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 static void wb_update_bandwidth_workfn(struct work_struct *work)
 376 {
 377         struct bdi_writeback *wb = container_of(to_delayed_work(work),
 378                                                 struct bdi_writeback, bw_dwork);
 379
 380         wb_update_bandwidth(wb);
 381 }
 382
 383 /*
 384  * Initial write bandwidth: 100 MB/s
 385  */
 386 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
 387
 388 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
 389                    gfp_t gfp)
 390 {
 391         int i, err;
 392
 393         memset(wb, 0, sizeof(*wb));
 394
 395         wb->bdi = bdi;
 396         wb->last_old_flush = jiffies;
 397         INIT_LIST_HEAD(&wb->b_dirty);
 398         INIT_LIST_HEAD(&wb->b_io);
 399         INIT_LIST_HEAD(&wb->b_more_io);
 400         INIT_LIST_HEAD(&wb->b_dirty_time);
 401         spin_lock_init(&wb->list_lock);
 402
 403         atomic_set(&wb->writeback_inodes, 0);
 404         wb->bw_time_stamp = jiffies;
 405         wb->balanced_dirty_ratelimit = INIT_BW;
 406         wb->dirty_ratelimit = INIT_BW;
 407         wb->write_bandwidth = INIT_BW;
 408         wb->avg_write_bandwidth = INIT_BW;
 409
 410         spin_lock_init(&wb->work_lock);
 411         INIT_LIST_HEAD(&wb->work_list);
 412         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
 413         INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
 414
 415         err = fprop_local_init_percpu(&wb->completions, gfp);
 416         if (err)
 417                 return err;
 418
 419         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
 420                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
 421                 if (err)
 422                         goto out_destroy_stat;
 423         }
 424
 425         return 0;
 426
 427 out_destroy_stat:
 428         while (i--)
 429                 percpu_counter_destroy(&wb->stat[i]);
 430         fprop_local_destroy_percpu(&wb->completions);
 431         return err;
 432 }
 433
 434 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
 435
 436 /*
 437  * Remove bdi from the global list and shutdown any threads we have running
 438  */
 439 static void wb_shutdown(struct bdi_writeback *wb)
 440 {
 441         /* Make sure nobody queues further work */
 442         spin_lock_irq(&wb->work_lock);
 443         if (!test_and_clear_bit(WB_registered, &wb->state)) {
 444                 spin_unlock_irq(&wb->work_lock);
 445                 return;
 446         }
 447         spin_unlock_irq(&wb->work_lock);
 448
 449         cgwb_remove_from_bdi_list(wb);
 450         /*
 451          * Drain work list and shutdown the delayed_work.  !WB_registered
 452          * tells wb_workfn() that @wb is dying and its work_list needs to
 453          * be drained no matter what.
 454          */
 455         mod_delayed_work(bdi_wq, &wb->dwork, 0);
 456         flush_delayed_work(&wb->dwork);
 457         WARN_ON(!list_empty(&wb->work_list));
 458         flush_delayed_work(&wb->bw_dwork);
 459 }
 460
 461 static void wb_exit(struct bdi_writeback *wb)
 462 {
 463         int i;
 464
 465         WARN_ON(delayed_work_pending(&wb->dwork));
 466
 467         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
 468                 percpu_counter_destroy(&wb->stat[i]);
 469
 470         fprop_local_destroy_percpu(&wb->completions);
 471 }
 472
 473 #ifdef CONFIG_CGROUP_WRITEBACK
 474
 475 #include <linux/memcontrol.h>
 476
 477 /*
 478  * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
 479  * memcg->cgwb_list.  bdi->cgwb_tree is also RCU protected.
 480  */
 481 static DEFINE_SPINLOCK(cgwb_lock);
 482 static struct workqueue_struct *cgwb_release_wq;
 483
 484 static LIST_HEAD(offline_cgwbs);
 485 static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
 486 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
 487
 488 static void cgwb_free_rcu(struct rcu_head *rcu_head)
 489 {
 490         struct bdi_writeback *wb = container_of(rcu_head,
 491                         struct bdi_writeback, rcu);
 492
 493         percpu_ref_exit(&wb->refcnt);
 494         kfree(wb);
 495 }
 496
 497 static void cgwb_release_workfn(struct work_struct *work)
 498 {
 499         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
 500                                                 release_work);
 501         struct backing_dev_info *bdi = wb->bdi;
 502
 503         mutex_lock(&wb->bdi->cgwb_release_mutex);
 504         wb_shutdown(wb);
 505
 506         css_put(wb->memcg_css);
 507         css_put(wb->blkcg_css);
 508         mutex_unlock(&wb->bdi->cgwb_release_mutex);
 509
 510         /* triggers blkg destruction if no online users left */
 511         blkcg_unpin_online(wb->blkcg_css);
 512
 513         fprop_local_destroy_percpu(&wb->memcg_completions);
 514
 515         spin_lock_irq(&cgwb_lock);
 516         list_del(&wb->offline_node);
 517         spin_unlock_irq(&cgwb_lock);
 518
 519         wb_exit(wb);
 520         bdi_put(bdi);
 521         WARN_ON_ONCE(!list_empty(&wb->b_attached));
 522         call_rcu(&wb->rcu, cgwb_free_rcu);
 523 }
 524
 525 static void cgwb_release(struct percpu_ref *refcnt)
 526 {
 527         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
 528                                                 refcnt);
 529         queue_work(cgwb_release_wq, &wb->release_work);
 530 }
 531
 532 static void cgwb_kill(struct bdi_writeback *wb)
 533 {
 534         lockdep_assert_held(&cgwb_lock);
 535
 536         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
 537         list_del(&wb->memcg_node);
 538         list_del(&wb->blkcg_node);
 539         list_add(&wb->offline_node, &offline_cgwbs);
 540         percpu_ref_kill(&wb->refcnt);
 541 }
 542
 543 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 544 {
 545         spin_lock_irq(&cgwb_lock);
 546         list_del_rcu(&wb->bdi_node);
 547         spin_unlock_irq(&cgwb_lock);
 548 }
 549
 550 static int cgwb_create(struct backing_dev_info *bdi,
 551                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
 552 {
 553         struct mem_cgroup *memcg;
 554         struct cgroup_subsys_state *blkcg_css;
 555         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
 556         struct bdi_writeback *wb;
 557         unsigned long flags;
 558         int ret = 0;
 559
 560         memcg = mem_cgroup_from_css(memcg_css);
 561         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 562         memcg_cgwb_list = &memcg->cgwb_list;
 563         blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
 564
 565         /* look up again under lock and discard on blkcg mismatch */
 566         spin_lock_irqsave(&cgwb_lock, flags);
 567         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 568         if (wb && wb->blkcg_css != blkcg_css) {
 569                 cgwb_kill(wb);
 570                 wb = NULL;
 571         }
 572         spin_unlock_irqrestore(&cgwb_lock, flags);
 573         if (wb)
 574                 goto out_put;
 575
 576         /* need to create a new one */
 577         wb = kmalloc(sizeof(*wb), gfp);
 578         if (!wb) {
 579                 ret = -ENOMEM;
 580                 goto out_put;
 581         }
 582
 583         ret = wb_init(wb, bdi, gfp);
 584         if (ret)
 585                 goto err_free;
 586
 587         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
 588         if (ret)
 589                 goto err_wb_exit;
 590
 591         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
 592         if (ret)
 593                 goto err_ref_exit;
 594
 595         wb->memcg_css = memcg_css;
 596         wb->blkcg_css = blkcg_css;
 597         INIT_LIST_HEAD(&wb->b_attached);
 598         INIT_WORK(&wb->release_work, cgwb_release_workfn);
 599         set_bit(WB_registered, &wb->state);
 600         bdi_get(bdi);
 601
 602         /*
 603          * The root wb determines the registered state of the whole bdi and
 604          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
 605          * whether they're still online.  Don't link @wb if any is dead.
 606          * See wb_memcg_offline() and wb_blkcg_offline().
 607          */
 608         ret = -ENODEV;
 609         spin_lock_irqsave(&cgwb_lock, flags);
 610         if (test_bit(WB_registered, &bdi->wb.state) &&
 611             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
 612                 /* we might have raced another instance of this function */
 613                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
 614                 if (!ret) {
 615                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
 616                         list_add(&wb->memcg_node, memcg_cgwb_list);
 617                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
 618                         blkcg_pin_online(blkcg_css);
 619                         css_get(memcg_css);
 620                         css_get(blkcg_css);
 621                 }
 622         }
 623         spin_unlock_irqrestore(&cgwb_lock, flags);
 624         if (ret) {
 625                 if (ret == -EEXIST)
 626                         ret = 0;
 627                 goto err_fprop_exit;
 628         }
 629         goto out_put;
 630
 631 err_fprop_exit:
 632         bdi_put(bdi);
 633         fprop_local_destroy_percpu(&wb->memcg_completions);
 634 err_ref_exit:
 635         percpu_ref_exit(&wb->refcnt);
 636 err_wb_exit:
 637         wb_exit(wb);
 638 err_free:
 639         kfree(wb);
 640 out_put:
 641         css_put(blkcg_css);
 642         return ret;
 643 }
 644
 645 /**
 646  * wb_get_lookup - get wb for a given memcg
 647  * @bdi: target bdi
 648  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
 649  *
 650  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
 651  * refcount incremented.
 652  *
 653  * This function uses css_get() on @memcg_css and thus expects its refcnt
 654  * to be positive on invocation.  IOW, rcu_read_lock() protection on
 655  * @memcg_css isn't enough.  try_get it before calling this function.
 656  *
 657  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
 658  * memcg on the default hierarchy, memcg association is guaranteed to be
 659  * more specific (equal or descendant to the associated blkcg) and thus can
 660  * identify both the memcg and blkcg associations.
 661  *
 662  * Because the blkcg associated with a memcg may change as blkcg is enabled
 663  * and disabled closer to root in the hierarchy, each wb keeps track of
 664  * both the memcg and blkcg associated with it and verifies the blkcg on
 665  * each lookup.  On mismatch, the existing wb is discarded and a new one is
 666  * created.
 667  */
 668 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
 669                                     struct cgroup_subsys_state *memcg_css)
 670 {
 671         struct bdi_writeback *wb;
 672
 673         if (!memcg_css->parent)
 674                 return &bdi->wb;
 675
 676         rcu_read_lock();
 677         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 678         if (wb) {
 679                 struct cgroup_subsys_state *blkcg_css;
 680
 681                 /* see whether the blkcg association has changed */
 682                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 683                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
 684                         wb = NULL;
 685                 css_put(blkcg_css);
 686         }
 687         rcu_read_unlock();
 688
 689         return wb;
 690 }
 691
 692 /**
 693  * wb_get_create - get wb for a given memcg, create if necessary
 694  * @bdi: target bdi
 695  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
 696  * @gfp: allocation mask to use
 697  *
 698  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
 699  * create one.  See wb_get_lookup() for more details.
 700  */
 701 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 702                                     struct cgroup_subsys_state *memcg_css,
 703                                     gfp_t gfp)
 704 {
 705         struct bdi_writeback *wb;
 706
 707         might_alloc(gfp);
 708
 709         do {
 710                 wb = wb_get_lookup(bdi, memcg_css);
 711         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
 712
 713         return wb;
 714 }
 715
 716 static int cgwb_bdi_init(struct backing_dev_info *bdi)
 717 {
 718         int ret;
 719
 720         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
 721         mutex_init(&bdi->cgwb_release_mutex);
 722         init_rwsem(&bdi->wb_switch_rwsem);
 723
 724         ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
 725         if (!ret) {
 726                 bdi->wb.memcg_css = &root_mem_cgroup->css;
 727                 bdi->wb.blkcg_css = blkcg_root_css;
 728         }
 729         return ret;
 730 }
 731
 732 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
 733 {
 734         struct radix_tree_iter iter;
 735         void **slot;
 736         struct bdi_writeback *wb;
 737
 738         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
 739
 740         spin_lock_irq(&cgwb_lock);
 741         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
 742                 cgwb_kill(*slot);
 743         spin_unlock_irq(&cgwb_lock);
 744
 745         mutex_lock(&bdi->cgwb_release_mutex);
 746         spin_lock_irq(&cgwb_lock);
 747         while (!list_empty(&bdi->wb_list)) {
 748                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
 749                                       bdi_node);
 750                 spin_unlock_irq(&cgwb_lock);
 751                 wb_shutdown(wb);
 752                 spin_lock_irq(&cgwb_lock);
 753         }
 754         spin_unlock_irq(&cgwb_lock);
 755         mutex_unlock(&bdi->cgwb_release_mutex);
 756 }
 757
 758 /*
 759  * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
 760  *
 761  * Try to release dying cgwbs by switching attached inodes to the nearest
 762  * living ancestor's writeback. Processed wbs are placed at the end
 763  * of the list to guarantee the forward progress.
 764  */
 765 static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
 766 {
 767         struct bdi_writeback *wb;
 768         LIST_HEAD(processed);
 769
 770         spin_lock_irq(&cgwb_lock);
 771
 772         while (!list_empty(&offline_cgwbs)) {
 773                 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
 774                                       offline_node);
 775                 list_move(&wb->offline_node, &processed);
 776
 777                 /*
 778                  * If wb is dirty, cleaning up the writeback by switching
 779                  * attached inodes will result in an effective removal of any
 780                  * bandwidth restrictions, which isn't the goal.  Instead,
 781                  * it can be postponed until the next time, when all io
 782                  * will be likely completed.  If in the meantime some inodes
 783                  * will get re-dirtied, they should be eventually switched to
 784                  * a new cgwb.
 785                  */
 786                 if (wb_has_dirty_io(wb))
 787                         continue;
 788
 789                 if (!wb_tryget(wb))
 790                         continue;
 791
 792                 spin_unlock_irq(&cgwb_lock);
 793                 while (cleanup_offline_cgwb(wb))
 794                         cond_resched();
 795                 spin_lock_irq(&cgwb_lock);
 796
 797                 wb_put(wb);
 798         }
 799
 800         if (!list_empty(&processed))
 801                 list_splice_tail(&processed, &offline_cgwbs);
 802
 803         spin_unlock_irq(&cgwb_lock);
 804 }
 805
 806 /**
 807  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
 808  * @memcg: memcg being offlined
 809  *
 810  * Also prevents creation of any new wb's associated with @memcg.
 811  */
 812 void wb_memcg_offline(struct mem_cgroup *memcg)
 813 {
 814         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
 815         struct bdi_writeback *wb, *next;
 816
 817         spin_lock_irq(&cgwb_lock);
 818         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
 819                 cgwb_kill(wb);
 820         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
 821         spin_unlock_irq(&cgwb_lock);
 822
 823         queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
 824 }
 825
 826 /**
 827  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
 828  * @css: blkcg being offlined
 829  *
 830  * Also prevents creation of any new wb's associated with @blkcg.
 831  */
 832 void wb_blkcg_offline(struct cgroup_subsys_state *css)
 833 {
 834         struct bdi_writeback *wb, *next;
 835         struct list_head *list = blkcg_get_cgwb_list(css);
 836
 837         spin_lock_irq(&cgwb_lock);
 838         list_for_each_entry_safe(wb, next, list, blkcg_node)
 839                 cgwb_kill(wb);
 840         list->next = NULL;      /* prevent new wb's */
 841         spin_unlock_irq(&cgwb_lock);
 842 }
 843
 844 static void cgwb_bdi_register(struct backing_dev_info *bdi)
 845 {
 846         spin_lock_irq(&cgwb_lock);
 847         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
 848         spin_unlock_irq(&cgwb_lock);
 849 }
 850
 851 static int __init cgwb_init(void)
 852 {
 853         /*
 854          * There can be many concurrent release work items overwhelming
 855          * system_wq.  Put them in a separate wq and limit concurrency.
 856          * There's no point in executing many of these in parallel.
 857          */
 858         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
 859         if (!cgwb_release_wq)
 860                 return -ENOMEM;
 861
 862         return 0;
 863 }
 864 subsys_initcall(cgwb_init);
 865
 866 #else   /* CONFIG_CGROUP_WRITEBACK */
 867
 868 static int cgwb_bdi_init(struct backing_dev_info *bdi)
 869 {
 870         return wb_init(&bdi->wb, bdi, GFP_KERNEL);
 871 }
 872
 873 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
 874
 875 static void cgwb_bdi_register(struct backing_dev_info *bdi)
 876 {
 877         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
 878 }
 879
 880 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 881 {
 882         list_del_rcu(&wb->bdi_node);
 883 }
 884
 885 #endif  /* CONFIG_CGROUP_WRITEBACK */
 886
 887 int bdi_init(struct backing_dev_info *bdi)
 888 {
 889         bdi->dev = NULL;
 890
 891         kref_init(&bdi->refcnt);
 892         bdi->min_ratio = 0;
 893         bdi->max_ratio = 100 * BDI_RATIO_SCALE;
 894         bdi->max_prop_frac = FPROP_FRAC_BASE;
 895         INIT_LIST_HEAD(&bdi->bdi_list);
 896         INIT_LIST_HEAD(&bdi->wb_list);
 897         init_waitqueue_head(&bdi->wb_waitq);
 898         bdi->last_bdp_sleep = jiffies;
 899
 900         return cgwb_bdi_init(bdi);
 901 }
 902
 903 struct backing_dev_info *bdi_alloc(int node_id)
 904 {
 905         struct backing_dev_info *bdi;
 906
 907         bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
 908         if (!bdi)
 909                 return NULL;
 910
 911         if (bdi_init(bdi)) {
 912                 kfree(bdi);
 913                 return NULL;
 914         }
 915         bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
 916         bdi->ra_pages = VM_READAHEAD_PAGES;
 917         bdi->io_pages = VM_READAHEAD_PAGES;
 918         timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
 919         return bdi;
 920 }
 921 EXPORT_SYMBOL(bdi_alloc);
 922
 923 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
 924 {
 925         struct rb_node **p = &bdi_tree.rb_node;
 926         struct rb_node *parent = NULL;
 927         struct backing_dev_info *bdi;
 928
 929         lockdep_assert_held(&bdi_lock);
 930
 931         while (*p) {
 932                 parent = *p;
 933                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
 934
 935                 if (bdi->id > id)
 936                         p = &(*p)->rb_left;
 937                 else if (bdi->id < id)
 938                         p = &(*p)->rb_right;
 939                 else
 940                         break;
 941         }
 942
 943         if (parentp)
 944                 *parentp = parent;
 945         return p;
 946 }
 947
 948 /**
 949  * bdi_get_by_id - lookup and get bdi from its id
 950  * @id: bdi id to lookup
 951  *
 952  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
 953  * doesn't exist or is already unregistered.
 954  */
 955 struct backing_dev_info *bdi_get_by_id(u64 id)
 956 {
 957         struct backing_dev_info *bdi = NULL;
 958         struct rb_node **p;
 959
 960         spin_lock_bh(&bdi_lock);
 961         p = bdi_lookup_rb_node(id, NULL);
 962         if (*p) {
 963                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
 964                 bdi_get(bdi);
 965         }
 966         spin_unlock_bh(&bdi_lock);
 967
 968         return bdi;
 969 }
 970
 971 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
 972 {
 973         struct device *dev;
 974         struct rb_node *parent, **p;
 975
 976         if (bdi->dev)   /* The driver needs to use separate queues per device */
 977                 return 0;
 978
 979         vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
 980         dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
 981         if (IS_ERR(dev))
 982                 return PTR_ERR(dev);
 983
 984         cgwb_bdi_register(bdi);
 985         bdi->dev = dev;
 986
 987         bdi_debug_register(bdi, dev_name(dev));
 988         set_bit(WB_registered, &bdi->wb.state);
 989
 990         spin_lock_bh(&bdi_lock);
 991
 992         bdi->id = ++bdi_id_cursor;
 993
 994         p = bdi_lookup_rb_node(bdi->id, &parent);
 995         rb_link_node(&bdi->rb_node, parent, p);
 996         rb_insert_color(&bdi->rb_node, &bdi_tree);
 997
 998         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 999
1000         spin_unlock_bh(&bdi_lock);
1001
1002         trace_writeback_bdi_register(bdi);
1003         return 0;
1004 }
1005
1006 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
1007 {
1008         va_list args;
1009         int ret;
1010
1011         va_start(args, fmt);
1012         ret = bdi_register_va(bdi, fmt, args);
1013         va_end(args);
1014         return ret;
1015 }
1016 EXPORT_SYMBOL(bdi_register);
1017
1018 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
1019 {
1020         WARN_ON_ONCE(bdi->owner);
1021         bdi->owner = owner;
1022         get_device(owner);
1023 }
1024
1025 /*
1026  * Remove bdi from bdi_list, and ensure that it is no longer visible
1027  */
1028 static void bdi_remove_from_list(struct backing_dev_info *bdi)
1029 {
1030         spin_lock_bh(&bdi_lock);
1031         rb_erase(&bdi->rb_node, &bdi_tree);
1032         list_del_rcu(&bdi->bdi_list);
1033         spin_unlock_bh(&bdi_lock);
1034
1035         synchronize_rcu_expedited();
1036 }
1037
1038 void bdi_unregister(struct backing_dev_info *bdi)
1039 {
1040         del_timer_sync(&bdi->laptop_mode_wb_timer);
1041
1042         /* make sure nobody finds us on the bdi_list anymore */
1043         bdi_remove_from_list(bdi);
1044         wb_shutdown(&bdi->wb);
1045         cgwb_bdi_unregister(bdi);
1046
1047         /*
1048          * If this BDI's min ratio has been set, use bdi_set_min_ratio() to
1049          * update the global bdi_min_ratio.
1050          */
1051         if (bdi->min_ratio)
1052                 bdi_set_min_ratio(bdi, 0);
1053
1054         if (bdi->dev) {
1055                 bdi_debug_unregister(bdi);
1056                 device_unregister(bdi->dev);
1057                 bdi->dev = NULL;
1058         }
1059
1060         if (bdi->owner) {
1061                 put_device(bdi->owner);
1062                 bdi->owner = NULL;
1063         }
1064 }
1065 EXPORT_SYMBOL(bdi_unregister);
1066
1067 static void release_bdi(struct kref *ref)
1068 {
1069         struct backing_dev_info *bdi =
1070                         container_of(ref, struct backing_dev_info, refcnt);
1071
1072         WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state));
1073         WARN_ON_ONCE(bdi->dev);
1074         wb_exit(&bdi->wb);
1075         kfree(bdi);
1076 }
1077
1078 void bdi_put(struct backing_dev_info *bdi)
1079 {
1080         kref_put(&bdi->refcnt, release_bdi);
1081 }
1082 EXPORT_SYMBOL(bdi_put);
1083
1084 struct backing_dev_info *inode_to_bdi(struct inode *inode)
1085 {
1086         struct super_block *sb;
1087
1088         if (!inode)
1089                 return &noop_backing_dev_info;
1090
1091         sb = inode->i_sb;
1092 #ifdef CONFIG_BLOCK
1093         if (sb_is_blkdev_sb(sb))
1094                 return I_BDEV(inode)->bd_disk->bdi;
1095 #endif
1096         return sb->s_bdi;
1097 }
1098 EXPORT_SYMBOL(inode_to_bdi);
1099
1100 const char *bdi_dev_name(struct backing_dev_info *bdi)
1101 {
1102         if (!bdi || !bdi->dev)
1103                 return bdi_unknown_name;
1104         return bdi->dev_name;
1105 }
1106 EXPORT_SYMBOL_GPL(bdi_dev_name);