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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/*
Johannes Weinerd08c4292011-10-31 17:07:05 -0700308 * bdi_min_ratio keeps the sum of the minimum dirty shares of all
309 * registered backing devices, which, for obvious reasons, can not
310 * exceed 100%.
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700311 */
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700312static unsigned int bdi_min_ratio;
313
314int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
315{
316 int ret = 0;
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700317
Jens Axboecfc4ba52009-09-14 13:12:40 +0200318 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700319 if (min_ratio > bdi->max_ratio) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700320 ret = -EINVAL;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700321 } else {
322 min_ratio -= bdi->min_ratio;
323 if (bdi_min_ratio + min_ratio < 100) {
324 bdi_min_ratio += min_ratio;
325 bdi->min_ratio += min_ratio;
326 } else {
327 ret = -EINVAL;
328 }
329 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200330 spin_unlock_bh(&bdi_lock);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700331
332 return ret;
333}
334
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700335int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
336{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700337 int ret = 0;
338
339 if (max_ratio > 100)
340 return -EINVAL;
341
Jens Axboecfc4ba52009-09-14 13:12:40 +0200342 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700343 if (bdi->min_ratio > max_ratio) {
344 ret = -EINVAL;
345 } else {
346 bdi->max_ratio = max_ratio;
347 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
348 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200349 spin_unlock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700350
351 return ret;
352}
353EXPORT_SYMBOL(bdi_set_max_ratio);
354
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700355/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356 * Work out the current dirty-memory clamping and background writeout
357 * thresholds.
358 *
359 * The main aim here is to lower them aggressively if there is a lot of mapped
360 * memory around. To avoid stressing page reclaim with lots of unreclaimable
361 * pages. It is better to clamp down on writers than to start swapping, and
362 * performing lots of scanning.
363 *
364 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
365 *
366 * We don't permit the clamping level to fall below 5% - that is getting rather
367 * excessive.
368 *
369 * We make sure that the background writeout level is below the adjusted
370 * clamping level.
371 */
Christoph Lameter1b424462007-05-06 14:48:59 -0700372
373static unsigned long highmem_dirtyable_memory(unsigned long total)
374{
375#ifdef CONFIG_HIGHMEM
376 int node;
377 unsigned long x = 0;
378
Lee Schermerhorn37b07e42007-10-16 01:25:39 -0700379 for_each_node_state(node, N_HIGH_MEMORY) {
Christoph Lameter1b424462007-05-06 14:48:59 -0700380 struct zone *z =
381 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
382
Wu Fengguangadea02a2009-09-21 17:01:42 -0700383 x += zone_page_state(z, NR_FREE_PAGES) +
384 zone_reclaimable_pages(z);
Christoph Lameter1b424462007-05-06 14:48:59 -0700385 }
386 /*
387 * Make sure that the number of highmem pages is never larger
388 * than the number of the total dirtyable memory. This can only
389 * occur in very strange VM situations but we want to make sure
390 * that this does not occur.
391 */
392 return min(x, total);
393#else
394 return 0;
395#endif
396}
397
Steven Rostedt3eefae92008-05-12 21:21:04 +0200398/**
399 * determine_dirtyable_memory - amount of memory that may be used
400 *
401 * Returns the numebr of pages that can currently be freed and used
402 * by the kernel for direct mappings.
403 */
404unsigned long determine_dirtyable_memory(void)
Christoph Lameter1b424462007-05-06 14:48:59 -0700405{
406 unsigned long x;
407
Wu Fengguangadea02a2009-09-21 17:01:42 -0700408 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
Bron Gondwana195cf452008-02-04 22:29:20 -0800409
410 if (!vm_highmem_is_dirtyable)
411 x -= highmem_dirtyable_memory(x);
412
Christoph Lameter1b424462007-05-06 14:48:59 -0700413 return x + 1; /* Ensure that we never return 0 */
414}
415
Wu Fengguangffd1f602011-06-19 22:18:42 -0600416static unsigned long hard_dirty_limit(unsigned long thresh)
417{
418 return max(thresh, global_dirty_limit);
419}
420
Randy Dunlap03ab4502010-08-14 13:05:17 -0700421/*
Wu Fengguang1babe182010-08-11 14:17:40 -0700422 * global_dirty_limits - background-writeback and dirty-throttling thresholds
423 *
424 * Calculate the dirty thresholds based on sysctl parameters
425 * - vm.dirty_background_ratio or vm.dirty_background_bytes
426 * - vm.dirty_ratio or vm.dirty_bytes
427 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
Minchan Kimebd13732011-01-04 01:36:48 +0900428 * real-time tasks.
Wu Fengguang1babe182010-08-11 14:17:40 -0700429 */
Wu Fengguang16c40422010-08-11 14:17:39 -0700430void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431{
David Rientjes364aeb22009-01-06 14:39:29 -0800432 unsigned long background;
433 unsigned long dirty;
Minchan Kim240c8792011-01-13 15:46:27 -0800434 unsigned long uninitialized_var(available_memory);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435 struct task_struct *tsk;
436
Minchan Kim240c8792011-01-13 15:46:27 -0800437 if (!vm_dirty_bytes || !dirty_background_bytes)
438 available_memory = determine_dirtyable_memory();
439
David Rientjes2da02992009-01-06 14:39:31 -0800440 if (vm_dirty_bytes)
441 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
Wu Fengguang4cbec4c2010-10-26 14:21:45 -0700442 else
443 dirty = (vm_dirty_ratio * available_memory) / 100;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444
David Rientjes2da02992009-01-06 14:39:31 -0800445 if (dirty_background_bytes)
446 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
447 else
448 background = (dirty_background_ratio * available_memory) / 100;
449
450 if (background >= dirty)
451 background = dirty / 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 tsk = current;
453 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
454 background += background / 4;
455 dirty += dirty / 4;
456 }
457 *pbackground = background;
458 *pdirty = dirty;
Wu Fengguange1cbe232010-12-06 22:34:29 -0600459 trace_global_dirty_state(background, dirty);
Wu Fengguang16c40422010-08-11 14:17:39 -0700460}
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700461
Wu Fengguang6f718652011-03-02 17:14:34 -0600462/**
Wu Fengguang1babe182010-08-11 14:17:40 -0700463 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
Wu Fengguang6f718652011-03-02 17:14:34 -0600464 * @bdi: the backing_dev_info to query
465 * @dirty: global dirty limit in pages
Wu Fengguang1babe182010-08-11 14:17:40 -0700466 *
Wu Fengguang6f718652011-03-02 17:14:34 -0600467 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
468 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
469 * And the "limit" in the name is not seriously taken as hard limit in
470 * balance_dirty_pages().
471 *
472 * It allocates high/low dirty limits to fast/slow devices, in order to prevent
Wu Fengguang1babe182010-08-11 14:17:40 -0700473 * - starving fast devices
474 * - piling up dirty pages (that will take long time to sync) on slow devices
475 *
476 * The bdi's share of dirty limit will be adapting to its throughput and
477 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
478 */
479unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
Wu Fengguang16c40422010-08-11 14:17:39 -0700480{
481 u64 bdi_dirty;
482 long numerator, denominator;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700483
Wu Fengguang16c40422010-08-11 14:17:39 -0700484 /*
485 * Calculate this BDI's share of the dirty ratio.
486 */
487 bdi_writeout_fraction(bdi, &numerator, &denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700488
Wu Fengguang16c40422010-08-11 14:17:39 -0700489 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
490 bdi_dirty *= numerator;
491 do_div(bdi_dirty, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700492
Wu Fengguang16c40422010-08-11 14:17:39 -0700493 bdi_dirty += (dirty * bdi->min_ratio) / 100;
494 if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
495 bdi_dirty = dirty * bdi->max_ratio / 100;
496
497 return bdi_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498}
499
Wu Fengguange98be2d2010-08-29 11:22:30 -0600500static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
501 unsigned long elapsed,
502 unsigned long written)
503{
504 const unsigned long period = roundup_pow_of_two(3 * HZ);
505 unsigned long avg = bdi->avg_write_bandwidth;
506 unsigned long old = bdi->write_bandwidth;
507 u64 bw;
508
509 /*
510 * bw = written * HZ / elapsed
511 *
512 * bw * elapsed + write_bandwidth * (period - elapsed)
513 * write_bandwidth = ---------------------------------------------------
514 * period
515 */
516 bw = written - bdi->written_stamp;
517 bw *= HZ;
518 if (unlikely(elapsed > period)) {
519 do_div(bw, elapsed);
520 avg = bw;
521 goto out;
522 }
523 bw += (u64)bdi->write_bandwidth * (period - elapsed);
524 bw >>= ilog2(period);
525
526 /*
527 * one more level of smoothing, for filtering out sudden spikes
528 */
529 if (avg > old && old >= (unsigned long)bw)
530 avg -= (avg - old) >> 3;
531
532 if (avg < old && old <= (unsigned long)bw)
533 avg += (old - avg) >> 3;
534
535out:
536 bdi->write_bandwidth = bw;
537 bdi->avg_write_bandwidth = avg;
538}
539
Wu Fengguangc42843f2011-03-02 15:54:09 -0600540/*
541 * The global dirtyable memory and dirty threshold could be suddenly knocked
542 * down by a large amount (eg. on the startup of KVM in a swapless system).
543 * This may throw the system into deep dirty exceeded state and throttle
544 * heavy/light dirtiers alike. To retain good responsiveness, maintain
545 * global_dirty_limit for tracking slowly down to the knocked down dirty
546 * threshold.
547 */
548static void update_dirty_limit(unsigned long thresh, unsigned long dirty)
549{
550 unsigned long limit = global_dirty_limit;
551
552 /*
553 * Follow up in one step.
554 */
555 if (limit < thresh) {
556 limit = thresh;
557 goto update;
558 }
559
560 /*
561 * Follow down slowly. Use the higher one as the target, because thresh
562 * may drop below dirty. This is exactly the reason to introduce
563 * global_dirty_limit which is guaranteed to lie above the dirty pages.
564 */
565 thresh = max(thresh, dirty);
566 if (limit > thresh) {
567 limit -= (limit - thresh) >> 5;
568 goto update;
569 }
570 return;
571update:
572 global_dirty_limit = limit;
573}
574
575static void global_update_bandwidth(unsigned long thresh,
576 unsigned long dirty,
577 unsigned long now)
578{
579 static DEFINE_SPINLOCK(dirty_lock);
580 static unsigned long update_time;
581
582 /*
583 * check locklessly first to optimize away locking for the most time
584 */
585 if (time_before(now, update_time + BANDWIDTH_INTERVAL))
586 return;
587
588 spin_lock(&dirty_lock);
589 if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) {
590 update_dirty_limit(thresh, dirty);
591 update_time = now;
592 }
593 spin_unlock(&dirty_lock);
594}
595
Wu Fengguange98be2d2010-08-29 11:22:30 -0600596void __bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -0600597 unsigned long thresh,
598 unsigned long dirty,
599 unsigned long bdi_thresh,
600 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -0600601 unsigned long start_time)
602{
603 unsigned long now = jiffies;
604 unsigned long elapsed = now - bdi->bw_time_stamp;
605 unsigned long written;
606
607 /*
608 * rate-limit, only update once every 200ms.
609 */
610 if (elapsed < BANDWIDTH_INTERVAL)
611 return;
612
613 written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
614
615 /*
616 * Skip quiet periods when disk bandwidth is under-utilized.
617 * (at least 1s idle time between two flusher runs)
618 */
619 if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
620 goto snapshot;
621
Wu Fengguangc42843f2011-03-02 15:54:09 -0600622 if (thresh)
623 global_update_bandwidth(thresh, dirty, now);
624
Wu Fengguange98be2d2010-08-29 11:22:30 -0600625 bdi_update_write_bandwidth(bdi, elapsed, written);
626
627snapshot:
628 bdi->written_stamp = written;
629 bdi->bw_time_stamp = now;
630}
631
632static void bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -0600633 unsigned long thresh,
634 unsigned long dirty,
635 unsigned long bdi_thresh,
636 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -0600637 unsigned long start_time)
638{
639 if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
640 return;
641 spin_lock(&bdi->wb.list_lock);
Wu Fengguangc42843f2011-03-02 15:54:09 -0600642 __bdi_update_bandwidth(bdi, thresh, dirty, bdi_thresh, bdi_dirty,
643 start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -0600644 spin_unlock(&bdi->wb.list_lock);
645}
646
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647/*
648 * balance_dirty_pages() must be called by processes which are generating dirty
649 * data. It looks at the number of dirty pages in the machine and will force
650 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
Jens Axboe5b0830c2009-09-23 19:37:09 +0200651 * If we're over `background_thresh' then the writeback threads are woken to
652 * perform some writeout.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800654static void balance_dirty_pages(struct address_space *mapping,
655 unsigned long write_chunk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700656{
Wu Fengguang77627412010-09-12 13:34:05 -0600657 unsigned long nr_reclaimable, bdi_nr_reclaimable;
658 unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
659 unsigned long bdi_dirty;
David Rientjes364aeb22009-01-06 14:39:29 -0800660 unsigned long background_thresh;
661 unsigned long dirty_thresh;
662 unsigned long bdi_thresh;
Jan Karabcff25f2011-07-01 13:31:25 -0600663 unsigned long task_bdi_thresh;
664 unsigned long min_task_bdi_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700665 unsigned long pages_written = 0;
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200666 unsigned long pause = 1;
Wu Fengguange50e3722010-08-11 14:17:37 -0700667 bool dirty_exceeded = false;
Jan Karabcff25f2011-07-01 13:31:25 -0600668 bool clear_dirty_exceeded = true;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669 struct backing_dev_info *bdi = mapping->backing_dev_info;
Wu Fengguange98be2d2010-08-29 11:22:30 -0600670 unsigned long start_time = jiffies;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671
672 for (;;) {
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800673 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
674 global_page_state(NR_UNSTABLE_NFS);
Wu Fengguang77627412010-09-12 13:34:05 -0600675 nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800676
Wu Fengguang16c40422010-08-11 14:17:39 -0700677 global_dirty_limits(&background_thresh, &dirty_thresh);
678
679 /*
680 * Throttle it only when the background writeback cannot
681 * catch-up. This avoids (excessively) small writeouts
682 * when the bdi limits are ramping up.
683 */
Wu Fengguang77627412010-09-12 13:34:05 -0600684 if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
Wu Fengguang16c40422010-08-11 14:17:39 -0700685 break;
686
687 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
Jan Karabcff25f2011-07-01 13:31:25 -0600688 min_task_bdi_thresh = task_min_dirty_limit(bdi_thresh);
689 task_bdi_thresh = task_dirty_limit(current, bdi_thresh);
Wu Fengguang16c40422010-08-11 14:17:39 -0700690
Wu Fengguange50e3722010-08-11 14:17:37 -0700691 /*
692 * In order to avoid the stacked BDI deadlock we need
693 * to ensure we accurately count the 'dirty' pages when
694 * the threshold is low.
695 *
696 * Otherwise it would be possible to get thresh+n pages
697 * reported dirty, even though there are thresh-m pages
698 * actually dirty; with m+n sitting in the percpu
699 * deltas.
700 */
Jan Karabcff25f2011-07-01 13:31:25 -0600701 if (task_bdi_thresh < 2 * bdi_stat_error(bdi)) {
Wu Fengguange50e3722010-08-11 14:17:37 -0700702 bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
Wu Fengguang77627412010-09-12 13:34:05 -0600703 bdi_dirty = bdi_nr_reclaimable +
704 bdi_stat_sum(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -0700705 } else {
706 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
Wu Fengguang77627412010-09-12 13:34:05 -0600707 bdi_dirty = bdi_nr_reclaimable +
708 bdi_stat(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -0700709 }
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800710
Wu Fengguange50e3722010-08-11 14:17:37 -0700711 /*
712 * The bdi thresh is somehow "soft" limit derived from the
713 * global "hard" limit. The former helps to prevent heavy IO
714 * bdi or process from holding back light ones; The latter is
715 * the last resort safeguard.
716 */
Jan Karabcff25f2011-07-01 13:31:25 -0600717 dirty_exceeded = (bdi_dirty > task_bdi_thresh) ||
Wu Fengguang77627412010-09-12 13:34:05 -0600718 (nr_dirty > dirty_thresh);
Jan Karabcff25f2011-07-01 13:31:25 -0600719 clear_dirty_exceeded = (bdi_dirty <= min_task_bdi_thresh) &&
720 (nr_dirty <= dirty_thresh);
Wu Fengguange50e3722010-08-11 14:17:37 -0700721
722 if (!dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700723 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700725 if (!bdi->dirty_exceeded)
726 bdi->dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727
Wu Fengguangc42843f2011-03-02 15:54:09 -0600728 bdi_update_bandwidth(bdi, dirty_thresh, nr_dirty,
729 bdi_thresh, bdi_dirty, start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -0600730
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
732 * Unstable writes are a feature of certain networked
733 * filesystems (i.e. NFS) in which data may have been
734 * written to the server's write cache, but has not yet
735 * been flushed to permanent storage.
Richard Kennedyd7831a02009-06-30 11:41:35 -0700736 * Only move pages to writeback if this bdi is over its
737 * threshold otherwise wait until the disk writes catch
738 * up.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 */
Wu Fengguangd46db3d2011-05-04 19:54:37 -0600740 trace_balance_dirty_start(bdi);
Jan Karabcff25f2011-07-01 13:31:25 -0600741 if (bdi_nr_reclaimable > task_bdi_thresh) {
Wu Fengguangd46db3d2011-05-04 19:54:37 -0600742 pages_written += writeback_inodes_wb(&bdi->wb,
743 write_chunk);
744 trace_balance_dirty_written(bdi, pages_written);
Wu Fengguange50e3722010-08-11 14:17:37 -0700745 if (pages_written >= write_chunk)
746 break; /* We've done our duty */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700747 }
Wu Fengguangd153ba62010-12-21 17:24:21 -0800748 __set_current_state(TASK_UNINTERRUPTIBLE);
Wu Fengguangd25105e2009-10-09 12:40:42 +0200749 io_schedule_timeout(pause);
Wu Fengguangd46db3d2011-05-04 19:54:37 -0600750 trace_balance_dirty_wait(bdi);
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200751
Wu Fengguangffd1f602011-06-19 22:18:42 -0600752 dirty_thresh = hard_dirty_limit(dirty_thresh);
753 /*
754 * max-pause area. If dirty exceeded but still within this
755 * area, no need to sleep for more than 200ms: (a) 8 pages per
756 * 200ms is typically more than enough to curb heavy dirtiers;
757 * (b) the pause time limit makes the dirtiers more responsive.
758 */
Wu Fengguangbb082292011-08-16 13:37:14 -0600759 if (nr_dirty < dirty_thresh &&
760 bdi_dirty < (task_bdi_thresh + bdi_thresh) / 2 &&
Wu Fengguangffd1f602011-06-19 22:18:42 -0600761 time_after(jiffies, start_time + MAX_PAUSE))
762 break;
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200763
764 /*
765 * Increase the delay for each loop, up to our previous
766 * default of taking a 100ms nap.
767 */
768 pause <<= 1;
769 if (pause > HZ / 10)
770 pause = HZ / 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771 }
772
Jan Karabcff25f2011-07-01 13:31:25 -0600773 /* Clear dirty_exceeded flag only when no task can exceed the limit */
774 if (clear_dirty_exceeded && bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700775 bdi->dirty_exceeded = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776
777 if (writeback_in_progress(bdi))
Jens Axboe5b0830c2009-09-23 19:37:09 +0200778 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779
780 /*
781 * In laptop mode, we wait until hitting the higher threshold before
782 * starting background writeout, and then write out all the way down
783 * to the lower threshold. So slow writers cause minimal disk activity.
784 *
785 * In normal mode, we start background writeout at the lower
786 * background_thresh, to keep the amount of dirty memory low.
787 */
788 if ((laptop_mode && pages_written) ||
Wu Fengguange50e3722010-08-11 14:17:37 -0700789 (!laptop_mode && (nr_reclaimable > background_thresh)))
Christoph Hellwigc5444192010-06-08 18:15:15 +0200790 bdi_start_background_writeback(bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791}
792
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200793void set_page_dirty_balance(struct page *page, int page_mkwrite)
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700794{
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200795 if (set_page_dirty(page) || page_mkwrite) {
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700796 struct address_space *mapping = page_mapping(page);
797
798 if (mapping)
799 balance_dirty_pages_ratelimited(mapping);
800 }
801}
802
Tejun Heo245b2e72009-06-24 15:13:48 +0900803static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
804
Linus Torvalds1da177e2005-04-16 15:20:36 -0700805/**
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800806 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -0700807 * @mapping: address_space which was dirtied
Martin Waitza5802902006-04-02 13:59:55 +0200808 * @nr_pages_dirtied: number of pages which the caller has just dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 *
810 * Processes which are dirtying memory should call in here once for each page
811 * which was newly dirtied. The function will periodically check the system's
812 * dirty state and will initiate writeback if needed.
813 *
814 * On really big machines, get_writeback_state is expensive, so try to avoid
815 * calling it too often (ratelimiting). But once we're over the dirty memory
816 * limit we decrease the ratelimiting by a lot, to prevent individual processes
817 * from overshooting the limit by (ratelimit_pages) each.
818 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800819void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
820 unsigned long nr_pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821{
Wu Fengguang36715ce2011-06-11 17:53:57 -0600822 struct backing_dev_info *bdi = mapping->backing_dev_info;
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800823 unsigned long ratelimit;
824 unsigned long *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825
Wu Fengguang36715ce2011-06-11 17:53:57 -0600826 if (!bdi_cap_account_dirty(bdi))
827 return;
828
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829 ratelimit = ratelimit_pages;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700830 if (mapping->backing_dev_info->dirty_exceeded)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831 ratelimit = 8;
832
833 /*
834 * Check the rate limiting. Also, we do not want to throttle real-time
835 * tasks in balance_dirty_pages(). Period.
836 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800837 preempt_disable();
Tejun Heo245b2e72009-06-24 15:13:48 +0900838 p = &__get_cpu_var(bdp_ratelimits);
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800839 *p += nr_pages_dirtied;
840 if (unlikely(*p >= ratelimit)) {
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800841 ratelimit = sync_writeback_pages(*p);
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800842 *p = 0;
843 preempt_enable();
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800844 balance_dirty_pages(mapping, ratelimit);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 return;
846 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800847 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848}
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800849EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700850
Andrew Morton232ea4d2007-02-28 20:13:21 -0800851void throttle_vm_writeout(gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700852{
David Rientjes364aeb22009-01-06 14:39:29 -0800853 unsigned long background_thresh;
854 unsigned long dirty_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700855
856 for ( ; ; ) {
Wu Fengguang16c40422010-08-11 14:17:39 -0700857 global_dirty_limits(&background_thresh, &dirty_thresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858
859 /*
860 * Boost the allowable dirty threshold a bit for page
861 * allocators so they don't get DoS'ed by heavy writers
862 */
863 dirty_thresh += dirty_thresh / 10; /* wheeee... */
864
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700865 if (global_page_state(NR_UNSTABLE_NFS) +
866 global_page_state(NR_WRITEBACK) <= dirty_thresh)
867 break;
Jens Axboe8aa7e842009-07-09 14:52:32 +0200868 congestion_wait(BLK_RW_ASYNC, HZ/10);
Fengguang Wu369f2382007-10-16 23:30:45 -0700869
870 /*
871 * The caller might hold locks which can prevent IO completion
872 * or progress in the filesystem. So we cannot just sit here
873 * waiting for IO to complete.
874 */
875 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
876 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877 }
878}
879
Linus Torvalds1da177e2005-04-16 15:20:36 -0700880/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
882 */
883int dirty_writeback_centisecs_handler(ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700884 void __user *buffer, size_t *length, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700885{
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700886 proc_dointvec(table, write, buffer, length, ppos);
Jens Axboe64231042010-05-21 20:00:35 +0200887 bdi_arm_supers_timer();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888 return 0;
889}
890
Jens Axboec2c49862010-05-20 09:18:47 +0200891#ifdef CONFIG_BLOCK
Matthew Garrett31373d02010-04-06 14:25:14 +0200892void laptop_mode_timer_fn(unsigned long data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893{
Matthew Garrett31373d02010-04-06 14:25:14 +0200894 struct request_queue *q = (struct request_queue *)data;
895 int nr_pages = global_page_state(NR_FILE_DIRTY) +
896 global_page_state(NR_UNSTABLE_NFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897
Matthew Garrett31373d02010-04-06 14:25:14 +0200898 /*
899 * We want to write everything out, not just down to the dirty
900 * threshold
901 */
Matthew Garrett31373d02010-04-06 14:25:14 +0200902 if (bdi_has_dirty_io(&q->backing_dev_info))
Christoph Hellwigc5444192010-06-08 18:15:15 +0200903 bdi_start_writeback(&q->backing_dev_info, nr_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904}
905
906/*
907 * We've spun up the disk and we're in laptop mode: schedule writeback
908 * of all dirty data a few seconds from now. If the flush is already scheduled
909 * then push it back - the user is still using the disk.
910 */
Matthew Garrett31373d02010-04-06 14:25:14 +0200911void laptop_io_completion(struct backing_dev_info *info)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912{
Matthew Garrett31373d02010-04-06 14:25:14 +0200913 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914}
915
916/*
917 * We're in laptop mode and we've just synced. The sync's writes will have
918 * caused another writeback to be scheduled by laptop_io_completion.
919 * Nothing needs to be written back anymore, so we unschedule the writeback.
920 */
921void laptop_sync_completion(void)
922{
Matthew Garrett31373d02010-04-06 14:25:14 +0200923 struct backing_dev_info *bdi;
924
925 rcu_read_lock();
926
927 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
928 del_timer(&bdi->laptop_mode_wb_timer);
929
930 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700931}
Jens Axboec2c49862010-05-20 09:18:47 +0200932#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933
934/*
935 * If ratelimit_pages is too high then we can get into dirty-data overload
936 * if a large number of processes all perform writes at the same time.
937 * If it is too low then SMP machines will call the (expensive)
938 * get_writeback_state too often.
939 *
940 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
941 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
942 * thresholds before writeback cuts in.
943 *
944 * But the limit should not be set too high. Because it also controls the
945 * amount of memory which the balance_dirty_pages() caller has to write back.
946 * If this is too large then the caller will block on the IO queue all the
947 * time. So limit it to four megabytes - the balance_dirty_pages() caller
948 * will write six megabyte chunks, max.
949 */
950
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700951void writeback_set_ratelimit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952{
Chandra Seetharaman40c99aa2006-09-29 02:01:24 -0700953 ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700954 if (ratelimit_pages < 16)
955 ratelimit_pages = 16;
956 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
957 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
958}
959
Chandra Seetharaman26c21432006-06-27 02:54:10 -0700960static int __cpuinit
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
962{
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700963 writeback_set_ratelimit();
Paul E. McKenneyaa0f0302007-02-10 01:46:37 -0800964 return NOTIFY_DONE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700965}
966
Chandra Seetharaman74b85f32006-06-27 02:54:09 -0700967static struct notifier_block __cpuinitdata ratelimit_nb = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 .notifier_call = ratelimit_handler,
969 .next = NULL,
970};
971
972/*
Linus Torvaldsdc6e29d2007-01-29 16:37:38 -0800973 * Called early on to tune the page writeback dirty limits.
974 *
975 * We used to scale dirty pages according to how total memory
976 * related to pages that could be allocated for buffers (by
977 * comparing nr_free_buffer_pages() to vm_total_pages.
978 *
979 * However, that was when we used "dirty_ratio" to scale with
980 * all memory, and we don't do that any more. "dirty_ratio"
981 * is now applied to total non-HIGHPAGE memory (by subtracting
982 * totalhigh_pages from vm_total_pages), and as such we can't
983 * get into the old insane situation any more where we had
984 * large amounts of dirty pages compared to a small amount of
985 * non-HIGHMEM memory.
986 *
987 * But we might still want to scale the dirty_ratio by how
988 * much memory the box has..
Linus Torvalds1da177e2005-04-16 15:20:36 -0700989 */
990void __init page_writeback_init(void)
991{
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700992 int shift;
993
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700994 writeback_set_ratelimit();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995 register_cpu_notifier(&ratelimit_nb);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700996
997 shift = calc_period_shift();
998 prop_descriptor_init(&vm_completions, shift);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700999 prop_descriptor_init(&vm_dirties, shift);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001000}
1001
David Howells811d7362006-08-29 19:06:09 +01001002/**
Jan Karaf446daa2010-08-09 17:19:12 -07001003 * tag_pages_for_writeback - tag pages to be written by write_cache_pages
1004 * @mapping: address space structure to write
1005 * @start: starting page index
1006 * @end: ending page index (inclusive)
1007 *
1008 * This function scans the page range from @start to @end (inclusive) and tags
1009 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
1010 * that write_cache_pages (or whoever calls this function) will then use
1011 * TOWRITE tag to identify pages eligible for writeback. This mechanism is
1012 * used to avoid livelocking of writeback by a process steadily creating new
1013 * dirty pages in the file (thus it is important for this function to be quick
1014 * so that it can tag pages faster than a dirtying process can create them).
1015 */
1016/*
1017 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
1018 */
Jan Karaf446daa2010-08-09 17:19:12 -07001019void tag_pages_for_writeback(struct address_space *mapping,
1020 pgoff_t start, pgoff_t end)
1021{
Randy Dunlap3c111a02010-08-11 14:17:30 -07001022#define WRITEBACK_TAG_BATCH 4096
Jan Karaf446daa2010-08-09 17:19:12 -07001023 unsigned long tagged;
1024
1025 do {
1026 spin_lock_irq(&mapping->tree_lock);
1027 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
1028 &start, end, WRITEBACK_TAG_BATCH,
1029 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
1030 spin_unlock_irq(&mapping->tree_lock);
1031 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
1032 cond_resched();
Jan Karad5ed3a42010-08-19 14:13:33 -07001033 /* We check 'start' to handle wrapping when end == ~0UL */
1034 } while (tagged >= WRITEBACK_TAG_BATCH && start);
Jan Karaf446daa2010-08-09 17:19:12 -07001035}
1036EXPORT_SYMBOL(tag_pages_for_writeback);
1037
1038/**
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001039 * 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 +01001040 * @mapping: address space structure to write
1041 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001042 * @writepage: function called for each page
1043 * @data: data passed to writepage function
David Howells811d7362006-08-29 19:06:09 +01001044 *
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001045 * If a page is already under I/O, write_cache_pages() skips it, even
David Howells811d7362006-08-29 19:06:09 +01001046 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
1047 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
1048 * and msync() need to guarantee that all the data which was dirty at the time
1049 * the call was made get new I/O started against them. If wbc->sync_mode is
1050 * WB_SYNC_ALL then we were called for data integrity and we must wait for
1051 * existing IO to complete.
Jan Karaf446daa2010-08-09 17:19:12 -07001052 *
1053 * To avoid livelocks (when other process dirties new pages), we first tag
1054 * pages which should be written back with TOWRITE tag and only then start
1055 * writing them. For data-integrity sync we have to be careful so that we do
1056 * not miss some pages (e.g., because some other process has cleared TOWRITE
1057 * tag we set). The rule we follow is that TOWRITE tag can be cleared only
1058 * by the process clearing the DIRTY tag (and submitting the page for IO).
David Howells811d7362006-08-29 19:06:09 +01001059 */
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001060int write_cache_pages(struct address_space *mapping,
1061 struct writeback_control *wbc, writepage_t writepage,
1062 void *data)
David Howells811d7362006-08-29 19:06:09 +01001063{
David Howells811d7362006-08-29 19:06:09 +01001064 int ret = 0;
1065 int done = 0;
David Howells811d7362006-08-29 19:06:09 +01001066 struct pagevec pvec;
1067 int nr_pages;
Nick Piggin31a12662009-01-06 14:39:04 -08001068 pgoff_t uninitialized_var(writeback_index);
David Howells811d7362006-08-29 19:06:09 +01001069 pgoff_t index;
1070 pgoff_t end; /* Inclusive */
Nick Pigginbd19e012009-01-06 14:39:06 -08001071 pgoff_t done_index;
Nick Piggin31a12662009-01-06 14:39:04 -08001072 int cycled;
David Howells811d7362006-08-29 19:06:09 +01001073 int range_whole = 0;
Jan Karaf446daa2010-08-09 17:19:12 -07001074 int tag;
David Howells811d7362006-08-29 19:06:09 +01001075
David Howells811d7362006-08-29 19:06:09 +01001076 pagevec_init(&pvec, 0);
1077 if (wbc->range_cyclic) {
Nick Piggin31a12662009-01-06 14:39:04 -08001078 writeback_index = mapping->writeback_index; /* prev offset */
1079 index = writeback_index;
1080 if (index == 0)
1081 cycled = 1;
1082 else
1083 cycled = 0;
David Howells811d7362006-08-29 19:06:09 +01001084 end = -1;
1085 } else {
1086 index = wbc->range_start >> PAGE_CACHE_SHIFT;
1087 end = wbc->range_end >> PAGE_CACHE_SHIFT;
1088 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
1089 range_whole = 1;
Nick Piggin31a12662009-01-06 14:39:04 -08001090 cycled = 1; /* ignore range_cyclic tests */
David Howells811d7362006-08-29 19:06:09 +01001091 }
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001092 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daa2010-08-09 17:19:12 -07001093 tag = PAGECACHE_TAG_TOWRITE;
1094 else
1095 tag = PAGECACHE_TAG_DIRTY;
David Howells811d7362006-08-29 19:06:09 +01001096retry:
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001097 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daa2010-08-09 17:19:12 -07001098 tag_pages_for_writeback(mapping, index, end);
Nick Pigginbd19e012009-01-06 14:39:06 -08001099 done_index = index;
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001100 while (!done && (index <= end)) {
1101 int i;
1102
Jan Karaf446daa2010-08-09 17:19:12 -07001103 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001104 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
1105 if (nr_pages == 0)
1106 break;
David Howells811d7362006-08-29 19:06:09 +01001107
David Howells811d7362006-08-29 19:06:09 +01001108 for (i = 0; i < nr_pages; i++) {
1109 struct page *page = pvec.pages[i];
1110
Nick Piggind5482cd2009-01-06 14:39:11 -08001111 /*
1112 * At this point, the page may be truncated or
1113 * invalidated (changing page->mapping to NULL), or
1114 * even swizzled back from swapper_space to tmpfs file
1115 * mapping. However, page->index will not change
1116 * because we have a reference on the page.
1117 */
1118 if (page->index > end) {
1119 /*
1120 * can't be range_cyclic (1st pass) because
1121 * end == -1 in that case.
1122 */
1123 done = 1;
1124 break;
1125 }
1126
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001127 done_index = page->index;
Nick Pigginbd19e012009-01-06 14:39:06 -08001128
David Howells811d7362006-08-29 19:06:09 +01001129 lock_page(page);
1130
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001131 /*
1132 * Page truncated or invalidated. We can freely skip it
1133 * then, even for data integrity operations: the page
1134 * has disappeared concurrently, so there could be no
1135 * real expectation of this data interity operation
1136 * even if there is now a new, dirty page at the same
1137 * pagecache address.
1138 */
David Howells811d7362006-08-29 19:06:09 +01001139 if (unlikely(page->mapping != mapping)) {
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001140continue_unlock:
David Howells811d7362006-08-29 19:06:09 +01001141 unlock_page(page);
1142 continue;
1143 }
1144
Nick Piggin515f4a02009-01-06 14:39:10 -08001145 if (!PageDirty(page)) {
1146 /* someone wrote it for us */
1147 goto continue_unlock;
1148 }
David Howells811d7362006-08-29 19:06:09 +01001149
Nick Piggin515f4a02009-01-06 14:39:10 -08001150 if (PageWriteback(page)) {
1151 if (wbc->sync_mode != WB_SYNC_NONE)
1152 wait_on_page_writeback(page);
1153 else
1154 goto continue_unlock;
1155 }
1156
1157 BUG_ON(PageWriteback(page));
1158 if (!clear_page_dirty_for_io(page))
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001159 goto continue_unlock;
David Howells811d7362006-08-29 19:06:09 +01001160
Dave Chinner9e094382010-07-07 13:24:08 +10001161 trace_wbc_writepage(wbc, mapping->backing_dev_info);
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001162 ret = (*writepage)(page, wbc, data);
Nick Piggin00266772009-01-06 14:39:06 -08001163 if (unlikely(ret)) {
1164 if (ret == AOP_WRITEPAGE_ACTIVATE) {
1165 unlock_page(page);
1166 ret = 0;
1167 } else {
1168 /*
1169 * done_index is set past this page,
1170 * so media errors will not choke
1171 * background writeout for the entire
1172 * file. This has consequences for
1173 * range_cyclic semantics (ie. it may
1174 * not be suitable for data integrity
1175 * writeout).
1176 */
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001177 done_index = page->index + 1;
Nick Piggin00266772009-01-06 14:39:06 -08001178 done = 1;
1179 break;
1180 }
Dave Chinner0b564922010-06-09 10:37:18 +10001181 }
David Howells811d7362006-08-29 19:06:09 +01001182
Dave Chinner546a1922010-08-24 11:44:34 +10001183 /*
1184 * We stop writing back only if we are not doing
1185 * integrity sync. In case of integrity sync we have to
1186 * keep going until we have written all the pages
1187 * we tagged for writeback prior to entering this loop.
1188 */
1189 if (--wbc->nr_to_write <= 0 &&
1190 wbc->sync_mode == WB_SYNC_NONE) {
1191 done = 1;
1192 break;
Nick Piggin05fe4782009-01-06 14:39:08 -08001193 }
David Howells811d7362006-08-29 19:06:09 +01001194 }
1195 pagevec_release(&pvec);
1196 cond_resched();
1197 }
Nick Piggin3a4c6802009-02-12 04:34:23 +01001198 if (!cycled && !done) {
David Howells811d7362006-08-29 19:06:09 +01001199 /*
Nick Piggin31a12662009-01-06 14:39:04 -08001200 * range_cyclic:
David Howells811d7362006-08-29 19:06:09 +01001201 * We hit the last page and there is more work to be done: wrap
1202 * back to the start of the file
1203 */
Nick Piggin31a12662009-01-06 14:39:04 -08001204 cycled = 1;
David Howells811d7362006-08-29 19:06:09 +01001205 index = 0;
Nick Piggin31a12662009-01-06 14:39:04 -08001206 end = writeback_index - 1;
David Howells811d7362006-08-29 19:06:09 +01001207 goto retry;
1208 }
Dave Chinner0b564922010-06-09 10:37:18 +10001209 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
1210 mapping->writeback_index = done_index;
Aneesh Kumar K.V06d6cf62008-07-11 19:27:31 -04001211
David Howells811d7362006-08-29 19:06:09 +01001212 return ret;
1213}
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001214EXPORT_SYMBOL(write_cache_pages);
1215
1216/*
1217 * Function used by generic_writepages to call the real writepage
1218 * function and set the mapping flags on error
1219 */
1220static int __writepage(struct page *page, struct writeback_control *wbc,
1221 void *data)
1222{
1223 struct address_space *mapping = data;
1224 int ret = mapping->a_ops->writepage(page, wbc);
1225 mapping_set_error(mapping, ret);
1226 return ret;
1227}
1228
1229/**
1230 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
1231 * @mapping: address space structure to write
1232 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
1233 *
1234 * This is a library function, which implements the writepages()
1235 * address_space_operation.
1236 */
1237int generic_writepages(struct address_space *mapping,
1238 struct writeback_control *wbc)
1239{
Shaohua Li9b6096a2011-03-17 10:47:06 +01001240 struct blk_plug plug;
1241 int ret;
1242
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001243 /* deal with chardevs and other special file */
1244 if (!mapping->a_ops->writepage)
1245 return 0;
1246
Shaohua Li9b6096a2011-03-17 10:47:06 +01001247 blk_start_plug(&plug);
1248 ret = write_cache_pages(mapping, wbc, __writepage, mapping);
1249 blk_finish_plug(&plug);
1250 return ret;
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001251}
David Howells811d7362006-08-29 19:06:09 +01001252
1253EXPORT_SYMBOL(generic_writepages);
1254
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1256{
Andrew Morton22905f72005-11-16 15:07:01 -08001257 int ret;
1258
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259 if (wbc->nr_to_write <= 0)
1260 return 0;
1261 if (mapping->a_ops->writepages)
Peter Zijlstrad08b3852006-09-25 23:30:57 -07001262 ret = mapping->a_ops->writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001263 else
1264 ret = generic_writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001265 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266}
1267
1268/**
1269 * write_one_page - write out a single page and optionally wait on I/O
Martin Waitz67be2dd2005-05-01 08:59:26 -07001270 * @page: the page to write
1271 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -07001272 *
1273 * The page must be locked by the caller and will be unlocked upon return.
1274 *
1275 * write_one_page() returns a negative error code if I/O failed.
1276 */
1277int write_one_page(struct page *page, int wait)
1278{
1279 struct address_space *mapping = page->mapping;
1280 int ret = 0;
1281 struct writeback_control wbc = {
1282 .sync_mode = WB_SYNC_ALL,
1283 .nr_to_write = 1,
1284 };
1285
1286 BUG_ON(!PageLocked(page));
1287
1288 if (wait)
1289 wait_on_page_writeback(page);
1290
1291 if (clear_page_dirty_for_io(page)) {
1292 page_cache_get(page);
1293 ret = mapping->a_ops->writepage(page, &wbc);
1294 if (ret == 0 && wait) {
1295 wait_on_page_writeback(page);
1296 if (PageError(page))
1297 ret = -EIO;
1298 }
1299 page_cache_release(page);
1300 } else {
1301 unlock_page(page);
1302 }
1303 return ret;
1304}
1305EXPORT_SYMBOL(write_one_page);
1306
1307/*
Ken Chen76719322007-02-10 01:43:15 -08001308 * For address_spaces which do not use buffers nor write back.
1309 */
1310int __set_page_dirty_no_writeback(struct page *page)
1311{
1312 if (!PageDirty(page))
Bob Liuc3f0da62011-01-13 15:45:49 -08001313 return !TestSetPageDirty(page);
Ken Chen76719322007-02-10 01:43:15 -08001314 return 0;
1315}
1316
1317/*
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001318 * Helper function for set_page_dirty family.
1319 * NOTE: This relies on being atomic wrt interrupts.
1320 */
1321void account_page_dirtied(struct page *page, struct address_space *mapping)
1322{
1323 if (mapping_cap_account_dirty(mapping)) {
1324 __inc_zone_page_state(page, NR_FILE_DIRTY);
Michael Rubinea941f02010-10-26 14:21:35 -07001325 __inc_zone_page_state(page, NR_DIRTIED);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001326 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
1327 task_dirty_inc(current);
1328 task_io_account_write(PAGE_CACHE_SIZE);
1329 }
1330}
Michael Rubin679ceac2010-08-20 02:31:26 -07001331EXPORT_SYMBOL(account_page_dirtied);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001332
1333/*
Michael Rubinf629d1c2010-10-26 14:21:33 -07001334 * Helper function for set_page_writeback family.
1335 * NOTE: Unlike account_page_dirtied this does not rely on being atomic
1336 * wrt interrupts.
1337 */
1338void account_page_writeback(struct page *page)
1339{
1340 inc_zone_page_state(page, NR_WRITEBACK);
1341}
1342EXPORT_SYMBOL(account_page_writeback);
1343
1344/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 * For address_spaces which do not use buffers. Just tag the page as dirty in
1346 * its radix tree.
1347 *
1348 * This is also used when a single buffer is being dirtied: we want to set the
1349 * page dirty in that case, but not all the buffers. This is a "bottom-up"
1350 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
1351 *
1352 * Most callers have locked the page, which pins the address_space in memory.
1353 * But zap_pte_range() does not lock the page, however in that case the
1354 * mapping is pinned by the vma's ->vm_file reference.
1355 *
1356 * We take care to handle the case where the page was truncated from the
Simon Arlott183ff222007-10-20 01:27:18 +02001357 * mapping by re-checking page_mapping() inside tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001358 */
1359int __set_page_dirty_nobuffers(struct page *page)
1360{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361 if (!TestSetPageDirty(page)) {
1362 struct address_space *mapping = page_mapping(page);
1363 struct address_space *mapping2;
1364
Andrew Morton8c085402006-12-10 02:19:24 -08001365 if (!mapping)
1366 return 1;
1367
Nick Piggin19fd6232008-07-25 19:45:32 -07001368 spin_lock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001369 mapping2 = page_mapping(page);
1370 if (mapping2) { /* Race with truncate? */
1371 BUG_ON(mapping2 != mapping);
Nick Piggin787d2212007-07-17 04:03:34 -07001372 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001373 account_page_dirtied(page, mapping);
Andrew Morton8c085402006-12-10 02:19:24 -08001374 radix_tree_tag_set(&mapping->page_tree,
1375 page_index(page), PAGECACHE_TAG_DIRTY);
1376 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001377 spin_unlock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001378 if (mapping->host) {
1379 /* !PageAnon && !swapper_space */
1380 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001382 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001384 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001385}
1386EXPORT_SYMBOL(__set_page_dirty_nobuffers);
1387
1388/*
1389 * When a writepage implementation decides that it doesn't want to write this
1390 * page for some reason, it should redirty the locked page via
1391 * redirty_page_for_writepage() and it should then unlock the page and return 0
1392 */
1393int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
1394{
1395 wbc->pages_skipped++;
1396 return __set_page_dirty_nobuffers(page);
1397}
1398EXPORT_SYMBOL(redirty_page_for_writepage);
1399
1400/*
Wu Fengguang6746aff2009-09-16 11:50:14 +02001401 * Dirty a page.
1402 *
1403 * For pages with a mapping this should be done under the page lock
1404 * for the benefit of asynchronous memory errors who prefer a consistent
1405 * dirty state. This rule can be broken in some special cases,
1406 * but should be better not to.
1407 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408 * If the mapping doesn't provide a set_page_dirty a_op, then
1409 * just fall through and assume that it wants buffer_heads.
1410 */
Nick Piggin1cf6e7d2009-02-18 14:48:18 -08001411int set_page_dirty(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412{
1413 struct address_space *mapping = page_mapping(page);
1414
1415 if (likely(mapping)) {
1416 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
Minchan Kim278df9f2011-03-22 16:32:54 -07001417 /*
1418 * readahead/lru_deactivate_page could remain
1419 * PG_readahead/PG_reclaim due to race with end_page_writeback
1420 * About readahead, if the page is written, the flags would be
1421 * reset. So no problem.
1422 * About lru_deactivate_page, if the page is redirty, the flag
1423 * will be reset. So no problem. but if the page is used by readahead
1424 * it will confuse readahead and make it restart the size rampup
1425 * process. But it's a trivial problem.
1426 */
1427 ClearPageReclaim(page);
David Howells93614012006-09-30 20:45:40 +02001428#ifdef CONFIG_BLOCK
1429 if (!spd)
1430 spd = __set_page_dirty_buffers;
1431#endif
1432 return (*spd)(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001433 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001434 if (!PageDirty(page)) {
1435 if (!TestSetPageDirty(page))
1436 return 1;
1437 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001438 return 0;
1439}
1440EXPORT_SYMBOL(set_page_dirty);
1441
1442/*
1443 * set_page_dirty() is racy if the caller has no reference against
1444 * page->mapping->host, and if the page is unlocked. This is because another
1445 * CPU could truncate the page off the mapping and then free the mapping.
1446 *
1447 * Usually, the page _is_ locked, or the caller is a user-space process which
1448 * holds a reference on the inode by having an open file.
1449 *
1450 * In other cases, the page should be locked before running set_page_dirty().
1451 */
1452int set_page_dirty_lock(struct page *page)
1453{
1454 int ret;
1455
Jens Axboe7eaceac2011-03-10 08:52:07 +01001456 lock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001457 ret = set_page_dirty(page);
1458 unlock_page(page);
1459 return ret;
1460}
1461EXPORT_SYMBOL(set_page_dirty_lock);
1462
1463/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 * Clear a page's dirty flag, while caring for dirty memory accounting.
1465 * Returns true if the page was previously dirty.
1466 *
1467 * This is for preparing to put the page under writeout. We leave the page
1468 * tagged as dirty in the radix tree so that a concurrent write-for-sync
1469 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
1470 * implementation will run either set_page_writeback() or set_page_dirty(),
1471 * at which stage we bring the page's dirty flag and radix-tree dirty tag
1472 * back into sync.
1473 *
1474 * This incoherency between the page's dirty flag and radix-tree tag is
1475 * unfortunate, but it only exists while the page is locked.
1476 */
1477int clear_page_dirty_for_io(struct page *page)
1478{
1479 struct address_space *mapping = page_mapping(page);
1480
Nick Piggin79352892007-07-19 01:47:22 -07001481 BUG_ON(!PageLocked(page));
1482
Linus Torvalds7658cc22006-12-29 10:00:58 -08001483 if (mapping && mapping_cap_account_dirty(mapping)) {
1484 /*
1485 * Yes, Virginia, this is indeed insane.
1486 *
1487 * We use this sequence to make sure that
1488 * (a) we account for dirty stats properly
1489 * (b) we tell the low-level filesystem to
1490 * mark the whole page dirty if it was
1491 * dirty in a pagetable. Only to then
1492 * (c) clean the page again and return 1 to
1493 * cause the writeback.
1494 *
1495 * This way we avoid all nasty races with the
1496 * dirty bit in multiple places and clearing
1497 * them concurrently from different threads.
1498 *
1499 * Note! Normally the "set_page_dirty(page)"
1500 * has no effect on the actual dirty bit - since
1501 * that will already usually be set. But we
1502 * need the side effects, and it can help us
1503 * avoid races.
1504 *
1505 * We basically use the page "master dirty bit"
1506 * as a serialization point for all the different
1507 * threads doing their things.
Linus Torvalds7658cc22006-12-29 10:00:58 -08001508 */
1509 if (page_mkclean(page))
1510 set_page_dirty(page);
Nick Piggin79352892007-07-19 01:47:22 -07001511 /*
1512 * We carefully synchronise fault handlers against
1513 * installing a dirty pte and marking the page dirty
1514 * at this point. We do this by having them hold the
1515 * page lock at some point after installing their
1516 * pte, but before marking the page dirty.
1517 * Pages are always locked coming in here, so we get
1518 * the desired exclusion. See mm/memory.c:do_wp_page()
1519 * for more comments.
1520 */
Linus Torvalds7658cc22006-12-29 10:00:58 -08001521 if (TestClearPageDirty(page)) {
Andrew Morton8c085402006-12-10 02:19:24 -08001522 dec_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07001523 dec_bdi_stat(mapping->backing_dev_info,
1524 BDI_RECLAIMABLE);
Linus Torvalds7658cc22006-12-29 10:00:58 -08001525 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001526 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001527 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001529 return TestClearPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530}
Hans Reiser58bb01a2005-11-18 01:10:53 -08001531EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001532
1533int test_clear_page_writeback(struct page *page)
1534{
1535 struct address_space *mapping = page_mapping(page);
1536 int ret;
1537
1538 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001539 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001540 unsigned long flags;
1541
Nick Piggin19fd6232008-07-25 19:45:32 -07001542 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543 ret = TestClearPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001544 if (ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545 radix_tree_tag_clear(&mapping->page_tree,
1546 page_index(page),
1547 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001548 if (bdi_cap_account_writeback(bdi)) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001549 __dec_bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001550 __bdi_writeout_inc(bdi);
1551 }
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001552 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001553 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 } else {
1555 ret = TestClearPageWriteback(page);
1556 }
Wu Fengguang99b12e32011-07-25 17:12:37 -07001557 if (ret) {
Andrew Mortond688abf2007-07-19 01:49:17 -07001558 dec_zone_page_state(page, NR_WRITEBACK);
Wu Fengguang99b12e32011-07-25 17:12:37 -07001559 inc_zone_page_state(page, NR_WRITTEN);
1560 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001561 return ret;
1562}
1563
1564int test_set_page_writeback(struct page *page)
1565{
1566 struct address_space *mapping = page_mapping(page);
1567 int ret;
1568
1569 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001570 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571 unsigned long flags;
1572
Nick Piggin19fd6232008-07-25 19:45:32 -07001573 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574 ret = TestSetPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001575 if (!ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576 radix_tree_tag_set(&mapping->page_tree,
1577 page_index(page),
1578 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001579 if (bdi_cap_account_writeback(bdi))
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001580 __inc_bdi_stat(bdi, BDI_WRITEBACK);
1581 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001582 if (!PageDirty(page))
1583 radix_tree_tag_clear(&mapping->page_tree,
1584 page_index(page),
1585 PAGECACHE_TAG_DIRTY);
Jan Karaf446daa2010-08-09 17:19:12 -07001586 radix_tree_tag_clear(&mapping->page_tree,
1587 page_index(page),
1588 PAGECACHE_TAG_TOWRITE);
Nick Piggin19fd6232008-07-25 19:45:32 -07001589 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001590 } else {
1591 ret = TestSetPageWriteback(page);
1592 }
Andrew Mortond688abf2007-07-19 01:49:17 -07001593 if (!ret)
Michael Rubinf629d1c2010-10-26 14:21:33 -07001594 account_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595 return ret;
1596
1597}
1598EXPORT_SYMBOL(test_set_page_writeback);
1599
1600/*
Nick Piggin00128182007-10-16 01:24:40 -07001601 * Return true if any of the pages in the mapping are marked with the
Linus Torvalds1da177e2005-04-16 15:20:36 -07001602 * passed tag.
1603 */
1604int mapping_tagged(struct address_space *mapping, int tag)
1605{
Konstantin Khlebnikov72c47832011-07-25 17:12:31 -07001606 return radix_tree_tagged(&mapping->page_tree, tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607}
1608EXPORT_SYMBOL(mapping_tagged);