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> | |
15 | #include <linux/module.h> | |
16 | #include <linux/spinlock.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/swap.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/pagemap.h> | |
22 | #include <linux/writeback.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/backing-dev.h> | |
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> | |
cf9a2ae8 | 35 | #include <linux/buffer_head.h> |
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 | ||
e98be2d5 WF |
44 | /* |
45 | * Estimate write bandwidth at 200ms intervals. | |
46 | */ | |
47 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) | |
48 | ||
6c14ae1e WF |
49 | #define RATELIMIT_CALC_SHIFT 10 |
50 | ||
1da177e4 LT |
51 | /* |
52 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
53 | * will look to see if it needs to force writeback or throttling. | |
54 | */ | |
55 | static long ratelimit_pages = 32; | |
56 | ||
1da177e4 LT |
57 | /* |
58 | * When balance_dirty_pages decides that the caller needs to perform some | |
59 | * non-background writeback, this is how many pages it will attempt to write. | |
3a2e9a5a | 60 | * It should be somewhat larger than dirtied pages to ensure that reasonably |
1da177e4 LT |
61 | * large amounts of I/O are submitted. |
62 | */ | |
3a2e9a5a | 63 | static inline long sync_writeback_pages(unsigned long dirtied) |
1da177e4 | 64 | { |
3a2e9a5a WF |
65 | if (dirtied < ratelimit_pages) |
66 | dirtied = ratelimit_pages; | |
67 | ||
68 | return dirtied + dirtied / 2; | |
1da177e4 LT |
69 | } |
70 | ||
71 | /* The following parameters are exported via /proc/sys/vm */ | |
72 | ||
73 | /* | |
5b0830cb | 74 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 75 | */ |
1b5e62b4 | 76 | int dirty_background_ratio = 10; |
1da177e4 | 77 | |
2da02997 DR |
78 | /* |
79 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
80 | * dirty_background_ratio * the amount of dirtyable memory | |
81 | */ | |
82 | unsigned long dirty_background_bytes; | |
83 | ||
195cf453 BG |
84 | /* |
85 | * free highmem will not be subtracted from the total free memory | |
86 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
87 | */ | |
88 | int vm_highmem_is_dirtyable; | |
89 | ||
1da177e4 LT |
90 | /* |
91 | * The generator of dirty data starts writeback at this percentage | |
92 | */ | |
1b5e62b4 | 93 | int vm_dirty_ratio = 20; |
1da177e4 | 94 | |
2da02997 DR |
95 | /* |
96 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
97 | * vm_dirty_ratio * the amount of dirtyable memory | |
98 | */ | |
99 | unsigned long vm_dirty_bytes; | |
100 | ||
1da177e4 | 101 | /* |
704503d8 | 102 | * The interval between `kupdate'-style writebacks |
1da177e4 | 103 | */ |
22ef37ee | 104 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 LT |
105 | |
106 | /* | |
704503d8 | 107 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 108 | */ |
22ef37ee | 109 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
110 | |
111 | /* | |
112 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
113 | */ | |
114 | int block_dump; | |
115 | ||
116 | /* | |
ed5b43f1 BS |
117 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
118 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
119 | */ |
120 | int laptop_mode; | |
121 | ||
122 | EXPORT_SYMBOL(laptop_mode); | |
123 | ||
124 | /* End of sysctl-exported parameters */ | |
125 | ||
c42843f2 | 126 | unsigned long global_dirty_limit; |
1da177e4 | 127 | |
04fbfdc1 PZ |
128 | /* |
129 | * Scale the writeback cache size proportional to the relative writeout speeds. | |
130 | * | |
131 | * We do this by keeping a floating proportion between BDIs, based on page | |
132 | * writeback completions [end_page_writeback()]. Those devices that write out | |
133 | * pages fastest will get the larger share, while the slower will get a smaller | |
134 | * share. | |
135 | * | |
136 | * We use page writeout completions because we are interested in getting rid of | |
137 | * dirty pages. Having them written out is the primary goal. | |
138 | * | |
139 | * We introduce a concept of time, a period over which we measure these events, | |
140 | * because demand can/will vary over time. The length of this period itself is | |
141 | * measured in page writeback completions. | |
142 | * | |
143 | */ | |
144 | static struct prop_descriptor vm_completions; | |
3e26c149 | 145 | static struct prop_descriptor vm_dirties; |
04fbfdc1 | 146 | |
04fbfdc1 PZ |
147 | /* |
148 | * couple the period to the dirty_ratio: | |
149 | * | |
150 | * period/2 ~ roundup_pow_of_two(dirty limit) | |
151 | */ | |
152 | static int calc_period_shift(void) | |
153 | { | |
154 | unsigned long dirty_total; | |
155 | ||
2da02997 DR |
156 | if (vm_dirty_bytes) |
157 | dirty_total = vm_dirty_bytes / PAGE_SIZE; | |
158 | else | |
159 | dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / | |
160 | 100; | |
04fbfdc1 PZ |
161 | return 2 + ilog2(dirty_total - 1); |
162 | } | |
163 | ||
164 | /* | |
2da02997 | 165 | * update the period when the dirty threshold changes. |
04fbfdc1 | 166 | */ |
2da02997 DR |
167 | static void update_completion_period(void) |
168 | { | |
169 | int shift = calc_period_shift(); | |
170 | prop_change_shift(&vm_completions, shift); | |
171 | prop_change_shift(&vm_dirties, shift); | |
172 | } | |
173 | ||
174 | int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
8d65af78 | 175 | void __user *buffer, size_t *lenp, |
2da02997 DR |
176 | loff_t *ppos) |
177 | { | |
178 | int ret; | |
179 | ||
8d65af78 | 180 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
181 | if (ret == 0 && write) |
182 | dirty_background_bytes = 0; | |
183 | return ret; | |
184 | } | |
185 | ||
186 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 187 | void __user *buffer, size_t *lenp, |
2da02997 DR |
188 | loff_t *ppos) |
189 | { | |
190 | int ret; | |
191 | ||
8d65af78 | 192 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
193 | if (ret == 0 && write) |
194 | dirty_background_ratio = 0; | |
195 | return ret; | |
196 | } | |
197 | ||
04fbfdc1 | 198 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 199 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
200 | loff_t *ppos) |
201 | { | |
202 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
203 | int ret; |
204 | ||
8d65af78 | 205 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 206 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
2da02997 DR |
207 | update_completion_period(); |
208 | vm_dirty_bytes = 0; | |
209 | } | |
210 | return ret; | |
211 | } | |
212 | ||
213 | ||
214 | int dirty_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 215 | void __user *buffer, size_t *lenp, |
2da02997 DR |
216 | loff_t *ppos) |
217 | { | |
fc3501d4 | 218 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
219 | int ret; |
220 | ||
8d65af78 | 221 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
222 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
223 | update_completion_period(); | |
224 | vm_dirty_ratio = 0; | |
04fbfdc1 PZ |
225 | } |
226 | return ret; | |
227 | } | |
228 | ||
229 | /* | |
230 | * Increment the BDI's writeout completion count and the global writeout | |
231 | * completion count. Called from test_clear_page_writeback(). | |
232 | */ | |
233 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
234 | { | |
f7d2b1ec | 235 | __inc_bdi_stat(bdi, BDI_WRITTEN); |
a42dde04 PZ |
236 | __prop_inc_percpu_max(&vm_completions, &bdi->completions, |
237 | bdi->max_prop_frac); | |
04fbfdc1 PZ |
238 | } |
239 | ||
dd5656e5 MS |
240 | void bdi_writeout_inc(struct backing_dev_info *bdi) |
241 | { | |
242 | unsigned long flags; | |
243 | ||
244 | local_irq_save(flags); | |
245 | __bdi_writeout_inc(bdi); | |
246 | local_irq_restore(flags); | |
247 | } | |
248 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); | |
249 | ||
1cf6e7d8 | 250 | void task_dirty_inc(struct task_struct *tsk) |
3e26c149 PZ |
251 | { |
252 | prop_inc_single(&vm_dirties, &tsk->dirties); | |
253 | } | |
254 | ||
04fbfdc1 PZ |
255 | /* |
256 | * Obtain an accurate fraction of the BDI's portion. | |
257 | */ | |
258 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
259 | long *numerator, long *denominator) | |
260 | { | |
3efaf0fa | 261 | prop_fraction_percpu(&vm_completions, &bdi->completions, |
04fbfdc1 | 262 | numerator, denominator); |
04fbfdc1 PZ |
263 | } |
264 | ||
3e26c149 PZ |
265 | static inline void task_dirties_fraction(struct task_struct *tsk, |
266 | long *numerator, long *denominator) | |
267 | { | |
268 | prop_fraction_single(&vm_dirties, &tsk->dirties, | |
269 | numerator, denominator); | |
270 | } | |
271 | ||
272 | /* | |
1babe183 | 273 | * task_dirty_limit - scale down dirty throttling threshold for one task |
3e26c149 PZ |
274 | * |
275 | * task specific dirty limit: | |
276 | * | |
277 | * dirty -= (dirty/8) * p_{t} | |
1babe183 WF |
278 | * |
279 | * To protect light/slow dirtying tasks from heavier/fast ones, we start | |
280 | * throttling individual tasks before reaching the bdi dirty limit. | |
281 | * Relatively low thresholds will be allocated to heavy dirtiers. So when | |
282 | * dirty pages grow large, heavy dirtiers will be throttled first, which will | |
283 | * effectively curb the growth of dirty pages. Light dirtiers with high enough | |
284 | * dirty threshold may never get throttled. | |
3e26c149 | 285 | */ |
bcff25fc | 286 | #define TASK_LIMIT_FRACTION 8 |
16c4042f WF |
287 | static unsigned long task_dirty_limit(struct task_struct *tsk, |
288 | unsigned long bdi_dirty) | |
3e26c149 PZ |
289 | { |
290 | long numerator, denominator; | |
16c4042f | 291 | unsigned long dirty = bdi_dirty; |
bcff25fc | 292 | u64 inv = dirty / TASK_LIMIT_FRACTION; |
3e26c149 PZ |
293 | |
294 | task_dirties_fraction(tsk, &numerator, &denominator); | |
295 | inv *= numerator; | |
296 | do_div(inv, denominator); | |
297 | ||
298 | dirty -= inv; | |
3e26c149 | 299 | |
16c4042f | 300 | return max(dirty, bdi_dirty/2); |
3e26c149 PZ |
301 | } |
302 | ||
bcff25fc JK |
303 | /* Minimum limit for any task */ |
304 | static unsigned long task_min_dirty_limit(unsigned long bdi_dirty) | |
305 | { | |
306 | return bdi_dirty - bdi_dirty / TASK_LIMIT_FRACTION; | |
307 | } | |
308 | ||
189d3c4a PZ |
309 | /* |
310 | * | |
311 | */ | |
189d3c4a PZ |
312 | static unsigned int bdi_min_ratio; |
313 | ||
314 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
315 | { | |
316 | int ret = 0; | |
189d3c4a | 317 | |
cfc4ba53 | 318 | spin_lock_bh(&bdi_lock); |
a42dde04 | 319 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 320 | ret = -EINVAL; |
a42dde04 PZ |
321 | } else { |
322 | min_ratio -= bdi->min_ratio; | |
323 | if (bdi_min_ratio + min_ratio < 100) { | |
324 | bdi_min_ratio += min_ratio; | |
325 | bdi->min_ratio += min_ratio; | |
326 | } else { | |
327 | ret = -EINVAL; | |
328 | } | |
329 | } | |
cfc4ba53 | 330 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
331 | |
332 | return ret; | |
333 | } | |
334 | ||
335 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
336 | { | |
a42dde04 PZ |
337 | int ret = 0; |
338 | ||
339 | if (max_ratio > 100) | |
340 | return -EINVAL; | |
341 | ||
cfc4ba53 | 342 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
343 | if (bdi->min_ratio > max_ratio) { |
344 | ret = -EINVAL; | |
345 | } else { | |
346 | bdi->max_ratio = max_ratio; | |
347 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
348 | } | |
cfc4ba53 | 349 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
350 | |
351 | return ret; | |
352 | } | |
a42dde04 | 353 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 354 | |
1da177e4 LT |
355 | /* |
356 | * Work out the current dirty-memory clamping and background writeout | |
357 | * thresholds. | |
358 | * | |
359 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
360 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
361 | * pages. It is better to clamp down on writers than to start swapping, and | |
362 | * performing lots of scanning. | |
363 | * | |
364 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
365 | * | |
366 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
367 | * excessive. | |
368 | * | |
369 | * We make sure that the background writeout level is below the adjusted | |
370 | * clamping level. | |
371 | */ | |
1b424464 CL |
372 | |
373 | static unsigned long highmem_dirtyable_memory(unsigned long total) | |
374 | { | |
375 | #ifdef CONFIG_HIGHMEM | |
376 | int node; | |
377 | unsigned long x = 0; | |
378 | ||
37b07e41 | 379 | for_each_node_state(node, N_HIGH_MEMORY) { |
1b424464 CL |
380 | struct zone *z = |
381 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
382 | ||
adea02a1 WF |
383 | x += zone_page_state(z, NR_FREE_PAGES) + |
384 | zone_reclaimable_pages(z); | |
1b424464 CL |
385 | } |
386 | /* | |
387 | * Make sure that the number of highmem pages is never larger | |
388 | * than the number of the total dirtyable memory. This can only | |
389 | * occur in very strange VM situations but we want to make sure | |
390 | * that this does not occur. | |
391 | */ | |
392 | return min(x, total); | |
393 | #else | |
394 | return 0; | |
395 | #endif | |
396 | } | |
397 | ||
3eefae99 SR |
398 | /** |
399 | * determine_dirtyable_memory - amount of memory that may be used | |
400 | * | |
401 | * Returns the numebr of pages that can currently be freed and used | |
402 | * by the kernel for direct mappings. | |
403 | */ | |
404 | unsigned long determine_dirtyable_memory(void) | |
1b424464 CL |
405 | { |
406 | unsigned long x; | |
407 | ||
adea02a1 | 408 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
195cf453 BG |
409 | |
410 | if (!vm_highmem_is_dirtyable) | |
411 | x -= highmem_dirtyable_memory(x); | |
412 | ||
1b424464 CL |
413 | return x + 1; /* Ensure that we never return 0 */ |
414 | } | |
415 | ||
6c14ae1e WF |
416 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
417 | unsigned long bg_thresh) | |
418 | { | |
419 | return (thresh + bg_thresh) / 2; | |
420 | } | |
421 | ||
ffd1f609 WF |
422 | static unsigned long hard_dirty_limit(unsigned long thresh) |
423 | { | |
424 | return max(thresh, global_dirty_limit); | |
425 | } | |
426 | ||
03ab450f | 427 | /* |
1babe183 WF |
428 | * global_dirty_limits - background-writeback and dirty-throttling thresholds |
429 | * | |
430 | * Calculate the dirty thresholds based on sysctl parameters | |
431 | * - vm.dirty_background_ratio or vm.dirty_background_bytes | |
432 | * - vm.dirty_ratio or vm.dirty_bytes | |
433 | * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ebd1373d | 434 | * real-time tasks. |
1babe183 | 435 | */ |
16c4042f | 436 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
1da177e4 | 437 | { |
364aeb28 DR |
438 | unsigned long background; |
439 | unsigned long dirty; | |
240c879f | 440 | unsigned long uninitialized_var(available_memory); |
1da177e4 LT |
441 | struct task_struct *tsk; |
442 | ||
240c879f MK |
443 | if (!vm_dirty_bytes || !dirty_background_bytes) |
444 | available_memory = determine_dirtyable_memory(); | |
445 | ||
2da02997 DR |
446 | if (vm_dirty_bytes) |
447 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
4cbec4c8 WF |
448 | else |
449 | dirty = (vm_dirty_ratio * available_memory) / 100; | |
1da177e4 | 450 | |
2da02997 DR |
451 | if (dirty_background_bytes) |
452 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
453 | else | |
454 | background = (dirty_background_ratio * available_memory) / 100; | |
1da177e4 | 455 | |
2da02997 DR |
456 | if (background >= dirty) |
457 | background = dirty / 2; | |
1da177e4 LT |
458 | tsk = current; |
459 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
460 | background += background / 4; | |
461 | dirty += dirty / 4; | |
462 | } | |
463 | *pbackground = background; | |
464 | *pdirty = dirty; | |
e1cbe236 | 465 | trace_global_dirty_state(background, dirty); |
16c4042f | 466 | } |
04fbfdc1 | 467 | |
6f718656 | 468 | /** |
1babe183 | 469 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
6f718656 WF |
470 | * @bdi: the backing_dev_info to query |
471 | * @dirty: global dirty limit in pages | |
1babe183 | 472 | * |
6f718656 WF |
473 | * Returns @bdi's dirty limit in pages. The term "dirty" in the context of |
474 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. | |
475 | * And the "limit" in the name is not seriously taken as hard limit in | |
476 | * balance_dirty_pages(). | |
1babe183 | 477 | * |
6f718656 | 478 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
479 | * - starving fast devices |
480 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
481 | * | |
482 | * The bdi's share of dirty limit will be adapting to its throughput and | |
483 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. | |
484 | */ | |
485 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) | |
16c4042f WF |
486 | { |
487 | u64 bdi_dirty; | |
488 | long numerator, denominator; | |
04fbfdc1 | 489 | |
16c4042f WF |
490 | /* |
491 | * Calculate this BDI's share of the dirty ratio. | |
492 | */ | |
493 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
04fbfdc1 | 494 | |
16c4042f WF |
495 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
496 | bdi_dirty *= numerator; | |
497 | do_div(bdi_dirty, denominator); | |
04fbfdc1 | 498 | |
16c4042f WF |
499 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
500 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) | |
501 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
502 | ||
503 | return bdi_dirty; | |
1da177e4 LT |
504 | } |
505 | ||
6c14ae1e WF |
506 | /* |
507 | * Dirty position control. | |
508 | * | |
509 | * (o) global/bdi setpoints | |
510 | * | |
511 | * We want the dirty pages be balanced around the global/bdi setpoints. | |
512 | * When the number of dirty pages is higher/lower than the setpoint, the | |
513 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
514 | * decreased/increased to bring the dirty pages back to the setpoint. | |
515 | * | |
516 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
517 | * | |
518 | * if (dirty < setpoint) scale up pos_ratio | |
519 | * if (dirty > setpoint) scale down pos_ratio | |
520 | * | |
521 | * if (bdi_dirty < bdi_setpoint) scale up pos_ratio | |
522 | * if (bdi_dirty > bdi_setpoint) scale down pos_ratio | |
523 | * | |
524 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
525 | * | |
526 | * (o) global control line | |
527 | * | |
528 | * ^ pos_ratio | |
529 | * | | |
530 | * | |<===== global dirty control scope ======>| | |
531 | * 2.0 .............* | |
532 | * | .* | |
533 | * | . * | |
534 | * | . * | |
535 | * | . * | |
536 | * | . * | |
537 | * | . * | |
538 | * 1.0 ................................* | |
539 | * | . . * | |
540 | * | . . * | |
541 | * | . . * | |
542 | * | . . * | |
543 | * | . . * | |
544 | * 0 +------------.------------------.----------------------*-------------> | |
545 | * freerun^ setpoint^ limit^ dirty pages | |
546 | * | |
547 | * (o) bdi control line | |
548 | * | |
549 | * ^ pos_ratio | |
550 | * | | |
551 | * | * | |
552 | * | * | |
553 | * | * | |
554 | * | * | |
555 | * | * |<=========== span ============>| | |
556 | * 1.0 .......................* | |
557 | * | . * | |
558 | * | . * | |
559 | * | . * | |
560 | * | . * | |
561 | * | . * | |
562 | * | . * | |
563 | * | . * | |
564 | * | . * | |
565 | * | . * | |
566 | * | . * | |
567 | * | . * | |
568 | * 1/4 ...............................................* * * * * * * * * * * * | |
569 | * | . . | |
570 | * | . . | |
571 | * | . . | |
572 | * 0 +----------------------.-------------------------------.-------------> | |
573 | * bdi_setpoint^ x_intercept^ | |
574 | * | |
575 | * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can | |
576 | * be smoothly throttled down to normal if it starts high in situations like | |
577 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
578 | * card's bdi_dirty may rush to many times higher than bdi_setpoint. | |
579 | * - the bdi dirty thresh drops quickly due to change of JBOD workload | |
580 | */ | |
581 | static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, | |
582 | unsigned long thresh, | |
583 | unsigned long bg_thresh, | |
584 | unsigned long dirty, | |
585 | unsigned long bdi_thresh, | |
586 | unsigned long bdi_dirty) | |
587 | { | |
588 | unsigned long write_bw = bdi->avg_write_bandwidth; | |
589 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); | |
590 | unsigned long limit = hard_dirty_limit(thresh); | |
591 | unsigned long x_intercept; | |
592 | unsigned long setpoint; /* dirty pages' target balance point */ | |
593 | unsigned long bdi_setpoint; | |
594 | unsigned long span; | |
595 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
596 | long x; | |
597 | ||
598 | if (unlikely(dirty >= limit)) | |
599 | return 0; | |
600 | ||
601 | /* | |
602 | * global setpoint | |
603 | * | |
604 | * setpoint - dirty 3 | |
605 | * f(dirty) := 1.0 + (----------------) | |
606 | * limit - setpoint | |
607 | * | |
608 | * it's a 3rd order polynomial that subjects to | |
609 | * | |
610 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
611 | * (2) f(setpoint) = 1.0 => the balance point | |
612 | * (3) f(limit) = 0 => the hard limit | |
613 | * (4) df/dx <= 0 => negative feedback control | |
614 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
615 | * => fast response on large errors; small oscillation near setpoint | |
616 | */ | |
617 | setpoint = (freerun + limit) / 2; | |
618 | x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, | |
619 | limit - setpoint + 1); | |
620 | pos_ratio = x; | |
621 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
622 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
623 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
624 | ||
625 | /* | |
626 | * We have computed basic pos_ratio above based on global situation. If | |
627 | * the bdi is over/under its share of dirty pages, we want to scale | |
628 | * pos_ratio further down/up. That is done by the following mechanism. | |
629 | */ | |
630 | ||
631 | /* | |
632 | * bdi setpoint | |
633 | * | |
634 | * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint) | |
635 | * | |
636 | * x_intercept - bdi_dirty | |
637 | * := -------------------------- | |
638 | * x_intercept - bdi_setpoint | |
639 | * | |
640 | * The main bdi control line is a linear function that subjects to | |
641 | * | |
642 | * (1) f(bdi_setpoint) = 1.0 | |
643 | * (2) k = - 1 / (8 * write_bw) (in single bdi case) | |
644 | * or equally: x_intercept = bdi_setpoint + 8 * write_bw | |
645 | * | |
646 | * For single bdi case, the dirty pages are observed to fluctuate | |
647 | * regularly within range | |
648 | * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2] | |
649 | * for various filesystems, where (2) can yield in a reasonable 12.5% | |
650 | * fluctuation range for pos_ratio. | |
651 | * | |
652 | * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its | |
653 | * own size, so move the slope over accordingly and choose a slope that | |
654 | * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh. | |
655 | */ | |
656 | if (unlikely(bdi_thresh > thresh)) | |
657 | bdi_thresh = thresh; | |
658 | /* | |
659 | * scale global setpoint to bdi's: | |
660 | * bdi_setpoint = setpoint * bdi_thresh / thresh | |
661 | */ | |
662 | x = div_u64((u64)bdi_thresh << 16, thresh + 1); | |
663 | bdi_setpoint = setpoint * (u64)x >> 16; | |
664 | /* | |
665 | * Use span=(8*write_bw) in single bdi case as indicated by | |
666 | * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case. | |
667 | * | |
668 | * bdi_thresh thresh - bdi_thresh | |
669 | * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh | |
670 | * thresh thresh | |
671 | */ | |
672 | span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16; | |
673 | x_intercept = bdi_setpoint + span; | |
674 | ||
675 | if (bdi_dirty < x_intercept - span / 4) { | |
676 | pos_ratio *= x_intercept - bdi_dirty; | |
677 | do_div(pos_ratio, x_intercept - bdi_setpoint + 1); | |
678 | } else | |
679 | pos_ratio /= 4; | |
680 | ||
681 | return pos_ratio; | |
682 | } | |
683 | ||
e98be2d5 WF |
684 | static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, |
685 | unsigned long elapsed, | |
686 | unsigned long written) | |
687 | { | |
688 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
689 | unsigned long avg = bdi->avg_write_bandwidth; | |
690 | unsigned long old = bdi->write_bandwidth; | |
691 | u64 bw; | |
692 | ||
693 | /* | |
694 | * bw = written * HZ / elapsed | |
695 | * | |
696 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
697 | * write_bandwidth = --------------------------------------------------- | |
698 | * period | |
699 | */ | |
700 | bw = written - bdi->written_stamp; | |
701 | bw *= HZ; | |
702 | if (unlikely(elapsed > period)) { | |
703 | do_div(bw, elapsed); | |
704 | avg = bw; | |
705 | goto out; | |
706 | } | |
707 | bw += (u64)bdi->write_bandwidth * (period - elapsed); | |
708 | bw >>= ilog2(period); | |
709 | ||
710 | /* | |
711 | * one more level of smoothing, for filtering out sudden spikes | |
712 | */ | |
713 | if (avg > old && old >= (unsigned long)bw) | |
714 | avg -= (avg - old) >> 3; | |
715 | ||
716 | if (avg < old && old <= (unsigned long)bw) | |
717 | avg += (old - avg) >> 3; | |
718 | ||
719 | out: | |
720 | bdi->write_bandwidth = bw; | |
721 | bdi->avg_write_bandwidth = avg; | |
722 | } | |
723 | ||
c42843f2 WF |
724 | /* |
725 | * The global dirtyable memory and dirty threshold could be suddenly knocked | |
726 | * down by a large amount (eg. on the startup of KVM in a swapless system). | |
727 | * This may throw the system into deep dirty exceeded state and throttle | |
728 | * heavy/light dirtiers alike. To retain good responsiveness, maintain | |
729 | * global_dirty_limit for tracking slowly down to the knocked down dirty | |
730 | * threshold. | |
731 | */ | |
732 | static void update_dirty_limit(unsigned long thresh, unsigned long dirty) | |
733 | { | |
734 | unsigned long limit = global_dirty_limit; | |
735 | ||
736 | /* | |
737 | * Follow up in one step. | |
738 | */ | |
739 | if (limit < thresh) { | |
740 | limit = thresh; | |
741 | goto update; | |
742 | } | |
743 | ||
744 | /* | |
745 | * Follow down slowly. Use the higher one as the target, because thresh | |
746 | * may drop below dirty. This is exactly the reason to introduce | |
747 | * global_dirty_limit which is guaranteed to lie above the dirty pages. | |
748 | */ | |
749 | thresh = max(thresh, dirty); | |
750 | if (limit > thresh) { | |
751 | limit -= (limit - thresh) >> 5; | |
752 | goto update; | |
753 | } | |
754 | return; | |
755 | update: | |
756 | global_dirty_limit = limit; | |
757 | } | |
758 | ||
759 | static void global_update_bandwidth(unsigned long thresh, | |
760 | unsigned long dirty, | |
761 | unsigned long now) | |
762 | { | |
763 | static DEFINE_SPINLOCK(dirty_lock); | |
764 | static unsigned long update_time; | |
765 | ||
766 | /* | |
767 | * check locklessly first to optimize away locking for the most time | |
768 | */ | |
769 | if (time_before(now, update_time + BANDWIDTH_INTERVAL)) | |
770 | return; | |
771 | ||
772 | spin_lock(&dirty_lock); | |
773 | if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) { | |
774 | update_dirty_limit(thresh, dirty); | |
775 | update_time = now; | |
776 | } | |
777 | spin_unlock(&dirty_lock); | |
778 | } | |
779 | ||
be3ffa27 WF |
780 | /* |
781 | * Maintain bdi->dirty_ratelimit, the base dirty throttle rate. | |
782 | * | |
783 | * Normal bdi tasks will be curbed at or below it in long term. | |
784 | * Obviously it should be around (write_bw / N) when there are N dd tasks. | |
785 | */ | |
786 | static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, | |
787 | unsigned long thresh, | |
788 | unsigned long bg_thresh, | |
789 | unsigned long dirty, | |
790 | unsigned long bdi_thresh, | |
791 | unsigned long bdi_dirty, | |
792 | unsigned long dirtied, | |
793 | unsigned long elapsed) | |
794 | { | |
795 | unsigned long write_bw = bdi->avg_write_bandwidth; | |
796 | unsigned long dirty_ratelimit = bdi->dirty_ratelimit; | |
797 | unsigned long dirty_rate; | |
798 | unsigned long task_ratelimit; | |
799 | unsigned long balanced_dirty_ratelimit; | |
800 | unsigned long pos_ratio; | |
801 | ||
802 | /* | |
803 | * The dirty rate will match the writeout rate in long term, except | |
804 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
805 | */ | |
806 | dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; | |
807 | ||
808 | pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, | |
809 | bdi_thresh, bdi_dirty); | |
810 | /* | |
811 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
812 | */ | |
813 | task_ratelimit = (u64)dirty_ratelimit * | |
814 | pos_ratio >> RATELIMIT_CALC_SHIFT; | |
815 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ | |
816 | ||
817 | /* | |
818 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
819 | * if there are N dd tasks, each throttled at task_ratelimit, the bdi's | |
820 | * dirty_rate will be measured to be (N * task_ratelimit). So the below | |
821 | * formula will yield the balanced rate limit (write_bw / N). | |
822 | * | |
823 | * Note that the expanded form is not a pure rate feedback: | |
824 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
825 | * but also takes pos_ratio into account: | |
826 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
827 | * | |
828 | * (1) is not realistic because pos_ratio also takes part in balancing | |
829 | * the dirty rate. Consider the state | |
830 | * pos_ratio = 0.5 (3) | |
831 | * rate = 2 * (write_bw / N) (4) | |
832 | * If (1) is used, it will stuck in that state! Because each dd will | |
833 | * be throttled at | |
834 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
835 | * yielding | |
836 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
837 | * put (6) into (1) we get | |
838 | * rate_(i+1) = rate_(i) (7) | |
839 | * | |
840 | * So we end up using (2) to always keep | |
841 | * rate_(i+1) ~= (write_bw / N) (8) | |
842 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
843 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
844 | * the dirty count meet the setpoint, but also where the slope of | |
845 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
846 | */ | |
847 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
848 | dirty_rate | 1); | |
849 | ||
850 | bdi->dirty_ratelimit = max(balanced_dirty_ratelimit, 1UL); | |
851 | } | |
852 | ||
e98be2d5 | 853 | void __bdi_update_bandwidth(struct backing_dev_info *bdi, |
c42843f2 | 854 | unsigned long thresh, |
af6a3113 | 855 | unsigned long bg_thresh, |
c42843f2 WF |
856 | unsigned long dirty, |
857 | unsigned long bdi_thresh, | |
858 | unsigned long bdi_dirty, | |
e98be2d5 WF |
859 | unsigned long start_time) |
860 | { | |
861 | unsigned long now = jiffies; | |
862 | unsigned long elapsed = now - bdi->bw_time_stamp; | |
be3ffa27 | 863 | unsigned long dirtied; |
e98be2d5 WF |
864 | unsigned long written; |
865 | ||
866 | /* | |
867 | * rate-limit, only update once every 200ms. | |
868 | */ | |
869 | if (elapsed < BANDWIDTH_INTERVAL) | |
870 | return; | |
871 | ||
be3ffa27 | 872 | dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); |
e98be2d5 WF |
873 | written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); |
874 | ||
875 | /* | |
876 | * Skip quiet periods when disk bandwidth is under-utilized. | |
877 | * (at least 1s idle time between two flusher runs) | |
878 | */ | |
879 | if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) | |
880 | goto snapshot; | |
881 | ||
be3ffa27 | 882 | if (thresh) { |
c42843f2 | 883 | global_update_bandwidth(thresh, dirty, now); |
be3ffa27 WF |
884 | bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, |
885 | bdi_thresh, bdi_dirty, | |
886 | dirtied, elapsed); | |
887 | } | |
e98be2d5 WF |
888 | bdi_update_write_bandwidth(bdi, elapsed, written); |
889 | ||
890 | snapshot: | |
be3ffa27 | 891 | bdi->dirtied_stamp = dirtied; |
e98be2d5 WF |
892 | bdi->written_stamp = written; |
893 | bdi->bw_time_stamp = now; | |
894 | } | |
895 | ||
896 | static void bdi_update_bandwidth(struct backing_dev_info *bdi, | |
c42843f2 | 897 | unsigned long thresh, |
af6a3113 | 898 | unsigned long bg_thresh, |
c42843f2 WF |
899 | unsigned long dirty, |
900 | unsigned long bdi_thresh, | |
901 | unsigned long bdi_dirty, | |
e98be2d5 WF |
902 | unsigned long start_time) |
903 | { | |
904 | if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) | |
905 | return; | |
906 | spin_lock(&bdi->wb.list_lock); | |
af6a3113 WF |
907 | __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, |
908 | bdi_thresh, bdi_dirty, start_time); | |
e98be2d5 WF |
909 | spin_unlock(&bdi->wb.list_lock); |
910 | } | |
911 | ||
1da177e4 LT |
912 | /* |
913 | * balance_dirty_pages() must be called by processes which are generating dirty | |
914 | * data. It looks at the number of dirty pages in the machine and will force | |
915 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
5b0830cb JA |
916 | * If we're over `background_thresh' then the writeback threads are woken to |
917 | * perform some writeout. | |
1da177e4 | 918 | */ |
3a2e9a5a WF |
919 | static void balance_dirty_pages(struct address_space *mapping, |
920 | unsigned long write_chunk) | |
1da177e4 | 921 | { |
7762741e WF |
922 | unsigned long nr_reclaimable, bdi_nr_reclaimable; |
923 | unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ | |
924 | unsigned long bdi_dirty; | |
6c14ae1e | 925 | unsigned long freerun; |
364aeb28 DR |
926 | unsigned long background_thresh; |
927 | unsigned long dirty_thresh; | |
928 | unsigned long bdi_thresh; | |
bcff25fc JK |
929 | unsigned long task_bdi_thresh; |
930 | unsigned long min_task_bdi_thresh; | |
1da177e4 | 931 | unsigned long pages_written = 0; |
87c6a9b2 | 932 | unsigned long pause = 1; |
e50e3720 | 933 | bool dirty_exceeded = false; |
bcff25fc | 934 | bool clear_dirty_exceeded = true; |
1da177e4 | 935 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
e98be2d5 | 936 | unsigned long start_time = jiffies; |
1da177e4 LT |
937 | |
938 | for (;;) { | |
5fce25a9 PZ |
939 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
940 | global_page_state(NR_UNSTABLE_NFS); | |
7762741e | 941 | nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
5fce25a9 | 942 | |
16c4042f WF |
943 | global_dirty_limits(&background_thresh, &dirty_thresh); |
944 | ||
945 | /* | |
946 | * Throttle it only when the background writeback cannot | |
947 | * catch-up. This avoids (excessively) small writeouts | |
948 | * when the bdi limits are ramping up. | |
949 | */ | |
6c14ae1e WF |
950 | freerun = dirty_freerun_ceiling(dirty_thresh, |
951 | background_thresh); | |
952 | if (nr_dirty <= freerun) | |
16c4042f WF |
953 | break; |
954 | ||
955 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); | |
bcff25fc JK |
956 | min_task_bdi_thresh = task_min_dirty_limit(bdi_thresh); |
957 | task_bdi_thresh = task_dirty_limit(current, bdi_thresh); | |
16c4042f | 958 | |
e50e3720 WF |
959 | /* |
960 | * In order to avoid the stacked BDI deadlock we need | |
961 | * to ensure we accurately count the 'dirty' pages when | |
962 | * the threshold is low. | |
963 | * | |
964 | * Otherwise it would be possible to get thresh+n pages | |
965 | * reported dirty, even though there are thresh-m pages | |
966 | * actually dirty; with m+n sitting in the percpu | |
967 | * deltas. | |
968 | */ | |
bcff25fc | 969 | if (task_bdi_thresh < 2 * bdi_stat_error(bdi)) { |
e50e3720 | 970 | bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); |
7762741e WF |
971 | bdi_dirty = bdi_nr_reclaimable + |
972 | bdi_stat_sum(bdi, BDI_WRITEBACK); | |
e50e3720 WF |
973 | } else { |
974 | bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); | |
7762741e WF |
975 | bdi_dirty = bdi_nr_reclaimable + |
976 | bdi_stat(bdi, BDI_WRITEBACK); | |
e50e3720 | 977 | } |
5fce25a9 | 978 | |
e50e3720 WF |
979 | /* |
980 | * The bdi thresh is somehow "soft" limit derived from the | |
981 | * global "hard" limit. The former helps to prevent heavy IO | |
982 | * bdi or process from holding back light ones; The latter is | |
983 | * the last resort safeguard. | |
984 | */ | |
bcff25fc | 985 | dirty_exceeded = (bdi_dirty > task_bdi_thresh) || |
7762741e | 986 | (nr_dirty > dirty_thresh); |
bcff25fc JK |
987 | clear_dirty_exceeded = (bdi_dirty <= min_task_bdi_thresh) && |
988 | (nr_dirty <= dirty_thresh); | |
e50e3720 WF |
989 | |
990 | if (!dirty_exceeded) | |
04fbfdc1 | 991 | break; |
1da177e4 | 992 | |
04fbfdc1 PZ |
993 | if (!bdi->dirty_exceeded) |
994 | bdi->dirty_exceeded = 1; | |
1da177e4 | 995 | |
af6a3113 WF |
996 | bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, |
997 | nr_dirty, bdi_thresh, bdi_dirty, | |
998 | start_time); | |
e98be2d5 | 999 | |
1da177e4 LT |
1000 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. |
1001 | * Unstable writes are a feature of certain networked | |
1002 | * filesystems (i.e. NFS) in which data may have been | |
1003 | * written to the server's write cache, but has not yet | |
1004 | * been flushed to permanent storage. | |
d7831a0b RK |
1005 | * Only move pages to writeback if this bdi is over its |
1006 | * threshold otherwise wait until the disk writes catch | |
1007 | * up. | |
1da177e4 | 1008 | */ |
d46db3d5 | 1009 | trace_balance_dirty_start(bdi); |
bcff25fc | 1010 | if (bdi_nr_reclaimable > task_bdi_thresh) { |
d46db3d5 WF |
1011 | pages_written += writeback_inodes_wb(&bdi->wb, |
1012 | write_chunk); | |
1013 | trace_balance_dirty_written(bdi, pages_written); | |
e50e3720 WF |
1014 | if (pages_written >= write_chunk) |
1015 | break; /* We've done our duty */ | |
04fbfdc1 | 1016 | } |
d153ba64 | 1017 | __set_current_state(TASK_UNINTERRUPTIBLE); |
d25105e8 | 1018 | io_schedule_timeout(pause); |
d46db3d5 | 1019 | trace_balance_dirty_wait(bdi); |
87c6a9b2 | 1020 | |
ffd1f609 WF |
1021 | dirty_thresh = hard_dirty_limit(dirty_thresh); |
1022 | /* | |
1023 | * max-pause area. If dirty exceeded but still within this | |
1024 | * area, no need to sleep for more than 200ms: (a) 8 pages per | |
1025 | * 200ms is typically more than enough to curb heavy dirtiers; | |
1026 | * (b) the pause time limit makes the dirtiers more responsive. | |
1027 | */ | |
bb082295 WF |
1028 | if (nr_dirty < dirty_thresh && |
1029 | bdi_dirty < (task_bdi_thresh + bdi_thresh) / 2 && | |
ffd1f609 WF |
1030 | time_after(jiffies, start_time + MAX_PAUSE)) |
1031 | break; | |
87c6a9b2 JA |
1032 | |
1033 | /* | |
1034 | * Increase the delay for each loop, up to our previous | |
1035 | * default of taking a 100ms nap. | |
1036 | */ | |
1037 | pause <<= 1; | |
1038 | if (pause > HZ / 10) | |
1039 | pause = HZ / 10; | |
1da177e4 LT |
1040 | } |
1041 | ||
bcff25fc JK |
1042 | /* Clear dirty_exceeded flag only when no task can exceed the limit */ |
1043 | if (clear_dirty_exceeded && bdi->dirty_exceeded) | |
04fbfdc1 | 1044 | bdi->dirty_exceeded = 0; |
1da177e4 LT |
1045 | |
1046 | if (writeback_in_progress(bdi)) | |
5b0830cb | 1047 | return; |
1da177e4 LT |
1048 | |
1049 | /* | |
1050 | * In laptop mode, we wait until hitting the higher threshold before | |
1051 | * starting background writeout, and then write out all the way down | |
1052 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1053 | * | |
1054 | * In normal mode, we start background writeout at the lower | |
1055 | * background_thresh, to keep the amount of dirty memory low. | |
1056 | */ | |
1057 | if ((laptop_mode && pages_written) || | |
e50e3720 | 1058 | (!laptop_mode && (nr_reclaimable > background_thresh))) |
c5444198 | 1059 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
1060 | } |
1061 | ||
a200ee18 | 1062 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 1063 | { |
a200ee18 | 1064 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
1065 | struct address_space *mapping = page_mapping(page); |
1066 | ||
1067 | if (mapping) | |
1068 | balance_dirty_pages_ratelimited(mapping); | |
1069 | } | |
1070 | } | |
1071 | ||
245b2e70 TH |
1072 | static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0; |
1073 | ||
1da177e4 | 1074 | /** |
fa5a734e | 1075 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 1076 | * @mapping: address_space which was dirtied |
a580290c | 1077 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
1078 | * |
1079 | * Processes which are dirtying memory should call in here once for each page | |
1080 | * which was newly dirtied. The function will periodically check the system's | |
1081 | * dirty state and will initiate writeback if needed. | |
1082 | * | |
1083 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
1084 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
1085 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
1086 | * from overshooting the limit by (ratelimit_pages) each. | |
1087 | */ | |
fa5a734e AM |
1088 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
1089 | unsigned long nr_pages_dirtied) | |
1da177e4 | 1090 | { |
36715cef | 1091 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
fa5a734e AM |
1092 | unsigned long ratelimit; |
1093 | unsigned long *p; | |
1da177e4 | 1094 | |
36715cef WF |
1095 | if (!bdi_cap_account_dirty(bdi)) |
1096 | return; | |
1097 | ||
1da177e4 | 1098 | ratelimit = ratelimit_pages; |
04fbfdc1 | 1099 | if (mapping->backing_dev_info->dirty_exceeded) |
1da177e4 LT |
1100 | ratelimit = 8; |
1101 | ||
1102 | /* | |
1103 | * Check the rate limiting. Also, we do not want to throttle real-time | |
1104 | * tasks in balance_dirty_pages(). Period. | |
1105 | */ | |
fa5a734e | 1106 | preempt_disable(); |
245b2e70 | 1107 | p = &__get_cpu_var(bdp_ratelimits); |
fa5a734e AM |
1108 | *p += nr_pages_dirtied; |
1109 | if (unlikely(*p >= ratelimit)) { | |
3a2e9a5a | 1110 | ratelimit = sync_writeback_pages(*p); |
fa5a734e AM |
1111 | *p = 0; |
1112 | preempt_enable(); | |
3a2e9a5a | 1113 | balance_dirty_pages(mapping, ratelimit); |
1da177e4 LT |
1114 | return; |
1115 | } | |
fa5a734e | 1116 | preempt_enable(); |
1da177e4 | 1117 | } |
fa5a734e | 1118 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 1119 | |
232ea4d6 | 1120 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 1121 | { |
364aeb28 DR |
1122 | unsigned long background_thresh; |
1123 | unsigned long dirty_thresh; | |
1da177e4 LT |
1124 | |
1125 | for ( ; ; ) { | |
16c4042f | 1126 | global_dirty_limits(&background_thresh, &dirty_thresh); |
1da177e4 LT |
1127 | |
1128 | /* | |
1129 | * Boost the allowable dirty threshold a bit for page | |
1130 | * allocators so they don't get DoS'ed by heavy writers | |
1131 | */ | |
1132 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
1133 | ||
c24f21bd CL |
1134 | if (global_page_state(NR_UNSTABLE_NFS) + |
1135 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
1136 | break; | |
8aa7e847 | 1137 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
1138 | |
1139 | /* | |
1140 | * The caller might hold locks which can prevent IO completion | |
1141 | * or progress in the filesystem. So we cannot just sit here | |
1142 | * waiting for IO to complete. | |
1143 | */ | |
1144 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
1145 | break; | |
1da177e4 LT |
1146 | } |
1147 | } | |
1148 | ||
1da177e4 LT |
1149 | /* |
1150 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1151 | */ | |
1152 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 1153 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1154 | { |
8d65af78 | 1155 | proc_dointvec(table, write, buffer, length, ppos); |
6423104b | 1156 | bdi_arm_supers_timer(); |
1da177e4 LT |
1157 | return 0; |
1158 | } | |
1159 | ||
c2c4986e | 1160 | #ifdef CONFIG_BLOCK |
31373d09 | 1161 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 1162 | { |
31373d09 MG |
1163 | struct request_queue *q = (struct request_queue *)data; |
1164 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
1165 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 | 1166 | |
31373d09 MG |
1167 | /* |
1168 | * We want to write everything out, not just down to the dirty | |
1169 | * threshold | |
1170 | */ | |
31373d09 | 1171 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
c5444198 | 1172 | bdi_start_writeback(&q->backing_dev_info, nr_pages); |
1da177e4 LT |
1173 | } |
1174 | ||
1175 | /* | |
1176 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
1177 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
1178 | * then push it back - the user is still using the disk. | |
1179 | */ | |
31373d09 | 1180 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 1181 | { |
31373d09 | 1182 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
1183 | } |
1184 | ||
1185 | /* | |
1186 | * We're in laptop mode and we've just synced. The sync's writes will have | |
1187 | * caused another writeback to be scheduled by laptop_io_completion. | |
1188 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
1189 | */ | |
1190 | void laptop_sync_completion(void) | |
1191 | { | |
31373d09 MG |
1192 | struct backing_dev_info *bdi; |
1193 | ||
1194 | rcu_read_lock(); | |
1195 | ||
1196 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
1197 | del_timer(&bdi->laptop_mode_wb_timer); | |
1198 | ||
1199 | rcu_read_unlock(); | |
1da177e4 | 1200 | } |
c2c4986e | 1201 | #endif |
1da177e4 LT |
1202 | |
1203 | /* | |
1204 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
1205 | * if a large number of processes all perform writes at the same time. | |
1206 | * If it is too low then SMP machines will call the (expensive) | |
1207 | * get_writeback_state too often. | |
1208 | * | |
1209 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
1210 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
1211 | * thresholds before writeback cuts in. | |
1212 | * | |
1213 | * But the limit should not be set too high. Because it also controls the | |
1214 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
1215 | * If this is too large then the caller will block on the IO queue all the | |
1216 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
1217 | * will write six megabyte chunks, max. | |
1218 | */ | |
1219 | ||
2d1d43f6 | 1220 | void writeback_set_ratelimit(void) |
1da177e4 | 1221 | { |
40c99aae | 1222 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
1223 | if (ratelimit_pages < 16) |
1224 | ratelimit_pages = 16; | |
1225 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
1226 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
1227 | } | |
1228 | ||
26c2143b | 1229 | static int __cpuinit |
1da177e4 LT |
1230 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
1231 | { | |
2d1d43f6 | 1232 | writeback_set_ratelimit(); |
aa0f0303 | 1233 | return NOTIFY_DONE; |
1da177e4 LT |
1234 | } |
1235 | ||
74b85f37 | 1236 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
1237 | .notifier_call = ratelimit_handler, |
1238 | .next = NULL, | |
1239 | }; | |
1240 | ||
1241 | /* | |
dc6e29da LT |
1242 | * Called early on to tune the page writeback dirty limits. |
1243 | * | |
1244 | * We used to scale dirty pages according to how total memory | |
1245 | * related to pages that could be allocated for buffers (by | |
1246 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
1247 | * | |
1248 | * However, that was when we used "dirty_ratio" to scale with | |
1249 | * all memory, and we don't do that any more. "dirty_ratio" | |
1250 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
1251 | * totalhigh_pages from vm_total_pages), and as such we can't | |
1252 | * get into the old insane situation any more where we had | |
1253 | * large amounts of dirty pages compared to a small amount of | |
1254 | * non-HIGHMEM memory. | |
1255 | * | |
1256 | * But we might still want to scale the dirty_ratio by how | |
1257 | * much memory the box has.. | |
1da177e4 LT |
1258 | */ |
1259 | void __init page_writeback_init(void) | |
1260 | { | |
04fbfdc1 PZ |
1261 | int shift; |
1262 | ||
2d1d43f6 | 1263 | writeback_set_ratelimit(); |
1da177e4 | 1264 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
1265 | |
1266 | shift = calc_period_shift(); | |
1267 | prop_descriptor_init(&vm_completions, shift); | |
3e26c149 | 1268 | prop_descriptor_init(&vm_dirties, shift); |
1da177e4 LT |
1269 | } |
1270 | ||
f446daae JK |
1271 | /** |
1272 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
1273 | * @mapping: address space structure to write | |
1274 | * @start: starting page index | |
1275 | * @end: ending page index (inclusive) | |
1276 | * | |
1277 | * This function scans the page range from @start to @end (inclusive) and tags | |
1278 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
1279 | * that write_cache_pages (or whoever calls this function) will then use | |
1280 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
1281 | * used to avoid livelocking of writeback by a process steadily creating new | |
1282 | * dirty pages in the file (thus it is important for this function to be quick | |
1283 | * so that it can tag pages faster than a dirtying process can create them). | |
1284 | */ | |
1285 | /* | |
1286 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
1287 | */ | |
f446daae JK |
1288 | void tag_pages_for_writeback(struct address_space *mapping, |
1289 | pgoff_t start, pgoff_t end) | |
1290 | { | |
3c111a07 | 1291 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
1292 | unsigned long tagged; |
1293 | ||
1294 | do { | |
1295 | spin_lock_irq(&mapping->tree_lock); | |
1296 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
1297 | &start, end, WRITEBACK_TAG_BATCH, | |
1298 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
1299 | spin_unlock_irq(&mapping->tree_lock); | |
1300 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
1301 | cond_resched(); | |
d5ed3a4a JK |
1302 | /* We check 'start' to handle wrapping when end == ~0UL */ |
1303 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
1304 | } |
1305 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
1306 | ||
811d736f | 1307 | /** |
0ea97180 | 1308 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
1309 | * @mapping: address space structure to write |
1310 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
1311 | * @writepage: function called for each page |
1312 | * @data: data passed to writepage function | |
811d736f | 1313 | * |
0ea97180 | 1314 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
1315 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
1316 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
1317 | * and msync() need to guarantee that all the data which was dirty at the time | |
1318 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
1319 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
1320 | * existing IO to complete. | |
f446daae JK |
1321 | * |
1322 | * To avoid livelocks (when other process dirties new pages), we first tag | |
1323 | * pages which should be written back with TOWRITE tag and only then start | |
1324 | * writing them. For data-integrity sync we have to be careful so that we do | |
1325 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
1326 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
1327 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 1328 | */ |
0ea97180 MS |
1329 | int write_cache_pages(struct address_space *mapping, |
1330 | struct writeback_control *wbc, writepage_t writepage, | |
1331 | void *data) | |
811d736f | 1332 | { |
811d736f DH |
1333 | int ret = 0; |
1334 | int done = 0; | |
811d736f DH |
1335 | struct pagevec pvec; |
1336 | int nr_pages; | |
31a12666 | 1337 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
1338 | pgoff_t index; |
1339 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 1340 | pgoff_t done_index; |
31a12666 | 1341 | int cycled; |
811d736f | 1342 | int range_whole = 0; |
f446daae | 1343 | int tag; |
811d736f | 1344 | |
811d736f DH |
1345 | pagevec_init(&pvec, 0); |
1346 | if (wbc->range_cyclic) { | |
31a12666 NP |
1347 | writeback_index = mapping->writeback_index; /* prev offset */ |
1348 | index = writeback_index; | |
1349 | if (index == 0) | |
1350 | cycled = 1; | |
1351 | else | |
1352 | cycled = 0; | |
811d736f DH |
1353 | end = -1; |
1354 | } else { | |
1355 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
1356 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
1357 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
1358 | range_whole = 1; | |
31a12666 | 1359 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 1360 | } |
6e6938b6 | 1361 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
1362 | tag = PAGECACHE_TAG_TOWRITE; |
1363 | else | |
1364 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 1365 | retry: |
6e6938b6 | 1366 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 1367 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 1368 | done_index = index; |
5a3d5c98 NP |
1369 | while (!done && (index <= end)) { |
1370 | int i; | |
1371 | ||
f446daae | 1372 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
1373 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
1374 | if (nr_pages == 0) | |
1375 | break; | |
811d736f | 1376 | |
811d736f DH |
1377 | for (i = 0; i < nr_pages; i++) { |
1378 | struct page *page = pvec.pages[i]; | |
1379 | ||
1380 | /* | |
d5482cdf NP |
1381 | * At this point, the page may be truncated or |
1382 | * invalidated (changing page->mapping to NULL), or | |
1383 | * even swizzled back from swapper_space to tmpfs file | |
1384 | * mapping. However, page->index will not change | |
1385 | * because we have a reference on the page. | |
811d736f | 1386 | */ |
d5482cdf NP |
1387 | if (page->index > end) { |
1388 | /* | |
1389 | * can't be range_cyclic (1st pass) because | |
1390 | * end == -1 in that case. | |
1391 | */ | |
1392 | done = 1; | |
1393 | break; | |
1394 | } | |
1395 | ||
cf15b07c | 1396 | done_index = page->index; |
d5482cdf | 1397 | |
811d736f DH |
1398 | lock_page(page); |
1399 | ||
5a3d5c98 NP |
1400 | /* |
1401 | * Page truncated or invalidated. We can freely skip it | |
1402 | * then, even for data integrity operations: the page | |
1403 | * has disappeared concurrently, so there could be no | |
1404 | * real expectation of this data interity operation | |
1405 | * even if there is now a new, dirty page at the same | |
1406 | * pagecache address. | |
1407 | */ | |
811d736f | 1408 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 1409 | continue_unlock: |
811d736f DH |
1410 | unlock_page(page); |
1411 | continue; | |
1412 | } | |
1413 | ||
515f4a03 NP |
1414 | if (!PageDirty(page)) { |
1415 | /* someone wrote it for us */ | |
1416 | goto continue_unlock; | |
1417 | } | |
1418 | ||
1419 | if (PageWriteback(page)) { | |
1420 | if (wbc->sync_mode != WB_SYNC_NONE) | |
1421 | wait_on_page_writeback(page); | |
1422 | else | |
1423 | goto continue_unlock; | |
1424 | } | |
811d736f | 1425 | |
515f4a03 NP |
1426 | BUG_ON(PageWriteback(page)); |
1427 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 1428 | goto continue_unlock; |
811d736f | 1429 | |
9e094383 | 1430 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 1431 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
1432 | if (unlikely(ret)) { |
1433 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
1434 | unlock_page(page); | |
1435 | ret = 0; | |
1436 | } else { | |
1437 | /* | |
1438 | * done_index is set past this page, | |
1439 | * so media errors will not choke | |
1440 | * background writeout for the entire | |
1441 | * file. This has consequences for | |
1442 | * range_cyclic semantics (ie. it may | |
1443 | * not be suitable for data integrity | |
1444 | * writeout). | |
1445 | */ | |
cf15b07c | 1446 | done_index = page->index + 1; |
00266770 NP |
1447 | done = 1; |
1448 | break; | |
1449 | } | |
0b564927 | 1450 | } |
00266770 | 1451 | |
546a1924 DC |
1452 | /* |
1453 | * We stop writing back only if we are not doing | |
1454 | * integrity sync. In case of integrity sync we have to | |
1455 | * keep going until we have written all the pages | |
1456 | * we tagged for writeback prior to entering this loop. | |
1457 | */ | |
1458 | if (--wbc->nr_to_write <= 0 && | |
1459 | wbc->sync_mode == WB_SYNC_NONE) { | |
1460 | done = 1; | |
1461 | break; | |
05fe478d | 1462 | } |
811d736f DH |
1463 | } |
1464 | pagevec_release(&pvec); | |
1465 | cond_resched(); | |
1466 | } | |
3a4c6800 | 1467 | if (!cycled && !done) { |
811d736f | 1468 | /* |
31a12666 | 1469 | * range_cyclic: |
811d736f DH |
1470 | * We hit the last page and there is more work to be done: wrap |
1471 | * back to the start of the file | |
1472 | */ | |
31a12666 | 1473 | cycled = 1; |
811d736f | 1474 | index = 0; |
31a12666 | 1475 | end = writeback_index - 1; |
811d736f DH |
1476 | goto retry; |
1477 | } | |
0b564927 DC |
1478 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
1479 | mapping->writeback_index = done_index; | |
06d6cf69 | 1480 | |
811d736f DH |
1481 | return ret; |
1482 | } | |
0ea97180 MS |
1483 | EXPORT_SYMBOL(write_cache_pages); |
1484 | ||
1485 | /* | |
1486 | * Function used by generic_writepages to call the real writepage | |
1487 | * function and set the mapping flags on error | |
1488 | */ | |
1489 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1490 | void *data) | |
1491 | { | |
1492 | struct address_space *mapping = data; | |
1493 | int ret = mapping->a_ops->writepage(page, wbc); | |
1494 | mapping_set_error(mapping, ret); | |
1495 | return ret; | |
1496 | } | |
1497 | ||
1498 | /** | |
1499 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1500 | * @mapping: address space structure to write | |
1501 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1502 | * | |
1503 | * This is a library function, which implements the writepages() | |
1504 | * address_space_operation. | |
1505 | */ | |
1506 | int generic_writepages(struct address_space *mapping, | |
1507 | struct writeback_control *wbc) | |
1508 | { | |
9b6096a6 SL |
1509 | struct blk_plug plug; |
1510 | int ret; | |
1511 | ||
0ea97180 MS |
1512 | /* deal with chardevs and other special file */ |
1513 | if (!mapping->a_ops->writepage) | |
1514 | return 0; | |
1515 | ||
9b6096a6 SL |
1516 | blk_start_plug(&plug); |
1517 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
1518 | blk_finish_plug(&plug); | |
1519 | return ret; | |
0ea97180 | 1520 | } |
811d736f DH |
1521 | |
1522 | EXPORT_SYMBOL(generic_writepages); | |
1523 | ||
1da177e4 LT |
1524 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1525 | { | |
22905f77 AM |
1526 | int ret; |
1527 | ||
1da177e4 LT |
1528 | if (wbc->nr_to_write <= 0) |
1529 | return 0; | |
1530 | if (mapping->a_ops->writepages) | |
d08b3851 | 1531 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1532 | else |
1533 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1534 | return ret; |
1da177e4 LT |
1535 | } |
1536 | ||
1537 | /** | |
1538 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1539 | * @page: the page to write |
1540 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1541 | * |
1542 | * The page must be locked by the caller and will be unlocked upon return. | |
1543 | * | |
1544 | * write_one_page() returns a negative error code if I/O failed. | |
1545 | */ | |
1546 | int write_one_page(struct page *page, int wait) | |
1547 | { | |
1548 | struct address_space *mapping = page->mapping; | |
1549 | int ret = 0; | |
1550 | struct writeback_control wbc = { | |
1551 | .sync_mode = WB_SYNC_ALL, | |
1552 | .nr_to_write = 1, | |
1553 | }; | |
1554 | ||
1555 | BUG_ON(!PageLocked(page)); | |
1556 | ||
1557 | if (wait) | |
1558 | wait_on_page_writeback(page); | |
1559 | ||
1560 | if (clear_page_dirty_for_io(page)) { | |
1561 | page_cache_get(page); | |
1562 | ret = mapping->a_ops->writepage(page, &wbc); | |
1563 | if (ret == 0 && wait) { | |
1564 | wait_on_page_writeback(page); | |
1565 | if (PageError(page)) | |
1566 | ret = -EIO; | |
1567 | } | |
1568 | page_cache_release(page); | |
1569 | } else { | |
1570 | unlock_page(page); | |
1571 | } | |
1572 | return ret; | |
1573 | } | |
1574 | EXPORT_SYMBOL(write_one_page); | |
1575 | ||
76719325 KC |
1576 | /* |
1577 | * For address_spaces which do not use buffers nor write back. | |
1578 | */ | |
1579 | int __set_page_dirty_no_writeback(struct page *page) | |
1580 | { | |
1581 | if (!PageDirty(page)) | |
c3f0da63 | 1582 | return !TestSetPageDirty(page); |
76719325 KC |
1583 | return 0; |
1584 | } | |
1585 | ||
e3a7cca1 ES |
1586 | /* |
1587 | * Helper function for set_page_dirty family. | |
1588 | * NOTE: This relies on being atomic wrt interrupts. | |
1589 | */ | |
1590 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1591 | { | |
1592 | if (mapping_cap_account_dirty(mapping)) { | |
1593 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
ea941f0e | 1594 | __inc_zone_page_state(page, NR_DIRTIED); |
e3a7cca1 | 1595 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
c8e28ce0 | 1596 | __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); |
e3a7cca1 ES |
1597 | task_dirty_inc(current); |
1598 | task_io_account_write(PAGE_CACHE_SIZE); | |
1599 | } | |
1600 | } | |
679ceace | 1601 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 1602 | |
f629d1c9 MR |
1603 | /* |
1604 | * Helper function for set_page_writeback family. | |
1605 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic | |
1606 | * wrt interrupts. | |
1607 | */ | |
1608 | void account_page_writeback(struct page *page) | |
1609 | { | |
1610 | inc_zone_page_state(page, NR_WRITEBACK); | |
1611 | } | |
1612 | EXPORT_SYMBOL(account_page_writeback); | |
1613 | ||
1da177e4 LT |
1614 | /* |
1615 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1616 | * its radix tree. | |
1617 | * | |
1618 | * This is also used when a single buffer is being dirtied: we want to set the | |
1619 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1620 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1621 | * | |
1622 | * Most callers have locked the page, which pins the address_space in memory. | |
1623 | * But zap_pte_range() does not lock the page, however in that case the | |
1624 | * mapping is pinned by the vma's ->vm_file reference. | |
1625 | * | |
1626 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1627 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1628 | */ |
1629 | int __set_page_dirty_nobuffers(struct page *page) | |
1630 | { | |
1da177e4 LT |
1631 | if (!TestSetPageDirty(page)) { |
1632 | struct address_space *mapping = page_mapping(page); | |
1633 | struct address_space *mapping2; | |
1634 | ||
8c08540f AM |
1635 | if (!mapping) |
1636 | return 1; | |
1637 | ||
19fd6231 | 1638 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1639 | mapping2 = page_mapping(page); |
1640 | if (mapping2) { /* Race with truncate? */ | |
1641 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1642 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1643 | account_page_dirtied(page, mapping); |
8c08540f AM |
1644 | radix_tree_tag_set(&mapping->page_tree, |
1645 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1646 | } | |
19fd6231 | 1647 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1648 | if (mapping->host) { |
1649 | /* !PageAnon && !swapper_space */ | |
1650 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1651 | } |
4741c9fd | 1652 | return 1; |
1da177e4 | 1653 | } |
4741c9fd | 1654 | return 0; |
1da177e4 LT |
1655 | } |
1656 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
1657 | ||
1658 | /* | |
1659 | * When a writepage implementation decides that it doesn't want to write this | |
1660 | * page for some reason, it should redirty the locked page via | |
1661 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
1662 | */ | |
1663 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
1664 | { | |
1665 | wbc->pages_skipped++; | |
1666 | return __set_page_dirty_nobuffers(page); | |
1667 | } | |
1668 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
1669 | ||
1670 | /* | |
6746aff7 WF |
1671 | * Dirty a page. |
1672 | * | |
1673 | * For pages with a mapping this should be done under the page lock | |
1674 | * for the benefit of asynchronous memory errors who prefer a consistent | |
1675 | * dirty state. This rule can be broken in some special cases, | |
1676 | * but should be better not to. | |
1677 | * | |
1da177e4 LT |
1678 | * If the mapping doesn't provide a set_page_dirty a_op, then |
1679 | * just fall through and assume that it wants buffer_heads. | |
1680 | */ | |
1cf6e7d8 | 1681 | int set_page_dirty(struct page *page) |
1da177e4 LT |
1682 | { |
1683 | struct address_space *mapping = page_mapping(page); | |
1684 | ||
1685 | if (likely(mapping)) { | |
1686 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
1687 | /* |
1688 | * readahead/lru_deactivate_page could remain | |
1689 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
1690 | * About readahead, if the page is written, the flags would be | |
1691 | * reset. So no problem. | |
1692 | * About lru_deactivate_page, if the page is redirty, the flag | |
1693 | * will be reset. So no problem. but if the page is used by readahead | |
1694 | * it will confuse readahead and make it restart the size rampup | |
1695 | * process. But it's a trivial problem. | |
1696 | */ | |
1697 | ClearPageReclaim(page); | |
9361401e DH |
1698 | #ifdef CONFIG_BLOCK |
1699 | if (!spd) | |
1700 | spd = __set_page_dirty_buffers; | |
1701 | #endif | |
1702 | return (*spd)(page); | |
1da177e4 | 1703 | } |
4741c9fd AM |
1704 | if (!PageDirty(page)) { |
1705 | if (!TestSetPageDirty(page)) | |
1706 | return 1; | |
1707 | } | |
1da177e4 LT |
1708 | return 0; |
1709 | } | |
1710 | EXPORT_SYMBOL(set_page_dirty); | |
1711 | ||
1712 | /* | |
1713 | * set_page_dirty() is racy if the caller has no reference against | |
1714 | * page->mapping->host, and if the page is unlocked. This is because another | |
1715 | * CPU could truncate the page off the mapping and then free the mapping. | |
1716 | * | |
1717 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
1718 | * holds a reference on the inode by having an open file. | |
1719 | * | |
1720 | * In other cases, the page should be locked before running set_page_dirty(). | |
1721 | */ | |
1722 | int set_page_dirty_lock(struct page *page) | |
1723 | { | |
1724 | int ret; | |
1725 | ||
7eaceacc | 1726 | lock_page(page); |
1da177e4 LT |
1727 | ret = set_page_dirty(page); |
1728 | unlock_page(page); | |
1729 | return ret; | |
1730 | } | |
1731 | EXPORT_SYMBOL(set_page_dirty_lock); | |
1732 | ||
1da177e4 LT |
1733 | /* |
1734 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
1735 | * Returns true if the page was previously dirty. | |
1736 | * | |
1737 | * This is for preparing to put the page under writeout. We leave the page | |
1738 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
1739 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
1740 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
1741 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
1742 | * back into sync. | |
1743 | * | |
1744 | * This incoherency between the page's dirty flag and radix-tree tag is | |
1745 | * unfortunate, but it only exists while the page is locked. | |
1746 | */ | |
1747 | int clear_page_dirty_for_io(struct page *page) | |
1748 | { | |
1749 | struct address_space *mapping = page_mapping(page); | |
1750 | ||
79352894 NP |
1751 | BUG_ON(!PageLocked(page)); |
1752 | ||
7658cc28 LT |
1753 | if (mapping && mapping_cap_account_dirty(mapping)) { |
1754 | /* | |
1755 | * Yes, Virginia, this is indeed insane. | |
1756 | * | |
1757 | * We use this sequence to make sure that | |
1758 | * (a) we account for dirty stats properly | |
1759 | * (b) we tell the low-level filesystem to | |
1760 | * mark the whole page dirty if it was | |
1761 | * dirty in a pagetable. Only to then | |
1762 | * (c) clean the page again and return 1 to | |
1763 | * cause the writeback. | |
1764 | * | |
1765 | * This way we avoid all nasty races with the | |
1766 | * dirty bit in multiple places and clearing | |
1767 | * them concurrently from different threads. | |
1768 | * | |
1769 | * Note! Normally the "set_page_dirty(page)" | |
1770 | * has no effect on the actual dirty bit - since | |
1771 | * that will already usually be set. But we | |
1772 | * need the side effects, and it can help us | |
1773 | * avoid races. | |
1774 | * | |
1775 | * We basically use the page "master dirty bit" | |
1776 | * as a serialization point for all the different | |
1777 | * threads doing their things. | |
7658cc28 LT |
1778 | */ |
1779 | if (page_mkclean(page)) | |
1780 | set_page_dirty(page); | |
79352894 NP |
1781 | /* |
1782 | * We carefully synchronise fault handlers against | |
1783 | * installing a dirty pte and marking the page dirty | |
1784 | * at this point. We do this by having them hold the | |
1785 | * page lock at some point after installing their | |
1786 | * pte, but before marking the page dirty. | |
1787 | * Pages are always locked coming in here, so we get | |
1788 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
1789 | * for more comments. | |
1790 | */ | |
7658cc28 | 1791 | if (TestClearPageDirty(page)) { |
8c08540f | 1792 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
1793 | dec_bdi_stat(mapping->backing_dev_info, |
1794 | BDI_RECLAIMABLE); | |
7658cc28 | 1795 | return 1; |
1da177e4 | 1796 | } |
7658cc28 | 1797 | return 0; |
1da177e4 | 1798 | } |
7658cc28 | 1799 | return TestClearPageDirty(page); |
1da177e4 | 1800 | } |
58bb01a9 | 1801 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
1802 | |
1803 | int test_clear_page_writeback(struct page *page) | |
1804 | { | |
1805 | struct address_space *mapping = page_mapping(page); | |
1806 | int ret; | |
1807 | ||
1808 | if (mapping) { | |
69cb51d1 | 1809 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1810 | unsigned long flags; |
1811 | ||
19fd6231 | 1812 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1813 | ret = TestClearPageWriteback(page); |
69cb51d1 | 1814 | if (ret) { |
1da177e4 LT |
1815 | radix_tree_tag_clear(&mapping->page_tree, |
1816 | page_index(page), | |
1817 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1818 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 1819 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
1820 | __bdi_writeout_inc(bdi); |
1821 | } | |
69cb51d1 | 1822 | } |
19fd6231 | 1823 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1824 | } else { |
1825 | ret = TestClearPageWriteback(page); | |
1826 | } | |
99b12e3d | 1827 | if (ret) { |
d688abf5 | 1828 | dec_zone_page_state(page, NR_WRITEBACK); |
99b12e3d WF |
1829 | inc_zone_page_state(page, NR_WRITTEN); |
1830 | } | |
1da177e4 LT |
1831 | return ret; |
1832 | } | |
1833 | ||
1834 | int test_set_page_writeback(struct page *page) | |
1835 | { | |
1836 | struct address_space *mapping = page_mapping(page); | |
1837 | int ret; | |
1838 | ||
1839 | if (mapping) { | |
69cb51d1 | 1840 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1841 | unsigned long flags; |
1842 | ||
19fd6231 | 1843 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1844 | ret = TestSetPageWriteback(page); |
69cb51d1 | 1845 | if (!ret) { |
1da177e4 LT |
1846 | radix_tree_tag_set(&mapping->page_tree, |
1847 | page_index(page), | |
1848 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1849 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
1850 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
1851 | } | |
1da177e4 LT |
1852 | if (!PageDirty(page)) |
1853 | radix_tree_tag_clear(&mapping->page_tree, | |
1854 | page_index(page), | |
1855 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
1856 | radix_tree_tag_clear(&mapping->page_tree, |
1857 | page_index(page), | |
1858 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 1859 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1860 | } else { |
1861 | ret = TestSetPageWriteback(page); | |
1862 | } | |
d688abf5 | 1863 | if (!ret) |
f629d1c9 | 1864 | account_page_writeback(page); |
1da177e4 LT |
1865 | return ret; |
1866 | ||
1867 | } | |
1868 | EXPORT_SYMBOL(test_set_page_writeback); | |
1869 | ||
1870 | /* | |
00128188 | 1871 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
1872 | * passed tag. |
1873 | */ | |
1874 | int mapping_tagged(struct address_space *mapping, int tag) | |
1875 | { | |
72c47832 | 1876 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
1877 | } |
1878 | EXPORT_SYMBOL(mapping_tagged); |