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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * mm/page-writeback.c.
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * Contains functions related to writing back dirty pages at the
7 * address_space level.
8 *
9 * 10Apr2002 akpm@zip.com.au
10 * Initial version
11 */
12
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/spinlock.h>
16#include <linux/fs.h>
17#include <linux/mm.h>
18#include <linux/swap.h>
19#include <linux/slab.h>
20#include <linux/pagemap.h>
21#include <linux/writeback.h>
22#include <linux/init.h>
23#include <linux/backing-dev.h>
24#include <linux/blkdev.h>
25#include <linux/mpage.h>
26#include <linux/percpu.h>
27#include <linux/notifier.h>
28#include <linux/smp.h>
29#include <linux/sysctl.h>
30#include <linux/cpu.h>
31#include <linux/syscalls.h>
32
33/*
34 * The maximum number of pages to writeout in a single bdflush/kupdate
35 * operation. We do this so we don't hold I_LOCK against an inode for
36 * enormous amounts of time, which would block a userspace task which has
37 * been forced to throttle against that inode. Also, the code reevaluates
38 * the dirty each time it has written this many pages.
39 */
40#define MAX_WRITEBACK_PAGES 1024
41
42/*
43 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
44 * will look to see if it needs to force writeback or throttling.
45 */
46static long ratelimit_pages = 32;
47
48static long total_pages; /* The total number of pages in the machine. */
Andrew Mortone236a162006-01-18 17:42:26 -080049static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */
Linus Torvalds1da177e2005-04-16 15:20:36 -070050
51/*
52 * When balance_dirty_pages decides that the caller needs to perform some
53 * non-background writeback, this is how many pages it will attempt to write.
54 * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably
55 * large amounts of I/O are submitted.
56 */
57static inline long sync_writeback_pages(void)
58{
59 return ratelimit_pages + ratelimit_pages / 2;
60}
61
62/* The following parameters are exported via /proc/sys/vm */
63
64/*
65 * Start background writeback (via pdflush) at this percentage
66 */
67int dirty_background_ratio = 10;
68
69/*
70 * The generator of dirty data starts writeback at this percentage
71 */
72int vm_dirty_ratio = 40;
73
74/*
Coywolf Qi Huntfd5403c2006-04-10 22:54:35 -070075 * The interval between `kupdate'-style writebacks, in jiffies
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 */
Bart Samwelf6ef9432006-03-24 03:15:48 -080077int dirty_writeback_interval = 5 * HZ;
Linus Torvalds1da177e2005-04-16 15:20:36 -070078
79/*
Coywolf Qi Huntfd5403c2006-04-10 22:54:35 -070080 * The longest number of jiffies for which data is allowed to remain dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 */
Bart Samwelf6ef9432006-03-24 03:15:48 -080082int dirty_expire_interval = 30 * HZ;
Linus Torvalds1da177e2005-04-16 15:20:36 -070083
84/*
85 * Flag that makes the machine dump writes/reads and block dirtyings.
86 */
87int block_dump;
88
89/*
Bart Samweled5b43f2006-03-24 03:15:49 -080090 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
91 * a full sync is triggered after this time elapses without any disk activity.
Linus Torvalds1da177e2005-04-16 15:20:36 -070092 */
93int laptop_mode;
94
95EXPORT_SYMBOL(laptop_mode);
96
97/* End of sysctl-exported parameters */
98
99
100static void background_writeout(unsigned long _min_pages);
101
102struct writeback_state
103{
104 unsigned long nr_dirty;
105 unsigned long nr_unstable;
106 unsigned long nr_mapped;
107 unsigned long nr_writeback;
108};
109
110static void get_writeback_state(struct writeback_state *wbs)
111{
112 wbs->nr_dirty = read_page_state(nr_dirty);
113 wbs->nr_unstable = read_page_state(nr_unstable);
114 wbs->nr_mapped = read_page_state(nr_mapped);
115 wbs->nr_writeback = read_page_state(nr_writeback);
116}
117
118/*
119 * Work out the current dirty-memory clamping and background writeout
120 * thresholds.
121 *
122 * The main aim here is to lower them aggressively if there is a lot of mapped
123 * memory around. To avoid stressing page reclaim with lots of unreclaimable
124 * pages. It is better to clamp down on writers than to start swapping, and
125 * performing lots of scanning.
126 *
127 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
128 *
129 * We don't permit the clamping level to fall below 5% - that is getting rather
130 * excessive.
131 *
132 * We make sure that the background writeout level is below the adjusted
133 * clamping level.
134 */
135static void
136get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
137 struct address_space *mapping)
138{
139 int background_ratio; /* Percentages */
140 int dirty_ratio;
141 int unmapped_ratio;
142 long background;
143 long dirty;
144 unsigned long available_memory = total_pages;
145 struct task_struct *tsk;
146
147 get_writeback_state(wbs);
148
149#ifdef CONFIG_HIGHMEM
150 /*
151 * If this mapping can only allocate from low memory,
152 * we exclude high memory from our count.
153 */
154 if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM))
155 available_memory -= totalhigh_pages;
156#endif
157
158
159 unmapped_ratio = 100 - (wbs->nr_mapped * 100) / total_pages;
160
161 dirty_ratio = vm_dirty_ratio;
162 if (dirty_ratio > unmapped_ratio / 2)
163 dirty_ratio = unmapped_ratio / 2;
164
165 if (dirty_ratio < 5)
166 dirty_ratio = 5;
167
168 background_ratio = dirty_background_ratio;
169 if (background_ratio >= dirty_ratio)
170 background_ratio = dirty_ratio / 2;
171
172 background = (background_ratio * available_memory) / 100;
173 dirty = (dirty_ratio * available_memory) / 100;
174 tsk = current;
175 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
176 background += background / 4;
177 dirty += dirty / 4;
178 }
179 *pbackground = background;
180 *pdirty = dirty;
181}
182
183/*
184 * balance_dirty_pages() must be called by processes which are generating dirty
185 * data. It looks at the number of dirty pages in the machine and will force
186 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
187 * If we're over `background_thresh' then pdflush is woken to perform some
188 * writeout.
189 */
190static void balance_dirty_pages(struct address_space *mapping)
191{
192 struct writeback_state wbs;
193 long nr_reclaimable;
194 long background_thresh;
195 long dirty_thresh;
196 unsigned long pages_written = 0;
197 unsigned long write_chunk = sync_writeback_pages();
198
199 struct backing_dev_info *bdi = mapping->backing_dev_info;
200
201 for (;;) {
202 struct writeback_control wbc = {
203 .bdi = bdi,
204 .sync_mode = WB_SYNC_NONE,
205 .older_than_this = NULL,
206 .nr_to_write = write_chunk,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700207 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208 };
209
210 get_dirty_limits(&wbs, &background_thresh,
211 &dirty_thresh, mapping);
212 nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
213 if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
214 break;
215
Andrew Mortone236a162006-01-18 17:42:26 -0800216 if (!dirty_exceeded)
217 dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218
219 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
220 * Unstable writes are a feature of certain networked
221 * filesystems (i.e. NFS) in which data may have been
222 * written to the server's write cache, but has not yet
223 * been flushed to permanent storage.
224 */
225 if (nr_reclaimable) {
226 writeback_inodes(&wbc);
227 get_dirty_limits(&wbs, &background_thresh,
228 &dirty_thresh, mapping);
229 nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
230 if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
231 break;
232 pages_written += write_chunk - wbc.nr_to_write;
233 if (pages_written >= write_chunk)
234 break; /* We've done our duty */
235 }
236 blk_congestion_wait(WRITE, HZ/10);
237 }
238
Andrew Mortone236a162006-01-18 17:42:26 -0800239 if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh && dirty_exceeded)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240 dirty_exceeded = 0;
241
242 if (writeback_in_progress(bdi))
243 return; /* pdflush is already working this queue */
244
245 /*
246 * In laptop mode, we wait until hitting the higher threshold before
247 * starting background writeout, and then write out all the way down
248 * to the lower threshold. So slow writers cause minimal disk activity.
249 *
250 * In normal mode, we start background writeout at the lower
251 * background_thresh, to keep the amount of dirty memory low.
252 */
253 if ((laptop_mode && pages_written) ||
254 (!laptop_mode && (nr_reclaimable > background_thresh)))
255 pdflush_operation(background_writeout, 0);
256}
257
258/**
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800259 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -0700260 * @mapping: address_space which was dirtied
Martin Waitza5802902006-04-02 13:59:55 +0200261 * @nr_pages_dirtied: number of pages which the caller has just dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 *
263 * Processes which are dirtying memory should call in here once for each page
264 * which was newly dirtied. The function will periodically check the system's
265 * dirty state and will initiate writeback if needed.
266 *
267 * On really big machines, get_writeback_state is expensive, so try to avoid
268 * calling it too often (ratelimiting). But once we're over the dirty memory
269 * limit we decrease the ratelimiting by a lot, to prevent individual processes
270 * from overshooting the limit by (ratelimit_pages) each.
271 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800272void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
273 unsigned long nr_pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274{
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800275 static DEFINE_PER_CPU(unsigned long, ratelimits) = 0;
276 unsigned long ratelimit;
277 unsigned long *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700278
279 ratelimit = ratelimit_pages;
280 if (dirty_exceeded)
281 ratelimit = 8;
282
283 /*
284 * Check the rate limiting. Also, we do not want to throttle real-time
285 * tasks in balance_dirty_pages(). Period.
286 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800287 preempt_disable();
288 p = &__get_cpu_var(ratelimits);
289 *p += nr_pages_dirtied;
290 if (unlikely(*p >= ratelimit)) {
291 *p = 0;
292 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 balance_dirty_pages(mapping);
294 return;
295 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800296 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297}
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800298EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299
300void throttle_vm_writeout(void)
301{
302 struct writeback_state wbs;
303 long background_thresh;
304 long dirty_thresh;
305
306 for ( ; ; ) {
307 get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
308
309 /*
310 * Boost the allowable dirty threshold a bit for page
311 * allocators so they don't get DoS'ed by heavy writers
312 */
313 dirty_thresh += dirty_thresh / 10; /* wheeee... */
314
315 if (wbs.nr_unstable + wbs.nr_writeback <= dirty_thresh)
316 break;
317 blk_congestion_wait(WRITE, HZ/10);
318 }
319}
320
321
322/*
323 * writeback at least _min_pages, and keep writing until the amount of dirty
324 * memory is less than the background threshold, or until we're all clean.
325 */
326static void background_writeout(unsigned long _min_pages)
327{
328 long min_pages = _min_pages;
329 struct writeback_control wbc = {
330 .bdi = NULL,
331 .sync_mode = WB_SYNC_NONE,
332 .older_than_this = NULL,
333 .nr_to_write = 0,
334 .nonblocking = 1,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700335 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336 };
337
338 for ( ; ; ) {
339 struct writeback_state wbs;
340 long background_thresh;
341 long dirty_thresh;
342
343 get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
344 if (wbs.nr_dirty + wbs.nr_unstable < background_thresh
345 && min_pages <= 0)
346 break;
347 wbc.encountered_congestion = 0;
348 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
349 wbc.pages_skipped = 0;
350 writeback_inodes(&wbc);
351 min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
352 if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
353 /* Wrote less than expected */
354 blk_congestion_wait(WRITE, HZ/10);
355 if (!wbc.encountered_congestion)
356 break;
357 }
358 }
359}
360
361/*
362 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
363 * the whole world. Returns 0 if a pdflush thread was dispatched. Returns
364 * -1 if all pdflush threads were busy.
365 */
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700366int wakeup_pdflush(long nr_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367{
368 if (nr_pages == 0) {
369 struct writeback_state wbs;
370
371 get_writeback_state(&wbs);
372 nr_pages = wbs.nr_dirty + wbs.nr_unstable;
373 }
374 return pdflush_operation(background_writeout, nr_pages);
375}
376
377static void wb_timer_fn(unsigned long unused);
378static void laptop_timer_fn(unsigned long unused);
379
Ingo Molnar8d06afa2005-09-09 13:10:40 -0700380static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0);
381static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382
383/*
384 * Periodic writeback of "old" data.
385 *
386 * Define "old": the first time one of an inode's pages is dirtied, we mark the
387 * dirtying-time in the inode's address_space. So this periodic writeback code
388 * just walks the superblock inode list, writing back any inodes which are
389 * older than a specific point in time.
390 *
Bart Samwelf6ef9432006-03-24 03:15:48 -0800391 * Try to run once per dirty_writeback_interval. But if a writeback event
392 * takes longer than a dirty_writeback_interval interval, then leave a
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393 * one-second gap.
394 *
395 * older_than_this takes precedence over nr_to_write. So we'll only write back
396 * all dirty pages if they are all attached to "old" mappings.
397 */
398static void wb_kupdate(unsigned long arg)
399{
400 unsigned long oldest_jif;
401 unsigned long start_jif;
402 unsigned long next_jif;
403 long nr_to_write;
404 struct writeback_state wbs;
405 struct writeback_control wbc = {
406 .bdi = NULL,
407 .sync_mode = WB_SYNC_NONE,
408 .older_than_this = &oldest_jif,
409 .nr_to_write = 0,
410 .nonblocking = 1,
411 .for_kupdate = 1,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700412 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 };
414
415 sync_supers();
416
417 get_writeback_state(&wbs);
Bart Samwelf6ef9432006-03-24 03:15:48 -0800418 oldest_jif = jiffies - dirty_expire_interval;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419 start_jif = jiffies;
Bart Samwelf6ef9432006-03-24 03:15:48 -0800420 next_jif = start_jif + dirty_writeback_interval;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421 nr_to_write = wbs.nr_dirty + wbs.nr_unstable +
422 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
423 while (nr_to_write > 0) {
424 wbc.encountered_congestion = 0;
425 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
426 writeback_inodes(&wbc);
427 if (wbc.nr_to_write > 0) {
428 if (wbc.encountered_congestion)
429 blk_congestion_wait(WRITE, HZ/10);
430 else
431 break; /* All the old data is written */
432 }
433 nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
434 }
435 if (time_before(next_jif, jiffies + HZ))
436 next_jif = jiffies + HZ;
Bart Samwelf6ef9432006-03-24 03:15:48 -0800437 if (dirty_writeback_interval)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438 mod_timer(&wb_timer, next_jif);
439}
440
441/*
442 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
443 */
444int dirty_writeback_centisecs_handler(ctl_table *table, int write,
445 struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
446{
Bart Samwelf6ef9432006-03-24 03:15:48 -0800447 proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
448 if (dirty_writeback_interval) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 mod_timer(&wb_timer,
Bart Samwelf6ef9432006-03-24 03:15:48 -0800450 jiffies + dirty_writeback_interval);
451 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 del_timer(&wb_timer);
453 }
454 return 0;
455}
456
457static void wb_timer_fn(unsigned long unused)
458{
459 if (pdflush_operation(wb_kupdate, 0) < 0)
460 mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
461}
462
463static void laptop_flush(unsigned long unused)
464{
465 sys_sync();
466}
467
468static void laptop_timer_fn(unsigned long unused)
469{
470 pdflush_operation(laptop_flush, 0);
471}
472
473/*
474 * We've spun up the disk and we're in laptop mode: schedule writeback
475 * of all dirty data a few seconds from now. If the flush is already scheduled
476 * then push it back - the user is still using the disk.
477 */
478void laptop_io_completion(void)
479{
Bart Samweled5b43f2006-03-24 03:15:49 -0800480 mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700481}
482
483/*
484 * We're in laptop mode and we've just synced. The sync's writes will have
485 * caused another writeback to be scheduled by laptop_io_completion.
486 * Nothing needs to be written back anymore, so we unschedule the writeback.
487 */
488void laptop_sync_completion(void)
489{
490 del_timer(&laptop_mode_wb_timer);
491}
492
493/*
494 * If ratelimit_pages is too high then we can get into dirty-data overload
495 * if a large number of processes all perform writes at the same time.
496 * If it is too low then SMP machines will call the (expensive)
497 * get_writeback_state too often.
498 *
499 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
500 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
501 * thresholds before writeback cuts in.
502 *
503 * But the limit should not be set too high. Because it also controls the
504 * amount of memory which the balance_dirty_pages() caller has to write back.
505 * If this is too large then the caller will block on the IO queue all the
506 * time. So limit it to four megabytes - the balance_dirty_pages() caller
507 * will write six megabyte chunks, max.
508 */
509
510static void set_ratelimit(void)
511{
512 ratelimit_pages = total_pages / (num_online_cpus() * 32);
513 if (ratelimit_pages < 16)
514 ratelimit_pages = 16;
515 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
516 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
517}
518
519static int
520ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
521{
522 set_ratelimit();
523 return 0;
524}
525
526static struct notifier_block ratelimit_nb = {
527 .notifier_call = ratelimit_handler,
528 .next = NULL,
529};
530
531/*
532 * If the machine has a large highmem:lowmem ratio then scale back the default
533 * dirty memory thresholds: allowing too much dirty highmem pins an excessive
534 * number of buffer_heads.
535 */
536void __init page_writeback_init(void)
537{
538 long buffer_pages = nr_free_buffer_pages();
539 long correction;
540
541 total_pages = nr_free_pagecache_pages();
542
543 correction = (100 * 4 * buffer_pages) / total_pages;
544
545 if (correction < 100) {
546 dirty_background_ratio *= correction;
547 dirty_background_ratio /= 100;
548 vm_dirty_ratio *= correction;
549 vm_dirty_ratio /= 100;
550
551 if (dirty_background_ratio <= 0)
552 dirty_background_ratio = 1;
553 if (vm_dirty_ratio <= 0)
554 vm_dirty_ratio = 1;
555 }
Bart Samwelf6ef9432006-03-24 03:15:48 -0800556 mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 set_ratelimit();
558 register_cpu_notifier(&ratelimit_nb);
559}
560
561int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
562{
Andrew Morton22905f72005-11-16 15:07:01 -0800563 int ret;
564
Linus Torvalds1da177e2005-04-16 15:20:36 -0700565 if (wbc->nr_to_write <= 0)
566 return 0;
Andrew Morton22905f72005-11-16 15:07:01 -0800567 wbc->for_writepages = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 if (mapping->a_ops->writepages)
Andrew Morton22905f72005-11-16 15:07:01 -0800569 ret = mapping->a_ops->writepages(mapping, wbc);
570 else
571 ret = generic_writepages(mapping, wbc);
572 wbc->for_writepages = 0;
573 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574}
575
576/**
577 * write_one_page - write out a single page and optionally wait on I/O
578 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700579 * @page: the page to write
580 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581 *
582 * The page must be locked by the caller and will be unlocked upon return.
583 *
584 * write_one_page() returns a negative error code if I/O failed.
585 */
586int write_one_page(struct page *page, int wait)
587{
588 struct address_space *mapping = page->mapping;
589 int ret = 0;
590 struct writeback_control wbc = {
591 .sync_mode = WB_SYNC_ALL,
592 .nr_to_write = 1,
593 };
594
595 BUG_ON(!PageLocked(page));
596
597 if (wait)
598 wait_on_page_writeback(page);
599
600 if (clear_page_dirty_for_io(page)) {
601 page_cache_get(page);
602 ret = mapping->a_ops->writepage(page, &wbc);
603 if (ret == 0 && wait) {
604 wait_on_page_writeback(page);
605 if (PageError(page))
606 ret = -EIO;
607 }
608 page_cache_release(page);
609 } else {
610 unlock_page(page);
611 }
612 return ret;
613}
614EXPORT_SYMBOL(write_one_page);
615
616/*
617 * For address_spaces which do not use buffers. Just tag the page as dirty in
618 * its radix tree.
619 *
620 * This is also used when a single buffer is being dirtied: we want to set the
621 * page dirty in that case, but not all the buffers. This is a "bottom-up"
622 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
623 *
624 * Most callers have locked the page, which pins the address_space in memory.
625 * But zap_pte_range() does not lock the page, however in that case the
626 * mapping is pinned by the vma's ->vm_file reference.
627 *
628 * We take care to handle the case where the page was truncated from the
629 * mapping by re-checking page_mapping() insode tree_lock.
630 */
631int __set_page_dirty_nobuffers(struct page *page)
632{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633 if (!TestSetPageDirty(page)) {
634 struct address_space *mapping = page_mapping(page);
635 struct address_space *mapping2;
636
637 if (mapping) {
638 write_lock_irq(&mapping->tree_lock);
639 mapping2 = page_mapping(page);
640 if (mapping2) { /* Race with truncate? */
641 BUG_ON(mapping2 != mapping);
642 if (mapping_cap_account_dirty(mapping))
643 inc_page_state(nr_dirty);
644 radix_tree_tag_set(&mapping->page_tree,
645 page_index(page), PAGECACHE_TAG_DIRTY);
646 }
647 write_unlock_irq(&mapping->tree_lock);
648 if (mapping->host) {
649 /* !PageAnon && !swapper_space */
650 __mark_inode_dirty(mapping->host,
651 I_DIRTY_PAGES);
652 }
653 }
Andrew Morton4741c9f2006-03-24 03:18:11 -0800654 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700655 }
Andrew Morton4741c9f2006-03-24 03:18:11 -0800656 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657}
658EXPORT_SYMBOL(__set_page_dirty_nobuffers);
659
660/*
661 * When a writepage implementation decides that it doesn't want to write this
662 * page for some reason, it should redirty the locked page via
663 * redirty_page_for_writepage() and it should then unlock the page and return 0
664 */
665int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
666{
667 wbc->pages_skipped++;
668 return __set_page_dirty_nobuffers(page);
669}
670EXPORT_SYMBOL(redirty_page_for_writepage);
671
672/*
673 * If the mapping doesn't provide a set_page_dirty a_op, then
674 * just fall through and assume that it wants buffer_heads.
675 */
676int fastcall set_page_dirty(struct page *page)
677{
678 struct address_space *mapping = page_mapping(page);
679
680 if (likely(mapping)) {
681 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
682 if (spd)
683 return (*spd)(page);
684 return __set_page_dirty_buffers(page);
685 }
Andrew Morton4741c9f2006-03-24 03:18:11 -0800686 if (!PageDirty(page)) {
687 if (!TestSetPageDirty(page))
688 return 1;
689 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690 return 0;
691}
692EXPORT_SYMBOL(set_page_dirty);
693
694/*
695 * set_page_dirty() is racy if the caller has no reference against
696 * page->mapping->host, and if the page is unlocked. This is because another
697 * CPU could truncate the page off the mapping and then free the mapping.
698 *
699 * Usually, the page _is_ locked, or the caller is a user-space process which
700 * holds a reference on the inode by having an open file.
701 *
702 * In other cases, the page should be locked before running set_page_dirty().
703 */
704int set_page_dirty_lock(struct page *page)
705{
706 int ret;
707
708 lock_page(page);
709 ret = set_page_dirty(page);
710 unlock_page(page);
711 return ret;
712}
713EXPORT_SYMBOL(set_page_dirty_lock);
714
715/*
716 * Clear a page's dirty flag, while caring for dirty memory accounting.
717 * Returns true if the page was previously dirty.
718 */
719int test_clear_page_dirty(struct page *page)
720{
721 struct address_space *mapping = page_mapping(page);
722 unsigned long flags;
723
724 if (mapping) {
725 write_lock_irqsave(&mapping->tree_lock, flags);
726 if (TestClearPageDirty(page)) {
727 radix_tree_tag_clear(&mapping->page_tree,
728 page_index(page),
729 PAGECACHE_TAG_DIRTY);
730 write_unlock_irqrestore(&mapping->tree_lock, flags);
731 if (mapping_cap_account_dirty(mapping))
732 dec_page_state(nr_dirty);
733 return 1;
734 }
735 write_unlock_irqrestore(&mapping->tree_lock, flags);
736 return 0;
737 }
738 return TestClearPageDirty(page);
739}
740EXPORT_SYMBOL(test_clear_page_dirty);
741
742/*
743 * Clear a page's dirty flag, while caring for dirty memory accounting.
744 * Returns true if the page was previously dirty.
745 *
746 * This is for preparing to put the page under writeout. We leave the page
747 * tagged as dirty in the radix tree so that a concurrent write-for-sync
748 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
749 * implementation will run either set_page_writeback() or set_page_dirty(),
750 * at which stage we bring the page's dirty flag and radix-tree dirty tag
751 * back into sync.
752 *
753 * This incoherency between the page's dirty flag and radix-tree tag is
754 * unfortunate, but it only exists while the page is locked.
755 */
756int clear_page_dirty_for_io(struct page *page)
757{
758 struct address_space *mapping = page_mapping(page);
759
760 if (mapping) {
761 if (TestClearPageDirty(page)) {
762 if (mapping_cap_account_dirty(mapping))
763 dec_page_state(nr_dirty);
764 return 1;
765 }
766 return 0;
767 }
768 return TestClearPageDirty(page);
769}
Hans Reiser58bb01a2005-11-18 01:10:53 -0800770EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771
772int test_clear_page_writeback(struct page *page)
773{
774 struct address_space *mapping = page_mapping(page);
775 int ret;
776
777 if (mapping) {
778 unsigned long flags;
779
780 write_lock_irqsave(&mapping->tree_lock, flags);
781 ret = TestClearPageWriteback(page);
782 if (ret)
783 radix_tree_tag_clear(&mapping->page_tree,
784 page_index(page),
785 PAGECACHE_TAG_WRITEBACK);
786 write_unlock_irqrestore(&mapping->tree_lock, flags);
787 } else {
788 ret = TestClearPageWriteback(page);
789 }
790 return ret;
791}
792
793int test_set_page_writeback(struct page *page)
794{
795 struct address_space *mapping = page_mapping(page);
796 int ret;
797
798 if (mapping) {
799 unsigned long flags;
800
801 write_lock_irqsave(&mapping->tree_lock, flags);
802 ret = TestSetPageWriteback(page);
803 if (!ret)
804 radix_tree_tag_set(&mapping->page_tree,
805 page_index(page),
806 PAGECACHE_TAG_WRITEBACK);
807 if (!PageDirty(page))
808 radix_tree_tag_clear(&mapping->page_tree,
809 page_index(page),
810 PAGECACHE_TAG_DIRTY);
811 write_unlock_irqrestore(&mapping->tree_lock, flags);
812 } else {
813 ret = TestSetPageWriteback(page);
814 }
815 return ret;
816
817}
818EXPORT_SYMBOL(test_set_page_writeback);
819
820/*
821 * Return true if any of the pages in the mapping are marged with the
822 * passed tag.
823 */
824int mapping_tagged(struct address_space *mapping, int tag)
825{
826 unsigned long flags;
827 int ret;
828
829 read_lock_irqsave(&mapping->tree_lock, flags);
830 ret = radix_tree_tagged(&mapping->page_tree, tag);
831 read_unlock_irqrestore(&mapping->tree_lock, flags);
832 return ret;
833}
834EXPORT_SYMBOL(mapping_tagged);