backing-dev.c revision 00821b002df7da867bb2c15b4f83f3706371383f
1 2#include <linux/wait.h> 3#include <linux/backing-dev.h> 4#include <linux/kthread.h> 5#include <linux/freezer.h> 6#include <linux/fs.h> 7#include <linux/pagemap.h> 8#include <linux/mm.h> 9#include <linux/sched.h> 10#include <linux/module.h> 11#include <linux/writeback.h> 12#include <linux/device.h> 13#include <trace/events/writeback.h> 14 15static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); 16 17struct backing_dev_info default_backing_dev_info = { 18 .name = "default", 19 .ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE, 20 .state = 0, 21 .capabilities = BDI_CAP_MAP_COPY, 22}; 23EXPORT_SYMBOL_GPL(default_backing_dev_info); 24 25struct backing_dev_info noop_backing_dev_info = { 26 .name = "noop", 27 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK, 28}; 29EXPORT_SYMBOL_GPL(noop_backing_dev_info); 30 31static struct class *bdi_class; 32 33/* 34 * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as 35 * reader side protection for bdi_pending_list. bdi_list has RCU reader side 36 * locking. 37 */ 38DEFINE_SPINLOCK(bdi_lock); 39LIST_HEAD(bdi_list); 40LIST_HEAD(bdi_pending_list); 41 42static struct task_struct *sync_supers_tsk; 43static struct timer_list sync_supers_timer; 44 45static int bdi_sync_supers(void *); 46static void sync_supers_timer_fn(unsigned long); 47 48void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2) 49{ 50 if (wb1 < wb2) { 51 spin_lock(&wb1->list_lock); 52 spin_lock_nested(&wb2->list_lock, 1); 53 } else { 54 spin_lock(&wb2->list_lock); 55 spin_lock_nested(&wb1->list_lock, 1); 56 } 57} 58 59#ifdef CONFIG_DEBUG_FS 60#include <linux/debugfs.h> 61#include <linux/seq_file.h> 62 63static struct dentry *bdi_debug_root; 64 65static void bdi_debug_init(void) 66{ 67 bdi_debug_root = debugfs_create_dir("bdi", NULL); 68} 69 70static int bdi_debug_stats_show(struct seq_file *m, void *v) 71{ 72 struct backing_dev_info *bdi = m->private; 73 struct bdi_writeback *wb = &bdi->wb; 74 unsigned long background_thresh; 75 unsigned long dirty_thresh; 76 unsigned long bdi_thresh; 77 unsigned long nr_dirty, nr_io, nr_more_io; 78 struct inode *inode; 79 80 nr_dirty = nr_io = nr_more_io = 0; 81 spin_lock(&wb->list_lock); 82 list_for_each_entry(inode, &wb->b_dirty, i_wb_list) 83 nr_dirty++; 84 list_for_each_entry(inode, &wb->b_io, i_wb_list) 85 nr_io++; 86 list_for_each_entry(inode, &wb->b_more_io, i_wb_list) 87 nr_more_io++; 88 spin_unlock(&wb->list_lock); 89 90 global_dirty_limits(&background_thresh, &dirty_thresh); 91 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); 92 93#define K(x) ((x) << (PAGE_SHIFT - 10)) 94 seq_printf(m, 95 "BdiWriteback: %10lu kB\n" 96 "BdiReclaimable: %10lu kB\n" 97 "BdiDirtyThresh: %10lu kB\n" 98 "DirtyThresh: %10lu kB\n" 99 "BackgroundThresh: %10lu kB\n" 100 "BdiWritten: %10lu kB\n" 101 "BdiWriteBandwidth: %10lu kBps\n" 102 "b_dirty: %10lu\n" 103 "b_io: %10lu\n" 104 "b_more_io: %10lu\n" 105 "bdi_list: %10u\n" 106 "state: %10lx\n", 107 (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)), 108 (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)), 109 K(bdi_thresh), 110 K(dirty_thresh), 111 K(background_thresh), 112 (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)), 113 (unsigned long) K(bdi->write_bandwidth), 114 nr_dirty, 115 nr_io, 116 nr_more_io, 117 !list_empty(&bdi->bdi_list), bdi->state); 118#undef K 119 120 return 0; 121} 122 123static int bdi_debug_stats_open(struct inode *inode, struct file *file) 124{ 125 return single_open(file, bdi_debug_stats_show, inode->i_private); 126} 127 128static const struct file_operations bdi_debug_stats_fops = { 129 .open = bdi_debug_stats_open, 130 .read = seq_read, 131 .llseek = seq_lseek, 132 .release = single_release, 133}; 134 135static void bdi_debug_register(struct backing_dev_info *bdi, const char *name) 136{ 137 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); 138 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir, 139 bdi, &bdi_debug_stats_fops); 140} 141 142static void bdi_debug_unregister(struct backing_dev_info *bdi) 143{ 144 debugfs_remove(bdi->debug_stats); 145 debugfs_remove(bdi->debug_dir); 146} 147#else 148static inline void bdi_debug_init(void) 149{ 150} 151static inline void bdi_debug_register(struct backing_dev_info *bdi, 152 const char *name) 153{ 154} 155static inline void bdi_debug_unregister(struct backing_dev_info *bdi) 156{ 157} 158#endif 159 160static ssize_t read_ahead_kb_store(struct device *dev, 161 struct device_attribute *attr, 162 const char *buf, size_t count) 163{ 164 struct backing_dev_info *bdi = dev_get_drvdata(dev); 165 char *end; 166 unsigned long read_ahead_kb; 167 ssize_t ret = -EINVAL; 168 169 read_ahead_kb = simple_strtoul(buf, &end, 10); 170 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { 171 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10); 172 ret = count; 173 } 174 return ret; 175} 176 177#define K(pages) ((pages) << (PAGE_SHIFT - 10)) 178 179#define BDI_SHOW(name, expr) \ 180static ssize_t name##_show(struct device *dev, \ 181 struct device_attribute *attr, char *page) \ 182{ \ 183 struct backing_dev_info *bdi = dev_get_drvdata(dev); \ 184 \ 185 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \ 186} 187 188BDI_SHOW(read_ahead_kb, K(bdi->ra_pages)) 189 190static ssize_t min_ratio_store(struct device *dev, 191 struct device_attribute *attr, const char *buf, size_t count) 192{ 193 struct backing_dev_info *bdi = dev_get_drvdata(dev); 194 char *end; 195 unsigned int ratio; 196 ssize_t ret = -EINVAL; 197 198 ratio = simple_strtoul(buf, &end, 10); 199 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { 200 ret = bdi_set_min_ratio(bdi, ratio); 201 if (!ret) 202 ret = count; 203 } 204 return ret; 205} 206BDI_SHOW(min_ratio, bdi->min_ratio) 207 208static ssize_t max_ratio_store(struct device *dev, 209 struct device_attribute *attr, const char *buf, size_t count) 210{ 211 struct backing_dev_info *bdi = dev_get_drvdata(dev); 212 char *end; 213 unsigned int ratio; 214 ssize_t ret = -EINVAL; 215 216 ratio = simple_strtoul(buf, &end, 10); 217 if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) { 218 ret = bdi_set_max_ratio(bdi, ratio); 219 if (!ret) 220 ret = count; 221 } 222 return ret; 223} 224BDI_SHOW(max_ratio, bdi->max_ratio) 225 226#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store) 227 228static struct device_attribute bdi_dev_attrs[] = { 229 __ATTR_RW(read_ahead_kb), 230 __ATTR_RW(min_ratio), 231 __ATTR_RW(max_ratio), 232 __ATTR_NULL, 233}; 234 235static __init int bdi_class_init(void) 236{ 237 bdi_class = class_create(THIS_MODULE, "bdi"); 238 if (IS_ERR(bdi_class)) 239 return PTR_ERR(bdi_class); 240 241 bdi_class->dev_attrs = bdi_dev_attrs; 242 bdi_debug_init(); 243 return 0; 244} 245postcore_initcall(bdi_class_init); 246 247static int __init default_bdi_init(void) 248{ 249 int err; 250 251 sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers"); 252 BUG_ON(IS_ERR(sync_supers_tsk)); 253 254 setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0); 255 bdi_arm_supers_timer(); 256 257 err = bdi_init(&default_backing_dev_info); 258 if (!err) 259 bdi_register(&default_backing_dev_info, NULL, "default"); 260 err = bdi_init(&noop_backing_dev_info); 261 262 return err; 263} 264subsys_initcall(default_bdi_init); 265 266int bdi_has_dirty_io(struct backing_dev_info *bdi) 267{ 268 return wb_has_dirty_io(&bdi->wb); 269} 270 271/* 272 * kupdated() used to do this. We cannot do it from the bdi_forker_thread() 273 * or we risk deadlocking on ->s_umount. The longer term solution would be 274 * to implement sync_supers_bdi() or similar and simply do it from the 275 * bdi writeback thread individually. 276 */ 277static int bdi_sync_supers(void *unused) 278{ 279 set_user_nice(current, 0); 280 281 while (!kthread_should_stop()) { 282 set_current_state(TASK_INTERRUPTIBLE); 283 schedule(); 284 285 /* 286 * Do this periodically, like kupdated() did before. 287 */ 288 sync_supers(); 289 } 290 291 return 0; 292} 293 294void bdi_arm_supers_timer(void) 295{ 296 unsigned long next; 297 298 if (!dirty_writeback_interval) 299 return; 300 301 next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies; 302 mod_timer(&sync_supers_timer, round_jiffies_up(next)); 303} 304 305static void sync_supers_timer_fn(unsigned long unused) 306{ 307 wake_up_process(sync_supers_tsk); 308 bdi_arm_supers_timer(); 309} 310 311static void wakeup_timer_fn(unsigned long data) 312{ 313 struct backing_dev_info *bdi = (struct backing_dev_info *)data; 314 315 spin_lock_bh(&bdi->wb_lock); 316 if (bdi->wb.task) { 317 trace_writeback_wake_thread(bdi); 318 wake_up_process(bdi->wb.task); 319 } else { 320 /* 321 * When bdi tasks are inactive for long time, they are killed. 322 * In this case we have to wake-up the forker thread which 323 * should create and run the bdi thread. 324 */ 325 trace_writeback_wake_forker_thread(bdi); 326 wake_up_process(default_backing_dev_info.wb.task); 327 } 328 spin_unlock_bh(&bdi->wb_lock); 329} 330 331/* 332 * This function is used when the first inode for this bdi is marked dirty. It 333 * wakes-up the corresponding bdi thread which should then take care of the 334 * periodic background write-out of dirty inodes. Since the write-out would 335 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just 336 * set up a timer which wakes the bdi thread up later. 337 * 338 * Note, we wouldn't bother setting up the timer, but this function is on the 339 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches 340 * by delaying the wake-up. 341 */ 342void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi) 343{ 344 unsigned long timeout; 345 346 timeout = msecs_to_jiffies(dirty_writeback_interval * 10); 347 mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout); 348} 349 350/* 351 * Calculate the longest interval (jiffies) bdi threads are allowed to be 352 * inactive. 353 */ 354static unsigned long bdi_longest_inactive(void) 355{ 356 unsigned long interval; 357 358 interval = msecs_to_jiffies(dirty_writeback_interval * 10); 359 return max(5UL * 60 * HZ, interval); 360} 361 362static int bdi_forker_thread(void *ptr) 363{ 364 struct bdi_writeback *me = ptr; 365 366 current->flags |= PF_SWAPWRITE; 367 set_freezable(); 368 369 /* 370 * Our parent may run at a different priority, just set us to normal 371 */ 372 set_user_nice(current, 0); 373 374 for (;;) { 375 struct task_struct *task = NULL; 376 struct backing_dev_info *bdi; 377 enum { 378 NO_ACTION, /* Nothing to do */ 379 FORK_THREAD, /* Fork bdi thread */ 380 KILL_THREAD, /* Kill inactive bdi thread */ 381 } action = NO_ACTION; 382 383 /* 384 * Temporary measure, we want to make sure we don't see 385 * dirty data on the default backing_dev_info 386 */ 387 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) { 388 del_timer(&me->wakeup_timer); 389 wb_do_writeback(me, 0); 390 } 391 392 spin_lock_bh(&bdi_lock); 393 set_current_state(TASK_INTERRUPTIBLE); 394 395 list_for_each_entry(bdi, &bdi_list, bdi_list) { 396 bool have_dirty_io; 397 398 if (!bdi_cap_writeback_dirty(bdi) || 399 bdi_cap_flush_forker(bdi)) 400 continue; 401 402 WARN(!test_bit(BDI_registered, &bdi->state), 403 "bdi %p/%s is not registered!\n", bdi, bdi->name); 404 405 have_dirty_io = !list_empty(&bdi->work_list) || 406 wb_has_dirty_io(&bdi->wb); 407 408 /* 409 * If the bdi has work to do, but the thread does not 410 * exist - create it. 411 */ 412 if (!bdi->wb.task && have_dirty_io) { 413 /* 414 * Set the pending bit - if someone will try to 415 * unregister this bdi - it'll wait on this bit. 416 */ 417 set_bit(BDI_pending, &bdi->state); 418 action = FORK_THREAD; 419 break; 420 } 421 422 spin_lock(&bdi->wb_lock); 423 424 /* 425 * If there is no work to do and the bdi thread was 426 * inactive long enough - kill it. The wb_lock is taken 427 * to make sure no-one adds more work to this bdi and 428 * wakes the bdi thread up. 429 */ 430 if (bdi->wb.task && !have_dirty_io && 431 time_after(jiffies, bdi->wb.last_active + 432 bdi_longest_inactive())) { 433 task = bdi->wb.task; 434 bdi->wb.task = NULL; 435 spin_unlock(&bdi->wb_lock); 436 set_bit(BDI_pending, &bdi->state); 437 action = KILL_THREAD; 438 break; 439 } 440 spin_unlock(&bdi->wb_lock); 441 } 442 spin_unlock_bh(&bdi_lock); 443 444 /* Keep working if default bdi still has things to do */ 445 if (!list_empty(&me->bdi->work_list)) 446 __set_current_state(TASK_RUNNING); 447 448 switch (action) { 449 case FORK_THREAD: 450 __set_current_state(TASK_RUNNING); 451 task = kthread_create(bdi_writeback_thread, &bdi->wb, 452 "flush-%s", dev_name(bdi->dev)); 453 if (IS_ERR(task)) { 454 /* 455 * If thread creation fails, force writeout of 456 * the bdi from the thread. Hopefully 1024 is 457 * large enough for efficient IO. 458 */ 459 writeback_inodes_wb(&bdi->wb, 1024); 460 } else { 461 /* 462 * The spinlock makes sure we do not lose 463 * wake-ups when racing with 'bdi_queue_work()'. 464 * And as soon as the bdi thread is visible, we 465 * can start it. 466 */ 467 spin_lock_bh(&bdi->wb_lock); 468 bdi->wb.task = task; 469 spin_unlock_bh(&bdi->wb_lock); 470 wake_up_process(task); 471 } 472 break; 473 474 case KILL_THREAD: 475 __set_current_state(TASK_RUNNING); 476 kthread_stop(task); 477 break; 478 479 case NO_ACTION: 480 if (!wb_has_dirty_io(me) || !dirty_writeback_interval) 481 /* 482 * There are no dirty data. The only thing we 483 * should now care about is checking for 484 * inactive bdi threads and killing them. Thus, 485 * let's sleep for longer time, save energy and 486 * be friendly for battery-driven devices. 487 */ 488 schedule_timeout(bdi_longest_inactive()); 489 else 490 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); 491 try_to_freeze(); 492 /* Back to the main loop */ 493 continue; 494 } 495 496 /* 497 * Clear pending bit and wakeup anybody waiting to tear us down. 498 */ 499 clear_bit(BDI_pending, &bdi->state); 500 smp_mb__after_clear_bit(); 501 wake_up_bit(&bdi->state, BDI_pending); 502 } 503 504 return 0; 505} 506 507/* 508 * Remove bdi from bdi_list, and ensure that it is no longer visible 509 */ 510static void bdi_remove_from_list(struct backing_dev_info *bdi) 511{ 512 spin_lock_bh(&bdi_lock); 513 list_del_rcu(&bdi->bdi_list); 514 spin_unlock_bh(&bdi_lock); 515 516 synchronize_rcu(); 517} 518 519int bdi_register(struct backing_dev_info *bdi, struct device *parent, 520 const char *fmt, ...) 521{ 522 va_list args; 523 struct device *dev; 524 525 if (bdi->dev) /* The driver needs to use separate queues per device */ 526 return 0; 527 528 va_start(args, fmt); 529 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args); 530 va_end(args); 531 if (IS_ERR(dev)) 532 return PTR_ERR(dev); 533 534 bdi->dev = dev; 535 536 /* 537 * Just start the forker thread for our default backing_dev_info, 538 * and add other bdi's to the list. They will get a thread created 539 * on-demand when they need it. 540 */ 541 if (bdi_cap_flush_forker(bdi)) { 542 struct bdi_writeback *wb = &bdi->wb; 543 544 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s", 545 dev_name(dev)); 546 if (IS_ERR(wb->task)) 547 return PTR_ERR(wb->task); 548 } 549 550 bdi_debug_register(bdi, dev_name(dev)); 551 set_bit(BDI_registered, &bdi->state); 552 553 spin_lock_bh(&bdi_lock); 554 list_add_tail_rcu(&bdi->bdi_list, &bdi_list); 555 spin_unlock_bh(&bdi_lock); 556 557 trace_writeback_bdi_register(bdi); 558 return 0; 559} 560EXPORT_SYMBOL(bdi_register); 561 562int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev) 563{ 564 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev)); 565} 566EXPORT_SYMBOL(bdi_register_dev); 567 568/* 569 * Remove bdi from the global list and shutdown any threads we have running 570 */ 571static void bdi_wb_shutdown(struct backing_dev_info *bdi) 572{ 573 if (!bdi_cap_writeback_dirty(bdi)) 574 return; 575 576 /* 577 * Make sure nobody finds us on the bdi_list anymore 578 */ 579 bdi_remove_from_list(bdi); 580 581 /* 582 * If setup is pending, wait for that to complete first 583 */ 584 wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait, 585 TASK_UNINTERRUPTIBLE); 586 587 /* 588 * Finally, kill the kernel thread. We don't need to be RCU 589 * safe anymore, since the bdi is gone from visibility. Force 590 * unfreeze of the thread before calling kthread_stop(), otherwise 591 * it would never exet if it is currently stuck in the refrigerator. 592 */ 593 if (bdi->wb.task) { 594 thaw_process(bdi->wb.task); 595 kthread_stop(bdi->wb.task); 596 } 597} 598 599/* 600 * This bdi is going away now, make sure that no super_blocks point to it 601 */ 602static void bdi_prune_sb(struct backing_dev_info *bdi) 603{ 604 struct super_block *sb; 605 606 spin_lock(&sb_lock); 607 list_for_each_entry(sb, &super_blocks, s_list) { 608 if (sb->s_bdi == bdi) 609 sb->s_bdi = &default_backing_dev_info; 610 } 611 spin_unlock(&sb_lock); 612} 613 614void bdi_unregister(struct backing_dev_info *bdi) 615{ 616 if (bdi->dev) { 617 trace_writeback_bdi_unregister(bdi); 618 bdi_prune_sb(bdi); 619 del_timer_sync(&bdi->wb.wakeup_timer); 620 621 if (!bdi_cap_flush_forker(bdi)) 622 bdi_wb_shutdown(bdi); 623 bdi_debug_unregister(bdi); 624 device_unregister(bdi->dev); 625 bdi->dev = NULL; 626 } 627} 628EXPORT_SYMBOL(bdi_unregister); 629 630static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi) 631{ 632 memset(wb, 0, sizeof(*wb)); 633 634 wb->bdi = bdi; 635 wb->last_old_flush = jiffies; 636 INIT_LIST_HEAD(&wb->b_dirty); 637 INIT_LIST_HEAD(&wb->b_io); 638 INIT_LIST_HEAD(&wb->b_more_io); 639 spin_lock_init(&wb->list_lock); 640 setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi); 641} 642 643/* 644 * Initial write bandwidth: 100 MB/s 645 */ 646#define INIT_BW (100 << (20 - PAGE_SHIFT)) 647 648int bdi_init(struct backing_dev_info *bdi) 649{ 650 int i, err; 651 652 bdi->dev = NULL; 653 654 bdi->min_ratio = 0; 655 bdi->max_ratio = 100; 656 bdi->max_prop_frac = PROP_FRAC_BASE; 657 spin_lock_init(&bdi->wb_lock); 658 INIT_LIST_HEAD(&bdi->bdi_list); 659 INIT_LIST_HEAD(&bdi->work_list); 660 661 bdi_wb_init(&bdi->wb, bdi); 662 663 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) { 664 err = percpu_counter_init(&bdi->bdi_stat[i], 0); 665 if (err) 666 goto err; 667 } 668 669 bdi->dirty_exceeded = 0; 670 671 bdi->bw_time_stamp = jiffies; 672 bdi->written_stamp = 0; 673 674 bdi->write_bandwidth = INIT_BW; 675 bdi->avg_write_bandwidth = INIT_BW; 676 677 err = prop_local_init_percpu(&bdi->completions); 678 679 if (err) { 680err: 681 while (i--) 682 percpu_counter_destroy(&bdi->bdi_stat[i]); 683 } 684 685 return err; 686} 687EXPORT_SYMBOL(bdi_init); 688 689void bdi_destroy(struct backing_dev_info *bdi) 690{ 691 int i; 692 693 /* 694 * Splice our entries to the default_backing_dev_info, if this 695 * bdi disappears 696 */ 697 if (bdi_has_dirty_io(bdi)) { 698 struct bdi_writeback *dst = &default_backing_dev_info.wb; 699 700 bdi_lock_two(&bdi->wb, dst); 701 list_splice(&bdi->wb.b_dirty, &dst->b_dirty); 702 list_splice(&bdi->wb.b_io, &dst->b_io); 703 list_splice(&bdi->wb.b_more_io, &dst->b_more_io); 704 spin_unlock(&bdi->wb.list_lock); 705 spin_unlock(&dst->list_lock); 706 } 707 708 bdi_unregister(bdi); 709 710 for (i = 0; i < NR_BDI_STAT_ITEMS; i++) 711 percpu_counter_destroy(&bdi->bdi_stat[i]); 712 713 prop_local_destroy_percpu(&bdi->completions); 714} 715EXPORT_SYMBOL(bdi_destroy); 716 717/* 718 * For use from filesystems to quickly init and register a bdi associated 719 * with dirty writeback 720 */ 721int bdi_setup_and_register(struct backing_dev_info *bdi, char *name, 722 unsigned int cap) 723{ 724 char tmp[32]; 725 int err; 726 727 bdi->name = name; 728 bdi->capabilities = cap; 729 err = bdi_init(bdi); 730 if (err) 731 return err; 732 733 sprintf(tmp, "%.28s%s", name, "-%d"); 734 err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq)); 735 if (err) { 736 bdi_destroy(bdi); 737 return err; 738 } 739 740 return 0; 741} 742EXPORT_SYMBOL(bdi_setup_and_register); 743 744static wait_queue_head_t congestion_wqh[2] = { 745 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]), 746 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1]) 747 }; 748static atomic_t nr_bdi_congested[2]; 749 750void clear_bdi_congested(struct backing_dev_info *bdi, int sync) 751{ 752 enum bdi_state bit; 753 wait_queue_head_t *wqh = &congestion_wqh[sync]; 754 755 bit = sync ? BDI_sync_congested : BDI_async_congested; 756 if (test_and_clear_bit(bit, &bdi->state)) 757 atomic_dec(&nr_bdi_congested[sync]); 758 smp_mb__after_clear_bit(); 759 if (waitqueue_active(wqh)) 760 wake_up(wqh); 761} 762EXPORT_SYMBOL(clear_bdi_congested); 763 764void set_bdi_congested(struct backing_dev_info *bdi, int sync) 765{ 766 enum bdi_state bit; 767 768 bit = sync ? BDI_sync_congested : BDI_async_congested; 769 if (!test_and_set_bit(bit, &bdi->state)) 770 atomic_inc(&nr_bdi_congested[sync]); 771} 772EXPORT_SYMBOL(set_bdi_congested); 773 774/** 775 * congestion_wait - wait for a backing_dev to become uncongested 776 * @sync: SYNC or ASYNC IO 777 * @timeout: timeout in jiffies 778 * 779 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit 780 * write congestion. If no backing_devs are congested then just wait for the 781 * next write to be completed. 782 */ 783long congestion_wait(int sync, long timeout) 784{ 785 long ret; 786 unsigned long start = jiffies; 787 DEFINE_WAIT(wait); 788 wait_queue_head_t *wqh = &congestion_wqh[sync]; 789 790 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); 791 ret = io_schedule_timeout(timeout); 792 finish_wait(wqh, &wait); 793 794 trace_writeback_congestion_wait(jiffies_to_usecs(timeout), 795 jiffies_to_usecs(jiffies - start)); 796 797 return ret; 798} 799EXPORT_SYMBOL(congestion_wait); 800 801/** 802 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes 803 * @zone: A zone to check if it is heavily congested 804 * @sync: SYNC or ASYNC IO 805 * @timeout: timeout in jiffies 806 * 807 * In the event of a congested backing_dev (any backing_dev) and the given 808 * @zone has experienced recent congestion, this waits for up to @timeout 809 * jiffies for either a BDI to exit congestion of the given @sync queue 810 * or a write to complete. 811 * 812 * In the absence of zone congestion, cond_resched() is called to yield 813 * the processor if necessary but otherwise does not sleep. 814 * 815 * The return value is 0 if the sleep is for the full timeout. Otherwise, 816 * it is the number of jiffies that were still remaining when the function 817 * returned. return_value == timeout implies the function did not sleep. 818 */ 819long wait_iff_congested(struct zone *zone, int sync, long timeout) 820{ 821 long ret; 822 unsigned long start = jiffies; 823 DEFINE_WAIT(wait); 824 wait_queue_head_t *wqh = &congestion_wqh[sync]; 825 826 /* 827 * If there is no congestion, or heavy congestion is not being 828 * encountered in the current zone, yield if necessary instead 829 * of sleeping on the congestion queue 830 */ 831 if (atomic_read(&nr_bdi_congested[sync]) == 0 || 832 !zone_is_reclaim_congested(zone)) { 833 cond_resched(); 834 835 /* In case we scheduled, work out time remaining */ 836 ret = timeout - (jiffies - start); 837 if (ret < 0) 838 ret = 0; 839 840 goto out; 841 } 842 843 /* Sleep until uncongested or a write happens */ 844 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); 845 ret = io_schedule_timeout(timeout); 846 finish_wait(wqh, &wait); 847 848out: 849 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout), 850 jiffies_to_usecs(jiffies - start)); 851 852 return ret; 853} 854EXPORT_SYMBOL(wait_iff_congested); 855