mm/backing-dev.c

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