page-writeback.c revision 6f7186562771ec9b629914df328048449ccddf4a
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 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited 41 * will look to see if it needs to force writeback or throttling. 42 */ 43static long ratelimit_pages = 32; 44 45/* 46 * When balance_dirty_pages decides that the caller needs to perform some 47 * non-background writeback, this is how many pages it will attempt to write. 48 * It should be somewhat larger than dirtied pages to ensure that reasonably 49 * large amounts of I/O are submitted. 50 */ 51static inline long sync_writeback_pages(unsigned long dirtied) 52{ 53 if (dirtied < ratelimit_pages) 54 dirtied = ratelimit_pages; 55 56 return dirtied + dirtied / 2; 57} 58 59/* The following parameters are exported via /proc/sys/vm */ 60 61/* 62 * Start background writeback (via writeback threads) at this percentage 63 */ 64int dirty_background_ratio = 10; 65 66/* 67 * dirty_background_bytes starts at 0 (disabled) so that it is a function of 68 * dirty_background_ratio * the amount of dirtyable memory 69 */ 70unsigned long dirty_background_bytes; 71 72/* 73 * free highmem will not be subtracted from the total free memory 74 * for calculating free ratios if vm_highmem_is_dirtyable is true 75 */ 76int vm_highmem_is_dirtyable; 77 78/* 79 * The generator of dirty data starts writeback at this percentage 80 */ 81int vm_dirty_ratio = 20; 82 83/* 84 * vm_dirty_bytes starts at 0 (disabled) so that it is a function of 85 * vm_dirty_ratio * the amount of dirtyable memory 86 */ 87unsigned long vm_dirty_bytes; 88 89/* 90 * The interval between `kupdate'-style writebacks 91 */ 92unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ 93 94/* 95 * The longest time for which data is allowed to remain dirty 96 */ 97unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ 98 99/* 100 * Flag that makes the machine dump writes/reads and block dirtyings. 101 */ 102int block_dump; 103 104/* 105 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: 106 * a full sync is triggered after this time elapses without any disk activity. 107 */ 108int laptop_mode; 109 110EXPORT_SYMBOL(laptop_mode); 111 112/* End of sysctl-exported parameters */ 113 114 115/* 116 * Scale the writeback cache size proportional to the relative writeout speeds. 117 * 118 * We do this by keeping a floating proportion between BDIs, based on page 119 * writeback completions [end_page_writeback()]. Those devices that write out 120 * pages fastest will get the larger share, while the slower will get a smaller 121 * share. 122 * 123 * We use page writeout completions because we are interested in getting rid of 124 * dirty pages. Having them written out is the primary goal. 125 * 126 * We introduce a concept of time, a period over which we measure these events, 127 * because demand can/will vary over time. The length of this period itself is 128 * measured in page writeback completions. 129 * 130 */ 131static struct prop_descriptor vm_completions; 132static struct prop_descriptor vm_dirties; 133 134/* 135 * couple the period to the dirty_ratio: 136 * 137 * period/2 ~ roundup_pow_of_two(dirty limit) 138 */ 139static int calc_period_shift(void) 140{ 141 unsigned long dirty_total; 142 143 if (vm_dirty_bytes) 144 dirty_total = vm_dirty_bytes / PAGE_SIZE; 145 else 146 dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 147 100; 148 return 2 + ilog2(dirty_total - 1); 149} 150 151/* 152 * update the period when the dirty threshold changes. 153 */ 154static void update_completion_period(void) 155{ 156 int shift = calc_period_shift(); 157 prop_change_shift(&vm_completions, shift); 158 prop_change_shift(&vm_dirties, shift); 159} 160 161int dirty_background_ratio_handler(struct ctl_table *table, int write, 162 void __user *buffer, size_t *lenp, 163 loff_t *ppos) 164{ 165 int ret; 166 167 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 168 if (ret == 0 && write) 169 dirty_background_bytes = 0; 170 return ret; 171} 172 173int dirty_background_bytes_handler(struct ctl_table *table, int write, 174 void __user *buffer, size_t *lenp, 175 loff_t *ppos) 176{ 177 int ret; 178 179 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); 180 if (ret == 0 && write) 181 dirty_background_ratio = 0; 182 return ret; 183} 184 185int dirty_ratio_handler(struct ctl_table *table, int write, 186 void __user *buffer, size_t *lenp, 187 loff_t *ppos) 188{ 189 int old_ratio = vm_dirty_ratio; 190 int ret; 191 192 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 193 if (ret == 0 && write && vm_dirty_ratio != old_ratio) { 194 update_completion_period(); 195 vm_dirty_bytes = 0; 196 } 197 return ret; 198} 199 200 201int dirty_bytes_handler(struct ctl_table *table, int write, 202 void __user *buffer, size_t *lenp, 203 loff_t *ppos) 204{ 205 unsigned long old_bytes = vm_dirty_bytes; 206 int ret; 207 208 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); 209 if (ret == 0 && write && vm_dirty_bytes != old_bytes) { 210 update_completion_period(); 211 vm_dirty_ratio = 0; 212 } 213 return ret; 214} 215 216/* 217 * Increment the BDI's writeout completion count and the global writeout 218 * completion count. Called from test_clear_page_writeback(). 219 */ 220static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) 221{ 222 __prop_inc_percpu_max(&vm_completions, &bdi->completions, 223 bdi->max_prop_frac); 224} 225 226void bdi_writeout_inc(struct backing_dev_info *bdi) 227{ 228 unsigned long flags; 229 230 local_irq_save(flags); 231 __bdi_writeout_inc(bdi); 232 local_irq_restore(flags); 233} 234EXPORT_SYMBOL_GPL(bdi_writeout_inc); 235 236void task_dirty_inc(struct task_struct *tsk) 237{ 238 prop_inc_single(&vm_dirties, &tsk->dirties); 239} 240 241/* 242 * Obtain an accurate fraction of the BDI's portion. 243 */ 244static void bdi_writeout_fraction(struct backing_dev_info *bdi, 245 long *numerator, long *denominator) 246{ 247 if (bdi_cap_writeback_dirty(bdi)) { 248 prop_fraction_percpu(&vm_completions, &bdi->completions, 249 numerator, denominator); 250 } else { 251 *numerator = 0; 252 *denominator = 1; 253 } 254} 255 256static inline void task_dirties_fraction(struct task_struct *tsk, 257 long *numerator, long *denominator) 258{ 259 prop_fraction_single(&vm_dirties, &tsk->dirties, 260 numerator, denominator); 261} 262 263/* 264 * task_dirty_limit - scale down dirty throttling threshold for one task 265 * 266 * task specific dirty limit: 267 * 268 * dirty -= (dirty/8) * p_{t} 269 * 270 * To protect light/slow dirtying tasks from heavier/fast ones, we start 271 * throttling individual tasks before reaching the bdi dirty limit. 272 * Relatively low thresholds will be allocated to heavy dirtiers. So when 273 * dirty pages grow large, heavy dirtiers will be throttled first, which will 274 * effectively curb the growth of dirty pages. Light dirtiers with high enough 275 * dirty threshold may never get throttled. 276 */ 277static unsigned long task_dirty_limit(struct task_struct *tsk, 278 unsigned long bdi_dirty) 279{ 280 long numerator, denominator; 281 unsigned long dirty = bdi_dirty; 282 u64 inv = dirty >> 3; 283 284 task_dirties_fraction(tsk, &numerator, &denominator); 285 inv *= numerator; 286 do_div(inv, denominator); 287 288 dirty -= inv; 289 290 return max(dirty, bdi_dirty/2); 291} 292 293/* 294 * 295 */ 296static unsigned int bdi_min_ratio; 297 298int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) 299{ 300 int ret = 0; 301 302 spin_lock_bh(&bdi_lock); 303 if (min_ratio > bdi->max_ratio) { 304 ret = -EINVAL; 305 } else { 306 min_ratio -= bdi->min_ratio; 307 if (bdi_min_ratio + min_ratio < 100) { 308 bdi_min_ratio += min_ratio; 309 bdi->min_ratio += min_ratio; 310 } else { 311 ret = -EINVAL; 312 } 313 } 314 spin_unlock_bh(&bdi_lock); 315 316 return ret; 317} 318 319int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) 320{ 321 int ret = 0; 322 323 if (max_ratio > 100) 324 return -EINVAL; 325 326 spin_lock_bh(&bdi_lock); 327 if (bdi->min_ratio > max_ratio) { 328 ret = -EINVAL; 329 } else { 330 bdi->max_ratio = max_ratio; 331 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; 332 } 333 spin_unlock_bh(&bdi_lock); 334 335 return ret; 336} 337EXPORT_SYMBOL(bdi_set_max_ratio); 338 339/* 340 * Work out the current dirty-memory clamping and background writeout 341 * thresholds. 342 * 343 * The main aim here is to lower them aggressively if there is a lot of mapped 344 * memory around. To avoid stressing page reclaim with lots of unreclaimable 345 * pages. It is better to clamp down on writers than to start swapping, and 346 * performing lots of scanning. 347 * 348 * We only allow 1/2 of the currently-unmapped memory to be dirtied. 349 * 350 * We don't permit the clamping level to fall below 5% - that is getting rather 351 * excessive. 352 * 353 * We make sure that the background writeout level is below the adjusted 354 * clamping level. 355 */ 356 357static unsigned long highmem_dirtyable_memory(unsigned long total) 358{ 359#ifdef CONFIG_HIGHMEM 360 int node; 361 unsigned long x = 0; 362 363 for_each_node_state(node, N_HIGH_MEMORY) { 364 struct zone *z = 365 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; 366 367 x += zone_page_state(z, NR_FREE_PAGES) + 368 zone_reclaimable_pages(z); 369 } 370 /* 371 * Make sure that the number of highmem pages is never larger 372 * than the number of the total dirtyable memory. This can only 373 * occur in very strange VM situations but we want to make sure 374 * that this does not occur. 375 */ 376 return min(x, total); 377#else 378 return 0; 379#endif 380} 381 382/** 383 * determine_dirtyable_memory - amount of memory that may be used 384 * 385 * Returns the numebr of pages that can currently be freed and used 386 * by the kernel for direct mappings. 387 */ 388unsigned long determine_dirtyable_memory(void) 389{ 390 unsigned long x; 391 392 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); 393 394 if (!vm_highmem_is_dirtyable) 395 x -= highmem_dirtyable_memory(x); 396 397 return x + 1; /* Ensure that we never return 0 */ 398} 399 400/* 401 * global_dirty_limits - background-writeback and dirty-throttling thresholds 402 * 403 * Calculate the dirty thresholds based on sysctl parameters 404 * - vm.dirty_background_ratio or vm.dirty_background_bytes 405 * - vm.dirty_ratio or vm.dirty_bytes 406 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and 407 * real-time tasks. 408 */ 409void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) 410{ 411 unsigned long background; 412 unsigned long dirty; 413 unsigned long uninitialized_var(available_memory); 414 struct task_struct *tsk; 415 416 if (!vm_dirty_bytes || !dirty_background_bytes) 417 available_memory = determine_dirtyable_memory(); 418 419 if (vm_dirty_bytes) 420 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); 421 else 422 dirty = (vm_dirty_ratio * available_memory) / 100; 423 424 if (dirty_background_bytes) 425 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); 426 else 427 background = (dirty_background_ratio * available_memory) / 100; 428 429 if (background >= dirty) 430 background = dirty / 2; 431 tsk = current; 432 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { 433 background += background / 4; 434 dirty += dirty / 4; 435 } 436 *pbackground = background; 437 *pdirty = dirty; 438} 439 440/** 441 * bdi_dirty_limit - @bdi's share of dirty throttling threshold 442 * @bdi: the backing_dev_info to query 443 * @dirty: global dirty limit in pages 444 * 445 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of 446 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. 447 * And the "limit" in the name is not seriously taken as hard limit in 448 * balance_dirty_pages(). 449 * 450 * It allocates high/low dirty limits to fast/slow devices, in order to prevent 451 * - starving fast devices 452 * - piling up dirty pages (that will take long time to sync) on slow devices 453 * 454 * The bdi's share of dirty limit will be adapting to its throughput and 455 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. 456 */ 457unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) 458{ 459 u64 bdi_dirty; 460 long numerator, denominator; 461 462 /* 463 * Calculate this BDI's share of the dirty ratio. 464 */ 465 bdi_writeout_fraction(bdi, &numerator, &denominator); 466 467 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; 468 bdi_dirty *= numerator; 469 do_div(bdi_dirty, denominator); 470 471 bdi_dirty += (dirty * bdi->min_ratio) / 100; 472 if (bdi_dirty > (dirty * bdi->max_ratio) / 100) 473 bdi_dirty = dirty * bdi->max_ratio / 100; 474 475 return bdi_dirty; 476} 477 478/* 479 * balance_dirty_pages() must be called by processes which are generating dirty 480 * data. It looks at the number of dirty pages in the machine and will force 481 * the caller to perform writeback if the system is over `vm_dirty_ratio'. 482 * If we're over `background_thresh' then the writeback threads are woken to 483 * perform some writeout. 484 */ 485static void balance_dirty_pages(struct address_space *mapping, 486 unsigned long write_chunk) 487{ 488 long nr_reclaimable, bdi_nr_reclaimable; 489 long nr_writeback, bdi_nr_writeback; 490 unsigned long background_thresh; 491 unsigned long dirty_thresh; 492 unsigned long bdi_thresh; 493 unsigned long pages_written = 0; 494 unsigned long pause = 1; 495 bool dirty_exceeded = false; 496 struct backing_dev_info *bdi = mapping->backing_dev_info; 497 498 for (;;) { 499 struct writeback_control wbc = { 500 .sync_mode = WB_SYNC_NONE, 501 .older_than_this = NULL, 502 .nr_to_write = write_chunk, 503 .range_cyclic = 1, 504 }; 505 506 nr_reclaimable = global_page_state(NR_FILE_DIRTY) + 507 global_page_state(NR_UNSTABLE_NFS); 508 nr_writeback = global_page_state(NR_WRITEBACK); 509 510 global_dirty_limits(&background_thresh, &dirty_thresh); 511 512 /* 513 * Throttle it only when the background writeback cannot 514 * catch-up. This avoids (excessively) small writeouts 515 * when the bdi limits are ramping up. 516 */ 517 if (nr_reclaimable + nr_writeback <= 518 (background_thresh + dirty_thresh) / 2) 519 break; 520 521 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); 522 bdi_thresh = task_dirty_limit(current, bdi_thresh); 523 524 /* 525 * In order to avoid the stacked BDI deadlock we need 526 * to ensure we accurately count the 'dirty' pages when 527 * the threshold is low. 528 * 529 * Otherwise it would be possible to get thresh+n pages 530 * reported dirty, even though there are thresh-m pages 531 * actually dirty; with m+n sitting in the percpu 532 * deltas. 533 */ 534 if (bdi_thresh < 2*bdi_stat_error(bdi)) { 535 bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); 536 bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); 537 } else { 538 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); 539 bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); 540 } 541 542 /* 543 * The bdi thresh is somehow "soft" limit derived from the 544 * global "hard" limit. The former helps to prevent heavy IO 545 * bdi or process from holding back light ones; The latter is 546 * the last resort safeguard. 547 */ 548 dirty_exceeded = 549 (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh) 550 || (nr_reclaimable + nr_writeback > dirty_thresh); 551 552 if (!dirty_exceeded) 553 break; 554 555 if (!bdi->dirty_exceeded) 556 bdi->dirty_exceeded = 1; 557 558 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. 559 * Unstable writes are a feature of certain networked 560 * filesystems (i.e. NFS) in which data may have been 561 * written to the server's write cache, but has not yet 562 * been flushed to permanent storage. 563 * Only move pages to writeback if this bdi is over its 564 * threshold otherwise wait until the disk writes catch 565 * up. 566 */ 567 trace_wbc_balance_dirty_start(&wbc, bdi); 568 if (bdi_nr_reclaimable > bdi_thresh) { 569 writeback_inodes_wb(&bdi->wb, &wbc); 570 pages_written += write_chunk - wbc.nr_to_write; 571 trace_wbc_balance_dirty_written(&wbc, bdi); 572 if (pages_written >= write_chunk) 573 break; /* We've done our duty */ 574 } 575 trace_wbc_balance_dirty_wait(&wbc, bdi); 576 __set_current_state(TASK_UNINTERRUPTIBLE); 577 io_schedule_timeout(pause); 578 579 /* 580 * Increase the delay for each loop, up to our previous 581 * default of taking a 100ms nap. 582 */ 583 pause <<= 1; 584 if (pause > HZ / 10) 585 pause = HZ / 10; 586 } 587 588 if (!dirty_exceeded && bdi->dirty_exceeded) 589 bdi->dirty_exceeded = 0; 590 591 if (writeback_in_progress(bdi)) 592 return; 593 594 /* 595 * In laptop mode, we wait until hitting the higher threshold before 596 * starting background writeout, and then write out all the way down 597 * to the lower threshold. So slow writers cause minimal disk activity. 598 * 599 * In normal mode, we start background writeout at the lower 600 * background_thresh, to keep the amount of dirty memory low. 601 */ 602 if ((laptop_mode && pages_written) || 603 (!laptop_mode && (nr_reclaimable > background_thresh))) 604 bdi_start_background_writeback(bdi); 605} 606 607void set_page_dirty_balance(struct page *page, int page_mkwrite) 608{ 609 if (set_page_dirty(page) || page_mkwrite) { 610 struct address_space *mapping = page_mapping(page); 611 612 if (mapping) 613 balance_dirty_pages_ratelimited(mapping); 614 } 615} 616 617static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0; 618 619/** 620 * balance_dirty_pages_ratelimited_nr - balance dirty memory state 621 * @mapping: address_space which was dirtied 622 * @nr_pages_dirtied: number of pages which the caller has just dirtied 623 * 624 * Processes which are dirtying memory should call in here once for each page 625 * which was newly dirtied. The function will periodically check the system's 626 * dirty state and will initiate writeback if needed. 627 * 628 * On really big machines, get_writeback_state is expensive, so try to avoid 629 * calling it too often (ratelimiting). But once we're over the dirty memory 630 * limit we decrease the ratelimiting by a lot, to prevent individual processes 631 * from overshooting the limit by (ratelimit_pages) each. 632 */ 633void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, 634 unsigned long nr_pages_dirtied) 635{ 636 unsigned long ratelimit; 637 unsigned long *p; 638 639 ratelimit = ratelimit_pages; 640 if (mapping->backing_dev_info->dirty_exceeded) 641 ratelimit = 8; 642 643 /* 644 * Check the rate limiting. Also, we do not want to throttle real-time 645 * tasks in balance_dirty_pages(). Period. 646 */ 647 preempt_disable(); 648 p = &__get_cpu_var(bdp_ratelimits); 649 *p += nr_pages_dirtied; 650 if (unlikely(*p >= ratelimit)) { 651 ratelimit = sync_writeback_pages(*p); 652 *p = 0; 653 preempt_enable(); 654 balance_dirty_pages(mapping, ratelimit); 655 return; 656 } 657 preempt_enable(); 658} 659EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); 660 661void throttle_vm_writeout(gfp_t gfp_mask) 662{ 663 unsigned long background_thresh; 664 unsigned long dirty_thresh; 665 666 for ( ; ; ) { 667 global_dirty_limits(&background_thresh, &dirty_thresh); 668 669 /* 670 * Boost the allowable dirty threshold a bit for page 671 * allocators so they don't get DoS'ed by heavy writers 672 */ 673 dirty_thresh += dirty_thresh / 10; /* wheeee... */ 674 675 if (global_page_state(NR_UNSTABLE_NFS) + 676 global_page_state(NR_WRITEBACK) <= dirty_thresh) 677 break; 678 congestion_wait(BLK_RW_ASYNC, HZ/10); 679 680 /* 681 * The caller might hold locks which can prevent IO completion 682 * or progress in the filesystem. So we cannot just sit here 683 * waiting for IO to complete. 684 */ 685 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) 686 break; 687 } 688} 689 690/* 691 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs 692 */ 693int dirty_writeback_centisecs_handler(ctl_table *table, int write, 694 void __user *buffer, size_t *length, loff_t *ppos) 695{ 696 proc_dointvec(table, write, buffer, length, ppos); 697 bdi_arm_supers_timer(); 698 return 0; 699} 700 701#ifdef CONFIG_BLOCK 702void laptop_mode_timer_fn(unsigned long data) 703{ 704 struct request_queue *q = (struct request_queue *)data; 705 int nr_pages = global_page_state(NR_FILE_DIRTY) + 706 global_page_state(NR_UNSTABLE_NFS); 707 708 /* 709 * We want to write everything out, not just down to the dirty 710 * threshold 711 */ 712 if (bdi_has_dirty_io(&q->backing_dev_info)) 713 bdi_start_writeback(&q->backing_dev_info, nr_pages); 714} 715 716/* 717 * We've spun up the disk and we're in laptop mode: schedule writeback 718 * of all dirty data a few seconds from now. If the flush is already scheduled 719 * then push it back - the user is still using the disk. 720 */ 721void laptop_io_completion(struct backing_dev_info *info) 722{ 723 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); 724} 725 726/* 727 * We're in laptop mode and we've just synced. The sync's writes will have 728 * caused another writeback to be scheduled by laptop_io_completion. 729 * Nothing needs to be written back anymore, so we unschedule the writeback. 730 */ 731void laptop_sync_completion(void) 732{ 733 struct backing_dev_info *bdi; 734 735 rcu_read_lock(); 736 737 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) 738 del_timer(&bdi->laptop_mode_wb_timer); 739 740 rcu_read_unlock(); 741} 742#endif 743 744/* 745 * If ratelimit_pages is too high then we can get into dirty-data overload 746 * if a large number of processes all perform writes at the same time. 747 * If it is too low then SMP machines will call the (expensive) 748 * get_writeback_state too often. 749 * 750 * Here we set ratelimit_pages to a level which ensures that when all CPUs are 751 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory 752 * thresholds before writeback cuts in. 753 * 754 * But the limit should not be set too high. Because it also controls the 755 * amount of memory which the balance_dirty_pages() caller has to write back. 756 * If this is too large then the caller will block on the IO queue all the 757 * time. So limit it to four megabytes - the balance_dirty_pages() caller 758 * will write six megabyte chunks, max. 759 */ 760 761void writeback_set_ratelimit(void) 762{ 763 ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); 764 if (ratelimit_pages < 16) 765 ratelimit_pages = 16; 766 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) 767 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; 768} 769 770static int __cpuinit 771ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) 772{ 773 writeback_set_ratelimit(); 774 return NOTIFY_DONE; 775} 776 777static struct notifier_block __cpuinitdata ratelimit_nb = { 778 .notifier_call = ratelimit_handler, 779 .next = NULL, 780}; 781 782/* 783 * Called early on to tune the page writeback dirty limits. 784 * 785 * We used to scale dirty pages according to how total memory 786 * related to pages that could be allocated for buffers (by 787 * comparing nr_free_buffer_pages() to vm_total_pages. 788 * 789 * However, that was when we used "dirty_ratio" to scale with 790 * all memory, and we don't do that any more. "dirty_ratio" 791 * is now applied to total non-HIGHPAGE memory (by subtracting 792 * totalhigh_pages from vm_total_pages), and as such we can't 793 * get into the old insane situation any more where we had 794 * large amounts of dirty pages compared to a small amount of 795 * non-HIGHMEM memory. 796 * 797 * But we might still want to scale the dirty_ratio by how 798 * much memory the box has.. 799 */ 800void __init page_writeback_init(void) 801{ 802 int shift; 803 804 writeback_set_ratelimit(); 805 register_cpu_notifier(&ratelimit_nb); 806 807 shift = calc_period_shift(); 808 prop_descriptor_init(&vm_completions, shift); 809 prop_descriptor_init(&vm_dirties, shift); 810} 811 812/** 813 * tag_pages_for_writeback - tag pages to be written by write_cache_pages 814 * @mapping: address space structure to write 815 * @start: starting page index 816 * @end: ending page index (inclusive) 817 * 818 * This function scans the page range from @start to @end (inclusive) and tags 819 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is 820 * that write_cache_pages (or whoever calls this function) will then use 821 * TOWRITE tag to identify pages eligible for writeback. This mechanism is 822 * used to avoid livelocking of writeback by a process steadily creating new 823 * dirty pages in the file (thus it is important for this function to be quick 824 * so that it can tag pages faster than a dirtying process can create them). 825 */ 826/* 827 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. 828 */ 829void tag_pages_for_writeback(struct address_space *mapping, 830 pgoff_t start, pgoff_t end) 831{ 832#define WRITEBACK_TAG_BATCH 4096 833 unsigned long tagged; 834 835 do { 836 spin_lock_irq(&mapping->tree_lock); 837 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, 838 &start, end, WRITEBACK_TAG_BATCH, 839 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); 840 spin_unlock_irq(&mapping->tree_lock); 841 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); 842 cond_resched(); 843 /* We check 'start' to handle wrapping when end == ~0UL */ 844 } while (tagged >= WRITEBACK_TAG_BATCH && start); 845} 846EXPORT_SYMBOL(tag_pages_for_writeback); 847 848/** 849 * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. 850 * @mapping: address space structure to write 851 * @wbc: subtract the number of written pages from *@wbc->nr_to_write 852 * @writepage: function called for each page 853 * @data: data passed to writepage function 854 * 855 * If a page is already under I/O, write_cache_pages() skips it, even 856 * if it's dirty. This is desirable behaviour for memory-cleaning writeback, 857 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() 858 * and msync() need to guarantee that all the data which was dirty at the time 859 * the call was made get new I/O started against them. If wbc->sync_mode is 860 * WB_SYNC_ALL then we were called for data integrity and we must wait for 861 * existing IO to complete. 862 * 863 * To avoid livelocks (when other process dirties new pages), we first tag 864 * pages which should be written back with TOWRITE tag and only then start 865 * writing them. For data-integrity sync we have to be careful so that we do 866 * not miss some pages (e.g., because some other process has cleared TOWRITE 867 * tag we set). The rule we follow is that TOWRITE tag can be cleared only 868 * by the process clearing the DIRTY tag (and submitting the page for IO). 869 */ 870int write_cache_pages(struct address_space *mapping, 871 struct writeback_control *wbc, writepage_t writepage, 872 void *data) 873{ 874 int ret = 0; 875 int done = 0; 876 struct pagevec pvec; 877 int nr_pages; 878 pgoff_t uninitialized_var(writeback_index); 879 pgoff_t index; 880 pgoff_t end; /* Inclusive */ 881 pgoff_t done_index; 882 int cycled; 883 int range_whole = 0; 884 int tag; 885 886 pagevec_init(&pvec, 0); 887 if (wbc->range_cyclic) { 888 writeback_index = mapping->writeback_index; /* prev offset */ 889 index = writeback_index; 890 if (index == 0) 891 cycled = 1; 892 else 893 cycled = 0; 894 end = -1; 895 } else { 896 index = wbc->range_start >> PAGE_CACHE_SHIFT; 897 end = wbc->range_end >> PAGE_CACHE_SHIFT; 898 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) 899 range_whole = 1; 900 cycled = 1; /* ignore range_cyclic tests */ 901 } 902 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) 903 tag = PAGECACHE_TAG_TOWRITE; 904 else 905 tag = PAGECACHE_TAG_DIRTY; 906retry: 907 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) 908 tag_pages_for_writeback(mapping, index, end); 909 done_index = index; 910 while (!done && (index <= end)) { 911 int i; 912 913 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, 914 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); 915 if (nr_pages == 0) 916 break; 917 918 for (i = 0; i < nr_pages; i++) { 919 struct page *page = pvec.pages[i]; 920 921 /* 922 * At this point, the page may be truncated or 923 * invalidated (changing page->mapping to NULL), or 924 * even swizzled back from swapper_space to tmpfs file 925 * mapping. However, page->index will not change 926 * because we have a reference on the page. 927 */ 928 if (page->index > end) { 929 /* 930 * can't be range_cyclic (1st pass) because 931 * end == -1 in that case. 932 */ 933 done = 1; 934 break; 935 } 936 937 done_index = page->index; 938 939 lock_page(page); 940 941 /* 942 * Page truncated or invalidated. We can freely skip it 943 * then, even for data integrity operations: the page 944 * has disappeared concurrently, so there could be no 945 * real expectation of this data interity operation 946 * even if there is now a new, dirty page at the same 947 * pagecache address. 948 */ 949 if (unlikely(page->mapping != mapping)) { 950continue_unlock: 951 unlock_page(page); 952 continue; 953 } 954 955 if (!PageDirty(page)) { 956 /* someone wrote it for us */ 957 goto continue_unlock; 958 } 959 960 if (PageWriteback(page)) { 961 if (wbc->sync_mode != WB_SYNC_NONE) 962 wait_on_page_writeback(page); 963 else 964 goto continue_unlock; 965 } 966 967 BUG_ON(PageWriteback(page)); 968 if (!clear_page_dirty_for_io(page)) 969 goto continue_unlock; 970 971 trace_wbc_writepage(wbc, mapping->backing_dev_info); 972 ret = (*writepage)(page, wbc, data); 973 if (unlikely(ret)) { 974 if (ret == AOP_WRITEPAGE_ACTIVATE) { 975 unlock_page(page); 976 ret = 0; 977 } else { 978 /* 979 * done_index is set past this page, 980 * so media errors will not choke 981 * background writeout for the entire 982 * file. This has consequences for 983 * range_cyclic semantics (ie. it may 984 * not be suitable for data integrity 985 * writeout). 986 */ 987 done_index = page->index + 1; 988 done = 1; 989 break; 990 } 991 } 992 993 /* 994 * We stop writing back only if we are not doing 995 * integrity sync. In case of integrity sync we have to 996 * keep going until we have written all the pages 997 * we tagged for writeback prior to entering this loop. 998 */ 999 if (--wbc->nr_to_write <= 0 && 1000 wbc->sync_mode == WB_SYNC_NONE) { 1001 done = 1; 1002 break; 1003 } 1004 } 1005 pagevec_release(&pvec); 1006 cond_resched(); 1007 } 1008 if (!cycled && !done) { 1009 /* 1010 * range_cyclic: 1011 * We hit the last page and there is more work to be done: wrap 1012 * back to the start of the file 1013 */ 1014 cycled = 1; 1015 index = 0; 1016 end = writeback_index - 1; 1017 goto retry; 1018 } 1019 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) 1020 mapping->writeback_index = done_index; 1021 1022 return ret; 1023} 1024EXPORT_SYMBOL(write_cache_pages); 1025 1026/* 1027 * Function used by generic_writepages to call the real writepage 1028 * function and set the mapping flags on error 1029 */ 1030static int __writepage(struct page *page, struct writeback_control *wbc, 1031 void *data) 1032{ 1033 struct address_space *mapping = data; 1034 int ret = mapping->a_ops->writepage(page, wbc); 1035 mapping_set_error(mapping, ret); 1036 return ret; 1037} 1038 1039/** 1040 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. 1041 * @mapping: address space structure to write 1042 * @wbc: subtract the number of written pages from *@wbc->nr_to_write 1043 * 1044 * This is a library function, which implements the writepages() 1045 * address_space_operation. 1046 */ 1047int generic_writepages(struct address_space *mapping, 1048 struct writeback_control *wbc) 1049{ 1050 struct blk_plug plug; 1051 int ret; 1052 1053 /* deal with chardevs and other special file */ 1054 if (!mapping->a_ops->writepage) 1055 return 0; 1056 1057 blk_start_plug(&plug); 1058 ret = write_cache_pages(mapping, wbc, __writepage, mapping); 1059 blk_finish_plug(&plug); 1060 return ret; 1061} 1062 1063EXPORT_SYMBOL(generic_writepages); 1064 1065int do_writepages(struct address_space *mapping, struct writeback_control *wbc) 1066{ 1067 int ret; 1068 1069 if (wbc->nr_to_write <= 0) 1070 return 0; 1071 if (mapping->a_ops->writepages) 1072 ret = mapping->a_ops->writepages(mapping, wbc); 1073 else 1074 ret = generic_writepages(mapping, wbc); 1075 return ret; 1076} 1077 1078/** 1079 * write_one_page - write out a single page and optionally wait on I/O 1080 * @page: the page to write 1081 * @wait: if true, wait on writeout 1082 * 1083 * The page must be locked by the caller and will be unlocked upon return. 1084 * 1085 * write_one_page() returns a negative error code if I/O failed. 1086 */ 1087int write_one_page(struct page *page, int wait) 1088{ 1089 struct address_space *mapping = page->mapping; 1090 int ret = 0; 1091 struct writeback_control wbc = { 1092 .sync_mode = WB_SYNC_ALL, 1093 .nr_to_write = 1, 1094 }; 1095 1096 BUG_ON(!PageLocked(page)); 1097 1098 if (wait) 1099 wait_on_page_writeback(page); 1100 1101 if (clear_page_dirty_for_io(page)) { 1102 page_cache_get(page); 1103 ret = mapping->a_ops->writepage(page, &wbc); 1104 if (ret == 0 && wait) { 1105 wait_on_page_writeback(page); 1106 if (PageError(page)) 1107 ret = -EIO; 1108 } 1109 page_cache_release(page); 1110 } else { 1111 unlock_page(page); 1112 } 1113 return ret; 1114} 1115EXPORT_SYMBOL(write_one_page); 1116 1117/* 1118 * For address_spaces which do not use buffers nor write back. 1119 */ 1120int __set_page_dirty_no_writeback(struct page *page) 1121{ 1122 if (!PageDirty(page)) 1123 return !TestSetPageDirty(page); 1124 return 0; 1125} 1126 1127/* 1128 * Helper function for set_page_dirty family. 1129 * NOTE: This relies on being atomic wrt interrupts. 1130 */ 1131void account_page_dirtied(struct page *page, struct address_space *mapping) 1132{ 1133 if (mapping_cap_account_dirty(mapping)) { 1134 __inc_zone_page_state(page, NR_FILE_DIRTY); 1135 __inc_zone_page_state(page, NR_DIRTIED); 1136 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); 1137 task_dirty_inc(current); 1138 task_io_account_write(PAGE_CACHE_SIZE); 1139 } 1140} 1141EXPORT_SYMBOL(account_page_dirtied); 1142 1143/* 1144 * Helper function for set_page_writeback family. 1145 * NOTE: Unlike account_page_dirtied this does not rely on being atomic 1146 * wrt interrupts. 1147 */ 1148void account_page_writeback(struct page *page) 1149{ 1150 inc_zone_page_state(page, NR_WRITEBACK); 1151 inc_zone_page_state(page, NR_WRITTEN); 1152} 1153EXPORT_SYMBOL(account_page_writeback); 1154 1155/* 1156 * For address_spaces which do not use buffers. Just tag the page as dirty in 1157 * its radix tree. 1158 * 1159 * This is also used when a single buffer is being dirtied: we want to set the 1160 * page dirty in that case, but not all the buffers. This is a "bottom-up" 1161 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. 1162 * 1163 * Most callers have locked the page, which pins the address_space in memory. 1164 * But zap_pte_range() does not lock the page, however in that case the 1165 * mapping is pinned by the vma's ->vm_file reference. 1166 * 1167 * We take care to handle the case where the page was truncated from the 1168 * mapping by re-checking page_mapping() inside tree_lock. 1169 */ 1170int __set_page_dirty_nobuffers(struct page *page) 1171{ 1172 if (!TestSetPageDirty(page)) { 1173 struct address_space *mapping = page_mapping(page); 1174 struct address_space *mapping2; 1175 1176 if (!mapping) 1177 return 1; 1178 1179 spin_lock_irq(&mapping->tree_lock); 1180 mapping2 = page_mapping(page); 1181 if (mapping2) { /* Race with truncate? */ 1182 BUG_ON(mapping2 != mapping); 1183 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); 1184 account_page_dirtied(page, mapping); 1185 radix_tree_tag_set(&mapping->page_tree, 1186 page_index(page), PAGECACHE_TAG_DIRTY); 1187 } 1188 spin_unlock_irq(&mapping->tree_lock); 1189 if (mapping->host) { 1190 /* !PageAnon && !swapper_space */ 1191 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 1192 } 1193 return 1; 1194 } 1195 return 0; 1196} 1197EXPORT_SYMBOL(__set_page_dirty_nobuffers); 1198 1199/* 1200 * When a writepage implementation decides that it doesn't want to write this 1201 * page for some reason, it should redirty the locked page via 1202 * redirty_page_for_writepage() and it should then unlock the page and return 0 1203 */ 1204int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) 1205{ 1206 wbc->pages_skipped++; 1207 return __set_page_dirty_nobuffers(page); 1208} 1209EXPORT_SYMBOL(redirty_page_for_writepage); 1210 1211/* 1212 * Dirty a page. 1213 * 1214 * For pages with a mapping this should be done under the page lock 1215 * for the benefit of asynchronous memory errors who prefer a consistent 1216 * dirty state. This rule can be broken in some special cases, 1217 * but should be better not to. 1218 * 1219 * If the mapping doesn't provide a set_page_dirty a_op, then 1220 * just fall through and assume that it wants buffer_heads. 1221 */ 1222int set_page_dirty(struct page *page) 1223{ 1224 struct address_space *mapping = page_mapping(page); 1225 1226 if (likely(mapping)) { 1227 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; 1228 /* 1229 * readahead/lru_deactivate_page could remain 1230 * PG_readahead/PG_reclaim due to race with end_page_writeback 1231 * About readahead, if the page is written, the flags would be 1232 * reset. So no problem. 1233 * About lru_deactivate_page, if the page is redirty, the flag 1234 * will be reset. So no problem. but if the page is used by readahead 1235 * it will confuse readahead and make it restart the size rampup 1236 * process. But it's a trivial problem. 1237 */ 1238 ClearPageReclaim(page); 1239#ifdef CONFIG_BLOCK 1240 if (!spd) 1241 spd = __set_page_dirty_buffers; 1242#endif 1243 return (*spd)(page); 1244 } 1245 if (!PageDirty(page)) { 1246 if (!TestSetPageDirty(page)) 1247 return 1; 1248 } 1249 return 0; 1250} 1251EXPORT_SYMBOL(set_page_dirty); 1252 1253/* 1254 * set_page_dirty() is racy if the caller has no reference against 1255 * page->mapping->host, and if the page is unlocked. This is because another 1256 * CPU could truncate the page off the mapping and then free the mapping. 1257 * 1258 * Usually, the page _is_ locked, or the caller is a user-space process which 1259 * holds a reference on the inode by having an open file. 1260 * 1261 * In other cases, the page should be locked before running set_page_dirty(). 1262 */ 1263int set_page_dirty_lock(struct page *page) 1264{ 1265 int ret; 1266 1267 lock_page(page); 1268 ret = set_page_dirty(page); 1269 unlock_page(page); 1270 return ret; 1271} 1272EXPORT_SYMBOL(set_page_dirty_lock); 1273 1274/* 1275 * Clear a page's dirty flag, while caring for dirty memory accounting. 1276 * Returns true if the page was previously dirty. 1277 * 1278 * This is for preparing to put the page under writeout. We leave the page 1279 * tagged as dirty in the radix tree so that a concurrent write-for-sync 1280 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage 1281 * implementation will run either set_page_writeback() or set_page_dirty(), 1282 * at which stage we bring the page's dirty flag and radix-tree dirty tag 1283 * back into sync. 1284 * 1285 * This incoherency between the page's dirty flag and radix-tree tag is 1286 * unfortunate, but it only exists while the page is locked. 1287 */ 1288int clear_page_dirty_for_io(struct page *page) 1289{ 1290 struct address_space *mapping = page_mapping(page); 1291 1292 BUG_ON(!PageLocked(page)); 1293 1294 if (mapping && mapping_cap_account_dirty(mapping)) { 1295 /* 1296 * Yes, Virginia, this is indeed insane. 1297 * 1298 * We use this sequence to make sure that 1299 * (a) we account for dirty stats properly 1300 * (b) we tell the low-level filesystem to 1301 * mark the whole page dirty if it was 1302 * dirty in a pagetable. Only to then 1303 * (c) clean the page again and return 1 to 1304 * cause the writeback. 1305 * 1306 * This way we avoid all nasty races with the 1307 * dirty bit in multiple places and clearing 1308 * them concurrently from different threads. 1309 * 1310 * Note! Normally the "set_page_dirty(page)" 1311 * has no effect on the actual dirty bit - since 1312 * that will already usually be set. But we 1313 * need the side effects, and it can help us 1314 * avoid races. 1315 * 1316 * We basically use the page "master dirty bit" 1317 * as a serialization point for all the different 1318 * threads doing their things. 1319 */ 1320 if (page_mkclean(page)) 1321 set_page_dirty(page); 1322 /* 1323 * We carefully synchronise fault handlers against 1324 * installing a dirty pte and marking the page dirty 1325 * at this point. We do this by having them hold the 1326 * page lock at some point after installing their 1327 * pte, but before marking the page dirty. 1328 * Pages are always locked coming in here, so we get 1329 * the desired exclusion. See mm/memory.c:do_wp_page() 1330 * for more comments. 1331 */ 1332 if (TestClearPageDirty(page)) { 1333 dec_zone_page_state(page, NR_FILE_DIRTY); 1334 dec_bdi_stat(mapping->backing_dev_info, 1335 BDI_RECLAIMABLE); 1336 return 1; 1337 } 1338 return 0; 1339 } 1340 return TestClearPageDirty(page); 1341} 1342EXPORT_SYMBOL(clear_page_dirty_for_io); 1343 1344int test_clear_page_writeback(struct page *page) 1345{ 1346 struct address_space *mapping = page_mapping(page); 1347 int ret; 1348 1349 if (mapping) { 1350 struct backing_dev_info *bdi = mapping->backing_dev_info; 1351 unsigned long flags; 1352 1353 spin_lock_irqsave(&mapping->tree_lock, flags); 1354 ret = TestClearPageWriteback(page); 1355 if (ret) { 1356 radix_tree_tag_clear(&mapping->page_tree, 1357 page_index(page), 1358 PAGECACHE_TAG_WRITEBACK); 1359 if (bdi_cap_account_writeback(bdi)) { 1360 __dec_bdi_stat(bdi, BDI_WRITEBACK); 1361 __bdi_writeout_inc(bdi); 1362 } 1363 } 1364 spin_unlock_irqrestore(&mapping->tree_lock, flags); 1365 } else { 1366 ret = TestClearPageWriteback(page); 1367 } 1368 if (ret) 1369 dec_zone_page_state(page, NR_WRITEBACK); 1370 return ret; 1371} 1372 1373int test_set_page_writeback(struct page *page) 1374{ 1375 struct address_space *mapping = page_mapping(page); 1376 int ret; 1377 1378 if (mapping) { 1379 struct backing_dev_info *bdi = mapping->backing_dev_info; 1380 unsigned long flags; 1381 1382 spin_lock_irqsave(&mapping->tree_lock, flags); 1383 ret = TestSetPageWriteback(page); 1384 if (!ret) { 1385 radix_tree_tag_set(&mapping->page_tree, 1386 page_index(page), 1387 PAGECACHE_TAG_WRITEBACK); 1388 if (bdi_cap_account_writeback(bdi)) 1389 __inc_bdi_stat(bdi, BDI_WRITEBACK); 1390 } 1391 if (!PageDirty(page)) 1392 radix_tree_tag_clear(&mapping->page_tree, 1393 page_index(page), 1394 PAGECACHE_TAG_DIRTY); 1395 radix_tree_tag_clear(&mapping->page_tree, 1396 page_index(page), 1397 PAGECACHE_TAG_TOWRITE); 1398 spin_unlock_irqrestore(&mapping->tree_lock, flags); 1399 } else { 1400 ret = TestSetPageWriteback(page); 1401 } 1402 if (!ret) 1403 account_page_writeback(page); 1404 return ret; 1405 1406} 1407EXPORT_SYMBOL(test_set_page_writeback); 1408 1409/* 1410 * Return true if any of the pages in the mapping are marked with the 1411 * passed tag. 1412 */ 1413int mapping_tagged(struct address_space *mapping, int tag) 1414{ 1415 int ret; 1416 rcu_read_lock(); 1417 ret = radix_tree_tagged(&mapping->page_tree, tag); 1418 rcu_read_unlock(); 1419 return ret; 1420} 1421EXPORT_SYMBOL(mapping_tagged); 1422