blob: efe68148f621959beb28987dd9430fff289f583f [file] [log] [blame]
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>
Paul Gortmakerb95f1b312011-10-16 02:01:52 -040015#include <linux/export.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#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>
Al Viroff01bb482011-09-16 02:31:11 -040035#include <linux/buffer_head.h> /* __set_page_dirty_buffers */
David Howells811d7362006-08-29 19:06:09 +010036#include <linux/pagevec.h>
Jan Karaeb608e32012-05-24 18:59:11 +020037#include <linux/timer.h>
Clark Williams8bd75c72013-02-07 09:47:07 -060038#include <linux/sched/rt.h>
Dave Chinner028c2dd2010-07-07 13:24:07 +100039#include <trace/events/writeback.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070040
41/*
Wu Fengguangffd1f602011-06-19 22:18:42 -060042 * Sleep at most 200ms at a time in balance_dirty_pages().
43 */
44#define MAX_PAUSE max(HZ/5, 1)
45
46/*
Wu Fengguang5b9b3572011-12-06 13:17:17 -060047 * Try to keep balance_dirty_pages() call intervals higher than this many pages
48 * by raising pause time to max_pause when falls below it.
49 */
50#define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10))
51
52/*
Wu Fengguange98be2d2010-08-29 11:22:30 -060053 * Estimate write bandwidth at 200ms intervals.
54 */
55#define BANDWIDTH_INTERVAL max(HZ/5, 1)
56
Wu Fengguang6c14ae12011-03-02 16:04:18 -060057#define RATELIMIT_CALC_SHIFT 10
58
Wu Fengguange98be2d2010-08-29 11:22:30 -060059/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
61 * will look to see if it needs to force writeback or throttling.
62 */
63static long ratelimit_pages = 32;
64
Linus Torvalds1da177e2005-04-16 15:20:36 -070065/* The following parameters are exported via /proc/sys/vm */
66
67/*
Jens Axboe5b0830c2009-09-23 19:37:09 +020068 * Start background writeback (via writeback threads) at this percentage
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080070int dirty_background_ratio = 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -070071
72/*
David Rientjes2da02992009-01-06 14:39:31 -080073 * dirty_background_bytes starts at 0 (disabled) so that it is a function of
74 * dirty_background_ratio * the amount of dirtyable memory
75 */
76unsigned long dirty_background_bytes;
77
78/*
Bron Gondwana195cf4532008-02-04 22:29:20 -080079 * free highmem will not be subtracted from the total free memory
80 * for calculating free ratios if vm_highmem_is_dirtyable is true
81 */
82int vm_highmem_is_dirtyable;
83
84/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 * The generator of dirty data starts writeback at this percentage
86 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080087int vm_dirty_ratio = 20;
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
89/*
David Rientjes2da02992009-01-06 14:39:31 -080090 * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
91 * vm_dirty_ratio * the amount of dirtyable memory
92 */
93unsigned long vm_dirty_bytes;
94
95/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -070096 * The interval between `kupdate'-style writebacks
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -070098unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -070099
Artem Bityutskiy91913a22012-03-21 22:33:00 -0400100EXPORT_SYMBOL_GPL(dirty_writeback_interval);
101
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -0700103 * The longest time for which data is allowed to remain dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -0700105unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106
107/*
108 * Flag that makes the machine dump writes/reads and block dirtyings.
109 */
110int block_dump;
111
112/*
Bart Samweled5b43f2006-03-24 03:15:49 -0800113 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
114 * a full sync is triggered after this time elapses without any disk activity.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 */
116int laptop_mode;
117
118EXPORT_SYMBOL(laptop_mode);
119
120/* End of sysctl-exported parameters */
121
Wu Fengguangc42843f2011-03-02 15:54:09 -0600122unsigned long global_dirty_limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124/*
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700125 * Scale the writeback cache size proportional to the relative writeout speeds.
126 *
127 * We do this by keeping a floating proportion between BDIs, based on page
128 * writeback completions [end_page_writeback()]. Those devices that write out
129 * pages fastest will get the larger share, while the slower will get a smaller
130 * share.
131 *
132 * We use page writeout completions because we are interested in getting rid of
133 * dirty pages. Having them written out is the primary goal.
134 *
135 * We introduce a concept of time, a period over which we measure these events,
136 * because demand can/will vary over time. The length of this period itself is
137 * measured in page writeback completions.
138 *
139 */
Jan Karaeb608e32012-05-24 18:59:11 +0200140static struct fprop_global writeout_completions;
141
142static void writeout_period(unsigned long t);
143/* Timer for aging of writeout_completions */
144static struct timer_list writeout_period_timer =
145 TIMER_DEFERRED_INITIALIZER(writeout_period, 0, 0);
146static unsigned long writeout_period_time = 0;
147
148/*
149 * Length of period for aging writeout fractions of bdis. This is an
150 * arbitrarily chosen number. The longer the period, the slower fractions will
151 * reflect changes in current writeout rate.
152 */
153#define VM_COMPLETIONS_PERIOD_LEN (3*HZ)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700154
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700155/*
Johannes Weiner1edf2232012-01-10 15:06:57 -0800156 * Work out the current dirty-memory clamping and background writeout
157 * thresholds.
158 *
159 * The main aim here is to lower them aggressively if there is a lot of mapped
160 * memory around. To avoid stressing page reclaim with lots of unreclaimable
161 * pages. It is better to clamp down on writers than to start swapping, and
162 * performing lots of scanning.
163 *
164 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
165 *
166 * We don't permit the clamping level to fall below 5% - that is getting rather
167 * excessive.
168 *
169 * We make sure that the background writeout level is below the adjusted
170 * clamping level.
171 */
Johannes Weinerccafa282012-01-10 15:07:44 -0800172
Johannes Weinera756cf52012-01-10 15:07:49 -0800173/*
174 * In a memory zone, there is a certain amount of pages we consider
175 * available for the page cache, which is essentially the number of
176 * free and reclaimable pages, minus some zone reserves to protect
177 * lowmem and the ability to uphold the zone's watermarks without
178 * requiring writeback.
179 *
180 * This number of dirtyable pages is the base value of which the
181 * user-configurable dirty ratio is the effictive number of pages that
182 * are allowed to be actually dirtied. Per individual zone, or
183 * globally by using the sum of dirtyable pages over all zones.
184 *
185 * Because the user is allowed to specify the dirty limit globally as
186 * absolute number of bytes, calculating the per-zone dirty limit can
187 * require translating the configured limit into a percentage of
188 * global dirtyable memory first.
189 */
190
Johannes Weiner1edf2232012-01-10 15:06:57 -0800191static unsigned long highmem_dirtyable_memory(unsigned long total)
192{
193#ifdef CONFIG_HIGHMEM
194 int node;
195 unsigned long x = 0;
196
197 for_each_node_state(node, N_HIGH_MEMORY) {
198 struct zone *z =
199 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
200
201 x += zone_page_state(z, NR_FREE_PAGES) +
Johannes Weinerab8fabd2012-01-10 15:07:42 -0800202 zone_reclaimable_pages(z) - z->dirty_balance_reserve;
Johannes Weiner1edf2232012-01-10 15:06:57 -0800203 }
204 /*
Sonny Raoc8b74c2f2012-12-20 15:05:07 -0800205 * Unreclaimable memory (kernel memory or anonymous memory
206 * without swap) can bring down the dirtyable pages below
207 * the zone's dirty balance reserve and the above calculation
208 * will underflow. However we still want to add in nodes
209 * which are below threshold (negative values) to get a more
210 * accurate calculation but make sure that the total never
211 * underflows.
212 */
213 if ((long)x < 0)
214 x = 0;
215
216 /*
Johannes Weiner1edf2232012-01-10 15:06:57 -0800217 * Make sure that the number of highmem pages is never larger
218 * than the number of the total dirtyable memory. This can only
219 * occur in very strange VM situations but we want to make sure
220 * that this does not occur.
221 */
222 return min(x, total);
223#else
224 return 0;
225#endif
226}
227
228/**
Johannes Weinerccafa282012-01-10 15:07:44 -0800229 * global_dirtyable_memory - number of globally dirtyable pages
Johannes Weiner1edf2232012-01-10 15:06:57 -0800230 *
Johannes Weinerccafa282012-01-10 15:07:44 -0800231 * Returns the global number of pages potentially available for dirty
232 * page cache. This is the base value for the global dirty limits.
Johannes Weiner1edf2232012-01-10 15:06:57 -0800233 */
H Hartley Sweeten18cf8cf2012-04-12 13:44:20 -0700234static unsigned long global_dirtyable_memory(void)
Johannes Weiner1edf2232012-01-10 15:06:57 -0800235{
236 unsigned long x;
237
Sonny Raoc8b74c2f2012-12-20 15:05:07 -0800238 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
239 x -= min(x, dirty_balance_reserve);
Johannes Weiner1edf2232012-01-10 15:06:57 -0800240
241 if (!vm_highmem_is_dirtyable)
242 x -= highmem_dirtyable_memory(x);
243
Paul Szabo75f7ad82013-02-22 16:34:42 -0800244 /* Subtract min_free_kbytes */
245 x -= min_t(unsigned long, x, min_free_kbytes >> (PAGE_SHIFT - 10));
246
Johannes Weiner1edf2232012-01-10 15:06:57 -0800247 return x + 1; /* Ensure that we never return 0 */
248}
249
250/*
Johannes Weinerccafa282012-01-10 15:07:44 -0800251 * global_dirty_limits - background-writeback and dirty-throttling thresholds
252 *
253 * Calculate the dirty thresholds based on sysctl parameters
254 * - vm.dirty_background_ratio or vm.dirty_background_bytes
255 * - vm.dirty_ratio or vm.dirty_bytes
256 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
257 * real-time tasks.
258 */
259void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
260{
261 unsigned long background;
262 unsigned long dirty;
263 unsigned long uninitialized_var(available_memory);
264 struct task_struct *tsk;
265
266 if (!vm_dirty_bytes || !dirty_background_bytes)
267 available_memory = global_dirtyable_memory();
268
269 if (vm_dirty_bytes)
270 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
271 else
272 dirty = (vm_dirty_ratio * available_memory) / 100;
273
274 if (dirty_background_bytes)
275 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
276 else
277 background = (dirty_background_ratio * available_memory) / 100;
278
279 if (background >= dirty)
280 background = dirty / 2;
281 tsk = current;
282 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
283 background += background / 4;
284 dirty += dirty / 4;
285 }
286 *pbackground = background;
287 *pdirty = dirty;
288 trace_global_dirty_state(background, dirty);
289}
290
Johannes Weinera756cf52012-01-10 15:07:49 -0800291/**
292 * zone_dirtyable_memory - number of dirtyable pages in a zone
293 * @zone: the zone
294 *
295 * Returns the zone's number of pages potentially available for dirty
296 * page cache. This is the base value for the per-zone dirty limits.
297 */
298static unsigned long zone_dirtyable_memory(struct zone *zone)
299{
300 /*
301 * The effective global number of dirtyable pages may exclude
302 * highmem as a big-picture measure to keep the ratio between
303 * dirty memory and lowmem reasonable.
304 *
305 * But this function is purely about the individual zone and a
306 * highmem zone can hold its share of dirty pages, so we don't
307 * care about vm_highmem_is_dirtyable here.
308 */
Sonny Raoc8b74c2f2012-12-20 15:05:07 -0800309 unsigned long nr_pages = zone_page_state(zone, NR_FREE_PAGES) +
310 zone_reclaimable_pages(zone);
311
312 /* don't allow this to underflow */
313 nr_pages -= min(nr_pages, zone->dirty_balance_reserve);
314 return nr_pages;
Johannes Weinera756cf52012-01-10 15:07:49 -0800315}
316
317/**
318 * zone_dirty_limit - maximum number of dirty pages allowed in a zone
319 * @zone: the zone
320 *
321 * Returns the maximum number of dirty pages allowed in a zone, based
322 * on the zone's dirtyable memory.
323 */
324static unsigned long zone_dirty_limit(struct zone *zone)
325{
326 unsigned long zone_memory = zone_dirtyable_memory(zone);
327 struct task_struct *tsk = current;
328 unsigned long dirty;
329
330 if (vm_dirty_bytes)
331 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) *
332 zone_memory / global_dirtyable_memory();
333 else
334 dirty = vm_dirty_ratio * zone_memory / 100;
335
336 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk))
337 dirty += dirty / 4;
338
339 return dirty;
340}
341
342/**
343 * zone_dirty_ok - tells whether a zone is within its dirty limits
344 * @zone: the zone to check
345 *
346 * Returns %true when the dirty pages in @zone are within the zone's
347 * dirty limit, %false if the limit is exceeded.
348 */
349bool zone_dirty_ok(struct zone *zone)
350{
351 unsigned long limit = zone_dirty_limit(zone);
352
353 return zone_page_state(zone, NR_FILE_DIRTY) +
354 zone_page_state(zone, NR_UNSTABLE_NFS) +
355 zone_page_state(zone, NR_WRITEBACK) <= limit;
356}
357
David Rientjes2da02992009-01-06 14:39:31 -0800358int dirty_background_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700359 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800360 loff_t *ppos)
361{
362 int ret;
363
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700364 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800365 if (ret == 0 && write)
366 dirty_background_bytes = 0;
367 return ret;
368}
369
370int dirty_background_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700371 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800372 loff_t *ppos)
373{
374 int ret;
375
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700376 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800377 if (ret == 0 && write)
378 dirty_background_ratio = 0;
379 return ret;
380}
381
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700382int dirty_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700383 void __user *buffer, size_t *lenp,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700384 loff_t *ppos)
385{
386 int old_ratio = vm_dirty_ratio;
David Rientjes2da02992009-01-06 14:39:31 -0800387 int ret;
388
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700389 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700390 if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
Jan Karaeb608e32012-05-24 18:59:11 +0200391 writeback_set_ratelimit();
David Rientjes2da02992009-01-06 14:39:31 -0800392 vm_dirty_bytes = 0;
393 }
394 return ret;
395}
396
David Rientjes2da02992009-01-06 14:39:31 -0800397int dirty_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700398 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800399 loff_t *ppos)
400{
Sven Wegenerfc3501d2009-02-11 13:04:23 -0800401 unsigned long old_bytes = vm_dirty_bytes;
David Rientjes2da02992009-01-06 14:39:31 -0800402 int ret;
403
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700404 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800405 if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
Jan Karaeb608e32012-05-24 18:59:11 +0200406 writeback_set_ratelimit();
David Rientjes2da02992009-01-06 14:39:31 -0800407 vm_dirty_ratio = 0;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700408 }
409 return ret;
410}
411
Jan Karaeb608e32012-05-24 18:59:11 +0200412static unsigned long wp_next_time(unsigned long cur_time)
413{
414 cur_time += VM_COMPLETIONS_PERIOD_LEN;
415 /* 0 has a special meaning... */
416 if (!cur_time)
417 return 1;
418 return cur_time;
419}
420
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700421/*
422 * Increment the BDI's writeout completion count and the global writeout
423 * completion count. Called from test_clear_page_writeback().
424 */
425static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
426{
Jan Karaf7d2b1e2010-12-08 22:44:24 -0600427 __inc_bdi_stat(bdi, BDI_WRITTEN);
Jan Karaeb608e32012-05-24 18:59:11 +0200428 __fprop_inc_percpu_max(&writeout_completions, &bdi->completions,
429 bdi->max_prop_frac);
430 /* First event after period switching was turned off? */
431 if (!unlikely(writeout_period_time)) {
432 /*
433 * We can race with other __bdi_writeout_inc calls here but
434 * it does not cause any harm since the resulting time when
435 * timer will fire and what is in writeout_period_time will be
436 * roughly the same.
437 */
438 writeout_period_time = wp_next_time(jiffies);
439 mod_timer(&writeout_period_timer, writeout_period_time);
440 }
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700441}
442
Miklos Szeredidd5656e2008-04-30 00:54:37 -0700443void bdi_writeout_inc(struct backing_dev_info *bdi)
444{
445 unsigned long flags;
446
447 local_irq_save(flags);
448 __bdi_writeout_inc(bdi);
449 local_irq_restore(flags);
450}
451EXPORT_SYMBOL_GPL(bdi_writeout_inc);
452
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700453/*
454 * Obtain an accurate fraction of the BDI's portion.
455 */
456static void bdi_writeout_fraction(struct backing_dev_info *bdi,
457 long *numerator, long *denominator)
458{
Jan Karaeb608e32012-05-24 18:59:11 +0200459 fprop_fraction_percpu(&writeout_completions, &bdi->completions,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700460 numerator, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700461}
462
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700463/*
Jan Karaeb608e32012-05-24 18:59:11 +0200464 * On idle system, we can be called long after we scheduled because we use
465 * deferred timers so count with missed periods.
466 */
467static void writeout_period(unsigned long t)
468{
469 int miss_periods = (jiffies - writeout_period_time) /
470 VM_COMPLETIONS_PERIOD_LEN;
471
472 if (fprop_new_period(&writeout_completions, miss_periods + 1)) {
473 writeout_period_time = wp_next_time(writeout_period_time +
474 miss_periods * VM_COMPLETIONS_PERIOD_LEN);
475 mod_timer(&writeout_period_timer, writeout_period_time);
476 } else {
477 /*
478 * Aging has zeroed all fractions. Stop wasting CPU on period
479 * updates.
480 */
481 writeout_period_time = 0;
482 }
483}
484
485/*
Johannes Weinerd08c4292011-10-31 17:07:05 -0700486 * bdi_min_ratio keeps the sum of the minimum dirty shares of all
487 * registered backing devices, which, for obvious reasons, can not
488 * exceed 100%.
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700489 */
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700490static unsigned int bdi_min_ratio;
491
492int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
493{
494 int ret = 0;
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700495
Jens Axboecfc4ba52009-09-14 13:12:40 +0200496 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700497 if (min_ratio > bdi->max_ratio) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700498 ret = -EINVAL;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700499 } else {
500 min_ratio -= bdi->min_ratio;
501 if (bdi_min_ratio + min_ratio < 100) {
502 bdi_min_ratio += min_ratio;
503 bdi->min_ratio += min_ratio;
504 } else {
505 ret = -EINVAL;
506 }
507 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200508 spin_unlock_bh(&bdi_lock);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700509
510 return ret;
511}
512
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700513int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
514{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700515 int ret = 0;
516
517 if (max_ratio > 100)
518 return -EINVAL;
519
Jens Axboecfc4ba52009-09-14 13:12:40 +0200520 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700521 if (bdi->min_ratio > max_ratio) {
522 ret = -EINVAL;
523 } else {
524 bdi->max_ratio = max_ratio;
Jan Karaeb608e32012-05-24 18:59:11 +0200525 bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700526 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200527 spin_unlock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700528
529 return ret;
530}
531EXPORT_SYMBOL(bdi_set_max_ratio);
532
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600533static unsigned long dirty_freerun_ceiling(unsigned long thresh,
534 unsigned long bg_thresh)
535{
536 return (thresh + bg_thresh) / 2;
537}
538
Wu Fengguangffd1f602011-06-19 22:18:42 -0600539static unsigned long hard_dirty_limit(unsigned long thresh)
540{
541 return max(thresh, global_dirty_limit);
542}
543
Wu Fengguang6f718652011-03-02 17:14:34 -0600544/**
Wu Fengguang1babe182010-08-11 14:17:40 -0700545 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
Wu Fengguang6f718652011-03-02 17:14:34 -0600546 * @bdi: the backing_dev_info to query
547 * @dirty: global dirty limit in pages
Wu Fengguang1babe182010-08-11 14:17:40 -0700548 *
Wu Fengguang6f718652011-03-02 17:14:34 -0600549 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
550 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
Wu Fengguangaed21ad2011-11-23 11:44:41 -0600551 *
552 * Note that balance_dirty_pages() will only seriously take it as a hard limit
553 * when sleeping max_pause per page is not enough to keep the dirty pages under
554 * control. For example, when the device is completely stalled due to some error
555 * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key.
556 * In the other normal situations, it acts more gently by throttling the tasks
557 * more (rather than completely block them) when the bdi dirty pages go high.
Wu Fengguang6f718652011-03-02 17:14:34 -0600558 *
559 * It allocates high/low dirty limits to fast/slow devices, in order to prevent
Wu Fengguang1babe182010-08-11 14:17:40 -0700560 * - starving fast devices
561 * - piling up dirty pages (that will take long time to sync) on slow devices
562 *
563 * The bdi's share of dirty limit will be adapting to its throughput and
564 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
565 */
566unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
Wu Fengguang16c40422010-08-11 14:17:39 -0700567{
568 u64 bdi_dirty;
569 long numerator, denominator;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700570
Wu Fengguang16c40422010-08-11 14:17:39 -0700571 /*
572 * Calculate this BDI's share of the dirty ratio.
573 */
574 bdi_writeout_fraction(bdi, &numerator, &denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700575
Wu Fengguang16c40422010-08-11 14:17:39 -0700576 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
577 bdi_dirty *= numerator;
578 do_div(bdi_dirty, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700579
Wu Fengguang16c40422010-08-11 14:17:39 -0700580 bdi_dirty += (dirty * bdi->min_ratio) / 100;
581 if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
582 bdi_dirty = dirty * bdi->max_ratio / 100;
583
584 return bdi_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585}
586
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600587/*
588 * Dirty position control.
589 *
590 * (o) global/bdi setpoints
591 *
592 * We want the dirty pages be balanced around the global/bdi setpoints.
593 * When the number of dirty pages is higher/lower than the setpoint, the
594 * dirty position control ratio (and hence task dirty ratelimit) will be
595 * decreased/increased to bring the dirty pages back to the setpoint.
596 *
597 * pos_ratio = 1 << RATELIMIT_CALC_SHIFT
598 *
599 * if (dirty < setpoint) scale up pos_ratio
600 * if (dirty > setpoint) scale down pos_ratio
601 *
602 * if (bdi_dirty < bdi_setpoint) scale up pos_ratio
603 * if (bdi_dirty > bdi_setpoint) scale down pos_ratio
604 *
605 * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT
606 *
607 * (o) global control line
608 *
609 * ^ pos_ratio
610 * |
611 * | |<===== global dirty control scope ======>|
612 * 2.0 .............*
613 * | .*
614 * | . *
615 * | . *
616 * | . *
617 * | . *
618 * | . *
619 * 1.0 ................................*
620 * | . . *
621 * | . . *
622 * | . . *
623 * | . . *
624 * | . . *
625 * 0 +------------.------------------.----------------------*------------->
626 * freerun^ setpoint^ limit^ dirty pages
627 *
628 * (o) bdi control line
629 *
630 * ^ pos_ratio
631 * |
632 * | *
633 * | *
634 * | *
635 * | *
636 * | * |<=========== span ============>|
637 * 1.0 .......................*
638 * | . *
639 * | . *
640 * | . *
641 * | . *
642 * | . *
643 * | . *
644 * | . *
645 * | . *
646 * | . *
647 * | . *
648 * | . *
649 * 1/4 ...............................................* * * * * * * * * * * *
650 * | . .
651 * | . .
652 * | . .
653 * 0 +----------------------.-------------------------------.------------->
654 * bdi_setpoint^ x_intercept^
655 *
656 * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can
657 * be smoothly throttled down to normal if it starts high in situations like
658 * - start writing to a slow SD card and a fast disk at the same time. The SD
659 * card's bdi_dirty may rush to many times higher than bdi_setpoint.
660 * - the bdi dirty thresh drops quickly due to change of JBOD workload
661 */
662static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
663 unsigned long thresh,
664 unsigned long bg_thresh,
665 unsigned long dirty,
666 unsigned long bdi_thresh,
667 unsigned long bdi_dirty)
668{
669 unsigned long write_bw = bdi->avg_write_bandwidth;
670 unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
671 unsigned long limit = hard_dirty_limit(thresh);
672 unsigned long x_intercept;
673 unsigned long setpoint; /* dirty pages' target balance point */
674 unsigned long bdi_setpoint;
675 unsigned long span;
676 long long pos_ratio; /* for scaling up/down the rate limit */
677 long x;
678
679 if (unlikely(dirty >= limit))
680 return 0;
681
682 /*
683 * global setpoint
684 *
685 * setpoint - dirty 3
686 * f(dirty) := 1.0 + (----------------)
687 * limit - setpoint
688 *
689 * it's a 3rd order polynomial that subjects to
690 *
691 * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast
692 * (2) f(setpoint) = 1.0 => the balance point
693 * (3) f(limit) = 0 => the hard limit
694 * (4) df/dx <= 0 => negative feedback control
695 * (5) the closer to setpoint, the smaller |df/dx| (and the reverse)
696 * => fast response on large errors; small oscillation near setpoint
697 */
698 setpoint = (freerun + limit) / 2;
paul.szabo@sydney.edu.aued84825b2013-01-20 11:02:10 +1100699 x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT,
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600700 limit - setpoint + 1);
701 pos_ratio = x;
702 pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
703 pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
704 pos_ratio += 1 << RATELIMIT_CALC_SHIFT;
705
706 /*
707 * We have computed basic pos_ratio above based on global situation. If
708 * the bdi is over/under its share of dirty pages, we want to scale
709 * pos_ratio further down/up. That is done by the following mechanism.
710 */
711
712 /*
713 * bdi setpoint
714 *
715 * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint)
716 *
717 * x_intercept - bdi_dirty
718 * := --------------------------
719 * x_intercept - bdi_setpoint
720 *
721 * The main bdi control line is a linear function that subjects to
722 *
723 * (1) f(bdi_setpoint) = 1.0
724 * (2) k = - 1 / (8 * write_bw) (in single bdi case)
725 * or equally: x_intercept = bdi_setpoint + 8 * write_bw
726 *
727 * For single bdi case, the dirty pages are observed to fluctuate
728 * regularly within range
729 * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2]
730 * for various filesystems, where (2) can yield in a reasonable 12.5%
731 * fluctuation range for pos_ratio.
732 *
733 * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its
734 * own size, so move the slope over accordingly and choose a slope that
735 * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh.
736 */
737 if (unlikely(bdi_thresh > thresh))
738 bdi_thresh = thresh;
Wu Fengguangaed21ad2011-11-23 11:44:41 -0600739 /*
740 * It's very possible that bdi_thresh is close to 0 not because the
741 * device is slow, but that it has remained inactive for long time.
742 * Honour such devices a reasonable good (hopefully IO efficient)
743 * threshold, so that the occasional writes won't be blocked and active
744 * writes can rampup the threshold quickly.
745 */
Wu Fengguang8927f662011-08-04 22:16:46 -0600746 bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600747 /*
748 * scale global setpoint to bdi's:
749 * bdi_setpoint = setpoint * bdi_thresh / thresh
750 */
751 x = div_u64((u64)bdi_thresh << 16, thresh + 1);
752 bdi_setpoint = setpoint * (u64)x >> 16;
753 /*
754 * Use span=(8*write_bw) in single bdi case as indicated by
755 * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case.
756 *
757 * bdi_thresh thresh - bdi_thresh
758 * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh
759 * thresh thresh
760 */
761 span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16;
762 x_intercept = bdi_setpoint + span;
763
764 if (bdi_dirty < x_intercept - span / 4) {
Wu Fengguang50657fc2011-10-11 17:06:33 -0600765 pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty),
766 x_intercept - bdi_setpoint + 1);
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600767 } else
768 pos_ratio /= 4;
769
Wu Fengguang8927f662011-08-04 22:16:46 -0600770 /*
771 * bdi reserve area, safeguard against dirty pool underrun and disk idle
772 * It may push the desired control point of global dirty pages higher
773 * than setpoint.
774 */
775 x_intercept = bdi_thresh / 2;
776 if (bdi_dirty < x_intercept) {
Wu Fengguang50657fc2011-10-11 17:06:33 -0600777 if (bdi_dirty > x_intercept / 8)
778 pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
779 else
Wu Fengguang8927f662011-08-04 22:16:46 -0600780 pos_ratio *= 8;
781 }
782
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600783 return pos_ratio;
784}
785
Wu Fengguange98be2d2010-08-29 11:22:30 -0600786static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
787 unsigned long elapsed,
788 unsigned long written)
789{
790 const unsigned long period = roundup_pow_of_two(3 * HZ);
791 unsigned long avg = bdi->avg_write_bandwidth;
792 unsigned long old = bdi->write_bandwidth;
793 u64 bw;
794
795 /*
796 * bw = written * HZ / elapsed
797 *
798 * bw * elapsed + write_bandwidth * (period - elapsed)
799 * write_bandwidth = ---------------------------------------------------
800 * period
801 */
802 bw = written - bdi->written_stamp;
803 bw *= HZ;
804 if (unlikely(elapsed > period)) {
805 do_div(bw, elapsed);
806 avg = bw;
807 goto out;
808 }
809 bw += (u64)bdi->write_bandwidth * (period - elapsed);
810 bw >>= ilog2(period);
811
812 /*
813 * one more level of smoothing, for filtering out sudden spikes
814 */
815 if (avg > old && old >= (unsigned long)bw)
816 avg -= (avg - old) >> 3;
817
818 if (avg < old && old <= (unsigned long)bw)
819 avg += (old - avg) >> 3;
820
821out:
822 bdi->write_bandwidth = bw;
823 bdi->avg_write_bandwidth = avg;
824}
825
Wu Fengguangc42843f2011-03-02 15:54:09 -0600826/*
827 * The global dirtyable memory and dirty threshold could be suddenly knocked
828 * down by a large amount (eg. on the startup of KVM in a swapless system).
829 * This may throw the system into deep dirty exceeded state and throttle
830 * heavy/light dirtiers alike. To retain good responsiveness, maintain
831 * global_dirty_limit for tracking slowly down to the knocked down dirty
832 * threshold.
833 */
834static void update_dirty_limit(unsigned long thresh, unsigned long dirty)
835{
836 unsigned long limit = global_dirty_limit;
837
838 /*
839 * Follow up in one step.
840 */
841 if (limit < thresh) {
842 limit = thresh;
843 goto update;
844 }
845
846 /*
847 * Follow down slowly. Use the higher one as the target, because thresh
848 * may drop below dirty. This is exactly the reason to introduce
849 * global_dirty_limit which is guaranteed to lie above the dirty pages.
850 */
851 thresh = max(thresh, dirty);
852 if (limit > thresh) {
853 limit -= (limit - thresh) >> 5;
854 goto update;
855 }
856 return;
857update:
858 global_dirty_limit = limit;
859}
860
861static void global_update_bandwidth(unsigned long thresh,
862 unsigned long dirty,
863 unsigned long now)
864{
865 static DEFINE_SPINLOCK(dirty_lock);
866 static unsigned long update_time;
867
868 /*
869 * check locklessly first to optimize away locking for the most time
870 */
871 if (time_before(now, update_time + BANDWIDTH_INTERVAL))
872 return;
873
874 spin_lock(&dirty_lock);
875 if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) {
876 update_dirty_limit(thresh, dirty);
877 update_time = now;
878 }
879 spin_unlock(&dirty_lock);
880}
881
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600882/*
883 * Maintain bdi->dirty_ratelimit, the base dirty throttle rate.
884 *
885 * Normal bdi tasks will be curbed at or below it in long term.
886 * Obviously it should be around (write_bw / N) when there are N dd tasks.
887 */
888static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
889 unsigned long thresh,
890 unsigned long bg_thresh,
891 unsigned long dirty,
892 unsigned long bdi_thresh,
893 unsigned long bdi_dirty,
894 unsigned long dirtied,
895 unsigned long elapsed)
896{
Wu Fengguang73811312011-08-26 15:53:24 -0600897 unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
898 unsigned long limit = hard_dirty_limit(thresh);
899 unsigned long setpoint = (freerun + limit) / 2;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600900 unsigned long write_bw = bdi->avg_write_bandwidth;
901 unsigned long dirty_ratelimit = bdi->dirty_ratelimit;
902 unsigned long dirty_rate;
903 unsigned long task_ratelimit;
904 unsigned long balanced_dirty_ratelimit;
905 unsigned long pos_ratio;
Wu Fengguang73811312011-08-26 15:53:24 -0600906 unsigned long step;
907 unsigned long x;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600908
909 /*
910 * The dirty rate will match the writeout rate in long term, except
911 * when dirty pages are truncated by userspace or re-dirtied by FS.
912 */
913 dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed;
914
915 pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty,
916 bdi_thresh, bdi_dirty);
917 /*
918 * task_ratelimit reflects each dd's dirty rate for the past 200ms.
919 */
920 task_ratelimit = (u64)dirty_ratelimit *
921 pos_ratio >> RATELIMIT_CALC_SHIFT;
922 task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */
923
924 /*
925 * A linear estimation of the "balanced" throttle rate. The theory is,
926 * if there are N dd tasks, each throttled at task_ratelimit, the bdi's
927 * dirty_rate will be measured to be (N * task_ratelimit). So the below
928 * formula will yield the balanced rate limit (write_bw / N).
929 *
930 * Note that the expanded form is not a pure rate feedback:
931 * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1)
932 * but also takes pos_ratio into account:
933 * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2)
934 *
935 * (1) is not realistic because pos_ratio also takes part in balancing
936 * the dirty rate. Consider the state
937 * pos_ratio = 0.5 (3)
938 * rate = 2 * (write_bw / N) (4)
939 * If (1) is used, it will stuck in that state! Because each dd will
940 * be throttled at
941 * task_ratelimit = pos_ratio * rate = (write_bw / N) (5)
942 * yielding
943 * dirty_rate = N * task_ratelimit = write_bw (6)
944 * put (6) into (1) we get
945 * rate_(i+1) = rate_(i) (7)
946 *
947 * So we end up using (2) to always keep
948 * rate_(i+1) ~= (write_bw / N) (8)
949 * regardless of the value of pos_ratio. As long as (8) is satisfied,
950 * pos_ratio is able to drive itself to 1.0, which is not only where
951 * the dirty count meet the setpoint, but also where the slope of
952 * pos_ratio is most flat and hence task_ratelimit is least fluctuated.
953 */
954 balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw,
955 dirty_rate | 1);
Wu Fengguangbdaac492011-08-03 14:30:36 -0600956 /*
957 * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw
958 */
959 if (unlikely(balanced_dirty_ratelimit > write_bw))
960 balanced_dirty_ratelimit = write_bw;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600961
Wu Fengguang73811312011-08-26 15:53:24 -0600962 /*
963 * We could safely do this and return immediately:
964 *
965 * bdi->dirty_ratelimit = balanced_dirty_ratelimit;
966 *
967 * However to get a more stable dirty_ratelimit, the below elaborated
Wanpeng Li331cbde2012-06-09 11:10:55 +0800968 * code makes use of task_ratelimit to filter out singular points and
Wu Fengguang73811312011-08-26 15:53:24 -0600969 * limit the step size.
970 *
971 * The below code essentially only uses the relative value of
972 *
973 * task_ratelimit - dirty_ratelimit
974 * = (pos_ratio - 1) * dirty_ratelimit
975 *
976 * which reflects the direction and size of dirty position error.
977 */
978
979 /*
980 * dirty_ratelimit will follow balanced_dirty_ratelimit iff
981 * task_ratelimit is on the same side of dirty_ratelimit, too.
982 * For example, when
983 * - dirty_ratelimit > balanced_dirty_ratelimit
984 * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint)
985 * lowering dirty_ratelimit will help meet both the position and rate
986 * control targets. Otherwise, don't update dirty_ratelimit if it will
987 * only help meet the rate target. After all, what the users ultimately
988 * feel and care are stable dirty rate and small position error.
989 *
990 * |task_ratelimit - dirty_ratelimit| is used to limit the step size
Wanpeng Li331cbde2012-06-09 11:10:55 +0800991 * and filter out the singular points of balanced_dirty_ratelimit. Which
Wu Fengguang73811312011-08-26 15:53:24 -0600992 * keeps jumping around randomly and can even leap far away at times
993 * due to the small 200ms estimation period of dirty_rate (we want to
994 * keep that period small to reduce time lags).
995 */
996 step = 0;
997 if (dirty < setpoint) {
998 x = min(bdi->balanced_dirty_ratelimit,
999 min(balanced_dirty_ratelimit, task_ratelimit));
1000 if (dirty_ratelimit < x)
1001 step = x - dirty_ratelimit;
1002 } else {
1003 x = max(bdi->balanced_dirty_ratelimit,
1004 max(balanced_dirty_ratelimit, task_ratelimit));
1005 if (dirty_ratelimit > x)
1006 step = dirty_ratelimit - x;
1007 }
1008
1009 /*
1010 * Don't pursue 100% rate matching. It's impossible since the balanced
1011 * rate itself is constantly fluctuating. So decrease the track speed
1012 * when it gets close to the target. Helps eliminate pointless tremors.
1013 */
1014 step >>= dirty_ratelimit / (2 * step + 1);
1015 /*
1016 * Limit the tracking speed to avoid overshooting.
1017 */
1018 step = (step + 7) / 8;
1019
1020 if (dirty_ratelimit < balanced_dirty_ratelimit)
1021 dirty_ratelimit += step;
1022 else
1023 dirty_ratelimit -= step;
1024
1025 bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
1026 bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
Wu Fengguangb48c1042011-03-02 17:22:49 -06001027
1028 trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001029}
1030
Wu Fengguange98be2d2010-08-29 11:22:30 -06001031void __bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001032 unsigned long thresh,
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001033 unsigned long bg_thresh,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001034 unsigned long dirty,
1035 unsigned long bdi_thresh,
1036 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -06001037 unsigned long start_time)
1038{
1039 unsigned long now = jiffies;
1040 unsigned long elapsed = now - bdi->bw_time_stamp;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001041 unsigned long dirtied;
Wu Fengguange98be2d2010-08-29 11:22:30 -06001042 unsigned long written;
1043
1044 /*
1045 * rate-limit, only update once every 200ms.
1046 */
1047 if (elapsed < BANDWIDTH_INTERVAL)
1048 return;
1049
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001050 dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]);
Wu Fengguange98be2d2010-08-29 11:22:30 -06001051 written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
1052
1053 /*
1054 * Skip quiet periods when disk bandwidth is under-utilized.
1055 * (at least 1s idle time between two flusher runs)
1056 */
1057 if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
1058 goto snapshot;
1059
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001060 if (thresh) {
Wu Fengguangc42843f2011-03-02 15:54:09 -06001061 global_update_bandwidth(thresh, dirty, now);
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001062 bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty,
1063 bdi_thresh, bdi_dirty,
1064 dirtied, elapsed);
1065 }
Wu Fengguange98be2d2010-08-29 11:22:30 -06001066 bdi_update_write_bandwidth(bdi, elapsed, written);
1067
1068snapshot:
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001069 bdi->dirtied_stamp = dirtied;
Wu Fengguange98be2d2010-08-29 11:22:30 -06001070 bdi->written_stamp = written;
1071 bdi->bw_time_stamp = now;
1072}
1073
1074static void bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001075 unsigned long thresh,
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001076 unsigned long bg_thresh,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001077 unsigned long dirty,
1078 unsigned long bdi_thresh,
1079 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -06001080 unsigned long start_time)
1081{
1082 if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
1083 return;
1084 spin_lock(&bdi->wb.list_lock);
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001085 __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty,
1086 bdi_thresh, bdi_dirty, start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -06001087 spin_unlock(&bdi->wb.list_lock);
1088}
1089
Linus Torvalds1da177e2005-04-16 15:20:36 -07001090/*
Namjae Jeond0e1d662012-12-11 16:00:21 -08001091 * After a task dirtied this many pages, balance_dirty_pages_ratelimited()
Wu Fengguang9d823e82011-06-11 18:10:12 -06001092 * will look to see if it needs to start dirty throttling.
1093 *
1094 * If dirty_poll_interval is too low, big NUMA machines will call the expensive
1095 * global_page_state() too often. So scale it near-sqrt to the safety margin
1096 * (the number of pages we may dirty without exceeding the dirty limits).
1097 */
1098static unsigned long dirty_poll_interval(unsigned long dirty,
1099 unsigned long thresh)
1100{
1101 if (thresh > dirty)
1102 return 1UL << (ilog2(thresh - dirty) >> 1);
1103
1104 return 1;
1105}
1106
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001107static long bdi_max_pause(struct backing_dev_info *bdi,
1108 unsigned long bdi_dirty)
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001109{
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001110 long bw = bdi->avg_write_bandwidth;
1111 long t;
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001112
1113 /*
1114 * Limit pause time for small memory systems. If sleeping for too long
1115 * time, a small pool of dirty/writeback pages may go empty and disk go
1116 * idle.
1117 *
1118 * 8 serves as the safety ratio.
1119 */
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001120 t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
1121 t++;
1122
1123 return min_t(long, t, MAX_PAUSE);
1124}
1125
1126static long bdi_min_pause(struct backing_dev_info *bdi,
1127 long max_pause,
1128 unsigned long task_ratelimit,
1129 unsigned long dirty_ratelimit,
1130 int *nr_dirtied_pause)
1131{
1132 long hi = ilog2(bdi->avg_write_bandwidth);
1133 long lo = ilog2(bdi->dirty_ratelimit);
1134 long t; /* target pause */
1135 long pause; /* estimated next pause */
1136 int pages; /* target nr_dirtied_pause */
1137
1138 /* target for 10ms pause on 1-dd case */
1139 t = max(1, HZ / 100);
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001140
1141 /*
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001142 * Scale up pause time for concurrent dirtiers in order to reduce CPU
1143 * overheads.
1144 *
1145 * (N * 10ms) on 2^N concurrent tasks.
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001146 */
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001147 if (hi > lo)
1148 t += (hi - lo) * (10 * HZ) / 1024;
1149
1150 /*
1151 * This is a bit convoluted. We try to base the next nr_dirtied_pause
1152 * on the much more stable dirty_ratelimit. However the next pause time
1153 * will be computed based on task_ratelimit and the two rate limits may
1154 * depart considerably at some time. Especially if task_ratelimit goes
1155 * below dirty_ratelimit/2 and the target pause is max_pause, the next
1156 * pause time will be max_pause*2 _trimmed down_ to max_pause. As a
1157 * result task_ratelimit won't be executed faithfully, which could
1158 * eventually bring down dirty_ratelimit.
1159 *
1160 * We apply two rules to fix it up:
1161 * 1) try to estimate the next pause time and if necessary, use a lower
1162 * nr_dirtied_pause so as not to exceed max_pause. When this happens,
1163 * nr_dirtied_pause will be "dancing" with task_ratelimit.
1164 * 2) limit the target pause time to max_pause/2, so that the normal
1165 * small fluctuations of task_ratelimit won't trigger rule (1) and
1166 * nr_dirtied_pause will remain as stable as dirty_ratelimit.
1167 */
1168 t = min(t, 1 + max_pause / 2);
1169 pages = dirty_ratelimit * t / roundup_pow_of_two(HZ);
1170
Wu Fengguang5b9b3572011-12-06 13:17:17 -06001171 /*
1172 * Tiny nr_dirtied_pause is found to hurt I/O performance in the test
1173 * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}.
1174 * When the 16 consecutive reads are often interrupted by some dirty
1175 * throttling pause during the async writes, cfq will go into idles
1176 * (deadline is fine). So push nr_dirtied_pause as high as possible
1177 * until reaches DIRTY_POLL_THRESH=32 pages.
1178 */
1179 if (pages < DIRTY_POLL_THRESH) {
1180 t = max_pause;
1181 pages = dirty_ratelimit * t / roundup_pow_of_two(HZ);
1182 if (pages > DIRTY_POLL_THRESH) {
1183 pages = DIRTY_POLL_THRESH;
1184 t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit;
1185 }
1186 }
1187
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001188 pause = HZ * pages / (task_ratelimit + 1);
1189 if (pause > max_pause) {
1190 t = max_pause;
1191 pages = task_ratelimit * t / roundup_pow_of_two(HZ);
1192 }
1193
1194 *nr_dirtied_pause = pages;
1195 /*
1196 * The minimal pause time will normally be half the target pause time.
1197 */
Wu Fengguang5b9b3572011-12-06 13:17:17 -06001198 return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t;
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001199}
1200
Wu Fengguang9d823e82011-06-11 18:10:12 -06001201/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202 * balance_dirty_pages() must be called by processes which are generating dirty
1203 * data. It looks at the number of dirty pages in the machine and will force
Wu Fengguang143dfe82010-08-27 18:45:12 -06001204 * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2.
Jens Axboe5b0830c2009-09-23 19:37:09 +02001205 * If we're over `background_thresh' then the writeback threads are woken to
1206 * perform some writeout.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001207 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +08001208static void balance_dirty_pages(struct address_space *mapping,
Wu Fengguang143dfe82010-08-27 18:45:12 -06001209 unsigned long pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210{
Wu Fengguang143dfe82010-08-27 18:45:12 -06001211 unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
1212 unsigned long bdi_reclaimable;
Wu Fengguang77627412010-09-12 13:34:05 -06001213 unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
1214 unsigned long bdi_dirty;
Wu Fengguang6c14ae12011-03-02 16:04:18 -06001215 unsigned long freerun;
David Rientjes364aeb22009-01-06 14:39:29 -08001216 unsigned long background_thresh;
1217 unsigned long dirty_thresh;
1218 unsigned long bdi_thresh;
Wu Fengguang83712352011-06-11 19:25:42 -06001219 long period;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001220 long pause;
1221 long max_pause;
1222 long min_pause;
1223 int nr_dirtied_pause;
Wu Fengguange50e3722010-08-11 14:17:37 -07001224 bool dirty_exceeded = false;
Wu Fengguang143dfe82010-08-27 18:45:12 -06001225 unsigned long task_ratelimit;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001226 unsigned long dirty_ratelimit;
Wu Fengguang143dfe82010-08-27 18:45:12 -06001227 unsigned long pos_ratio;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001228 struct backing_dev_info *bdi = mapping->backing_dev_info;
Wu Fengguange98be2d2010-08-29 11:22:30 -06001229 unsigned long start_time = jiffies;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230
1231 for (;;) {
Wu Fengguang83712352011-06-11 19:25:42 -06001232 unsigned long now = jiffies;
1233
Wu Fengguang143dfe82010-08-27 18:45:12 -06001234 /*
1235 * Unstable writes are a feature of certain networked
1236 * filesystems (i.e. NFS) in which data may have been
1237 * written to the server's write cache, but has not yet
1238 * been flushed to permanent storage.
1239 */
Peter Zijlstra5fce25a2007-11-14 16:59:15 -08001240 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
1241 global_page_state(NR_UNSTABLE_NFS);
Wu Fengguang77627412010-09-12 13:34:05 -06001242 nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
Peter Zijlstra5fce25a2007-11-14 16:59:15 -08001243
Wu Fengguang16c40422010-08-11 14:17:39 -07001244 global_dirty_limits(&background_thresh, &dirty_thresh);
1245
1246 /*
1247 * Throttle it only when the background writeback cannot
1248 * catch-up. This avoids (excessively) small writeouts
1249 * when the bdi limits are ramping up.
1250 */
Wu Fengguang6c14ae12011-03-02 16:04:18 -06001251 freerun = dirty_freerun_ceiling(dirty_thresh,
1252 background_thresh);
Wu Fengguang83712352011-06-11 19:25:42 -06001253 if (nr_dirty <= freerun) {
1254 current->dirty_paused_when = now;
1255 current->nr_dirtied = 0;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001256 current->nr_dirtied_pause =
1257 dirty_poll_interval(nr_dirty, dirty_thresh);
Wu Fengguang16c40422010-08-11 14:17:39 -07001258 break;
Wu Fengguang83712352011-06-11 19:25:42 -06001259 }
Wu Fengguang16c40422010-08-11 14:17:39 -07001260
Wu Fengguang143dfe82010-08-27 18:45:12 -06001261 if (unlikely(!writeback_in_progress(bdi)))
1262 bdi_start_background_writeback(bdi);
1263
1264 /*
1265 * bdi_thresh is not treated as some limiting factor as
1266 * dirty_thresh, due to reasons
1267 * - in JBOD setup, bdi_thresh can fluctuate a lot
1268 * - in a system with HDD and USB key, the USB key may somehow
1269 * go into state (bdi_dirty >> bdi_thresh) either because
1270 * bdi_dirty starts high, or because bdi_thresh drops low.
1271 * In this case we don't want to hard throttle the USB key
1272 * dirtiers for 100 seconds until bdi_dirty drops under
1273 * bdi_thresh. Instead the auxiliary bdi control line in
1274 * bdi_position_ratio() will let the dirtier task progress
1275 * at some rate <= (write_bw / 2) for bringing down bdi_dirty.
1276 */
Wu Fengguang16c40422010-08-11 14:17:39 -07001277 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
Wu Fengguang16c40422010-08-11 14:17:39 -07001278
Wu Fengguange50e3722010-08-11 14:17:37 -07001279 /*
1280 * In order to avoid the stacked BDI deadlock we need
1281 * to ensure we accurately count the 'dirty' pages when
1282 * the threshold is low.
1283 *
1284 * Otherwise it would be possible to get thresh+n pages
1285 * reported dirty, even though there are thresh-m pages
1286 * actually dirty; with m+n sitting in the percpu
1287 * deltas.
1288 */
Wu Fengguang143dfe82010-08-27 18:45:12 -06001289 if (bdi_thresh < 2 * bdi_stat_error(bdi)) {
1290 bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
1291 bdi_dirty = bdi_reclaimable +
Wu Fengguang77627412010-09-12 13:34:05 -06001292 bdi_stat_sum(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -07001293 } else {
Wu Fengguang143dfe82010-08-27 18:45:12 -06001294 bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
1295 bdi_dirty = bdi_reclaimable +
Wu Fengguang77627412010-09-12 13:34:05 -06001296 bdi_stat(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -07001297 }
Peter Zijlstra5fce25a2007-11-14 16:59:15 -08001298
Wu Fengguang82791942011-12-03 21:26:01 -06001299 dirty_exceeded = (bdi_dirty > bdi_thresh) &&
Wu Fengguang77627412010-09-12 13:34:05 -06001300 (nr_dirty > dirty_thresh);
Wu Fengguang143dfe82010-08-27 18:45:12 -06001301 if (dirty_exceeded && !bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001302 bdi->dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001304 bdi_update_bandwidth(bdi, dirty_thresh, background_thresh,
1305 nr_dirty, bdi_thresh, bdi_dirty,
1306 start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -06001307
Wu Fengguang143dfe82010-08-27 18:45:12 -06001308 dirty_ratelimit = bdi->dirty_ratelimit;
1309 pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
1310 background_thresh, nr_dirty,
1311 bdi_thresh, bdi_dirty);
Wu Fengguang3a73dbb2011-11-07 19:19:28 +08001312 task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >>
1313 RATELIMIT_CALC_SHIFT;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001314 max_pause = bdi_max_pause(bdi, bdi_dirty);
1315 min_pause = bdi_min_pause(bdi, max_pause,
1316 task_ratelimit, dirty_ratelimit,
1317 &nr_dirtied_pause);
1318
Wu Fengguang3a73dbb2011-11-07 19:19:28 +08001319 if (unlikely(task_ratelimit == 0)) {
Wu Fengguang83712352011-06-11 19:25:42 -06001320 period = max_pause;
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001321 pause = max_pause;
Wu Fengguang143dfe82010-08-27 18:45:12 -06001322 goto pause;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 }
Wu Fengguang83712352011-06-11 19:25:42 -06001324 period = HZ * pages_dirtied / task_ratelimit;
1325 pause = period;
1326 if (current->dirty_paused_when)
1327 pause -= now - current->dirty_paused_when;
1328 /*
1329 * For less than 1s think time (ext3/4 may block the dirtier
1330 * for up to 800ms from time to time on 1-HDD; so does xfs,
1331 * however at much less frequency), try to compensate it in
1332 * future periods by updating the virtual time; otherwise just
1333 * do a reset, as it may be a light dirtier.
1334 */
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001335 if (pause < min_pause) {
Wu Fengguangece13ac2010-08-29 23:33:20 -06001336 trace_balance_dirty_pages(bdi,
1337 dirty_thresh,
1338 background_thresh,
1339 nr_dirty,
1340 bdi_thresh,
1341 bdi_dirty,
1342 dirty_ratelimit,
1343 task_ratelimit,
1344 pages_dirtied,
Wu Fengguang83712352011-06-11 19:25:42 -06001345 period,
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001346 min(pause, 0L),
Wu Fengguangece13ac2010-08-29 23:33:20 -06001347 start_time);
Wu Fengguang83712352011-06-11 19:25:42 -06001348 if (pause < -HZ) {
1349 current->dirty_paused_when = now;
1350 current->nr_dirtied = 0;
1351 } else if (period) {
1352 current->dirty_paused_when += period;
1353 current->nr_dirtied = 0;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001354 } else if (current->nr_dirtied_pause <= pages_dirtied)
1355 current->nr_dirtied_pause += pages_dirtied;
Wu Fengguang57fc9782011-06-11 19:32:32 -06001356 break;
1357 }
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001358 if (unlikely(pause > max_pause)) {
1359 /* for occasional dropped task_ratelimit */
1360 now += min(pause - max_pause, max_pause);
1361 pause = max_pause;
1362 }
Wu Fengguang143dfe82010-08-27 18:45:12 -06001363
1364pause:
Wu Fengguangece13ac2010-08-29 23:33:20 -06001365 trace_balance_dirty_pages(bdi,
1366 dirty_thresh,
1367 background_thresh,
1368 nr_dirty,
1369 bdi_thresh,
1370 bdi_dirty,
1371 dirty_ratelimit,
1372 task_ratelimit,
1373 pages_dirtied,
Wu Fengguang83712352011-06-11 19:25:42 -06001374 period,
Wu Fengguangece13ac2010-08-29 23:33:20 -06001375 pause,
1376 start_time);
Jan Kara499d05e2011-11-16 19:34:48 +08001377 __set_current_state(TASK_KILLABLE);
Wu Fengguangd25105e2009-10-09 12:40:42 +02001378 io_schedule_timeout(pause);
Jens Axboe87c6a9b2009-09-17 19:59:14 +02001379
Wu Fengguang83712352011-06-11 19:25:42 -06001380 current->dirty_paused_when = now + pause;
1381 current->nr_dirtied = 0;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001382 current->nr_dirtied_pause = nr_dirtied_pause;
Wu Fengguang83712352011-06-11 19:25:42 -06001383
Wu Fengguangffd1f602011-06-19 22:18:42 -06001384 /*
Wu Fengguang1df64712011-11-13 19:47:32 -06001385 * This is typically equal to (nr_dirty < dirty_thresh) and can
1386 * also keep "1000+ dd on a slow USB stick" under control.
Wu Fengguangffd1f602011-06-19 22:18:42 -06001387 */
Wu Fengguang1df64712011-11-13 19:47:32 -06001388 if (task_ratelimit)
Wu Fengguangffd1f602011-06-19 22:18:42 -06001389 break;
Jan Kara499d05e2011-11-16 19:34:48 +08001390
Wu Fengguangc5c63432011-12-02 10:21:33 -06001391 /*
1392 * In the case of an unresponding NFS server and the NFS dirty
1393 * pages exceeds dirty_thresh, give the other good bdi's a pipe
1394 * to go through, so that tasks on them still remain responsive.
1395 *
1396 * In theory 1 page is enough to keep the comsumer-producer
1397 * pipe going: the flusher cleans 1 page => the task dirties 1
1398 * more page. However bdi_dirty has accounting errors. So use
1399 * the larger and more IO friendly bdi_stat_error.
1400 */
1401 if (bdi_dirty <= bdi_stat_error(bdi))
1402 break;
1403
Jan Kara499d05e2011-11-16 19:34:48 +08001404 if (fatal_signal_pending(current))
1405 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001406 }
1407
Wu Fengguang143dfe82010-08-27 18:45:12 -06001408 if (!dirty_exceeded && bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001409 bdi->dirty_exceeded = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001410
1411 if (writeback_in_progress(bdi))
Jens Axboe5b0830c2009-09-23 19:37:09 +02001412 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413
1414 /*
1415 * In laptop mode, we wait until hitting the higher threshold before
1416 * starting background writeout, and then write out all the way down
1417 * to the lower threshold. So slow writers cause minimal disk activity.
1418 *
1419 * In normal mode, we start background writeout at the lower
1420 * background_thresh, to keep the amount of dirty memory low.
1421 */
Wu Fengguang143dfe82010-08-27 18:45:12 -06001422 if (laptop_mode)
1423 return;
1424
1425 if (nr_reclaimable > background_thresh)
Christoph Hellwigc5444192010-06-08 18:15:15 +02001426 bdi_start_background_writeback(bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001427}
1428
Peter Zijlstraa200ee12007-10-08 18:54:37 +02001429void set_page_dirty_balance(struct page *page, int page_mkwrite)
Peter Zijlstraedc79b22006-09-25 23:30:58 -07001430{
Peter Zijlstraa200ee12007-10-08 18:54:37 +02001431 if (set_page_dirty(page) || page_mkwrite) {
Peter Zijlstraedc79b22006-09-25 23:30:58 -07001432 struct address_space *mapping = page_mapping(page);
1433
1434 if (mapping)
1435 balance_dirty_pages_ratelimited(mapping);
1436 }
1437}
1438
Wu Fengguang9d823e82011-06-11 18:10:12 -06001439static DEFINE_PER_CPU(int, bdp_ratelimits);
Tejun Heo245b2e72009-06-24 15:13:48 +09001440
Wu Fengguang54848d72011-04-05 13:21:19 -06001441/*
1442 * Normal tasks are throttled by
1443 * loop {
1444 * dirty tsk->nr_dirtied_pause pages;
1445 * take a snap in balance_dirty_pages();
1446 * }
1447 * However there is a worst case. If every task exit immediately when dirtied
1448 * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be
1449 * called to throttle the page dirties. The solution is to save the not yet
1450 * throttled page dirties in dirty_throttle_leaks on task exit and charge them
1451 * randomly into the running tasks. This works well for the above worst case,
1452 * as the new task will pick up and accumulate the old task's leaked dirty
1453 * count and eventually get throttled.
1454 */
1455DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
1456
Linus Torvalds1da177e2005-04-16 15:20:36 -07001457/**
Namjae Jeond0e1d662012-12-11 16:00:21 -08001458 * balance_dirty_pages_ratelimited - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -07001459 * @mapping: address_space which was dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460 *
1461 * Processes which are dirtying memory should call in here once for each page
1462 * which was newly dirtied. The function will periodically check the system's
1463 * dirty state and will initiate writeback if needed.
1464 *
1465 * On really big machines, get_writeback_state is expensive, so try to avoid
1466 * calling it too often (ratelimiting). But once we're over the dirty memory
1467 * limit we decrease the ratelimiting by a lot, to prevent individual processes
1468 * from overshooting the limit by (ratelimit_pages) each.
1469 */
Namjae Jeond0e1d662012-12-11 16:00:21 -08001470void balance_dirty_pages_ratelimited(struct address_space *mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471{
Wu Fengguang36715ce2011-06-11 17:53:57 -06001472 struct backing_dev_info *bdi = mapping->backing_dev_info;
Wu Fengguang9d823e82011-06-11 18:10:12 -06001473 int ratelimit;
1474 int *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475
Wu Fengguang36715ce2011-06-11 17:53:57 -06001476 if (!bdi_cap_account_dirty(bdi))
1477 return;
1478
Wu Fengguang9d823e82011-06-11 18:10:12 -06001479 ratelimit = current->nr_dirtied_pause;
1480 if (bdi->dirty_exceeded)
1481 ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001482
Andrew Mortonfa5a7342006-03-24 03:18:10 -08001483 preempt_disable();
Wu Fengguang9d823e82011-06-11 18:10:12 -06001484 /*
1485 * This prevents one CPU to accumulate too many dirtied pages without
1486 * calling into balance_dirty_pages(), which can happen when there are
1487 * 1000+ tasks, all of them start dirtying pages at exactly the same
1488 * time, hence all honoured too large initial task->nr_dirtied_pause.
1489 */
Tejun Heo245b2e72009-06-24 15:13:48 +09001490 p = &__get_cpu_var(bdp_ratelimits);
Wu Fengguang9d823e82011-06-11 18:10:12 -06001491 if (unlikely(current->nr_dirtied >= ratelimit))
Andrew Mortonfa5a7342006-03-24 03:18:10 -08001492 *p = 0;
Wu Fengguangd3bc1fe2011-04-14 07:52:37 -06001493 else if (unlikely(*p >= ratelimit_pages)) {
1494 *p = 0;
1495 ratelimit = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496 }
Wu Fengguang54848d72011-04-05 13:21:19 -06001497 /*
1498 * Pick up the dirtied pages by the exited tasks. This avoids lots of
1499 * short-lived tasks (eg. gcc invocations in a kernel build) escaping
1500 * the dirty throttling and livelock other long-run dirtiers.
1501 */
1502 p = &__get_cpu_var(dirty_throttle_leaks);
1503 if (*p > 0 && current->nr_dirtied < ratelimit) {
Namjae Jeond0e1d662012-12-11 16:00:21 -08001504 unsigned long nr_pages_dirtied;
Wu Fengguang54848d72011-04-05 13:21:19 -06001505 nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied);
1506 *p -= nr_pages_dirtied;
1507 current->nr_dirtied += nr_pages_dirtied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -08001509 preempt_enable();
Wu Fengguang9d823e82011-06-11 18:10:12 -06001510
1511 if (unlikely(current->nr_dirtied >= ratelimit))
1512 balance_dirty_pages(mapping, current->nr_dirtied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001513}
Namjae Jeond0e1d662012-12-11 16:00:21 -08001514EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515
Andrew Morton232ea4d2007-02-28 20:13:21 -08001516void throttle_vm_writeout(gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517{
David Rientjes364aeb22009-01-06 14:39:29 -08001518 unsigned long background_thresh;
1519 unsigned long dirty_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520
1521 for ( ; ; ) {
Wu Fengguang16c40422010-08-11 14:17:39 -07001522 global_dirty_limits(&background_thresh, &dirty_thresh);
Fengguang Wu47a13332012-03-21 16:34:09 -07001523 dirty_thresh = hard_dirty_limit(dirty_thresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524
1525 /*
1526 * Boost the allowable dirty threshold a bit for page
1527 * allocators so they don't get DoS'ed by heavy writers
1528 */
1529 dirty_thresh += dirty_thresh / 10; /* wheeee... */
1530
Christoph Lameterc24f21b2006-06-30 01:55:42 -07001531 if (global_page_state(NR_UNSTABLE_NFS) +
1532 global_page_state(NR_WRITEBACK) <= dirty_thresh)
1533 break;
Jens Axboe8aa7e842009-07-09 14:52:32 +02001534 congestion_wait(BLK_RW_ASYNC, HZ/10);
Fengguang Wu369f2382007-10-16 23:30:45 -07001535
1536 /*
1537 * The caller might hold locks which can prevent IO completion
1538 * or progress in the filesystem. So we cannot just sit here
1539 * waiting for IO to complete.
1540 */
1541 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
1542 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543 }
1544}
1545
Linus Torvalds1da177e2005-04-16 15:20:36 -07001546/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
1548 */
1549int dirty_writeback_centisecs_handler(ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001550 void __user *buffer, size_t *length, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551{
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001552 proc_dointvec(table, write, buffer, length, ppos);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553 return 0;
1554}
1555
Jens Axboec2c49862010-05-20 09:18:47 +02001556#ifdef CONFIG_BLOCK
Matthew Garrett31373d02010-04-06 14:25:14 +02001557void laptop_mode_timer_fn(unsigned long data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558{
Matthew Garrett31373d02010-04-06 14:25:14 +02001559 struct request_queue *q = (struct request_queue *)data;
1560 int nr_pages = global_page_state(NR_FILE_DIRTY) +
1561 global_page_state(NR_UNSTABLE_NFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562
Matthew Garrett31373d02010-04-06 14:25:14 +02001563 /*
1564 * We want to write everything out, not just down to the dirty
1565 * threshold
1566 */
Matthew Garrett31373d02010-04-06 14:25:14 +02001567 if (bdi_has_dirty_io(&q->backing_dev_info))
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -06001568 bdi_start_writeback(&q->backing_dev_info, nr_pages,
1569 WB_REASON_LAPTOP_TIMER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570}
1571
1572/*
1573 * We've spun up the disk and we're in laptop mode: schedule writeback
1574 * of all dirty data a few seconds from now. If the flush is already scheduled
1575 * then push it back - the user is still using the disk.
1576 */
Matthew Garrett31373d02010-04-06 14:25:14 +02001577void laptop_io_completion(struct backing_dev_info *info)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001578{
Matthew Garrett31373d02010-04-06 14:25:14 +02001579 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001580}
1581
1582/*
1583 * We're in laptop mode and we've just synced. The sync's writes will have
1584 * caused another writeback to be scheduled by laptop_io_completion.
1585 * Nothing needs to be written back anymore, so we unschedule the writeback.
1586 */
1587void laptop_sync_completion(void)
1588{
Matthew Garrett31373d02010-04-06 14:25:14 +02001589 struct backing_dev_info *bdi;
1590
1591 rcu_read_lock();
1592
1593 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
1594 del_timer(&bdi->laptop_mode_wb_timer);
1595
1596 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597}
Jens Axboec2c49862010-05-20 09:18:47 +02001598#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599
1600/*
1601 * If ratelimit_pages is too high then we can get into dirty-data overload
1602 * if a large number of processes all perform writes at the same time.
1603 * If it is too low then SMP machines will call the (expensive)
1604 * get_writeback_state too often.
1605 *
1606 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
1607 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
Wu Fengguang9d823e82011-06-11 18:10:12 -06001608 * thresholds.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001609 */
1610
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -07001611void writeback_set_ratelimit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001612{
Wu Fengguang9d823e82011-06-11 18:10:12 -06001613 unsigned long background_thresh;
1614 unsigned long dirty_thresh;
1615 global_dirty_limits(&background_thresh, &dirty_thresh);
Fengguang Wu68809c72012-05-06 13:21:42 +08001616 global_dirty_limit = dirty_thresh;
Wu Fengguang9d823e82011-06-11 18:10:12 -06001617 ratelimit_pages = dirty_thresh / (num_online_cpus() * 32);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 if (ratelimit_pages < 16)
1619 ratelimit_pages = 16;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001620}
1621
Chandra Seetharaman26c21432006-06-27 02:54:10 -07001622static int __cpuinit
Srivatsa S. Bhat2f60d622012-09-28 20:27:49 +08001623ratelimit_handler(struct notifier_block *self, unsigned long action,
1624 void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625{
Srivatsa S. Bhat2f60d622012-09-28 20:27:49 +08001626
1627 switch (action & ~CPU_TASKS_FROZEN) {
1628 case CPU_ONLINE:
1629 case CPU_DEAD:
1630 writeback_set_ratelimit();
1631 return NOTIFY_OK;
1632 default:
1633 return NOTIFY_DONE;
1634 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001635}
1636
Chandra Seetharaman74b85f32006-06-27 02:54:09 -07001637static struct notifier_block __cpuinitdata ratelimit_nb = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638 .notifier_call = ratelimit_handler,
1639 .next = NULL,
1640};
1641
1642/*
Linus Torvaldsdc6e29d2007-01-29 16:37:38 -08001643 * Called early on to tune the page writeback dirty limits.
1644 *
1645 * We used to scale dirty pages according to how total memory
1646 * related to pages that could be allocated for buffers (by
1647 * comparing nr_free_buffer_pages() to vm_total_pages.
1648 *
1649 * However, that was when we used "dirty_ratio" to scale with
1650 * all memory, and we don't do that any more. "dirty_ratio"
1651 * is now applied to total non-HIGHPAGE memory (by subtracting
1652 * totalhigh_pages from vm_total_pages), and as such we can't
1653 * get into the old insane situation any more where we had
1654 * large amounts of dirty pages compared to a small amount of
1655 * non-HIGHMEM memory.
1656 *
1657 * But we might still want to scale the dirty_ratio by how
1658 * much memory the box has..
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659 */
1660void __init page_writeback_init(void)
1661{
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -07001662 writeback_set_ratelimit();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663 register_cpu_notifier(&ratelimit_nb);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001664
Jan Karaeb608e32012-05-24 18:59:11 +02001665 fprop_global_init(&writeout_completions);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666}
1667
David Howells811d7362006-08-29 19:06:09 +01001668/**
Jan Karaf446daae2010-08-09 17:19:12 -07001669 * tag_pages_for_writeback - tag pages to be written by write_cache_pages
1670 * @mapping: address space structure to write
1671 * @start: starting page index
1672 * @end: ending page index (inclusive)
1673 *
1674 * This function scans the page range from @start to @end (inclusive) and tags
1675 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
1676 * that write_cache_pages (or whoever calls this function) will then use
1677 * TOWRITE tag to identify pages eligible for writeback. This mechanism is
1678 * used to avoid livelocking of writeback by a process steadily creating new
1679 * dirty pages in the file (thus it is important for this function to be quick
1680 * so that it can tag pages faster than a dirtying process can create them).
1681 */
1682/*
1683 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
1684 */
Jan Karaf446daae2010-08-09 17:19:12 -07001685void tag_pages_for_writeback(struct address_space *mapping,
1686 pgoff_t start, pgoff_t end)
1687{
Randy Dunlap3c111a02010-08-11 14:17:30 -07001688#define WRITEBACK_TAG_BATCH 4096
Jan Karaf446daae2010-08-09 17:19:12 -07001689 unsigned long tagged;
1690
1691 do {
1692 spin_lock_irq(&mapping->tree_lock);
1693 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
1694 &start, end, WRITEBACK_TAG_BATCH,
1695 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
1696 spin_unlock_irq(&mapping->tree_lock);
1697 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
1698 cond_resched();
Jan Karad5ed3a42010-08-19 14:13:33 -07001699 /* We check 'start' to handle wrapping when end == ~0UL */
1700 } while (tagged >= WRITEBACK_TAG_BATCH && start);
Jan Karaf446daae2010-08-09 17:19:12 -07001701}
1702EXPORT_SYMBOL(tag_pages_for_writeback);
1703
1704/**
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001705 * 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 +01001706 * @mapping: address space structure to write
1707 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001708 * @writepage: function called for each page
1709 * @data: data passed to writepage function
David Howells811d7362006-08-29 19:06:09 +01001710 *
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001711 * If a page is already under I/O, write_cache_pages() skips it, even
David Howells811d7362006-08-29 19:06:09 +01001712 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
1713 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
1714 * and msync() need to guarantee that all the data which was dirty at the time
1715 * the call was made get new I/O started against them. If wbc->sync_mode is
1716 * WB_SYNC_ALL then we were called for data integrity and we must wait for
1717 * existing IO to complete.
Jan Karaf446daae2010-08-09 17:19:12 -07001718 *
1719 * To avoid livelocks (when other process dirties new pages), we first tag
1720 * pages which should be written back with TOWRITE tag and only then start
1721 * writing them. For data-integrity sync we have to be careful so that we do
1722 * not miss some pages (e.g., because some other process has cleared TOWRITE
1723 * tag we set). The rule we follow is that TOWRITE tag can be cleared only
1724 * by the process clearing the DIRTY tag (and submitting the page for IO).
David Howells811d7362006-08-29 19:06:09 +01001725 */
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001726int write_cache_pages(struct address_space *mapping,
1727 struct writeback_control *wbc, writepage_t writepage,
1728 void *data)
David Howells811d7362006-08-29 19:06:09 +01001729{
David Howells811d7362006-08-29 19:06:09 +01001730 int ret = 0;
1731 int done = 0;
David Howells811d7362006-08-29 19:06:09 +01001732 struct pagevec pvec;
1733 int nr_pages;
Nick Piggin31a12662009-01-06 14:39:04 -08001734 pgoff_t uninitialized_var(writeback_index);
David Howells811d7362006-08-29 19:06:09 +01001735 pgoff_t index;
1736 pgoff_t end; /* Inclusive */
Nick Pigginbd19e012009-01-06 14:39:06 -08001737 pgoff_t done_index;
Nick Piggin31a12662009-01-06 14:39:04 -08001738 int cycled;
David Howells811d7362006-08-29 19:06:09 +01001739 int range_whole = 0;
Jan Karaf446daae2010-08-09 17:19:12 -07001740 int tag;
David Howells811d7362006-08-29 19:06:09 +01001741
David Howells811d7362006-08-29 19:06:09 +01001742 pagevec_init(&pvec, 0);
1743 if (wbc->range_cyclic) {
Nick Piggin31a12662009-01-06 14:39:04 -08001744 writeback_index = mapping->writeback_index; /* prev offset */
1745 index = writeback_index;
1746 if (index == 0)
1747 cycled = 1;
1748 else
1749 cycled = 0;
David Howells811d7362006-08-29 19:06:09 +01001750 end = -1;
1751 } else {
1752 index = wbc->range_start >> PAGE_CACHE_SHIFT;
1753 end = wbc->range_end >> PAGE_CACHE_SHIFT;
1754 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
1755 range_whole = 1;
Nick Piggin31a12662009-01-06 14:39:04 -08001756 cycled = 1; /* ignore range_cyclic tests */
David Howells811d7362006-08-29 19:06:09 +01001757 }
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001758 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daae2010-08-09 17:19:12 -07001759 tag = PAGECACHE_TAG_TOWRITE;
1760 else
1761 tag = PAGECACHE_TAG_DIRTY;
David Howells811d7362006-08-29 19:06:09 +01001762retry:
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001763 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daae2010-08-09 17:19:12 -07001764 tag_pages_for_writeback(mapping, index, end);
Nick Pigginbd19e012009-01-06 14:39:06 -08001765 done_index = index;
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001766 while (!done && (index <= end)) {
1767 int i;
1768
Jan Karaf446daae2010-08-09 17:19:12 -07001769 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001770 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
1771 if (nr_pages == 0)
1772 break;
David Howells811d7362006-08-29 19:06:09 +01001773
David Howells811d7362006-08-29 19:06:09 +01001774 for (i = 0; i < nr_pages; i++) {
1775 struct page *page = pvec.pages[i];
1776
Nick Piggind5482cd2009-01-06 14:39:11 -08001777 /*
1778 * At this point, the page may be truncated or
1779 * invalidated (changing page->mapping to NULL), or
1780 * even swizzled back from swapper_space to tmpfs file
1781 * mapping. However, page->index will not change
1782 * because we have a reference on the page.
1783 */
1784 if (page->index > end) {
1785 /*
1786 * can't be range_cyclic (1st pass) because
1787 * end == -1 in that case.
1788 */
1789 done = 1;
1790 break;
1791 }
1792
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001793 done_index = page->index;
Nick Pigginbd19e012009-01-06 14:39:06 -08001794
David Howells811d7362006-08-29 19:06:09 +01001795 lock_page(page);
1796
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001797 /*
1798 * Page truncated or invalidated. We can freely skip it
1799 * then, even for data integrity operations: the page
1800 * has disappeared concurrently, so there could be no
1801 * real expectation of this data interity operation
1802 * even if there is now a new, dirty page at the same
1803 * pagecache address.
1804 */
David Howells811d7362006-08-29 19:06:09 +01001805 if (unlikely(page->mapping != mapping)) {
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001806continue_unlock:
David Howells811d7362006-08-29 19:06:09 +01001807 unlock_page(page);
1808 continue;
1809 }
1810
Nick Piggin515f4a02009-01-06 14:39:10 -08001811 if (!PageDirty(page)) {
1812 /* someone wrote it for us */
1813 goto continue_unlock;
1814 }
David Howells811d7362006-08-29 19:06:09 +01001815
Nick Piggin515f4a02009-01-06 14:39:10 -08001816 if (PageWriteback(page)) {
1817 if (wbc->sync_mode != WB_SYNC_NONE)
1818 wait_on_page_writeback(page);
1819 else
1820 goto continue_unlock;
1821 }
1822
1823 BUG_ON(PageWriteback(page));
1824 if (!clear_page_dirty_for_io(page))
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001825 goto continue_unlock;
David Howells811d7362006-08-29 19:06:09 +01001826
Dave Chinner9e094382010-07-07 13:24:08 +10001827 trace_wbc_writepage(wbc, mapping->backing_dev_info);
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001828 ret = (*writepage)(page, wbc, data);
Nick Piggin00266772009-01-06 14:39:06 -08001829 if (unlikely(ret)) {
1830 if (ret == AOP_WRITEPAGE_ACTIVATE) {
1831 unlock_page(page);
1832 ret = 0;
1833 } else {
1834 /*
1835 * done_index is set past this page,
1836 * so media errors will not choke
1837 * background writeout for the entire
1838 * file. This has consequences for
1839 * range_cyclic semantics (ie. it may
1840 * not be suitable for data integrity
1841 * writeout).
1842 */
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001843 done_index = page->index + 1;
Nick Piggin00266772009-01-06 14:39:06 -08001844 done = 1;
1845 break;
1846 }
Dave Chinner0b564922010-06-09 10:37:18 +10001847 }
David Howells811d7362006-08-29 19:06:09 +01001848
Dave Chinner546a1922010-08-24 11:44:34 +10001849 /*
1850 * We stop writing back only if we are not doing
1851 * integrity sync. In case of integrity sync we have to
1852 * keep going until we have written all the pages
1853 * we tagged for writeback prior to entering this loop.
1854 */
1855 if (--wbc->nr_to_write <= 0 &&
1856 wbc->sync_mode == WB_SYNC_NONE) {
1857 done = 1;
1858 break;
Nick Piggin05fe4782009-01-06 14:39:08 -08001859 }
David Howells811d7362006-08-29 19:06:09 +01001860 }
1861 pagevec_release(&pvec);
1862 cond_resched();
1863 }
Nick Piggin3a4c6802009-02-12 04:34:23 +01001864 if (!cycled && !done) {
David Howells811d7362006-08-29 19:06:09 +01001865 /*
Nick Piggin31a12662009-01-06 14:39:04 -08001866 * range_cyclic:
David Howells811d7362006-08-29 19:06:09 +01001867 * We hit the last page and there is more work to be done: wrap
1868 * back to the start of the file
1869 */
Nick Piggin31a12662009-01-06 14:39:04 -08001870 cycled = 1;
David Howells811d7362006-08-29 19:06:09 +01001871 index = 0;
Nick Piggin31a12662009-01-06 14:39:04 -08001872 end = writeback_index - 1;
David Howells811d7362006-08-29 19:06:09 +01001873 goto retry;
1874 }
Dave Chinner0b564922010-06-09 10:37:18 +10001875 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
1876 mapping->writeback_index = done_index;
Aneesh Kumar K.V06d6cf62008-07-11 19:27:31 -04001877
David Howells811d7362006-08-29 19:06:09 +01001878 return ret;
1879}
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001880EXPORT_SYMBOL(write_cache_pages);
1881
1882/*
1883 * Function used by generic_writepages to call the real writepage
1884 * function and set the mapping flags on error
1885 */
1886static int __writepage(struct page *page, struct writeback_control *wbc,
1887 void *data)
1888{
1889 struct address_space *mapping = data;
1890 int ret = mapping->a_ops->writepage(page, wbc);
1891 mapping_set_error(mapping, ret);
1892 return ret;
1893}
1894
1895/**
1896 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
1897 * @mapping: address space structure to write
1898 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
1899 *
1900 * This is a library function, which implements the writepages()
1901 * address_space_operation.
1902 */
1903int generic_writepages(struct address_space *mapping,
1904 struct writeback_control *wbc)
1905{
Shaohua Li9b6096a2011-03-17 10:47:06 +01001906 struct blk_plug plug;
1907 int ret;
1908
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001909 /* deal with chardevs and other special file */
1910 if (!mapping->a_ops->writepage)
1911 return 0;
1912
Shaohua Li9b6096a2011-03-17 10:47:06 +01001913 blk_start_plug(&plug);
1914 ret = write_cache_pages(mapping, wbc, __writepage, mapping);
1915 blk_finish_plug(&plug);
1916 return ret;
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001917}
David Howells811d7362006-08-29 19:06:09 +01001918
1919EXPORT_SYMBOL(generic_writepages);
1920
Linus Torvalds1da177e2005-04-16 15:20:36 -07001921int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1922{
Andrew Morton22905f72005-11-16 15:07:01 -08001923 int ret;
1924
Linus Torvalds1da177e2005-04-16 15:20:36 -07001925 if (wbc->nr_to_write <= 0)
1926 return 0;
1927 if (mapping->a_ops->writepages)
Peter Zijlstrad08b3852006-09-25 23:30:57 -07001928 ret = mapping->a_ops->writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001929 else
1930 ret = generic_writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001931 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001932}
1933
1934/**
1935 * write_one_page - write out a single page and optionally wait on I/O
Martin Waitz67be2dd2005-05-01 08:59:26 -07001936 * @page: the page to write
1937 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -07001938 *
1939 * The page must be locked by the caller and will be unlocked upon return.
1940 *
1941 * write_one_page() returns a negative error code if I/O failed.
1942 */
1943int write_one_page(struct page *page, int wait)
1944{
1945 struct address_space *mapping = page->mapping;
1946 int ret = 0;
1947 struct writeback_control wbc = {
1948 .sync_mode = WB_SYNC_ALL,
1949 .nr_to_write = 1,
1950 };
1951
1952 BUG_ON(!PageLocked(page));
1953
1954 if (wait)
1955 wait_on_page_writeback(page);
1956
1957 if (clear_page_dirty_for_io(page)) {
1958 page_cache_get(page);
1959 ret = mapping->a_ops->writepage(page, &wbc);
1960 if (ret == 0 && wait) {
1961 wait_on_page_writeback(page);
1962 if (PageError(page))
1963 ret = -EIO;
1964 }
1965 page_cache_release(page);
1966 } else {
1967 unlock_page(page);
1968 }
1969 return ret;
1970}
1971EXPORT_SYMBOL(write_one_page);
1972
1973/*
Ken Chen76719322007-02-10 01:43:15 -08001974 * For address_spaces which do not use buffers nor write back.
1975 */
1976int __set_page_dirty_no_writeback(struct page *page)
1977{
1978 if (!PageDirty(page))
Bob Liuc3f0da62011-01-13 15:45:49 -08001979 return !TestSetPageDirty(page);
Ken Chen76719322007-02-10 01:43:15 -08001980 return 0;
1981}
1982
1983/*
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001984 * Helper function for set_page_dirty family.
1985 * NOTE: This relies on being atomic wrt interrupts.
1986 */
1987void account_page_dirtied(struct page *page, struct address_space *mapping)
1988{
Tejun Heo9fb0a7d2013-01-11 13:06:37 -08001989 trace_writeback_dirty_page(page, mapping);
1990
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001991 if (mapping_cap_account_dirty(mapping)) {
1992 __inc_zone_page_state(page, NR_FILE_DIRTY);
Michael Rubinea941f02010-10-26 14:21:35 -07001993 __inc_zone_page_state(page, NR_DIRTIED);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001994 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
Wu Fengguangc8e28ce2011-01-23 10:07:47 -06001995 __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001996 task_io_account_write(PAGE_CACHE_SIZE);
Wu Fengguangd3bc1fe2011-04-14 07:52:37 -06001997 current->nr_dirtied++;
1998 this_cpu_inc(bdp_ratelimits);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001999 }
2000}
Michael Rubin679ceac2010-08-20 02:31:26 -07002001EXPORT_SYMBOL(account_page_dirtied);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07002002
2003/*
Michael Rubinf629d1c2010-10-26 14:21:33 -07002004 * Helper function for set_page_writeback family.
2005 * NOTE: Unlike account_page_dirtied this does not rely on being atomic
2006 * wrt interrupts.
2007 */
2008void account_page_writeback(struct page *page)
2009{
2010 inc_zone_page_state(page, NR_WRITEBACK);
2011}
2012EXPORT_SYMBOL(account_page_writeback);
2013
2014/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015 * For address_spaces which do not use buffers. Just tag the page as dirty in
2016 * its radix tree.
2017 *
2018 * This is also used when a single buffer is being dirtied: we want to set the
2019 * page dirty in that case, but not all the buffers. This is a "bottom-up"
2020 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
2021 *
2022 * Most callers have locked the page, which pins the address_space in memory.
2023 * But zap_pte_range() does not lock the page, however in that case the
2024 * mapping is pinned by the vma's ->vm_file reference.
2025 *
2026 * We take care to handle the case where the page was truncated from the
Simon Arlott183ff222007-10-20 01:27:18 +02002027 * mapping by re-checking page_mapping() inside tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002028 */
2029int __set_page_dirty_nobuffers(struct page *page)
2030{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002031 if (!TestSetPageDirty(page)) {
2032 struct address_space *mapping = page_mapping(page);
2033 struct address_space *mapping2;
2034
Andrew Morton8c085402006-12-10 02:19:24 -08002035 if (!mapping)
2036 return 1;
2037
Nick Piggin19fd6232008-07-25 19:45:32 -07002038 spin_lock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08002039 mapping2 = page_mapping(page);
2040 if (mapping2) { /* Race with truncate? */
2041 BUG_ON(mapping2 != mapping);
Nick Piggin787d2212007-07-17 04:03:34 -07002042 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -07002043 account_page_dirtied(page, mapping);
Andrew Morton8c085402006-12-10 02:19:24 -08002044 radix_tree_tag_set(&mapping->page_tree,
2045 page_index(page), PAGECACHE_TAG_DIRTY);
2046 }
Nick Piggin19fd6232008-07-25 19:45:32 -07002047 spin_unlock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08002048 if (mapping->host) {
2049 /* !PageAnon && !swapper_space */
2050 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002051 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08002052 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08002054 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002055}
2056EXPORT_SYMBOL(__set_page_dirty_nobuffers);
2057
2058/*
Wu Fengguang2f800fb2011-08-08 15:22:00 -06002059 * Call this whenever redirtying a page, to de-account the dirty counters
2060 * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written
2061 * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to
2062 * systematic errors in balanced_dirty_ratelimit and the dirty pages position
2063 * control.
2064 */
2065void account_page_redirty(struct page *page)
2066{
2067 struct address_space *mapping = page->mapping;
2068 if (mapping && mapping_cap_account_dirty(mapping)) {
2069 current->nr_dirtied--;
2070 dec_zone_page_state(page, NR_DIRTIED);
2071 dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
2072 }
2073}
2074EXPORT_SYMBOL(account_page_redirty);
2075
2076/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077 * When a writepage implementation decides that it doesn't want to write this
2078 * page for some reason, it should redirty the locked page via
2079 * redirty_page_for_writepage() and it should then unlock the page and return 0
2080 */
2081int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
2082{
2083 wbc->pages_skipped++;
Wu Fengguang2f800fb2011-08-08 15:22:00 -06002084 account_page_redirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002085 return __set_page_dirty_nobuffers(page);
2086}
2087EXPORT_SYMBOL(redirty_page_for_writepage);
2088
2089/*
Wu Fengguang6746aff2009-09-16 11:50:14 +02002090 * Dirty a page.
2091 *
2092 * For pages with a mapping this should be done under the page lock
2093 * for the benefit of asynchronous memory errors who prefer a consistent
2094 * dirty state. This rule can be broken in some special cases,
2095 * but should be better not to.
2096 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097 * If the mapping doesn't provide a set_page_dirty a_op, then
2098 * just fall through and assume that it wants buffer_heads.
2099 */
Nick Piggin1cf6e7d2009-02-18 14:48:18 -08002100int set_page_dirty(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101{
2102 struct address_space *mapping = page_mapping(page);
2103
2104 if (likely(mapping)) {
2105 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
Minchan Kim278df9f2011-03-22 16:32:54 -07002106 /*
2107 * readahead/lru_deactivate_page could remain
2108 * PG_readahead/PG_reclaim due to race with end_page_writeback
2109 * About readahead, if the page is written, the flags would be
2110 * reset. So no problem.
2111 * About lru_deactivate_page, if the page is redirty, the flag
2112 * will be reset. So no problem. but if the page is used by readahead
2113 * it will confuse readahead and make it restart the size rampup
2114 * process. But it's a trivial problem.
2115 */
2116 ClearPageReclaim(page);
David Howells93614012006-09-30 20:45:40 +02002117#ifdef CONFIG_BLOCK
2118 if (!spd)
2119 spd = __set_page_dirty_buffers;
2120#endif
2121 return (*spd)(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08002123 if (!PageDirty(page)) {
2124 if (!TestSetPageDirty(page))
2125 return 1;
2126 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127 return 0;
2128}
2129EXPORT_SYMBOL(set_page_dirty);
2130
2131/*
2132 * set_page_dirty() is racy if the caller has no reference against
2133 * page->mapping->host, and if the page is unlocked. This is because another
2134 * CPU could truncate the page off the mapping and then free the mapping.
2135 *
2136 * Usually, the page _is_ locked, or the caller is a user-space process which
2137 * holds a reference on the inode by having an open file.
2138 *
2139 * In other cases, the page should be locked before running set_page_dirty().
2140 */
2141int set_page_dirty_lock(struct page *page)
2142{
2143 int ret;
2144
Jens Axboe7eaceac2011-03-10 08:52:07 +01002145 lock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002146 ret = set_page_dirty(page);
2147 unlock_page(page);
2148 return ret;
2149}
2150EXPORT_SYMBOL(set_page_dirty_lock);
2151
2152/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002153 * Clear a page's dirty flag, while caring for dirty memory accounting.
2154 * Returns true if the page was previously dirty.
2155 *
2156 * This is for preparing to put the page under writeout. We leave the page
2157 * tagged as dirty in the radix tree so that a concurrent write-for-sync
2158 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
2159 * implementation will run either set_page_writeback() or set_page_dirty(),
2160 * at which stage we bring the page's dirty flag and radix-tree dirty tag
2161 * back into sync.
2162 *
2163 * This incoherency between the page's dirty flag and radix-tree tag is
2164 * unfortunate, but it only exists while the page is locked.
2165 */
2166int clear_page_dirty_for_io(struct page *page)
2167{
2168 struct address_space *mapping = page_mapping(page);
2169
Nick Piggin79352892007-07-19 01:47:22 -07002170 BUG_ON(!PageLocked(page));
2171
Linus Torvalds7658cc22006-12-29 10:00:58 -08002172 if (mapping && mapping_cap_account_dirty(mapping)) {
2173 /*
2174 * Yes, Virginia, this is indeed insane.
2175 *
2176 * We use this sequence to make sure that
2177 * (a) we account for dirty stats properly
2178 * (b) we tell the low-level filesystem to
2179 * mark the whole page dirty if it was
2180 * dirty in a pagetable. Only to then
2181 * (c) clean the page again and return 1 to
2182 * cause the writeback.
2183 *
2184 * This way we avoid all nasty races with the
2185 * dirty bit in multiple places and clearing
2186 * them concurrently from different threads.
2187 *
2188 * Note! Normally the "set_page_dirty(page)"
2189 * has no effect on the actual dirty bit - since
2190 * that will already usually be set. But we
2191 * need the side effects, and it can help us
2192 * avoid races.
2193 *
2194 * We basically use the page "master dirty bit"
2195 * as a serialization point for all the different
2196 * threads doing their things.
Linus Torvalds7658cc22006-12-29 10:00:58 -08002197 */
2198 if (page_mkclean(page))
2199 set_page_dirty(page);
Nick Piggin79352892007-07-19 01:47:22 -07002200 /*
2201 * We carefully synchronise fault handlers against
2202 * installing a dirty pte and marking the page dirty
2203 * at this point. We do this by having them hold the
2204 * page lock at some point after installing their
2205 * pte, but before marking the page dirty.
2206 * Pages are always locked coming in here, so we get
2207 * the desired exclusion. See mm/memory.c:do_wp_page()
2208 * for more comments.
2209 */
Linus Torvalds7658cc22006-12-29 10:00:58 -08002210 if (TestClearPageDirty(page)) {
Andrew Morton8c085402006-12-10 02:19:24 -08002211 dec_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07002212 dec_bdi_stat(mapping->backing_dev_info,
2213 BDI_RECLAIMABLE);
Linus Torvalds7658cc22006-12-29 10:00:58 -08002214 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002215 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08002216 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08002218 return TestClearPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002219}
Hans Reiser58bb01a2005-11-18 01:10:53 -08002220EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002221
2222int test_clear_page_writeback(struct page *page)
2223{
2224 struct address_space *mapping = page_mapping(page);
2225 int ret;
2226
2227 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002228 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002229 unsigned long flags;
2230
Nick Piggin19fd6232008-07-25 19:45:32 -07002231 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232 ret = TestClearPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002233 if (ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002234 radix_tree_tag_clear(&mapping->page_tree,
2235 page_index(page),
2236 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07002237 if (bdi_cap_account_writeback(bdi)) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002238 __dec_bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07002239 __bdi_writeout_inc(bdi);
2240 }
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002241 }
Nick Piggin19fd6232008-07-25 19:45:32 -07002242 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002243 } else {
2244 ret = TestClearPageWriteback(page);
2245 }
Wu Fengguang99b12e32011-07-25 17:12:37 -07002246 if (ret) {
Andrew Mortond688abf2007-07-19 01:49:17 -07002247 dec_zone_page_state(page, NR_WRITEBACK);
Wu Fengguang99b12e32011-07-25 17:12:37 -07002248 inc_zone_page_state(page, NR_WRITTEN);
2249 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250 return ret;
2251}
2252
2253int test_set_page_writeback(struct page *page)
2254{
2255 struct address_space *mapping = page_mapping(page);
2256 int ret;
2257
2258 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002259 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002260 unsigned long flags;
2261
Nick Piggin19fd6232008-07-25 19:45:32 -07002262 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263 ret = TestSetPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002264 if (!ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265 radix_tree_tag_set(&mapping->page_tree,
2266 page_index(page),
2267 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07002268 if (bdi_cap_account_writeback(bdi))
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002269 __inc_bdi_stat(bdi, BDI_WRITEBACK);
2270 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002271 if (!PageDirty(page))
2272 radix_tree_tag_clear(&mapping->page_tree,
2273 page_index(page),
2274 PAGECACHE_TAG_DIRTY);
Jan Karaf446daae2010-08-09 17:19:12 -07002275 radix_tree_tag_clear(&mapping->page_tree,
2276 page_index(page),
2277 PAGECACHE_TAG_TOWRITE);
Nick Piggin19fd6232008-07-25 19:45:32 -07002278 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279 } else {
2280 ret = TestSetPageWriteback(page);
2281 }
Andrew Mortond688abf2007-07-19 01:49:17 -07002282 if (!ret)
Michael Rubinf629d1c2010-10-26 14:21:33 -07002283 account_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002284 return ret;
2285
2286}
2287EXPORT_SYMBOL(test_set_page_writeback);
2288
2289/*
Nick Piggin00128182007-10-16 01:24:40 -07002290 * Return true if any of the pages in the mapping are marked with the
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291 * passed tag.
2292 */
2293int mapping_tagged(struct address_space *mapping, int tag)
2294{
Konstantin Khlebnikov72c47832011-07-25 17:12:31 -07002295 return radix_tree_tagged(&mapping->page_tree, tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002296}
2297EXPORT_SYMBOL(mapping_tagged);
Darrick J. Wong1d1d1a72013-02-21 16:42:51 -08002298
2299/**
2300 * wait_for_stable_page() - wait for writeback to finish, if necessary.
2301 * @page: The page to wait on.
2302 *
2303 * This function determines if the given page is related to a backing device
2304 * that requires page contents to be held stable during writeback. If so, then
2305 * it will wait for any pending writeback to complete.
2306 */
2307void wait_for_stable_page(struct page *page)
2308{
2309 struct address_space *mapping = page_mapping(page);
2310 struct backing_dev_info *bdi = mapping->backing_dev_info;
2311
2312 if (!bdi_cap_stable_pages_required(bdi))
2313 return;
Darrick J. Wongffecfd12013-02-21 16:42:55 -08002314#ifdef CONFIG_NEED_BOUNCE_POOL
2315 if (mapping->host->i_sb->s_flags & MS_SNAP_STABLE)
2316 return;
2317#endif /* CONFIG_NEED_BOUNCE_POOL */
Darrick J. Wong1d1d1a72013-02-21 16:42:51 -08002318
2319 wait_on_page_writeback(page);
2320}
2321EXPORT_SYMBOL_GPL(wait_for_stable_page);