block/blk-cgroup.c

   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
  37 /*
  38  * blkcg_pol_mutex protects blkcg_policy[] and policy [de]activation.
  39  * blkcg_pol_register_mutex nests outside of it and synchronizes entire
  40  * policy [un]register operations including cgroup file additions /
  41  * removals.  Putting cgroup file registration outside blkcg_pol_mutex
  42  * allows grabbing it from cgroup callbacks.
  43  */
  44 static DEFINE_MUTEX(blkcg_pol_register_mutex);
  45 static DEFINE_MUTEX(blkcg_pol_mutex);
  46
  47 struct blkcg blkcg_root;
  48 EXPORT_SYMBOL_GPL(blkcg_root);
  49
  50 struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
  51 EXPORT_SYMBOL_GPL(blkcg_root_css);
  52
  53 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
  54
  55 static LIST_HEAD(all_blkcgs);           /* protected by blkcg_pol_mutex */
  56
  57 bool blkcg_debug_stats = false;
  58 static struct workqueue_struct *blkcg_punt_bio_wq;
  59
  60 #define BLKG_DESTROY_BATCH_SIZE  64
  61
  62 static bool blkcg_policy_enabled(struct request_queue *q,
  63                                  const struct blkcg_policy *pol)
  64 {
  65         return pol && test_bit(pol->plid, q->blkcg_pols);
  66 }
  67
  68 /**
  69  * blkg_free - free a blkg
  70  * @blkg: blkg to free
  71  *
  72  * Free @blkg which may be partially allocated.
  73  */
  74 static void blkg_free(struct blkcg_gq *blkg)
  75 {
  76         int i;
  77
  78         if (!blkg)
  79                 return;
  80
  81         for (i = 0; i < BLKCG_MAX_POLS; i++)
  82                 if (blkg->pd[i])
  83                         blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
  84
  85         if (blkg->q)
  86                 blk_put_queue(blkg->q);
  87         free_percpu(blkg->iostat_cpu);
  88         percpu_ref_exit(&blkg->refcnt);
  89         kfree(blkg);
  90 }
  91
  92 static void __blkg_release(struct rcu_head *rcu)
  93 {
  94         struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
  95
  96         WARN_ON(!bio_list_empty(&blkg->async_bios));
  97
  98         /* release the blkcg and parent blkg refs this blkg has been holding */
  99         css_put(&blkg->blkcg->css);
 100         if (blkg->parent)
 101                 blkg_put(blkg->parent);
 102         blkg_free(blkg);
 103 }
 104
 105 /*
 106  * A group is RCU protected, but having an rcu lock does not mean that one
 107  * can access all the fields of blkg and assume these are valid.  For
 108  * example, don't try to follow throtl_data and request queue links.
 109  *
 110  * Having a reference to blkg under an rcu allows accesses to only values
 111  * local to groups like group stats and group rate limits.
 112  */
 113 static void blkg_release(struct percpu_ref *ref)
 114 {
 115         struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
 116
 117         call_rcu(&blkg->rcu_head, __blkg_release);
 118 }
 119
 120 static void blkg_async_bio_workfn(struct work_struct *work)
 121 {
 122         struct blkcg_gq *blkg = container_of(work, struct blkcg_gq,
 123                                              async_bio_work);
 124         struct bio_list bios = BIO_EMPTY_LIST;
 125         struct bio *bio;
 126         struct blk_plug plug;
 127         bool need_plug = false;
 128
 129         /* as long as there are pending bios, @blkg can't go away */
 130         spin_lock_bh(&blkg->async_bio_lock);
 131         bio_list_merge(&bios, &blkg->async_bios);
 132         bio_list_init(&blkg->async_bios);
 133         spin_unlock_bh(&blkg->async_bio_lock);
 134
 135         /* start plug only when bio_list contains at least 2 bios */
 136         if (bios.head && bios.head->bi_next) {
 137                 need_plug = true;
 138                 blk_start_plug(&plug);
 139         }
 140         while ((bio = bio_list_pop(&bios)))
 141                 submit_bio(bio);
 142         if (need_plug)
 143                 blk_finish_plug(&plug);
 144 }
 145
 146 /**
 147  * blkg_alloc - allocate a blkg
 148  * @blkcg: block cgroup the new blkg is associated with
 149  * @q: request_queue the new blkg is associated with
 150  * @gfp_mask: allocation mask to use
 151  *
 152  * Allocate a new blkg assocating @blkcg and @q.
 153  */
 154 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 155                                    gfp_t gfp_mask)
 156 {
 157         struct blkcg_gq *blkg;
 158         int i, cpu;
 159
 160         /* alloc and init base part */
 161         blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
 162         if (!blkg)
 163                 return NULL;
 164
 165         if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
 166                 goto err_free;
 167
 168         blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
 169         if (!blkg->iostat_cpu)
 170                 goto err_free;
 171
 172         if (!blk_get_queue(q))
 173                 goto err_free;
 174
 175         blkg->q = q;
 176         INIT_LIST_HEAD(&blkg->q_node);
 177         spin_lock_init(&blkg->async_bio_lock);
 178         bio_list_init(&blkg->async_bios);
 179         INIT_WORK(&blkg->async_bio_work, blkg_async_bio_workfn);
 180         blkg->blkcg = blkcg;
 181
 182         u64_stats_init(&blkg->iostat.sync);
 183         for_each_possible_cpu(cpu)
 184                 u64_stats_init(&per_cpu_ptr(blkg->iostat_cpu, cpu)->sync);
 185
 186         for (i = 0; i < BLKCG_MAX_POLS; i++) {
 187                 struct blkcg_policy *pol = blkcg_policy[i];
 188                 struct blkg_policy_data *pd;
 189
 190                 if (!blkcg_policy_enabled(q, pol))
 191                         continue;
 192
 193                 /* alloc per-policy data and attach it to blkg */
 194                 pd = pol->pd_alloc_fn(gfp_mask, q, blkcg);
 195                 if (!pd)
 196                         goto err_free;
 197
 198                 blkg->pd[i] = pd;
 199                 pd->blkg = blkg;
 200                 pd->plid = i;
 201         }
 202
 203         return blkg;
 204
 205 err_free:
 206         blkg_free(blkg);
 207         return NULL;
 208 }
 209
 210 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
 211                                       struct request_queue *q, bool update_hint)
 212 {
 213         struct blkcg_gq *blkg;
 214
 215         /*
 216          * Hint didn't match.  Look up from the radix tree.  Note that the
 217          * hint can only be updated under queue_lock as otherwise @blkg
 218          * could have already been removed from blkg_tree.  The caller is
 219          * responsible for grabbing queue_lock if @update_hint.
 220          */
 221         blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
 222         if (blkg && blkg->q == q) {
 223                 if (update_hint) {
 224                         lockdep_assert_held(&q->queue_lock);
 225                         rcu_assign_pointer(blkcg->blkg_hint, blkg);
 226                 }
 227                 return blkg;
 228         }
 229
 230         return NULL;
 231 }
 232 EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
 233
 234 /*
 235  * If @new_blkg is %NULL, this function tries to allocate a new one as
 236  * necessary using %GFP_NOWAIT.  @new_blkg is always consumed on return.
 237  */
 238 static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 239                                     struct request_queue *q,
 240                                     struct blkcg_gq *new_blkg)
 241 {
 242         struct blkcg_gq *blkg;
 243         int i, ret;
 244
 245         WARN_ON_ONCE(!rcu_read_lock_held());
 246         lockdep_assert_held(&q->queue_lock);
 247
 248         /* request_queue is dying, do not create/recreate a blkg */
 249         if (blk_queue_dying(q)) {
 250                 ret = -ENODEV;
 251                 goto err_free_blkg;
 252         }
 253
 254         /* blkg holds a reference to blkcg */
 255         if (!css_tryget_online(&blkcg->css)) {
 256                 ret = -ENODEV;
 257                 goto err_free_blkg;
 258         }
 259
 260         /* allocate */
 261         if (!new_blkg) {
 262                 new_blkg = blkg_alloc(blkcg, q, GFP_NOWAIT | __GFP_NOWARN);
 263                 if (unlikely(!new_blkg)) {
 264                         ret = -ENOMEM;
 265                         goto err_put_css;
 266                 }
 267         }
 268         blkg = new_blkg;
 269
 270         /* link parent */
 271         if (blkcg_parent(blkcg)) {
 272                 blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
 273                 if (WARN_ON_ONCE(!blkg->parent)) {
 274                         ret = -ENODEV;
 275                         goto err_put_css;
 276                 }
 277                 blkg_get(blkg->parent);
 278         }
 279
 280         /* invoke per-policy init */
 281         for (i = 0; i < BLKCG_MAX_POLS; i++) {
 282                 struct blkcg_policy *pol = blkcg_policy[i];
 283
 284                 if (blkg->pd[i] && pol->pd_init_fn)
 285                         pol->pd_init_fn(blkg->pd[i]);
 286         }
 287
 288         /* insert */
 289         spin_lock(&blkcg->lock);
 290         ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
 291         if (likely(!ret)) {
 292                 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
 293                 list_add(&blkg->q_node, &q->blkg_list);
 294
 295                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
 296                         struct blkcg_policy *pol = blkcg_policy[i];
 297
 298                         if (blkg->pd[i] && pol->pd_online_fn)
 299                                 pol->pd_online_fn(blkg->pd[i]);
 300                 }
 301         }
 302         blkg->online = true;
 303         spin_unlock(&blkcg->lock);
 304
 305         if (!ret)
 306                 return blkg;
 307
 308         /* @blkg failed fully initialized, use the usual release path */
 309         blkg_put(blkg);
 310         return ERR_PTR(ret);
 311
 312 err_put_css:
 313         css_put(&blkcg->css);
 314 err_free_blkg:
 315         blkg_free(new_blkg);
 316         return ERR_PTR(ret);
 317 }
 318
 319 /**
 320  * blkg_lookup_create - lookup blkg, try to create one if not there
 321  * @blkcg: blkcg of interest
 322  * @q: request_queue of interest
 323  *
 324  * Lookup blkg for the @blkcg - @q pair.  If it doesn't exist, try to
 325  * create one.  blkg creation is performed recursively from blkcg_root such
 326  * that all non-root blkg's have access to the parent blkg.  This function
 327  * should be called under RCU read lock and takes @q->queue_lock.
 328  *
 329  * Returns the blkg or the closest blkg if blkg_create() fails as it walks
 330  * down from root.
 331  */
 332 static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 333                 struct request_queue *q)
 334 {
 335         struct blkcg_gq *blkg;
 336         unsigned long flags;
 337
 338         WARN_ON_ONCE(!rcu_read_lock_held());
 339
 340         blkg = blkg_lookup(blkcg, q);
 341         if (blkg)
 342                 return blkg;
 343
 344         spin_lock_irqsave(&q->queue_lock, flags);
 345         blkg = __blkg_lookup(blkcg, q, true);
 346         if (blkg)
 347                 goto found;
 348
 349         /*
 350          * Create blkgs walking down from blkcg_root to @blkcg, so that all
 351          * non-root blkgs have access to their parents.  Returns the closest
 352          * blkg to the intended blkg should blkg_create() fail.
 353          */
 354         while (true) {
 355                 struct blkcg *pos = blkcg;
 356                 struct blkcg *parent = blkcg_parent(blkcg);
 357                 struct blkcg_gq *ret_blkg = q->root_blkg;
 358
 359                 while (parent) {
 360                         blkg = __blkg_lookup(parent, q, false);
 361                         if (blkg) {
 362                                 /* remember closest blkg */
 363                                 ret_blkg = blkg;
 364                                 break;
 365                         }
 366                         pos = parent;
 367                         parent = blkcg_parent(parent);
 368                 }
 369
 370                 blkg = blkg_create(pos, q, NULL);
 371                 if (IS_ERR(blkg)) {
 372                         blkg = ret_blkg;
 373                         break;
 374                 }
 375                 if (pos == blkcg)
 376                         break;
 377         }
 378
 379 found:
 380         spin_unlock_irqrestore(&q->queue_lock, flags);
 381         return blkg;
 382 }
 383
 384 static void blkg_destroy(struct blkcg_gq *blkg)
 385 {
 386         struct blkcg *blkcg = blkg->blkcg;
 387         int i;
 388
 389         lockdep_assert_held(&blkg->q->queue_lock);
 390         lockdep_assert_held(&blkcg->lock);
 391
 392         /* Something wrong if we are trying to remove same group twice */
 393         WARN_ON_ONCE(list_empty(&blkg->q_node));
 394         WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
 395
 396         for (i = 0; i < BLKCG_MAX_POLS; i++) {
 397                 struct blkcg_policy *pol = blkcg_policy[i];
 398
 399                 if (blkg->pd[i] && pol->pd_offline_fn)
 400                         pol->pd_offline_fn(blkg->pd[i]);
 401         }
 402
 403         blkg->online = false;
 404
 405         radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
 406         list_del_init(&blkg->q_node);
 407         hlist_del_init_rcu(&blkg->blkcg_node);
 408
 409         /*
 410          * Both setting lookup hint to and clearing it from @blkg are done
 411          * under queue_lock.  If it's not pointing to @blkg now, it never
 412          * will.  Hint assignment itself can race safely.
 413          */
 414         if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
 415                 rcu_assign_pointer(blkcg->blkg_hint, NULL);
 416
 417         /*
 418          * Put the reference taken at the time of creation so that when all
 419          * queues are gone, group can be destroyed.
 420          */
 421         percpu_ref_kill(&blkg->refcnt);
 422 }
 423
 424 /**
 425  * blkg_destroy_all - destroy all blkgs associated with a request_queue
 426  * @q: request_queue of interest
 427  *
 428  * Destroy all blkgs associated with @q.
 429  */
 430 static void blkg_destroy_all(struct request_queue *q)
 431 {
 432         struct blkcg_gq *blkg, *n;
 433         int count = BLKG_DESTROY_BATCH_SIZE;
 434
 435 restart:
 436         spin_lock_irq(&q->queue_lock);
 437         list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
 438                 struct blkcg *blkcg = blkg->blkcg;
 439
 440                 spin_lock(&blkcg->lock);
 441                 blkg_destroy(blkg);
 442                 spin_unlock(&blkcg->lock);
 443
 444                 /*
 445                  * in order to avoid holding the spin lock for too long, release
 446                  * it when a batch of blkgs are destroyed.
 447                  */
 448                 if (!(--count)) {
 449                         count = BLKG_DESTROY_BATCH_SIZE;
 450                         spin_unlock_irq(&q->queue_lock);
 451                         cond_resched();
 452                         goto restart;
 453                 }
 454         }
 455
 456         q->root_blkg = NULL;
 457         spin_unlock_irq(&q->queue_lock);
 458 }
 459
 460 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
 461                              struct cftype *cftype, u64 val)
 462 {
 463         struct blkcg *blkcg = css_to_blkcg(css);
 464         struct blkcg_gq *blkg;
 465         int i, cpu;
 466
 467         mutex_lock(&blkcg_pol_mutex);
 468         spin_lock_irq(&blkcg->lock);
 469
 470         /*
 471          * Note that stat reset is racy - it doesn't synchronize against
 472          * stat updates.  This is a debug feature which shouldn't exist
 473          * anyway.  If you get hit by a race, retry.
 474          */
 475         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
 476                 for_each_possible_cpu(cpu) {
 477                         struct blkg_iostat_set *bis =
 478                                 per_cpu_ptr(blkg->iostat_cpu, cpu);
 479                         memset(bis, 0, sizeof(*bis));
 480                 }
 481                 memset(&blkg->iostat, 0, sizeof(blkg->iostat));
 482
 483                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
 484                         struct blkcg_policy *pol = blkcg_policy[i];
 485
 486                         if (blkg->pd[i] && pol->pd_reset_stats_fn)
 487                                 pol->pd_reset_stats_fn(blkg->pd[i]);
 488                 }
 489         }
 490
 491         spin_unlock_irq(&blkcg->lock);
 492         mutex_unlock(&blkcg_pol_mutex);
 493         return 0;
 494 }
 495
 496 const char *blkg_dev_name(struct blkcg_gq *blkg)
 497 {
 498         if (!blkg->q->disk || !blkg->q->disk->bdi->dev)
 499                 return NULL;
 500         return bdi_dev_name(blkg->q->disk->bdi);
 501 }
 502
 503 /**
 504  * blkcg_print_blkgs - helper for printing per-blkg data
 505  * @sf: seq_file to print to
 506  * @blkcg: blkcg of interest
 507  * @prfill: fill function to print out a blkg
 508  * @pol: policy in question
 509  * @data: data to be passed to @prfill
 510  * @show_total: to print out sum of prfill return values or not
 511  *
 512  * This function invokes @prfill on each blkg of @blkcg if pd for the
 513  * policy specified by @pol exists.  @prfill is invoked with @sf, the
 514  * policy data and @data and the matching queue lock held.  If @show_total
 515  * is %true, the sum of the return values from @prfill is printed with
 516  * "Total" label at the end.
 517  *
 518  * This is to be used to construct print functions for
 519  * cftype->read_seq_string method.
 520  */
 521 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 522                        u64 (*prfill)(struct seq_file *,
 523                                      struct blkg_policy_data *, int),
 524                        const struct blkcg_policy *pol, int data,
 525                        bool show_total)
 526 {
 527         struct blkcg_gq *blkg;
 528         u64 total = 0;
 529
 530         rcu_read_lock();
 531         hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
 532                 spin_lock_irq(&blkg->q->queue_lock);
 533                 if (blkcg_policy_enabled(blkg->q, pol))
 534                         total += prfill(sf, blkg->pd[pol->plid], data);
 535                 spin_unlock_irq(&blkg->q->queue_lock);
 536         }
 537         rcu_read_unlock();
 538
 539         if (show_total)
 540                 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
 541 }
 542 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
 543
 544 /**
 545  * __blkg_prfill_u64 - prfill helper for a single u64 value
 546  * @sf: seq_file to print to
 547  * @pd: policy private data of interest
 548  * @v: value to print
 549  *
 550  * Print @v to @sf for the device assocaited with @pd.
 551  */
 552 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
 553 {
 554         const char *dname = blkg_dev_name(pd->blkg);
 555
 556         if (!dname)
 557                 return 0;
 558
 559         seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
 560         return v;
 561 }
 562 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
 563
 564 /* Performs queue bypass and policy enabled checks then looks up blkg. */
 565 static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
 566                                           const struct blkcg_policy *pol,
 567                                           struct request_queue *q)
 568 {
 569         WARN_ON_ONCE(!rcu_read_lock_held());
 570         lockdep_assert_held(&q->queue_lock);
 571
 572         if (!blkcg_policy_enabled(q, pol))
 573                 return ERR_PTR(-EOPNOTSUPP);
 574         return __blkg_lookup(blkcg, q, true /* update_hint */);
 575 }
 576
 577 /**
 578  * blkcg_conf_open_bdev - parse and open bdev for per-blkg config update
 579  * @inputp: input string pointer
 580  *
 581  * Parse the device node prefix part, MAJ:MIN, of per-blkg config update
 582  * from @input and get and return the matching bdev.  *@inputp is
 583  * updated to point past the device node prefix.  Returns an ERR_PTR()
 584  * value on error.
 585  *
 586  * Use this function iff blkg_conf_prep() can't be used for some reason.
 587  */
 588 struct block_device *blkcg_conf_open_bdev(char **inputp)
 589 {
 590         char *input = *inputp;
 591         unsigned int major, minor;
 592         struct block_device *bdev;
 593         int key_len;
 594
 595         if (sscanf(input, "%u:%u%n", &major, &minor, &key_len) != 2)
 596                 return ERR_PTR(-EINVAL);
 597
 598         input += key_len;
 599         if (!isspace(*input))
 600                 return ERR_PTR(-EINVAL);
 601         input = skip_spaces(input);
 602
 603         bdev = blkdev_get_no_open(MKDEV(major, minor));
 604         if (!bdev)
 605                 return ERR_PTR(-ENODEV);
 606         if (bdev_is_partition(bdev)) {
 607                 blkdev_put_no_open(bdev);
 608                 return ERR_PTR(-ENODEV);
 609         }
 610
 611         *inputp = input;
 612         return bdev;
 613 }
 614
 615 /**
 616  * blkg_conf_prep - parse and prepare for per-blkg config update
 617  * @blkcg: target block cgroup
 618  * @pol: target policy
 619  * @input: input string
 620  * @ctx: blkg_conf_ctx to be filled
 621  *
 622  * Parse per-blkg config update from @input and initialize @ctx with the
 623  * result.  @ctx->blkg points to the blkg to be updated and @ctx->body the
 624  * part of @input following MAJ:MIN.  This function returns with RCU read
 625  * lock and queue lock held and must be paired with blkg_conf_finish().
 626  */
 627 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 628                    char *input, struct blkg_conf_ctx *ctx)
 629         __acquires(rcu) __acquires(&bdev->bd_queue->queue_lock)
 630 {
 631         struct block_device *bdev;
 632         struct request_queue *q;
 633         struct blkcg_gq *blkg;
 634         int ret;
 635
 636         bdev = blkcg_conf_open_bdev(&input);
 637         if (IS_ERR(bdev))
 638                 return PTR_ERR(bdev);
 639
 640         q = bdev_get_queue(bdev);
 641
 642         /*
 643          * blkcg_deactivate_policy() requires queue to be frozen, we can grab
 644          * q_usage_counter to prevent concurrent with blkcg_deactivate_policy().
 645          */
 646         ret = blk_queue_enter(q, 0);
 647         if (ret)
 648                 goto fail;
 649
 650         rcu_read_lock();
 651         spin_lock_irq(&q->queue_lock);
 652
 653         blkg = blkg_lookup_check(blkcg, pol, q);
 654         if (IS_ERR(blkg)) {
 655                 ret = PTR_ERR(blkg);
 656                 goto fail_unlock;
 657         }
 658
 659         if (blkg)
 660                 goto success;
 661
 662         /*
 663          * Create blkgs walking down from blkcg_root to @blkcg, so that all
 664          * non-root blkgs have access to their parents.
 665          */
 666         while (true) {
 667                 struct blkcg *pos = blkcg;
 668                 struct blkcg *parent;
 669                 struct blkcg_gq *new_blkg;
 670
 671                 parent = blkcg_parent(blkcg);
 672                 while (parent && !__blkg_lookup(parent, q, false)) {
 673                         pos = parent;
 674                         parent = blkcg_parent(parent);
 675                 }
 676
 677                 /* Drop locks to do new blkg allocation with GFP_KERNEL. */
 678                 spin_unlock_irq(&q->queue_lock);
 679                 rcu_read_unlock();
 680
 681                 new_blkg = blkg_alloc(pos, q, GFP_KERNEL);
 682                 if (unlikely(!new_blkg)) {
 683                         ret = -ENOMEM;
 684                         goto fail_exit_queue;
 685                 }
 686
 687                 if (radix_tree_preload(GFP_KERNEL)) {
 688                         blkg_free(new_blkg);
 689                         ret = -ENOMEM;
 690                         goto fail_exit_queue;
 691                 }
 692
 693                 rcu_read_lock();
 694                 spin_lock_irq(&q->queue_lock);
 695
 696                 blkg = blkg_lookup_check(pos, pol, q);
 697                 if (IS_ERR(blkg)) {
 698                         ret = PTR_ERR(blkg);
 699                         blkg_free(new_blkg);
 700                         goto fail_preloaded;
 701                 }
 702
 703                 if (blkg) {
 704                         blkg_free(new_blkg);
 705                 } else {
 706                         blkg = blkg_create(pos, q, new_blkg);
 707                         if (IS_ERR(blkg)) {
 708                                 ret = PTR_ERR(blkg);
 709                                 goto fail_preloaded;
 710                         }
 711                 }
 712
 713                 radix_tree_preload_end();
 714
 715                 if (pos == blkcg)
 716                         goto success;
 717         }
 718 success:
 719         blk_queue_exit(q);
 720         ctx->bdev = bdev;
 721         ctx->blkg = blkg;
 722         ctx->body = input;
 723         return 0;
 724
 725 fail_preloaded:
 726         radix_tree_preload_end();
 727 fail_unlock:
 728         spin_unlock_irq(&q->queue_lock);
 729         rcu_read_unlock();
 730 fail_exit_queue:
 731         blk_queue_exit(q);
 732 fail:
 733         blkdev_put_no_open(bdev);
 734         /*
 735          * If queue was bypassing, we should retry.  Do so after a
 736          * short msleep().  It isn't strictly necessary but queue
 737          * can be bypassing for some time and it's always nice to
 738          * avoid busy looping.
 739          */
 740         if (ret == -EBUSY) {
 741                 msleep(10);
 742                 ret = restart_syscall();
 743         }
 744         return ret;
 745 }
 746 EXPORT_SYMBOL_GPL(blkg_conf_prep);
 747
 748 /**
 749  * blkg_conf_finish - finish up per-blkg config update
 750  * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
 751  *
 752  * Finish up after per-blkg config update.  This function must be paired
 753  * with blkg_conf_prep().
 754  */
 755 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
 756         __releases(&ctx->bdev->bd_queue->queue_lock) __releases(rcu)
 757 {
 758         spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);
 759         rcu_read_unlock();
 760         blkdev_put_no_open(ctx->bdev);
 761 }
 762 EXPORT_SYMBOL_GPL(blkg_conf_finish);
 763
 764 static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)
 765 {
 766         int i;
 767
 768         for (i = 0; i < BLKG_IOSTAT_NR; i++) {
 769                 dst->bytes[i] = src->bytes[i];
 770                 dst->ios[i] = src->ios[i];
 771         }
 772 }
 773
 774 static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)
 775 {
 776         int i;
 777
 778         for (i = 0; i < BLKG_IOSTAT_NR; i++) {
 779                 dst->bytes[i] += src->bytes[i];
 780                 dst->ios[i] += src->ios[i];
 781         }
 782 }
 783
 784 static void blkg_iostat_sub(struct blkg_iostat *dst, struct blkg_iostat *src)
 785 {
 786         int i;
 787
 788         for (i = 0; i < BLKG_IOSTAT_NR; i++) {
 789                 dst->bytes[i] -= src->bytes[i];
 790                 dst->ios[i] -= src->ios[i];
 791         }
 792 }
 793
 794 static void blkcg_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 795 {
 796         struct blkcg *blkcg = css_to_blkcg(css);
 797         struct blkcg_gq *blkg;
 798
 799         /* Root-level stats are sourced from system-wide IO stats */
 800         if (!cgroup_parent(css->cgroup))
 801                 return;
 802
 803         rcu_read_lock();
 804
 805         hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
 806                 struct blkcg_gq *parent = blkg->parent;
 807                 struct blkg_iostat_set *bisc = per_cpu_ptr(blkg->iostat_cpu, cpu);
 808                 struct blkg_iostat cur, delta;
 809                 unsigned long flags;
 810                 unsigned int seq;
 811
 812                 /* fetch the current per-cpu values */
 813                 do {
 814                         seq = u64_stats_fetch_begin(&bisc->sync);
 815                         blkg_iostat_set(&cur, &bisc->cur);
 816                 } while (u64_stats_fetch_retry(&bisc->sync, seq));
 817
 818                 /* propagate percpu delta to global */
 819                 flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
 820                 blkg_iostat_set(&delta, &cur);
 821                 blkg_iostat_sub(&delta, &bisc->last);
 822                 blkg_iostat_add(&blkg->iostat.cur, &delta);
 823                 blkg_iostat_add(&bisc->last, &delta);
 824                 u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
 825
 826                 /* propagate global delta to parent (unless that's root) */
 827                 if (parent && parent->parent) {
 828                         flags = u64_stats_update_begin_irqsave(&parent->iostat.sync);
 829                         blkg_iostat_set(&delta, &blkg->iostat.cur);
 830                         blkg_iostat_sub(&delta, &blkg->iostat.last);
 831                         blkg_iostat_add(&parent->iostat.cur, &delta);
 832                         blkg_iostat_add(&blkg->iostat.last, &delta);
 833                         u64_stats_update_end_irqrestore(&parent->iostat.sync, flags);
 834                 }
 835         }
 836
 837         rcu_read_unlock();
 838 }
 839
 840 /*
 841  * We source root cgroup stats from the system-wide stats to avoid
 842  * tracking the same information twice and incurring overhead when no
 843  * cgroups are defined. For that reason, cgroup_rstat_flush in
 844  * blkcg_print_stat does not actually fill out the iostat in the root
 845  * cgroup's blkcg_gq.
 846  *
 847  * However, we would like to re-use the printing code between the root and
 848  * non-root cgroups to the extent possible. For that reason, we simulate
 849  * flushing the root cgroup's stats by explicitly filling in the iostat
 850  * with disk level statistics.
 851  */
 852 static void blkcg_fill_root_iostats(void)
 853 {
 854         struct class_dev_iter iter;
 855         struct device *dev;
 856
 857         class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
 858         while ((dev = class_dev_iter_next(&iter))) {
 859                 struct block_device *bdev = dev_to_bdev(dev);
 860                 struct blkcg_gq *blkg =
 861                         blk_queue_root_blkg(bdev_get_queue(bdev));
 862                 struct blkg_iostat tmp;
 863                 int cpu;
 864                 unsigned long flags;
 865
 866                 memset(&tmp, 0, sizeof(tmp));
 867                 for_each_possible_cpu(cpu) {
 868                         struct disk_stats *cpu_dkstats;
 869
 870                         cpu_dkstats = per_cpu_ptr(bdev->bd_stats, cpu);
 871                         tmp.ios[BLKG_IOSTAT_READ] +=
 872                                 cpu_dkstats->ios[STAT_READ];
 873                         tmp.ios[BLKG_IOSTAT_WRITE] +=
 874                                 cpu_dkstats->ios[STAT_WRITE];
 875                         tmp.ios[BLKG_IOSTAT_DISCARD] +=
 876                                 cpu_dkstats->ios[STAT_DISCARD];
 877                         // convert sectors to bytes
 878                         tmp.bytes[BLKG_IOSTAT_READ] +=
 879                                 cpu_dkstats->sectors[STAT_READ] << 9;
 880                         tmp.bytes[BLKG_IOSTAT_WRITE] +=
 881                                 cpu_dkstats->sectors[STAT_WRITE] << 9;
 882                         tmp.bytes[BLKG_IOSTAT_DISCARD] +=
 883                                 cpu_dkstats->sectors[STAT_DISCARD] << 9;
 884                 }
 885
 886                 flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync);
 887                 blkg_iostat_set(&blkg->iostat.cur, &tmp);
 888                 u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
 889         }
 890 }
 891
 892 static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)
 893 {
 894         struct blkg_iostat_set *bis = &blkg->iostat;
 895         u64 rbytes, wbytes, rios, wios, dbytes, dios;
 896         bool has_stats = false;
 897         const char *dname;
 898         unsigned seq;
 899         int i;
 900
 901         if (!blkg->online)
 902                 return;
 903
 904         dname = blkg_dev_name(blkg);
 905         if (!dname)
 906                 return;
 907
 908         seq_printf(s, "%s ", dname);
 909
 910         do {
 911                 seq = u64_stats_fetch_begin(&bis->sync);
 912
 913                 rbytes = bis->cur.bytes[BLKG_IOSTAT_READ];
 914                 wbytes = bis->cur.bytes[BLKG_IOSTAT_WRITE];
 915                 dbytes = bis->cur.bytes[BLKG_IOSTAT_DISCARD];
 916                 rios = bis->cur.ios[BLKG_IOSTAT_READ];
 917                 wios = bis->cur.ios[BLKG_IOSTAT_WRITE];
 918                 dios = bis->cur.ios[BLKG_IOSTAT_DISCARD];
 919         } while (u64_stats_fetch_retry(&bis->sync, seq));
 920
 921         if (rbytes || wbytes || rios || wios) {
 922                 has_stats = true;
 923                 seq_printf(s, "rbytes=%llu wbytes=%llu rios=%llu wios=%llu dbytes=%llu dios=%llu",
 924                         rbytes, wbytes, rios, wios,
 925                         dbytes, dios);
 926         }
 927
 928         if (blkcg_debug_stats && atomic_read(&blkg->use_delay)) {
 929                 has_stats = true;
 930                 seq_printf(s, " use_delay=%d delay_nsec=%llu",
 931                         atomic_read(&blkg->use_delay),
 932                         atomic64_read(&blkg->delay_nsec));
 933         }
 934
 935         for (i = 0; i < BLKCG_MAX_POLS; i++) {
 936                 struct blkcg_policy *pol = blkcg_policy[i];
 937
 938                 if (!blkg->pd[i] || !pol->pd_stat_fn)
 939                         continue;
 940
 941                 if (pol->pd_stat_fn(blkg->pd[i], s))
 942                         has_stats = true;
 943         }
 944
 945         if (has_stats)
 946                 seq_printf(s, "\n");
 947 }
 948
 949 static int blkcg_print_stat(struct seq_file *sf, void *v)
 950 {
 951         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
 952         struct blkcg_gq *blkg;
 953
 954         if (!seq_css(sf)->parent)
 955                 blkcg_fill_root_iostats();
 956         else
 957                 cgroup_rstat_flush(blkcg->css.cgroup);
 958
 959         rcu_read_lock();
 960         hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
 961                 spin_lock_irq(&blkg->q->queue_lock);
 962                 blkcg_print_one_stat(blkg, sf);
 963                 spin_unlock_irq(&blkg->q->queue_lock);
 964         }
 965         rcu_read_unlock();
 966         return 0;
 967 }
 968
 969 static struct cftype blkcg_files[] = {
 970         {
 971                 .name = "stat",
 972                 .seq_show = blkcg_print_stat,
 973         },
 974         { }     /* terminate */
 975 };
 976
 977 static struct cftype blkcg_legacy_files[] = {
 978         {
 979                 .name = "reset_stats",
 980                 .write_u64 = blkcg_reset_stats,
 981         },
 982         { }     /* terminate */
 983 };
 984
 985 /*
 986  * blkcg destruction is a three-stage process.
 987  *
 988  * 1. Destruction starts.  The blkcg_css_offline() callback is invoked
 989  *    which offlines writeback.  Here we tie the next stage of blkg destruction
 990  *    to the completion of writeback associated with the blkcg.  This lets us
 991  *    avoid punting potentially large amounts of outstanding writeback to root
 992  *    while maintaining any ongoing policies.  The next stage is triggered when
 993  *    the nr_cgwbs count goes to zero.
 994  *
 995  * 2. When the nr_cgwbs count goes to zero, blkcg_destroy_blkgs() is called
 996  *    and handles the destruction of blkgs.  Here the css reference held by
 997  *    the blkg is put back eventually allowing blkcg_css_free() to be called.
 998  *    This work may occur in cgwb_release_workfn() on the cgwb_release
 999  *    workqueue.  Any submitted ios that fail to get the blkg ref will be
1000  *    punted to the root_blkg.
1001  *
1002  * 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called.
1003  *    This finally frees the blkcg.
1004  */
1005
1006 /**
1007  * blkcg_css_offline - cgroup css_offline callback
1008  * @css: css of interest
1009  *
1010  * This function is called when @css is about to go away.  Here the cgwbs are
1011  * offlined first and only once writeback associated with the blkcg has
1012  * finished do we start step 2 (see above).
1013  */
1014 static void blkcg_css_offline(struct cgroup_subsys_state *css)
1015 {
1016         struct blkcg *blkcg = css_to_blkcg(css);
1017
1018         /* this prevents anyone from attaching or migrating to this blkcg */
1019         wb_blkcg_offline(blkcg);
1020
1021         /* put the base online pin allowing step 2 to be triggered */
1022         blkcg_unpin_online(blkcg);
1023 }
1024
1025 /**
1026  * blkcg_destroy_blkgs - responsible for shooting down blkgs
1027  * @blkcg: blkcg of interest
1028  *
1029  * blkgs should be removed while holding both q and blkcg locks.  As blkcg lock
1030  * is nested inside q lock, this function performs reverse double lock dancing.
1031  * Destroying the blkgs releases the reference held on the blkcg's css allowing
1032  * blkcg_css_free to eventually be called.
1033  *
1034  * This is the blkcg counterpart of ioc_release_fn().
1035  */
1036 void blkcg_destroy_blkgs(struct blkcg *blkcg)
1037 {
1038         might_sleep();
1039
1040         spin_lock_irq(&blkcg->lock);
1041
1042         while (!hlist_empty(&blkcg->blkg_list)) {
1043                 struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
1044                                                 struct blkcg_gq, blkcg_node);
1045                 struct request_queue *q = blkg->q;
1046
1047                 if (need_resched() || !spin_trylock(&q->queue_lock)) {
1048                         /*
1049                          * Given that the system can accumulate a huge number
1050                          * of blkgs in pathological cases, check to see if we
1051                          * need to rescheduling to avoid softlockup.
1052                          */
1053                         spin_unlock_irq(&blkcg->lock);
1054                         cond_resched();
1055                         spin_lock_irq(&blkcg->lock);
1056                         continue;
1057                 }
1058
1059                 blkg_destroy(blkg);
1060                 spin_unlock(&q->queue_lock);
1061         }
1062
1063         spin_unlock_irq(&blkcg->lock);
1064 }
1065
1066 static void blkcg_css_free(struct cgroup_subsys_state *css)
1067 {
1068         struct blkcg *blkcg = css_to_blkcg(css);
1069         int i;
1070
1071         mutex_lock(&blkcg_pol_mutex);
1072
1073         list_del(&blkcg->all_blkcgs_node);
1074
1075         for (i = 0; i < BLKCG_MAX_POLS; i++)
1076                 if (blkcg->cpd[i])
1077                         blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1078
1079         mutex_unlock(&blkcg_pol_mutex);
1080
1081         kfree(blkcg);
1082 }
1083
1084 static struct cgroup_subsys_state *
1085 blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
1086 {
1087         struct blkcg *blkcg;
1088         struct cgroup_subsys_state *ret;
1089         int i;
1090
1091         mutex_lock(&blkcg_pol_mutex);
1092
1093         if (!parent_css) {
1094                 blkcg = &blkcg_root;
1095         } else {
1096                 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
1097                 if (!blkcg) {
1098                         ret = ERR_PTR(-ENOMEM);
1099                         goto unlock;
1100                 }
1101         }
1102
1103         for (i = 0; i < BLKCG_MAX_POLS ; i++) {
1104                 struct blkcg_policy *pol = blkcg_policy[i];
1105                 struct blkcg_policy_data *cpd;
1106
1107                 /*
1108                  * If the policy hasn't been attached yet, wait for it
1109                  * to be attached before doing anything else. Otherwise,
1110                  * check if the policy requires any specific per-cgroup
1111                  * data: if it does, allocate and initialize it.
1112                  */
1113                 if (!pol || !pol->cpd_alloc_fn)
1114                         continue;
1115
1116                 cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1117                 if (!cpd) {
1118                         ret = ERR_PTR(-ENOMEM);
1119                         goto free_pd_blkcg;
1120                 }
1121                 blkcg->cpd[i] = cpd;
1122                 cpd->blkcg = blkcg;
1123                 cpd->plid = i;
1124                 if (pol->cpd_init_fn)
1125                         pol->cpd_init_fn(cpd);
1126         }
1127
1128         spin_lock_init(&blkcg->lock);
1129         refcount_set(&blkcg->online_pin, 1);
1130         INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN);
1131         INIT_HLIST_HEAD(&blkcg->blkg_list);
1132 #ifdef CONFIG_CGROUP_WRITEBACK
1133         INIT_LIST_HEAD(&blkcg->cgwb_list);
1134 #endif
1135         list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs);
1136
1137         mutex_unlock(&blkcg_pol_mutex);
1138         return &blkcg->css;
1139
1140 free_pd_blkcg:
1141         for (i--; i >= 0; i--)
1142                 if (blkcg->cpd[i])
1143                         blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]);
1144
1145         if (blkcg != &blkcg_root)
1146                 kfree(blkcg);
1147 unlock:
1148         mutex_unlock(&blkcg_pol_mutex);
1149         return ret;
1150 }
1151
1152 static int blkcg_css_online(struct cgroup_subsys_state *css)
1153 {
1154         struct blkcg *blkcg = css_to_blkcg(css);
1155         struct blkcg *parent = blkcg_parent(blkcg);
1156
1157         /*
1158          * blkcg_pin_online() is used to delay blkcg offline so that blkgs
1159          * don't go offline while cgwbs are still active on them.  Pin the
1160          * parent so that offline always happens towards the root.
1161          */
1162         if (parent)
1163                 blkcg_pin_online(parent);
1164         return 0;
1165 }
1166
1167 /**
1168  * blkcg_init_queue - initialize blkcg part of request queue
1169  * @q: request_queue to initialize
1170  *
1171  * Called from blk_alloc_queue(). Responsible for initializing blkcg
1172  * part of new request_queue @q.
1173  *
1174  * RETURNS:
1175  * 0 on success, -errno on failure.
1176  */
1177 int blkcg_init_queue(struct request_queue *q)
1178 {
1179         struct blkcg_gq *new_blkg, *blkg;
1180         bool preloaded;
1181         int ret;
1182
1183         INIT_LIST_HEAD(&q->blkg_list);
1184
1185         new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
1186         if (!new_blkg)
1187                 return -ENOMEM;
1188
1189         preloaded = !radix_tree_preload(GFP_KERNEL);
1190
1191         /* Make sure the root blkg exists. */
1192         rcu_read_lock();
1193         spin_lock_irq(&q->queue_lock);
1194         blkg = blkg_create(&blkcg_root, q, new_blkg);
1195         if (IS_ERR(blkg))
1196                 goto err_unlock;
1197         q->root_blkg = blkg;
1198         spin_unlock_irq(&q->queue_lock);
1199         rcu_read_unlock();
1200
1201         if (preloaded)
1202                 radix_tree_preload_end();
1203
1204         ret = blk_ioprio_init(q);
1205         if (ret)
1206                 goto err_destroy_all;
1207
1208         ret = blk_throtl_init(q);
1209         if (ret)
1210                 goto err_destroy_all;
1211
1212         ret = blk_iolatency_init(q);
1213         if (ret) {
1214                 blk_throtl_exit(q);
1215                 goto err_destroy_all;
1216         }
1217
1218         return 0;
1219
1220 err_destroy_all:
1221         blkg_destroy_all(q);
1222         return ret;
1223 err_unlock:
1224         spin_unlock_irq(&q->queue_lock);
1225         rcu_read_unlock();
1226         if (preloaded)
1227                 radix_tree_preload_end();
1228         return PTR_ERR(blkg);
1229 }
1230
1231 /**
1232  * blkcg_exit_queue - exit and release blkcg part of request_queue
1233  * @q: request_queue being released
1234  *
1235  * Called from blk_exit_queue().  Responsible for exiting blkcg part.
1236  */
1237 void blkcg_exit_queue(struct request_queue *q)
1238 {
1239         blkg_destroy_all(q);
1240         blk_throtl_exit(q);
1241 }
1242
1243 static void blkcg_bind(struct cgroup_subsys_state *root_css)
1244 {
1245         int i;
1246
1247         mutex_lock(&blkcg_pol_mutex);
1248
1249         for (i = 0; i < BLKCG_MAX_POLS; i++) {
1250                 struct blkcg_policy *pol = blkcg_policy[i];
1251                 struct blkcg *blkcg;
1252
1253                 if (!pol || !pol->cpd_bind_fn)
1254                         continue;
1255
1256                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
1257                         if (blkcg->cpd[pol->plid])
1258                                 pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
1259         }
1260         mutex_unlock(&blkcg_pol_mutex);
1261 }
1262
1263 static void blkcg_exit(struct task_struct *tsk)
1264 {
1265         if (tsk->throttle_queue)
1266                 blk_put_queue(tsk->throttle_queue);
1267         tsk->throttle_queue = NULL;
1268 }
1269
1270 struct cgroup_subsys io_cgrp_subsys = {
1271         .css_alloc = blkcg_css_alloc,
1272         .css_online = blkcg_css_online,
1273         .css_offline = blkcg_css_offline,
1274         .css_free = blkcg_css_free,
1275         .css_rstat_flush = blkcg_rstat_flush,
1276         .bind = blkcg_bind,
1277         .dfl_cftypes = blkcg_files,
1278         .legacy_cftypes = blkcg_legacy_files,
1279         .legacy_name = "blkio",
1280         .exit = blkcg_exit,
1281 #ifdef CONFIG_MEMCG
1282         /*
1283          * This ensures that, if available, memcg is automatically enabled
1284          * together on the default hierarchy so that the owner cgroup can
1285          * be retrieved from writeback pages.
1286          */
1287         .depends_on = 1 << memory_cgrp_id,
1288 #endif
1289 };
1290 EXPORT_SYMBOL_GPL(io_cgrp_subsys);
1291
1292 /**
1293  * blkcg_activate_policy - activate a blkcg policy on a request_queue
1294  * @q: request_queue of interest
1295  * @pol: blkcg policy to activate
1296  *
1297  * Activate @pol on @q.  Requires %GFP_KERNEL context.  @q goes through
1298  * bypass mode to populate its blkgs with policy_data for @pol.
1299  *
1300  * Activation happens with @q bypassed, so nobody would be accessing blkgs
1301  * from IO path.  Update of each blkg is protected by both queue and blkcg
1302  * locks so that holding either lock and testing blkcg_policy_enabled() is
1303  * always enough for dereferencing policy data.
1304  *
1305  * The caller is responsible for synchronizing [de]activations and policy
1306  * [un]registerations.  Returns 0 on success, -errno on failure.
1307  */
1308 int blkcg_activate_policy(struct request_queue *q,
1309                           const struct blkcg_policy *pol)
1310 {
1311         struct blkg_policy_data *pd_prealloc = NULL;
1312         struct blkcg_gq *blkg, *pinned_blkg = NULL;
1313         int ret;
1314
1315         if (blkcg_policy_enabled(q, pol))
1316                 return 0;
1317
1318         if (queue_is_mq(q))
1319                 blk_mq_freeze_queue(q);
1320 retry:
1321         spin_lock_irq(&q->queue_lock);
1322
1323         /* blkg_list is pushed at the head, reverse walk to allocate parents first */
1324         list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
1325                 struct blkg_policy_data *pd;
1326
1327                 if (blkg->pd[pol->plid])
1328                         continue;
1329
1330                 /* If prealloc matches, use it; otherwise try GFP_NOWAIT */
1331                 if (blkg == pinned_blkg) {
1332                         pd = pd_prealloc;
1333                         pd_prealloc = NULL;
1334                 } else {
1335                         pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q,
1336                                               blkg->blkcg);
1337                 }
1338
1339                 if (!pd) {
1340                         /*
1341                          * GFP_NOWAIT failed.  Free the existing one and
1342                          * prealloc for @blkg w/ GFP_KERNEL.
1343                          */
1344                         if (pinned_blkg)
1345                                 blkg_put(pinned_blkg);
1346                         blkg_get(blkg);
1347                         pinned_blkg = blkg;
1348
1349                         spin_unlock_irq(&q->queue_lock);
1350
1351                         if (pd_prealloc)
1352                                 pol->pd_free_fn(pd_prealloc);
1353                         pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q,
1354                                                        blkg->blkcg);
1355                         if (pd_prealloc)
1356                                 goto retry;
1357                         else
1358                                 goto enomem;
1359                 }
1360
1361                 blkg->pd[pol->plid] = pd;
1362                 pd->blkg = blkg;
1363                 pd->plid = pol->plid;
1364         }
1365
1366         /* all allocated, init in the same order */
1367         if (pol->pd_init_fn)
1368                 list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)
1369                         pol->pd_init_fn(blkg->pd[pol->plid]);
1370
1371         __set_bit(pol->plid, q->blkcg_pols);
1372         ret = 0;
1373
1374         spin_unlock_irq(&q->queue_lock);
1375 out:
1376         if (queue_is_mq(q))
1377                 blk_mq_unfreeze_queue(q);
1378         if (pinned_blkg)
1379                 blkg_put(pinned_blkg);
1380         if (pd_prealloc)
1381                 pol->pd_free_fn(pd_prealloc);
1382         return ret;
1383
1384 enomem:
1385         /* alloc failed, nothing's initialized yet, free everything */
1386         spin_lock_irq(&q->queue_lock);
1387         list_for_each_entry(blkg, &q->blkg_list, q_node) {
1388                 struct blkcg *blkcg = blkg->blkcg;
1389
1390                 spin_lock(&blkcg->lock);
1391                 if (blkg->pd[pol->plid]) {
1392                         pol->pd_free_fn(blkg->pd[pol->plid]);
1393                         blkg->pd[pol->plid] = NULL;
1394                 }
1395                 spin_unlock(&blkcg->lock);
1396         }
1397         spin_unlock_irq(&q->queue_lock);
1398         ret = -ENOMEM;
1399         goto out;
1400 }
1401 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
1402
1403 /**
1404  * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
1405  * @q: request_queue of interest
1406  * @pol: blkcg policy to deactivate
1407  *
1408  * Deactivate @pol on @q.  Follows the same synchronization rules as
1409  * blkcg_activate_policy().
1410  */
1411 void blkcg_deactivate_policy(struct request_queue *q,
1412                              const struct blkcg_policy *pol)
1413 {
1414         struct blkcg_gq *blkg;
1415
1416         if (!blkcg_policy_enabled(q, pol))
1417                 return;
1418
1419         if (queue_is_mq(q))
1420                 blk_mq_freeze_queue(q);
1421
1422         spin_lock_irq(&q->queue_lock);
1423
1424         __clear_bit(pol->plid, q->blkcg_pols);
1425
1426         list_for_each_entry(blkg, &q->blkg_list, q_node) {
1427                 struct blkcg *blkcg = blkg->blkcg;
1428
1429                 spin_lock(&blkcg->lock);
1430                 if (blkg->pd[pol->plid]) {
1431                         if (pol->pd_offline_fn)
1432                                 pol->pd_offline_fn(blkg->pd[pol->plid]);
1433                         pol->pd_free_fn(blkg->pd[pol->plid]);
1434                         blkg->pd[pol->plid] = NULL;
1435                 }
1436                 spin_unlock(&blkcg->lock);
1437         }
1438
1439         spin_unlock_irq(&q->queue_lock);
1440
1441         if (queue_is_mq(q))
1442                 blk_mq_unfreeze_queue(q);
1443 }
1444 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
1445
1446 /**
1447  * blkcg_policy_register - register a blkcg policy
1448  * @pol: blkcg policy to register
1449  *
1450  * Register @pol with blkcg core.  Might sleep and @pol may be modified on
1451  * successful registration.  Returns 0 on success and -errno on failure.
1452  */
1453 int blkcg_policy_register(struct blkcg_policy *pol)
1454 {
1455         struct blkcg *blkcg;
1456         int i, ret;
1457
1458         mutex_lock(&blkcg_pol_register_mutex);
1459         mutex_lock(&blkcg_pol_mutex);
1460
1461         /* find an empty slot */
1462         ret = -ENOSPC;
1463         for (i = 0; i < BLKCG_MAX_POLS; i++)
1464                 if (!blkcg_policy[i])
1465                         break;
1466         if (i >= BLKCG_MAX_POLS) {
1467                 pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");
1468                 goto err_unlock;
1469         }
1470
1471         /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
1472         if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
1473                 (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
1474                 goto err_unlock;
1475
1476         /* register @pol */
1477         pol->plid = i;
1478         blkcg_policy[pol->plid] = pol;
1479
1480         /* allocate and install cpd's */
1481         if (pol->cpd_alloc_fn) {
1482                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1483                         struct blkcg_policy_data *cpd;
1484
1485                         cpd = pol->cpd_alloc_fn(GFP_KERNEL);
1486                         if (!cpd)
1487                                 goto err_free_cpds;
1488
1489                         blkcg->cpd[pol->plid] = cpd;
1490                         cpd->blkcg = blkcg;
1491                         cpd->plid = pol->plid;
1492                         if (pol->cpd_init_fn)
1493                                 pol->cpd_init_fn(cpd);
1494                 }
1495         }
1496
1497         mutex_unlock(&blkcg_pol_mutex);
1498
1499         /* everything is in place, add intf files for the new policy */
1500         if (pol->dfl_cftypes)
1501                 WARN_ON(cgroup_add_dfl_cftypes(&io_cgrp_subsys,
1502                                                pol->dfl_cftypes));
1503         if (pol->legacy_cftypes)
1504                 WARN_ON(cgroup_add_legacy_cftypes(&io_cgrp_subsys,
1505                                                   pol->legacy_cftypes));
1506         mutex_unlock(&blkcg_pol_register_mutex);
1507         return 0;
1508
1509 err_free_cpds:
1510         if (pol->cpd_free_fn) {
1511                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1512                         if (blkcg->cpd[pol->plid]) {
1513                                 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1514                                 blkcg->cpd[pol->plid] = NULL;
1515                         }
1516                 }
1517         }
1518         blkcg_policy[pol->plid] = NULL;
1519 err_unlock:
1520         mutex_unlock(&blkcg_pol_mutex);
1521         mutex_unlock(&blkcg_pol_register_mutex);
1522         return ret;
1523 }
1524 EXPORT_SYMBOL_GPL(blkcg_policy_register);
1525
1526 /**
1527  * blkcg_policy_unregister - unregister a blkcg policy
1528  * @pol: blkcg policy to unregister
1529  *
1530  * Undo blkcg_policy_register(@pol).  Might sleep.
1531  */
1532 void blkcg_policy_unregister(struct blkcg_policy *pol)
1533 {
1534         struct blkcg *blkcg;
1535
1536         mutex_lock(&blkcg_pol_register_mutex);
1537
1538         if (WARN_ON(blkcg_policy[pol->plid] != pol))
1539                 goto out_unlock;
1540
1541         /* kill the intf files first */
1542         if (pol->dfl_cftypes)
1543                 cgroup_rm_cftypes(pol->dfl_cftypes);
1544         if (pol->legacy_cftypes)
1545                 cgroup_rm_cftypes(pol->legacy_cftypes);
1546
1547         /* remove cpds and unregister */
1548         mutex_lock(&blkcg_pol_mutex);
1549
1550         if (pol->cpd_free_fn) {
1551                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
1552                         if (blkcg->cpd[pol->plid]) {
1553                                 pol->cpd_free_fn(blkcg->cpd[pol->plid]);
1554                                 blkcg->cpd[pol->plid] = NULL;
1555                         }
1556                 }
1557         }
1558         blkcg_policy[pol->plid] = NULL;
1559
1560         mutex_unlock(&blkcg_pol_mutex);
1561 out_unlock:
1562         mutex_unlock(&blkcg_pol_register_mutex);
1563 }
1564 EXPORT_SYMBOL_GPL(blkcg_policy_unregister);
1565
1566 bool __blkcg_punt_bio_submit(struct bio *bio)
1567 {
1568         struct blkcg_gq *blkg = bio->bi_blkg;
1569
1570         /* consume the flag first */
1571         bio->bi_opf &= ~REQ_CGROUP_PUNT;
1572
1573         /* never bounce for the root cgroup */
1574         if (!blkg->parent)
1575                 return false;
1576
1577         spin_lock_bh(&blkg->async_bio_lock);
1578         bio_list_add(&blkg->async_bios, bio);
1579         spin_unlock_bh(&blkg->async_bio_lock);
1580
1581         queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work);
1582         return true;
1583 }
1584
1585 /*
1586  * Scale the accumulated delay based on how long it has been since we updated
1587  * the delay.  We only call this when we are adding delay, in case it's been a
1588  * while since we added delay, and when we are checking to see if we need to
1589  * delay a task, to account for any delays that may have occurred.
1590  */
1591 static void blkcg_scale_delay(struct blkcg_gq *blkg, u64 now)
1592 {
1593         u64 old = atomic64_read(&blkg->delay_start);
1594
1595         /* negative use_delay means no scaling, see blkcg_set_delay() */
1596         if (atomic_read(&blkg->use_delay) < 0)
1597                 return;
1598
1599         /*
1600          * We only want to scale down every second.  The idea here is that we
1601          * want to delay people for min(delay_nsec, NSEC_PER_SEC) in a certain
1602          * time window.  We only want to throttle tasks for recent delay that
1603          * has occurred, in 1 second time windows since that's the maximum
1604          * things can be throttled.  We save the current delay window in
1605          * blkg->last_delay so we know what amount is still left to be charged
1606          * to the blkg from this point onward.  blkg->last_use keeps track of
1607          * the use_delay counter.  The idea is if we're unthrottling the blkg we
1608          * are ok with whatever is happening now, and we can take away more of
1609          * the accumulated delay as we've already throttled enough that
1610          * everybody is happy with their IO latencies.
1611          */
1612         if (time_before64(old + NSEC_PER_SEC, now) &&
1613             atomic64_cmpxchg(&blkg->delay_start, old, now) == old) {
1614                 u64 cur = atomic64_read(&blkg->delay_nsec);
1615                 u64 sub = min_t(u64, blkg->last_delay, now - old);
1616                 int cur_use = atomic_read(&blkg->use_delay);
1617
1618                 /*
1619                  * We've been unthrottled, subtract a larger chunk of our
1620                  * accumulated delay.
1621                  */
1622                 if (cur_use < blkg->last_use)
1623                         sub = max_t(u64, sub, blkg->last_delay >> 1);
1624
1625                 /*
1626                  * This shouldn't happen, but handle it anyway.  Our delay_nsec
1627                  * should only ever be growing except here where we subtract out
1628                  * min(last_delay, 1 second), but lord knows bugs happen and I'd
1629                  * rather not end up with negative numbers.
1630                  */
1631                 if (unlikely(cur < sub)) {
1632                         atomic64_set(&blkg->delay_nsec, 0);
1633                         blkg->last_delay = 0;
1634                 } else {
1635                         atomic64_sub(sub, &blkg->delay_nsec);
1636                         blkg->last_delay = cur - sub;
1637                 }
1638                 blkg->last_use = cur_use;
1639         }
1640 }
1641
1642 /*
1643  * This is called when we want to actually walk up the hierarchy and check to
1644  * see if we need to throttle, and then actually throttle if there is some
1645  * accumulated delay.  This should only be called upon return to user space so
1646  * we're not holding some lock that would induce a priority inversion.
1647  */
1648 static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
1649 {
1650         unsigned long pflags;
1651         bool clamp;
1652         u64 now = ktime_to_ns(ktime_get());
1653         u64 exp;
1654         u64 delay_nsec = 0;
1655         int tok;
1656
1657         while (blkg->parent) {
1658                 int use_delay = atomic_read(&blkg->use_delay);
1659
1660                 if (use_delay) {
1661                         u64 this_delay;
1662
1663                         blkcg_scale_delay(blkg, now);
1664                         this_delay = atomic64_read(&blkg->delay_nsec);
1665                         if (this_delay > delay_nsec) {
1666                                 delay_nsec = this_delay;
1667                                 clamp = use_delay > 0;
1668                         }
1669                 }
1670                 blkg = blkg->parent;
1671         }
1672
1673         if (!delay_nsec)
1674                 return;
1675
1676         /*
1677          * Let's not sleep for all eternity if we've amassed a huge delay.
1678          * Swapping or metadata IO can accumulate 10's of seconds worth of
1679          * delay, and we want userspace to be able to do _something_ so cap the
1680          * delays at 0.25s. If there's 10's of seconds worth of delay then the
1681          * tasks will be delayed for 0.25 second for every syscall. If
1682          * blkcg_set_delay() was used as indicated by negative use_delay, the
1683          * caller is responsible for regulating the range.
1684          */
1685         if (clamp)
1686                 delay_nsec = min_t(u64, delay_nsec, 250 * NSEC_PER_MSEC);
1687
1688         if (use_memdelay)
1689                 psi_memstall_enter(&pflags);
1690
1691         exp = ktime_add_ns(now, delay_nsec);
1692         tok = io_schedule_prepare();
1693         do {
1694                 __set_current_state(TASK_KILLABLE);
1695                 if (!schedule_hrtimeout(&exp, HRTIMER_MODE_ABS))
1696                         break;
1697         } while (!fatal_signal_pending(current));
1698         io_schedule_finish(tok);
1699
1700         if (use_memdelay)
1701                 psi_memstall_leave(&pflags);
1702 }
1703
1704 /**
1705  * blkcg_maybe_throttle_current - throttle the current task if it has been marked
1706  *
1707  * This is only called if we've been marked with set_notify_resume().  Obviously
1708  * we can be set_notify_resume() for reasons other than blkcg throttling, so we
1709  * check to see if current->throttle_queue is set and if not this doesn't do
1710  * anything.  This should only ever be called by the resume code, it's not meant
1711  * to be called by people willy-nilly as it will actually do the work to
1712  * throttle the task if it is setup for throttling.
1713  */
1714 void blkcg_maybe_throttle_current(void)
1715 {
1716         struct request_queue *q = current->throttle_queue;
1717         struct cgroup_subsys_state *css;
1718         struct blkcg *blkcg;
1719         struct blkcg_gq *blkg;
1720         bool use_memdelay = current->use_memdelay;
1721
1722         if (!q)
1723                 return;
1724
1725         current->throttle_queue = NULL;
1726         current->use_memdelay = false;
1727
1728         rcu_read_lock();
1729         css = kthread_blkcg();
1730         if (css)
1731                 blkcg = css_to_blkcg(css);
1732         else
1733                 blkcg = css_to_blkcg(task_css(current, io_cgrp_id));
1734
1735         if (!blkcg)
1736                 goto out;
1737         blkg = blkg_lookup(blkcg, q);
1738         if (!blkg)
1739                 goto out;
1740         if (!blkg_tryget(blkg))
1741                 goto out;
1742         rcu_read_unlock();
1743
1744         blkcg_maybe_throttle_blkg(blkg, use_memdelay);
1745         blkg_put(blkg);
1746         blk_put_queue(q);
1747         return;
1748 out:
1749         rcu_read_unlock();
1750         blk_put_queue(q);
1751 }
1752
1753 /**
1754  * blkcg_schedule_throttle - this task needs to check for throttling
1755  * @q: the request queue IO was submitted on
1756  * @use_memdelay: do we charge this to memory delay for PSI
1757  *
1758  * This is called by the IO controller when we know there's delay accumulated
1759  * for the blkg for this task.  We do not pass the blkg because there are places
1760  * we call this that may not have that information, the swapping code for
1761  * instance will only have a request_queue at that point.  This set's the
1762  * notify_resume for the task to check and see if it requires throttling before
1763  * returning to user space.
1764  *
1765  * We will only schedule once per syscall.  You can call this over and over
1766  * again and it will only do the check once upon return to user space, and only
1767  * throttle once.  If the task needs to be throttled again it'll need to be
1768  * re-set at the next time we see the task.
1769  */
1770 void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay)
1771 {
1772         if (unlikely(current->flags & PF_KTHREAD))
1773                 return;
1774
1775         if (current->throttle_queue != q) {
1776                 if (!blk_get_queue(q))
1777                         return;
1778
1779                 if (current->throttle_queue)
1780                         blk_put_queue(current->throttle_queue);
1781                 current->throttle_queue = q;
1782         }
1783
1784         if (use_memdelay)
1785                 current->use_memdelay = use_memdelay;
1786         set_notify_resume(current);
1787 }
1788
1789 /**
1790  * blkcg_add_delay - add delay to this blkg
1791  * @blkg: blkg of interest
1792  * @now: the current time in nanoseconds
1793  * @delta: how many nanoseconds of delay to add
1794  *
1795  * Charge @delta to the blkg's current delay accumulation.  This is used to
1796  * throttle tasks if an IO controller thinks we need more throttling.
1797  */
1798 void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
1799 {
1800         if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
1801                 return;
1802         blkcg_scale_delay(blkg, now);
1803         atomic64_add(delta, &blkg->delay_nsec);
1804 }
1805
1806 /**
1807  * blkg_tryget_closest - try and get a blkg ref on the closet blkg
1808  * @bio: target bio
1809  * @css: target css
1810  *
1811  * As the failure mode here is to walk up the blkg tree, this ensure that the
1812  * blkg->parent pointers are always valid.  This returns the blkg that it ended
1813  * up taking a reference on or %NULL if no reference was taken.
1814  */
1815 static inline struct blkcg_gq *blkg_tryget_closest(struct bio *bio,
1816                 struct cgroup_subsys_state *css)
1817 {
1818         struct blkcg_gq *blkg, *ret_blkg = NULL;
1819
1820         rcu_read_lock();
1821         blkg = blkg_lookup_create(css_to_blkcg(css),
1822                                   bdev_get_queue(bio->bi_bdev));
1823         while (blkg) {
1824                 if (blkg_tryget(blkg)) {
1825                         ret_blkg = blkg;
1826                         break;
1827                 }
1828                 blkg = blkg->parent;
1829         }
1830         rcu_read_unlock();
1831
1832         return ret_blkg;
1833 }
1834
1835 /**
1836  * bio_associate_blkg_from_css - associate a bio with a specified css
1837  * @bio: target bio
1838  * @css: target css
1839  *
1840  * Associate @bio with the blkg found by combining the css's blkg and the
1841  * request_queue of the @bio.  An association failure is handled by walking up
1842  * the blkg tree.  Therefore, the blkg associated can be anything between @blkg
1843  * and q->root_blkg.  This situation only happens when a cgroup is dying and
1844  * then the remaining bios will spill to the closest alive blkg.
1845  *
1846  * A reference will be taken on the blkg and will be released when @bio is
1847  * freed.
1848  */
1849 void bio_associate_blkg_from_css(struct bio *bio,
1850                                  struct cgroup_subsys_state *css)
1851 {
1852         if (bio->bi_blkg)
1853                 blkg_put(bio->bi_blkg);
1854
1855         if (css && css->parent) {
1856                 bio->bi_blkg = blkg_tryget_closest(bio, css);
1857         } else {
1858                 blkg_get(bdev_get_queue(bio->bi_bdev)->root_blkg);
1859                 bio->bi_blkg = bdev_get_queue(bio->bi_bdev)->root_blkg;
1860         }
1861 }
1862 EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
1863
1864 /**
1865  * bio_associate_blkg - associate a bio with a blkg
1866  * @bio: target bio
1867  *
1868  * Associate @bio with the blkg found from the bio's css and request_queue.
1869  * If one is not found, bio_lookup_blkg() creates the blkg.  If a blkg is
1870  * already associated, the css is reused and association redone as the
1871  * request_queue may have changed.
1872  */
1873 void bio_associate_blkg(struct bio *bio)
1874 {
1875         struct cgroup_subsys_state *css;
1876
1877         rcu_read_lock();
1878
1879         if (bio->bi_blkg)
1880                 css = &bio_blkcg(bio)->css;
1881         else
1882                 css = blkcg_css();
1883
1884         bio_associate_blkg_from_css(bio, css);
1885
1886         rcu_read_unlock();
1887 }
1888 EXPORT_SYMBOL_GPL(bio_associate_blkg);
1889
1890 /**
1891  * bio_clone_blkg_association - clone blkg association from src to dst bio
1892  * @dst: destination bio
1893  * @src: source bio
1894  */
1895 void bio_clone_blkg_association(struct bio *dst, struct bio *src)
1896 {
1897         if (src->bi_blkg) {
1898                 if (dst->bi_blkg)
1899                         blkg_put(dst->bi_blkg);
1900                 blkg_get(src->bi_blkg);
1901                 dst->bi_blkg = src->bi_blkg;
1902         }
1903 }
1904 EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
1905
1906 static int blk_cgroup_io_type(struct bio *bio)
1907 {
1908         if (op_is_discard(bio->bi_opf))
1909                 return BLKG_IOSTAT_DISCARD;
1910         if (op_is_write(bio->bi_opf))
1911                 return BLKG_IOSTAT_WRITE;
1912         return BLKG_IOSTAT_READ;
1913 }
1914
1915 void blk_cgroup_bio_start(struct bio *bio)
1916 {
1917         int rwd = blk_cgroup_io_type(bio), cpu;
1918         struct blkg_iostat_set *bis;
1919         unsigned long flags;
1920
1921         cpu = get_cpu();
1922         bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu);
1923         flags = u64_stats_update_begin_irqsave(&bis->sync);
1924
1925         /*
1926          * If the bio is flagged with BIO_CGROUP_ACCT it means this is a split
1927          * bio and we would have already accounted for the size of the bio.
1928          */
1929         if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
1930                 bio_set_flag(bio, BIO_CGROUP_ACCT);
1931                 bis->cur.bytes[rwd] += bio->bi_iter.bi_size;
1932         }
1933         bis->cur.ios[rwd]++;
1934
1935         u64_stats_update_end_irqrestore(&bis->sync, flags);
1936         if (cgroup_subsys_on_dfl(io_cgrp_subsys))
1937                 cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu);
1938         put_cpu();
1939 }
1940
1941 static int __init blkcg_init(void)
1942 {
1943         blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",
1944                                             WQ_MEM_RECLAIM | WQ_FREEZABLE |
1945                                             WQ_UNBOUND | WQ_SYSFS, 0);
1946         if (!blkcg_punt_bio_wq)
1947                 return -ENOMEM;
1948         return 0;
1949 }
1950 subsys_initcall(blkcg_init);
1951
1952 module_param(blkcg_debug_stats, bool, 0644);
1953 MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not");