Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
f30c2269 | 2 | * mm/page-writeback.c |
1da177e4 LT |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. | |
04fbfdc1 | 5 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
1da177e4 LT |
6 | * |
7 | * Contains functions related to writing back dirty pages at the | |
8 | * address_space level. | |
9 | * | |
e1f8e874 | 10 | * 10Apr2002 Andrew Morton |
1da177e4 LT |
11 | * Initial version |
12 | */ | |
13 | ||
14 | #include <linux/kernel.h> | |
b95f1b31 | 15 | #include <linux/export.h> |
1da177e4 LT |
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> | |
55e829af | 25 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
26 | #include <linux/blkdev.h> |
27 | #include <linux/mpage.h> | |
d08b3851 | 28 | #include <linux/rmap.h> |
1da177e4 LT |
29 | #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> | |
ff01bb48 | 35 | #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ |
811d736f | 36 | #include <linux/pagevec.h> |
eb608e3a | 37 | #include <linux/timer.h> |
028c2dd1 | 38 | #include <trace/events/writeback.h> |
1da177e4 | 39 | |
ffd1f609 WF |
40 | /* |
41 | * Sleep at most 200ms at a time in balance_dirty_pages(). | |
42 | */ | |
43 | #define MAX_PAUSE max(HZ/5, 1) | |
44 | ||
5b9b3574 WF |
45 | /* |
46 | * 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 | ||
e98be2d5 WF |
51 | /* |
52 | * Estimate write bandwidth at 200ms intervals. | |
53 | */ | |
54 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) | |
55 | ||
6c14ae1e WF |
56 | #define RATELIMIT_CALC_SHIFT 10 |
57 | ||
1da177e4 LT |
58 | /* |
59 | * 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 | */ | |
62 | static long ratelimit_pages = 32; | |
63 | ||
1da177e4 LT |
64 | /* The following parameters are exported via /proc/sys/vm */ |
65 | ||
66 | /* | |
5b0830cb | 67 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 68 | */ |
1b5e62b4 | 69 | int dirty_background_ratio = 10; |
1da177e4 | 70 | |
2da02997 DR |
71 | /* |
72 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
73 | * dirty_background_ratio * the amount of dirtyable memory | |
74 | */ | |
75 | unsigned long dirty_background_bytes; | |
76 | ||
195cf453 BG |
77 | /* |
78 | * free highmem will not be subtracted from the total free memory | |
79 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
80 | */ | |
81 | int vm_highmem_is_dirtyable; | |
82 | ||
1da177e4 LT |
83 | /* |
84 | * The generator of dirty data starts writeback at this percentage | |
85 | */ | |
1b5e62b4 | 86 | int vm_dirty_ratio = 20; |
1da177e4 | 87 | |
2da02997 DR |
88 | /* |
89 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
90 | * vm_dirty_ratio * the amount of dirtyable memory | |
91 | */ | |
92 | unsigned long vm_dirty_bytes; | |
93 | ||
1da177e4 | 94 | /* |
704503d8 | 95 | * The interval between `kupdate'-style writebacks |
1da177e4 | 96 | */ |
22ef37ee | 97 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 | 98 | |
91913a29 AB |
99 | EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
100 | ||
1da177e4 | 101 | /* |
704503d8 | 102 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 103 | */ |
22ef37ee | 104 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
105 | |
106 | /* | |
107 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
108 | */ | |
109 | int block_dump; | |
110 | ||
111 | /* | |
ed5b43f1 BS |
112 | * 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. | |
1da177e4 LT |
114 | */ |
115 | int laptop_mode; | |
116 | ||
117 | EXPORT_SYMBOL(laptop_mode); | |
118 | ||
119 | /* End of sysctl-exported parameters */ | |
120 | ||
c42843f2 | 121 | unsigned long global_dirty_limit; |
1da177e4 | 122 | |
04fbfdc1 PZ |
123 | /* |
124 | * 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 | */ | |
eb608e3a JK |
139 | static struct fprop_global writeout_completions; |
140 | ||
141 | static void writeout_period(unsigned long t); | |
142 | /* Timer for aging of writeout_completions */ | |
143 | static struct timer_list writeout_period_timer = | |
144 | TIMER_DEFERRED_INITIALIZER(writeout_period, 0, 0); | |
145 | static 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) | |
04fbfdc1 | 153 | |
1edf2234 JW |
154 | /* |
155 | * 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 | */ | |
ccafa287 | 171 | |
a756cf59 JW |
172 | /* |
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 | ||
1edf2234 JW |
190 | static 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) + | |
ab8fabd4 | 201 | zone_reclaimable_pages(z) - z->dirty_balance_reserve; |
1edf2234 | 202 | } |
c8b74c2f SR |
203 | /* |
204 | * 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 | ||
1edf2234 JW |
215 | /* |
216 | * 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 | /** | |
ccafa287 | 228 | * global_dirtyable_memory - number of globally dirtyable pages |
1edf2234 | 229 | * |
ccafa287 JW |
230 | * Returns the global number of pages potentially available for dirty |
231 | * page cache. This is the base value for the global dirty limits. | |
1edf2234 | 232 | */ |
18cf8cf8 | 233 | static unsigned long global_dirtyable_memory(void) |
1edf2234 JW |
234 | { |
235 | unsigned long x; | |
236 | ||
c8b74c2f SR |
237 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
238 | x -= min(x, dirty_balance_reserve); | |
1edf2234 JW |
239 | |
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 | ||
ccafa287 JW |
246 | /* |
247 | * 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 | */ | |
255 | void 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 | ||
a756cf59 JW |
287 | /** |
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 | */ | |
294 | static 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 | */ | |
c8b74c2f SR |
305 | 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; | |
a756cf59 JW |
311 | } |
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 | */ | |
320 | static 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 | */ | |
345 | bool 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 | ||
2da02997 | 354 | int dirty_background_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 355 | void __user *buffer, size_t *lenp, |
2da02997 DR |
356 | loff_t *ppos) |
357 | { | |
358 | int ret; | |
359 | ||
8d65af78 | 360 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
361 | if (ret == 0 && write) |
362 | dirty_background_bytes = 0; | |
363 | return ret; | |
364 | } | |
365 | ||
366 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 367 | void __user *buffer, size_t *lenp, |
2da02997 DR |
368 | loff_t *ppos) |
369 | { | |
370 | int ret; | |
371 | ||
8d65af78 | 372 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
373 | if (ret == 0 && write) |
374 | dirty_background_ratio = 0; | |
375 | return ret; | |
376 | } | |
377 | ||
04fbfdc1 | 378 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 379 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
380 | loff_t *ppos) |
381 | { | |
382 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
383 | int ret; |
384 | ||
8d65af78 | 385 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 386 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
eb608e3a | 387 | writeback_set_ratelimit(); |
2da02997 DR |
388 | vm_dirty_bytes = 0; |
389 | } | |
390 | return ret; | |
391 | } | |
392 | ||
2da02997 | 393 | int dirty_bytes_handler(struct ctl_table *table, int write, |
8d65af78 | 394 | void __user *buffer, size_t *lenp, |
2da02997 DR |
395 | loff_t *ppos) |
396 | { | |
fc3501d4 | 397 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
398 | int ret; |
399 | ||
8d65af78 | 400 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 | 401 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
eb608e3a | 402 | writeback_set_ratelimit(); |
2da02997 | 403 | vm_dirty_ratio = 0; |
04fbfdc1 PZ |
404 | } |
405 | return ret; | |
406 | } | |
407 | ||
eb608e3a JK |
408 | static 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 | ||
04fbfdc1 PZ |
417 | /* |
418 | * Increment the BDI's writeout completion count and the global writeout | |
419 | * completion count. Called from test_clear_page_writeback(). | |
420 | */ | |
421 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
422 | { | |
f7d2b1ec | 423 | __inc_bdi_stat(bdi, BDI_WRITTEN); |
eb608e3a JK |
424 | __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 | } | |
04fbfdc1 PZ |
437 | } |
438 | ||
dd5656e5 MS |
439 | void 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 | } | |
447 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); | |
448 | ||
04fbfdc1 PZ |
449 | /* |
450 | * Obtain an accurate fraction of the BDI's portion. | |
451 | */ | |
452 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
453 | long *numerator, long *denominator) | |
454 | { | |
eb608e3a | 455 | fprop_fraction_percpu(&writeout_completions, &bdi->completions, |
04fbfdc1 | 456 | numerator, denominator); |
04fbfdc1 PZ |
457 | } |
458 | ||
eb608e3a JK |
459 | /* |
460 | * On idle system, we can be called long after we scheduled because we use | |
461 | * deferred timers so count with missed periods. | |
462 | */ | |
463 | static 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 | ||
189d3c4a | 481 | /* |
d08c429b JW |
482 | * 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%. | |
189d3c4a | 485 | */ |
189d3c4a PZ |
486 | static unsigned int bdi_min_ratio; |
487 | ||
488 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
489 | { | |
490 | int ret = 0; | |
189d3c4a | 491 | |
cfc4ba53 | 492 | spin_lock_bh(&bdi_lock); |
a42dde04 | 493 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 494 | ret = -EINVAL; |
a42dde04 PZ |
495 | } 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 | } | |
cfc4ba53 | 504 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
505 | |
506 | return ret; | |
507 | } | |
508 | ||
509 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
510 | { | |
a42dde04 PZ |
511 | int ret = 0; |
512 | ||
513 | if (max_ratio > 100) | |
514 | return -EINVAL; | |
515 | ||
cfc4ba53 | 516 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
517 | if (bdi->min_ratio > max_ratio) { |
518 | ret = -EINVAL; | |
519 | } else { | |
520 | bdi->max_ratio = max_ratio; | |
eb608e3a | 521 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
a42dde04 | 522 | } |
cfc4ba53 | 523 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
524 | |
525 | return ret; | |
526 | } | |
a42dde04 | 527 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 528 | |
6c14ae1e WF |
529 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
530 | unsigned long bg_thresh) | |
531 | { | |
532 | return (thresh + bg_thresh) / 2; | |
533 | } | |
534 | ||
ffd1f609 WF |
535 | static unsigned long hard_dirty_limit(unsigned long thresh) |
536 | { | |
537 | return max(thresh, global_dirty_limit); | |
538 | } | |
539 | ||
6f718656 | 540 | /** |
1babe183 | 541 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
6f718656 WF |
542 | * @bdi: the backing_dev_info to query |
543 | * @dirty: global dirty limit in pages | |
1babe183 | 544 | * |
6f718656 WF |
545 | * 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. | |
aed21ad2 WF |
547 | * |
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. | |
1babe183 | 554 | * |
6f718656 | 555 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
556 | * - 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 | */ | |
562 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) | |
16c4042f WF |
563 | { |
564 | u64 bdi_dirty; | |
565 | long numerator, denominator; | |
04fbfdc1 | 566 | |
16c4042f WF |
567 | /* |
568 | * Calculate this BDI's share of the dirty ratio. | |
569 | */ | |
570 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
04fbfdc1 | 571 | |
16c4042f WF |
572 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
573 | bdi_dirty *= numerator; | |
574 | do_div(bdi_dirty, denominator); | |
04fbfdc1 | 575 | |
16c4042f WF |
576 | 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; | |
1da177e4 LT |
581 | } |
582 | ||
6c14ae1e WF |
583 | /* |
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 | */ | |
658 | static 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; | |
aed21ad2 WF |
735 | /* |
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 | */ | |
8927f66c | 742 | bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); |
6c14ae1e WF |
743 | /* |
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) { | |
50657fc4 WF |
761 | pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), |
762 | x_intercept - bdi_setpoint + 1); | |
6c14ae1e WF |
763 | } else |
764 | pos_ratio /= 4; | |
765 | ||
8927f66c WF |
766 | /* |
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) { | |
50657fc4 WF |
773 | if (bdi_dirty > x_intercept / 8) |
774 | pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty); | |
775 | else | |
8927f66c WF |
776 | pos_ratio *= 8; |
777 | } | |
778 | ||
6c14ae1e WF |
779 | return pos_ratio; |
780 | } | |
781 | ||
e98be2d5 WF |
782 | static 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 | ||
817 | out: | |
818 | bdi->write_bandwidth = bw; | |
819 | bdi->avg_write_bandwidth = avg; | |
820 | } | |
821 | ||
c42843f2 WF |
822 | /* |
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 | */ | |
830 | static 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; | |
853 | update: | |
854 | global_dirty_limit = limit; | |
855 | } | |
856 | ||
857 | static 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 | ||
be3ffa27 WF |
878 | /* |
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 | */ | |
884 | static 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 | { | |
7381131c WF |
893 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); |
894 | unsigned long limit = hard_dirty_limit(thresh); | |
895 | unsigned long setpoint = (freerun + limit) / 2; | |
be3ffa27 WF |
896 | 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; | |
7381131c WF |
902 | unsigned long step; |
903 | unsigned long x; | |
be3ffa27 WF |
904 | |
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); | |
bdaac490 WF |
952 | /* |
953 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw | |
954 | */ | |
955 | if (unlikely(balanced_dirty_ratelimit > write_bw)) | |
956 | balanced_dirty_ratelimit = write_bw; | |
be3ffa27 | 957 | |
7381131c WF |
958 | /* |
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 | |
331cbdee | 964 | * code makes use of task_ratelimit to filter out singular points and |
7381131c WF |
965 | * 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 | |
331cbdee | 987 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
7381131c WF |
988 | * 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; | |
b48c104d WF |
1023 | |
1024 | trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit); | |
be3ffa27 WF |
1025 | } |
1026 | ||
e98be2d5 | 1027 | void __bdi_update_bandwidth(struct backing_dev_info *bdi, |
c42843f2 | 1028 | unsigned long thresh, |
af6a3113 | 1029 | unsigned long bg_thresh, |
c42843f2 WF |
1030 | unsigned long dirty, |
1031 | unsigned long bdi_thresh, | |
1032 | unsigned long bdi_dirty, | |
e98be2d5 WF |
1033 | unsigned long start_time) |
1034 | { | |
1035 | unsigned long now = jiffies; | |
1036 | unsigned long elapsed = now - bdi->bw_time_stamp; | |
be3ffa27 | 1037 | unsigned long dirtied; |
e98be2d5 WF |
1038 | unsigned long written; |
1039 | ||
1040 | /* | |
1041 | * rate-limit, only update once every 200ms. | |
1042 | */ | |
1043 | if (elapsed < BANDWIDTH_INTERVAL) | |
1044 | return; | |
1045 | ||
be3ffa27 | 1046 | dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); |
e98be2d5 WF |
1047 | 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 | ||
be3ffa27 | 1056 | if (thresh) { |
c42843f2 | 1057 | global_update_bandwidth(thresh, dirty, now); |
be3ffa27 WF |
1058 | bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, |
1059 | bdi_thresh, bdi_dirty, | |
1060 | dirtied, elapsed); | |
1061 | } | |
e98be2d5 WF |
1062 | bdi_update_write_bandwidth(bdi, elapsed, written); |
1063 | ||
1064 | snapshot: | |
be3ffa27 | 1065 | bdi->dirtied_stamp = dirtied; |
e98be2d5 WF |
1066 | bdi->written_stamp = written; |
1067 | bdi->bw_time_stamp = now; | |
1068 | } | |
1069 | ||
1070 | static void bdi_update_bandwidth(struct backing_dev_info *bdi, | |
c42843f2 | 1071 | unsigned long thresh, |
af6a3113 | 1072 | unsigned long bg_thresh, |
c42843f2 WF |
1073 | unsigned long dirty, |
1074 | unsigned long bdi_thresh, | |
1075 | unsigned long bdi_dirty, | |
e98be2d5 WF |
1076 | 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); | |
af6a3113 WF |
1081 | __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, |
1082 | bdi_thresh, bdi_dirty, start_time); | |
e98be2d5 WF |
1083 | spin_unlock(&bdi->wb.list_lock); |
1084 | } | |
1085 | ||
9d823e8f | 1086 | /* |
d0e1d66b | 1087 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
9d823e8f WF |
1088 | * 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 | */ | |
1094 | static 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 | ||
7ccb9ad5 WF |
1103 | static long bdi_max_pause(struct backing_dev_info *bdi, |
1104 | unsigned long bdi_dirty) | |
c8462cc9 | 1105 | { |
7ccb9ad5 WF |
1106 | long bw = bdi->avg_write_bandwidth; |
1107 | long t; | |
c8462cc9 | 1108 | |
7ccb9ad5 WF |
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 | */ | |
1116 | 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 | ||
1122 | static 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) | |
c8462cc9 | 1127 | { |
7ccb9ad5 WF |
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 */ | |
c8462cc9 | 1133 | |
7ccb9ad5 WF |
1134 | /* target for 10ms pause on 1-dd case */ |
1135 | t = max(1, HZ / 100); | |
c8462cc9 WF |
1136 | |
1137 | /* | |
1138 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
1139 | * overheads. | |
1140 | * | |
7ccb9ad5 | 1141 | * (N * 10ms) on 2^N concurrent tasks. |
c8462cc9 WF |
1142 | */ |
1143 | if (hi > lo) | |
7ccb9ad5 | 1144 | t += (hi - lo) * (10 * HZ) / 1024; |
c8462cc9 WF |
1145 | |
1146 | /* | |
7ccb9ad5 WF |
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. | |
c8462cc9 | 1155 | * |
7ccb9ad5 WF |
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. | |
c8462cc9 | 1163 | */ |
7ccb9ad5 WF |
1164 | t = min(t, 1 + max_pause / 2); |
1165 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
c8462cc9 WF |
1166 | |
1167 | /* | |
5b9b3574 WF |
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. | |
c8462cc9 | 1174 | */ |
5b9b3574 WF |
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 | ||
7ccb9ad5 WF |
1184 | 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 | } | |
c8462cc9 | 1189 | |
7ccb9ad5 | 1190 | *nr_dirtied_pause = pages; |
c8462cc9 | 1191 | /* |
7ccb9ad5 | 1192 | * The minimal pause time will normally be half the target pause time. |
c8462cc9 | 1193 | */ |
5b9b3574 | 1194 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
c8462cc9 WF |
1195 | } |
1196 | ||
1da177e4 LT |
1197 | /* |
1198 | * 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 | |
143dfe86 | 1200 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1201 | * If we're over `background_thresh' then the writeback threads are woken to |
1202 | * perform some writeout. | |
1da177e4 | 1203 | */ |
3a2e9a5a | 1204 | static void balance_dirty_pages(struct address_space *mapping, |
143dfe86 | 1205 | unsigned long pages_dirtied) |
1da177e4 | 1206 | { |
143dfe86 WF |
1207 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
1208 | unsigned long bdi_reclaimable; | |
7762741e WF |
1209 | unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ |
1210 | unsigned long bdi_dirty; | |
6c14ae1e | 1211 | unsigned long freerun; |
364aeb28 DR |
1212 | unsigned long background_thresh; |
1213 | unsigned long dirty_thresh; | |
1214 | unsigned long bdi_thresh; | |
83712358 | 1215 | long period; |
7ccb9ad5 WF |
1216 | long pause; |
1217 | long max_pause; | |
1218 | long min_pause; | |
1219 | int nr_dirtied_pause; | |
e50e3720 | 1220 | bool dirty_exceeded = false; |
143dfe86 | 1221 | unsigned long task_ratelimit; |
7ccb9ad5 | 1222 | unsigned long dirty_ratelimit; |
143dfe86 | 1223 | unsigned long pos_ratio; |
1da177e4 | 1224 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
e98be2d5 | 1225 | unsigned long start_time = jiffies; |
1da177e4 LT |
1226 | |
1227 | for (;;) { | |
83712358 WF |
1228 | unsigned long now = jiffies; |
1229 | ||
143dfe86 WF |
1230 | /* |
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 | */ | |
5fce25a9 PZ |
1236 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
1237 | global_page_state(NR_UNSTABLE_NFS); | |
7762741e | 1238 | nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
5fce25a9 | 1239 | |
16c4042f WF |
1240 | 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 | */ | |
6c14ae1e WF |
1247 | freerun = dirty_freerun_ceiling(dirty_thresh, |
1248 | background_thresh); | |
83712358 WF |
1249 | if (nr_dirty <= freerun) { |
1250 | current->dirty_paused_when = now; | |
1251 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1252 | current->nr_dirtied_pause = |
1253 | dirty_poll_interval(nr_dirty, dirty_thresh); | |
16c4042f | 1254 | break; |
83712358 | 1255 | } |
16c4042f | 1256 | |
143dfe86 WF |
1257 | 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 | */ | |
16c4042f | 1273 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); |
16c4042f | 1274 | |
e50e3720 WF |
1275 | /* |
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 | */ | |
143dfe86 WF |
1285 | if (bdi_thresh < 2 * bdi_stat_error(bdi)) { |
1286 | bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); | |
1287 | bdi_dirty = bdi_reclaimable + | |
7762741e | 1288 | bdi_stat_sum(bdi, BDI_WRITEBACK); |
e50e3720 | 1289 | } else { |
143dfe86 WF |
1290 | bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
1291 | bdi_dirty = bdi_reclaimable + | |
7762741e | 1292 | bdi_stat(bdi, BDI_WRITEBACK); |
e50e3720 | 1293 | } |
5fce25a9 | 1294 | |
82791940 | 1295 | dirty_exceeded = (bdi_dirty > bdi_thresh) && |
7762741e | 1296 | (nr_dirty > dirty_thresh); |
143dfe86 | 1297 | if (dirty_exceeded && !bdi->dirty_exceeded) |
04fbfdc1 | 1298 | bdi->dirty_exceeded = 1; |
1da177e4 | 1299 | |
af6a3113 WF |
1300 | bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, |
1301 | nr_dirty, bdi_thresh, bdi_dirty, | |
1302 | start_time); | |
e98be2d5 | 1303 | |
143dfe86 WF |
1304 | dirty_ratelimit = bdi->dirty_ratelimit; |
1305 | pos_ratio = bdi_position_ratio(bdi, dirty_thresh, | |
1306 | background_thresh, nr_dirty, | |
1307 | bdi_thresh, bdi_dirty); | |
3a73dbbc WF |
1308 | task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> |
1309 | RATELIMIT_CALC_SHIFT; | |
7ccb9ad5 WF |
1310 | 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 | ||
3a73dbbc | 1315 | if (unlikely(task_ratelimit == 0)) { |
83712358 | 1316 | period = max_pause; |
c8462cc9 | 1317 | pause = max_pause; |
143dfe86 | 1318 | goto pause; |
04fbfdc1 | 1319 | } |
83712358 WF |
1320 | 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 | */ | |
7ccb9ad5 | 1331 | if (pause < min_pause) { |
ece13ac3 WF |
1332 | 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, | |
83712358 | 1341 | period, |
7ccb9ad5 | 1342 | min(pause, 0L), |
ece13ac3 | 1343 | start_time); |
83712358 WF |
1344 | 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; | |
7ccb9ad5 WF |
1350 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
1351 | current->nr_dirtied_pause += pages_dirtied; | |
57fc978c | 1352 | break; |
04fbfdc1 | 1353 | } |
7ccb9ad5 WF |
1354 | if (unlikely(pause > max_pause)) { |
1355 | /* for occasional dropped task_ratelimit */ | |
1356 | now += min(pause - max_pause, max_pause); | |
1357 | pause = max_pause; | |
1358 | } | |
143dfe86 WF |
1359 | |
1360 | pause: | |
ece13ac3 WF |
1361 | 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, | |
83712358 | 1370 | period, |
ece13ac3 WF |
1371 | pause, |
1372 | start_time); | |
499d05ec | 1373 | __set_current_state(TASK_KILLABLE); |
d25105e8 | 1374 | io_schedule_timeout(pause); |
87c6a9b2 | 1375 | |
83712358 WF |
1376 | current->dirty_paused_when = now + pause; |
1377 | current->nr_dirtied = 0; | |
7ccb9ad5 | 1378 | current->nr_dirtied_pause = nr_dirtied_pause; |
83712358 | 1379 | |
ffd1f609 | 1380 | /* |
1df64719 WF |
1381 | * This is typically equal to (nr_dirty < dirty_thresh) and can |
1382 | * also keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1383 | */ |
1df64719 | 1384 | if (task_ratelimit) |
ffd1f609 | 1385 | break; |
499d05ec | 1386 | |
c5c6343c WF |
1387 | /* |
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 | ||
499d05ec JK |
1400 | if (fatal_signal_pending(current)) |
1401 | break; | |
1da177e4 LT |
1402 | } |
1403 | ||
143dfe86 | 1404 | if (!dirty_exceeded && bdi->dirty_exceeded) |
04fbfdc1 | 1405 | bdi->dirty_exceeded = 0; |
1da177e4 LT |
1406 | |
1407 | if (writeback_in_progress(bdi)) | |
5b0830cb | 1408 | return; |
1da177e4 LT |
1409 | |
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 | */ | |
143dfe86 WF |
1418 | if (laptop_mode) |
1419 | return; | |
1420 | ||
1421 | if (nr_reclaimable > background_thresh) | |
c5444198 | 1422 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
1423 | } |
1424 | ||
a200ee18 | 1425 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 1426 | { |
a200ee18 | 1427 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
1428 | struct address_space *mapping = page_mapping(page); |
1429 | ||
1430 | if (mapping) | |
1431 | balance_dirty_pages_ratelimited(mapping); | |
1432 | } | |
1433 | } | |
1434 | ||
9d823e8f | 1435 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1436 | |
54848d73 WF |
1437 | /* |
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 | */ | |
1451 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1452 | ||
1da177e4 | 1453 | /** |
d0e1d66b | 1454 | * balance_dirty_pages_ratelimited - balance dirty memory state |
67be2dd1 | 1455 | * @mapping: address_space which was dirtied |
1da177e4 LT |
1456 | * |
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 | */ | |
d0e1d66b | 1466 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
1da177e4 | 1467 | { |
36715cef | 1468 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
9d823e8f WF |
1469 | int ratelimit; |
1470 | int *p; | |
1da177e4 | 1471 | |
36715cef WF |
1472 | if (!bdi_cap_account_dirty(bdi)) |
1473 | return; | |
1474 | ||
9d823e8f WF |
1475 | ratelimit = current->nr_dirtied_pause; |
1476 | if (bdi->dirty_exceeded) | |
1477 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); | |
1478 | ||
9d823e8f | 1479 | preempt_disable(); |
1da177e4 | 1480 | /* |
9d823e8f WF |
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. | |
1da177e4 | 1485 | */ |
245b2e70 | 1486 | p = &__get_cpu_var(bdp_ratelimits); |
9d823e8f | 1487 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1488 | *p = 0; |
d3bc1fef WF |
1489 | else if (unlikely(*p >= ratelimit_pages)) { |
1490 | *p = 0; | |
1491 | ratelimit = 0; | |
1da177e4 | 1492 | } |
54848d73 WF |
1493 | /* |
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) { | |
d0e1d66b | 1500 | unsigned long nr_pages_dirtied; |
54848d73 WF |
1501 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
1502 | *p -= nr_pages_dirtied; | |
1503 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1504 | } |
fa5a734e | 1505 | preempt_enable(); |
9d823e8f WF |
1506 | |
1507 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
1508 | balance_dirty_pages(mapping, current->nr_dirtied); | |
1da177e4 | 1509 | } |
d0e1d66b | 1510 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
1da177e4 | 1511 | |
232ea4d6 | 1512 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 1513 | { |
364aeb28 DR |
1514 | unsigned long background_thresh; |
1515 | unsigned long dirty_thresh; | |
1da177e4 LT |
1516 | |
1517 | for ( ; ; ) { | |
16c4042f | 1518 | global_dirty_limits(&background_thresh, &dirty_thresh); |
47a13333 | 1519 | dirty_thresh = hard_dirty_limit(dirty_thresh); |
1da177e4 LT |
1520 | |
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 | ||
c24f21bd CL |
1527 | if (global_page_state(NR_UNSTABLE_NFS) + |
1528 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
1529 | break; | |
8aa7e847 | 1530 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
1531 | |
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; | |
1da177e4 LT |
1539 | } |
1540 | } | |
1541 | ||
1da177e4 LT |
1542 | /* |
1543 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1544 | */ | |
1545 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 1546 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1547 | { |
8d65af78 | 1548 | proc_dointvec(table, write, buffer, length, ppos); |
1da177e4 LT |
1549 | return 0; |
1550 | } | |
1551 | ||
c2c4986e | 1552 | #ifdef CONFIG_BLOCK |
31373d09 | 1553 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 1554 | { |
31373d09 MG |
1555 | 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); | |
1da177e4 | 1558 | |
31373d09 MG |
1559 | /* |
1560 | * We want to write everything out, not just down to the dirty | |
1561 | * threshold | |
1562 | */ | |
31373d09 | 1563 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
0e175a18 CW |
1564 | bdi_start_writeback(&q->backing_dev_info, nr_pages, |
1565 | WB_REASON_LAPTOP_TIMER); | |
1da177e4 LT |
1566 | } |
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 | */ | |
31373d09 | 1573 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 1574 | { |
31373d09 | 1575 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
1576 | } |
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 | */ | |
1583 | void laptop_sync_completion(void) | |
1584 | { | |
31373d09 MG |
1585 | 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(); | |
1da177e4 | 1593 | } |
c2c4986e | 1594 | #endif |
1da177e4 LT |
1595 | |
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 | |
9d823e8f | 1604 | * thresholds. |
1da177e4 LT |
1605 | */ |
1606 | ||
2d1d43f6 | 1607 | void writeback_set_ratelimit(void) |
1da177e4 | 1608 | { |
9d823e8f WF |
1609 | unsigned long background_thresh; |
1610 | unsigned long dirty_thresh; | |
1611 | global_dirty_limits(&background_thresh, &dirty_thresh); | |
68809c71 | 1612 | global_dirty_limit = dirty_thresh; |
9d823e8f | 1613 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
1da177e4 LT |
1614 | if (ratelimit_pages < 16) |
1615 | ratelimit_pages = 16; | |
1da177e4 LT |
1616 | } |
1617 | ||
26c2143b | 1618 | static int __cpuinit |
2f60d628 SB |
1619 | ratelimit_handler(struct notifier_block *self, unsigned long action, |
1620 | void *hcpu) | |
1da177e4 | 1621 | { |
2f60d628 SB |
1622 | |
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 | } | |
1da177e4 LT |
1631 | } |
1632 | ||
74b85f37 | 1633 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
1634 | .notifier_call = ratelimit_handler, |
1635 | .next = NULL, | |
1636 | }; | |
1637 | ||
1638 | /* | |
dc6e29da LT |
1639 | * 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.. | |
1da177e4 LT |
1655 | */ |
1656 | void __init page_writeback_init(void) | |
1657 | { | |
2d1d43f6 | 1658 | writeback_set_ratelimit(); |
1da177e4 | 1659 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 | 1660 | |
eb608e3a | 1661 | fprop_global_init(&writeout_completions); |
1da177e4 LT |
1662 | } |
1663 | ||
f446daae JK |
1664 | /** |
1665 | * 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 | */ | |
f446daae JK |
1681 | void tag_pages_for_writeback(struct address_space *mapping, |
1682 | pgoff_t start, pgoff_t end) | |
1683 | { | |
3c111a07 | 1684 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
1685 | 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(); | |
d5ed3a4a JK |
1695 | /* We check 'start' to handle wrapping when end == ~0UL */ |
1696 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
1697 | } |
1698 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
1699 | ||
811d736f | 1700 | /** |
0ea97180 | 1701 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
1702 | * @mapping: address space structure to write |
1703 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
1704 | * @writepage: function called for each page |
1705 | * @data: data passed to writepage function | |
811d736f | 1706 | * |
0ea97180 | 1707 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
1708 | * 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. | |
f446daae JK |
1714 | * |
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). | |
811d736f | 1721 | */ |
0ea97180 MS |
1722 | int write_cache_pages(struct address_space *mapping, |
1723 | struct writeback_control *wbc, writepage_t writepage, | |
1724 | void *data) | |
811d736f | 1725 | { |
811d736f DH |
1726 | int ret = 0; |
1727 | int done = 0; | |
811d736f DH |
1728 | struct pagevec pvec; |
1729 | int nr_pages; | |
31a12666 | 1730 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
1731 | pgoff_t index; |
1732 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 1733 | pgoff_t done_index; |
31a12666 | 1734 | int cycled; |
811d736f | 1735 | int range_whole = 0; |
f446daae | 1736 | int tag; |
811d736f | 1737 | |
811d736f DH |
1738 | pagevec_init(&pvec, 0); |
1739 | if (wbc->range_cyclic) { | |
31a12666 NP |
1740 | writeback_index = mapping->writeback_index; /* prev offset */ |
1741 | index = writeback_index; | |
1742 | if (index == 0) | |
1743 | cycled = 1; | |
1744 | else | |
1745 | cycled = 0; | |
811d736f DH |
1746 | 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; | |
31a12666 | 1752 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 1753 | } |
6e6938b6 | 1754 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
1755 | tag = PAGECACHE_TAG_TOWRITE; |
1756 | else | |
1757 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 1758 | retry: |
6e6938b6 | 1759 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 1760 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 1761 | done_index = index; |
5a3d5c98 NP |
1762 | while (!done && (index <= end)) { |
1763 | int i; | |
1764 | ||
f446daae | 1765 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
1766 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
1767 | if (nr_pages == 0) | |
1768 | break; | |
811d736f | 1769 | |
811d736f DH |
1770 | for (i = 0; i < nr_pages; i++) { |
1771 | struct page *page = pvec.pages[i]; | |
1772 | ||
1773 | /* | |
d5482cdf NP |
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. | |
811d736f | 1779 | */ |
d5482cdf NP |
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 | ||
cf15b07c | 1789 | done_index = page->index; |
d5482cdf | 1790 | |
811d736f DH |
1791 | lock_page(page); |
1792 | ||
5a3d5c98 NP |
1793 | /* |
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 | */ | |
811d736f | 1801 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 1802 | continue_unlock: |
811d736f DH |
1803 | unlock_page(page); |
1804 | continue; | |
1805 | } | |
1806 | ||
515f4a03 NP |
1807 | if (!PageDirty(page)) { |
1808 | /* someone wrote it for us */ | |
1809 | goto continue_unlock; | |
1810 | } | |
1811 | ||
1812 | if (PageWriteback(page)) { | |
1813 | if (wbc->sync_mode != WB_SYNC_NONE) | |
1814 | wait_on_page_writeback(page); | |
1815 | else | |
1816 | goto continue_unlock; | |
1817 | } | |
811d736f | 1818 | |
515f4a03 NP |
1819 | BUG_ON(PageWriteback(page)); |
1820 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 1821 | goto continue_unlock; |
811d736f | 1822 | |
9e094383 | 1823 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 1824 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
1825 | 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 | */ | |
cf15b07c | 1839 | done_index = page->index + 1; |
00266770 NP |
1840 | done = 1; |
1841 | break; | |
1842 | } | |
0b564927 | 1843 | } |
00266770 | 1844 | |
546a1924 DC |
1845 | /* |
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; | |
05fe478d | 1855 | } |
811d736f DH |
1856 | } |
1857 | pagevec_release(&pvec); | |
1858 | cond_resched(); | |
1859 | } | |
3a4c6800 | 1860 | if (!cycled && !done) { |
811d736f | 1861 | /* |
31a12666 | 1862 | * range_cyclic: |
811d736f DH |
1863 | * We hit the last page and there is more work to be done: wrap |
1864 | * back to the start of the file | |
1865 | */ | |
31a12666 | 1866 | cycled = 1; |
811d736f | 1867 | index = 0; |
31a12666 | 1868 | end = writeback_index - 1; |
811d736f DH |
1869 | goto retry; |
1870 | } | |
0b564927 DC |
1871 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
1872 | mapping->writeback_index = done_index; | |
06d6cf69 | 1873 | |
811d736f DH |
1874 | return ret; |
1875 | } | |
0ea97180 MS |
1876 | EXPORT_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 | */ | |
1882 | static 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 | */ | |
1899 | int generic_writepages(struct address_space *mapping, | |
1900 | struct writeback_control *wbc) | |
1901 | { | |
9b6096a6 SL |
1902 | struct blk_plug plug; |
1903 | int ret; | |
1904 | ||
0ea97180 MS |
1905 | /* deal with chardevs and other special file */ |
1906 | if (!mapping->a_ops->writepage) | |
1907 | return 0; | |
1908 | ||
9b6096a6 SL |
1909 | blk_start_plug(&plug); |
1910 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
1911 | blk_finish_plug(&plug); | |
1912 | return ret; | |
0ea97180 | 1913 | } |
811d736f DH |
1914 | |
1915 | EXPORT_SYMBOL(generic_writepages); | |
1916 | ||
1da177e4 LT |
1917 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1918 | { | |
22905f77 AM |
1919 | int ret; |
1920 | ||
1da177e4 LT |
1921 | if (wbc->nr_to_write <= 0) |
1922 | return 0; | |
1923 | if (mapping->a_ops->writepages) | |
d08b3851 | 1924 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1925 | else |
1926 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1927 | return ret; |
1da177e4 LT |
1928 | } |
1929 | ||
1930 | /** | |
1931 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1932 | * @page: the page to write |
1933 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1934 | * |
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 | */ | |
1939 | int 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 | } | |
1967 | EXPORT_SYMBOL(write_one_page); | |
1968 | ||
76719325 KC |
1969 | /* |
1970 | * For address_spaces which do not use buffers nor write back. | |
1971 | */ | |
1972 | int __set_page_dirty_no_writeback(struct page *page) | |
1973 | { | |
1974 | if (!PageDirty(page)) | |
c3f0da63 | 1975 | return !TestSetPageDirty(page); |
76719325 KC |
1976 | return 0; |
1977 | } | |
1978 | ||
e3a7cca1 ES |
1979 | /* |
1980 | * Helper function for set_page_dirty family. | |
1981 | * NOTE: This relies on being atomic wrt interrupts. | |
1982 | */ | |
1983 | void 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); | |
ea941f0e | 1987 | __inc_zone_page_state(page, NR_DIRTIED); |
e3a7cca1 | 1988 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
c8e28ce0 | 1989 | __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); |
e3a7cca1 | 1990 | task_io_account_write(PAGE_CACHE_SIZE); |
d3bc1fef WF |
1991 | current->nr_dirtied++; |
1992 | this_cpu_inc(bdp_ratelimits); | |
e3a7cca1 ES |
1993 | } |
1994 | } | |
679ceace | 1995 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 1996 | |
f629d1c9 MR |
1997 | /* |
1998 | * Helper function for set_page_writeback family. | |
1999 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic | |
2000 | * wrt interrupts. | |
2001 | */ | |
2002 | void account_page_writeback(struct page *page) | |
2003 | { | |
2004 | inc_zone_page_state(page, NR_WRITEBACK); | |
2005 | } | |
2006 | EXPORT_SYMBOL(account_page_writeback); | |
2007 | ||
1da177e4 LT |
2008 | /* |
2009 | * 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 | |
183ff22b | 2021 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
2022 | */ |
2023 | int __set_page_dirty_nobuffers(struct page *page) | |
2024 | { | |
1da177e4 LT |
2025 | if (!TestSetPageDirty(page)) { |
2026 | struct address_space *mapping = page_mapping(page); | |
2027 | struct address_space *mapping2; | |
2028 | ||
8c08540f AM |
2029 | if (!mapping) |
2030 | return 1; | |
2031 | ||
19fd6231 | 2032 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
2033 | mapping2 = page_mapping(page); |
2034 | if (mapping2) { /* Race with truncate? */ | |
2035 | BUG_ON(mapping2 != mapping); | |
787d2214 | 2036 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 2037 | account_page_dirtied(page, mapping); |
8c08540f AM |
2038 | radix_tree_tag_set(&mapping->page_tree, |
2039 | page_index(page), PAGECACHE_TAG_DIRTY); | |
2040 | } | |
19fd6231 | 2041 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
2042 | if (mapping->host) { |
2043 | /* !PageAnon && !swapper_space */ | |
2044 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 2045 | } |
4741c9fd | 2046 | return 1; |
1da177e4 | 2047 | } |
4741c9fd | 2048 | return 0; |
1da177e4 LT |
2049 | } |
2050 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
2051 | ||
2f800fbd WF |
2052 | /* |
2053 | * 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 | */ | |
2059 | void 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 | } | |
2068 | EXPORT_SYMBOL(account_page_redirty); | |
2069 | ||
1da177e4 LT |
2070 | /* |
2071 | * 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 | */ | |
2075 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
2076 | { | |
2077 | wbc->pages_skipped++; | |
2f800fbd | 2078 | account_page_redirty(page); |
1da177e4 LT |
2079 | return __set_page_dirty_nobuffers(page); |
2080 | } | |
2081 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
2082 | ||
2083 | /* | |
6746aff7 WF |
2084 | * 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 | * | |
1da177e4 LT |
2091 | * 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 | */ | |
1cf6e7d8 | 2094 | int set_page_dirty(struct page *page) |
1da177e4 LT |
2095 | { |
2096 | struct address_space *mapping = page_mapping(page); | |
2097 | ||
2098 | if (likely(mapping)) { | |
2099 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
2100 | /* |
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); | |
9361401e DH |
2111 | #ifdef CONFIG_BLOCK |
2112 | if (!spd) | |
2113 | spd = __set_page_dirty_buffers; | |
2114 | #endif | |
2115 | return (*spd)(page); | |
1da177e4 | 2116 | } |
4741c9fd AM |
2117 | if (!PageDirty(page)) { |
2118 | if (!TestSetPageDirty(page)) | |
2119 | return 1; | |
2120 | } | |
1da177e4 LT |
2121 | return 0; |
2122 | } | |
2123 | EXPORT_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 | */ | |
2135 | int set_page_dirty_lock(struct page *page) | |
2136 | { | |
2137 | int ret; | |
2138 | ||
7eaceacc | 2139 | lock_page(page); |
1da177e4 LT |
2140 | ret = set_page_dirty(page); |
2141 | unlock_page(page); | |
2142 | return ret; | |
2143 | } | |
2144 | EXPORT_SYMBOL(set_page_dirty_lock); | |
2145 | ||
1da177e4 LT |
2146 | /* |
2147 | * 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 | */ | |
2160 | int clear_page_dirty_for_io(struct page *page) | |
2161 | { | |
2162 | struct address_space *mapping = page_mapping(page); | |
2163 | ||
79352894 NP |
2164 | BUG_ON(!PageLocked(page)); |
2165 | ||
7658cc28 LT |
2166 | 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. | |
7658cc28 LT |
2191 | */ |
2192 | if (page_mkclean(page)) | |
2193 | set_page_dirty(page); | |
79352894 NP |
2194 | /* |
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 | */ | |
7658cc28 | 2204 | if (TestClearPageDirty(page)) { |
8c08540f | 2205 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
2206 | dec_bdi_stat(mapping->backing_dev_info, |
2207 | BDI_RECLAIMABLE); | |
7658cc28 | 2208 | return 1; |
1da177e4 | 2209 | } |
7658cc28 | 2210 | return 0; |
1da177e4 | 2211 | } |
7658cc28 | 2212 | return TestClearPageDirty(page); |
1da177e4 | 2213 | } |
58bb01a9 | 2214 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
2215 | |
2216 | int test_clear_page_writeback(struct page *page) | |
2217 | { | |
2218 | struct address_space *mapping = page_mapping(page); | |
2219 | int ret; | |
2220 | ||
2221 | if (mapping) { | |
69cb51d1 | 2222 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
2223 | unsigned long flags; |
2224 | ||
19fd6231 | 2225 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2226 | ret = TestClearPageWriteback(page); |
69cb51d1 | 2227 | if (ret) { |
1da177e4 LT |
2228 | radix_tree_tag_clear(&mapping->page_tree, |
2229 | page_index(page), | |
2230 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2231 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 2232 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
2233 | __bdi_writeout_inc(bdi); |
2234 | } | |
69cb51d1 | 2235 | } |
19fd6231 | 2236 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2237 | } else { |
2238 | ret = TestClearPageWriteback(page); | |
2239 | } | |
99b12e3d | 2240 | if (ret) { |
d688abf5 | 2241 | dec_zone_page_state(page, NR_WRITEBACK); |
99b12e3d WF |
2242 | inc_zone_page_state(page, NR_WRITTEN); |
2243 | } | |
1da177e4 LT |
2244 | return ret; |
2245 | } | |
2246 | ||
2247 | int test_set_page_writeback(struct page *page) | |
2248 | { | |
2249 | struct address_space *mapping = page_mapping(page); | |
2250 | int ret; | |
2251 | ||
2252 | if (mapping) { | |
69cb51d1 | 2253 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
2254 | unsigned long flags; |
2255 | ||
19fd6231 | 2256 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2257 | ret = TestSetPageWriteback(page); |
69cb51d1 | 2258 | if (!ret) { |
1da177e4 LT |
2259 | radix_tree_tag_set(&mapping->page_tree, |
2260 | page_index(page), | |
2261 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2262 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
2263 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
2264 | } | |
1da177e4 LT |
2265 | if (!PageDirty(page)) |
2266 | radix_tree_tag_clear(&mapping->page_tree, | |
2267 | page_index(page), | |
2268 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
2269 | radix_tree_tag_clear(&mapping->page_tree, |
2270 | page_index(page), | |
2271 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 2272 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2273 | } else { |
2274 | ret = TestSetPageWriteback(page); | |
2275 | } | |
d688abf5 | 2276 | if (!ret) |
f629d1c9 | 2277 | account_page_writeback(page); |
1da177e4 LT |
2278 | return ret; |
2279 | ||
2280 | } | |
2281 | EXPORT_SYMBOL(test_set_page_writeback); | |
2282 | ||
2283 | /* | |
00128188 | 2284 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
2285 | * passed tag. |
2286 | */ | |
2287 | int mapping_tagged(struct address_space *mapping, int tag) | |
2288 | { | |
72c47832 | 2289 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
2290 | } |
2291 | EXPORT_SYMBOL(mapping_tagged); |