include/linux/backing-dev.h

   1 /*
   2  * include/linux/backing-dev.h
   3  *
   4  * low-level device information and state which is propagated up through
   5  * to high-level code.
   6  */
   7
   8 #ifndef _LINUX_BACKING_DEV_H
   9 #define _LINUX_BACKING_DEV_H
  10
  11 #include <linux/kernel.h>
  12 #include <linux/fs.h>
  13 #include <linux/sched.h>
  14 #include <linux/blkdev.h>
  15 #include <linux/writeback.h>
  16 #include <linux/blk-cgroup.h>
  17 #include <linux/backing-dev-defs.h>
  18 #include <linux/slab.h>
  19
  20 int __must_check bdi_init(struct backing_dev_info *bdi);
  21 void bdi_exit(struct backing_dev_info *bdi);
  22
  23 __printf(3, 4)
  24 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
  25                 const char *fmt, ...);
  26 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
  27 void bdi_unregister(struct backing_dev_info *bdi);
  28
  29 int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
  30 void bdi_destroy(struct backing_dev_info *bdi);
  31
  32 void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
  33                         bool range_cyclic, enum wb_reason reason);
  34 void wb_start_background_writeback(struct bdi_writeback *wb);
  35 void wb_workfn(struct work_struct *work);
  36 void wb_wakeup_delayed(struct bdi_writeback *wb);
  37
  38 extern spinlock_t bdi_lock;
  39 extern struct list_head bdi_list;
  40
  41 extern struct workqueue_struct *bdi_wq;
  42
  43 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
  44 {
  45         return test_bit(WB_has_dirty_io, &wb->state);
  46 }
  47
  48 static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
  49 {
  50         /*
  51          * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
  52          * any dirty wbs.  See wb_update_write_bandwidth().
  53          */
  54         return atomic_long_read(&bdi->tot_write_bandwidth);
  55 }
  56
  57 static inline void __add_wb_stat(struct bdi_writeback *wb,
  58                                  enum wb_stat_item item, s64 amount)
  59 {
  60         __percpu_counter_add(&wb->stat[item], amount, WB_STAT_BATCH);
  61 }
  62
  63 static inline void __inc_wb_stat(struct bdi_writeback *wb,
  64                                  enum wb_stat_item item)
  65 {
  66         __add_wb_stat(wb, item, 1);
  67 }
  68
  69 static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  70 {
  71         unsigned long flags;
  72
  73         local_irq_save(flags);
  74         __inc_wb_stat(wb, item);
  75         local_irq_restore(flags);
  76 }
  77
  78 static inline void __dec_wb_stat(struct bdi_writeback *wb,
  79                                  enum wb_stat_item item)
  80 {
  81         __add_wb_stat(wb, item, -1);
  82 }
  83
  84 static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  85 {
  86         unsigned long flags;
  87
  88         local_irq_save(flags);
  89         __dec_wb_stat(wb, item);
  90         local_irq_restore(flags);
  91 }
  92
  93 static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  94 {
  95         return percpu_counter_read_positive(&wb->stat[item]);
  96 }
  97
  98 static inline s64 __wb_stat_sum(struct bdi_writeback *wb,
  99                                 enum wb_stat_item item)
 100 {
 101         return percpu_counter_sum_positive(&wb->stat[item]);
 102 }
 103
 104 static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
 105 {
 106         s64 sum;
 107         unsigned long flags;
 108
 109         local_irq_save(flags);
 110         sum = __wb_stat_sum(wb, item);
 111         local_irq_restore(flags);
 112
 113         return sum;
 114 }
 115
 116 extern void wb_writeout_inc(struct bdi_writeback *wb);
 117
 118 /*
 119  * maximal error of a stat counter.
 120  */
 121 static inline unsigned long wb_stat_error(struct bdi_writeback *wb)
 122 {
 123 #ifdef CONFIG_SMP
 124         return nr_cpu_ids * WB_STAT_BATCH;
 125 #else
 126         return 1;
 127 #endif
 128 }
 129
 130 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 131 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 132
 133 /*
 134  * Flags in backing_dev_info::capability
 135  *
 136  * The first three flags control whether dirty pages will contribute to the
 137  * VM's accounting and whether writepages() should be called for dirty pages
 138  * (something that would not, for example, be appropriate for ramfs)
 139  *
 140  * WARNING: these flags are closely related and should not normally be
 141  * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 142  * three flags into a single convenience macro.
 143  *
 144  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 145  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 146  * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 147  * BDI_CAP_STRICTLIMIT:    Keep number of dirty pages below bdi threshold.
 148  *
 149  * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
 150  */
 151 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001
 152 #define BDI_CAP_NO_WRITEBACK    0x00000002
 153 #define BDI_CAP_NO_ACCT_WB      0x00000004
 154 #define BDI_CAP_STABLE_WRITES   0x00000008
 155 #define BDI_CAP_STRICTLIMIT     0x00000010
 156 #define BDI_CAP_CGROUP_WRITEBACK 0x00000020
 157
 158 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 159         (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 160
 161 extern struct backing_dev_info noop_backing_dev_info;
 162
 163 /**
 164  * writeback_in_progress - determine whether there is writeback in progress
 165  * @wb: bdi_writeback of interest
 166  *
 167  * Determine whether there is writeback waiting to be handled against a
 168  * bdi_writeback.
 169  */
 170 static inline bool writeback_in_progress(struct bdi_writeback *wb)
 171 {
 172         return test_bit(WB_writeback_running, &wb->state);
 173 }
 174
 175 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
 176 {
 177         struct super_block *sb;
 178
 179         if (!inode)
 180                 return &noop_backing_dev_info;
 181
 182         sb = inode->i_sb;
 183 #ifdef CONFIG_BLOCK
 184         if (sb_is_blkdev_sb(sb))
 185                 return blk_get_backing_dev_info(I_BDEV(inode));
 186 #endif
 187         return sb->s_bdi;
 188 }
 189
 190 static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 191 {
 192         struct backing_dev_info *bdi = wb->bdi;
 193
 194         if (bdi->congested_fn)
 195                 return bdi->congested_fn(bdi->congested_data, cong_bits);
 196         return wb->congested->state & cong_bits;
 197 }
 198
 199 long congestion_wait(int sync, long timeout);
 200 long wait_iff_congested(struct zone *zone, int sync, long timeout);
 201 int pdflush_proc_obsolete(struct ctl_table *table, int write,
 202                 void __user *buffer, size_t *lenp, loff_t *ppos);
 203
 204 static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
 205 {
 206         return bdi->capabilities & BDI_CAP_STABLE_WRITES;
 207 }
 208
 209 static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 210 {
 211         return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 212 }
 213
 214 static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 215 {
 216         return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 217 }
 218
 219 static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 220 {
 221         /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
 222         return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
 223                                       BDI_CAP_NO_WRITEBACK));
 224 }
 225
 226 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 227 {
 228         return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
 229 }
 230
 231 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 232 {
 233         return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
 234 }
 235
 236 static inline int bdi_sched_wait(void *word)
 237 {
 238         schedule();
 239         return 0;
 240 }
 241
 242 #ifdef CONFIG_CGROUP_WRITEBACK
 243
 244 struct bdi_writeback_congested *
 245 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
 246 void wb_congested_put(struct bdi_writeback_congested *congested);
 247 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 248                                     struct cgroup_subsys_state *memcg_css,
 249                                     gfp_t gfp);
 250 void wb_memcg_offline(struct mem_cgroup *memcg);
 251 void wb_blkcg_offline(struct blkcg *blkcg);
 252 int inode_congested(struct inode *inode, int cong_bits);
 253
 254 /**
 255  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
 256  * @inode: inode of interest
 257  *
 258  * cgroup writeback requires support from both the bdi and filesystem.
 259  * Also, both memcg and iocg have to be on the default hierarchy.  Test
 260  * whether all conditions are met.
 261  *
 262  * Note that the test result may change dynamically on the same inode
 263  * depending on how memcg and iocg are configured.
 264  */
 265 static inline bool inode_cgwb_enabled(struct inode *inode)
 266 {
 267         struct backing_dev_info *bdi = inode_to_bdi(inode);
 268
 269         return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
 270                 cgroup_subsys_on_dfl(io_cgrp_subsys) &&
 271                 bdi_cap_account_dirty(bdi) &&
 272                 (bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
 273                 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
 274 }
 275
 276 /**
 277  * wb_find_current - find wb for %current on a bdi
 278  * @bdi: bdi of interest
 279  *
 280  * Find the wb of @bdi which matches both the memcg and blkcg of %current.
 281  * Must be called under rcu_read_lock() which protects the returend wb.
 282  * NULL if not found.
 283  */
 284 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 285 {
 286         struct cgroup_subsys_state *memcg_css;
 287         struct bdi_writeback *wb;
 288
 289         memcg_css = task_css(current, memory_cgrp_id);
 290         if (!memcg_css->parent)
 291                 return &bdi->wb;
 292
 293         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 294
 295         /*
 296          * %current's blkcg equals the effective blkcg of its memcg.  No
 297          * need to use the relatively expensive cgroup_get_e_css().
 298          */
 299         if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
 300                 return wb;
 301         return NULL;
 302 }
 303
 304 /**
 305  * wb_get_create_current - get or create wb for %current on a bdi
 306  * @bdi: bdi of interest
 307  * @gfp: allocation mask
 308  *
 309  * Equivalent to wb_get_create() on %current's memcg.  This function is
 310  * called from a relatively hot path and optimizes the common cases using
 311  * wb_find_current().
 312  */
 313 static inline struct bdi_writeback *
 314 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 315 {
 316         struct bdi_writeback *wb;
 317
 318         rcu_read_lock();
 319         wb = wb_find_current(bdi);
 320         if (wb && unlikely(!wb_tryget(wb)))
 321                 wb = NULL;
 322         rcu_read_unlock();
 323
 324         if (unlikely(!wb)) {
 325                 struct cgroup_subsys_state *memcg_css;
 326
 327                 memcg_css = task_get_css(current, memory_cgrp_id);
 328                 wb = wb_get_create(bdi, memcg_css, gfp);
 329                 css_put(memcg_css);
 330         }
 331         return wb;
 332 }
 333
 334 /**
 335  * inode_to_wb_is_valid - test whether an inode has a wb associated
 336  * @inode: inode of interest
 337  *
 338  * Returns %true if @inode has a wb associated.  May be called without any
 339  * locking.
 340  */
 341 static inline bool inode_to_wb_is_valid(struct inode *inode)
 342 {
 343         return inode->i_wb;
 344 }
 345
 346 /**
 347  * inode_to_wb - determine the wb of an inode
 348  * @inode: inode of interest
 349  *
 350  * Returns the wb @inode is currently associated with.  The caller must be
 351  * holding either @inode->i_lock, @inode->i_mapping->tree_lock, or the
 352  * associated wb's list_lock.
 353  */
 354 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
 355 {
 356 #ifdef CONFIG_LOCKDEP
 357         WARN_ON_ONCE(debug_locks &&
 358                      (!lockdep_is_held(&inode->i_lock) &&
 359                       !lockdep_is_held(&inode->i_mapping->tree_lock) &&
 360                       !lockdep_is_held(&inode->i_wb->list_lock)));
 361 #endif
 362         return inode->i_wb;
 363 }
 364
 365 /**
 366  * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
 367  * @inode: target inode
 368  * @lockedp: temp bool output param, to be passed to the end function
 369  *
 370  * The caller wants to access the wb associated with @inode but isn't
 371  * holding inode->i_lock, mapping->tree_lock or wb->list_lock.  This
 372  * function determines the wb associated with @inode and ensures that the
 373  * association doesn't change until the transaction is finished with
 374  * unlocked_inode_to_wb_end().
 375  *
 376  * The caller must call unlocked_inode_to_wb_end() with *@lockdep
 377  * afterwards and can't sleep during transaction.  IRQ may or may not be
 378  * disabled on return.
 379  */
 380 static inline struct bdi_writeback *
 381 unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
 382 {
 383         rcu_read_lock();
 384
 385         /*
 386          * Paired with store_release in inode_switch_wb_work_fn() and
 387          * ensures that we see the new wb if we see cleared I_WB_SWITCH.
 388          */
 389         *lockedp = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
 390
 391         if (unlikely(*lockedp))
 392                 spin_lock_irq(&inode->i_mapping->tree_lock);
 393
 394         /*
 395          * Protected by either !I_WB_SWITCH + rcu_read_lock() or tree_lock.
 396          * inode_to_wb() will bark.  Deref directly.
 397          */
 398         return inode->i_wb;
 399 }
 400
 401 /**
 402  * unlocked_inode_to_wb_end - end inode wb access transaction
 403  * @inode: target inode
 404  * @locked: *@lockedp from unlocked_inode_to_wb_begin()
 405  */
 406 static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
 407 {
 408         if (unlikely(locked))
 409                 spin_unlock_irq(&inode->i_mapping->tree_lock);
 410
 411         rcu_read_unlock();
 412 }
 413
 414 #else   /* CONFIG_CGROUP_WRITEBACK */
 415
 416 static inline bool inode_cgwb_enabled(struct inode *inode)
 417 {
 418         return false;
 419 }
 420
 421 static inline struct bdi_writeback_congested *
 422 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
 423 {
 424         atomic_inc(&bdi->wb_congested->refcnt);
 425         return bdi->wb_congested;
 426 }
 427
 428 static inline void wb_congested_put(struct bdi_writeback_congested *congested)
 429 {
 430         if (atomic_dec_and_test(&congested->refcnt))
 431                 kfree(congested);
 432 }
 433
 434 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 435 {
 436         return &bdi->wb;
 437 }
 438
 439 static inline struct bdi_writeback *
 440 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 441 {
 442         return &bdi->wb;
 443 }
 444
 445 static inline bool inode_to_wb_is_valid(struct inode *inode)
 446 {
 447         return true;
 448 }
 449
 450 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
 451 {
 452         return &inode_to_bdi(inode)->wb;
 453 }
 454
 455 static inline struct bdi_writeback *
 456 unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
 457 {
 458         return inode_to_wb(inode);
 459 }
 460
 461 static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
 462 {
 463 }
 464
 465 static inline void wb_memcg_offline(struct mem_cgroup *memcg)
 466 {
 467 }
 468
 469 static inline void wb_blkcg_offline(struct blkcg *blkcg)
 470 {
 471 }
 472
 473 static inline int inode_congested(struct inode *inode, int cong_bits)
 474 {
 475         return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
 476 }
 477
 478 #endif  /* CONFIG_CGROUP_WRITEBACK */
 479
 480 static inline int inode_read_congested(struct inode *inode)
 481 {
 482         return inode_congested(inode, 1 << WB_sync_congested);
 483 }
 484
 485 static inline int inode_write_congested(struct inode *inode)
 486 {
 487         return inode_congested(inode, 1 << WB_async_congested);
 488 }
 489
 490 static inline int inode_rw_congested(struct inode *inode)
 491 {
 492         return inode_congested(inode, (1 << WB_sync_congested) |
 493                                       (1 << WB_async_congested));
 494 }
 495
 496 static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
 497 {
 498         return wb_congested(&bdi->wb, cong_bits);
 499 }
 500
 501 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 502 {
 503         return bdi_congested(bdi, 1 << WB_sync_congested);
 504 }
 505
 506 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 507 {
 508         return bdi_congested(bdi, 1 << WB_async_congested);
 509 }
 510
 511 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 512 {
 513         return bdi_congested(bdi, (1 << WB_sync_congested) |
 514                                   (1 << WB_async_congested));
 515 }
 516
 517 #endif  /* _LINUX_BACKING_DEV_H */