block/blk-cgroup.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _BLK_CGROUP_PRIVATE_H
   3 #define _BLK_CGROUP_PRIVATE_H
   4 /*
   5  * block cgroup private header
   6  *
   7  * Based on ideas and code from CFQ, CFS and BFQ:
   8  * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
   9  *
  10  * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
  11  *                    Paolo Valente <paolo.valente@unimore.it>
  12  *
  13  * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
  14  *                    Nauman Rafique <nauman@google.com>
  15  */
  16
  17 #include <linux/blk-cgroup.h>
  18 #include <linux/cgroup.h>
  19 #include <linux/kthread.h>
  20 #include <linux/blk-mq.h>
  21
  22 struct blkcg_gq;
  23 struct blkg_policy_data;
  24
  25
  26 /* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
  27 #define BLKG_STAT_CPU_BATCH     (INT_MAX / 2)
  28
  29 #ifdef CONFIG_BLK_CGROUP
  30
  31 enum blkg_iostat_type {
  32         BLKG_IOSTAT_READ,
  33         BLKG_IOSTAT_WRITE,
  34         BLKG_IOSTAT_DISCARD,
  35
  36         BLKG_IOSTAT_NR,
  37 };
  38
  39 struct blkg_iostat {
  40         u64                             bytes[BLKG_IOSTAT_NR];
  41         u64                             ios[BLKG_IOSTAT_NR];
  42 };
  43
  44 struct blkg_iostat_set {
  45         struct u64_stats_sync           sync;
  46         struct blkg_iostat              cur;
  47         struct blkg_iostat              last;
  48 };
  49
  50 /* association between a blk cgroup and a request queue */
  51 struct blkcg_gq {
  52         /* Pointer to the associated request_queue */
  53         struct request_queue            *q;
  54         struct list_head                q_node;
  55         struct hlist_node               blkcg_node;
  56         struct blkcg                    *blkcg;
  57
  58         /* all non-root blkcg_gq's are guaranteed to have access to parent */
  59         struct blkcg_gq                 *parent;
  60
  61         /* reference count */
  62         struct percpu_ref               refcnt;
  63
  64         /* is this blkg online? protected by both blkcg and q locks */
  65         bool                            online;
  66
  67         struct blkg_iostat_set __percpu *iostat_cpu;
  68         struct blkg_iostat_set          iostat;
  69
  70         struct blkg_policy_data         *pd[BLKCG_MAX_POLS];
  71
  72         spinlock_t                      async_bio_lock;
  73         struct bio_list                 async_bios;
  74         union {
  75                 struct work_struct      async_bio_work;
  76                 struct work_struct      free_work;
  77         };
  78
  79         atomic_t                        use_delay;
  80         atomic64_t                      delay_nsec;
  81         atomic64_t                      delay_start;
  82         u64                             last_delay;
  83         int                             last_use;
  84
  85         struct rcu_head                 rcu_head;
  86 };
  87
  88 struct blkcg {
  89         struct cgroup_subsys_state      css;
  90         spinlock_t                      lock;
  91         refcount_t                      online_pin;
  92
  93         struct radix_tree_root          blkg_tree;
  94         struct blkcg_gq __rcu           *blkg_hint;
  95         struct hlist_head               blkg_list;
  96
  97         struct blkcg_policy_data        *cpd[BLKCG_MAX_POLS];
  98
  99         struct list_head                all_blkcgs_node;
 100 #ifdef CONFIG_BLK_CGROUP_FC_APPID
 101         char                            fc_app_id[FC_APPID_LEN];
 102 #endif
 103 #ifdef CONFIG_CGROUP_WRITEBACK
 104         struct list_head                cgwb_list;
 105 #endif
 106 };
 107
 108 static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 109 {
 110         return css ? container_of(css, struct blkcg, css) : NULL;
 111 }
 112
 113 /*
 114  * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
 115  * request_queue (q).  This is used by blkcg policies which need to track
 116  * information per blkcg - q pair.
 117  *
 118  * There can be multiple active blkcg policies and each blkg:policy pair is
 119  * represented by a blkg_policy_data which is allocated and freed by each
 120  * policy's pd_alloc/free_fn() methods.  A policy can allocate private data
 121  * area by allocating larger data structure which embeds blkg_policy_data
 122  * at the beginning.
 123  */
 124 struct blkg_policy_data {
 125         /* the blkg and policy id this per-policy data belongs to */
 126         struct blkcg_gq                 *blkg;
 127         int                             plid;
 128 };
 129
 130 /*
 131  * Policies that need to keep per-blkcg data which is independent from any
 132  * request_queue associated to it should implement cpd_alloc/free_fn()
 133  * methods.  A policy can allocate private data area by allocating larger
 134  * data structure which embeds blkcg_policy_data at the beginning.
 135  * cpd_init() is invoked to let each policy handle per-blkcg data.
 136  */
 137 struct blkcg_policy_data {
 138         /* the blkcg and policy id this per-policy data belongs to */
 139         struct blkcg                    *blkcg;
 140         int                             plid;
 141 };
 142
 143 typedef struct blkcg_policy_data *(blkcg_pol_alloc_cpd_fn)(gfp_t gfp);
 144 typedef void (blkcg_pol_init_cpd_fn)(struct blkcg_policy_data *cpd);
 145 typedef void (blkcg_pol_free_cpd_fn)(struct blkcg_policy_data *cpd);
 146 typedef void (blkcg_pol_bind_cpd_fn)(struct blkcg_policy_data *cpd);
 147 typedef struct blkg_policy_data *(blkcg_pol_alloc_pd_fn)(gfp_t gfp,
 148                                 struct request_queue *q, struct blkcg *blkcg);
 149 typedef void (blkcg_pol_init_pd_fn)(struct blkg_policy_data *pd);
 150 typedef void (blkcg_pol_online_pd_fn)(struct blkg_policy_data *pd);
 151 typedef void (blkcg_pol_offline_pd_fn)(struct blkg_policy_data *pd);
 152 typedef void (blkcg_pol_free_pd_fn)(struct blkg_policy_data *pd);
 153 typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkg_policy_data *pd);
 154 typedef void (blkcg_pol_stat_pd_fn)(struct blkg_policy_data *pd,
 155                                 struct seq_file *s);
 156
 157 struct blkcg_policy {
 158         int                             plid;
 159         /* cgroup files for the policy */
 160         struct cftype                   *dfl_cftypes;
 161         struct cftype                   *legacy_cftypes;
 162
 163         /* operations */
 164         blkcg_pol_alloc_cpd_fn          *cpd_alloc_fn;
 165         blkcg_pol_init_cpd_fn           *cpd_init_fn;
 166         blkcg_pol_free_cpd_fn           *cpd_free_fn;
 167         blkcg_pol_bind_cpd_fn           *cpd_bind_fn;
 168
 169         blkcg_pol_alloc_pd_fn           *pd_alloc_fn;
 170         blkcg_pol_init_pd_fn            *pd_init_fn;
 171         blkcg_pol_online_pd_fn          *pd_online_fn;
 172         blkcg_pol_offline_pd_fn         *pd_offline_fn;
 173         blkcg_pol_free_pd_fn            *pd_free_fn;
 174         blkcg_pol_reset_pd_stats_fn     *pd_reset_stats_fn;
 175         blkcg_pol_stat_pd_fn            *pd_stat_fn;
 176 };
 177
 178 extern struct blkcg blkcg_root;
 179 extern bool blkcg_debug_stats;
 180
 181 struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
 182                                       struct request_queue *q, bool update_hint);
 183 int blkcg_init_queue(struct request_queue *q);
 184 void blkcg_exit_queue(struct request_queue *q);
 185
 186 /* Blkio controller policy registration */
 187 int blkcg_policy_register(struct blkcg_policy *pol);
 188 void blkcg_policy_unregister(struct blkcg_policy *pol);
 189 int blkcg_activate_policy(struct request_queue *q,
 190                           const struct blkcg_policy *pol);
 191 void blkcg_deactivate_policy(struct request_queue *q,
 192                              const struct blkcg_policy *pol);
 193
 194 const char *blkg_dev_name(struct blkcg_gq *blkg);
 195 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 196                        u64 (*prfill)(struct seq_file *,
 197                                      struct blkg_policy_data *, int),
 198                        const struct blkcg_policy *pol, int data,
 199                        bool show_total);
 200 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
 201
 202 struct blkg_conf_ctx {
 203         struct block_device             *bdev;
 204         struct blkcg_gq                 *blkg;
 205         char                            *body;
 206 };
 207
 208 struct block_device *blkcg_conf_open_bdev(char **inputp);
 209 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 210                    char *input, struct blkg_conf_ctx *ctx);
 211 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 212
 213 /**
 214  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
 215  * @return: true if this bio needs to be submitted with the root blkg context.
 216  *
 217  * In order to avoid priority inversions we sometimes need to issue a bio as if
 218  * it were attached to the root blkg, and then backcharge to the actual owning
 219  * blkg.  The idea is we do bio_blkcg_css() to look up the actual context for
 220  * the bio and attach the appropriate blkg to the bio.  Then we call this helper
 221  * and if it is true run with the root blkg for that queue and then do any
 222  * backcharging to the originating cgroup once the io is complete.
 223  */
 224 static inline bool bio_issue_as_root_blkg(struct bio *bio)
 225 {
 226         return (bio->bi_opf & (REQ_META | REQ_SWAP)) != 0;
 227 }
 228
 229 /**
 230  * __blkg_lookup - internal version of blkg_lookup()
 231  * @blkcg: blkcg of interest
 232  * @q: request_queue of interest
 233  * @update_hint: whether to update lookup hint with the result or not
 234  *
 235  * This is internal version and shouldn't be used by policy
 236  * implementations.  Looks up blkgs for the @blkcg - @q pair regardless of
 237  * @q's bypass state.  If @update_hint is %true, the caller should be
 238  * holding @q->queue_lock and lookup hint is updated on success.
 239  */
 240 static inline struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
 241                                              struct request_queue *q,
 242                                              bool update_hint)
 243 {
 244         struct blkcg_gq *blkg;
 245
 246         if (blkcg == &blkcg_root)
 247                 return q->root_blkg;
 248
 249         blkg = rcu_dereference(blkcg->blkg_hint);
 250         if (blkg && blkg->q == q)
 251                 return blkg;
 252
 253         return blkg_lookup_slowpath(blkcg, q, update_hint);
 254 }
 255
 256 /**
 257  * blkg_lookup - lookup blkg for the specified blkcg - q pair
 258  * @blkcg: blkcg of interest
 259  * @q: request_queue of interest
 260  *
 261  * Lookup blkg for the @blkcg - @q pair.  This function should be called
 262  * under RCU read lock.
 263  */
 264 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
 265                                            struct request_queue *q)
 266 {
 267         WARN_ON_ONCE(!rcu_read_lock_held());
 268         return __blkg_lookup(blkcg, q, false);
 269 }
 270
 271 /**
 272  * blk_queue_root_blkg - return blkg for the (blkcg_root, @q) pair
 273  * @q: request_queue of interest
 274  *
 275  * Lookup blkg for @q at the root level. See also blkg_lookup().
 276  */
 277 static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
 278 {
 279         return q->root_blkg;
 280 }
 281
 282 /**
 283  * blkg_to_pdata - get policy private data
 284  * @blkg: blkg of interest
 285  * @pol: policy of interest
 286  *
 287  * Return pointer to private data associated with the @blkg-@pol pair.
 288  */
 289 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 290                                                   struct blkcg_policy *pol)
 291 {
 292         return blkg ? blkg->pd[pol->plid] : NULL;
 293 }
 294
 295 static inline struct blkcg_policy_data *blkcg_to_cpd(struct blkcg *blkcg,
 296                                                      struct blkcg_policy *pol)
 297 {
 298         return blkcg ? blkcg->cpd[pol->plid] : NULL;
 299 }
 300
 301 /**
 302  * pdata_to_blkg - get blkg associated with policy private data
 303  * @pd: policy private data of interest
 304  *
 305  * @pd is policy private data.  Determine the blkg it's associated with.
 306  */
 307 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
 308 {
 309         return pd ? pd->blkg : NULL;
 310 }
 311
 312 static inline struct blkcg *cpd_to_blkcg(struct blkcg_policy_data *cpd)
 313 {
 314         return cpd ? cpd->blkcg : NULL;
 315 }
 316
 317 /**
 318  * blkg_path - format cgroup path of blkg
 319  * @blkg: blkg of interest
 320  * @buf: target buffer
 321  * @buflen: target buffer length
 322  *
 323  * Format the path of the cgroup of @blkg into @buf.
 324  */
 325 static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
 326 {
 327         return cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
 328 }
 329
 330 /**
 331  * blkg_get - get a blkg reference
 332  * @blkg: blkg to get
 333  *
 334  * The caller should be holding an existing reference.
 335  */
 336 static inline void blkg_get(struct blkcg_gq *blkg)
 337 {
 338         percpu_ref_get(&blkg->refcnt);
 339 }
 340
 341 /**
 342  * blkg_tryget - try and get a blkg reference
 343  * @blkg: blkg to get
 344  *
 345  * This is for use when doing an RCU lookup of the blkg.  We may be in the midst
 346  * of freeing this blkg, so we can only use it if the refcnt is not zero.
 347  */
 348 static inline bool blkg_tryget(struct blkcg_gq *blkg)
 349 {
 350         return blkg && percpu_ref_tryget(&blkg->refcnt);
 351 }
 352
 353 /**
 354  * blkg_put - put a blkg reference
 355  * @blkg: blkg to put
 356  */
 357 static inline void blkg_put(struct blkcg_gq *blkg)
 358 {
 359         percpu_ref_put(&blkg->refcnt);
 360 }
 361
 362 /**
 363  * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
 364  * @d_blkg: loop cursor pointing to the current descendant
 365  * @pos_css: used for iteration
 366  * @p_blkg: target blkg to walk descendants of
 367  *
 368  * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
 369  * read locked.  If called under either blkcg or queue lock, the iteration
 370  * is guaranteed to include all and only online blkgs.  The caller may
 371  * update @pos_css by calling css_rightmost_descendant() to skip subtree.
 372  * @p_blkg is included in the iteration and the first node to be visited.
 373  */
 374 #define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)           \
 375         css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)   \
 376                 if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),    \
 377                                               (p_blkg)->q, false)))
 378
 379 /**
 380  * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
 381  * @d_blkg: loop cursor pointing to the current descendant
 382  * @pos_css: used for iteration
 383  * @p_blkg: target blkg to walk descendants of
 384  *
 385  * Similar to blkg_for_each_descendant_pre() but performs post-order
 386  * traversal instead.  Synchronization rules are the same.  @p_blkg is
 387  * included in the iteration and the last node to be visited.
 388  */
 389 #define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)          \
 390         css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)  \
 391                 if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),    \
 392                                               (p_blkg)->q, false)))
 393
 394 bool __blkcg_punt_bio_submit(struct bio *bio);
 395
 396 static inline bool blkcg_punt_bio_submit(struct bio *bio)
 397 {
 398         if (bio->bi_opf & REQ_CGROUP_PUNT)
 399                 return __blkcg_punt_bio_submit(bio);
 400         else
 401                 return false;
 402 }
 403
 404 static inline void blkcg_bio_issue_init(struct bio *bio)
 405 {
 406         bio_issue_init(&bio->bi_issue, bio_sectors(bio));
 407 }
 408
 409 static inline void blkcg_use_delay(struct blkcg_gq *blkg)
 410 {
 411         if (WARN_ON_ONCE(atomic_read(&blkg->use_delay) < 0))
 412                 return;
 413         if (atomic_add_return(1, &blkg->use_delay) == 1)
 414                 atomic_inc(&blkg->blkcg->css.cgroup->congestion_count);
 415 }
 416
 417 static inline int blkcg_unuse_delay(struct blkcg_gq *blkg)
 418 {
 419         int old = atomic_read(&blkg->use_delay);
 420
 421         if (WARN_ON_ONCE(old < 0))
 422                 return 0;
 423         if (old == 0)
 424                 return 0;
 425
 426         /*
 427          * We do this song and dance because we can race with somebody else
 428          * adding or removing delay.  If we just did an atomic_dec we'd end up
 429          * negative and we'd already be in trouble.  We need to subtract 1 and
 430          * then check to see if we were the last delay so we can drop the
 431          * congestion count on the cgroup.
 432          */
 433         while (old) {
 434                 int cur = atomic_cmpxchg(&blkg->use_delay, old, old - 1);
 435                 if (cur == old)
 436                         break;
 437                 old = cur;
 438         }
 439
 440         if (old == 0)
 441                 return 0;
 442         if (old == 1)
 443                 atomic_dec(&blkg->blkcg->css.cgroup->congestion_count);
 444         return 1;
 445 }
 446
 447 /**
 448  * blkcg_set_delay - Enable allocator delay mechanism with the specified delay amount
 449  * @blkg: target blkg
 450  * @delay: delay duration in nsecs
 451  *
 452  * When enabled with this function, the delay is not decayed and must be
 453  * explicitly cleared with blkcg_clear_delay(). Must not be mixed with
 454  * blkcg_[un]use_delay() and blkcg_add_delay() usages.
 455  */
 456 static inline void blkcg_set_delay(struct blkcg_gq *blkg, u64 delay)
 457 {
 458         int old = atomic_read(&blkg->use_delay);
 459
 460         /* We only want 1 person setting the congestion count for this blkg. */
 461         if (!old && atomic_cmpxchg(&blkg->use_delay, old, -1) == old)
 462                 atomic_inc(&blkg->blkcg->css.cgroup->congestion_count);
 463
 464         atomic64_set(&blkg->delay_nsec, delay);
 465 }
 466
 467 /**
 468  * blkcg_clear_delay - Disable allocator delay mechanism
 469  * @blkg: target blkg
 470  *
 471  * Disable use_delay mechanism. See blkcg_set_delay().
 472  */
 473 static inline void blkcg_clear_delay(struct blkcg_gq *blkg)
 474 {
 475         int old = atomic_read(&blkg->use_delay);
 476
 477         /* We only want 1 person clearing the congestion count for this blkg. */
 478         if (old && atomic_cmpxchg(&blkg->use_delay, old, 0) == old)
 479                 atomic_dec(&blkg->blkcg->css.cgroup->congestion_count);
 480 }
 481
 482 /**
 483  * blk_cgroup_mergeable - Determine whether to allow or disallow merges
 484  * @rq: request to merge into
 485  * @bio: bio to merge
 486  *
 487  * @bio and @rq should belong to the same cgroup and their issue_as_root should
 488  * match. The latter is necessary as we don't want to throttle e.g. a metadata
 489  * update because it happens to be next to a regular IO.
 490  */
 491 static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio)
 492 {
 493         return rq->bio->bi_blkg == bio->bi_blkg &&
 494                 bio_issue_as_root_blkg(rq->bio) == bio_issue_as_root_blkg(bio);
 495 }
 496
 497 void blk_cgroup_bio_start(struct bio *bio);
 498 void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta);
 499 #else   /* CONFIG_BLK_CGROUP */
 500
 501 struct blkg_policy_data {
 502 };
 503
 504 struct blkcg_policy_data {
 505 };
 506
 507 struct blkcg_policy {
 508 };
 509
 510 struct blkcg {
 511 };
 512
 513 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
 514 static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
 515 { return NULL; }
 516 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
 517 static inline void blkcg_exit_queue(struct request_queue *q) { }
 518 static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
 519 static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
 520 static inline int blkcg_activate_policy(struct request_queue *q,
 521                                         const struct blkcg_policy *pol) { return 0; }
 522 static inline void blkcg_deactivate_policy(struct request_queue *q,
 523                                            const struct blkcg_policy *pol) { }
 524
 525 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 526                                                   struct blkcg_policy *pol) { return NULL; }
 527 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
 528 static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
 529 static inline void blkg_get(struct blkcg_gq *blkg) { }
 530 static inline void blkg_put(struct blkcg_gq *blkg) { }
 531
 532 static inline bool blkcg_punt_bio_submit(struct bio *bio) { return false; }
 533 static inline void blkcg_bio_issue_init(struct bio *bio) { }
 534 static inline void blk_cgroup_bio_start(struct bio *bio) { }
 535 static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }
 536
 537 #define blk_queue_for_each_rl(rl, q)    \
 538         for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
 539
 540 #endif  /* CONFIG_BLK_CGROUP */
 541
 542 #endif /* _BLK_CGROUP_PRIVATE_H */