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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>
Dave Chinner028c2dd2010-07-07 13:24:07 +100037#include <trace/events/writeback.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038
39/*
Wu Fengguangffd1f602011-06-19 22:18:42 -060040 * Sleep at most 200ms at a time in balance_dirty_pages().
41 */
42#define MAX_PAUSE max(HZ/5, 1)
43
44/*
Wu Fengguange98be2d2010-08-29 11:22:30 -060045 * Estimate write bandwidth at 200ms intervals.
46 */
47#define BANDWIDTH_INTERVAL max(HZ/5, 1)
48
49/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
51 * will look to see if it needs to force writeback or throttling.
52 */
53static long ratelimit_pages = 32;
54
Linus Torvalds1da177e2005-04-16 15:20:36 -070055/*
56 * When balance_dirty_pages decides that the caller needs to perform some
57 * non-background writeback, this is how many pages it will attempt to write.
Wu Fengguang3a2e9a52009-09-23 21:56:00 +080058 * It should be somewhat larger than dirtied pages to ensure that reasonably
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 * large amounts of I/O are submitted.
60 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +080061static inline long sync_writeback_pages(unsigned long dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -070062{
Wu Fengguang3a2e9a52009-09-23 21:56:00 +080063 if (dirtied < ratelimit_pages)
64 dirtied = ratelimit_pages;
65
66 return dirtied + dirtied / 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -070067}
68
69/* The following parameters are exported via /proc/sys/vm */
70
71/*
Jens Axboe5b0830c2009-09-23 19:37:09 +020072 * Start background writeback (via writeback threads) at this percentage
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080074int dirty_background_ratio = 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -070075
76/*
David Rientjes2da02992009-01-06 14:39:31 -080077 * dirty_background_bytes starts at 0 (disabled) so that it is a function of
78 * dirty_background_ratio * the amount of dirtyable memory
79 */
80unsigned long dirty_background_bytes;
81
82/*
Bron Gondwana195cf452008-02-04 22:29:20 -080083 * free highmem will not be subtracted from the total free memory
84 * for calculating free ratios if vm_highmem_is_dirtyable is true
85 */
86int vm_highmem_is_dirtyable;
87
88/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 * The generator of dirty data starts writeback at this percentage
90 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080091int vm_dirty_ratio = 20;
Linus Torvalds1da177e2005-04-16 15:20:36 -070092
93/*
David Rientjes2da02992009-01-06 14:39:31 -080094 * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
95 * vm_dirty_ratio * the amount of dirtyable memory
96 */
97unsigned long vm_dirty_bytes;
98
99/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -0700100 * The interval between `kupdate'-style writebacks
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -0700102unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103
104/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -0700105 * The longest time for which data is allowed to remain dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -0700107unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108
109/*
110 * Flag that makes the machine dump writes/reads and block dirtyings.
111 */
112int block_dump;
113
114/*
Bart Samweled5b43f2006-03-24 03:15:49 -0800115 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
116 * a full sync is triggered after this time elapses without any disk activity.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117 */
118int laptop_mode;
119
120EXPORT_SYMBOL(laptop_mode);
121
122/* End of sysctl-exported parameters */
123
Wu Fengguangc42843f2011-03-02 15:54:09 -0600124unsigned long global_dirty_limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126/*
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700127 * Scale the writeback cache size proportional to the relative writeout speeds.
128 *
129 * We do this by keeping a floating proportion between BDIs, based on page
130 * writeback completions [end_page_writeback()]. Those devices that write out
131 * pages fastest will get the larger share, while the slower will get a smaller
132 * share.
133 *
134 * We use page writeout completions because we are interested in getting rid of
135 * dirty pages. Having them written out is the primary goal.
136 *
137 * We introduce a concept of time, a period over which we measure these events,
138 * because demand can/will vary over time. The length of this period itself is
139 * measured in page writeback completions.
140 *
141 */
142static struct prop_descriptor vm_completions;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700143static struct prop_descriptor vm_dirties;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700144
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700145/*
146 * couple the period to the dirty_ratio:
147 *
148 * period/2 ~ roundup_pow_of_two(dirty limit)
149 */
150static int calc_period_shift(void)
151{
152 unsigned long dirty_total;
153
David Rientjes2da02992009-01-06 14:39:31 -0800154 if (vm_dirty_bytes)
155 dirty_total = vm_dirty_bytes / PAGE_SIZE;
156 else
157 dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
158 100;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700159 return 2 + ilog2(dirty_total - 1);
160}
161
162/*
David Rientjes2da02992009-01-06 14:39:31 -0800163 * update the period when the dirty threshold changes.
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700164 */
David Rientjes2da02992009-01-06 14:39:31 -0800165static void update_completion_period(void)
166{
167 int shift = calc_period_shift();
168 prop_change_shift(&vm_completions, shift);
169 prop_change_shift(&vm_dirties, shift);
170}
171
172int dirty_background_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700173 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800174 loff_t *ppos)
175{
176 int ret;
177
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700178 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800179 if (ret == 0 && write)
180 dirty_background_bytes = 0;
181 return ret;
182}
183
184int dirty_background_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700185 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800186 loff_t *ppos)
187{
188 int ret;
189
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700190 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800191 if (ret == 0 && write)
192 dirty_background_ratio = 0;
193 return ret;
194}
195
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700196int dirty_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700197 void __user *buffer, size_t *lenp,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700198 loff_t *ppos)
199{
200 int old_ratio = vm_dirty_ratio;
David Rientjes2da02992009-01-06 14:39:31 -0800201 int ret;
202
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700203 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700204 if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
David Rientjes2da02992009-01-06 14:39:31 -0800205 update_completion_period();
206 vm_dirty_bytes = 0;
207 }
208 return ret;
209}
210
211
212int dirty_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700213 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800214 loff_t *ppos)
215{
Sven Wegenerfc3501d2009-02-11 13:04:23 -0800216 unsigned long old_bytes = vm_dirty_bytes;
David Rientjes2da02992009-01-06 14:39:31 -0800217 int ret;
218
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700219 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800220 if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
221 update_completion_period();
222 vm_dirty_ratio = 0;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700223 }
224 return ret;
225}
226
227/*
228 * Increment the BDI's writeout completion count and the global writeout
229 * completion count. Called from test_clear_page_writeback().
230 */
231static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
232{
Jan Karaf7d2b1e2010-12-08 22:44:24 -0600233 __inc_bdi_stat(bdi, BDI_WRITTEN);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700234 __prop_inc_percpu_max(&vm_completions, &bdi->completions,
235 bdi->max_prop_frac);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700236}
237
Miklos Szeredidd5656e2008-04-30 00:54:37 -0700238void bdi_writeout_inc(struct backing_dev_info *bdi)
239{
240 unsigned long flags;
241
242 local_irq_save(flags);
243 __bdi_writeout_inc(bdi);
244 local_irq_restore(flags);
245}
246EXPORT_SYMBOL_GPL(bdi_writeout_inc);
247
Nick Piggin1cf6e7d2009-02-18 14:48:18 -0800248void task_dirty_inc(struct task_struct *tsk)
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700249{
250 prop_inc_single(&vm_dirties, &tsk->dirties);
251}
252
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700253/*
254 * Obtain an accurate fraction of the BDI's portion.
255 */
256static void bdi_writeout_fraction(struct backing_dev_info *bdi,
257 long *numerator, long *denominator)
258{
Wu Fengguang3efaf0f2010-12-16 22:22:00 -0600259 prop_fraction_percpu(&vm_completions, &bdi->completions,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700260 numerator, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700261}
262
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700263static inline void task_dirties_fraction(struct task_struct *tsk,
264 long *numerator, long *denominator)
265{
266 prop_fraction_single(&vm_dirties, &tsk->dirties,
267 numerator, denominator);
268}
269
270/*
Wu Fengguang1babe182010-08-11 14:17:40 -0700271 * task_dirty_limit - scale down dirty throttling threshold for one task
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700272 *
273 * task specific dirty limit:
274 *
275 * dirty -= (dirty/8) * p_{t}
Wu Fengguang1babe182010-08-11 14:17:40 -0700276 *
277 * To protect light/slow dirtying tasks from heavier/fast ones, we start
278 * throttling individual tasks before reaching the bdi dirty limit.
279 * Relatively low thresholds will be allocated to heavy dirtiers. So when
280 * dirty pages grow large, heavy dirtiers will be throttled first, which will
281 * effectively curb the growth of dirty pages. Light dirtiers with high enough
282 * dirty threshold may never get throttled.
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700283 */
Jan Karabcff25f2011-07-01 13:31:25 -0600284#define TASK_LIMIT_FRACTION 8
Wu Fengguang16c40422010-08-11 14:17:39 -0700285static unsigned long task_dirty_limit(struct task_struct *tsk,
286 unsigned long bdi_dirty)
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700287{
288 long numerator, denominator;
Wu Fengguang16c40422010-08-11 14:17:39 -0700289 unsigned long dirty = bdi_dirty;
Jan Karabcff25f2011-07-01 13:31:25 -0600290 u64 inv = dirty / TASK_LIMIT_FRACTION;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700291
292 task_dirties_fraction(tsk, &numerator, &denominator);
293 inv *= numerator;
294 do_div(inv, denominator);
295
296 dirty -= inv;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700297
Wu Fengguang16c40422010-08-11 14:17:39 -0700298 return max(dirty, bdi_dirty/2);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700299}
300
Jan Karabcff25f2011-07-01 13:31:25 -0600301/* Minimum limit for any task */
302static unsigned long task_min_dirty_limit(unsigned long bdi_dirty)
303{
304 return bdi_dirty - bdi_dirty / TASK_LIMIT_FRACTION;
305}
306
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700307/*
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700308 *
309 */
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700310static unsigned int bdi_min_ratio;
311
312int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
313{
314 int ret = 0;
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700315
Jens Axboecfc4ba52009-09-14 13:12:40 +0200316 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700317 if (min_ratio > bdi->max_ratio) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700318 ret = -EINVAL;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700319 } else {
320 min_ratio -= bdi->min_ratio;
321 if (bdi_min_ratio + min_ratio < 100) {
322 bdi_min_ratio += min_ratio;
323 bdi->min_ratio += min_ratio;
324 } else {
325 ret = -EINVAL;
326 }
327 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200328 spin_unlock_bh(&bdi_lock);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700329
330 return ret;
331}
332
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700333int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
334{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700335 int ret = 0;
336
337 if (max_ratio > 100)
338 return -EINVAL;
339
Jens Axboecfc4ba52009-09-14 13:12:40 +0200340 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700341 if (bdi->min_ratio > max_ratio) {
342 ret = -EINVAL;
343 } else {
344 bdi->max_ratio = max_ratio;
345 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
346 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200347 spin_unlock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700348
349 return ret;
350}
351EXPORT_SYMBOL(bdi_set_max_ratio);
352
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700353/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 * Work out the current dirty-memory clamping and background writeout
355 * thresholds.
356 *
357 * The main aim here is to lower them aggressively if there is a lot of mapped
358 * memory around. To avoid stressing page reclaim with lots of unreclaimable
359 * pages. It is better to clamp down on writers than to start swapping, and
360 * performing lots of scanning.
361 *
362 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
363 *
364 * We don't permit the clamping level to fall below 5% - that is getting rather
365 * excessive.
366 *
367 * We make sure that the background writeout level is below the adjusted
368 * clamping level.
369 */
Christoph Lameter1b424462007-05-06 14:48:59 -0700370
371static unsigned long highmem_dirtyable_memory(unsigned long total)
372{
373#ifdef CONFIG_HIGHMEM
374 int node;
375 unsigned long x = 0;
376
Lee Schermerhorn37b07e42007-10-16 01:25:39 -0700377 for_each_node_state(node, N_HIGH_MEMORY) {
Christoph Lameter1b424462007-05-06 14:48:59 -0700378 struct zone *z =
379 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
380
Wu Fengguangadea02a2009-09-21 17:01:42 -0700381 x += zone_page_state(z, NR_FREE_PAGES) +
382 zone_reclaimable_pages(z);
Christoph Lameter1b424462007-05-06 14:48:59 -0700383 }
384 /*
385 * Make sure that the number of highmem pages is never larger
386 * than the number of the total dirtyable memory. This can only
387 * occur in very strange VM situations but we want to make sure
388 * that this does not occur.
389 */
390 return min(x, total);
391#else
392 return 0;
393#endif
394}
395
Steven Rostedt3eefae92008-05-12 21:21:04 +0200396/**
397 * determine_dirtyable_memory - amount of memory that may be used
398 *
399 * Returns the numebr of pages that can currently be freed and used
400 * by the kernel for direct mappings.
401 */
402unsigned long determine_dirtyable_memory(void)
Christoph Lameter1b424462007-05-06 14:48:59 -0700403{
404 unsigned long x;
405
Wu Fengguangadea02a2009-09-21 17:01:42 -0700406 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
Bron Gondwana195cf452008-02-04 22:29:20 -0800407
408 if (!vm_highmem_is_dirtyable)
409 x -= highmem_dirtyable_memory(x);
410
Christoph Lameter1b424462007-05-06 14:48:59 -0700411 return x + 1; /* Ensure that we never return 0 */
412}
413
Wu Fengguangffd1f602011-06-19 22:18:42 -0600414static unsigned long hard_dirty_limit(unsigned long thresh)
415{
416 return max(thresh, global_dirty_limit);
417}
418
Randy Dunlap03ab4502010-08-14 13:05:17 -0700419/*
Wu Fengguang1babe182010-08-11 14:17:40 -0700420 * global_dirty_limits - background-writeback and dirty-throttling thresholds
421 *
422 * Calculate the dirty thresholds based on sysctl parameters
423 * - vm.dirty_background_ratio or vm.dirty_background_bytes
424 * - vm.dirty_ratio or vm.dirty_bytes
425 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
Minchan Kimebd13732011-01-04 01:36:48 +0900426 * real-time tasks.
Wu Fengguang1babe182010-08-11 14:17:40 -0700427 */
Wu Fengguang16c40422010-08-11 14:17:39 -0700428void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429{
David Rientjes364aeb22009-01-06 14:39:29 -0800430 unsigned long background;
431 unsigned long dirty;
Minchan Kim240c8792011-01-13 15:46:27 -0800432 unsigned long uninitialized_var(available_memory);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 struct task_struct *tsk;
434
Minchan Kim240c8792011-01-13 15:46:27 -0800435 if (!vm_dirty_bytes || !dirty_background_bytes)
436 available_memory = determine_dirtyable_memory();
437
David Rientjes2da02992009-01-06 14:39:31 -0800438 if (vm_dirty_bytes)
439 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
Wu Fengguang4cbec4c2010-10-26 14:21:45 -0700440 else
441 dirty = (vm_dirty_ratio * available_memory) / 100;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442
David Rientjes2da02992009-01-06 14:39:31 -0800443 if (dirty_background_bytes)
444 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
445 else
446 background = (dirty_background_ratio * available_memory) / 100;
447
448 if (background >= dirty)
449 background = dirty / 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450 tsk = current;
451 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
452 background += background / 4;
453 dirty += dirty / 4;
454 }
455 *pbackground = background;
456 *pdirty = dirty;
Wu Fengguange1cbe232010-12-06 22:34:29 -0600457 trace_global_dirty_state(background, dirty);
Wu Fengguang16c40422010-08-11 14:17:39 -0700458}
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700459
Wu Fengguang6f718652011-03-02 17:14:34 -0600460/**
Wu Fengguang1babe182010-08-11 14:17:40 -0700461 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
Wu Fengguang6f718652011-03-02 17:14:34 -0600462 * @bdi: the backing_dev_info to query
463 * @dirty: global dirty limit in pages
Wu Fengguang1babe182010-08-11 14:17:40 -0700464 *
Wu Fengguang6f718652011-03-02 17:14:34 -0600465 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
466 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
467 * And the "limit" in the name is not seriously taken as hard limit in
468 * balance_dirty_pages().
469 *
470 * It allocates high/low dirty limits to fast/slow devices, in order to prevent
Wu Fengguang1babe182010-08-11 14:17:40 -0700471 * - starving fast devices
472 * - piling up dirty pages (that will take long time to sync) on slow devices
473 *
474 * The bdi's share of dirty limit will be adapting to its throughput and
475 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
476 */
477unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
Wu Fengguang16c40422010-08-11 14:17:39 -0700478{
479 u64 bdi_dirty;
480 long numerator, denominator;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700481
Wu Fengguang16c40422010-08-11 14:17:39 -0700482 /*
483 * Calculate this BDI's share of the dirty ratio.
484 */
485 bdi_writeout_fraction(bdi, &numerator, &denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700486
Wu Fengguang16c40422010-08-11 14:17:39 -0700487 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
488 bdi_dirty *= numerator;
489 do_div(bdi_dirty, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700490
Wu Fengguang16c40422010-08-11 14:17:39 -0700491 bdi_dirty += (dirty * bdi->min_ratio) / 100;
492 if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
493 bdi_dirty = dirty * bdi->max_ratio / 100;
494
495 return bdi_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496}
497
Wu Fengguange98be2d2010-08-29 11:22:30 -0600498static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
499 unsigned long elapsed,
500 unsigned long written)
501{
502 const unsigned long period = roundup_pow_of_two(3 * HZ);
503 unsigned long avg = bdi->avg_write_bandwidth;
504 unsigned long old = bdi->write_bandwidth;
505 u64 bw;
506
507 /*
508 * bw = written * HZ / elapsed
509 *
510 * bw * elapsed + write_bandwidth * (period - elapsed)
511 * write_bandwidth = ---------------------------------------------------
512 * period
513 */
514 bw = written - bdi->written_stamp;
515 bw *= HZ;
516 if (unlikely(elapsed > period)) {
517 do_div(bw, elapsed);
518 avg = bw;
519 goto out;
520 }
521 bw += (u64)bdi->write_bandwidth * (period - elapsed);
522 bw >>= ilog2(period);
523
524 /*
525 * one more level of smoothing, for filtering out sudden spikes
526 */
527 if (avg > old && old >= (unsigned long)bw)
528 avg -= (avg - old) >> 3;
529
530 if (avg < old && old <= (unsigned long)bw)
531 avg += (old - avg) >> 3;
532
533out:
534 bdi->write_bandwidth = bw;
535 bdi->avg_write_bandwidth = avg;
536}
537
Wu Fengguangc42843f2011-03-02 15:54:09 -0600538/*
539 * The global dirtyable memory and dirty threshold could be suddenly knocked
540 * down by a large amount (eg. on the startup of KVM in a swapless system).
541 * This may throw the system into deep dirty exceeded state and throttle
542 * heavy/light dirtiers alike. To retain good responsiveness, maintain
543 * global_dirty_limit for tracking slowly down to the knocked down dirty
544 * threshold.
545 */
546static void update_dirty_limit(unsigned long thresh, unsigned long dirty)
547{
548 unsigned long limit = global_dirty_limit;
549
550 /*
551 * Follow up in one step.
552 */
553 if (limit < thresh) {
554 limit = thresh;
555 goto update;
556 }
557
558 /*
559 * Follow down slowly. Use the higher one as the target, because thresh
560 * may drop below dirty. This is exactly the reason to introduce
561 * global_dirty_limit which is guaranteed to lie above the dirty pages.
562 */
563 thresh = max(thresh, dirty);
564 if (limit > thresh) {
565 limit -= (limit - thresh) >> 5;
566 goto update;
567 }
568 return;
569update:
570 global_dirty_limit = limit;
571}
572
573static void global_update_bandwidth(unsigned long thresh,
574 unsigned long dirty,
575 unsigned long now)
576{
577 static DEFINE_SPINLOCK(dirty_lock);
578 static unsigned long update_time;
579
580 /*
581 * check locklessly first to optimize away locking for the most time
582 */
583 if (time_before(now, update_time + BANDWIDTH_INTERVAL))
584 return;
585
586 spin_lock(&dirty_lock);
587 if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) {
588 update_dirty_limit(thresh, dirty);
589 update_time = now;
590 }
591 spin_unlock(&dirty_lock);
592}
593
Wu Fengguange98be2d2010-08-29 11:22:30 -0600594void __bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -0600595 unsigned long thresh,
596 unsigned long dirty,
597 unsigned long bdi_thresh,
598 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -0600599 unsigned long start_time)
600{
601 unsigned long now = jiffies;
602 unsigned long elapsed = now - bdi->bw_time_stamp;
603 unsigned long written;
604
605 /*
606 * rate-limit, only update once every 200ms.
607 */
608 if (elapsed < BANDWIDTH_INTERVAL)
609 return;
610
611 written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
612
613 /*
614 * Skip quiet periods when disk bandwidth is under-utilized.
615 * (at least 1s idle time between two flusher runs)
616 */
617 if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
618 goto snapshot;
619
Wu Fengguangc42843f2011-03-02 15:54:09 -0600620 if (thresh)
621 global_update_bandwidth(thresh, dirty, now);
622
Wu Fengguange98be2d2010-08-29 11:22:30 -0600623 bdi_update_write_bandwidth(bdi, elapsed, written);
624
625snapshot:
626 bdi->written_stamp = written;
627 bdi->bw_time_stamp = now;
628}
629
630static void bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -0600631 unsigned long thresh,
632 unsigned long dirty,
633 unsigned long bdi_thresh,
634 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -0600635 unsigned long start_time)
636{
637 if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
638 return;
639 spin_lock(&bdi->wb.list_lock);
Wu Fengguangc42843f2011-03-02 15:54:09 -0600640 __bdi_update_bandwidth(bdi, thresh, dirty, bdi_thresh, bdi_dirty,
641 start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -0600642 spin_unlock(&bdi->wb.list_lock);
643}
644
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645/*
646 * balance_dirty_pages() must be called by processes which are generating dirty
647 * data. It looks at the number of dirty pages in the machine and will force
648 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
Jens Axboe5b0830c2009-09-23 19:37:09 +0200649 * If we're over `background_thresh' then the writeback threads are woken to
650 * perform some writeout.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800652static void balance_dirty_pages(struct address_space *mapping,
653 unsigned long write_chunk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654{
Wu Fengguang77627412010-09-12 13:34:05 -0600655 unsigned long nr_reclaimable, bdi_nr_reclaimable;
656 unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
657 unsigned long bdi_dirty;
David Rientjes364aeb22009-01-06 14:39:29 -0800658 unsigned long background_thresh;
659 unsigned long dirty_thresh;
660 unsigned long bdi_thresh;
Jan Karabcff25f2011-07-01 13:31:25 -0600661 unsigned long task_bdi_thresh;
662 unsigned long min_task_bdi_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700663 unsigned long pages_written = 0;
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200664 unsigned long pause = 1;
Wu Fengguange50e3722010-08-11 14:17:37 -0700665 bool dirty_exceeded = false;
Jan Karabcff25f2011-07-01 13:31:25 -0600666 bool clear_dirty_exceeded = true;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 struct backing_dev_info *bdi = mapping->backing_dev_info;
Wu Fengguange98be2d2010-08-29 11:22:30 -0600668 unsigned long start_time = jiffies;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669
670 for (;;) {
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800671 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
672 global_page_state(NR_UNSTABLE_NFS);
Wu Fengguang77627412010-09-12 13:34:05 -0600673 nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800674
Wu Fengguang16c40422010-08-11 14:17:39 -0700675 global_dirty_limits(&background_thresh, &dirty_thresh);
676
677 /*
678 * Throttle it only when the background writeback cannot
679 * catch-up. This avoids (excessively) small writeouts
680 * when the bdi limits are ramping up.
681 */
Wu Fengguang77627412010-09-12 13:34:05 -0600682 if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
Wu Fengguang16c40422010-08-11 14:17:39 -0700683 break;
684
685 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
Jan Karabcff25f2011-07-01 13:31:25 -0600686 min_task_bdi_thresh = task_min_dirty_limit(bdi_thresh);
687 task_bdi_thresh = task_dirty_limit(current, bdi_thresh);
Wu Fengguang16c40422010-08-11 14:17:39 -0700688
Wu Fengguange50e3722010-08-11 14:17:37 -0700689 /*
690 * In order to avoid the stacked BDI deadlock we need
691 * to ensure we accurately count the 'dirty' pages when
692 * the threshold is low.
693 *
694 * Otherwise it would be possible to get thresh+n pages
695 * reported dirty, even though there are thresh-m pages
696 * actually dirty; with m+n sitting in the percpu
697 * deltas.
698 */
Jan Karabcff25f2011-07-01 13:31:25 -0600699 if (task_bdi_thresh < 2 * bdi_stat_error(bdi)) {
Wu Fengguange50e3722010-08-11 14:17:37 -0700700 bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
Wu Fengguang77627412010-09-12 13:34:05 -0600701 bdi_dirty = bdi_nr_reclaimable +
702 bdi_stat_sum(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -0700703 } else {
704 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
Wu Fengguang77627412010-09-12 13:34:05 -0600705 bdi_dirty = bdi_nr_reclaimable +
706 bdi_stat(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -0700707 }
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800708
Wu Fengguange50e3722010-08-11 14:17:37 -0700709 /*
710 * The bdi thresh is somehow "soft" limit derived from the
711 * global "hard" limit. The former helps to prevent heavy IO
712 * bdi or process from holding back light ones; The latter is
713 * the last resort safeguard.
714 */
Jan Karabcff25f2011-07-01 13:31:25 -0600715 dirty_exceeded = (bdi_dirty > task_bdi_thresh) ||
Wu Fengguang77627412010-09-12 13:34:05 -0600716 (nr_dirty > dirty_thresh);
Jan Karabcff25f2011-07-01 13:31:25 -0600717 clear_dirty_exceeded = (bdi_dirty <= min_task_bdi_thresh) &&
718 (nr_dirty <= dirty_thresh);
Wu Fengguange50e3722010-08-11 14:17:37 -0700719
720 if (!dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700721 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700723 if (!bdi->dirty_exceeded)
724 bdi->dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725
Wu Fengguangc42843f2011-03-02 15:54:09 -0600726 bdi_update_bandwidth(bdi, dirty_thresh, nr_dirty,
727 bdi_thresh, bdi_dirty, start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -0600728
Linus Torvalds1da177e2005-04-16 15:20:36 -0700729 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
730 * Unstable writes are a feature of certain networked
731 * filesystems (i.e. NFS) in which data may have been
732 * written to the server's write cache, but has not yet
733 * been flushed to permanent storage.
Richard Kennedyd7831a02009-06-30 11:41:35 -0700734 * Only move pages to writeback if this bdi is over its
735 * threshold otherwise wait until the disk writes catch
736 * up.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737 */
Wu Fengguangd46db3d2011-05-04 19:54:37 -0600738 trace_balance_dirty_start(bdi);
Jan Karabcff25f2011-07-01 13:31:25 -0600739 if (bdi_nr_reclaimable > task_bdi_thresh) {
Wu Fengguangd46db3d2011-05-04 19:54:37 -0600740 pages_written += writeback_inodes_wb(&bdi->wb,
741 write_chunk);
742 trace_balance_dirty_written(bdi, pages_written);
Wu Fengguange50e3722010-08-11 14:17:37 -0700743 if (pages_written >= write_chunk)
744 break; /* We've done our duty */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745 }
Wu Fengguangd153ba62010-12-21 17:24:21 -0800746 __set_current_state(TASK_UNINTERRUPTIBLE);
Wu Fengguangd25105e2009-10-09 12:40:42 +0200747 io_schedule_timeout(pause);
Wu Fengguangd46db3d2011-05-04 19:54:37 -0600748 trace_balance_dirty_wait(bdi);
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200749
Wu Fengguangffd1f602011-06-19 22:18:42 -0600750 dirty_thresh = hard_dirty_limit(dirty_thresh);
751 /*
752 * max-pause area. If dirty exceeded but still within this
753 * area, no need to sleep for more than 200ms: (a) 8 pages per
754 * 200ms is typically more than enough to curb heavy dirtiers;
755 * (b) the pause time limit makes the dirtiers more responsive.
756 */
757 if (nr_dirty < dirty_thresh +
758 dirty_thresh / DIRTY_MAXPAUSE_AREA &&
759 time_after(jiffies, start_time + MAX_PAUSE))
760 break;
761 /*
762 * pass-good area. When some bdi gets blocked (eg. NFS server
763 * not responding), or write bandwidth dropped dramatically due
764 * to concurrent reads, or dirty threshold suddenly dropped and
765 * the dirty pages cannot be brought down anytime soon (eg. on
766 * slow USB stick), at least let go of the good bdi's.
767 */
768 if (nr_dirty < dirty_thresh +
769 dirty_thresh / DIRTY_PASSGOOD_AREA &&
770 bdi_dirty < bdi_thresh)
771 break;
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200772
773 /*
774 * Increase the delay for each loop, up to our previous
775 * default of taking a 100ms nap.
776 */
777 pause <<= 1;
778 if (pause > HZ / 10)
779 pause = HZ / 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700780 }
781
Jan Karabcff25f2011-07-01 13:31:25 -0600782 /* Clear dirty_exceeded flag only when no task can exceed the limit */
783 if (clear_dirty_exceeded && bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700784 bdi->dirty_exceeded = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700785
786 if (writeback_in_progress(bdi))
Jens Axboe5b0830c2009-09-23 19:37:09 +0200787 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788
789 /*
790 * In laptop mode, we wait until hitting the higher threshold before
791 * starting background writeout, and then write out all the way down
792 * to the lower threshold. So slow writers cause minimal disk activity.
793 *
794 * In normal mode, we start background writeout at the lower
795 * background_thresh, to keep the amount of dirty memory low.
796 */
797 if ((laptop_mode && pages_written) ||
Wu Fengguange50e3722010-08-11 14:17:37 -0700798 (!laptop_mode && (nr_reclaimable > background_thresh)))
Christoph Hellwigc5444192010-06-08 18:15:15 +0200799 bdi_start_background_writeback(bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800}
801
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200802void set_page_dirty_balance(struct page *page, int page_mkwrite)
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700803{
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200804 if (set_page_dirty(page) || page_mkwrite) {
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700805 struct address_space *mapping = page_mapping(page);
806
807 if (mapping)
808 balance_dirty_pages_ratelimited(mapping);
809 }
810}
811
Tejun Heo245b2e72009-06-24 15:13:48 +0900812static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
813
Linus Torvalds1da177e2005-04-16 15:20:36 -0700814/**
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800815 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -0700816 * @mapping: address_space which was dirtied
Martin Waitza5802902006-04-02 13:59:55 +0200817 * @nr_pages_dirtied: number of pages which the caller has just dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 *
819 * Processes which are dirtying memory should call in here once for each page
820 * which was newly dirtied. The function will periodically check the system's
821 * dirty state and will initiate writeback if needed.
822 *
823 * On really big machines, get_writeback_state is expensive, so try to avoid
824 * calling it too often (ratelimiting). But once we're over the dirty memory
825 * limit we decrease the ratelimiting by a lot, to prevent individual processes
826 * from overshooting the limit by (ratelimit_pages) each.
827 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800828void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
829 unsigned long nr_pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830{
Wu Fengguang36715ce2011-06-11 17:53:57 -0600831 struct backing_dev_info *bdi = mapping->backing_dev_info;
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800832 unsigned long ratelimit;
833 unsigned long *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834
Wu Fengguang36715ce2011-06-11 17:53:57 -0600835 if (!bdi_cap_account_dirty(bdi))
836 return;
837
Linus Torvalds1da177e2005-04-16 15:20:36 -0700838 ratelimit = ratelimit_pages;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700839 if (mapping->backing_dev_info->dirty_exceeded)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700840 ratelimit = 8;
841
842 /*
843 * Check the rate limiting. Also, we do not want to throttle real-time
844 * tasks in balance_dirty_pages(). Period.
845 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800846 preempt_disable();
Tejun Heo245b2e72009-06-24 15:13:48 +0900847 p = &__get_cpu_var(bdp_ratelimits);
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800848 *p += nr_pages_dirtied;
849 if (unlikely(*p >= ratelimit)) {
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800850 ratelimit = sync_writeback_pages(*p);
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800851 *p = 0;
852 preempt_enable();
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800853 balance_dirty_pages(mapping, ratelimit);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 return;
855 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800856 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700857}
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800858EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859
Andrew Morton232ea4d2007-02-28 20:13:21 -0800860void throttle_vm_writeout(gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861{
David Rientjes364aeb22009-01-06 14:39:29 -0800862 unsigned long background_thresh;
863 unsigned long dirty_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864
865 for ( ; ; ) {
Wu Fengguang16c40422010-08-11 14:17:39 -0700866 global_dirty_limits(&background_thresh, &dirty_thresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700867
868 /*
869 * Boost the allowable dirty threshold a bit for page
870 * allocators so they don't get DoS'ed by heavy writers
871 */
872 dirty_thresh += dirty_thresh / 10; /* wheeee... */
873
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700874 if (global_page_state(NR_UNSTABLE_NFS) +
875 global_page_state(NR_WRITEBACK) <= dirty_thresh)
876 break;
Jens Axboe8aa7e842009-07-09 14:52:32 +0200877 congestion_wait(BLK_RW_ASYNC, HZ/10);
Fengguang Wu369f2382007-10-16 23:30:45 -0700878
879 /*
880 * The caller might hold locks which can prevent IO completion
881 * or progress in the filesystem. So we cannot just sit here
882 * waiting for IO to complete.
883 */
884 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
885 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886 }
887}
888
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
891 */
892int dirty_writeback_centisecs_handler(ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700893 void __user *buffer, size_t *length, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700894{
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700895 proc_dointvec(table, write, buffer, length, ppos);
Jens Axboe64231042010-05-21 20:00:35 +0200896 bdi_arm_supers_timer();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897 return 0;
898}
899
Jens Axboec2c49862010-05-20 09:18:47 +0200900#ifdef CONFIG_BLOCK
Matthew Garrett31373d02010-04-06 14:25:14 +0200901void laptop_mode_timer_fn(unsigned long data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700902{
Matthew Garrett31373d02010-04-06 14:25:14 +0200903 struct request_queue *q = (struct request_queue *)data;
904 int nr_pages = global_page_state(NR_FILE_DIRTY) +
905 global_page_state(NR_UNSTABLE_NFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906
Matthew Garrett31373d02010-04-06 14:25:14 +0200907 /*
908 * We want to write everything out, not just down to the dirty
909 * threshold
910 */
Matthew Garrett31373d02010-04-06 14:25:14 +0200911 if (bdi_has_dirty_io(&q->backing_dev_info))
Christoph Hellwigc5444192010-06-08 18:15:15 +0200912 bdi_start_writeback(&q->backing_dev_info, nr_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700913}
914
915/*
916 * We've spun up the disk and we're in laptop mode: schedule writeback
917 * of all dirty data a few seconds from now. If the flush is already scheduled
918 * then push it back - the user is still using the disk.
919 */
Matthew Garrett31373d02010-04-06 14:25:14 +0200920void laptop_io_completion(struct backing_dev_info *info)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700921{
Matthew Garrett31373d02010-04-06 14:25:14 +0200922 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700923}
924
925/*
926 * We're in laptop mode and we've just synced. The sync's writes will have
927 * caused another writeback to be scheduled by laptop_io_completion.
928 * Nothing needs to be written back anymore, so we unschedule the writeback.
929 */
930void laptop_sync_completion(void)
931{
Matthew Garrett31373d02010-04-06 14:25:14 +0200932 struct backing_dev_info *bdi;
933
934 rcu_read_lock();
935
936 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
937 del_timer(&bdi->laptop_mode_wb_timer);
938
939 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940}
Jens Axboec2c49862010-05-20 09:18:47 +0200941#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942
943/*
944 * If ratelimit_pages is too high then we can get into dirty-data overload
945 * if a large number of processes all perform writes at the same time.
946 * If it is too low then SMP machines will call the (expensive)
947 * get_writeback_state too often.
948 *
949 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
950 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
951 * thresholds before writeback cuts in.
952 *
953 * But the limit should not be set too high. Because it also controls the
954 * amount of memory which the balance_dirty_pages() caller has to write back.
955 * If this is too large then the caller will block on the IO queue all the
956 * time. So limit it to four megabytes - the balance_dirty_pages() caller
957 * will write six megabyte chunks, max.
958 */
959
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700960void writeback_set_ratelimit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961{
Chandra Seetharaman40c99aa2006-09-29 02:01:24 -0700962 ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963 if (ratelimit_pages < 16)
964 ratelimit_pages = 16;
965 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
966 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
967}
968
Chandra Seetharaman26c21432006-06-27 02:54:10 -0700969static int __cpuinit
Linus Torvalds1da177e2005-04-16 15:20:36 -0700970ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
971{
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700972 writeback_set_ratelimit();
Paul E. McKenneyaa0f0302007-02-10 01:46:37 -0800973 return NOTIFY_DONE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974}
975
Chandra Seetharaman74b85f32006-06-27 02:54:09 -0700976static struct notifier_block __cpuinitdata ratelimit_nb = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 .notifier_call = ratelimit_handler,
978 .next = NULL,
979};
980
981/*
Linus Torvaldsdc6e29d2007-01-29 16:37:38 -0800982 * Called early on to tune the page writeback dirty limits.
983 *
984 * We used to scale dirty pages according to how total memory
985 * related to pages that could be allocated for buffers (by
986 * comparing nr_free_buffer_pages() to vm_total_pages.
987 *
988 * However, that was when we used "dirty_ratio" to scale with
989 * all memory, and we don't do that any more. "dirty_ratio"
990 * is now applied to total non-HIGHPAGE memory (by subtracting
991 * totalhigh_pages from vm_total_pages), and as such we can't
992 * get into the old insane situation any more where we had
993 * large amounts of dirty pages compared to a small amount of
994 * non-HIGHMEM memory.
995 *
996 * But we might still want to scale the dirty_ratio by how
997 * much memory the box has..
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998 */
999void __init page_writeback_init(void)
1000{
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001001 int shift;
1002
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -07001003 writeback_set_ratelimit();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004 register_cpu_notifier(&ratelimit_nb);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001005
1006 shift = calc_period_shift();
1007 prop_descriptor_init(&vm_completions, shift);
Peter Zijlstra3e26c142007-10-16 23:25:50 -07001008 prop_descriptor_init(&vm_dirties, shift);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009}
1010
David Howells811d7362006-08-29 19:06:09 +01001011/**
Jan Karaf446daa2010-08-09 17:19:12 -07001012 * tag_pages_for_writeback - tag pages to be written by write_cache_pages
1013 * @mapping: address space structure to write
1014 * @start: starting page index
1015 * @end: ending page index (inclusive)
1016 *
1017 * This function scans the page range from @start to @end (inclusive) and tags
1018 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
1019 * that write_cache_pages (or whoever calls this function) will then use
1020 * TOWRITE tag to identify pages eligible for writeback. This mechanism is
1021 * used to avoid livelocking of writeback by a process steadily creating new
1022 * dirty pages in the file (thus it is important for this function to be quick
1023 * so that it can tag pages faster than a dirtying process can create them).
1024 */
1025/*
1026 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
1027 */
Jan Karaf446daa2010-08-09 17:19:12 -07001028void tag_pages_for_writeback(struct address_space *mapping,
1029 pgoff_t start, pgoff_t end)
1030{
Randy Dunlap3c111a02010-08-11 14:17:30 -07001031#define WRITEBACK_TAG_BATCH 4096
Jan Karaf446daa2010-08-09 17:19:12 -07001032 unsigned long tagged;
1033
1034 do {
1035 spin_lock_irq(&mapping->tree_lock);
1036 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
1037 &start, end, WRITEBACK_TAG_BATCH,
1038 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
1039 spin_unlock_irq(&mapping->tree_lock);
1040 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
1041 cond_resched();
Jan Karad5ed3a42010-08-19 14:13:33 -07001042 /* We check 'start' to handle wrapping when end == ~0UL */
1043 } while (tagged >= WRITEBACK_TAG_BATCH && start);
Jan Karaf446daa2010-08-09 17:19:12 -07001044}
1045EXPORT_SYMBOL(tag_pages_for_writeback);
1046
1047/**
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001048 * 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 +01001049 * @mapping: address space structure to write
1050 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001051 * @writepage: function called for each page
1052 * @data: data passed to writepage function
David Howells811d7362006-08-29 19:06:09 +01001053 *
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001054 * If a page is already under I/O, write_cache_pages() skips it, even
David Howells811d7362006-08-29 19:06:09 +01001055 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
1056 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
1057 * and msync() need to guarantee that all the data which was dirty at the time
1058 * the call was made get new I/O started against them. If wbc->sync_mode is
1059 * WB_SYNC_ALL then we were called for data integrity and we must wait for
1060 * existing IO to complete.
Jan Karaf446daa2010-08-09 17:19:12 -07001061 *
1062 * To avoid livelocks (when other process dirties new pages), we first tag
1063 * pages which should be written back with TOWRITE tag and only then start
1064 * writing them. For data-integrity sync we have to be careful so that we do
1065 * not miss some pages (e.g., because some other process has cleared TOWRITE
1066 * tag we set). The rule we follow is that TOWRITE tag can be cleared only
1067 * by the process clearing the DIRTY tag (and submitting the page for IO).
David Howells811d7362006-08-29 19:06:09 +01001068 */
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001069int write_cache_pages(struct address_space *mapping,
1070 struct writeback_control *wbc, writepage_t writepage,
1071 void *data)
David Howells811d7362006-08-29 19:06:09 +01001072{
David Howells811d7362006-08-29 19:06:09 +01001073 int ret = 0;
1074 int done = 0;
David Howells811d7362006-08-29 19:06:09 +01001075 struct pagevec pvec;
1076 int nr_pages;
Nick Piggin31a12662009-01-06 14:39:04 -08001077 pgoff_t uninitialized_var(writeback_index);
David Howells811d7362006-08-29 19:06:09 +01001078 pgoff_t index;
1079 pgoff_t end; /* Inclusive */
Nick Pigginbd19e012009-01-06 14:39:06 -08001080 pgoff_t done_index;
Nick Piggin31a12662009-01-06 14:39:04 -08001081 int cycled;
David Howells811d7362006-08-29 19:06:09 +01001082 int range_whole = 0;
Jan Karaf446daa2010-08-09 17:19:12 -07001083 int tag;
David Howells811d7362006-08-29 19:06:09 +01001084
David Howells811d7362006-08-29 19:06:09 +01001085 pagevec_init(&pvec, 0);
1086 if (wbc->range_cyclic) {
Nick Piggin31a12662009-01-06 14:39:04 -08001087 writeback_index = mapping->writeback_index; /* prev offset */
1088 index = writeback_index;
1089 if (index == 0)
1090 cycled = 1;
1091 else
1092 cycled = 0;
David Howells811d7362006-08-29 19:06:09 +01001093 end = -1;
1094 } else {
1095 index = wbc->range_start >> PAGE_CACHE_SHIFT;
1096 end = wbc->range_end >> PAGE_CACHE_SHIFT;
1097 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
1098 range_whole = 1;
Nick Piggin31a12662009-01-06 14:39:04 -08001099 cycled = 1; /* ignore range_cyclic tests */
David Howells811d7362006-08-29 19:06:09 +01001100 }
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001101 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daa2010-08-09 17:19:12 -07001102 tag = PAGECACHE_TAG_TOWRITE;
1103 else
1104 tag = PAGECACHE_TAG_DIRTY;
David Howells811d7362006-08-29 19:06:09 +01001105retry:
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001106 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daa2010-08-09 17:19:12 -07001107 tag_pages_for_writeback(mapping, index, end);
Nick Pigginbd19e012009-01-06 14:39:06 -08001108 done_index = index;
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001109 while (!done && (index <= end)) {
1110 int i;
1111
Jan Karaf446daa2010-08-09 17:19:12 -07001112 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001113 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
1114 if (nr_pages == 0)
1115 break;
David Howells811d7362006-08-29 19:06:09 +01001116
David Howells811d7362006-08-29 19:06:09 +01001117 for (i = 0; i < nr_pages; i++) {
1118 struct page *page = pvec.pages[i];
1119
Nick Piggind5482cd2009-01-06 14:39:11 -08001120 /*
1121 * At this point, the page may be truncated or
1122 * invalidated (changing page->mapping to NULL), or
1123 * even swizzled back from swapper_space to tmpfs file
1124 * mapping. However, page->index will not change
1125 * because we have a reference on the page.
1126 */
1127 if (page->index > end) {
1128 /*
1129 * can't be range_cyclic (1st pass) because
1130 * end == -1 in that case.
1131 */
1132 done = 1;
1133 break;
1134 }
1135
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001136 done_index = page->index;
Nick Pigginbd19e012009-01-06 14:39:06 -08001137
David Howells811d7362006-08-29 19:06:09 +01001138 lock_page(page);
1139
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001140 /*
1141 * Page truncated or invalidated. We can freely skip it
1142 * then, even for data integrity operations: the page
1143 * has disappeared concurrently, so there could be no
1144 * real expectation of this data interity operation
1145 * even if there is now a new, dirty page at the same
1146 * pagecache address.
1147 */
David Howells811d7362006-08-29 19:06:09 +01001148 if (unlikely(page->mapping != mapping)) {
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001149continue_unlock:
David Howells811d7362006-08-29 19:06:09 +01001150 unlock_page(page);
1151 continue;
1152 }
1153
Nick Piggin515f4a02009-01-06 14:39:10 -08001154 if (!PageDirty(page)) {
1155 /* someone wrote it for us */
1156 goto continue_unlock;
1157 }
David Howells811d7362006-08-29 19:06:09 +01001158
Nick Piggin515f4a02009-01-06 14:39:10 -08001159 if (PageWriteback(page)) {
1160 if (wbc->sync_mode != WB_SYNC_NONE)
1161 wait_on_page_writeback(page);
1162 else
1163 goto continue_unlock;
1164 }
1165
1166 BUG_ON(PageWriteback(page));
1167 if (!clear_page_dirty_for_io(page))
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001168 goto continue_unlock;
David Howells811d7362006-08-29 19:06:09 +01001169
Dave Chinner9e094382010-07-07 13:24:08 +10001170 trace_wbc_writepage(wbc, mapping->backing_dev_info);
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001171 ret = (*writepage)(page, wbc, data);
Nick Piggin00266772009-01-06 14:39:06 -08001172 if (unlikely(ret)) {
1173 if (ret == AOP_WRITEPAGE_ACTIVATE) {
1174 unlock_page(page);
1175 ret = 0;
1176 } else {
1177 /*
1178 * done_index is set past this page,
1179 * so media errors will not choke
1180 * background writeout for the entire
1181 * file. This has consequences for
1182 * range_cyclic semantics (ie. it may
1183 * not be suitable for data integrity
1184 * writeout).
1185 */
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001186 done_index = page->index + 1;
Nick Piggin00266772009-01-06 14:39:06 -08001187 done = 1;
1188 break;
1189 }
Dave Chinner0b564922010-06-09 10:37:18 +10001190 }
David Howells811d7362006-08-29 19:06:09 +01001191
Dave Chinner546a1922010-08-24 11:44:34 +10001192 /*
1193 * We stop writing back only if we are not doing
1194 * integrity sync. In case of integrity sync we have to
1195 * keep going until we have written all the pages
1196 * we tagged for writeback prior to entering this loop.
1197 */
1198 if (--wbc->nr_to_write <= 0 &&
1199 wbc->sync_mode == WB_SYNC_NONE) {
1200 done = 1;
1201 break;
Nick Piggin05fe4782009-01-06 14:39:08 -08001202 }
David Howells811d7362006-08-29 19:06:09 +01001203 }
1204 pagevec_release(&pvec);
1205 cond_resched();
1206 }
Nick Piggin3a4c6802009-02-12 04:34:23 +01001207 if (!cycled && !done) {
David Howells811d7362006-08-29 19:06:09 +01001208 /*
Nick Piggin31a12662009-01-06 14:39:04 -08001209 * range_cyclic:
David Howells811d7362006-08-29 19:06:09 +01001210 * We hit the last page and there is more work to be done: wrap
1211 * back to the start of the file
1212 */
Nick Piggin31a12662009-01-06 14:39:04 -08001213 cycled = 1;
David Howells811d7362006-08-29 19:06:09 +01001214 index = 0;
Nick Piggin31a12662009-01-06 14:39:04 -08001215 end = writeback_index - 1;
David Howells811d7362006-08-29 19:06:09 +01001216 goto retry;
1217 }
Dave Chinner0b564922010-06-09 10:37:18 +10001218 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
1219 mapping->writeback_index = done_index;
Aneesh Kumar K.V06d6cf62008-07-11 19:27:31 -04001220
David Howells811d7362006-08-29 19:06:09 +01001221 return ret;
1222}
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001223EXPORT_SYMBOL(write_cache_pages);
1224
1225/*
1226 * Function used by generic_writepages to call the real writepage
1227 * function and set the mapping flags on error
1228 */
1229static int __writepage(struct page *page, struct writeback_control *wbc,
1230 void *data)
1231{
1232 struct address_space *mapping = data;
1233 int ret = mapping->a_ops->writepage(page, wbc);
1234 mapping_set_error(mapping, ret);
1235 return ret;
1236}
1237
1238/**
1239 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
1240 * @mapping: address space structure to write
1241 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
1242 *
1243 * This is a library function, which implements the writepages()
1244 * address_space_operation.
1245 */
1246int generic_writepages(struct address_space *mapping,
1247 struct writeback_control *wbc)
1248{
Shaohua Li9b6096a2011-03-17 10:47:06 +01001249 struct blk_plug plug;
1250 int ret;
1251
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001252 /* deal with chardevs and other special file */
1253 if (!mapping->a_ops->writepage)
1254 return 0;
1255
Shaohua Li9b6096a2011-03-17 10:47:06 +01001256 blk_start_plug(&plug);
1257 ret = write_cache_pages(mapping, wbc, __writepage, mapping);
1258 blk_finish_plug(&plug);
1259 return ret;
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001260}
David Howells811d7362006-08-29 19:06:09 +01001261
1262EXPORT_SYMBOL(generic_writepages);
1263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1265{
Andrew Morton22905f72005-11-16 15:07:01 -08001266 int ret;
1267
Linus Torvalds1da177e2005-04-16 15:20:36 -07001268 if (wbc->nr_to_write <= 0)
1269 return 0;
1270 if (mapping->a_ops->writepages)
Peter Zijlstrad08b3852006-09-25 23:30:57 -07001271 ret = mapping->a_ops->writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001272 else
1273 ret = generic_writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001274 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001275}
1276
1277/**
1278 * write_one_page - write out a single page and optionally wait on I/O
Martin Waitz67be2dd2005-05-01 08:59:26 -07001279 * @page: the page to write
1280 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281 *
1282 * The page must be locked by the caller and will be unlocked upon return.
1283 *
1284 * write_one_page() returns a negative error code if I/O failed.
1285 */
1286int write_one_page(struct page *page, int wait)
1287{
1288 struct address_space *mapping = page->mapping;
1289 int ret = 0;
1290 struct writeback_control wbc = {
1291 .sync_mode = WB_SYNC_ALL,
1292 .nr_to_write = 1,
1293 };
1294
1295 BUG_ON(!PageLocked(page));
1296
1297 if (wait)
1298 wait_on_page_writeback(page);
1299
1300 if (clear_page_dirty_for_io(page)) {
1301 page_cache_get(page);
1302 ret = mapping->a_ops->writepage(page, &wbc);
1303 if (ret == 0 && wait) {
1304 wait_on_page_writeback(page);
1305 if (PageError(page))
1306 ret = -EIO;
1307 }
1308 page_cache_release(page);
1309 } else {
1310 unlock_page(page);
1311 }
1312 return ret;
1313}
1314EXPORT_SYMBOL(write_one_page);
1315
1316/*
Ken Chen76719322007-02-10 01:43:15 -08001317 * For address_spaces which do not use buffers nor write back.
1318 */
1319int __set_page_dirty_no_writeback(struct page *page)
1320{
1321 if (!PageDirty(page))
Bob Liuc3f0da62011-01-13 15:45:49 -08001322 return !TestSetPageDirty(page);
Ken Chen76719322007-02-10 01:43:15 -08001323 return 0;
1324}
1325
1326/*
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001327 * Helper function for set_page_dirty family.
1328 * NOTE: This relies on being atomic wrt interrupts.
1329 */
1330void account_page_dirtied(struct page *page, struct address_space *mapping)
1331{
1332 if (mapping_cap_account_dirty(mapping)) {
1333 __inc_zone_page_state(page, NR_FILE_DIRTY);
Michael Rubinea941f02010-10-26 14:21:35 -07001334 __inc_zone_page_state(page, NR_DIRTIED);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001335 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
1336 task_dirty_inc(current);
1337 task_io_account_write(PAGE_CACHE_SIZE);
1338 }
1339}
Michael Rubin679ceac2010-08-20 02:31:26 -07001340EXPORT_SYMBOL(account_page_dirtied);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001341
1342/*
Michael Rubinf629d1c2010-10-26 14:21:33 -07001343 * Helper function for set_page_writeback family.
1344 * NOTE: Unlike account_page_dirtied this does not rely on being atomic
1345 * wrt interrupts.
1346 */
1347void account_page_writeback(struct page *page)
1348{
1349 inc_zone_page_state(page, NR_WRITEBACK);
1350}
1351EXPORT_SYMBOL(account_page_writeback);
1352
1353/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 * For address_spaces which do not use buffers. Just tag the page as dirty in
1355 * its radix tree.
1356 *
1357 * This is also used when a single buffer is being dirtied: we want to set the
1358 * page dirty in that case, but not all the buffers. This is a "bottom-up"
1359 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
1360 *
1361 * Most callers have locked the page, which pins the address_space in memory.
1362 * But zap_pte_range() does not lock the page, however in that case the
1363 * mapping is pinned by the vma's ->vm_file reference.
1364 *
1365 * We take care to handle the case where the page was truncated from the
Simon Arlott183ff222007-10-20 01:27:18 +02001366 * mapping by re-checking page_mapping() inside tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 */
1368int __set_page_dirty_nobuffers(struct page *page)
1369{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370 if (!TestSetPageDirty(page)) {
1371 struct address_space *mapping = page_mapping(page);
1372 struct address_space *mapping2;
1373
Andrew Morton8c085402006-12-10 02:19:24 -08001374 if (!mapping)
1375 return 1;
1376
Nick Piggin19fd6232008-07-25 19:45:32 -07001377 spin_lock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001378 mapping2 = page_mapping(page);
1379 if (mapping2) { /* Race with truncate? */
1380 BUG_ON(mapping2 != mapping);
Nick Piggin787d2212007-07-17 04:03:34 -07001381 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001382 account_page_dirtied(page, mapping);
Andrew Morton8c085402006-12-10 02:19:24 -08001383 radix_tree_tag_set(&mapping->page_tree,
1384 page_index(page), PAGECACHE_TAG_DIRTY);
1385 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001386 spin_unlock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001387 if (mapping->host) {
1388 /* !PageAnon && !swapper_space */
1389 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001391 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001393 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394}
1395EXPORT_SYMBOL(__set_page_dirty_nobuffers);
1396
1397/*
1398 * When a writepage implementation decides that it doesn't want to write this
1399 * page for some reason, it should redirty the locked page via
1400 * redirty_page_for_writepage() and it should then unlock the page and return 0
1401 */
1402int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
1403{
1404 wbc->pages_skipped++;
1405 return __set_page_dirty_nobuffers(page);
1406}
1407EXPORT_SYMBOL(redirty_page_for_writepage);
1408
1409/*
Wu Fengguang6746aff2009-09-16 11:50:14 +02001410 * Dirty a page.
1411 *
1412 * For pages with a mapping this should be done under the page lock
1413 * for the benefit of asynchronous memory errors who prefer a consistent
1414 * dirty state. This rule can be broken in some special cases,
1415 * but should be better not to.
1416 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417 * If the mapping doesn't provide a set_page_dirty a_op, then
1418 * just fall through and assume that it wants buffer_heads.
1419 */
Nick Piggin1cf6e7d2009-02-18 14:48:18 -08001420int set_page_dirty(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421{
1422 struct address_space *mapping = page_mapping(page);
1423
1424 if (likely(mapping)) {
1425 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
Minchan Kim278df9f2011-03-22 16:32:54 -07001426 /*
1427 * readahead/lru_deactivate_page could remain
1428 * PG_readahead/PG_reclaim due to race with end_page_writeback
1429 * About readahead, if the page is written, the flags would be
1430 * reset. So no problem.
1431 * About lru_deactivate_page, if the page is redirty, the flag
1432 * will be reset. So no problem. but if the page is used by readahead
1433 * it will confuse readahead and make it restart the size rampup
1434 * process. But it's a trivial problem.
1435 */
1436 ClearPageReclaim(page);
David Howells93614012006-09-30 20:45:40 +02001437#ifdef CONFIG_BLOCK
1438 if (!spd)
1439 spd = __set_page_dirty_buffers;
1440#endif
1441 return (*spd)(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001443 if (!PageDirty(page)) {
1444 if (!TestSetPageDirty(page))
1445 return 1;
1446 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001447 return 0;
1448}
1449EXPORT_SYMBOL(set_page_dirty);
1450
1451/*
1452 * set_page_dirty() is racy if the caller has no reference against
1453 * page->mapping->host, and if the page is unlocked. This is because another
1454 * CPU could truncate the page off the mapping and then free the mapping.
1455 *
1456 * Usually, the page _is_ locked, or the caller is a user-space process which
1457 * holds a reference on the inode by having an open file.
1458 *
1459 * In other cases, the page should be locked before running set_page_dirty().
1460 */
1461int set_page_dirty_lock(struct page *page)
1462{
1463 int ret;
1464
Jens Axboe7eaceac2011-03-10 08:52:07 +01001465 lock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466 ret = set_page_dirty(page);
1467 unlock_page(page);
1468 return ret;
1469}
1470EXPORT_SYMBOL(set_page_dirty_lock);
1471
1472/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 * Clear a page's dirty flag, while caring for dirty memory accounting.
1474 * Returns true if the page was previously dirty.
1475 *
1476 * This is for preparing to put the page under writeout. We leave the page
1477 * tagged as dirty in the radix tree so that a concurrent write-for-sync
1478 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
1479 * implementation will run either set_page_writeback() or set_page_dirty(),
1480 * at which stage we bring the page's dirty flag and radix-tree dirty tag
1481 * back into sync.
1482 *
1483 * This incoherency between the page's dirty flag and radix-tree tag is
1484 * unfortunate, but it only exists while the page is locked.
1485 */
1486int clear_page_dirty_for_io(struct page *page)
1487{
1488 struct address_space *mapping = page_mapping(page);
1489
Nick Piggin79352892007-07-19 01:47:22 -07001490 BUG_ON(!PageLocked(page));
1491
Linus Torvalds7658cc22006-12-29 10:00:58 -08001492 if (mapping && mapping_cap_account_dirty(mapping)) {
1493 /*
1494 * Yes, Virginia, this is indeed insane.
1495 *
1496 * We use this sequence to make sure that
1497 * (a) we account for dirty stats properly
1498 * (b) we tell the low-level filesystem to
1499 * mark the whole page dirty if it was
1500 * dirty in a pagetable. Only to then
1501 * (c) clean the page again and return 1 to
1502 * cause the writeback.
1503 *
1504 * This way we avoid all nasty races with the
1505 * dirty bit in multiple places and clearing
1506 * them concurrently from different threads.
1507 *
1508 * Note! Normally the "set_page_dirty(page)"
1509 * has no effect on the actual dirty bit - since
1510 * that will already usually be set. But we
1511 * need the side effects, and it can help us
1512 * avoid races.
1513 *
1514 * We basically use the page "master dirty bit"
1515 * as a serialization point for all the different
1516 * threads doing their things.
Linus Torvalds7658cc22006-12-29 10:00:58 -08001517 */
1518 if (page_mkclean(page))
1519 set_page_dirty(page);
Nick Piggin79352892007-07-19 01:47:22 -07001520 /*
1521 * We carefully synchronise fault handlers against
1522 * installing a dirty pte and marking the page dirty
1523 * at this point. We do this by having them hold the
1524 * page lock at some point after installing their
1525 * pte, but before marking the page dirty.
1526 * Pages are always locked coming in here, so we get
1527 * the desired exclusion. See mm/memory.c:do_wp_page()
1528 * for more comments.
1529 */
Linus Torvalds7658cc22006-12-29 10:00:58 -08001530 if (TestClearPageDirty(page)) {
Andrew Morton8c085402006-12-10 02:19:24 -08001531 dec_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07001532 dec_bdi_stat(mapping->backing_dev_info,
1533 BDI_RECLAIMABLE);
Linus Torvalds7658cc22006-12-29 10:00:58 -08001534 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001535 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001536 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001537 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001538 return TestClearPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539}
Hans Reiser58bb01a2005-11-18 01:10:53 -08001540EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001541
1542int test_clear_page_writeback(struct page *page)
1543{
1544 struct address_space *mapping = page_mapping(page);
1545 int ret;
1546
1547 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001548 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001549 unsigned long flags;
1550
Nick Piggin19fd6232008-07-25 19:45:32 -07001551 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 ret = TestClearPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001553 if (ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 radix_tree_tag_clear(&mapping->page_tree,
1555 page_index(page),
1556 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001557 if (bdi_cap_account_writeback(bdi)) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001558 __dec_bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001559 __bdi_writeout_inc(bdi);
1560 }
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001561 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001562 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563 } else {
1564 ret = TestClearPageWriteback(page);
1565 }
Wu Fengguang99b12e32011-07-25 17:12:37 -07001566 if (ret) {
Andrew Mortond688abf2007-07-19 01:49:17 -07001567 dec_zone_page_state(page, NR_WRITEBACK);
Wu Fengguang99b12e32011-07-25 17:12:37 -07001568 inc_zone_page_state(page, NR_WRITTEN);
1569 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570 return ret;
1571}
1572
1573int test_set_page_writeback(struct page *page)
1574{
1575 struct address_space *mapping = page_mapping(page);
1576 int ret;
1577
1578 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001579 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001580 unsigned long flags;
1581
Nick Piggin19fd6232008-07-25 19:45:32 -07001582 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001583 ret = TestSetPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001584 if (!ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585 radix_tree_tag_set(&mapping->page_tree,
1586 page_index(page),
1587 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001588 if (bdi_cap_account_writeback(bdi))
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001589 __inc_bdi_stat(bdi, BDI_WRITEBACK);
1590 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591 if (!PageDirty(page))
1592 radix_tree_tag_clear(&mapping->page_tree,
1593 page_index(page),
1594 PAGECACHE_TAG_DIRTY);
Jan Karaf446daa2010-08-09 17:19:12 -07001595 radix_tree_tag_clear(&mapping->page_tree,
1596 page_index(page),
1597 PAGECACHE_TAG_TOWRITE);
Nick Piggin19fd6232008-07-25 19:45:32 -07001598 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599 } else {
1600 ret = TestSetPageWriteback(page);
1601 }
Andrew Mortond688abf2007-07-19 01:49:17 -07001602 if (!ret)
Michael Rubinf629d1c2010-10-26 14:21:33 -07001603 account_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604 return ret;
1605
1606}
1607EXPORT_SYMBOL(test_set_page_writeback);
1608
1609/*
Nick Piggin00128182007-10-16 01:24:40 -07001610 * Return true if any of the pages in the mapping are marked with the
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611 * passed tag.
1612 */
1613int mapping_tagged(struct address_space *mapping, int tag)
1614{
Konstantin Khlebnikov72c47832011-07-25 17:12:31 -07001615 return radix_tree_tagged(&mapping->page_tree, tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001616}
1617EXPORT_SYMBOL(mapping_tagged);