include/linux/blk-cgroup.h

   1 #ifndef _BLK_CGROUP_H
   2 #define _BLK_CGROUP_H
   3 /*
   4  * Common Block IO controller cgroup interface
   5  *
   6  * Based on ideas and code from CFQ, CFS and BFQ:
   7  * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
   8  *
   9  * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
  10  *                    Paolo Valente <paolo.valente@unimore.it>
  11  *
  12  * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
  13  *                    Nauman Rafique <nauman@google.com>
  14  */
  15
  16 #include <linux/cgroup.h>
  17 #include <linux/u64_stats_sync.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/radix-tree.h>
  20 #include <linux/blkdev.h>
  21 #include <linux/atomic.h>
  22
  23 /* Max limits for throttle policy */
  24 #define THROTL_IOPS_MAX         UINT_MAX
  25
  26 #ifdef CONFIG_BLK_CGROUP
  27
  28 enum blkg_rwstat_type {
  29         BLKG_RWSTAT_READ,
  30         BLKG_RWSTAT_WRITE,
  31         BLKG_RWSTAT_SYNC,
  32         BLKG_RWSTAT_ASYNC,
  33
  34         BLKG_RWSTAT_NR,
  35         BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
  36 };
  37
  38 struct blkcg_gq;
  39
  40 struct blkcg {
  41         struct cgroup_subsys_state      css;
  42         spinlock_t                      lock;
  43
  44         struct radix_tree_root          blkg_tree;
  45         struct blkcg_gq                 *blkg_hint;
  46         struct hlist_head               blkg_list;
  47
  48         struct blkcg_policy_data        *cpd[BLKCG_MAX_POLS];
  49
  50         struct list_head                all_blkcgs_node;
  51 #ifdef CONFIG_CGROUP_WRITEBACK
  52         struct list_head                cgwb_list;
  53 #endif
  54 };
  55
  56 struct blkg_stat {
  57         struct u64_stats_sync           syncp;
  58         uint64_t                        cnt;
  59 };
  60
  61 struct blkg_rwstat {
  62         struct u64_stats_sync           syncp;
  63         uint64_t                        cnt[BLKG_RWSTAT_NR];
  64 };
  65
  66 /*
  67  * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
  68  * request_queue (q).  This is used by blkcg policies which need to track
  69  * information per blkcg - q pair.
  70  *
  71  * There can be multiple active blkcg policies and each blkg:policy pair is
  72  * represented by a blkg_policy_data which is allocated and freed by each
  73  * policy's pd_alloc/free_fn() methods.  A policy can allocate private data
  74  * area by allocating larger data structure which embeds blkg_policy_data
  75  * at the beginning.
  76  */
  77 struct blkg_policy_data {
  78         /* the blkg and policy id this per-policy data belongs to */
  79         struct blkcg_gq                 *blkg;
  80         int                             plid;
  81 };
  82
  83 /*
  84  * Policies that need to keep per-blkcg data which is independent from any
  85  * request_queue associated to it should implement cpd_alloc/free_fn()
  86  * methods.  A policy can allocate private data area by allocating larger
  87  * data structure which embeds blkcg_policy_data at the beginning.
  88  * cpd_init() is invoked to let each policy handle per-blkcg data.
  89  */
  90 struct blkcg_policy_data {
  91         /* the blkcg and policy id this per-policy data belongs to */
  92         struct blkcg                    *blkcg;
  93         int                             plid;
  94 };
  95
  96 /* association between a blk cgroup and a request queue */
  97 struct blkcg_gq {
  98         /* Pointer to the associated request_queue */
  99         struct request_queue            *q;
 100         struct list_head                q_node;
 101         struct hlist_node               blkcg_node;
 102         struct blkcg                    *blkcg;
 103
 104         /*
 105          * Each blkg gets congested separately and the congestion state is
 106          * propagated to the matching bdi_writeback_congested.
 107          */
 108         struct bdi_writeback_congested  *wb_congested;
 109
 110         /* all non-root blkcg_gq's are guaranteed to have access to parent */
 111         struct blkcg_gq                 *parent;
 112
 113         /* request allocation list for this blkcg-q pair */
 114         struct request_list             rl;
 115
 116         /* reference count */
 117         atomic_t                        refcnt;
 118
 119         /* is this blkg online? protected by both blkcg and q locks */
 120         bool                            online;
 121
 122         struct blkg_policy_data         *pd[BLKCG_MAX_POLS];
 123
 124         struct rcu_head                 rcu_head;
 125 };
 126
 127 typedef struct blkcg_policy_data *(blkcg_pol_alloc_cpd_fn)(gfp_t gfp);
 128 typedef void (blkcg_pol_init_cpd_fn)(struct blkcg_policy_data *cpd);
 129 typedef void (blkcg_pol_free_cpd_fn)(struct blkcg_policy_data *cpd);
 130 typedef struct blkg_policy_data *(blkcg_pol_alloc_pd_fn)(gfp_t gfp, int node);
 131 typedef void (blkcg_pol_init_pd_fn)(struct blkg_policy_data *pd);
 132 typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
 133 typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data *pd);
 134 typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
 135 typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data *pd);
 136
 137 struct blkcg_policy {
 138         int                             plid;
 139         /* cgroup files for the policy */
 140         struct cftype                   *cftypes;
 141
 142         /* operations */
 143         blkcg_pol_alloc_cpd_fn          *cpd_alloc_fn;
 144         blkcg_pol_init_cpd_fn           *cpd_init_fn;
 145         blkcg_pol_free_cpd_fn           *cpd_free_fn;
 146
 147         blkcg_pol_alloc_pd_fn           *pd_alloc_fn;
 148         blkcg_pol_init_pd_fn            *pd_init_fn;
 149         blkcg_pol_online_pd_fn          *pd_online_fn;
 150         blkcg_pol_offline_pd_fn         *pd_offline_fn;
 151         blkcg_pol_free_pd_fn            *pd_free_fn;
 152         blkcg_pol_reset_pd_stats_fn     *pd_reset_stats_fn;
 153 };
 154
 155 extern struct blkcg blkcg_root;
 156 extern struct cgroup_subsys_state * const blkcg_root_css;
 157
 158 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
 159                                       struct request_queue *q, bool update_hint);
 160 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 161                                     struct request_queue *q);
 162 int blkcg_init_queue(struct request_queue *q);
 163 void blkcg_drain_queue(struct request_queue *q);
 164 void blkcg_exit_queue(struct request_queue *q);
 165
 166 /* Blkio controller policy registration */
 167 int blkcg_policy_register(struct blkcg_policy *pol);
 168 void blkcg_policy_unregister(struct blkcg_policy *pol);
 169 int blkcg_activate_policy(struct request_queue *q,
 170                           const struct blkcg_policy *pol);
 171 void blkcg_deactivate_policy(struct request_queue *q,
 172                              const struct blkcg_policy *pol);
 173
 174 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 175                        u64 (*prfill)(struct seq_file *,
 176                                      struct blkg_policy_data *, int),
 177                        const struct blkcg_policy *pol, int data,
 178                        bool show_total);
 179 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
 180 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 181                          const struct blkg_rwstat *rwstat);
 182 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
 183 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 184                        int off);
 185
 186 u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off);
 187 struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
 188                                              int off);
 189
 190 struct blkg_conf_ctx {
 191         struct gendisk                  *disk;
 192         struct blkcg_gq                 *blkg;
 193         u64                             v;
 194 };
 195
 196 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 197                    const char *input, struct blkg_conf_ctx *ctx);
 198 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 199
 200
 201 static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 202 {
 203         return css ? container_of(css, struct blkcg, css) : NULL;
 204 }
 205
 206 static inline struct blkcg *task_blkcg(struct task_struct *tsk)
 207 {
 208         return css_to_blkcg(task_css(tsk, blkio_cgrp_id));
 209 }
 210
 211 static inline struct blkcg *bio_blkcg(struct bio *bio)
 212 {
 213         if (bio && bio->bi_css)
 214                 return css_to_blkcg(bio->bi_css);
 215         return task_blkcg(current);
 216 }
 217
 218 static inline struct cgroup_subsys_state *
 219 task_get_blkcg_css(struct task_struct *task)
 220 {
 221         return task_get_css(task, blkio_cgrp_id);
 222 }
 223
 224 /**
 225  * blkcg_parent - get the parent of a blkcg
 226  * @blkcg: blkcg of interest
 227  *
 228  * Return the parent blkcg of @blkcg.  Can be called anytime.
 229  */
 230 static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
 231 {
 232         return css_to_blkcg(blkcg->css.parent);
 233 }
 234
 235 /**
 236  * __blkg_lookup - internal version of blkg_lookup()
 237  * @blkcg: blkcg of interest
 238  * @q: request_queue of interest
 239  * @update_hint: whether to update lookup hint with the result or not
 240  *
 241  * This is internal version and shouldn't be used by policy
 242  * implementations.  Looks up blkgs for the @blkcg - @q pair regardless of
 243  * @q's bypass state.  If @update_hint is %true, the caller should be
 244  * holding @q->queue_lock and lookup hint is updated on success.
 245  */
 246 static inline struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
 247                                              struct request_queue *q,
 248                                              bool update_hint)
 249 {
 250         struct blkcg_gq *blkg;
 251
 252         if (blkcg == &blkcg_root)
 253                 return q->root_blkg;
 254
 255         blkg = rcu_dereference(blkcg->blkg_hint);
 256         if (blkg && blkg->q == q)
 257                 return blkg;
 258
 259         return blkg_lookup_slowpath(blkcg, q, update_hint);
 260 }
 261
 262 /**
 263  * blkg_lookup - lookup blkg for the specified blkcg - q pair
 264  * @blkcg: blkcg of interest
 265  * @q: request_queue of interest
 266  *
 267  * Lookup blkg for the @blkcg - @q pair.  This function should be called
 268  * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
 269  * - see blk_queue_bypass_start() for details.
 270  */
 271 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
 272                                            struct request_queue *q)
 273 {
 274         WARN_ON_ONCE(!rcu_read_lock_held());
 275
 276         if (unlikely(blk_queue_bypass(q)))
 277                 return NULL;
 278         return __blkg_lookup(blkcg, q, false);
 279 }
 280
 281 /**
 282  * blkg_to_pdata - get policy private data
 283  * @blkg: blkg of interest
 284  * @pol: policy of interest
 285  *
 286  * Return pointer to private data associated with the @blkg-@pol pair.
 287  */
 288 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 289                                                   struct blkcg_policy *pol)
 290 {
 291         return blkg ? blkg->pd[pol->plid] : NULL;
 292 }
 293
 294 static inline struct blkcg_policy_data *blkcg_to_cpd(struct blkcg *blkcg,
 295                                                      struct blkcg_policy *pol)
 296 {
 297         return blkcg ? blkcg->cpd[pol->plid] : NULL;
 298 }
 299
 300 /**
 301  * pdata_to_blkg - get blkg associated with policy private data
 302  * @pd: policy private data of interest
 303  *
 304  * @pd is policy private data.  Determine the blkg it's associated with.
 305  */
 306 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
 307 {
 308         return pd ? pd->blkg : NULL;
 309 }
 310
 311 static inline struct blkcg *cpd_to_blkcg(struct blkcg_policy_data *cpd)
 312 {
 313         return cpd ? cpd->blkcg : NULL;
 314 }
 315
 316 /**
 317  * blkg_path - format cgroup path of blkg
 318  * @blkg: blkg of interest
 319  * @buf: target buffer
 320  * @buflen: target buffer length
 321  *
 322  * Format the path of the cgroup of @blkg into @buf.
 323  */
 324 static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
 325 {
 326         char *p;
 327
 328         p = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
 329         if (!p) {
 330                 strncpy(buf, "<unavailable>", buflen);
 331                 return -ENAMETOOLONG;
 332         }
 333
 334         memmove(buf, p, buf + buflen - p);
 335         return 0;
 336 }
 337
 338 /**
 339  * blkg_get - get a blkg reference
 340  * @blkg: blkg to get
 341  *
 342  * The caller should be holding an existing reference.
 343  */
 344 static inline void blkg_get(struct blkcg_gq *blkg)
 345 {
 346         WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
 347         atomic_inc(&blkg->refcnt);
 348 }
 349
 350 void __blkg_release_rcu(struct rcu_head *rcu);
 351
 352 /**
 353  * blkg_put - put a blkg reference
 354  * @blkg: blkg to put
 355  */
 356 static inline void blkg_put(struct blkcg_gq *blkg)
 357 {
 358         WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
 359         if (atomic_dec_and_test(&blkg->refcnt))
 360                 call_rcu(&blkg->rcu_head, __blkg_release_rcu);
 361 }
 362
 363 /**
 364  * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
 365  * @d_blkg: loop cursor pointing to the current descendant
 366  * @pos_css: used for iteration
 367  * @p_blkg: target blkg to walk descendants of
 368  *
 369  * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
 370  * read locked.  If called under either blkcg or queue lock, the iteration
 371  * is guaranteed to include all and only online blkgs.  The caller may
 372  * update @pos_css by calling css_rightmost_descendant() to skip subtree.
 373  * @p_blkg is included in the iteration and the first node to be visited.
 374  */
 375 #define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)           \
 376         css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)   \
 377                 if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),    \
 378                                               (p_blkg)->q, false)))
 379
 380 /**
 381  * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
 382  * @d_blkg: loop cursor pointing to the current descendant
 383  * @pos_css: used for iteration
 384  * @p_blkg: target blkg to walk descendants of
 385  *
 386  * Similar to blkg_for_each_descendant_pre() but performs post-order
 387  * traversal instead.  Synchronization rules are the same.  @p_blkg is
 388  * included in the iteration and the last node to be visited.
 389  */
 390 #define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)          \
 391         css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)  \
 392                 if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),    \
 393                                               (p_blkg)->q, false)))
 394
 395 /**
 396  * blk_get_rl - get request_list to use
 397  * @q: request_queue of interest
 398  * @bio: bio which will be attached to the allocated request (may be %NULL)
 399  *
 400  * The caller wants to allocate a request from @q to use for @bio.  Find
 401  * the request_list to use and obtain a reference on it.  Should be called
 402  * under queue_lock.  This function is guaranteed to return non-%NULL
 403  * request_list.
 404  */
 405 static inline struct request_list *blk_get_rl(struct request_queue *q,
 406                                               struct bio *bio)
 407 {
 408         struct blkcg *blkcg;
 409         struct blkcg_gq *blkg;
 410
 411         rcu_read_lock();
 412
 413         blkcg = bio_blkcg(bio);
 414
 415         /* bypass blkg lookup and use @q->root_rl directly for root */
 416         if (blkcg == &blkcg_root)
 417                 goto root_rl;
 418
 419         /*
 420          * Try to use blkg->rl.  blkg lookup may fail under memory pressure
 421          * or if either the blkcg or queue is going away.  Fall back to
 422          * root_rl in such cases.
 423          */
 424         blkg = blkg_lookup(blkcg, q);
 425         if (unlikely(!blkg))
 426                 goto root_rl;
 427
 428         blkg_get(blkg);
 429         rcu_read_unlock();
 430         return &blkg->rl;
 431 root_rl:
 432         rcu_read_unlock();
 433         return &q->root_rl;
 434 }
 435
 436 /**
 437  * blk_put_rl - put request_list
 438  * @rl: request_list to put
 439  *
 440  * Put the reference acquired by blk_get_rl().  Should be called under
 441  * queue_lock.
 442  */
 443 static inline void blk_put_rl(struct request_list *rl)
 444 {
 445         if (rl->blkg->blkcg != &blkcg_root)
 446                 blkg_put(rl->blkg);
 447 }
 448
 449 /**
 450  * blk_rq_set_rl - associate a request with a request_list
 451  * @rq: request of interest
 452  * @rl: target request_list
 453  *
 454  * Associate @rq with @rl so that accounting and freeing can know the
 455  * request_list @rq came from.
 456  */
 457 static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
 458 {
 459         rq->rl = rl;
 460 }
 461
 462 /**
 463  * blk_rq_rl - return the request_list a request came from
 464  * @rq: request of interest
 465  *
 466  * Return the request_list @rq is allocated from.
 467  */
 468 static inline struct request_list *blk_rq_rl(struct request *rq)
 469 {
 470         return rq->rl;
 471 }
 472
 473 struct request_list *__blk_queue_next_rl(struct request_list *rl,
 474                                          struct request_queue *q);
 475 /**
 476  * blk_queue_for_each_rl - iterate through all request_lists of a request_queue
 477  *
 478  * Should be used under queue_lock.
 479  */
 480 #define blk_queue_for_each_rl(rl, q)    \
 481         for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))
 482
 483 static inline void blkg_stat_init(struct blkg_stat *stat)
 484 {
 485         u64_stats_init(&stat->syncp);
 486 }
 487
 488 /**
 489  * blkg_stat_add - add a value to a blkg_stat
 490  * @stat: target blkg_stat
 491  * @val: value to add
 492  *
 493  * Add @val to @stat.  The caller is responsible for synchronizing calls to
 494  * this function.
 495  */
 496 static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
 497 {
 498         u64_stats_update_begin(&stat->syncp);
 499         stat->cnt += val;
 500         u64_stats_update_end(&stat->syncp);
 501 }
 502
 503 /**
 504  * blkg_stat_read - read the current value of a blkg_stat
 505  * @stat: blkg_stat to read
 506  *
 507  * Read the current value of @stat.  This function can be called without
 508  * synchroniztion and takes care of u64 atomicity.
 509  */
 510 static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
 511 {
 512         unsigned int start;
 513         uint64_t v;
 514
 515         do {
 516                 start = u64_stats_fetch_begin_irq(&stat->syncp);
 517                 v = stat->cnt;
 518         } while (u64_stats_fetch_retry_irq(&stat->syncp, start));
 519
 520         return v;
 521 }
 522
 523 /**
 524  * blkg_stat_reset - reset a blkg_stat
 525  * @stat: blkg_stat to reset
 526  */
 527 static inline void blkg_stat_reset(struct blkg_stat *stat)
 528 {
 529         stat->cnt = 0;
 530 }
 531
 532 /**
 533  * blkg_stat_merge - merge a blkg_stat into another
 534  * @to: the destination blkg_stat
 535  * @from: the source
 536  *
 537  * Add @from's count to @to.
 538  */
 539 static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from)
 540 {
 541         blkg_stat_add(to, blkg_stat_read(from));
 542 }
 543
 544 static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
 545 {
 546         u64_stats_init(&rwstat->syncp);
 547 }
 548
 549 /**
 550  * blkg_rwstat_add - add a value to a blkg_rwstat
 551  * @rwstat: target blkg_rwstat
 552  * @rw: mask of REQ_{WRITE|SYNC}
 553  * @val: value to add
 554  *
 555  * Add @val to @rwstat.  The counters are chosen according to @rw.  The
 556  * caller is responsible for synchronizing calls to this function.
 557  */
 558 static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
 559                                    int rw, uint64_t val)
 560 {
 561         u64_stats_update_begin(&rwstat->syncp);
 562
 563         if (rw & REQ_WRITE)
 564                 rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
 565         else
 566                 rwstat->cnt[BLKG_RWSTAT_READ] += val;
 567         if (rw & REQ_SYNC)
 568                 rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
 569         else
 570                 rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
 571
 572         u64_stats_update_end(&rwstat->syncp);
 573 }
 574
 575 /**
 576  * blkg_rwstat_read - read the current values of a blkg_rwstat
 577  * @rwstat: blkg_rwstat to read
 578  *
 579  * Read the current snapshot of @rwstat and return it as the return value.
 580  * This function can be called without synchronization and takes care of
 581  * u64 atomicity.
 582  */
 583 static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
 584 {
 585         unsigned int start;
 586         struct blkg_rwstat tmp;
 587
 588         do {
 589                 start = u64_stats_fetch_begin_irq(&rwstat->syncp);
 590                 tmp = *rwstat;
 591         } while (u64_stats_fetch_retry_irq(&rwstat->syncp, start));
 592
 593         return tmp;
 594 }
 595
 596 /**
 597  * blkg_rwstat_total - read the total count of a blkg_rwstat
 598  * @rwstat: blkg_rwstat to read
 599  *
 600  * Return the total count of @rwstat regardless of the IO direction.  This
 601  * function can be called without synchronization and takes care of u64
 602  * atomicity.
 603  */
 604 static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
 605 {
 606         struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
 607
 608         return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
 609 }
 610
 611 /**
 612  * blkg_rwstat_reset - reset a blkg_rwstat
 613  * @rwstat: blkg_rwstat to reset
 614  */
 615 static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
 616 {
 617         memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
 618 }
 619
 620 /**
 621  * blkg_rwstat_merge - merge a blkg_rwstat into another
 622  * @to: the destination blkg_rwstat
 623  * @from: the source
 624  *
 625  * Add @from's counts to @to.
 626  */
 627 static inline void blkg_rwstat_merge(struct blkg_rwstat *to,
 628                                      struct blkg_rwstat *from)
 629 {
 630         struct blkg_rwstat v = blkg_rwstat_read(from);
 631         int i;
 632
 633         u64_stats_update_begin(&to->syncp);
 634         for (i = 0; i < BLKG_RWSTAT_NR; i++)
 635                 to->cnt[i] += v.cnt[i];
 636         u64_stats_update_end(&to->syncp);
 637 }
 638
 639 #ifdef CONFIG_BLK_DEV_THROTTLING
 640 extern bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
 641                            struct bio *bio);
 642 #else
 643 static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
 644                                   struct bio *bio) { return false; }
 645 #endif
 646
 647 static inline bool blkcg_bio_issue_check(struct request_queue *q,
 648                                          struct bio *bio)
 649 {
 650         struct blkcg *blkcg;
 651         struct blkcg_gq *blkg;
 652         bool throtl = false;
 653
 654         rcu_read_lock();
 655         blkcg = bio_blkcg(bio);
 656
 657         blkg = blkg_lookup(blkcg, q);
 658         if (unlikely(!blkg)) {
 659                 spin_lock_irq(q->queue_lock);
 660                 blkg = blkg_lookup_create(blkcg, q);
 661                 if (IS_ERR(blkg))
 662                         blkg = NULL;
 663                 spin_unlock_irq(q->queue_lock);
 664         }
 665
 666         throtl = blk_throtl_bio(q, blkg, bio);
 667
 668         rcu_read_unlock();
 669         return !throtl;
 670 }
 671
 672 #else   /* CONFIG_BLK_CGROUP */
 673
 674 struct blkcg {
 675 };
 676
 677 struct blkg_policy_data {
 678 };
 679
 680 struct blkcg_policy_data {
 681 };
 682
 683 struct blkcg_gq {
 684 };
 685
 686 struct blkcg_policy {
 687 };
 688
 689 #define blkcg_root_css  ((struct cgroup_subsys_state *)ERR_PTR(-EINVAL))
 690
 691 static inline struct cgroup_subsys_state *
 692 task_get_blkcg_css(struct task_struct *task)
 693 {
 694         return NULL;
 695 }
 696
 697 #ifdef CONFIG_BLOCK
 698
 699 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
 700 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
 701 static inline void blkcg_drain_queue(struct request_queue *q) { }
 702 static inline void blkcg_exit_queue(struct request_queue *q) { }
 703 static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
 704 static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
 705 static inline int blkcg_activate_policy(struct request_queue *q,
 706                                         const struct blkcg_policy *pol) { return 0; }
 707 static inline void blkcg_deactivate_policy(struct request_queue *q,
 708                                            const struct blkcg_policy *pol) { }
 709
 710 static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
 711
 712 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 713                                                   struct blkcg_policy *pol) { return NULL; }
 714 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
 715 static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
 716 static inline void blkg_get(struct blkcg_gq *blkg) { }
 717 static inline void blkg_put(struct blkcg_gq *blkg) { }
 718
 719 static inline struct request_list *blk_get_rl(struct request_queue *q,
 720                                               struct bio *bio) { return &q->root_rl; }
 721 static inline void blk_put_rl(struct request_list *rl) { }
 722 static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl) { }
 723 static inline struct request_list *blk_rq_rl(struct request *rq) { return &rq->q->root_rl; }
 724
 725 static inline bool blkcg_bio_issue_check(struct request_queue *q,
 726                                          struct bio *bio) { return true; }
 727
 728 #define blk_queue_for_each_rl(rl, q)    \
 729         for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
 730
 731 #endif  /* CONFIG_BLOCK */
 732 #endif  /* CONFIG_BLK_CGROUP */
 733 #endif  /* _BLK_CGROUP_H */