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