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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Uwe Zeisbergerf30c2262006-10-03 23:01:26 +02002 * mm/page-writeback.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07003 *
4 * Copyright (C) 2002, Linus Torvalds.
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07005 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 *
7 * Contains functions related to writing back dirty pages at the
8 * address_space level.
9 *
Francois Camie1f8e872008-10-15 22:01:59 -070010 * 10Apr2002 Andrew Morton
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 * 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>
Andrew Morton55e829a2006-12-10 02:19:27 -080025#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#include <linux/blkdev.h>
27#include <linux/mpage.h>
Peter Zijlstrad08b3852006-09-25 23:30:57 -070028#include <linux/rmap.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070029#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>
David Howellscf9a2ae2006-08-29 19:05:54 +010035#include <linux/buffer_head.h>
David Howells811d7362006-08-29 19:06:09 +010036#include <linux/pagevec.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38/*
39 * The maximum number of pages to writeout in a single bdflush/kupdate
Joern Engel1c0eeaf2007-10-16 23:30:44 -070040 * operation. We do this so we don't hold I_SYNC against an inode for
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 * enormous amounts of time, which would block a userspace task which has
42 * been forced to throttle against that inode. Also, the code reevaluates
43 * the dirty each time it has written this many pages.
44 */
45#define MAX_WRITEBACK_PAGES 1024
46
47/*
48 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
49 * will look to see if it needs to force writeback or throttling.
50 */
51static long ratelimit_pages = 32;
52
Linus Torvalds1da177e2005-04-16 15:20:36 -070053/*
54 * When balance_dirty_pages decides that the caller needs to perform some
55 * non-background writeback, this is how many pages it will attempt to write.
56 * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably
57 * large amounts of I/O are submitted.
58 */
59static inline long sync_writeback_pages(void)
60{
61 return ratelimit_pages + ratelimit_pages / 2;
62}
63
64/* The following parameters are exported via /proc/sys/vm */
65
66/*
67 * Start background writeback (via pdflush) at this percentage
68 */
Linus Torvalds07db59b2007-04-27 09:10:47 -070069int dirty_background_ratio = 5;
Linus Torvalds1da177e2005-04-16 15:20:36 -070070
71/*
Bron Gondwana195cf452008-02-04 22:29:20 -080072 * free highmem will not be subtracted from the total free memory
73 * for calculating free ratios if vm_highmem_is_dirtyable is true
74 */
75int vm_highmem_is_dirtyable;
76
77/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 * The generator of dirty data starts writeback at this percentage
79 */
Linus Torvalds07db59b2007-04-27 09:10:47 -070080int vm_dirty_ratio = 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -070081
82/*
Coywolf Qi Huntfd5403c2006-04-10 22:54:35 -070083 * The interval between `kupdate'-style writebacks, in jiffies
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 */
Bart Samwelf6ef9432006-03-24 03:15:48 -080085int dirty_writeback_interval = 5 * HZ;
Linus Torvalds1da177e2005-04-16 15:20:36 -070086
87/*
Coywolf Qi Huntfd5403c2006-04-10 22:54:35 -070088 * The longest number of jiffies for which data is allowed to remain dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 */
Bart Samwelf6ef9432006-03-24 03:15:48 -080090int dirty_expire_interval = 30 * HZ;
Linus Torvalds1da177e2005-04-16 15:20:36 -070091
92/*
93 * Flag that makes the machine dump writes/reads and block dirtyings.
94 */
95int block_dump;
96
97/*
Bart Samweled5b43f2006-03-24 03:15:49 -080098 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
99 * a full sync is triggered after this time elapses without any disk activity.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 */
101int laptop_mode;
102
103EXPORT_SYMBOL(laptop_mode);
104
105/* End of sysctl-exported parameters */
106
107
108static void background_writeout(unsigned long _min_pages);
109
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110/*
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700111 * Scale the writeback cache size proportional to the relative writeout speeds.
112 *
113 * We do this by keeping a floating proportion between BDIs, based on page
114 * writeback completions [end_page_writeback()]. Those devices that write out
115 * pages fastest will get the larger share, while the slower will get a smaller
116 * share.
117 *
118 * We use page writeout completions because we are interested in getting rid of
119 * dirty pages. Having them written out is the primary goal.
120 *
121 * We introduce a concept of time, a period over which we measure these events,
122 * because demand can/will vary over time. The length of this period itself is
123 * measured in page writeback completions.
124 *
125 */
126static struct prop_descriptor vm_completions;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700127static struct prop_descriptor vm_dirties;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700128
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700129/*
130 * couple the period to the dirty_ratio:
131 *
132 * period/2 ~ roundup_pow_of_two(dirty limit)
133 */
134static int calc_period_shift(void)
135{
136 unsigned long dirty_total;
137
138 dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 100;
139 return 2 + ilog2(dirty_total - 1);
140}
141
142/*
143 * update the period when the dirty ratio changes.
144 */
145int dirty_ratio_handler(struct ctl_table *table, int write,
146 struct file *filp, void __user *buffer, size_t *lenp,
147 loff_t *ppos)
148{
149 int old_ratio = vm_dirty_ratio;
150 int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
151 if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
152 int shift = calc_period_shift();
153 prop_change_shift(&vm_completions, shift);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700154 prop_change_shift(&vm_dirties, shift);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700155 }
156 return ret;
157}
158
159/*
160 * Increment the BDI's writeout completion count and the global writeout
161 * completion count. Called from test_clear_page_writeback().
162 */
163static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
164{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700165 __prop_inc_percpu_max(&vm_completions, &bdi->completions,
166 bdi->max_prop_frac);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700167}
168
Miklos Szeredidd5656e2008-04-30 00:54:37 -0700169void bdi_writeout_inc(struct backing_dev_info *bdi)
170{
171 unsigned long flags;
172
173 local_irq_save(flags);
174 __bdi_writeout_inc(bdi);
175 local_irq_restore(flags);
176}
177EXPORT_SYMBOL_GPL(bdi_writeout_inc);
178
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700179static inline void task_dirty_inc(struct task_struct *tsk)
180{
181 prop_inc_single(&vm_dirties, &tsk->dirties);
182}
183
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700184/*
185 * Obtain an accurate fraction of the BDI's portion.
186 */
187static void bdi_writeout_fraction(struct backing_dev_info *bdi,
188 long *numerator, long *denominator)
189{
190 if (bdi_cap_writeback_dirty(bdi)) {
191 prop_fraction_percpu(&vm_completions, &bdi->completions,
192 numerator, denominator);
193 } else {
194 *numerator = 0;
195 *denominator = 1;
196 }
197}
198
199/*
200 * Clip the earned share of dirty pages to that which is actually available.
201 * This avoids exceeding the total dirty_limit when the floating averages
202 * fluctuate too quickly.
203 */
204static void
205clip_bdi_dirty_limit(struct backing_dev_info *bdi, long dirty, long *pbdi_dirty)
206{
207 long avail_dirty;
208
209 avail_dirty = dirty -
210 (global_page_state(NR_FILE_DIRTY) +
211 global_page_state(NR_WRITEBACK) +
Miklos Szeredifc3ba692008-04-30 00:54:38 -0700212 global_page_state(NR_UNSTABLE_NFS) +
213 global_page_state(NR_WRITEBACK_TEMP));
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700214
215 if (avail_dirty < 0)
216 avail_dirty = 0;
217
218 avail_dirty += bdi_stat(bdi, BDI_RECLAIMABLE) +
219 bdi_stat(bdi, BDI_WRITEBACK);
220
221 *pbdi_dirty = min(*pbdi_dirty, avail_dirty);
222}
223
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700224static inline void task_dirties_fraction(struct task_struct *tsk,
225 long *numerator, long *denominator)
226{
227 prop_fraction_single(&vm_dirties, &tsk->dirties,
228 numerator, denominator);
229}
230
231/*
232 * scale the dirty limit
233 *
234 * task specific dirty limit:
235 *
236 * dirty -= (dirty/8) * p_{t}
237 */
Adrian Bunkf61eaf92008-02-04 22:29:08 -0800238static void task_dirty_limit(struct task_struct *tsk, long *pdirty)
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700239{
240 long numerator, denominator;
241 long dirty = *pdirty;
242 u64 inv = dirty >> 3;
243
244 task_dirties_fraction(tsk, &numerator, &denominator);
245 inv *= numerator;
246 do_div(inv, denominator);
247
248 dirty -= inv;
249 if (dirty < *pdirty/2)
250 dirty = *pdirty/2;
251
252 *pdirty = dirty;
253}
254
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700255/*
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700256 *
257 */
258static DEFINE_SPINLOCK(bdi_lock);
259static unsigned int bdi_min_ratio;
260
261int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
262{
263 int ret = 0;
264 unsigned long flags;
265
266 spin_lock_irqsave(&bdi_lock, flags);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700267 if (min_ratio > bdi->max_ratio) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700268 ret = -EINVAL;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700269 } else {
270 min_ratio -= bdi->min_ratio;
271 if (bdi_min_ratio + min_ratio < 100) {
272 bdi_min_ratio += min_ratio;
273 bdi->min_ratio += min_ratio;
274 } else {
275 ret = -EINVAL;
276 }
277 }
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700278 spin_unlock_irqrestore(&bdi_lock, flags);
279
280 return ret;
281}
282
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700283int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
284{
285 unsigned long flags;
286 int ret = 0;
287
288 if (max_ratio > 100)
289 return -EINVAL;
290
291 spin_lock_irqsave(&bdi_lock, flags);
292 if (bdi->min_ratio > max_ratio) {
293 ret = -EINVAL;
294 } else {
295 bdi->max_ratio = max_ratio;
296 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
297 }
298 spin_unlock_irqrestore(&bdi_lock, flags);
299
300 return ret;
301}
302EXPORT_SYMBOL(bdi_set_max_ratio);
303
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700304/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305 * Work out the current dirty-memory clamping and background writeout
306 * thresholds.
307 *
308 * The main aim here is to lower them aggressively if there is a lot of mapped
309 * memory around. To avoid stressing page reclaim with lots of unreclaimable
310 * pages. It is better to clamp down on writers than to start swapping, and
311 * performing lots of scanning.
312 *
313 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
314 *
315 * We don't permit the clamping level to fall below 5% - that is getting rather
316 * excessive.
317 *
318 * We make sure that the background writeout level is below the adjusted
319 * clamping level.
320 */
Christoph Lameter1b424462007-05-06 14:48:59 -0700321
322static unsigned long highmem_dirtyable_memory(unsigned long total)
323{
324#ifdef CONFIG_HIGHMEM
325 int node;
326 unsigned long x = 0;
327
Lee Schermerhorn37b07e42007-10-16 01:25:39 -0700328 for_each_node_state(node, N_HIGH_MEMORY) {
Christoph Lameter1b424462007-05-06 14:48:59 -0700329 struct zone *z =
330 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
331
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700332 x += zone_page_state(z, NR_FREE_PAGES) + zone_lru_pages(z);
Christoph Lameter1b424462007-05-06 14:48:59 -0700333 }
334 /*
335 * Make sure that the number of highmem pages is never larger
336 * than the number of the total dirtyable memory. This can only
337 * occur in very strange VM situations but we want to make sure
338 * that this does not occur.
339 */
340 return min(x, total);
341#else
342 return 0;
343#endif
344}
345
Steven Rostedt3eefae92008-05-12 21:21:04 +0200346/**
347 * determine_dirtyable_memory - amount of memory that may be used
348 *
349 * Returns the numebr of pages that can currently be freed and used
350 * by the kernel for direct mappings.
351 */
352unsigned long determine_dirtyable_memory(void)
Christoph Lameter1b424462007-05-06 14:48:59 -0700353{
354 unsigned long x;
355
Rik van Riel4f98a2f2008-10-18 20:26:32 -0700356 x = global_page_state(NR_FREE_PAGES) + global_lru_pages();
Bron Gondwana195cf452008-02-04 22:29:20 -0800357
358 if (!vm_highmem_is_dirtyable)
359 x -= highmem_dirtyable_memory(x);
360
Christoph Lameter1b424462007-05-06 14:48:59 -0700361 return x + 1; /* Ensure that we never return 0 */
362}
363
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700364void
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700365get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
366 struct backing_dev_info *bdi)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367{
368 int background_ratio; /* Percentages */
369 int dirty_ratio;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370 long background;
371 long dirty;
Christoph Lameter1b424462007-05-06 14:48:59 -0700372 unsigned long available_memory = determine_dirtyable_memory();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373 struct task_struct *tsk;
374
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 dirty_ratio = vm_dirty_ratio;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 if (dirty_ratio < 5)
377 dirty_ratio = 5;
378
379 background_ratio = dirty_background_ratio;
380 if (background_ratio >= dirty_ratio)
381 background_ratio = dirty_ratio / 2;
382
383 background = (background_ratio * available_memory) / 100;
384 dirty = (dirty_ratio * available_memory) / 100;
385 tsk = current;
386 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
387 background += background / 4;
388 dirty += dirty / 4;
389 }
390 *pbackground = background;
391 *pdirty = dirty;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700392
393 if (bdi) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700394 u64 bdi_dirty;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700395 long numerator, denominator;
396
397 /*
398 * Calculate this BDI's share of the dirty ratio.
399 */
400 bdi_writeout_fraction(bdi, &numerator, &denominator);
401
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700402 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700403 bdi_dirty *= numerator;
404 do_div(bdi_dirty, denominator);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700405 bdi_dirty += (dirty * bdi->min_ratio) / 100;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700406 if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
407 bdi_dirty = dirty * bdi->max_ratio / 100;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700408
409 *pbdi_dirty = bdi_dirty;
410 clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700411 task_dirty_limit(current, pbdi_dirty);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700412 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413}
414
415/*
416 * balance_dirty_pages() must be called by processes which are generating dirty
417 * data. It looks at the number of dirty pages in the machine and will force
418 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
419 * If we're over `background_thresh' then pdflush is woken to perform some
420 * writeout.
421 */
422static void balance_dirty_pages(struct address_space *mapping)
423{
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800424 long nr_reclaimable, bdi_nr_reclaimable;
425 long nr_writeback, bdi_nr_writeback;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 long background_thresh;
427 long dirty_thresh;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700428 long bdi_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429 unsigned long pages_written = 0;
430 unsigned long write_chunk = sync_writeback_pages();
431
432 struct backing_dev_info *bdi = mapping->backing_dev_info;
433
434 for (;;) {
435 struct writeback_control wbc = {
436 .bdi = bdi,
437 .sync_mode = WB_SYNC_NONE,
438 .older_than_this = NULL,
439 .nr_to_write = write_chunk,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700440 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441 };
442
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700443 get_dirty_limits(&background_thresh, &dirty_thresh,
444 &bdi_thresh, bdi);
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800445
446 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
447 global_page_state(NR_UNSTABLE_NFS);
448 nr_writeback = global_page_state(NR_WRITEBACK);
449
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700450 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
451 bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800452
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700453 if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
454 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800456 /*
457 * Throttle it only when the background writeback cannot
458 * catch-up. This avoids (excessively) small writeouts
459 * when the bdi limits are ramping up.
460 */
461 if (nr_reclaimable + nr_writeback <
462 (background_thresh + dirty_thresh) / 2)
463 break;
464
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700465 if (!bdi->dirty_exceeded)
466 bdi->dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467
468 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
469 * Unstable writes are a feature of certain networked
470 * filesystems (i.e. NFS) in which data may have been
471 * written to the server's write cache, but has not yet
472 * been flushed to permanent storage.
473 */
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700474 if (bdi_nr_reclaimable) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 writeback_inodes(&wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476 pages_written += write_chunk - wbc.nr_to_write;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700477 get_dirty_limits(&background_thresh, &dirty_thresh,
478 &bdi_thresh, bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479 }
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700480
481 /*
482 * In order to avoid the stacked BDI deadlock we need
483 * to ensure we accurately count the 'dirty' pages when
484 * the threshold is low.
485 *
486 * Otherwise it would be possible to get thresh+n pages
487 * reported dirty, even though there are thresh-m pages
488 * actually dirty; with m+n sitting in the percpu
489 * deltas.
490 */
491 if (bdi_thresh < 2*bdi_stat_error(bdi)) {
492 bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
493 bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
494 } else if (bdi_nr_reclaimable) {
495 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
496 bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
497 }
498
499 if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
500 break;
501 if (pages_written >= write_chunk)
502 break; /* We've done our duty */
503
Andrew Morton3fcfab12006-10-19 23:28:16 -0700504 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505 }
506
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700507 if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh &&
508 bdi->dirty_exceeded)
509 bdi->dirty_exceeded = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510
511 if (writeback_in_progress(bdi))
512 return; /* pdflush is already working this queue */
513
514 /*
515 * In laptop mode, we wait until hitting the higher threshold before
516 * starting background writeout, and then write out all the way down
517 * to the lower threshold. So slow writers cause minimal disk activity.
518 *
519 * In normal mode, we start background writeout at the lower
520 * background_thresh, to keep the amount of dirty memory low.
521 */
522 if ((laptop_mode && pages_written) ||
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700523 (!laptop_mode && (global_page_state(NR_FILE_DIRTY)
524 + global_page_state(NR_UNSTABLE_NFS)
525 > background_thresh)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526 pdflush_operation(background_writeout, 0);
527}
528
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200529void set_page_dirty_balance(struct page *page, int page_mkwrite)
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700530{
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200531 if (set_page_dirty(page) || page_mkwrite) {
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700532 struct address_space *mapping = page_mapping(page);
533
534 if (mapping)
535 balance_dirty_pages_ratelimited(mapping);
536 }
537}
538
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539/**
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800540 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -0700541 * @mapping: address_space which was dirtied
Martin Waitza5802902006-04-02 13:59:55 +0200542 * @nr_pages_dirtied: number of pages which the caller has just dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 *
544 * Processes which are dirtying memory should call in here once for each page
545 * which was newly dirtied. The function will periodically check the system's
546 * dirty state and will initiate writeback if needed.
547 *
548 * On really big machines, get_writeback_state is expensive, so try to avoid
549 * calling it too often (ratelimiting). But once we're over the dirty memory
550 * limit we decrease the ratelimiting by a lot, to prevent individual processes
551 * from overshooting the limit by (ratelimit_pages) each.
552 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800553void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
554 unsigned long nr_pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555{
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800556 static DEFINE_PER_CPU(unsigned long, ratelimits) = 0;
557 unsigned long ratelimit;
558 unsigned long *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559
560 ratelimit = ratelimit_pages;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700561 if (mapping->backing_dev_info->dirty_exceeded)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700562 ratelimit = 8;
563
564 /*
565 * Check the rate limiting. Also, we do not want to throttle real-time
566 * tasks in balance_dirty_pages(). Period.
567 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800568 preempt_disable();
569 p = &__get_cpu_var(ratelimits);
570 *p += nr_pages_dirtied;
571 if (unlikely(*p >= ratelimit)) {
572 *p = 0;
573 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574 balance_dirty_pages(mapping);
575 return;
576 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800577 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578}
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800579EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580
Andrew Morton232ea4d2007-02-28 20:13:21 -0800581void throttle_vm_writeout(gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583 long background_thresh;
584 long dirty_thresh;
585
586 for ( ; ; ) {
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700587 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700588
589 /*
590 * Boost the allowable dirty threshold a bit for page
591 * allocators so they don't get DoS'ed by heavy writers
592 */
593 dirty_thresh += dirty_thresh / 10; /* wheeee... */
594
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700595 if (global_page_state(NR_UNSTABLE_NFS) +
596 global_page_state(NR_WRITEBACK) <= dirty_thresh)
597 break;
Andrew Morton3fcfab12006-10-19 23:28:16 -0700598 congestion_wait(WRITE, HZ/10);
Fengguang Wu369f2382007-10-16 23:30:45 -0700599
600 /*
601 * The caller might hold locks which can prevent IO completion
602 * or progress in the filesystem. So we cannot just sit here
603 * waiting for IO to complete.
604 */
605 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
606 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 }
608}
609
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610/*
611 * writeback at least _min_pages, and keep writing until the amount of dirty
612 * memory is less than the background threshold, or until we're all clean.
613 */
614static void background_writeout(unsigned long _min_pages)
615{
616 long min_pages = _min_pages;
617 struct writeback_control wbc = {
618 .bdi = NULL,
619 .sync_mode = WB_SYNC_NONE,
620 .older_than_this = NULL,
621 .nr_to_write = 0,
622 .nonblocking = 1,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700623 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624 };
625
626 for ( ; ; ) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 long background_thresh;
628 long dirty_thresh;
629
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700630 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700631 if (global_page_state(NR_FILE_DIRTY) +
632 global_page_state(NR_UNSTABLE_NFS) < background_thresh
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633 && min_pages <= 0)
634 break;
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800635 wbc.more_io = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636 wbc.encountered_congestion = 0;
637 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
638 wbc.pages_skipped = 0;
639 writeback_inodes(&wbc);
640 min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
641 if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
642 /* Wrote less than expected */
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800643 if (wbc.encountered_congestion || wbc.more_io)
644 congestion_wait(WRITE, HZ/10);
645 else
Linus Torvalds1da177e2005-04-16 15:20:36 -0700646 break;
647 }
648 }
649}
650
651/*
652 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
653 * the whole world. Returns 0 if a pdflush thread was dispatched. Returns
654 * -1 if all pdflush threads were busy.
655 */
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700656int wakeup_pdflush(long nr_pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657{
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700658 if (nr_pages == 0)
659 nr_pages = global_page_state(NR_FILE_DIRTY) +
660 global_page_state(NR_UNSTABLE_NFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661 return pdflush_operation(background_writeout, nr_pages);
662}
663
664static void wb_timer_fn(unsigned long unused);
665static void laptop_timer_fn(unsigned long unused);
666
Ingo Molnar8d06afa2005-09-09 13:10:40 -0700667static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0);
668static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669
670/*
671 * Periodic writeback of "old" data.
672 *
673 * Define "old": the first time one of an inode's pages is dirtied, we mark the
674 * dirtying-time in the inode's address_space. So this periodic writeback code
675 * just walks the superblock inode list, writing back any inodes which are
676 * older than a specific point in time.
677 *
Bart Samwelf6ef9432006-03-24 03:15:48 -0800678 * Try to run once per dirty_writeback_interval. But if a writeback event
679 * takes longer than a dirty_writeback_interval interval, then leave a
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 * one-second gap.
681 *
682 * older_than_this takes precedence over nr_to_write. So we'll only write back
683 * all dirty pages if they are all attached to "old" mappings.
684 */
685static void wb_kupdate(unsigned long arg)
686{
687 unsigned long oldest_jif;
688 unsigned long start_jif;
689 unsigned long next_jif;
690 long nr_to_write;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691 struct writeback_control wbc = {
692 .bdi = NULL,
693 .sync_mode = WB_SYNC_NONE,
694 .older_than_this = &oldest_jif,
695 .nr_to_write = 0,
696 .nonblocking = 1,
697 .for_kupdate = 1,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700698 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699 };
700
701 sync_supers();
702
Bart Samwelf6ef9432006-03-24 03:15:48 -0800703 oldest_jif = jiffies - dirty_expire_interval;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 start_jif = jiffies;
Bart Samwelf6ef9432006-03-24 03:15:48 -0800705 next_jif = start_jif + dirty_writeback_interval;
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700706 nr_to_write = global_page_state(NR_FILE_DIRTY) +
707 global_page_state(NR_UNSTABLE_NFS) +
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
709 while (nr_to_write > 0) {
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800710 wbc.more_io = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 wbc.encountered_congestion = 0;
712 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
713 writeback_inodes(&wbc);
714 if (wbc.nr_to_write > 0) {
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800715 if (wbc.encountered_congestion || wbc.more_io)
Andrew Morton3fcfab12006-10-19 23:28:16 -0700716 congestion_wait(WRITE, HZ/10);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717 else
718 break; /* All the old data is written */
719 }
720 nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
721 }
722 if (time_before(next_jif, jiffies + HZ))
723 next_jif = jiffies + HZ;
Bart Samwelf6ef9432006-03-24 03:15:48 -0800724 if (dirty_writeback_interval)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725 mod_timer(&wb_timer, next_jif);
726}
727
728/*
729 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
730 */
731int dirty_writeback_centisecs_handler(ctl_table *table, int write,
Andrew Morton3e733f02007-07-15 23:41:05 -0700732 struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733{
Bart Samwelf6ef9432006-03-24 03:15:48 -0800734 proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
Andrew Morton3e733f02007-07-15 23:41:05 -0700735 if (dirty_writeback_interval)
736 mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
737 else
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738 del_timer(&wb_timer);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 return 0;
740}
741
742static void wb_timer_fn(unsigned long unused)
743{
744 if (pdflush_operation(wb_kupdate, 0) < 0)
745 mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
746}
747
748static void laptop_flush(unsigned long unused)
749{
750 sys_sync();
751}
752
753static void laptop_timer_fn(unsigned long unused)
754{
755 pdflush_operation(laptop_flush, 0);
756}
757
758/*
759 * We've spun up the disk and we're in laptop mode: schedule writeback
760 * of all dirty data a few seconds from now. If the flush is already scheduled
761 * then push it back - the user is still using the disk.
762 */
763void laptop_io_completion(void)
764{
Bart Samweled5b43f2006-03-24 03:15:49 -0800765 mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766}
767
768/*
769 * We're in laptop mode and we've just synced. The sync's writes will have
770 * caused another writeback to be scheduled by laptop_io_completion.
771 * Nothing needs to be written back anymore, so we unschedule the writeback.
772 */
773void laptop_sync_completion(void)
774{
775 del_timer(&laptop_mode_wb_timer);
776}
777
778/*
779 * If ratelimit_pages is too high then we can get into dirty-data overload
780 * if a large number of processes all perform writes at the same time.
781 * If it is too low then SMP machines will call the (expensive)
782 * get_writeback_state too often.
783 *
784 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
785 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
786 * thresholds before writeback cuts in.
787 *
788 * But the limit should not be set too high. Because it also controls the
789 * amount of memory which the balance_dirty_pages() caller has to write back.
790 * If this is too large then the caller will block on the IO queue all the
791 * time. So limit it to four megabytes - the balance_dirty_pages() caller
792 * will write six megabyte chunks, max.
793 */
794
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700795void writeback_set_ratelimit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700796{
Chandra Seetharaman40c99aa2006-09-29 02:01:24 -0700797 ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 if (ratelimit_pages < 16)
799 ratelimit_pages = 16;
800 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
801 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
802}
803
Chandra Seetharaman26c21432006-06-27 02:54:10 -0700804static int __cpuinit
Linus Torvalds1da177e2005-04-16 15:20:36 -0700805ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
806{
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700807 writeback_set_ratelimit();
Paul E. McKenneyaa0f0302007-02-10 01:46:37 -0800808 return NOTIFY_DONE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809}
810
Chandra Seetharaman74b85f32006-06-27 02:54:09 -0700811static struct notifier_block __cpuinitdata ratelimit_nb = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 .notifier_call = ratelimit_handler,
813 .next = NULL,
814};
815
816/*
Linus Torvaldsdc6e29d2007-01-29 16:37:38 -0800817 * Called early on to tune the page writeback dirty limits.
818 *
819 * We used to scale dirty pages according to how total memory
820 * related to pages that could be allocated for buffers (by
821 * comparing nr_free_buffer_pages() to vm_total_pages.
822 *
823 * However, that was when we used "dirty_ratio" to scale with
824 * all memory, and we don't do that any more. "dirty_ratio"
825 * is now applied to total non-HIGHPAGE memory (by subtracting
826 * totalhigh_pages from vm_total_pages), and as such we can't
827 * get into the old insane situation any more where we had
828 * large amounts of dirty pages compared to a small amount of
829 * non-HIGHMEM memory.
830 *
831 * But we might still want to scale the dirty_ratio by how
832 * much memory the box has..
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 */
834void __init page_writeback_init(void)
835{
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700836 int shift;
837
Bart Samwelf6ef9432006-03-24 03:15:48 -0800838 mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700839 writeback_set_ratelimit();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700840 register_cpu_notifier(&ratelimit_nb);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700841
842 shift = calc_period_shift();
843 prop_descriptor_init(&vm_completions, shift);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700844 prop_descriptor_init(&vm_dirties, shift);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845}
846
David Howells811d7362006-08-29 19:06:09 +0100847/**
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700848 * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
David Howells811d7362006-08-29 19:06:09 +0100849 * @mapping: address space structure to write
850 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700851 * @writepage: function called for each page
852 * @data: data passed to writepage function
David Howells811d7362006-08-29 19:06:09 +0100853 *
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700854 * If a page is already under I/O, write_cache_pages() skips it, even
David Howells811d7362006-08-29 19:06:09 +0100855 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
856 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
857 * and msync() need to guarantee that all the data which was dirty at the time
858 * the call was made get new I/O started against them. If wbc->sync_mode is
859 * WB_SYNC_ALL then we were called for data integrity and we must wait for
860 * existing IO to complete.
David Howells811d7362006-08-29 19:06:09 +0100861 */
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700862int write_cache_pages(struct address_space *mapping,
863 struct writeback_control *wbc, writepage_t writepage,
864 void *data)
David Howells811d7362006-08-29 19:06:09 +0100865{
866 struct backing_dev_info *bdi = mapping->backing_dev_info;
867 int ret = 0;
868 int done = 0;
David Howells811d7362006-08-29 19:06:09 +0100869 struct pagevec pvec;
870 int nr_pages;
871 pgoff_t index;
872 pgoff_t end; /* Inclusive */
873 int scanned = 0;
874 int range_whole = 0;
Aneesh Kumar K.V17bc6c32008-10-16 10:09:17 -0400875 long nr_to_write = wbc->nr_to_write;
David Howells811d7362006-08-29 19:06:09 +0100876
877 if (wbc->nonblocking && bdi_write_congested(bdi)) {
878 wbc->encountered_congestion = 1;
879 return 0;
880 }
881
David Howells811d7362006-08-29 19:06:09 +0100882 pagevec_init(&pvec, 0);
883 if (wbc->range_cyclic) {
884 index = mapping->writeback_index; /* Start from prev offset */
885 end = -1;
886 } else {
887 index = wbc->range_start >> PAGE_CACHE_SHIFT;
888 end = wbc->range_end >> PAGE_CACHE_SHIFT;
889 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
890 range_whole = 1;
891 scanned = 1;
892 }
893retry:
894 while (!done && (index <= end) &&
895 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
896 PAGECACHE_TAG_DIRTY,
897 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
898 unsigned i;
899
900 scanned = 1;
901 for (i = 0; i < nr_pages; i++) {
902 struct page *page = pvec.pages[i];
903
904 /*
905 * At this point we hold neither mapping->tree_lock nor
906 * lock on the page itself: the page may be truncated or
907 * invalidated (changing page->mapping to NULL), or even
908 * swizzled back from swapper_space to tmpfs file
909 * mapping
910 */
911 lock_page(page);
912
913 if (unlikely(page->mapping != mapping)) {
914 unlock_page(page);
915 continue;
916 }
917
918 if (!wbc->range_cyclic && page->index > end) {
919 done = 1;
920 unlock_page(page);
921 continue;
922 }
923
924 if (wbc->sync_mode != WB_SYNC_NONE)
925 wait_on_page_writeback(page);
926
927 if (PageWriteback(page) ||
928 !clear_page_dirty_for_io(page)) {
929 unlock_page(page);
930 continue;
931 }
932
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700933 ret = (*writepage)(page, wbc, data);
David Howells811d7362006-08-29 19:06:09 +0100934
Andrew Mortone4230032007-10-16 23:26:02 -0700935 if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
David Howells811d7362006-08-29 19:06:09 +0100936 unlock_page(page);
Andrew Mortone4230032007-10-16 23:26:02 -0700937 ret = 0;
938 }
Aneesh Kumar K.V17bc6c32008-10-16 10:09:17 -0400939 if (ret || (--nr_to_write <= 0))
David Howells811d7362006-08-29 19:06:09 +0100940 done = 1;
941 if (wbc->nonblocking && bdi_write_congested(bdi)) {
942 wbc->encountered_congestion = 1;
943 done = 1;
944 }
945 }
946 pagevec_release(&pvec);
947 cond_resched();
948 }
949 if (!scanned && !done) {
950 /*
951 * We hit the last page and there is more work to be done: wrap
952 * back to the start of the file
953 */
954 scanned = 1;
955 index = 0;
956 goto retry;
957 }
Aneesh Kumar K.V17bc6c32008-10-16 10:09:17 -0400958 if (!wbc->no_nrwrite_index_update) {
959 if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
960 mapping->writeback_index = index;
961 wbc->nr_to_write = nr_to_write;
962 }
Aneesh Kumar K.V06d6cf62008-07-11 19:27:31 -0400963
David Howells811d7362006-08-29 19:06:09 +0100964 return ret;
965}
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700966EXPORT_SYMBOL(write_cache_pages);
967
968/*
969 * Function used by generic_writepages to call the real writepage
970 * function and set the mapping flags on error
971 */
972static int __writepage(struct page *page, struct writeback_control *wbc,
973 void *data)
974{
975 struct address_space *mapping = data;
976 int ret = mapping->a_ops->writepage(page, wbc);
977 mapping_set_error(mapping, ret);
978 return ret;
979}
980
981/**
982 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
983 * @mapping: address space structure to write
984 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
985 *
986 * This is a library function, which implements the writepages()
987 * address_space_operation.
988 */
989int generic_writepages(struct address_space *mapping,
990 struct writeback_control *wbc)
991{
992 /* deal with chardevs and other special file */
993 if (!mapping->a_ops->writepage)
994 return 0;
995
996 return write_cache_pages(mapping, wbc, __writepage, mapping);
997}
David Howells811d7362006-08-29 19:06:09 +0100998
999EXPORT_SYMBOL(generic_writepages);
1000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001001int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1002{
Andrew Morton22905f72005-11-16 15:07:01 -08001003 int ret;
1004
Linus Torvalds1da177e2005-04-16 15:20:36 -07001005 if (wbc->nr_to_write <= 0)
1006 return 0;
Andrew Morton22905f72005-11-16 15:07:01 -08001007 wbc->for_writepages = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 if (mapping->a_ops->writepages)
Peter Zijlstrad08b3852006-09-25 23:30:57 -07001009 ret = mapping->a_ops->writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001010 else
1011 ret = generic_writepages(mapping, wbc);
1012 wbc->for_writepages = 0;
1013 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014}
1015
1016/**
1017 * write_one_page - write out a single page and optionally wait on I/O
Martin Waitz67be2dd2005-05-01 08:59:26 -07001018 * @page: the page to write
1019 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 *
1021 * The page must be locked by the caller and will be unlocked upon return.
1022 *
1023 * write_one_page() returns a negative error code if I/O failed.
1024 */
1025int write_one_page(struct page *page, int wait)
1026{
1027 struct address_space *mapping = page->mapping;
1028 int ret = 0;
1029 struct writeback_control wbc = {
1030 .sync_mode = WB_SYNC_ALL,
1031 .nr_to_write = 1,
1032 };
1033
1034 BUG_ON(!PageLocked(page));
1035
1036 if (wait)
1037 wait_on_page_writeback(page);
1038
1039 if (clear_page_dirty_for_io(page)) {
1040 page_cache_get(page);
1041 ret = mapping->a_ops->writepage(page, &wbc);
1042 if (ret == 0 && wait) {
1043 wait_on_page_writeback(page);
1044 if (PageError(page))
1045 ret = -EIO;
1046 }
1047 page_cache_release(page);
1048 } else {
1049 unlock_page(page);
1050 }
1051 return ret;
1052}
1053EXPORT_SYMBOL(write_one_page);
1054
1055/*
Ken Chen76719322007-02-10 01:43:15 -08001056 * For address_spaces which do not use buffers nor write back.
1057 */
1058int __set_page_dirty_no_writeback(struct page *page)
1059{
1060 if (!PageDirty(page))
1061 SetPageDirty(page);
1062 return 0;
1063}
1064
1065/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 * For address_spaces which do not use buffers. Just tag the page as dirty in
1067 * its radix tree.
1068 *
1069 * This is also used when a single buffer is being dirtied: we want to set the
1070 * page dirty in that case, but not all the buffers. This is a "bottom-up"
1071 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
1072 *
1073 * Most callers have locked the page, which pins the address_space in memory.
1074 * But zap_pte_range() does not lock the page, however in that case the
1075 * mapping is pinned by the vma's ->vm_file reference.
1076 *
1077 * We take care to handle the case where the page was truncated from the
Simon Arlott183ff222007-10-20 01:27:18 +02001078 * mapping by re-checking page_mapping() inside tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079 */
1080int __set_page_dirty_nobuffers(struct page *page)
1081{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 if (!TestSetPageDirty(page)) {
1083 struct address_space *mapping = page_mapping(page);
1084 struct address_space *mapping2;
1085
Andrew Morton8c085402006-12-10 02:19:24 -08001086 if (!mapping)
1087 return 1;
1088
Nick Piggin19fd6232008-07-25 19:45:32 -07001089 spin_lock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001090 mapping2 = page_mapping(page);
1091 if (mapping2) { /* Race with truncate? */
1092 BUG_ON(mapping2 != mapping);
Nick Piggin787d2212007-07-17 04:03:34 -07001093 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
Andrew Morton55e829a2006-12-10 02:19:27 -08001094 if (mapping_cap_account_dirty(mapping)) {
Andrew Morton8c085402006-12-10 02:19:24 -08001095 __inc_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07001096 __inc_bdi_stat(mapping->backing_dev_info,
1097 BDI_RECLAIMABLE);
Andrew Morton55e829a2006-12-10 02:19:27 -08001098 task_io_account_write(PAGE_CACHE_SIZE);
1099 }
Andrew Morton8c085402006-12-10 02:19:24 -08001100 radix_tree_tag_set(&mapping->page_tree,
1101 page_index(page), PAGECACHE_TAG_DIRTY);
1102 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001103 spin_unlock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001104 if (mapping->host) {
1105 /* !PageAnon && !swapper_space */
1106 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001108 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001110 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111}
1112EXPORT_SYMBOL(__set_page_dirty_nobuffers);
1113
1114/*
1115 * When a writepage implementation decides that it doesn't want to write this
1116 * page for some reason, it should redirty the locked page via
1117 * redirty_page_for_writepage() and it should then unlock the page and return 0
1118 */
1119int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
1120{
1121 wbc->pages_skipped++;
1122 return __set_page_dirty_nobuffers(page);
1123}
1124EXPORT_SYMBOL(redirty_page_for_writepage);
1125
1126/*
1127 * If the mapping doesn't provide a set_page_dirty a_op, then
1128 * just fall through and assume that it wants buffer_heads.
1129 */
Peter Zijlstra3e26c142007-10-16 23:25:50 -07001130static int __set_page_dirty(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001131{
1132 struct address_space *mapping = page_mapping(page);
1133
1134 if (likely(mapping)) {
1135 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
David Howells93614012006-09-30 20:45:40 +02001136#ifdef CONFIG_BLOCK
1137 if (!spd)
1138 spd = __set_page_dirty_buffers;
1139#endif
1140 return (*spd)(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001141 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001142 if (!PageDirty(page)) {
1143 if (!TestSetPageDirty(page))
1144 return 1;
1145 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146 return 0;
1147}
Peter Zijlstra3e26c142007-10-16 23:25:50 -07001148
Harvey Harrison920c7a52008-02-04 22:29:26 -08001149int set_page_dirty(struct page *page)
Peter Zijlstra3e26c142007-10-16 23:25:50 -07001150{
1151 int ret = __set_page_dirty(page);
1152 if (ret)
1153 task_dirty_inc(current);
1154 return ret;
1155}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156EXPORT_SYMBOL(set_page_dirty);
1157
1158/*
1159 * set_page_dirty() is racy if the caller has no reference against
1160 * page->mapping->host, and if the page is unlocked. This is because another
1161 * CPU could truncate the page off the mapping and then free the mapping.
1162 *
1163 * Usually, the page _is_ locked, or the caller is a user-space process which
1164 * holds a reference on the inode by having an open file.
1165 *
1166 * In other cases, the page should be locked before running set_page_dirty().
1167 */
1168int set_page_dirty_lock(struct page *page)
1169{
1170 int ret;
1171
Nick Piggindb376482006-09-25 23:31:24 -07001172 lock_page_nosync(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001173 ret = set_page_dirty(page);
1174 unlock_page(page);
1175 return ret;
1176}
1177EXPORT_SYMBOL(set_page_dirty_lock);
1178
1179/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180 * Clear a page's dirty flag, while caring for dirty memory accounting.
1181 * Returns true if the page was previously dirty.
1182 *
1183 * This is for preparing to put the page under writeout. We leave the page
1184 * tagged as dirty in the radix tree so that a concurrent write-for-sync
1185 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
1186 * implementation will run either set_page_writeback() or set_page_dirty(),
1187 * at which stage we bring the page's dirty flag and radix-tree dirty tag
1188 * back into sync.
1189 *
1190 * This incoherency between the page's dirty flag and radix-tree tag is
1191 * unfortunate, but it only exists while the page is locked.
1192 */
1193int clear_page_dirty_for_io(struct page *page)
1194{
1195 struct address_space *mapping = page_mapping(page);
1196
Nick Piggin79352892007-07-19 01:47:22 -07001197 BUG_ON(!PageLocked(page));
1198
Fengguang Wufe3cba12007-07-19 01:48:07 -07001199 ClearPageReclaim(page);
Linus Torvalds7658cc22006-12-29 10:00:58 -08001200 if (mapping && mapping_cap_account_dirty(mapping)) {
1201 /*
1202 * Yes, Virginia, this is indeed insane.
1203 *
1204 * We use this sequence to make sure that
1205 * (a) we account for dirty stats properly
1206 * (b) we tell the low-level filesystem to
1207 * mark the whole page dirty if it was
1208 * dirty in a pagetable. Only to then
1209 * (c) clean the page again and return 1 to
1210 * cause the writeback.
1211 *
1212 * This way we avoid all nasty races with the
1213 * dirty bit in multiple places and clearing
1214 * them concurrently from different threads.
1215 *
1216 * Note! Normally the "set_page_dirty(page)"
1217 * has no effect on the actual dirty bit - since
1218 * that will already usually be set. But we
1219 * need the side effects, and it can help us
1220 * avoid races.
1221 *
1222 * We basically use the page "master dirty bit"
1223 * as a serialization point for all the different
1224 * threads doing their things.
Linus Torvalds7658cc22006-12-29 10:00:58 -08001225 */
1226 if (page_mkclean(page))
1227 set_page_dirty(page);
Nick Piggin79352892007-07-19 01:47:22 -07001228 /*
1229 * We carefully synchronise fault handlers against
1230 * installing a dirty pte and marking the page dirty
1231 * at this point. We do this by having them hold the
1232 * page lock at some point after installing their
1233 * pte, but before marking the page dirty.
1234 * Pages are always locked coming in here, so we get
1235 * the desired exclusion. See mm/memory.c:do_wp_page()
1236 * for more comments.
1237 */
Linus Torvalds7658cc22006-12-29 10:00:58 -08001238 if (TestClearPageDirty(page)) {
Andrew Morton8c085402006-12-10 02:19:24 -08001239 dec_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07001240 dec_bdi_stat(mapping->backing_dev_info,
1241 BDI_RECLAIMABLE);
Linus Torvalds7658cc22006-12-29 10:00:58 -08001242 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001244 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001246 return TestClearPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247}
Hans Reiser58bb01a2005-11-18 01:10:53 -08001248EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249
1250int test_clear_page_writeback(struct page *page)
1251{
1252 struct address_space *mapping = page_mapping(page);
1253 int ret;
1254
1255 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001256 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 unsigned long flags;
1258
Nick Piggin19fd6232008-07-25 19:45:32 -07001259 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260 ret = TestClearPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001261 if (ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262 radix_tree_tag_clear(&mapping->page_tree,
1263 page_index(page),
1264 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001265 if (bdi_cap_account_writeback(bdi)) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001266 __dec_bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001267 __bdi_writeout_inc(bdi);
1268 }
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001269 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001270 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 } else {
1272 ret = TestClearPageWriteback(page);
1273 }
Andrew Mortond688abf2007-07-19 01:49:17 -07001274 if (ret)
1275 dec_zone_page_state(page, NR_WRITEBACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 return ret;
1277}
1278
1279int test_set_page_writeback(struct page *page)
1280{
1281 struct address_space *mapping = page_mapping(page);
1282 int ret;
1283
1284 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001285 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 unsigned long flags;
1287
Nick Piggin19fd6232008-07-25 19:45:32 -07001288 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001289 ret = TestSetPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001290 if (!ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001291 radix_tree_tag_set(&mapping->page_tree,
1292 page_index(page),
1293 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001294 if (bdi_cap_account_writeback(bdi))
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001295 __inc_bdi_stat(bdi, BDI_WRITEBACK);
1296 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001297 if (!PageDirty(page))
1298 radix_tree_tag_clear(&mapping->page_tree,
1299 page_index(page),
1300 PAGECACHE_TAG_DIRTY);
Nick Piggin19fd6232008-07-25 19:45:32 -07001301 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001302 } else {
1303 ret = TestSetPageWriteback(page);
1304 }
Andrew Mortond688abf2007-07-19 01:49:17 -07001305 if (!ret)
1306 inc_zone_page_state(page, NR_WRITEBACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 return ret;
1308
1309}
1310EXPORT_SYMBOL(test_set_page_writeback);
1311
1312/*
Nick Piggin00128182007-10-16 01:24:40 -07001313 * Return true if any of the pages in the mapping are marked with the
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314 * passed tag.
1315 */
1316int mapping_tagged(struct address_space *mapping, int tag)
1317{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318 int ret;
Nick Piggin00128182007-10-16 01:24:40 -07001319 rcu_read_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320 ret = radix_tree_tagged(&mapping->page_tree, tag);
Nick Piggin00128182007-10-16 01:24:40 -07001321 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001322 return ret;
1323}
1324EXPORT_SYMBOL(mapping_tagged);