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Commit | Line | Data |
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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> | |
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 | /* The following parameters are exported via /proc/sys/vm */ |
58 | ||
59 | /* | |
5b0830cb | 60 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 61 | */ |
1b5e62b4 | 62 | int dirty_background_ratio = 10; |
1da177e4 | 63 | |
2da02997 DR |
64 | /* |
65 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
66 | * dirty_background_ratio * the amount of dirtyable memory | |
67 | */ | |
68 | unsigned long dirty_background_bytes; | |
69 | ||
195cf453 BG |
70 | /* |
71 | * free highmem will not be subtracted from the total free memory | |
72 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
73 | */ | |
74 | int vm_highmem_is_dirtyable; | |
75 | ||
1da177e4 LT |
76 | /* |
77 | * The generator of dirty data starts writeback at this percentage | |
78 | */ | |
1b5e62b4 | 79 | int vm_dirty_ratio = 20; |
1da177e4 | 80 | |
2da02997 DR |
81 | /* |
82 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
83 | * vm_dirty_ratio * the amount of dirtyable memory | |
84 | */ | |
85 | unsigned long vm_dirty_bytes; | |
86 | ||
1da177e4 | 87 | /* |
704503d8 | 88 | * The interval between `kupdate'-style writebacks |
1da177e4 | 89 | */ |
22ef37ee | 90 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 LT |
91 | |
92 | /* | |
704503d8 | 93 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 94 | */ |
22ef37ee | 95 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
96 | |
97 | /* | |
98 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
99 | */ | |
100 | int block_dump; | |
101 | ||
102 | /* | |
ed5b43f1 BS |
103 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
104 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
105 | */ |
106 | int laptop_mode; | |
107 | ||
108 | EXPORT_SYMBOL(laptop_mode); | |
109 | ||
110 | /* End of sysctl-exported parameters */ | |
111 | ||
c42843f2 | 112 | unsigned long global_dirty_limit; |
1da177e4 | 113 | |
04fbfdc1 PZ |
114 | /* |
115 | * Scale the writeback cache size proportional to the relative writeout speeds. | |
116 | * | |
117 | * We do this by keeping a floating proportion between BDIs, based on page | |
118 | * writeback completions [end_page_writeback()]. Those devices that write out | |
119 | * pages fastest will get the larger share, while the slower will get a smaller | |
120 | * share. | |
121 | * | |
122 | * We use page writeout completions because we are interested in getting rid of | |
123 | * dirty pages. Having them written out is the primary goal. | |
124 | * | |
125 | * We introduce a concept of time, a period over which we measure these events, | |
126 | * because demand can/will vary over time. The length of this period itself is | |
127 | * measured in page writeback completions. | |
128 | * | |
129 | */ | |
130 | static struct prop_descriptor vm_completions; | |
131 | ||
04fbfdc1 PZ |
132 | /* |
133 | * couple the period to the dirty_ratio: | |
134 | * | |
135 | * period/2 ~ roundup_pow_of_two(dirty limit) | |
136 | */ | |
137 | static int calc_period_shift(void) | |
138 | { | |
139 | unsigned long dirty_total; | |
140 | ||
2da02997 DR |
141 | if (vm_dirty_bytes) |
142 | dirty_total = vm_dirty_bytes / PAGE_SIZE; | |
143 | else | |
144 | dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / | |
145 | 100; | |
04fbfdc1 PZ |
146 | return 2 + ilog2(dirty_total - 1); |
147 | } | |
148 | ||
149 | /* | |
2da02997 | 150 | * update the period when the dirty threshold changes. |
04fbfdc1 | 151 | */ |
2da02997 DR |
152 | static void update_completion_period(void) |
153 | { | |
154 | int shift = calc_period_shift(); | |
155 | prop_change_shift(&vm_completions, shift); | |
9d823e8f WF |
156 | |
157 | writeback_set_ratelimit(); | |
2da02997 DR |
158 | } |
159 | ||
160 | int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
8d65af78 | 161 | void __user *buffer, size_t *lenp, |
2da02997 DR |
162 | loff_t *ppos) |
163 | { | |
164 | int ret; | |
165 | ||
8d65af78 | 166 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
167 | if (ret == 0 && write) |
168 | dirty_background_bytes = 0; | |
169 | return ret; | |
170 | } | |
171 | ||
172 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 173 | void __user *buffer, size_t *lenp, |
2da02997 DR |
174 | loff_t *ppos) |
175 | { | |
176 | int ret; | |
177 | ||
8d65af78 | 178 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
179 | if (ret == 0 && write) |
180 | dirty_background_ratio = 0; | |
181 | return ret; | |
182 | } | |
183 | ||
04fbfdc1 | 184 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 185 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
186 | loff_t *ppos) |
187 | { | |
188 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
189 | int ret; |
190 | ||
8d65af78 | 191 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 192 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
2da02997 DR |
193 | update_completion_period(); |
194 | vm_dirty_bytes = 0; | |
195 | } | |
196 | return ret; | |
197 | } | |
198 | ||
199 | ||
200 | int dirty_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 201 | void __user *buffer, size_t *lenp, |
2da02997 DR |
202 | loff_t *ppos) |
203 | { | |
fc3501d4 | 204 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
205 | int ret; |
206 | ||
8d65af78 | 207 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
208 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
209 | update_completion_period(); | |
210 | vm_dirty_ratio = 0; | |
04fbfdc1 PZ |
211 | } |
212 | return ret; | |
213 | } | |
214 | ||
215 | /* | |
216 | * Increment the BDI's writeout completion count and the global writeout | |
217 | * completion count. Called from test_clear_page_writeback(). | |
218 | */ | |
219 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
220 | { | |
f7d2b1ec | 221 | __inc_bdi_stat(bdi, BDI_WRITTEN); |
a42dde04 PZ |
222 | __prop_inc_percpu_max(&vm_completions, &bdi->completions, |
223 | bdi->max_prop_frac); | |
04fbfdc1 PZ |
224 | } |
225 | ||
dd5656e5 MS |
226 | void bdi_writeout_inc(struct backing_dev_info *bdi) |
227 | { | |
228 | unsigned long flags; | |
229 | ||
230 | local_irq_save(flags); | |
231 | __bdi_writeout_inc(bdi); | |
232 | local_irq_restore(flags); | |
233 | } | |
234 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); | |
235 | ||
04fbfdc1 PZ |
236 | /* |
237 | * Obtain an accurate fraction of the BDI's portion. | |
238 | */ | |
239 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
240 | long *numerator, long *denominator) | |
241 | { | |
3efaf0fa | 242 | prop_fraction_percpu(&vm_completions, &bdi->completions, |
04fbfdc1 | 243 | numerator, denominator); |
04fbfdc1 PZ |
244 | } |
245 | ||
189d3c4a | 246 | /* |
d08c429b JW |
247 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
248 | * registered backing devices, which, for obvious reasons, can not | |
249 | * exceed 100%. | |
189d3c4a | 250 | */ |
189d3c4a PZ |
251 | static unsigned int bdi_min_ratio; |
252 | ||
253 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
254 | { | |
255 | int ret = 0; | |
189d3c4a | 256 | |
cfc4ba53 | 257 | spin_lock_bh(&bdi_lock); |
a42dde04 | 258 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 259 | ret = -EINVAL; |
a42dde04 PZ |
260 | } else { |
261 | min_ratio -= bdi->min_ratio; | |
262 | if (bdi_min_ratio + min_ratio < 100) { | |
263 | bdi_min_ratio += min_ratio; | |
264 | bdi->min_ratio += min_ratio; | |
265 | } else { | |
266 | ret = -EINVAL; | |
267 | } | |
268 | } | |
cfc4ba53 | 269 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
270 | |
271 | return ret; | |
272 | } | |
273 | ||
274 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
275 | { | |
a42dde04 PZ |
276 | int ret = 0; |
277 | ||
278 | if (max_ratio > 100) | |
279 | return -EINVAL; | |
280 | ||
cfc4ba53 | 281 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
282 | if (bdi->min_ratio > max_ratio) { |
283 | ret = -EINVAL; | |
284 | } else { | |
285 | bdi->max_ratio = max_ratio; | |
286 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
287 | } | |
cfc4ba53 | 288 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
289 | |
290 | return ret; | |
291 | } | |
a42dde04 | 292 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 293 | |
1da177e4 LT |
294 | /* |
295 | * Work out the current dirty-memory clamping and background writeout | |
296 | * thresholds. | |
297 | * | |
298 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
299 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
300 | * pages. It is better to clamp down on writers than to start swapping, and | |
301 | * performing lots of scanning. | |
302 | * | |
303 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
304 | * | |
305 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
306 | * excessive. | |
307 | * | |
308 | * We make sure that the background writeout level is below the adjusted | |
309 | * clamping level. | |
310 | */ | |
1b424464 CL |
311 | |
312 | static unsigned long highmem_dirtyable_memory(unsigned long total) | |
313 | { | |
314 | #ifdef CONFIG_HIGHMEM | |
315 | int node; | |
316 | unsigned long x = 0; | |
317 | ||
37b07e41 | 318 | for_each_node_state(node, N_HIGH_MEMORY) { |
1b424464 CL |
319 | struct zone *z = |
320 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
321 | ||
adea02a1 WF |
322 | x += zone_page_state(z, NR_FREE_PAGES) + |
323 | zone_reclaimable_pages(z); | |
1b424464 CL |
324 | } |
325 | /* | |
326 | * Make sure that the number of highmem pages is never larger | |
327 | * than the number of the total dirtyable memory. This can only | |
328 | * occur in very strange VM situations but we want to make sure | |
329 | * that this does not occur. | |
330 | */ | |
331 | return min(x, total); | |
332 | #else | |
333 | return 0; | |
334 | #endif | |
335 | } | |
336 | ||
3eefae99 SR |
337 | /** |
338 | * determine_dirtyable_memory - amount of memory that may be used | |
339 | * | |
340 | * Returns the numebr of pages that can currently be freed and used | |
341 | * by the kernel for direct mappings. | |
342 | */ | |
343 | unsigned long determine_dirtyable_memory(void) | |
1b424464 CL |
344 | { |
345 | unsigned long x; | |
346 | ||
adea02a1 | 347 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
195cf453 BG |
348 | |
349 | if (!vm_highmem_is_dirtyable) | |
350 | x -= highmem_dirtyable_memory(x); | |
351 | ||
1b424464 CL |
352 | return x + 1; /* Ensure that we never return 0 */ |
353 | } | |
354 | ||
6c14ae1e WF |
355 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
356 | unsigned long bg_thresh) | |
357 | { | |
358 | return (thresh + bg_thresh) / 2; | |
359 | } | |
360 | ||
ffd1f609 WF |
361 | static unsigned long hard_dirty_limit(unsigned long thresh) |
362 | { | |
363 | return max(thresh, global_dirty_limit); | |
364 | } | |
365 | ||
03ab450f | 366 | /* |
1babe183 WF |
367 | * global_dirty_limits - background-writeback and dirty-throttling thresholds |
368 | * | |
369 | * Calculate the dirty thresholds based on sysctl parameters | |
370 | * - vm.dirty_background_ratio or vm.dirty_background_bytes | |
371 | * - vm.dirty_ratio or vm.dirty_bytes | |
372 | * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ebd1373d | 373 | * real-time tasks. |
1babe183 | 374 | */ |
16c4042f | 375 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
1da177e4 | 376 | { |
364aeb28 DR |
377 | unsigned long background; |
378 | unsigned long dirty; | |
240c879f | 379 | unsigned long uninitialized_var(available_memory); |
1da177e4 LT |
380 | struct task_struct *tsk; |
381 | ||
240c879f MK |
382 | if (!vm_dirty_bytes || !dirty_background_bytes) |
383 | available_memory = determine_dirtyable_memory(); | |
384 | ||
2da02997 DR |
385 | if (vm_dirty_bytes) |
386 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
4cbec4c8 WF |
387 | else |
388 | dirty = (vm_dirty_ratio * available_memory) / 100; | |
1da177e4 | 389 | |
2da02997 DR |
390 | if (dirty_background_bytes) |
391 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
392 | else | |
393 | background = (dirty_background_ratio * available_memory) / 100; | |
1da177e4 | 394 | |
2da02997 DR |
395 | if (background >= dirty) |
396 | background = dirty / 2; | |
1da177e4 LT |
397 | tsk = current; |
398 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
399 | background += background / 4; | |
400 | dirty += dirty / 4; | |
401 | } | |
402 | *pbackground = background; | |
403 | *pdirty = dirty; | |
e1cbe236 | 404 | trace_global_dirty_state(background, dirty); |
16c4042f | 405 | } |
04fbfdc1 | 406 | |
6f718656 | 407 | /** |
1babe183 | 408 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
6f718656 WF |
409 | * @bdi: the backing_dev_info to query |
410 | * @dirty: global dirty limit in pages | |
1babe183 | 411 | * |
6f718656 WF |
412 | * Returns @bdi's dirty limit in pages. The term "dirty" in the context of |
413 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. | |
aed21ad2 WF |
414 | * |
415 | * Note that balance_dirty_pages() will only seriously take it as a hard limit | |
416 | * when sleeping max_pause per page is not enough to keep the dirty pages under | |
417 | * control. For example, when the device is completely stalled due to some error | |
418 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. | |
419 | * In the other normal situations, it acts more gently by throttling the tasks | |
420 | * more (rather than completely block them) when the bdi dirty pages go high. | |
1babe183 | 421 | * |
6f718656 | 422 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
423 | * - starving fast devices |
424 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
425 | * | |
426 | * The bdi's share of dirty limit will be adapting to its throughput and | |
427 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. | |
428 | */ | |
429 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) | |
16c4042f WF |
430 | { |
431 | u64 bdi_dirty; | |
432 | long numerator, denominator; | |
04fbfdc1 | 433 | |
16c4042f WF |
434 | /* |
435 | * Calculate this BDI's share of the dirty ratio. | |
436 | */ | |
437 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
04fbfdc1 | 438 | |
16c4042f WF |
439 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
440 | bdi_dirty *= numerator; | |
441 | do_div(bdi_dirty, denominator); | |
04fbfdc1 | 442 | |
16c4042f WF |
443 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
444 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) | |
445 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
446 | ||
447 | return bdi_dirty; | |
1da177e4 LT |
448 | } |
449 | ||
6c14ae1e WF |
450 | /* |
451 | * Dirty position control. | |
452 | * | |
453 | * (o) global/bdi setpoints | |
454 | * | |
455 | * We want the dirty pages be balanced around the global/bdi setpoints. | |
456 | * When the number of dirty pages is higher/lower than the setpoint, the | |
457 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
458 | * decreased/increased to bring the dirty pages back to the setpoint. | |
459 | * | |
460 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
461 | * | |
462 | * if (dirty < setpoint) scale up pos_ratio | |
463 | * if (dirty > setpoint) scale down pos_ratio | |
464 | * | |
465 | * if (bdi_dirty < bdi_setpoint) scale up pos_ratio | |
466 | * if (bdi_dirty > bdi_setpoint) scale down pos_ratio | |
467 | * | |
468 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
469 | * | |
470 | * (o) global control line | |
471 | * | |
472 | * ^ pos_ratio | |
473 | * | | |
474 | * | |<===== global dirty control scope ======>| | |
475 | * 2.0 .............* | |
476 | * | .* | |
477 | * | . * | |
478 | * | . * | |
479 | * | . * | |
480 | * | . * | |
481 | * | . * | |
482 | * 1.0 ................................* | |
483 | * | . . * | |
484 | * | . . * | |
485 | * | . . * | |
486 | * | . . * | |
487 | * | . . * | |
488 | * 0 +------------.------------------.----------------------*-------------> | |
489 | * freerun^ setpoint^ limit^ dirty pages | |
490 | * | |
491 | * (o) bdi control line | |
492 | * | |
493 | * ^ pos_ratio | |
494 | * | | |
495 | * | * | |
496 | * | * | |
497 | * | * | |
498 | * | * | |
499 | * | * |<=========== span ============>| | |
500 | * 1.0 .......................* | |
501 | * | . * | |
502 | * | . * | |
503 | * | . * | |
504 | * | . * | |
505 | * | . * | |
506 | * | . * | |
507 | * | . * | |
508 | * | . * | |
509 | * | . * | |
510 | * | . * | |
511 | * | . * | |
512 | * 1/4 ...............................................* * * * * * * * * * * * | |
513 | * | . . | |
514 | * | . . | |
515 | * | . . | |
516 | * 0 +----------------------.-------------------------------.-------------> | |
517 | * bdi_setpoint^ x_intercept^ | |
518 | * | |
519 | * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can | |
520 | * be smoothly throttled down to normal if it starts high in situations like | |
521 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
522 | * card's bdi_dirty may rush to many times higher than bdi_setpoint. | |
523 | * - the bdi dirty thresh drops quickly due to change of JBOD workload | |
524 | */ | |
525 | static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, | |
526 | unsigned long thresh, | |
527 | unsigned long bg_thresh, | |
528 | unsigned long dirty, | |
529 | unsigned long bdi_thresh, | |
530 | unsigned long bdi_dirty) | |
531 | { | |
532 | unsigned long write_bw = bdi->avg_write_bandwidth; | |
533 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); | |
534 | unsigned long limit = hard_dirty_limit(thresh); | |
535 | unsigned long x_intercept; | |
536 | unsigned long setpoint; /* dirty pages' target balance point */ | |
537 | unsigned long bdi_setpoint; | |
538 | unsigned long span; | |
539 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
540 | long x; | |
541 | ||
542 | if (unlikely(dirty >= limit)) | |
543 | return 0; | |
544 | ||
545 | /* | |
546 | * global setpoint | |
547 | * | |
548 | * setpoint - dirty 3 | |
549 | * f(dirty) := 1.0 + (----------------) | |
550 | * limit - setpoint | |
551 | * | |
552 | * it's a 3rd order polynomial that subjects to | |
553 | * | |
554 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
555 | * (2) f(setpoint) = 1.0 => the balance point | |
556 | * (3) f(limit) = 0 => the hard limit | |
557 | * (4) df/dx <= 0 => negative feedback control | |
558 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
559 | * => fast response on large errors; small oscillation near setpoint | |
560 | */ | |
561 | setpoint = (freerun + limit) / 2; | |
562 | x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, | |
563 | limit - setpoint + 1); | |
564 | pos_ratio = x; | |
565 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
566 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
567 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
568 | ||
569 | /* | |
570 | * We have computed basic pos_ratio above based on global situation. If | |
571 | * the bdi is over/under its share of dirty pages, we want to scale | |
572 | * pos_ratio further down/up. That is done by the following mechanism. | |
573 | */ | |
574 | ||
575 | /* | |
576 | * bdi setpoint | |
577 | * | |
578 | * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint) | |
579 | * | |
580 | * x_intercept - bdi_dirty | |
581 | * := -------------------------- | |
582 | * x_intercept - bdi_setpoint | |
583 | * | |
584 | * The main bdi control line is a linear function that subjects to | |
585 | * | |
586 | * (1) f(bdi_setpoint) = 1.0 | |
587 | * (2) k = - 1 / (8 * write_bw) (in single bdi case) | |
588 | * or equally: x_intercept = bdi_setpoint + 8 * write_bw | |
589 | * | |
590 | * For single bdi case, the dirty pages are observed to fluctuate | |
591 | * regularly within range | |
592 | * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2] | |
593 | * for various filesystems, where (2) can yield in a reasonable 12.5% | |
594 | * fluctuation range for pos_ratio. | |
595 | * | |
596 | * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its | |
597 | * own size, so move the slope over accordingly and choose a slope that | |
598 | * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh. | |
599 | */ | |
600 | if (unlikely(bdi_thresh > thresh)) | |
601 | bdi_thresh = thresh; | |
aed21ad2 WF |
602 | /* |
603 | * It's very possible that bdi_thresh is close to 0 not because the | |
604 | * device is slow, but that it has remained inactive for long time. | |
605 | * Honour such devices a reasonable good (hopefully IO efficient) | |
606 | * threshold, so that the occasional writes won't be blocked and active | |
607 | * writes can rampup the threshold quickly. | |
608 | */ | |
8927f66c | 609 | bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); |
6c14ae1e WF |
610 | /* |
611 | * scale global setpoint to bdi's: | |
612 | * bdi_setpoint = setpoint * bdi_thresh / thresh | |
613 | */ | |
614 | x = div_u64((u64)bdi_thresh << 16, thresh + 1); | |
615 | bdi_setpoint = setpoint * (u64)x >> 16; | |
616 | /* | |
617 | * Use span=(8*write_bw) in single bdi case as indicated by | |
618 | * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case. | |
619 | * | |
620 | * bdi_thresh thresh - bdi_thresh | |
621 | * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh | |
622 | * thresh thresh | |
623 | */ | |
624 | span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16; | |
625 | x_intercept = bdi_setpoint + span; | |
626 | ||
627 | if (bdi_dirty < x_intercept - span / 4) { | |
50657fc4 WF |
628 | pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), |
629 | x_intercept - bdi_setpoint + 1); | |
6c14ae1e WF |
630 | } else |
631 | pos_ratio /= 4; | |
632 | ||
8927f66c WF |
633 | /* |
634 | * bdi reserve area, safeguard against dirty pool underrun and disk idle | |
635 | * It may push the desired control point of global dirty pages higher | |
636 | * than setpoint. | |
637 | */ | |
638 | x_intercept = bdi_thresh / 2; | |
639 | if (bdi_dirty < x_intercept) { | |
50657fc4 WF |
640 | if (bdi_dirty > x_intercept / 8) |
641 | pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty); | |
642 | else | |
8927f66c WF |
643 | pos_ratio *= 8; |
644 | } | |
645 | ||
6c14ae1e WF |
646 | return pos_ratio; |
647 | } | |
648 | ||
e98be2d5 WF |
649 | static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, |
650 | unsigned long elapsed, | |
651 | unsigned long written) | |
652 | { | |
653 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
654 | unsigned long avg = bdi->avg_write_bandwidth; | |
655 | unsigned long old = bdi->write_bandwidth; | |
656 | u64 bw; | |
657 | ||
658 | /* | |
659 | * bw = written * HZ / elapsed | |
660 | * | |
661 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
662 | * write_bandwidth = --------------------------------------------------- | |
663 | * period | |
664 | */ | |
665 | bw = written - bdi->written_stamp; | |
666 | bw *= HZ; | |
667 | if (unlikely(elapsed > period)) { | |
668 | do_div(bw, elapsed); | |
669 | avg = bw; | |
670 | goto out; | |
671 | } | |
672 | bw += (u64)bdi->write_bandwidth * (period - elapsed); | |
673 | bw >>= ilog2(period); | |
674 | ||
675 | /* | |
676 | * one more level of smoothing, for filtering out sudden spikes | |
677 | */ | |
678 | if (avg > old && old >= (unsigned long)bw) | |
679 | avg -= (avg - old) >> 3; | |
680 | ||
681 | if (avg < old && old <= (unsigned long)bw) | |
682 | avg += (old - avg) >> 3; | |
683 | ||
684 | out: | |
685 | bdi->write_bandwidth = bw; | |
686 | bdi->avg_write_bandwidth = avg; | |
687 | } | |
688 | ||
c42843f2 WF |
689 | /* |
690 | * The global dirtyable memory and dirty threshold could be suddenly knocked | |
691 | * down by a large amount (eg. on the startup of KVM in a swapless system). | |
692 | * This may throw the system into deep dirty exceeded state and throttle | |
693 | * heavy/light dirtiers alike. To retain good responsiveness, maintain | |
694 | * global_dirty_limit for tracking slowly down to the knocked down dirty | |
695 | * threshold. | |
696 | */ | |
697 | static void update_dirty_limit(unsigned long thresh, unsigned long dirty) | |
698 | { | |
699 | unsigned long limit = global_dirty_limit; | |
700 | ||
701 | /* | |
702 | * Follow up in one step. | |
703 | */ | |
704 | if (limit < thresh) { | |
705 | limit = thresh; | |
706 | goto update; | |
707 | } | |
708 | ||
709 | /* | |
710 | * Follow down slowly. Use the higher one as the target, because thresh | |
711 | * may drop below dirty. This is exactly the reason to introduce | |
712 | * global_dirty_limit which is guaranteed to lie above the dirty pages. | |
713 | */ | |
714 | thresh = max(thresh, dirty); | |
715 | if (limit > thresh) { | |
716 | limit -= (limit - thresh) >> 5; | |
717 | goto update; | |
718 | } | |
719 | return; | |
720 | update: | |
721 | global_dirty_limit = limit; | |
722 | } | |
723 | ||
724 | static void global_update_bandwidth(unsigned long thresh, | |
725 | unsigned long dirty, | |
726 | unsigned long now) | |
727 | { | |
728 | static DEFINE_SPINLOCK(dirty_lock); | |
729 | static unsigned long update_time; | |
730 | ||
731 | /* | |
732 | * check locklessly first to optimize away locking for the most time | |
733 | */ | |
734 | if (time_before(now, update_time + BANDWIDTH_INTERVAL)) | |
735 | return; | |
736 | ||
737 | spin_lock(&dirty_lock); | |
738 | if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) { | |
739 | update_dirty_limit(thresh, dirty); | |
740 | update_time = now; | |
741 | } | |
742 | spin_unlock(&dirty_lock); | |
743 | } | |
744 | ||
be3ffa27 WF |
745 | /* |
746 | * Maintain bdi->dirty_ratelimit, the base dirty throttle rate. | |
747 | * | |
748 | * Normal bdi tasks will be curbed at or below it in long term. | |
749 | * Obviously it should be around (write_bw / N) when there are N dd tasks. | |
750 | */ | |
751 | static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, | |
752 | unsigned long thresh, | |
753 | unsigned long bg_thresh, | |
754 | unsigned long dirty, | |
755 | unsigned long bdi_thresh, | |
756 | unsigned long bdi_dirty, | |
757 | unsigned long dirtied, | |
758 | unsigned long elapsed) | |
759 | { | |
7381131c WF |
760 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); |
761 | unsigned long limit = hard_dirty_limit(thresh); | |
762 | unsigned long setpoint = (freerun + limit) / 2; | |
be3ffa27 WF |
763 | unsigned long write_bw = bdi->avg_write_bandwidth; |
764 | unsigned long dirty_ratelimit = bdi->dirty_ratelimit; | |
765 | unsigned long dirty_rate; | |
766 | unsigned long task_ratelimit; | |
767 | unsigned long balanced_dirty_ratelimit; | |
768 | unsigned long pos_ratio; | |
7381131c WF |
769 | unsigned long step; |
770 | unsigned long x; | |
be3ffa27 WF |
771 | |
772 | /* | |
773 | * The dirty rate will match the writeout rate in long term, except | |
774 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
775 | */ | |
776 | dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; | |
777 | ||
778 | pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, | |
779 | bdi_thresh, bdi_dirty); | |
780 | /* | |
781 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
782 | */ | |
783 | task_ratelimit = (u64)dirty_ratelimit * | |
784 | pos_ratio >> RATELIMIT_CALC_SHIFT; | |
785 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ | |
786 | ||
787 | /* | |
788 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
789 | * if there are N dd tasks, each throttled at task_ratelimit, the bdi's | |
790 | * dirty_rate will be measured to be (N * task_ratelimit). So the below | |
791 | * formula will yield the balanced rate limit (write_bw / N). | |
792 | * | |
793 | * Note that the expanded form is not a pure rate feedback: | |
794 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
795 | * but also takes pos_ratio into account: | |
796 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
797 | * | |
798 | * (1) is not realistic because pos_ratio also takes part in balancing | |
799 | * the dirty rate. Consider the state | |
800 | * pos_ratio = 0.5 (3) | |
801 | * rate = 2 * (write_bw / N) (4) | |
802 | * If (1) is used, it will stuck in that state! Because each dd will | |
803 | * be throttled at | |
804 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
805 | * yielding | |
806 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
807 | * put (6) into (1) we get | |
808 | * rate_(i+1) = rate_(i) (7) | |
809 | * | |
810 | * So we end up using (2) to always keep | |
811 | * rate_(i+1) ~= (write_bw / N) (8) | |
812 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
813 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
814 | * the dirty count meet the setpoint, but also where the slope of | |
815 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
816 | */ | |
817 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
818 | dirty_rate | 1); | |
819 | ||
7381131c WF |
820 | /* |
821 | * We could safely do this and return immediately: | |
822 | * | |
823 | * bdi->dirty_ratelimit = balanced_dirty_ratelimit; | |
824 | * | |
825 | * However to get a more stable dirty_ratelimit, the below elaborated | |
826 | * code makes use of task_ratelimit to filter out sigular points and | |
827 | * limit the step size. | |
828 | * | |
829 | * The below code essentially only uses the relative value of | |
830 | * | |
831 | * task_ratelimit - dirty_ratelimit | |
832 | * = (pos_ratio - 1) * dirty_ratelimit | |
833 | * | |
834 | * which reflects the direction and size of dirty position error. | |
835 | */ | |
836 | ||
837 | /* | |
838 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff | |
839 | * task_ratelimit is on the same side of dirty_ratelimit, too. | |
840 | * For example, when | |
841 | * - dirty_ratelimit > balanced_dirty_ratelimit | |
842 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) | |
843 | * lowering dirty_ratelimit will help meet both the position and rate | |
844 | * control targets. Otherwise, don't update dirty_ratelimit if it will | |
845 | * only help meet the rate target. After all, what the users ultimately | |
846 | * feel and care are stable dirty rate and small position error. | |
847 | * | |
848 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size | |
849 | * and filter out the sigular points of balanced_dirty_ratelimit. Which | |
850 | * keeps jumping around randomly and can even leap far away at times | |
851 | * due to the small 200ms estimation period of dirty_rate (we want to | |
852 | * keep that period small to reduce time lags). | |
853 | */ | |
854 | step = 0; | |
855 | if (dirty < setpoint) { | |
856 | x = min(bdi->balanced_dirty_ratelimit, | |
857 | min(balanced_dirty_ratelimit, task_ratelimit)); | |
858 | if (dirty_ratelimit < x) | |
859 | step = x - dirty_ratelimit; | |
860 | } else { | |
861 | x = max(bdi->balanced_dirty_ratelimit, | |
862 | max(balanced_dirty_ratelimit, task_ratelimit)); | |
863 | if (dirty_ratelimit > x) | |
864 | step = dirty_ratelimit - x; | |
865 | } | |
866 | ||
867 | /* | |
868 | * Don't pursue 100% rate matching. It's impossible since the balanced | |
869 | * rate itself is constantly fluctuating. So decrease the track speed | |
870 | * when it gets close to the target. Helps eliminate pointless tremors. | |
871 | */ | |
872 | step >>= dirty_ratelimit / (2 * step + 1); | |
873 | /* | |
874 | * Limit the tracking speed to avoid overshooting. | |
875 | */ | |
876 | step = (step + 7) / 8; | |
877 | ||
878 | if (dirty_ratelimit < balanced_dirty_ratelimit) | |
879 | dirty_ratelimit += step; | |
880 | else | |
881 | dirty_ratelimit -= step; | |
882 | ||
883 | bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL); | |
884 | bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit; | |
b48c104d WF |
885 | |
886 | trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit); | |
be3ffa27 WF |
887 | } |
888 | ||
e98be2d5 | 889 | void __bdi_update_bandwidth(struct backing_dev_info *bdi, |
c42843f2 | 890 | unsigned long thresh, |
af6a3113 | 891 | unsigned long bg_thresh, |
c42843f2 WF |
892 | unsigned long dirty, |
893 | unsigned long bdi_thresh, | |
894 | unsigned long bdi_dirty, | |
e98be2d5 WF |
895 | unsigned long start_time) |
896 | { | |
897 | unsigned long now = jiffies; | |
898 | unsigned long elapsed = now - bdi->bw_time_stamp; | |
be3ffa27 | 899 | unsigned long dirtied; |
e98be2d5 WF |
900 | unsigned long written; |
901 | ||
902 | /* | |
903 | * rate-limit, only update once every 200ms. | |
904 | */ | |
905 | if (elapsed < BANDWIDTH_INTERVAL) | |
906 | return; | |
907 | ||
be3ffa27 | 908 | dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); |
e98be2d5 WF |
909 | written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); |
910 | ||
911 | /* | |
912 | * Skip quiet periods when disk bandwidth is under-utilized. | |
913 | * (at least 1s idle time between two flusher runs) | |
914 | */ | |
915 | if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) | |
916 | goto snapshot; | |
917 | ||
be3ffa27 | 918 | if (thresh) { |
c42843f2 | 919 | global_update_bandwidth(thresh, dirty, now); |
be3ffa27 WF |
920 | bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, |
921 | bdi_thresh, bdi_dirty, | |
922 | dirtied, elapsed); | |
923 | } | |
e98be2d5 WF |
924 | bdi_update_write_bandwidth(bdi, elapsed, written); |
925 | ||
926 | snapshot: | |
be3ffa27 | 927 | bdi->dirtied_stamp = dirtied; |
e98be2d5 WF |
928 | bdi->written_stamp = written; |
929 | bdi->bw_time_stamp = now; | |
930 | } | |
931 | ||
932 | static void bdi_update_bandwidth(struct backing_dev_info *bdi, | |
c42843f2 | 933 | unsigned long thresh, |
af6a3113 | 934 | unsigned long bg_thresh, |
c42843f2 WF |
935 | unsigned long dirty, |
936 | unsigned long bdi_thresh, | |
937 | unsigned long bdi_dirty, | |
e98be2d5 WF |
938 | unsigned long start_time) |
939 | { | |
940 | if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) | |
941 | return; | |
942 | spin_lock(&bdi->wb.list_lock); | |
af6a3113 WF |
943 | __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, |
944 | bdi_thresh, bdi_dirty, start_time); | |
e98be2d5 WF |
945 | spin_unlock(&bdi->wb.list_lock); |
946 | } | |
947 | ||
9d823e8f WF |
948 | /* |
949 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited_nr() | |
950 | * will look to see if it needs to start dirty throttling. | |
951 | * | |
952 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive | |
953 | * global_page_state() too often. So scale it near-sqrt to the safety margin | |
954 | * (the number of pages we may dirty without exceeding the dirty limits). | |
955 | */ | |
956 | static unsigned long dirty_poll_interval(unsigned long dirty, | |
957 | unsigned long thresh) | |
958 | { | |
959 | if (thresh > dirty) | |
960 | return 1UL << (ilog2(thresh - dirty) >> 1); | |
961 | ||
962 | return 1; | |
963 | } | |
964 | ||
c8462cc9 WF |
965 | static unsigned long bdi_max_pause(struct backing_dev_info *bdi, |
966 | unsigned long bdi_dirty) | |
967 | { | |
968 | unsigned long bw = bdi->avg_write_bandwidth; | |
969 | unsigned long hi = ilog2(bw); | |
970 | unsigned long lo = ilog2(bdi->dirty_ratelimit); | |
971 | unsigned long t; | |
972 | ||
973 | /* target for 20ms max pause on 1-dd case */ | |
974 | t = HZ / 50; | |
975 | ||
976 | /* | |
977 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
978 | * overheads. | |
979 | * | |
980 | * (N * 20ms) on 2^N concurrent tasks. | |
981 | */ | |
982 | if (hi > lo) | |
983 | t += (hi - lo) * (20 * HZ) / 1024; | |
984 | ||
985 | /* | |
986 | * Limit pause time for small memory systems. If sleeping for too long | |
987 | * time, a small pool of dirty/writeback pages may go empty and disk go | |
988 | * idle. | |
989 | * | |
990 | * 8 serves as the safety ratio. | |
991 | */ | |
82e230a0 | 992 | t = min(t, bdi_dirty * HZ / (8 * bw + 1)); |
c8462cc9 WF |
993 | |
994 | /* | |
995 | * The pause time will be settled within range (max_pause/4, max_pause). | |
996 | * Apply a minimal value of 4 to get a non-zero max_pause/4. | |
997 | */ | |
998 | return clamp_val(t, 4, MAX_PAUSE); | |
999 | } | |
1000 | ||
1da177e4 LT |
1001 | /* |
1002 | * balance_dirty_pages() must be called by processes which are generating dirty | |
1003 | * data. It looks at the number of dirty pages in the machine and will force | |
143dfe86 | 1004 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1005 | * If we're over `background_thresh' then the writeback threads are woken to |
1006 | * perform some writeout. | |
1da177e4 | 1007 | */ |
3a2e9a5a | 1008 | static void balance_dirty_pages(struct address_space *mapping, |
143dfe86 | 1009 | unsigned long pages_dirtied) |
1da177e4 | 1010 | { |
143dfe86 WF |
1011 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
1012 | unsigned long bdi_reclaimable; | |
7762741e WF |
1013 | unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ |
1014 | unsigned long bdi_dirty; | |
6c14ae1e | 1015 | unsigned long freerun; |
364aeb28 DR |
1016 | unsigned long background_thresh; |
1017 | unsigned long dirty_thresh; | |
1018 | unsigned long bdi_thresh; | |
143dfe86 | 1019 | long pause = 0; |
50657fc4 | 1020 | long uninitialized_var(max_pause); |
e50e3720 | 1021 | bool dirty_exceeded = false; |
143dfe86 | 1022 | unsigned long task_ratelimit; |
50657fc4 | 1023 | unsigned long uninitialized_var(dirty_ratelimit); |
143dfe86 | 1024 | unsigned long pos_ratio; |
1da177e4 | 1025 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
e98be2d5 | 1026 | unsigned long start_time = jiffies; |
1da177e4 LT |
1027 | |
1028 | for (;;) { | |
143dfe86 WF |
1029 | /* |
1030 | * Unstable writes are a feature of certain networked | |
1031 | * filesystems (i.e. NFS) in which data may have been | |
1032 | * written to the server's write cache, but has not yet | |
1033 | * been flushed to permanent storage. | |
1034 | */ | |
5fce25a9 PZ |
1035 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
1036 | global_page_state(NR_UNSTABLE_NFS); | |
7762741e | 1037 | nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
5fce25a9 | 1038 | |
16c4042f WF |
1039 | global_dirty_limits(&background_thresh, &dirty_thresh); |
1040 | ||
1041 | /* | |
1042 | * Throttle it only when the background writeback cannot | |
1043 | * catch-up. This avoids (excessively) small writeouts | |
1044 | * when the bdi limits are ramping up. | |
1045 | */ | |
6c14ae1e WF |
1046 | freerun = dirty_freerun_ceiling(dirty_thresh, |
1047 | background_thresh); | |
1048 | if (nr_dirty <= freerun) | |
16c4042f WF |
1049 | break; |
1050 | ||
143dfe86 WF |
1051 | if (unlikely(!writeback_in_progress(bdi))) |
1052 | bdi_start_background_writeback(bdi); | |
1053 | ||
1054 | /* | |
1055 | * bdi_thresh is not treated as some limiting factor as | |
1056 | * dirty_thresh, due to reasons | |
1057 | * - in JBOD setup, bdi_thresh can fluctuate a lot | |
1058 | * - in a system with HDD and USB key, the USB key may somehow | |
1059 | * go into state (bdi_dirty >> bdi_thresh) either because | |
1060 | * bdi_dirty starts high, or because bdi_thresh drops low. | |
1061 | * In this case we don't want to hard throttle the USB key | |
1062 | * dirtiers for 100 seconds until bdi_dirty drops under | |
1063 | * bdi_thresh. Instead the auxiliary bdi control line in | |
1064 | * bdi_position_ratio() will let the dirtier task progress | |
1065 | * at some rate <= (write_bw / 2) for bringing down bdi_dirty. | |
1066 | */ | |
16c4042f | 1067 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); |
16c4042f | 1068 | |
e50e3720 WF |
1069 | /* |
1070 | * In order to avoid the stacked BDI deadlock we need | |
1071 | * to ensure we accurately count the 'dirty' pages when | |
1072 | * the threshold is low. | |
1073 | * | |
1074 | * Otherwise it would be possible to get thresh+n pages | |
1075 | * reported dirty, even though there are thresh-m pages | |
1076 | * actually dirty; with m+n sitting in the percpu | |
1077 | * deltas. | |
1078 | */ | |
143dfe86 WF |
1079 | if (bdi_thresh < 2 * bdi_stat_error(bdi)) { |
1080 | bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); | |
1081 | bdi_dirty = bdi_reclaimable + | |
7762741e | 1082 | bdi_stat_sum(bdi, BDI_WRITEBACK); |
e50e3720 | 1083 | } else { |
143dfe86 WF |
1084 | bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
1085 | bdi_dirty = bdi_reclaimable + | |
7762741e | 1086 | bdi_stat(bdi, BDI_WRITEBACK); |
e50e3720 | 1087 | } |
5fce25a9 | 1088 | |
143dfe86 | 1089 | dirty_exceeded = (bdi_dirty > bdi_thresh) || |
7762741e | 1090 | (nr_dirty > dirty_thresh); |
143dfe86 | 1091 | if (dirty_exceeded && !bdi->dirty_exceeded) |
04fbfdc1 | 1092 | bdi->dirty_exceeded = 1; |
1da177e4 | 1093 | |
af6a3113 WF |
1094 | bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, |
1095 | nr_dirty, bdi_thresh, bdi_dirty, | |
1096 | start_time); | |
e98be2d5 | 1097 | |
c8462cc9 WF |
1098 | max_pause = bdi_max_pause(bdi, bdi_dirty); |
1099 | ||
143dfe86 WF |
1100 | dirty_ratelimit = bdi->dirty_ratelimit; |
1101 | pos_ratio = bdi_position_ratio(bdi, dirty_thresh, | |
1102 | background_thresh, nr_dirty, | |
1103 | bdi_thresh, bdi_dirty); | |
3a73dbbc WF |
1104 | task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> |
1105 | RATELIMIT_CALC_SHIFT; | |
1106 | if (unlikely(task_ratelimit == 0)) { | |
c8462cc9 | 1107 | pause = max_pause; |
143dfe86 | 1108 | goto pause; |
04fbfdc1 | 1109 | } |
3a73dbbc | 1110 | pause = HZ * pages_dirtied / task_ratelimit; |
57fc978c | 1111 | if (unlikely(pause <= 0)) { |
ece13ac3 WF |
1112 | trace_balance_dirty_pages(bdi, |
1113 | dirty_thresh, | |
1114 | background_thresh, | |
1115 | nr_dirty, | |
1116 | bdi_thresh, | |
1117 | bdi_dirty, | |
1118 | dirty_ratelimit, | |
1119 | task_ratelimit, | |
1120 | pages_dirtied, | |
1121 | pause, | |
1122 | start_time); | |
57fc978c WF |
1123 | pause = 1; /* avoid resetting nr_dirtied_pause below */ |
1124 | break; | |
04fbfdc1 | 1125 | } |
c8462cc9 | 1126 | pause = min(pause, max_pause); |
143dfe86 WF |
1127 | |
1128 | pause: | |
ece13ac3 WF |
1129 | trace_balance_dirty_pages(bdi, |
1130 | dirty_thresh, | |
1131 | background_thresh, | |
1132 | nr_dirty, | |
1133 | bdi_thresh, | |
1134 | bdi_dirty, | |
1135 | dirty_ratelimit, | |
1136 | task_ratelimit, | |
1137 | pages_dirtied, | |
1138 | pause, | |
1139 | start_time); | |
499d05ec | 1140 | __set_current_state(TASK_KILLABLE); |
d25105e8 | 1141 | io_schedule_timeout(pause); |
87c6a9b2 | 1142 | |
ffd1f609 | 1143 | /* |
1df64719 WF |
1144 | * This is typically equal to (nr_dirty < dirty_thresh) and can |
1145 | * also keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1146 | */ |
1df64719 | 1147 | if (task_ratelimit) |
ffd1f609 | 1148 | break; |
499d05ec | 1149 | |
c5c6343c WF |
1150 | /* |
1151 | * In the case of an unresponding NFS server and the NFS dirty | |
1152 | * pages exceeds dirty_thresh, give the other good bdi's a pipe | |
1153 | * to go through, so that tasks on them still remain responsive. | |
1154 | * | |
1155 | * In theory 1 page is enough to keep the comsumer-producer | |
1156 | * pipe going: the flusher cleans 1 page => the task dirties 1 | |
1157 | * more page. However bdi_dirty has accounting errors. So use | |
1158 | * the larger and more IO friendly bdi_stat_error. | |
1159 | */ | |
1160 | if (bdi_dirty <= bdi_stat_error(bdi)) | |
1161 | break; | |
1162 | ||
499d05ec JK |
1163 | if (fatal_signal_pending(current)) |
1164 | break; | |
1da177e4 LT |
1165 | } |
1166 | ||
143dfe86 | 1167 | if (!dirty_exceeded && bdi->dirty_exceeded) |
04fbfdc1 | 1168 | bdi->dirty_exceeded = 0; |
1da177e4 | 1169 | |
9d823e8f | 1170 | current->nr_dirtied = 0; |
57fc978c WF |
1171 | if (pause == 0) { /* in freerun area */ |
1172 | current->nr_dirtied_pause = | |
1173 | dirty_poll_interval(nr_dirty, dirty_thresh); | |
1174 | } else if (pause <= max_pause / 4 && | |
1175 | pages_dirtied >= current->nr_dirtied_pause) { | |
1176 | current->nr_dirtied_pause = clamp_val( | |
1177 | dirty_ratelimit * (max_pause / 2) / HZ, | |
1178 | pages_dirtied + pages_dirtied / 8, | |
1179 | pages_dirtied * 4); | |
1180 | } else if (pause >= max_pause) { | |
1181 | current->nr_dirtied_pause = 1 | clamp_val( | |
1182 | dirty_ratelimit * (max_pause / 2) / HZ, | |
1183 | pages_dirtied / 4, | |
1184 | pages_dirtied - pages_dirtied / 8); | |
1185 | } | |
9d823e8f | 1186 | |
1da177e4 | 1187 | if (writeback_in_progress(bdi)) |
5b0830cb | 1188 | return; |
1da177e4 LT |
1189 | |
1190 | /* | |
1191 | * In laptop mode, we wait until hitting the higher threshold before | |
1192 | * starting background writeout, and then write out all the way down | |
1193 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1194 | * | |
1195 | * In normal mode, we start background writeout at the lower | |
1196 | * background_thresh, to keep the amount of dirty memory low. | |
1197 | */ | |
143dfe86 WF |
1198 | if (laptop_mode) |
1199 | return; | |
1200 | ||
1201 | if (nr_reclaimable > background_thresh) | |
c5444198 | 1202 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
1203 | } |
1204 | ||
a200ee18 | 1205 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 1206 | { |
a200ee18 | 1207 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
1208 | struct address_space *mapping = page_mapping(page); |
1209 | ||
1210 | if (mapping) | |
1211 | balance_dirty_pages_ratelimited(mapping); | |
1212 | } | |
1213 | } | |
1214 | ||
9d823e8f | 1215 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1216 | |
54848d73 WF |
1217 | /* |
1218 | * Normal tasks are throttled by | |
1219 | * loop { | |
1220 | * dirty tsk->nr_dirtied_pause pages; | |
1221 | * take a snap in balance_dirty_pages(); | |
1222 | * } | |
1223 | * However there is a worst case. If every task exit immediately when dirtied | |
1224 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be | |
1225 | * called to throttle the page dirties. The solution is to save the not yet | |
1226 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them | |
1227 | * randomly into the running tasks. This works well for the above worst case, | |
1228 | * as the new task will pick up and accumulate the old task's leaked dirty | |
1229 | * count and eventually get throttled. | |
1230 | */ | |
1231 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1232 | ||
1da177e4 | 1233 | /** |
fa5a734e | 1234 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 1235 | * @mapping: address_space which was dirtied |
a580290c | 1236 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
1237 | * |
1238 | * Processes which are dirtying memory should call in here once for each page | |
1239 | * which was newly dirtied. The function will periodically check the system's | |
1240 | * dirty state and will initiate writeback if needed. | |
1241 | * | |
1242 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
1243 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
1244 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
1245 | * from overshooting the limit by (ratelimit_pages) each. | |
1246 | */ | |
fa5a734e AM |
1247 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
1248 | unsigned long nr_pages_dirtied) | |
1da177e4 | 1249 | { |
36715cef | 1250 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
9d823e8f WF |
1251 | int ratelimit; |
1252 | int *p; | |
1da177e4 | 1253 | |
36715cef WF |
1254 | if (!bdi_cap_account_dirty(bdi)) |
1255 | return; | |
1256 | ||
9d823e8f WF |
1257 | ratelimit = current->nr_dirtied_pause; |
1258 | if (bdi->dirty_exceeded) | |
1259 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); | |
1260 | ||
1261 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1262 | |
9d823e8f | 1263 | preempt_disable(); |
1da177e4 | 1264 | /* |
9d823e8f WF |
1265 | * This prevents one CPU to accumulate too many dirtied pages without |
1266 | * calling into balance_dirty_pages(), which can happen when there are | |
1267 | * 1000+ tasks, all of them start dirtying pages at exactly the same | |
1268 | * time, hence all honoured too large initial task->nr_dirtied_pause. | |
1da177e4 | 1269 | */ |
245b2e70 | 1270 | p = &__get_cpu_var(bdp_ratelimits); |
9d823e8f | 1271 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1272 | *p = 0; |
9d823e8f WF |
1273 | else { |
1274 | *p += nr_pages_dirtied; | |
1275 | if (unlikely(*p >= ratelimit_pages)) { | |
1276 | *p = 0; | |
1277 | ratelimit = 0; | |
1278 | } | |
1da177e4 | 1279 | } |
54848d73 WF |
1280 | /* |
1281 | * Pick up the dirtied pages by the exited tasks. This avoids lots of | |
1282 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping | |
1283 | * the dirty throttling and livelock other long-run dirtiers. | |
1284 | */ | |
1285 | p = &__get_cpu_var(dirty_throttle_leaks); | |
1286 | if (*p > 0 && current->nr_dirtied < ratelimit) { | |
1287 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); | |
1288 | *p -= nr_pages_dirtied; | |
1289 | current->nr_dirtied += nr_pages_dirtied; | |
1290 | } | |
fa5a734e | 1291 | preempt_enable(); |
9d823e8f WF |
1292 | |
1293 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
1294 | balance_dirty_pages(mapping, current->nr_dirtied); | |
1da177e4 | 1295 | } |
fa5a734e | 1296 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 1297 | |
232ea4d6 | 1298 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 1299 | { |
364aeb28 DR |
1300 | unsigned long background_thresh; |
1301 | unsigned long dirty_thresh; | |
1da177e4 LT |
1302 | |
1303 | for ( ; ; ) { | |
16c4042f | 1304 | global_dirty_limits(&background_thresh, &dirty_thresh); |
1da177e4 LT |
1305 | |
1306 | /* | |
1307 | * Boost the allowable dirty threshold a bit for page | |
1308 | * allocators so they don't get DoS'ed by heavy writers | |
1309 | */ | |
1310 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
1311 | ||
c24f21bd CL |
1312 | if (global_page_state(NR_UNSTABLE_NFS) + |
1313 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
1314 | break; | |
8aa7e847 | 1315 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
1316 | |
1317 | /* | |
1318 | * The caller might hold locks which can prevent IO completion | |
1319 | * or progress in the filesystem. So we cannot just sit here | |
1320 | * waiting for IO to complete. | |
1321 | */ | |
1322 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
1323 | break; | |
1da177e4 LT |
1324 | } |
1325 | } | |
1326 | ||
1da177e4 LT |
1327 | /* |
1328 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1329 | */ | |
1330 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 1331 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1332 | { |
8d65af78 | 1333 | proc_dointvec(table, write, buffer, length, ppos); |
6423104b | 1334 | bdi_arm_supers_timer(); |
1da177e4 LT |
1335 | return 0; |
1336 | } | |
1337 | ||
c2c4986e | 1338 | #ifdef CONFIG_BLOCK |
31373d09 | 1339 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 1340 | { |
31373d09 MG |
1341 | struct request_queue *q = (struct request_queue *)data; |
1342 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
1343 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 | 1344 | |
31373d09 MG |
1345 | /* |
1346 | * We want to write everything out, not just down to the dirty | |
1347 | * threshold | |
1348 | */ | |
31373d09 | 1349 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
0e175a18 CW |
1350 | bdi_start_writeback(&q->backing_dev_info, nr_pages, |
1351 | WB_REASON_LAPTOP_TIMER); | |
1da177e4 LT |
1352 | } |
1353 | ||
1354 | /* | |
1355 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
1356 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
1357 | * then push it back - the user is still using the disk. | |
1358 | */ | |
31373d09 | 1359 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 1360 | { |
31373d09 | 1361 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
1362 | } |
1363 | ||
1364 | /* | |
1365 | * We're in laptop mode and we've just synced. The sync's writes will have | |
1366 | * caused another writeback to be scheduled by laptop_io_completion. | |
1367 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
1368 | */ | |
1369 | void laptop_sync_completion(void) | |
1370 | { | |
31373d09 MG |
1371 | struct backing_dev_info *bdi; |
1372 | ||
1373 | rcu_read_lock(); | |
1374 | ||
1375 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
1376 | del_timer(&bdi->laptop_mode_wb_timer); | |
1377 | ||
1378 | rcu_read_unlock(); | |
1da177e4 | 1379 | } |
c2c4986e | 1380 | #endif |
1da177e4 LT |
1381 | |
1382 | /* | |
1383 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
1384 | * if a large number of processes all perform writes at the same time. | |
1385 | * If it is too low then SMP machines will call the (expensive) | |
1386 | * get_writeback_state too often. | |
1387 | * | |
1388 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
1389 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
9d823e8f | 1390 | * thresholds. |
1da177e4 LT |
1391 | */ |
1392 | ||
2d1d43f6 | 1393 | void writeback_set_ratelimit(void) |
1da177e4 | 1394 | { |
9d823e8f WF |
1395 | unsigned long background_thresh; |
1396 | unsigned long dirty_thresh; | |
1397 | global_dirty_limits(&background_thresh, &dirty_thresh); | |
1398 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); | |
1da177e4 LT |
1399 | if (ratelimit_pages < 16) |
1400 | ratelimit_pages = 16; | |
1da177e4 LT |
1401 | } |
1402 | ||
26c2143b | 1403 | static int __cpuinit |
1da177e4 LT |
1404 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
1405 | { | |
2d1d43f6 | 1406 | writeback_set_ratelimit(); |
aa0f0303 | 1407 | return NOTIFY_DONE; |
1da177e4 LT |
1408 | } |
1409 | ||
74b85f37 | 1410 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
1411 | .notifier_call = ratelimit_handler, |
1412 | .next = NULL, | |
1413 | }; | |
1414 | ||
1415 | /* | |
dc6e29da LT |
1416 | * Called early on to tune the page writeback dirty limits. |
1417 | * | |
1418 | * We used to scale dirty pages according to how total memory | |
1419 | * related to pages that could be allocated for buffers (by | |
1420 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
1421 | * | |
1422 | * However, that was when we used "dirty_ratio" to scale with | |
1423 | * all memory, and we don't do that any more. "dirty_ratio" | |
1424 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
1425 | * totalhigh_pages from vm_total_pages), and as such we can't | |
1426 | * get into the old insane situation any more where we had | |
1427 | * large amounts of dirty pages compared to a small amount of | |
1428 | * non-HIGHMEM memory. | |
1429 | * | |
1430 | * But we might still want to scale the dirty_ratio by how | |
1431 | * much memory the box has.. | |
1da177e4 LT |
1432 | */ |
1433 | void __init page_writeback_init(void) | |
1434 | { | |
04fbfdc1 PZ |
1435 | int shift; |
1436 | ||
2d1d43f6 | 1437 | writeback_set_ratelimit(); |
1da177e4 | 1438 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
1439 | |
1440 | shift = calc_period_shift(); | |
1441 | prop_descriptor_init(&vm_completions, shift); | |
1da177e4 LT |
1442 | } |
1443 | ||
f446daae JK |
1444 | /** |
1445 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
1446 | * @mapping: address space structure to write | |
1447 | * @start: starting page index | |
1448 | * @end: ending page index (inclusive) | |
1449 | * | |
1450 | * This function scans the page range from @start to @end (inclusive) and tags | |
1451 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
1452 | * that write_cache_pages (or whoever calls this function) will then use | |
1453 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
1454 | * used to avoid livelocking of writeback by a process steadily creating new | |
1455 | * dirty pages in the file (thus it is important for this function to be quick | |
1456 | * so that it can tag pages faster than a dirtying process can create them). | |
1457 | */ | |
1458 | /* | |
1459 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
1460 | */ | |
f446daae JK |
1461 | void tag_pages_for_writeback(struct address_space *mapping, |
1462 | pgoff_t start, pgoff_t end) | |
1463 | { | |
3c111a07 | 1464 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
1465 | unsigned long tagged; |
1466 | ||
1467 | do { | |
1468 | spin_lock_irq(&mapping->tree_lock); | |
1469 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
1470 | &start, end, WRITEBACK_TAG_BATCH, | |
1471 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
1472 | spin_unlock_irq(&mapping->tree_lock); | |
1473 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
1474 | cond_resched(); | |
d5ed3a4a JK |
1475 | /* We check 'start' to handle wrapping when end == ~0UL */ |
1476 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
1477 | } |
1478 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
1479 | ||
811d736f | 1480 | /** |
0ea97180 | 1481 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
1482 | * @mapping: address space structure to write |
1483 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
1484 | * @writepage: function called for each page |
1485 | * @data: data passed to writepage function | |
811d736f | 1486 | * |
0ea97180 | 1487 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
1488 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
1489 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
1490 | * and msync() need to guarantee that all the data which was dirty at the time | |
1491 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
1492 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
1493 | * existing IO to complete. | |
f446daae JK |
1494 | * |
1495 | * To avoid livelocks (when other process dirties new pages), we first tag | |
1496 | * pages which should be written back with TOWRITE tag and only then start | |
1497 | * writing them. For data-integrity sync we have to be careful so that we do | |
1498 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
1499 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
1500 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 1501 | */ |
0ea97180 MS |
1502 | int write_cache_pages(struct address_space *mapping, |
1503 | struct writeback_control *wbc, writepage_t writepage, | |
1504 | void *data) | |
811d736f | 1505 | { |
811d736f DH |
1506 | int ret = 0; |
1507 | int done = 0; | |
811d736f DH |
1508 | struct pagevec pvec; |
1509 | int nr_pages; | |
31a12666 | 1510 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
1511 | pgoff_t index; |
1512 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 1513 | pgoff_t done_index; |
31a12666 | 1514 | int cycled; |
811d736f | 1515 | int range_whole = 0; |
f446daae | 1516 | int tag; |
811d736f | 1517 | |
811d736f DH |
1518 | pagevec_init(&pvec, 0); |
1519 | if (wbc->range_cyclic) { | |
31a12666 NP |
1520 | writeback_index = mapping->writeback_index; /* prev offset */ |
1521 | index = writeback_index; | |
1522 | if (index == 0) | |
1523 | cycled = 1; | |
1524 | else | |
1525 | cycled = 0; | |
811d736f DH |
1526 | end = -1; |
1527 | } else { | |
1528 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
1529 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
1530 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
1531 | range_whole = 1; | |
31a12666 | 1532 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 1533 | } |
6e6938b6 | 1534 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
1535 | tag = PAGECACHE_TAG_TOWRITE; |
1536 | else | |
1537 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 1538 | retry: |
6e6938b6 | 1539 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 1540 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 1541 | done_index = index; |
5a3d5c98 NP |
1542 | while (!done && (index <= end)) { |
1543 | int i; | |
1544 | ||
f446daae | 1545 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
1546 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
1547 | if (nr_pages == 0) | |
1548 | break; | |
811d736f | 1549 | |
811d736f DH |
1550 | for (i = 0; i < nr_pages; i++) { |
1551 | struct page *page = pvec.pages[i]; | |
1552 | ||
1553 | /* | |
d5482cdf NP |
1554 | * At this point, the page may be truncated or |
1555 | * invalidated (changing page->mapping to NULL), or | |
1556 | * even swizzled back from swapper_space to tmpfs file | |
1557 | * mapping. However, page->index will not change | |
1558 | * because we have a reference on the page. | |
811d736f | 1559 | */ |
d5482cdf NP |
1560 | if (page->index > end) { |
1561 | /* | |
1562 | * can't be range_cyclic (1st pass) because | |
1563 | * end == -1 in that case. | |
1564 | */ | |
1565 | done = 1; | |
1566 | break; | |
1567 | } | |
1568 | ||
cf15b07c | 1569 | done_index = page->index; |
d5482cdf | 1570 | |
811d736f DH |
1571 | lock_page(page); |
1572 | ||
5a3d5c98 NP |
1573 | /* |
1574 | * Page truncated or invalidated. We can freely skip it | |
1575 | * then, even for data integrity operations: the page | |
1576 | * has disappeared concurrently, so there could be no | |
1577 | * real expectation of this data interity operation | |
1578 | * even if there is now a new, dirty page at the same | |
1579 | * pagecache address. | |
1580 | */ | |
811d736f | 1581 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 1582 | continue_unlock: |
811d736f DH |
1583 | unlock_page(page); |
1584 | continue; | |
1585 | } | |
1586 | ||
515f4a03 NP |
1587 | if (!PageDirty(page)) { |
1588 | /* someone wrote it for us */ | |
1589 | goto continue_unlock; | |
1590 | } | |
1591 | ||
1592 | if (PageWriteback(page)) { | |
1593 | if (wbc->sync_mode != WB_SYNC_NONE) | |
1594 | wait_on_page_writeback(page); | |
1595 | else | |
1596 | goto continue_unlock; | |
1597 | } | |
811d736f | 1598 | |
515f4a03 NP |
1599 | BUG_ON(PageWriteback(page)); |
1600 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 1601 | goto continue_unlock; |
811d736f | 1602 | |
9e094383 | 1603 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 1604 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
1605 | if (unlikely(ret)) { |
1606 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
1607 | unlock_page(page); | |
1608 | ret = 0; | |
1609 | } else { | |
1610 | /* | |
1611 | * done_index is set past this page, | |
1612 | * so media errors will not choke | |
1613 | * background writeout for the entire | |
1614 | * file. This has consequences for | |
1615 | * range_cyclic semantics (ie. it may | |
1616 | * not be suitable for data integrity | |
1617 | * writeout). | |
1618 | */ | |
cf15b07c | 1619 | done_index = page->index + 1; |
00266770 NP |
1620 | done = 1; |
1621 | break; | |
1622 | } | |
0b564927 | 1623 | } |
00266770 | 1624 | |
546a1924 DC |
1625 | /* |
1626 | * We stop writing back only if we are not doing | |
1627 | * integrity sync. In case of integrity sync we have to | |
1628 | * keep going until we have written all the pages | |
1629 | * we tagged for writeback prior to entering this loop. | |
1630 | */ | |
1631 | if (--wbc->nr_to_write <= 0 && | |
1632 | wbc->sync_mode == WB_SYNC_NONE) { | |
1633 | done = 1; | |
1634 | break; | |
05fe478d | 1635 | } |
811d736f DH |
1636 | } |
1637 | pagevec_release(&pvec); | |
1638 | cond_resched(); | |
1639 | } | |
3a4c6800 | 1640 | if (!cycled && !done) { |
811d736f | 1641 | /* |
31a12666 | 1642 | * range_cyclic: |
811d736f DH |
1643 | * We hit the last page and there is more work to be done: wrap |
1644 | * back to the start of the file | |
1645 | */ | |
31a12666 | 1646 | cycled = 1; |
811d736f | 1647 | index = 0; |
31a12666 | 1648 | end = writeback_index - 1; |
811d736f DH |
1649 | goto retry; |
1650 | } | |
0b564927 DC |
1651 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
1652 | mapping->writeback_index = done_index; | |
06d6cf69 | 1653 | |
811d736f DH |
1654 | return ret; |
1655 | } | |
0ea97180 MS |
1656 | EXPORT_SYMBOL(write_cache_pages); |
1657 | ||
1658 | /* | |
1659 | * Function used by generic_writepages to call the real writepage | |
1660 | * function and set the mapping flags on error | |
1661 | */ | |
1662 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1663 | void *data) | |
1664 | { | |
1665 | struct address_space *mapping = data; | |
1666 | int ret = mapping->a_ops->writepage(page, wbc); | |
1667 | mapping_set_error(mapping, ret); | |
1668 | return ret; | |
1669 | } | |
1670 | ||
1671 | /** | |
1672 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1673 | * @mapping: address space structure to write | |
1674 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1675 | * | |
1676 | * This is a library function, which implements the writepages() | |
1677 | * address_space_operation. | |
1678 | */ | |
1679 | int generic_writepages(struct address_space *mapping, | |
1680 | struct writeback_control *wbc) | |
1681 | { | |
9b6096a6 SL |
1682 | struct blk_plug plug; |
1683 | int ret; | |
1684 | ||
0ea97180 MS |
1685 | /* deal with chardevs and other special file */ |
1686 | if (!mapping->a_ops->writepage) | |
1687 | return 0; | |
1688 | ||
9b6096a6 SL |
1689 | blk_start_plug(&plug); |
1690 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
1691 | blk_finish_plug(&plug); | |
1692 | return ret; | |
0ea97180 | 1693 | } |
811d736f DH |
1694 | |
1695 | EXPORT_SYMBOL(generic_writepages); | |
1696 | ||
1da177e4 LT |
1697 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1698 | { | |
22905f77 AM |
1699 | int ret; |
1700 | ||
1da177e4 LT |
1701 | if (wbc->nr_to_write <= 0) |
1702 | return 0; | |
1703 | if (mapping->a_ops->writepages) | |
d08b3851 | 1704 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1705 | else |
1706 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1707 | return ret; |
1da177e4 LT |
1708 | } |
1709 | ||
1710 | /** | |
1711 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1712 | * @page: the page to write |
1713 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1714 | * |
1715 | * The page must be locked by the caller and will be unlocked upon return. | |
1716 | * | |
1717 | * write_one_page() returns a negative error code if I/O failed. | |
1718 | */ | |
1719 | int write_one_page(struct page *page, int wait) | |
1720 | { | |
1721 | struct address_space *mapping = page->mapping; | |
1722 | int ret = 0; | |
1723 | struct writeback_control wbc = { | |
1724 | .sync_mode = WB_SYNC_ALL, | |
1725 | .nr_to_write = 1, | |
1726 | }; | |
1727 | ||
1728 | BUG_ON(!PageLocked(page)); | |
1729 | ||
1730 | if (wait) | |
1731 | wait_on_page_writeback(page); | |
1732 | ||
1733 | if (clear_page_dirty_for_io(page)) { | |
1734 | page_cache_get(page); | |
1735 | ret = mapping->a_ops->writepage(page, &wbc); | |
1736 | if (ret == 0 && wait) { | |
1737 | wait_on_page_writeback(page); | |
1738 | if (PageError(page)) | |
1739 | ret = -EIO; | |
1740 | } | |
1741 | page_cache_release(page); | |
1742 | } else { | |
1743 | unlock_page(page); | |
1744 | } | |
1745 | return ret; | |
1746 | } | |
1747 | EXPORT_SYMBOL(write_one_page); | |
1748 | ||
76719325 KC |
1749 | /* |
1750 | * For address_spaces which do not use buffers nor write back. | |
1751 | */ | |
1752 | int __set_page_dirty_no_writeback(struct page *page) | |
1753 | { | |
1754 | if (!PageDirty(page)) | |
c3f0da63 | 1755 | return !TestSetPageDirty(page); |
76719325 KC |
1756 | return 0; |
1757 | } | |
1758 | ||
e3a7cca1 ES |
1759 | /* |
1760 | * Helper function for set_page_dirty family. | |
1761 | * NOTE: This relies on being atomic wrt interrupts. | |
1762 | */ | |
1763 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1764 | { | |
1765 | if (mapping_cap_account_dirty(mapping)) { | |
1766 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
ea941f0e | 1767 | __inc_zone_page_state(page, NR_DIRTIED); |
e3a7cca1 | 1768 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
c8e28ce0 | 1769 | __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); |
e3a7cca1 ES |
1770 | task_io_account_write(PAGE_CACHE_SIZE); |
1771 | } | |
1772 | } | |
679ceace | 1773 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 1774 | |
f629d1c9 MR |
1775 | /* |
1776 | * Helper function for set_page_writeback family. | |
1777 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic | |
1778 | * wrt interrupts. | |
1779 | */ | |
1780 | void account_page_writeback(struct page *page) | |
1781 | { | |
1782 | inc_zone_page_state(page, NR_WRITEBACK); | |
1783 | } | |
1784 | EXPORT_SYMBOL(account_page_writeback); | |
1785 | ||
1da177e4 LT |
1786 | /* |
1787 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1788 | * its radix tree. | |
1789 | * | |
1790 | * This is also used when a single buffer is being dirtied: we want to set the | |
1791 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1792 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1793 | * | |
1794 | * Most callers have locked the page, which pins the address_space in memory. | |
1795 | * But zap_pte_range() does not lock the page, however in that case the | |
1796 | * mapping is pinned by the vma's ->vm_file reference. | |
1797 | * | |
1798 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1799 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1800 | */ |
1801 | int __set_page_dirty_nobuffers(struct page *page) | |
1802 | { | |
1da177e4 LT |
1803 | if (!TestSetPageDirty(page)) { |
1804 | struct address_space *mapping = page_mapping(page); | |
1805 | struct address_space *mapping2; | |
1806 | ||
8c08540f AM |
1807 | if (!mapping) |
1808 | return 1; | |
1809 | ||
19fd6231 | 1810 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1811 | mapping2 = page_mapping(page); |
1812 | if (mapping2) { /* Race with truncate? */ | |
1813 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1814 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1815 | account_page_dirtied(page, mapping); |
8c08540f AM |
1816 | radix_tree_tag_set(&mapping->page_tree, |
1817 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1818 | } | |
19fd6231 | 1819 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1820 | if (mapping->host) { |
1821 | /* !PageAnon && !swapper_space */ | |
1822 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1823 | } |
4741c9fd | 1824 | return 1; |
1da177e4 | 1825 | } |
4741c9fd | 1826 | return 0; |
1da177e4 LT |
1827 | } |
1828 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
1829 | ||
1830 | /* | |
1831 | * When a writepage implementation decides that it doesn't want to write this | |
1832 | * page for some reason, it should redirty the locked page via | |
1833 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
1834 | */ | |
1835 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
1836 | { | |
1837 | wbc->pages_skipped++; | |
1838 | return __set_page_dirty_nobuffers(page); | |
1839 | } | |
1840 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
1841 | ||
1842 | /* | |
6746aff7 WF |
1843 | * Dirty a page. |
1844 | * | |
1845 | * For pages with a mapping this should be done under the page lock | |
1846 | * for the benefit of asynchronous memory errors who prefer a consistent | |
1847 | * dirty state. This rule can be broken in some special cases, | |
1848 | * but should be better not to. | |
1849 | * | |
1da177e4 LT |
1850 | * If the mapping doesn't provide a set_page_dirty a_op, then |
1851 | * just fall through and assume that it wants buffer_heads. | |
1852 | */ | |
1cf6e7d8 | 1853 | int set_page_dirty(struct page *page) |
1da177e4 LT |
1854 | { |
1855 | struct address_space *mapping = page_mapping(page); | |
1856 | ||
1857 | if (likely(mapping)) { | |
1858 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
1859 | /* |
1860 | * readahead/lru_deactivate_page could remain | |
1861 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
1862 | * About readahead, if the page is written, the flags would be | |
1863 | * reset. So no problem. | |
1864 | * About lru_deactivate_page, if the page is redirty, the flag | |
1865 | * will be reset. So no problem. but if the page is used by readahead | |
1866 | * it will confuse readahead and make it restart the size rampup | |
1867 | * process. But it's a trivial problem. | |
1868 | */ | |
1869 | ClearPageReclaim(page); | |
9361401e DH |
1870 | #ifdef CONFIG_BLOCK |
1871 | if (!spd) | |
1872 | spd = __set_page_dirty_buffers; | |
1873 | #endif | |
1874 | return (*spd)(page); | |
1da177e4 | 1875 | } |
4741c9fd AM |
1876 | if (!PageDirty(page)) { |
1877 | if (!TestSetPageDirty(page)) | |
1878 | return 1; | |
1879 | } | |
1da177e4 LT |
1880 | return 0; |
1881 | } | |
1882 | EXPORT_SYMBOL(set_page_dirty); | |
1883 | ||
1884 | /* | |
1885 | * set_page_dirty() is racy if the caller has no reference against | |
1886 | * page->mapping->host, and if the page is unlocked. This is because another | |
1887 | * CPU could truncate the page off the mapping and then free the mapping. | |
1888 | * | |
1889 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
1890 | * holds a reference on the inode by having an open file. | |
1891 | * | |
1892 | * In other cases, the page should be locked before running set_page_dirty(). | |
1893 | */ | |
1894 | int set_page_dirty_lock(struct page *page) | |
1895 | { | |
1896 | int ret; | |
1897 | ||
7eaceacc | 1898 | lock_page(page); |
1da177e4 LT |
1899 | ret = set_page_dirty(page); |
1900 | unlock_page(page); | |
1901 | return ret; | |
1902 | } | |
1903 | EXPORT_SYMBOL(set_page_dirty_lock); | |
1904 | ||
1da177e4 LT |
1905 | /* |
1906 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
1907 | * Returns true if the page was previously dirty. | |
1908 | * | |
1909 | * This is for preparing to put the page under writeout. We leave the page | |
1910 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
1911 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
1912 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
1913 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
1914 | * back into sync. | |
1915 | * | |
1916 | * This incoherency between the page's dirty flag and radix-tree tag is | |
1917 | * unfortunate, but it only exists while the page is locked. | |
1918 | */ | |
1919 | int clear_page_dirty_for_io(struct page *page) | |
1920 | { | |
1921 | struct address_space *mapping = page_mapping(page); | |
1922 | ||
79352894 NP |
1923 | BUG_ON(!PageLocked(page)); |
1924 | ||
7658cc28 LT |
1925 | if (mapping && mapping_cap_account_dirty(mapping)) { |
1926 | /* | |
1927 | * Yes, Virginia, this is indeed insane. | |
1928 | * | |
1929 | * We use this sequence to make sure that | |
1930 | * (a) we account for dirty stats properly | |
1931 | * (b) we tell the low-level filesystem to | |
1932 | * mark the whole page dirty if it was | |
1933 | * dirty in a pagetable. Only to then | |
1934 | * (c) clean the page again and return 1 to | |
1935 | * cause the writeback. | |
1936 | * | |
1937 | * This way we avoid all nasty races with the | |
1938 | * dirty bit in multiple places and clearing | |
1939 | * them concurrently from different threads. | |
1940 | * | |
1941 | * Note! Normally the "set_page_dirty(page)" | |
1942 | * has no effect on the actual dirty bit - since | |
1943 | * that will already usually be set. But we | |
1944 | * need the side effects, and it can help us | |
1945 | * avoid races. | |
1946 | * | |
1947 | * We basically use the page "master dirty bit" | |
1948 | * as a serialization point for all the different | |
1949 | * threads doing their things. | |
7658cc28 LT |
1950 | */ |
1951 | if (page_mkclean(page)) | |
1952 | set_page_dirty(page); | |
79352894 NP |
1953 | /* |
1954 | * We carefully synchronise fault handlers against | |
1955 | * installing a dirty pte and marking the page dirty | |
1956 | * at this point. We do this by having them hold the | |
1957 | * page lock at some point after installing their | |
1958 | * pte, but before marking the page dirty. | |
1959 | * Pages are always locked coming in here, so we get | |
1960 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
1961 | * for more comments. | |
1962 | */ | |
7658cc28 | 1963 | if (TestClearPageDirty(page)) { |
8c08540f | 1964 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
1965 | dec_bdi_stat(mapping->backing_dev_info, |
1966 | BDI_RECLAIMABLE); | |
7658cc28 | 1967 | return 1; |
1da177e4 | 1968 | } |
7658cc28 | 1969 | return 0; |
1da177e4 | 1970 | } |
7658cc28 | 1971 | return TestClearPageDirty(page); |
1da177e4 | 1972 | } |
58bb01a9 | 1973 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
1974 | |
1975 | int test_clear_page_writeback(struct page *page) | |
1976 | { | |
1977 | struct address_space *mapping = page_mapping(page); | |
1978 | int ret; | |
1979 | ||
1980 | if (mapping) { | |
69cb51d1 | 1981 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1982 | unsigned long flags; |
1983 | ||
19fd6231 | 1984 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1985 | ret = TestClearPageWriteback(page); |
69cb51d1 | 1986 | if (ret) { |
1da177e4 LT |
1987 | radix_tree_tag_clear(&mapping->page_tree, |
1988 | page_index(page), | |
1989 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1990 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 1991 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
1992 | __bdi_writeout_inc(bdi); |
1993 | } | |
69cb51d1 | 1994 | } |
19fd6231 | 1995 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1996 | } else { |
1997 | ret = TestClearPageWriteback(page); | |
1998 | } | |
99b12e3d | 1999 | if (ret) { |
d688abf5 | 2000 | dec_zone_page_state(page, NR_WRITEBACK); |
99b12e3d WF |
2001 | inc_zone_page_state(page, NR_WRITTEN); |
2002 | } | |
1da177e4 LT |
2003 | return ret; |
2004 | } | |
2005 | ||
2006 | int test_set_page_writeback(struct page *page) | |
2007 | { | |
2008 | struct address_space *mapping = page_mapping(page); | |
2009 | int ret; | |
2010 | ||
2011 | if (mapping) { | |
69cb51d1 | 2012 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
2013 | unsigned long flags; |
2014 | ||
19fd6231 | 2015 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2016 | ret = TestSetPageWriteback(page); |
69cb51d1 | 2017 | if (!ret) { |
1da177e4 LT |
2018 | radix_tree_tag_set(&mapping->page_tree, |
2019 | page_index(page), | |
2020 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2021 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
2022 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
2023 | } | |
1da177e4 LT |
2024 | if (!PageDirty(page)) |
2025 | radix_tree_tag_clear(&mapping->page_tree, | |
2026 | page_index(page), | |
2027 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
2028 | radix_tree_tag_clear(&mapping->page_tree, |
2029 | page_index(page), | |
2030 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 2031 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2032 | } else { |
2033 | ret = TestSetPageWriteback(page); | |
2034 | } | |
d688abf5 | 2035 | if (!ret) |
f629d1c9 | 2036 | account_page_writeback(page); |
1da177e4 LT |
2037 | return ret; |
2038 | ||
2039 | } | |
2040 | EXPORT_SYMBOL(test_set_page_writeback); | |
2041 | ||
2042 | /* | |
00128188 | 2043 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
2044 | * passed tag. |
2045 | */ | |
2046 | int mapping_tagged(struct address_space *mapping, int tag) | |
2047 | { | |
72c47832 | 2048 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
2049 | } |
2050 | EXPORT_SYMBOL(mapping_tagged); |