new_blkg)) { 399 ret = -ENOMEM; 400 goto err_put_css; 401 } 402 } 403 blkg = new_blkg; 404 405 /* link parent */ 406 if (blkcg_parent(blkcg)) { 407 blkg->parent = blkg_lookup(blkcg_parent(blkcg), disk->queue); 408 if (WARN_ON_ONCE(!blkg->parent)) { 409 ret = -ENODEV; 410 goto err_put_css; 411 } 412 blkg_get(blkg->parent); 413 } 414 415 /* invoke per-policy init */ 416 for (i = 0; i < BLKCG_MAX_POLS; i++) { 417 struct blkcg_policy *pol = blkcg_policy[i]; 418 419 if (blkg->pd[i] && pol->pd_init_fn) 420 pol->pd_init_fn(blkg->pd[i]); 421 } 422 423 /* insert */ 424 spin_lock(&blkcg->lock); 425 ret = radix_tree_insert(&blkcg->blkg_tree, disk->queue->id, blkg); 426 if (likely(!ret)) { 427 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list); 428 list_add(&blkg->q_node, &disk->queue->blkg_list); 429 430 for (i = 0; i < BLKCG_MAX_POLS; i++) { 431 struct blkcg_policy *pol = blkcg_policy[i]; 432 433 if (blkg->pd[i]) { 434 if (pol->pd_online_fn) 435 pol->pd_online_fn(blkg->pd[i]); 436 blkg->pd[i]->online = true; 437 } 438 } 439 } 440 blkg->online = true; 441 spin_unlock(&blkcg->lock); 442 443 if (!ret) 444 return blkg; 445 446 /* @blkg failed fully initialized, use the usual release path */ 447 blkg_put(blkg); 448 return ERR_PTR(ret); 449 450err_put_css: 451 css_put(&blkcg->css); 452err_free_blkg: 453 if (new_blkg) 454 blkg_free(new_blkg); 455 return ERR_PTR(ret); 456} 457 458/** 459 * blkg_lookup_create - lookup blkg, try to create one if not there 460 * @blkcg: blkcg of interest 461 * @disk: gendisk of interest 462 * 463 * Lookup blkg for the @blkcg - @disk pair. If it doesn't exist, try to 464 * create one. blkg creation is performed recursively from blkcg_root such 465 * that all non-root blkg's have access to the parent blkg. This function 466 * should be called under RCU read lock and takes @disk->queue->queue_lock. 467 * 468 * Returns the blkg or the closest blkg if blkg_create() fails as it walks 469 * down from root. 470 */ 471static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, 472 struct gendisk *disk) 473{ 474 struct request_queue *q = disk->queue; 475 struct blkcg_gq *blkg; 476 unsigned long flags; 477 478 WARN_ON_ONCE(!rcu_read_lock_held()); 479 480 blkg = blkg_lookup(blkcg, q); 481 if (blkg) 482 return blkg; 483 484 spin_lock_irqsave(&q->queue_lock, flags); 485 blkg = blkg_lookup(blkcg, q); 486 if (blkg) { 487 if (blkcg != &blkcg_root && 488 blkg != rcu_dereference(blkcg->blkg_hint)) 489 rcu_assign_pointer(blkcg->blkg_hint, blkg); 490 goto found; 491 } 492 493 /* 494 * Create blkgs walking down from blkcg_root to @blkcg, so that all 495 * non-root blkgs have access to their parents. Returns the closest 496 * blkg to the intended blkg should blkg_create() fail. 497 */ 498 while (true) { 499 struct blkcg *pos = blkcg; 500 struct blkcg *parent = blkcg_parent(blkcg); 501 struct blkcg_gq *ret_blkg = q->root_blkg; 502 503 while (parent) { 504 blkg = blkg_lookup(parent, q); 505 if (blkg) { 506 /* remember closest blkg */ 507 ret_blkg = blkg; 508 break; 509 } 510 pos = parent; 511 parent = blkcg_parent(parent); 512 } 513 514 blkg = blkg_create(pos, disk, NULL); 515 if (IS_ERR(blkg)) { 516 blkg = ret_blkg; 517 break; 518 } 519 if (pos == blkcg) 520 break; 521 } 522 523found: 524 spin_unlock_irqrestore(&q->queue_lock, flags); 525 return blkg; 526} 527 528static void blkg_destroy(struct blkcg_gq *blkg) 529{ 530 struct blkcg *blkcg = blkg->blkcg; 531 int i; 532 533 lockdep_assert_held(&blkg->q->queue_lock); 534 lockdep_assert_held(&blkcg->lock); 535 536 /* 537 * blkg stays on the queue list until blkg_free_workfn(), see details in 538 * blkg_free_workfn(), hence this function can be called from 539 * blkcg_destroy_blkgs() first and again from blkg_destroy_all() before 540 * blkg_free_workfn(). 541 */ 542 if (hlist_unhashed(&blkg->blkcg_node)) 543 return; 544 545 for (i = 0; i < BLKCG_MAX_POLS; i++) { 546 struct blkcg_policy *pol = blkcg_policy[i]; 547 548 if (blkg->pd[i] && blkg->pd[i]->online) { 549 blkg->pd[i]->online = false; 550 if (pol->pd_offline_fn) 551 pol->pd_offline_fn(blkg->pd[i]); 552 } 553 } 554 555 blkg->online = false; 556 557 radix_tree_delete(&blkcg->blkg_tree, blkg->q->id); 558 hlist_del_init_rcu(&blkg->blkcg_node); 559 560 /* 561 * Both setting lookup hint to and clearing it from @blkg are done 562 * under queue_lock. If it's not pointing to @blkg now, it never 563 * will. Hint assignment itself can race safely. 564 */ 565 if (rcu_access_pointer(blkcg->blkg_hint) == blkg) 566 rcu_assign_pointer(blkcg->blkg_hint, NULL); 567 568 /* 569 * Put the reference taken at the time of creation so that when all 570 * queues are gone, group can be destroyed. 571 */ 572 percpu_ref_kill(&blkg->refcnt); 573} 574 575static void blkg_destroy_all(struct gendisk *disk) 576{ 577 struct request_queue *q = disk->queue; 578 struct blkcg_gq *blkg; 579 int count = BLKG_DESTROY_BATCH_SIZE; 580 int i; 581 582restart: 583 spin_lock_irq(&q->queue_lock); 584 list_for_each_entry(blkg, &q->blkg_list, q_node) { 585 struct blkcg *blkcg = blkg->blkcg; 586 587 if (hlist_unhashed(&blkg->blkcg_node)) 588 continue; 589 590 spin_lock(&blkcg->lock); 591 blkg_destroy(blkg); 592 spin_unlock(&blkcg->lock); 593 594 /* 595 * in order to avoid holding the spin lock for too long, release 596 * it when a batch of blkgs are destroyed. 597 */ 598 if (!(--count)) { 599 count = BLKG_DESTROY_BATCH_SIZE; 600 spin_unlock_irq(&q->queue_lock); 601 cond_resched(); 602 goto restart; 603 } 604 } 605 606 /* 607 * Mark policy deactivated since policy offline has been done, and 608 * the free is scheduled, so future blkcg_deactivate_policy() can 609 * be bypassed 610 */ 611 for (i = 0; i < BLKCG_MAX_POLS; i++) { 612 struct blkcg_policy *pol = blkcg_policy[i]; 613 614 if (pol) 615 __clear_bit(pol->plid, q->blkcg_pols); 616 } 617 618 q->root_blkg = NULL; 619 spin_unlock_irq(&q->queue_lock); 620} 621 622static int blkcg_reset_stats(struct cgroup_subsys_state *css, 623 struct cftype *cftype, u64 val) 624{ 625 struct blkcg *blkcg = css_to_blkcg(css); 626 struct blkcg_gq *blkg; 627 int i, cpu; 628 629 mutex_lock(&blkcg_pol_mutex); 630 spin_lock_irq(&blkcg->lock); 631 632 /* 633 * Note that stat reset is racy - it doesn't synchronize against 634 * stat updates. This is a debug feature which shouldn't exist 635 * anyway. If you get hit by a race, retry. 636 */ 637 hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) { 638 for_each_possible_cpu(cpu) { 639 struct blkg_iostat_set *bis = 640 per_cpu_ptr(blkg->iostat_cpu, cpu); 641 memset(bis, 0, sizeof(*bis)); 642 643 /* Re-initialize the cleared blkg_iostat_set */ 644 u64_stats_init(&bis->sync); 645 bis->blkg = blkg; 646 } 647 memset(&blkg->iostat, 0, sizeof(blkg->iostat)); 648 u64_stats_init(&blkg->iostat.sync); 649 650 for (i = 0; i < BLKCG_MAX_POLS; i++) { 651 struct blkcg_policy *pol = blkcg_policy[i]; 652 653 if (blkg->pd[i] && pol->pd_reset_stats_fn) 654 pol->pd_reset_stats_fn(blkg->pd[i]); 655 } 656 } 657 658 spin_unlock_irq(&blkcg->lock); 659 mutex_unlock(&blkcg_pol_mutex); 660 return 0; 661} 662 663const char *blkg_dev_name(struct blkcg_gq *blkg) 664{ 665 if (!blkg->q->disk) 666 return NULL; 667 return bdi_dev_name(blkg->q->disk->bdi); 668} 669 670/** 671 * blkcg_print_blkgs - helper for printing per-blkg data 672 * @sf: seq_file to print to 673 * @blkcg: blkcg of interest 674 * @prfill: fill function to print out a blkg 675 * @pol: policy in question 676 * @data: data to be passed to @prfill 677 * @show_total: to print out sum of prfill return values or not 678 * 679 * This function invokes @prfill on each blkg of @blkcg if pd for the 680 * policy specified by @pol exists. @prfill is invoked with @sf, the 681 * policy data and @data and the matching queue lock held. If @show_total 682 * is %true, the sum of the return values from @prfill is printed with 683 * "Total" label at the end. 684 * 685 * This is to be used to construct print functions for 686 * cftype->read_seq_string method. 687 */ 688void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg, 689 u64 (*prfill)(struct seq_file *, 690 struct blkg_policy_data *, int), 691 const struct blkcg_policy *pol, int data, 692 bool show_total) 693{ 694 struct blkcg_gq *blkg; 695 u64 total = 0; 696 697 rcu_read_lock(); 698 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { 699 spin_lock_irq(&blkg->q->queue_lock); 700 if (blkcg_policy_enabled(blkg->q, pol)) 701 total += prfill(sf, blkg->pd[pol->plid], data); 702 spin_unlock_irq(&blkg->q->queue_lock); 703 } 704 rcu_read_unlock(); 705 706 if (show_total) 707 seq_printf(sf, "Total %llu\n", (unsigned long long)total); 708} 709EXPORT_SYMBOL_GPL(blkcg_print_blkgs); 710 711/** 712 * __blkg_prfill_u64 - prfill helper for a single u64 value 713 * @sf: seq_file to print to 714 * @pd: policy private data of interest 715 * @v: value to print 716 * 717 * Print @v to @sf for the device associated with @pd. 718 */ 719u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v) 720{ 721 const char *dname = blkg_dev_name(pd->blkg); 722 723 if (!dname) 724 return 0; 725 726 seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v); 727 return v; 728} 729EXPORT_SYMBOL_GPL(__blkg_prfill_u64); 730 731/** 732 * blkg_conf_init - initialize a blkg_conf_ctx 733 * @ctx: blkg_conf_ctx to initialize 734 * @input: input string 735 * 736 * Initialize @ctx which can be used to parse blkg config input string @input. 737 * Once initialized, @ctx can be used with blkg_conf_open_bdev() and 738 * blkg_conf_prep(), and must be cleaned up with blkg_conf_exit(). 739 */ 740void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input) 741{ 742 *ctx = (struct blkg_conf_ctx){ .input = input }; 743} 744EXPORT_SYMBOL_GPL(blkg_conf_init); 745 746/** 747 * blkg_conf_open_bdev - parse and open bdev for per-blkg config update 748 * @ctx: blkg_conf_ctx initialized with blkg_conf_init() 749 * 750 * Parse the device node prefix part, MAJ:MIN, of per-blkg config update from 751 * @ctx->input and get and store the matching bdev in @ctx->bdev. @ctx->body is 752 * set to point past the device node prefix. 753 * 754 * This function may be called multiple times on @ctx and the extra calls become 755 * NOOPs. blkg_conf_prep() implicitly calls this function. Use this function 756 * explicitly if bdev access is needed without resolving the blkcg / policy part 757 * of @ctx->input. Returns -errno on error. 758 */ 759int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx) 760{ 761 char *input = ctx->input; 762 unsigned int major, minor; 763 struct block_device *bdev; 764 int key_len; 765 766 if (ctx->bdev) 767 return 0; 768 769 if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2) 770 return -EINVAL; 771 772 input += key_len; 773 if (!isspace(*input)) 774 return -EINVAL; 775 input = skip_spaces(input); 776 777 bdev = blkdev_get_no_open(MKDEV(major, minor)); 778 if (!bdev) 779 return -ENODEV; 780 if (bdev_is_partition(bdev)) { 781 blkdev_put_no_open(bdev); 782 return -ENODEV; 783 } 784 785 mutex_lock(&bdev->bd_queue->rq_qos_mutex); 786 if (!disk_live(bdev->bd_disk)) { 787 blkdev_put_no_open(bdev); 788 mutex_unlock(&bdev->bd_queue->rq_qos_mutex); 789 return -ENODEV; 790 } 791 792 ctx->body = input; 793 ctx->bdev = bdev; 794 return 0; 795} 796 797/** 798 * blkg_conf_prep - parse and prepare for per-blkg config update 799 * @blkcg: target block cgroup 800 * @pol: target policy 801 * @ctx: blkg_conf_ctx initialized with blkg_conf_init() 802 * 803 * Parse per-blkg config update from @ctx->input and initialize @ctx 804 * accordingly. On success, @ctx->body points to the part of @ctx->input 805 * following MAJ:MIN, @ctx->bdev points to the target block device and 806 * @ctx->blkg to the blkg being configured. 807 * 808 * blkg_conf_open_bdev() may be called on @ctx beforehand. On success, this 809 * function returns with queue lock held and must be followed by 810 * blkg_conf_exit(). 811 */ 812int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol, 813 struct blkg_conf_ctx *ctx) 814 __acquires(&bdev->bd_queue->queue_lock) 815{ 816 struct gendisk *disk; 817 struct request_queue *q; 818 struct blkcg_gq *blkg; 819 int ret; 820 821 ret = blkg_conf_open_bdev(ctx); 822 if (ret) 823 return ret; 824 825 disk = ctx->bdev->bd_disk; 826 q = disk->queue; 827 828 /* 829 * blkcg_deactivate_policy() requires queue to be frozen, we can grab 830 * q_usage_counter to prevent concurrent with blkcg_deactivate_policy(). 831 */ 832 ret = blk_queue_enter(q, 0); 833 if (ret) 834 goto fail; 835 836 spin_lock_irq(&q->queue_lock); 837 838 if (!blkcg_policy_enabled(q, pol)) { 839 ret = -EOPNOTSUPP; 840 goto fail_unlock; 841 } 842 843 blkg = blkg_lookup(blkcg, q); 844 if (blkg) 845 goto success; 846 847 /* 848 * Create blkgs walking down from blkcg_root to @blkcg, so that all 849 * non-root blkgs have access to their parents. 850 */ 851 while (true) { 852 struct blkcg *pos = blkcg; 853 struct blkcg *parent; 854 struct blkcg_gq *new_blkg; 855 856 parent = blkcg_parent(blkcg); 857 while (parent && !blkg_lookup(parent, q)) { 858 pos = parent; 859 parent = blkcg_parent(parent); 860 } 861 862 /* Drop locks to do new blkg allocation with GFP_KERNEL. */ 863 spin_unlock_irq(&q->queue_lock); 864 865 new_blkg = blkg_alloc(pos, disk, GFP_KERNEL); 866 if (unlikely(!new_blkg)) { 867 ret = -ENOMEM; 868 goto fail_exit_queue; 869 } 870 871 if (radix_tree_preload(GFP_KERNEL)) { 872 blkg_free(new_blkg); 873 ret = -ENOMEM; 874 goto fail_exit_queue; 875 } 876 877 spin_lock_irq(&q->queue_lock); 878 879 if (!blkcg_policy_enabled(q, pol)) { 880 blkg_free(new_blkg); 881 ret = -EOPNOTSUPP; 882 goto fail_preloaded; 883 } 884 885 blkg = blkg_lookup(pos, q); 886 if (blkg) { 887 blkg_free(new_blkg); 888 } else { 889 blkg = blkg_create(pos, disk, new_blkg); 890 if (IS_ERR(blkg)) { 891 ret = PTR_ERR(blkg); 892 goto fail_preloaded; 893 } 894 } 895 896 radix_tree_preload_end(); 897 898 if (pos == blkcg) 899 goto success; 900 } 901success: 902 blk_queue_exit(q); 903 ctx->blkg = blkg; 904 return 0; 905 906fail_preloaded: 907 radix_tree_preload_end(); 908fail_unlock: 909 spin_unlock_irq(&q->queue_lock); 910fail_exit_queue: 911 blk_queue_exit(q); 912fail: 913 /* 914 * If queue was bypassing, we should retry. Do so after a 915 * short msleep(). It isn't strictly necessary but queue 916 * can be bypassing for some time and it's always nice to 917 * avoid busy looping. 918 */ 919 if (ret == -EBUSY) { 920 msleep(10); 921 ret = restart_syscall(); 922 } 923 return ret; 924} 925EXPORT_SYMBOL_GPL(blkg_conf_prep); 926 927/** 928 * blkg_conf_exit - clean up per-blkg config update 929 * @ctx: blkg_conf_ctx initialized with blkg_conf_init() 930 * 931 * Clean up after per-blkg config update. This function must be called on all 932 * blkg_conf_ctx's initialized with blkg_conf_init(). 933 */ 934void blkg_conf_exit(struct blkg_conf_ctx *ctx) 935 __releases(&ctx->bdev->bd_queue->queue_lock) 936 __releases(&ctx->bdev->bd_queue->rq_qos_mutex) 937{ 938 if (ctx->blkg) { 939 spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock); 940 ctx->blkg = NULL; 941 } 942 943 if (ctx->bdev) { 944 mutex_unlock(&ctx->bdev->bd_queue->rq_qos_mutex); 945 blkdev_put_no_open(ctx->bdev); 946 ctx->body = NULL; 947 ctx->bdev = NULL; 948 } 949} 950EXPORT_SYMBOL_GPL(blkg_conf_exit); 951 952static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src) 953{ 954 int i; 955 956 for (i = 0; i < BLKG_IOSTAT_NR; i++) { 957 dst->bytes[i] = src->bytes[i]; 958 dst->ios[i] = src->ios[i]; 959 } 960} 961 962static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src) 963{ 964 int i; 965 966 for (i = 0; i < BLKG_IOSTAT_NR; i++) { 967 dst->bytes[i] += src->bytes[i]; 968 dst->ios[i] += src->ios[i]; 969 } 970} 971 972static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src) 973{ 974 int i; 975 976 for (i = 0; i < BLKG_IOSTAT_NR; i++) { 977 dst->bytes[i] -= src->bytes[i]; 978 dst->ios[i] -= src->ios[i]; 979 } 980} 981 982static void blkcg_iostat_update(struct blkcg_gq *blkg, struct blkg_iostat *cur, 983 struct blkg_iostat *last) 984{ 985 struct blkg_iostat delta; 986 unsigned long flags; 987 988 /* propagate percpu delta to global */ 989 flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync); 990 blkg_iostat_set(&delta, cur); 991 blkg_iostat_sub(&delta, last); 992 blkg_iostat_add(&blkg->iostat.cur, &delta); 993 blkg_iostat_add(last, &delta); 994 u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags); 995} 996 997static void __blkcg_rstat_flush(struct blkcg *blkcg, int cpu) 998{ 999 struct llist_head *lhead = per_cpu_ptr(blkcg->lhead, cpu); 1000 struct llist_node *lnode; 1001 struct blkg_iostat_set *bisc, *next_bisc; 1002 unsigned long flags; 1003 1004 rcu_read_lock(); 1005 1006 lnode = llist_del_all(lhead); 1007 if (!lnode) 1008 goto out; 1009 1010 /* 1011 * For covering concurrent parent blkg update from blkg_release(). 1012 * 1013 * When flushing from cgroup, cgroup_rstat_lock is always held, so 1014 * this lock won't cause contention most of time. 1015 */ 1016 raw_spin_lock_irqsave(&blkg_stat_lock, flags); 1017 1018 /* 1019 * Iterate only the iostat_cpu's queued in the lockless list. 1020 */ 1021 llist_for_each_entry_safe(bisc, next_bisc, lnode, lnode) { 1022 struct blkcg_gq *blkg = bisc->blkg; 1023 struct blkcg_gq *parent = blkg->parent; 1024 struct blkg_iostat cur; 1025 unsigned int seq; 1026 1027 WRITE_ONCE(bisc->lqueued, false); 1028 1029 /* fetch the current per-cpu values */ 1030 do { 1031 seq = u64_stats_fetch_begin(&bisc->sync); 1032 blkg_iostat_set(&cur, &bisc->cur); 1033 } while (u64_stats_fetch_retry(&bisc->sync, seq)); 1034 1035 blkcg_iostat_update(blkg, &cur, &bisc->last); 1036 1037 /* propagate global delta to parent (unless that's root) */ 1038 if (parent && parent->parent) 1039 blkcg_iostat_update(parent, &blkg->iostat.cur, 1040 &blkg->iostat.last); 1041 } 1042 raw_spin_unlock_irqrestore(&blkg_stat_lock, flags); 1043out: 1044 rcu_read_unlock(); 1045} 1046 1047static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu) 1048{ 1049 /* Root-level stats are sourced from system-wide IO stats */ 1050 if (cgroup_parent(css->cgroup)) 1051 __blkcg_rstat_flush(css_to_blkcg(css), cpu); 1052} 1053 1054/* 1055 * We source root cgroup stats from the system-wide stats to avoid 1056 * tracking the same information twice and incurring overhead when no 1057 * cgroups are defined. For that reason, cgroup_rstat_flush in 1058 * blkcg_print_stat does not actually fill out the iostat in the root 1059 * cgroup's blkcg_gq. 1060 * 1061 * However, we would like to re-use the printing code between the root and 1062 * non-root cgroups to the extent possible. For that reason, we simulate 1063 * flushing the root cgroup's stats by explicitly filling in the iostat 1064 * with disk level statistics. 1065 */ 1066static void blkcg_fill_root_iostats(void) 1067{ 1068 struct class_dev_iter iter; 1069 struct device *dev; 1070 1071 class_dev_iter_init(&iter, &block_class, NULL, &disk_type); 1072 while ((dev = class_dev_iter_next(&iter))) { 1073 struct block_device *bdev = dev_to_bdev(dev); 1074 struct blkcg_gq *blkg = bdev->bd_disk->queue->root_blkg; 1075 struct blkg_iostat tmp; 1076 int cpu; 1077 unsigned long flags; 1078 1079 memset(&tmp, 0, sizeof(tmp)); 1080 for_each_possible_cpu(cpu) { 1081 struct disk_stats *cpu_dkstats; 1082 1083 cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu); 1084 tmp.ios[BLKG_IOSTAT_READ] += 1085 cpu_dkstats->ios[STAT_READ]; 1086 tmp.ios[BLKG_IOSTAT_WRITE] += 1087 cpu_dkstats->ios[STAT_WRITE]; 1088 tmp.ios[BLKG_IOSTAT_DISCARD] += 1089 cpu_dkstats->ios[STAT_DISCARD]; 1090 // convert sectors to bytes 1091 tmp.bytes[BLKG_IOSTAT_READ] += 1092 cpu_dkstats->sectors[STAT_READ] << 9; 1093 tmp.bytes[BLKG_IOSTAT_WRITE] += 1094 cpu_dkstats->sectors[STAT_WRITE] << 9; 1095 tmp.bytes[BLKG_IOSTAT_DISCARD] += 1096 cpu_dkstats->sectors[STAT_DISCARD] << 9; 1097 } 1098 1099 flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync); 1100 blkg_iostat_set(&blkg->iostat.cur, &tmp); 1101 u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags); 1102 } 1103} 1104 1105static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s) 1106{ 1107 struct blkg_iostat_set *bis = &blkg->iostat; 1108 u64 rbytes, wbytes, rios, wios, dbytes, dios; 1109 const char *dname; 1110 unsigned seq; 1111 int i; 1112 1113 if (!blkg->online) 1114 return; 1115 1116 dname = blkg_dev_name(blkg); 1117 if (!dname) 1118 return; 1119 1120 seq_printf(s, "%s ", dname); 1121 1122 do { 1123 seq = u64_stats_fetch_begin(&bis->sync); 1124 1125 rbytes = bis->cur.bytes[BLKG_IOSTAT_READ]; 1126 wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE]; 1127 dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD]; 1128 rios = bis->cur.ios[BLKG_IOSTAT_READ]; 1129 wios = bis->cur.ios[BLKG_IOSTAT_WRITE]; 1130 dios = bis->cur.ios[BLKG_IOSTAT_DISCARD]; 1131 } while (u64_stats_fetch_retry(&bis->sync, seq)); 1132 1133 if (rbytes || wbytes || rios || wios) { 1134 seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu", 1135 rbytes, wbytes, rios, wios, 1136 dbytes, dios); 1137 } 1138 1139 if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) { 1140 seq_printf(s, " use_delay=%d delay_nsec=%llu", 1141 atomic_read(&blkg->use_delay), 1142 atomic64_read(&blkg->delay_nsec)); 1143 } 1144 1145 for (i = 0; i < BLKCG_MAX_POLS; i++) { 1146 struct blkcg_policy *pol = blkcg_policy[i]; 1147 1148 if (!blkg->pd[i] || !pol->pd_stat_fn) 1149 continue; 1150 1151 pol->pd_stat_fn(blkg->pd[i], s); 1152 } 1153 1154 seq_puts(s, "\n"); 1155} 1156 1157static int blkcg_print_stat(struct seq_file *sf, void *v) 1158{ 1159 struct blkcg *blkcg = css_to_blkcg(seq_css(sf)); 1160 struct blkcg_gq *blkg; 1161 1162 if (!seq_css(sf)->parent) 1163 blkcg_fill_root_iostats(); 1164 else 1165 cgroup_rstat_flush(blkcg->css.cgroup); 1166 1167 rcu_read_lock(); 1168 hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) { 1169 spin_lock_irq(&blkg->q->queue_lock); 1170 blkcg_print_one_stat(blkg, sf); 1171 spin_unlock_irq(&blkg->q->queue_lock); 1172 } 1173 rcu_read_unlock(); 1174 return 0; 1175} 1176 1177static struct cftype blkcg_files[] = { 1178 { 1179 .name = "stat", 1180 .seq_show = blkcg_print_stat, 1181 }, 1182 { } /* terminate */ 1183}; 1184 1185static struct cftype blkcg_legacy_files[] = { 1186 { 1187 .name = "reset_stats", 1188 .write_u64 = blkcg_reset_stats, 1189 }, 1190 { } /* terminate */ 1191}; 1192 1193#ifdef CONFIG_CGROUP_WRITEBACK 1194struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css) 1195{ 1196 return &css_to_blkcg(css)->cgwb_list; 1197} 1198#endif 1199 1200/* 1201 * blkcg destruction is a three-stage process. 1202 * 1203 * 1. Destruction starts. The blkcg_css_offline() callback is invoked 1204 * which offlines writeback. Here we tie the next stage of blkg destruction 1205 * to the completion of writeback associated with the blkcg. This lets us 1206 * avoid punting potentially large amounts of outstanding writeback to root 1207 * while maintaining any ongoing policies. The next stage is triggered when 1208 * the nr_cgwbs count goes to zero. 1209 * 1210 * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called 1211 * and handles the destruction of blkgs. Here the css reference held by 1212 * the blkg is put back eventually allowing blkcg_css_free() to be called. 1213 * This work may occur in cgwb_release_workfn() on the cgwb_release 1214 * workqueue. Any submitted ios that fail to get the blkg ref will be 1215 * punted to the root_blkg. 1216 * 1217 * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called. 1218 * This finally frees the blkcg. 1219 */ 1220 1221/** 1222 * blkcg_destroy_blkgs - responsible for shooting down blkgs 1223 * @blkcg: blkcg of interest 1224 * 1225 * blkgs should be removed while holding both q and blkcg locks. As blkcg lock 1226 * is nested inside q lock, this function performs reverse double lock dancing. 1227 * Destroying the blkgs releases the reference held on the blkcg's css allowing 1228 * blkcg_css_free to eventually be called. 1229 * 1230 * This is the blkcg counterpart of ioc_release_fn(). 1231 */ 1232static void blkcg_destroy_blkgs(struct blkcg *blkcg) 1233{ 1234 might_sleep(); 1235 1236 spin_lock_irq(&blkcg->lock); 1237 1238 while (!hlist_empty(&blkcg->blkg_list)) { 1239 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first, 1240 struct blkcg_gq, blkcg_node); 1241 struct request_queue *q = blkg->q; 1242 1243 if (need_resched() || !spin_trylock(&q->queue_lock)) { 1244 /* 1245 * Given that the system can accumulate a huge number 1246 * of blkgs in pathological cases, check to see if we 1247 * need to rescheduling to avoid softlockup. 1248 */ 1249 spin_unlock_irq(&blkcg->lock); 1250 cond_resched(); 1251 spin_lock_irq(&blkcg->lock); 1252 continue; 1253 } 1254 1255 blkg_destroy(blkg); 1256 spin_unlock(&q->queue_lock); 1257 } 1258 1259 spin_unlock_irq(&blkcg->lock); 1260} 1261 1262/** 1263 * blkcg_pin_online - pin online state 1264 * @blkcg_css: blkcg of interest 1265 * 1266 * While pinned, a blkcg is kept online. This is primarily used to 1267 * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline 1268 * while an associated cgwb is still active. 1269 */ 1270void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css) 1271{ 1272 refcount_inc(&css_to_blkcg(blkcg_css)->online_pin); 1273} 1274 1275/** 1276 * blkcg_unpin_online - unpin online state 1277 * @blkcg_css: blkcg of interest 1278 * 1279 * This is primarily used to impedance-match blkg and cgwb lifetimes so 1280 * that blkg doesn't go offline while an associated cgwb is still active. 1281 * When this count goes to zero, all active cgwbs have finished so the 1282 * blkcg can continue destruction by calling blkcg_destroy_blkgs(). 1283 */ 1284void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css) 1285{ 1286 struct blkcg *blkcg = css_to_blkcg(blkcg_css); 1287 1288 do { 1289 if (!refcount_dec_and_test(&blkcg->online_pin)) 1290 break; 1291 blkcg_destroy_blkgs(blkcg); 1292 blkcg = blkcg_parent(blkcg); 1293 } while (blkcg); 1294} 1295 1296/** 1297 * blkcg_css_offline - cgroup css_offline callback 1298 * @css: css of interest 1299 * 1300 * This function is called when @css is about to go away. Here the cgwbs are 1301 * offlined first and only once writeback associated with the blkcg has 1302 * finished do we start step 2 (see above). 1303 */ 1304static void blkcg_css_offline(struct cgroup_subsys_state *css) 1305{ 1306 /* this prevents anyone from attaching or migrating to this blkcg */ 1307 wb_blkcg_offline(css); 1308 1309 /* put the base online pin allowing step 2 to be triggered */ 1310 blkcg_unpin_online(css); 1311} 1312 1313static void blkcg_css_free(struct cgroup_subsys_state *css) 1314{ 1315 struct blkcg *blkcg = css_to_blkcg(css); 1316 int i; 1317 1318 mutex_lock(&blkcg_pol_mutex); 1319 1320 list_del(&blkcg->all_blkcgs_node); 1321 1322 for (i = 0; i < BLKCG_MAX_POLS; i++) 1323 if (blkcg->cpd[i]) 1324 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]); 1325 1326 mutex_unlock(&blkcg_pol_mutex); 1327 1328 free_percpu(blkcg->lhead); 1329 kfree(blkcg); 1330} 1331 1332static struct cgroup_subsys_state * 1333blkcg_css_alloc(struct cgroup_subsys_state *parent_css) 1334{ 1335 struct blkcg *blkcg; 1336 int i; 1337 1338 mutex_lock(&blkcg_pol_mutex); 1339 1340 if (!parent_css) { 1341 blkcg = &blkcg_root; 1342 } else { 1343 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL); 1344 if (!blkcg) 1345 goto unlock; 1346 } 1347 1348 if (init_blkcg_llists(blkcg)) 1349 goto free_blkcg; 1350 1351 for (i = 0; i < BLKCG_MAX_POLS ; i++) { 1352 struct blkcg_policy *pol = blkcg_policy[i]; 1353 struct blkcg_policy_data *cpd; 1354 1355 /* 1356 * If the policy hasn't been attached yet, wait for it 1357 * to be attached before doing anything else. Otherwise, 1358 * check if the policy requires any specific per-cgroup 1359 * data: if it does, allocate and initialize it. 1360 */ 1361 if (!pol || !pol->cpd_alloc_fn) 1362 continue; 1363 1364 cpd = pol->cpd_alloc_fn(GFP_KERNEL); 1365 if (!cpd) 1366 goto free_pd_blkcg; 1367 1368 blkcg->cpd[i] = cpd; 1369 cpd->blkcg = blkcg; 1370 cpd->plid = i; 1371 } 1372 1373 spin_lock_init(&blkcg->lock); 1374 refcount_set(&blkcg->online_pin, 1); 1375 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN); 1376 INIT_HLIST_HEAD(&blkcg->blkg_list); 1377#ifdef CONFIG_CGROUP_WRITEBACK 1378 INIT_LIST_HEAD(&blkcg->cgwb_list); 1379#endif 1380 list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs); 1381 1382 mutex_unlock(&blkcg_pol_mutex); 1383 return &blkcg->css; 1384 1385free_pd_blkcg: 1386 for (i--; i >= 0; i--) 1387 if (blkcg->cpd[i]) 1388 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]); 1389 free_percpu(blkcg->lhead); 1390free_blkcg: 1391 if (blkcg != &blkcg_root) 1392 kfree(blkcg); 1393unlock: 1394 mutex_unlock(&blkcg_pol_mutex); 1395 return ERR_PTR(-ENOMEM); 1396} 1397 1398static int blkcg_css_online(struct cgroup_subsys_state *css) 1399{ 1400 struct blkcg *parent = blkcg_parent(css_to_blkcg(css)); 1401 1402 /* 1403 * blkcg_pin_online() is used to delay blkcg offline so that blkgs 1404 * don't go offline while cgwbs are still active on them. Pin the 1405 * parent so that offline always happens towards the root. 1406 */ 1407 if (parent) 1408 blkcg_pin_online(&parent->css); 1409 return 0; 1410} 1411 1412void blkg_init_queue(struct request_queue *q) 1413{ 1414 INIT_LIST_HEAD(&q->blkg_list); 1415 mutex_init(&q->blkcg_mutex); 1416} 1417 1418int blkcg_init_disk(struct gendisk *disk) 1419{ 1420 struct request_queue *q = disk->queue; 1421 struct blkcg_gq *new_blkg, *blkg; 1422 bool preloaded; 1423 int ret; 1424 1425 new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL); 1426 if (!new_blkg) 1427 return -ENOMEM; 1428 1429 preloaded = !radix_tree_preload(GFP_KERNEL); 1430 1431 /* Make sure the root blkg exists. */ 1432 /* spin_lock_irq can serve as RCU read-side critical section. */ 1433 spin_lock_irq(&q->queue_lock); 1434 blkg = blkg_create(&blkcg_root, disk, new_blkg); 1435 if (IS_ERR(blkg)) 1436 goto err_unlock; 1437 q->root_blkg = blkg; 1438 spin_unlock_irq(&q->queue_lock); 1439 1440 if (preloaded) 1441 radix_tree_preload_end(); 1442 1443 ret = blk_ioprio_init(disk); 1444 if (ret) 1445 goto err_destroy_all; 1446 1447 ret = blk_throtl_init(disk); 1448 if (ret) 1449 goto err_ioprio_exit; 1450 1451 return 0; 1452 1453err_ioprio_exit: 1454 blk_ioprio_exit(disk); 1455err_destroy_all: 1456 blkg_destroy_all(disk); 1457 return ret; 1458err_unlock: 1459 spin_unlock_irq(&q->queue_lock); 1460 if (preloaded) 1461 radix_tree_preload_end(); 1462 return PTR_ERR(blkg); 1463} 1464 1465void blkcg_exit_disk(struct gendisk *disk) 1466{ 1467 blkg_destroy_all(disk); 1468 blk_throtl_exit(disk); 1469} 1470 1471static void blkcg_exit(struct task_struct *tsk) 1472{ 1473 if (tsk->throttle_disk) 1474 put_disk(tsk->throttle_disk); 1475 tsk->throttle_disk = NULL; 1476} 1477 1478struct cgroup_subsys io_cgrp_subsys = { 1479 .css_alloc = blkcg_css_alloc, 1480 .css_online = blkcg_css_online, 1481 .css_offline = blkcg_css_offline, 1482 .css_free = blkcg_css_free, 1483 .css_rstat_flush = blkcg_rstat_flush, 1484 .dfl_cftypes = blkcg_files, 1485 .legacy_cftypes = blkcg_legacy_files, 1486 .legacy_name = "blkio", 1487 .exit = blkcg_exit, 1488#ifdef CONFIG_MEMCG 1489 /* 1490 * This ensures that, if available, memcg is automatically enabled 1491 * together on the default hierarchy so that the owner cgroup can 1492 * be retrieved from writeback pages. 1493 */ 1494 .depends_on = 1 << memory_cgrp_id, 1495#endif 1496}; 1497EXPORT_SYMBOL_GPL(io_cgrp_subsys); 1498 1499/** 1500 * blkcg_activate_policy - activate a blkcg policy on a gendisk 1501 * @disk: gendisk of interest 1502 * @pol: blkcg policy to activate 1503 * 1504 * Activate @pol on @disk. Requires %GFP_KERNEL context. @disk goes through 1505 * bypass mode to populate its blkgs with policy_data for @pol. 1506 * 1507 * Activation happens with @disk bypassed, so nobody would be accessing blkgs 1508 * from IO path. Update of each blkg is protected by both queue and blkcg 1509 * locks so that holding either lock and testing blkcg_policy_enabled() is 1510 * always enough for dereferencing policy data. 1511 * 1512 * The caller is responsible for synchronizing [de]activations and policy 1513 * [un]registerations. Returns 0 on success, -errno on failure. 1514 */ 1515int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol) 1516{ 1517 struct request_queue *q = disk->queue; 1518 struct blkg_policy_data *pd_prealloc = NULL; 1519 struct blkcg_gq *blkg, *pinned_blkg = NULL; 1520 int ret; 1521 1522 if (blkcg_policy_enabled(q, pol)) 1523 return 0; 1524 1525 if (queue_is_mq(q)) 1526 blk_mq_freeze_queue(q); 1527retry: 1528 spin_lock_irq(&q->queue_lock); 1529 1530 /* blkg_list is pushed at the head, reverse walk to initialize parents first */ 1531 list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) { 1532 struct blkg_policy_data *pd; 1533 1534 if (blkg->pd[pol->plid]) 1535 continue; 1536 1537 /* If prealloc matches, use it; otherwise try GFP_NOWAIT */ 1538 if (blkg == pinned_blkg) { 1539 pd = pd_prealloc; 1540 pd_prealloc = NULL; 1541 } else { 1542 pd = pol->pd_alloc_fn(disk, blkg->blkcg, 1543 GFP_NOWAIT | __GFP_NOWARN); 1544 } 1545 1546 if (!pd) { 1547 /* 1548 * GFP_NOWAIT failed. Free the existing one and 1549 * prealloc for @blkg w/ GFP_KERNEL. 1550 */ 1551 if (pinned_blkg) 1552 blkg_put(pinned_blkg); 1553 blkg_get(blkg); 1554 pinned_blkg = blkg; 1555 1556 spin_unlock_irq(&q->queue_lock); 1557 1558 if (pd_prealloc) 1559 pol->pd_free_fn(pd_prealloc); 1560 pd_prealloc = pol->pd_alloc_fn(disk, blkg->blkcg, 1561 GFP_KERNEL); 1562 if (pd_prealloc) 1563 goto retry; 1564 else 1565 goto enomem; 1566 } 1567 1568 spin_lock(&blkg->blkcg->lock); 1569 1570 pd->blkg = blkg; 1571 pd->plid = pol->plid; 1572 blkg->pd[pol->plid] = pd; 1573 1574 if (pol->pd_init_fn) 1575 pol->pd_init_fn(pd); 1576 1577 if (pol->pd_online_fn) 1578 pol->pd_online_fn(pd); 1579 pd->online = true; 1580 1581 spin_unlock(&blkg->blkcg->lock); 1582 } 1583 1584 __set_bit(pol->plid, q->blkcg_pols); 1585 ret = 0; 1586 1587 spin_unlock_irq(&q->queue_lock); 1588out: 1589 if (queue_is_mq(q)) 1590 blk_mq_unfreeze_queue(q); 1591 if (pinned_blkg) 1592 blkg_put(pinned_blkg); 1593 if (pd_prealloc) 1594 pol->pd_free_fn(pd_prealloc); 1595 return ret; 1596 1597enomem: 1598 /* alloc failed, take down everything */ 1599 spin_lock_irq(&q->queue_lock); 1600 list_for_each_entry(blkg, &q->blkg_list, q_node) { 1601 struct blkcg *blkcg = blkg->blkcg; 1602 struct blkg_policy_data *pd; 1603 1604 spin_lock(&blkcg->lock); 1605 pd = blkg->pd[pol->plid]; 1606 if (pd) { 1607 if (pd->online && pol->pd_offline_fn) 1608 pol->pd_offline_fn(pd); 1609 pd->online = false; 1610 pol->pd_free_fn(pd); 1611 blkg->pd[pol->plid] = NULL; 1612 } 1613 spin_unlock(&blkcg->lock); 1614 } 1615 spin_unlock_irq(&q->queue_lock); 1616 ret = -ENOMEM; 1617 goto out; 1618} 1619EXPORT_SYMBOL_GPL(blkcg_activate_policy); 1620 1621/** 1622 * blkcg_deactivate_policy - deactivate a blkcg policy on a gendisk 1623 * @disk: gendisk of interest 1624 * @pol: blkcg policy to deactivate 1625 * 1626 * Deactivate @pol on @disk. Follows the same synchronization rules as 1627 * blkcg_activate_policy(). 1628 */ 1629void blkcg_deactivate_policy(struct gendisk *disk, 1630 const struct blkcg_policy *pol) 1631{ 1632 struct request_queue *q = disk->queue; 1633 struct blkcg_gq *blkg; 1634 1635 if (!blkcg_policy_enabled(q, pol)) 1636 return; 1637 1638 if (queue_is_mq(q)) 1639 blk_mq_freeze_queue(q); 1640 1641 mutex_lock(&q->blkcg_mutex); 1642 spin_lock_irq(&q->queue_lock); 1643 1644 __clear_bit(pol->plid, q->blkcg_pols); 1645 1646 list_for_each_entry(blkg, &q->blkg_list, q_node) { 1647 struct blkcg *blkcg = blkg->blkcg; 1648 1649 spin_lock(&blkcg->lock); 1650 if (blkg->pd[pol->plid]) { 1651 if (blkg->pd[pol->plid]->online && pol->pd_offline_fn) 1652 pol->pd_offline_fn(blkg->pd[pol->plid]); 1653 pol->pd_free_fn(blkg->pd[pol->plid]); 1654 blkg->pd[pol->plid] = NULL; 1655 } 1656 spin_unlock(&blkcg->lock); 1657 } 1658 1659 spin_unlock_irq(&q->queue_lock); 1660 mutex_unlock(&q->blkcg_mutex); 1661 1662 if (queue_is_mq(q)) 1663 blk_mq_unfreeze_queue(q); 1664} 1665EXPORT_SYMBOL_GPL(blkcg_deactivate_policy); 1666 1667static void blkcg_free_all_cpd(struct blkcg_policy *pol) 1668{ 1669 struct blkcg *blkcg; 1670 1671 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) { 1672 if (blkcg->cpd[pol->plid]) { 1673 pol->cpd_free_fn(blkcg->cpd[pol->plid]); 1674 blkcg->cpd[pol->plid] = NULL; 1675 } 1676 } 1677} 1678 1679/** 1680 * blkcg_policy_register - register a blkcg policy 1681 * @pol: blkcg policy to register 1682 * 1683 * Register @pol with blkcg core. Might sleep and @pol may be modified on 1684 * successful registration. Returns 0 on success and -errno on failure. 1685 */ 1686int blkcg_policy_register(struct blkcg_policy *pol) 1687{ 1688 struct blkcg *blkcg; 1689 int i, ret; 1690 1691 mutex_lock(&blkcg_pol_register_mutex); 1692 mutex_lock(&blkcg_pol_mutex); 1693 1694 /* find an empty slot */ 1695 ret = -ENOSPC; 1696 for (i = 0; i < BLKCG_MAX_POLS; i++) 1697 if (!blkcg_policy[i]) 1698 break; 1699 if (i >= BLKCG_MAX_POLS) { 1700 pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n"); 1701 goto err_unlock; 1702 } 1703 1704 /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */ 1705 if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) || 1706 (!pol->pd_alloc_fn ^ !pol->pd_free_fn)) 1707 goto err_unlock; 1708 1709 /* register @pol */ 1710 pol->plid = i; 1711 blkcg_policy[pol->plid] = pol; 1712 1713 /* allocate and install cpd's */ 1714 if (pol->cpd_alloc_fn) { 1715 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) { 1716 struct blkcg_policy_data *cpd; 1717 1718 cpd = pol->cpd_alloc_fn(GFP_KERNEL); 1719 if (!cpd) 1720 goto err_free_cpds; 1721 1722 blkcg->cpd[pol->plid] = cpd; 1723 cpd->blkcg = blkcg; 1724 cpd->plid = pol->plid; 1725 } 1726 } 1727 1728 mutex_unlock(&blkcg_pol_mutex); 1729 1730 /* everything is in place, add intf files for the new policy */ 1731 if (pol->dfl_cftypes) 1732 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys, 1733 pol->dfl_cftypes)); 1734 if (pol->legacy_cftypes) 1735 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys, 1736 pol->legacy_cftypes)); 1737 mutex_unlock(&blkcg_pol_register_mutex); 1738 return 0; 1739 1740err_free_cpds: 1741 if (pol->cpd_free_fn) 1742 blkcg_free_all_cpd(pol); 1743 1744 blkcg_policy[pol->plid] = NULL; 1745err_unlock: 1746 mutex_unlock(&blkcg_pol_mutex); 1747 mutex_unlock(&blkcg_pol_register_mutex); 1748 return ret; 1749} 1750EXPORT_SYMBOL_GPL(blkcg_policy_register); 1751 1752/** 1753 * blkcg_policy_unregister - unregister a blkcg policy 1754 * @pol: blkcg policy to unregister 1755 * 1756 * Undo blkcg_policy_register(@pol). Might sleep. 1757 */ 1758void blkcg_policy_unregister(struct blkcg_policy *pol) 1759{ 1760 mutex_lock(&blkcg_pol_register_mutex); 1761 1762 if (WARN_ON(blkcg_policy[pol->plid] != pol)) 1763 goto out_unlock; 1764 1765 /* kill the intf files first */ 1766 if (pol->dfl_cftypes) 1767 cgroup_rm_cftypes(pol->dfl_cftypes); 1768 if (pol->legacy_cftypes) 1769 cgroup_rm_cftypes(pol->legacy_cftypes); 1770 1771 /* remove cpds and unregister */ 1772 mutex_lock(&blkcg_pol_mutex); 1773 1774 if (pol->cpd_free_fn) 1775 blkcg_free_all_cpd(pol); 1776 1777 blkcg_policy[pol->plid] = NULL; 1778 1779 mutex_unlock(&blkcg_pol_mutex); 1780out_unlock: 1781 mutex_unlock(&blkcg_pol_register_mutex); 1782} 1783EXPORT_SYMBOL_GPL(blkcg_policy_unregister); 1784 1785/* 1786 * Scale the accumulated delay based on how long it has been since we updated 1787 * the delay. We only call this when we are adding delay, in case it's been a 1788 * while since we added delay, and when we are checking to see if we need to 1789 * delay a task, to account for any delays that may have occurred. 1790 */ 1791static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now) 1792{ 1793 u64 old = atomic64_read(&blkg->delay_start); 1794 1795 /* negative use_delay means no scaling, see blkcg_set_delay() */ 1796 if (atomic_read(&blkg->use_delay) < 0) 1797 return; 1798 1799 /* 1800 * We only want to scale down every second. The idea here is that we 1801 * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain 1802 * time window. We only want to throttle tasks for recent delay that 1803 * has occurred, in 1 second time windows since that's the maximum 1804 * things can be throttled. We save the current delay window in 1805 * blkg->last_delay so we know what amount is still left to be charged 1806 * to the blkg from this point onward. blkg->last_use keeps track of 1807 * the use_delay counter. The idea is if we're unthrottling the blkg we 1808 * are ok with whatever is happening now, and we can take away more of 1809 * the accumulated delay as we've already throttled enough that 1810 * everybody is happy with their IO latencies. 1811 */ 1812 if (time_before64(old + NSEC_PER_SEC, now) && 1813 atomic64_try_cmpxchg(&blkg->delay_start, &old, now)) { 1814 u64 cur = atomic64_read(&blkg->delay_nsec); 1815 u64 sub = min_t(u64, blkg->last_delay, now - old); 1816 int cur_use = atomic_read(&blkg->use_delay); 1817 1818 /* 1819 * We've been unthrottled, subtract a larger chunk of our 1820 * accumulated delay. 1821 */ 1822 if (cur_use < blkg->last_use) 1823 sub = max_t(u64, sub, blkg->last_delay >> 1); 1824 1825 /* 1826 * This shouldn't happen, but handle it anyway. Our delay_nsec 1827 * should only ever be growing except here where we subtract out 1828 * min(last_delay, 1 second), but lord knows bugs happen and I'd 1829 * rather not end up with negative numbers. 1830 */ 1831 if (unlikely(cur < sub)) { 1832 atomic64_set(&blkg->delay_nsec, 0); 1833 blkg->last_delay = 0; 1834 } else { 1835 atomic64_sub(sub, &blkg->delay_nsec); 1836 blkg->last_delay = cur - sub; 1837 } 1838 blkg->last_use = cur_use; 1839 } 1840} 1841 1842/* 1843 * This is called when we want to actually walk up the hierarchy and check to 1844 * see if we need to throttle, and then actually throttle if there is some 1845 * accumulated delay. This should only be called upon return to user space so 1846 * we're not holding some lock that would induce a priority inversion. 1847 */ 1848static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay) 1849{ 1850 unsigned long pflags; 1851 bool clamp; 1852 u64 now = blk_time_get_ns(); 1853 u64 exp; 1854 u64 delay_nsec = 0; 1855 int tok; 1856 1857 while (blkg->parent) { 1858 int use_delay = atomic_read(&blkg->use_delay); 1859 1860 if (use_delay) { 1861 u64 this_delay; 1862 1863 blkcg_scale_delay(blkg, now); 1864 this_delay = atomic64_read(&blkg->delay_nsec); 1865 if (this_delay > delay_nsec) { 1866 delay_nsec = this_delay; 1867 clamp = use_delay > 0; 1868 } 1869 } 1870 blkg = blkg->parent; 1871 } 1872 1873 if (!delay_nsec) 1874 return; 1875 1876 /* 1877 * Let's not sleep for all eternity if we've amassed a huge delay. 1878 * Swapping or metadata IO can accumulate 10's of seconds worth of 1879 * delay, and we want userspace to be able to do _something_ so cap the 1880 * delays at 0.25s. If there's 10's of seconds worth of delay then the 1881 * tasks will be delayed for 0.25 second for every syscall. If 1882 * blkcg_set_delay() was used as indicated by negative use_delay, the 1883 * caller is responsible for regulating the range. 1884 */ 1885 if (clamp) 1886 delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC); 1887 1888 if (use_memdelay) 1889 psi_memstall_enter(&pflags); 1890 1891 exp = ktime_add_ns(now, delay_nsec); 1892 tok = io_schedule_prepare(); 1893 do { 1894 __set_current_state(TASK_KILLABLE); 1895 if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS)) 1896 break; 1897 } while (!fatal_signal_pending(current)); 1898 io_schedule_finish(tok); 1899 1900 if (use_memdelay) 1901 psi_memstall_leave(&pflags); 1902} 1903 1904/** 1905 * blkcg_maybe_throttle_current - throttle the current task if it has been marked 1906 * 1907 * This is only called if we've been marked with set_notify_resume(). Obviously 1908 * we can be set_notify_resume() for reasons other than blkcg throttling, so we 1909 * check to see if current->throttle_disk is set and if not this doesn't do 1910 * anything. This should only ever be called by the resume code, it's not meant 1911 * to be called by people willy-nilly as it will actually do the work to 1912 * throttle the task if it is setup for throttling. 1913 */ 1914void blkcg_maybe_throttle_current(void) 1915{ 1916 struct gendisk *disk = current->throttle_disk; 1917 struct blkcg *blkcg; 1918 struct blkcg_gq *blkg; 1919 bool use_memdelay = current->use_memdelay; 1920 1921 if (!disk) 1922 return; 1923 1924 current->throttle_disk = NULL; 1925 current->use_memdelay = false; 1926 1927 rcu_read_lock(); 1928 blkcg = css_to_blkcg(blkcg_css()); 1929 if (!blkcg) 1930 goto out; 1931 blkg = blkg_lookup(blkcg, disk->queue); 1932 if (!blkg) 1933 goto out; 1934 if (!blkg_tryget(blkg)) 1935 goto out; 1936 rcu_read_unlock(); 1937 1938 blkcg_maybe_throttle_blkg(blkg, use_memdelay); 1939 blkg_put(blkg); 1940 put_disk(disk); 1941 return; 1942out: 1943 rcu_read_unlock(); 1944} 1945 1946/** 1947 * blkcg_schedule_throttle - this task needs to check for throttling 1948 * @disk: disk to throttle 1949 * @use_memdelay: do we charge this to memory delay for PSI 1950 * 1951 * This is called by the IO controller when we know there's delay accumulated 1952 * for the blkg for this task. We do not pass the blkg because there are places 1953 * we call this that may not have that information, the swapping code for 1954 * instance will only have a block_device at that point. This set's the 1955 * notify_resume for the task to check and see if it requires throttling before 1956 * returning to user space. 1957 * 1958 * We will only schedule once per syscall. You can call this over and over 1959 * again and it will only do the check once upon return to user space, and only 1960 * throttle once. If the task needs to be throttled again it'll need to be 1961 * re-set at the next time we see the task. 1962 */ 1963void blkcg_schedule_throttle(struct gendisk *disk, bool use_memdelay) 1964{ 1965 if (unlikely(current->flags & PF_KTHREAD)) 1966 return; 1967 1968 if (current->throttle_disk != disk) { 1969 if (test_bit(GD_DEAD, &disk->state)) 1970 return; 1971 get_device(disk_to_dev(disk)); 1972 1973 if (current->throttle_disk) 1974 put_disk(current->throttle_disk); 1975 current->throttle_disk = disk; 1976 } 1977 1978 if (use_memdelay) 1979 current->use_memdelay = use_memdelay; 1980 set_notify_resume(current); 1981} 1982 1983/** 1984 * blkcg_add_delay - add delay to this blkg 1985 * @blkg: blkg of interest 1986 * @now: the current time in nanoseconds 1987 * @delta: how many nanoseconds of delay to add 1988 * 1989 * Charge @delta to the blkg's current delay accumulation. This is used to 1990 * throttle tasks if an IO controller thinks we need more throttling. 1991 */ 1992void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta) 1993{ 1994 if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0)) 1995 return; 1996 blkcg_scale_delay(blkg, now); 1997 atomic64_add(delta, &blkg->delay_nsec); 1998} 1999 2000/** 2001 * blkg_tryget_closest - try and get a blkg ref on the closet blkg 2002 * @bio: target bio 2003 * @css: target css 2004 * 2005 * As the failure mode here is to walk up the blkg tree, this ensure that the 2006 * blkg->parent pointers are always valid. This returns the blkg that it ended 2007 * up taking a reference on or %NULL if no reference was taken. 2008 */ 2009static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio, 2010 struct cgroup_subsys_state *css) 2011{ 2012 struct blkcg_gq *blkg, *ret_blkg = NULL; 2013 2014 rcu_read_lock(); 2015 blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_bdev->bd_disk); 2016 while (blkg) { 2017 if (blkg_tryget(blkg)) { 2018 ret_blkg = blkg; 2019 break; 2020 } 2021 blkg = blkg->parent; 2022 } 2023 rcu_read_unlock(); 2024 2025 return ret_blkg; 2026} 2027 2028/** 2029 * bio_associate_blkg_from_css - associate a bio with a specified css 2030 * @bio: target bio 2031 * @css: target css 2032 * 2033 * Associate @bio with the blkg found by combining the css's blkg and the 2034 * request_queue of the @bio. An association failure is handled by walking up 2035 * the blkg tree. Therefore, the blkg associated can be anything between @blkg 2036 * and q->root_blkg. This situation only happens when a cgroup is dying and 2037 * then the remaining bios will spill to the closest alive blkg. 2038 * 2039 * A reference will be taken on the blkg and will be released when @bio is 2040 * freed. 2041 */ 2042void bio_associate_blkg_from_css(struct bio *bio, 2043 struct cgroup_subsys_state *css) 2044{ 2045 if (bio->bi_blkg) 2046 blkg_put(bio->bi_blkg); 2047 2048 if (css && css->parent) { 2049 bio->bi_blkg = blkg_tryget_closest(bio, css); 2050 } else { 2051 blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg); 2052 bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg; 2053 } 2054} 2055EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); 2056 2057/** 2058 * bio_associate_blkg - associate a bio with a blkg 2059 * @bio: target bio 2060 * 2061 * Associate @bio with the blkg found from the bio's css and request_queue. 2062 * If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is 2063 * already associated, the css is reused and association redone as the 2064 * request_queue may have changed. 2065 */ 2066void bio_associate_blkg(struct bio *bio) 2067{ 2068 struct cgroup_subsys_state *css; 2069 2070 if (blk_op_is_passthrough(bio->bi_opf)) 2071 return; 2072 2073 rcu_read_lock(); 2074 2075 if (bio->bi_blkg) 2076 css = bio_blkcg_css(bio); 2077 else 2078 css = blkcg_css(); 2079 2080 bio_associate_blkg_from_css(bio, css); 2081 2082 rcu_read_unlock(); 2083} 2084EXPORT_SYMBOL_GPL(bio_associate_blkg); 2085 2086/** 2087 * bio_clone_blkg_association - clone blkg association from src to dst bio 2088 * @dst: destination bio 2089 * @src: source bio 2090 */ 2091void bio_clone_blkg_association(struct bio *dst, struct bio *src) 2092{ 2093 if (src->bi_blkg) 2094 bio_associate_blkg_from_css(dst, bio_blkcg_css(src)); 2095} 2096EXPORT_SYMBOL_GPL(bio_clone_blkg_association); 2097 2098static int blk_cgroup_io_type(struct bio *bio) 2099{ 2100 if (op_is_discard(bio->bi_opf)) 2101 return BLKG_IOSTAT_DISCARD; 2102 if (op_is_write(bio->bi_opf)) 2103 return BLKG_IOSTAT_WRITE; 2104 return BLKG_IOSTAT_READ; 2105} 2106 2107void blk_cgroup_bio_start(struct bio *bio) 2108{ 2109 struct blkcg *blkcg = bio->bi_blkg->blkcg; 2110 int rwd = blk_cgroup_io_type(bio), cpu; 2111 struct blkg_iostat_set *bis; 2112 unsigned long flags; 2113 2114 if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) 2115 return; 2116 2117 /* Root-level stats are sourced from system-wide IO stats */ 2118 if (!cgroup_parent(blkcg->css.cgroup)) 2119 return; 2120 2121 cpu = get_cpu(); 2122 bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu); 2123 flags = u64_stats_update_begin_irqsave(&bis->sync); 2124 2125 /* 2126 * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split 2127 * bio and we would have already accounted for the size of the bio. 2128 */ 2129 if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { 2130 bio_set_flag(bio, BIO_CGROUP_ACCT); 2131 bis->cur.bytes[rwd] += bio->bi_iter.bi_size; 2132 } 2133 bis->cur.ios[rwd]++; 2134 2135 /* 2136 * If the iostat_cpu isn't in a lockless list, put it into the 2137 * list to indicate that a stat update is pending. 2138 */ 2139 if (!READ_ONCE(bis->lqueued)) { 2140 struct llist_head *lhead = this_cpu_ptr(blkcg->lhead); 2141 2142 llist_add(&bis->lnode, lhead); 2143 WRITE_ONCE(bis->lqueued, true); 2144 } 2145 2146 u64_stats_update_end_irqrestore(&bis->sync, flags); 2147 cgroup_rstat_updated(blkcg->css.cgroup, cpu); 2148 put_cpu(); 2149} 2150 2151bool blk_cgroup_congested(void) 2152{ 2153 struct cgroup_subsys_state *css; 2154 bool ret = false; 2155 2156 rcu_read_lock(); 2157 for (css = blkcg_css(); css; css = css->parent) { 2158 if (atomic_read(&css->cgroup->congestion_count)) { 2159 ret = true; 2160 break; 2161 } 2162 } 2163 rcu_read_unlock(); 2164 return ret; 2165} 2166 2167module_param(blkcg_debug_stats, bool, 0644); 2168MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not"); 2169