Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
[linux-2.6.git] / mm / page-writeback.c
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  */
43 static 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  */
51 static 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  */
64 int 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  */
70 unsigned 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  */
76 int vm_highmem_is_dirtyable;
77
78 /*
79  * The generator of dirty data starts writeback at this percentage
80  */
81 int 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  */
87 unsigned long vm_dirty_bytes;
88
89 /*
90  * The interval between `kupdate'-style writebacks
91  */
92 unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
93
94 /*
95  * The longest time for which data is allowed to remain dirty
96  */
97 unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
98
99 /*
100  * Flag that makes the machine dump writes/reads and block dirtyings.
101  */
102 int 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  */
108 int laptop_mode;
109
110 EXPORT_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  */
131 static struct prop_descriptor vm_completions;
132 static 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  */
139 static 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  */
154 static 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
161 int 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
173 int 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
185 int 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
201 int 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  */
220 static 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
226 void 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 }
234 EXPORT_SYMBOL_GPL(bdi_writeout_inc);
235
236 void 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  */
244 static 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
256 static 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  */
277 static 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  */
296 static unsigned int bdi_min_ratio;
297
298 int 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
319 int 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 }
337 EXPORT_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
357 static 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  */
388 unsigned 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  */
409 void 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  *
443  * Allocate high/low dirty limits to fast/slow devices, in order to prevent
444  * - starving fast devices
445  * - piling up dirty pages (that will take long time to sync) on slow devices
446  *
447  * The bdi's share of dirty limit will be adapting to its throughput and
448  * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
449  */
450 unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
451 {
452         u64 bdi_dirty;
453         long numerator, denominator;
454
455         /*
456          * Calculate this BDI's share of the dirty ratio.
457          */
458         bdi_writeout_fraction(bdi, &numerator, &denominator);
459
460         bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
461         bdi_dirty *= numerator;
462         do_div(bdi_dirty, denominator);
463
464         bdi_dirty += (dirty * bdi->min_ratio) / 100;
465         if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
466                 bdi_dirty = dirty * bdi->max_ratio / 100;
467
468         return bdi_dirty;
469 }
470
471 /*
472  * balance_dirty_pages() must be called by processes which are generating dirty
473  * data.  It looks at the number of dirty pages in the machine and will force
474  * the caller to perform writeback if the system is over `vm_dirty_ratio'.
475  * If we're over `background_thresh' then the writeback threads are woken to
476  * perform some writeout.
477  */
478 static void balance_dirty_pages(struct address_space *mapping,
479                                 unsigned long write_chunk)
480 {
481         long nr_reclaimable, bdi_nr_reclaimable;
482         long nr_writeback, bdi_nr_writeback;
483         unsigned long background_thresh;
484         unsigned long dirty_thresh;
485         unsigned long bdi_thresh;
486         unsigned long pages_written = 0;
487         unsigned long pause = 1;
488         bool dirty_exceeded = false;
489         struct backing_dev_info *bdi = mapping->backing_dev_info;
490
491         for (;;) {
492                 struct writeback_control wbc = {
493                         .sync_mode      = WB_SYNC_NONE,
494                         .older_than_this = NULL,
495                         .nr_to_write    = write_chunk,
496                         .range_cyclic   = 1,
497                 };
498
499                 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
500                                         global_page_state(NR_UNSTABLE_NFS);
501                 nr_writeback = global_page_state(NR_WRITEBACK);
502
503                 global_dirty_limits(&background_thresh, &dirty_thresh);
504
505                 /*
506                  * Throttle it only when the background writeback cannot
507                  * catch-up. This avoids (excessively) small writeouts
508                  * when the bdi limits are ramping up.
509                  */
510                 if (nr_reclaimable + nr_writeback <=
511                                 (background_thresh + dirty_thresh) / 2)
512                         break;
513
514                 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
515                 bdi_thresh = task_dirty_limit(current, bdi_thresh);
516
517                 /*
518                  * In order to avoid the stacked BDI deadlock we need
519                  * to ensure we accurately count the 'dirty' pages when
520                  * the threshold is low.
521                  *
522                  * Otherwise it would be possible to get thresh+n pages
523                  * reported dirty, even though there are thresh-m pages
524                  * actually dirty; with m+n sitting in the percpu
525                  * deltas.
526                  */
527                 if (bdi_thresh < 2*bdi_stat_error(bdi)) {
528                         bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
529                         bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
530                 } else {
531                         bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
532                         bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
533                 }
534
535                 /*
536                  * The bdi thresh is somehow "soft" limit derived from the
537                  * global "hard" limit. The former helps to prevent heavy IO
538                  * bdi or process from holding back light ones; The latter is
539                  * the last resort safeguard.
540                  */
541                 dirty_exceeded =
542                         (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
543                         || (nr_reclaimable + nr_writeback > dirty_thresh);
544
545                 if (!dirty_exceeded)
546                         break;
547
548                 if (!bdi->dirty_exceeded)
549                         bdi->dirty_exceeded = 1;
550
551                 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
552                  * Unstable writes are a feature of certain networked
553                  * filesystems (i.e. NFS) in which data may have been
554                  * written to the server's write cache, but has not yet
555                  * been flushed to permanent storage.
556                  * Only move pages to writeback if this bdi is over its
557                  * threshold otherwise wait until the disk writes catch
558                  * up.
559                  */
560                 trace_wbc_balance_dirty_start(&wbc, bdi);
561                 if (bdi_nr_reclaimable > bdi_thresh) {
562                         writeback_inodes_wb(&bdi->wb, &wbc);
563                         pages_written += write_chunk - wbc.nr_to_write;
564                         trace_wbc_balance_dirty_written(&wbc, bdi);
565                         if (pages_written >= write_chunk)
566                                 break;          /* We've done our duty */
567                 }
568                 trace_wbc_balance_dirty_wait(&wbc, bdi);
569                 __set_current_state(TASK_UNINTERRUPTIBLE);
570                 io_schedule_timeout(pause);
571
572                 /*
573                  * Increase the delay for each loop, up to our previous
574                  * default of taking a 100ms nap.
575                  */
576                 pause <<= 1;
577                 if (pause > HZ / 10)
578                         pause = HZ / 10;
579         }
580
581         if (!dirty_exceeded && bdi->dirty_exceeded)
582                 bdi->dirty_exceeded = 0;
583
584         if (writeback_in_progress(bdi))
585                 return;
586
587         /*
588          * In laptop mode, we wait until hitting the higher threshold before
589          * starting background writeout, and then write out all the way down
590          * to the lower threshold.  So slow writers cause minimal disk activity.
591          *
592          * In normal mode, we start background writeout at the lower
593          * background_thresh, to keep the amount of dirty memory low.
594          */
595         if ((laptop_mode && pages_written) ||
596             (!laptop_mode && (nr_reclaimable > background_thresh)))
597                 bdi_start_background_writeback(bdi);
598 }
599
600 void set_page_dirty_balance(struct page *page, int page_mkwrite)
601 {
602         if (set_page_dirty(page) || page_mkwrite) {
603                 struct address_space *mapping = page_mapping(page);
604
605                 if (mapping)
606                         balance_dirty_pages_ratelimited(mapping);
607         }
608 }
609
610 static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
611
612 /**
613  * balance_dirty_pages_ratelimited_nr - balance dirty memory state
614  * @mapping: address_space which was dirtied
615  * @nr_pages_dirtied: number of pages which the caller has just dirtied
616  *
617  * Processes which are dirtying memory should call in here once for each page
618  * which was newly dirtied.  The function will periodically check the system's
619  * dirty state and will initiate writeback if needed.
620  *
621  * On really big machines, get_writeback_state is expensive, so try to avoid
622  * calling it too often (ratelimiting).  But once we're over the dirty memory
623  * limit we decrease the ratelimiting by a lot, to prevent individual processes
624  * from overshooting the limit by (ratelimit_pages) each.
625  */
626 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
627                                         unsigned long nr_pages_dirtied)
628 {
629         unsigned long ratelimit;
630         unsigned long *p;
631
632         ratelimit = ratelimit_pages;
633         if (mapping->backing_dev_info->dirty_exceeded)
634                 ratelimit = 8;
635
636         /*
637          * Check the rate limiting. Also, we do not want to throttle real-time
638          * tasks in balance_dirty_pages(). Period.
639          */
640         preempt_disable();
641         p =  &__get_cpu_var(bdp_ratelimits);
642         *p += nr_pages_dirtied;
643         if (unlikely(*p >= ratelimit)) {
644                 ratelimit = sync_writeback_pages(*p);
645                 *p = 0;
646                 preempt_enable();
647                 balance_dirty_pages(mapping, ratelimit);
648                 return;
649         }
650         preempt_enable();
651 }
652 EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
653
654 void throttle_vm_writeout(gfp_t gfp_mask)
655 {
656         unsigned long background_thresh;
657         unsigned long dirty_thresh;
658
659         for ( ; ; ) {
660                 global_dirty_limits(&background_thresh, &dirty_thresh);
661
662                 /*
663                  * Boost the allowable dirty threshold a bit for page
664                  * allocators so they don't get DoS'ed by heavy writers
665                  */
666                 dirty_thresh += dirty_thresh / 10;      /* wheeee... */
667
668                 if (global_page_state(NR_UNSTABLE_NFS) +
669                         global_page_state(NR_WRITEBACK) <= dirty_thresh)
670                                 break;
671                 congestion_wait(BLK_RW_ASYNC, HZ/10);
672
673                 /*
674                  * The caller might hold locks which can prevent IO completion
675                  * or progress in the filesystem.  So we cannot just sit here
676                  * waiting for IO to complete.
677                  */
678                 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
679                         break;
680         }
681 }
682
683 /*
684  * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
685  */
686 int dirty_writeback_centisecs_handler(ctl_table *table, int write,
687         void __user *buffer, size_t *length, loff_t *ppos)
688 {
689         proc_dointvec(table, write, buffer, length, ppos);
690         bdi_arm_supers_timer();
691         return 0;
692 }
693
694 #ifdef CONFIG_BLOCK
695 void laptop_mode_timer_fn(unsigned long data)
696 {
697         struct request_queue *q = (struct request_queue *)data;
698         int nr_pages = global_page_state(NR_FILE_DIRTY) +
699                 global_page_state(NR_UNSTABLE_NFS);
700
701         /*
702          * We want to write everything out, not just down to the dirty
703          * threshold
704          */
705         if (bdi_has_dirty_io(&q->backing_dev_info))
706                 bdi_start_writeback(&q->backing_dev_info, nr_pages);
707 }
708
709 /*
710  * We've spun up the disk and we're in laptop mode: schedule writeback
711  * of all dirty data a few seconds from now.  If the flush is already scheduled
712  * then push it back - the user is still using the disk.
713  */
714 void laptop_io_completion(struct backing_dev_info *info)
715 {
716         mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
717 }
718
719 /*
720  * We're in laptop mode and we've just synced. The sync's writes will have
721  * caused another writeback to be scheduled by laptop_io_completion.
722  * Nothing needs to be written back anymore, so we unschedule the writeback.
723  */
724 void laptop_sync_completion(void)
725 {
726         struct backing_dev_info *bdi;
727
728         rcu_read_lock();
729
730         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
731                 del_timer(&bdi->laptop_mode_wb_timer);
732
733         rcu_read_unlock();
734 }
735 #endif
736
737 /*
738  * If ratelimit_pages is too high then we can get into dirty-data overload
739  * if a large number of processes all perform writes at the same time.
740  * If it is too low then SMP machines will call the (expensive)
741  * get_writeback_state too often.
742  *
743  * Here we set ratelimit_pages to a level which ensures that when all CPUs are
744  * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
745  * thresholds before writeback cuts in.
746  *
747  * But the limit should not be set too high.  Because it also controls the
748  * amount of memory which the balance_dirty_pages() caller has to write back.
749  * If this is too large then the caller will block on the IO queue all the
750  * time.  So limit it to four megabytes - the balance_dirty_pages() caller
751  * will write six megabyte chunks, max.
752  */
753
754 void writeback_set_ratelimit(void)
755 {
756         ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
757         if (ratelimit_pages < 16)
758                 ratelimit_pages = 16;
759         if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
760                 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
761 }
762
763 static int __cpuinit
764 ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
765 {
766         writeback_set_ratelimit();
767         return NOTIFY_DONE;
768 }
769
770 static struct notifier_block __cpuinitdata ratelimit_nb = {
771         .notifier_call  = ratelimit_handler,
772         .next           = NULL,
773 };
774
775 /*
776  * Called early on to tune the page writeback dirty limits.
777  *
778  * We used to scale dirty pages according to how total memory
779  * related to pages that could be allocated for buffers (by
780  * comparing nr_free_buffer_pages() to vm_total_pages.
781  *
782  * However, that was when we used "dirty_ratio" to scale with
783  * all memory, and we don't do that any more. "dirty_ratio"
784  * is now applied to total non-HIGHPAGE memory (by subtracting
785  * totalhigh_pages from vm_total_pages), and as such we can't
786  * get into the old insane situation any more where we had
787  * large amounts of dirty pages compared to a small amount of
788  * non-HIGHMEM memory.
789  *
790  * But we might still want to scale the dirty_ratio by how
791  * much memory the box has..
792  */
793 void __init page_writeback_init(void)
794 {
795         int shift;
796
797         writeback_set_ratelimit();
798         register_cpu_notifier(&ratelimit_nb);
799
800         shift = calc_period_shift();
801         prop_descriptor_init(&vm_completions, shift);
802         prop_descriptor_init(&vm_dirties, shift);
803 }
804
805 /**
806  * tag_pages_for_writeback - tag pages to be written by write_cache_pages
807  * @mapping: address space structure to write
808  * @start: starting page index
809  * @end: ending page index (inclusive)
810  *
811  * This function scans the page range from @start to @end (inclusive) and tags
812  * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
813  * that write_cache_pages (or whoever calls this function) will then use
814  * TOWRITE tag to identify pages eligible for writeback.  This mechanism is
815  * used to avoid livelocking of writeback by a process steadily creating new
816  * dirty pages in the file (thus it is important for this function to be quick
817  * so that it can tag pages faster than a dirtying process can create them).
818  */
819 /*
820  * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
821  */
822 void tag_pages_for_writeback(struct address_space *mapping,
823                              pgoff_t start, pgoff_t end)
824 {
825 #define WRITEBACK_TAG_BATCH 4096
826         unsigned long tagged;
827
828         do {
829                 spin_lock_irq(&mapping->tree_lock);
830                 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
831                                 &start, end, WRITEBACK_TAG_BATCH,
832                                 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
833                 spin_unlock_irq(&mapping->tree_lock);
834                 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
835                 cond_resched();
836                 /* We check 'start' to handle wrapping when end == ~0UL */
837         } while (tagged >= WRITEBACK_TAG_BATCH && start);
838 }
839 EXPORT_SYMBOL(tag_pages_for_writeback);
840
841 /**
842  * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
843  * @mapping: address space structure to write
844  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
845  * @writepage: function called for each page
846  * @data: data passed to writepage function
847  *
848  * If a page is already under I/O, write_cache_pages() skips it, even
849  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
850  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
851  * and msync() need to guarantee that all the data which was dirty at the time
852  * the call was made get new I/O started against them.  If wbc->sync_mode is
853  * WB_SYNC_ALL then we were called for data integrity and we must wait for
854  * existing IO to complete.
855  *
856  * To avoid livelocks (when other process dirties new pages), we first tag
857  * pages which should be written back with TOWRITE tag and only then start
858  * writing them. For data-integrity sync we have to be careful so that we do
859  * not miss some pages (e.g., because some other process has cleared TOWRITE
860  * tag we set). The rule we follow is that TOWRITE tag can be cleared only
861  * by the process clearing the DIRTY tag (and submitting the page for IO).
862  */
863 int write_cache_pages(struct address_space *mapping,
864                       struct writeback_control *wbc, writepage_t writepage,
865                       void *data)
866 {
867         int ret = 0;
868         int done = 0;
869         struct pagevec pvec;
870         int nr_pages;
871         pgoff_t uninitialized_var(writeback_index);
872         pgoff_t index;
873         pgoff_t end;            /* Inclusive */
874         pgoff_t done_index;
875         int cycled;
876         int range_whole = 0;
877         int tag;
878
879         pagevec_init(&pvec, 0);
880         if (wbc->range_cyclic) {
881                 writeback_index = mapping->writeback_index; /* prev offset */
882                 index = writeback_index;
883                 if (index == 0)
884                         cycled = 1;
885                 else
886                         cycled = 0;
887                 end = -1;
888         } else {
889                 index = wbc->range_start >> PAGE_CACHE_SHIFT;
890                 end = wbc->range_end >> PAGE_CACHE_SHIFT;
891                 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
892                         range_whole = 1;
893                 cycled = 1; /* ignore range_cyclic tests */
894         }
895         if (wbc->sync_mode == WB_SYNC_ALL)
896                 tag = PAGECACHE_TAG_TOWRITE;
897         else
898                 tag = PAGECACHE_TAG_DIRTY;
899 retry:
900         if (wbc->sync_mode == WB_SYNC_ALL)
901                 tag_pages_for_writeback(mapping, index, end);
902         done_index = index;
903         while (!done && (index <= end)) {
904                 int i;
905
906                 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
907                               min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
908                 if (nr_pages == 0)
909                         break;
910
911                 for (i = 0; i < nr_pages; i++) {
912                         struct page *page = pvec.pages[i];
913
914                         /*
915                          * At this point, the page may be truncated or
916                          * invalidated (changing page->mapping to NULL), or
917                          * even swizzled back from swapper_space to tmpfs file
918                          * mapping. However, page->index will not change
919                          * because we have a reference on the page.
920                          */
921                         if (page->index > end) {
922                                 /*
923                                  * can't be range_cyclic (1st pass) because
924                                  * end == -1 in that case.
925                                  */
926                                 done = 1;
927                                 break;
928                         }
929
930                         done_index = page->index;
931
932                         lock_page(page);
933
934                         /*
935                          * Page truncated or invalidated. We can freely skip it
936                          * then, even for data integrity operations: the page
937                          * has disappeared concurrently, so there could be no
938                          * real expectation of this data interity operation
939                          * even if there is now a new, dirty page at the same
940                          * pagecache address.
941                          */
942                         if (unlikely(page->mapping != mapping)) {
943 continue_unlock:
944                                 unlock_page(page);
945                                 continue;
946                         }
947
948                         if (!PageDirty(page)) {
949                                 /* someone wrote it for us */
950                                 goto continue_unlock;
951                         }
952
953                         if (PageWriteback(page)) {
954                                 if (wbc->sync_mode != WB_SYNC_NONE)
955                                         wait_on_page_writeback(page);
956                                 else
957                                         goto continue_unlock;
958                         }
959
960                         BUG_ON(PageWriteback(page));
961                         if (!clear_page_dirty_for_io(page))
962                                 goto continue_unlock;
963
964                         trace_wbc_writepage(wbc, mapping->backing_dev_info);
965                         ret = (*writepage)(page, wbc, data);
966                         if (unlikely(ret)) {
967                                 if (ret == AOP_WRITEPAGE_ACTIVATE) {
968                                         unlock_page(page);
969                                         ret = 0;
970                                 } else {
971                                         /*
972                                          * done_index is set past this page,
973                                          * so media errors will not choke
974                                          * background writeout for the entire
975                                          * file. This has consequences for
976                                          * range_cyclic semantics (ie. it may
977                                          * not be suitable for data integrity
978                                          * writeout).
979                                          */
980                                         done_index = page->index + 1;
981                                         done = 1;
982                                         break;
983                                 }
984                         }
985
986                         /*
987                          * We stop writing back only if we are not doing
988                          * integrity sync. In case of integrity sync we have to
989                          * keep going until we have written all the pages
990                          * we tagged for writeback prior to entering this loop.
991                          */
992                         if (--wbc->nr_to_write <= 0 &&
993                             wbc->sync_mode == WB_SYNC_NONE) {
994                                 done = 1;
995                                 break;
996                         }
997                 }
998                 pagevec_release(&pvec);
999                 cond_resched();
1000         }
1001         if (!cycled && !done) {
1002                 /*
1003                  * range_cyclic:
1004                  * We hit the last page and there is more work to be done: wrap
1005                  * back to the start of the file
1006                  */
1007                 cycled = 1;
1008                 index = 0;
1009                 end = writeback_index - 1;
1010                 goto retry;
1011         }
1012         if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
1013                 mapping->writeback_index = done_index;
1014
1015         return ret;
1016 }
1017 EXPORT_SYMBOL(write_cache_pages);
1018
1019 /*
1020  * Function used by generic_writepages to call the real writepage
1021  * function and set the mapping flags on error
1022  */
1023 static int __writepage(struct page *page, struct writeback_control *wbc,
1024                        void *data)
1025 {
1026         struct address_space *mapping = data;
1027         int ret = mapping->a_ops->writepage(page, wbc);
1028         mapping_set_error(mapping, ret);
1029         return ret;
1030 }
1031
1032 /**
1033  * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
1034  * @mapping: address space structure to write
1035  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
1036  *
1037  * This is a library function, which implements the writepages()
1038  * address_space_operation.
1039  */
1040 int generic_writepages(struct address_space *mapping,
1041                        struct writeback_control *wbc)
1042 {
1043         struct blk_plug plug;
1044         int ret;
1045
1046         /* deal with chardevs and other special file */
1047         if (!mapping->a_ops->writepage)
1048                 return 0;
1049
1050         blk_start_plug(&plug);
1051         ret = write_cache_pages(mapping, wbc, __writepage, mapping);
1052         blk_finish_plug(&plug);
1053         return ret;
1054 }
1055
1056 EXPORT_SYMBOL(generic_writepages);
1057
1058 int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1059 {
1060         int ret;
1061
1062         if (wbc->nr_to_write <= 0)
1063                 return 0;
1064         if (mapping->a_ops->writepages)
1065                 ret = mapping->a_ops->writepages(mapping, wbc);
1066         else
1067                 ret = generic_writepages(mapping, wbc);
1068         return ret;
1069 }
1070
1071 /**
1072  * write_one_page - write out a single page and optionally wait on I/O
1073  * @page: the page to write
1074  * @wait: if true, wait on writeout
1075  *
1076  * The page must be locked by the caller and will be unlocked upon return.
1077  *
1078  * write_one_page() returns a negative error code if I/O failed.
1079  */
1080 int write_one_page(struct page *page, int wait)
1081 {
1082         struct address_space *mapping = page->mapping;
1083         int ret = 0;
1084         struct writeback_control wbc = {
1085                 .sync_mode = WB_SYNC_ALL,
1086                 .nr_to_write = 1,
1087         };
1088
1089         BUG_ON(!PageLocked(page));
1090
1091         if (wait)
1092                 wait_on_page_writeback(page);
1093
1094         if (clear_page_dirty_for_io(page)) {
1095                 page_cache_get(page);
1096                 ret = mapping->a_ops->writepage(page, &wbc);
1097                 if (ret == 0 && wait) {
1098                         wait_on_page_writeback(page);
1099                         if (PageError(page))
1100                                 ret = -EIO;
1101                 }
1102                 page_cache_release(page);
1103         } else {
1104                 unlock_page(page);
1105         }
1106         return ret;
1107 }
1108 EXPORT_SYMBOL(write_one_page);
1109
1110 /*
1111  * For address_spaces which do not use buffers nor write back.
1112  */
1113 int __set_page_dirty_no_writeback(struct page *page)
1114 {
1115         if (!PageDirty(page))
1116                 return !TestSetPageDirty(page);
1117         return 0;
1118 }
1119
1120 /*
1121  * Helper function for set_page_dirty family.
1122  * NOTE: This relies on being atomic wrt interrupts.
1123  */
1124 void account_page_dirtied(struct page *page, struct address_space *mapping)
1125 {
1126         if (mapping_cap_account_dirty(mapping)) {
1127                 __inc_zone_page_state(page, NR_FILE_DIRTY);
1128                 __inc_zone_page_state(page, NR_DIRTIED);
1129                 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
1130                 task_dirty_inc(current);
1131                 task_io_account_write(PAGE_CACHE_SIZE);
1132         }
1133 }
1134 EXPORT_SYMBOL(account_page_dirtied);
1135
1136 /*
1137  * Helper function for set_page_writeback family.
1138  * NOTE: Unlike account_page_dirtied this does not rely on being atomic
1139  * wrt interrupts.
1140  */
1141 void account_page_writeback(struct page *page)
1142 {
1143         inc_zone_page_state(page, NR_WRITEBACK);
1144         inc_zone_page_state(page, NR_WRITTEN);
1145 }
1146 EXPORT_SYMBOL(account_page_writeback);
1147
1148 /*
1149  * For address_spaces which do not use buffers.  Just tag the page as dirty in
1150  * its radix tree.
1151  *
1152  * This is also used when a single buffer is being dirtied: we want to set the
1153  * page dirty in that case, but not all the buffers.  This is a "bottom-up"
1154  * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
1155  *
1156  * Most callers have locked the page, which pins the address_space in memory.
1157  * But zap_pte_range() does not lock the page, however in that case the
1158  * mapping is pinned by the vma's ->vm_file reference.
1159  *
1160  * We take care to handle the case where the page was truncated from the
1161  * mapping by re-checking page_mapping() inside tree_lock.
1162  */
1163 int __set_page_dirty_nobuffers(struct page *page)
1164 {
1165         if (!TestSetPageDirty(page)) {
1166                 struct address_space *mapping = page_mapping(page);
1167                 struct address_space *mapping2;
1168
1169                 if (!mapping)
1170                         return 1;
1171
1172                 spin_lock_irq(&mapping->tree_lock);
1173                 mapping2 = page_mapping(page);
1174                 if (mapping2) { /* Race with truncate? */
1175                         BUG_ON(mapping2 != mapping);
1176                         WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
1177                         account_page_dirtied(page, mapping);
1178                         radix_tree_tag_set(&mapping->page_tree,
1179                                 page_index(page), PAGECACHE_TAG_DIRTY);
1180                 }
1181                 spin_unlock_irq(&mapping->tree_lock);
1182                 if (mapping->host) {
1183                         /* !PageAnon && !swapper_space */
1184                         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1185                 }
1186                 return 1;
1187         }
1188         return 0;
1189 }
1190 EXPORT_SYMBOL(__set_page_dirty_nobuffers);
1191
1192 /*
1193  * When a writepage implementation decides that it doesn't want to write this
1194  * page for some reason, it should redirty the locked page via
1195  * redirty_page_for_writepage() and it should then unlock the page and return 0
1196  */
1197 int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
1198 {
1199         wbc->pages_skipped++;
1200         return __set_page_dirty_nobuffers(page);
1201 }
1202 EXPORT_SYMBOL(redirty_page_for_writepage);
1203
1204 /*
1205  * Dirty a page.
1206  *
1207  * For pages with a mapping this should be done under the page lock
1208  * for the benefit of asynchronous memory errors who prefer a consistent
1209  * dirty state. This rule can be broken in some special cases,
1210  * but should be better not to.
1211  *
1212  * If the mapping doesn't provide a set_page_dirty a_op, then
1213  * just fall through and assume that it wants buffer_heads.
1214  */
1215 int set_page_dirty(struct page *page)
1216 {
1217         struct address_space *mapping = page_mapping(page);
1218
1219         if (likely(mapping)) {
1220                 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
1221                 /*
1222                  * readahead/lru_deactivate_page could remain
1223                  * PG_readahead/PG_reclaim due to race with end_page_writeback
1224                  * About readahead, if the page is written, the flags would be
1225                  * reset. So no problem.
1226                  * About lru_deactivate_page, if the page is redirty, the flag
1227                  * will be reset. So no problem. but if the page is used by readahead
1228                  * it will confuse readahead and make it restart the size rampup
1229                  * process. But it's a trivial problem.
1230                  */
1231                 ClearPageReclaim(page);
1232 #ifdef CONFIG_BLOCK
1233                 if (!spd)
1234                         spd = __set_page_dirty_buffers;
1235 #endif
1236                 return (*spd)(page);
1237         }
1238         if (!PageDirty(page)) {
1239                 if (!TestSetPageDirty(page))
1240                         return 1;
1241         }
1242         return 0;
1243 }
1244 EXPORT_SYMBOL(set_page_dirty);
1245
1246 /*
1247  * set_page_dirty() is racy if the caller has no reference against
1248  * page->mapping->host, and if the page is unlocked.  This is because another
1249  * CPU could truncate the page off the mapping and then free the mapping.
1250  *
1251  * Usually, the page _is_ locked, or the caller is a user-space process which
1252  * holds a reference on the inode by having an open file.
1253  *
1254  * In other cases, the page should be locked before running set_page_dirty().
1255  */
1256 int set_page_dirty_lock(struct page *page)
1257 {
1258         int ret;
1259
1260         lock_page(page);
1261         ret = set_page_dirty(page);
1262         unlock_page(page);
1263         return ret;
1264 }
1265 EXPORT_SYMBOL(set_page_dirty_lock);
1266
1267 /*
1268  * Clear a page's dirty flag, while caring for dirty memory accounting.
1269  * Returns true if the page was previously dirty.
1270  *
1271  * This is for preparing to put the page under writeout.  We leave the page
1272  * tagged as dirty in the radix tree so that a concurrent write-for-sync
1273  * can discover it via a PAGECACHE_TAG_DIRTY walk.  The ->writepage
1274  * implementation will run either set_page_writeback() or set_page_dirty(),
1275  * at which stage we bring the page's dirty flag and radix-tree dirty tag
1276  * back into sync.
1277  *
1278  * This incoherency between the page's dirty flag and radix-tree tag is
1279  * unfortunate, but it only exists while the page is locked.
1280  */
1281 int clear_page_dirty_for_io(struct page *page)
1282 {
1283         struct address_space *mapping = page_mapping(page);
1284
1285         BUG_ON(!PageLocked(page));
1286
1287         if (mapping && mapping_cap_account_dirty(mapping)) {
1288                 /*
1289                  * Yes, Virginia, this is indeed insane.
1290                  *
1291                  * We use this sequence to make sure that
1292                  *  (a) we account for dirty stats properly
1293                  *  (b) we tell the low-level filesystem to
1294                  *      mark the whole page dirty if it was
1295                  *      dirty in a pagetable. Only to then
1296                  *  (c) clean the page again and return 1 to
1297                  *      cause the writeback.
1298                  *
1299                  * This way we avoid all nasty races with the
1300                  * dirty bit in multiple places and clearing
1301                  * them concurrently from different threads.
1302                  *
1303                  * Note! Normally the "set_page_dirty(page)"
1304                  * has no effect on the actual dirty bit - since
1305                  * that will already usually be set. But we
1306                  * need the side effects, and it can help us
1307                  * avoid races.
1308                  *
1309                  * We basically use the page "master dirty bit"
1310                  * as a serialization point for all the different
1311                  * threads doing their things.
1312                  */
1313                 if (page_mkclean(page))
1314                         set_page_dirty(page);
1315                 /*
1316                  * We carefully synchronise fault handlers against
1317                  * installing a dirty pte and marking the page dirty
1318                  * at this point. We do this by having them hold the
1319                  * page lock at some point after installing their
1320                  * pte, but before marking the page dirty.
1321                  * Pages are always locked coming in here, so we get
1322                  * the desired exclusion. See mm/memory.c:do_wp_page()
1323                  * for more comments.
1324                  */
1325                 if (TestClearPageDirty(page)) {
1326                         dec_zone_page_state(page, NR_FILE_DIRTY);
1327                         dec_bdi_stat(mapping->backing_dev_info,
1328                                         BDI_RECLAIMABLE);
1329                         return 1;
1330                 }
1331                 return 0;
1332         }
1333         return TestClearPageDirty(page);
1334 }
1335 EXPORT_SYMBOL(clear_page_dirty_for_io);
1336
1337 int test_clear_page_writeback(struct page *page)
1338 {
1339         struct address_space *mapping = page_mapping(page);
1340         int ret;
1341
1342         if (mapping) {
1343                 struct backing_dev_info *bdi = mapping->backing_dev_info;
1344                 unsigned long flags;
1345
1346                 spin_lock_irqsave(&mapping->tree_lock, flags);
1347                 ret = TestClearPageWriteback(page);
1348                 if (ret) {
1349                         radix_tree_tag_clear(&mapping->page_tree,
1350                                                 page_index(page),
1351                                                 PAGECACHE_TAG_WRITEBACK);
1352                         if (bdi_cap_account_writeback(bdi)) {
1353                                 __dec_bdi_stat(bdi, BDI_WRITEBACK);
1354                                 __bdi_writeout_inc(bdi);
1355                         }
1356                 }
1357                 spin_unlock_irqrestore(&mapping->tree_lock, flags);
1358         } else {
1359                 ret = TestClearPageWriteback(page);
1360         }
1361         if (ret)
1362                 dec_zone_page_state(page, NR_WRITEBACK);
1363         return ret;
1364 }
1365
1366 int test_set_page_writeback(struct page *page)
1367 {
1368         struct address_space *mapping = page_mapping(page);
1369         int ret;
1370
1371         if (mapping) {
1372                 struct backing_dev_info *bdi = mapping->backing_dev_info;
1373                 unsigned long flags;
1374
1375                 spin_lock_irqsave(&mapping->tree_lock, flags);
1376                 ret = TestSetPageWriteback(page);
1377                 if (!ret) {
1378                         radix_tree_tag_set(&mapping->page_tree,
1379                                                 page_index(page),
1380                                                 PAGECACHE_TAG_WRITEBACK);
1381                         if (bdi_cap_account_writeback(bdi))
1382                                 __inc_bdi_stat(bdi, BDI_WRITEBACK);
1383                 }
1384                 if (!PageDirty(page))
1385                         radix_tree_tag_clear(&mapping->page_tree,
1386                                                 page_index(page),
1387                                                 PAGECACHE_TAG_DIRTY);
1388                 radix_tree_tag_clear(&mapping->page_tree,
1389                                      page_index(page),
1390                                      PAGECACHE_TAG_TOWRITE);
1391                 spin_unlock_irqrestore(&mapping->tree_lock, flags);
1392         } else {
1393                 ret = TestSetPageWriteback(page);
1394         }
1395         if (!ret)
1396                 account_page_writeback(page);
1397         return ret;
1398
1399 }
1400 EXPORT_SYMBOL(test_set_page_writeback);
1401
1402 /*
1403  * Return true if any of the pages in the mapping are marked with the
1404  * passed tag.
1405  */
1406 int mapping_tagged(struct address_space *mapping, int tag)
1407 {
1408         int ret;
1409         rcu_read_lock();
1410         ret = radix_tree_tagged(&mapping->page_tree, tag);
1411         rcu_read_unlock();
1412         return ret;
1413 }
1414 EXPORT_SYMBOL(mapping_tagged);