page-writeback.c revision 7762741e3af69720186802e945229b6a5afd5c49
1/* 2 * mm/page-writeback.c 3 * 4 * Copyright (C) 2002, Linus Torvalds. 5 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> 6 * 7 * Contains functions related to writing back dirty pages at the 8 * address_space level. 9 * 10 * 10Apr2002 Andrew Morton 11 * Initial version 12 */ 13 14#include <linux/kernel.h> 15#include <linux/module.h> 16#include <linux/spinlock.h> 17#include <linux/fs.h> 18#include <linux/mm.h> 19#include <linux/swap.h> 20#include <linux/slab.h> 21#include <linux/pagemap.h> 22#include <linux/writeback.h> 23#include <linux/init.h> 24#include <linux/backing-dev.h> 25#include <linux/task_io_accounting_ops.h> 26#include <linux/blkdev.h> 27#include <linux/mpage.h> 28#include <linux/rmap.h> 29#include <linux/percpu.h> 30#include <linux/notifier.h> 31#include <linux/smp.h> 32#include <linux/sysctl.h> 33#include <linux/cpu.h> 34#include <linux/syscalls.h> 35#include <linux/buffer_head.h> 36#include <linux/pagevec.h> 37#include <trace/events/writeback.h> 38 39/* 40 * Estimate write bandwidth at 200ms intervals. 41 */ 42#define BANDWIDTH_INTERVAL max(HZ/5, 1) 43 44/* 45 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited 46 * will look to see if it needs to force writeback or throttling. 47 */ 48static long ratelimit_pages = 32; 49 50/* 51 * When balance_dirty_pages decides that the caller needs to perform some 52 * non-background writeback, this is how many pages it will attempt to write. 53 * It should be somewhat larger than dirtied pages to ensure that reasonably 54 * large amounts of I/O are submitted. 55 */ 56static inline long sync_writeback_pages(unsigned long dirtied) 57{ 58 if (dirtied < ratelimit_pages) 59 dirtied = ratelimit_pages; 60 61 return dirtied + dirtied / 2; 62} 63 64/* The following parameters are exported via /proc/sys/vm */ 65 66/* 67 * Start background writeback (via writeback threads) at this percentage 68 */ 69int dirty_background_ratio = 10; 70 71/* 72 * dirty_background_bytes starts at 0 (disabled) so that it is a function of 73 * dirty_background_ratio * the amount of dirtyable memory 74 */ 75unsigned long dirty_background_bytes; 76 77/* 78 * free highmem will not be subtracted from the total free memory 79 * for calculating free ratios if vm_highmem_is_dirtyable is true 80 */ 81int vm_highmem_is_dirtyable; 82 83/* 84 * The generator of dirty data starts writeback at this percentage 85 */ 86int vm_dirty_ratio = 20; 87 88/* 89 * vm_dirty_bytes starts at 0 (disabled) so that it is a function of 90 * vm_dirty_ratio * the amount of dirtyable memory 91 */ 92unsigned long vm_dirty_bytes; 93 94/* 95 * The interval between `kupdate'-style writebacks 96 */ 97unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ 98 99/* 100 * The longest time for which data is allowed to remain dirty 101 */ 102unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ 103 104/* 105 * Flag that makes the machine dump writes/reads and block dirtyings. 106 */ 107int block_dump; 108 109/* 110 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: 111 * a full sync is triggered after this time elapses without any disk activity. 112 */ 113int laptop_mode; 114 115EXPORT_SYMBOL(laptop_mode); 116 117/* End of sysctl-exported parameters */ 118 119 120/* 121 * Scale the writeback cache size proportional to the relative writeout speeds. 122 * 123 * We do this by keeping a floating proportion between BDIs, based on page 124 * writeback completions [end_page_writeback()]. Those devices that write out 125 * pages fastest will get the larger share, while the slower will get a smaller 126 * share. 127 * 128 * We use page writeout completions because we are interested in getting rid of 129 * dirty pages. Having them written out is the primary goal. 130 * 131 * We introduce a concept of time, a period over which we measure these events, 132 * because demand can/will vary over time. The length of this period itself is 133 * measured in page writeback completions. 134 * 135 */ 136static struct prop_descriptor vm_completions; 137static struct prop_descriptor vm_dirties; 138 139/* 140 * couple the period to the dirty_ratio: 141 * 142 * period/2 ~ roundup_pow_of_two(dirty limit) 143 */ 144static int calc_period_shift(void) 145{ 146 unsigned long dirty_total; 147 148 if (vm_dirty_bytes) 149 dirty_total = vm_dirty_bytes / PAGE_SIZE; 150 else 151 dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 152 100; 153 return 2 + ilog2(dirty_total - 1); 154} 155 156/* 157 * update the period when the dirty threshold changes. 158 */ 159static void update_completion_period(void) 160{ 161 int shift = calc_period_shift(); 162 prop_change_shift(&vm_completions, shift); 163 prop_change_shift(&vm_dirties, shift); 164} 165 166int dirty_background_ratio_handler(struct ctl_table *table, int write, 167 void __user *buffer, size_t *lenp, 168 loff_t *ppos) 169{ 170 int ret; 171 172 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 173 if (ret == 0 && write) 174 dirty_background_bytes = 0; 175 return ret; 176} 177 178int dirty_background_bytes_handler(struct ctl_table *table, int write, 179 void __user *buffer, size_t *lenp, 180 loff_t *ppos) 181{ 182 int ret; 183 184 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); 185 if (ret == 0 && write) 186 dirty_background_ratio = 0; 187 return ret; 188} 189 190int dirty_ratio_handler(struct ctl_table *table, int write, 191 void __user *buffer, size_t *lenp, 192 loff_t *ppos) 193{ 194 int old_ratio = vm_dirty_ratio; 195 int ret; 196 197 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 198 if (ret == 0 && write && vm_dirty_ratio != old_ratio) { 199 update_completion_period(); 200 vm_dirty_bytes = 0; 201 } 202 return ret; 203} 204 205 206int dirty_bytes_handler(struct ctl_table *table, int write, 207 void __user *buffer, size_t *lenp, 208 loff_t *ppos) 209{ 210 unsigned long old_bytes = vm_dirty_bytes; 211 int ret; 212 213 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); 214 if (ret == 0 && write && vm_dirty_bytes != old_bytes) { 215 update_completion_period(); 216 vm_dirty_ratio = 0; 217 } 218 return ret; 219} 220 221/* 222 * Increment the BDI's writeout completion count and the global writeout 223 * completion count. Called from test_clear_page_writeback(). 224 */ 225static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) 226{ 227 __inc_bdi_stat(bdi, BDI_WRITTEN); 228 __prop_inc_percpu_max(&vm_completions, &bdi->completions, 229 bdi->max_prop_frac); 230} 231 232void bdi_writeout_inc(struct backing_dev_info *bdi) 233{ 234 unsigned long flags; 235 236 local_irq_save(flags); 237 __bdi_writeout_inc(bdi); 238 local_irq_restore(flags); 239} 240EXPORT_SYMBOL_GPL(bdi_writeout_inc); 241 242void task_dirty_inc(struct task_struct *tsk) 243{ 244 prop_inc_single(&vm_dirties, &tsk->dirties); 245} 246 247/* 248 * Obtain an accurate fraction of the BDI's portion. 249 */ 250static void bdi_writeout_fraction(struct backing_dev_info *bdi, 251 long *numerator, long *denominator) 252{ 253 prop_fraction_percpu(&vm_completions, &bdi->completions, 254 numerator, denominator); 255} 256 257static inline void task_dirties_fraction(struct task_struct *tsk, 258 long *numerator, long *denominator) 259{ 260 prop_fraction_single(&vm_dirties, &tsk->dirties, 261 numerator, denominator); 262} 263 264/* 265 * task_dirty_limit - scale down dirty throttling threshold for one task 266 * 267 * task specific dirty limit: 268 * 269 * dirty -= (dirty/8) * p_{t} 270 * 271 * To protect light/slow dirtying tasks from heavier/fast ones, we start 272 * throttling individual tasks before reaching the bdi dirty limit. 273 * Relatively low thresholds will be allocated to heavy dirtiers. So when 274 * dirty pages grow large, heavy dirtiers will be throttled first, which will 275 * effectively curb the growth of dirty pages. Light dirtiers with high enough 276 * dirty threshold may never get throttled. 277 */ 278static unsigned long task_dirty_limit(struct task_struct *tsk, 279 unsigned long bdi_dirty) 280{ 281 long numerator, denominator; 282 unsigned long dirty = bdi_dirty; 283 u64 inv = dirty >> 3; 284 285 task_dirties_fraction(tsk, &numerator, &denominator); 286 inv *= numerator; 287 do_div(inv, denominator); 288 289 dirty -= inv; 290 291 return max(dirty, bdi_dirty/2); 292} 293 294/* 295 * 296 */ 297static unsigned int bdi_min_ratio; 298 299int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) 300{ 301 int ret = 0; 302 303 spin_lock_bh(&bdi_lock); 304 if (min_ratio > bdi->max_ratio) { 305 ret = -EINVAL; 306 } else { 307 min_ratio -= bdi->min_ratio; 308 if (bdi_min_ratio + min_ratio < 100) { 309 bdi_min_ratio += min_ratio; 310 bdi->min_ratio += min_ratio; 311 } else { 312 ret = -EINVAL; 313 } 314 } 315 spin_unlock_bh(&bdi_lock); 316 317 return ret; 318} 319 320int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) 321{ 322 int ret = 0; 323 324 if (max_ratio > 100) 325 return -EINVAL; 326 327 spin_lock_bh(&bdi_lock); 328 if (bdi->min_ratio > max_ratio) { 329 ret = -EINVAL; 330 } else { 331 bdi->max_ratio = max_ratio; 332 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; 333 } 334 spin_unlock_bh(&bdi_lock); 335 336 return ret; 337} 338EXPORT_SYMBOL(bdi_set_max_ratio); 339 340/* 341 * Work out the current dirty-memory clamping and background writeout 342 * thresholds. 343 * 344 * The main aim here is to lower them aggressively if there is a lot of mapped 345 * memory around. To avoid stressing page reclaim with lots of unreclaimable 346 * pages. It is better to clamp down on writers than to start swapping, and 347 * performing lots of scanning. 348 * 349 * We only allow 1/2 of the currently-unmapped memory to be dirtied. 350 * 351 * We don't permit the clamping level to fall below 5% - that is getting rather 352 * excessive. 353 * 354 * We make sure that the background writeout level is below the adjusted 355 * clamping level. 356 */ 357 358static unsigned long highmem_dirtyable_memory(unsigned long total) 359{ 360#ifdef CONFIG_HIGHMEM 361 int node; 362 unsigned long x = 0; 363 364 for_each_node_state(node, N_HIGH_MEMORY) { 365 struct zone *z = 366 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; 367 368 x += zone_page_state(z, NR_FREE_PAGES) + 369 zone_reclaimable_pages(z); 370 } 371 /* 372 * Make sure that the number of highmem pages is never larger 373 * than the number of the total dirtyable memory. This can only 374 * occur in very strange VM situations but we want to make sure 375 * that this does not occur. 376 */ 377 return min(x, total); 378#else 379 return 0; 380#endif 381} 382 383/** 384 * determine_dirtyable_memory - amount of memory that may be used 385 * 386 * Returns the numebr of pages that can currently be freed and used 387 * by the kernel for direct mappings. 388 */ 389unsigned long determine_dirtyable_memory(void) 390{ 391 unsigned long x; 392 393 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); 394 395 if (!vm_highmem_is_dirtyable) 396 x -= highmem_dirtyable_memory(x); 397 398 return x + 1; /* Ensure that we never return 0 */ 399} 400 401/* 402 * global_dirty_limits - background-writeback and dirty-throttling thresholds 403 * 404 * Calculate the dirty thresholds based on sysctl parameters 405 * - vm.dirty_background_ratio or vm.dirty_background_bytes 406 * - vm.dirty_ratio or vm.dirty_bytes 407 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and 408 * real-time tasks. 409 */ 410void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) 411{ 412 unsigned long background; 413 unsigned long dirty; 414 unsigned long uninitialized_var(available_memory); 415 struct task_struct *tsk; 416 417 if (!vm_dirty_bytes || !dirty_background_bytes) 418 available_memory = determine_dirtyable_memory(); 419 420 if (vm_dirty_bytes) 421 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); 422 else 423 dirty = (vm_dirty_ratio * available_memory) / 100; 424 425 if (dirty_background_bytes) 426 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); 427 else 428 background = (dirty_background_ratio * available_memory) / 100; 429 430 if (background >= dirty) 431 background = dirty / 2; 432 tsk = current; 433 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { 434 background += background / 4; 435 dirty += dirty / 4; 436 } 437 *pbackground = background; 438 *pdirty = dirty; 439} 440 441/** 442 * bdi_dirty_limit - @bdi's share of dirty throttling threshold 443 * @bdi: the backing_dev_info to query 444 * @dirty: global dirty limit in pages 445 * 446 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of 447 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. 448 * And the "limit" in the name is not seriously taken as hard limit in 449 * balance_dirty_pages(). 450 * 451 * It allocates high/low dirty limits to fast/slow devices, in order to prevent 452 * - starving fast devices 453 * - piling up dirty pages (that will take long time to sync) on slow devices 454 * 455 * The bdi's share of dirty limit will be adapting to its throughput and 456 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. 457 */ 458unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) 459{ 460 u64 bdi_dirty; 461 long numerator, denominator; 462 463 /* 464 * Calculate this BDI's share of the dirty ratio. 465 */ 466 bdi_writeout_fraction(bdi, &numerator, &denominator); 467 468 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; 469 bdi_dirty *= numerator; 470 do_div(bdi_dirty, denominator); 471 472 bdi_dirty += (dirty * bdi->min_ratio) / 100; 473 if (bdi_dirty > (dirty * bdi->max_ratio) / 100) 474 bdi_dirty = dirty * bdi->max_ratio / 100; 475 476 return bdi_dirty; 477} 478 479static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, 480 unsigned long elapsed, 481 unsigned long written) 482{ 483 const unsigned long period = roundup_pow_of_two(3 * HZ); 484 unsigned long avg = bdi->avg_write_bandwidth; 485 unsigned long old = bdi->write_bandwidth; 486 u64 bw; 487 488 /* 489 * bw = written * HZ / elapsed 490 * 491 * bw * elapsed + write_bandwidth * (period - elapsed) 492 * write_bandwidth = --------------------------------------------------- 493 * period 494 */ 495 bw = written - bdi->written_stamp; 496 bw *= HZ; 497 if (unlikely(elapsed > period)) { 498 do_div(bw, elapsed); 499 avg = bw; 500 goto out; 501 } 502 bw += (u64)bdi->write_bandwidth * (period - elapsed); 503 bw >>= ilog2(period); 504 505 /* 506 * one more level of smoothing, for filtering out sudden spikes 507 */ 508 if (avg > old && old >= (unsigned long)bw) 509 avg -= (avg - old) >> 3; 510 511 if (avg < old && old <= (unsigned long)bw) 512 avg += (old - avg) >> 3; 513 514out: 515 bdi->write_bandwidth = bw; 516 bdi->avg_write_bandwidth = avg; 517} 518 519void __bdi_update_bandwidth(struct backing_dev_info *bdi, 520 unsigned long start_time) 521{ 522 unsigned long now = jiffies; 523 unsigned long elapsed = now - bdi->bw_time_stamp; 524 unsigned long written; 525 526 /* 527 * rate-limit, only update once every 200ms. 528 */ 529 if (elapsed < BANDWIDTH_INTERVAL) 530 return; 531 532 written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); 533 534 /* 535 * Skip quiet periods when disk bandwidth is under-utilized. 536 * (at least 1s idle time between two flusher runs) 537 */ 538 if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) 539 goto snapshot; 540 541 bdi_update_write_bandwidth(bdi, elapsed, written); 542 543snapshot: 544 bdi->written_stamp = written; 545 bdi->bw_time_stamp = now; 546} 547 548static void bdi_update_bandwidth(struct backing_dev_info *bdi, 549 unsigned long start_time) 550{ 551 if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) 552 return; 553 spin_lock(&bdi->wb.list_lock); 554 __bdi_update_bandwidth(bdi, start_time); 555 spin_unlock(&bdi->wb.list_lock); 556} 557 558/* 559 * balance_dirty_pages() must be called by processes which are generating dirty 560 * data. It looks at the number of dirty pages in the machine and will force 561 * the caller to perform writeback if the system is over `vm_dirty_ratio'. 562 * If we're over `background_thresh' then the writeback threads are woken to 563 * perform some writeout. 564 */ 565static void balance_dirty_pages(struct address_space *mapping, 566 unsigned long write_chunk) 567{ 568 unsigned long nr_reclaimable, bdi_nr_reclaimable; 569 unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ 570 unsigned long bdi_dirty; 571 unsigned long background_thresh; 572 unsigned long dirty_thresh; 573 unsigned long bdi_thresh; 574 unsigned long pages_written = 0; 575 unsigned long pause = 1; 576 bool dirty_exceeded = false; 577 struct backing_dev_info *bdi = mapping->backing_dev_info; 578 unsigned long start_time = jiffies; 579 580 for (;;) { 581 nr_reclaimable = global_page_state(NR_FILE_DIRTY) + 582 global_page_state(NR_UNSTABLE_NFS); 583 nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); 584 585 global_dirty_limits(&background_thresh, &dirty_thresh); 586 587 /* 588 * Throttle it only when the background writeback cannot 589 * catch-up. This avoids (excessively) small writeouts 590 * when the bdi limits are ramping up. 591 */ 592 if (nr_dirty <= (background_thresh + dirty_thresh) / 2) 593 break; 594 595 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); 596 bdi_thresh = task_dirty_limit(current, bdi_thresh); 597 598 /* 599 * In order to avoid the stacked BDI deadlock we need 600 * to ensure we accurately count the 'dirty' pages when 601 * the threshold is low. 602 * 603 * Otherwise it would be possible to get thresh+n pages 604 * reported dirty, even though there are thresh-m pages 605 * actually dirty; with m+n sitting in the percpu 606 * deltas. 607 */ 608 if (bdi_thresh < 2*bdi_stat_error(bdi)) { 609 bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); 610 bdi_dirty = bdi_nr_reclaimable + 611 bdi_stat_sum(bdi, BDI_WRITEBACK); 612 } else { 613 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); 614 bdi_dirty = bdi_nr_reclaimable + 615 bdi_stat(bdi, BDI_WRITEBACK); 616 } 617 618 /* 619 * The bdi thresh is somehow "soft" limit derived from the 620 * global "hard" limit. The former helps to prevent heavy IO 621 * bdi or process from holding back light ones; The latter is 622 * the last resort safeguard. 623 */ 624 dirty_exceeded = (bdi_dirty > bdi_thresh) || 625 (nr_dirty > dirty_thresh); 626 627 if (!dirty_exceeded) 628 break; 629 630 if (!bdi->dirty_exceeded) 631 bdi->dirty_exceeded = 1; 632 633 bdi_update_bandwidth(bdi, start_time); 634 635 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. 636 * Unstable writes are a feature of certain networked 637 * filesystems (i.e. NFS) in which data may have been 638 * written to the server's write cache, but has not yet 639 * been flushed to permanent storage. 640 * Only move pages to writeback if this bdi is over its 641 * threshold otherwise wait until the disk writes catch 642 * up. 643 */ 644 trace_balance_dirty_start(bdi); 645 if (bdi_nr_reclaimable > bdi_thresh) { 646 pages_written += writeback_inodes_wb(&bdi->wb, 647 write_chunk); 648 trace_balance_dirty_written(bdi, pages_written); 649 if (pages_written >= write_chunk) 650 break; /* We've done our duty */ 651 } 652 __set_current_state(TASK_UNINTERRUPTIBLE); 653 io_schedule_timeout(pause); 654 trace_balance_dirty_wait(bdi); 655 656 /* 657 * Increase the delay for each loop, up to our previous 658 * default of taking a 100ms nap. 659 */ 660 pause <<= 1; 661 if (pause > HZ / 10) 662 pause = HZ / 10; 663 } 664 665 if (!dirty_exceeded && bdi->dirty_exceeded) 666 bdi->dirty_exceeded = 0; 667 668 if (writeback_in_progress(bdi)) 669 return; 670 671 /* 672 * In laptop mode, we wait until hitting the higher threshold before 673 * starting background writeout, and then write out all the way down 674 * to the lower threshold. So slow writers cause minimal disk activity. 675 * 676 * In normal mode, we start background writeout at the lower 677 * background_thresh, to keep the amount of dirty memory low. 678 */ 679 if ((laptop_mode && pages_written) || 680 (!laptop_mode && (nr_reclaimable > background_thresh))) 681 bdi_start_background_writeback(bdi); 682} 683 684void set_page_dirty_balance(struct page *page, int page_mkwrite) 685{ 686 if (set_page_dirty(page) || page_mkwrite) { 687 struct address_space *mapping = page_mapping(page); 688 689 if (mapping) 690 balance_dirty_pages_ratelimited(mapping); 691 } 692} 693 694static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0; 695 696/** 697 * balance_dirty_pages_ratelimited_nr - balance dirty memory state 698 * @mapping: address_space which was dirtied 699 * @nr_pages_dirtied: number of pages which the caller has just dirtied 700 * 701 * Processes which are dirtying memory should call in here once for each page 702 * which was newly dirtied. The function will periodically check the system's 703 * dirty state and will initiate writeback if needed. 704 * 705 * On really big machines, get_writeback_state is expensive, so try to avoid 706 * calling it too often (ratelimiting). But once we're over the dirty memory 707 * limit we decrease the ratelimiting by a lot, to prevent individual processes 708 * from overshooting the limit by (ratelimit_pages) each. 709 */ 710void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, 711 unsigned long nr_pages_dirtied) 712{ 713 struct backing_dev_info *bdi = mapping->backing_dev_info; 714 unsigned long ratelimit; 715 unsigned long *p; 716 717 if (!bdi_cap_account_dirty(bdi)) 718 return; 719 720 ratelimit = ratelimit_pages; 721 if (mapping->backing_dev_info->dirty_exceeded) 722 ratelimit = 8; 723 724 /* 725 * Check the rate limiting. Also, we do not want to throttle real-time 726 * tasks in balance_dirty_pages(). Period. 727 */ 728 preempt_disable(); 729 p = &__get_cpu_var(bdp_ratelimits); 730 *p += nr_pages_dirtied; 731 if (unlikely(*p >= ratelimit)) { 732 ratelimit = sync_writeback_pages(*p); 733 *p = 0; 734 preempt_enable(); 735 balance_dirty_pages(mapping, ratelimit); 736 return; 737 } 738 preempt_enable(); 739} 740EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); 741 742void throttle_vm_writeout(gfp_t gfp_mask) 743{ 744 unsigned long background_thresh; 745 unsigned long dirty_thresh; 746 747 for ( ; ; ) { 748 global_dirty_limits(&background_thresh, &dirty_thresh); 749 750 /* 751 * Boost the allowable dirty threshold a bit for page 752 * allocators so they don't get DoS'ed by heavy writers 753 */ 754 dirty_thresh += dirty_thresh / 10; /* wheeee... */ 755 756 if (global_page_state(NR_UNSTABLE_NFS) + 757 global_page_state(NR_WRITEBACK) <= dirty_thresh) 758 break; 759 congestion_wait(BLK_RW_ASYNC, HZ/10); 760 761 /* 762 * The caller might hold locks which can prevent IO completion 763 * or progress in the filesystem. So we cannot just sit here 764 * waiting for IO to complete. 765 */ 766 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) 767 break; 768 } 769} 770 771/* 772 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs 773 */ 774int dirty_writeback_centisecs_handler(ctl_table *table, int write, 775 void __user *buffer, size_t *length, loff_t *ppos) 776{ 777 proc_dointvec(table, write, buffer, length, ppos); 778 bdi_arm_supers_timer(); 779 return 0; 780} 781 782#ifdef CONFIG_BLOCK 783void laptop_mode_timer_fn(unsigned long data) 784{ 785 struct request_queue *q = (struct request_queue *)data; 786 int nr_pages = global_page_state(NR_FILE_DIRTY) + 787 global_page_state(NR_UNSTABLE_NFS); 788 789 /* 790 * We want to write everything out, not just down to the dirty 791 * threshold 792 */ 793 if (bdi_has_dirty_io(&q->backing_dev_info)) 794 bdi_start_writeback(&q->backing_dev_info, nr_pages); 795} 796 797/* 798 * We've spun up the disk and we're in laptop mode: schedule writeback 799 * of all dirty data a few seconds from now. If the flush is already scheduled 800 * then push it back - the user is still using the disk. 801 */ 802void laptop_io_completion(struct backing_dev_info *info) 803{ 804 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); 805} 806 807/* 808 * We're in laptop mode and we've just synced. The sync's writes will have 809 * caused another writeback to be scheduled by laptop_io_completion. 810 * Nothing needs to be written back anymore, so we unschedule the writeback. 811 */ 812void laptop_sync_completion(void) 813{ 814 struct backing_dev_info *bdi; 815 816 rcu_read_lock(); 817 818 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) 819 del_timer(&bdi->laptop_mode_wb_timer); 820 821 rcu_read_unlock(); 822} 823#endif 824 825/* 826 * If ratelimit_pages is too high then we can get into dirty-data overload 827 * if a large number of processes all perform writes at the same time. 828 * If it is too low then SMP machines will call the (expensive) 829 * get_writeback_state too often. 830 * 831 * Here we set ratelimit_pages to a level which ensures that when all CPUs are 832 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory 833 * thresholds before writeback cuts in. 834 * 835 * But the limit should not be set too high. Because it also controls the 836 * amount of memory which the balance_dirty_pages() caller has to write back. 837 * If this is too large then the caller will block on the IO queue all the 838 * time. So limit it to four megabytes - the balance_dirty_pages() caller 839 * will write six megabyte chunks, max. 840 */ 841 842void writeback_set_ratelimit(void) 843{ 844 ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); 845 if (ratelimit_pages < 16) 846 ratelimit_pages = 16; 847 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) 848 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; 849} 850 851static int __cpuinit 852ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) 853{ 854 writeback_set_ratelimit(); 855 return NOTIFY_DONE; 856} 857 858static struct notifier_block __cpuinitdata ratelimit_nb = { 859 .notifier_call = ratelimit_handler, 860 .next = NULL, 861}; 862 863/* 864 * Called early on to tune the page writeback dirty limits. 865 * 866 * We used to scale dirty pages according to how total memory 867 * related to pages that could be allocated for buffers (by 868 * comparing nr_free_buffer_pages() to vm_total_pages. 869 * 870 * However, that was when we used "dirty_ratio" to scale with 871 * all memory, and we don't do that any more. "dirty_ratio" 872 * is now applied to total non-HIGHPAGE memory (by subtracting 873 * totalhigh_pages from vm_total_pages), and as such we can't 874 * get into the old insane situation any more where we had 875 * large amounts of dirty pages compared to a small amount of 876 * non-HIGHMEM memory. 877 * 878 * But we might still want to scale the dirty_ratio by how 879 * much memory the box has.. 880 */ 881void __init page_writeback_init(void) 882{ 883 int shift; 884 885 writeback_set_ratelimit(); 886 register_cpu_notifier(&ratelimit_nb); 887 888 shift = calc_period_shift(); 889 prop_descriptor_init(&vm_completions, shift); 890 prop_descriptor_init(&vm_dirties, shift); 891} 892 893/** 894 * tag_pages_for_writeback - tag pages to be written by write_cache_pages 895 * @mapping: address space structure to write 896 * @start: starting page index 897 * @end: ending page index (inclusive) 898 * 899 * This function scans the page range from @start to @end (inclusive) and tags 900 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is 901 * that write_cache_pages (or whoever calls this function) will then use 902 * TOWRITE tag to identify pages eligible for writeback. This mechanism is 903 * used to avoid livelocking of writeback by a process steadily creating new 904 * dirty pages in the file (thus it is important for this function to be quick 905 * so that it can tag pages faster than a dirtying process can create them). 906 */ 907/* 908 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. 909 */ 910void tag_pages_for_writeback(struct address_space *mapping, 911 pgoff_t start, pgoff_t end) 912{ 913#define WRITEBACK_TAG_BATCH 4096 914 unsigned long tagged; 915 916 do { 917 spin_lock_irq(&mapping->tree_lock); 918 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, 919 &start, end, WRITEBACK_TAG_BATCH, 920 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); 921 spin_unlock_irq(&mapping->tree_lock); 922 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); 923 cond_resched(); 924 /* We check 'start' to handle wrapping when end == ~0UL */ 925 } while (tagged >= WRITEBACK_TAG_BATCH && start); 926} 927EXPORT_SYMBOL(tag_pages_for_writeback); 928 929/** 930 * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. 931 * @mapping: address space structure to write 932 * @wbc: subtract the number of written pages from *@wbc->nr_to_write 933 * @writepage: function called for each page 934 * @data: data passed to writepage function 935 * 936 * If a page is already under I/O, write_cache_pages() skips it, even 937 * if it's dirty. This is desirable behaviour for memory-cleaning writeback, 938 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() 939 * and msync() need to guarantee that all the data which was dirty at the time 940 * the call was made get new I/O started against them. If wbc->sync_mode is 941 * WB_SYNC_ALL then we were called for data integrity and we must wait for 942 * existing IO to complete. 943 * 944 * To avoid livelocks (when other process dirties new pages), we first tag 945 * pages which should be written back with TOWRITE tag and only then start 946 * writing them. For data-integrity sync we have to be careful so that we do 947 * not miss some pages (e.g., because some other process has cleared TOWRITE 948 * tag we set). The rule we follow is that TOWRITE tag can be cleared only 949 * by the process clearing the DIRTY tag (and submitting the page for IO). 950 */ 951int write_cache_pages(struct address_space *mapping, 952 struct writeback_control *wbc, writepage_t writepage, 953 void *data) 954{ 955 int ret = 0; 956 int done = 0; 957 struct pagevec pvec; 958 int nr_pages; 959 pgoff_t uninitialized_var(writeback_index); 960 pgoff_t index; 961 pgoff_t end; /* Inclusive */ 962 pgoff_t done_index; 963 int cycled; 964 int range_whole = 0; 965 int tag; 966 967 pagevec_init(&pvec, 0); 968 if (wbc->range_cyclic) { 969 writeback_index = mapping->writeback_index; /* prev offset */ 970 index = writeback_index; 971 if (index == 0) 972 cycled = 1; 973 else 974 cycled = 0; 975 end = -1; 976 } else { 977 index = wbc->range_start >> PAGE_CACHE_SHIFT; 978 end = wbc->range_end >> PAGE_CACHE_SHIFT; 979 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) 980 range_whole = 1; 981 cycled = 1; /* ignore range_cyclic tests */ 982 } 983 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) 984 tag = PAGECACHE_TAG_TOWRITE; 985 else 986 tag = PAGECACHE_TAG_DIRTY; 987retry: 988 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) 989 tag_pages_for_writeback(mapping, index, end); 990 done_index = index; 991 while (!done && (index <= end)) { 992 int i; 993 994 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, 995 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); 996 if (nr_pages == 0) 997 break; 998 999 for (i = 0; i < nr_pages; i++) { 1000 struct page *page = pvec.pages[i]; 1001 1002 /* 1003 * At this point, the page may be truncated or 1004 * invalidated (changing page->mapping to NULL), or 1005 * even swizzled back from swapper_space to tmpfs file 1006 * mapping. However, page->index will not change 1007 * because we have a reference on the page. 1008 */ 1009 if (page->index > end) { 1010 /* 1011 * can't be range_cyclic (1st pass) because 1012 * end == -1 in that case. 1013 */ 1014 done = 1; 1015 break; 1016 } 1017 1018 done_index = page->index; 1019 1020 lock_page(page); 1021 1022 /* 1023 * Page truncated or invalidated. We can freely skip it 1024 * then, even for data integrity operations: the page 1025 * has disappeared concurrently, so there could be no 1026 * real expectation of this data interity operation 1027 * even if there is now a new, dirty page at the same 1028 * pagecache address. 1029 */ 1030 if (unlikely(page->mapping != mapping)) { 1031continue_unlock: 1032 unlock_page(page); 1033 continue; 1034 } 1035 1036 if (!PageDirty(page)) { 1037 /* someone wrote it for us */ 1038 goto continue_unlock; 1039 } 1040 1041 if (PageWriteback(page)) { 1042 if (wbc->sync_mode != WB_SYNC_NONE) 1043 wait_on_page_writeback(page); 1044 else 1045 goto continue_unlock; 1046 } 1047 1048 BUG_ON(PageWriteback(page)); 1049 if (!clear_page_dirty_for_io(page)) 1050 goto continue_unlock; 1051 1052 trace_wbc_writepage(wbc, mapping->backing_dev_info); 1053 ret = (*writepage)(page, wbc, data); 1054 if (unlikely(ret)) { 1055 if (ret == AOP_WRITEPAGE_ACTIVATE) { 1056 unlock_page(page); 1057 ret = 0; 1058 } else { 1059 /* 1060 * done_index is set past this page, 1061 * so media errors will not choke 1062 * background writeout for the entire 1063 * file. This has consequences for 1064 * range_cyclic semantics (ie. it may 1065 * not be suitable for data integrity 1066 * writeout). 1067 */ 1068 done_index = page->index + 1; 1069 done = 1; 1070 break; 1071 } 1072 } 1073 1074 /* 1075 * We stop writing back only if we are not doing 1076 * integrity sync. In case of integrity sync we have to 1077 * keep going until we have written all the pages 1078 * we tagged for writeback prior to entering this loop. 1079 */ 1080 if (--wbc->nr_to_write <= 0 && 1081 wbc->sync_mode == WB_SYNC_NONE) { 1082 done = 1; 1083 break; 1084 } 1085 } 1086 pagevec_release(&pvec); 1087 cond_resched(); 1088 } 1089 if (!cycled && !done) { 1090 /* 1091 * range_cyclic: 1092 * We hit the last page and there is more work to be done: wrap 1093 * back to the start of the file 1094 */ 1095 cycled = 1; 1096 index = 0; 1097 end = writeback_index - 1; 1098 goto retry; 1099 } 1100 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) 1101 mapping->writeback_index = done_index; 1102 1103 return ret; 1104} 1105EXPORT_SYMBOL(write_cache_pages); 1106 1107/* 1108 * Function used by generic_writepages to call the real writepage 1109 * function and set the mapping flags on error 1110 */ 1111static int __writepage(struct page *page, struct writeback_control *wbc, 1112 void *data) 1113{ 1114 struct address_space *mapping = data; 1115 int ret = mapping->a_ops->writepage(page, wbc); 1116 mapping_set_error(mapping, ret); 1117 return ret; 1118} 1119 1120/** 1121 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. 1122 * @mapping: address space structure to write 1123 * @wbc: subtract the number of written pages from *@wbc->nr_to_write 1124 * 1125 * This is a library function, which implements the writepages() 1126 * address_space_operation. 1127 */ 1128int generic_writepages(struct address_space *mapping, 1129 struct writeback_control *wbc) 1130{ 1131 struct blk_plug plug; 1132 int ret; 1133 1134 /* deal with chardevs and other special file */ 1135 if (!mapping->a_ops->writepage) 1136 return 0; 1137 1138 blk_start_plug(&plug); 1139 ret = write_cache_pages(mapping, wbc, __writepage, mapping); 1140 blk_finish_plug(&plug); 1141 return ret; 1142} 1143 1144EXPORT_SYMBOL(generic_writepages); 1145 1146int do_writepages(struct address_space *mapping, struct writeback_control *wbc) 1147{ 1148 int ret; 1149 1150 if (wbc->nr_to_write <= 0) 1151 return 0; 1152 if (mapping->a_ops->writepages) 1153 ret = mapping->a_ops->writepages(mapping, wbc); 1154 else 1155 ret = generic_writepages(mapping, wbc); 1156 return ret; 1157} 1158 1159/** 1160 * write_one_page - write out a single page and optionally wait on I/O 1161 * @page: the page to write 1162 * @wait: if true, wait on writeout 1163 * 1164 * The page must be locked by the caller and will be unlocked upon return. 1165 * 1166 * write_one_page() returns a negative error code if I/O failed. 1167 */ 1168int write_one_page(struct page *page, int wait) 1169{ 1170 struct address_space *mapping = page->mapping; 1171 int ret = 0; 1172 struct writeback_control wbc = { 1173 .sync_mode = WB_SYNC_ALL, 1174 .nr_to_write = 1, 1175 }; 1176 1177 BUG_ON(!PageLocked(page)); 1178 1179 if (wait) 1180 wait_on_page_writeback(page); 1181 1182 if (clear_page_dirty_for_io(page)) { 1183 page_cache_get(page); 1184 ret = mapping->a_ops->writepage(page, &wbc); 1185 if (ret == 0 && wait) { 1186 wait_on_page_writeback(page); 1187 if (PageError(page)) 1188 ret = -EIO; 1189 } 1190 page_cache_release(page); 1191 } else { 1192 unlock_page(page); 1193 } 1194 return ret; 1195} 1196EXPORT_SYMBOL(write_one_page); 1197 1198/* 1199 * For address_spaces which do not use buffers nor write back. 1200 */ 1201int __set_page_dirty_no_writeback(struct page *page) 1202{ 1203 if (!PageDirty(page)) 1204 return !TestSetPageDirty(page); 1205 return 0; 1206} 1207 1208/* 1209 * Helper function for set_page_dirty family. 1210 * NOTE: This relies on being atomic wrt interrupts. 1211 */ 1212void account_page_dirtied(struct page *page, struct address_space *mapping) 1213{ 1214 if (mapping_cap_account_dirty(mapping)) { 1215 __inc_zone_page_state(page, NR_FILE_DIRTY); 1216 __inc_zone_page_state(page, NR_DIRTIED); 1217 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 1218 task_dirty_inc(current); 1219 task_io_account_write(PAGE_CACHE_SIZE); 1220 } 1221} 1222EXPORT_SYMBOL(account_page_dirtied); 1223 1224/* 1225 * Helper function for set_page_writeback family. 1226 * NOTE: Unlike account_page_dirtied this does not rely on being atomic 1227 * wrt interrupts. 1228 */ 1229void account_page_writeback(struct page *page) 1230{ 1231 inc_zone_page_state(page, NR_WRITEBACK); 1232 inc_zone_page_state(page, NR_WRITTEN); 1233} 1234EXPORT_SYMBOL(account_page_writeback); 1235 1236/* 1237 * For address_spaces which do not use buffers. Just tag the page as dirty in 1238 * its radix tree. 1239 * 1240 * This is also used when a single buffer is being dirtied: we want to set the 1241 * page dirty in that case, but not all the buffers. This is a "bottom-up" 1242 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. 1243 * 1244 * Most callers have locked the page, which pins the address_space in memory. 1245 * But zap_pte_range() does not lock the page, however in that case the 1246 * mapping is pinned by the vma's ->vm_file reference. 1247 * 1248 * We take care to handle the case where the page was truncated from the 1249 * mapping by re-checking page_mapping() inside tree_lock. 1250 */ 1251int __set_page_dirty_nobuffers(struct page *page) 1252{ 1253 if (!TestSetPageDirty(page)) { 1254 struct address_space *mapping = page_mapping(page); 1255 struct address_space *mapping2; 1256 1257 if (!mapping) 1258 return 1; 1259 1260 spin_lock_irq(&mapping->tree_lock); 1261 mapping2 = page_mapping(page); 1262 if (mapping2) { /* Race with truncate? */ 1263 BUG_ON(mapping2 != mapping); 1264 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); 1265 account_page_dirtied(page, mapping); 1266 radix_tree_tag_set(&mapping->page_tree, 1267 page_index(page), PAGECACHE_TAG_DIRTY); 1268 } 1269 spin_unlock_irq(&mapping->tree_lock); 1270 if (mapping->host) { 1271 /* !PageAnon && !swapper_space */ 1272 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 1273 } 1274 return 1; 1275 } 1276 return 0; 1277} 1278EXPORT_SYMBOL(__set_page_dirty_nobuffers); 1279 1280/* 1281 * When a writepage implementation decides that it doesn't want to write this 1282 * page for some reason, it should redirty the locked page via 1283 * redirty_page_for_writepage() and it should then unlock the page and return 0 1284 */ 1285int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) 1286{ 1287 wbc->pages_skipped++; 1288 return __set_page_dirty_nobuffers(page); 1289} 1290EXPORT_SYMBOL(redirty_page_for_writepage); 1291 1292/* 1293 * Dirty a page. 1294 * 1295 * For pages with a mapping this should be done under the page lock 1296 * for the benefit of asynchronous memory errors who prefer a consistent 1297 * dirty state. This rule can be broken in some special cases, 1298 * but should be better not to. 1299 * 1300 * If the mapping doesn't provide a set_page_dirty a_op, then 1301 * just fall through and assume that it wants buffer_heads. 1302 */ 1303int set_page_dirty(struct page *page) 1304{ 1305 struct address_space *mapping = page_mapping(page); 1306 1307 if (likely(mapping)) { 1308 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; 1309 /* 1310 * readahead/lru_deactivate_page could remain 1311 * PG_readahead/PG_reclaim due to race with end_page_writeback 1312 * About readahead, if the page is written, the flags would be 1313 * reset. So no problem. 1314 * About lru_deactivate_page, if the page is redirty, the flag 1315 * will be reset. So no problem. but if the page is used by readahead 1316 * it will confuse readahead and make it restart the size rampup 1317 * process. But it's a trivial problem. 1318 */ 1319 ClearPageReclaim(page); 1320#ifdef CONFIG_BLOCK 1321 if (!spd) 1322 spd = __set_page_dirty_buffers; 1323#endif 1324 return (*spd)(page); 1325 } 1326 if (!PageDirty(page)) { 1327 if (!TestSetPageDirty(page)) 1328 return 1; 1329 } 1330 return 0; 1331} 1332EXPORT_SYMBOL(set_page_dirty); 1333 1334/* 1335 * set_page_dirty() is racy if the caller has no reference against 1336 * page->mapping->host, and if the page is unlocked. This is because another 1337 * CPU could truncate the page off the mapping and then free the mapping. 1338 * 1339 * Usually, the page _is_ locked, or the caller is a user-space process which 1340 * holds a reference on the inode by having an open file. 1341 * 1342 * In other cases, the page should be locked before running set_page_dirty(). 1343 */ 1344int set_page_dirty_lock(struct page *page) 1345{ 1346 int ret; 1347 1348 lock_page(page); 1349 ret = set_page_dirty(page); 1350 unlock_page(page); 1351 return ret; 1352} 1353EXPORT_SYMBOL(set_page_dirty_lock); 1354 1355/* 1356 * Clear a page's dirty flag, while caring for dirty memory accounting. 1357 * Returns true if the page was previously dirty. 1358 * 1359 * This is for preparing to put the page under writeout. We leave the page 1360 * tagged as dirty in the radix tree so that a concurrent write-for-sync 1361 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage 1362 * implementation will run either set_page_writeback() or set_page_dirty(), 1363 * at which stage we bring the page's dirty flag and radix-tree dirty tag 1364 * back into sync. 1365 * 1366 * This incoherency between the page's dirty flag and radix-tree tag is 1367 * unfortunate, but it only exists while the page is locked. 1368 */ 1369int clear_page_dirty_for_io(struct page *page) 1370{ 1371 struct address_space *mapping = page_mapping(page); 1372 1373 BUG_ON(!PageLocked(page)); 1374 1375 if (mapping && mapping_cap_account_dirty(mapping)) { 1376 /* 1377 * Yes, Virginia, this is indeed insane. 1378 * 1379 * We use this sequence to make sure that 1380 * (a) we account for dirty stats properly 1381 * (b) we tell the low-level filesystem to 1382 * mark the whole page dirty if it was 1383 * dirty in a pagetable. Only to then 1384 * (c) clean the page again and return 1 to 1385 * cause the writeback. 1386 * 1387 * This way we avoid all nasty races with the 1388 * dirty bit in multiple places and clearing 1389 * them concurrently from different threads. 1390 * 1391 * Note! Normally the "set_page_dirty(page)" 1392 * has no effect on the actual dirty bit - since 1393 * that will already usually be set. But we 1394 * need the side effects, and it can help us 1395 * avoid races. 1396 * 1397 * We basically use the page "master dirty bit" 1398 * as a serialization point for all the different 1399 * threads doing their things. 1400 */ 1401 if (page_mkclean(page)) 1402 set_page_dirty(page); 1403 /* 1404 * We carefully synchronise fault handlers against 1405 * installing a dirty pte and marking the page dirty 1406 * at this point. We do this by having them hold the 1407 * page lock at some point after installing their 1408 * pte, but before marking the page dirty. 1409 * Pages are always locked coming in here, so we get 1410 * the desired exclusion. See mm/memory.c:do_wp_page() 1411 * for more comments. 1412 */ 1413 if (TestClearPageDirty(page)) { 1414 dec_zone_page_state(page, NR_FILE_DIRTY); 1415 dec_bdi_stat(mapping->backing_dev_info, 1416 BDI_RECLAIMABLE); 1417 return 1; 1418 } 1419 return 0; 1420 } 1421 return TestClearPageDirty(page); 1422} 1423EXPORT_SYMBOL(clear_page_dirty_for_io); 1424 1425int test_clear_page_writeback(struct page *page) 1426{ 1427 struct address_space *mapping = page_mapping(page); 1428 int ret; 1429 1430 if (mapping) { 1431 struct backing_dev_info *bdi = mapping->backing_dev_info; 1432 unsigned long flags; 1433 1434 spin_lock_irqsave(&mapping->tree_lock, flags); 1435 ret = TestClearPageWriteback(page); 1436 if (ret) { 1437 radix_tree_tag_clear(&mapping->page_tree, 1438 page_index(page), 1439 PAGECACHE_TAG_WRITEBACK); 1440 if (bdi_cap_account_writeback(bdi)) { 1441 __dec_bdi_stat(bdi, BDI_WRITEBACK); 1442 __bdi_writeout_inc(bdi); 1443 } 1444 } 1445 spin_unlock_irqrestore(&mapping->tree_lock, flags); 1446 } else { 1447 ret = TestClearPageWriteback(page); 1448 } 1449 if (ret) 1450 dec_zone_page_state(page, NR_WRITEBACK); 1451 return ret; 1452} 1453 1454int test_set_page_writeback(struct page *page) 1455{ 1456 struct address_space *mapping = page_mapping(page); 1457 int ret; 1458 1459 if (mapping) { 1460 struct backing_dev_info *bdi = mapping->backing_dev_info; 1461 unsigned long flags; 1462 1463 spin_lock_irqsave(&mapping->tree_lock, flags); 1464 ret = TestSetPageWriteback(page); 1465 if (!ret) { 1466 radix_tree_tag_set(&mapping->page_tree, 1467 page_index(page), 1468 PAGECACHE_TAG_WRITEBACK); 1469 if (bdi_cap_account_writeback(bdi)) 1470 __inc_bdi_stat(bdi, BDI_WRITEBACK); 1471 } 1472 if (!PageDirty(page)) 1473 radix_tree_tag_clear(&mapping->page_tree, 1474 page_index(page), 1475 PAGECACHE_TAG_DIRTY); 1476 radix_tree_tag_clear(&mapping->page_tree, 1477 page_index(page), 1478 PAGECACHE_TAG_TOWRITE); 1479 spin_unlock_irqrestore(&mapping->tree_lock, flags); 1480 } else { 1481 ret = TestSetPageWriteback(page); 1482 } 1483 if (!ret) 1484 account_page_writeback(page); 1485 return ret; 1486 1487} 1488EXPORT_SYMBOL(test_set_page_writeback); 1489 1490/* 1491 * Return true if any of the pages in the mapping are marked with the 1492 * passed tag. 1493 */ 1494int mapping_tagged(struct address_space *mapping, int tag) 1495{ 1496 int ret; 1497 rcu_read_lock(); 1498 ret = radix_tree_tagged(&mapping->page_tree, tag); 1499 rcu_read_unlock(); 1500 return ret; 1501} 1502EXPORT_SYMBOL(mapping_tagged); 1503