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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Uwe Zeisbergerf30c2262006-10-03 23:01:26 +02002 * mm/page-writeback.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07003 *
4 * Copyright (C) 2002, Linus Torvalds.
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07005 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 *
7 * Contains functions related to writing back dirty pages at the
8 * address_space level.
9 *
Francois Camie1f8e872008-10-15 22:01:59 -070010 * 10Apr2002 Andrew Morton
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 * Initial version
12 */
13
14#include <linux/kernel.h>
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>
Dave Chinner028c2dd2010-07-07 13:24:07 +100038#include <trace/events/writeback.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070039
40/*
Wu Fengguangffd1f602011-06-19 22:18:42 -060041 * Sleep at most 200ms at a time in balance_dirty_pages().
42 */
43#define MAX_PAUSE max(HZ/5, 1)
44
45/*
Wu Fengguang5b9b3572011-12-06 13:17:17 -060046 * Try to keep balance_dirty_pages() call intervals higher than this many pages
47 * by raising pause time to max_pause when falls below it.
48 */
49#define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10))
50
51/*
Wu Fengguange98be2d2010-08-29 11:22:30 -060052 * Estimate write bandwidth at 200ms intervals.
53 */
54#define BANDWIDTH_INTERVAL max(HZ/5, 1)
55
Wu Fengguang6c14ae12011-03-02 16:04:18 -060056#define RATELIMIT_CALC_SHIFT 10
57
Wu Fengguange98be2d2010-08-29 11:22:30 -060058/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
60 * will look to see if it needs to force writeback or throttling.
61 */
62static long ratelimit_pages = 32;
63
Linus Torvalds1da177e2005-04-16 15:20:36 -070064/* The following parameters are exported via /proc/sys/vm */
65
66/*
Jens Axboe5b0830c2009-09-23 19:37:09 +020067 * Start background writeback (via writeback threads) at this percentage
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080069int dirty_background_ratio = 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -070070
71/*
David Rientjes2da02992009-01-06 14:39:31 -080072 * dirty_background_bytes starts at 0 (disabled) so that it is a function of
73 * dirty_background_ratio * the amount of dirtyable memory
74 */
75unsigned long dirty_background_bytes;
76
77/*
Bron Gondwana195cf4532008-02-04 22:29:20 -080078 * free highmem will not be subtracted from the total free memory
79 * for calculating free ratios if vm_highmem_is_dirtyable is true
80 */
81int vm_highmem_is_dirtyable;
82
83/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 * The generator of dirty data starts writeback at this percentage
85 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080086int vm_dirty_ratio = 20;
Linus Torvalds1da177e2005-04-16 15:20:36 -070087
88/*
David Rientjes2da02992009-01-06 14:39:31 -080089 * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
90 * vm_dirty_ratio * the amount of dirtyable memory
91 */
92unsigned long vm_dirty_bytes;
93
94/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -070095 * The interval between `kupdate'-style writebacks
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -070097unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -070098
Artem Bityutskiy91913a22012-03-21 22:33:00 -040099EXPORT_SYMBOL_GPL(dirty_writeback_interval);
100
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -0700102 * The longest time for which data is allowed to remain dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -0700104unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105
106/*
107 * Flag that makes the machine dump writes/reads and block dirtyings.
108 */
109int block_dump;
110
111/*
Bart Samweled5b43f2006-03-24 03:15:49 -0800112 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
113 * a full sync is triggered after this time elapses without any disk activity.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 */
115int laptop_mode;
116
117EXPORT_SYMBOL(laptop_mode);
118
119/* End of sysctl-exported parameters */
120
Wu Fengguangc42843f2011-03-02 15:54:09 -0600121unsigned long global_dirty_limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123/*
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700124 * Scale the writeback cache size proportional to the relative writeout speeds.
125 *
126 * We do this by keeping a floating proportion between BDIs, based on page
127 * writeback completions [end_page_writeback()]. Those devices that write out
128 * pages fastest will get the larger share, while the slower will get a smaller
129 * share.
130 *
131 * We use page writeout completions because we are interested in getting rid of
132 * dirty pages. Having them written out is the primary goal.
133 *
134 * We introduce a concept of time, a period over which we measure these events,
135 * because demand can/will vary over time. The length of this period itself is
136 * measured in page writeback completions.
137 *
138 */
Jan Karaeb608e32012-05-24 18:59:11 +0200139static struct fprop_global writeout_completions;
140
141static void writeout_period(unsigned long t);
142/* Timer for aging of writeout_completions */
143static struct timer_list writeout_period_timer =
144 TIMER_DEFERRED_INITIALIZER(writeout_period, 0, 0);
145static unsigned long writeout_period_time = 0;
146
147/*
148 * Length of period for aging writeout fractions of bdis. This is an
149 * arbitrarily chosen number. The longer the period, the slower fractions will
150 * reflect changes in current writeout rate.
151 */
152#define VM_COMPLETIONS_PERIOD_LEN (3*HZ)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700153
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700154/*
Johannes Weiner1edf2232012-01-10 15:06:57 -0800155 * Work out the current dirty-memory clamping and background writeout
156 * thresholds.
157 *
158 * The main aim here is to lower them aggressively if there is a lot of mapped
159 * memory around. To avoid stressing page reclaim with lots of unreclaimable
160 * pages. It is better to clamp down on writers than to start swapping, and
161 * performing lots of scanning.
162 *
163 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
164 *
165 * We don't permit the clamping level to fall below 5% - that is getting rather
166 * excessive.
167 *
168 * We make sure that the background writeout level is below the adjusted
169 * clamping level.
170 */
Johannes Weinerccafa282012-01-10 15:07:44 -0800171
Johannes Weinera756cf52012-01-10 15:07:49 -0800172/*
173 * In a memory zone, there is a certain amount of pages we consider
174 * available for the page cache, which is essentially the number of
175 * free and reclaimable pages, minus some zone reserves to protect
176 * lowmem and the ability to uphold the zone's watermarks without
177 * requiring writeback.
178 *
179 * This number of dirtyable pages is the base value of which the
180 * user-configurable dirty ratio is the effictive number of pages that
181 * are allowed to be actually dirtied. Per individual zone, or
182 * globally by using the sum of dirtyable pages over all zones.
183 *
184 * Because the user is allowed to specify the dirty limit globally as
185 * absolute number of bytes, calculating the per-zone dirty limit can
186 * require translating the configured limit into a percentage of
187 * global dirtyable memory first.
188 */
189
Johannes Weiner1edf2232012-01-10 15:06:57 -0800190static unsigned long highmem_dirtyable_memory(unsigned long total)
191{
192#ifdef CONFIG_HIGHMEM
193 int node;
194 unsigned long x = 0;
195
196 for_each_node_state(node, N_HIGH_MEMORY) {
197 struct zone *z =
198 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
199
200 x += zone_page_state(z, NR_FREE_PAGES) +
Johannes Weinerab8fabd2012-01-10 15:07:42 -0800201 zone_reclaimable_pages(z) - z->dirty_balance_reserve;
Johannes Weiner1edf2232012-01-10 15:06:57 -0800202 }
203 /*
Sonny Raoc8b74c2f2012-12-20 15:05:07 -0800204 * Unreclaimable memory (kernel memory or anonymous memory
205 * without swap) can bring down the dirtyable pages below
206 * the zone's dirty balance reserve and the above calculation
207 * will underflow. However we still want to add in nodes
208 * which are below threshold (negative values) to get a more
209 * accurate calculation but make sure that the total never
210 * underflows.
211 */
212 if ((long)x < 0)
213 x = 0;
214
215 /*
Johannes Weiner1edf2232012-01-10 15:06:57 -0800216 * Make sure that the number of highmem pages is never larger
217 * than the number of the total dirtyable memory. This can only
218 * occur in very strange VM situations but we want to make sure
219 * that this does not occur.
220 */
221 return min(x, total);
222#else
223 return 0;
224#endif
225}
226
227/**
Johannes Weinerccafa282012-01-10 15:07:44 -0800228 * global_dirtyable_memory - number of globally dirtyable pages
Johannes Weiner1edf2232012-01-10 15:06:57 -0800229 *
Johannes Weinerccafa282012-01-10 15:07:44 -0800230 * Returns the global number of pages potentially available for dirty
231 * page cache. This is the base value for the global dirty limits.
Johannes Weiner1edf2232012-01-10 15:06:57 -0800232 */
H Hartley Sweeten18cf8cf2012-04-12 13:44:20 -0700233static unsigned long global_dirtyable_memory(void)
Johannes Weiner1edf2232012-01-10 15:06:57 -0800234{
235 unsigned long x;
236
Sonny Raoc8b74c2f2012-12-20 15:05:07 -0800237 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
238 x -= min(x, dirty_balance_reserve);
Johannes Weiner1edf2232012-01-10 15:06:57 -0800239
240 if (!vm_highmem_is_dirtyable)
241 x -= highmem_dirtyable_memory(x);
242
243 return x + 1; /* Ensure that we never return 0 */
244}
245
246/*
Johannes Weinerccafa282012-01-10 15:07:44 -0800247 * global_dirty_limits - background-writeback and dirty-throttling thresholds
248 *
249 * Calculate the dirty thresholds based on sysctl parameters
250 * - vm.dirty_background_ratio or vm.dirty_background_bytes
251 * - vm.dirty_ratio or vm.dirty_bytes
252 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
253 * real-time tasks.
254 */
255void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
256{
257 unsigned long background;
258 unsigned long dirty;
259 unsigned long uninitialized_var(available_memory);
260 struct task_struct *tsk;
261
262 if (!vm_dirty_bytes || !dirty_background_bytes)
263 available_memory = global_dirtyable_memory();
264
265 if (vm_dirty_bytes)
266 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
267 else
268 dirty = (vm_dirty_ratio * available_memory) / 100;
269
270 if (dirty_background_bytes)
271 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
272 else
273 background = (dirty_background_ratio * available_memory) / 100;
274
275 if (background >= dirty)
276 background = dirty / 2;
277 tsk = current;
278 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
279 background += background / 4;
280 dirty += dirty / 4;
281 }
282 *pbackground = background;
283 *pdirty = dirty;
284 trace_global_dirty_state(background, dirty);
285}
286
Johannes Weinera756cf52012-01-10 15:07:49 -0800287/**
288 * zone_dirtyable_memory - number of dirtyable pages in a zone
289 * @zone: the zone
290 *
291 * Returns the zone's number of pages potentially available for dirty
292 * page cache. This is the base value for the per-zone dirty limits.
293 */
294static unsigned long zone_dirtyable_memory(struct zone *zone)
295{
296 /*
297 * The effective global number of dirtyable pages may exclude
298 * highmem as a big-picture measure to keep the ratio between
299 * dirty memory and lowmem reasonable.
300 *
301 * But this function is purely about the individual zone and a
302 * highmem zone can hold its share of dirty pages, so we don't
303 * care about vm_highmem_is_dirtyable here.
304 */
Sonny Raoc8b74c2f2012-12-20 15:05:07 -0800305 unsigned long nr_pages = zone_page_state(zone, NR_FREE_PAGES) +
306 zone_reclaimable_pages(zone);
307
308 /* don't allow this to underflow */
309 nr_pages -= min(nr_pages, zone->dirty_balance_reserve);
310 return nr_pages;
Johannes Weinera756cf52012-01-10 15:07:49 -0800311}
312
313/**
314 * zone_dirty_limit - maximum number of dirty pages allowed in a zone
315 * @zone: the zone
316 *
317 * Returns the maximum number of dirty pages allowed in a zone, based
318 * on the zone's dirtyable memory.
319 */
320static unsigned long zone_dirty_limit(struct zone *zone)
321{
322 unsigned long zone_memory = zone_dirtyable_memory(zone);
323 struct task_struct *tsk = current;
324 unsigned long dirty;
325
326 if (vm_dirty_bytes)
327 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) *
328 zone_memory / global_dirtyable_memory();
329 else
330 dirty = vm_dirty_ratio * zone_memory / 100;
331
332 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk))
333 dirty += dirty / 4;
334
335 return dirty;
336}
337
338/**
339 * zone_dirty_ok - tells whether a zone is within its dirty limits
340 * @zone: the zone to check
341 *
342 * Returns %true when the dirty pages in @zone are within the zone's
343 * dirty limit, %false if the limit is exceeded.
344 */
345bool zone_dirty_ok(struct zone *zone)
346{
347 unsigned long limit = zone_dirty_limit(zone);
348
349 return zone_page_state(zone, NR_FILE_DIRTY) +
350 zone_page_state(zone, NR_UNSTABLE_NFS) +
351 zone_page_state(zone, NR_WRITEBACK) <= limit;
352}
353
David Rientjes2da02992009-01-06 14:39:31 -0800354int dirty_background_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700355 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800356 loff_t *ppos)
357{
358 int ret;
359
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700360 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800361 if (ret == 0 && write)
362 dirty_background_bytes = 0;
363 return ret;
364}
365
366int dirty_background_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700367 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800368 loff_t *ppos)
369{
370 int ret;
371
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700372 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800373 if (ret == 0 && write)
374 dirty_background_ratio = 0;
375 return ret;
376}
377
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700378int dirty_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700379 void __user *buffer, size_t *lenp,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700380 loff_t *ppos)
381{
382 int old_ratio = vm_dirty_ratio;
David Rientjes2da02992009-01-06 14:39:31 -0800383 int ret;
384
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700385 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700386 if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
Jan Karaeb608e32012-05-24 18:59:11 +0200387 writeback_set_ratelimit();
David Rientjes2da02992009-01-06 14:39:31 -0800388 vm_dirty_bytes = 0;
389 }
390 return ret;
391}
392
David Rientjes2da02992009-01-06 14:39:31 -0800393int dirty_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700394 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800395 loff_t *ppos)
396{
Sven Wegenerfc3501d2009-02-11 13:04:23 -0800397 unsigned long old_bytes = vm_dirty_bytes;
David Rientjes2da02992009-01-06 14:39:31 -0800398 int ret;
399
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700400 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800401 if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
Jan Karaeb608e32012-05-24 18:59:11 +0200402 writeback_set_ratelimit();
David Rientjes2da02992009-01-06 14:39:31 -0800403 vm_dirty_ratio = 0;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700404 }
405 return ret;
406}
407
Jan Karaeb608e32012-05-24 18:59:11 +0200408static unsigned long wp_next_time(unsigned long cur_time)
409{
410 cur_time += VM_COMPLETIONS_PERIOD_LEN;
411 /* 0 has a special meaning... */
412 if (!cur_time)
413 return 1;
414 return cur_time;
415}
416
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700417/*
418 * Increment the BDI's writeout completion count and the global writeout
419 * completion count. Called from test_clear_page_writeback().
420 */
421static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
422{
Jan Karaf7d2b1e2010-12-08 22:44:24 -0600423 __inc_bdi_stat(bdi, BDI_WRITTEN);
Jan Karaeb608e32012-05-24 18:59:11 +0200424 __fprop_inc_percpu_max(&writeout_completions, &bdi->completions,
425 bdi->max_prop_frac);
426 /* First event after period switching was turned off? */
427 if (!unlikely(writeout_period_time)) {
428 /*
429 * We can race with other __bdi_writeout_inc calls here but
430 * it does not cause any harm since the resulting time when
431 * timer will fire and what is in writeout_period_time will be
432 * roughly the same.
433 */
434 writeout_period_time = wp_next_time(jiffies);
435 mod_timer(&writeout_period_timer, writeout_period_time);
436 }
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700437}
438
Miklos Szeredidd5656e2008-04-30 00:54:37 -0700439void bdi_writeout_inc(struct backing_dev_info *bdi)
440{
441 unsigned long flags;
442
443 local_irq_save(flags);
444 __bdi_writeout_inc(bdi);
445 local_irq_restore(flags);
446}
447EXPORT_SYMBOL_GPL(bdi_writeout_inc);
448
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700449/*
450 * Obtain an accurate fraction of the BDI's portion.
451 */
452static void bdi_writeout_fraction(struct backing_dev_info *bdi,
453 long *numerator, long *denominator)
454{
Jan Karaeb608e32012-05-24 18:59:11 +0200455 fprop_fraction_percpu(&writeout_completions, &bdi->completions,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700456 numerator, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700457}
458
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700459/*
Jan Karaeb608e32012-05-24 18:59:11 +0200460 * On idle system, we can be called long after we scheduled because we use
461 * deferred timers so count with missed periods.
462 */
463static void writeout_period(unsigned long t)
464{
465 int miss_periods = (jiffies - writeout_period_time) /
466 VM_COMPLETIONS_PERIOD_LEN;
467
468 if (fprop_new_period(&writeout_completions, miss_periods + 1)) {
469 writeout_period_time = wp_next_time(writeout_period_time +
470 miss_periods * VM_COMPLETIONS_PERIOD_LEN);
471 mod_timer(&writeout_period_timer, writeout_period_time);
472 } else {
473 /*
474 * Aging has zeroed all fractions. Stop wasting CPU on period
475 * updates.
476 */
477 writeout_period_time = 0;
478 }
479}
480
481/*
Johannes Weinerd08c4292011-10-31 17:07:05 -0700482 * bdi_min_ratio keeps the sum of the minimum dirty shares of all
483 * registered backing devices, which, for obvious reasons, can not
484 * exceed 100%.
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700485 */
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700486static unsigned int bdi_min_ratio;
487
488int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
489{
490 int ret = 0;
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700491
Jens Axboecfc4ba52009-09-14 13:12:40 +0200492 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700493 if (min_ratio > bdi->max_ratio) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700494 ret = -EINVAL;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700495 } else {
496 min_ratio -= bdi->min_ratio;
497 if (bdi_min_ratio + min_ratio < 100) {
498 bdi_min_ratio += min_ratio;
499 bdi->min_ratio += min_ratio;
500 } else {
501 ret = -EINVAL;
502 }
503 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200504 spin_unlock_bh(&bdi_lock);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700505
506 return ret;
507}
508
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700509int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
510{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700511 int ret = 0;
512
513 if (max_ratio > 100)
514 return -EINVAL;
515
Jens Axboecfc4ba52009-09-14 13:12:40 +0200516 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700517 if (bdi->min_ratio > max_ratio) {
518 ret = -EINVAL;
519 } else {
520 bdi->max_ratio = max_ratio;
Jan Karaeb608e32012-05-24 18:59:11 +0200521 bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700522 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200523 spin_unlock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700524
525 return ret;
526}
527EXPORT_SYMBOL(bdi_set_max_ratio);
528
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600529static unsigned long dirty_freerun_ceiling(unsigned long thresh,
530 unsigned long bg_thresh)
531{
532 return (thresh + bg_thresh) / 2;
533}
534
Wu Fengguangffd1f602011-06-19 22:18:42 -0600535static unsigned long hard_dirty_limit(unsigned long thresh)
536{
537 return max(thresh, global_dirty_limit);
538}
539
Wu Fengguang6f718652011-03-02 17:14:34 -0600540/**
Wu Fengguang1babe182010-08-11 14:17:40 -0700541 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
Wu Fengguang6f718652011-03-02 17:14:34 -0600542 * @bdi: the backing_dev_info to query
543 * @dirty: global dirty limit in pages
Wu Fengguang1babe182010-08-11 14:17:40 -0700544 *
Wu Fengguang6f718652011-03-02 17:14:34 -0600545 * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
546 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
Wu Fengguangaed21ad2011-11-23 11:44:41 -0600547 *
548 * Note that balance_dirty_pages() will only seriously take it as a hard limit
549 * when sleeping max_pause per page is not enough to keep the dirty pages under
550 * control. For example, when the device is completely stalled due to some error
551 * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key.
552 * In the other normal situations, it acts more gently by throttling the tasks
553 * more (rather than completely block them) when the bdi dirty pages go high.
Wu Fengguang6f718652011-03-02 17:14:34 -0600554 *
555 * It allocates high/low dirty limits to fast/slow devices, in order to prevent
Wu Fengguang1babe182010-08-11 14:17:40 -0700556 * - starving fast devices
557 * - piling up dirty pages (that will take long time to sync) on slow devices
558 *
559 * The bdi's share of dirty limit will be adapting to its throughput and
560 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
561 */
562unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
Wu Fengguang16c40422010-08-11 14:17:39 -0700563{
564 u64 bdi_dirty;
565 long numerator, denominator;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700566
Wu Fengguang16c40422010-08-11 14:17:39 -0700567 /*
568 * Calculate this BDI's share of the dirty ratio.
569 */
570 bdi_writeout_fraction(bdi, &numerator, &denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700571
Wu Fengguang16c40422010-08-11 14:17:39 -0700572 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
573 bdi_dirty *= numerator;
574 do_div(bdi_dirty, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700575
Wu Fengguang16c40422010-08-11 14:17:39 -0700576 bdi_dirty += (dirty * bdi->min_ratio) / 100;
577 if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
578 bdi_dirty = dirty * bdi->max_ratio / 100;
579
580 return bdi_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581}
582
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600583/*
584 * Dirty position control.
585 *
586 * (o) global/bdi setpoints
587 *
588 * We want the dirty pages be balanced around the global/bdi setpoints.
589 * When the number of dirty pages is higher/lower than the setpoint, the
590 * dirty position control ratio (and hence task dirty ratelimit) will be
591 * decreased/increased to bring the dirty pages back to the setpoint.
592 *
593 * pos_ratio = 1 << RATELIMIT_CALC_SHIFT
594 *
595 * if (dirty < setpoint) scale up pos_ratio
596 * if (dirty > setpoint) scale down pos_ratio
597 *
598 * if (bdi_dirty < bdi_setpoint) scale up pos_ratio
599 * if (bdi_dirty > bdi_setpoint) scale down pos_ratio
600 *
601 * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT
602 *
603 * (o) global control line
604 *
605 * ^ pos_ratio
606 * |
607 * | |<===== global dirty control scope ======>|
608 * 2.0 .............*
609 * | .*
610 * | . *
611 * | . *
612 * | . *
613 * | . *
614 * | . *
615 * 1.0 ................................*
616 * | . . *
617 * | . . *
618 * | . . *
619 * | . . *
620 * | . . *
621 * 0 +------------.------------------.----------------------*------------->
622 * freerun^ setpoint^ limit^ dirty pages
623 *
624 * (o) bdi control line
625 *
626 * ^ pos_ratio
627 * |
628 * | *
629 * | *
630 * | *
631 * | *
632 * | * |<=========== span ============>|
633 * 1.0 .......................*
634 * | . *
635 * | . *
636 * | . *
637 * | . *
638 * | . *
639 * | . *
640 * | . *
641 * | . *
642 * | . *
643 * | . *
644 * | . *
645 * 1/4 ...............................................* * * * * * * * * * * *
646 * | . .
647 * | . .
648 * | . .
649 * 0 +----------------------.-------------------------------.------------->
650 * bdi_setpoint^ x_intercept^
651 *
652 * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can
653 * be smoothly throttled down to normal if it starts high in situations like
654 * - start writing to a slow SD card and a fast disk at the same time. The SD
655 * card's bdi_dirty may rush to many times higher than bdi_setpoint.
656 * - the bdi dirty thresh drops quickly due to change of JBOD workload
657 */
658static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
659 unsigned long thresh,
660 unsigned long bg_thresh,
661 unsigned long dirty,
662 unsigned long bdi_thresh,
663 unsigned long bdi_dirty)
664{
665 unsigned long write_bw = bdi->avg_write_bandwidth;
666 unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
667 unsigned long limit = hard_dirty_limit(thresh);
668 unsigned long x_intercept;
669 unsigned long setpoint; /* dirty pages' target balance point */
670 unsigned long bdi_setpoint;
671 unsigned long span;
672 long long pos_ratio; /* for scaling up/down the rate limit */
673 long x;
674
675 if (unlikely(dirty >= limit))
676 return 0;
677
678 /*
679 * global setpoint
680 *
681 * setpoint - dirty 3
682 * f(dirty) := 1.0 + (----------------)
683 * limit - setpoint
684 *
685 * it's a 3rd order polynomial that subjects to
686 *
687 * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast
688 * (2) f(setpoint) = 1.0 => the balance point
689 * (3) f(limit) = 0 => the hard limit
690 * (4) df/dx <= 0 => negative feedback control
691 * (5) the closer to setpoint, the smaller |df/dx| (and the reverse)
692 * => fast response on large errors; small oscillation near setpoint
693 */
694 setpoint = (freerun + limit) / 2;
695 x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT,
696 limit - setpoint + 1);
697 pos_ratio = x;
698 pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
699 pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
700 pos_ratio += 1 << RATELIMIT_CALC_SHIFT;
701
702 /*
703 * We have computed basic pos_ratio above based on global situation. If
704 * the bdi is over/under its share of dirty pages, we want to scale
705 * pos_ratio further down/up. That is done by the following mechanism.
706 */
707
708 /*
709 * bdi setpoint
710 *
711 * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint)
712 *
713 * x_intercept - bdi_dirty
714 * := --------------------------
715 * x_intercept - bdi_setpoint
716 *
717 * The main bdi control line is a linear function that subjects to
718 *
719 * (1) f(bdi_setpoint) = 1.0
720 * (2) k = - 1 / (8 * write_bw) (in single bdi case)
721 * or equally: x_intercept = bdi_setpoint + 8 * write_bw
722 *
723 * For single bdi case, the dirty pages are observed to fluctuate
724 * regularly within range
725 * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2]
726 * for various filesystems, where (2) can yield in a reasonable 12.5%
727 * fluctuation range for pos_ratio.
728 *
729 * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its
730 * own size, so move the slope over accordingly and choose a slope that
731 * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh.
732 */
733 if (unlikely(bdi_thresh > thresh))
734 bdi_thresh = thresh;
Wu Fengguangaed21ad2011-11-23 11:44:41 -0600735 /*
736 * It's very possible that bdi_thresh is close to 0 not because the
737 * device is slow, but that it has remained inactive for long time.
738 * Honour such devices a reasonable good (hopefully IO efficient)
739 * threshold, so that the occasional writes won't be blocked and active
740 * writes can rampup the threshold quickly.
741 */
Wu Fengguang8927f662011-08-04 22:16:46 -0600742 bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600743 /*
744 * scale global setpoint to bdi's:
745 * bdi_setpoint = setpoint * bdi_thresh / thresh
746 */
747 x = div_u64((u64)bdi_thresh << 16, thresh + 1);
748 bdi_setpoint = setpoint * (u64)x >> 16;
749 /*
750 * Use span=(8*write_bw) in single bdi case as indicated by
751 * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case.
752 *
753 * bdi_thresh thresh - bdi_thresh
754 * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh
755 * thresh thresh
756 */
757 span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16;
758 x_intercept = bdi_setpoint + span;
759
760 if (bdi_dirty < x_intercept - span / 4) {
Wu Fengguang50657fc2011-10-11 17:06:33 -0600761 pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty),
762 x_intercept - bdi_setpoint + 1);
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600763 } else
764 pos_ratio /= 4;
765
Wu Fengguang8927f662011-08-04 22:16:46 -0600766 /*
767 * bdi reserve area, safeguard against dirty pool underrun and disk idle
768 * It may push the desired control point of global dirty pages higher
769 * than setpoint.
770 */
771 x_intercept = bdi_thresh / 2;
772 if (bdi_dirty < x_intercept) {
Wu Fengguang50657fc2011-10-11 17:06:33 -0600773 if (bdi_dirty > x_intercept / 8)
774 pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
775 else
Wu Fengguang8927f662011-08-04 22:16:46 -0600776 pos_ratio *= 8;
777 }
778
Wu Fengguang6c14ae12011-03-02 16:04:18 -0600779 return pos_ratio;
780}
781
Wu Fengguange98be2d2010-08-29 11:22:30 -0600782static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
783 unsigned long elapsed,
784 unsigned long written)
785{
786 const unsigned long period = roundup_pow_of_two(3 * HZ);
787 unsigned long avg = bdi->avg_write_bandwidth;
788 unsigned long old = bdi->write_bandwidth;
789 u64 bw;
790
791 /*
792 * bw = written * HZ / elapsed
793 *
794 * bw * elapsed + write_bandwidth * (period - elapsed)
795 * write_bandwidth = ---------------------------------------------------
796 * period
797 */
798 bw = written - bdi->written_stamp;
799 bw *= HZ;
800 if (unlikely(elapsed > period)) {
801 do_div(bw, elapsed);
802 avg = bw;
803 goto out;
804 }
805 bw += (u64)bdi->write_bandwidth * (period - elapsed);
806 bw >>= ilog2(period);
807
808 /*
809 * one more level of smoothing, for filtering out sudden spikes
810 */
811 if (avg > old && old >= (unsigned long)bw)
812 avg -= (avg - old) >> 3;
813
814 if (avg < old && old <= (unsigned long)bw)
815 avg += (old - avg) >> 3;
816
817out:
818 bdi->write_bandwidth = bw;
819 bdi->avg_write_bandwidth = avg;
820}
821
Wu Fengguangc42843f2011-03-02 15:54:09 -0600822/*
823 * The global dirtyable memory and dirty threshold could be suddenly knocked
824 * down by a large amount (eg. on the startup of KVM in a swapless system).
825 * This may throw the system into deep dirty exceeded state and throttle
826 * heavy/light dirtiers alike. To retain good responsiveness, maintain
827 * global_dirty_limit for tracking slowly down to the knocked down dirty
828 * threshold.
829 */
830static void update_dirty_limit(unsigned long thresh, unsigned long dirty)
831{
832 unsigned long limit = global_dirty_limit;
833
834 /*
835 * Follow up in one step.
836 */
837 if (limit < thresh) {
838 limit = thresh;
839 goto update;
840 }
841
842 /*
843 * Follow down slowly. Use the higher one as the target, because thresh
844 * may drop below dirty. This is exactly the reason to introduce
845 * global_dirty_limit which is guaranteed to lie above the dirty pages.
846 */
847 thresh = max(thresh, dirty);
848 if (limit > thresh) {
849 limit -= (limit - thresh) >> 5;
850 goto update;
851 }
852 return;
853update:
854 global_dirty_limit = limit;
855}
856
857static void global_update_bandwidth(unsigned long thresh,
858 unsigned long dirty,
859 unsigned long now)
860{
861 static DEFINE_SPINLOCK(dirty_lock);
862 static unsigned long update_time;
863
864 /*
865 * check locklessly first to optimize away locking for the most time
866 */
867 if (time_before(now, update_time + BANDWIDTH_INTERVAL))
868 return;
869
870 spin_lock(&dirty_lock);
871 if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) {
872 update_dirty_limit(thresh, dirty);
873 update_time = now;
874 }
875 spin_unlock(&dirty_lock);
876}
877
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600878/*
879 * Maintain bdi->dirty_ratelimit, the base dirty throttle rate.
880 *
881 * Normal bdi tasks will be curbed at or below it in long term.
882 * Obviously it should be around (write_bw / N) when there are N dd tasks.
883 */
884static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
885 unsigned long thresh,
886 unsigned long bg_thresh,
887 unsigned long dirty,
888 unsigned long bdi_thresh,
889 unsigned long bdi_dirty,
890 unsigned long dirtied,
891 unsigned long elapsed)
892{
Wu Fengguang73811312011-08-26 15:53:24 -0600893 unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
894 unsigned long limit = hard_dirty_limit(thresh);
895 unsigned long setpoint = (freerun + limit) / 2;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600896 unsigned long write_bw = bdi->avg_write_bandwidth;
897 unsigned long dirty_ratelimit = bdi->dirty_ratelimit;
898 unsigned long dirty_rate;
899 unsigned long task_ratelimit;
900 unsigned long balanced_dirty_ratelimit;
901 unsigned long pos_ratio;
Wu Fengguang73811312011-08-26 15:53:24 -0600902 unsigned long step;
903 unsigned long x;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600904
905 /*
906 * The dirty rate will match the writeout rate in long term, except
907 * when dirty pages are truncated by userspace or re-dirtied by FS.
908 */
909 dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed;
910
911 pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty,
912 bdi_thresh, bdi_dirty);
913 /*
914 * task_ratelimit reflects each dd's dirty rate for the past 200ms.
915 */
916 task_ratelimit = (u64)dirty_ratelimit *
917 pos_ratio >> RATELIMIT_CALC_SHIFT;
918 task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */
919
920 /*
921 * A linear estimation of the "balanced" throttle rate. The theory is,
922 * if there are N dd tasks, each throttled at task_ratelimit, the bdi's
923 * dirty_rate will be measured to be (N * task_ratelimit). So the below
924 * formula will yield the balanced rate limit (write_bw / N).
925 *
926 * Note that the expanded form is not a pure rate feedback:
927 * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1)
928 * but also takes pos_ratio into account:
929 * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2)
930 *
931 * (1) is not realistic because pos_ratio also takes part in balancing
932 * the dirty rate. Consider the state
933 * pos_ratio = 0.5 (3)
934 * rate = 2 * (write_bw / N) (4)
935 * If (1) is used, it will stuck in that state! Because each dd will
936 * be throttled at
937 * task_ratelimit = pos_ratio * rate = (write_bw / N) (5)
938 * yielding
939 * dirty_rate = N * task_ratelimit = write_bw (6)
940 * put (6) into (1) we get
941 * rate_(i+1) = rate_(i) (7)
942 *
943 * So we end up using (2) to always keep
944 * rate_(i+1) ~= (write_bw / N) (8)
945 * regardless of the value of pos_ratio. As long as (8) is satisfied,
946 * pos_ratio is able to drive itself to 1.0, which is not only where
947 * the dirty count meet the setpoint, but also where the slope of
948 * pos_ratio is most flat and hence task_ratelimit is least fluctuated.
949 */
950 balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw,
951 dirty_rate | 1);
Wu Fengguangbdaac492011-08-03 14:30:36 -0600952 /*
953 * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw
954 */
955 if (unlikely(balanced_dirty_ratelimit > write_bw))
956 balanced_dirty_ratelimit = write_bw;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -0600957
Wu Fengguang73811312011-08-26 15:53:24 -0600958 /*
959 * We could safely do this and return immediately:
960 *
961 * bdi->dirty_ratelimit = balanced_dirty_ratelimit;
962 *
963 * However to get a more stable dirty_ratelimit, the below elaborated
Wanpeng Li331cbde2012-06-09 11:10:55 +0800964 * code makes use of task_ratelimit to filter out singular points and
Wu Fengguang73811312011-08-26 15:53:24 -0600965 * limit the step size.
966 *
967 * The below code essentially only uses the relative value of
968 *
969 * task_ratelimit - dirty_ratelimit
970 * = (pos_ratio - 1) * dirty_ratelimit
971 *
972 * which reflects the direction and size of dirty position error.
973 */
974
975 /*
976 * dirty_ratelimit will follow balanced_dirty_ratelimit iff
977 * task_ratelimit is on the same side of dirty_ratelimit, too.
978 * For example, when
979 * - dirty_ratelimit > balanced_dirty_ratelimit
980 * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint)
981 * lowering dirty_ratelimit will help meet both the position and rate
982 * control targets. Otherwise, don't update dirty_ratelimit if it will
983 * only help meet the rate target. After all, what the users ultimately
984 * feel and care are stable dirty rate and small position error.
985 *
986 * |task_ratelimit - dirty_ratelimit| is used to limit the step size
Wanpeng Li331cbde2012-06-09 11:10:55 +0800987 * and filter out the singular points of balanced_dirty_ratelimit. Which
Wu Fengguang73811312011-08-26 15:53:24 -0600988 * keeps jumping around randomly and can even leap far away at times
989 * due to the small 200ms estimation period of dirty_rate (we want to
990 * keep that period small to reduce time lags).
991 */
992 step = 0;
993 if (dirty < setpoint) {
994 x = min(bdi->balanced_dirty_ratelimit,
995 min(balanced_dirty_ratelimit, task_ratelimit));
996 if (dirty_ratelimit < x)
997 step = x - dirty_ratelimit;
998 } else {
999 x = max(bdi->balanced_dirty_ratelimit,
1000 max(balanced_dirty_ratelimit, task_ratelimit));
1001 if (dirty_ratelimit > x)
1002 step = dirty_ratelimit - x;
1003 }
1004
1005 /*
1006 * Don't pursue 100% rate matching. It's impossible since the balanced
1007 * rate itself is constantly fluctuating. So decrease the track speed
1008 * when it gets close to the target. Helps eliminate pointless tremors.
1009 */
1010 step >>= dirty_ratelimit / (2 * step + 1);
1011 /*
1012 * Limit the tracking speed to avoid overshooting.
1013 */
1014 step = (step + 7) / 8;
1015
1016 if (dirty_ratelimit < balanced_dirty_ratelimit)
1017 dirty_ratelimit += step;
1018 else
1019 dirty_ratelimit -= step;
1020
1021 bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
1022 bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
Wu Fengguangb48c1042011-03-02 17:22:49 -06001023
1024 trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001025}
1026
Wu Fengguange98be2d2010-08-29 11:22:30 -06001027void __bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001028 unsigned long thresh,
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001029 unsigned long bg_thresh,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001030 unsigned long dirty,
1031 unsigned long bdi_thresh,
1032 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -06001033 unsigned long start_time)
1034{
1035 unsigned long now = jiffies;
1036 unsigned long elapsed = now - bdi->bw_time_stamp;
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001037 unsigned long dirtied;
Wu Fengguange98be2d2010-08-29 11:22:30 -06001038 unsigned long written;
1039
1040 /*
1041 * rate-limit, only update once every 200ms.
1042 */
1043 if (elapsed < BANDWIDTH_INTERVAL)
1044 return;
1045
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001046 dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]);
Wu Fengguange98be2d2010-08-29 11:22:30 -06001047 written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
1048
1049 /*
1050 * Skip quiet periods when disk bandwidth is under-utilized.
1051 * (at least 1s idle time between two flusher runs)
1052 */
1053 if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
1054 goto snapshot;
1055
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001056 if (thresh) {
Wu Fengguangc42843f2011-03-02 15:54:09 -06001057 global_update_bandwidth(thresh, dirty, now);
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001058 bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty,
1059 bdi_thresh, bdi_dirty,
1060 dirtied, elapsed);
1061 }
Wu Fengguange98be2d2010-08-29 11:22:30 -06001062 bdi_update_write_bandwidth(bdi, elapsed, written);
1063
1064snapshot:
Wu Fengguangbe3ffa22011-06-12 10:51:31 -06001065 bdi->dirtied_stamp = dirtied;
Wu Fengguange98be2d2010-08-29 11:22:30 -06001066 bdi->written_stamp = written;
1067 bdi->bw_time_stamp = now;
1068}
1069
1070static void bdi_update_bandwidth(struct backing_dev_info *bdi,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001071 unsigned long thresh,
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001072 unsigned long bg_thresh,
Wu Fengguangc42843f2011-03-02 15:54:09 -06001073 unsigned long dirty,
1074 unsigned long bdi_thresh,
1075 unsigned long bdi_dirty,
Wu Fengguange98be2d2010-08-29 11:22:30 -06001076 unsigned long start_time)
1077{
1078 if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
1079 return;
1080 spin_lock(&bdi->wb.list_lock);
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001081 __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty,
1082 bdi_thresh, bdi_dirty, start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -06001083 spin_unlock(&bdi->wb.list_lock);
1084}
1085
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086/*
Namjae Jeond0e1d662012-12-11 16:00:21 -08001087 * After a task dirtied this many pages, balance_dirty_pages_ratelimited()
Wu Fengguang9d823e82011-06-11 18:10:12 -06001088 * will look to see if it needs to start dirty throttling.
1089 *
1090 * If dirty_poll_interval is too low, big NUMA machines will call the expensive
1091 * global_page_state() too often. So scale it near-sqrt to the safety margin
1092 * (the number of pages we may dirty without exceeding the dirty limits).
1093 */
1094static unsigned long dirty_poll_interval(unsigned long dirty,
1095 unsigned long thresh)
1096{
1097 if (thresh > dirty)
1098 return 1UL << (ilog2(thresh - dirty) >> 1);
1099
1100 return 1;
1101}
1102
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001103static long bdi_max_pause(struct backing_dev_info *bdi,
1104 unsigned long bdi_dirty)
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001105{
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001106 long bw = bdi->avg_write_bandwidth;
1107 long t;
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001108
1109 /*
1110 * Limit pause time for small memory systems. If sleeping for too long
1111 * time, a small pool of dirty/writeback pages may go empty and disk go
1112 * idle.
1113 *
1114 * 8 serves as the safety ratio.
1115 */
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001116 t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
1117 t++;
1118
1119 return min_t(long, t, MAX_PAUSE);
1120}
1121
1122static long bdi_min_pause(struct backing_dev_info *bdi,
1123 long max_pause,
1124 unsigned long task_ratelimit,
1125 unsigned long dirty_ratelimit,
1126 int *nr_dirtied_pause)
1127{
1128 long hi = ilog2(bdi->avg_write_bandwidth);
1129 long lo = ilog2(bdi->dirty_ratelimit);
1130 long t; /* target pause */
1131 long pause; /* estimated next pause */
1132 int pages; /* target nr_dirtied_pause */
1133
1134 /* target for 10ms pause on 1-dd case */
1135 t = max(1, HZ / 100);
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001136
1137 /*
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001138 * Scale up pause time for concurrent dirtiers in order to reduce CPU
1139 * overheads.
1140 *
1141 * (N * 10ms) on 2^N concurrent tasks.
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001142 */
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001143 if (hi > lo)
1144 t += (hi - lo) * (10 * HZ) / 1024;
1145
1146 /*
1147 * This is a bit convoluted. We try to base the next nr_dirtied_pause
1148 * on the much more stable dirty_ratelimit. However the next pause time
1149 * will be computed based on task_ratelimit and the two rate limits may
1150 * depart considerably at some time. Especially if task_ratelimit goes
1151 * below dirty_ratelimit/2 and the target pause is max_pause, the next
1152 * pause time will be max_pause*2 _trimmed down_ to max_pause. As a
1153 * result task_ratelimit won't be executed faithfully, which could
1154 * eventually bring down dirty_ratelimit.
1155 *
1156 * We apply two rules to fix it up:
1157 * 1) try to estimate the next pause time and if necessary, use a lower
1158 * nr_dirtied_pause so as not to exceed max_pause. When this happens,
1159 * nr_dirtied_pause will be "dancing" with task_ratelimit.
1160 * 2) limit the target pause time to max_pause/2, so that the normal
1161 * small fluctuations of task_ratelimit won't trigger rule (1) and
1162 * nr_dirtied_pause will remain as stable as dirty_ratelimit.
1163 */
1164 t = min(t, 1 + max_pause / 2);
1165 pages = dirty_ratelimit * t / roundup_pow_of_two(HZ);
1166
Wu Fengguang5b9b3572011-12-06 13:17:17 -06001167 /*
1168 * Tiny nr_dirtied_pause is found to hurt I/O performance in the test
1169 * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}.
1170 * When the 16 consecutive reads are often interrupted by some dirty
1171 * throttling pause during the async writes, cfq will go into idles
1172 * (deadline is fine). So push nr_dirtied_pause as high as possible
1173 * until reaches DIRTY_POLL_THRESH=32 pages.
1174 */
1175 if (pages < DIRTY_POLL_THRESH) {
1176 t = max_pause;
1177 pages = dirty_ratelimit * t / roundup_pow_of_two(HZ);
1178 if (pages > DIRTY_POLL_THRESH) {
1179 pages = DIRTY_POLL_THRESH;
1180 t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit;
1181 }
1182 }
1183
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001184 pause = HZ * pages / (task_ratelimit + 1);
1185 if (pause > max_pause) {
1186 t = max_pause;
1187 pages = task_ratelimit * t / roundup_pow_of_two(HZ);
1188 }
1189
1190 *nr_dirtied_pause = pages;
1191 /*
1192 * The minimal pause time will normally be half the target pause time.
1193 */
Wu Fengguang5b9b3572011-12-06 13:17:17 -06001194 return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t;
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001195}
1196
Wu Fengguang9d823e82011-06-11 18:10:12 -06001197/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001198 * balance_dirty_pages() must be called by processes which are generating dirty
1199 * data. It looks at the number of dirty pages in the machine and will force
Wu Fengguang143dfe82010-08-27 18:45:12 -06001200 * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2.
Jens Axboe5b0830c2009-09-23 19:37:09 +02001201 * If we're over `background_thresh' then the writeback threads are woken to
1202 * perform some writeout.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001203 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +08001204static void balance_dirty_pages(struct address_space *mapping,
Wu Fengguang143dfe82010-08-27 18:45:12 -06001205 unsigned long pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001206{
Wu Fengguang143dfe82010-08-27 18:45:12 -06001207 unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
1208 unsigned long bdi_reclaimable;
Wu Fengguang77627412010-09-12 13:34:05 -06001209 unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
1210 unsigned long bdi_dirty;
Wu Fengguang6c14ae12011-03-02 16:04:18 -06001211 unsigned long freerun;
David Rientjes364aeb22009-01-06 14:39:29 -08001212 unsigned long background_thresh;
1213 unsigned long dirty_thresh;
1214 unsigned long bdi_thresh;
Wu Fengguang83712352011-06-11 19:25:42 -06001215 long period;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001216 long pause;
1217 long max_pause;
1218 long min_pause;
1219 int nr_dirtied_pause;
Wu Fengguange50e3722010-08-11 14:17:37 -07001220 bool dirty_exceeded = false;
Wu Fengguang143dfe82010-08-27 18:45:12 -06001221 unsigned long task_ratelimit;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001222 unsigned long dirty_ratelimit;
Wu Fengguang143dfe82010-08-27 18:45:12 -06001223 unsigned long pos_ratio;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001224 struct backing_dev_info *bdi = mapping->backing_dev_info;
Wu Fengguange98be2d2010-08-29 11:22:30 -06001225 unsigned long start_time = jiffies;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226
1227 for (;;) {
Wu Fengguang83712352011-06-11 19:25:42 -06001228 unsigned long now = jiffies;
1229
Wu Fengguang143dfe82010-08-27 18:45:12 -06001230 /*
1231 * Unstable writes are a feature of certain networked
1232 * filesystems (i.e. NFS) in which data may have been
1233 * written to the server's write cache, but has not yet
1234 * been flushed to permanent storage.
1235 */
Peter Zijlstra5fce25a2007-11-14 16:59:15 -08001236 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
1237 global_page_state(NR_UNSTABLE_NFS);
Wu Fengguang77627412010-09-12 13:34:05 -06001238 nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
Peter Zijlstra5fce25a2007-11-14 16:59:15 -08001239
Wu Fengguang16c40422010-08-11 14:17:39 -07001240 global_dirty_limits(&background_thresh, &dirty_thresh);
1241
1242 /*
1243 * Throttle it only when the background writeback cannot
1244 * catch-up. This avoids (excessively) small writeouts
1245 * when the bdi limits are ramping up.
1246 */
Wu Fengguang6c14ae12011-03-02 16:04:18 -06001247 freerun = dirty_freerun_ceiling(dirty_thresh,
1248 background_thresh);
Wu Fengguang83712352011-06-11 19:25:42 -06001249 if (nr_dirty <= freerun) {
1250 current->dirty_paused_when = now;
1251 current->nr_dirtied = 0;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001252 current->nr_dirtied_pause =
1253 dirty_poll_interval(nr_dirty, dirty_thresh);
Wu Fengguang16c40422010-08-11 14:17:39 -07001254 break;
Wu Fengguang83712352011-06-11 19:25:42 -06001255 }
Wu Fengguang16c40422010-08-11 14:17:39 -07001256
Wu Fengguang143dfe82010-08-27 18:45:12 -06001257 if (unlikely(!writeback_in_progress(bdi)))
1258 bdi_start_background_writeback(bdi);
1259
1260 /*
1261 * bdi_thresh is not treated as some limiting factor as
1262 * dirty_thresh, due to reasons
1263 * - in JBOD setup, bdi_thresh can fluctuate a lot
1264 * - in a system with HDD and USB key, the USB key may somehow
1265 * go into state (bdi_dirty >> bdi_thresh) either because
1266 * bdi_dirty starts high, or because bdi_thresh drops low.
1267 * In this case we don't want to hard throttle the USB key
1268 * dirtiers for 100 seconds until bdi_dirty drops under
1269 * bdi_thresh. Instead the auxiliary bdi control line in
1270 * bdi_position_ratio() will let the dirtier task progress
1271 * at some rate <= (write_bw / 2) for bringing down bdi_dirty.
1272 */
Wu Fengguang16c40422010-08-11 14:17:39 -07001273 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
Wu Fengguang16c40422010-08-11 14:17:39 -07001274
Wu Fengguange50e3722010-08-11 14:17:37 -07001275 /*
1276 * In order to avoid the stacked BDI deadlock we need
1277 * to ensure we accurately count the 'dirty' pages when
1278 * the threshold is low.
1279 *
1280 * Otherwise it would be possible to get thresh+n pages
1281 * reported dirty, even though there are thresh-m pages
1282 * actually dirty; with m+n sitting in the percpu
1283 * deltas.
1284 */
Wu Fengguang143dfe82010-08-27 18:45:12 -06001285 if (bdi_thresh < 2 * bdi_stat_error(bdi)) {
1286 bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
1287 bdi_dirty = bdi_reclaimable +
Wu Fengguang77627412010-09-12 13:34:05 -06001288 bdi_stat_sum(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -07001289 } else {
Wu Fengguang143dfe82010-08-27 18:45:12 -06001290 bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
1291 bdi_dirty = bdi_reclaimable +
Wu Fengguang77627412010-09-12 13:34:05 -06001292 bdi_stat(bdi, BDI_WRITEBACK);
Wu Fengguange50e3722010-08-11 14:17:37 -07001293 }
Peter Zijlstra5fce25a2007-11-14 16:59:15 -08001294
Wu Fengguang82791942011-12-03 21:26:01 -06001295 dirty_exceeded = (bdi_dirty > bdi_thresh) &&
Wu Fengguang77627412010-09-12 13:34:05 -06001296 (nr_dirty > dirty_thresh);
Wu Fengguang143dfe82010-08-27 18:45:12 -06001297 if (dirty_exceeded && !bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001298 bdi->dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001299
Wu Fengguangaf6a3112011-10-03 20:46:17 -06001300 bdi_update_bandwidth(bdi, dirty_thresh, background_thresh,
1301 nr_dirty, bdi_thresh, bdi_dirty,
1302 start_time);
Wu Fengguange98be2d2010-08-29 11:22:30 -06001303
Wu Fengguang143dfe82010-08-27 18:45:12 -06001304 dirty_ratelimit = bdi->dirty_ratelimit;
1305 pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
1306 background_thresh, nr_dirty,
1307 bdi_thresh, bdi_dirty);
Wu Fengguang3a73dbb2011-11-07 19:19:28 +08001308 task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >>
1309 RATELIMIT_CALC_SHIFT;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001310 max_pause = bdi_max_pause(bdi, bdi_dirty);
1311 min_pause = bdi_min_pause(bdi, max_pause,
1312 task_ratelimit, dirty_ratelimit,
1313 &nr_dirtied_pause);
1314
Wu Fengguang3a73dbb2011-11-07 19:19:28 +08001315 if (unlikely(task_ratelimit == 0)) {
Wu Fengguang83712352011-06-11 19:25:42 -06001316 period = max_pause;
Wu Fengguangc8462cc2011-06-11 19:21:43 -06001317 pause = max_pause;
Wu Fengguang143dfe82010-08-27 18:45:12 -06001318 goto pause;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 }
Wu Fengguang83712352011-06-11 19:25:42 -06001320 period = HZ * pages_dirtied / task_ratelimit;
1321 pause = period;
1322 if (current->dirty_paused_when)
1323 pause -= now - current->dirty_paused_when;
1324 /*
1325 * For less than 1s think time (ext3/4 may block the dirtier
1326 * for up to 800ms from time to time on 1-HDD; so does xfs,
1327 * however at much less frequency), try to compensate it in
1328 * future periods by updating the virtual time; otherwise just
1329 * do a reset, as it may be a light dirtier.
1330 */
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001331 if (pause < min_pause) {
Wu Fengguangece13ac2010-08-29 23:33:20 -06001332 trace_balance_dirty_pages(bdi,
1333 dirty_thresh,
1334 background_thresh,
1335 nr_dirty,
1336 bdi_thresh,
1337 bdi_dirty,
1338 dirty_ratelimit,
1339 task_ratelimit,
1340 pages_dirtied,
Wu Fengguang83712352011-06-11 19:25:42 -06001341 period,
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001342 min(pause, 0L),
Wu Fengguangece13ac2010-08-29 23:33:20 -06001343 start_time);
Wu Fengguang83712352011-06-11 19:25:42 -06001344 if (pause < -HZ) {
1345 current->dirty_paused_when = now;
1346 current->nr_dirtied = 0;
1347 } else if (period) {
1348 current->dirty_paused_when += period;
1349 current->nr_dirtied = 0;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001350 } else if (current->nr_dirtied_pause <= pages_dirtied)
1351 current->nr_dirtied_pause += pages_dirtied;
Wu Fengguang57fc9782011-06-11 19:32:32 -06001352 break;
1353 }
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001354 if (unlikely(pause > max_pause)) {
1355 /* for occasional dropped task_ratelimit */
1356 now += min(pause - max_pause, max_pause);
1357 pause = max_pause;
1358 }
Wu Fengguang143dfe82010-08-27 18:45:12 -06001359
1360pause:
Wu Fengguangece13ac2010-08-29 23:33:20 -06001361 trace_balance_dirty_pages(bdi,
1362 dirty_thresh,
1363 background_thresh,
1364 nr_dirty,
1365 bdi_thresh,
1366 bdi_dirty,
1367 dirty_ratelimit,
1368 task_ratelimit,
1369 pages_dirtied,
Wu Fengguang83712352011-06-11 19:25:42 -06001370 period,
Wu Fengguangece13ac2010-08-29 23:33:20 -06001371 pause,
1372 start_time);
Jan Kara499d05e2011-11-16 19:34:48 +08001373 __set_current_state(TASK_KILLABLE);
Wu Fengguangd25105e2009-10-09 12:40:42 +02001374 io_schedule_timeout(pause);
Jens Axboe87c6a9b2009-09-17 19:59:14 +02001375
Wu Fengguang83712352011-06-11 19:25:42 -06001376 current->dirty_paused_when = now + pause;
1377 current->nr_dirtied = 0;
Wu Fengguang7ccb9ad2011-11-30 11:08:55 -06001378 current->nr_dirtied_pause = nr_dirtied_pause;
Wu Fengguang83712352011-06-11 19:25:42 -06001379
Wu Fengguangffd1f602011-06-19 22:18:42 -06001380 /*
Wu Fengguang1df64712011-11-13 19:47:32 -06001381 * This is typically equal to (nr_dirty < dirty_thresh) and can
1382 * also keep "1000+ dd on a slow USB stick" under control.
Wu Fengguangffd1f602011-06-19 22:18:42 -06001383 */
Wu Fengguang1df64712011-11-13 19:47:32 -06001384 if (task_ratelimit)
Wu Fengguangffd1f602011-06-19 22:18:42 -06001385 break;
Jan Kara499d05e2011-11-16 19:34:48 +08001386
Wu Fengguangc5c63432011-12-02 10:21:33 -06001387 /*
1388 * In the case of an unresponding NFS server and the NFS dirty
1389 * pages exceeds dirty_thresh, give the other good bdi's a pipe
1390 * to go through, so that tasks on them still remain responsive.
1391 *
1392 * In theory 1 page is enough to keep the comsumer-producer
1393 * pipe going: the flusher cleans 1 page => the task dirties 1
1394 * more page. However bdi_dirty has accounting errors. So use
1395 * the larger and more IO friendly bdi_stat_error.
1396 */
1397 if (bdi_dirty <= bdi_stat_error(bdi))
1398 break;
1399
Jan Kara499d05e2011-11-16 19:34:48 +08001400 if (fatal_signal_pending(current))
1401 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001402 }
1403
Wu Fengguang143dfe82010-08-27 18:45:12 -06001404 if (!dirty_exceeded && bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001405 bdi->dirty_exceeded = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001406
1407 if (writeback_in_progress(bdi))
Jens Axboe5b0830c2009-09-23 19:37:09 +02001408 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409
1410 /*
1411 * In laptop mode, we wait until hitting the higher threshold before
1412 * starting background writeout, and then write out all the way down
1413 * to the lower threshold. So slow writers cause minimal disk activity.
1414 *
1415 * In normal mode, we start background writeout at the lower
1416 * background_thresh, to keep the amount of dirty memory low.
1417 */
Wu Fengguang143dfe82010-08-27 18:45:12 -06001418 if (laptop_mode)
1419 return;
1420
1421 if (nr_reclaimable > background_thresh)
Christoph Hellwigc5444192010-06-08 18:15:15 +02001422 bdi_start_background_writeback(bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423}
1424
Peter Zijlstraa200ee12007-10-08 18:54:37 +02001425void set_page_dirty_balance(struct page *page, int page_mkwrite)
Peter Zijlstraedc79b22006-09-25 23:30:58 -07001426{
Peter Zijlstraa200ee12007-10-08 18:54:37 +02001427 if (set_page_dirty(page) || page_mkwrite) {
Peter Zijlstraedc79b22006-09-25 23:30:58 -07001428 struct address_space *mapping = page_mapping(page);
1429
1430 if (mapping)
1431 balance_dirty_pages_ratelimited(mapping);
1432 }
1433}
1434
Wu Fengguang9d823e82011-06-11 18:10:12 -06001435static DEFINE_PER_CPU(int, bdp_ratelimits);
Tejun Heo245b2e72009-06-24 15:13:48 +09001436
Wu Fengguang54848d72011-04-05 13:21:19 -06001437/*
1438 * Normal tasks are throttled by
1439 * loop {
1440 * dirty tsk->nr_dirtied_pause pages;
1441 * take a snap in balance_dirty_pages();
1442 * }
1443 * However there is a worst case. If every task exit immediately when dirtied
1444 * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be
1445 * called to throttle the page dirties. The solution is to save the not yet
1446 * throttled page dirties in dirty_throttle_leaks on task exit and charge them
1447 * randomly into the running tasks. This works well for the above worst case,
1448 * as the new task will pick up and accumulate the old task's leaked dirty
1449 * count and eventually get throttled.
1450 */
1451DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
1452
Linus Torvalds1da177e2005-04-16 15:20:36 -07001453/**
Namjae Jeond0e1d662012-12-11 16:00:21 -08001454 * balance_dirty_pages_ratelimited - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -07001455 * @mapping: address_space which was dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456 *
1457 * Processes which are dirtying memory should call in here once for each page
1458 * which was newly dirtied. The function will periodically check the system's
1459 * dirty state and will initiate writeback if needed.
1460 *
1461 * On really big machines, get_writeback_state is expensive, so try to avoid
1462 * calling it too often (ratelimiting). But once we're over the dirty memory
1463 * limit we decrease the ratelimiting by a lot, to prevent individual processes
1464 * from overshooting the limit by (ratelimit_pages) each.
1465 */
Namjae Jeond0e1d662012-12-11 16:00:21 -08001466void balance_dirty_pages_ratelimited(struct address_space *mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467{
Wu Fengguang36715ce2011-06-11 17:53:57 -06001468 struct backing_dev_info *bdi = mapping->backing_dev_info;
Wu Fengguang9d823e82011-06-11 18:10:12 -06001469 int ratelimit;
1470 int *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471
Wu Fengguang36715ce2011-06-11 17:53:57 -06001472 if (!bdi_cap_account_dirty(bdi))
1473 return;
1474
Wu Fengguang9d823e82011-06-11 18:10:12 -06001475 ratelimit = current->nr_dirtied_pause;
1476 if (bdi->dirty_exceeded)
1477 ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478
Andrew Mortonfa5a7342006-03-24 03:18:10 -08001479 preempt_disable();
Wu Fengguang9d823e82011-06-11 18:10:12 -06001480 /*
1481 * This prevents one CPU to accumulate too many dirtied pages without
1482 * calling into balance_dirty_pages(), which can happen when there are
1483 * 1000+ tasks, all of them start dirtying pages at exactly the same
1484 * time, hence all honoured too large initial task->nr_dirtied_pause.
1485 */
Tejun Heo245b2e72009-06-24 15:13:48 +09001486 p = &__get_cpu_var(bdp_ratelimits);
Wu Fengguang9d823e82011-06-11 18:10:12 -06001487 if (unlikely(current->nr_dirtied >= ratelimit))
Andrew Mortonfa5a7342006-03-24 03:18:10 -08001488 *p = 0;
Wu Fengguangd3bc1fe2011-04-14 07:52:37 -06001489 else if (unlikely(*p >= ratelimit_pages)) {
1490 *p = 0;
1491 ratelimit = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001492 }
Wu Fengguang54848d72011-04-05 13:21:19 -06001493 /*
1494 * Pick up the dirtied pages by the exited tasks. This avoids lots of
1495 * short-lived tasks (eg. gcc invocations in a kernel build) escaping
1496 * the dirty throttling and livelock other long-run dirtiers.
1497 */
1498 p = &__get_cpu_var(dirty_throttle_leaks);
1499 if (*p > 0 && current->nr_dirtied < ratelimit) {
Namjae Jeond0e1d662012-12-11 16:00:21 -08001500 unsigned long nr_pages_dirtied;
Wu Fengguang54848d72011-04-05 13:21:19 -06001501 nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied);
1502 *p -= nr_pages_dirtied;
1503 current->nr_dirtied += nr_pages_dirtied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -08001505 preempt_enable();
Wu Fengguang9d823e82011-06-11 18:10:12 -06001506
1507 if (unlikely(current->nr_dirtied >= ratelimit))
1508 balance_dirty_pages(mapping, current->nr_dirtied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001509}
Namjae Jeond0e1d662012-12-11 16:00:21 -08001510EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001511
Andrew Morton232ea4d2007-02-28 20:13:21 -08001512void throttle_vm_writeout(gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001513{
David Rientjes364aeb22009-01-06 14:39:29 -08001514 unsigned long background_thresh;
1515 unsigned long dirty_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001516
1517 for ( ; ; ) {
Wu Fengguang16c40422010-08-11 14:17:39 -07001518 global_dirty_limits(&background_thresh, &dirty_thresh);
Fengguang Wu47a13332012-03-21 16:34:09 -07001519 dirty_thresh = hard_dirty_limit(dirty_thresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520
1521 /*
1522 * Boost the allowable dirty threshold a bit for page
1523 * allocators so they don't get DoS'ed by heavy writers
1524 */
1525 dirty_thresh += dirty_thresh / 10; /* wheeee... */
1526
Christoph Lameterc24f21b2006-06-30 01:55:42 -07001527 if (global_page_state(NR_UNSTABLE_NFS) +
1528 global_page_state(NR_WRITEBACK) <= dirty_thresh)
1529 break;
Jens Axboe8aa7e842009-07-09 14:52:32 +02001530 congestion_wait(BLK_RW_ASYNC, HZ/10);
Fengguang Wu369f2382007-10-16 23:30:45 -07001531
1532 /*
1533 * The caller might hold locks which can prevent IO completion
1534 * or progress in the filesystem. So we cannot just sit here
1535 * waiting for IO to complete.
1536 */
1537 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
1538 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539 }
1540}
1541
Linus Torvalds1da177e2005-04-16 15:20:36 -07001542/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
1544 */
1545int dirty_writeback_centisecs_handler(ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001546 void __user *buffer, size_t *length, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547{
Alexey Dobriyan8d65af72009-09-23 15:57:19 -07001548 proc_dointvec(table, write, buffer, length, ppos);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001549 return 0;
1550}
1551
Jens Axboec2c49862010-05-20 09:18:47 +02001552#ifdef CONFIG_BLOCK
Matthew Garrett31373d02010-04-06 14:25:14 +02001553void laptop_mode_timer_fn(unsigned long data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554{
Matthew Garrett31373d02010-04-06 14:25:14 +02001555 struct request_queue *q = (struct request_queue *)data;
1556 int nr_pages = global_page_state(NR_FILE_DIRTY) +
1557 global_page_state(NR_UNSTABLE_NFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558
Matthew Garrett31373d02010-04-06 14:25:14 +02001559 /*
1560 * We want to write everything out, not just down to the dirty
1561 * threshold
1562 */
Matthew Garrett31373d02010-04-06 14:25:14 +02001563 if (bdi_has_dirty_io(&q->backing_dev_info))
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -06001564 bdi_start_writeback(&q->backing_dev_info, nr_pages,
1565 WB_REASON_LAPTOP_TIMER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566}
1567
1568/*
1569 * We've spun up the disk and we're in laptop mode: schedule writeback
1570 * of all dirty data a few seconds from now. If the flush is already scheduled
1571 * then push it back - the user is still using the disk.
1572 */
Matthew Garrett31373d02010-04-06 14:25:14 +02001573void laptop_io_completion(struct backing_dev_info *info)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001574{
Matthew Garrett31373d02010-04-06 14:25:14 +02001575 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576}
1577
1578/*
1579 * We're in laptop mode and we've just synced. The sync's writes will have
1580 * caused another writeback to be scheduled by laptop_io_completion.
1581 * Nothing needs to be written back anymore, so we unschedule the writeback.
1582 */
1583void laptop_sync_completion(void)
1584{
Matthew Garrett31373d02010-04-06 14:25:14 +02001585 struct backing_dev_info *bdi;
1586
1587 rcu_read_lock();
1588
1589 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
1590 del_timer(&bdi->laptop_mode_wb_timer);
1591
1592 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001593}
Jens Axboec2c49862010-05-20 09:18:47 +02001594#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595
1596/*
1597 * If ratelimit_pages is too high then we can get into dirty-data overload
1598 * if a large number of processes all perform writes at the same time.
1599 * If it is too low then SMP machines will call the (expensive)
1600 * get_writeback_state too often.
1601 *
1602 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
1603 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
Wu Fengguang9d823e82011-06-11 18:10:12 -06001604 * thresholds.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605 */
1606
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -07001607void writeback_set_ratelimit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001608{
Wu Fengguang9d823e82011-06-11 18:10:12 -06001609 unsigned long background_thresh;
1610 unsigned long dirty_thresh;
1611 global_dirty_limits(&background_thresh, &dirty_thresh);
Fengguang Wu68809c72012-05-06 13:21:42 +08001612 global_dirty_limit = dirty_thresh;
Wu Fengguang9d823e82011-06-11 18:10:12 -06001613 ratelimit_pages = dirty_thresh / (num_online_cpus() * 32);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001614 if (ratelimit_pages < 16)
1615 ratelimit_pages = 16;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001616}
1617
Chandra Seetharaman26c21432006-06-27 02:54:10 -07001618static int __cpuinit
Srivatsa S. Bhat2f60d622012-09-28 20:27:49 +08001619ratelimit_handler(struct notifier_block *self, unsigned long action,
1620 void *hcpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621{
Srivatsa S. Bhat2f60d622012-09-28 20:27:49 +08001622
1623 switch (action & ~CPU_TASKS_FROZEN) {
1624 case CPU_ONLINE:
1625 case CPU_DEAD:
1626 writeback_set_ratelimit();
1627 return NOTIFY_OK;
1628 default:
1629 return NOTIFY_DONE;
1630 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631}
1632
Chandra Seetharaman74b85f32006-06-27 02:54:09 -07001633static struct notifier_block __cpuinitdata ratelimit_nb = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634 .notifier_call = ratelimit_handler,
1635 .next = NULL,
1636};
1637
1638/*
Linus Torvaldsdc6e29d2007-01-29 16:37:38 -08001639 * Called early on to tune the page writeback dirty limits.
1640 *
1641 * We used to scale dirty pages according to how total memory
1642 * related to pages that could be allocated for buffers (by
1643 * comparing nr_free_buffer_pages() to vm_total_pages.
1644 *
1645 * However, that was when we used "dirty_ratio" to scale with
1646 * all memory, and we don't do that any more. "dirty_ratio"
1647 * is now applied to total non-HIGHPAGE memory (by subtracting
1648 * totalhigh_pages from vm_total_pages), and as such we can't
1649 * get into the old insane situation any more where we had
1650 * large amounts of dirty pages compared to a small amount of
1651 * non-HIGHMEM memory.
1652 *
1653 * But we might still want to scale the dirty_ratio by how
1654 * much memory the box has..
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 */
1656void __init page_writeback_init(void)
1657{
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -07001658 writeback_set_ratelimit();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659 register_cpu_notifier(&ratelimit_nb);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001660
Jan Karaeb608e32012-05-24 18:59:11 +02001661 fprop_global_init(&writeout_completions);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662}
1663
David Howells811d7362006-08-29 19:06:09 +01001664/**
Jan Karaf446daae2010-08-09 17:19:12 -07001665 * tag_pages_for_writeback - tag pages to be written by write_cache_pages
1666 * @mapping: address space structure to write
1667 * @start: starting page index
1668 * @end: ending page index (inclusive)
1669 *
1670 * This function scans the page range from @start to @end (inclusive) and tags
1671 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
1672 * that write_cache_pages (or whoever calls this function) will then use
1673 * TOWRITE tag to identify pages eligible for writeback. This mechanism is
1674 * used to avoid livelocking of writeback by a process steadily creating new
1675 * dirty pages in the file (thus it is important for this function to be quick
1676 * so that it can tag pages faster than a dirtying process can create them).
1677 */
1678/*
1679 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
1680 */
Jan Karaf446daae2010-08-09 17:19:12 -07001681void tag_pages_for_writeback(struct address_space *mapping,
1682 pgoff_t start, pgoff_t end)
1683{
Randy Dunlap3c111a02010-08-11 14:17:30 -07001684#define WRITEBACK_TAG_BATCH 4096
Jan Karaf446daae2010-08-09 17:19:12 -07001685 unsigned long tagged;
1686
1687 do {
1688 spin_lock_irq(&mapping->tree_lock);
1689 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
1690 &start, end, WRITEBACK_TAG_BATCH,
1691 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
1692 spin_unlock_irq(&mapping->tree_lock);
1693 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
1694 cond_resched();
Jan Karad5ed3a42010-08-19 14:13:33 -07001695 /* We check 'start' to handle wrapping when end == ~0UL */
1696 } while (tagged >= WRITEBACK_TAG_BATCH && start);
Jan Karaf446daae2010-08-09 17:19:12 -07001697}
1698EXPORT_SYMBOL(tag_pages_for_writeback);
1699
1700/**
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001701 * 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 +01001702 * @mapping: address space structure to write
1703 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001704 * @writepage: function called for each page
1705 * @data: data passed to writepage function
David Howells811d7362006-08-29 19:06:09 +01001706 *
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001707 * If a page is already under I/O, write_cache_pages() skips it, even
David Howells811d7362006-08-29 19:06:09 +01001708 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
1709 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
1710 * and msync() need to guarantee that all the data which was dirty at the time
1711 * the call was made get new I/O started against them. If wbc->sync_mode is
1712 * WB_SYNC_ALL then we were called for data integrity and we must wait for
1713 * existing IO to complete.
Jan Karaf446daae2010-08-09 17:19:12 -07001714 *
1715 * To avoid livelocks (when other process dirties new pages), we first tag
1716 * pages which should be written back with TOWRITE tag and only then start
1717 * writing them. For data-integrity sync we have to be careful so that we do
1718 * not miss some pages (e.g., because some other process has cleared TOWRITE
1719 * tag we set). The rule we follow is that TOWRITE tag can be cleared only
1720 * by the process clearing the DIRTY tag (and submitting the page for IO).
David Howells811d7362006-08-29 19:06:09 +01001721 */
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001722int write_cache_pages(struct address_space *mapping,
1723 struct writeback_control *wbc, writepage_t writepage,
1724 void *data)
David Howells811d7362006-08-29 19:06:09 +01001725{
David Howells811d7362006-08-29 19:06:09 +01001726 int ret = 0;
1727 int done = 0;
David Howells811d7362006-08-29 19:06:09 +01001728 struct pagevec pvec;
1729 int nr_pages;
Nick Piggin31a12662009-01-06 14:39:04 -08001730 pgoff_t uninitialized_var(writeback_index);
David Howells811d7362006-08-29 19:06:09 +01001731 pgoff_t index;
1732 pgoff_t end; /* Inclusive */
Nick Pigginbd19e012009-01-06 14:39:06 -08001733 pgoff_t done_index;
Nick Piggin31a12662009-01-06 14:39:04 -08001734 int cycled;
David Howells811d7362006-08-29 19:06:09 +01001735 int range_whole = 0;
Jan Karaf446daae2010-08-09 17:19:12 -07001736 int tag;
David Howells811d7362006-08-29 19:06:09 +01001737
David Howells811d7362006-08-29 19:06:09 +01001738 pagevec_init(&pvec, 0);
1739 if (wbc->range_cyclic) {
Nick Piggin31a12662009-01-06 14:39:04 -08001740 writeback_index = mapping->writeback_index; /* prev offset */
1741 index = writeback_index;
1742 if (index == 0)
1743 cycled = 1;
1744 else
1745 cycled = 0;
David Howells811d7362006-08-29 19:06:09 +01001746 end = -1;
1747 } else {
1748 index = wbc->range_start >> PAGE_CACHE_SHIFT;
1749 end = wbc->range_end >> PAGE_CACHE_SHIFT;
1750 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
1751 range_whole = 1;
Nick Piggin31a12662009-01-06 14:39:04 -08001752 cycled = 1; /* ignore range_cyclic tests */
David Howells811d7362006-08-29 19:06:09 +01001753 }
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001754 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daae2010-08-09 17:19:12 -07001755 tag = PAGECACHE_TAG_TOWRITE;
1756 else
1757 tag = PAGECACHE_TAG_DIRTY;
David Howells811d7362006-08-29 19:06:09 +01001758retry:
Wu Fengguang6e6938b2010-06-06 10:38:15 -06001759 if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
Jan Karaf446daae2010-08-09 17:19:12 -07001760 tag_pages_for_writeback(mapping, index, end);
Nick Pigginbd19e012009-01-06 14:39:06 -08001761 done_index = index;
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001762 while (!done && (index <= end)) {
1763 int i;
1764
Jan Karaf446daae2010-08-09 17:19:12 -07001765 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001766 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
1767 if (nr_pages == 0)
1768 break;
David Howells811d7362006-08-29 19:06:09 +01001769
David Howells811d7362006-08-29 19:06:09 +01001770 for (i = 0; i < nr_pages; i++) {
1771 struct page *page = pvec.pages[i];
1772
Nick Piggind5482cd2009-01-06 14:39:11 -08001773 /*
1774 * At this point, the page may be truncated or
1775 * invalidated (changing page->mapping to NULL), or
1776 * even swizzled back from swapper_space to tmpfs file
1777 * mapping. However, page->index will not change
1778 * because we have a reference on the page.
1779 */
1780 if (page->index > end) {
1781 /*
1782 * can't be range_cyclic (1st pass) because
1783 * end == -1 in that case.
1784 */
1785 done = 1;
1786 break;
1787 }
1788
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001789 done_index = page->index;
Nick Pigginbd19e012009-01-06 14:39:06 -08001790
David Howells811d7362006-08-29 19:06:09 +01001791 lock_page(page);
1792
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001793 /*
1794 * Page truncated or invalidated. We can freely skip it
1795 * then, even for data integrity operations: the page
1796 * has disappeared concurrently, so there could be no
1797 * real expectation of this data interity operation
1798 * even if there is now a new, dirty page at the same
1799 * pagecache address.
1800 */
David Howells811d7362006-08-29 19:06:09 +01001801 if (unlikely(page->mapping != mapping)) {
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001802continue_unlock:
David Howells811d7362006-08-29 19:06:09 +01001803 unlock_page(page);
1804 continue;
1805 }
1806
Nick Piggin515f4a02009-01-06 14:39:10 -08001807 if (!PageDirty(page)) {
1808 /* someone wrote it for us */
1809 goto continue_unlock;
1810 }
David Howells811d7362006-08-29 19:06:09 +01001811
Nick Piggin515f4a02009-01-06 14:39:10 -08001812 if (PageWriteback(page)) {
1813 if (wbc->sync_mode != WB_SYNC_NONE)
1814 wait_on_page_writeback(page);
1815 else
1816 goto continue_unlock;
1817 }
1818
1819 BUG_ON(PageWriteback(page));
1820 if (!clear_page_dirty_for_io(page))
Nick Piggin5a3d5c92009-01-06 14:39:09 -08001821 goto continue_unlock;
David Howells811d7362006-08-29 19:06:09 +01001822
Dave Chinner9e094382010-07-07 13:24:08 +10001823 trace_wbc_writepage(wbc, mapping->backing_dev_info);
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001824 ret = (*writepage)(page, wbc, data);
Nick Piggin00266772009-01-06 14:39:06 -08001825 if (unlikely(ret)) {
1826 if (ret == AOP_WRITEPAGE_ACTIVATE) {
1827 unlock_page(page);
1828 ret = 0;
1829 } else {
1830 /*
1831 * done_index is set past this page,
1832 * so media errors will not choke
1833 * background writeout for the entire
1834 * file. This has consequences for
1835 * range_cyclic semantics (ie. it may
1836 * not be suitable for data integrity
1837 * writeout).
1838 */
Jun'ichi Nomuracf15b072011-03-22 16:33:40 -07001839 done_index = page->index + 1;
Nick Piggin00266772009-01-06 14:39:06 -08001840 done = 1;
1841 break;
1842 }
Dave Chinner0b564922010-06-09 10:37:18 +10001843 }
David Howells811d7362006-08-29 19:06:09 +01001844
Dave Chinner546a1922010-08-24 11:44:34 +10001845 /*
1846 * We stop writing back only if we are not doing
1847 * integrity sync. In case of integrity sync we have to
1848 * keep going until we have written all the pages
1849 * we tagged for writeback prior to entering this loop.
1850 */
1851 if (--wbc->nr_to_write <= 0 &&
1852 wbc->sync_mode == WB_SYNC_NONE) {
1853 done = 1;
1854 break;
Nick Piggin05fe4782009-01-06 14:39:08 -08001855 }
David Howells811d7362006-08-29 19:06:09 +01001856 }
1857 pagevec_release(&pvec);
1858 cond_resched();
1859 }
Nick Piggin3a4c6802009-02-12 04:34:23 +01001860 if (!cycled && !done) {
David Howells811d7362006-08-29 19:06:09 +01001861 /*
Nick Piggin31a12662009-01-06 14:39:04 -08001862 * range_cyclic:
David Howells811d7362006-08-29 19:06:09 +01001863 * We hit the last page and there is more work to be done: wrap
1864 * back to the start of the file
1865 */
Nick Piggin31a12662009-01-06 14:39:04 -08001866 cycled = 1;
David Howells811d7362006-08-29 19:06:09 +01001867 index = 0;
Nick Piggin31a12662009-01-06 14:39:04 -08001868 end = writeback_index - 1;
David Howells811d7362006-08-29 19:06:09 +01001869 goto retry;
1870 }
Dave Chinner0b564922010-06-09 10:37:18 +10001871 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
1872 mapping->writeback_index = done_index;
Aneesh Kumar K.V06d6cf62008-07-11 19:27:31 -04001873
David Howells811d7362006-08-29 19:06:09 +01001874 return ret;
1875}
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001876EXPORT_SYMBOL(write_cache_pages);
1877
1878/*
1879 * Function used by generic_writepages to call the real writepage
1880 * function and set the mapping flags on error
1881 */
1882static int __writepage(struct page *page, struct writeback_control *wbc,
1883 void *data)
1884{
1885 struct address_space *mapping = data;
1886 int ret = mapping->a_ops->writepage(page, wbc);
1887 mapping_set_error(mapping, ret);
1888 return ret;
1889}
1890
1891/**
1892 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
1893 * @mapping: address space structure to write
1894 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
1895 *
1896 * This is a library function, which implements the writepages()
1897 * address_space_operation.
1898 */
1899int generic_writepages(struct address_space *mapping,
1900 struct writeback_control *wbc)
1901{
Shaohua Li9b6096a2011-03-17 10:47:06 +01001902 struct blk_plug plug;
1903 int ret;
1904
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001905 /* deal with chardevs and other special file */
1906 if (!mapping->a_ops->writepage)
1907 return 0;
1908
Shaohua Li9b6096a2011-03-17 10:47:06 +01001909 blk_start_plug(&plug);
1910 ret = write_cache_pages(mapping, wbc, __writepage, mapping);
1911 blk_finish_plug(&plug);
1912 return ret;
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001913}
David Howells811d7362006-08-29 19:06:09 +01001914
1915EXPORT_SYMBOL(generic_writepages);
1916
Linus Torvalds1da177e2005-04-16 15:20:36 -07001917int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1918{
Andrew Morton22905f72005-11-16 15:07:01 -08001919 int ret;
1920
Linus Torvalds1da177e2005-04-16 15:20:36 -07001921 if (wbc->nr_to_write <= 0)
1922 return 0;
1923 if (mapping->a_ops->writepages)
Peter Zijlstrad08b3852006-09-25 23:30:57 -07001924 ret = mapping->a_ops->writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001925 else
1926 ret = generic_writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001927 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001928}
1929
1930/**
1931 * write_one_page - write out a single page and optionally wait on I/O
Martin Waitz67be2dd2005-05-01 08:59:26 -07001932 * @page: the page to write
1933 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -07001934 *
1935 * The page must be locked by the caller and will be unlocked upon return.
1936 *
1937 * write_one_page() returns a negative error code if I/O failed.
1938 */
1939int write_one_page(struct page *page, int wait)
1940{
1941 struct address_space *mapping = page->mapping;
1942 int ret = 0;
1943 struct writeback_control wbc = {
1944 .sync_mode = WB_SYNC_ALL,
1945 .nr_to_write = 1,
1946 };
1947
1948 BUG_ON(!PageLocked(page));
1949
1950 if (wait)
1951 wait_on_page_writeback(page);
1952
1953 if (clear_page_dirty_for_io(page)) {
1954 page_cache_get(page);
1955 ret = mapping->a_ops->writepage(page, &wbc);
1956 if (ret == 0 && wait) {
1957 wait_on_page_writeback(page);
1958 if (PageError(page))
1959 ret = -EIO;
1960 }
1961 page_cache_release(page);
1962 } else {
1963 unlock_page(page);
1964 }
1965 return ret;
1966}
1967EXPORT_SYMBOL(write_one_page);
1968
1969/*
Ken Chen76719322007-02-10 01:43:15 -08001970 * For address_spaces which do not use buffers nor write back.
1971 */
1972int __set_page_dirty_no_writeback(struct page *page)
1973{
1974 if (!PageDirty(page))
Bob Liuc3f0da62011-01-13 15:45:49 -08001975 return !TestSetPageDirty(page);
Ken Chen76719322007-02-10 01:43:15 -08001976 return 0;
1977}
1978
1979/*
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001980 * Helper function for set_page_dirty family.
1981 * NOTE: This relies on being atomic wrt interrupts.
1982 */
1983void account_page_dirtied(struct page *page, struct address_space *mapping)
1984{
1985 if (mapping_cap_account_dirty(mapping)) {
1986 __inc_zone_page_state(page, NR_FILE_DIRTY);
Michael Rubinea941f02010-10-26 14:21:35 -07001987 __inc_zone_page_state(page, NR_DIRTIED);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001988 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
Wu Fengguangc8e28ce2011-01-23 10:07:47 -06001989 __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001990 task_io_account_write(PAGE_CACHE_SIZE);
Wu Fengguangd3bc1fe2011-04-14 07:52:37 -06001991 current->nr_dirtied++;
1992 this_cpu_inc(bdp_ratelimits);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001993 }
1994}
Michael Rubin679ceac2010-08-20 02:31:26 -07001995EXPORT_SYMBOL(account_page_dirtied);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001996
1997/*
Michael Rubinf629d1c2010-10-26 14:21:33 -07001998 * Helper function for set_page_writeback family.
1999 * NOTE: Unlike account_page_dirtied this does not rely on being atomic
2000 * wrt interrupts.
2001 */
2002void account_page_writeback(struct page *page)
2003{
2004 inc_zone_page_state(page, NR_WRITEBACK);
2005}
2006EXPORT_SYMBOL(account_page_writeback);
2007
2008/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002009 * For address_spaces which do not use buffers. Just tag the page as dirty in
2010 * its radix tree.
2011 *
2012 * This is also used when a single buffer is being dirtied: we want to set the
2013 * page dirty in that case, but not all the buffers. This is a "bottom-up"
2014 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
2015 *
2016 * Most callers have locked the page, which pins the address_space in memory.
2017 * But zap_pte_range() does not lock the page, however in that case the
2018 * mapping is pinned by the vma's ->vm_file reference.
2019 *
2020 * We take care to handle the case where the page was truncated from the
Simon Arlott183ff222007-10-20 01:27:18 +02002021 * mapping by re-checking page_mapping() inside tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022 */
2023int __set_page_dirty_nobuffers(struct page *page)
2024{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025 if (!TestSetPageDirty(page)) {
2026 struct address_space *mapping = page_mapping(page);
2027 struct address_space *mapping2;
2028
Andrew Morton8c085402006-12-10 02:19:24 -08002029 if (!mapping)
2030 return 1;
2031
Nick Piggin19fd6232008-07-25 19:45:32 -07002032 spin_lock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08002033 mapping2 = page_mapping(page);
2034 if (mapping2) { /* Race with truncate? */
2035 BUG_ON(mapping2 != mapping);
Nick Piggin787d2212007-07-17 04:03:34 -07002036 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -07002037 account_page_dirtied(page, mapping);
Andrew Morton8c085402006-12-10 02:19:24 -08002038 radix_tree_tag_set(&mapping->page_tree,
2039 page_index(page), PAGECACHE_TAG_DIRTY);
2040 }
Nick Piggin19fd6232008-07-25 19:45:32 -07002041 spin_unlock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08002042 if (mapping->host) {
2043 /* !PageAnon && !swapper_space */
2044 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08002046 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08002048 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002049}
2050EXPORT_SYMBOL(__set_page_dirty_nobuffers);
2051
2052/*
Wu Fengguang2f800fb2011-08-08 15:22:00 -06002053 * Call this whenever redirtying a page, to de-account the dirty counters
2054 * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written
2055 * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to
2056 * systematic errors in balanced_dirty_ratelimit and the dirty pages position
2057 * control.
2058 */
2059void account_page_redirty(struct page *page)
2060{
2061 struct address_space *mapping = page->mapping;
2062 if (mapping && mapping_cap_account_dirty(mapping)) {
2063 current->nr_dirtied--;
2064 dec_zone_page_state(page, NR_DIRTIED);
2065 dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
2066 }
2067}
2068EXPORT_SYMBOL(account_page_redirty);
2069
2070/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002071 * When a writepage implementation decides that it doesn't want to write this
2072 * page for some reason, it should redirty the locked page via
2073 * redirty_page_for_writepage() and it should then unlock the page and return 0
2074 */
2075int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
2076{
2077 wbc->pages_skipped++;
Wu Fengguang2f800fb2011-08-08 15:22:00 -06002078 account_page_redirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002079 return __set_page_dirty_nobuffers(page);
2080}
2081EXPORT_SYMBOL(redirty_page_for_writepage);
2082
2083/*
Wu Fengguang6746aff2009-09-16 11:50:14 +02002084 * Dirty a page.
2085 *
2086 * For pages with a mapping this should be done under the page lock
2087 * for the benefit of asynchronous memory errors who prefer a consistent
2088 * dirty state. This rule can be broken in some special cases,
2089 * but should be better not to.
2090 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07002091 * If the mapping doesn't provide a set_page_dirty a_op, then
2092 * just fall through and assume that it wants buffer_heads.
2093 */
Nick Piggin1cf6e7d2009-02-18 14:48:18 -08002094int set_page_dirty(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095{
2096 struct address_space *mapping = page_mapping(page);
2097
2098 if (likely(mapping)) {
2099 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
Minchan Kim278df9f2011-03-22 16:32:54 -07002100 /*
2101 * readahead/lru_deactivate_page could remain
2102 * PG_readahead/PG_reclaim due to race with end_page_writeback
2103 * About readahead, if the page is written, the flags would be
2104 * reset. So no problem.
2105 * About lru_deactivate_page, if the page is redirty, the flag
2106 * will be reset. So no problem. but if the page is used by readahead
2107 * it will confuse readahead and make it restart the size rampup
2108 * process. But it's a trivial problem.
2109 */
2110 ClearPageReclaim(page);
David Howells93614012006-09-30 20:45:40 +02002111#ifdef CONFIG_BLOCK
2112 if (!spd)
2113 spd = __set_page_dirty_buffers;
2114#endif
2115 return (*spd)(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08002117 if (!PageDirty(page)) {
2118 if (!TestSetPageDirty(page))
2119 return 1;
2120 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121 return 0;
2122}
2123EXPORT_SYMBOL(set_page_dirty);
2124
2125/*
2126 * set_page_dirty() is racy if the caller has no reference against
2127 * page->mapping->host, and if the page is unlocked. This is because another
2128 * CPU could truncate the page off the mapping and then free the mapping.
2129 *
2130 * Usually, the page _is_ locked, or the caller is a user-space process which
2131 * holds a reference on the inode by having an open file.
2132 *
2133 * In other cases, the page should be locked before running set_page_dirty().
2134 */
2135int set_page_dirty_lock(struct page *page)
2136{
2137 int ret;
2138
Jens Axboe7eaceac2011-03-10 08:52:07 +01002139 lock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002140 ret = set_page_dirty(page);
2141 unlock_page(page);
2142 return ret;
2143}
2144EXPORT_SYMBOL(set_page_dirty_lock);
2145
2146/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147 * Clear a page's dirty flag, while caring for dirty memory accounting.
2148 * Returns true if the page was previously dirty.
2149 *
2150 * This is for preparing to put the page under writeout. We leave the page
2151 * tagged as dirty in the radix tree so that a concurrent write-for-sync
2152 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
2153 * implementation will run either set_page_writeback() or set_page_dirty(),
2154 * at which stage we bring the page's dirty flag and radix-tree dirty tag
2155 * back into sync.
2156 *
2157 * This incoherency between the page's dirty flag and radix-tree tag is
2158 * unfortunate, but it only exists while the page is locked.
2159 */
2160int clear_page_dirty_for_io(struct page *page)
2161{
2162 struct address_space *mapping = page_mapping(page);
2163
Nick Piggin79352892007-07-19 01:47:22 -07002164 BUG_ON(!PageLocked(page));
2165
Linus Torvalds7658cc22006-12-29 10:00:58 -08002166 if (mapping && mapping_cap_account_dirty(mapping)) {
2167 /*
2168 * Yes, Virginia, this is indeed insane.
2169 *
2170 * We use this sequence to make sure that
2171 * (a) we account for dirty stats properly
2172 * (b) we tell the low-level filesystem to
2173 * mark the whole page dirty if it was
2174 * dirty in a pagetable. Only to then
2175 * (c) clean the page again and return 1 to
2176 * cause the writeback.
2177 *
2178 * This way we avoid all nasty races with the
2179 * dirty bit in multiple places and clearing
2180 * them concurrently from different threads.
2181 *
2182 * Note! Normally the "set_page_dirty(page)"
2183 * has no effect on the actual dirty bit - since
2184 * that will already usually be set. But we
2185 * need the side effects, and it can help us
2186 * avoid races.
2187 *
2188 * We basically use the page "master dirty bit"
2189 * as a serialization point for all the different
2190 * threads doing their things.
Linus Torvalds7658cc22006-12-29 10:00:58 -08002191 */
2192 if (page_mkclean(page))
2193 set_page_dirty(page);
Nick Piggin79352892007-07-19 01:47:22 -07002194 /*
2195 * We carefully synchronise fault handlers against
2196 * installing a dirty pte and marking the page dirty
2197 * at this point. We do this by having them hold the
2198 * page lock at some point after installing their
2199 * pte, but before marking the page dirty.
2200 * Pages are always locked coming in here, so we get
2201 * the desired exclusion. See mm/memory.c:do_wp_page()
2202 * for more comments.
2203 */
Linus Torvalds7658cc22006-12-29 10:00:58 -08002204 if (TestClearPageDirty(page)) {
Andrew Morton8c085402006-12-10 02:19:24 -08002205 dec_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07002206 dec_bdi_stat(mapping->backing_dev_info,
2207 BDI_RECLAIMABLE);
Linus Torvalds7658cc22006-12-29 10:00:58 -08002208 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08002210 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08002212 return TestClearPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002213}
Hans Reiser58bb01a2005-11-18 01:10:53 -08002214EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002215
2216int test_clear_page_writeback(struct page *page)
2217{
2218 struct address_space *mapping = page_mapping(page);
2219 int ret;
2220
2221 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002222 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002223 unsigned long flags;
2224
Nick Piggin19fd6232008-07-25 19:45:32 -07002225 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002226 ret = TestClearPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002227 if (ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002228 radix_tree_tag_clear(&mapping->page_tree,
2229 page_index(page),
2230 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07002231 if (bdi_cap_account_writeback(bdi)) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002232 __dec_bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07002233 __bdi_writeout_inc(bdi);
2234 }
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002235 }
Nick Piggin19fd6232008-07-25 19:45:32 -07002236 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002237 } else {
2238 ret = TestClearPageWriteback(page);
2239 }
Wu Fengguang99b12e32011-07-25 17:12:37 -07002240 if (ret) {
Andrew Mortond688abf2007-07-19 01:49:17 -07002241 dec_zone_page_state(page, NR_WRITEBACK);
Wu Fengguang99b12e32011-07-25 17:12:37 -07002242 inc_zone_page_state(page, NR_WRITTEN);
2243 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002244 return ret;
2245}
2246
2247int test_set_page_writeback(struct page *page)
2248{
2249 struct address_space *mapping = page_mapping(page);
2250 int ret;
2251
2252 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002253 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254 unsigned long flags;
2255
Nick Piggin19fd6232008-07-25 19:45:32 -07002256 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002257 ret = TestSetPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002258 if (!ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002259 radix_tree_tag_set(&mapping->page_tree,
2260 page_index(page),
2261 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07002262 if (bdi_cap_account_writeback(bdi))
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07002263 __inc_bdi_stat(bdi, BDI_WRITEBACK);
2264 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265 if (!PageDirty(page))
2266 radix_tree_tag_clear(&mapping->page_tree,
2267 page_index(page),
2268 PAGECACHE_TAG_DIRTY);
Jan Karaf446daae2010-08-09 17:19:12 -07002269 radix_tree_tag_clear(&mapping->page_tree,
2270 page_index(page),
2271 PAGECACHE_TAG_TOWRITE);
Nick Piggin19fd6232008-07-25 19:45:32 -07002272 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002273 } else {
2274 ret = TestSetPageWriteback(page);
2275 }
Andrew Mortond688abf2007-07-19 01:49:17 -07002276 if (!ret)
Michael Rubinf629d1c2010-10-26 14:21:33 -07002277 account_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278 return ret;
2279
2280}
2281EXPORT_SYMBOL(test_set_page_writeback);
2282
2283/*
Nick Piggin00128182007-10-16 01:24:40 -07002284 * Return true if any of the pages in the mapping are marked with the
Linus Torvalds1da177e2005-04-16 15:20:36 -07002285 * passed tag.
2286 */
2287int mapping_tagged(struct address_space *mapping, int tag)
2288{
Konstantin Khlebnikov72c47832011-07-25 17:12:31 -07002289 return radix_tree_tagged(&mapping->page_tree, tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002290}
2291EXPORT_SYMBOL(mapping_tagged);