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> |
028c2dd1 | 37 | #include <trace/events/writeback.h> |
1da177e4 | 38 | |
ffd1f609 WF |
39 | /* |
40 | * Sleep at most 200ms at a time in balance_dirty_pages(). | |
41 | */ | |
42 | #define MAX_PAUSE max(HZ/5, 1) | |
43 | ||
5b9b3574 WF |
44 | /* |
45 | * Try to keep balance_dirty_pages() call intervals higher than this many pages | |
46 | * by raising pause time to max_pause when falls below it. | |
47 | */ | |
48 | #define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) | |
49 | ||
e98be2d5 WF |
50 | /* |
51 | * Estimate write bandwidth at 200ms intervals. | |
52 | */ | |
53 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) | |
54 | ||
6c14ae1e WF |
55 | #define RATELIMIT_CALC_SHIFT 10 |
56 | ||
1da177e4 LT |
57 | /* |
58 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
59 | * will look to see if it needs to force writeback or throttling. | |
60 | */ | |
61 | static long ratelimit_pages = 32; | |
62 | ||
1da177e4 LT |
63 | /* The following parameters are exported via /proc/sys/vm */ |
64 | ||
65 | /* | |
5b0830cb | 66 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 67 | */ |
1b5e62b4 | 68 | int dirty_background_ratio = 10; |
1da177e4 | 69 | |
2da02997 DR |
70 | /* |
71 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
72 | * dirty_background_ratio * the amount of dirtyable memory | |
73 | */ | |
74 | unsigned long dirty_background_bytes; | |
75 | ||
195cf453 BG |
76 | /* |
77 | * free highmem will not be subtracted from the total free memory | |
78 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
79 | */ | |
80 | int vm_highmem_is_dirtyable; | |
81 | ||
1da177e4 LT |
82 | /* |
83 | * The generator of dirty data starts writeback at this percentage | |
84 | */ | |
1b5e62b4 | 85 | int vm_dirty_ratio = 20; |
1da177e4 | 86 | |
2da02997 DR |
87 | /* |
88 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
89 | * vm_dirty_ratio * the amount of dirtyable memory | |
90 | */ | |
91 | unsigned long vm_dirty_bytes; | |
92 | ||
1da177e4 | 93 | /* |
704503d8 | 94 | * The interval between `kupdate'-style writebacks |
1da177e4 | 95 | */ |
22ef37ee | 96 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 | 97 | |
91913a29 AB |
98 | EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
99 | ||
1da177e4 | 100 | /* |
704503d8 | 101 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 102 | */ |
22ef37ee | 103 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
104 | |
105 | /* | |
106 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
107 | */ | |
108 | int block_dump; | |
109 | ||
110 | /* | |
ed5b43f1 BS |
111 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
112 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
113 | */ |
114 | int laptop_mode; | |
115 | ||
116 | EXPORT_SYMBOL(laptop_mode); | |
117 | ||
118 | /* End of sysctl-exported parameters */ | |
119 | ||
c42843f2 | 120 | unsigned long global_dirty_limit; |
1da177e4 | 121 | |
04fbfdc1 PZ |
122 | /* |
123 | * Scale the writeback cache size proportional to the relative writeout speeds. | |
124 | * | |
125 | * We do this by keeping a floating proportion between BDIs, based on page | |
126 | * writeback completions [end_page_writeback()]. Those devices that write out | |
127 | * pages fastest will get the larger share, while the slower will get a smaller | |
128 | * share. | |
129 | * | |
130 | * We use page writeout completions because we are interested in getting rid of | |
131 | * dirty pages. Having them written out is the primary goal. | |
132 | * | |
133 | * We introduce a concept of time, a period over which we measure these events, | |
134 | * because demand can/will vary over time. The length of this period itself is | |
135 | * measured in page writeback completions. | |
136 | * | |
137 | */ | |
138 | static struct prop_descriptor vm_completions; | |
139 | ||
1edf2234 JW |
140 | /* |
141 | * Work out the current dirty-memory clamping and background writeout | |
142 | * thresholds. | |
143 | * | |
144 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
145 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
146 | * pages. It is better to clamp down on writers than to start swapping, and | |
147 | * performing lots of scanning. | |
148 | * | |
149 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
150 | * | |
151 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
152 | * excessive. | |
153 | * | |
154 | * We make sure that the background writeout level is below the adjusted | |
155 | * clamping level. | |
156 | */ | |
ccafa287 | 157 | |
a756cf59 JW |
158 | /* |
159 | * In a memory zone, there is a certain amount of pages we consider | |
160 | * available for the page cache, which is essentially the number of | |
161 | * free and reclaimable pages, minus some zone reserves to protect | |
162 | * lowmem and the ability to uphold the zone's watermarks without | |
163 | * requiring writeback. | |
164 | * | |
165 | * This number of dirtyable pages is the base value of which the | |
166 | * user-configurable dirty ratio is the effictive number of pages that | |
167 | * are allowed to be actually dirtied. Per individual zone, or | |
168 | * globally by using the sum of dirtyable pages over all zones. | |
169 | * | |
170 | * Because the user is allowed to specify the dirty limit globally as | |
171 | * absolute number of bytes, calculating the per-zone dirty limit can | |
172 | * require translating the configured limit into a percentage of | |
173 | * global dirtyable memory first. | |
174 | */ | |
175 | ||
1edf2234 JW |
176 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
177 | { | |
178 | #ifdef CONFIG_HIGHMEM | |
179 | int node; | |
180 | unsigned long x = 0; | |
181 | ||
182 | for_each_node_state(node, N_HIGH_MEMORY) { | |
183 | struct zone *z = | |
184 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
185 | ||
186 | x += zone_page_state(z, NR_FREE_PAGES) + | |
ab8fabd4 | 187 | zone_reclaimable_pages(z) - z->dirty_balance_reserve; |
1edf2234 JW |
188 | } |
189 | /* | |
190 | * Make sure that the number of highmem pages is never larger | |
191 | * than the number of the total dirtyable memory. This can only | |
192 | * occur in very strange VM situations but we want to make sure | |
193 | * that this does not occur. | |
194 | */ | |
195 | return min(x, total); | |
196 | #else | |
197 | return 0; | |
198 | #endif | |
199 | } | |
200 | ||
201 | /** | |
ccafa287 | 202 | * global_dirtyable_memory - number of globally dirtyable pages |
1edf2234 | 203 | * |
ccafa287 JW |
204 | * Returns the global number of pages potentially available for dirty |
205 | * page cache. This is the base value for the global dirty limits. | |
1edf2234 | 206 | */ |
18cf8cf8 | 207 | static unsigned long global_dirtyable_memory(void) |
1edf2234 JW |
208 | { |
209 | unsigned long x; | |
210 | ||
ab8fabd4 JW |
211 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() - |
212 | dirty_balance_reserve; | |
1edf2234 JW |
213 | |
214 | if (!vm_highmem_is_dirtyable) | |
215 | x -= highmem_dirtyable_memory(x); | |
216 | ||
217 | return x + 1; /* Ensure that we never return 0 */ | |
218 | } | |
219 | ||
ccafa287 JW |
220 | /* |
221 | * global_dirty_limits - background-writeback and dirty-throttling thresholds | |
222 | * | |
223 | * Calculate the dirty thresholds based on sysctl parameters | |
224 | * - vm.dirty_background_ratio or vm.dirty_background_bytes | |
225 | * - vm.dirty_ratio or vm.dirty_bytes | |
226 | * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
227 | * real-time tasks. | |
228 | */ | |
229 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) | |
230 | { | |
231 | unsigned long background; | |
232 | unsigned long dirty; | |
233 | unsigned long uninitialized_var(available_memory); | |
234 | struct task_struct *tsk; | |
235 | ||
236 | if (!vm_dirty_bytes || !dirty_background_bytes) | |
237 | available_memory = global_dirtyable_memory(); | |
238 | ||
239 | if (vm_dirty_bytes) | |
240 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
241 | else | |
242 | dirty = (vm_dirty_ratio * available_memory) / 100; | |
243 | ||
244 | if (dirty_background_bytes) | |
245 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
246 | else | |
247 | background = (dirty_background_ratio * available_memory) / 100; | |
248 | ||
249 | if (background >= dirty) | |
250 | background = dirty / 2; | |
251 | tsk = current; | |
252 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
253 | background += background / 4; | |
254 | dirty += dirty / 4; | |
255 | } | |
256 | *pbackground = background; | |
257 | *pdirty = dirty; | |
258 | trace_global_dirty_state(background, dirty); | |
259 | } | |
260 | ||
a756cf59 JW |
261 | /** |
262 | * zone_dirtyable_memory - number of dirtyable pages in a zone | |
263 | * @zone: the zone | |
264 | * | |
265 | * Returns the zone's number of pages potentially available for dirty | |
266 | * page cache. This is the base value for the per-zone dirty limits. | |
267 | */ | |
268 | static unsigned long zone_dirtyable_memory(struct zone *zone) | |
269 | { | |
270 | /* | |
271 | * The effective global number of dirtyable pages may exclude | |
272 | * highmem as a big-picture measure to keep the ratio between | |
273 | * dirty memory and lowmem reasonable. | |
274 | * | |
275 | * But this function is purely about the individual zone and a | |
276 | * highmem zone can hold its share of dirty pages, so we don't | |
277 | * care about vm_highmem_is_dirtyable here. | |
278 | */ | |
279 | return zone_page_state(zone, NR_FREE_PAGES) + | |
280 | zone_reclaimable_pages(zone) - | |
281 | zone->dirty_balance_reserve; | |
282 | } | |
283 | ||
284 | /** | |
285 | * zone_dirty_limit - maximum number of dirty pages allowed in a zone | |
286 | * @zone: the zone | |
287 | * | |
288 | * Returns the maximum number of dirty pages allowed in a zone, based | |
289 | * on the zone's dirtyable memory. | |
290 | */ | |
291 | static unsigned long zone_dirty_limit(struct zone *zone) | |
292 | { | |
293 | unsigned long zone_memory = zone_dirtyable_memory(zone); | |
294 | struct task_struct *tsk = current; | |
295 | unsigned long dirty; | |
296 | ||
297 | if (vm_dirty_bytes) | |
298 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * | |
299 | zone_memory / global_dirtyable_memory(); | |
300 | else | |
301 | dirty = vm_dirty_ratio * zone_memory / 100; | |
302 | ||
303 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) | |
304 | dirty += dirty / 4; | |
305 | ||
306 | return dirty; | |
307 | } | |
308 | ||
309 | /** | |
310 | * zone_dirty_ok - tells whether a zone is within its dirty limits | |
311 | * @zone: the zone to check | |
312 | * | |
313 | * Returns %true when the dirty pages in @zone are within the zone's | |
314 | * dirty limit, %false if the limit is exceeded. | |
315 | */ | |
316 | bool zone_dirty_ok(struct zone *zone) | |
317 | { | |
318 | unsigned long limit = zone_dirty_limit(zone); | |
319 | ||
320 | return zone_page_state(zone, NR_FILE_DIRTY) + | |
321 | zone_page_state(zone, NR_UNSTABLE_NFS) + | |
322 | zone_page_state(zone, NR_WRITEBACK) <= limit; | |
323 | } | |
324 | ||
04fbfdc1 PZ |
325 | /* |
326 | * couple the period to the dirty_ratio: | |
327 | * | |
328 | * period/2 ~ roundup_pow_of_two(dirty limit) | |
329 | */ | |
330 | static int calc_period_shift(void) | |
331 | { | |
332 | unsigned long dirty_total; | |
333 | ||
2da02997 DR |
334 | if (vm_dirty_bytes) |
335 | dirty_total = vm_dirty_bytes / PAGE_SIZE; | |
336 | else | |
ccafa287 | 337 | dirty_total = (vm_dirty_ratio * global_dirtyable_memory()) / |
2da02997 | 338 | 100; |
04fbfdc1 PZ |
339 | return 2 + ilog2(dirty_total - 1); |
340 | } | |
341 | ||
342 | /* | |
2da02997 | 343 | * update the period when the dirty threshold changes. |
04fbfdc1 | 344 | */ |
2da02997 DR |
345 | static void update_completion_period(void) |
346 | { | |
347 | int shift = calc_period_shift(); | |
348 | prop_change_shift(&vm_completions, shift); | |
9d823e8f WF |
349 | |
350 | writeback_set_ratelimit(); | |
2da02997 DR |
351 | } |
352 | ||
353 | int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
8d65af78 | 354 | void __user *buffer, size_t *lenp, |
2da02997 DR |
355 | loff_t *ppos) |
356 | { | |
357 | int ret; | |
358 | ||
8d65af78 | 359 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
360 | if (ret == 0 && write) |
361 | dirty_background_bytes = 0; | |
362 | return ret; | |
363 | } | |
364 | ||
365 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 366 | void __user *buffer, size_t *lenp, |
2da02997 DR |
367 | loff_t *ppos) |
368 | { | |
369 | int ret; | |
370 | ||
8d65af78 | 371 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
372 | if (ret == 0 && write) |
373 | dirty_background_ratio = 0; | |
374 | return ret; | |
375 | } | |
376 | ||
04fbfdc1 | 377 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 378 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
379 | loff_t *ppos) |
380 | { | |
381 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
382 | int ret; |
383 | ||
8d65af78 | 384 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 385 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
2da02997 DR |
386 | update_completion_period(); |
387 | vm_dirty_bytes = 0; | |
388 | } | |
389 | return ret; | |
390 | } | |
391 | ||
2da02997 | 392 | int dirty_bytes_handler(struct ctl_table *table, int write, |
8d65af78 | 393 | void __user *buffer, size_t *lenp, |
2da02997 DR |
394 | loff_t *ppos) |
395 | { | |
fc3501d4 | 396 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
397 | int ret; |
398 | ||
8d65af78 | 399 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
400 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
401 | update_completion_period(); | |
402 | vm_dirty_ratio = 0; | |
04fbfdc1 PZ |
403 | } |
404 | return ret; | |
405 | } | |
406 | ||
407 | /* | |
408 | * Increment the BDI's writeout completion count and the global writeout | |
409 | * completion count. Called from test_clear_page_writeback(). | |
410 | */ | |
411 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
412 | { | |
f7d2b1ec | 413 | __inc_bdi_stat(bdi, BDI_WRITTEN); |
a42dde04 PZ |
414 | __prop_inc_percpu_max(&vm_completions, &bdi->completions, |
415 | bdi->max_prop_frac); | |
04fbfdc1 PZ |
416 | } |
417 | ||
dd5656e5 MS |
418 | void bdi_writeout_inc(struct backing_dev_info *bdi) |
419 | { | |
420 | unsigned long flags; | |
421 | ||
422 | local_irq_save(flags); | |
423 | __bdi_writeout_inc(bdi); | |
424 | local_irq_restore(flags); | |
425 | } | |
426 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); | |
427 | ||
04fbfdc1 PZ |
428 | /* |
429 | * Obtain an accurate fraction of the BDI's portion. | |
430 | */ | |
431 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
432 | long *numerator, long *denominator) | |
433 | { | |
3efaf0fa | 434 | prop_fraction_percpu(&vm_completions, &bdi->completions, |
04fbfdc1 | 435 | numerator, denominator); |
04fbfdc1 PZ |
436 | } |
437 | ||
189d3c4a | 438 | /* |
d08c429b JW |
439 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
440 | * registered backing devices, which, for obvious reasons, can not | |
441 | * exceed 100%. | |
189d3c4a | 442 | */ |
189d3c4a PZ |
443 | static unsigned int bdi_min_ratio; |
444 | ||
445 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
446 | { | |
447 | int ret = 0; | |
189d3c4a | 448 | |
cfc4ba53 | 449 | spin_lock_bh(&bdi_lock); |
a42dde04 | 450 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 451 | ret = -EINVAL; |
a42dde04 PZ |
452 | } else { |
453 | min_ratio -= bdi->min_ratio; | |
454 | if (bdi_min_ratio + min_ratio < 100) { | |
455 | bdi_min_ratio += min_ratio; | |
456 | bdi->min_ratio += min_ratio; | |
457 | } else { | |
458 | ret = -EINVAL; | |
459 | } | |
460 | } | |
cfc4ba53 | 461 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
462 | |
463 | return ret; | |
464 | } | |
465 | ||
466 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
467 | { | |
a42dde04 PZ |
468 | int ret = 0; |
469 | ||
470 | if (max_ratio > 100) | |
471 | return -EINVAL; | |
472 | ||
cfc4ba53 | 473 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
474 | if (bdi->min_ratio > max_ratio) { |
475 | ret = -EINVAL; | |
476 | } else { | |
477 | bdi->max_ratio = max_ratio; | |
478 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
479 | } | |
cfc4ba53 | 480 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
481 | |
482 | return ret; | |
483 | } | |
a42dde04 | 484 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 485 | |
6c14ae1e WF |
486 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
487 | unsigned long bg_thresh) | |
488 | { | |
489 | return (thresh + bg_thresh) / 2; | |
490 | } | |
491 | ||
ffd1f609 WF |
492 | static unsigned long hard_dirty_limit(unsigned long thresh) |
493 | { | |
494 | return max(thresh, global_dirty_limit); | |
495 | } | |
496 | ||
6f718656 | 497 | /** |
1babe183 | 498 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
6f718656 WF |
499 | * @bdi: the backing_dev_info to query |
500 | * @dirty: global dirty limit in pages | |
1babe183 | 501 | * |
6f718656 WF |
502 | * Returns @bdi's dirty limit in pages. The term "dirty" in the context of |
503 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. | |
aed21ad2 WF |
504 | * |
505 | * Note that balance_dirty_pages() will only seriously take it as a hard limit | |
506 | * when sleeping max_pause per page is not enough to keep the dirty pages under | |
507 | * control. For example, when the device is completely stalled due to some error | |
508 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. | |
509 | * In the other normal situations, it acts more gently by throttling the tasks | |
510 | * more (rather than completely block them) when the bdi dirty pages go high. | |
1babe183 | 511 | * |
6f718656 | 512 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
513 | * - starving fast devices |
514 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
515 | * | |
516 | * The bdi's share of dirty limit will be adapting to its throughput and | |
517 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. | |
518 | */ | |
519 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) | |
16c4042f WF |
520 | { |
521 | u64 bdi_dirty; | |
522 | long numerator, denominator; | |
04fbfdc1 | 523 | |
16c4042f WF |
524 | /* |
525 | * Calculate this BDI's share of the dirty ratio. | |
526 | */ | |
527 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
04fbfdc1 | 528 | |
16c4042f WF |
529 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
530 | bdi_dirty *= numerator; | |
531 | do_div(bdi_dirty, denominator); | |
04fbfdc1 | 532 | |
16c4042f WF |
533 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
534 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) | |
535 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
536 | ||
537 | return bdi_dirty; | |
1da177e4 LT |
538 | } |
539 | ||
6c14ae1e WF |
540 | /* |
541 | * Dirty position control. | |
542 | * | |
543 | * (o) global/bdi setpoints | |
544 | * | |
545 | * We want the dirty pages be balanced around the global/bdi setpoints. | |
546 | * When the number of dirty pages is higher/lower than the setpoint, the | |
547 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
548 | * decreased/increased to bring the dirty pages back to the setpoint. | |
549 | * | |
550 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
551 | * | |
552 | * if (dirty < setpoint) scale up pos_ratio | |
553 | * if (dirty > setpoint) scale down pos_ratio | |
554 | * | |
555 | * if (bdi_dirty < bdi_setpoint) scale up pos_ratio | |
556 | * if (bdi_dirty > bdi_setpoint) scale down pos_ratio | |
557 | * | |
558 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
559 | * | |
560 | * (o) global control line | |
561 | * | |
562 | * ^ pos_ratio | |
563 | * | | |
564 | * | |<===== global dirty control scope ======>| | |
565 | * 2.0 .............* | |
566 | * | .* | |
567 | * | . * | |
568 | * | . * | |
569 | * | . * | |
570 | * | . * | |
571 | * | . * | |
572 | * 1.0 ................................* | |
573 | * | . . * | |
574 | * | . . * | |
575 | * | . . * | |
576 | * | . . * | |
577 | * | . . * | |
578 | * 0 +------------.------------------.----------------------*-------------> | |
579 | * freerun^ setpoint^ limit^ dirty pages | |
580 | * | |
581 | * (o) bdi control line | |
582 | * | |
583 | * ^ pos_ratio | |
584 | * | | |
585 | * | * | |
586 | * | * | |
587 | * | * | |
588 | * | * | |
589 | * | * |<=========== span ============>| | |
590 | * 1.0 .......................* | |
591 | * | . * | |
592 | * | . * | |
593 | * | . * | |
594 | * | . * | |
595 | * | . * | |
596 | * | . * | |
597 | * | . * | |
598 | * | . * | |
599 | * | . * | |
600 | * | . * | |
601 | * | . * | |
602 | * 1/4 ...............................................* * * * * * * * * * * * | |
603 | * | . . | |
604 | * | . . | |
605 | * | . . | |
606 | * 0 +----------------------.-------------------------------.-------------> | |
607 | * bdi_setpoint^ x_intercept^ | |
608 | * | |
609 | * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can | |
610 | * be smoothly throttled down to normal if it starts high in situations like | |
611 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
612 | * card's bdi_dirty may rush to many times higher than bdi_setpoint. | |
613 | * - the bdi dirty thresh drops quickly due to change of JBOD workload | |
614 | */ | |
615 | static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, | |
616 | unsigned long thresh, | |
617 | unsigned long bg_thresh, | |
618 | unsigned long dirty, | |
619 | unsigned long bdi_thresh, | |
620 | unsigned long bdi_dirty) | |
621 | { | |
622 | unsigned long write_bw = bdi->avg_write_bandwidth; | |
623 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); | |
624 | unsigned long limit = hard_dirty_limit(thresh); | |
625 | unsigned long x_intercept; | |
626 | unsigned long setpoint; /* dirty pages' target balance point */ | |
627 | unsigned long bdi_setpoint; | |
628 | unsigned long span; | |
629 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
630 | long x; | |
631 | ||
632 | if (unlikely(dirty >= limit)) | |
633 | return 0; | |
634 | ||
635 | /* | |
636 | * global setpoint | |
637 | * | |
638 | * setpoint - dirty 3 | |
639 | * f(dirty) := 1.0 + (----------------) | |
640 | * limit - setpoint | |
641 | * | |
642 | * it's a 3rd order polynomial that subjects to | |
643 | * | |
644 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
645 | * (2) f(setpoint) = 1.0 => the balance point | |
646 | * (3) f(limit) = 0 => the hard limit | |
647 | * (4) df/dx <= 0 => negative feedback control | |
648 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
649 | * => fast response on large errors; small oscillation near setpoint | |
650 | */ | |
651 | setpoint = (freerun + limit) / 2; | |
652 | x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, | |
653 | limit - setpoint + 1); | |
654 | pos_ratio = x; | |
655 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
656 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
657 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
658 | ||
659 | /* | |
660 | * We have computed basic pos_ratio above based on global situation. If | |
661 | * the bdi is over/under its share of dirty pages, we want to scale | |
662 | * pos_ratio further down/up. That is done by the following mechanism. | |
663 | */ | |
664 | ||
665 | /* | |
666 | * bdi setpoint | |
667 | * | |
668 | * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint) | |
669 | * | |
670 | * x_intercept - bdi_dirty | |
671 | * := -------------------------- | |
672 | * x_intercept - bdi_setpoint | |
673 | * | |
674 | * The main bdi control line is a linear function that subjects to | |
675 | * | |
676 | * (1) f(bdi_setpoint) = 1.0 | |
677 | * (2) k = - 1 / (8 * write_bw) (in single bdi case) | |
678 | * or equally: x_intercept = bdi_setpoint + 8 * write_bw | |
679 | * | |
680 | * For single bdi case, the dirty pages are observed to fluctuate | |
681 | * regularly within range | |
682 | * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2] | |
683 | * for various filesystems, where (2) can yield in a reasonable 12.5% | |
684 | * fluctuation range for pos_ratio. | |
685 | * | |
686 | * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its | |
687 | * own size, so move the slope over accordingly and choose a slope that | |
688 | * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh. | |
689 | */ | |
690 | if (unlikely(bdi_thresh > thresh)) | |
691 | bdi_thresh = thresh; | |
aed21ad2 WF |
692 | /* |
693 | * It's very possible that bdi_thresh is close to 0 not because the | |
694 | * device is slow, but that it has remained inactive for long time. | |
695 | * Honour such devices a reasonable good (hopefully IO efficient) | |
696 | * threshold, so that the occasional writes won't be blocked and active | |
697 | * writes can rampup the threshold quickly. | |
698 | */ | |
8927f66c | 699 | bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); |
6c14ae1e WF |
700 | /* |
701 | * scale global setpoint to bdi's: | |
702 | * bdi_setpoint = setpoint * bdi_thresh / thresh | |
703 | */ | |
704 | x = div_u64((u64)bdi_thresh << 16, thresh + 1); | |
705 | bdi_setpoint = setpoint * (u64)x >> 16; | |
706 | /* | |
707 | * Use span=(8*write_bw) in single bdi case as indicated by | |
708 | * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case. | |
709 | * | |
710 | * bdi_thresh thresh - bdi_thresh | |
711 | * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh | |
712 | * thresh thresh | |
713 | */ | |
714 | span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16; | |
715 | x_intercept = bdi_setpoint + span; | |
716 | ||
717 | if (bdi_dirty < x_intercept - span / 4) { | |
50657fc4 WF |
718 | pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), |
719 | x_intercept - bdi_setpoint + 1); | |
6c14ae1e WF |
720 | } else |
721 | pos_ratio /= 4; | |
722 | ||
8927f66c WF |
723 | /* |
724 | * bdi reserve area, safeguard against dirty pool underrun and disk idle | |
725 | * It may push the desired control point of global dirty pages higher | |
726 | * than setpoint. | |
727 | */ | |
728 | x_intercept = bdi_thresh / 2; | |
729 | if (bdi_dirty < x_intercept) { | |
50657fc4 WF |
730 | if (bdi_dirty > x_intercept / 8) |
731 | pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty); | |
732 | else | |
8927f66c WF |
733 | pos_ratio *= 8; |
734 | } | |
735 | ||
6c14ae1e WF |
736 | return pos_ratio; |
737 | } | |
738 | ||
e98be2d5 WF |
739 | static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, |
740 | unsigned long elapsed, | |
741 | unsigned long written) | |
742 | { | |
743 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
744 | unsigned long avg = bdi->avg_write_bandwidth; | |
745 | unsigned long old = bdi->write_bandwidth; | |
746 | u64 bw; | |
747 | ||
748 | /* | |
749 | * bw = written * HZ / elapsed | |
750 | * | |
751 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
752 | * write_bandwidth = --------------------------------------------------- | |
753 | * period | |
754 | */ | |
755 | bw = written - bdi->written_stamp; | |
756 | bw *= HZ; | |
757 | if (unlikely(elapsed > period)) { | |
758 | do_div(bw, elapsed); | |
759 | avg = bw; | |
760 | goto out; | |
761 | } | |
762 | bw += (u64)bdi->write_bandwidth * (period - elapsed); | |
763 | bw >>= ilog2(period); | |
764 | ||
765 | /* | |
766 | * one more level of smoothing, for filtering out sudden spikes | |
767 | */ | |
768 | if (avg > old && old >= (unsigned long)bw) | |
769 | avg -= (avg - old) >> 3; | |
770 | ||
771 | if (avg < old && old <= (unsigned long)bw) | |
772 | avg += (old - avg) >> 3; | |
773 | ||
774 | out: | |
775 | bdi->write_bandwidth = bw; | |
776 | bdi->avg_write_bandwidth = avg; | |
777 | } | |
778 | ||
c42843f2 WF |
779 | /* |
780 | * The global dirtyable memory and dirty threshold could be suddenly knocked | |
781 | * down by a large amount (eg. on the startup of KVM in a swapless system). | |
782 | * This may throw the system into deep dirty exceeded state and throttle | |
783 | * heavy/light dirtiers alike. To retain good responsiveness, maintain | |
784 | * global_dirty_limit for tracking slowly down to the knocked down dirty | |
785 | * threshold. | |
786 | */ | |
787 | static void update_dirty_limit(unsigned long thresh, unsigned long dirty) | |
788 | { | |
789 | unsigned long limit = global_dirty_limit; | |
790 | ||
791 | /* | |
792 | * Follow up in one step. | |
793 | */ | |
794 | if (limit < thresh) { | |
795 | limit = thresh; | |
796 | goto update; | |
797 | } | |
798 | ||
799 | /* | |
800 | * Follow down slowly. Use the higher one as the target, because thresh | |
801 | * may drop below dirty. This is exactly the reason to introduce | |
802 | * global_dirty_limit which is guaranteed to lie above the dirty pages. | |
803 | */ | |
804 | thresh = max(thresh, dirty); | |
805 | if (limit > thresh) { | |
806 | limit -= (limit - thresh) >> 5; | |
807 | goto update; | |
808 | } | |
809 | return; | |
810 | update: | |
811 | global_dirty_limit = limit; | |
812 | } | |
813 | ||
814 | static void global_update_bandwidth(unsigned long thresh, | |
815 | unsigned long dirty, | |
816 | unsigned long now) | |
817 | { | |
818 | static DEFINE_SPINLOCK(dirty_lock); | |
819 | static unsigned long update_time; | |
820 | ||
821 | /* | |
822 | * check locklessly first to optimize away locking for the most time | |
823 | */ | |
824 | if (time_before(now, update_time + BANDWIDTH_INTERVAL)) | |
825 | return; | |
826 | ||
827 | spin_lock(&dirty_lock); | |
828 | if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) { | |
829 | update_dirty_limit(thresh, dirty); | |
830 | update_time = now; | |
831 | } | |
832 | spin_unlock(&dirty_lock); | |
833 | } | |
834 | ||
be3ffa27 WF |
835 | /* |
836 | * Maintain bdi->dirty_ratelimit, the base dirty throttle rate. | |
837 | * | |
838 | * Normal bdi tasks will be curbed at or below it in long term. | |
839 | * Obviously it should be around (write_bw / N) when there are N dd tasks. | |
840 | */ | |
841 | static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, | |
842 | unsigned long thresh, | |
843 | unsigned long bg_thresh, | |
844 | unsigned long dirty, | |
845 | unsigned long bdi_thresh, | |
846 | unsigned long bdi_dirty, | |
847 | unsigned long dirtied, | |
848 | unsigned long elapsed) | |
849 | { | |
7381131c WF |
850 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); |
851 | unsigned long limit = hard_dirty_limit(thresh); | |
852 | unsigned long setpoint = (freerun + limit) / 2; | |
be3ffa27 WF |
853 | unsigned long write_bw = bdi->avg_write_bandwidth; |
854 | unsigned long dirty_ratelimit = bdi->dirty_ratelimit; | |
855 | unsigned long dirty_rate; | |
856 | unsigned long task_ratelimit; | |
857 | unsigned long balanced_dirty_ratelimit; | |
858 | unsigned long pos_ratio; | |
7381131c WF |
859 | unsigned long step; |
860 | unsigned long x; | |
be3ffa27 WF |
861 | |
862 | /* | |
863 | * The dirty rate will match the writeout rate in long term, except | |
864 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
865 | */ | |
866 | dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; | |
867 | ||
868 | pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, | |
869 | bdi_thresh, bdi_dirty); | |
870 | /* | |
871 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
872 | */ | |
873 | task_ratelimit = (u64)dirty_ratelimit * | |
874 | pos_ratio >> RATELIMIT_CALC_SHIFT; | |
875 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ | |
876 | ||
877 | /* | |
878 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
879 | * if there are N dd tasks, each throttled at task_ratelimit, the bdi's | |
880 | * dirty_rate will be measured to be (N * task_ratelimit). So the below | |
881 | * formula will yield the balanced rate limit (write_bw / N). | |
882 | * | |
883 | * Note that the expanded form is not a pure rate feedback: | |
884 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
885 | * but also takes pos_ratio into account: | |
886 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
887 | * | |
888 | * (1) is not realistic because pos_ratio also takes part in balancing | |
889 | * the dirty rate. Consider the state | |
890 | * pos_ratio = 0.5 (3) | |
891 | * rate = 2 * (write_bw / N) (4) | |
892 | * If (1) is used, it will stuck in that state! Because each dd will | |
893 | * be throttled at | |
894 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
895 | * yielding | |
896 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
897 | * put (6) into (1) we get | |
898 | * rate_(i+1) = rate_(i) (7) | |
899 | * | |
900 | * So we end up using (2) to always keep | |
901 | * rate_(i+1) ~= (write_bw / N) (8) | |
902 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
903 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
904 | * the dirty count meet the setpoint, but also where the slope of | |
905 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
906 | */ | |
907 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
908 | dirty_rate | 1); | |
bdaac490 WF |
909 | /* |
910 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw | |
911 | */ | |
912 | if (unlikely(balanced_dirty_ratelimit > write_bw)) | |
913 | balanced_dirty_ratelimit = write_bw; | |
be3ffa27 | 914 | |
7381131c WF |
915 | /* |
916 | * We could safely do this and return immediately: | |
917 | * | |
918 | * bdi->dirty_ratelimit = balanced_dirty_ratelimit; | |
919 | * | |
920 | * However to get a more stable dirty_ratelimit, the below elaborated | |
921 | * code makes use of task_ratelimit to filter out sigular points and | |
922 | * limit the step size. | |
923 | * | |
924 | * The below code essentially only uses the relative value of | |
925 | * | |
926 | * task_ratelimit - dirty_ratelimit | |
927 | * = (pos_ratio - 1) * dirty_ratelimit | |
928 | * | |
929 | * which reflects the direction and size of dirty position error. | |
930 | */ | |
931 | ||
932 | /* | |
933 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff | |
934 | * task_ratelimit is on the same side of dirty_ratelimit, too. | |
935 | * For example, when | |
936 | * - dirty_ratelimit > balanced_dirty_ratelimit | |
937 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) | |
938 | * lowering dirty_ratelimit will help meet both the position and rate | |
939 | * control targets. Otherwise, don't update dirty_ratelimit if it will | |
940 | * only help meet the rate target. After all, what the users ultimately | |
941 | * feel and care are stable dirty rate and small position error. | |
942 | * | |
943 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size | |
944 | * and filter out the sigular points of balanced_dirty_ratelimit. Which | |
945 | * keeps jumping around randomly and can even leap far away at times | |
946 | * due to the small 200ms estimation period of dirty_rate (we want to | |
947 | * keep that period small to reduce time lags). | |
948 | */ | |
949 | step = 0; | |
950 | if (dirty < setpoint) { | |
951 | x = min(bdi->balanced_dirty_ratelimit, | |
952 | min(balanced_dirty_ratelimit, task_ratelimit)); | |
953 | if (dirty_ratelimit < x) | |
954 | step = x - dirty_ratelimit; | |
955 | } else { | |
956 | x = max(bdi->balanced_dirty_ratelimit, | |
957 | max(balanced_dirty_ratelimit, task_ratelimit)); | |
958 | if (dirty_ratelimit > x) | |
959 | step = dirty_ratelimit - x; | |
960 | } | |
961 | ||
962 | /* | |
963 | * Don't pursue 100% rate matching. It's impossible since the balanced | |
964 | * rate itself is constantly fluctuating. So decrease the track speed | |
965 | * when it gets close to the target. Helps eliminate pointless tremors. | |
966 | */ | |
967 | step >>= dirty_ratelimit / (2 * step + 1); | |
968 | /* | |
969 | * Limit the tracking speed to avoid overshooting. | |
970 | */ | |
971 | step = (step + 7) / 8; | |
972 | ||
973 | if (dirty_ratelimit < balanced_dirty_ratelimit) | |
974 | dirty_ratelimit += step; | |
975 | else | |
976 | dirty_ratelimit -= step; | |
977 | ||
978 | bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL); | |
979 | bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit; | |
b48c104d WF |
980 | |
981 | trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit); | |
be3ffa27 WF |
982 | } |
983 | ||
e98be2d5 | 984 | void __bdi_update_bandwidth(struct backing_dev_info *bdi, |
c42843f2 | 985 | unsigned long thresh, |
af6a3113 | 986 | unsigned long bg_thresh, |
c42843f2 WF |
987 | unsigned long dirty, |
988 | unsigned long bdi_thresh, | |
989 | unsigned long bdi_dirty, | |
e98be2d5 WF |
990 | unsigned long start_time) |
991 | { | |
992 | unsigned long now = jiffies; | |
993 | unsigned long elapsed = now - bdi->bw_time_stamp; | |
be3ffa27 | 994 | unsigned long dirtied; |
e98be2d5 WF |
995 | unsigned long written; |
996 | ||
997 | /* | |
998 | * rate-limit, only update once every 200ms. | |
999 | */ | |
1000 | if (elapsed < BANDWIDTH_INTERVAL) | |
1001 | return; | |
1002 | ||
be3ffa27 | 1003 | dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); |
e98be2d5 WF |
1004 | written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); |
1005 | ||
1006 | /* | |
1007 | * Skip quiet periods when disk bandwidth is under-utilized. | |
1008 | * (at least 1s idle time between two flusher runs) | |
1009 | */ | |
1010 | if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) | |
1011 | goto snapshot; | |
1012 | ||
be3ffa27 | 1013 | if (thresh) { |
c42843f2 | 1014 | global_update_bandwidth(thresh, dirty, now); |
be3ffa27 WF |
1015 | bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, |
1016 | bdi_thresh, bdi_dirty, | |
1017 | dirtied, elapsed); | |
1018 | } | |
e98be2d5 WF |
1019 | bdi_update_write_bandwidth(bdi, elapsed, written); |
1020 | ||
1021 | snapshot: | |
be3ffa27 | 1022 | bdi->dirtied_stamp = dirtied; |
e98be2d5 WF |
1023 | bdi->written_stamp = written; |
1024 | bdi->bw_time_stamp = now; | |
1025 | } | |
1026 | ||
1027 | static 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 | if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) | |
1036 | return; | |
1037 | spin_lock(&bdi->wb.list_lock); | |
af6a3113 WF |
1038 | __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, |
1039 | bdi_thresh, bdi_dirty, start_time); | |
e98be2d5 WF |
1040 | spin_unlock(&bdi->wb.list_lock); |
1041 | } | |
1042 | ||
9d823e8f WF |
1043 | /* |
1044 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited_nr() | |
1045 | * will look to see if it needs to start dirty throttling. | |
1046 | * | |
1047 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive | |
1048 | * global_page_state() too often. So scale it near-sqrt to the safety margin | |
1049 | * (the number of pages we may dirty without exceeding the dirty limits). | |
1050 | */ | |
1051 | static unsigned long dirty_poll_interval(unsigned long dirty, | |
1052 | unsigned long thresh) | |
1053 | { | |
1054 | if (thresh > dirty) | |
1055 | return 1UL << (ilog2(thresh - dirty) >> 1); | |
1056 | ||
1057 | return 1; | |
1058 | } | |
1059 | ||
7ccb9ad5 WF |
1060 | static long bdi_max_pause(struct backing_dev_info *bdi, |
1061 | unsigned long bdi_dirty) | |
c8462cc9 | 1062 | { |
7ccb9ad5 WF |
1063 | long bw = bdi->avg_write_bandwidth; |
1064 | long t; | |
c8462cc9 | 1065 | |
7ccb9ad5 WF |
1066 | /* |
1067 | * Limit pause time for small memory systems. If sleeping for too long | |
1068 | * time, a small pool of dirty/writeback pages may go empty and disk go | |
1069 | * idle. | |
1070 | * | |
1071 | * 8 serves as the safety ratio. | |
1072 | */ | |
1073 | t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); | |
1074 | t++; | |
1075 | ||
1076 | return min_t(long, t, MAX_PAUSE); | |
1077 | } | |
1078 | ||
1079 | static long bdi_min_pause(struct backing_dev_info *bdi, | |
1080 | long max_pause, | |
1081 | unsigned long task_ratelimit, | |
1082 | unsigned long dirty_ratelimit, | |
1083 | int *nr_dirtied_pause) | |
c8462cc9 | 1084 | { |
7ccb9ad5 WF |
1085 | long hi = ilog2(bdi->avg_write_bandwidth); |
1086 | long lo = ilog2(bdi->dirty_ratelimit); | |
1087 | long t; /* target pause */ | |
1088 | long pause; /* estimated next pause */ | |
1089 | int pages; /* target nr_dirtied_pause */ | |
c8462cc9 | 1090 | |
7ccb9ad5 WF |
1091 | /* target for 10ms pause on 1-dd case */ |
1092 | t = max(1, HZ / 100); | |
c8462cc9 WF |
1093 | |
1094 | /* | |
1095 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
1096 | * overheads. | |
1097 | * | |
7ccb9ad5 | 1098 | * (N * 10ms) on 2^N concurrent tasks. |
c8462cc9 WF |
1099 | */ |
1100 | if (hi > lo) | |
7ccb9ad5 | 1101 | t += (hi - lo) * (10 * HZ) / 1024; |
c8462cc9 WF |
1102 | |
1103 | /* | |
7ccb9ad5 WF |
1104 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
1105 | * on the much more stable dirty_ratelimit. However the next pause time | |
1106 | * will be computed based on task_ratelimit and the two rate limits may | |
1107 | * depart considerably at some time. Especially if task_ratelimit goes | |
1108 | * below dirty_ratelimit/2 and the target pause is max_pause, the next | |
1109 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a | |
1110 | * result task_ratelimit won't be executed faithfully, which could | |
1111 | * eventually bring down dirty_ratelimit. | |
c8462cc9 | 1112 | * |
7ccb9ad5 WF |
1113 | * We apply two rules to fix it up: |
1114 | * 1) try to estimate the next pause time and if necessary, use a lower | |
1115 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, | |
1116 | * nr_dirtied_pause will be "dancing" with task_ratelimit. | |
1117 | * 2) limit the target pause time to max_pause/2, so that the normal | |
1118 | * small fluctuations of task_ratelimit won't trigger rule (1) and | |
1119 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. | |
c8462cc9 | 1120 | */ |
7ccb9ad5 WF |
1121 | t = min(t, 1 + max_pause / 2); |
1122 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
c8462cc9 WF |
1123 | |
1124 | /* | |
5b9b3574 WF |
1125 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
1126 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. | |
1127 | * When the 16 consecutive reads are often interrupted by some dirty | |
1128 | * throttling pause during the async writes, cfq will go into idles | |
1129 | * (deadline is fine). So push nr_dirtied_pause as high as possible | |
1130 | * until reaches DIRTY_POLL_THRESH=32 pages. | |
c8462cc9 | 1131 | */ |
5b9b3574 WF |
1132 | if (pages < DIRTY_POLL_THRESH) { |
1133 | t = max_pause; | |
1134 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
1135 | if (pages > DIRTY_POLL_THRESH) { | |
1136 | pages = DIRTY_POLL_THRESH; | |
1137 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; | |
1138 | } | |
1139 | } | |
1140 | ||
7ccb9ad5 WF |
1141 | pause = HZ * pages / (task_ratelimit + 1); |
1142 | if (pause > max_pause) { | |
1143 | t = max_pause; | |
1144 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); | |
1145 | } | |
c8462cc9 | 1146 | |
7ccb9ad5 | 1147 | *nr_dirtied_pause = pages; |
c8462cc9 | 1148 | /* |
7ccb9ad5 | 1149 | * The minimal pause time will normally be half the target pause time. |
c8462cc9 | 1150 | */ |
5b9b3574 | 1151 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
c8462cc9 WF |
1152 | } |
1153 | ||
1da177e4 LT |
1154 | /* |
1155 | * balance_dirty_pages() must be called by processes which are generating dirty | |
1156 | * data. It looks at the number of dirty pages in the machine and will force | |
143dfe86 | 1157 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1158 | * If we're over `background_thresh' then the writeback threads are woken to |
1159 | * perform some writeout. | |
1da177e4 | 1160 | */ |
3a2e9a5a | 1161 | static void balance_dirty_pages(struct address_space *mapping, |
143dfe86 | 1162 | unsigned long pages_dirtied) |
1da177e4 | 1163 | { |
143dfe86 WF |
1164 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
1165 | unsigned long bdi_reclaimable; | |
7762741e WF |
1166 | unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ |
1167 | unsigned long bdi_dirty; | |
6c14ae1e | 1168 | unsigned long freerun; |
364aeb28 DR |
1169 | unsigned long background_thresh; |
1170 | unsigned long dirty_thresh; | |
1171 | unsigned long bdi_thresh; | |
83712358 | 1172 | long period; |
7ccb9ad5 WF |
1173 | long pause; |
1174 | long max_pause; | |
1175 | long min_pause; | |
1176 | int nr_dirtied_pause; | |
e50e3720 | 1177 | bool dirty_exceeded = false; |
143dfe86 | 1178 | unsigned long task_ratelimit; |
7ccb9ad5 | 1179 | unsigned long dirty_ratelimit; |
143dfe86 | 1180 | unsigned long pos_ratio; |
1da177e4 | 1181 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
e98be2d5 | 1182 | unsigned long start_time = jiffies; |
1da177e4 LT |
1183 | |
1184 | for (;;) { | |
83712358 WF |
1185 | unsigned long now = jiffies; |
1186 | ||
143dfe86 WF |
1187 | /* |
1188 | * Unstable writes are a feature of certain networked | |
1189 | * filesystems (i.e. NFS) in which data may have been | |
1190 | * written to the server's write cache, but has not yet | |
1191 | * been flushed to permanent storage. | |
1192 | */ | |
5fce25a9 PZ |
1193 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
1194 | global_page_state(NR_UNSTABLE_NFS); | |
7762741e | 1195 | nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
5fce25a9 | 1196 | |
16c4042f WF |
1197 | global_dirty_limits(&background_thresh, &dirty_thresh); |
1198 | ||
1199 | /* | |
1200 | * Throttle it only when the background writeback cannot | |
1201 | * catch-up. This avoids (excessively) small writeouts | |
1202 | * when the bdi limits are ramping up. | |
1203 | */ | |
6c14ae1e WF |
1204 | freerun = dirty_freerun_ceiling(dirty_thresh, |
1205 | background_thresh); | |
83712358 WF |
1206 | if (nr_dirty <= freerun) { |
1207 | current->dirty_paused_when = now; | |
1208 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1209 | current->nr_dirtied_pause = |
1210 | dirty_poll_interval(nr_dirty, dirty_thresh); | |
16c4042f | 1211 | break; |
83712358 | 1212 | } |
16c4042f | 1213 | |
143dfe86 WF |
1214 | if (unlikely(!writeback_in_progress(bdi))) |
1215 | bdi_start_background_writeback(bdi); | |
1216 | ||
1217 | /* | |
1218 | * bdi_thresh is not treated as some limiting factor as | |
1219 | * dirty_thresh, due to reasons | |
1220 | * - in JBOD setup, bdi_thresh can fluctuate a lot | |
1221 | * - in a system with HDD and USB key, the USB key may somehow | |
1222 | * go into state (bdi_dirty >> bdi_thresh) either because | |
1223 | * bdi_dirty starts high, or because bdi_thresh drops low. | |
1224 | * In this case we don't want to hard throttle the USB key | |
1225 | * dirtiers for 100 seconds until bdi_dirty drops under | |
1226 | * bdi_thresh. Instead the auxiliary bdi control line in | |
1227 | * bdi_position_ratio() will let the dirtier task progress | |
1228 | * at some rate <= (write_bw / 2) for bringing down bdi_dirty. | |
1229 | */ | |
16c4042f | 1230 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); |
16c4042f | 1231 | |
e50e3720 WF |
1232 | /* |
1233 | * In order to avoid the stacked BDI deadlock we need | |
1234 | * to ensure we accurately count the 'dirty' pages when | |
1235 | * the threshold is low. | |
1236 | * | |
1237 | * Otherwise it would be possible to get thresh+n pages | |
1238 | * reported dirty, even though there are thresh-m pages | |
1239 | * actually dirty; with m+n sitting in the percpu | |
1240 | * deltas. | |
1241 | */ | |
143dfe86 WF |
1242 | if (bdi_thresh < 2 * bdi_stat_error(bdi)) { |
1243 | bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); | |
1244 | bdi_dirty = bdi_reclaimable + | |
7762741e | 1245 | bdi_stat_sum(bdi, BDI_WRITEBACK); |
e50e3720 | 1246 | } else { |
143dfe86 WF |
1247 | bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
1248 | bdi_dirty = bdi_reclaimable + | |
7762741e | 1249 | bdi_stat(bdi, BDI_WRITEBACK); |
e50e3720 | 1250 | } |
5fce25a9 | 1251 | |
82791940 | 1252 | dirty_exceeded = (bdi_dirty > bdi_thresh) && |
7762741e | 1253 | (nr_dirty > dirty_thresh); |
143dfe86 | 1254 | if (dirty_exceeded && !bdi->dirty_exceeded) |
04fbfdc1 | 1255 | bdi->dirty_exceeded = 1; |
1da177e4 | 1256 | |
af6a3113 WF |
1257 | bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, |
1258 | nr_dirty, bdi_thresh, bdi_dirty, | |
1259 | start_time); | |
e98be2d5 | 1260 | |
143dfe86 WF |
1261 | dirty_ratelimit = bdi->dirty_ratelimit; |
1262 | pos_ratio = bdi_position_ratio(bdi, dirty_thresh, | |
1263 | background_thresh, nr_dirty, | |
1264 | bdi_thresh, bdi_dirty); | |
3a73dbbc WF |
1265 | task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> |
1266 | RATELIMIT_CALC_SHIFT; | |
7ccb9ad5 WF |
1267 | max_pause = bdi_max_pause(bdi, bdi_dirty); |
1268 | min_pause = bdi_min_pause(bdi, max_pause, | |
1269 | task_ratelimit, dirty_ratelimit, | |
1270 | &nr_dirtied_pause); | |
1271 | ||
3a73dbbc | 1272 | if (unlikely(task_ratelimit == 0)) { |
83712358 | 1273 | period = max_pause; |
c8462cc9 | 1274 | pause = max_pause; |
143dfe86 | 1275 | goto pause; |
04fbfdc1 | 1276 | } |
83712358 WF |
1277 | period = HZ * pages_dirtied / task_ratelimit; |
1278 | pause = period; | |
1279 | if (current->dirty_paused_when) | |
1280 | pause -= now - current->dirty_paused_when; | |
1281 | /* | |
1282 | * For less than 1s think time (ext3/4 may block the dirtier | |
1283 | * for up to 800ms from time to time on 1-HDD; so does xfs, | |
1284 | * however at much less frequency), try to compensate it in | |
1285 | * future periods by updating the virtual time; otherwise just | |
1286 | * do a reset, as it may be a light dirtier. | |
1287 | */ | |
7ccb9ad5 | 1288 | if (pause < min_pause) { |
ece13ac3 WF |
1289 | trace_balance_dirty_pages(bdi, |
1290 | dirty_thresh, | |
1291 | background_thresh, | |
1292 | nr_dirty, | |
1293 | bdi_thresh, | |
1294 | bdi_dirty, | |
1295 | dirty_ratelimit, | |
1296 | task_ratelimit, | |
1297 | pages_dirtied, | |
83712358 | 1298 | period, |
7ccb9ad5 | 1299 | min(pause, 0L), |
ece13ac3 | 1300 | start_time); |
83712358 WF |
1301 | if (pause < -HZ) { |
1302 | current->dirty_paused_when = now; | |
1303 | current->nr_dirtied = 0; | |
1304 | } else if (period) { | |
1305 | current->dirty_paused_when += period; | |
1306 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1307 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
1308 | current->nr_dirtied_pause += pages_dirtied; | |
57fc978c | 1309 | break; |
04fbfdc1 | 1310 | } |
7ccb9ad5 WF |
1311 | if (unlikely(pause > max_pause)) { |
1312 | /* for occasional dropped task_ratelimit */ | |
1313 | now += min(pause - max_pause, max_pause); | |
1314 | pause = max_pause; | |
1315 | } | |
143dfe86 WF |
1316 | |
1317 | pause: | |
ece13ac3 WF |
1318 | trace_balance_dirty_pages(bdi, |
1319 | dirty_thresh, | |
1320 | background_thresh, | |
1321 | nr_dirty, | |
1322 | bdi_thresh, | |
1323 | bdi_dirty, | |
1324 | dirty_ratelimit, | |
1325 | task_ratelimit, | |
1326 | pages_dirtied, | |
83712358 | 1327 | period, |
ece13ac3 WF |
1328 | pause, |
1329 | start_time); | |
499d05ec | 1330 | __set_current_state(TASK_KILLABLE); |
d25105e8 | 1331 | io_schedule_timeout(pause); |
87c6a9b2 | 1332 | |
83712358 WF |
1333 | current->dirty_paused_when = now + pause; |
1334 | current->nr_dirtied = 0; | |
7ccb9ad5 | 1335 | current->nr_dirtied_pause = nr_dirtied_pause; |
83712358 | 1336 | |
ffd1f609 | 1337 | /* |
1df64719 WF |
1338 | * This is typically equal to (nr_dirty < dirty_thresh) and can |
1339 | * also keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1340 | */ |
1df64719 | 1341 | if (task_ratelimit) |
ffd1f609 | 1342 | break; |
499d05ec | 1343 | |
c5c6343c WF |
1344 | /* |
1345 | * In the case of an unresponding NFS server and the NFS dirty | |
1346 | * pages exceeds dirty_thresh, give the other good bdi's a pipe | |
1347 | * to go through, so that tasks on them still remain responsive. | |
1348 | * | |
1349 | * In theory 1 page is enough to keep the comsumer-producer | |
1350 | * pipe going: the flusher cleans 1 page => the task dirties 1 | |
1351 | * more page. However bdi_dirty has accounting errors. So use | |
1352 | * the larger and more IO friendly bdi_stat_error. | |
1353 | */ | |
1354 | if (bdi_dirty <= bdi_stat_error(bdi)) | |
1355 | break; | |
1356 | ||
499d05ec JK |
1357 | if (fatal_signal_pending(current)) |
1358 | break; | |
1da177e4 LT |
1359 | } |
1360 | ||
143dfe86 | 1361 | if (!dirty_exceeded && bdi->dirty_exceeded) |
04fbfdc1 | 1362 | bdi->dirty_exceeded = 0; |
1da177e4 LT |
1363 | |
1364 | if (writeback_in_progress(bdi)) | |
5b0830cb | 1365 | return; |
1da177e4 LT |
1366 | |
1367 | /* | |
1368 | * In laptop mode, we wait until hitting the higher threshold before | |
1369 | * starting background writeout, and then write out all the way down | |
1370 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1371 | * | |
1372 | * In normal mode, we start background writeout at the lower | |
1373 | * background_thresh, to keep the amount of dirty memory low. | |
1374 | */ | |
143dfe86 WF |
1375 | if (laptop_mode) |
1376 | return; | |
1377 | ||
1378 | if (nr_reclaimable > background_thresh) | |
c5444198 | 1379 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
1380 | } |
1381 | ||
a200ee18 | 1382 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 1383 | { |
a200ee18 | 1384 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
1385 | struct address_space *mapping = page_mapping(page); |
1386 | ||
1387 | if (mapping) | |
1388 | balance_dirty_pages_ratelimited(mapping); | |
1389 | } | |
1390 | } | |
1391 | ||
9d823e8f | 1392 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1393 | |
54848d73 WF |
1394 | /* |
1395 | * Normal tasks are throttled by | |
1396 | * loop { | |
1397 | * dirty tsk->nr_dirtied_pause pages; | |
1398 | * take a snap in balance_dirty_pages(); | |
1399 | * } | |
1400 | * However there is a worst case. If every task exit immediately when dirtied | |
1401 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be | |
1402 | * called to throttle the page dirties. The solution is to save the not yet | |
1403 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them | |
1404 | * randomly into the running tasks. This works well for the above worst case, | |
1405 | * as the new task will pick up and accumulate the old task's leaked dirty | |
1406 | * count and eventually get throttled. | |
1407 | */ | |
1408 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1409 | ||
1da177e4 | 1410 | /** |
fa5a734e | 1411 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 1412 | * @mapping: address_space which was dirtied |
a580290c | 1413 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
1414 | * |
1415 | * Processes which are dirtying memory should call in here once for each page | |
1416 | * which was newly dirtied. The function will periodically check the system's | |
1417 | * dirty state and will initiate writeback if needed. | |
1418 | * | |
1419 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
1420 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
1421 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
1422 | * from overshooting the limit by (ratelimit_pages) each. | |
1423 | */ | |
fa5a734e AM |
1424 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
1425 | unsigned long nr_pages_dirtied) | |
1da177e4 | 1426 | { |
36715cef | 1427 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
9d823e8f WF |
1428 | int ratelimit; |
1429 | int *p; | |
1da177e4 | 1430 | |
36715cef WF |
1431 | if (!bdi_cap_account_dirty(bdi)) |
1432 | return; | |
1433 | ||
9d823e8f WF |
1434 | ratelimit = current->nr_dirtied_pause; |
1435 | if (bdi->dirty_exceeded) | |
1436 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); | |
1437 | ||
9d823e8f | 1438 | preempt_disable(); |
1da177e4 | 1439 | /* |
9d823e8f WF |
1440 | * This prevents one CPU to accumulate too many dirtied pages without |
1441 | * calling into balance_dirty_pages(), which can happen when there are | |
1442 | * 1000+ tasks, all of them start dirtying pages at exactly the same | |
1443 | * time, hence all honoured too large initial task->nr_dirtied_pause. | |
1da177e4 | 1444 | */ |
245b2e70 | 1445 | p = &__get_cpu_var(bdp_ratelimits); |
9d823e8f | 1446 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1447 | *p = 0; |
d3bc1fef WF |
1448 | else if (unlikely(*p >= ratelimit_pages)) { |
1449 | *p = 0; | |
1450 | ratelimit = 0; | |
1da177e4 | 1451 | } |
54848d73 WF |
1452 | /* |
1453 | * Pick up the dirtied pages by the exited tasks. This avoids lots of | |
1454 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping | |
1455 | * the dirty throttling and livelock other long-run dirtiers. | |
1456 | */ | |
1457 | p = &__get_cpu_var(dirty_throttle_leaks); | |
1458 | if (*p > 0 && current->nr_dirtied < ratelimit) { | |
1459 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); | |
1460 | *p -= nr_pages_dirtied; | |
1461 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1462 | } |
fa5a734e | 1463 | preempt_enable(); |
9d823e8f WF |
1464 | |
1465 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
1466 | balance_dirty_pages(mapping, current->nr_dirtied); | |
1da177e4 | 1467 | } |
fa5a734e | 1468 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 1469 | |
232ea4d6 | 1470 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 1471 | { |
364aeb28 DR |
1472 | unsigned long background_thresh; |
1473 | unsigned long dirty_thresh; | |
1da177e4 LT |
1474 | |
1475 | for ( ; ; ) { | |
16c4042f | 1476 | global_dirty_limits(&background_thresh, &dirty_thresh); |
47a13333 | 1477 | dirty_thresh = hard_dirty_limit(dirty_thresh); |
1da177e4 LT |
1478 | |
1479 | /* | |
1480 | * Boost the allowable dirty threshold a bit for page | |
1481 | * allocators so they don't get DoS'ed by heavy writers | |
1482 | */ | |
1483 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
1484 | ||
c24f21bd CL |
1485 | if (global_page_state(NR_UNSTABLE_NFS) + |
1486 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
1487 | break; | |
8aa7e847 | 1488 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
1489 | |
1490 | /* | |
1491 | * The caller might hold locks which can prevent IO completion | |
1492 | * or progress in the filesystem. So we cannot just sit here | |
1493 | * waiting for IO to complete. | |
1494 | */ | |
1495 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
1496 | break; | |
1da177e4 LT |
1497 | } |
1498 | } | |
1499 | ||
1da177e4 LT |
1500 | /* |
1501 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1502 | */ | |
1503 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 1504 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1505 | { |
8d65af78 | 1506 | proc_dointvec(table, write, buffer, length, ppos); |
6423104b | 1507 | bdi_arm_supers_timer(); |
1da177e4 LT |
1508 | return 0; |
1509 | } | |
1510 | ||
c2c4986e | 1511 | #ifdef CONFIG_BLOCK |
31373d09 | 1512 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 1513 | { |
31373d09 MG |
1514 | struct request_queue *q = (struct request_queue *)data; |
1515 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
1516 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 | 1517 | |
31373d09 MG |
1518 | /* |
1519 | * We want to write everything out, not just down to the dirty | |
1520 | * threshold | |
1521 | */ | |
31373d09 | 1522 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
0e175a18 CW |
1523 | bdi_start_writeback(&q->backing_dev_info, nr_pages, |
1524 | WB_REASON_LAPTOP_TIMER); | |
1da177e4 LT |
1525 | } |
1526 | ||
1527 | /* | |
1528 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
1529 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
1530 | * then push it back - the user is still using the disk. | |
1531 | */ | |
31373d09 | 1532 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 1533 | { |
31373d09 | 1534 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
1535 | } |
1536 | ||
1537 | /* | |
1538 | * We're in laptop mode and we've just synced. The sync's writes will have | |
1539 | * caused another writeback to be scheduled by laptop_io_completion. | |
1540 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
1541 | */ | |
1542 | void laptop_sync_completion(void) | |
1543 | { | |
31373d09 MG |
1544 | struct backing_dev_info *bdi; |
1545 | ||
1546 | rcu_read_lock(); | |
1547 | ||
1548 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
1549 | del_timer(&bdi->laptop_mode_wb_timer); | |
1550 | ||
1551 | rcu_read_unlock(); | |
1da177e4 | 1552 | } |
c2c4986e | 1553 | #endif |
1da177e4 LT |
1554 | |
1555 | /* | |
1556 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
1557 | * if a large number of processes all perform writes at the same time. | |
1558 | * If it is too low then SMP machines will call the (expensive) | |
1559 | * get_writeback_state too often. | |
1560 | * | |
1561 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
1562 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
9d823e8f | 1563 | * thresholds. |
1da177e4 LT |
1564 | */ |
1565 | ||
2d1d43f6 | 1566 | void writeback_set_ratelimit(void) |
1da177e4 | 1567 | { |
9d823e8f WF |
1568 | unsigned long background_thresh; |
1569 | unsigned long dirty_thresh; | |
1570 | global_dirty_limits(&background_thresh, &dirty_thresh); | |
68809c71 | 1571 | global_dirty_limit = dirty_thresh; |
9d823e8f | 1572 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
1da177e4 LT |
1573 | if (ratelimit_pages < 16) |
1574 | ratelimit_pages = 16; | |
1da177e4 LT |
1575 | } |
1576 | ||
26c2143b | 1577 | static int __cpuinit |
1da177e4 LT |
1578 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
1579 | { | |
2d1d43f6 | 1580 | writeback_set_ratelimit(); |
aa0f0303 | 1581 | return NOTIFY_DONE; |
1da177e4 LT |
1582 | } |
1583 | ||
74b85f37 | 1584 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
1585 | .notifier_call = ratelimit_handler, |
1586 | .next = NULL, | |
1587 | }; | |
1588 | ||
1589 | /* | |
dc6e29da LT |
1590 | * Called early on to tune the page writeback dirty limits. |
1591 | * | |
1592 | * We used to scale dirty pages according to how total memory | |
1593 | * related to pages that could be allocated for buffers (by | |
1594 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
1595 | * | |
1596 | * However, that was when we used "dirty_ratio" to scale with | |
1597 | * all memory, and we don't do that any more. "dirty_ratio" | |
1598 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
1599 | * totalhigh_pages from vm_total_pages), and as such we can't | |
1600 | * get into the old insane situation any more where we had | |
1601 | * large amounts of dirty pages compared to a small amount of | |
1602 | * non-HIGHMEM memory. | |
1603 | * | |
1604 | * But we might still want to scale the dirty_ratio by how | |
1605 | * much memory the box has.. | |
1da177e4 LT |
1606 | */ |
1607 | void __init page_writeback_init(void) | |
1608 | { | |
04fbfdc1 PZ |
1609 | int shift; |
1610 | ||
2d1d43f6 | 1611 | writeback_set_ratelimit(); |
1da177e4 | 1612 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
1613 | |
1614 | shift = calc_period_shift(); | |
1615 | prop_descriptor_init(&vm_completions, shift); | |
1da177e4 LT |
1616 | } |
1617 | ||
f446daae JK |
1618 | /** |
1619 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
1620 | * @mapping: address space structure to write | |
1621 | * @start: starting page index | |
1622 | * @end: ending page index (inclusive) | |
1623 | * | |
1624 | * This function scans the page range from @start to @end (inclusive) and tags | |
1625 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
1626 | * that write_cache_pages (or whoever calls this function) will then use | |
1627 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
1628 | * used to avoid livelocking of writeback by a process steadily creating new | |
1629 | * dirty pages in the file (thus it is important for this function to be quick | |
1630 | * so that it can tag pages faster than a dirtying process can create them). | |
1631 | */ | |
1632 | /* | |
1633 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
1634 | */ | |
f446daae JK |
1635 | void tag_pages_for_writeback(struct address_space *mapping, |
1636 | pgoff_t start, pgoff_t end) | |
1637 | { | |
3c111a07 | 1638 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
1639 | unsigned long tagged; |
1640 | ||
1641 | do { | |
1642 | spin_lock_irq(&mapping->tree_lock); | |
1643 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
1644 | &start, end, WRITEBACK_TAG_BATCH, | |
1645 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
1646 | spin_unlock_irq(&mapping->tree_lock); | |
1647 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
1648 | cond_resched(); | |
d5ed3a4a JK |
1649 | /* We check 'start' to handle wrapping when end == ~0UL */ |
1650 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
1651 | } |
1652 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
1653 | ||
811d736f | 1654 | /** |
0ea97180 | 1655 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
1656 | * @mapping: address space structure to write |
1657 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
1658 | * @writepage: function called for each page |
1659 | * @data: data passed to writepage function | |
811d736f | 1660 | * |
0ea97180 | 1661 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
1662 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
1663 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
1664 | * and msync() need to guarantee that all the data which was dirty at the time | |
1665 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
1666 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
1667 | * existing IO to complete. | |
f446daae JK |
1668 | * |
1669 | * To avoid livelocks (when other process dirties new pages), we first tag | |
1670 | * pages which should be written back with TOWRITE tag and only then start | |
1671 | * writing them. For data-integrity sync we have to be careful so that we do | |
1672 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
1673 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
1674 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 1675 | */ |
0ea97180 MS |
1676 | int write_cache_pages(struct address_space *mapping, |
1677 | struct writeback_control *wbc, writepage_t writepage, | |
1678 | void *data) | |
811d736f | 1679 | { |
811d736f DH |
1680 | int ret = 0; |
1681 | int done = 0; | |
811d736f DH |
1682 | struct pagevec pvec; |
1683 | int nr_pages; | |
31a12666 | 1684 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
1685 | pgoff_t index; |
1686 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 1687 | pgoff_t done_index; |
31a12666 | 1688 | int cycled; |
811d736f | 1689 | int range_whole = 0; |
f446daae | 1690 | int tag; |
811d736f | 1691 | |
811d736f DH |
1692 | pagevec_init(&pvec, 0); |
1693 | if (wbc->range_cyclic) { | |
31a12666 NP |
1694 | writeback_index = mapping->writeback_index; /* prev offset */ |
1695 | index = writeback_index; | |
1696 | if (index == 0) | |
1697 | cycled = 1; | |
1698 | else | |
1699 | cycled = 0; | |
811d736f DH |
1700 | end = -1; |
1701 | } else { | |
1702 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
1703 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
1704 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
1705 | range_whole = 1; | |
31a12666 | 1706 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 1707 | } |
6e6938b6 | 1708 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
1709 | tag = PAGECACHE_TAG_TOWRITE; |
1710 | else | |
1711 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 1712 | retry: |
6e6938b6 | 1713 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 1714 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 1715 | done_index = index; |
5a3d5c98 NP |
1716 | while (!done && (index <= end)) { |
1717 | int i; | |
1718 | ||
f446daae | 1719 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
1720 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
1721 | if (nr_pages == 0) | |
1722 | break; | |
811d736f | 1723 | |
811d736f DH |
1724 | for (i = 0; i < nr_pages; i++) { |
1725 | struct page *page = pvec.pages[i]; | |
1726 | ||
1727 | /* | |
d5482cdf NP |
1728 | * At this point, the page may be truncated or |
1729 | * invalidated (changing page->mapping to NULL), or | |
1730 | * even swizzled back from swapper_space to tmpfs file | |
1731 | * mapping. However, page->index will not change | |
1732 | * because we have a reference on the page. | |
811d736f | 1733 | */ |
d5482cdf NP |
1734 | if (page->index > end) { |
1735 | /* | |
1736 | * can't be range_cyclic (1st pass) because | |
1737 | * end == -1 in that case. | |
1738 | */ | |
1739 | done = 1; | |
1740 | break; | |
1741 | } | |
1742 | ||
cf15b07c | 1743 | done_index = page->index; |
d5482cdf | 1744 | |
811d736f DH |
1745 | lock_page(page); |
1746 | ||
5a3d5c98 NP |
1747 | /* |
1748 | * Page truncated or invalidated. We can freely skip it | |
1749 | * then, even for data integrity operations: the page | |
1750 | * has disappeared concurrently, so there could be no | |
1751 | * real expectation of this data interity operation | |
1752 | * even if there is now a new, dirty page at the same | |
1753 | * pagecache address. | |
1754 | */ | |
811d736f | 1755 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 1756 | continue_unlock: |
811d736f DH |
1757 | unlock_page(page); |
1758 | continue; | |
1759 | } | |
1760 | ||
515f4a03 NP |
1761 | if (!PageDirty(page)) { |
1762 | /* someone wrote it for us */ | |
1763 | goto continue_unlock; | |
1764 | } | |
1765 | ||
1766 | if (PageWriteback(page)) { | |
1767 | if (wbc->sync_mode != WB_SYNC_NONE) | |
1768 | wait_on_page_writeback(page); | |
1769 | else | |
1770 | goto continue_unlock; | |
1771 | } | |
811d736f | 1772 | |
515f4a03 NP |
1773 | BUG_ON(PageWriteback(page)); |
1774 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 1775 | goto continue_unlock; |
811d736f | 1776 | |
9e094383 | 1777 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 1778 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
1779 | if (unlikely(ret)) { |
1780 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
1781 | unlock_page(page); | |
1782 | ret = 0; | |
1783 | } else { | |
1784 | /* | |
1785 | * done_index is set past this page, | |
1786 | * so media errors will not choke | |
1787 | * background writeout for the entire | |
1788 | * file. This has consequences for | |
1789 | * range_cyclic semantics (ie. it may | |
1790 | * not be suitable for data integrity | |
1791 | * writeout). | |
1792 | */ | |
cf15b07c | 1793 | done_index = page->index + 1; |
00266770 NP |
1794 | done = 1; |
1795 | break; | |
1796 | } | |
0b564927 | 1797 | } |
00266770 | 1798 | |
546a1924 DC |
1799 | /* |
1800 | * We stop writing back only if we are not doing | |
1801 | * integrity sync. In case of integrity sync we have to | |
1802 | * keep going until we have written all the pages | |
1803 | * we tagged for writeback prior to entering this loop. | |
1804 | */ | |
1805 | if (--wbc->nr_to_write <= 0 && | |
1806 | wbc->sync_mode == WB_SYNC_NONE) { | |
1807 | done = 1; | |
1808 | break; | |
05fe478d | 1809 | } |
811d736f DH |
1810 | } |
1811 | pagevec_release(&pvec); | |
1812 | cond_resched(); | |
1813 | } | |
3a4c6800 | 1814 | if (!cycled && !done) { |
811d736f | 1815 | /* |
31a12666 | 1816 | * range_cyclic: |
811d736f DH |
1817 | * We hit the last page and there is more work to be done: wrap |
1818 | * back to the start of the file | |
1819 | */ | |
31a12666 | 1820 | cycled = 1; |
811d736f | 1821 | index = 0; |
31a12666 | 1822 | end = writeback_index - 1; |
811d736f DH |
1823 | goto retry; |
1824 | } | |
0b564927 DC |
1825 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
1826 | mapping->writeback_index = done_index; | |
06d6cf69 | 1827 | |
811d736f DH |
1828 | return ret; |
1829 | } | |
0ea97180 MS |
1830 | EXPORT_SYMBOL(write_cache_pages); |
1831 | ||
1832 | /* | |
1833 | * Function used by generic_writepages to call the real writepage | |
1834 | * function and set the mapping flags on error | |
1835 | */ | |
1836 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1837 | void *data) | |
1838 | { | |
1839 | struct address_space *mapping = data; | |
1840 | int ret = mapping->a_ops->writepage(page, wbc); | |
1841 | mapping_set_error(mapping, ret); | |
1842 | return ret; | |
1843 | } | |
1844 | ||
1845 | /** | |
1846 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1847 | * @mapping: address space structure to write | |
1848 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1849 | * | |
1850 | * This is a library function, which implements the writepages() | |
1851 | * address_space_operation. | |
1852 | */ | |
1853 | int generic_writepages(struct address_space *mapping, | |
1854 | struct writeback_control *wbc) | |
1855 | { | |
9b6096a6 SL |
1856 | struct blk_plug plug; |
1857 | int ret; | |
1858 | ||
0ea97180 MS |
1859 | /* deal with chardevs and other special file */ |
1860 | if (!mapping->a_ops->writepage) | |
1861 | return 0; | |
1862 | ||
9b6096a6 SL |
1863 | blk_start_plug(&plug); |
1864 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
1865 | blk_finish_plug(&plug); | |
1866 | return ret; | |
0ea97180 | 1867 | } |
811d736f DH |
1868 | |
1869 | EXPORT_SYMBOL(generic_writepages); | |
1870 | ||
1da177e4 LT |
1871 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1872 | { | |
22905f77 AM |
1873 | int ret; |
1874 | ||
1da177e4 LT |
1875 | if (wbc->nr_to_write <= 0) |
1876 | return 0; | |
1877 | if (mapping->a_ops->writepages) | |
d08b3851 | 1878 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1879 | else |
1880 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1881 | return ret; |
1da177e4 LT |
1882 | } |
1883 | ||
1884 | /** | |
1885 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1886 | * @page: the page to write |
1887 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1888 | * |
1889 | * The page must be locked by the caller and will be unlocked upon return. | |
1890 | * | |
1891 | * write_one_page() returns a negative error code if I/O failed. | |
1892 | */ | |
1893 | int write_one_page(struct page *page, int wait) | |
1894 | { | |
1895 | struct address_space *mapping = page->mapping; | |
1896 | int ret = 0; | |
1897 | struct writeback_control wbc = { | |
1898 | .sync_mode = WB_SYNC_ALL, | |
1899 | .nr_to_write = 1, | |
1900 | }; | |
1901 | ||
1902 | BUG_ON(!PageLocked(page)); | |
1903 | ||
1904 | if (wait) | |
1905 | wait_on_page_writeback(page); | |
1906 | ||
1907 | if (clear_page_dirty_for_io(page)) { | |
1908 | page_cache_get(page); | |
1909 | ret = mapping->a_ops->writepage(page, &wbc); | |
1910 | if (ret == 0 && wait) { | |
1911 | wait_on_page_writeback(page); | |
1912 | if (PageError(page)) | |
1913 | ret = -EIO; | |
1914 | } | |
1915 | page_cache_release(page); | |
1916 | } else { | |
1917 | unlock_page(page); | |
1918 | } | |
1919 | return ret; | |
1920 | } | |
1921 | EXPORT_SYMBOL(write_one_page); | |
1922 | ||
76719325 KC |
1923 | /* |
1924 | * For address_spaces which do not use buffers nor write back. | |
1925 | */ | |
1926 | int __set_page_dirty_no_writeback(struct page *page) | |
1927 | { | |
1928 | if (!PageDirty(page)) | |
c3f0da63 | 1929 | return !TestSetPageDirty(page); |
76719325 KC |
1930 | return 0; |
1931 | } | |
1932 | ||
e3a7cca1 ES |
1933 | /* |
1934 | * Helper function for set_page_dirty family. | |
1935 | * NOTE: This relies on being atomic wrt interrupts. | |
1936 | */ | |
1937 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1938 | { | |
1939 | if (mapping_cap_account_dirty(mapping)) { | |
1940 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
ea941f0e | 1941 | __inc_zone_page_state(page, NR_DIRTIED); |
e3a7cca1 | 1942 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
c8e28ce0 | 1943 | __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); |
e3a7cca1 | 1944 | task_io_account_write(PAGE_CACHE_SIZE); |
d3bc1fef WF |
1945 | current->nr_dirtied++; |
1946 | this_cpu_inc(bdp_ratelimits); | |
e3a7cca1 ES |
1947 | } |
1948 | } | |
679ceace | 1949 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 1950 | |
f629d1c9 MR |
1951 | /* |
1952 | * Helper function for set_page_writeback family. | |
1953 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic | |
1954 | * wrt interrupts. | |
1955 | */ | |
1956 | void account_page_writeback(struct page *page) | |
1957 | { | |
1958 | inc_zone_page_state(page, NR_WRITEBACK); | |
1959 | } | |
1960 | EXPORT_SYMBOL(account_page_writeback); | |
1961 | ||
1da177e4 LT |
1962 | /* |
1963 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1964 | * its radix tree. | |
1965 | * | |
1966 | * This is also used when a single buffer is being dirtied: we want to set the | |
1967 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1968 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1969 | * | |
1970 | * Most callers have locked the page, which pins the address_space in memory. | |
1971 | * But zap_pte_range() does not lock the page, however in that case the | |
1972 | * mapping is pinned by the vma's ->vm_file reference. | |
1973 | * | |
1974 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1975 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1976 | */ |
1977 | int __set_page_dirty_nobuffers(struct page *page) | |
1978 | { | |
1da177e4 LT |
1979 | if (!TestSetPageDirty(page)) { |
1980 | struct address_space *mapping = page_mapping(page); | |
1981 | struct address_space *mapping2; | |
1982 | ||
8c08540f AM |
1983 | if (!mapping) |
1984 | return 1; | |
1985 | ||
19fd6231 | 1986 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1987 | mapping2 = page_mapping(page); |
1988 | if (mapping2) { /* Race with truncate? */ | |
1989 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1990 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1991 | account_page_dirtied(page, mapping); |
8c08540f AM |
1992 | radix_tree_tag_set(&mapping->page_tree, |
1993 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1994 | } | |
19fd6231 | 1995 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1996 | if (mapping->host) { |
1997 | /* !PageAnon && !swapper_space */ | |
1998 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1999 | } |
4741c9fd | 2000 | return 1; |
1da177e4 | 2001 | } |
4741c9fd | 2002 | return 0; |
1da177e4 LT |
2003 | } |
2004 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
2005 | ||
2f800fbd WF |
2006 | /* |
2007 | * Call this whenever redirtying a page, to de-account the dirty counters | |
2008 | * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written | |
2009 | * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to | |
2010 | * systematic errors in balanced_dirty_ratelimit and the dirty pages position | |
2011 | * control. | |
2012 | */ | |
2013 | void account_page_redirty(struct page *page) | |
2014 | { | |
2015 | struct address_space *mapping = page->mapping; | |
2016 | if (mapping && mapping_cap_account_dirty(mapping)) { | |
2017 | current->nr_dirtied--; | |
2018 | dec_zone_page_state(page, NR_DIRTIED); | |
2019 | dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); | |
2020 | } | |
2021 | } | |
2022 | EXPORT_SYMBOL(account_page_redirty); | |
2023 | ||
1da177e4 LT |
2024 | /* |
2025 | * When a writepage implementation decides that it doesn't want to write this | |
2026 | * page for some reason, it should redirty the locked page via | |
2027 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
2028 | */ | |
2029 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
2030 | { | |
2031 | wbc->pages_skipped++; | |
2f800fbd | 2032 | account_page_redirty(page); |
1da177e4 LT |
2033 | return __set_page_dirty_nobuffers(page); |
2034 | } | |
2035 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
2036 | ||
2037 | /* | |
6746aff7 WF |
2038 | * Dirty a page. |
2039 | * | |
2040 | * For pages with a mapping this should be done under the page lock | |
2041 | * for the benefit of asynchronous memory errors who prefer a consistent | |
2042 | * dirty state. This rule can be broken in some special cases, | |
2043 | * but should be better not to. | |
2044 | * | |
1da177e4 LT |
2045 | * If the mapping doesn't provide a set_page_dirty a_op, then |
2046 | * just fall through and assume that it wants buffer_heads. | |
2047 | */ | |
1cf6e7d8 | 2048 | int set_page_dirty(struct page *page) |
1da177e4 LT |
2049 | { |
2050 | struct address_space *mapping = page_mapping(page); | |
2051 | ||
2052 | if (likely(mapping)) { | |
2053 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
2054 | /* |
2055 | * readahead/lru_deactivate_page could remain | |
2056 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
2057 | * About readahead, if the page is written, the flags would be | |
2058 | * reset. So no problem. | |
2059 | * About lru_deactivate_page, if the page is redirty, the flag | |
2060 | * will be reset. So no problem. but if the page is used by readahead | |
2061 | * it will confuse readahead and make it restart the size rampup | |
2062 | * process. But it's a trivial problem. | |
2063 | */ | |
2064 | ClearPageReclaim(page); | |
9361401e DH |
2065 | #ifdef CONFIG_BLOCK |
2066 | if (!spd) | |
2067 | spd = __set_page_dirty_buffers; | |
2068 | #endif | |
2069 | return (*spd)(page); | |
1da177e4 | 2070 | } |
4741c9fd AM |
2071 | if (!PageDirty(page)) { |
2072 | if (!TestSetPageDirty(page)) | |
2073 | return 1; | |
2074 | } | |
1da177e4 LT |
2075 | return 0; |
2076 | } | |
2077 | EXPORT_SYMBOL(set_page_dirty); | |
2078 | ||
2079 | /* | |
2080 | * set_page_dirty() is racy if the caller has no reference against | |
2081 | * page->mapping->host, and if the page is unlocked. This is because another | |
2082 | * CPU could truncate the page off the mapping and then free the mapping. | |
2083 | * | |
2084 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
2085 | * holds a reference on the inode by having an open file. | |
2086 | * | |
2087 | * In other cases, the page should be locked before running set_page_dirty(). | |
2088 | */ | |
2089 | int set_page_dirty_lock(struct page *page) | |
2090 | { | |
2091 | int ret; | |
2092 | ||
7eaceacc | 2093 | lock_page(page); |
1da177e4 LT |
2094 | ret = set_page_dirty(page); |
2095 | unlock_page(page); | |
2096 | return ret; | |
2097 | } | |
2098 | EXPORT_SYMBOL(set_page_dirty_lock); | |
2099 | ||
1da177e4 LT |
2100 | /* |
2101 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
2102 | * Returns true if the page was previously dirty. | |
2103 | * | |
2104 | * This is for preparing to put the page under writeout. We leave the page | |
2105 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
2106 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
2107 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
2108 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
2109 | * back into sync. | |
2110 | * | |
2111 | * This incoherency between the page's dirty flag and radix-tree tag is | |
2112 | * unfortunate, but it only exists while the page is locked. | |
2113 | */ | |
2114 | int clear_page_dirty_for_io(struct page *page) | |
2115 | { | |
2116 | struct address_space *mapping = page_mapping(page); | |
2117 | ||
79352894 NP |
2118 | BUG_ON(!PageLocked(page)); |
2119 | ||
7658cc28 LT |
2120 | if (mapping && mapping_cap_account_dirty(mapping)) { |
2121 | /* | |
2122 | * Yes, Virginia, this is indeed insane. | |
2123 | * | |
2124 | * We use this sequence to make sure that | |
2125 | * (a) we account for dirty stats properly | |
2126 | * (b) we tell the low-level filesystem to | |
2127 | * mark the whole page dirty if it was | |
2128 | * dirty in a pagetable. Only to then | |
2129 | * (c) clean the page again and return 1 to | |
2130 | * cause the writeback. | |
2131 | * | |
2132 | * This way we avoid all nasty races with the | |
2133 | * dirty bit in multiple places and clearing | |
2134 | * them concurrently from different threads. | |
2135 | * | |
2136 | * Note! Normally the "set_page_dirty(page)" | |
2137 | * has no effect on the actual dirty bit - since | |
2138 | * that will already usually be set. But we | |
2139 | * need the side effects, and it can help us | |
2140 | * avoid races. | |
2141 | * | |
2142 | * We basically use the page "master dirty bit" | |
2143 | * as a serialization point for all the different | |
2144 | * threads doing their things. | |
7658cc28 LT |
2145 | */ |
2146 | if (page_mkclean(page)) | |
2147 | set_page_dirty(page); | |
79352894 NP |
2148 | /* |
2149 | * We carefully synchronise fault handlers against | |
2150 | * installing a dirty pte and marking the page dirty | |
2151 | * at this point. We do this by having them hold the | |
2152 | * page lock at some point after installing their | |
2153 | * pte, but before marking the page dirty. | |
2154 | * Pages are always locked coming in here, so we get | |
2155 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
2156 | * for more comments. | |
2157 | */ | |
7658cc28 | 2158 | if (TestClearPageDirty(page)) { |
8c08540f | 2159 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
2160 | dec_bdi_stat(mapping->backing_dev_info, |
2161 | BDI_RECLAIMABLE); | |
7658cc28 | 2162 | return 1; |
1da177e4 | 2163 | } |
7658cc28 | 2164 | return 0; |
1da177e4 | 2165 | } |
7658cc28 | 2166 | return TestClearPageDirty(page); |
1da177e4 | 2167 | } |
58bb01a9 | 2168 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
2169 | |
2170 | int test_clear_page_writeback(struct page *page) | |
2171 | { | |
2172 | struct address_space *mapping = page_mapping(page); | |
2173 | int ret; | |
2174 | ||
2175 | if (mapping) { | |
69cb51d1 | 2176 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
2177 | unsigned long flags; |
2178 | ||
19fd6231 | 2179 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2180 | ret = TestClearPageWriteback(page); |
69cb51d1 | 2181 | if (ret) { |
1da177e4 LT |
2182 | radix_tree_tag_clear(&mapping->page_tree, |
2183 | page_index(page), | |
2184 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2185 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 2186 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
2187 | __bdi_writeout_inc(bdi); |
2188 | } | |
69cb51d1 | 2189 | } |
19fd6231 | 2190 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2191 | } else { |
2192 | ret = TestClearPageWriteback(page); | |
2193 | } | |
99b12e3d | 2194 | if (ret) { |
d688abf5 | 2195 | dec_zone_page_state(page, NR_WRITEBACK); |
99b12e3d WF |
2196 | inc_zone_page_state(page, NR_WRITTEN); |
2197 | } | |
1da177e4 LT |
2198 | return ret; |
2199 | } | |
2200 | ||
2201 | int test_set_page_writeback(struct page *page) | |
2202 | { | |
2203 | struct address_space *mapping = page_mapping(page); | |
2204 | int ret; | |
2205 | ||
2206 | if (mapping) { | |
69cb51d1 | 2207 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
2208 | unsigned long flags; |
2209 | ||
19fd6231 | 2210 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2211 | ret = TestSetPageWriteback(page); |
69cb51d1 | 2212 | if (!ret) { |
1da177e4 LT |
2213 | radix_tree_tag_set(&mapping->page_tree, |
2214 | page_index(page), | |
2215 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2216 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
2217 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
2218 | } | |
1da177e4 LT |
2219 | if (!PageDirty(page)) |
2220 | radix_tree_tag_clear(&mapping->page_tree, | |
2221 | page_index(page), | |
2222 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
2223 | radix_tree_tag_clear(&mapping->page_tree, |
2224 | page_index(page), | |
2225 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 2226 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2227 | } else { |
2228 | ret = TestSetPageWriteback(page); | |
2229 | } | |
d688abf5 | 2230 | if (!ret) |
f629d1c9 | 2231 | account_page_writeback(page); |
1da177e4 LT |
2232 | return ret; |
2233 | ||
2234 | } | |
2235 | EXPORT_SYMBOL(test_set_page_writeback); | |
2236 | ||
2237 | /* | |
00128188 | 2238 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
2239 | * passed tag. |
2240 | */ | |
2241 | int mapping_tagged(struct address_space *mapping, int tag) | |
2242 | { | |
72c47832 | 2243 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
2244 | } |
2245 | EXPORT_SYMBOL(mapping_tagged); |