Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
f30c2269 | 2 | * mm/page-writeback.c |
1da177e4 LT |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. | |
04fbfdc1 | 5 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
1da177e4 LT |
6 | * |
7 | * Contains functions related to writing back dirty pages at the | |
8 | * address_space level. | |
9 | * | |
e1f8e874 | 10 | * 10Apr2002 Andrew Morton |
1da177e4 LT |
11 | * Initial version |
12 | */ | |
13 | ||
14 | #include <linux/kernel.h> | |
15 | #include <linux/module.h> | |
16 | #include <linux/spinlock.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/swap.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/pagemap.h> | |
22 | #include <linux/writeback.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/backing-dev.h> | |
55e829af | 25 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
26 | #include <linux/blkdev.h> |
27 | #include <linux/mpage.h> | |
d08b3851 | 28 | #include <linux/rmap.h> |
1da177e4 LT |
29 | #include <linux/percpu.h> |
30 | #include <linux/notifier.h> | |
31 | #include <linux/smp.h> | |
32 | #include <linux/sysctl.h> | |
33 | #include <linux/cpu.h> | |
34 | #include <linux/syscalls.h> | |
cf9a2ae8 | 35 | #include <linux/buffer_head.h> |
811d736f | 36 | #include <linux/pagevec.h> |
028c2dd1 | 37 | #include <trace/events/writeback.h> |
1da177e4 | 38 | |
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 | /* | |
264 | * scale the dirty limit | |
265 | * | |
266 | * task specific dirty limit: | |
267 | * | |
268 | * dirty -= (dirty/8) * p_{t} | |
269 | */ | |
dcf975d5 | 270 | static void task_dirty_limit(struct task_struct *tsk, unsigned long *pdirty) |
3e26c149 PZ |
271 | { |
272 | long numerator, denominator; | |
dcf975d5 | 273 | unsigned long dirty = *pdirty; |
3e26c149 PZ |
274 | u64 inv = dirty >> 3; |
275 | ||
276 | task_dirties_fraction(tsk, &numerator, &denominator); | |
277 | inv *= numerator; | |
278 | do_div(inv, denominator); | |
279 | ||
280 | dirty -= inv; | |
281 | if (dirty < *pdirty/2) | |
282 | dirty = *pdirty/2; | |
283 | ||
284 | *pdirty = dirty; | |
285 | } | |
286 | ||
189d3c4a PZ |
287 | /* |
288 | * | |
289 | */ | |
189d3c4a PZ |
290 | static unsigned int bdi_min_ratio; |
291 | ||
292 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
293 | { | |
294 | int ret = 0; | |
189d3c4a | 295 | |
cfc4ba53 | 296 | spin_lock_bh(&bdi_lock); |
a42dde04 | 297 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 298 | ret = -EINVAL; |
a42dde04 PZ |
299 | } else { |
300 | min_ratio -= bdi->min_ratio; | |
301 | if (bdi_min_ratio + min_ratio < 100) { | |
302 | bdi_min_ratio += min_ratio; | |
303 | bdi->min_ratio += min_ratio; | |
304 | } else { | |
305 | ret = -EINVAL; | |
306 | } | |
307 | } | |
cfc4ba53 | 308 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
309 | |
310 | return ret; | |
311 | } | |
312 | ||
313 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
314 | { | |
a42dde04 PZ |
315 | int ret = 0; |
316 | ||
317 | if (max_ratio > 100) | |
318 | return -EINVAL; | |
319 | ||
cfc4ba53 | 320 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
321 | if (bdi->min_ratio > max_ratio) { |
322 | ret = -EINVAL; | |
323 | } else { | |
324 | bdi->max_ratio = max_ratio; | |
325 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
326 | } | |
cfc4ba53 | 327 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
328 | |
329 | return ret; | |
330 | } | |
a42dde04 | 331 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 332 | |
1da177e4 LT |
333 | /* |
334 | * Work out the current dirty-memory clamping and background writeout | |
335 | * thresholds. | |
336 | * | |
337 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
338 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
339 | * pages. It is better to clamp down on writers than to start swapping, and | |
340 | * performing lots of scanning. | |
341 | * | |
342 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
343 | * | |
344 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
345 | * excessive. | |
346 | * | |
347 | * We make sure that the background writeout level is below the adjusted | |
348 | * clamping level. | |
349 | */ | |
1b424464 CL |
350 | |
351 | static unsigned long highmem_dirtyable_memory(unsigned long total) | |
352 | { | |
353 | #ifdef CONFIG_HIGHMEM | |
354 | int node; | |
355 | unsigned long x = 0; | |
356 | ||
37b07e41 | 357 | for_each_node_state(node, N_HIGH_MEMORY) { |
1b424464 CL |
358 | struct zone *z = |
359 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
360 | ||
adea02a1 WF |
361 | x += zone_page_state(z, NR_FREE_PAGES) + |
362 | zone_reclaimable_pages(z); | |
1b424464 CL |
363 | } |
364 | /* | |
365 | * Make sure that the number of highmem pages is never larger | |
366 | * than the number of the total dirtyable memory. This can only | |
367 | * occur in very strange VM situations but we want to make sure | |
368 | * that this does not occur. | |
369 | */ | |
370 | return min(x, total); | |
371 | #else | |
372 | return 0; | |
373 | #endif | |
374 | } | |
375 | ||
3eefae99 SR |
376 | /** |
377 | * determine_dirtyable_memory - amount of memory that may be used | |
378 | * | |
379 | * Returns the numebr of pages that can currently be freed and used | |
380 | * by the kernel for direct mappings. | |
381 | */ | |
382 | unsigned long determine_dirtyable_memory(void) | |
1b424464 CL |
383 | { |
384 | unsigned long x; | |
385 | ||
adea02a1 | 386 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
195cf453 BG |
387 | |
388 | if (!vm_highmem_is_dirtyable) | |
389 | x -= highmem_dirtyable_memory(x); | |
390 | ||
1b424464 CL |
391 | return x + 1; /* Ensure that we never return 0 */ |
392 | } | |
393 | ||
cf0ca9fe | 394 | void |
364aeb28 DR |
395 | get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty, |
396 | unsigned long *pbdi_dirty, struct backing_dev_info *bdi) | |
1da177e4 | 397 | { |
364aeb28 DR |
398 | unsigned long background; |
399 | unsigned long dirty; | |
1b424464 | 400 | unsigned long available_memory = determine_dirtyable_memory(); |
1da177e4 LT |
401 | struct task_struct *tsk; |
402 | ||
2da02997 DR |
403 | if (vm_dirty_bytes) |
404 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
405 | else { | |
406 | int dirty_ratio; | |
407 | ||
408 | dirty_ratio = vm_dirty_ratio; | |
409 | if (dirty_ratio < 5) | |
410 | dirty_ratio = 5; | |
411 | dirty = (dirty_ratio * available_memory) / 100; | |
412 | } | |
1da177e4 | 413 | |
2da02997 DR |
414 | if (dirty_background_bytes) |
415 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
416 | else | |
417 | background = (dirty_background_ratio * available_memory) / 100; | |
1da177e4 | 418 | |
2da02997 DR |
419 | if (background >= dirty) |
420 | background = dirty / 2; | |
1da177e4 LT |
421 | tsk = current; |
422 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
423 | background += background / 4; | |
424 | dirty += dirty / 4; | |
425 | } | |
426 | *pbackground = background; | |
427 | *pdirty = dirty; | |
04fbfdc1 PZ |
428 | |
429 | if (bdi) { | |
189d3c4a | 430 | u64 bdi_dirty; |
04fbfdc1 PZ |
431 | long numerator, denominator; |
432 | ||
433 | /* | |
434 | * Calculate this BDI's share of the dirty ratio. | |
435 | */ | |
436 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
437 | ||
189d3c4a | 438 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
04fbfdc1 PZ |
439 | bdi_dirty *= numerator; |
440 | do_div(bdi_dirty, denominator); | |
189d3c4a | 441 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
a42dde04 PZ |
442 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) |
443 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
04fbfdc1 PZ |
444 | |
445 | *pbdi_dirty = bdi_dirty; | |
3e26c149 | 446 | task_dirty_limit(current, pbdi_dirty); |
04fbfdc1 | 447 | } |
1da177e4 LT |
448 | } |
449 | ||
450 | /* | |
451 | * balance_dirty_pages() must be called by processes which are generating dirty | |
452 | * data. It looks at the number of dirty pages in the machine and will force | |
453 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
5b0830cb JA |
454 | * If we're over `background_thresh' then the writeback threads are woken to |
455 | * perform some writeout. | |
1da177e4 | 456 | */ |
3a2e9a5a WF |
457 | static void balance_dirty_pages(struct address_space *mapping, |
458 | unsigned long write_chunk) | |
1da177e4 | 459 | { |
5fce25a9 PZ |
460 | long nr_reclaimable, bdi_nr_reclaimable; |
461 | long nr_writeback, bdi_nr_writeback; | |
364aeb28 DR |
462 | unsigned long background_thresh; |
463 | unsigned long dirty_thresh; | |
464 | unsigned long bdi_thresh; | |
1da177e4 | 465 | unsigned long pages_written = 0; |
87c6a9b2 | 466 | unsigned long pause = 1; |
e50e3720 | 467 | bool dirty_exceeded = false; |
1da177e4 LT |
468 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
469 | ||
470 | for (;;) { | |
471 | struct writeback_control wbc = { | |
1da177e4 LT |
472 | .sync_mode = WB_SYNC_NONE, |
473 | .older_than_this = NULL, | |
474 | .nr_to_write = write_chunk, | |
111ebb6e | 475 | .range_cyclic = 1, |
1da177e4 LT |
476 | }; |
477 | ||
04fbfdc1 PZ |
478 | get_dirty_limits(&background_thresh, &dirty_thresh, |
479 | &bdi_thresh, bdi); | |
5fce25a9 PZ |
480 | |
481 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + | |
482 | global_page_state(NR_UNSTABLE_NFS); | |
483 | nr_writeback = global_page_state(NR_WRITEBACK); | |
484 | ||
e50e3720 WF |
485 | /* |
486 | * In order to avoid the stacked BDI deadlock we need | |
487 | * to ensure we accurately count the 'dirty' pages when | |
488 | * the threshold is low. | |
489 | * | |
490 | * Otherwise it would be possible to get thresh+n pages | |
491 | * reported dirty, even though there are thresh-m pages | |
492 | * actually dirty; with m+n sitting in the percpu | |
493 | * deltas. | |
494 | */ | |
495 | if (bdi_thresh < 2*bdi_stat_error(bdi)) { | |
496 | bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); | |
497 | bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); | |
498 | } else { | |
499 | bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); | |
500 | bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); | |
501 | } | |
5fce25a9 | 502 | |
e50e3720 WF |
503 | /* |
504 | * The bdi thresh is somehow "soft" limit derived from the | |
505 | * global "hard" limit. The former helps to prevent heavy IO | |
506 | * bdi or process from holding back light ones; The latter is | |
507 | * the last resort safeguard. | |
508 | */ | |
509 | dirty_exceeded = | |
510 | (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh) | |
511 | || (nr_reclaimable + nr_writeback >= dirty_thresh); | |
512 | ||
513 | if (!dirty_exceeded) | |
04fbfdc1 | 514 | break; |
1da177e4 | 515 | |
5fce25a9 PZ |
516 | /* |
517 | * Throttle it only when the background writeback cannot | |
518 | * catch-up. This avoids (excessively) small writeouts | |
519 | * when the bdi limits are ramping up. | |
520 | */ | |
521 | if (nr_reclaimable + nr_writeback < | |
522 | (background_thresh + dirty_thresh) / 2) | |
523 | break; | |
524 | ||
04fbfdc1 PZ |
525 | if (!bdi->dirty_exceeded) |
526 | bdi->dirty_exceeded = 1; | |
1da177e4 LT |
527 | |
528 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. | |
529 | * Unstable writes are a feature of certain networked | |
530 | * filesystems (i.e. NFS) in which data may have been | |
531 | * written to the server's write cache, but has not yet | |
532 | * been flushed to permanent storage. | |
d7831a0b RK |
533 | * Only move pages to writeback if this bdi is over its |
534 | * threshold otherwise wait until the disk writes catch | |
535 | * up. | |
1da177e4 | 536 | */ |
028c2dd1 | 537 | trace_wbc_balance_dirty_start(&wbc, bdi); |
d7831a0b | 538 | if (bdi_nr_reclaimable > bdi_thresh) { |
9c3a8ee8 | 539 | writeback_inodes_wb(&bdi->wb, &wbc); |
1da177e4 | 540 | pages_written += write_chunk - wbc.nr_to_write; |
028c2dd1 | 541 | trace_wbc_balance_dirty_written(&wbc, bdi); |
e50e3720 WF |
542 | if (pages_written >= write_chunk) |
543 | break; /* We've done our duty */ | |
04fbfdc1 | 544 | } |
028c2dd1 | 545 | trace_wbc_balance_dirty_wait(&wbc, bdi); |
d25105e8 WF |
546 | __set_current_state(TASK_INTERRUPTIBLE); |
547 | io_schedule_timeout(pause); | |
87c6a9b2 JA |
548 | |
549 | /* | |
550 | * Increase the delay for each loop, up to our previous | |
551 | * default of taking a 100ms nap. | |
552 | */ | |
553 | pause <<= 1; | |
554 | if (pause > HZ / 10) | |
555 | pause = HZ / 10; | |
1da177e4 LT |
556 | } |
557 | ||
e50e3720 | 558 | if (!dirty_exceeded && bdi->dirty_exceeded) |
04fbfdc1 | 559 | bdi->dirty_exceeded = 0; |
1da177e4 LT |
560 | |
561 | if (writeback_in_progress(bdi)) | |
5b0830cb | 562 | return; |
1da177e4 LT |
563 | |
564 | /* | |
565 | * In laptop mode, we wait until hitting the higher threshold before | |
566 | * starting background writeout, and then write out all the way down | |
567 | * to the lower threshold. So slow writers cause minimal disk activity. | |
568 | * | |
569 | * In normal mode, we start background writeout at the lower | |
570 | * background_thresh, to keep the amount of dirty memory low. | |
571 | */ | |
572 | if ((laptop_mode && pages_written) || | |
e50e3720 | 573 | (!laptop_mode && (nr_reclaimable > background_thresh))) |
c5444198 | 574 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
575 | } |
576 | ||
a200ee18 | 577 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 578 | { |
a200ee18 | 579 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
580 | struct address_space *mapping = page_mapping(page); |
581 | ||
582 | if (mapping) | |
583 | balance_dirty_pages_ratelimited(mapping); | |
584 | } | |
585 | } | |
586 | ||
245b2e70 TH |
587 | static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0; |
588 | ||
1da177e4 | 589 | /** |
fa5a734e | 590 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 591 | * @mapping: address_space which was dirtied |
a580290c | 592 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
593 | * |
594 | * Processes which are dirtying memory should call in here once for each page | |
595 | * which was newly dirtied. The function will periodically check the system's | |
596 | * dirty state and will initiate writeback if needed. | |
597 | * | |
598 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
599 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
600 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
601 | * from overshooting the limit by (ratelimit_pages) each. | |
602 | */ | |
fa5a734e AM |
603 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
604 | unsigned long nr_pages_dirtied) | |
1da177e4 | 605 | { |
fa5a734e AM |
606 | unsigned long ratelimit; |
607 | unsigned long *p; | |
1da177e4 LT |
608 | |
609 | ratelimit = ratelimit_pages; | |
04fbfdc1 | 610 | if (mapping->backing_dev_info->dirty_exceeded) |
1da177e4 LT |
611 | ratelimit = 8; |
612 | ||
613 | /* | |
614 | * Check the rate limiting. Also, we do not want to throttle real-time | |
615 | * tasks in balance_dirty_pages(). Period. | |
616 | */ | |
fa5a734e | 617 | preempt_disable(); |
245b2e70 | 618 | p = &__get_cpu_var(bdp_ratelimits); |
fa5a734e AM |
619 | *p += nr_pages_dirtied; |
620 | if (unlikely(*p >= ratelimit)) { | |
3a2e9a5a | 621 | ratelimit = sync_writeback_pages(*p); |
fa5a734e AM |
622 | *p = 0; |
623 | preempt_enable(); | |
3a2e9a5a | 624 | balance_dirty_pages(mapping, ratelimit); |
1da177e4 LT |
625 | return; |
626 | } | |
fa5a734e | 627 | preempt_enable(); |
1da177e4 | 628 | } |
fa5a734e | 629 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 630 | |
232ea4d6 | 631 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 632 | { |
364aeb28 DR |
633 | unsigned long background_thresh; |
634 | unsigned long dirty_thresh; | |
1da177e4 LT |
635 | |
636 | for ( ; ; ) { | |
04fbfdc1 | 637 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); |
1da177e4 LT |
638 | |
639 | /* | |
640 | * Boost the allowable dirty threshold a bit for page | |
641 | * allocators so they don't get DoS'ed by heavy writers | |
642 | */ | |
643 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
644 | ||
c24f21bd CL |
645 | if (global_page_state(NR_UNSTABLE_NFS) + |
646 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
647 | break; | |
8aa7e847 | 648 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
649 | |
650 | /* | |
651 | * The caller might hold locks which can prevent IO completion | |
652 | * or progress in the filesystem. So we cannot just sit here | |
653 | * waiting for IO to complete. | |
654 | */ | |
655 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
656 | break; | |
1da177e4 LT |
657 | } |
658 | } | |
659 | ||
1da177e4 LT |
660 | /* |
661 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
662 | */ | |
663 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 664 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 665 | { |
8d65af78 | 666 | proc_dointvec(table, write, buffer, length, ppos); |
6423104b | 667 | bdi_arm_supers_timer(); |
1da177e4 LT |
668 | return 0; |
669 | } | |
670 | ||
c2c4986e | 671 | #ifdef CONFIG_BLOCK |
31373d09 | 672 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 673 | { |
31373d09 MG |
674 | struct request_queue *q = (struct request_queue *)data; |
675 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
676 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 | 677 | |
31373d09 MG |
678 | /* |
679 | * We want to write everything out, not just down to the dirty | |
680 | * threshold | |
681 | */ | |
31373d09 | 682 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
c5444198 | 683 | bdi_start_writeback(&q->backing_dev_info, nr_pages); |
1da177e4 LT |
684 | } |
685 | ||
686 | /* | |
687 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
688 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
689 | * then push it back - the user is still using the disk. | |
690 | */ | |
31373d09 | 691 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 692 | { |
31373d09 | 693 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
694 | } |
695 | ||
696 | /* | |
697 | * We're in laptop mode and we've just synced. The sync's writes will have | |
698 | * caused another writeback to be scheduled by laptop_io_completion. | |
699 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
700 | */ | |
701 | void laptop_sync_completion(void) | |
702 | { | |
31373d09 MG |
703 | struct backing_dev_info *bdi; |
704 | ||
705 | rcu_read_lock(); | |
706 | ||
707 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
708 | del_timer(&bdi->laptop_mode_wb_timer); | |
709 | ||
710 | rcu_read_unlock(); | |
1da177e4 | 711 | } |
c2c4986e | 712 | #endif |
1da177e4 LT |
713 | |
714 | /* | |
715 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
716 | * if a large number of processes all perform writes at the same time. | |
717 | * If it is too low then SMP machines will call the (expensive) | |
718 | * get_writeback_state too often. | |
719 | * | |
720 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
721 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
722 | * thresholds before writeback cuts in. | |
723 | * | |
724 | * But the limit should not be set too high. Because it also controls the | |
725 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
726 | * If this is too large then the caller will block on the IO queue all the | |
727 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
728 | * will write six megabyte chunks, max. | |
729 | */ | |
730 | ||
2d1d43f6 | 731 | void writeback_set_ratelimit(void) |
1da177e4 | 732 | { |
40c99aae | 733 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
734 | if (ratelimit_pages < 16) |
735 | ratelimit_pages = 16; | |
736 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
737 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
738 | } | |
739 | ||
26c2143b | 740 | static int __cpuinit |
1da177e4 LT |
741 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
742 | { | |
2d1d43f6 | 743 | writeback_set_ratelimit(); |
aa0f0303 | 744 | return NOTIFY_DONE; |
1da177e4 LT |
745 | } |
746 | ||
74b85f37 | 747 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
748 | .notifier_call = ratelimit_handler, |
749 | .next = NULL, | |
750 | }; | |
751 | ||
752 | /* | |
dc6e29da LT |
753 | * Called early on to tune the page writeback dirty limits. |
754 | * | |
755 | * We used to scale dirty pages according to how total memory | |
756 | * related to pages that could be allocated for buffers (by | |
757 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
758 | * | |
759 | * However, that was when we used "dirty_ratio" to scale with | |
760 | * all memory, and we don't do that any more. "dirty_ratio" | |
761 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
762 | * totalhigh_pages from vm_total_pages), and as such we can't | |
763 | * get into the old insane situation any more where we had | |
764 | * large amounts of dirty pages compared to a small amount of | |
765 | * non-HIGHMEM memory. | |
766 | * | |
767 | * But we might still want to scale the dirty_ratio by how | |
768 | * much memory the box has.. | |
1da177e4 LT |
769 | */ |
770 | void __init page_writeback_init(void) | |
771 | { | |
04fbfdc1 PZ |
772 | int shift; |
773 | ||
2d1d43f6 | 774 | writeback_set_ratelimit(); |
1da177e4 | 775 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
776 | |
777 | shift = calc_period_shift(); | |
778 | prop_descriptor_init(&vm_completions, shift); | |
3e26c149 | 779 | prop_descriptor_init(&vm_dirties, shift); |
1da177e4 LT |
780 | } |
781 | ||
f446daae JK |
782 | /** |
783 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
784 | * @mapping: address space structure to write | |
785 | * @start: starting page index | |
786 | * @end: ending page index (inclusive) | |
787 | * | |
788 | * This function scans the page range from @start to @end (inclusive) and tags | |
789 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
790 | * that write_cache_pages (or whoever calls this function) will then use | |
791 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
792 | * used to avoid livelocking of writeback by a process steadily creating new | |
793 | * dirty pages in the file (thus it is important for this function to be quick | |
794 | * so that it can tag pages faster than a dirtying process can create them). | |
795 | */ | |
796 | /* | |
797 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
798 | */ | |
f446daae JK |
799 | void tag_pages_for_writeback(struct address_space *mapping, |
800 | pgoff_t start, pgoff_t end) | |
801 | { | |
3c111a07 | 802 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
803 | unsigned long tagged; |
804 | ||
805 | do { | |
806 | spin_lock_irq(&mapping->tree_lock); | |
807 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
808 | &start, end, WRITEBACK_TAG_BATCH, | |
809 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
810 | spin_unlock_irq(&mapping->tree_lock); | |
811 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
812 | cond_resched(); | |
813 | } while (tagged >= WRITEBACK_TAG_BATCH); | |
814 | } | |
815 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
816 | ||
811d736f | 817 | /** |
0ea97180 | 818 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
819 | * @mapping: address space structure to write |
820 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
821 | * @writepage: function called for each page |
822 | * @data: data passed to writepage function | |
811d736f | 823 | * |
0ea97180 | 824 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
825 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
826 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
827 | * and msync() need to guarantee that all the data which was dirty at the time | |
828 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
829 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
830 | * existing IO to complete. | |
f446daae JK |
831 | * |
832 | * To avoid livelocks (when other process dirties new pages), we first tag | |
833 | * pages which should be written back with TOWRITE tag and only then start | |
834 | * writing them. For data-integrity sync we have to be careful so that we do | |
835 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
836 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
837 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 838 | */ |
0ea97180 MS |
839 | int write_cache_pages(struct address_space *mapping, |
840 | struct writeback_control *wbc, writepage_t writepage, | |
841 | void *data) | |
811d736f | 842 | { |
811d736f DH |
843 | int ret = 0; |
844 | int done = 0; | |
811d736f DH |
845 | struct pagevec pvec; |
846 | int nr_pages; | |
31a12666 | 847 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
848 | pgoff_t index; |
849 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 850 | pgoff_t done_index; |
31a12666 | 851 | int cycled; |
811d736f | 852 | int range_whole = 0; |
f446daae | 853 | int tag; |
811d736f | 854 | |
811d736f DH |
855 | pagevec_init(&pvec, 0); |
856 | if (wbc->range_cyclic) { | |
31a12666 NP |
857 | writeback_index = mapping->writeback_index; /* prev offset */ |
858 | index = writeback_index; | |
859 | if (index == 0) | |
860 | cycled = 1; | |
861 | else | |
862 | cycled = 0; | |
811d736f DH |
863 | end = -1; |
864 | } else { | |
865 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
866 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
867 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
868 | range_whole = 1; | |
31a12666 | 869 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 870 | } |
f446daae JK |
871 | if (wbc->sync_mode == WB_SYNC_ALL) |
872 | tag = PAGECACHE_TAG_TOWRITE; | |
873 | else | |
874 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 875 | retry: |
f446daae JK |
876 | if (wbc->sync_mode == WB_SYNC_ALL) |
877 | tag_pages_for_writeback(mapping, index, end); | |
bd19e012 | 878 | done_index = index; |
5a3d5c98 NP |
879 | while (!done && (index <= end)) { |
880 | int i; | |
881 | ||
f446daae | 882 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
883 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
884 | if (nr_pages == 0) | |
885 | break; | |
811d736f | 886 | |
811d736f DH |
887 | for (i = 0; i < nr_pages; i++) { |
888 | struct page *page = pvec.pages[i]; | |
889 | ||
890 | /* | |
d5482cdf NP |
891 | * At this point, the page may be truncated or |
892 | * invalidated (changing page->mapping to NULL), or | |
893 | * even swizzled back from swapper_space to tmpfs file | |
894 | * mapping. However, page->index will not change | |
895 | * because we have a reference on the page. | |
811d736f | 896 | */ |
d5482cdf NP |
897 | if (page->index > end) { |
898 | /* | |
899 | * can't be range_cyclic (1st pass) because | |
900 | * end == -1 in that case. | |
901 | */ | |
902 | done = 1; | |
903 | break; | |
904 | } | |
905 | ||
906 | done_index = page->index + 1; | |
907 | ||
811d736f DH |
908 | lock_page(page); |
909 | ||
5a3d5c98 NP |
910 | /* |
911 | * Page truncated or invalidated. We can freely skip it | |
912 | * then, even for data integrity operations: the page | |
913 | * has disappeared concurrently, so there could be no | |
914 | * real expectation of this data interity operation | |
915 | * even if there is now a new, dirty page at the same | |
916 | * pagecache address. | |
917 | */ | |
811d736f | 918 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 919 | continue_unlock: |
811d736f DH |
920 | unlock_page(page); |
921 | continue; | |
922 | } | |
923 | ||
515f4a03 NP |
924 | if (!PageDirty(page)) { |
925 | /* someone wrote it for us */ | |
926 | goto continue_unlock; | |
927 | } | |
928 | ||
929 | if (PageWriteback(page)) { | |
930 | if (wbc->sync_mode != WB_SYNC_NONE) | |
931 | wait_on_page_writeback(page); | |
932 | else | |
933 | goto continue_unlock; | |
934 | } | |
811d736f | 935 | |
515f4a03 NP |
936 | BUG_ON(PageWriteback(page)); |
937 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 938 | goto continue_unlock; |
811d736f | 939 | |
9e094383 | 940 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 941 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
942 | if (unlikely(ret)) { |
943 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
944 | unlock_page(page); | |
945 | ret = 0; | |
946 | } else { | |
947 | /* | |
948 | * done_index is set past this page, | |
949 | * so media errors will not choke | |
950 | * background writeout for the entire | |
951 | * file. This has consequences for | |
952 | * range_cyclic semantics (ie. it may | |
953 | * not be suitable for data integrity | |
954 | * writeout). | |
955 | */ | |
956 | done = 1; | |
957 | break; | |
958 | } | |
0b564927 | 959 | } |
00266770 | 960 | |
0b564927 DC |
961 | if (wbc->nr_to_write > 0) { |
962 | if (--wbc->nr_to_write == 0 && | |
89e12190 FC |
963 | wbc->sync_mode == WB_SYNC_NONE) { |
964 | /* | |
965 | * We stop writing back only if we are | |
966 | * not doing integrity sync. In case of | |
967 | * integrity sync we have to keep going | |
968 | * because someone may be concurrently | |
969 | * dirtying pages, and we might have | |
970 | * synced a lot of newly appeared dirty | |
971 | * pages, but have not synced all of the | |
972 | * old dirty pages. | |
973 | */ | |
974 | done = 1; | |
975 | break; | |
976 | } | |
05fe478d | 977 | } |
811d736f DH |
978 | } |
979 | pagevec_release(&pvec); | |
980 | cond_resched(); | |
981 | } | |
3a4c6800 | 982 | if (!cycled && !done) { |
811d736f | 983 | /* |
31a12666 | 984 | * range_cyclic: |
811d736f DH |
985 | * We hit the last page and there is more work to be done: wrap |
986 | * back to the start of the file | |
987 | */ | |
31a12666 | 988 | cycled = 1; |
811d736f | 989 | index = 0; |
31a12666 | 990 | end = writeback_index - 1; |
811d736f DH |
991 | goto retry; |
992 | } | |
0b564927 DC |
993 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
994 | mapping->writeback_index = done_index; | |
06d6cf69 | 995 | |
811d736f DH |
996 | return ret; |
997 | } | |
0ea97180 MS |
998 | EXPORT_SYMBOL(write_cache_pages); |
999 | ||
1000 | /* | |
1001 | * Function used by generic_writepages to call the real writepage | |
1002 | * function and set the mapping flags on error | |
1003 | */ | |
1004 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1005 | void *data) | |
1006 | { | |
1007 | struct address_space *mapping = data; | |
1008 | int ret = mapping->a_ops->writepage(page, wbc); | |
1009 | mapping_set_error(mapping, ret); | |
1010 | return ret; | |
1011 | } | |
1012 | ||
1013 | /** | |
1014 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1015 | * @mapping: address space structure to write | |
1016 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1017 | * | |
1018 | * This is a library function, which implements the writepages() | |
1019 | * address_space_operation. | |
1020 | */ | |
1021 | int generic_writepages(struct address_space *mapping, | |
1022 | struct writeback_control *wbc) | |
1023 | { | |
1024 | /* deal with chardevs and other special file */ | |
1025 | if (!mapping->a_ops->writepage) | |
1026 | return 0; | |
1027 | ||
1028 | return write_cache_pages(mapping, wbc, __writepage, mapping); | |
1029 | } | |
811d736f DH |
1030 | |
1031 | EXPORT_SYMBOL(generic_writepages); | |
1032 | ||
1da177e4 LT |
1033 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1034 | { | |
22905f77 AM |
1035 | int ret; |
1036 | ||
1da177e4 LT |
1037 | if (wbc->nr_to_write <= 0) |
1038 | return 0; | |
1039 | if (mapping->a_ops->writepages) | |
d08b3851 | 1040 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1041 | else |
1042 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1043 | return ret; |
1da177e4 LT |
1044 | } |
1045 | ||
1046 | /** | |
1047 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1048 | * @page: the page to write |
1049 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1050 | * |
1051 | * The page must be locked by the caller and will be unlocked upon return. | |
1052 | * | |
1053 | * write_one_page() returns a negative error code if I/O failed. | |
1054 | */ | |
1055 | int write_one_page(struct page *page, int wait) | |
1056 | { | |
1057 | struct address_space *mapping = page->mapping; | |
1058 | int ret = 0; | |
1059 | struct writeback_control wbc = { | |
1060 | .sync_mode = WB_SYNC_ALL, | |
1061 | .nr_to_write = 1, | |
1062 | }; | |
1063 | ||
1064 | BUG_ON(!PageLocked(page)); | |
1065 | ||
1066 | if (wait) | |
1067 | wait_on_page_writeback(page); | |
1068 | ||
1069 | if (clear_page_dirty_for_io(page)) { | |
1070 | page_cache_get(page); | |
1071 | ret = mapping->a_ops->writepage(page, &wbc); | |
1072 | if (ret == 0 && wait) { | |
1073 | wait_on_page_writeback(page); | |
1074 | if (PageError(page)) | |
1075 | ret = -EIO; | |
1076 | } | |
1077 | page_cache_release(page); | |
1078 | } else { | |
1079 | unlock_page(page); | |
1080 | } | |
1081 | return ret; | |
1082 | } | |
1083 | EXPORT_SYMBOL(write_one_page); | |
1084 | ||
76719325 KC |
1085 | /* |
1086 | * For address_spaces which do not use buffers nor write back. | |
1087 | */ | |
1088 | int __set_page_dirty_no_writeback(struct page *page) | |
1089 | { | |
1090 | if (!PageDirty(page)) | |
1091 | SetPageDirty(page); | |
1092 | return 0; | |
1093 | } | |
1094 | ||
e3a7cca1 ES |
1095 | /* |
1096 | * Helper function for set_page_dirty family. | |
1097 | * NOTE: This relies on being atomic wrt interrupts. | |
1098 | */ | |
1099 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1100 | { | |
1101 | if (mapping_cap_account_dirty(mapping)) { | |
1102 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
1103 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); | |
1104 | task_dirty_inc(current); | |
1105 | task_io_account_write(PAGE_CACHE_SIZE); | |
1106 | } | |
1107 | } | |
1108 | ||
1da177e4 LT |
1109 | /* |
1110 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1111 | * its radix tree. | |
1112 | * | |
1113 | * This is also used when a single buffer is being dirtied: we want to set the | |
1114 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1115 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1116 | * | |
1117 | * Most callers have locked the page, which pins the address_space in memory. | |
1118 | * But zap_pte_range() does not lock the page, however in that case the | |
1119 | * mapping is pinned by the vma's ->vm_file reference. | |
1120 | * | |
1121 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1122 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1123 | */ |
1124 | int __set_page_dirty_nobuffers(struct page *page) | |
1125 | { | |
1da177e4 LT |
1126 | if (!TestSetPageDirty(page)) { |
1127 | struct address_space *mapping = page_mapping(page); | |
1128 | struct address_space *mapping2; | |
1129 | ||
8c08540f AM |
1130 | if (!mapping) |
1131 | return 1; | |
1132 | ||
19fd6231 | 1133 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1134 | mapping2 = page_mapping(page); |
1135 | if (mapping2) { /* Race with truncate? */ | |
1136 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1137 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1138 | account_page_dirtied(page, mapping); |
8c08540f AM |
1139 | radix_tree_tag_set(&mapping->page_tree, |
1140 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1141 | } | |
19fd6231 | 1142 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1143 | if (mapping->host) { |
1144 | /* !PageAnon && !swapper_space */ | |
1145 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1146 | } |
4741c9fd | 1147 | return 1; |
1da177e4 | 1148 | } |
4741c9fd | 1149 | return 0; |
1da177e4 LT |
1150 | } |
1151 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
1152 | ||
1153 | /* | |
1154 | * When a writepage implementation decides that it doesn't want to write this | |
1155 | * page for some reason, it should redirty the locked page via | |
1156 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
1157 | */ | |
1158 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
1159 | { | |
1160 | wbc->pages_skipped++; | |
1161 | return __set_page_dirty_nobuffers(page); | |
1162 | } | |
1163 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
1164 | ||
1165 | /* | |
6746aff7 WF |
1166 | * Dirty a page. |
1167 | * | |
1168 | * For pages with a mapping this should be done under the page lock | |
1169 | * for the benefit of asynchronous memory errors who prefer a consistent | |
1170 | * dirty state. This rule can be broken in some special cases, | |
1171 | * but should be better not to. | |
1172 | * | |
1da177e4 LT |
1173 | * If the mapping doesn't provide a set_page_dirty a_op, then |
1174 | * just fall through and assume that it wants buffer_heads. | |
1175 | */ | |
1cf6e7d8 | 1176 | int set_page_dirty(struct page *page) |
1da177e4 LT |
1177 | { |
1178 | struct address_space *mapping = page_mapping(page); | |
1179 | ||
1180 | if (likely(mapping)) { | |
1181 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
9361401e DH |
1182 | #ifdef CONFIG_BLOCK |
1183 | if (!spd) | |
1184 | spd = __set_page_dirty_buffers; | |
1185 | #endif | |
1186 | return (*spd)(page); | |
1da177e4 | 1187 | } |
4741c9fd AM |
1188 | if (!PageDirty(page)) { |
1189 | if (!TestSetPageDirty(page)) | |
1190 | return 1; | |
1191 | } | |
1da177e4 LT |
1192 | return 0; |
1193 | } | |
1194 | EXPORT_SYMBOL(set_page_dirty); | |
1195 | ||
1196 | /* | |
1197 | * set_page_dirty() is racy if the caller has no reference against | |
1198 | * page->mapping->host, and if the page is unlocked. This is because another | |
1199 | * CPU could truncate the page off the mapping and then free the mapping. | |
1200 | * | |
1201 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
1202 | * holds a reference on the inode by having an open file. | |
1203 | * | |
1204 | * In other cases, the page should be locked before running set_page_dirty(). | |
1205 | */ | |
1206 | int set_page_dirty_lock(struct page *page) | |
1207 | { | |
1208 | int ret; | |
1209 | ||
db37648c | 1210 | lock_page_nosync(page); |
1da177e4 LT |
1211 | ret = set_page_dirty(page); |
1212 | unlock_page(page); | |
1213 | return ret; | |
1214 | } | |
1215 | EXPORT_SYMBOL(set_page_dirty_lock); | |
1216 | ||
1da177e4 LT |
1217 | /* |
1218 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
1219 | * Returns true if the page was previously dirty. | |
1220 | * | |
1221 | * This is for preparing to put the page under writeout. We leave the page | |
1222 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
1223 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
1224 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
1225 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
1226 | * back into sync. | |
1227 | * | |
1228 | * This incoherency between the page's dirty flag and radix-tree tag is | |
1229 | * unfortunate, but it only exists while the page is locked. | |
1230 | */ | |
1231 | int clear_page_dirty_for_io(struct page *page) | |
1232 | { | |
1233 | struct address_space *mapping = page_mapping(page); | |
1234 | ||
79352894 NP |
1235 | BUG_ON(!PageLocked(page)); |
1236 | ||
fe3cba17 | 1237 | ClearPageReclaim(page); |
7658cc28 LT |
1238 | if (mapping && mapping_cap_account_dirty(mapping)) { |
1239 | /* | |
1240 | * Yes, Virginia, this is indeed insane. | |
1241 | * | |
1242 | * We use this sequence to make sure that | |
1243 | * (a) we account for dirty stats properly | |
1244 | * (b) we tell the low-level filesystem to | |
1245 | * mark the whole page dirty if it was | |
1246 | * dirty in a pagetable. Only to then | |
1247 | * (c) clean the page again and return 1 to | |
1248 | * cause the writeback. | |
1249 | * | |
1250 | * This way we avoid all nasty races with the | |
1251 | * dirty bit in multiple places and clearing | |
1252 | * them concurrently from different threads. | |
1253 | * | |
1254 | * Note! Normally the "set_page_dirty(page)" | |
1255 | * has no effect on the actual dirty bit - since | |
1256 | * that will already usually be set. But we | |
1257 | * need the side effects, and it can help us | |
1258 | * avoid races. | |
1259 | * | |
1260 | * We basically use the page "master dirty bit" | |
1261 | * as a serialization point for all the different | |
1262 | * threads doing their things. | |
7658cc28 LT |
1263 | */ |
1264 | if (page_mkclean(page)) | |
1265 | set_page_dirty(page); | |
79352894 NP |
1266 | /* |
1267 | * We carefully synchronise fault handlers against | |
1268 | * installing a dirty pte and marking the page dirty | |
1269 | * at this point. We do this by having them hold the | |
1270 | * page lock at some point after installing their | |
1271 | * pte, but before marking the page dirty. | |
1272 | * Pages are always locked coming in here, so we get | |
1273 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
1274 | * for more comments. | |
1275 | */ | |
7658cc28 | 1276 | if (TestClearPageDirty(page)) { |
8c08540f | 1277 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
1278 | dec_bdi_stat(mapping->backing_dev_info, |
1279 | BDI_RECLAIMABLE); | |
7658cc28 | 1280 | return 1; |
1da177e4 | 1281 | } |
7658cc28 | 1282 | return 0; |
1da177e4 | 1283 | } |
7658cc28 | 1284 | return TestClearPageDirty(page); |
1da177e4 | 1285 | } |
58bb01a9 | 1286 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
1287 | |
1288 | int test_clear_page_writeback(struct page *page) | |
1289 | { | |
1290 | struct address_space *mapping = page_mapping(page); | |
1291 | int ret; | |
1292 | ||
1293 | if (mapping) { | |
69cb51d1 | 1294 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1295 | unsigned long flags; |
1296 | ||
19fd6231 | 1297 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1298 | ret = TestClearPageWriteback(page); |
69cb51d1 | 1299 | if (ret) { |
1da177e4 LT |
1300 | radix_tree_tag_clear(&mapping->page_tree, |
1301 | page_index(page), | |
1302 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1303 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 1304 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
1305 | __bdi_writeout_inc(bdi); |
1306 | } | |
69cb51d1 | 1307 | } |
19fd6231 | 1308 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1309 | } else { |
1310 | ret = TestClearPageWriteback(page); | |
1311 | } | |
d688abf5 AM |
1312 | if (ret) |
1313 | dec_zone_page_state(page, NR_WRITEBACK); | |
1da177e4 LT |
1314 | return ret; |
1315 | } | |
1316 | ||
1317 | int test_set_page_writeback(struct page *page) | |
1318 | { | |
1319 | struct address_space *mapping = page_mapping(page); | |
1320 | int ret; | |
1321 | ||
1322 | if (mapping) { | |
69cb51d1 | 1323 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1324 | unsigned long flags; |
1325 | ||
19fd6231 | 1326 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1327 | ret = TestSetPageWriteback(page); |
69cb51d1 | 1328 | if (!ret) { |
1da177e4 LT |
1329 | radix_tree_tag_set(&mapping->page_tree, |
1330 | page_index(page), | |
1331 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1332 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
1333 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
1334 | } | |
1da177e4 LT |
1335 | if (!PageDirty(page)) |
1336 | radix_tree_tag_clear(&mapping->page_tree, | |
1337 | page_index(page), | |
1338 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
1339 | radix_tree_tag_clear(&mapping->page_tree, |
1340 | page_index(page), | |
1341 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 1342 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1343 | } else { |
1344 | ret = TestSetPageWriteback(page); | |
1345 | } | |
d688abf5 AM |
1346 | if (!ret) |
1347 | inc_zone_page_state(page, NR_WRITEBACK); | |
1da177e4 LT |
1348 | return ret; |
1349 | ||
1350 | } | |
1351 | EXPORT_SYMBOL(test_set_page_writeback); | |
1352 | ||
1353 | /* | |
00128188 | 1354 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
1355 | * passed tag. |
1356 | */ | |
1357 | int mapping_tagged(struct address_space *mapping, int tag) | |
1358 | { | |
1da177e4 | 1359 | int ret; |
00128188 | 1360 | rcu_read_lock(); |
1da177e4 | 1361 | ret = radix_tree_tagged(&mapping->page_tree, tag); |
00128188 | 1362 | rcu_read_unlock(); |
1da177e4 LT |
1363 | return ret; |
1364 | } | |
1365 | EXPORT_SYMBOL(mapping_tagged); |