Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
f30c2269 | 2 | * mm/page-writeback.c |
1da177e4 LT |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. | |
04fbfdc1 | 5 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
1da177e4 LT |
6 | * |
7 | * Contains functions related to writing back dirty pages at the | |
8 | * address_space level. | |
9 | * | |
e1f8e874 | 10 | * 10Apr2002 Andrew Morton |
1da177e4 LT |
11 | * Initial version |
12 | */ | |
13 | ||
14 | #include <linux/kernel.h> | |
15 | #include <linux/module.h> | |
16 | #include <linux/spinlock.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/swap.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/pagemap.h> | |
22 | #include <linux/writeback.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/backing-dev.h> | |
55e829af | 25 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
26 | #include <linux/blkdev.h> |
27 | #include <linux/mpage.h> | |
d08b3851 | 28 | #include <linux/rmap.h> |
1da177e4 LT |
29 | #include <linux/percpu.h> |
30 | #include <linux/notifier.h> | |
31 | #include <linux/smp.h> | |
32 | #include <linux/sysctl.h> | |
33 | #include <linux/cpu.h> | |
34 | #include <linux/syscalls.h> | |
cf9a2ae8 | 35 | #include <linux/buffer_head.h> |
811d736f | 36 | #include <linux/pagevec.h> |
028c2dd1 | 37 | #include <trace/events/writeback.h> |
1da177e4 | 38 | |
ffd1f609 WF |
39 | /* |
40 | * Sleep at most 200ms at a time in balance_dirty_pages(). | |
41 | */ | |
42 | #define MAX_PAUSE max(HZ/5, 1) | |
43 | ||
e98be2d5 WF |
44 | /* |
45 | * Estimate write bandwidth at 200ms intervals. | |
46 | */ | |
47 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) | |
48 | ||
1da177e4 LT |
49 | /* |
50 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
51 | * will look to see if it needs to force writeback or throttling. | |
52 | */ | |
53 | static long ratelimit_pages = 32; | |
54 | ||
1da177e4 LT |
55 | /* |
56 | * When balance_dirty_pages decides that the caller needs to perform some | |
57 | * non-background writeback, this is how many pages it will attempt to write. | |
3a2e9a5a | 58 | * It should be somewhat larger than dirtied pages to ensure that reasonably |
1da177e4 LT |
59 | * large amounts of I/O are submitted. |
60 | */ | |
3a2e9a5a | 61 | static inline long sync_writeback_pages(unsigned long dirtied) |
1da177e4 | 62 | { |
3a2e9a5a WF |
63 | if (dirtied < ratelimit_pages) |
64 | dirtied = ratelimit_pages; | |
65 | ||
66 | return dirtied + dirtied / 2; | |
1da177e4 LT |
67 | } |
68 | ||
69 | /* The following parameters are exported via /proc/sys/vm */ | |
70 | ||
71 | /* | |
5b0830cb | 72 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 73 | */ |
1b5e62b4 | 74 | int dirty_background_ratio = 10; |
1da177e4 | 75 | |
2da02997 DR |
76 | /* |
77 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
78 | * dirty_background_ratio * the amount of dirtyable memory | |
79 | */ | |
80 | unsigned long dirty_background_bytes; | |
81 | ||
195cf453 BG |
82 | /* |
83 | * free highmem will not be subtracted from the total free memory | |
84 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
85 | */ | |
86 | int vm_highmem_is_dirtyable; | |
87 | ||
1da177e4 LT |
88 | /* |
89 | * The generator of dirty data starts writeback at this percentage | |
90 | */ | |
1b5e62b4 | 91 | int vm_dirty_ratio = 20; |
1da177e4 | 92 | |
2da02997 DR |
93 | /* |
94 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
95 | * vm_dirty_ratio * the amount of dirtyable memory | |
96 | */ | |
97 | unsigned long vm_dirty_bytes; | |
98 | ||
1da177e4 | 99 | /* |
704503d8 | 100 | * The interval between `kupdate'-style writebacks |
1da177e4 | 101 | */ |
22ef37ee | 102 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 LT |
103 | |
104 | /* | |
704503d8 | 105 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 106 | */ |
22ef37ee | 107 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
108 | |
109 | /* | |
110 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
111 | */ | |
112 | int block_dump; | |
113 | ||
114 | /* | |
ed5b43f1 BS |
115 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
116 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
117 | */ |
118 | int laptop_mode; | |
119 | ||
120 | EXPORT_SYMBOL(laptop_mode); | |
121 | ||
122 | /* End of sysctl-exported parameters */ | |
123 | ||
c42843f2 | 124 | unsigned long global_dirty_limit; |
1da177e4 | 125 | |
04fbfdc1 PZ |
126 | /* |
127 | * Scale the writeback cache size proportional to the relative writeout speeds. | |
128 | * | |
129 | * We do this by keeping a floating proportion between BDIs, based on page | |
130 | * writeback completions [end_page_writeback()]. Those devices that write out | |
131 | * pages fastest will get the larger share, while the slower will get a smaller | |
132 | * share. | |
133 | * | |
134 | * We use page writeout completions because we are interested in getting rid of | |
135 | * dirty pages. Having them written out is the primary goal. | |
136 | * | |
137 | * We introduce a concept of time, a period over which we measure these events, | |
138 | * because demand can/will vary over time. The length of this period itself is | |
139 | * measured in page writeback completions. | |
140 | * | |
141 | */ | |
142 | static struct prop_descriptor vm_completions; | |
3e26c149 | 143 | static struct prop_descriptor vm_dirties; |
04fbfdc1 | 144 | |
04fbfdc1 PZ |
145 | /* |
146 | * couple the period to the dirty_ratio: | |
147 | * | |
148 | * period/2 ~ roundup_pow_of_two(dirty limit) | |
149 | */ | |
150 | static int calc_period_shift(void) | |
151 | { | |
152 | unsigned long dirty_total; | |
153 | ||
2da02997 DR |
154 | if (vm_dirty_bytes) |
155 | dirty_total = vm_dirty_bytes / PAGE_SIZE; | |
156 | else | |
157 | dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / | |
158 | 100; | |
04fbfdc1 PZ |
159 | return 2 + ilog2(dirty_total - 1); |
160 | } | |
161 | ||
162 | /* | |
2da02997 | 163 | * update the period when the dirty threshold changes. |
04fbfdc1 | 164 | */ |
2da02997 DR |
165 | static void update_completion_period(void) |
166 | { | |
167 | int shift = calc_period_shift(); | |
168 | prop_change_shift(&vm_completions, shift); | |
169 | prop_change_shift(&vm_dirties, shift); | |
170 | } | |
171 | ||
172 | int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
8d65af78 | 173 | void __user *buffer, size_t *lenp, |
2da02997 DR |
174 | loff_t *ppos) |
175 | { | |
176 | int ret; | |
177 | ||
8d65af78 | 178 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
179 | if (ret == 0 && write) |
180 | dirty_background_bytes = 0; | |
181 | return ret; | |
182 | } | |
183 | ||
184 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 185 | void __user *buffer, size_t *lenp, |
2da02997 DR |
186 | loff_t *ppos) |
187 | { | |
188 | int ret; | |
189 | ||
8d65af78 | 190 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
191 | if (ret == 0 && write) |
192 | dirty_background_ratio = 0; | |
193 | return ret; | |
194 | } | |
195 | ||
04fbfdc1 | 196 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 197 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
198 | loff_t *ppos) |
199 | { | |
200 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
201 | int ret; |
202 | ||
8d65af78 | 203 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 204 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
2da02997 DR |
205 | update_completion_period(); |
206 | vm_dirty_bytes = 0; | |
207 | } | |
208 | return ret; | |
209 | } | |
210 | ||
211 | ||
212 | int dirty_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 213 | void __user *buffer, size_t *lenp, |
2da02997 DR |
214 | loff_t *ppos) |
215 | { | |
fc3501d4 | 216 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
217 | int ret; |
218 | ||
8d65af78 | 219 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
220 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
221 | update_completion_period(); | |
222 | vm_dirty_ratio = 0; | |
04fbfdc1 PZ |
223 | } |
224 | return ret; | |
225 | } | |
226 | ||
227 | /* | |
228 | * Increment the BDI's writeout completion count and the global writeout | |
229 | * completion count. Called from test_clear_page_writeback(). | |
230 | */ | |
231 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
232 | { | |
f7d2b1ec | 233 | __inc_bdi_stat(bdi, BDI_WRITTEN); |
a42dde04 PZ |
234 | __prop_inc_percpu_max(&vm_completions, &bdi->completions, |
235 | bdi->max_prop_frac); | |
04fbfdc1 PZ |
236 | } |
237 | ||
dd5656e5 MS |
238 | void bdi_writeout_inc(struct backing_dev_info *bdi) |
239 | { | |
240 | unsigned long flags; | |
241 | ||
242 | local_irq_save(flags); | |
243 | __bdi_writeout_inc(bdi); | |
244 | local_irq_restore(flags); | |
245 | } | |
246 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); | |
247 | ||
1cf6e7d8 | 248 | void task_dirty_inc(struct task_struct *tsk) |
3e26c149 PZ |
249 | { |
250 | prop_inc_single(&vm_dirties, &tsk->dirties); | |
251 | } | |
252 | ||
04fbfdc1 PZ |
253 | /* |
254 | * Obtain an accurate fraction of the BDI's portion. | |
255 | */ | |
256 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
257 | long *numerator, long *denominator) | |
258 | { | |
3efaf0fa | 259 | prop_fraction_percpu(&vm_completions, &bdi->completions, |
04fbfdc1 | 260 | numerator, denominator); |
04fbfdc1 PZ |
261 | } |
262 | ||
3e26c149 PZ |
263 | static inline void task_dirties_fraction(struct task_struct *tsk, |
264 | long *numerator, long *denominator) | |
265 | { | |
266 | prop_fraction_single(&vm_dirties, &tsk->dirties, | |
267 | numerator, denominator); | |
268 | } | |
269 | ||
270 | /* | |
1babe183 | 271 | * task_dirty_limit - scale down dirty throttling threshold for one task |
3e26c149 PZ |
272 | * |
273 | * task specific dirty limit: | |
274 | * | |
275 | * dirty -= (dirty/8) * p_{t} | |
1babe183 WF |
276 | * |
277 | * To protect light/slow dirtying tasks from heavier/fast ones, we start | |
278 | * throttling individual tasks before reaching the bdi dirty limit. | |
279 | * Relatively low thresholds will be allocated to heavy dirtiers. So when | |
280 | * dirty pages grow large, heavy dirtiers will be throttled first, which will | |
281 | * effectively curb the growth of dirty pages. Light dirtiers with high enough | |
282 | * dirty threshold may never get throttled. | |
3e26c149 | 283 | */ |
bcff25fc | 284 | #define TASK_LIMIT_FRACTION 8 |
16c4042f WF |
285 | static unsigned long task_dirty_limit(struct task_struct *tsk, |
286 | unsigned long bdi_dirty) | |
3e26c149 PZ |
287 | { |
288 | long numerator, denominator; | |
16c4042f | 289 | unsigned long dirty = bdi_dirty; |
bcff25fc | 290 | u64 inv = dirty / TASK_LIMIT_FRACTION; |
3e26c149 PZ |
291 | |
292 | task_dirties_fraction(tsk, &numerator, &denominator); | |
293 | inv *= numerator; | |
294 | do_div(inv, denominator); | |
295 | ||
296 | dirty -= inv; | |
3e26c149 | 297 | |
16c4042f | 298 | return max(dirty, bdi_dirty/2); |
3e26c149 PZ |
299 | } |
300 | ||
bcff25fc JK |
301 | /* Minimum limit for any task */ |
302 | static unsigned long task_min_dirty_limit(unsigned long bdi_dirty) | |
303 | { | |
304 | return bdi_dirty - bdi_dirty / TASK_LIMIT_FRACTION; | |
305 | } | |
306 | ||
189d3c4a | 307 | /* |
d08c429b JW |
308 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
309 | * registered backing devices, which, for obvious reasons, can not | |
310 | * exceed 100%. | |
189d3c4a | 311 | */ |
189d3c4a PZ |
312 | static unsigned int bdi_min_ratio; |
313 | ||
314 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
315 | { | |
316 | int ret = 0; | |
189d3c4a | 317 | |
cfc4ba53 | 318 | spin_lock_bh(&bdi_lock); |
a42dde04 | 319 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 320 | ret = -EINVAL; |
a42dde04 PZ |
321 | } else { |
322 | min_ratio -= bdi->min_ratio; | |
323 | if (bdi_min_ratio + min_ratio < 100) { | |
324 | bdi_min_ratio += min_ratio; | |
325 | bdi->min_ratio += min_ratio; | |
326 | } else { | |
327 | ret = -EINVAL; | |
328 | } | |
329 | } | |
cfc4ba53 | 330 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
331 | |
332 | return ret; | |
333 | } | |
334 | ||
335 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
336 | { | |
a42dde04 PZ |
337 | int ret = 0; |
338 | ||
339 | if (max_ratio > 100) | |
340 | return -EINVAL; | |
341 | ||
cfc4ba53 | 342 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
343 | if (bdi->min_ratio > max_ratio) { |
344 | ret = -EINVAL; | |
345 | } else { | |
346 | bdi->max_ratio = max_ratio; | |
347 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
348 | } | |
cfc4ba53 | 349 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
350 | |
351 | return ret; | |
352 | } | |
a42dde04 | 353 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 354 | |
1da177e4 LT |
355 | /* |
356 | * Work out the current dirty-memory clamping and background writeout | |
357 | * thresholds. | |
358 | * | |
359 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
360 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
361 | * pages. It is better to clamp down on writers than to start swapping, and | |
362 | * performing lots of scanning. | |
363 | * | |
364 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
365 | * | |
366 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
367 | * excessive. | |
368 | * | |
369 | * We make sure that the background writeout level is below the adjusted | |
370 | * clamping level. | |
371 | */ | |
1b424464 CL |
372 | |
373 | static unsigned long highmem_dirtyable_memory(unsigned long total) | |
374 | { | |
375 | #ifdef CONFIG_HIGHMEM | |
376 | int node; | |
377 | unsigned long x = 0; | |
378 | ||
37b07e41 | 379 | for_each_node_state(node, N_HIGH_MEMORY) { |
1b424464 CL |
380 | struct zone *z = |
381 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
382 | ||
adea02a1 WF |
383 | x += zone_page_state(z, NR_FREE_PAGES) + |
384 | zone_reclaimable_pages(z); | |
1b424464 CL |
385 | } |
386 | /* | |
387 | * Make sure that the number of highmem pages is never larger | |
388 | * than the number of the total dirtyable memory. This can only | |
389 | * occur in very strange VM situations but we want to make sure | |
390 | * that this does not occur. | |
391 | */ | |
392 | return min(x, total); | |
393 | #else | |
394 | return 0; | |
395 | #endif | |
396 | } | |
397 | ||
3eefae99 SR |
398 | /** |
399 | * determine_dirtyable_memory - amount of memory that may be used | |
400 | * | |
401 | * Returns the numebr of pages that can currently be freed and used | |
402 | * by the kernel for direct mappings. | |
403 | */ | |
404 | unsigned long determine_dirtyable_memory(void) | |
1b424464 CL |
405 | { |
406 | unsigned long x; | |
407 | ||
adea02a1 | 408 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); |
195cf453 BG |
409 | |
410 | if (!vm_highmem_is_dirtyable) | |
411 | x -= highmem_dirtyable_memory(x); | |
412 | ||
1b424464 CL |
413 | return x + 1; /* Ensure that we never return 0 */ |
414 | } | |
415 | ||
ffd1f609 WF |
416 | static unsigned long hard_dirty_limit(unsigned long thresh) |
417 | { | |
418 | return max(thresh, global_dirty_limit); | |
419 | } | |
420 | ||
03ab450f | 421 | /* |
1babe183 WF |
422 | * global_dirty_limits - background-writeback and dirty-throttling thresholds |
423 | * | |
424 | * Calculate the dirty thresholds based on sysctl parameters | |
425 | * - vm.dirty_background_ratio or vm.dirty_background_bytes | |
426 | * - vm.dirty_ratio or vm.dirty_bytes | |
427 | * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ebd1373d | 428 | * real-time tasks. |
1babe183 | 429 | */ |
16c4042f | 430 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
1da177e4 | 431 | { |
364aeb28 DR |
432 | unsigned long background; |
433 | unsigned long dirty; | |
240c879f | 434 | unsigned long uninitialized_var(available_memory); |
1da177e4 LT |
435 | struct task_struct *tsk; |
436 | ||
240c879f MK |
437 | if (!vm_dirty_bytes || !dirty_background_bytes) |
438 | available_memory = determine_dirtyable_memory(); | |
439 | ||
2da02997 DR |
440 | if (vm_dirty_bytes) |
441 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
4cbec4c8 WF |
442 | else |
443 | dirty = (vm_dirty_ratio * available_memory) / 100; | |
1da177e4 | 444 | |
2da02997 DR |
445 | if (dirty_background_bytes) |
446 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
447 | else | |
448 | background = (dirty_background_ratio * available_memory) / 100; | |
1da177e4 | 449 | |
2da02997 DR |
450 | if (background >= dirty) |
451 | background = dirty / 2; | |
1da177e4 LT |
452 | tsk = current; |
453 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
454 | background += background / 4; | |
455 | dirty += dirty / 4; | |
456 | } | |
457 | *pbackground = background; | |
458 | *pdirty = dirty; | |
e1cbe236 | 459 | trace_global_dirty_state(background, dirty); |
16c4042f | 460 | } |
04fbfdc1 | 461 | |
6f718656 | 462 | /** |
1babe183 | 463 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
6f718656 WF |
464 | * @bdi: the backing_dev_info to query |
465 | * @dirty: global dirty limit in pages | |
1babe183 | 466 | * |
6f718656 WF |
467 | * Returns @bdi's dirty limit in pages. The term "dirty" in the context of |
468 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. | |
469 | * And the "limit" in the name is not seriously taken as hard limit in | |
470 | * balance_dirty_pages(). | |
1babe183 | 471 | * |
6f718656 | 472 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
473 | * - starving fast devices |
474 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
475 | * | |
476 | * The bdi's share of dirty limit will be adapting to its throughput and | |
477 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. | |
478 | */ | |
479 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) | |
16c4042f WF |
480 | { |
481 | u64 bdi_dirty; | |
482 | long numerator, denominator; | |
04fbfdc1 | 483 | |
16c4042f WF |
484 | /* |
485 | * Calculate this BDI's share of the dirty ratio. | |
486 | */ | |
487 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
04fbfdc1 | 488 | |
16c4042f WF |
489 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
490 | bdi_dirty *= numerator; | |
491 | do_div(bdi_dirty, denominator); | |
04fbfdc1 | 492 | |
16c4042f WF |
493 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
494 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) | |
495 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
496 | ||
497 | return bdi_dirty; | |
1da177e4 LT |
498 | } |
499 | ||
e98be2d5 WF |
500 | static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, |
501 | unsigned long elapsed, | |
502 | unsigned long written) | |
503 | { | |
504 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
505 | unsigned long avg = bdi->avg_write_bandwidth; | |
506 | unsigned long old = bdi->write_bandwidth; | |
507 | u64 bw; | |
508 | ||
509 | /* | |
510 | * bw = written * HZ / elapsed | |
511 | * | |
512 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
513 | * write_bandwidth = --------------------------------------------------- | |
514 | * period | |
515 | */ | |
516 | bw = written - bdi->written_stamp; | |
517 | bw *= HZ; | |
518 | if (unlikely(elapsed > period)) { | |
519 | do_div(bw, elapsed); | |
520 | avg = bw; | |
521 | goto out; | |
522 | } | |
523 | bw += (u64)bdi->write_bandwidth * (period - elapsed); | |
524 | bw >>= ilog2(period); | |
525 | ||
526 | /* | |
527 | * one more level of smoothing, for filtering out sudden spikes | |
528 | */ | |
529 | if (avg > old && old >= (unsigned long)bw) | |
530 | avg -= (avg - old) >> 3; | |
531 | ||
532 | if (avg < old && old <= (unsigned long)bw) | |
533 | avg += (old - avg) >> 3; | |
534 | ||
535 | out: | |
536 | bdi->write_bandwidth = bw; | |
537 | bdi->avg_write_bandwidth = avg; | |
538 | } | |
539 | ||
c42843f2 WF |
540 | /* |
541 | * The global dirtyable memory and dirty threshold could be suddenly knocked | |
542 | * down by a large amount (eg. on the startup of KVM in a swapless system). | |
543 | * This may throw the system into deep dirty exceeded state and throttle | |
544 | * heavy/light dirtiers alike. To retain good responsiveness, maintain | |
545 | * global_dirty_limit for tracking slowly down to the knocked down dirty | |
546 | * threshold. | |
547 | */ | |
548 | static void update_dirty_limit(unsigned long thresh, unsigned long dirty) | |
549 | { | |
550 | unsigned long limit = global_dirty_limit; | |
551 | ||
552 | /* | |
553 | * Follow up in one step. | |
554 | */ | |
555 | if (limit < thresh) { | |
556 | limit = thresh; | |
557 | goto update; | |
558 | } | |
559 | ||
560 | /* | |
561 | * Follow down slowly. Use the higher one as the target, because thresh | |
562 | * may drop below dirty. This is exactly the reason to introduce | |
563 | * global_dirty_limit which is guaranteed to lie above the dirty pages. | |
564 | */ | |
565 | thresh = max(thresh, dirty); | |
566 | if (limit > thresh) { | |
567 | limit -= (limit - thresh) >> 5; | |
568 | goto update; | |
569 | } | |
570 | return; | |
571 | update: | |
572 | global_dirty_limit = limit; | |
573 | } | |
574 | ||
575 | static void global_update_bandwidth(unsigned long thresh, | |
576 | unsigned long dirty, | |
577 | unsigned long now) | |
578 | { | |
579 | static DEFINE_SPINLOCK(dirty_lock); | |
580 | static unsigned long update_time; | |
581 | ||
582 | /* | |
583 | * check locklessly first to optimize away locking for the most time | |
584 | */ | |
585 | if (time_before(now, update_time + BANDWIDTH_INTERVAL)) | |
586 | return; | |
587 | ||
588 | spin_lock(&dirty_lock); | |
589 | if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) { | |
590 | update_dirty_limit(thresh, dirty); | |
591 | update_time = now; | |
592 | } | |
593 | spin_unlock(&dirty_lock); | |
594 | } | |
595 | ||
e98be2d5 | 596 | void __bdi_update_bandwidth(struct backing_dev_info *bdi, |
c42843f2 WF |
597 | unsigned long thresh, |
598 | unsigned long dirty, | |
599 | unsigned long bdi_thresh, | |
600 | unsigned long bdi_dirty, | |
e98be2d5 WF |
601 | unsigned long start_time) |
602 | { | |
603 | unsigned long now = jiffies; | |
604 | unsigned long elapsed = now - bdi->bw_time_stamp; | |
605 | unsigned long written; | |
606 | ||
607 | /* | |
608 | * rate-limit, only update once every 200ms. | |
609 | */ | |
610 | if (elapsed < BANDWIDTH_INTERVAL) | |
611 | return; | |
612 | ||
613 | written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); | |
614 | ||
615 | /* | |
616 | * Skip quiet periods when disk bandwidth is under-utilized. | |
617 | * (at least 1s idle time between two flusher runs) | |
618 | */ | |
619 | if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) | |
620 | goto snapshot; | |
621 | ||
c42843f2 WF |
622 | if (thresh) |
623 | global_update_bandwidth(thresh, dirty, now); | |
624 | ||
e98be2d5 WF |
625 | bdi_update_write_bandwidth(bdi, elapsed, written); |
626 | ||
627 | snapshot: | |
628 | bdi->written_stamp = written; | |
629 | bdi->bw_time_stamp = now; | |
630 | } | |
631 | ||
632 | static void bdi_update_bandwidth(struct backing_dev_info *bdi, | |
c42843f2 WF |
633 | unsigned long thresh, |
634 | unsigned long dirty, | |
635 | unsigned long bdi_thresh, | |
636 | unsigned long bdi_dirty, | |
e98be2d5 WF |
637 | unsigned long start_time) |
638 | { | |
639 | if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) | |
640 | return; | |
641 | spin_lock(&bdi->wb.list_lock); | |
c42843f2 WF |
642 | __bdi_update_bandwidth(bdi, thresh, dirty, bdi_thresh, bdi_dirty, |
643 | start_time); | |
e98be2d5 WF |
644 | spin_unlock(&bdi->wb.list_lock); |
645 | } | |
646 | ||
1da177e4 LT |
647 | /* |
648 | * balance_dirty_pages() must be called by processes which are generating dirty | |
649 | * data. It looks at the number of dirty pages in the machine and will force | |
650 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
5b0830cb JA |
651 | * If we're over `background_thresh' then the writeback threads are woken to |
652 | * perform some writeout. | |
1da177e4 | 653 | */ |
3a2e9a5a WF |
654 | static void balance_dirty_pages(struct address_space *mapping, |
655 | unsigned long write_chunk) | |
1da177e4 | 656 | { |
7762741e WF |
657 | unsigned long nr_reclaimable, bdi_nr_reclaimable; |
658 | unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ | |
659 | unsigned long bdi_dirty; | |
364aeb28 DR |
660 | unsigned long background_thresh; |
661 | unsigned long dirty_thresh; | |
662 | unsigned long bdi_thresh; | |
bcff25fc JK |
663 | unsigned long task_bdi_thresh; |
664 | unsigned long min_task_bdi_thresh; | |
1da177e4 | 665 | unsigned long pages_written = 0; |
87c6a9b2 | 666 | unsigned long pause = 1; |
e50e3720 | 667 | bool dirty_exceeded = false; |
bcff25fc | 668 | bool clear_dirty_exceeded = true; |
1da177e4 | 669 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
e98be2d5 | 670 | unsigned long start_time = jiffies; |
1da177e4 LT |
671 | |
672 | for (;;) { | |
5fce25a9 PZ |
673 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
674 | global_page_state(NR_UNSTABLE_NFS); | |
7762741e | 675 | nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
5fce25a9 | 676 | |
16c4042f WF |
677 | global_dirty_limits(&background_thresh, &dirty_thresh); |
678 | ||
679 | /* | |
680 | * Throttle it only when the background writeback cannot | |
681 | * catch-up. This avoids (excessively) small writeouts | |
682 | * when the bdi limits are ramping up. | |
683 | */ | |
7762741e | 684 | if (nr_dirty <= (background_thresh + dirty_thresh) / 2) |
16c4042f WF |
685 | break; |
686 | ||
687 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); | |
bcff25fc JK |
688 | min_task_bdi_thresh = task_min_dirty_limit(bdi_thresh); |
689 | task_bdi_thresh = task_dirty_limit(current, bdi_thresh); | |
16c4042f | 690 | |
e50e3720 WF |
691 | /* |
692 | * In order to avoid the stacked BDI deadlock we need | |
693 | * to ensure we accurately count the 'dirty' pages when | |
694 | * the threshold is low. | |
695 | * | |
696 | * Otherwise it would be possible to get thresh+n pages | |
697 | * reported dirty, even though there are thresh-m pages | |
698 | * actually dirty; with m+n sitting in the percpu | |
699 | * deltas. | |
700 | */ | |
bcff25fc | 701 | if (task_bdi_thresh < 2 * bdi_stat_error(bdi)) { |
e50e3720 | 702 | bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); |
7762741e WF |
703 | bdi_dirty = bdi_nr_reclaimable + |
704 | bdi_stat_sum(bdi, BDI_WRITEBACK); | |
e50e3720 WF |
705 | } else { |
706 | bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); | |
7762741e WF |
707 | bdi_dirty = bdi_nr_reclaimable + |
708 | bdi_stat(bdi, BDI_WRITEBACK); | |
e50e3720 | 709 | } |
5fce25a9 | 710 | |
e50e3720 WF |
711 | /* |
712 | * The bdi thresh is somehow "soft" limit derived from the | |
713 | * global "hard" limit. The former helps to prevent heavy IO | |
714 | * bdi or process from holding back light ones; The latter is | |
715 | * the last resort safeguard. | |
716 | */ | |
bcff25fc | 717 | dirty_exceeded = (bdi_dirty > task_bdi_thresh) || |
7762741e | 718 | (nr_dirty > dirty_thresh); |
bcff25fc JK |
719 | clear_dirty_exceeded = (bdi_dirty <= min_task_bdi_thresh) && |
720 | (nr_dirty <= dirty_thresh); | |
e50e3720 WF |
721 | |
722 | if (!dirty_exceeded) | |
04fbfdc1 | 723 | break; |
1da177e4 | 724 | |
04fbfdc1 PZ |
725 | if (!bdi->dirty_exceeded) |
726 | bdi->dirty_exceeded = 1; | |
1da177e4 | 727 | |
c42843f2 WF |
728 | bdi_update_bandwidth(bdi, dirty_thresh, nr_dirty, |
729 | bdi_thresh, bdi_dirty, start_time); | |
e98be2d5 | 730 | |
1da177e4 LT |
731 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. |
732 | * Unstable writes are a feature of certain networked | |
733 | * filesystems (i.e. NFS) in which data may have been | |
734 | * written to the server's write cache, but has not yet | |
735 | * been flushed to permanent storage. | |
d7831a0b RK |
736 | * Only move pages to writeback if this bdi is over its |
737 | * threshold otherwise wait until the disk writes catch | |
738 | * up. | |
1da177e4 | 739 | */ |
d46db3d5 | 740 | trace_balance_dirty_start(bdi); |
bcff25fc | 741 | if (bdi_nr_reclaimable > task_bdi_thresh) { |
d46db3d5 WF |
742 | pages_written += writeback_inodes_wb(&bdi->wb, |
743 | write_chunk); | |
744 | trace_balance_dirty_written(bdi, pages_written); | |
e50e3720 WF |
745 | if (pages_written >= write_chunk) |
746 | break; /* We've done our duty */ | |
04fbfdc1 | 747 | } |
d153ba64 | 748 | __set_current_state(TASK_UNINTERRUPTIBLE); |
d25105e8 | 749 | io_schedule_timeout(pause); |
d46db3d5 | 750 | trace_balance_dirty_wait(bdi); |
87c6a9b2 | 751 | |
ffd1f609 WF |
752 | dirty_thresh = hard_dirty_limit(dirty_thresh); |
753 | /* | |
754 | * max-pause area. If dirty exceeded but still within this | |
755 | * area, no need to sleep for more than 200ms: (a) 8 pages per | |
756 | * 200ms is typically more than enough to curb heavy dirtiers; | |
757 | * (b) the pause time limit makes the dirtiers more responsive. | |
758 | */ | |
bb082295 WF |
759 | if (nr_dirty < dirty_thresh && |
760 | bdi_dirty < (task_bdi_thresh + bdi_thresh) / 2 && | |
ffd1f609 WF |
761 | time_after(jiffies, start_time + MAX_PAUSE)) |
762 | break; | |
87c6a9b2 JA |
763 | |
764 | /* | |
765 | * Increase the delay for each loop, up to our previous | |
766 | * default of taking a 100ms nap. | |
767 | */ | |
768 | pause <<= 1; | |
769 | if (pause > HZ / 10) | |
770 | pause = HZ / 10; | |
1da177e4 LT |
771 | } |
772 | ||
bcff25fc JK |
773 | /* Clear dirty_exceeded flag only when no task can exceed the limit */ |
774 | if (clear_dirty_exceeded && bdi->dirty_exceeded) | |
04fbfdc1 | 775 | bdi->dirty_exceeded = 0; |
1da177e4 LT |
776 | |
777 | if (writeback_in_progress(bdi)) | |
5b0830cb | 778 | return; |
1da177e4 LT |
779 | |
780 | /* | |
781 | * In laptop mode, we wait until hitting the higher threshold before | |
782 | * starting background writeout, and then write out all the way down | |
783 | * to the lower threshold. So slow writers cause minimal disk activity. | |
784 | * | |
785 | * In normal mode, we start background writeout at the lower | |
786 | * background_thresh, to keep the amount of dirty memory low. | |
787 | */ | |
788 | if ((laptop_mode && pages_written) || | |
e50e3720 | 789 | (!laptop_mode && (nr_reclaimable > background_thresh))) |
c5444198 | 790 | bdi_start_background_writeback(bdi); |
1da177e4 LT |
791 | } |
792 | ||
a200ee18 | 793 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 794 | { |
a200ee18 | 795 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
796 | struct address_space *mapping = page_mapping(page); |
797 | ||
798 | if (mapping) | |
799 | balance_dirty_pages_ratelimited(mapping); | |
800 | } | |
801 | } | |
802 | ||
245b2e70 TH |
803 | static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0; |
804 | ||
1da177e4 | 805 | /** |
fa5a734e | 806 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 807 | * @mapping: address_space which was dirtied |
a580290c | 808 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
809 | * |
810 | * Processes which are dirtying memory should call in here once for each page | |
811 | * which was newly dirtied. The function will periodically check the system's | |
812 | * dirty state and will initiate writeback if needed. | |
813 | * | |
814 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
815 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
816 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
817 | * from overshooting the limit by (ratelimit_pages) each. | |
818 | */ | |
fa5a734e AM |
819 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
820 | unsigned long nr_pages_dirtied) | |
1da177e4 | 821 | { |
36715cef | 822 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
fa5a734e AM |
823 | unsigned long ratelimit; |
824 | unsigned long *p; | |
1da177e4 | 825 | |
36715cef WF |
826 | if (!bdi_cap_account_dirty(bdi)) |
827 | return; | |
828 | ||
1da177e4 | 829 | ratelimit = ratelimit_pages; |
04fbfdc1 | 830 | if (mapping->backing_dev_info->dirty_exceeded) |
1da177e4 LT |
831 | ratelimit = 8; |
832 | ||
833 | /* | |
834 | * Check the rate limiting. Also, we do not want to throttle real-time | |
835 | * tasks in balance_dirty_pages(). Period. | |
836 | */ | |
fa5a734e | 837 | preempt_disable(); |
245b2e70 | 838 | p = &__get_cpu_var(bdp_ratelimits); |
fa5a734e AM |
839 | *p += nr_pages_dirtied; |
840 | if (unlikely(*p >= ratelimit)) { | |
3a2e9a5a | 841 | ratelimit = sync_writeback_pages(*p); |
fa5a734e AM |
842 | *p = 0; |
843 | preempt_enable(); | |
3a2e9a5a | 844 | balance_dirty_pages(mapping, ratelimit); |
1da177e4 LT |
845 | return; |
846 | } | |
fa5a734e | 847 | preempt_enable(); |
1da177e4 | 848 | } |
fa5a734e | 849 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 850 | |
232ea4d6 | 851 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 852 | { |
364aeb28 DR |
853 | unsigned long background_thresh; |
854 | unsigned long dirty_thresh; | |
1da177e4 LT |
855 | |
856 | for ( ; ; ) { | |
16c4042f | 857 | global_dirty_limits(&background_thresh, &dirty_thresh); |
1da177e4 LT |
858 | |
859 | /* | |
860 | * Boost the allowable dirty threshold a bit for page | |
861 | * allocators so they don't get DoS'ed by heavy writers | |
862 | */ | |
863 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
864 | ||
c24f21bd CL |
865 | if (global_page_state(NR_UNSTABLE_NFS) + |
866 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
867 | break; | |
8aa7e847 | 868 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
869 | |
870 | /* | |
871 | * The caller might hold locks which can prevent IO completion | |
872 | * or progress in the filesystem. So we cannot just sit here | |
873 | * waiting for IO to complete. | |
874 | */ | |
875 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
876 | break; | |
1da177e4 LT |
877 | } |
878 | } | |
879 | ||
1da177e4 LT |
880 | /* |
881 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
882 | */ | |
883 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
8d65af78 | 884 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 885 | { |
8d65af78 | 886 | proc_dointvec(table, write, buffer, length, ppos); |
6423104b | 887 | bdi_arm_supers_timer(); |
1da177e4 LT |
888 | return 0; |
889 | } | |
890 | ||
c2c4986e | 891 | #ifdef CONFIG_BLOCK |
31373d09 | 892 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 893 | { |
31373d09 MG |
894 | struct request_queue *q = (struct request_queue *)data; |
895 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
896 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 | 897 | |
31373d09 MG |
898 | /* |
899 | * We want to write everything out, not just down to the dirty | |
900 | * threshold | |
901 | */ | |
31373d09 | 902 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
c5444198 | 903 | bdi_start_writeback(&q->backing_dev_info, nr_pages); |
1da177e4 LT |
904 | } |
905 | ||
906 | /* | |
907 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
908 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
909 | * then push it back - the user is still using the disk. | |
910 | */ | |
31373d09 | 911 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 912 | { |
31373d09 | 913 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
914 | } |
915 | ||
916 | /* | |
917 | * We're in laptop mode and we've just synced. The sync's writes will have | |
918 | * caused another writeback to be scheduled by laptop_io_completion. | |
919 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
920 | */ | |
921 | void laptop_sync_completion(void) | |
922 | { | |
31373d09 MG |
923 | struct backing_dev_info *bdi; |
924 | ||
925 | rcu_read_lock(); | |
926 | ||
927 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
928 | del_timer(&bdi->laptop_mode_wb_timer); | |
929 | ||
930 | rcu_read_unlock(); | |
1da177e4 | 931 | } |
c2c4986e | 932 | #endif |
1da177e4 LT |
933 | |
934 | /* | |
935 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
936 | * if a large number of processes all perform writes at the same time. | |
937 | * If it is too low then SMP machines will call the (expensive) | |
938 | * get_writeback_state too often. | |
939 | * | |
940 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
941 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
942 | * thresholds before writeback cuts in. | |
943 | * | |
944 | * But the limit should not be set too high. Because it also controls the | |
945 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
946 | * If this is too large then the caller will block on the IO queue all the | |
947 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
948 | * will write six megabyte chunks, max. | |
949 | */ | |
950 | ||
2d1d43f6 | 951 | void writeback_set_ratelimit(void) |
1da177e4 | 952 | { |
40c99aae | 953 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
954 | if (ratelimit_pages < 16) |
955 | ratelimit_pages = 16; | |
956 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
957 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
958 | } | |
959 | ||
26c2143b | 960 | static int __cpuinit |
1da177e4 LT |
961 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
962 | { | |
2d1d43f6 | 963 | writeback_set_ratelimit(); |
aa0f0303 | 964 | return NOTIFY_DONE; |
1da177e4 LT |
965 | } |
966 | ||
74b85f37 | 967 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
968 | .notifier_call = ratelimit_handler, |
969 | .next = NULL, | |
970 | }; | |
971 | ||
972 | /* | |
dc6e29da LT |
973 | * Called early on to tune the page writeback dirty limits. |
974 | * | |
975 | * We used to scale dirty pages according to how total memory | |
976 | * related to pages that could be allocated for buffers (by | |
977 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
978 | * | |
979 | * However, that was when we used "dirty_ratio" to scale with | |
980 | * all memory, and we don't do that any more. "dirty_ratio" | |
981 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
982 | * totalhigh_pages from vm_total_pages), and as such we can't | |
983 | * get into the old insane situation any more where we had | |
984 | * large amounts of dirty pages compared to a small amount of | |
985 | * non-HIGHMEM memory. | |
986 | * | |
987 | * But we might still want to scale the dirty_ratio by how | |
988 | * much memory the box has.. | |
1da177e4 LT |
989 | */ |
990 | void __init page_writeback_init(void) | |
991 | { | |
04fbfdc1 PZ |
992 | int shift; |
993 | ||
2d1d43f6 | 994 | writeback_set_ratelimit(); |
1da177e4 | 995 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
996 | |
997 | shift = calc_period_shift(); | |
998 | prop_descriptor_init(&vm_completions, shift); | |
3e26c149 | 999 | prop_descriptor_init(&vm_dirties, shift); |
1da177e4 LT |
1000 | } |
1001 | ||
f446daae JK |
1002 | /** |
1003 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
1004 | * @mapping: address space structure to write | |
1005 | * @start: starting page index | |
1006 | * @end: ending page index (inclusive) | |
1007 | * | |
1008 | * This function scans the page range from @start to @end (inclusive) and tags | |
1009 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
1010 | * that write_cache_pages (or whoever calls this function) will then use | |
1011 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
1012 | * used to avoid livelocking of writeback by a process steadily creating new | |
1013 | * dirty pages in the file (thus it is important for this function to be quick | |
1014 | * so that it can tag pages faster than a dirtying process can create them). | |
1015 | */ | |
1016 | /* | |
1017 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
1018 | */ | |
f446daae JK |
1019 | void tag_pages_for_writeback(struct address_space *mapping, |
1020 | pgoff_t start, pgoff_t end) | |
1021 | { | |
3c111a07 | 1022 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
1023 | unsigned long tagged; |
1024 | ||
1025 | do { | |
1026 | spin_lock_irq(&mapping->tree_lock); | |
1027 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
1028 | &start, end, WRITEBACK_TAG_BATCH, | |
1029 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
1030 | spin_unlock_irq(&mapping->tree_lock); | |
1031 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
1032 | cond_resched(); | |
d5ed3a4a JK |
1033 | /* We check 'start' to handle wrapping when end == ~0UL */ |
1034 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
1035 | } |
1036 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
1037 | ||
811d736f | 1038 | /** |
0ea97180 | 1039 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
1040 | * @mapping: address space structure to write |
1041 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
1042 | * @writepage: function called for each page |
1043 | * @data: data passed to writepage function | |
811d736f | 1044 | * |
0ea97180 | 1045 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
1046 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
1047 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
1048 | * and msync() need to guarantee that all the data which was dirty at the time | |
1049 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
1050 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
1051 | * existing IO to complete. | |
f446daae JK |
1052 | * |
1053 | * To avoid livelocks (when other process dirties new pages), we first tag | |
1054 | * pages which should be written back with TOWRITE tag and only then start | |
1055 | * writing them. For data-integrity sync we have to be careful so that we do | |
1056 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
1057 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
1058 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 1059 | */ |
0ea97180 MS |
1060 | int write_cache_pages(struct address_space *mapping, |
1061 | struct writeback_control *wbc, writepage_t writepage, | |
1062 | void *data) | |
811d736f | 1063 | { |
811d736f DH |
1064 | int ret = 0; |
1065 | int done = 0; | |
811d736f DH |
1066 | struct pagevec pvec; |
1067 | int nr_pages; | |
31a12666 | 1068 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
1069 | pgoff_t index; |
1070 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 1071 | pgoff_t done_index; |
31a12666 | 1072 | int cycled; |
811d736f | 1073 | int range_whole = 0; |
f446daae | 1074 | int tag; |
811d736f | 1075 | |
811d736f DH |
1076 | pagevec_init(&pvec, 0); |
1077 | if (wbc->range_cyclic) { | |
31a12666 NP |
1078 | writeback_index = mapping->writeback_index; /* prev offset */ |
1079 | index = writeback_index; | |
1080 | if (index == 0) | |
1081 | cycled = 1; | |
1082 | else | |
1083 | cycled = 0; | |
811d736f DH |
1084 | end = -1; |
1085 | } else { | |
1086 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
1087 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
1088 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
1089 | range_whole = 1; | |
31a12666 | 1090 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 1091 | } |
6e6938b6 | 1092 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
1093 | tag = PAGECACHE_TAG_TOWRITE; |
1094 | else | |
1095 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 1096 | retry: |
6e6938b6 | 1097 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 1098 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 1099 | done_index = index; |
5a3d5c98 NP |
1100 | while (!done && (index <= end)) { |
1101 | int i; | |
1102 | ||
f446daae | 1103 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
1104 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
1105 | if (nr_pages == 0) | |
1106 | break; | |
811d736f | 1107 | |
811d736f DH |
1108 | for (i = 0; i < nr_pages; i++) { |
1109 | struct page *page = pvec.pages[i]; | |
1110 | ||
1111 | /* | |
d5482cdf NP |
1112 | * At this point, the page may be truncated or |
1113 | * invalidated (changing page->mapping to NULL), or | |
1114 | * even swizzled back from swapper_space to tmpfs file | |
1115 | * mapping. However, page->index will not change | |
1116 | * because we have a reference on the page. | |
811d736f | 1117 | */ |
d5482cdf NP |
1118 | if (page->index > end) { |
1119 | /* | |
1120 | * can't be range_cyclic (1st pass) because | |
1121 | * end == -1 in that case. | |
1122 | */ | |
1123 | done = 1; | |
1124 | break; | |
1125 | } | |
1126 | ||
cf15b07c | 1127 | done_index = page->index; |
d5482cdf | 1128 | |
811d736f DH |
1129 | lock_page(page); |
1130 | ||
5a3d5c98 NP |
1131 | /* |
1132 | * Page truncated or invalidated. We can freely skip it | |
1133 | * then, even for data integrity operations: the page | |
1134 | * has disappeared concurrently, so there could be no | |
1135 | * real expectation of this data interity operation | |
1136 | * even if there is now a new, dirty page at the same | |
1137 | * pagecache address. | |
1138 | */ | |
811d736f | 1139 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 1140 | continue_unlock: |
811d736f DH |
1141 | unlock_page(page); |
1142 | continue; | |
1143 | } | |
1144 | ||
515f4a03 NP |
1145 | if (!PageDirty(page)) { |
1146 | /* someone wrote it for us */ | |
1147 | goto continue_unlock; | |
1148 | } | |
1149 | ||
1150 | if (PageWriteback(page)) { | |
1151 | if (wbc->sync_mode != WB_SYNC_NONE) | |
1152 | wait_on_page_writeback(page); | |
1153 | else | |
1154 | goto continue_unlock; | |
1155 | } | |
811d736f | 1156 | |
515f4a03 NP |
1157 | BUG_ON(PageWriteback(page)); |
1158 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 1159 | goto continue_unlock; |
811d736f | 1160 | |
9e094383 | 1161 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
0ea97180 | 1162 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
1163 | if (unlikely(ret)) { |
1164 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
1165 | unlock_page(page); | |
1166 | ret = 0; | |
1167 | } else { | |
1168 | /* | |
1169 | * done_index is set past this page, | |
1170 | * so media errors will not choke | |
1171 | * background writeout for the entire | |
1172 | * file. This has consequences for | |
1173 | * range_cyclic semantics (ie. it may | |
1174 | * not be suitable for data integrity | |
1175 | * writeout). | |
1176 | */ | |
cf15b07c | 1177 | done_index = page->index + 1; |
00266770 NP |
1178 | done = 1; |
1179 | break; | |
1180 | } | |
0b564927 | 1181 | } |
00266770 | 1182 | |
546a1924 DC |
1183 | /* |
1184 | * We stop writing back only if we are not doing | |
1185 | * integrity sync. In case of integrity sync we have to | |
1186 | * keep going until we have written all the pages | |
1187 | * we tagged for writeback prior to entering this loop. | |
1188 | */ | |
1189 | if (--wbc->nr_to_write <= 0 && | |
1190 | wbc->sync_mode == WB_SYNC_NONE) { | |
1191 | done = 1; | |
1192 | break; | |
05fe478d | 1193 | } |
811d736f DH |
1194 | } |
1195 | pagevec_release(&pvec); | |
1196 | cond_resched(); | |
1197 | } | |
3a4c6800 | 1198 | if (!cycled && !done) { |
811d736f | 1199 | /* |
31a12666 | 1200 | * range_cyclic: |
811d736f DH |
1201 | * We hit the last page and there is more work to be done: wrap |
1202 | * back to the start of the file | |
1203 | */ | |
31a12666 | 1204 | cycled = 1; |
811d736f | 1205 | index = 0; |
31a12666 | 1206 | end = writeback_index - 1; |
811d736f DH |
1207 | goto retry; |
1208 | } | |
0b564927 DC |
1209 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
1210 | mapping->writeback_index = done_index; | |
06d6cf69 | 1211 | |
811d736f DH |
1212 | return ret; |
1213 | } | |
0ea97180 MS |
1214 | EXPORT_SYMBOL(write_cache_pages); |
1215 | ||
1216 | /* | |
1217 | * Function used by generic_writepages to call the real writepage | |
1218 | * function and set the mapping flags on error | |
1219 | */ | |
1220 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1221 | void *data) | |
1222 | { | |
1223 | struct address_space *mapping = data; | |
1224 | int ret = mapping->a_ops->writepage(page, wbc); | |
1225 | mapping_set_error(mapping, ret); | |
1226 | return ret; | |
1227 | } | |
1228 | ||
1229 | /** | |
1230 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1231 | * @mapping: address space structure to write | |
1232 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1233 | * | |
1234 | * This is a library function, which implements the writepages() | |
1235 | * address_space_operation. | |
1236 | */ | |
1237 | int generic_writepages(struct address_space *mapping, | |
1238 | struct writeback_control *wbc) | |
1239 | { | |
9b6096a6 SL |
1240 | struct blk_plug plug; |
1241 | int ret; | |
1242 | ||
0ea97180 MS |
1243 | /* deal with chardevs and other special file */ |
1244 | if (!mapping->a_ops->writepage) | |
1245 | return 0; | |
1246 | ||
9b6096a6 SL |
1247 | blk_start_plug(&plug); |
1248 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
1249 | blk_finish_plug(&plug); | |
1250 | return ret; | |
0ea97180 | 1251 | } |
811d736f DH |
1252 | |
1253 | EXPORT_SYMBOL(generic_writepages); | |
1254 | ||
1da177e4 LT |
1255 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1256 | { | |
22905f77 AM |
1257 | int ret; |
1258 | ||
1da177e4 LT |
1259 | if (wbc->nr_to_write <= 0) |
1260 | return 0; | |
1261 | if (mapping->a_ops->writepages) | |
d08b3851 | 1262 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1263 | else |
1264 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 1265 | return ret; |
1da177e4 LT |
1266 | } |
1267 | ||
1268 | /** | |
1269 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1270 | * @page: the page to write |
1271 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1272 | * |
1273 | * The page must be locked by the caller and will be unlocked upon return. | |
1274 | * | |
1275 | * write_one_page() returns a negative error code if I/O failed. | |
1276 | */ | |
1277 | int write_one_page(struct page *page, int wait) | |
1278 | { | |
1279 | struct address_space *mapping = page->mapping; | |
1280 | int ret = 0; | |
1281 | struct writeback_control wbc = { | |
1282 | .sync_mode = WB_SYNC_ALL, | |
1283 | .nr_to_write = 1, | |
1284 | }; | |
1285 | ||
1286 | BUG_ON(!PageLocked(page)); | |
1287 | ||
1288 | if (wait) | |
1289 | wait_on_page_writeback(page); | |
1290 | ||
1291 | if (clear_page_dirty_for_io(page)) { | |
1292 | page_cache_get(page); | |
1293 | ret = mapping->a_ops->writepage(page, &wbc); | |
1294 | if (ret == 0 && wait) { | |
1295 | wait_on_page_writeback(page); | |
1296 | if (PageError(page)) | |
1297 | ret = -EIO; | |
1298 | } | |
1299 | page_cache_release(page); | |
1300 | } else { | |
1301 | unlock_page(page); | |
1302 | } | |
1303 | return ret; | |
1304 | } | |
1305 | EXPORT_SYMBOL(write_one_page); | |
1306 | ||
76719325 KC |
1307 | /* |
1308 | * For address_spaces which do not use buffers nor write back. | |
1309 | */ | |
1310 | int __set_page_dirty_no_writeback(struct page *page) | |
1311 | { | |
1312 | if (!PageDirty(page)) | |
c3f0da63 | 1313 | return !TestSetPageDirty(page); |
76719325 KC |
1314 | return 0; |
1315 | } | |
1316 | ||
e3a7cca1 ES |
1317 | /* |
1318 | * Helper function for set_page_dirty family. | |
1319 | * NOTE: This relies on being atomic wrt interrupts. | |
1320 | */ | |
1321 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1322 | { | |
1323 | if (mapping_cap_account_dirty(mapping)) { | |
1324 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
ea941f0e | 1325 | __inc_zone_page_state(page, NR_DIRTIED); |
e3a7cca1 ES |
1326 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
1327 | task_dirty_inc(current); | |
1328 | task_io_account_write(PAGE_CACHE_SIZE); | |
1329 | } | |
1330 | } | |
679ceace | 1331 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 1332 | |
f629d1c9 MR |
1333 | /* |
1334 | * Helper function for set_page_writeback family. | |
1335 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic | |
1336 | * wrt interrupts. | |
1337 | */ | |
1338 | void account_page_writeback(struct page *page) | |
1339 | { | |
1340 | inc_zone_page_state(page, NR_WRITEBACK); | |
1341 | } | |
1342 | EXPORT_SYMBOL(account_page_writeback); | |
1343 | ||
1da177e4 LT |
1344 | /* |
1345 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1346 | * its radix tree. | |
1347 | * | |
1348 | * This is also used when a single buffer is being dirtied: we want to set the | |
1349 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1350 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1351 | * | |
1352 | * Most callers have locked the page, which pins the address_space in memory. | |
1353 | * But zap_pte_range() does not lock the page, however in that case the | |
1354 | * mapping is pinned by the vma's ->vm_file reference. | |
1355 | * | |
1356 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1357 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1358 | */ |
1359 | int __set_page_dirty_nobuffers(struct page *page) | |
1360 | { | |
1da177e4 LT |
1361 | if (!TestSetPageDirty(page)) { |
1362 | struct address_space *mapping = page_mapping(page); | |
1363 | struct address_space *mapping2; | |
1364 | ||
8c08540f AM |
1365 | if (!mapping) |
1366 | return 1; | |
1367 | ||
19fd6231 | 1368 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1369 | mapping2 = page_mapping(page); |
1370 | if (mapping2) { /* Race with truncate? */ | |
1371 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1372 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1373 | account_page_dirtied(page, mapping); |
8c08540f AM |
1374 | radix_tree_tag_set(&mapping->page_tree, |
1375 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1376 | } | |
19fd6231 | 1377 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1378 | if (mapping->host) { |
1379 | /* !PageAnon && !swapper_space */ | |
1380 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1381 | } |
4741c9fd | 1382 | return 1; |
1da177e4 | 1383 | } |
4741c9fd | 1384 | return 0; |
1da177e4 LT |
1385 | } |
1386 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
1387 | ||
1388 | /* | |
1389 | * When a writepage implementation decides that it doesn't want to write this | |
1390 | * page for some reason, it should redirty the locked page via | |
1391 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
1392 | */ | |
1393 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
1394 | { | |
1395 | wbc->pages_skipped++; | |
1396 | return __set_page_dirty_nobuffers(page); | |
1397 | } | |
1398 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
1399 | ||
1400 | /* | |
6746aff7 WF |
1401 | * Dirty a page. |
1402 | * | |
1403 | * For pages with a mapping this should be done under the page lock | |
1404 | * for the benefit of asynchronous memory errors who prefer a consistent | |
1405 | * dirty state. This rule can be broken in some special cases, | |
1406 | * but should be better not to. | |
1407 | * | |
1da177e4 LT |
1408 | * If the mapping doesn't provide a set_page_dirty a_op, then |
1409 | * just fall through and assume that it wants buffer_heads. | |
1410 | */ | |
1cf6e7d8 | 1411 | int set_page_dirty(struct page *page) |
1da177e4 LT |
1412 | { |
1413 | struct address_space *mapping = page_mapping(page); | |
1414 | ||
1415 | if (likely(mapping)) { | |
1416 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
1417 | /* |
1418 | * readahead/lru_deactivate_page could remain | |
1419 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
1420 | * About readahead, if the page is written, the flags would be | |
1421 | * reset. So no problem. | |
1422 | * About lru_deactivate_page, if the page is redirty, the flag | |
1423 | * will be reset. So no problem. but if the page is used by readahead | |
1424 | * it will confuse readahead and make it restart the size rampup | |
1425 | * process. But it's a trivial problem. | |
1426 | */ | |
1427 | ClearPageReclaim(page); | |
9361401e DH |
1428 | #ifdef CONFIG_BLOCK |
1429 | if (!spd) | |
1430 | spd = __set_page_dirty_buffers; | |
1431 | #endif | |
1432 | return (*spd)(page); | |
1da177e4 | 1433 | } |
4741c9fd AM |
1434 | if (!PageDirty(page)) { |
1435 | if (!TestSetPageDirty(page)) | |
1436 | return 1; | |
1437 | } | |
1da177e4 LT |
1438 | return 0; |
1439 | } | |
1440 | EXPORT_SYMBOL(set_page_dirty); | |
1441 | ||
1442 | /* | |
1443 | * set_page_dirty() is racy if the caller has no reference against | |
1444 | * page->mapping->host, and if the page is unlocked. This is because another | |
1445 | * CPU could truncate the page off the mapping and then free the mapping. | |
1446 | * | |
1447 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
1448 | * holds a reference on the inode by having an open file. | |
1449 | * | |
1450 | * In other cases, the page should be locked before running set_page_dirty(). | |
1451 | */ | |
1452 | int set_page_dirty_lock(struct page *page) | |
1453 | { | |
1454 | int ret; | |
1455 | ||
7eaceacc | 1456 | lock_page(page); |
1da177e4 LT |
1457 | ret = set_page_dirty(page); |
1458 | unlock_page(page); | |
1459 | return ret; | |
1460 | } | |
1461 | EXPORT_SYMBOL(set_page_dirty_lock); | |
1462 | ||
1da177e4 LT |
1463 | /* |
1464 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
1465 | * Returns true if the page was previously dirty. | |
1466 | * | |
1467 | * This is for preparing to put the page under writeout. We leave the page | |
1468 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
1469 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
1470 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
1471 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
1472 | * back into sync. | |
1473 | * | |
1474 | * This incoherency between the page's dirty flag and radix-tree tag is | |
1475 | * unfortunate, but it only exists while the page is locked. | |
1476 | */ | |
1477 | int clear_page_dirty_for_io(struct page *page) | |
1478 | { | |
1479 | struct address_space *mapping = page_mapping(page); | |
1480 | ||
79352894 NP |
1481 | BUG_ON(!PageLocked(page)); |
1482 | ||
7658cc28 LT |
1483 | if (mapping && mapping_cap_account_dirty(mapping)) { |
1484 | /* | |
1485 | * Yes, Virginia, this is indeed insane. | |
1486 | * | |
1487 | * We use this sequence to make sure that | |
1488 | * (a) we account for dirty stats properly | |
1489 | * (b) we tell the low-level filesystem to | |
1490 | * mark the whole page dirty if it was | |
1491 | * dirty in a pagetable. Only to then | |
1492 | * (c) clean the page again and return 1 to | |
1493 | * cause the writeback. | |
1494 | * | |
1495 | * This way we avoid all nasty races with the | |
1496 | * dirty bit in multiple places and clearing | |
1497 | * them concurrently from different threads. | |
1498 | * | |
1499 | * Note! Normally the "set_page_dirty(page)" | |
1500 | * has no effect on the actual dirty bit - since | |
1501 | * that will already usually be set. But we | |
1502 | * need the side effects, and it can help us | |
1503 | * avoid races. | |
1504 | * | |
1505 | * We basically use the page "master dirty bit" | |
1506 | * as a serialization point for all the different | |
1507 | * threads doing their things. | |
7658cc28 LT |
1508 | */ |
1509 | if (page_mkclean(page)) | |
1510 | set_page_dirty(page); | |
79352894 NP |
1511 | /* |
1512 | * We carefully synchronise fault handlers against | |
1513 | * installing a dirty pte and marking the page dirty | |
1514 | * at this point. We do this by having them hold the | |
1515 | * page lock at some point after installing their | |
1516 | * pte, but before marking the page dirty. | |
1517 | * Pages are always locked coming in here, so we get | |
1518 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
1519 | * for more comments. | |
1520 | */ | |
7658cc28 | 1521 | if (TestClearPageDirty(page)) { |
8c08540f | 1522 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
1523 | dec_bdi_stat(mapping->backing_dev_info, |
1524 | BDI_RECLAIMABLE); | |
7658cc28 | 1525 | return 1; |
1da177e4 | 1526 | } |
7658cc28 | 1527 | return 0; |
1da177e4 | 1528 | } |
7658cc28 | 1529 | return TestClearPageDirty(page); |
1da177e4 | 1530 | } |
58bb01a9 | 1531 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
1532 | |
1533 | int test_clear_page_writeback(struct page *page) | |
1534 | { | |
1535 | struct address_space *mapping = page_mapping(page); | |
1536 | int ret; | |
1537 | ||
1538 | if (mapping) { | |
69cb51d1 | 1539 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1540 | unsigned long flags; |
1541 | ||
19fd6231 | 1542 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1543 | ret = TestClearPageWriteback(page); |
69cb51d1 | 1544 | if (ret) { |
1da177e4 LT |
1545 | radix_tree_tag_clear(&mapping->page_tree, |
1546 | page_index(page), | |
1547 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1548 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 1549 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
1550 | __bdi_writeout_inc(bdi); |
1551 | } | |
69cb51d1 | 1552 | } |
19fd6231 | 1553 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1554 | } else { |
1555 | ret = TestClearPageWriteback(page); | |
1556 | } | |
99b12e3d | 1557 | if (ret) { |
d688abf5 | 1558 | dec_zone_page_state(page, NR_WRITEBACK); |
99b12e3d WF |
1559 | inc_zone_page_state(page, NR_WRITTEN); |
1560 | } | |
1da177e4 LT |
1561 | return ret; |
1562 | } | |
1563 | ||
1564 | int test_set_page_writeback(struct page *page) | |
1565 | { | |
1566 | struct address_space *mapping = page_mapping(page); | |
1567 | int ret; | |
1568 | ||
1569 | if (mapping) { | |
69cb51d1 | 1570 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1571 | unsigned long flags; |
1572 | ||
19fd6231 | 1573 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1574 | ret = TestSetPageWriteback(page); |
69cb51d1 | 1575 | if (!ret) { |
1da177e4 LT |
1576 | radix_tree_tag_set(&mapping->page_tree, |
1577 | page_index(page), | |
1578 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1579 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
1580 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
1581 | } | |
1da177e4 LT |
1582 | if (!PageDirty(page)) |
1583 | radix_tree_tag_clear(&mapping->page_tree, | |
1584 | page_index(page), | |
1585 | PAGECACHE_TAG_DIRTY); | |
f446daae JK |
1586 | radix_tree_tag_clear(&mapping->page_tree, |
1587 | page_index(page), | |
1588 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 1589 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1590 | } else { |
1591 | ret = TestSetPageWriteback(page); | |
1592 | } | |
d688abf5 | 1593 | if (!ret) |
f629d1c9 | 1594 | account_page_writeback(page); |
1da177e4 LT |
1595 | return ret; |
1596 | ||
1597 | } | |
1598 | EXPORT_SYMBOL(test_set_page_writeback); | |
1599 | ||
1600 | /* | |
00128188 | 1601 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
1602 | * passed tag. |
1603 | */ | |
1604 | int mapping_tagged(struct address_space *mapping, int tag) | |
1605 | { | |
72c47832 | 1606 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
1607 | } |
1608 | EXPORT_SYMBOL(mapping_tagged); |