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); 1015