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         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  19 };
  20 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
  21
  22 static struct class *bdi_class;
  23 static const char *bdi_unknown_name = "(unknown)";
  24
  25 /*
  26  * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
  27  * reader side locking.
  28  */
  29 DEFINE_SPINLOCK(bdi_lock);
  30 static u64 bdi_id_cursor;
  31 static struct rb_root bdi_tree = RB_ROOT;
  32 LIST_HEAD(bdi_list);
  33
  34 /* bdi_wq serves all asynchronous writeback tasks */
  35 struct workqueue_struct *bdi_wq;
  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 #define K(x) ((x) << (PAGE_SHIFT - 10))
  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 #undef K
 104
 105         return 0;
 106 }
 107 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
 108
 109 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
 110 {
 111         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
 112
 113         debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
 114                             &bdi_debug_stats_fops);
 115 }
 116
 117 static void bdi_debug_unregister(struct backing_dev_info *bdi)
 118 {
 119         debugfs_remove_recursive(bdi->debug_dir);
 120 }
 121 #else
 122 static inline void bdi_debug_init(void)
 123 {
 124 }
 125 static inline void bdi_debug_register(struct backing_dev_info *bdi,
 126                                       const char *name)
 127 {
 128 }
 129 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
 130 {
 131 }
 132 #endif
 133
 134 static ssize_t read_ahead_kb_store(struct device *dev,
 135                                   struct device_attribute *attr,
 136                                   const char *buf, size_t count)
 137 {
 138         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 139         unsigned long read_ahead_kb;
 140         ssize_t ret;
 141
 142         ret = kstrtoul(buf, 10, &read_ahead_kb);
 143         if (ret < 0)
 144                 return ret;
 145
 146         bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
 147
 148         return count;
 149 }
 150
 151 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
 152
 153 #define BDI_SHOW(name, expr)                                            \
 154 static ssize_t name##_show(struct device *dev,                          \
 155                            struct device_attribute *attr, char *page)   \
 156 {                                                                       \
 157         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
 158                                                                         \
 159         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
 160 }                                                                       \
 161 static DEVICE_ATTR_RW(name);
 162
 163 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
 164
 165 static ssize_t min_ratio_store(struct device *dev,
 166                 struct device_attribute *attr, const char *buf, size_t count)
 167 {
 168         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 169         unsigned int ratio;
 170         ssize_t ret;
 171
 172         ret = kstrtouint(buf, 10, &ratio);
 173         if (ret < 0)
 174                 return ret;
 175
 176         ret = bdi_set_min_ratio(bdi, ratio);
 177         if (!ret)
 178                 ret = count;
 179
 180         return ret;
 181 }
 182 BDI_SHOW(min_ratio, bdi->min_ratio)
 183
 184 static ssize_t max_ratio_store(struct device *dev,
 185                 struct device_attribute *attr, const char *buf, size_t count)
 186 {
 187         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 188         unsigned int ratio;
 189         ssize_t ret;
 190
 191         ret = kstrtouint(buf, 10, &ratio);
 192         if (ret < 0)
 193                 return ret;
 194
 195         ret = bdi_set_max_ratio(bdi, ratio);
 196         if (!ret)
 197                 ret = count;
 198
 199         return ret;
 200 }
 201 BDI_SHOW(max_ratio, bdi->max_ratio)
 202
 203 static ssize_t stable_pages_required_show(struct device *dev,
 204                                           struct device_attribute *attr,
 205                                           char *page)
 206 {
 207         struct backing_dev_info *bdi = dev_get_drvdata(dev);
 208
 209         return snprintf(page, PAGE_SIZE-1, "%d\n",
 210                         bdi_cap_stable_pages_required(bdi) ? 1 : 0);
 211 }
 212 static DEVICE_ATTR_RO(stable_pages_required);
 213
 214 static struct attribute *bdi_dev_attrs[] = {
 215         &dev_attr_read_ahead_kb.attr,
 216         &dev_attr_min_ratio.attr,
 217         &dev_attr_max_ratio.attr,
 218         &dev_attr_stable_pages_required.attr,
 219         NULL,
 220 };
 221 ATTRIBUTE_GROUPS(bdi_dev);
 222
 223 static __init int bdi_class_init(void)
 224 {
 225         bdi_class = class_create(THIS_MODULE, "bdi");
 226         if (IS_ERR(bdi_class))
 227                 return PTR_ERR(bdi_class);
 228
 229         bdi_class->dev_groups = bdi_dev_groups;
 230         bdi_debug_init();
 231
 232         return 0;
 233 }
 234 postcore_initcall(bdi_class_init);
 235
 236 static int bdi_init(struct backing_dev_info *bdi);
 237
 238 static int __init default_bdi_init(void)
 239 {
 240         int err;
 241
 242         bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
 243                                  WQ_SYSFS, 0);
 244         if (!bdi_wq)
 245                 return -ENOMEM;
 246
 247         err = bdi_init(&noop_backing_dev_info);
 248
 249         return err;
 250 }
 251 subsys_initcall(default_bdi_init);
 252
 253 /*
 254  * This function is used when the first inode for this wb is marked dirty. It
 255  * wakes-up the corresponding bdi thread which should then take care of the
 256  * periodic background write-out of dirty inodes. Since the write-out would
 257  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
 258  * set up a timer which wakes the bdi thread up later.
 259  *
 260  * Note, we wouldn't bother setting up the timer, but this function is on the
 261  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
 262  * by delaying the wake-up.
 263  *
 264  * We have to be careful not to postpone flush work if it is scheduled for
 265  * earlier. Thus we use queue_delayed_work().
 266  */
 267 void wb_wakeup_delayed(struct bdi_writeback *wb)
 268 {
 269         unsigned long timeout;
 270
 271         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
 272         spin_lock_bh(&wb->work_lock);
 273         if (test_bit(WB_registered, &wb->state))
 274                 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
 275         spin_unlock_bh(&wb->work_lock);
 276 }
 277
 278 /*
 279  * Initial write bandwidth: 100 MB/s
 280  */
 281 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
 282
 283 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
 284                    gfp_t gfp)
 285 {
 286         int i, err;
 287
 288         memset(wb, 0, sizeof(*wb));
 289
 290         if (wb != &bdi->wb)
 291                 bdi_get(bdi);
 292         wb->bdi = bdi;
 293         wb->last_old_flush = jiffies;
 294         INIT_LIST_HEAD(&wb->b_dirty);
 295         INIT_LIST_HEAD(&wb->b_io);
 296         INIT_LIST_HEAD(&wb->b_more_io);
 297         INIT_LIST_HEAD(&wb->b_dirty_time);
 298         spin_lock_init(&wb->list_lock);
 299
 300         wb->bw_time_stamp = jiffies;
 301         wb->balanced_dirty_ratelimit = INIT_BW;
 302         wb->dirty_ratelimit = INIT_BW;
 303         wb->write_bandwidth = INIT_BW;
 304         wb->avg_write_bandwidth = INIT_BW;
 305
 306         spin_lock_init(&wb->work_lock);
 307         INIT_LIST_HEAD(&wb->work_list);
 308         INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
 309         wb->dirty_sleep = jiffies;
 310
 311         err = fprop_local_init_percpu(&wb->completions, gfp);
 312         if (err)
 313                 goto out_put_bdi;
 314
 315         for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
 316                 err = percpu_counter_init(&wb->stat[i], 0, gfp);
 317                 if (err)
 318                         goto out_destroy_stat;
 319         }
 320
 321         return 0;
 322
 323 out_destroy_stat:
 324         while (i--)
 325                 percpu_counter_destroy(&wb->stat[i]);
 326         fprop_local_destroy_percpu(&wb->completions);
 327 out_put_bdi:
 328         if (wb != &bdi->wb)
 329                 bdi_put(bdi);
 330         return err;
 331 }
 332
 333 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
 334
 335 /*
 336  * Remove bdi from the global list and shutdown any threads we have running
 337  */
 338 static void wb_shutdown(struct bdi_writeback *wb)
 339 {
 340         /* Make sure nobody queues further work */
 341         spin_lock_bh(&wb->work_lock);
 342         if (!test_and_clear_bit(WB_registered, &wb->state)) {
 343                 spin_unlock_bh(&wb->work_lock);
 344                 return;
 345         }
 346         spin_unlock_bh(&wb->work_lock);
 347
 348         cgwb_remove_from_bdi_list(wb);
 349         /*
 350          * Drain work list and shutdown the delayed_work.  !WB_registered
 351          * tells wb_workfn() that @wb is dying and its work_list needs to
 352          * be drained no matter what.
 353          */
 354         mod_delayed_work(bdi_wq, &wb->dwork, 0);
 355         flush_delayed_work(&wb->dwork);
 356         WARN_ON(!list_empty(&wb->work_list));
 357 }
 358
 359 static void wb_exit(struct bdi_writeback *wb)
 360 {
 361         int i;
 362
 363         WARN_ON(delayed_work_pending(&wb->dwork));
 364
 365         for (i = 0; i < NR_WB_STAT_ITEMS; i++)
 366                 percpu_counter_destroy(&wb->stat[i]);
 367
 368         fprop_local_destroy_percpu(&wb->completions);
 369         if (wb != &wb->bdi->wb)
 370                 bdi_put(wb->bdi);
 371 }
 372
 373 #ifdef CONFIG_CGROUP_WRITEBACK
 374
 375 #include <linux/memcontrol.h>
 376
 377 /*
 378  * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, and memcg->cgwb_list.
 379  * bdi->cgwb_tree is also RCU protected.
 380  */
 381 static DEFINE_SPINLOCK(cgwb_lock);
 382 static struct workqueue_struct *cgwb_release_wq;
 383
 384 static void cgwb_release_workfn(struct work_struct *work)
 385 {
 386         struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
 387                                                 release_work);
 388         struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
 389
 390         mutex_lock(&wb->bdi->cgwb_release_mutex);
 391         wb_shutdown(wb);
 392
 393         css_put(wb->memcg_css);
 394         css_put(wb->blkcg_css);
 395         mutex_unlock(&wb->bdi->cgwb_release_mutex);
 396
 397         /* triggers blkg destruction if no online users left */
 398         blkcg_unpin_online(blkcg);
 399
 400         fprop_local_destroy_percpu(&wb->memcg_completions);
 401         percpu_ref_exit(&wb->refcnt);
 402         wb_exit(wb);
 403         kfree_rcu(wb, rcu);
 404 }
 405
 406 static void cgwb_release(struct percpu_ref *refcnt)
 407 {
 408         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
 409                                                 refcnt);
 410         queue_work(cgwb_release_wq, &wb->release_work);
 411 }
 412
 413 static void cgwb_kill(struct bdi_writeback *wb)
 414 {
 415         lockdep_assert_held(&cgwb_lock);
 416
 417         WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
 418         list_del(&wb->memcg_node);
 419         list_del(&wb->blkcg_node);
 420         percpu_ref_kill(&wb->refcnt);
 421 }
 422
 423 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 424 {
 425         spin_lock_irq(&cgwb_lock);
 426         list_del_rcu(&wb->bdi_node);
 427         spin_unlock_irq(&cgwb_lock);
 428 }
 429
 430 static int cgwb_create(struct backing_dev_info *bdi,
 431                        struct cgroup_subsys_state *memcg_css, gfp_t gfp)
 432 {
 433         struct mem_cgroup *memcg;
 434         struct cgroup_subsys_state *blkcg_css;
 435         struct blkcg *blkcg;
 436         struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
 437         struct bdi_writeback *wb;
 438         unsigned long flags;
 439         int ret = 0;
 440
 441         memcg = mem_cgroup_from_css(memcg_css);
 442         blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 443         blkcg = css_to_blkcg(blkcg_css);
 444         memcg_cgwb_list = &memcg->cgwb_list;
 445         blkcg_cgwb_list = &blkcg->cgwb_list;
 446
 447         /* look up again under lock and discard on blkcg mismatch */
 448         spin_lock_irqsave(&cgwb_lock, flags);
 449         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 450         if (wb && wb->blkcg_css != blkcg_css) {
 451                 cgwb_kill(wb);
 452                 wb = NULL;
 453         }
 454         spin_unlock_irqrestore(&cgwb_lock, flags);
 455         if (wb)
 456                 goto out_put;
 457
 458         /* need to create a new one */
 459         wb = kmalloc(sizeof(*wb), gfp);
 460         if (!wb) {
 461                 ret = -ENOMEM;
 462                 goto out_put;
 463         }
 464
 465         ret = wb_init(wb, bdi, gfp);
 466         if (ret)
 467                 goto err_free;
 468
 469         ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
 470         if (ret)
 471                 goto err_wb_exit;
 472
 473         ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
 474         if (ret)
 475                 goto err_ref_exit;
 476
 477         wb->memcg_css = memcg_css;
 478         wb->blkcg_css = blkcg_css;
 479         INIT_WORK(&wb->release_work, cgwb_release_workfn);
 480         set_bit(WB_registered, &wb->state);
 481
 482         /*
 483          * The root wb determines the registered state of the whole bdi and
 484          * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
 485          * whether they're still online.  Don't link @wb if any is dead.
 486          * See wb_memcg_offline() and wb_blkcg_offline().
 487          */
 488         ret = -ENODEV;
 489         spin_lock_irqsave(&cgwb_lock, flags);
 490         if (test_bit(WB_registered, &bdi->wb.state) &&
 491             blkcg_cgwb_list->next && memcg_cgwb_list->next) {
 492                 /* we might have raced another instance of this function */
 493                 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
 494                 if (!ret) {
 495                         list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
 496                         list_add(&wb->memcg_node, memcg_cgwb_list);
 497                         list_add(&wb->blkcg_node, blkcg_cgwb_list);
 498                         blkcg_pin_online(blkcg);
 499                         css_get(memcg_css);
 500                         css_get(blkcg_css);
 501                 }
 502         }
 503         spin_unlock_irqrestore(&cgwb_lock, flags);
 504         if (ret) {
 505                 if (ret == -EEXIST)
 506                         ret = 0;
 507                 goto err_fprop_exit;
 508         }
 509         goto out_put;
 510
 511 err_fprop_exit:
 512         fprop_local_destroy_percpu(&wb->memcg_completions);
 513 err_ref_exit:
 514         percpu_ref_exit(&wb->refcnt);
 515 err_wb_exit:
 516         wb_exit(wb);
 517 err_free:
 518         kfree(wb);
 519 out_put:
 520         css_put(blkcg_css);
 521         return ret;
 522 }
 523
 524 /**
 525  * wb_get_lookup - get wb for a given memcg
 526  * @bdi: target bdi
 527  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
 528  *
 529  * Try to get the wb for @memcg_css on @bdi.  The returned wb has its
 530  * refcount incremented.
 531  *
 532  * This function uses css_get() on @memcg_css and thus expects its refcnt
 533  * to be positive on invocation.  IOW, rcu_read_lock() protection on
 534  * @memcg_css isn't enough.  try_get it before calling this function.
 535  *
 536  * A wb is keyed by its associated memcg.  As blkcg implicitly enables
 537  * memcg on the default hierarchy, memcg association is guaranteed to be
 538  * more specific (equal or descendant to the associated blkcg) and thus can
 539  * identify both the memcg and blkcg associations.
 540  *
 541  * Because the blkcg associated with a memcg may change as blkcg is enabled
 542  * and disabled closer to root in the hierarchy, each wb keeps track of
 543  * both the memcg and blkcg associated with it and verifies the blkcg on
 544  * each lookup.  On mismatch, the existing wb is discarded and a new one is
 545  * created.
 546  */
 547 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
 548                                     struct cgroup_subsys_state *memcg_css)
 549 {
 550         struct bdi_writeback *wb;
 551
 552         if (!memcg_css->parent)
 553                 return &bdi->wb;
 554
 555         rcu_read_lock();
 556         wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
 557         if (wb) {
 558                 struct cgroup_subsys_state *blkcg_css;
 559
 560                 /* see whether the blkcg association has changed */
 561                 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 562                 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
 563                         wb = NULL;
 564                 css_put(blkcg_css);
 565         }
 566         rcu_read_unlock();
 567
 568         return wb;
 569 }
 570
 571 /**
 572  * wb_get_create - get wb for a given memcg, create if necessary
 573  * @bdi: target bdi
 574  * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
 575  * @gfp: allocation mask to use
 576  *
 577  * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
 578  * create one.  See wb_get_lookup() for more details.
 579  */
 580 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 581                                     struct cgroup_subsys_state *memcg_css,
 582                                     gfp_t gfp)
 583 {
 584         struct bdi_writeback *wb;
 585
 586         might_sleep_if(gfpflags_allow_blocking(gfp));
 587
 588         if (!memcg_css->parent)
 589                 return &bdi->wb;
 590
 591         do {
 592                 wb = wb_get_lookup(bdi, memcg_css);
 593         } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
 594
 595         return wb;
 596 }
 597
 598 static int cgwb_bdi_init(struct backing_dev_info *bdi)
 599 {
 600         int ret;
 601
 602         INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
 603         mutex_init(&bdi->cgwb_release_mutex);
 604         init_rwsem(&bdi->wb_switch_rwsem);
 605
 606         ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
 607         if (!ret) {
 608                 bdi->wb.memcg_css = &root_mem_cgroup->css;
 609                 bdi->wb.blkcg_css = blkcg_root_css;
 610         }
 611         return ret;
 612 }
 613
 614 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
 615 {
 616         struct radix_tree_iter iter;
 617         void **slot;
 618         struct bdi_writeback *wb;
 619
 620         WARN_ON(test_bit(WB_registered, &bdi->wb.state));
 621
 622         spin_lock_irq(&cgwb_lock);
 623         radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
 624                 cgwb_kill(*slot);
 625         spin_unlock_irq(&cgwb_lock);
 626
 627         mutex_lock(&bdi->cgwb_release_mutex);
 628         spin_lock_irq(&cgwb_lock);
 629         while (!list_empty(&bdi->wb_list)) {
 630                 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
 631                                       bdi_node);
 632                 spin_unlock_irq(&cgwb_lock);
 633                 wb_shutdown(wb);
 634                 spin_lock_irq(&cgwb_lock);
 635         }
 636         spin_unlock_irq(&cgwb_lock);
 637         mutex_unlock(&bdi->cgwb_release_mutex);
 638 }
 639
 640 /**
 641  * wb_memcg_offline - kill all wb's associated with a memcg being offlined
 642  * @memcg: memcg being offlined
 643  *
 644  * Also prevents creation of any new wb's associated with @memcg.
 645  */
 646 void wb_memcg_offline(struct mem_cgroup *memcg)
 647 {
 648         struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
 649         struct bdi_writeback *wb, *next;
 650
 651         spin_lock_irq(&cgwb_lock);
 652         list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
 653                 cgwb_kill(wb);
 654         memcg_cgwb_list->next = NULL;   /* prevent new wb's */
 655         spin_unlock_irq(&cgwb_lock);
 656 }
 657
 658 /**
 659  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
 660  * @blkcg: blkcg being offlined
 661  *
 662  * Also prevents creation of any new wb's associated with @blkcg.
 663  */
 664 void wb_blkcg_offline(struct blkcg *blkcg)
 665 {
 666         struct bdi_writeback *wb, *next;
 667
 668         spin_lock_irq(&cgwb_lock);
 669         list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
 670                 cgwb_kill(wb);
 671         blkcg->cgwb_list.next = NULL;   /* prevent new wb's */
 672         spin_unlock_irq(&cgwb_lock);
 673 }
 674
 675 static void cgwb_bdi_register(struct backing_dev_info *bdi)
 676 {
 677         spin_lock_irq(&cgwb_lock);
 678         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
 679         spin_unlock_irq(&cgwb_lock);
 680 }
 681
 682 static int __init cgwb_init(void)
 683 {
 684         /*
 685          * There can be many concurrent release work items overwhelming
 686          * system_wq.  Put them in a separate wq and limit concurrency.
 687          * There's no point in executing many of these in parallel.
 688          */
 689         cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
 690         if (!cgwb_release_wq)
 691                 return -ENOMEM;
 692
 693         return 0;
 694 }
 695 subsys_initcall(cgwb_init);
 696
 697 #else   /* CONFIG_CGROUP_WRITEBACK */
 698
 699 static int cgwb_bdi_init(struct backing_dev_info *bdi)
 700 {
 701         return wb_init(&bdi->wb, bdi, GFP_KERNEL);
 702 }
 703
 704 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
 705
 706 static void cgwb_bdi_register(struct backing_dev_info *bdi)
 707 {
 708         list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
 709 }
 710
 711 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
 712 {
 713         list_del_rcu(&wb->bdi_node);
 714 }
 715
 716 #endif  /* CONFIG_CGROUP_WRITEBACK */
 717
 718 static int bdi_init(struct backing_dev_info *bdi)
 719 {
 720         int ret;
 721
 722         bdi->dev = NULL;
 723
 724         kref_init(&bdi->refcnt);
 725         bdi->min_ratio = 0;
 726         bdi->max_ratio = 100;
 727         bdi->max_prop_frac = FPROP_FRAC_BASE;
 728         INIT_LIST_HEAD(&bdi->bdi_list);
 729         INIT_LIST_HEAD(&bdi->wb_list);
 730         init_waitqueue_head(&bdi->wb_waitq);
 731
 732         ret = cgwb_bdi_init(bdi);
 733
 734         return ret;
 735 }
 736
 737 struct backing_dev_info *bdi_alloc(int node_id)
 738 {
 739         struct backing_dev_info *bdi;
 740
 741         bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
 742         if (!bdi)
 743                 return NULL;
 744
 745         if (bdi_init(bdi)) {
 746                 kfree(bdi);
 747                 return NULL;
 748         }
 749         return bdi;
 750 }
 751 EXPORT_SYMBOL(bdi_alloc);
 752
 753 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
 754 {
 755         struct rb_node **p = &bdi_tree.rb_node;
 756         struct rb_node *parent = NULL;
 757         struct backing_dev_info *bdi;
 758
 759         lockdep_assert_held(&bdi_lock);
 760
 761         while (*p) {
 762                 parent = *p;
 763                 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
 764
 765                 if (bdi->id > id)
 766                         p = &(*p)->rb_left;
 767                 else if (bdi->id < id)
 768                         p = &(*p)->rb_right;
 769                 else
 770                         break;
 771         }
 772
 773         if (parentp)
 774                 *parentp = parent;
 775         return p;
 776 }
 777
 778 /**
 779  * bdi_get_by_id - lookup and get bdi from its id
 780  * @id: bdi id to lookup
 781  *
 782  * Find bdi matching @id and get it.  Returns NULL if the matching bdi
 783  * doesn't exist or is already unregistered.
 784  */
 785 struct backing_dev_info *bdi_get_by_id(u64 id)
 786 {
 787         struct backing_dev_info *bdi = NULL;
 788         struct rb_node **p;
 789
 790         spin_lock_bh(&bdi_lock);
 791         p = bdi_lookup_rb_node(id, NULL);
 792         if (*p) {
 793                 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
 794                 bdi_get(bdi);
 795         }
 796         spin_unlock_bh(&bdi_lock);
 797
 798         return bdi;
 799 }
 800
 801 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
 802 {
 803         struct device *dev;
 804         struct rb_node *parent, **p;
 805
 806         if (bdi->dev)   /* The driver needs to use separate queues per device */
 807                 return 0;
 808
 809         vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
 810         dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
 811         if (IS_ERR(dev))
 812                 return PTR_ERR(dev);
 813
 814         cgwb_bdi_register(bdi);
 815         bdi->dev = dev;
 816
 817         bdi_debug_register(bdi, dev_name(dev));
 818         set_bit(WB_registered, &bdi->wb.state);
 819
 820         spin_lock_bh(&bdi_lock);
 821
 822         bdi->id = ++bdi_id_cursor;
 823
 824         p = bdi_lookup_rb_node(bdi->id, &parent);
 825         rb_link_node(&bdi->rb_node, parent, p);
 826         rb_insert_color(&bdi->rb_node, &bdi_tree);
 827
 828         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
 829
 830         spin_unlock_bh(&bdi_lock);
 831
 832         trace_writeback_bdi_register(bdi);
 833         return 0;
 834 }
 835
 836 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
 837 {
 838         va_list args;
 839         int ret;
 840
 841         va_start(args, fmt);
 842         ret = bdi_register_va(bdi, fmt, args);
 843         va_end(args);
 844         return ret;
 845 }
 846 EXPORT_SYMBOL(bdi_register);
 847
 848 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
 849 {
 850         WARN_ON_ONCE(bdi->owner);
 851         bdi->owner = owner;
 852         get_device(owner);
 853 }
 854
 855 /*
 856  * Remove bdi from bdi_list, and ensure that it is no longer visible
 857  */
 858 static void bdi_remove_from_list(struct backing_dev_info *bdi)
 859 {
 860         spin_lock_bh(&bdi_lock);
 861         rb_erase(&bdi->rb_node, &bdi_tree);
 862         list_del_rcu(&bdi->bdi_list);
 863         spin_unlock_bh(&bdi_lock);
 864
 865         synchronize_rcu_expedited();
 866 }
 867
 868 void bdi_unregister(struct backing_dev_info *bdi)
 869 {
 870         /* make sure nobody finds us on the bdi_list anymore */
 871         bdi_remove_from_list(bdi);
 872         wb_shutdown(&bdi->wb);
 873         cgwb_bdi_unregister(bdi);
 874
 875         if (bdi->dev) {
 876                 bdi_debug_unregister(bdi);
 877                 device_unregister(bdi->dev);
 878                 bdi->dev = NULL;
 879         }
 880
 881         if (bdi->owner) {
 882                 put_device(bdi->owner);
 883                 bdi->owner = NULL;
 884         }
 885 }
 886
 887 static void release_bdi(struct kref *ref)
 888 {
 889         struct backing_dev_info *bdi =
 890                         container_of(ref, struct backing_dev_info, refcnt);
 891
 892         if (test_bit(WB_registered, &bdi->wb.state))
 893                 bdi_unregister(bdi);
 894         WARN_ON_ONCE(bdi->dev);
 895         wb_exit(&bdi->wb);
 896         kfree(bdi);
 897 }
 898
 899 void bdi_put(struct backing_dev_info *bdi)
 900 {
 901         kref_put(&bdi->refcnt, release_bdi);
 902 }
 903 EXPORT_SYMBOL(bdi_put);
 904
 905 const char *bdi_dev_name(struct backing_dev_info *bdi)
 906 {
 907         if (!bdi || !bdi->dev)
 908                 return bdi_unknown_name;
 909         return bdi->dev_name;
 910 }
 911 EXPORT_SYMBOL_GPL(bdi_dev_name);
 912
 913 static wait_queue_head_t congestion_wqh[2] = {
 914                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 915                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 916         };
 917 static atomic_t nr_wb_congested[2];
 918
 919 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 920 {
 921         wait_queue_head_t *wqh = &congestion_wqh[sync];
 922         enum wb_congested_state bit;
 923
 924         bit = sync ? WB_sync_congested : WB_async_congested;
 925         if (test_and_clear_bit(bit, &bdi->wb.congested))
 926                 atomic_dec(&nr_wb_congested[sync]);
 927         smp_mb__after_atomic();
 928         if (waitqueue_active(wqh))
 929                 wake_up(wqh);
 930 }
 931 EXPORT_SYMBOL(clear_bdi_congested);
 932
 933 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 934 {
 935         enum wb_congested_state bit;
 936
 937         bit = sync ? WB_sync_congested : WB_async_congested;
 938         if (!test_and_set_bit(bit, &bdi->wb.congested))
 939                 atomic_inc(&nr_wb_congested[sync]);
 940 }
 941 EXPORT_SYMBOL(set_bdi_congested);
 942
 943 /**
 944  * congestion_wait - wait for a backing_dev to become uncongested
 945  * @sync: SYNC or ASYNC IO
 946  * @timeout: timeout in jiffies
 947  *
 948  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
 949  * write congestion.  If no backing_devs are congested then just wait for the
 950  * next write to be completed.
 951  */
 952 long congestion_wait(int sync, long timeout)
 953 {
 954         long ret;
 955         unsigned long start = jiffies;
 956         DEFINE_WAIT(wait);
 957         wait_queue_head_t *wqh = &congestion_wqh[sync];
 958
 959         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 960         ret = io_schedule_timeout(timeout);
 961         finish_wait(wqh, &wait);
 962
 963         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
 964                                         jiffies_to_usecs(jiffies - start));
 965
 966         return ret;
 967 }
 968 EXPORT_SYMBOL(congestion_wait);
 969
 970 /**
 971  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
 972  * @sync: SYNC or ASYNC IO
 973  * @timeout: timeout in jiffies
 974  *
 975  * In the event of a congested backing_dev (any backing_dev) this waits
 976  * for up to @timeout jiffies for either a BDI to exit congestion of the
 977  * given @sync queue or a write to complete.
 978  *
 979  * The return value is 0 if the sleep is for the full timeout. Otherwise,
 980  * it is the number of jiffies that were still remaining when the function
 981  * returned. return_value == timeout implies the function did not sleep.
 982  */
 983 long wait_iff_congested(int sync, long timeout)
 984 {
 985         long ret;
 986         unsigned long start = jiffies;
 987         DEFINE_WAIT(wait);
 988         wait_queue_head_t *wqh = &congestion_wqh[sync];
 989
 990         /*
 991          * If there is no congestion, yield if necessary instead
 992          * of sleeping on the congestion queue
 993          */
 994         if (atomic_read(&nr_wb_congested[sync]) == 0) {
 995                 cond_resched();
 996
 997                 /* In case we scheduled, work out time remaining */
 998                 ret = timeout - (jiffies - start);
 999                 if (ret < 0)
1000                         ret = 0;
1001
1002                 goto out;
1003         }
1004
1005         /* Sleep until uncongested or a write happens */
1006         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1007         ret = io_schedule_timeout(timeout);
1008         finish_wait(wqh, &wait);
1009
1010 out:
1011         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1012                                         jiffies_to_usecs(jiffies - start));
1013
1014         return ret;
1015 }
1016 EXPORT_SYMBOL(wait_iff_congested);