1 // SPDX-License-Identifier: GPL-2.0-only 2 3 #include <linux/blkdev.h> 4 #include <linux/wait.h> 5 #include <linux/rbtree.h> 6 #include <linux/kthread.h> 7 #include <linux/backing-dev.h> 8 #include <linux/blk-cgroup.h> 9 #include <linux/freezer.h> 10 #include <linux/fs.h> 11 #include <linux/pagemap.h> 12 #include <linux/mm.h> 13 #include <linux/sched/mm.h> 14 #include <linux/sched.h> 15 #include <linux/module.h> 16 #include <linux/writeback.h> 17 #include <linux/device.h> 18 #include <trace/events/writeback.h> 19 #include "internal.h" 20 21 struct backing_dev_info noop_backing_dev_info; 22 EXPORT_SYMBOL_GPL(noop_backing_dev_info); 23 24 static const char *bdi_unknown_name = "(unknown)"; 25 26 /* 27 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU 28 * reader side locking. 29 */ 30 DEFINE_SPINLOCK(bdi_lock); 31 static u64 bdi_id_cursor; 32 static struct rb_root bdi_tree = RB_ROOT; 33 LIST_HEAD(bdi_list); 34 35 /* bdi_wq serves all asynchronous writeback tasks */ 36 struct workqueue_struct *bdi_wq; 37 38 #ifdef CONFIG_DEBUG_FS 39 #include <linux/debugfs.h> 40 #include <linux/seq_file.h> 41 42 static struct dentry *bdi_debug_root; 43 44 static void bdi_debug_init(void) 45 { 46 bdi_debug_root = debugfs_create_dir("bdi", NULL); 47 } 48 49 static int bdi_debug_stats_show(struct seq_file *m, void *v) 50 { 51 struct backing_dev_info *bdi = m->private; 52 struct bdi_writeback *wb = &bdi->wb; 53 unsigned long background_thresh; 54 unsigned long dirty_thresh; 55 unsigned long wb_thresh; 56 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time; 57 struct inode *inode; 58 59 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0; 60 spin_lock(&wb->list_lock); 61 list_for_each_entry(inode, &wb->b_dirty, i_io_list) 62 nr_dirty++; 63 list_for_each_entry(inode, &wb->b_io, i_io_list) 64 nr_io++; 65 list_for_each_entry(inode, &wb->b_more_io, i_io_list) 66 nr_more_io++; 67 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list) 68 if (inode->i_state & I_DIRTY_TIME) 69 nr_dirty_time++; 70 spin_unlock(&wb->list_lock); 71 72 global_dirty_limits(&background_thresh, &dirty_thresh); 73 wb_thresh = wb_calc_thresh(wb, dirty_thresh); 74 75 seq_printf(m, 76 "BdiWriteback: %10lu kB\n" 77 "BdiReclaimable: %10lu kB\n" 78 "BdiDirtyThresh: %10lu kB\n" 79 "DirtyThresh: %10lu kB\n" 80 "BackgroundThresh: %10lu kB\n" 81 "BdiDirtied: %10lu kB\n" 82 "BdiWritten: %10lu kB\n" 83 "BdiWriteBandwidth: %10lu kBps\n" 84 "b_dirty: %10lu\n" 85 "b_io: %10lu\n" 86 "b_more_io: %10lu\n" 87 "b_dirty_time: %10lu\n" 88 "bdi_list: %10u\n" 89 "state: %10lx\n", 90 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)), 91 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)), 92 K(wb_thresh), 93 K(dirty_thresh), 94 K(background_thresh), 95 (unsigned long) K(wb_stat(wb, WB_DIRTIED)), 96 (unsigned long) K(wb_stat(wb, WB_WRITTEN)), 97 (unsigned long) K(wb->write_bandwidth), 98 nr_dirty, 99 nr_io, 100 nr_more_io, 101 nr_dirty_time, 102 !list_empty(&bdi->bdi_list), bdi->wb.state); 103 104 return 0; 105 } 106 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats); 107 108 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name) 109 { 110 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); 111 112 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi, 113 &bdi_debug_stats_fops); 114 } 115 116 static void bdi_debug_unregister(struct backing_dev_info *bdi) 117 { 118 debugfs_remove_recursive(bdi->debug_dir); 119 } 120 #else 121 static inline void bdi_debug_init(void) 122 { 123 } 124 static inline void bdi_debug_register(struct backing_dev_info *bdi, 125 const char *name) 126 { 127 } 128 static inline void bdi_debug_unregister(struct backing_dev_info *bdi) 129 { 130 } 131 #endif 132 133 static ssize_t read_ahead_kb_store(struct device *dev, 134 struct device_attribute *attr, 135 const char *buf, size_t count) 136 { 137 struct backing_dev_info *bdi = dev_get_drvdata(dev); 138 unsigned long read_ahead_kb; 139 ssize_t ret; 140 141 ret = kstrtoul(buf, 10, &read_ahead_kb); 142 if (ret < 0) 143 return ret; 144 145 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10); 146 147 return count; 148 } 149 150 #define BDI_SHOW(name, expr) \ 151 static ssize_t name##_show(struct device *dev, \ 152 struct device_attribute *attr, char *buf) \ 153 { \ 154 struct backing_dev_info *bdi = dev_get_drvdata(dev); \ 155 \ 156 return sysfs_emit(buf, "%lld\n", (long long)expr); \ 157 } \ 158 static DEVICE_ATTR_RW(name); 159 160 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages)) 161 162 static ssize_t min_ratio_store(struct device *dev, 163 struct device_attribute *attr, const char *buf, size_t count) 164 { 165 struct backing_dev_info *bdi = dev_get_drvdata(dev); 166 unsigned int ratio; 167 ssize_t ret; 168 169 ret = kstrtouint(buf, 10, &ratio); 170 if (ret < 0) 171 return ret; 172 173 ret = bdi_set_min_ratio(bdi, ratio); 174 if (!ret) 175 ret = count; 176 177 return ret; 178 } 179 BDI_SHOW(min_ratio, bdi->min_ratio / BDI_RATIO_SCALE) 180 181 static ssize_t min_ratio_fine_store(struct device *dev, 182 struct device_attribute *attr, const char *buf, size_t count) 183 { 184 struct backing_dev_info *bdi = dev_get_drvdata(dev); 185 unsigned int ratio; 186 ssize_t ret; 187 188 ret = kstrtouint(buf, 10, &ratio); 189 if (ret < 0) 190 return ret; 191 192 ret = bdi_set_min_ratio_no_scale(bdi, ratio); 193 if (!ret) 194 ret = count; 195 196 return ret; 197 } 198 BDI_SHOW(min_ratio_fine, bdi->min_ratio) 199 200 static ssize_t max_ratio_store(struct device *dev, 201 struct device_attribute *attr, const char *buf, size_t count) 202 { 203 struct backing_dev_info *bdi = dev_get_drvdata(dev); 204 unsigned int ratio; 205 ssize_t ret; 206 207 ret = kstrtouint(buf, 10, &ratio); 208 if (ret < 0) 209 return ret; 210 211 ret = bdi_set_max_ratio(bdi, ratio); 212 if (!ret) 213 ret = count; 214 215 return ret; 216 } 217 BDI_SHOW(max_ratio, bdi->max_ratio / BDI_RATIO_SCALE) 218 219 static ssize_t max_ratio_fine_store(struct device *dev, 220 struct device_attribute *attr, const char *buf, size_t count) 221 { 222 struct backing_dev_info *bdi = dev_get_drvdata(dev); 223 unsigned int ratio; 224 ssize_t ret; 225 226 ret = kstrtouint(buf, 10, &ratio); 227 if (ret < 0) 228 return ret; 229 230 ret = bdi_set_max_ratio_no_scale(bdi, ratio); 231 if (!ret) 232 ret = count; 233 234 return ret; 235 } 236 BDI_SHOW(max_ratio_fine, bdi->max_ratio) 237 238 static ssize_t min_bytes_show(struct device *dev, 239 struct device_attribute *attr, 240 char *buf) 241 { 242 struct backing_dev_info *bdi = dev_get_drvdata(dev); 243 244 return sysfs_emit(buf, "%llu\n", bdi_get_min_bytes(bdi)); 245 } 246 247 static ssize_t min_bytes_store(struct device *dev, 248 struct device_attribute *attr, const char *buf, size_t count) 249 { 250 struct backing_dev_info *bdi = dev_get_drvdata(dev); 251 u64 bytes; 252 ssize_t ret; 253 254 ret = kstrtoull(buf, 10, &bytes); 255 if (ret < 0) 256 return ret; 257 258 ret = bdi_set_min_bytes(bdi, bytes); 259 if (!ret) 260 ret = count; 261 262 return ret; 263 } 264 static DEVICE_ATTR_RW(min_bytes); 265 266 static ssize_t max_bytes_show(struct device *dev, 267 struct device_attribute *attr, 268 char *buf) 269 { 270 struct backing_dev_info *bdi = dev_get_drvdata(dev); 271 272 return sysfs_emit(buf, "%llu\n", bdi_get_max_bytes(bdi)); 273 } 274 275 static ssize_t max_bytes_store(struct device *dev, 276 struct device_attribute *attr, const char *buf, size_t count) 277 { 278 struct backing_dev_info *bdi = dev_get_drvdata(dev); 279 u64 bytes; 280 ssize_t ret; 281 282 ret = kstrtoull(buf, 10, &bytes); 283 if (ret < 0) 284 return ret; 285 286 ret = bdi_set_max_bytes(bdi, bytes); 287 if (!ret) 288 ret = count; 289 290 return ret; 291 } 292 static DEVICE_ATTR_RW(max_bytes); 293 294 static ssize_t stable_pages_required_show(struct device *dev, 295 struct device_attribute *attr, 296 char *buf) 297 { 298 dev_warn_once(dev, 299 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n"); 300 return sysfs_emit(buf, "%d\n", 0); 301 } 302 static DEVICE_ATTR_RO(stable_pages_required); 303 304 static ssize_t strict_limit_store(struct device *dev, 305 struct device_attribute *attr, const char *buf, size_t count) 306 { 307 struct backing_dev_info *bdi = dev_get_drvdata(dev); 308 unsigned int strict_limit; 309 ssize_t ret; 310 311 ret = kstrtouint(buf, 10, &strict_limit); 312 if (ret < 0) 313 return ret; 314 315 ret = bdi_set_strict_limit(bdi, strict_limit); 316 if (!ret) 317 ret = count; 318 319 return ret; 320 } 321 322 static ssize_t strict_limit_show(struct device *dev, 323 struct device_attribute *attr, char *buf) 324 { 325 struct backing_dev_info *bdi = dev_get_drvdata(dev); 326 327 return sysfs_emit(buf, "%d\n", 328 !!(bdi->capabilities & BDI_CAP_STRICTLIMIT)); 329 } 330 static DEVICE_ATTR_RW(strict_limit); 331 332 static struct attribute *bdi_dev_attrs[] = { 333 &dev_attr_read_ahead_kb.attr, 334 &dev_attr_min_ratio.attr, 335 &dev_attr_min_ratio_fine.attr, 336 &dev_attr_max_ratio.attr, 337 &dev_attr_max_ratio_fine.attr, 338 &dev_attr_min_bytes.attr, 339 &dev_attr_max_bytes.attr, 340 &dev_attr_stable_pages_required.attr, 341 &dev_attr_strict_limit.attr, 342 NULL, 343 }; 344 ATTRIBUTE_GROUPS(bdi_dev); 345 346 static const struct class bdi_class = { 347 .name = "bdi", 348 .dev_groups = bdi_dev_groups, 349 }; 350 351 static __init int bdi_class_init(void) 352 { 353 int ret; 354 355 ret = class_register(&bdi_class); 356 if (ret) 357 return ret; 358 359 bdi_debug_init(); 360 361 return 0; 362 } 363 postcore_initcall(bdi_class_init); 364 365 static int __init default_bdi_init(void) 366 { 367 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND | 368 WQ_SYSFS, 0); 369 if (!bdi_wq) 370 return -ENOMEM; 371 return 0; 372 } 373 subsys_initcall(default_bdi_init); 374 375 static void wb_update_bandwidth_workfn(struct work_struct *work) 376 { 377 struct bdi_writeback *wb = container_of(to_delayed_work(work), 378 struct bdi_writeback, bw_dwork); 379 380 wb_update_bandwidth(wb); 381 } 382 383 /* 384 * Initial write bandwidth: 100 MB/s 385 */ 386 #define INIT_BW (100 << (20 - PAGE_SHIFT)) 387 388 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi, 389 gfp_t gfp) 390 { 391 int i, err; 392 393 memset(wb, 0, sizeof(*wb)); 394 395 wb->bdi = bdi; 396 wb->last_old_flush = jiffies; 397 INIT_LIST_HEAD(&wb->b_dirty); 398 INIT_LIST_HEAD(&wb->b_io); 399 INIT_LIST_HEAD(&wb->b_more_io); 400 INIT_LIST_HEAD(&wb->b_dirty_time); 401 spin_lock_init(&wb->list_lock); 402 403 atomic_set(&wb->writeback_inodes, 0); 404 wb->bw_time_stamp = jiffies; 405 wb->balanced_dirty_ratelimit = INIT_BW; 406 wb->dirty_ratelimit = INIT_BW; 407 wb->write_bandwidth = INIT_BW; 408 wb->avg_write_bandwidth = INIT_BW; 409 410 spin_lock_init(&wb->work_lock); 411 INIT_LIST_HEAD(&wb->work_list); 412 INIT_DELAYED_WORK(&wb->dwork, wb_workfn); 413 INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn); 414 415 err = fprop_local_init_percpu(&wb->completions, gfp); 416 if (err) 417 return err; 418 419 for (i = 0; i < NR_WB_STAT_ITEMS; i++) { 420 err = percpu_counter_init(&wb->stat[i], 0, gfp); 421 if (err) 422 goto out_destroy_stat; 423 } 424 425 return 0; 426 427 out_destroy_stat: 428 while (i--) 429 percpu_counter_destroy(&wb->stat[i]); 430 fprop_local_destroy_percpu(&wb->completions); 431 return err; 432 } 433 434 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb); 435 436 /* 437 * Remove bdi from the global list and shutdown any threads we have running 438 */ 439 static void wb_shutdown(struct bdi_writeback *wb) 440 { 441 /* Make sure nobody queues further work */ 442 spin_lock_irq(&wb->work_lock); 443 if (!test_and_clear_bit(WB_registered, &wb->state)) { 444 spin_unlock_irq(&wb->work_lock); 445 return; 446 } 447 spin_unlock_irq(&wb->work_lock); 448 449 cgwb_remove_from_bdi_list(wb); 450 /* 451 * Drain work list and shutdown the delayed_work. !WB_registered 452 * tells wb_workfn() that @wb is dying and its work_list needs to 453 * be drained no matter what. 454 */ 455 mod_delayed_work(bdi_wq, &wb->dwork, 0); 456 flush_delayed_work(&wb->dwork); 457 WARN_ON(!list_empty(&wb->work_list)); 458 flush_delayed_work(&wb->bw_dwork); 459 } 460 461 static void wb_exit(struct bdi_writeback *wb) 462 { 463 int i; 464 465 WARN_ON(delayed_work_pending(&wb->dwork)); 466 467 for (i = 0; i < NR_WB_STAT_ITEMS; i++) 468 percpu_counter_destroy(&wb->stat[i]); 469 470 fprop_local_destroy_percpu(&wb->completions); 471 } 472 473 #ifdef CONFIG_CGROUP_WRITEBACK 474 475 #include <linux/memcontrol.h> 476 477 /* 478 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and 479 * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected. 480 */ 481 static DEFINE_SPINLOCK(cgwb_lock); 482 static struct workqueue_struct *cgwb_release_wq; 483 484 static LIST_HEAD(offline_cgwbs); 485 static void cleanup_offline_cgwbs_workfn(struct work_struct *work); 486 static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn); 487 488 static void cgwb_free_rcu(struct rcu_head *rcu_head) 489 { 490 struct bdi_writeback *wb = container_of(rcu_head, 491 struct bdi_writeback, rcu); 492 493 percpu_ref_exit(&wb->refcnt); 494 kfree(wb); 495 } 496 497 static void cgwb_release_workfn(struct work_struct *work) 498 { 499 struct bdi_writeback *wb = container_of(work, struct bdi_writeback, 500 release_work); 501 struct backing_dev_info *bdi = wb->bdi; 502 503 mutex_lock(&wb->bdi->cgwb_release_mutex); 504 wb_shutdown(wb); 505 506 css_put(wb->memcg_css); 507 css_put(wb->blkcg_css); 508 mutex_unlock(&wb->bdi->cgwb_release_mutex); 509 510 /* triggers blkg destruction if no online users left */ 511 blkcg_unpin_online(wb->blkcg_css); 512 513 fprop_local_destroy_percpu(&wb->memcg_completions); 514 515 spin_lock_irq(&cgwb_lock); 516 list_del(&wb->offline_node); 517 spin_unlock_irq(&cgwb_lock); 518 519 wb_exit(wb); 520 bdi_put(bdi); 521 WARN_ON_ONCE(!list_empty(&wb->b_attached)); 522 call_rcu(&wb->rcu, cgwb_free_rcu); 523 } 524 525 static void cgwb_release(struct percpu_ref *refcnt) 526 { 527 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback, 528 refcnt); 529 queue_work(cgwb_release_wq, &wb->release_work); 530 } 531 532 static void cgwb_kill(struct bdi_writeback *wb) 533 { 534 lockdep_assert_held(&cgwb_lock); 535 536 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id)); 537 list_del(&wb->memcg_node); 538 list_del(&wb->blkcg_node); 539 list_add(&wb->offline_node, &offline_cgwbs); 540 percpu_ref_kill(&wb->refcnt); 541 } 542 543 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb) 544 { 545 spin_lock_irq(&cgwb_lock); 546 list_del_rcu(&wb->bdi_node); 547 spin_unlock_irq(&cgwb_lock); 548 } 549 550 static int cgwb_create(struct backing_dev_info *bdi, 551 struct cgroup_subsys_state *memcg_css, gfp_t gfp) 552 { 553 struct mem_cgroup *memcg; 554 struct cgroup_subsys_state *blkcg_css; 555 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list; 556 struct bdi_writeback *wb; 557 unsigned long flags; 558 int ret = 0; 559 560 memcg = mem_cgroup_from_css(memcg_css); 561 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys); 562 memcg_cgwb_list = &memcg->cgwb_list; 563 blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css); 564 565 /* look up again under lock and discard on blkcg mismatch */ 566 spin_lock_irqsave(&cgwb_lock, flags); 567 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); 568 if (wb && wb->blkcg_css != blkcg_css) { 569 cgwb_kill(wb); 570 wb = NULL; 571 } 572 spin_unlock_irqrestore(&cgwb_lock, flags); 573 if (wb) 574 goto out_put; 575 576 /* need to create a new one */ 577 wb = kmalloc(sizeof(*wb), gfp); 578 if (!wb) { 579 ret = -ENOMEM; 580 goto out_put; 581 } 582 583 ret = wb_init(wb, bdi, gfp); 584 if (ret) 585 goto err_free; 586 587 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp); 588 if (ret) 589 goto err_wb_exit; 590 591 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp); 592 if (ret) 593 goto err_ref_exit; 594 595 wb->memcg_css = memcg_css; 596 wb->blkcg_css = blkcg_css; 597 INIT_LIST_HEAD(&wb->b_attached); 598 INIT_WORK(&wb->release_work, cgwb_release_workfn); 599 set_bit(WB_registered, &wb->state); 600 bdi_get(bdi); 601 602 /* 603 * The root wb determines the registered state of the whole bdi and 604 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate 605 * whether they're still online. Don't link @wb if any is dead. 606 * See wb_memcg_offline() and wb_blkcg_offline(). 607 */ 608 ret = -ENODEV; 609 spin_lock_irqsave(&cgwb_lock, flags); 610 if (test_bit(WB_registered, &bdi->wb.state) && 611 blkcg_cgwb_list->next && memcg_cgwb_list->next) { 612 /* we might have raced another instance of this function */ 613 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb); 614 if (!ret) { 615 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list); 616 list_add(&wb->memcg_node, memcg_cgwb_list); 617 list_add(&wb->blkcg_node, blkcg_cgwb_list); 618 blkcg_pin_online(blkcg_css); 619 css_get(memcg_css); 620 css_get(blkcg_css); 621 } 622 } 623 spin_unlock_irqrestore(&cgwb_lock, flags); 624 if (ret) { 625 if (ret == -EEXIST) 626 ret = 0; 627 goto err_fprop_exit; 628 } 629 goto out_put; 630 631 err_fprop_exit: 632 bdi_put(bdi); 633 fprop_local_destroy_percpu(&wb->memcg_completions); 634 err_ref_exit: 635 percpu_ref_exit(&wb->refcnt); 636 err_wb_exit: 637 wb_exit(wb); 638 err_free: 639 kfree(wb); 640 out_put: 641 css_put(blkcg_css); 642 return ret; 643 } 644 645 /** 646 * wb_get_lookup - get wb for a given memcg 647 * @bdi: target bdi 648 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) 649 * 650 * Try to get the wb for @memcg_css on @bdi. The returned wb has its 651 * refcount incremented. 652 * 653 * This function uses css_get() on @memcg_css and thus expects its refcnt 654 * to be positive on invocation. IOW, rcu_read_lock() protection on 655 * @memcg_css isn't enough. try_get it before calling this function. 656 * 657 * A wb is keyed by its associated memcg. As blkcg implicitly enables 658 * memcg on the default hierarchy, memcg association is guaranteed to be 659 * more specific (equal or descendant to the associated blkcg) and thus can 660 * identify both the memcg and blkcg associations. 661 * 662 * Because the blkcg associated with a memcg may change as blkcg is enabled 663 * and disabled closer to root in the hierarchy, each wb keeps track of 664 * both the memcg and blkcg associated with it and verifies the blkcg on 665 * each lookup. On mismatch, the existing wb is discarded and a new one is 666 * created. 667 */ 668 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi, 669 struct cgroup_subsys_state *memcg_css) 670 { 671 struct bdi_writeback *wb; 672 673 if (!memcg_css->parent) 674 return &bdi->wb; 675 676 rcu_read_lock(); 677 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); 678 if (wb) { 679 struct cgroup_subsys_state *blkcg_css; 680 681 /* see whether the blkcg association has changed */ 682 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys); 683 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb))) 684 wb = NULL; 685 css_put(blkcg_css); 686 } 687 rcu_read_unlock(); 688 689 return wb; 690 } 691 692 /** 693 * wb_get_create - get wb for a given memcg, create if necessary 694 * @bdi: target bdi 695 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) 696 * @gfp: allocation mask to use 697 * 698 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to 699 * create one. See wb_get_lookup() for more details. 700 */ 701 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, 702 struct cgroup_subsys_state *memcg_css, 703 gfp_t gfp) 704 { 705 struct bdi_writeback *wb; 706 707 might_alloc(gfp); 708 709 do { 710 wb = wb_get_lookup(bdi, memcg_css); 711 } while (!wb && !cgwb_create(bdi, memcg_css, gfp)); 712 713 return wb; 714 } 715 716 static int cgwb_bdi_init(struct backing_dev_info *bdi) 717 { 718 int ret; 719 720 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC); 721 mutex_init(&bdi->cgwb_release_mutex); 722 init_rwsem(&bdi->wb_switch_rwsem); 723 724 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL); 725 if (!ret) { 726 bdi->wb.memcg_css = &root_mem_cgroup->css; 727 bdi->wb.blkcg_css = blkcg_root_css; 728 } 729 return ret; 730 } 731 732 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) 733 { 734 struct radix_tree_iter iter; 735 void **slot; 736 struct bdi_writeback *wb; 737 738 WARN_ON(test_bit(WB_registered, &bdi->wb.state)); 739 740 spin_lock_irq(&cgwb_lock); 741 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0) 742 cgwb_kill(*slot); 743 spin_unlock_irq(&cgwb_lock); 744 745 mutex_lock(&bdi->cgwb_release_mutex); 746 spin_lock_irq(&cgwb_lock); 747 while (!list_empty(&bdi->wb_list)) { 748 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback, 749 bdi_node); 750 spin_unlock_irq(&cgwb_lock); 751 wb_shutdown(wb); 752 spin_lock_irq(&cgwb_lock); 753 } 754 spin_unlock_irq(&cgwb_lock); 755 mutex_unlock(&bdi->cgwb_release_mutex); 756 } 757 758 /* 759 * cleanup_offline_cgwbs_workfn - try to release dying cgwbs 760 * 761 * Try to release dying cgwbs by switching attached inodes to the nearest 762 * living ancestor's writeback. Processed wbs are placed at the end 763 * of the list to guarantee the forward progress. 764 */ 765 static void cleanup_offline_cgwbs_workfn(struct work_struct *work) 766 { 767 struct bdi_writeback *wb; 768 LIST_HEAD(processed); 769 770 spin_lock_irq(&cgwb_lock); 771 772 while (!list_empty(&offline_cgwbs)) { 773 wb = list_first_entry(&offline_cgwbs, struct bdi_writeback, 774 offline_node); 775 list_move(&wb->offline_node, &processed); 776 777 /* 778 * If wb is dirty, cleaning up the writeback by switching 779 * attached inodes will result in an effective removal of any 780 * bandwidth restrictions, which isn't the goal. Instead, 781 * it can be postponed until the next time, when all io 782 * will be likely completed. If in the meantime some inodes 783 * will get re-dirtied, they should be eventually switched to 784 * a new cgwb. 785 */ 786 if (wb_has_dirty_io(wb)) 787 continue; 788 789 if (!wb_tryget(wb)) 790 continue; 791 792 spin_unlock_irq(&cgwb_lock); 793 while (cleanup_offline_cgwb(wb)) 794 cond_resched(); 795 spin_lock_irq(&cgwb_lock); 796 797 wb_put(wb); 798 } 799 800 if (!list_empty(&processed)) 801 list_splice_tail(&processed, &offline_cgwbs); 802 803 spin_unlock_irq(&cgwb_lock); 804 } 805 806 /** 807 * wb_memcg_offline - kill all wb's associated with a memcg being offlined 808 * @memcg: memcg being offlined 809 * 810 * Also prevents creation of any new wb's associated with @memcg. 811 */ 812 void wb_memcg_offline(struct mem_cgroup *memcg) 813 { 814 struct list_head *memcg_cgwb_list = &memcg->cgwb_list; 815 struct bdi_writeback *wb, *next; 816 817 spin_lock_irq(&cgwb_lock); 818 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node) 819 cgwb_kill(wb); 820 memcg_cgwb_list->next = NULL; /* prevent new wb's */ 821 spin_unlock_irq(&cgwb_lock); 822 823 queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work); 824 } 825 826 /** 827 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined 828 * @css: blkcg being offlined 829 * 830 * Also prevents creation of any new wb's associated with @blkcg. 831 */ 832 void wb_blkcg_offline(struct cgroup_subsys_state *css) 833 { 834 struct bdi_writeback *wb, *next; 835 struct list_head *list = blkcg_get_cgwb_list(css); 836 837 spin_lock_irq(&cgwb_lock); 838 list_for_each_entry_safe(wb, next, list, blkcg_node) 839 cgwb_kill(wb); 840 list->next = NULL; /* prevent new wb's */ 841 spin_unlock_irq(&cgwb_lock); 842 } 843 844 static void cgwb_bdi_register(struct backing_dev_info *bdi) 845 { 846 spin_lock_irq(&cgwb_lock); 847 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list); 848 spin_unlock_irq(&cgwb_lock); 849 } 850 851 static int __init cgwb_init(void) 852 { 853 /* 854 * There can be many concurrent release work items overwhelming 855 * system_wq. Put them in a separate wq and limit concurrency. 856 * There's no point in executing many of these in parallel. 857 */ 858 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1); 859 if (!cgwb_release_wq) 860 return -ENOMEM; 861 862 return 0; 863 } 864 subsys_initcall(cgwb_init); 865 866 #else /* CONFIG_CGROUP_WRITEBACK */ 867 868 static int cgwb_bdi_init(struct backing_dev_info *bdi) 869 { 870 return wb_init(&bdi->wb, bdi, GFP_KERNEL); 871 } 872 873 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { } 874 875 static void cgwb_bdi_register(struct backing_dev_info *bdi) 876 { 877 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list); 878 } 879 880 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb) 881 { 882 list_del_rcu(&wb->bdi_node); 883 } 884 885 #endif /* CONFIG_CGROUP_WRITEBACK */ 886 887 int bdi_init(struct backing_dev_info *bdi) 888 { 889 bdi->dev = NULL; 890 891 kref_init(&bdi->refcnt); 892 bdi->min_ratio = 0; 893 bdi->max_ratio = 100 * BDI_RATIO_SCALE; 894 bdi->max_prop_frac = FPROP_FRAC_BASE; 895 INIT_LIST_HEAD(&bdi->bdi_list); 896 INIT_LIST_HEAD(&bdi->wb_list); 897 init_waitqueue_head(&bdi->wb_waitq); 898 bdi->last_bdp_sleep = jiffies; 899 900 return cgwb_bdi_init(bdi); 901 } 902 903 struct backing_dev_info *bdi_alloc(int node_id) 904 { 905 struct backing_dev_info *bdi; 906 907 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id); 908 if (!bdi) 909 return NULL; 910 911 if (bdi_init(bdi)) { 912 kfree(bdi); 913 return NULL; 914 } 915 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT; 916 bdi->ra_pages = VM_READAHEAD_PAGES; 917 bdi->io_pages = VM_READAHEAD_PAGES; 918 timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0); 919 return bdi; 920 } 921 EXPORT_SYMBOL(bdi_alloc); 922 923 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp) 924 { 925 struct rb_node **p = &bdi_tree.rb_node; 926 struct rb_node *parent = NULL; 927 struct backing_dev_info *bdi; 928 929 lockdep_assert_held(&bdi_lock); 930 931 while (*p) { 932 parent = *p; 933 bdi = rb_entry(parent, struct backing_dev_info, rb_node); 934 935 if (bdi->id > id) 936 p = &(*p)->rb_left; 937 else if (bdi->id < id) 938 p = &(*p)->rb_right; 939 else 940 break; 941 } 942 943 if (parentp) 944 *parentp = parent; 945 return p; 946 } 947 948 /** 949 * bdi_get_by_id - lookup and get bdi from its id 950 * @id: bdi id to lookup 951 * 952 * Find bdi matching @id and get it. Returns NULL if the matching bdi 953 * doesn't exist or is already unregistered. 954 */ 955 struct backing_dev_info *bdi_get_by_id(u64 id) 956 { 957 struct backing_dev_info *bdi = NULL; 958 struct rb_node **p; 959 960 spin_lock_bh(&bdi_lock); 961 p = bdi_lookup_rb_node(id, NULL); 962 if (*p) { 963 bdi = rb_entry(*p, struct backing_dev_info, rb_node); 964 bdi_get(bdi); 965 } 966 spin_unlock_bh(&bdi_lock); 967 968 return bdi; 969 } 970 971 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) 972 { 973 struct device *dev; 974 struct rb_node *parent, **p; 975 976 if (bdi->dev) /* The driver needs to use separate queues per device */ 977 return 0; 978 979 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args); 980 dev = device_create(&bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name); 981 if (IS_ERR(dev)) 982 return PTR_ERR(dev); 983 984 cgwb_bdi_register(bdi); 985 bdi->dev = dev; 986 987 bdi_debug_register(bdi, dev_name(dev)); 988 set_bit(WB_registered, &bdi->wb.state); 989 990 spin_lock_bh(&bdi_lock); 991 992 bdi->id = ++bdi_id_cursor; 993 994 p = bdi_lookup_rb_node(bdi->id, &parent); 995 rb_link_node(&bdi->rb_node, parent, p); 996 rb_insert_color(&bdi->rb_node, &bdi_tree); 997 998 list_add_tail_rcu(&bdi->bdi_list, &bdi_list); 999 1000 spin_unlock_bh(&bdi_lock); 1001 1002 trace_writeback_bdi_register(bdi); 1003 return 0; 1004 } 1005 1006 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...) 1007 { 1008 va_list args; 1009 int ret; 1010 1011 va_start(args, fmt); 1012 ret = bdi_register_va(bdi, fmt, args); 1013 va_end(args); 1014 return ret; 1015 } 1016 EXPORT_SYMBOL(bdi_register); 1017 1018 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner) 1019 { 1020 WARN_ON_ONCE(bdi->owner); 1021 bdi->owner = owner; 1022 get_device(owner); 1023 } 1024 1025 /* 1026 * Remove bdi from bdi_list, and ensure that it is no longer visible 1027 */ 1028 static void bdi_remove_from_list(struct backing_dev_info *bdi) 1029 { 1030 spin_lock_bh(&bdi_lock); 1031 rb_erase(&bdi->rb_node, &bdi_tree); 1032 list_del_rcu(&bdi->bdi_list); 1033 spin_unlock_bh(&bdi_lock); 1034 1035 synchronize_rcu_expedited(); 1036 } 1037 1038 void bdi_unregister(struct backing_dev_info *bdi) 1039 { 1040 del_timer_sync(&bdi->laptop_mode_wb_timer); 1041 1042 /* make sure nobody finds us on the bdi_list anymore */ 1043 bdi_remove_from_list(bdi); 1044 wb_shutdown(&bdi->wb); 1045 cgwb_bdi_unregister(bdi); 1046 1047 /* 1048 * If this BDI's min ratio has been set, use bdi_set_min_ratio() to 1049 * update the global bdi_min_ratio. 1050 */ 1051 if (bdi->min_ratio) 1052 bdi_set_min_ratio(bdi, 0); 1053 1054 if (bdi->dev) { 1055 bdi_debug_unregister(bdi); 1056 device_unregister(bdi->dev); 1057 bdi->dev = NULL; 1058 } 1059 1060 if (bdi->owner) { 1061 put_device(bdi->owner); 1062 bdi->owner = NULL; 1063 } 1064 } 1065 EXPORT_SYMBOL(bdi_unregister); 1066 1067 static void release_bdi(struct kref *ref) 1068 { 1069 struct backing_dev_info *bdi = 1070 container_of(ref, struct backing_dev_info, refcnt); 1071 1072 WARN_ON_ONCE(test_bit(WB_registered, &bdi->wb.state)); 1073 WARN_ON_ONCE(bdi->dev); 1074 wb_exit(&bdi->wb); 1075 kfree(bdi); 1076 } 1077 1078 void bdi_put(struct backing_dev_info *bdi) 1079 { 1080 kref_put(&bdi->refcnt, release_bdi); 1081 } 1082 EXPORT_SYMBOL(bdi_put); 1083 1084 struct backing_dev_info *inode_to_bdi(struct inode *inode) 1085 { 1086 struct super_block *sb; 1087 1088 if (!inode) 1089 return &noop_backing_dev_info; 1090 1091 sb = inode->i_sb; 1092 #ifdef CONFIG_BLOCK 1093 if (sb_is_blkdev_sb(sb)) 1094 return I_BDEV(inode)->bd_disk->bdi; 1095 #endif 1096 return sb->s_bdi; 1097 } 1098 EXPORT_SYMBOL(inode_to_bdi); 1099 1100 const char *bdi_dev_name(struct backing_dev_info *bdi) 1101 { 1102 if (!bdi || !bdi->dev) 1103 return bdi_unknown_name; 1104 return bdi->dev_name; 1105 } 1106 EXPORT_SYMBOL_GPL(bdi_dev_name); 1107