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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Uwe Zeisbergerf30c2262006-10-03 23:01:26 +02002 * mm/page-writeback.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07003 *
4 * Copyright (C) 2002, Linus Torvalds.
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07005 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 *
7 * Contains functions related to writing back dirty pages at the
8 * address_space level.
9 *
Francois Camie1f8e872008-10-15 22:01:59 -070010 * 10Apr2002 Andrew Morton
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 * Initial version
12 */
13
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/spinlock.h>
17#include <linux/fs.h>
18#include <linux/mm.h>
19#include <linux/swap.h>
20#include <linux/slab.h>
21#include <linux/pagemap.h>
22#include <linux/writeback.h>
23#include <linux/init.h>
24#include <linux/backing-dev.h>
Andrew Morton55e829a2006-12-10 02:19:27 -080025#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#include <linux/blkdev.h>
27#include <linux/mpage.h>
Peter Zijlstrad08b3852006-09-25 23:30:57 -070028#include <linux/rmap.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070029#include <linux/percpu.h>
30#include <linux/notifier.h>
31#include <linux/smp.h>
32#include <linux/sysctl.h>
33#include <linux/cpu.h>
34#include <linux/syscalls.h>
David Howellscf9a2ae2006-08-29 19:05:54 +010035#include <linux/buffer_head.h>
David Howells811d7362006-08-29 19:06:09 +010036#include <linux/pagevec.h>
Dave Chinner028c2dd2010-07-07 13:24:07 +100037#include <trace/events/writeback.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038
39/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
41 * will look to see if it needs to force writeback or throttling.
42 */
43static long ratelimit_pages = 32;
44
Linus Torvalds1da177e2005-04-16 15:20:36 -070045/*
46 * When balance_dirty_pages decides that the caller needs to perform some
47 * non-background writeback, this is how many pages it will attempt to write.
Wu Fengguang3a2e9a52009-09-23 21:56:00 +080048 * It should be somewhat larger than dirtied pages to ensure that reasonably
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 * large amounts of I/O are submitted.
50 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +080051static inline long sync_writeback_pages(unsigned long dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -070052{
Wu Fengguang3a2e9a52009-09-23 21:56:00 +080053 if (dirtied < ratelimit_pages)
54 dirtied = ratelimit_pages;
55
56 return dirtied + dirtied / 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -070057}
58
59/* The following parameters are exported via /proc/sys/vm */
60
61/*
Jens Axboe5b0830c2009-09-23 19:37:09 +020062 * Start background writeback (via writeback threads) at this percentage
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080064int dirty_background_ratio = 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -070065
66/*
David Rientjes2da02992009-01-06 14:39:31 -080067 * dirty_background_bytes starts at 0 (disabled) so that it is a function of
68 * dirty_background_ratio * the amount of dirtyable memory
69 */
70unsigned long dirty_background_bytes;
71
72/*
Bron Gondwana195cf4532008-02-04 22:29:20 -080073 * free highmem will not be subtracted from the total free memory
74 * for calculating free ratios if vm_highmem_is_dirtyable is true
75 */
76int vm_highmem_is_dirtyable;
77
78/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 * The generator of dirty data starts writeback at this percentage
80 */
Wu Fengguang1b5e62b2009-03-23 08:57:38 +080081int vm_dirty_ratio = 20;
Linus Torvalds1da177e2005-04-16 15:20:36 -070082
83/*
David Rientjes2da02992009-01-06 14:39:31 -080084 * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
85 * vm_dirty_ratio * the amount of dirtyable memory
86 */
87unsigned long vm_dirty_bytes;
88
89/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -070090 * The interval between `kupdate'-style writebacks
Linus Torvalds1da177e2005-04-16 15:20:36 -070091 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -070092unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -070093
94/*
Alexey Dobriyan704503d2009-03-31 15:23:18 -070095 * The longest time for which data is allowed to remain dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 */
Toshiyuki Okajima22ef37e2009-05-16 22:56:28 -070097unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */
Linus Torvalds1da177e2005-04-16 15:20:36 -070098
99/*
100 * Flag that makes the machine dump writes/reads and block dirtyings.
101 */
102int block_dump;
103
104/*
Bart Samweled5b43f2006-03-24 03:15:49 -0800105 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
106 * a full sync is triggered after this time elapses without any disk activity.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 */
108int laptop_mode;
109
110EXPORT_SYMBOL(laptop_mode);
111
112/* End of sysctl-exported parameters */
113
114
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115/*
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700116 * Scale the writeback cache size proportional to the relative writeout speeds.
117 *
118 * We do this by keeping a floating proportion between BDIs, based on page
119 * writeback completions [end_page_writeback()]. Those devices that write out
120 * pages fastest will get the larger share, while the slower will get a smaller
121 * share.
122 *
123 * We use page writeout completions because we are interested in getting rid of
124 * dirty pages. Having them written out is the primary goal.
125 *
126 * We introduce a concept of time, a period over which we measure these events,
127 * because demand can/will vary over time. The length of this period itself is
128 * measured in page writeback completions.
129 *
130 */
131static struct prop_descriptor vm_completions;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700132static struct prop_descriptor vm_dirties;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700133
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700134/*
135 * couple the period to the dirty_ratio:
136 *
137 * period/2 ~ roundup_pow_of_two(dirty limit)
138 */
139static int calc_period_shift(void)
140{
141 unsigned long dirty_total;
142
David Rientjes2da02992009-01-06 14:39:31 -0800143 if (vm_dirty_bytes)
144 dirty_total = vm_dirty_bytes / PAGE_SIZE;
145 else
146 dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
147 100;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700148 return 2 + ilog2(dirty_total - 1);
149}
150
151/*
David Rientjes2da02992009-01-06 14:39:31 -0800152 * update the period when the dirty threshold changes.
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700153 */
David Rientjes2da02992009-01-06 14:39:31 -0800154static void update_completion_period(void)
155{
156 int shift = calc_period_shift();
157 prop_change_shift(&vm_completions, shift);
158 prop_change_shift(&vm_dirties, shift);
159}
160
161int dirty_background_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700162 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800163 loff_t *ppos)
164{
165 int ret;
166
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700167 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800168 if (ret == 0 && write)
169 dirty_background_bytes = 0;
170 return ret;
171}
172
173int dirty_background_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700174 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800175 loff_t *ppos)
176{
177 int ret;
178
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700179 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800180 if (ret == 0 && write)
181 dirty_background_ratio = 0;
182 return ret;
183}
184
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700185int dirty_ratio_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700186 void __user *buffer, size_t *lenp,
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700187 loff_t *ppos)
188{
189 int old_ratio = vm_dirty_ratio;
David Rientjes2da02992009-01-06 14:39:31 -0800190 int ret;
191
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700192 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700193 if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
David Rientjes2da02992009-01-06 14:39:31 -0800194 update_completion_period();
195 vm_dirty_bytes = 0;
196 }
197 return ret;
198}
199
200
201int dirty_bytes_handler(struct ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700202 void __user *buffer, size_t *lenp,
David Rientjes2da02992009-01-06 14:39:31 -0800203 loff_t *ppos)
204{
Sven Wegenerfc3501d2009-02-11 13:04:23 -0800205 unsigned long old_bytes = vm_dirty_bytes;
David Rientjes2da02992009-01-06 14:39:31 -0800206 int ret;
207
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700208 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
David Rientjes2da02992009-01-06 14:39:31 -0800209 if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
210 update_completion_period();
211 vm_dirty_ratio = 0;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700212 }
213 return ret;
214}
215
216/*
217 * Increment the BDI's writeout completion count and the global writeout
218 * completion count. Called from test_clear_page_writeback().
219 */
220static inline void __bdi_writeout_inc(struct backing_dev_info *bdi)
221{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700222 __prop_inc_percpu_max(&vm_completions, &bdi->completions,
223 bdi->max_prop_frac);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700224}
225
Miklos Szeredidd5656e2008-04-30 00:54:37 -0700226void bdi_writeout_inc(struct backing_dev_info *bdi)
227{
228 unsigned long flags;
229
230 local_irq_save(flags);
231 __bdi_writeout_inc(bdi);
232 local_irq_restore(flags);
233}
234EXPORT_SYMBOL_GPL(bdi_writeout_inc);
235
Nick Piggin1cf6e7d2009-02-18 14:48:18 -0800236void task_dirty_inc(struct task_struct *tsk)
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700237{
238 prop_inc_single(&vm_dirties, &tsk->dirties);
239}
240
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700241/*
242 * Obtain an accurate fraction of the BDI's portion.
243 */
244static void bdi_writeout_fraction(struct backing_dev_info *bdi,
245 long *numerator, long *denominator)
246{
247 if (bdi_cap_writeback_dirty(bdi)) {
248 prop_fraction_percpu(&vm_completions, &bdi->completions,
249 numerator, denominator);
250 } else {
251 *numerator = 0;
252 *denominator = 1;
253 }
254}
255
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700256static inline void task_dirties_fraction(struct task_struct *tsk,
257 long *numerator, long *denominator)
258{
259 prop_fraction_single(&vm_dirties, &tsk->dirties,
260 numerator, denominator);
261}
262
263/*
Wu Fengguang1babe182010-08-11 14:17:40 -0700264 * task_dirty_limit - scale down dirty throttling threshold for one task
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700265 *
266 * task specific dirty limit:
267 *
268 * dirty -= (dirty/8) * p_{t}
Wu Fengguang1babe182010-08-11 14:17:40 -0700269 *
270 * To protect light/slow dirtying tasks from heavier/fast ones, we start
271 * throttling individual tasks before reaching the bdi dirty limit.
272 * Relatively low thresholds will be allocated to heavy dirtiers. So when
273 * dirty pages grow large, heavy dirtiers will be throttled first, which will
274 * effectively curb the growth of dirty pages. Light dirtiers with high enough
275 * dirty threshold may never get throttled.
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700276 */
Wu Fengguang16c40422010-08-11 14:17:39 -0700277static unsigned long task_dirty_limit(struct task_struct *tsk,
278 unsigned long bdi_dirty)
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700279{
280 long numerator, denominator;
Wu Fengguang16c40422010-08-11 14:17:39 -0700281 unsigned long dirty = bdi_dirty;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700282 u64 inv = dirty >> 3;
283
284 task_dirties_fraction(tsk, &numerator, &denominator);
285 inv *= numerator;
286 do_div(inv, denominator);
287
288 dirty -= inv;
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700289
Wu Fengguang16c40422010-08-11 14:17:39 -0700290 return max(dirty, bdi_dirty/2);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700291}
292
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700293/*
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700294 *
295 */
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700296static unsigned int bdi_min_ratio;
297
298int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
299{
300 int ret = 0;
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700301
Jens Axboecfc4ba52009-09-14 13:12:40 +0200302 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700303 if (min_ratio > bdi->max_ratio) {
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700304 ret = -EINVAL;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700305 } else {
306 min_ratio -= bdi->min_ratio;
307 if (bdi_min_ratio + min_ratio < 100) {
308 bdi_min_ratio += min_ratio;
309 bdi->min_ratio += min_ratio;
310 } else {
311 ret = -EINVAL;
312 }
313 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200314 spin_unlock_bh(&bdi_lock);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700315
316 return ret;
317}
318
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700319int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
320{
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700321 int ret = 0;
322
323 if (max_ratio > 100)
324 return -EINVAL;
325
Jens Axboecfc4ba52009-09-14 13:12:40 +0200326 spin_lock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700327 if (bdi->min_ratio > max_ratio) {
328 ret = -EINVAL;
329 } else {
330 bdi->max_ratio = max_ratio;
331 bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
332 }
Jens Axboecfc4ba52009-09-14 13:12:40 +0200333 spin_unlock_bh(&bdi_lock);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700334
335 return ret;
336}
337EXPORT_SYMBOL(bdi_set_max_ratio);
338
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700339/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700340 * Work out the current dirty-memory clamping and background writeout
341 * thresholds.
342 *
343 * The main aim here is to lower them aggressively if there is a lot of mapped
344 * memory around. To avoid stressing page reclaim with lots of unreclaimable
345 * pages. It is better to clamp down on writers than to start swapping, and
346 * performing lots of scanning.
347 *
348 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
349 *
350 * We don't permit the clamping level to fall below 5% - that is getting rather
351 * excessive.
352 *
353 * We make sure that the background writeout level is below the adjusted
354 * clamping level.
355 */
Christoph Lameter1b424462007-05-06 14:48:59 -0700356
357static unsigned long highmem_dirtyable_memory(unsigned long total)
358{
359#ifdef CONFIG_HIGHMEM
360 int node;
361 unsigned long x = 0;
362
Lee Schermerhorn37b07e42007-10-16 01:25:39 -0700363 for_each_node_state(node, N_HIGH_MEMORY) {
Christoph Lameter1b424462007-05-06 14:48:59 -0700364 struct zone *z =
365 &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
366
Wu Fengguangadea02a2009-09-21 17:01:42 -0700367 x += zone_page_state(z, NR_FREE_PAGES) +
368 zone_reclaimable_pages(z);
Christoph Lameter1b424462007-05-06 14:48:59 -0700369 }
370 /*
371 * Make sure that the number of highmem pages is never larger
372 * than the number of the total dirtyable memory. This can only
373 * occur in very strange VM situations but we want to make sure
374 * that this does not occur.
375 */
376 return min(x, total);
377#else
378 return 0;
379#endif
380}
381
Steven Rostedt3eefae92008-05-12 21:21:04 +0200382/**
383 * determine_dirtyable_memory - amount of memory that may be used
384 *
385 * Returns the numebr of pages that can currently be freed and used
386 * by the kernel for direct mappings.
387 */
388unsigned long determine_dirtyable_memory(void)
Christoph Lameter1b424462007-05-06 14:48:59 -0700389{
390 unsigned long x;
391
Wu Fengguangadea02a2009-09-21 17:01:42 -0700392 x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
Bron Gondwana195cf4532008-02-04 22:29:20 -0800393
394 if (!vm_highmem_is_dirtyable)
395 x -= highmem_dirtyable_memory(x);
396
Christoph Lameter1b424462007-05-06 14:48:59 -0700397 return x + 1; /* Ensure that we never return 0 */
398}
399
Randy Dunlap03ab4502010-08-14 13:05:17 -0700400/*
Wu Fengguang1babe182010-08-11 14:17:40 -0700401 * global_dirty_limits - background-writeback and dirty-throttling thresholds
402 *
403 * Calculate the dirty thresholds based on sysctl parameters
404 * - vm.dirty_background_ratio or vm.dirty_background_bytes
405 * - vm.dirty_ratio or vm.dirty_bytes
406 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
407 * runtime tasks.
408 */
Wu Fengguang16c40422010-08-11 14:17:39 -0700409void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410{
David Rientjes364aeb22009-01-06 14:39:29 -0800411 unsigned long background;
412 unsigned long dirty;
Christoph Lameter1b424462007-05-06 14:48:59 -0700413 unsigned long available_memory = determine_dirtyable_memory();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414 struct task_struct *tsk;
415
David Rientjes2da02992009-01-06 14:39:31 -0800416 if (vm_dirty_bytes)
417 dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
418 else {
419 int dirty_ratio;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420
David Rientjes2da02992009-01-06 14:39:31 -0800421 dirty_ratio = vm_dirty_ratio;
422 if (dirty_ratio < 5)
423 dirty_ratio = 5;
424 dirty = (dirty_ratio * available_memory) / 100;
425 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426
David Rientjes2da02992009-01-06 14:39:31 -0800427 if (dirty_background_bytes)
428 background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
429 else
430 background = (dirty_background_ratio * available_memory) / 100;
431
432 if (background >= dirty)
433 background = dirty / 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700434 tsk = current;
435 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
436 background += background / 4;
437 dirty += dirty / 4;
438 }
439 *pbackground = background;
440 *pdirty = dirty;
Wu Fengguang16c40422010-08-11 14:17:39 -0700441}
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700442
Randy Dunlap03ab4502010-08-14 13:05:17 -0700443/*
Wu Fengguang1babe182010-08-11 14:17:40 -0700444 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
445 *
446 * Allocate high/low dirty limits to fast/slow devices, in order to prevent
447 * - starving fast devices
448 * - piling up dirty pages (that will take long time to sync) on slow devices
449 *
450 * The bdi's share of dirty limit will be adapting to its throughput and
451 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
452 */
453unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
Wu Fengguang16c40422010-08-11 14:17:39 -0700454{
455 u64 bdi_dirty;
456 long numerator, denominator;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700457
Wu Fengguang16c40422010-08-11 14:17:39 -0700458 /*
459 * Calculate this BDI's share of the dirty ratio.
460 */
461 bdi_writeout_fraction(bdi, &numerator, &denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700462
Wu Fengguang16c40422010-08-11 14:17:39 -0700463 bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
464 bdi_dirty *= numerator;
465 do_div(bdi_dirty, denominator);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700466
Wu Fengguang16c40422010-08-11 14:17:39 -0700467 bdi_dirty += (dirty * bdi->min_ratio) / 100;
468 if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
469 bdi_dirty = dirty * bdi->max_ratio / 100;
470
471 return bdi_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472}
473
474/*
475 * balance_dirty_pages() must be called by processes which are generating dirty
476 * data. It looks at the number of dirty pages in the machine and will force
477 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
Jens Axboe5b0830c2009-09-23 19:37:09 +0200478 * If we're over `background_thresh' then the writeback threads are woken to
479 * perform some writeout.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 */
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800481static void balance_dirty_pages(struct address_space *mapping,
482 unsigned long write_chunk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700483{
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800484 long nr_reclaimable, bdi_nr_reclaimable;
485 long nr_writeback, bdi_nr_writeback;
David Rientjes364aeb22009-01-06 14:39:29 -0800486 unsigned long background_thresh;
487 unsigned long dirty_thresh;
488 unsigned long bdi_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 unsigned long pages_written = 0;
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200490 unsigned long pause = 1;
Wu Fengguange50e3722010-08-11 14:17:37 -0700491 bool dirty_exceeded = false;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492 struct backing_dev_info *bdi = mapping->backing_dev_info;
493
494 for (;;) {
495 struct writeback_control wbc = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496 .sync_mode = WB_SYNC_NONE,
497 .older_than_this = NULL,
498 .nr_to_write = write_chunk,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -0700499 .range_cyclic = 1,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500 };
501
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800502 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
503 global_page_state(NR_UNSTABLE_NFS);
504 nr_writeback = global_page_state(NR_WRITEBACK);
505
Wu Fengguang16c40422010-08-11 14:17:39 -0700506 global_dirty_limits(&background_thresh, &dirty_thresh);
507
508 /*
509 * Throttle it only when the background writeback cannot
510 * catch-up. This avoids (excessively) small writeouts
511 * when the bdi limits are ramping up.
512 */
513 if (nr_reclaimable + nr_writeback <
514 (background_thresh + dirty_thresh) / 2)
515 break;
516
517 bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
518 bdi_thresh = task_dirty_limit(current, bdi_thresh);
519
Wu Fengguange50e3722010-08-11 14:17:37 -0700520 /*
521 * In order to avoid the stacked BDI deadlock we need
522 * to ensure we accurately count the 'dirty' pages when
523 * the threshold is low.
524 *
525 * Otherwise it would be possible to get thresh+n pages
526 * reported dirty, even though there are thresh-m pages
527 * actually dirty; with m+n sitting in the percpu
528 * deltas.
529 */
530 if (bdi_thresh < 2*bdi_stat_error(bdi)) {
531 bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
532 bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
533 } else {
534 bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
535 bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
536 }
Peter Zijlstra5fce25a2007-11-14 16:59:15 -0800537
Wu Fengguange50e3722010-08-11 14:17:37 -0700538 /*
539 * The bdi thresh is somehow "soft" limit derived from the
540 * global "hard" limit. The former helps to prevent heavy IO
541 * bdi or process from holding back light ones; The latter is
542 * the last resort safeguard.
543 */
544 dirty_exceeded =
545 (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
546 || (nr_reclaimable + nr_writeback >= dirty_thresh);
547
548 if (!dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700549 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700551 if (!bdi->dirty_exceeded)
552 bdi->dirty_exceeded = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553
554 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
555 * Unstable writes are a feature of certain networked
556 * filesystems (i.e. NFS) in which data may have been
557 * written to the server's write cache, but has not yet
558 * been flushed to permanent storage.
Richard Kennedyd7831a02009-06-30 11:41:35 -0700559 * Only move pages to writeback if this bdi is over its
560 * threshold otherwise wait until the disk writes catch
561 * up.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700562 */
Dave Chinner028c2dd2010-07-07 13:24:07 +1000563 trace_wbc_balance_dirty_start(&wbc, bdi);
Richard Kennedyd7831a02009-06-30 11:41:35 -0700564 if (bdi_nr_reclaimable > bdi_thresh) {
Christoph Hellwig9c3a8ee2010-06-10 12:07:27 +0200565 writeback_inodes_wb(&bdi->wb, &wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566 pages_written += write_chunk - wbc.nr_to_write;
Dave Chinner028c2dd2010-07-07 13:24:07 +1000567 trace_wbc_balance_dirty_written(&wbc, bdi);
Wu Fengguange50e3722010-08-11 14:17:37 -0700568 if (pages_written >= write_chunk)
569 break; /* We've done our duty */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 }
Dave Chinner028c2dd2010-07-07 13:24:07 +1000571 trace_wbc_balance_dirty_wait(&wbc, bdi);
Wu Fengguangd25105e2009-10-09 12:40:42 +0200572 __set_current_state(TASK_INTERRUPTIBLE);
573 io_schedule_timeout(pause);
Jens Axboe87c6a9b2009-09-17 19:59:14 +0200574
575 /*
576 * Increase the delay for each loop, up to our previous
577 * default of taking a 100ms nap.
578 */
579 pause <<= 1;
580 if (pause > HZ / 10)
581 pause = HZ / 10;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 }
583
Wu Fengguange50e3722010-08-11 14:17:37 -0700584 if (!dirty_exceeded && bdi->dirty_exceeded)
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700585 bdi->dirty_exceeded = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586
587 if (writeback_in_progress(bdi))
Jens Axboe5b0830c2009-09-23 19:37:09 +0200588 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589
590 /*
591 * In laptop mode, we wait until hitting the higher threshold before
592 * starting background writeout, and then write out all the way down
593 * to the lower threshold. So slow writers cause minimal disk activity.
594 *
595 * In normal mode, we start background writeout at the lower
596 * background_thresh, to keep the amount of dirty memory low.
597 */
598 if ((laptop_mode && pages_written) ||
Wu Fengguange50e3722010-08-11 14:17:37 -0700599 (!laptop_mode && (nr_reclaimable > background_thresh)))
Christoph Hellwigc5444192010-06-08 18:15:15 +0200600 bdi_start_background_writeback(bdi);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601}
602
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200603void set_page_dirty_balance(struct page *page, int page_mkwrite)
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700604{
Peter Zijlstraa200ee12007-10-08 18:54:37 +0200605 if (set_page_dirty(page) || page_mkwrite) {
Peter Zijlstraedc79b22006-09-25 23:30:58 -0700606 struct address_space *mapping = page_mapping(page);
607
608 if (mapping)
609 balance_dirty_pages_ratelimited(mapping);
610 }
611}
612
Tejun Heo245b2e72009-06-24 15:13:48 +0900613static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
614
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615/**
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800616 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
Martin Waitz67be2dd2005-05-01 08:59:26 -0700617 * @mapping: address_space which was dirtied
Martin Waitza5802902006-04-02 13:59:55 +0200618 * @nr_pages_dirtied: number of pages which the caller has just dirtied
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619 *
620 * Processes which are dirtying memory should call in here once for each page
621 * which was newly dirtied. The function will periodically check the system's
622 * dirty state and will initiate writeback if needed.
623 *
624 * On really big machines, get_writeback_state is expensive, so try to avoid
625 * calling it too often (ratelimiting). But once we're over the dirty memory
626 * limit we decrease the ratelimiting by a lot, to prevent individual processes
627 * from overshooting the limit by (ratelimit_pages) each.
628 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800629void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
630 unsigned long nr_pages_dirtied)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631{
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800632 unsigned long ratelimit;
633 unsigned long *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634
635 ratelimit = ratelimit_pages;
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700636 if (mapping->backing_dev_info->dirty_exceeded)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700637 ratelimit = 8;
638
639 /*
640 * Check the rate limiting. Also, we do not want to throttle real-time
641 * tasks in balance_dirty_pages(). Period.
642 */
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800643 preempt_disable();
Tejun Heo245b2e72009-06-24 15:13:48 +0900644 p = &__get_cpu_var(bdp_ratelimits);
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800645 *p += nr_pages_dirtied;
646 if (unlikely(*p >= ratelimit)) {
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800647 ratelimit = sync_writeback_pages(*p);
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800648 *p = 0;
649 preempt_enable();
Wu Fengguang3a2e9a52009-09-23 21:56:00 +0800650 balance_dirty_pages(mapping, ratelimit);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 return;
652 }
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800653 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654}
Andrew Mortonfa5a7342006-03-24 03:18:10 -0800655EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700656
Andrew Morton232ea4d2007-02-28 20:13:21 -0800657void throttle_vm_writeout(gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700658{
David Rientjes364aeb22009-01-06 14:39:29 -0800659 unsigned long background_thresh;
660 unsigned long dirty_thresh;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661
662 for ( ; ; ) {
Wu Fengguang16c40422010-08-11 14:17:39 -0700663 global_dirty_limits(&background_thresh, &dirty_thresh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664
665 /*
666 * Boost the allowable dirty threshold a bit for page
667 * allocators so they don't get DoS'ed by heavy writers
668 */
669 dirty_thresh += dirty_thresh / 10; /* wheeee... */
670
Christoph Lameterc24f21b2006-06-30 01:55:42 -0700671 if (global_page_state(NR_UNSTABLE_NFS) +
672 global_page_state(NR_WRITEBACK) <= dirty_thresh)
673 break;
Jens Axboe8aa7e842009-07-09 14:52:32 +0200674 congestion_wait(BLK_RW_ASYNC, HZ/10);
Fengguang Wu369f2382007-10-16 23:30:45 -0700675
676 /*
677 * The caller might hold locks which can prevent IO completion
678 * or progress in the filesystem. So we cannot just sit here
679 * waiting for IO to complete.
680 */
681 if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO))
682 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 }
684}
685
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
688 */
689int dirty_writeback_centisecs_handler(ctl_table *table, int write,
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700690 void __user *buffer, size_t *length, loff_t *ppos)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691{
Alexey Dobriyan8d65af72009-09-23 15:57:19 -0700692 proc_dointvec(table, write, buffer, length, ppos);
Jens Axboe64231042010-05-21 20:00:35 +0200693 bdi_arm_supers_timer();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694 return 0;
695}
696
Jens Axboec2c49862010-05-20 09:18:47 +0200697#ifdef CONFIG_BLOCK
Matthew Garrett31373d02010-04-06 14:25:14 +0200698void laptop_mode_timer_fn(unsigned long data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699{
Matthew Garrett31373d02010-04-06 14:25:14 +0200700 struct request_queue *q = (struct request_queue *)data;
701 int nr_pages = global_page_state(NR_FILE_DIRTY) +
702 global_page_state(NR_UNSTABLE_NFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703
Matthew Garrett31373d02010-04-06 14:25:14 +0200704 /*
705 * We want to write everything out, not just down to the dirty
706 * threshold
707 */
Matthew Garrett31373d02010-04-06 14:25:14 +0200708 if (bdi_has_dirty_io(&q->backing_dev_info))
Christoph Hellwigc5444192010-06-08 18:15:15 +0200709 bdi_start_writeback(&q->backing_dev_info, nr_pages);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710}
711
712/*
713 * We've spun up the disk and we're in laptop mode: schedule writeback
714 * of all dirty data a few seconds from now. If the flush is already scheduled
715 * then push it back - the user is still using the disk.
716 */
Matthew Garrett31373d02010-04-06 14:25:14 +0200717void laptop_io_completion(struct backing_dev_info *info)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700718{
Matthew Garrett31373d02010-04-06 14:25:14 +0200719 mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720}
721
722/*
723 * We're in laptop mode and we've just synced. The sync's writes will have
724 * caused another writeback to be scheduled by laptop_io_completion.
725 * Nothing needs to be written back anymore, so we unschedule the writeback.
726 */
727void laptop_sync_completion(void)
728{
Matthew Garrett31373d02010-04-06 14:25:14 +0200729 struct backing_dev_info *bdi;
730
731 rcu_read_lock();
732
733 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
734 del_timer(&bdi->laptop_mode_wb_timer);
735
736 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737}
Jens Axboec2c49862010-05-20 09:18:47 +0200738#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739
740/*
741 * If ratelimit_pages is too high then we can get into dirty-data overload
742 * if a large number of processes all perform writes at the same time.
743 * If it is too low then SMP machines will call the (expensive)
744 * get_writeback_state too often.
745 *
746 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
747 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
748 * thresholds before writeback cuts in.
749 *
750 * But the limit should not be set too high. Because it also controls the
751 * amount of memory which the balance_dirty_pages() caller has to write back.
752 * If this is too large then the caller will block on the IO queue all the
753 * time. So limit it to four megabytes - the balance_dirty_pages() caller
754 * will write six megabyte chunks, max.
755 */
756
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700757void writeback_set_ratelimit(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700758{
Chandra Seetharaman40c99aa2006-09-29 02:01:24 -0700759 ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 if (ratelimit_pages < 16)
761 ratelimit_pages = 16;
762 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
763 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
764}
765
Chandra Seetharaman26c21432006-06-27 02:54:10 -0700766static int __cpuinit
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
768{
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700769 writeback_set_ratelimit();
Paul E. McKenneyaa0f0302007-02-10 01:46:37 -0800770 return NOTIFY_DONE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771}
772
Chandra Seetharaman74b85f32006-06-27 02:54:09 -0700773static struct notifier_block __cpuinitdata ratelimit_nb = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774 .notifier_call = ratelimit_handler,
775 .next = NULL,
776};
777
778/*
Linus Torvaldsdc6e29d2007-01-29 16:37:38 -0800779 * Called early on to tune the page writeback dirty limits.
780 *
781 * We used to scale dirty pages according to how total memory
782 * related to pages that could be allocated for buffers (by
783 * comparing nr_free_buffer_pages() to vm_total_pages.
784 *
785 * However, that was when we used "dirty_ratio" to scale with
786 * all memory, and we don't do that any more. "dirty_ratio"
787 * is now applied to total non-HIGHPAGE memory (by subtracting
788 * totalhigh_pages from vm_total_pages), and as such we can't
789 * get into the old insane situation any more where we had
790 * large amounts of dirty pages compared to a small amount of
791 * non-HIGHMEM memory.
792 *
793 * But we might still want to scale the dirty_ratio by how
794 * much memory the box has..
Linus Torvalds1da177e2005-04-16 15:20:36 -0700795 */
796void __init page_writeback_init(void)
797{
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700798 int shift;
799
Chandra Seetharaman2d1d43f2006-09-29 02:01:25 -0700800 writeback_set_ratelimit();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801 register_cpu_notifier(&ratelimit_nb);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700802
803 shift = calc_period_shift();
804 prop_descriptor_init(&vm_completions, shift);
Peter Zijlstra3e26c142007-10-16 23:25:50 -0700805 prop_descriptor_init(&vm_dirties, shift);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806}
807
David Howells811d7362006-08-29 19:06:09 +0100808/**
Jan Karaf446daae2010-08-09 17:19:12 -0700809 * tag_pages_for_writeback - tag pages to be written by write_cache_pages
810 * @mapping: address space structure to write
811 * @start: starting page index
812 * @end: ending page index (inclusive)
813 *
814 * This function scans the page range from @start to @end (inclusive) and tags
815 * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is
816 * that write_cache_pages (or whoever calls this function) will then use
817 * TOWRITE tag to identify pages eligible for writeback. This mechanism is
818 * used to avoid livelocking of writeback by a process steadily creating new
819 * dirty pages in the file (thus it is important for this function to be quick
820 * so that it can tag pages faster than a dirtying process can create them).
821 */
822/*
823 * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
824 */
Jan Karaf446daae2010-08-09 17:19:12 -0700825void tag_pages_for_writeback(struct address_space *mapping,
826 pgoff_t start, pgoff_t end)
827{
Randy Dunlap3c111a02010-08-11 14:17:30 -0700828#define WRITEBACK_TAG_BATCH 4096
Jan Karaf446daae2010-08-09 17:19:12 -0700829 unsigned long tagged;
830
831 do {
832 spin_lock_irq(&mapping->tree_lock);
833 tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree,
834 &start, end, WRITEBACK_TAG_BATCH,
835 PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
836 spin_unlock_irq(&mapping->tree_lock);
837 WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH);
838 cond_resched();
Jan Karad5ed3a42010-08-19 14:13:33 -0700839 /* We check 'start' to handle wrapping when end == ~0UL */
840 } while (tagged >= WRITEBACK_TAG_BATCH && start);
Jan Karaf446daae2010-08-09 17:19:12 -0700841}
842EXPORT_SYMBOL(tag_pages_for_writeback);
843
844/**
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700845 * 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 +0100846 * @mapping: address space structure to write
847 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700848 * @writepage: function called for each page
849 * @data: data passed to writepage function
David Howells811d7362006-08-29 19:06:09 +0100850 *
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700851 * If a page is already under I/O, write_cache_pages() skips it, even
David Howells811d7362006-08-29 19:06:09 +0100852 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
853 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
854 * and msync() need to guarantee that all the data which was dirty at the time
855 * the call was made get new I/O started against them. If wbc->sync_mode is
856 * WB_SYNC_ALL then we were called for data integrity and we must wait for
857 * existing IO to complete.
Jan Karaf446daae2010-08-09 17:19:12 -0700858 *
859 * To avoid livelocks (when other process dirties new pages), we first tag
860 * pages which should be written back with TOWRITE tag and only then start
861 * writing them. For data-integrity sync we have to be careful so that we do
862 * not miss some pages (e.g., because some other process has cleared TOWRITE
863 * tag we set). The rule we follow is that TOWRITE tag can be cleared only
864 * by the process clearing the DIRTY tag (and submitting the page for IO).
David Howells811d7362006-08-29 19:06:09 +0100865 */
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700866int write_cache_pages(struct address_space *mapping,
867 struct writeback_control *wbc, writepage_t writepage,
868 void *data)
David Howells811d7362006-08-29 19:06:09 +0100869{
David Howells811d7362006-08-29 19:06:09 +0100870 int ret = 0;
871 int done = 0;
David Howells811d7362006-08-29 19:06:09 +0100872 struct pagevec pvec;
873 int nr_pages;
Nick Piggin31a12662009-01-06 14:39:04 -0800874 pgoff_t uninitialized_var(writeback_index);
David Howells811d7362006-08-29 19:06:09 +0100875 pgoff_t index;
876 pgoff_t end; /* Inclusive */
Nick Pigginbd19e012009-01-06 14:39:06 -0800877 pgoff_t done_index;
Nick Piggin31a12662009-01-06 14:39:04 -0800878 int cycled;
David Howells811d7362006-08-29 19:06:09 +0100879 int range_whole = 0;
Jan Karaf446daae2010-08-09 17:19:12 -0700880 int tag;
David Howells811d7362006-08-29 19:06:09 +0100881
David Howells811d7362006-08-29 19:06:09 +0100882 pagevec_init(&pvec, 0);
883 if (wbc->range_cyclic) {
Nick Piggin31a12662009-01-06 14:39:04 -0800884 writeback_index = mapping->writeback_index; /* prev offset */
885 index = writeback_index;
886 if (index == 0)
887 cycled = 1;
888 else
889 cycled = 0;
David Howells811d7362006-08-29 19:06:09 +0100890 end = -1;
891 } else {
892 index = wbc->range_start >> PAGE_CACHE_SHIFT;
893 end = wbc->range_end >> PAGE_CACHE_SHIFT;
894 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
895 range_whole = 1;
Nick Piggin31a12662009-01-06 14:39:04 -0800896 cycled = 1; /* ignore range_cyclic tests */
David Howells811d7362006-08-29 19:06:09 +0100897 }
Jan Karaf446daae2010-08-09 17:19:12 -0700898 if (wbc->sync_mode == WB_SYNC_ALL)
899 tag = PAGECACHE_TAG_TOWRITE;
900 else
901 tag = PAGECACHE_TAG_DIRTY;
David Howells811d7362006-08-29 19:06:09 +0100902retry:
Jan Karaf446daae2010-08-09 17:19:12 -0700903 if (wbc->sync_mode == WB_SYNC_ALL)
904 tag_pages_for_writeback(mapping, index, end);
Nick Pigginbd19e012009-01-06 14:39:06 -0800905 done_index = index;
Nick Piggin5a3d5c92009-01-06 14:39:09 -0800906 while (!done && (index <= end)) {
907 int i;
908
Jan Karaf446daae2010-08-09 17:19:12 -0700909 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
Nick Piggin5a3d5c92009-01-06 14:39:09 -0800910 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
911 if (nr_pages == 0)
912 break;
David Howells811d7362006-08-29 19:06:09 +0100913
David Howells811d7362006-08-29 19:06:09 +0100914 for (i = 0; i < nr_pages; i++) {
915 struct page *page = pvec.pages[i];
916
Nick Piggind5482cd2009-01-06 14:39:11 -0800917 /*
918 * At this point, the page may be truncated or
919 * invalidated (changing page->mapping to NULL), or
920 * even swizzled back from swapper_space to tmpfs file
921 * mapping. However, page->index will not change
922 * because we have a reference on the page.
923 */
924 if (page->index > end) {
925 /*
926 * can't be range_cyclic (1st pass) because
927 * end == -1 in that case.
928 */
929 done = 1;
930 break;
931 }
932
Nick Pigginbd19e012009-01-06 14:39:06 -0800933 done_index = page->index + 1;
934
David Howells811d7362006-08-29 19:06:09 +0100935 lock_page(page);
936
Nick Piggin5a3d5c92009-01-06 14:39:09 -0800937 /*
938 * Page truncated or invalidated. We can freely skip it
939 * then, even for data integrity operations: the page
940 * has disappeared concurrently, so there could be no
941 * real expectation of this data interity operation
942 * even if there is now a new, dirty page at the same
943 * pagecache address.
944 */
David Howells811d7362006-08-29 19:06:09 +0100945 if (unlikely(page->mapping != mapping)) {
Nick Piggin5a3d5c92009-01-06 14:39:09 -0800946continue_unlock:
David Howells811d7362006-08-29 19:06:09 +0100947 unlock_page(page);
948 continue;
949 }
950
Nick Piggin515f4a02009-01-06 14:39:10 -0800951 if (!PageDirty(page)) {
952 /* someone wrote it for us */
953 goto continue_unlock;
954 }
David Howells811d7362006-08-29 19:06:09 +0100955
Nick Piggin515f4a02009-01-06 14:39:10 -0800956 if (PageWriteback(page)) {
957 if (wbc->sync_mode != WB_SYNC_NONE)
958 wait_on_page_writeback(page);
959 else
960 goto continue_unlock;
961 }
962
963 BUG_ON(PageWriteback(page));
964 if (!clear_page_dirty_for_io(page))
Nick Piggin5a3d5c92009-01-06 14:39:09 -0800965 goto continue_unlock;
David Howells811d7362006-08-29 19:06:09 +0100966
Dave Chinner9e094382010-07-07 13:24:08 +1000967 trace_wbc_writepage(wbc, mapping->backing_dev_info);
Miklos Szeredi0ea97182007-05-10 22:22:51 -0700968 ret = (*writepage)(page, wbc, data);
Nick Piggin00266772009-01-06 14:39:06 -0800969 if (unlikely(ret)) {
970 if (ret == AOP_WRITEPAGE_ACTIVATE) {
971 unlock_page(page);
972 ret = 0;
973 } else {
974 /*
975 * done_index is set past this page,
976 * so media errors will not choke
977 * background writeout for the entire
978 * file. This has consequences for
979 * range_cyclic semantics (ie. it may
980 * not be suitable for data integrity
981 * writeout).
982 */
983 done = 1;
984 break;
985 }
Dave Chinner0b564922010-06-09 10:37:18 +1000986 }
David Howells811d7362006-08-29 19:06:09 +0100987
Dave Chinner546a1922010-08-24 11:44:34 +1000988 /*
989 * We stop writing back only if we are not doing
990 * integrity sync. In case of integrity sync we have to
991 * keep going until we have written all the pages
992 * we tagged for writeback prior to entering this loop.
993 */
994 if (--wbc->nr_to_write <= 0 &&
995 wbc->sync_mode == WB_SYNC_NONE) {
996 done = 1;
997 break;
Nick Piggin05fe4782009-01-06 14:39:08 -0800998 }
David Howells811d7362006-08-29 19:06:09 +0100999 }
1000 pagevec_release(&pvec);
1001 cond_resched();
1002 }
Nick Piggin3a4c6802009-02-12 04:34:23 +01001003 if (!cycled && !done) {
David Howells811d7362006-08-29 19:06:09 +01001004 /*
Nick Piggin31a12662009-01-06 14:39:04 -08001005 * range_cyclic:
David Howells811d7362006-08-29 19:06:09 +01001006 * We hit the last page and there is more work to be done: wrap
1007 * back to the start of the file
1008 */
Nick Piggin31a12662009-01-06 14:39:04 -08001009 cycled = 1;
David Howells811d7362006-08-29 19:06:09 +01001010 index = 0;
Nick Piggin31a12662009-01-06 14:39:04 -08001011 end = writeback_index - 1;
David Howells811d7362006-08-29 19:06:09 +01001012 goto retry;
1013 }
Dave Chinner0b564922010-06-09 10:37:18 +10001014 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
1015 mapping->writeback_index = done_index;
Aneesh Kumar K.V06d6cf62008-07-11 19:27:31 -04001016
David Howells811d7362006-08-29 19:06:09 +01001017 return ret;
1018}
Miklos Szeredi0ea97182007-05-10 22:22:51 -07001019EXPORT_SYMBOL(write_cache_pages);
1020
1021/*
1022 * Function used by generic_writepages to call the real writepage
1023 * function and set the mapping flags on error
1024 */
1025static int __writepage(struct page *page, struct writeback_control *wbc,
1026 void *data)
1027{
1028 struct address_space *mapping = data;
1029 int ret = mapping->a_ops->writepage(page, wbc);
1030 mapping_set_error(mapping, ret);
1031 return ret;
1032}
1033
1034/**
1035 * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them.
1036 * @mapping: address space structure to write
1037 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
1038 *
1039 * This is a library function, which implements the writepages()
1040 * address_space_operation.
1041 */
1042int generic_writepages(struct address_space *mapping,
1043 struct writeback_control *wbc)
1044{
1045 /* deal with chardevs and other special file */
1046 if (!mapping->a_ops->writepage)
1047 return 0;
1048
1049 return write_cache_pages(mapping, wbc, __writepage, mapping);
1050}
David Howells811d7362006-08-29 19:06:09 +01001051
1052EXPORT_SYMBOL(generic_writepages);
1053
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
1055{
Andrew Morton22905f72005-11-16 15:07:01 -08001056 int ret;
1057
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 if (wbc->nr_to_write <= 0)
1059 return 0;
1060 if (mapping->a_ops->writepages)
Peter Zijlstrad08b3852006-09-25 23:30:57 -07001061 ret = mapping->a_ops->writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001062 else
1063 ret = generic_writepages(mapping, wbc);
Andrew Morton22905f72005-11-16 15:07:01 -08001064 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065}
1066
1067/**
1068 * write_one_page - write out a single page and optionally wait on I/O
Martin Waitz67be2dd2005-05-01 08:59:26 -07001069 * @page: the page to write
1070 * @wait: if true, wait on writeout
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 *
1072 * The page must be locked by the caller and will be unlocked upon return.
1073 *
1074 * write_one_page() returns a negative error code if I/O failed.
1075 */
1076int write_one_page(struct page *page, int wait)
1077{
1078 struct address_space *mapping = page->mapping;
1079 int ret = 0;
1080 struct writeback_control wbc = {
1081 .sync_mode = WB_SYNC_ALL,
1082 .nr_to_write = 1,
1083 };
1084
1085 BUG_ON(!PageLocked(page));
1086
1087 if (wait)
1088 wait_on_page_writeback(page);
1089
1090 if (clear_page_dirty_for_io(page)) {
1091 page_cache_get(page);
1092 ret = mapping->a_ops->writepage(page, &wbc);
1093 if (ret == 0 && wait) {
1094 wait_on_page_writeback(page);
1095 if (PageError(page))
1096 ret = -EIO;
1097 }
1098 page_cache_release(page);
1099 } else {
1100 unlock_page(page);
1101 }
1102 return ret;
1103}
1104EXPORT_SYMBOL(write_one_page);
1105
1106/*
Ken Chen76719322007-02-10 01:43:15 -08001107 * For address_spaces which do not use buffers nor write back.
1108 */
1109int __set_page_dirty_no_writeback(struct page *page)
1110{
1111 if (!PageDirty(page))
1112 SetPageDirty(page);
1113 return 0;
1114}
1115
1116/*
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001117 * Helper function for set_page_dirty family.
1118 * NOTE: This relies on being atomic wrt interrupts.
1119 */
1120void account_page_dirtied(struct page *page, struct address_space *mapping)
1121{
1122 if (mapping_cap_account_dirty(mapping)) {
1123 __inc_zone_page_state(page, NR_FILE_DIRTY);
1124 __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
1125 task_dirty_inc(current);
1126 task_io_account_write(PAGE_CACHE_SIZE);
1127 }
1128}
Michael Rubin679ceac2010-08-20 02:31:26 -07001129EXPORT_SYMBOL(account_page_dirtied);
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001130
1131/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 * For address_spaces which do not use buffers. Just tag the page as dirty in
1133 * its radix tree.
1134 *
1135 * This is also used when a single buffer is being dirtied: we want to set the
1136 * page dirty in that case, but not all the buffers. This is a "bottom-up"
1137 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
1138 *
1139 * Most callers have locked the page, which pins the address_space in memory.
1140 * But zap_pte_range() does not lock the page, however in that case the
1141 * mapping is pinned by the vma's ->vm_file reference.
1142 *
1143 * We take care to handle the case where the page was truncated from the
Simon Arlott183ff222007-10-20 01:27:18 +02001144 * mapping by re-checking page_mapping() inside tree_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 */
1146int __set_page_dirty_nobuffers(struct page *page)
1147{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148 if (!TestSetPageDirty(page)) {
1149 struct address_space *mapping = page_mapping(page);
1150 struct address_space *mapping2;
1151
Andrew Morton8c085402006-12-10 02:19:24 -08001152 if (!mapping)
1153 return 1;
1154
Nick Piggin19fd6232008-07-25 19:45:32 -07001155 spin_lock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001156 mapping2 = page_mapping(page);
1157 if (mapping2) { /* Race with truncate? */
1158 BUG_ON(mapping2 != mapping);
Nick Piggin787d2212007-07-17 04:03:34 -07001159 WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -07001160 account_page_dirtied(page, mapping);
Andrew Morton8c085402006-12-10 02:19:24 -08001161 radix_tree_tag_set(&mapping->page_tree,
1162 page_index(page), PAGECACHE_TAG_DIRTY);
1163 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001164 spin_unlock_irq(&mapping->tree_lock);
Andrew Morton8c085402006-12-10 02:19:24 -08001165 if (mapping->host) {
1166 /* !PageAnon && !swapper_space */
1167 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001168 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001169 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001171 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172}
1173EXPORT_SYMBOL(__set_page_dirty_nobuffers);
1174
1175/*
1176 * When a writepage implementation decides that it doesn't want to write this
1177 * page for some reason, it should redirty the locked page via
1178 * redirty_page_for_writepage() and it should then unlock the page and return 0
1179 */
1180int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
1181{
1182 wbc->pages_skipped++;
1183 return __set_page_dirty_nobuffers(page);
1184}
1185EXPORT_SYMBOL(redirty_page_for_writepage);
1186
1187/*
Wu Fengguang6746aff2009-09-16 11:50:14 +02001188 * Dirty a page.
1189 *
1190 * For pages with a mapping this should be done under the page lock
1191 * for the benefit of asynchronous memory errors who prefer a consistent
1192 * dirty state. This rule can be broken in some special cases,
1193 * but should be better not to.
1194 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195 * If the mapping doesn't provide a set_page_dirty a_op, then
1196 * just fall through and assume that it wants buffer_heads.
1197 */
Nick Piggin1cf6e7d2009-02-18 14:48:18 -08001198int set_page_dirty(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199{
1200 struct address_space *mapping = page_mapping(page);
1201
1202 if (likely(mapping)) {
1203 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
David Howells93614012006-09-30 20:45:40 +02001204#ifdef CONFIG_BLOCK
1205 if (!spd)
1206 spd = __set_page_dirty_buffers;
1207#endif
1208 return (*spd)(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001209 }
Andrew Morton4741c9f2006-03-24 03:18:11 -08001210 if (!PageDirty(page)) {
1211 if (!TestSetPageDirty(page))
1212 return 1;
1213 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 return 0;
1215}
1216EXPORT_SYMBOL(set_page_dirty);
1217
1218/*
1219 * set_page_dirty() is racy if the caller has no reference against
1220 * page->mapping->host, and if the page is unlocked. This is because another
1221 * CPU could truncate the page off the mapping and then free the mapping.
1222 *
1223 * Usually, the page _is_ locked, or the caller is a user-space process which
1224 * holds a reference on the inode by having an open file.
1225 *
1226 * In other cases, the page should be locked before running set_page_dirty().
1227 */
1228int set_page_dirty_lock(struct page *page)
1229{
1230 int ret;
1231
Nick Piggindb376482006-09-25 23:31:24 -07001232 lock_page_nosync(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 ret = set_page_dirty(page);
1234 unlock_page(page);
1235 return ret;
1236}
1237EXPORT_SYMBOL(set_page_dirty_lock);
1238
1239/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240 * Clear a page's dirty flag, while caring for dirty memory accounting.
1241 * Returns true if the page was previously dirty.
1242 *
1243 * This is for preparing to put the page under writeout. We leave the page
1244 * tagged as dirty in the radix tree so that a concurrent write-for-sync
1245 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
1246 * implementation will run either set_page_writeback() or set_page_dirty(),
1247 * at which stage we bring the page's dirty flag and radix-tree dirty tag
1248 * back into sync.
1249 *
1250 * This incoherency between the page's dirty flag and radix-tree tag is
1251 * unfortunate, but it only exists while the page is locked.
1252 */
1253int clear_page_dirty_for_io(struct page *page)
1254{
1255 struct address_space *mapping = page_mapping(page);
1256
Nick Piggin79352892007-07-19 01:47:22 -07001257 BUG_ON(!PageLocked(page));
1258
Fengguang Wufe3cba12007-07-19 01:48:07 -07001259 ClearPageReclaim(page);
Linus Torvalds7658cc22006-12-29 10:00:58 -08001260 if (mapping && mapping_cap_account_dirty(mapping)) {
1261 /*
1262 * Yes, Virginia, this is indeed insane.
1263 *
1264 * We use this sequence to make sure that
1265 * (a) we account for dirty stats properly
1266 * (b) we tell the low-level filesystem to
1267 * mark the whole page dirty if it was
1268 * dirty in a pagetable. Only to then
1269 * (c) clean the page again and return 1 to
1270 * cause the writeback.
1271 *
1272 * This way we avoid all nasty races with the
1273 * dirty bit in multiple places and clearing
1274 * them concurrently from different threads.
1275 *
1276 * Note! Normally the "set_page_dirty(page)"
1277 * has no effect on the actual dirty bit - since
1278 * that will already usually be set. But we
1279 * need the side effects, and it can help us
1280 * avoid races.
1281 *
1282 * We basically use the page "master dirty bit"
1283 * as a serialization point for all the different
1284 * threads doing their things.
Linus Torvalds7658cc22006-12-29 10:00:58 -08001285 */
1286 if (page_mkclean(page))
1287 set_page_dirty(page);
Nick Piggin79352892007-07-19 01:47:22 -07001288 /*
1289 * We carefully synchronise fault handlers against
1290 * installing a dirty pte and marking the page dirty
1291 * at this point. We do this by having them hold the
1292 * page lock at some point after installing their
1293 * pte, but before marking the page dirty.
1294 * Pages are always locked coming in here, so we get
1295 * the desired exclusion. See mm/memory.c:do_wp_page()
1296 * for more comments.
1297 */
Linus Torvalds7658cc22006-12-29 10:00:58 -08001298 if (TestClearPageDirty(page)) {
Andrew Morton8c085402006-12-10 02:19:24 -08001299 dec_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -07001300 dec_bdi_stat(mapping->backing_dev_info,
1301 BDI_RECLAIMABLE);
Linus Torvalds7658cc22006-12-29 10:00:58 -08001302 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001304 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305 }
Linus Torvalds7658cc22006-12-29 10:00:58 -08001306 return TestClearPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307}
Hans Reiser58bb01a2005-11-18 01:10:53 -08001308EXPORT_SYMBOL(clear_page_dirty_for_io);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001309
1310int test_clear_page_writeback(struct page *page)
1311{
1312 struct address_space *mapping = page_mapping(page);
1313 int ret;
1314
1315 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001316 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317 unsigned long flags;
1318
Nick Piggin19fd6232008-07-25 19:45:32 -07001319 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320 ret = TestClearPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001321 if (ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001322 radix_tree_tag_clear(&mapping->page_tree,
1323 page_index(page),
1324 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001325 if (bdi_cap_account_writeback(bdi)) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001326 __dec_bdi_stat(bdi, BDI_WRITEBACK);
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -07001327 __bdi_writeout_inc(bdi);
1328 }
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001329 }
Nick Piggin19fd6232008-07-25 19:45:32 -07001330 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331 } else {
1332 ret = TestClearPageWriteback(page);
1333 }
Andrew Mortond688abf2007-07-19 01:49:17 -07001334 if (ret)
1335 dec_zone_page_state(page, NR_WRITEBACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 return ret;
1337}
1338
1339int test_set_page_writeback(struct page *page)
1340{
1341 struct address_space *mapping = page_mapping(page);
1342 int ret;
1343
1344 if (mapping) {
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001345 struct backing_dev_info *bdi = mapping->backing_dev_info;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346 unsigned long flags;
1347
Nick Piggin19fd6232008-07-25 19:45:32 -07001348 spin_lock_irqsave(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 ret = TestSetPageWriteback(page);
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001350 if (!ret) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 radix_tree_tag_set(&mapping->page_tree,
1352 page_index(page),
1353 PAGECACHE_TAG_WRITEBACK);
Miklos Szeredie4ad08f2008-04-30 00:54:37 -07001354 if (bdi_cap_account_writeback(bdi))
Peter Zijlstra69cb51d2007-10-16 23:25:48 -07001355 __inc_bdi_stat(bdi, BDI_WRITEBACK);
1356 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357 if (!PageDirty(page))
1358 radix_tree_tag_clear(&mapping->page_tree,
1359 page_index(page),
1360 PAGECACHE_TAG_DIRTY);
Jan Karaf446daae2010-08-09 17:19:12 -07001361 radix_tree_tag_clear(&mapping->page_tree,
1362 page_index(page),
1363 PAGECACHE_TAG_TOWRITE);
Nick Piggin19fd6232008-07-25 19:45:32 -07001364 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365 } else {
1366 ret = TestSetPageWriteback(page);
1367 }
Andrew Mortond688abf2007-07-19 01:49:17 -07001368 if (!ret)
1369 inc_zone_page_state(page, NR_WRITEBACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370 return ret;
1371
1372}
1373EXPORT_SYMBOL(test_set_page_writeback);
1374
1375/*
Nick Piggin00128182007-10-16 01:24:40 -07001376 * Return true if any of the pages in the mapping are marked with the
Linus Torvalds1da177e2005-04-16 15:20:36 -07001377 * passed tag.
1378 */
1379int mapping_tagged(struct address_space *mapping, int tag)
1380{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381 int ret;
Nick Piggin00128182007-10-16 01:24:40 -07001382 rcu_read_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383 ret = radix_tree_tagged(&mapping->page_tree, tag);
Nick Piggin00128182007-10-16 01:24:40 -07001384 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001385 return ret;
1386}
1387EXPORT_SYMBOL(mapping_tagged);