include/linux/backing-dev.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * include/linux/backing-dev.h
   4  *
   5  * low-level device information and state which is propagated up through
   6  * to high-level code.
   7  */
   8
   9 #ifndef _LINUX_BACKING_DEV_H
  10 #define _LINUX_BACKING_DEV_H
  11
  12 #include <linux/kernel.h>
  13 #include <linux/fs.h>
  14 #include <linux/sched.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/device.h>
  17 #include <linux/writeback.h>
  18 #include <linux/blk-cgroup.h>
  19 #include <linux/backing-dev-defs.h>
  20 #include <linux/slab.h>
  21
  22 static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
  23 {
  24         kref_get(&bdi->refcnt);
  25         return bdi;
  26 }
  27
  28 struct backing_dev_info *bdi_get_by_id(u64 id);
  29 void bdi_put(struct backing_dev_info *bdi);
  30
  31 __printf(2, 3)
  32 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...);
  33 __printf(2, 0)
  34 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt,
  35                     va_list args);
  36 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner);
  37 void bdi_unregister(struct backing_dev_info *bdi);
  38
  39 struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id);
  40 static inline struct backing_dev_info *bdi_alloc(gfp_t gfp_mask)
  41 {
  42         return bdi_alloc_node(gfp_mask, NUMA_NO_NODE);
  43 }
  44
  45 void wb_start_background_writeback(struct bdi_writeback *wb);
  46 void wb_workfn(struct work_struct *work);
  47 void wb_wakeup_delayed(struct bdi_writeback *wb);
  48
  49 void wb_wait_for_completion(struct wb_completion *done);
  50
  51 extern spinlock_t bdi_lock;
  52 extern struct list_head bdi_list;
  53
  54 extern struct workqueue_struct *bdi_wq;
  55 extern struct workqueue_struct *bdi_async_bio_wq;
  56
  57 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
  58 {
  59         return test_bit(WB_has_dirty_io, &wb->state);
  60 }
  61
  62 static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
  63 {
  64         /*
  65          * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
  66          * any dirty wbs.  See wb_update_write_bandwidth().
  67          */
  68         return atomic_long_read(&bdi->tot_write_bandwidth);
  69 }
  70
  71 static inline void __add_wb_stat(struct bdi_writeback *wb,
  72                                  enum wb_stat_item item, s64 amount)
  73 {
  74         percpu_counter_add_batch(&wb->stat[item], amount, WB_STAT_BATCH);
  75 }
  76
  77 static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  78 {
  79         __add_wb_stat(wb, item, 1);
  80 }
  81
  82 static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  83 {
  84         __add_wb_stat(wb, item, -1);
  85 }
  86
  87 static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  88 {
  89         return percpu_counter_read_positive(&wb->stat[item]);
  90 }
  91
  92 static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
  93 {
  94         return percpu_counter_sum_positive(&wb->stat[item]);
  95 }
  96
  97 extern void wb_writeout_inc(struct bdi_writeback *wb);
  98
  99 /*
 100  * maximal error of a stat counter.
 101  */
 102 static inline unsigned long wb_stat_error(void)
 103 {
 104 #ifdef CONFIG_SMP
 105         return nr_cpu_ids * WB_STAT_BATCH;
 106 #else
 107         return 1;
 108 #endif
 109 }
 110
 111 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 112 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 113
 114 /*
 115  * Flags in backing_dev_info::capability
 116  *
 117  * The first three flags control whether dirty pages will contribute to the
 118  * VM's accounting and whether writepages() should be called for dirty pages
 119  * (something that would not, for example, be appropriate for ramfs)
 120  *
 121  * WARNING: these flags are closely related and should not normally be
 122  * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 123  * three flags into a single convenience macro.
 124  *
 125  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 126  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 127  * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 128  * BDI_CAP_STRICTLIMIT:    Keep number of dirty pages below bdi threshold.
 129  *
 130  * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
 131  * BDI_CAP_SYNCHRONOUS_IO: Device is so fast that asynchronous IO would be
 132  *                         inefficient.
 133  */
 134 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001
 135 #define BDI_CAP_NO_WRITEBACK    0x00000002
 136 #define BDI_CAP_NO_ACCT_WB      0x00000004
 137 #define BDI_CAP_STABLE_WRITES   0x00000008
 138 #define BDI_CAP_STRICTLIMIT     0x00000010
 139 #define BDI_CAP_CGROUP_WRITEBACK 0x00000020
 140 #define BDI_CAP_SYNCHRONOUS_IO  0x00000040
 141
 142 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 143         (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 144
 145 extern struct backing_dev_info noop_backing_dev_info;
 146
 147 /**
 148  * writeback_in_progress - determine whether there is writeback in progress
 149  * @wb: bdi_writeback of interest
 150  *
 151  * Determine whether there is writeback waiting to be handled against a
 152  * bdi_writeback.
 153  */
 154 static inline bool writeback_in_progress(struct bdi_writeback *wb)
 155 {
 156         return test_bit(WB_writeback_running, &wb->state);
 157 }
 158
 159 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
 160 {
 161         struct super_block *sb;
 162
 163         if (!inode)
 164                 return &noop_backing_dev_info;
 165
 166         sb = inode->i_sb;
 167 #ifdef CONFIG_BLOCK
 168         if (sb_is_blkdev_sb(sb))
 169                 return I_BDEV(inode)->bd_bdi;
 170 #endif
 171         return sb->s_bdi;
 172 }
 173
 174 static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 175 {
 176         struct backing_dev_info *bdi = wb->bdi;
 177
 178         if (bdi->congested_fn)
 179                 return bdi->congested_fn(bdi->congested_data, cong_bits);
 180         return wb->congested->state & cong_bits;
 181 }
 182
 183 long congestion_wait(int sync, long timeout);
 184 long wait_iff_congested(int sync, long timeout);
 185
 186 static inline bool bdi_cap_synchronous_io(struct backing_dev_info *bdi)
 187 {
 188         return bdi->capabilities & BDI_CAP_SYNCHRONOUS_IO;
 189 }
 190
 191 static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
 192 {
 193         return bdi->capabilities & BDI_CAP_STABLE_WRITES;
 194 }
 195
 196 static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 197 {
 198         return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 199 }
 200
 201 static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 202 {
 203         return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 204 }
 205
 206 static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 207 {
 208         /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
 209         return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
 210                                       BDI_CAP_NO_WRITEBACK));
 211 }
 212
 213 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 214 {
 215         return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
 216 }
 217
 218 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 219 {
 220         return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
 221 }
 222
 223 static inline int bdi_sched_wait(void *word)
 224 {
 225         schedule();
 226         return 0;
 227 }
 228
 229 #ifdef CONFIG_CGROUP_WRITEBACK
 230
 231 struct bdi_writeback_congested *
 232 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
 233 void wb_congested_put(struct bdi_writeback_congested *congested);
 234 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
 235                                     struct cgroup_subsys_state *memcg_css);
 236 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 237                                     struct cgroup_subsys_state *memcg_css,
 238                                     gfp_t gfp);
 239 void wb_memcg_offline(struct mem_cgroup *memcg);
 240 void wb_blkcg_offline(struct blkcg *blkcg);
 241 int inode_congested(struct inode *inode, int cong_bits);
 242
 243 /**
 244  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
 245  * @inode: inode of interest
 246  *
 247  * cgroup writeback requires support from both the bdi and filesystem.
 248  * Also, both memcg and iocg have to be on the default hierarchy.  Test
 249  * whether all conditions are met.
 250  *
 251  * Note that the test result may change dynamically on the same inode
 252  * depending on how memcg and iocg are configured.
 253  */
 254 static inline bool inode_cgwb_enabled(struct inode *inode)
 255 {
 256         struct backing_dev_info *bdi = inode_to_bdi(inode);
 257
 258         return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
 259                 cgroup_subsys_on_dfl(io_cgrp_subsys) &&
 260                 bdi_cap_account_dirty(bdi) &&
 261                 (bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
 262                 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
 263 }
 264
 265 /**
 266  * wb_find_current - find wb for %current on a bdi
 267  * @bdi: bdi of interest
 268  *
 269  * Find the wb of @bdi which matches both the memcg and blkcg of %current.
 270  * Must be called under rcu_read_lock() which protects the returend wb.
 271  * NULL if not found.
 272  */
 273 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 274 {
 275         struct cgroup_subsys_state *memcg_css;
 276         struct bdi_writeback *wb;
 277
 278         memcg_css = task_css(current, memory_cgrp_id);
 279         if (!memcg_css->parent)
 280                 return &bdi->wb;
 281
 282         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 283
 284         /*
 285          * %current's blkcg equals the effective blkcg of its memcg.  No
 286          * need to use the relatively expensive cgroup_get_e_css().
 287          */
 288         if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
 289                 return wb;
 290         return NULL;
 291 }
 292
 293 /**
 294  * wb_get_create_current - get or create wb for %current on a bdi
 295  * @bdi: bdi of interest
 296  * @gfp: allocation mask
 297  *
 298  * Equivalent to wb_get_create() on %current's memcg.  This function is
 299  * called from a relatively hot path and optimizes the common cases using
 300  * wb_find_current().
 301  */
 302 static inline struct bdi_writeback *
 303 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 304 {
 305         struct bdi_writeback *wb;
 306
 307         rcu_read_lock();
 308         wb = wb_find_current(bdi);
 309         if (wb && unlikely(!wb_tryget(wb)))
 310                 wb = NULL;
 311         rcu_read_unlock();
 312
 313         if (unlikely(!wb)) {
 314                 struct cgroup_subsys_state *memcg_css;
 315
 316                 memcg_css = task_get_css(current, memory_cgrp_id);
 317                 wb = wb_get_create(bdi, memcg_css, gfp);
 318                 css_put(memcg_css);
 319         }
 320         return wb;
 321 }
 322
 323 /**
 324  * inode_to_wb_is_valid - test whether an inode has a wb associated
 325  * @inode: inode of interest
 326  *
 327  * Returns %true if @inode has a wb associated.  May be called without any
 328  * locking.
 329  */
 330 static inline bool inode_to_wb_is_valid(struct inode *inode)
 331 {
 332         return inode->i_wb;
 333 }
 334
 335 /**
 336  * inode_to_wb - determine the wb of an inode
 337  * @inode: inode of interest
 338  *
 339  * Returns the wb @inode is currently associated with.  The caller must be
 340  * holding either @inode->i_lock, the i_pages lock, or the
 341  * associated wb's list_lock.
 342  */
 343 static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
 344 {
 345 #ifdef CONFIG_LOCKDEP
 346         WARN_ON_ONCE(debug_locks &&
 347                      (!lockdep_is_held(&inode->i_lock) &&
 348                       !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
 349                       !lockdep_is_held(&inode->i_wb->list_lock)));
 350 #endif
 351         return inode->i_wb;
 352 }
 353
 354 /**
 355  * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
 356  * @inode: target inode
 357  * @cookie: output param, to be passed to the end function
 358  *
 359  * The caller wants to access the wb associated with @inode but isn't
 360  * holding inode->i_lock, the i_pages lock or wb->list_lock.  This
 361  * function determines the wb associated with @inode and ensures that the
 362  * association doesn't change until the transaction is finished with
 363  * unlocked_inode_to_wb_end().
 364  *
 365  * The caller must call unlocked_inode_to_wb_end() with *@cookie afterwards and
 366  * can't sleep during the transaction.  IRQs may or may not be disabled on
 367  * return.
 368  */
 369 static inline struct bdi_writeback *
 370 unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
 371 {
 372         rcu_read_lock();
 373
 374         /*
 375          * Paired with store_release in inode_switch_wbs_work_fn() and
 376          * ensures that we see the new wb if we see cleared I_WB_SWITCH.
 377          */
 378         cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
 379
 380         if (unlikely(cookie->locked))
 381                 xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags);
 382
 383         /*
 384          * Protected by either !I_WB_SWITCH + rcu_read_lock() or the i_pages
 385          * lock.  inode_to_wb() will bark.  Deref directly.
 386          */
 387         return inode->i_wb;
 388 }
 389
 390 /**
 391  * unlocked_inode_to_wb_end - end inode wb access transaction
 392  * @inode: target inode
 393  * @cookie: @cookie from unlocked_inode_to_wb_begin()
 394  */
 395 static inline void unlocked_inode_to_wb_end(struct inode *inode,
 396                                             struct wb_lock_cookie *cookie)
 397 {
 398         if (unlikely(cookie->locked))
 399                 xa_unlock_irqrestore(&inode->i_mapping->i_pages, cookie->flags);
 400
 401         rcu_read_unlock();
 402 }
 403
 404 #else   /* CONFIG_CGROUP_WRITEBACK */
 405
 406 static inline bool inode_cgwb_enabled(struct inode *inode)
 407 {
 408         return false;
 409 }
 410
 411 static inline struct bdi_writeback_congested *
 412 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
 413 {
 414         refcount_inc(&bdi->wb_congested->refcnt);
 415         return bdi->wb_congested;
 416 }
 417
 418 static inline void wb_congested_put(struct bdi_writeback_congested *congested)
 419 {
 420         if (refcount_dec_and_test(&congested->refcnt))
 421                 kfree(congested);
 422 }
 423
 424 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 425 {
 426         return &bdi->wb;
 427 }
 428
 429 static inline struct bdi_writeback *
 430 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 431 {
 432         return &bdi->wb;
 433 }
 434
 435 static inline bool inode_to_wb_is_valid(struct inode *inode)
 436 {
 437         return true;
 438 }
 439
 440 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
 441 {
 442         return &inode_to_bdi(inode)->wb;
 443 }
 444
 445 static inline struct bdi_writeback *
 446 unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
 447 {
 448         return inode_to_wb(inode);
 449 }
 450
 451 static inline void unlocked_inode_to_wb_end(struct inode *inode,
 452                                             struct wb_lock_cookie *cookie)
 453 {
 454 }
 455
 456 static inline void wb_memcg_offline(struct mem_cgroup *memcg)
 457 {
 458 }
 459
 460 static inline void wb_blkcg_offline(struct blkcg *blkcg)
 461 {
 462 }
 463
 464 static inline int inode_congested(struct inode *inode, int cong_bits)
 465 {
 466         return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
 467 }
 468
 469 #endif  /* CONFIG_CGROUP_WRITEBACK */
 470
 471 static inline int inode_read_congested(struct inode *inode)
 472 {
 473         return inode_congested(inode, 1 << WB_sync_congested);
 474 }
 475
 476 static inline int inode_write_congested(struct inode *inode)
 477 {
 478         return inode_congested(inode, 1 << WB_async_congested);
 479 }
 480
 481 static inline int inode_rw_congested(struct inode *inode)
 482 {
 483         return inode_congested(inode, (1 << WB_sync_congested) |
 484                                       (1 << WB_async_congested));
 485 }
 486
 487 static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
 488 {
 489         return wb_congested(&bdi->wb, cong_bits);
 490 }
 491
 492 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 493 {
 494         return bdi_congested(bdi, 1 << WB_sync_congested);
 495 }
 496
 497 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 498 {
 499         return bdi_congested(bdi, 1 << WB_async_congested);
 500 }
 501
 502 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 503 {
 504         return bdi_congested(bdi, (1 << WB_sync_congested) |
 505                                   (1 << WB_async_congested));
 506 }
 507
 508 extern const char *bdi_unknown_name;
 509
 510 static inline const char *bdi_dev_name(struct backing_dev_info *bdi)
 511 {
 512         if (!bdi || !bdi->dev)
 513                 return bdi_unknown_name;
 514         return dev_name(bdi->dev);
 515 }
 516
 517 #endif  /* _LINUX_BACKING_DEV_H */