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/device.h>
  16 #include <linux/writeback.h>
  17 #include <linux/backing-dev-defs.h>
  18 #include <linux/slab.h>
  19
  20 struct blkcg;
  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 void bdi_set_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(int node_id);
  40
  41 void wb_start_background_writeback(struct bdi_writeback *wb);
  42 void wb_workfn(struct work_struct *work);
  43 void wb_wakeup_delayed(struct bdi_writeback *wb);
  44
  45 void wb_wait_for_completion(struct wb_completion *done);
  46
  47 extern spinlock_t bdi_lock;
  48 extern struct list_head bdi_list;
  49
  50 extern struct workqueue_struct *bdi_wq;
  51 extern struct workqueue_struct *bdi_async_bio_wq;
  52
  53 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
  54 {
  55         return test_bit(WB_has_dirty_io, &wb->state);
  56 }
  57
  58 static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
  59 {
  60         /*
  61          * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
  62          * any dirty wbs.  See wb_update_write_bandwidth().
  63          */
  64         return atomic_long_read(&bdi->tot_write_bandwidth);
  65 }
  66
  67 static inline void wb_stat_mod(struct bdi_writeback *wb,
  68                                  enum wb_stat_item item, s64 amount)
  69 {
  70         percpu_counter_add_batch(&wb->stat[item], amount, WB_STAT_BATCH);
  71 }
  72
  73 static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  74 {
  75         wb_stat_mod(wb, item, 1);
  76 }
  77
  78 static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  79 {
  80         wb_stat_mod(wb, item, -1);
  81 }
  82
  83 static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
  84 {
  85         return percpu_counter_read_positive(&wb->stat[item]);
  86 }
  87
  88 static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
  89 {
  90         return percpu_counter_sum_positive(&wb->stat[item]);
  91 }
  92
  93 extern void wb_writeout_inc(struct bdi_writeback *wb);
  94
  95 /*
  96  * maximal error of a stat counter.
  97  */
  98 static inline unsigned long wb_stat_error(void)
  99 {
 100 #ifdef CONFIG_SMP
 101         return nr_cpu_ids * WB_STAT_BATCH;
 102 #else
 103         return 1;
 104 #endif
 105 }
 106
 107 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 108 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 109
 110 /*
 111  * Flags in backing_dev_info::capability
 112  *
 113  * BDI_CAP_WRITEBACK:           Supports dirty page writeback, and dirty pages
 114  *                              should contribute to accounting
 115  * BDI_CAP_WRITEBACK_ACCT:      Automatically account writeback pages
 116  * BDI_CAP_STRICTLIMIT:         Keep number of dirty pages below bdi threshold
 117  */
 118 #define BDI_CAP_WRITEBACK               (1 << 0)
 119 #define BDI_CAP_WRITEBACK_ACCT          (1 << 1)
 120 #define BDI_CAP_STRICTLIMIT             (1 << 2)
 121
 122 extern struct backing_dev_info noop_backing_dev_info;
 123
 124 /**
 125  * writeback_in_progress - determine whether there is writeback in progress
 126  * @wb: bdi_writeback of interest
 127  *
 128  * Determine whether there is writeback waiting to be handled against a
 129  * bdi_writeback.
 130  */
 131 static inline bool writeback_in_progress(struct bdi_writeback *wb)
 132 {
 133         return test_bit(WB_writeback_running, &wb->state);
 134 }
 135
 136 struct backing_dev_info *inode_to_bdi(struct inode *inode);
 137
 138 static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 139 {
 140         return wb->congested & cong_bits;
 141 }
 142
 143 long congestion_wait(int sync, long timeout);
 144 long wait_iff_congested(int sync, long timeout);
 145
 146 static inline bool mapping_can_writeback(struct address_space *mapping)
 147 {
 148         return inode_to_bdi(mapping->host)->capabilities & BDI_CAP_WRITEBACK;
 149 }
 150
 151 static inline int bdi_sched_wait(void *word)
 152 {
 153         schedule();
 154         return 0;
 155 }
 156
 157 #ifdef CONFIG_CGROUP_WRITEBACK
 158
 159 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
 160                                     struct cgroup_subsys_state *memcg_css);
 161 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 162                                     struct cgroup_subsys_state *memcg_css,
 163                                     gfp_t gfp);
 164 void wb_memcg_offline(struct mem_cgroup *memcg);
 165 void wb_blkcg_offline(struct blkcg *blkcg);
 166 int inode_congested(struct inode *inode, int cong_bits);
 167
 168 /**
 169  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
 170  * @inode: inode of interest
 171  *
 172  * Cgroup writeback requires support from the filesystem.  Also, both memcg and
 173  * iocg have to be on the default hierarchy.  Test whether all conditions are
 174  * met.
 175  *
 176  * Note that the test result may change dynamically on the same inode
 177  * depending on how memcg and iocg are configured.
 178  */
 179 static inline bool inode_cgwb_enabled(struct inode *inode)
 180 {
 181         struct backing_dev_info *bdi = inode_to_bdi(inode);
 182
 183         return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
 184                 cgroup_subsys_on_dfl(io_cgrp_subsys) &&
 185                 (bdi->capabilities & BDI_CAP_WRITEBACK) &&
 186                 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
 187 }
 188
 189 /**
 190  * wb_find_current - find wb for %current on a bdi
 191  * @bdi: bdi of interest
 192  *
 193  * Find the wb of @bdi which matches both the memcg and blkcg of %current.
 194  * Must be called under rcu_read_lock() which protects the returend wb.
 195  * NULL if not found.
 196  */
 197 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 198 {
 199         struct cgroup_subsys_state *memcg_css;
 200         struct bdi_writeback *wb;
 201
 202         memcg_css = task_css(current, memory_cgrp_id);
 203         if (!memcg_css->parent)
 204                 return &bdi->wb;
 205
 206         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 207
 208         /*
 209          * %current's blkcg equals the effective blkcg of its memcg.  No
 210          * need to use the relatively expensive cgroup_get_e_css().
 211          */
 212         if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
 213                 return wb;
 214         return NULL;
 215 }
 216
 217 /**
 218  * wb_get_create_current - get or create wb for %current on a bdi
 219  * @bdi: bdi of interest
 220  * @gfp: allocation mask
 221  *
 222  * Equivalent to wb_get_create() on %current's memcg.  This function is
 223  * called from a relatively hot path and optimizes the common cases using
 224  * wb_find_current().
 225  */
 226 static inline struct bdi_writeback *
 227 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 228 {
 229         struct bdi_writeback *wb;
 230
 231         rcu_read_lock();
 232         wb = wb_find_current(bdi);
 233         if (wb && unlikely(!wb_tryget(wb)))
 234                 wb = NULL;
 235         rcu_read_unlock();
 236
 237         if (unlikely(!wb)) {
 238                 struct cgroup_subsys_state *memcg_css;
 239
 240                 memcg_css = task_get_css(current, memory_cgrp_id);
 241                 wb = wb_get_create(bdi, memcg_css, gfp);
 242                 css_put(memcg_css);
 243         }
 244         return wb;
 245 }
 246
 247 /**
 248  * inode_to_wb_is_valid - test whether an inode has a wb associated
 249  * @inode: inode of interest
 250  *
 251  * Returns %true if @inode has a wb associated.  May be called without any
 252  * locking.
 253  */
 254 static inline bool inode_to_wb_is_valid(struct inode *inode)
 255 {
 256         return inode->i_wb;
 257 }
 258
 259 /**
 260  * inode_to_wb - determine the wb of an inode
 261  * @inode: inode of interest
 262  *
 263  * Returns the wb @inode is currently associated with.  The caller must be
 264  * holding either @inode->i_lock, the i_pages lock, or the
 265  * associated wb's list_lock.
 266  */
 267 static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
 268 {
 269 #ifdef CONFIG_LOCKDEP
 270         WARN_ON_ONCE(debug_locks &&
 271                      (!lockdep_is_held(&inode->i_lock) &&
 272                       !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
 273                       !lockdep_is_held(&inode->i_wb->list_lock)));
 274 #endif
 275         return inode->i_wb;
 276 }
 277
 278 static inline struct bdi_writeback *inode_to_wb_wbc(
 279                                 struct inode *inode,
 280                                 struct writeback_control *wbc)
 281 {
 282         /*
 283          * If wbc does not have inode attached, it means cgroup writeback was
 284          * disabled when wbc started. Just use the default wb in that case.
 285          */
 286         return wbc->wb ? wbc->wb : &inode_to_bdi(inode)->wb;
 287 }
 288
 289 /**
 290  * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
 291  * @inode: target inode
 292  * @cookie: output param, to be passed to the end function
 293  *
 294  * The caller wants to access the wb associated with @inode but isn't
 295  * holding inode->i_lock, the i_pages lock or wb->list_lock.  This
 296  * function determines the wb associated with @inode and ensures that the
 297  * association doesn't change until the transaction is finished with
 298  * unlocked_inode_to_wb_end().
 299  *
 300  * The caller must call unlocked_inode_to_wb_end() with *@cookie afterwards and
 301  * can't sleep during the transaction.  IRQs may or may not be disabled on
 302  * return.
 303  */
 304 static inline struct bdi_writeback *
 305 unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
 306 {
 307         rcu_read_lock();
 308
 309         /*
 310          * Paired with store_release in inode_switch_wbs_work_fn() and
 311          * ensures that we see the new wb if we see cleared I_WB_SWITCH.
 312          */
 313         cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
 314
 315         if (unlikely(cookie->locked))
 316                 xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags);
 317
 318         /*
 319          * Protected by either !I_WB_SWITCH + rcu_read_lock() or the i_pages
 320          * lock.  inode_to_wb() will bark.  Deref directly.
 321          */
 322         return inode->i_wb;
 323 }
 324
 325 /**
 326  * unlocked_inode_to_wb_end - end inode wb access transaction
 327  * @inode: target inode
 328  * @cookie: @cookie from unlocked_inode_to_wb_begin()
 329  */
 330 static inline void unlocked_inode_to_wb_end(struct inode *inode,
 331                                             struct wb_lock_cookie *cookie)
 332 {
 333         if (unlikely(cookie->locked))
 334                 xa_unlock_irqrestore(&inode->i_mapping->i_pages, cookie->flags);
 335
 336         rcu_read_unlock();
 337 }
 338
 339 #else   /* CONFIG_CGROUP_WRITEBACK */
 340
 341 static inline bool inode_cgwb_enabled(struct inode *inode)
 342 {
 343         return false;
 344 }
 345
 346 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 347 {
 348         return &bdi->wb;
 349 }
 350
 351 static inline struct bdi_writeback *
 352 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 353 {
 354         return &bdi->wb;
 355 }
 356
 357 static inline bool inode_to_wb_is_valid(struct inode *inode)
 358 {
 359         return true;
 360 }
 361
 362 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
 363 {
 364         return &inode_to_bdi(inode)->wb;
 365 }
 366
 367 static inline struct bdi_writeback *inode_to_wb_wbc(
 368                                 struct inode *inode,
 369                                 struct writeback_control *wbc)
 370 {
 371         return inode_to_wb(inode);
 372 }
 373
 374
 375 static inline struct bdi_writeback *
 376 unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
 377 {
 378         return inode_to_wb(inode);
 379 }
 380
 381 static inline void unlocked_inode_to_wb_end(struct inode *inode,
 382                                             struct wb_lock_cookie *cookie)
 383 {
 384 }
 385
 386 static inline void wb_memcg_offline(struct mem_cgroup *memcg)
 387 {
 388 }
 389
 390 static inline void wb_blkcg_offline(struct blkcg *blkcg)
 391 {
 392 }
 393
 394 static inline int inode_congested(struct inode *inode, int cong_bits)
 395 {
 396         return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
 397 }
 398
 399 #endif  /* CONFIG_CGROUP_WRITEBACK */
 400
 401 static inline int inode_read_congested(struct inode *inode)
 402 {
 403         return inode_congested(inode, 1 << WB_sync_congested);
 404 }
 405
 406 static inline int inode_write_congested(struct inode *inode)
 407 {
 408         return inode_congested(inode, 1 << WB_async_congested);
 409 }
 410
 411 static inline int inode_rw_congested(struct inode *inode)
 412 {
 413         return inode_congested(inode, (1 << WB_sync_congested) |
 414                                       (1 << WB_async_congested));
 415 }
 416
 417 static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
 418 {
 419         return wb_congested(&bdi->wb, cong_bits);
 420 }
 421
 422 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 423 {
 424         return bdi_congested(bdi, 1 << WB_sync_congested);
 425 }
 426
 427 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 428 {
 429         return bdi_congested(bdi, 1 << WB_async_congested);
 430 }
 431
 432 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 433 {
 434         return bdi_congested(bdi, (1 << WB_sync_congested) |
 435                                   (1 << WB_async_congested));
 436 }
 437
 438 const char *bdi_dev_name(struct backing_dev_info *bdi);
 439
 440 #endif  /* _LINUX_BACKING_DEV_H */