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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> | |
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 | |
1da177e4 LT |
39 | /* |
40 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
41 | * will look to see if it needs to force writeback or throttling. | |
42 | */ | |
43 | static long ratelimit_pages = 32; | |
44 | ||
1da177e4 LT |
45 | /* |
46 | * When balance_dirty_pages decides that the caller needs to perform some | |
47 | * non-background writeback, this is how many pages it will attempt to write. | |
3a2e9a5a | 48 | * It should be somewhat larger than dirtied pages to ensure that reasonably |
1da177e4 LT |
49 | * large amounts of I/O are submitted. |
50 | */ | |
3a2e9a5a | 51 | static inline long sync_writeback_pages(unsigned long dirtied) |
1da177e4 | 52 | { |
3a2e9a5a WF |
53 | if (dirtied < ratelimit_pages) |
54 | dirtied = ratelimit_pages; | |
55 | ||
56 | return dirtied + dirtied / 2; | |
1da177e4 LT |
57 | } |
58 | ||
59 | /* The following parameters are exported via /proc/sys/vm */ | |
60 | ||
61 | /* | |
5b0830cb | 62 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 63 | */ |
1b5e62b4 | 64 | int dirty_background_ratio = 10; |
1da177e4 | 65 | |
2da02997 DR |
66 | /* |
67 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
68 | * dirty_background_ratio * the amount of dirtyable memory | |
69 | */ | |
70 | unsigned long dirty_background_bytes; | |
71 | ||
195cf453 BG |
72 | /* |
73 | * free highmem will not be subtracted from the total free memory | |
74 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
75 | */ | |
76 | int vm_highmem_is_dirtyable; | |
77 | ||
1da177e4 LT |
78 | /* |
79 | * The generator of dirty data starts writeback at this percentage | |
80 | */ | |
1b5e62b4 | 81 | int vm_dirty_ratio = 20; |
1da177e4 | 82 | |
2da02997 DR |
83 | /* |
84 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
85 | * vm_dirty_ratio * the amount of dirtyable memory | |
86 | */ | |
87 | unsigned long vm_dirty_bytes; | |
88 | ||
1da177e4 | 89 | /* |
704503d8 | 90 | * The interval between `kupdate'-style writebacks |
1da177e4 | 91 | */ |
22ef37ee | 92 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 LT |
93 | |
94 | /* | |
704503d8 | 95 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 96 | */ |
22ef37ee | 97 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
98 | |
99 | /* | |
100 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
101 | */ | |
102 | int block_dump; | |
103 | ||
104 | /* | |
ed5b43f1 BS |
105 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
106 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
107 | */ |
108 | int laptop_mode; | |
109 | ||
110 | EXPORT_SYMBOL(laptop_mode); | |
111 | ||
112 | /* End of sysctl-exported parameters */ | |
113 | ||
114 | ||
04fbfdc1 PZ |
115 | /* |
116 | * Scale the writeback cache size proportional to the relative writeout speeds. | |
117 | * | |
118 | * We do this by keeping a floating proportion between BDIs, based on page | |
119 | * writeback completions [end_page_writeback()]. Those devices that write out | |
120 | * pages fastest will get the larger share, while the slower will get a smaller | |
121 | * share. | |
122 | * | |
123 | * We use page writeout completions because we are interested in getting rid of | |
124 | * dirty pages. Having them written out is the primary goal. | |
125 | * | |
126 | * We introduce a concept of time, a period over which we measure these events, | |
127 | * because demand can/will vary over time. The length of this period itself is | |
128 | * measured in page writeback completions. | |
129 | * | |
130 | */ | |
131 | static struct prop_descriptor vm_completions; | |
3e26c149 | 132 | static struct prop_descriptor vm_dirties; |
04fbfdc1 | 133 | |
04fbfdc1 PZ |
134 | /* |
135 | * couple the period to the dirty_ratio: | |
136 | * | |
137 | * period/2 ~ roundup_pow_of_two(dirty limit) | |
138 | */ | |
139 | static int calc_period_shift(void) | |
140 | { | |
141 | unsigned long dirty_total; | |
142 | ||
2da02997 DR |
143 | if (vm_dirty_bytes) |
144 | dirty_total = vm_dirty_bytes / PAGE_SIZE; | |
145 | else | |
146 | dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / | |
147 | 100; | |
04fbfdc1 PZ |
148 | return 2 + ilog2(dirty_total - 1); |
149 | } | |
150 | ||
151 | /* | |
2da02997 | 152 | * update the period when the dirty threshold changes. |
04fbfdc1 | 153 | */ |
2da02997 DR |
154 | static void update_completion_period(void) |
155 | { | |
156 | int shift = calc_period_shift(); | |
157 | prop_change_shift(&vm_completions, shift); | |
158 | prop_change_shift(&vm_dirties, shift); | |
159 | } | |
160 | ||
161 | int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
8d65af78 | 162 | void __user *buffer, size_t *lenp, |
2da02997 DR |
163 | loff_t *ppos) |
164 | { | |
165 | int ret; | |
166 | ||
8d65af78 | 167 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
168 | if (ret == 0 && write) |
169 | dirty_background_bytes = 0; | |
170 | return ret; | |
171 | } | |
172 | ||
173 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 174 | void __user *buffer, size_t *lenp, |
2da02997 DR |
175 | loff_t *ppos) |
176 | { | |
177 | int ret; | |
178 | ||
8d65af78 | 179 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
180 | if (ret == 0 && write) |
181 | dirty_background_ratio = 0; | |
182 | return ret; | |
183 | } | |
184 | ||
04fbfdc1 | 185 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 186 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
187 | loff_t *ppos) |
188 | { | |
189 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
190 | int ret; |
191 | ||
8d65af78 | 192 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 193 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
2da02997 DR |
194 | update_completion_period(); |
195 | vm_dirty_bytes = 0; | |
196 | } | |
197 | return ret; | |
198 | } | |
199 | ||
200 | ||
201 | int dirty_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 202 | void __user *buffer, size_t *lenp, |
2da02997 DR |
203 | loff_t *ppos) |
204 | { | |
fc3501d4 | 205 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
206 | int ret; |
207 | ||
8d65af78 | 208 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
209 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
210 | update_completion_period(); | |
211 | vm_dirty_ratio = 0; | |
04fbfdc1 PZ |
212 | } |
213 | return ret; | |
214 | } | |
215 | ||
216 | /* | |
217 | * Increment the BDI's writeout completion count and the global writeout | |
218 | * completion count. Called from test_clear_page_writeback(). | |
219 | */ | |
220 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
221 | { | |
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 | ||
1cf6e7d8 | 236 | void task_dirty_inc(struct task_struct *tsk) |
3e26c149 PZ |
237 | { |
238 | prop_inc_single(&vm_dirties, &tsk->dirties); | |
239 | } | |
240 | ||
04fbfdc1 PZ |
241 | /* |
242 | * Obtain an accurate fraction of the BDI's portion. | |
243 | */ | |
244 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
245 | long *numerator, long *denominator) | |
246 | { | |
247 | if (bdi_cap_writeback_dirty(bdi)) { | |
248 | prop_fraction_percpu(&vm_completions, &bdi->completions, | |
249 | numerator, denominator); | |
250 | } else { | |
251 | *numerator = 0; | |
252 | *denominator = 1; | |
253 | } | |
254 | } | |
255 | ||
3e26c149 PZ |
256 | static inline void task_dirties_fraction(struct task_struct *tsk, |
257 | long *numerator, long *denominator) | |
258 | { | |
259 | prop_fraction_single(&vm_dirties, &tsk->dirties, | |
260 | numerator, denominator); | |
261 | } | |
262 | ||
263 | /* | |
1babe183 | 264 | * task_dirty_limit - scale down dirty throttling threshold for one task |
3e26c149 PZ |
265 | * |
266 | * task specific dirty limit: | |
267 | * | |
268 | * dirty -= (dirty/8) * p_{t} | |
1babe183 WF |
269 | * |
270 | * To protect light/slow dirtying tasks from heavier/fast ones, we start | |
271 | * throttling individual tasks before reaching the bdi dirty limit. | |
272 | * Relatively low thresholds will be allocated to heavy dirtiers. So when | |
273 | * dirty pages grow large, heavy dirtiers will be throttled first, which will | |
274 | * effectively curb the growth of dirty pages. Light dirtiers with high enough | |
275 | * dirty threshold may never get throttled. | |
3e26c149 | 276 | */ |
16c4042f WF |
277 | static unsigned long task_dirty_limit(struct task_struct *tsk, |
278 | unsigned long bdi_dirty) | |
3e26c149 PZ |
279 | { |
280 | long numerator, denominator; | |
16c4042f | 281 | unsigned long dirty = bdi_dirty; |
3e26c149 PZ |
282 | u64 inv = dirty >> 3; |
283 | ||
284 | task_dirties_fraction(tsk, &numerator, &denominator); | |
285 | inv *= numerator; | |
286 | do_div(inv, denominator); | |
287 | ||
288 | dirty -= inv; | |
3e26c149 | 289 | |
16c4042f | 290 | return max(dirty, bdi_dirty/2); |
3e26c149 PZ |
291 | } |
292 | ||
189d3c4a PZ |
293 | /* |
294 | * | |
295 | */ | |
189d3c4a PZ |
296 | static unsigned int bdi_min_ratio; |
297 | ||
298 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
299 | { | |
300 | int ret = 0; | |
189d3c4a | 301 | |
cfc4ba53 | 302 | spin_lock_bh(&bdi_lock); |
a42dde04 | 303 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 304 | ret = -EINVAL; |
a42dde04 PZ |
305 | } else { |
306 | min_ratio -= bdi->min_ratio; | |
307 | if (bdi_min_ratio + min_ratio < 100) { | |
308 | bdi_min_ratio += min_ratio; | |
309 | bdi->min_ratio += min_ratio; | |
310 | } else { | |
311 | ret = -EINVAL; | |
312 | } | |
313 | } | |
cfc4ba53 | 314 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
315 | |
316 | return ret; | |
317 | } | |
318 | ||
319 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
320 | { | |
a42dde04 PZ |
321 | int ret = 0; |
322 | ||
323 | if (max_ratio > 100) | |
324 | return -EINVAL; | |
325 | ||
cfc4ba53 | 326 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
327 | if (bdi->min_ratio > max_ratio) { |
328 | ret = -EINVAL; | |
329 | } else { | |
330 | bdi->max_ratio = max_ratio; | |
331 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
332 | } | |
cfc4ba53 | 333 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
334 | |
335 | return ret; | |
336 | } | |
a42dde04 | 337 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 338 | |
1da177e4 LT |
339 | /* |
340 | * Work out the current dirty-memory clamping and background writeout | |
341 | * thresholds. | |
342 | * | |
343 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
344 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
345 | * pages. It is better to clamp down on writers than to start swapping, and | |
346 | * performing lots of scanning. | |
347 | * | |
348 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
349 | * | |
350 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
351 | * excessive. | |
352 | * | |
353 | * We make sure that the background writeout level is below the adjusted | |
354 | * clamping level. | |
355 | */ | |
1b424464 CL |
356 | |
357 | static unsigned long highmem_dirtyable_memory(unsigned long total) | |
358 | { | |
359 | #ifdef CONFIG_HIGHMEM | |
360 | int node; | |
361 | unsigned long x = 0; | |
362 | ||
37b07e41 | 363 | for_each_node_state(node, N_HIGH_MEMORY) { |
1b424464 CL |
364 | struct zone *z = |
365 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
366 | ||
adea02a1 WF |
367 | x += zone_page_state(z, NR_FREE_PAGES) + |
368 | zone_reclaimable_pages(z); | |
1b424464 CL |
369 | } |
370 | /* | |
371 | * Make sure that the number of highmem pages is never larger | |
372 | * than the number of the total dirtyable memory. This can only | |
373 | * occur in very strange VM situations but we want to make sure | |
374 | * that this does not occur. | |
375 | */ | |
376 | return min(x, total); | |
377 | #else | |
378 | return 0; | |
379 | #endif | |
380 | } | |
381 | ||
3eefae99 SR |
382 | /** |
383 | * determine_dirtyable_memory - amount of memory that may be used | |
384 | * | |
385 | * Returns the numebr of pages that can currently be freed and used | |
386 | * by the kernel for direct mappings. | |
387 | */ | |
388 | unsigned long determine_dirtyable_memory(void) | |
1b424464 CL |
389 | { |
390 | unsigned long x; | |
391 | ||
adea02a1 | 392 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
195cf453 BG |
393 | |
394 | if (!vm_highmem_is_dirtyable) | |
395 | x -= highmem_dirtyable_memory(x); | |
396 | ||
1b424464 CL |
397 | return x + 1; /* Ensure that we never return 0 */ |
398 | } | |
399 | ||
03ab450f | 400 | /* |
1babe183 WF |
401 | * global_dirty_limits - background-writeback and dirty-throttling thresholds |
402 | * | |
403 | * Calculate the dirty thresholds based on sysctl parameters | |
404 | * - vm.dirty_background_ratio or vm.dirty_background_bytes | |
405 | * - vm.dirty_ratio or vm.dirty_bytes | |
406 | * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ebd1373d | 407 | * real-time tasks. |
1babe183 | 408 | */ |
16c4042f | 409 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
1da177e4 | 410 | { |
364aeb28 DR |
411 | unsigned long background; |
412 | unsigned long dirty; | |
240c879f | 413 | unsigned long uninitialized_var(available_memory); |
1da177e4 LT |
414 | struct task_struct *tsk; |
415 | ||
240c879f MK |
416 | if (!vm_dirty_bytes || !dirty_background_bytes) |
417 | available_memory = determine_dirtyable_memory(); | |
418 | ||
2da02997 DR |
419 | if (vm_dirty_bytes) |
420 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
4cbec4c8 WF |
421 | else |
422 | dirty = (vm_dirty_ratio * available_memory) / 100; | |
1da177e4 | 423 | |
2da02997 DR |
424 | if (dirty_background_bytes) |
425 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
426 | else | |
427 | background = (dirty_background_ratio * available_memory) / 100; | |
1da177e4 | 428 | |
2da02997 DR |
429 | if (background >= dirty) |
430 | background = dirty / 2; | |
1da177e4 LT |
431 | tsk = current; |
432 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
433 | background += background / 4; | |
434 | dirty += dirty / 4; | |
435 | } | |
436 | *pbackground = background; | |
437 | *pdirty = dirty; | |
16c4042f | 438 | } |
04fbfdc1 | 439 | |
03ab450f | 440 | /* |
1babe183 WF |
441 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
442 | * | |
443 | * Allocate high/low dirty limits to fast/slow devices, in order to prevent | |
444 | * - starving fast devices | |
445 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
446 | * | |
447 | * The bdi's share of dirty limit will be adapting to its throughput and | |
448 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. | |
449 | */ | |
450 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) | |
16c4042f WF |
451 | { |
452 | u64 bdi_dirty; | |
453 | long numerator, denominator; | |
04fbfdc1 | 454 | |
16c4042f WF |
455 | /* |
456 | * Calculate this BDI's share of the dirty ratio. | |
457 | */ | |
458 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
04fbfdc1 | 459 | |
16c4042f WF |
460 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
461 | bdi_dirty *= numerator; | |
462 | do_div(bdi_dirty, denominator); | |
04fbfdc1 | 463 | |
16c4042f WF |
464 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
465 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) | |
466 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
467 | ||
468 | return bdi_dirty; | |
1da177e4 LT |
469 | } |
470 | ||
471 | /* | |
472 | * balance_dirty_pages() must be called by processes which are generating dirty | |
473 | * data. It looks at the number of dirty pages in the machine and will force | |
474 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
5b0830cb JA |
475 | * If we're over `background_thresh' then the writeback threads are woken to |
476 | * perform some writeout. | |
1da177e4 | 477 | */ |
3a2e9a5a WF |
478 | static void balance_dirty_pages(struct address_space *mapping, |
479 | unsigned long write_chunk) | |
1da177e4 | 480 | { |
5fce25a9 PZ |
481 | long nr_reclaimable, bdi_nr_reclaimable; |
482 | long nr_writeback, bdi_nr_writeback; | |
364aeb28 DR |
483 | unsigned long background_thresh; |
484 | unsigned long dirty_thresh; | |
485 | unsigned long bdi_thresh; | |
1da177e4 | 486 | unsigned long pages_written = 0; |
87c6a9b2 | 487 | unsigned long pause = 1; |
e50e3720 | 488 | bool dirty_exceeded = false; |
1da177e4 LT |
489 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
490 | ||
491 | for (;;) { | |
492 | struct writeback_control wbc = { | |
1da177e4 LT |
493 | .sync_mode = WB_SYNC_NONE, |
494 | .older_than_this = NULL, | |
495 | .nr_to_write = write_chunk, | |
111ebb6e | 496 | .range_cyclic = 1, |
1da177e4 LT |
497 | }; |
498 | ||
5fce25a9 PZ |
499 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
500 | global_page_state(NR_UNSTABLE_NFS); | |
501 | nr_writeback = global_page_state(NR_WRITEBACK); | |
502 | ||
16c4042f WF |
503 | global_dirty_limits(&background_thresh, &dirty_thresh); |
504 | ||
505 | /* | |
506 | * Throttle it only when the background writeback cannot | |
507 | * catch-up. This avoids (excessively) small writeouts | |
508 | * when the bdi limits are ramping up. | |
509 | */ | |
4cbec4c8 | 510 | if (nr_reclaimable + nr_writeback <= |
16c4042f WF |
511 | (background_thresh + dirty_thresh) / 2) |
512 | break; | |
513 | ||
514 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); | |
515 | bdi_thresh = task_dirty_limit(current, bdi_thresh); | |
516 | ||
e50e3720 WF |
517 | /* |
518 | * In order to avoid the stacked BDI deadlock we need | |
519 | * to ensure we accurately count the 'dirty' pages when | |
520 | * the threshold is low. | |
521 | * | |
522 | * Otherwise it would be possible to get thresh+n pages | |
523 | * reported dirty, even though there are thresh-m pages | |
524 | * actually dirty; with m+n sitting in the percpu | |
525 | * deltas. | |
526 | */ | |
527 | if (bdi_thresh < 2*bdi_stat_error(bdi)) { | |
528 | bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); | |
529 | bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); | |
530 | } else { | |
531 | bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); | |
532 | bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); | |
533 | } | |
5fce25a9 | 534 | |
e50e3720 WF |
535 | /* |
536 | * The bdi thresh is somehow "soft" limit derived from the | |
537 | * global "hard" limit. The former helps to prevent heavy IO | |
538 | * bdi or process from holding back light ones; The latter is | |
539 | * the last resort safeguard. | |
540 | */ | |
541 | dirty_exceeded = | |
4cbec4c8 WF |
542 | (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh) |
543 | || (nr_reclaimable + nr_writeback > dirty_thresh); | |
e50e3720 WF |
544 | |
545 | if (!dirty_exceeded) | |
04fbfdc1 | 546 | break; |
1da177e4 | 547 | |
04fbfdc1 PZ |
548 | if (!bdi->dirty_exceeded) |
549 | bdi->dirty_exceeded = 1; | |
1da177e4 LT |
550 | |
551 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. | |
552 | * Unstable writes are a feature of certain networked | |
553 | * filesystems (i.e. NFS) in which data may have been | |
554 | * written to the server's write cache, but has not yet | |
555 | * been flushed to permanent storage. | |
d7831a0b RK |
556 | * Only move pages to writeback if this bdi is over its |
557 | * threshold otherwise wait until the disk writes catch | |
558 | * up. | |
1da177e4 | 559 | */ |
028c2dd1 | 560 | trace_wbc_balance_dirty_start(&wbc, bdi); |
d7831a0b | 561 | if (bdi_nr_reclaimable > bdi_thresh) { |
9c3a8ee8 | 562 | writeback_inodes_wb(&bdi->wb, &wbc); |
1da177e4 | 563 | pages_written += write_chunk - wbc.nr_to_write; |
028c2dd1 | 564 | trace_wbc_balance_dirty_written(&wbc, bdi); |
e50e3720 WF |
565 | if (pages_written >= write_chunk) |
566 | break; /* We've done our duty */ | |
04fbfdc1 | 567 | } |
028c2dd1 | 568 | trace_wbc_balance_dirty_wait(&wbc, bdi); |
d153ba64 | 569 | __set_current_state(TASK_UNINTERRUPTIBLE); |
d25105e8 | 570 | io_schedule_timeout(pause); |
87c6a9b2 JA |
571 | |
572 | /* | |
573 | * Increase the delay for each loop, up to our previous | |
574 | * default of taking a 100ms nap. | |
575 | */ | |
576 | pause <<= 1; | |
577 | if (pause > HZ / 10) | |
578 | pause = HZ / 10; | |
1da177e4 LT |
579 | } |
580 | ||
e50e3720 | 581 | if (!dirty_exceeded && bdi->dirty_exceeded) |
04fbfdc1 | 582 | bdi->dirty_exceeded = 0; |
1da177e4 LT |
583 | |
584 | if (writeback_in_progress(bdi)) | |
5b0830cb | 585 | return; |
1da177e4 LT |
586 | |
587 | /* | |
588 | * In laptop mode, we wait until hitting the higher threshold before | |
589 | * starting background writeout, and then write out all the way down | |
590 | * to the lower threshold. So slow writers cause minimal disk activity. | |
591 | * | |
592 | * In normal mode, we start background writeout at the lower | |
593 | * background_thresh, to keep the amount of dirty memory low. | |
594 | */ | |
595 | if ((laptop_mode && pages_written) || | |
e50e3720 | 596 | (!laptop_mode && (nr_reclaimable > background_thresh))) |
c5444198 | 597 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
598 | } |
599 | ||
a200ee18 | 600 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 601 | { |
a200ee18 | 602 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
603 | struct address_space *mapping = page_mapping(page); |
604 | ||
605 | if (mapping) | |
606 | balance_dirty_pages_ratelimited(mapping); | |
607 | } | |
608 | } | |
609 | ||
245b2e70 TH |
610 | static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0; |
611 | ||
1da177e4 | 612 | /** |
fa5a734e | 613 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 614 | * @mapping: address_space which was dirtied |
a580290c | 615 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
616 | * |
617 | * Processes which are dirtying memory should call in here once for each page | |
618 | * which was newly dirtied. The function will periodically check the system's | |
619 | * dirty state and will initiate writeback if needed. | |
620 | * | |
621 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
622 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
623 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
624 | * from overshooting the limit by (ratelimit_pages) each. | |
625 | */ | |
fa5a734e AM |
626 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
627 | unsigned long nr_pages_dirtied) | |
1da177e4 | 628 | { |
fa5a734e AM |
629 | unsigned long ratelimit; |
630 | unsigned long *p; | |
1da177e4 LT |
631 | |
632 | ratelimit = ratelimit_pages; | |
04fbfdc1 | 633 | if (mapping->backing_dev_info->dirty_exceeded) |
1da177e4 LT |
634 | ratelimit = 8; |
635 | ||
636 | /* | |
637 | * Check the rate limiting. Also, we do not want to throttle real-time | |
638 | * tasks in balance_dirty_pages(). Period. | |
639 | */ | |
fa5a734e | 640 | preempt_disable(); |
245b2e70 | 641 | p = &__get_cpu_var(bdp_ratelimits); |
fa5a734e AM |
642 | *p += nr_pages_dirtied; |
643 | if (unlikely(*p >= ratelimit)) { | |
3a2e9a5a | 644 | ratelimit = sync_writeback_pages(*p); |
fa5a734e AM |
645 | *p = 0; |
646 | preempt_enable(); | |
3a2e9a5a | 647 | balance_dirty_pages(mapping, ratelimit); |
1da177e4 LT |
648 | return; |
649 | } | |
fa5a734e | 650 | preempt_enable(); |
1da177e4 | 651 | } |
fa5a734e | 652 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 653 | |
232ea4d6 | 654 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 655 | { |
364aeb28 DR |
656 | unsigned long background_thresh; |
657 | unsigned long dirty_thresh; | |
1da177e4 LT |
658 | |
659 | for ( ; ; ) { | |
16c4042f | 660 | global_dirty_limits(&background_thresh, &dirty_thresh); |
1da177e4 LT |
661 | |
662 | /* | |
663 | * Boost the allowable dirty threshold a bit for page | |
664 | * allocators so they don't get DoS'ed by heavy writers | |
665 | */ | |
666 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
667 | ||
c24f21bd CL |
668 | if (global_page_state(NR_UNSTABLE_NFS) + |
669 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
670 | break; | |
8aa7e847 | 671 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
672 | |
673 | /* | |
674 | * The caller might hold locks which can prevent IO completion | |
675 | * or progress in the filesystem. So we cannot just sit here | |
676 | * waiting for IO to complete. | |
677 | */ | |
678 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
679 | break; | |
1da177e4 LT |
680 | } |
681 | } | |
682 | ||
1da177e4 LT |
683 | /* |
684 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
685 | */ | |
686 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 687 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 688 | { |
8d65af78 | 689 | proc_dointvec(table, write, buffer, length, ppos); |
6423104b | 690 | bdi_arm_supers_timer(); |
1da177e4 LT |
691 | return 0; |
692 | } | |
693 | ||
c2c4986e | 694 | #ifdef CONFIG_BLOCK |
31373d09 | 695 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 696 | { |
31373d09 MG |
697 | struct request_queue *q = (struct request_queue *)data; |
698 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
699 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 | 700 | |
31373d09 MG |
701 | /* |
702 | * We want to write everything out, not just down to the dirty | |
703 | * threshold | |
704 | */ | |
31373d09 | 705 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
c5444198 | 706 | bdi_start_writeback(&q->backing_dev_info, nr_pages); |
1da177e4 LT |
707 | } |
708 | ||
709 | /* | |
710 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
711 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
712 | * then push it back - the user is still using the disk. | |
713 | */ | |
31373d09 | 714 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 715 | { |
31373d09 | 716 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
717 | } |
718 | ||
719 | /* | |
720 | * We're in laptop mode and we've just synced. The sync's writes will have | |
721 | * caused another writeback to be scheduled by laptop_io_completion. | |
722 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
723 | */ | |
724 | void laptop_sync_completion(void) | |
725 | { | |
31373d09 MG |
726 | struct backing_dev_info *bdi; |
727 | ||
728 | rcu_read_lock(); | |
729 | ||
730 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
731 | del_timer(&bdi->laptop_mode_wb_timer); | |
732 | ||
733 | rcu_read_unlock(); | |
1da177e4 | 734 | } |
c2c4986e | 735 | #endif |
1da177e4 LT |
736 | |
737 | /* | |
738 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
739 | * if a large number of processes all perform writes at the same time. | |
740 | * If it is too low then SMP machines will call the (expensive) | |
741 | * get_writeback_state too often. | |
742 | * | |
743 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
744 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
745 | * thresholds before writeback cuts in. | |
746 | * | |
747 | * But the limit should not be set too high. Because it also controls the | |
748 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
749 | * If this is too large then the caller will block on the IO queue all the | |
750 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
751 | * will write six megabyte chunks, max. | |
752 | */ | |
753 | ||
2d1d43f6 | 754 | void writeback_set_ratelimit(void) |
1da177e4 | 755 | { |
40c99aae | 756 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
757 | if (ratelimit_pages < 16) |
758 | ratelimit_pages = 16; | |
759 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
760 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
761 | } | |
762 | ||
26c2143b | 763 | static int __cpuinit |
1da177e4 LT |
764 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
765 | { | |
2d1d43f6 | 766 | writeback_set_ratelimit(); |
aa0f0303 | 767 | return NOTIFY_DONE; |
1da177e4 LT |
768 | } |
769 | ||
74b85f37 | 770 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
771 | .notifier_call = ratelimit_handler, |
772 | .next = NULL, | |
773 | }; | |
774 | ||
775 | /* | |
dc6e29da LT |
776 | * Called early on to tune the page writeback dirty limits. |
777 | * | |
778 | * We used to scale dirty pages according to how total memory | |
779 | * related to pages that could be allocated for buffers (by | |
780 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
781 | * | |
782 | * However, that was when we used "dirty_ratio" to scale with | |
783 | * all memory, and we don't do that any more. "dirty_ratio" | |
784 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
785 | * totalhigh_pages from vm_total_pages), and as such we can't | |
786 | * get into the old insane situation any more where we had | |
787 | * large amounts of dirty pages compared to a small amount of | |
788 | * non-HIGHMEM memory. | |
789 | * | |
790 | * But we might still want to scale the dirty_ratio by how | |
791 | * much memory the box has.. | |
1da177e4 LT |
792 | */ |
793 | void __init page_writeback_init(void) | |
794 | { | |
04fbfdc1 PZ |
795 | int shift; |
796 | ||
2d1d43f6 | 797 | writeback_set_ratelimit(); |
1da177e4 | 798 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
799 | |
800 | shift = calc_period_shift(); | |
801 | prop_descriptor_init(&vm_completions, shift); | |
3e26c149 | 802 | prop_descriptor_init(&vm_dirties, shift); |
1da177e4 LT |
803 | } |
804 | ||
f446daae JK |
805 | /** |
806 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
807 | * @mapping: address space structure to write | |
808 | * @start: starting page index | |
809 | * @end: ending page index (inclusive) | |
810 | * | |
811 | * This function scans the page range from @start to @end (inclusive) and tags | |
812 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
813 | * that write_cache_pages (or whoever calls this function) will then use | |
814 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
815 | * used to avoid livelocking of writeback by a process steadily creating new | |
816 | * dirty pages in the file (thus it is important for this function to be quick | |
817 | * so that it can tag pages faster than a dirtying process can create them). | |
818 | */ | |
819 | /* | |
820 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
821 | */ | |
f446daae JK |
822 | void tag_pages_for_writeback(struct address_space *mapping, |
823 | pgoff_t start, pgoff_t end) | |
824 | { | |
3c111a07 | 825 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
826 | unsigned long tagged; |
827 | ||
828 | do { | |
829 | spin_lock_irq(&mapping->tree_lock); | |
830 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
831 | &start, end, WRITEBACK_TAG_BATCH, | |
832 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
833 | spin_unlock_irq(&mapping->tree_lock); | |
834 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
835 | cond_resched(); | |
d5ed3a4a JK |
836 | /* We check 'start' to handle wrapping when end == ~0UL */ |
837 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
838 | } |
839 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
840 | ||
811d736f | 841 | /** |
0ea97180 | 842 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
843 | * @mapping: address space structure to write |
844 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
845 | * @writepage: function called for each page |
846 | * @data: data passed to writepage function | |
811d736f | 847 | * |
0ea97180 | 848 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
849 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
850 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
851 | * and msync() need to guarantee that all the data which was dirty at the time | |
852 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
853 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
854 | * existing IO to complete. | |
f446daae JK |
855 | * |
856 | * To avoid livelocks (when other process dirties new pages), we first tag | |
857 | * pages which should be written back with TOWRITE tag and only then start | |
858 | * writing them. For data-integrity sync we have to be careful so that we do | |
859 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
860 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
861 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 862 | */ |
0ea97180 MS |
863 | int write_cache_pages(struct address_space *mapping, |
864 | struct writeback_control *wbc, writepage_t writepage, | |
865 | void *data) | |
811d736f | 866 | { |
811d736f DH |
867 | int ret = 0; |
868 | int done = 0; | |
811d736f DH |
869 | struct pagevec pvec; |
870 | int nr_pages; | |
31a12666 | 871 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
872 | pgoff_t index; |
873 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 874 | pgoff_t done_index; |
31a12666 | 875 | int cycled; |
811d736f | 876 | int range_whole = 0; |
f446daae | 877 | int tag; |
811d736f | 878 | |
811d736f DH |
879 | pagevec_init(&pvec, 0); |
880 | if (wbc->range_cyclic) { | |
31a12666 NP |
881 | writeback_index = mapping->writeback_index; /* prev offset */ |
882 | index = writeback_index; | |
883 | if (index == 0) | |
884 | cycled = 1; | |
885 | else | |
886 | cycled = 0; | |
811d736f DH |
887 | end = -1; |
888 | } else { | |
889 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
890 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
891 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
892 | range_whole = 1; | |
31a12666 | 893 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 894 | } |
f446daae JK |
895 | if (wbc->sync_mode == WB_SYNC_ALL) |
896 | tag = PAGECACHE_TAG_TOWRITE; | |
897 | else | |
898 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 899 | retry: |
f446daae JK |
900 | if (wbc->sync_mode == WB_SYNC_ALL) |
901 | tag_pages_for_writeback(mapping, index, end); | |
bd19e012 | 902 | done_index = index; |
5a3d5c98 NP |
903 | while (!done && (index <= end)) { |
904 | int i; | |
905 | ||
f446daae | 906 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
907 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
908 | if (nr_pages == 0) | |
909 | break; | |
811d736f | 910 | |
811d736f DH |
911 | for (i = 0; i < nr_pages; i++) { |
912 | struct page *page = pvec.pages[i]; | |
913 | ||
914 | /* | |
d5482cdf NP |
915 | * At this point, the page may be truncated or |
916 | * invalidated (changing page->mapping to NULL), or | |
917 | * even swizzled back from swapper_space to tmpfs file | |
918 | * mapping. However, page->index will not change | |
919 | * because we have a reference on the page. | |
811d736f | 920 | */ |
d5482cdf NP |
921 | if (page->index > end) { |
922 | /* | |
923 | * can't be range_cyclic (1st pass) because | |
924 | * end == -1 in that case. | |
925 | */ | |
926 | done = 1; | |
927 | break; | |
928 | } | |
929 | ||
cf15b07c | 930 | done_index = page->index; |
d5482cdf | 931 | |
811d736f DH |
932 | lock_page(page); |
933 | ||
5a3d5c98 NP |
934 | /* |
935 | * Page truncated or invalidated. We can freely skip it | |
936 | * then, even for data integrity operations: the page | |
937 | * has disappeared concurrently, so there could be no | |
938 | * real expectation of this data interity operation | |
939 | * even if there is now a new, dirty page at the same | |
940 | * pagecache address. | |
941 | */ | |
811d736f | 942 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 943 | continue_unlock: |
811d736f DH |
944 | unlock_page(page); |
945 | continue; | |
946 | } | |
947 | ||
515f4a03 NP |
948 | if (!PageDirty(page)) { |
949 | /* someone wrote it for us */ | |
950 | goto continue_unlock; | |
951 | } | |
952 | ||
953 | if (PageWriteback(page)) { | |
954 | if (wbc->sync_mode != WB_SYNC_NONE) | |
955 | wait_on_page_writeback(page); | |
956 | else | |
957 | goto continue_unlock; | |
958 | } | |
811d736f | 959 | |
515f4a03 NP |
960 | BUG_ON(PageWriteback(page)); |
961 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 962 | goto continue_unlock; |
811d736f | 963 | |
9e094383 | 964 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 965 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
966 | if (unlikely(ret)) { |
967 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
968 | unlock_page(page); | |
969 | ret = 0; | |
970 | } else { | |
971 | /* | |
972 | * done_index is set past this page, | |
973 | * so media errors will not choke | |
974 | * background writeout for the entire | |
975 | * file. This has consequences for | |
976 | * range_cyclic semantics (ie. it may | |
977 | * not be suitable for data integrity | |
978 | * writeout). | |
979 | */ | |
cf15b07c | 980 | done_index = page->index + 1; |
00266770 NP |
981 | done = 1; |
982 | break; | |
983 | } | |
0b564927 | 984 | } |
00266770 | 985 | |
546a1924 DC |
986 | /* |
987 | * We stop writing back only if we are not doing | |
988 | * integrity sync. In case of integrity sync we have to | |
989 | * keep going until we have written all the pages | |
990 | * we tagged for writeback prior to entering this loop. | |
991 | */ | |
992 | if (--wbc->nr_to_write <= 0 && | |
993 | wbc->sync_mode == WB_SYNC_NONE) { | |
994 | done = 1; | |
995 | break; | |
05fe478d | 996 | } |
811d736f DH |
997 | } |
998 | pagevec_release(&pvec); | |
999 | cond_resched(); | |
1000 | } | |
3a4c6800 | 1001 | if (!cycled && !done) { |
811d736f | 1002 | /* |
31a12666 | 1003 | * range_cyclic: |
811d736f DH |
1004 | * We hit the last page and there is more work to be done: wrap |
1005 | * back to the start of the file | |
1006 | */ | |
31a12666 | 1007 | cycled = 1; |
811d736f | 1008 | index = 0; |
31a12666 | 1009 | end = writeback_index - 1; |
811d736f DH |
1010 | goto retry; |
1011 | } | |
0b564927 DC |
1012 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
1013 | mapping->writeback_index = done_index; | |
06d6cf69 | 1014 | |
811d736f DH |
1015 | return ret; |
1016 | } | |
0ea97180 MS |
1017 | EXPORT_SYMBOL(write_cache_pages); |
1018 | ||
1019 | /* | |
1020 | * Function used by generic_writepages to call the real writepage | |
1021 | * function and set the mapping flags on error | |
1022 | */ | |
1023 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1024 | void *data) | |
1025 | { | |
1026 | struct address_space *mapping = data; | |
1027 | int ret = mapping->a_ops->writepage(page, wbc); | |
1028 | mapping_set_error(mapping, ret); | |
1029 | return ret; | |
1030 | } | |
1031 | ||
1032 | /** | |
1033 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1034 | * @mapping: address space structure to write | |
1035 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1036 | * | |
1037 | * This is a library function, which implements the writepages() | |
1038 | * address_space_operation. | |
1039 | */ | |
1040 | int generic_writepages(struct address_space *mapping, | |
1041 | struct writeback_control *wbc) | |
1042 | { | |
9b6096a6 SL |
1043 | struct blk_plug plug; |
1044 | int ret; | |
1045 | ||
0ea97180 MS |
1046 | /* deal with chardevs and other special file */ |
1047 | if (!mapping->a_ops->writepage) | |
1048 | return 0; | |
1049 | ||
9b6096a6 SL |
1050 | blk_start_plug(&plug); |
1051 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
1052 | blk_finish_plug(&plug); | |
1053 | return ret; | |
0ea97180 | 1054 | } |
811d736f DH |
1055 | |
1056 | EXPORT_SYMBOL(generic_writepages); | |
1057 | ||
1da177e4 LT |
1058 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1059 | { | |
22905f77 AM |
1060 | int ret; |
1061 | ||
1da177e4 LT |
1062 | if (wbc->nr_to_write <= 0) |
1063 | return 0; | |
1064 | if (mapping->a_ops->writepages) | |
d08b3851 | 1065 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1066 | else |
1067 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1068 | return ret; |
1da177e4 LT |
1069 | } |
1070 | ||
1071 | /** | |
1072 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1073 | * @page: the page to write |
1074 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1075 | * |
1076 | * The page must be locked by the caller and will be unlocked upon return. | |
1077 | * | |
1078 | * write_one_page() returns a negative error code if I/O failed. | |
1079 | */ | |
1080 | int write_one_page(struct page *page, int wait) | |
1081 | { | |
1082 | struct address_space *mapping = page->mapping; | |
1083 | int ret = 0; | |
1084 | struct writeback_control wbc = { | |
1085 | .sync_mode = WB_SYNC_ALL, | |
1086 | .nr_to_write = 1, | |
1087 | }; | |
1088 | ||
1089 | BUG_ON(!PageLocked(page)); | |
1090 | ||
1091 | if (wait) | |
1092 | wait_on_page_writeback(page); | |
1093 | ||
1094 | if (clear_page_dirty_for_io(page)) { | |
1095 | page_cache_get(page); | |
1096 | ret = mapping->a_ops->writepage(page, &wbc); | |
1097 | if (ret == 0 && wait) { | |
1098 | wait_on_page_writeback(page); | |
1099 | if (PageError(page)) | |
1100 | ret = -EIO; | |
1101 | } | |
1102 | page_cache_release(page); | |
1103 | } else { | |
1104 | unlock_page(page); | |
1105 | } | |
1106 | return ret; | |
1107 | } | |
1108 | EXPORT_SYMBOL(write_one_page); | |
1109 | ||
76719325 KC |
1110 | /* |
1111 | * For address_spaces which do not use buffers nor write back. | |
1112 | */ | |
1113 | int __set_page_dirty_no_writeback(struct page *page) | |
1114 | { | |
1115 | if (!PageDirty(page)) | |
c3f0da63 | 1116 | return !TestSetPageDirty(page); |
76719325 KC |
1117 | return 0; |
1118 | } | |
1119 | ||
e3a7cca1 ES |
1120 | /* |
1121 | * Helper function for set_page_dirty family. | |
1122 | * NOTE: This relies on being atomic wrt interrupts. | |
1123 | */ | |
1124 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1125 | { | |
1126 | if (mapping_cap_account_dirty(mapping)) { | |
1127 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
ea941f0e | 1128 | __inc_zone_page_state(page, NR_DIRTIED); |
e3a7cca1 ES |
1129 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
1130 | task_dirty_inc(current); | |
1131 | task_io_account_write(PAGE_CACHE_SIZE); | |
1132 | } | |
1133 | } | |
679ceace | 1134 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 1135 | |
f629d1c9 MR |
1136 | /* |
1137 | * Helper function for set_page_writeback family. | |
1138 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic | |
1139 | * wrt interrupts. | |
1140 | */ | |
1141 | void account_page_writeback(struct page *page) | |
1142 | { | |
1143 | inc_zone_page_state(page, NR_WRITEBACK); | |
ea941f0e | 1144 | inc_zone_page_state(page, NR_WRITTEN); |
f629d1c9 MR |
1145 | } |
1146 | EXPORT_SYMBOL(account_page_writeback); | |
1147 | ||
1da177e4 LT |
1148 | /* |
1149 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1150 | * its radix tree. | |
1151 | * | |
1152 | * This is also used when a single buffer is being dirtied: we want to set the | |
1153 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1154 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1155 | * | |
1156 | * Most callers have locked the page, which pins the address_space in memory. | |
1157 | * But zap_pte_range() does not lock the page, however in that case the | |
1158 | * mapping is pinned by the vma's ->vm_file reference. | |
1159 | * | |
1160 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1161 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1162 | */ |
1163 | int __set_page_dirty_nobuffers(struct page *page) | |
1164 | { | |
1da177e4 LT |
1165 | if (!TestSetPageDirty(page)) { |
1166 | struct address_space *mapping = page_mapping(page); | |
1167 | struct address_space *mapping2; | |
1168 | ||
8c08540f AM |
1169 | if (!mapping) |
1170 | return 1; | |
1171 | ||
19fd6231 | 1172 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1173 | mapping2 = page_mapping(page); |
1174 | if (mapping2) { /* Race with truncate? */ | |
1175 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1176 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1177 | account_page_dirtied(page, mapping); |
8c08540f AM |
1178 | radix_tree_tag_set(&mapping->page_tree, |
1179 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1180 | } | |
19fd6231 | 1181 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1182 | if (mapping->host) { |
1183 | /* !PageAnon && !swapper_space */ | |
1184 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1185 | } |
4741c9fd | 1186 | return 1; |
1da177e4 | 1187 | } |
4741c9fd | 1188 | return 0; |
1da177e4 LT |
1189 | } |
1190 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
1191 | ||
1192 | /* | |
1193 | * When a writepage implementation decides that it doesn't want to write this | |
1194 | * page for some reason, it should redirty the locked page via | |
1195 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
1196 | */ | |
1197 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
1198 | { | |
1199 | wbc->pages_skipped++; | |
1200 | return __set_page_dirty_nobuffers(page); | |
1201 | } | |
1202 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
1203 | ||
1204 | /* | |
6746aff7 WF |
1205 | * Dirty a page. |
1206 | * | |
1207 | * For pages with a mapping this should be done under the page lock | |
1208 | * for the benefit of asynchronous memory errors who prefer a consistent | |
1209 | * dirty state. This rule can be broken in some special cases, | |
1210 | * but should be better not to. | |
1211 | * | |
1da177e4 LT |
1212 | * If the mapping doesn't provide a set_page_dirty a_op, then |
1213 | * just fall through and assume that it wants buffer_heads. | |
1214 | */ | |
1cf6e7d8 | 1215 | int set_page_dirty(struct page *page) |
1da177e4 LT |
1216 | { |
1217 | struct address_space *mapping = page_mapping(page); | |
1218 | ||
1219 | if (likely(mapping)) { | |
1220 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
1221 | /* |
1222 | * readahead/lru_deactivate_page could remain | |
1223 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
1224 | * About readahead, if the page is written, the flags would be | |
1225 | * reset. So no problem. | |
1226 | * About lru_deactivate_page, if the page is redirty, the flag | |
1227 | * will be reset. So no problem. but if the page is used by readahead | |
1228 | * it will confuse readahead and make it restart the size rampup | |
1229 | * process. But it's a trivial problem. | |
1230 | */ | |
1231 | ClearPageReclaim(page); | |
9361401e DH |
1232 | #ifdef CONFIG_BLOCK |
1233 | if (!spd) | |
1234 | spd = __set_page_dirty_buffers; | |
1235 | #endif | |
1236 | return (*spd)(page); | |
1da177e4 | 1237 | } |
4741c9fd AM |
1238 | if (!PageDirty(page)) { |
1239 | if (!TestSetPageDirty(page)) | |
1240 | return 1; | |
1241 | } | |
1da177e4 LT |
1242 | return 0; |
1243 | } | |
1244 | EXPORT_SYMBOL(set_page_dirty); | |
1245 | ||
1246 | /* | |
1247 | * set_page_dirty() is racy if the caller has no reference against | |
1248 | * page->mapping->host, and if the page is unlocked. This is because another | |
1249 | * CPU could truncate the page off the mapping and then free the mapping. | |
1250 | * | |
1251 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
1252 | * holds a reference on the inode by having an open file. | |
1253 | * | |
1254 | * In other cases, the page should be locked before running set_page_dirty(). | |
1255 | */ | |
1256 | int set_page_dirty_lock(struct page *page) | |
1257 | { | |
1258 | int ret; | |
1259 | ||
7eaceacc | 1260 | lock_page(page); |
1da177e4 LT |
1261 | ret = set_page_dirty(page); |
1262 | unlock_page(page); | |
1263 | return ret; | |
1264 | } | |
1265 | EXPORT_SYMBOL(set_page_dirty_lock); | |
1266 | ||
1da177e4 LT |
1267 | /* |
1268 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
1269 | * Returns true if the page was previously dirty. | |
1270 | * | |
1271 | * This is for preparing to put the page under writeout. We leave the page | |
1272 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
1273 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
1274 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
1275 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
1276 | * back into sync. | |
1277 | * | |
1278 | * This incoherency between the page's dirty flag and radix-tree tag is | |
1279 | * unfortunate, but it only exists while the page is locked. | |
1280 | */ | |
1281 | int clear_page_dirty_for_io(struct page *page) | |
1282 | { | |
1283 | struct address_space *mapping = page_mapping(page); | |
1284 | ||
79352894 NP |
1285 | BUG_ON(!PageLocked(page)); |
1286 | ||
7658cc28 LT |
1287 | if (mapping && mapping_cap_account_dirty(mapping)) { |
1288 | /* | |
1289 | * Yes, Virginia, this is indeed insane. | |
1290 | * | |
1291 | * We use this sequence to make sure that | |
1292 | * (a) we account for dirty stats properly | |
1293 | * (b) we tell the low-level filesystem to | |
1294 | * mark the whole page dirty if it was | |
1295 | * dirty in a pagetable. Only to then | |
1296 | * (c) clean the page again and return 1 to | |
1297 | * cause the writeback. | |
1298 | * | |
1299 | * This way we avoid all nasty races with the | |
1300 | * dirty bit in multiple places and clearing | |
1301 | * them concurrently from different threads. | |
1302 | * | |
1303 | * Note! Normally the "set_page_dirty(page)" | |
1304 | * has no effect on the actual dirty bit - since | |
1305 | * that will already usually be set. But we | |
1306 | * need the side effects, and it can help us | |
1307 | * avoid races. | |
1308 | * | |
1309 | * We basically use the page "master dirty bit" | |
1310 | * as a serialization point for all the different | |
1311 | * threads doing their things. | |
7658cc28 LT |
1312 | */ |
1313 | if (page_mkclean(page)) | |
1314 | set_page_dirty(page); | |
79352894 NP |
1315 | /* |
1316 | * We carefully synchronise fault handlers against | |
1317 | * installing a dirty pte and marking the page dirty | |
1318 | * at this point. We do this by having them hold the | |
1319 | * page lock at some point after installing their | |
1320 | * pte, but before marking the page dirty. | |
1321 | * Pages are always locked coming in here, so we get | |
1322 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
1323 | * for more comments. | |
1324 | */ | |
7658cc28 | 1325 | if (TestClearPageDirty(page)) { |
8c08540f | 1326 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
1327 | dec_bdi_stat(mapping->backing_dev_info, |
1328 | BDI_RECLAIMABLE); | |
7658cc28 | 1329 | return 1; |
1da177e4 | 1330 | } |
7658cc28 | 1331 | return 0; |
1da177e4 | 1332 | } |
7658cc28 | 1333 | return TestClearPageDirty(page); |
1da177e4 | 1334 | } |
58bb01a9 | 1335 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
1336 | |
1337 | int test_clear_page_writeback(struct page *page) | |
1338 | { | |
1339 | struct address_space *mapping = page_mapping(page); | |
1340 | int ret; | |
1341 | ||
1342 | if (mapping) { | |
69cb51d1 | 1343 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1344 | unsigned long flags; |
1345 | ||
19fd6231 | 1346 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1347 | ret = TestClearPageWriteback(page); |
69cb51d1 | 1348 | if (ret) { |
1da177e4 LT |
1349 | radix_tree_tag_clear(&mapping->page_tree, |
1350 | page_index(page), | |
1351 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1352 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 1353 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
1354 | __bdi_writeout_inc(bdi); |
1355 | } | |
69cb51d1 | 1356 | } |
19fd6231 | 1357 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1358 | } else { |
1359 | ret = TestClearPageWriteback(page); | |
1360 | } | |
d688abf5 AM |
1361 | if (ret) |
1362 | dec_zone_page_state(page, NR_WRITEBACK); | |
1da177e4 LT |
1363 | return ret; |
1364 | } | |
1365 | ||
1366 | int test_set_page_writeback(struct page *page) | |
1367 | { | |
1368 | struct address_space *mapping = page_mapping(page); | |
1369 | int ret; | |
1370 | ||
1371 | if (mapping) { | |
69cb51d1 | 1372 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1373 | unsigned long flags; |
1374 | ||
19fd6231 | 1375 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1376 | ret = TestSetPageWriteback(page); |
69cb51d1 | 1377 | if (!ret) { |
1da177e4 LT |
1378 | radix_tree_tag_set(&mapping->page_tree, |
1379 | page_index(page), | |
1380 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1381 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
1382 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
1383 | } | |
1da177e4 LT |
1384 | if (!PageDirty(page)) |
1385 | radix_tree_tag_clear(&mapping->page_tree, | |
1386 | page_index(page), | |
1387 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
1388 | radix_tree_tag_clear(&mapping->page_tree, |
1389 | page_index(page), | |
1390 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 1391 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1392 | } else { |
1393 | ret = TestSetPageWriteback(page); | |
1394 | } | |
d688abf5 | 1395 | if (!ret) |
f629d1c9 | 1396 | account_page_writeback(page); |
1da177e4 LT |
1397 | return ret; |
1398 | ||
1399 | } | |
1400 | EXPORT_SYMBOL(test_set_page_writeback); | |
1401 | ||
1402 | /* | |
00128188 | 1403 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
1404 | * passed tag. |
1405 | */ | |
1406 | int mapping_tagged(struct address_space *mapping, int tag) | |
1407 | { | |
72c47832 | 1408 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
1409 | } |
1410 | EXPORT_SYMBOL(mapping_tagged); |