mm/backing-dev.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <linux/blkdev.h>
   4 #include <linux/wait.h>
   5 #include <linux/rbtree.h>
   6 #include <linux/kthread.h>
   7 #include <linux/backing-dev.h>
   8 #include <linux/blk-cgroup.h>
   9 #include <linux/freezer.h>
  10 #include <linux/fs.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/mm.h>
  13 #include <linux/sched/mm.h>
  14 #include <linux/sched.h>
  15 #include <linux/module.h>
  16 #include <linux/writeback.h>
  17 #include <linux/device.h>
  18 #include <trace/events/writeback.h>
  19 #include "internal.h"
  20
  21 struct backing_dev_info noop_backing_dev_info;
  22 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
  23
  24 static const char *bdi_unknown_name = "(unknown)";
  25
  26 /*
  27  * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
  28  * reader side locking.
  29  */
  30 DEFINE_SPINLOCK(bdi_lock);
  31 static u64 bdi_id_cursor;
  32 static struct rb_root bdi_tree = RB_ROOT;
  33 LIST_HEAD(bdi_list);
  34
  35 /* bdi_wq serves all asynchronous writeback tasks */
  36 struct workqueue_struct *bdi_wq;
  37
  38 #ifdef CONFIG_DEBUG_FS
  39 #include <linux/debugfs.h>
  40 #include <linux/seq_file.h>
  41
  42 static struct dentry *bdi_debug_root;
  43
  44 static void bdi_debug_init(void)
  45 {
  46         bdi_debug_root = debugfs_create_dir("bdi", NULL);
  47 }
  48
  49 static int bdi_debug_stats_show(struct seq_file *m, void *v)
  50 {
  51         struct backing_dev_info *bdi = m->private;
  52         struct bdi_writeback *wb = &bdi->wb;
  53         unsigned long background_thresh;
  54         unsigned long dirty_thresh;
  55         unsigned long wb_thresh;
  56         unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
  57         struct inode *inode;
  58
  59         nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
  60         spin_lock(&wb->list_lock);
  61         list_for_each_entry(inode, &wb->b_dirty, i_io_list)
  62                 nr_dirty++;
  63         list_for_each_entry(inode, &wb->b_io, i_io_list)
  64                 nr_io++;
  65         list_for_each_entry(inode, &wb->b_more_io, i_io_list)
  66                 nr_more_io++;
  67         list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
  68                 if (inode->i_state & I_DIRTY_TIME)
  69                         nr_dirty_time++;
  70         spin_unlock(&wb->list_lock);
  71
  72         global_dirty_limits(&background_thresh, &dirty_thresh);
  73         wb_thresh = wb_calc_thresh(wb, dirty_thresh);
  74
  75         seq_printf(m,
  76                    "BdiWriteback:       %10lu kB\n"
  77                    "BdiReclaimable:     %10lu kB\n"
  78                    "BdiDirtyThresh:     %10lu kB\n"
  79                    "DirtyThresh:        %10lu kB\n"
  80                    "BackgroundThresh:   %10lu kB\n"
  81                    "BdiDirtied:         %10lu kB\n"
  82                    "BdiWritten:         %10lu kB\n"
  83                    "BdiWriteBandwidth:  %10lu kBps\n"
  84                    "b_dirty:            %10lu\n"
  85                    "b_io:               %10lu\n"
  86                    "b_more_io:          %10lu\n"
  87                    "b_dirty_time:       %10lu\n"
  88                    "bdi_list:           %10u\n"
  89                    "state:              %10lx\n",
  90                    (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
  91                    (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
  92                    K(wb_thresh),
  93                    K(dirty_thresh),
  94                    K(background_thresh),
  95                    (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
  96                    (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
  97                    (unsigned long) K(wb->write_bandwidth),
  98                    nr_dirty,
  99                    nr_io,
 100                    nr_more_io,
 101                    nr_dirty_time,
 102                    !list_empty(&bdi->bdi_list), bdi->wb.state);
 103
 104         return 0;
 105 }
 106 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
 107
 108 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 109 {
 110         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 111
 112         debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
 113                             &bdi_debug_stats_fops);
 114 }
 115
 116 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 117 {
 118         debugfs_remove_recursive(bdi->debug_dir);
 119 }
 120 #else
 121 static inline void bdi_debug_init(void)
 122 {
 123 }
 124 static inline void bdi_debug_register(struct backing_dev_info *bdi,
 125                                       const char *name)
 126 {
 127 }
 128 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 129 {
 130 }
 131 #endif
 132
 133 static ssize_t read_ahead_kb_store(struct device *dev,
 134                                   struct device_attribute *attr,
 135                                   const char *buf, size_t count)
 136 {
 137         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 138         unsigned long read_ahead_kb;
 139         ssize_t ret;
 140
 141         ret = kstrtoul(buf, 10, &read_ahead_kb);
 142         if (ret < 0)
 143                 return ret;
 144
 145         bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 146
 147         return count;
 148 }
 149
 150 #define BDI_SHOW(name, expr)                                            \
 151 static ssize_t name##_show(struct device *dev,                          \
 152                            struct device_attribute *attr, char *buf)    \
 153 {                                                                       \
 154         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 155                                                                         \
 156         return sysfs_emit(buf, "%lld\n", (long long)expr);              \
 157 }                                                                       \
 158 static DEVICE_ATTR_RW(name);
 159
 160 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 161
 162 static ssize_t min_ratio_store(struct device *dev,
 163                 struct device_attribute *attr, const char *buf, size_t count)
 164 {
 165         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 166         unsigned int ratio;
 167         ssize_t ret;
 168
 169         ret = kstrtouint(buf, 10, &ratio);
 170         if (ret < 0)
 171                 return ret;
 172
 173         ret = bdi_set_min_ratio(bdi, ratio);
 174         if (!ret)
 175                 ret = count;
 176
 177         return ret;
 178 }
 179 BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE)
 180
 181 static ssize_t min_ratio_fine_store(struct device *dev,
 182                 struct device_attribute *attr, const char *buf, size_t count)
 183 {
 184         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 185         unsigned int ratio;
 186         ssize_t ret;
 187
 188         ret = kstrtouint(buf, 10, &ratio);
 189         if (ret < 0)
 190                 return ret;
 191
 192         ret = bdi_set_min_ratio_no_scale(bdi, ratio);
 193         if (!ret)
 194                 ret = count;
 195
 196         return ret;
 197 }
 198 BDI_SHOW(min_ratio_fine, bdi->min_ratio)
 199
 200 static ssize_t max_ratio_store(struct device *dev,
 201                 struct device_attribute *attr, const char *buf, size_t count)
 202 {
 203         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 204         unsigned int ratio;
 205         ssize_t ret;
 206
 207         ret = kstrtouint(buf, 10, &ratio);
 208         if (ret < 0)
 209                 return ret;
 210
 211         ret = bdi_set_max_ratio(bdi, ratio);
 212         if (!ret)
 213                 ret = count;
 214
 215         return ret;
 216 }
 217 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE)
 218
 219 static ssize_t max_ratio_fine_store(struct device *dev,
 220                 struct device_attribute *attr, const char *buf, size_t count)
 221 {
 222         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 223         unsigned int ratio;
 224         ssize_t ret;
 225
 226         ret = kstrtouint(buf, 10, &ratio);
 227         if (ret < 0)
 228                 return ret;
 229
 230         ret = bdi_set_max_ratio_no_scale(bdi, ratio);
 231         if (!ret)
 232                 ret = count;
 233
 234         return ret;
 235 }
 236 BDI_SHOW(max_ratio_fine, bdi->max_ratio)
 237
 238 static ssize_t min_bytes_show(struct device *dev,
 239                               struct device_attribute *attr,
 240                               char *buf)
 241 {
 242         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 243
 244         return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi));
 245 }
 246
 247 static ssize_t min_bytes_store(struct device *dev,
 248                 struct device_attribute *attr, const char *buf, size_t count)
 249 {
 250         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 251         u64 bytes;
 252         ssize_t ret;
 253
 254         ret = kstrtoull(buf, 10, &bytes);
 255         if (ret < 0)
 256                 return ret;
 257
 258         ret = bdi_set_min_bytes(bdi, bytes);
 259         if (!ret)
 260                 ret = count;
 261
 262         return ret;
 263 }
 264 static DEVICE_ATTR_RW(min_bytes);
 265
 266 static ssize_t max_bytes_show(struct device *dev,
 267                               struct device_attribute *attr,
 268                               char *buf)
 269 {
 270         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 271
 272         return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi));
 273 }
 274
 275 static ssize_t max_bytes_store(struct device *dev,
 276                 struct device_attribute *attr, const char *buf, size_t count)
 277 {
 278         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 279         u64 bytes;
 280         ssize_t ret;
 281
 282         ret = kstrtoull(buf, 10, &bytes);
 283         if (ret < 0)
 284                 return ret;
 285
 286         ret = bdi_set_max_bytes(bdi, bytes);
 287         if (!ret)
 288                 ret = count;
 289
 290         return ret;
 291 }
 292 static DEVICE_ATTR_RW(max_bytes);
 293
 294 static ssize_t stable_pages_required_show(struct device *dev,
 295                                           struct device_attribute *attr,
 296                                           char *buf)
 297 {
 298         dev_warn_once(dev,
 299                 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
 300         return sysfs_emit(buf, "%d\n", 0);
 301 }
 302 static DEVICE_ATTR_RO(stable_pages_required);
 303
 304 static ssize_t strict_limit_store(struct device *dev,
 305                 struct device_attribute *attr, const char *buf, size_t count)
 306 {
 307         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 308         unsigned int strict_limit;
 309         ssize_t ret;
 310
 311         ret = kstrtouint(buf, 10, &strict_limit);
 312         if (ret < 0)
 313                 return ret;
 314
 315         ret = bdi_set_strict_limit(bdi, strict_limit);
 316         if (!ret)
 317                 ret = count;
 318
 319         return ret;
 320 }
 321
 322 static ssize_t strict_limit_show(struct device *dev,
 323                 struct device_attribute *attr, char *buf)
 324 {
 325         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 326
 327         return sysfs_emit(buf, "%d\n",
 328                         !!(bdi->capabilities & BDI_CAP_STRICTLIMIT));
 329 }
 330 static DEVICE_ATTR_RW(strict_limit);
 331
 332 static struct attribute *bdi_dev_attrs[] = {
 333         &dev_attr_read_ahead_kb.attr,
 334         &dev_attr_min_ratio.attr,
 335         &dev_attr_min_ratio_fine.attr,
 336         &dev_attr_max_ratio.attr,
 337         &dev_attr_max_ratio_fine.attr,
 338         &dev_attr_min_bytes.attr,
 339         &dev_attr_max_bytes.attr,
 340         &dev_attr_stable_pages_required.attr,
 341         &dev_attr_strict_limit.attr,
 342         NULL,
 343 };
 344 ATTRIBUTE_GROUPS(bdi_dev);
 345
 346 static const struct class bdi_class = {
 347         .name           = "bdi",
 348         .dev_groups     = bdi_dev_groups,
 349 };
 350
 351 static __init int bdi_class_init(void)
 352 {
 353         int ret;
 354
 355         ret = class_register(&bdi_class);
 356         if (ret)
 357                 return ret;
 358
 359         bdi_debug_init();
 360
 361         return 0;
 362 }
 363 postcore_initcall(bdi_class_init);
 364
 365 static int __init default_bdi_init(void)
 366 {
 367         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
 368                                  WQ_SYSFS, 0);
 369         if (!bdi_wq)
 370                 return -ENOMEM;
 371         return 0;
 372 }
 373 subsys_initcall(default_bdi_init);
 374
 375 /*
 376  * This function is used when the first inode for this wb is marked dirty. It
 377  * wakes-up the corresponding bdi thread which should then take care of the
 378  * periodic background write-out of dirty inodes. Since the write-out would
 379  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
 380  * set up a timer which wakes the bdi thread up later.
 381  *
 382  * Note, we wouldn't bother setting up the timer, but this function is on the
 383  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
 384  * by delaying the wake-up.
 385  *
 386  * We have to be careful not to postpone flush work if it is scheduled for
 387  * earlier. Thus we use queue_delayed_work().
 388  */
 389 void wb_wakeup_delayed(struct bdi_writeback *wb)
 390 {
 391         unsigned long timeout;
 392
 393         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
 394         spin_lock_irq(&wb->work_lock);
 395         if (test_bit(WB_registered, &wb->state))
 396                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
 397         spin_unlock_irq(&wb->work_lock);
 398 }
 399
 400 static void wb_update_bandwidth_workfn(struct work_struct *work)
 401 {
 402         struct bdi_writeback *wb = container_of(to_delayed_work(work),
 403                                                 struct bdi_writeback, bw_dwork);
 404
 405         wb_update_bandwidth(wb);
 406 }
 407
 408 /*
 409  * Initial write bandwidth: 100 MB/s
 410  */
 411 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
 412
 413 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
 414                    gfp_t gfp)
 415 {
 416         int i, err;
 417
 418         memset(wb, 0, sizeof(*wb));
 419
 420         wb->bdi = bdi;
 421         wb->last_old_flush = jiffies;
 422         INIT_LIST_HEAD(&wb->b_dirty);
 423         INIT_LIST_HEAD(&wb->b_io);
 424         INIT_LIST_HEAD(&wb->b_more_io);
 425         INIT_LIST_HEAD(&wb->b_dirty_time);
 426         spin_lock_init(&wb->list_lock);
 427
 428         atomic_set(&wb->writeback_inodes, 0);
 429         wb->bw_time_stamp = jiffies;
 430         wb->balanced_dirty_ratelimit = INIT_BW;
 431         wb->dirty_ratelimit = INIT_BW;
 432         wb->write_bandwidth = INIT_BW;
 433         wb->avg_write_bandwidth = INIT_BW;
 434
 435         spin_lock_init(&wb->work_lock);
 436         INIT_LIST_HEAD(&wb->work_list);
 437         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
 438         INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
 439         wb->dirty_sleep = jiffies;
 440
 441         err = fprop_local_init_percpu(&wb->completions, gfp);
 442         if (err)
 443                 return err;
 444
 445         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
 446                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
 447                 if (err)
 448                         goto out_destroy_stat;
 449         }
 450
 451         return 0;
 452
 453 out_destroy_stat:
 454         while (i--)
 455                 percpu_counter_destroy(&wb->stat[i]);
 456         fprop_local_destroy_percpu(&wb->completions);
 457         return err;
 458 }
 459
 460 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
 461
 462 /*
 463  * Remove bdi from the global list and shutdown any threads we have running
 464  */
 465 static void wb_shutdown(struct bdi_writeback *wb)
 466 {
 467         /* Make sure nobody queues further work */
 468         spin_lock_irq(&wb->work_lock);
 469         if (!test_and_clear_bit(WB_registered, &wb->state)) {
 470                 spin_unlock_irq(&wb->work_lock);
 471                 return;
 472         }
 473         spin_unlock_irq(&wb->work_lock);
 474
 475         cgwb_remove_from_bdi_list(wb);
 476         /*
 477          * Drain work list and shutdown the delayed_work.  !WB_registered
 478          * tells wb_workfn() that @wb is dying and its work_list needs to
 479          * be drained no matter what.
 480          */
 481         mod_delayed_work(bdi_wq, &wb->dwork, 0);
 482         flush_delayed_work(&wb->dwork);
 483         WARN_ON(!list_empty(&wb->work_list));
 484         flush_delayed_work(&wb->bw_dwork);
 485 }
 486
 487 static void wb_exit(struct bdi_writeback *wb)
 488 {
 489         int i;
 490
 491         WARN_ON(delayed_work_pending(&wb->dwork));
 492
 493         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
 494                 percpu_counter_destroy(&wb->stat[i]);
 495
 496         fprop_local_destroy_percpu(&wb->completions);
 497 }
 498
 499 #ifdef CONFIG_CGROUP_WRITEBACK
 500
 501 #include <linux/memcontrol.h>
 502
 503 /*
 504  * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
 505  * memcg->cgwb_list.  bdi->cgwb_tree is also RCU protected.
 506  */
 507 static DEFINE_SPINLOCK(cgwb_lock);
 508 static struct workqueue_struct *cgwb_release_wq;
 509
 510 static LIST_HEAD(offline_cgwbs);
 511 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
 512 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
 513
 514 static void cgwb_free_rcu(struct rcu_head *rcu_head)
 515 {
 516         struct bdi_writeback *wb = container_of(rcu_head,
 517                         struct bdi_writeback, rcu);
 518
 519         percpu_ref_exit(&wb->refcnt);
 520         kfree(wb);
 521 }
 522
 523 static void cgwb_release_workfn(struct work_struct *work)
 524 {
 525         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
 526                                                 release_work);
 527         struct backing_dev_info *bdi = wb->bdi;
 528
 529         mutex_lock(&wb->bdi->cgwb_release_mutex);
 530         wb_shutdown(wb);
 531
 532         css_put(wb->memcg_css);
 533         css_put(wb->blkcg_css);
 534         mutex_unlock(&wb->bdi->cgwb_release_mutex);
 535
 536         /* triggers blkg destruction if no online users left */
 537         blkcg_unpin_online(wb->blkcg_css);
 538
 539         fprop_local_destroy_percpu(&wb->memcg_completions);
 540
 541         spin_lock_irq(&cgwb_lock);
 542         list_del(&wb->offline_node);
 543         spin_unlock_irq(&cgwb_lock);
 544
 545         wb_exit(wb);
 546         bdi_put(bdi);
 547         WARN_ON_ONCE(!list_empty(&wb->b_attached));
 548         call_rcu(&wb->rcu, cgwb_free_rcu);
 549 }
 550
 551 static void cgwb_release(struct percpu_ref *refcnt)
 552 {
 553         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
 554                                                 refcnt);
 555         queue_work(cgwb_release_wq, &wb->release_work);
 556 }
 557
 558 static void cgwb_kill(struct bdi_writeback *wb)
 559 {
 560         lockdep_assert_held(&cgwb_lock);
 561
 562         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
 563         list_del(&wb->memcg_node);
 564         list_del(&wb->blkcg_node);
 565         list_add(&wb->offline_node, &offline_cgwbs);
 566         percpu_ref_kill(&wb->refcnt);
 567 }
 568
 569 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 570 {
 571         spin_lock_irq(&cgwb_lock);
 572         list_del_rcu(&wb->bdi_node);
 573         spin_unlock_irq(&cgwb_lock);
 574 }
 575
 576 static int cgwb_create(struct backing_dev_info *bdi,
 577                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
 578 {
 579         struct mem_cgroup *memcg;
 580         struct cgroup_subsys_state *blkcg_css;
 581         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
 582         struct bdi_writeback *wb;
 583         unsigned long flags;
 584         int ret = 0;
 585
 586         memcg = mem_cgroup_from_css(memcg_css);
 587         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 588         memcg_cgwb_list = &memcg->cgwb_list;
 589         blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
 590
 591         /* look up again under lock and discard on blkcg mismatch */
 592         spin_lock_irqsave(&cgwb_lock, flags);
 593         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 594         if (wb && wb->blkcg_css != blkcg_css) {
 595                 cgwb_kill(wb);
 596                 wb = NULL;
 597         }
 598         spin_unlock_irqrestore(&cgwb_lock, flags);
 599         if (wb)
 600                 goto out_put;
 601
 602         /* need to create a new one */
 603         wb = kmalloc(sizeof(*wb), gfp);
 604         if (!wb) {
 605                 ret = -ENOMEM;
 606                 goto out_put;
 607         }
 608
 609         ret = wb_init(wb, bdi, gfp);
 610         if (ret)
 611                 goto err_free;
 612
 613         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
 614         if (ret)
 615                 goto err_wb_exit;
 616
 617         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
 618         if (ret)
 619                 goto err_ref_exit;
 620
 621         wb->memcg_css = memcg_css;
 622         wb->blkcg_css = blkcg_css;
 623         INIT_LIST_HEAD(&wb->b_attached);
 624         INIT_WORK(&wb->release_work, cgwb_release_workfn);
 625         set_bit(WB_registered, &wb->state);
 626         bdi_get(bdi);
 627
 628         /*
 629          * The root wb determines the registered state of the whole bdi and
 630          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
 631          * whether they're still online.  Don't link @wb if any is dead.
 632          * See wb_memcg_offline() and wb_blkcg_offline().
 633          */
 634         ret = -ENODEV;
 635         spin_lock_irqsave(&cgwb_lock, flags);
 636         if (test_bit(WB_registered, &bdi->wb.state) &&
 637             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
 638                 /* we might have raced another instance of this function */
 639                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
 640                 if (!ret) {
 641                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
 642                         list_add(&wb->memcg_node, memcg_cgwb_list);
 643                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
 644                         blkcg_pin_online(blkcg_css);
 645                         css_get(memcg_css);
 646                         css_get(blkcg_css);
 647                 }
 648         }
 649         spin_unlock_irqrestore(&cgwb_lock, flags);
 650         if (ret) {
 651                 if (ret == -EEXIST)
 652                         ret = 0;
 653                 goto err_fprop_exit;
 654         }
 655         goto out_put;
 656
 657 err_fprop_exit:
 658         bdi_put(bdi);
 659         fprop_local_destroy_percpu(&wb->memcg_completions);
 660 err_ref_exit:
 661         percpu_ref_exit(&wb->refcnt);
 662 err_wb_exit:
 663         wb_exit(wb);
 664 err_free:
 665         kfree(wb);
 666 out_put:
 667         css_put(blkcg_css);
 668         return ret;
 669 }
 670
 671 /**
 672  * wb_get_lookup - get wb for a given memcg
 673  * @bdi: target bdi
 674  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
 675  *
 676  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
 677  * refcount incremented.
 678  *
 679  * This function uses css_get() on @memcg_css and thus expects its refcnt
 680  * to be positive on invocation.  IOW, rcu_read_lock() protection on
 681  * @memcg_css isn't enough.  try_get it before calling this function.
 682  *
 683  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
 684  * memcg on the default hierarchy, memcg association is guaranteed to be
 685  * more specific (equal or descendant to the associated blkcg) and thus can
 686  * identify both the memcg and blkcg associations.
 687  *
 688  * Because the blkcg associated with a memcg may change as blkcg is enabled
 689  * and disabled closer to root in the hierarchy, each wb keeps track of
 690  * both the memcg and blkcg associated with it and verifies the blkcg on
 691  * each lookup.  On mismatch, the existing wb is discarded and a new one is
 692  * created.
 693  */
 694 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
 695                                     struct cgroup_subsys_state *memcg_css)
 696 {
 697         struct bdi_writeback *wb;
 698
 699         if (!memcg_css->parent)
 700                 return &bdi->wb;
 701
 702         rcu_read_lock();
 703         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 704         if (wb) {
 705                 struct cgroup_subsys_state *blkcg_css;
 706
 707                 /* see whether the blkcg association has changed */
 708                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 709                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
 710                         wb = NULL;
 711                 css_put(blkcg_css);
 712         }
 713         rcu_read_unlock();
 714
 715         return wb;
 716 }
 717
 718 /**
 719  * wb_get_create - get wb for a given memcg, create if necessary
 720  * @bdi: target bdi
 721  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
 722  * @gfp: allocation mask to use
 723  *
 724  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
 725  * create one.  See wb_get_lookup() for more details.
 726  */
 727 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 728                                     struct cgroup_subsys_state *memcg_css,
 729                                     gfp_t gfp)
 730 {
 731         struct bdi_writeback *wb;
 732
 733         might_alloc(gfp);
 734
 735         do {
 736                 wb = wb_get_lookup(bdi, memcg_css);
 737         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
 738
 739         return wb;
 740 }
 741
 742 static int cgwb_bdi_init(struct backing_dev_info *bdi)
 743 {
 744         int ret;
 745
 746         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
 747         mutex_init(&bdi->cgwb_release_mutex);
 748         init_rwsem(&bdi->wb_switch_rwsem);
 749
 750         ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
 751         if (!ret) {
 752                 bdi->wb.memcg_css = &root_mem_cgroup->css;
 753                 bdi->wb.blkcg_css = blkcg_root_css;
 754         }
 755         return ret;
 756 }
 757
 758 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
 759 {
 760         struct radix_tree_iter iter;
 761         void **slot;
 762         struct bdi_writeback *wb;
 763
 764         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
 765
 766         spin_lock_irq(&cgwb_lock);
 767         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
 768                 cgwb_kill(*slot);
 769         spin_unlock_irq(&cgwb_lock);
 770
 771         mutex_lock(&bdi->cgwb_release_mutex);
 772         spin_lock_irq(&cgwb_lock);
 773         while (!list_empty(&bdi->wb_list)) {
 774                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
 775                                       bdi_node);
 776                 spin_unlock_irq(&cgwb_lock);
 777                 wb_shutdown(wb);
 778                 spin_lock_irq(&cgwb_lock);
 779         }
 780         spin_unlock_irq(&cgwb_lock);
 781         mutex_unlock(&bdi->cgwb_release_mutex);
 782 }
 783
 784 /*
 785  * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
 786  *
 787  * Try to release dying cgwbs by switching attached inodes to the nearest
 788  * living ancestor's writeback. Processed wbs are placed at the end
 789  * of the list to guarantee the forward progress.
 790  */
 791 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
 792 {
 793         struct bdi_writeback *wb;
 794         LIST_HEAD(processed);
 795
 796         spin_lock_irq(&cgwb_lock);
 797
 798         while (!list_empty(&offline_cgwbs)) {
 799                 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
 800                                       offline_node);
 801                 list_move(&wb->offline_node, &processed);
 802
 803                 /*
 804                  * If wb is dirty, cleaning up the writeback by switching
 805                  * attached inodes will result in an effective removal of any
 806                  * bandwidth restrictions, which isn't the goal.  Instead,
 807                  * it can be postponed until the next time, when all io
 808                  * will be likely completed.  If in the meantime some inodes
 809                  * will get re-dirtied, they should be eventually switched to
 810                  * a new cgwb.
 811                  */
 812                 if (wb_has_dirty_io(wb))
 813                         continue;
 814
 815                 if (!wb_tryget(wb))
 816                         continue;
 817
 818                 spin_unlock_irq(&cgwb_lock);
 819                 while (cleanup_offline_cgwb(wb))
 820                         cond_resched();
 821                 spin_lock_irq(&cgwb_lock);
 822
 823                 wb_put(wb);
 824         }
 825
 826         if (!list_empty(&processed))
 827                 list_splice_tail(&processed, &offline_cgwbs);
 828
 829         spin_unlock_irq(&cgwb_lock);
 830 }
 831
 832 /**
 833  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
 834  * @memcg: memcg being offlined
 835  *
 836  * Also prevents creation of any new wb's associated with @memcg.
 837  */
 838 void wb_memcg_offline(struct mem_cgroup *memcg)
 839 {
 840         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
 841         struct bdi_writeback *wb, *next;
 842
 843         spin_lock_irq(&cgwb_lock);
 844         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
 845                 cgwb_kill(wb);
 846         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
 847         spin_unlock_irq(&cgwb_lock);
 848
 849         queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
 850 }
 851
 852 /**
 853  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
 854  * @css: blkcg being offlined
 855  *
 856  * Also prevents creation of any new wb's associated with @blkcg.
 857  */
 858 void wb_blkcg_offline(struct cgroup_subsys_state *css)
 859 {
 860         struct bdi_writeback *wb, *next;
 861         struct list_head *list = blkcg_get_cgwb_list(css);
 862
 863         spin_lock_irq(&cgwb_lock);
 864         list_for_each_entry_safe(wb, next, list, blkcg_node)
 865                 cgwb_kill(wb);
 866         list->next = NULL;      /* prevent new wb's */
 867         spin_unlock_irq(&cgwb_lock);
 868 }
 869
 870 static void cgwb_bdi_register(struct backing_dev_info *bdi)
 871 {
 872         spin_lock_irq(&cgwb_lock);
 873         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
 874         spin_unlock_irq(&cgwb_lock);
 875 }
 876
 877 static int __init cgwb_init(void)
 878 {
 879         /*
 880          * There can be many concurrent release work items overwhelming
 881          * system_wq.  Put them in a separate wq and limit concurrency.
 882          * There's no point in executing many of these in parallel.
 883          */
 884         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
 885         if (!cgwb_release_wq)
 886                 return -ENOMEM;
 887
 888         return 0;
 889 }
 890 subsys_initcall(cgwb_init);
 891
 892 #else   /* CONFIG_CGROUP_WRITEBACK */
 893
 894 static int cgwb_bdi_init(struct backing_dev_info *bdi)
 895 {
 896         return wb_init(&bdi->wb, bdi, GFP_KERNEL);
 897 }
 898
 899 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
 900
 901 static void cgwb_bdi_register(struct backing_dev_info *bdi)
 902 {
 903         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
 904 }
 905
 906 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 907 {
 908         list_del_rcu(&wb->bdi_node);
 909 }
 910
 911 #endif  /* CONFIG_CGROUP_WRITEBACK */
 912
 913 int bdi_init(struct backing_dev_info *bdi)
 914 {
 915         bdi->dev = NULL;
 916
 917         kref_init(&bdi->refcnt);
 918         bdi->min_ratio = 0;
 919         bdi->max_ratio = 100 * BDI_RATIO_SCALE;
 920         bdi->max_prop_frac = FPROP_FRAC_BASE;
 921         INIT_LIST_HEAD(&bdi->bdi_list);
 922         INIT_LIST_HEAD(&bdi->wb_list);
 923         init_waitqueue_head(&bdi->wb_waitq);
 924
 925         return cgwb_bdi_init(bdi);
 926 }
 927
 928 struct backing_dev_info *bdi_alloc(int node_id)
 929 {
 930         struct backing_dev_info *bdi;
 931
 932         bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
 933         if (!bdi)
 934                 return NULL;
 935
 936         if (bdi_init(bdi)) {
 937                 kfree(bdi);
 938                 return NULL;
 939         }
 940         bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
 941         bdi->ra_pages = VM_READAHEAD_PAGES;
 942         bdi->io_pages = VM_READAHEAD_PAGES;
 943         timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
 944         return bdi;
 945 }
 946 EXPORT_SYMBOL(bdi_alloc);
 947
 948 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
 949 {
 950         struct rb_node **p = &bdi_tree.rb_node;
 951         struct rb_node *parent = NULL;
 952         struct backing_dev_info *bdi;
 953
 954         lockdep_assert_held(&bdi_lock);
 955
 956         while (*p) {
 957                 parent = *p;
 958                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
 959
 960                 if (bdi->id > id)
 961                         p = &(*p)->rb_left;
 962                 else if (bdi->id < id)
 963                         p = &(*p)->rb_right;
 964                 else
 965                         break;
 966         }
 967
 968         if (parentp)
 969                 *parentp = parent;
 970         return p;
 971 }
 972
 973 /**
 974  * bdi_get_by_id - lookup and get bdi from its id
 975  * @id: bdi id to lookup
 976  *
 977  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
 978  * doesn't exist or is already unregistered.
 979  */
 980 struct backing_dev_info *bdi_get_by_id(u64 id)
 981 {
 982         struct backing_dev_info *bdi = NULL;
 983         struct rb_node **p;
 984
 985         spin_lock_bh(&bdi_lock);
 986         p = bdi_lookup_rb_node(id, NULL);
 987         if (*p) {
 988                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
 989                 bdi_get(bdi);
 990         }
 991         spin_unlock_bh(&bdi_lock);
 992
 993         return bdi;
 994 }
 995
 996 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
 997 {
 998         struct device *dev;
 999         struct rb_node *parent, **p;
1000
1001         if (bdi->dev)   /* The driver needs to use separate queues per device */
1002                 return 0;
1003
1004         vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
1005         dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
1006         if (IS_ERR(dev))
1007                 return PTR_ERR(dev);
1008
1009         cgwb_bdi_register(bdi);
1010         bdi->dev = dev;
1011
1012         bdi_debug_register(bdi, dev_name(dev));
1013         set_bit(WB_registered, &bdi->wb.state);
1014
1015         spin_lock_bh(&bdi_lock);
1016
1017         bdi->id = ++bdi_id_cursor;
1018
1019         p = bdi_lookup_rb_node(bdi->id, &parent);
1020         rb_link_node(&bdi->rb_node, parent, p);
1021         rb_insert_color(&bdi->rb_node, &bdi_tree);
1022
1023         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
1024
1025         spin_unlock_bh(&bdi_lock);
1026
1027         trace_writeback_bdi_register(bdi);
1028         return 0;
1029 }
1030
1031 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1032 {
1033         va_list args;
1034         int ret;
1035
1036         va_start(args, fmt);
1037         ret = bdi_register_va(bdi, fmt, args);
1038         va_end(args);
1039         return ret;
1040 }
1041 EXPORT_SYMBOL(bdi_register);
1042
1043 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1044 {
1045         WARN_ON_ONCE(bdi->owner);
1046         bdi->owner = owner;
1047         get_device(owner);
1048 }
1049
1050 /*
1051  * Remove bdi from bdi_list, and ensure that it is no longer visible
1052  */
1053 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1054 {
1055         spin_lock_bh(&bdi_lock);
1056         rb_erase(&bdi->rb_node, &bdi_tree);
1057         list_del_rcu(&bdi->bdi_list);
1058         spin_unlock_bh(&bdi_lock);
1059
1060         synchronize_rcu_expedited();
1061 }
1062
1063 void bdi_unregister(struct backing_dev_info *bdi)
1064 {
1065         del_timer_sync(&bdi->laptop_mode_wb_timer);
1066
1067         /* make sure nobody finds us on the bdi_list anymore */
1068         bdi_remove_from_list(bdi);
1069         wb_shutdown(&bdi->wb);
1070         cgwb_bdi_unregister(bdi);
1071
1072         /*
1073          * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1074          * update the global bdi_min_ratio.
1075          */
1076         if (bdi->min_ratio)
1077                 bdi_set_min_ratio(bdi, 0);
1078
1079         if (bdi->dev) {
1080                 bdi_debug_unregister(bdi);
1081                 device_unregister(bdi->dev);
1082                 bdi->dev = NULL;
1083         }
1084
1085         if (bdi->owner) {
1086                 put_device(bdi->owner);
1087                 bdi->owner = NULL;
1088         }
1089 }
1090 EXPORT_SYMBOL(bdi_unregister);
1091
1092 static void release_bdi(struct kref *ref)
1093 {
1094         struct backing_dev_info *bdi =
1095                         container_of(ref, struct backing_dev_info, refcnt);
1096
1097         WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1098         WARN_ON_ONCE(bdi->dev);
1099         wb_exit(&bdi->wb);
1100         kfree(bdi);
1101 }
1102
1103 void bdi_put(struct backing_dev_info *bdi)
1104 {
1105         kref_put(&bdi->refcnt, release_bdi);
1106 }
1107 EXPORT_SYMBOL(bdi_put);
1108
1109 struct backing_dev_info *inode_to_bdi(struct inode *inode)
1110 {
1111         struct super_block *sb;
1112
1113         if (!inode)
1114                 return &noop_backing_dev_info;
1115
1116         sb = inode->i_sb;
1117 #ifdef CONFIG_BLOCK
1118         if (sb_is_blkdev_sb(sb))
1119                 return I_BDEV(inode)->bd_disk->bdi;
1120 #endif
1121         return sb->s_bdi;
1122 }
1123 EXPORT_SYMBOL(inode_to_bdi);
1124
1125 const char *bdi_dev_name(struct backing_dev_info *bdi)
1126 {
1127         if (!bdi || !bdi->dev)
1128                 return bdi_unknown_name;
1129         return bdi->dev_name;
1130 }
1131 EXPORT_SYMBOL_GPL(bdi_dev_name);