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> |
1da177e4 LT |
37 | |
38 | /* | |
39 | * The maximum number of pages to writeout in a single bdflush/kupdate | |
1c0eeaf5 | 40 | * operation. We do this so we don't hold I_SYNC against an inode for |
1da177e4 LT |
41 | * enormous amounts of time, which would block a userspace task which has |
42 | * been forced to throttle against that inode. Also, the code reevaluates | |
43 | * the dirty each time it has written this many pages. | |
44 | */ | |
45 | #define MAX_WRITEBACK_PAGES 1024 | |
46 | ||
47 | /* | |
48 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
49 | * will look to see if it needs to force writeback or throttling. | |
50 | */ | |
51 | static long ratelimit_pages = 32; | |
52 | ||
1da177e4 LT |
53 | /* |
54 | * When balance_dirty_pages decides that the caller needs to perform some | |
55 | * non-background writeback, this is how many pages it will attempt to write. | |
56 | * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably | |
57 | * large amounts of I/O are submitted. | |
58 | */ | |
59 | static inline long sync_writeback_pages(void) | |
60 | { | |
61 | return ratelimit_pages + ratelimit_pages / 2; | |
62 | } | |
63 | ||
64 | /* The following parameters are exported via /proc/sys/vm */ | |
65 | ||
66 | /* | |
67 | * Start background writeback (via pdflush) at this percentage | |
68 | */ | |
1b5e62b4 | 69 | int dirty_background_ratio = 10; |
1da177e4 | 70 | |
2da02997 DR |
71 | /* |
72 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
73 | * dirty_background_ratio * the amount of dirtyable memory | |
74 | */ | |
75 | unsigned long dirty_background_bytes; | |
76 | ||
195cf453 BG |
77 | /* |
78 | * free highmem will not be subtracted from the total free memory | |
79 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
80 | */ | |
81 | int vm_highmem_is_dirtyable; | |
82 | ||
1da177e4 LT |
83 | /* |
84 | * The generator of dirty data starts writeback at this percentage | |
85 | */ | |
1b5e62b4 | 86 | int vm_dirty_ratio = 20; |
1da177e4 | 87 | |
2da02997 DR |
88 | /* |
89 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
90 | * vm_dirty_ratio * the amount of dirtyable memory | |
91 | */ | |
92 | unsigned long vm_dirty_bytes; | |
93 | ||
1da177e4 | 94 | /* |
704503d8 | 95 | * The interval between `kupdate'-style writebacks |
1da177e4 | 96 | */ |
704503d8 | 97 | unsigned int dirty_writeback_interval = 5 * 100; /* sentiseconds */ |
1da177e4 LT |
98 | |
99 | /* | |
704503d8 | 100 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 101 | */ |
704503d8 | 102 | unsigned int dirty_expire_interval = 30 * 100; /* sentiseconds */ |
1da177e4 LT |
103 | |
104 | /* | |
105 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
106 | */ | |
107 | int block_dump; | |
108 | ||
109 | /* | |
ed5b43f1 BS |
110 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
111 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
112 | */ |
113 | int laptop_mode; | |
114 | ||
115 | EXPORT_SYMBOL(laptop_mode); | |
116 | ||
117 | /* End of sysctl-exported parameters */ | |
118 | ||
119 | ||
120 | static void background_writeout(unsigned long _min_pages); | |
121 | ||
04fbfdc1 PZ |
122 | /* |
123 | * Scale the writeback cache size proportional to the relative writeout speeds. | |
124 | * | |
125 | * We do this by keeping a floating proportion between BDIs, based on page | |
126 | * writeback completions [end_page_writeback()]. Those devices that write out | |
127 | * pages fastest will get the larger share, while the slower will get a smaller | |
128 | * share. | |
129 | * | |
130 | * We use page writeout completions because we are interested in getting rid of | |
131 | * dirty pages. Having them written out is the primary goal. | |
132 | * | |
133 | * We introduce a concept of time, a period over which we measure these events, | |
134 | * because demand can/will vary over time. The length of this period itself is | |
135 | * measured in page writeback completions. | |
136 | * | |
137 | */ | |
138 | static struct prop_descriptor vm_completions; | |
3e26c149 | 139 | static struct prop_descriptor vm_dirties; |
04fbfdc1 | 140 | |
04fbfdc1 PZ |
141 | /* |
142 | * couple the period to the dirty_ratio: | |
143 | * | |
144 | * period/2 ~ roundup_pow_of_two(dirty limit) | |
145 | */ | |
146 | static int calc_period_shift(void) | |
147 | { | |
148 | unsigned long dirty_total; | |
149 | ||
2da02997 DR |
150 | if (vm_dirty_bytes) |
151 | dirty_total = vm_dirty_bytes / PAGE_SIZE; | |
152 | else | |
153 | dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / | |
154 | 100; | |
04fbfdc1 PZ |
155 | return 2 + ilog2(dirty_total - 1); |
156 | } | |
157 | ||
158 | /* | |
2da02997 | 159 | * update the period when the dirty threshold changes. |
04fbfdc1 | 160 | */ |
2da02997 DR |
161 | static void update_completion_period(void) |
162 | { | |
163 | int shift = calc_period_shift(); | |
164 | prop_change_shift(&vm_completions, shift); | |
165 | prop_change_shift(&vm_dirties, shift); | |
166 | } | |
167 | ||
168 | int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
169 | struct file *filp, void __user *buffer, size_t *lenp, | |
170 | loff_t *ppos) | |
171 | { | |
172 | int ret; | |
173 | ||
174 | ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos); | |
175 | if (ret == 0 && write) | |
176 | dirty_background_bytes = 0; | |
177 | return ret; | |
178 | } | |
179 | ||
180 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
181 | struct file *filp, void __user *buffer, size_t *lenp, | |
182 | loff_t *ppos) | |
183 | { | |
184 | int ret; | |
185 | ||
186 | ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos); | |
187 | if (ret == 0 && write) | |
188 | dirty_background_ratio = 0; | |
189 | return ret; | |
190 | } | |
191 | ||
04fbfdc1 PZ |
192 | int dirty_ratio_handler(struct ctl_table *table, int write, |
193 | struct file *filp, void __user *buffer, size_t *lenp, | |
194 | loff_t *ppos) | |
195 | { | |
196 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
197 | int ret; |
198 | ||
199 | ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos); | |
04fbfdc1 | 200 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
2da02997 DR |
201 | update_completion_period(); |
202 | vm_dirty_bytes = 0; | |
203 | } | |
204 | return ret; | |
205 | } | |
206 | ||
207 | ||
208 | int dirty_bytes_handler(struct ctl_table *table, int write, | |
209 | struct file *filp, void __user *buffer, size_t *lenp, | |
210 | loff_t *ppos) | |
211 | { | |
fc3501d4 | 212 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
213 | int ret; |
214 | ||
215 | ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos); | |
216 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { | |
217 | update_completion_period(); | |
218 | vm_dirty_ratio = 0; | |
04fbfdc1 PZ |
219 | } |
220 | return ret; | |
221 | } | |
222 | ||
223 | /* | |
224 | * Increment the BDI's writeout completion count and the global writeout | |
225 | * completion count. Called from test_clear_page_writeback(). | |
226 | */ | |
227 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) | |
228 | { | |
a42dde04 PZ |
229 | __prop_inc_percpu_max(&vm_completions, &bdi->completions, |
230 | bdi->max_prop_frac); | |
04fbfdc1 PZ |
231 | } |
232 | ||
dd5656e5 MS |
233 | void bdi_writeout_inc(struct backing_dev_info *bdi) |
234 | { | |
235 | unsigned long flags; | |
236 | ||
237 | local_irq_save(flags); | |
238 | __bdi_writeout_inc(bdi); | |
239 | local_irq_restore(flags); | |
240 | } | |
241 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); | |
242 | ||
1cf6e7d8 | 243 | void task_dirty_inc(struct task_struct *tsk) |
3e26c149 PZ |
244 | { |
245 | prop_inc_single(&vm_dirties, &tsk->dirties); | |
246 | } | |
247 | ||
04fbfdc1 PZ |
248 | /* |
249 | * Obtain an accurate fraction of the BDI's portion. | |
250 | */ | |
251 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, | |
252 | long *numerator, long *denominator) | |
253 | { | |
254 | if (bdi_cap_writeback_dirty(bdi)) { | |
255 | prop_fraction_percpu(&vm_completions, &bdi->completions, | |
256 | numerator, denominator); | |
257 | } else { | |
258 | *numerator = 0; | |
259 | *denominator = 1; | |
260 | } | |
261 | } | |
262 | ||
263 | /* | |
264 | * Clip the earned share of dirty pages to that which is actually available. | |
265 | * This avoids exceeding the total dirty_limit when the floating averages | |
266 | * fluctuate too quickly. | |
267 | */ | |
268 | static void | |
269 | clip_bdi_dirty_limit(struct backing_dev_info *bdi, long dirty, long *pbdi_dirty) | |
270 | { | |
271 | long avail_dirty; | |
272 | ||
273 | avail_dirty = dirty - | |
274 | (global_page_state(NR_FILE_DIRTY) + | |
275 | global_page_state(NR_WRITEBACK) + | |
fc3ba692 MS |
276 | global_page_state(NR_UNSTABLE_NFS) + |
277 | global_page_state(NR_WRITEBACK_TEMP)); | |
04fbfdc1 PZ |
278 | |
279 | if (avail_dirty < 0) | |
280 | avail_dirty = 0; | |
281 | ||
282 | avail_dirty += bdi_stat(bdi, BDI_RECLAIMABLE) + | |
283 | bdi_stat(bdi, BDI_WRITEBACK); | |
284 | ||
285 | *pbdi_dirty = min(*pbdi_dirty, avail_dirty); | |
286 | } | |
287 | ||
3e26c149 PZ |
288 | static inline void task_dirties_fraction(struct task_struct *tsk, |
289 | long *numerator, long *denominator) | |
290 | { | |
291 | prop_fraction_single(&vm_dirties, &tsk->dirties, | |
292 | numerator, denominator); | |
293 | } | |
294 | ||
295 | /* | |
296 | * scale the dirty limit | |
297 | * | |
298 | * task specific dirty limit: | |
299 | * | |
300 | * dirty -= (dirty/8) * p_{t} | |
301 | */ | |
f61eaf9f | 302 | static void task_dirty_limit(struct task_struct *tsk, long *pdirty) |
3e26c149 PZ |
303 | { |
304 | long numerator, denominator; | |
305 | long dirty = *pdirty; | |
306 | u64 inv = dirty >> 3; | |
307 | ||
308 | task_dirties_fraction(tsk, &numerator, &denominator); | |
309 | inv *= numerator; | |
310 | do_div(inv, denominator); | |
311 | ||
312 | dirty -= inv; | |
313 | if (dirty < *pdirty/2) | |
314 | dirty = *pdirty/2; | |
315 | ||
316 | *pdirty = dirty; | |
317 | } | |
318 | ||
189d3c4a PZ |
319 | /* |
320 | * | |
321 | */ | |
322 | static DEFINE_SPINLOCK(bdi_lock); | |
323 | static unsigned int bdi_min_ratio; | |
324 | ||
325 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
326 | { | |
327 | int ret = 0; | |
328 | unsigned long flags; | |
329 | ||
330 | spin_lock_irqsave(&bdi_lock, flags); | |
a42dde04 | 331 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 332 | ret = -EINVAL; |
a42dde04 PZ |
333 | } else { |
334 | min_ratio -= bdi->min_ratio; | |
335 | if (bdi_min_ratio + min_ratio < 100) { | |
336 | bdi_min_ratio += min_ratio; | |
337 | bdi->min_ratio += min_ratio; | |
338 | } else { | |
339 | ret = -EINVAL; | |
340 | } | |
341 | } | |
342 | spin_unlock_irqrestore(&bdi_lock, flags); | |
343 | ||
344 | return ret; | |
345 | } | |
346 | ||
347 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
348 | { | |
349 | unsigned long flags; | |
350 | int ret = 0; | |
351 | ||
352 | if (max_ratio > 100) | |
353 | return -EINVAL; | |
354 | ||
355 | spin_lock_irqsave(&bdi_lock, flags); | |
356 | if (bdi->min_ratio > max_ratio) { | |
357 | ret = -EINVAL; | |
358 | } else { | |
359 | bdi->max_ratio = max_ratio; | |
360 | bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; | |
361 | } | |
189d3c4a PZ |
362 | spin_unlock_irqrestore(&bdi_lock, flags); |
363 | ||
364 | return ret; | |
365 | } | |
a42dde04 | 366 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 367 | |
1da177e4 LT |
368 | /* |
369 | * Work out the current dirty-memory clamping and background writeout | |
370 | * thresholds. | |
371 | * | |
372 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
373 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
374 | * pages. It is better to clamp down on writers than to start swapping, and | |
375 | * performing lots of scanning. | |
376 | * | |
377 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
378 | * | |
379 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
380 | * excessive. | |
381 | * | |
382 | * We make sure that the background writeout level is below the adjusted | |
383 | * clamping level. | |
384 | */ | |
1b424464 CL |
385 | |
386 | static unsigned long highmem_dirtyable_memory(unsigned long total) | |
387 | { | |
388 | #ifdef CONFIG_HIGHMEM | |
389 | int node; | |
390 | unsigned long x = 0; | |
391 | ||
37b07e41 | 392 | for_each_node_state(node, N_HIGH_MEMORY) { |
1b424464 CL |
393 | struct zone *z = |
394 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; | |
395 | ||
4f98a2fe | 396 | x += zone_page_state(z, NR_FREE_PAGES) + zone_lru_pages(z); |
1b424464 CL |
397 | } |
398 | /* | |
399 | * Make sure that the number of highmem pages is never larger | |
400 | * than the number of the total dirtyable memory. This can only | |
401 | * occur in very strange VM situations but we want to make sure | |
402 | * that this does not occur. | |
403 | */ | |
404 | return min(x, total); | |
405 | #else | |
406 | return 0; | |
407 | #endif | |
408 | } | |
409 | ||
3eefae99 SR |
410 | /** |
411 | * determine_dirtyable_memory - amount of memory that may be used | |
412 | * | |
413 | * Returns the numebr of pages that can currently be freed and used | |
414 | * by the kernel for direct mappings. | |
415 | */ | |
416 | unsigned long determine_dirtyable_memory(void) | |
1b424464 CL |
417 | { |
418 | unsigned long x; | |
419 | ||
4f98a2fe | 420 | x = global_page_state(NR_FREE_PAGES) + global_lru_pages(); |
195cf453 BG |
421 | |
422 | if (!vm_highmem_is_dirtyable) | |
423 | x -= highmem_dirtyable_memory(x); | |
424 | ||
1b424464 CL |
425 | return x + 1; /* Ensure that we never return 0 */ |
426 | } | |
427 | ||
cf0ca9fe | 428 | void |
364aeb28 DR |
429 | get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty, |
430 | unsigned long *pbdi_dirty, struct backing_dev_info *bdi) | |
1da177e4 | 431 | { |
364aeb28 DR |
432 | unsigned long background; |
433 | unsigned long dirty; | |
1b424464 | 434 | unsigned long available_memory = determine_dirtyable_memory(); |
1da177e4 LT |
435 | struct task_struct *tsk; |
436 | ||
2da02997 DR |
437 | if (vm_dirty_bytes) |
438 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); | |
439 | else { | |
440 | int dirty_ratio; | |
441 | ||
442 | dirty_ratio = vm_dirty_ratio; | |
443 | if (dirty_ratio < 5) | |
444 | dirty_ratio = 5; | |
445 | dirty = (dirty_ratio * available_memory) / 100; | |
446 | } | |
1da177e4 | 447 | |
2da02997 DR |
448 | if (dirty_background_bytes) |
449 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); | |
450 | else | |
451 | background = (dirty_background_ratio * available_memory) / 100; | |
1da177e4 | 452 | |
2da02997 DR |
453 | if (background >= dirty) |
454 | background = dirty / 2; | |
1da177e4 LT |
455 | tsk = current; |
456 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
457 | background += background / 4; | |
458 | dirty += dirty / 4; | |
459 | } | |
460 | *pbackground = background; | |
461 | *pdirty = dirty; | |
04fbfdc1 PZ |
462 | |
463 | if (bdi) { | |
189d3c4a | 464 | u64 bdi_dirty; |
04fbfdc1 PZ |
465 | long numerator, denominator; |
466 | ||
467 | /* | |
468 | * Calculate this BDI's share of the dirty ratio. | |
469 | */ | |
470 | bdi_writeout_fraction(bdi, &numerator, &denominator); | |
471 | ||
189d3c4a | 472 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
04fbfdc1 PZ |
473 | bdi_dirty *= numerator; |
474 | do_div(bdi_dirty, denominator); | |
189d3c4a | 475 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
a42dde04 PZ |
476 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) |
477 | bdi_dirty = dirty * bdi->max_ratio / 100; | |
04fbfdc1 PZ |
478 | |
479 | *pbdi_dirty = bdi_dirty; | |
480 | clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty); | |
3e26c149 | 481 | task_dirty_limit(current, pbdi_dirty); |
04fbfdc1 | 482 | } |
1da177e4 LT |
483 | } |
484 | ||
485 | /* | |
486 | * balance_dirty_pages() must be called by processes which are generating dirty | |
487 | * data. It looks at the number of dirty pages in the machine and will force | |
488 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
489 | * If we're over `background_thresh' then pdflush is woken to perform some | |
490 | * writeout. | |
491 | */ | |
492 | static void balance_dirty_pages(struct address_space *mapping) | |
493 | { | |
5fce25a9 PZ |
494 | long nr_reclaimable, bdi_nr_reclaimable; |
495 | long nr_writeback, bdi_nr_writeback; | |
364aeb28 DR |
496 | unsigned long background_thresh; |
497 | unsigned long dirty_thresh; | |
498 | unsigned long bdi_thresh; | |
1da177e4 LT |
499 | unsigned long pages_written = 0; |
500 | unsigned long write_chunk = sync_writeback_pages(); | |
501 | ||
502 | struct backing_dev_info *bdi = mapping->backing_dev_info; | |
503 | ||
504 | for (;;) { | |
505 | struct writeback_control wbc = { | |
506 | .bdi = bdi, | |
507 | .sync_mode = WB_SYNC_NONE, | |
508 | .older_than_this = NULL, | |
509 | .nr_to_write = write_chunk, | |
111ebb6e | 510 | .range_cyclic = 1, |
1da177e4 LT |
511 | }; |
512 | ||
04fbfdc1 PZ |
513 | get_dirty_limits(&background_thresh, &dirty_thresh, |
514 | &bdi_thresh, bdi); | |
5fce25a9 PZ |
515 | |
516 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + | |
517 | global_page_state(NR_UNSTABLE_NFS); | |
518 | nr_writeback = global_page_state(NR_WRITEBACK); | |
519 | ||
04fbfdc1 PZ |
520 | bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
521 | bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); | |
5fce25a9 | 522 | |
04fbfdc1 PZ |
523 | if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) |
524 | break; | |
1da177e4 | 525 | |
5fce25a9 PZ |
526 | /* |
527 | * Throttle it only when the background writeback cannot | |
528 | * catch-up. This avoids (excessively) small writeouts | |
529 | * when the bdi limits are ramping up. | |
530 | */ | |
531 | if (nr_reclaimable + nr_writeback < | |
532 | (background_thresh + dirty_thresh) / 2) | |
533 | break; | |
534 | ||
04fbfdc1 PZ |
535 | if (!bdi->dirty_exceeded) |
536 | bdi->dirty_exceeded = 1; | |
1da177e4 LT |
537 | |
538 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. | |
539 | * Unstable writes are a feature of certain networked | |
540 | * filesystems (i.e. NFS) in which data may have been | |
541 | * written to the server's write cache, but has not yet | |
542 | * been flushed to permanent storage. | |
543 | */ | |
04fbfdc1 | 544 | if (bdi_nr_reclaimable) { |
1da177e4 | 545 | writeback_inodes(&wbc); |
1da177e4 | 546 | pages_written += write_chunk - wbc.nr_to_write; |
04fbfdc1 PZ |
547 | get_dirty_limits(&background_thresh, &dirty_thresh, |
548 | &bdi_thresh, bdi); | |
549 | } | |
550 | ||
551 | /* | |
552 | * In order to avoid the stacked BDI deadlock we need | |
553 | * to ensure we accurately count the 'dirty' pages when | |
554 | * the threshold is low. | |
555 | * | |
556 | * Otherwise it would be possible to get thresh+n pages | |
557 | * reported dirty, even though there are thresh-m pages | |
558 | * actually dirty; with m+n sitting in the percpu | |
559 | * deltas. | |
560 | */ | |
561 | if (bdi_thresh < 2*bdi_stat_error(bdi)) { | |
562 | bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); | |
563 | bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); | |
564 | } else if (bdi_nr_reclaimable) { | |
565 | bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); | |
566 | bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); | |
1da177e4 | 567 | } |
04fbfdc1 PZ |
568 | |
569 | if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) | |
570 | break; | |
571 | if (pages_written >= write_chunk) | |
572 | break; /* We've done our duty */ | |
573 | ||
3fcfab16 | 574 | congestion_wait(WRITE, HZ/10); |
1da177e4 LT |
575 | } |
576 | ||
04fbfdc1 PZ |
577 | if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh && |
578 | bdi->dirty_exceeded) | |
579 | bdi->dirty_exceeded = 0; | |
1da177e4 LT |
580 | |
581 | if (writeback_in_progress(bdi)) | |
582 | return; /* pdflush is already working this queue */ | |
583 | ||
584 | /* | |
585 | * In laptop mode, we wait until hitting the higher threshold before | |
586 | * starting background writeout, and then write out all the way down | |
587 | * to the lower threshold. So slow writers cause minimal disk activity. | |
588 | * | |
589 | * In normal mode, we start background writeout at the lower | |
590 | * background_thresh, to keep the amount of dirty memory low. | |
591 | */ | |
592 | if ((laptop_mode && pages_written) || | |
04fbfdc1 PZ |
593 | (!laptop_mode && (global_page_state(NR_FILE_DIRTY) |
594 | + global_page_state(NR_UNSTABLE_NFS) | |
595 | > background_thresh))) | |
1da177e4 LT |
596 | pdflush_operation(background_writeout, 0); |
597 | } | |
598 | ||
a200ee18 | 599 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
edc79b2a | 600 | { |
a200ee18 | 601 | if (set_page_dirty(page) || page_mkwrite) { |
edc79b2a PZ |
602 | struct address_space *mapping = page_mapping(page); |
603 | ||
604 | if (mapping) | |
605 | balance_dirty_pages_ratelimited(mapping); | |
606 | } | |
607 | } | |
608 | ||
1da177e4 | 609 | /** |
fa5a734e | 610 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 611 | * @mapping: address_space which was dirtied |
a580290c | 612 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
613 | * |
614 | * Processes which are dirtying memory should call in here once for each page | |
615 | * which was newly dirtied. The function will periodically check the system's | |
616 | * dirty state and will initiate writeback if needed. | |
617 | * | |
618 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
619 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
620 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
621 | * from overshooting the limit by (ratelimit_pages) each. | |
622 | */ | |
fa5a734e AM |
623 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
624 | unsigned long nr_pages_dirtied) | |
1da177e4 | 625 | { |
fa5a734e AM |
626 | static DEFINE_PER_CPU(unsigned long, ratelimits) = 0; |
627 | unsigned long ratelimit; | |
628 | unsigned long *p; | |
1da177e4 LT |
629 | |
630 | ratelimit = ratelimit_pages; | |
04fbfdc1 | 631 | if (mapping->backing_dev_info->dirty_exceeded) |
1da177e4 LT |
632 | ratelimit = 8; |
633 | ||
634 | /* | |
635 | * Check the rate limiting. Also, we do not want to throttle real-time | |
636 | * tasks in balance_dirty_pages(). Period. | |
637 | */ | |
fa5a734e AM |
638 | preempt_disable(); |
639 | p = &__get_cpu_var(ratelimits); | |
640 | *p += nr_pages_dirtied; | |
641 | if (unlikely(*p >= ratelimit)) { | |
642 | *p = 0; | |
643 | preempt_enable(); | |
1da177e4 LT |
644 | balance_dirty_pages(mapping); |
645 | return; | |
646 | } | |
fa5a734e | 647 | preempt_enable(); |
1da177e4 | 648 | } |
fa5a734e | 649 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 650 | |
232ea4d6 | 651 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 652 | { |
364aeb28 DR |
653 | unsigned long background_thresh; |
654 | unsigned long dirty_thresh; | |
1da177e4 LT |
655 | |
656 | for ( ; ; ) { | |
04fbfdc1 | 657 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); |
1da177e4 LT |
658 | |
659 | /* | |
660 | * Boost the allowable dirty threshold a bit for page | |
661 | * allocators so they don't get DoS'ed by heavy writers | |
662 | */ | |
663 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
664 | ||
c24f21bd CL |
665 | if (global_page_state(NR_UNSTABLE_NFS) + |
666 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
667 | break; | |
3fcfab16 | 668 | congestion_wait(WRITE, HZ/10); |
369f2389 FW |
669 | |
670 | /* | |
671 | * The caller might hold locks which can prevent IO completion | |
672 | * or progress in the filesystem. So we cannot just sit here | |
673 | * waiting for IO to complete. | |
674 | */ | |
675 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
676 | break; | |
1da177e4 LT |
677 | } |
678 | } | |
679 | ||
1da177e4 LT |
680 | /* |
681 | * writeback at least _min_pages, and keep writing until the amount of dirty | |
682 | * memory is less than the background threshold, or until we're all clean. | |
683 | */ | |
684 | static void background_writeout(unsigned long _min_pages) | |
685 | { | |
686 | long min_pages = _min_pages; | |
687 | struct writeback_control wbc = { | |
688 | .bdi = NULL, | |
689 | .sync_mode = WB_SYNC_NONE, | |
690 | .older_than_this = NULL, | |
691 | .nr_to_write = 0, | |
692 | .nonblocking = 1, | |
111ebb6e | 693 | .range_cyclic = 1, |
1da177e4 LT |
694 | }; |
695 | ||
696 | for ( ; ; ) { | |
364aeb28 DR |
697 | unsigned long background_thresh; |
698 | unsigned long dirty_thresh; | |
1da177e4 | 699 | |
04fbfdc1 | 700 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); |
c24f21bd CL |
701 | if (global_page_state(NR_FILE_DIRTY) + |
702 | global_page_state(NR_UNSTABLE_NFS) < background_thresh | |
1da177e4 LT |
703 | && min_pages <= 0) |
704 | break; | |
8bc3be27 | 705 | wbc.more_io = 0; |
1da177e4 LT |
706 | wbc.encountered_congestion = 0; |
707 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
708 | wbc.pages_skipped = 0; | |
709 | writeback_inodes(&wbc); | |
710 | min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
711 | if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { | |
712 | /* Wrote less than expected */ | |
8bc3be27 FW |
713 | if (wbc.encountered_congestion || wbc.more_io) |
714 | congestion_wait(WRITE, HZ/10); | |
715 | else | |
1da177e4 LT |
716 | break; |
717 | } | |
718 | } | |
719 | } | |
720 | ||
721 | /* | |
722 | * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back | |
723 | * the whole world. Returns 0 if a pdflush thread was dispatched. Returns | |
724 | * -1 if all pdflush threads were busy. | |
725 | */ | |
687a21ce | 726 | int wakeup_pdflush(long nr_pages) |
1da177e4 | 727 | { |
c24f21bd CL |
728 | if (nr_pages == 0) |
729 | nr_pages = global_page_state(NR_FILE_DIRTY) + | |
730 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 LT |
731 | return pdflush_operation(background_writeout, nr_pages); |
732 | } | |
733 | ||
734 | static void wb_timer_fn(unsigned long unused); | |
735 | static void laptop_timer_fn(unsigned long unused); | |
736 | ||
8d06afab IM |
737 | static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0); |
738 | static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0); | |
1da177e4 LT |
739 | |
740 | /* | |
741 | * Periodic writeback of "old" data. | |
742 | * | |
743 | * Define "old": the first time one of an inode's pages is dirtied, we mark the | |
744 | * dirtying-time in the inode's address_space. So this periodic writeback code | |
745 | * just walks the superblock inode list, writing back any inodes which are | |
746 | * older than a specific point in time. | |
747 | * | |
f6ef9438 BS |
748 | * Try to run once per dirty_writeback_interval. But if a writeback event |
749 | * takes longer than a dirty_writeback_interval interval, then leave a | |
1da177e4 LT |
750 | * one-second gap. |
751 | * | |
752 | * older_than_this takes precedence over nr_to_write. So we'll only write back | |
753 | * all dirty pages if they are all attached to "old" mappings. | |
754 | */ | |
755 | static void wb_kupdate(unsigned long arg) | |
756 | { | |
757 | unsigned long oldest_jif; | |
758 | unsigned long start_jif; | |
759 | unsigned long next_jif; | |
760 | long nr_to_write; | |
1da177e4 LT |
761 | struct writeback_control wbc = { |
762 | .bdi = NULL, | |
763 | .sync_mode = WB_SYNC_NONE, | |
764 | .older_than_this = &oldest_jif, | |
765 | .nr_to_write = 0, | |
766 | .nonblocking = 1, | |
767 | .for_kupdate = 1, | |
111ebb6e | 768 | .range_cyclic = 1, |
1da177e4 LT |
769 | }; |
770 | ||
771 | sync_supers(); | |
772 | ||
704503d8 | 773 | oldest_jif = jiffies - msecs_to_jiffies(dirty_expire_interval); |
1da177e4 | 774 | start_jif = jiffies; |
704503d8 | 775 | next_jif = start_jif + msecs_to_jiffies(dirty_writeback_interval * 10); |
c24f21bd CL |
776 | nr_to_write = global_page_state(NR_FILE_DIRTY) + |
777 | global_page_state(NR_UNSTABLE_NFS) + | |
1da177e4 LT |
778 | (inodes_stat.nr_inodes - inodes_stat.nr_unused); |
779 | while (nr_to_write > 0) { | |
8bc3be27 | 780 | wbc.more_io = 0; |
1da177e4 LT |
781 | wbc.encountered_congestion = 0; |
782 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
783 | writeback_inodes(&wbc); | |
784 | if (wbc.nr_to_write > 0) { | |
8bc3be27 | 785 | if (wbc.encountered_congestion || wbc.more_io) |
3fcfab16 | 786 | congestion_wait(WRITE, HZ/10); |
1da177e4 LT |
787 | else |
788 | break; /* All the old data is written */ | |
789 | } | |
790 | nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
791 | } | |
792 | if (time_before(next_jif, jiffies + HZ)) | |
793 | next_jif = jiffies + HZ; | |
f6ef9438 | 794 | if (dirty_writeback_interval) |
1da177e4 LT |
795 | mod_timer(&wb_timer, next_jif); |
796 | } | |
797 | ||
798 | /* | |
799 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
800 | */ | |
801 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
3e733f07 | 802 | struct file *file, void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 803 | { |
704503d8 | 804 | proc_dointvec(table, write, file, buffer, length, ppos); |
3e733f07 | 805 | if (dirty_writeback_interval) |
704503d8 AD |
806 | mod_timer(&wb_timer, jiffies + |
807 | msecs_to_jiffies(dirty_writeback_interval * 10)); | |
3e733f07 | 808 | else |
1da177e4 | 809 | del_timer(&wb_timer); |
1da177e4 LT |
810 | return 0; |
811 | } | |
812 | ||
813 | static void wb_timer_fn(unsigned long unused) | |
814 | { | |
815 | if (pdflush_operation(wb_kupdate, 0) < 0) | |
816 | mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */ | |
817 | } | |
818 | ||
819 | static void laptop_flush(unsigned long unused) | |
820 | { | |
821 | sys_sync(); | |
822 | } | |
823 | ||
824 | static void laptop_timer_fn(unsigned long unused) | |
825 | { | |
826 | pdflush_operation(laptop_flush, 0); | |
827 | } | |
828 | ||
829 | /* | |
830 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
831 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
832 | * then push it back - the user is still using the disk. | |
833 | */ | |
834 | void laptop_io_completion(void) | |
835 | { | |
ed5b43f1 | 836 | mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
837 | } |
838 | ||
839 | /* | |
840 | * We're in laptop mode and we've just synced. The sync's writes will have | |
841 | * caused another writeback to be scheduled by laptop_io_completion. | |
842 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
843 | */ | |
844 | void laptop_sync_completion(void) | |
845 | { | |
846 | del_timer(&laptop_mode_wb_timer); | |
847 | } | |
848 | ||
849 | /* | |
850 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
851 | * if a large number of processes all perform writes at the same time. | |
852 | * If it is too low then SMP machines will call the (expensive) | |
853 | * get_writeback_state too often. | |
854 | * | |
855 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
856 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
857 | * thresholds before writeback cuts in. | |
858 | * | |
859 | * But the limit should not be set too high. Because it also controls the | |
860 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
861 | * If this is too large then the caller will block on the IO queue all the | |
862 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
863 | * will write six megabyte chunks, max. | |
864 | */ | |
865 | ||
2d1d43f6 | 866 | void writeback_set_ratelimit(void) |
1da177e4 | 867 | { |
40c99aae | 868 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
869 | if (ratelimit_pages < 16) |
870 | ratelimit_pages = 16; | |
871 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
872 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
873 | } | |
874 | ||
26c2143b | 875 | static int __cpuinit |
1da177e4 LT |
876 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
877 | { | |
2d1d43f6 | 878 | writeback_set_ratelimit(); |
aa0f0303 | 879 | return NOTIFY_DONE; |
1da177e4 LT |
880 | } |
881 | ||
74b85f37 | 882 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
883 | .notifier_call = ratelimit_handler, |
884 | .next = NULL, | |
885 | }; | |
886 | ||
887 | /* | |
dc6e29da LT |
888 | * Called early on to tune the page writeback dirty limits. |
889 | * | |
890 | * We used to scale dirty pages according to how total memory | |
891 | * related to pages that could be allocated for buffers (by | |
892 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
893 | * | |
894 | * However, that was when we used "dirty_ratio" to scale with | |
895 | * all memory, and we don't do that any more. "dirty_ratio" | |
896 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
897 | * totalhigh_pages from vm_total_pages), and as such we can't | |
898 | * get into the old insane situation any more where we had | |
899 | * large amounts of dirty pages compared to a small amount of | |
900 | * non-HIGHMEM memory. | |
901 | * | |
902 | * But we might still want to scale the dirty_ratio by how | |
903 | * much memory the box has.. | |
1da177e4 LT |
904 | */ |
905 | void __init page_writeback_init(void) | |
906 | { | |
04fbfdc1 PZ |
907 | int shift; |
908 | ||
704503d8 AD |
909 | mod_timer(&wb_timer, |
910 | jiffies + msecs_to_jiffies(dirty_writeback_interval * 10)); | |
2d1d43f6 | 911 | writeback_set_ratelimit(); |
1da177e4 | 912 | register_cpu_notifier(&ratelimit_nb); |
04fbfdc1 PZ |
913 | |
914 | shift = calc_period_shift(); | |
915 | prop_descriptor_init(&vm_completions, shift); | |
3e26c149 | 916 | prop_descriptor_init(&vm_dirties, shift); |
1da177e4 LT |
917 | } |
918 | ||
811d736f | 919 | /** |
0ea97180 | 920 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
921 | * @mapping: address space structure to write |
922 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
923 | * @writepage: function called for each page |
924 | * @data: data passed to writepage function | |
811d736f | 925 | * |
0ea97180 | 926 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
927 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
928 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
929 | * and msync() need to guarantee that all the data which was dirty at the time | |
930 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
931 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
932 | * existing IO to complete. | |
811d736f | 933 | */ |
0ea97180 MS |
934 | int write_cache_pages(struct address_space *mapping, |
935 | struct writeback_control *wbc, writepage_t writepage, | |
936 | void *data) | |
811d736f DH |
937 | { |
938 | struct backing_dev_info *bdi = mapping->backing_dev_info; | |
939 | int ret = 0; | |
940 | int done = 0; | |
811d736f DH |
941 | struct pagevec pvec; |
942 | int nr_pages; | |
31a12666 | 943 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
944 | pgoff_t index; |
945 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 946 | pgoff_t done_index; |
31a12666 | 947 | int cycled; |
811d736f | 948 | int range_whole = 0; |
17bc6c30 | 949 | long nr_to_write = wbc->nr_to_write; |
811d736f DH |
950 | |
951 | if (wbc->nonblocking && bdi_write_congested(bdi)) { | |
952 | wbc->encountered_congestion = 1; | |
953 | return 0; | |
954 | } | |
955 | ||
811d736f DH |
956 | pagevec_init(&pvec, 0); |
957 | if (wbc->range_cyclic) { | |
31a12666 NP |
958 | writeback_index = mapping->writeback_index; /* prev offset */ |
959 | index = writeback_index; | |
960 | if (index == 0) | |
961 | cycled = 1; | |
962 | else | |
963 | cycled = 0; | |
811d736f DH |
964 | end = -1; |
965 | } else { | |
966 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
967 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
968 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
969 | range_whole = 1; | |
31a12666 | 970 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f DH |
971 | } |
972 | retry: | |
bd19e012 | 973 | done_index = index; |
5a3d5c98 NP |
974 | while (!done && (index <= end)) { |
975 | int i; | |
976 | ||
977 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, | |
978 | PAGECACHE_TAG_DIRTY, | |
979 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); | |
980 | if (nr_pages == 0) | |
981 | break; | |
811d736f | 982 | |
811d736f DH |
983 | for (i = 0; i < nr_pages; i++) { |
984 | struct page *page = pvec.pages[i]; | |
985 | ||
986 | /* | |
d5482cdf NP |
987 | * At this point, the page may be truncated or |
988 | * invalidated (changing page->mapping to NULL), or | |
989 | * even swizzled back from swapper_space to tmpfs file | |
990 | * mapping. However, page->index will not change | |
991 | * because we have a reference on the page. | |
811d736f | 992 | */ |
d5482cdf NP |
993 | if (page->index > end) { |
994 | /* | |
995 | * can't be range_cyclic (1st pass) because | |
996 | * end == -1 in that case. | |
997 | */ | |
998 | done = 1; | |
999 | break; | |
1000 | } | |
1001 | ||
1002 | done_index = page->index + 1; | |
1003 | ||
811d736f DH |
1004 | lock_page(page); |
1005 | ||
5a3d5c98 NP |
1006 | /* |
1007 | * Page truncated or invalidated. We can freely skip it | |
1008 | * then, even for data integrity operations: the page | |
1009 | * has disappeared concurrently, so there could be no | |
1010 | * real expectation of this data interity operation | |
1011 | * even if there is now a new, dirty page at the same | |
1012 | * pagecache address. | |
1013 | */ | |
811d736f | 1014 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 1015 | continue_unlock: |
811d736f DH |
1016 | unlock_page(page); |
1017 | continue; | |
1018 | } | |
1019 | ||
515f4a03 NP |
1020 | if (!PageDirty(page)) { |
1021 | /* someone wrote it for us */ | |
1022 | goto continue_unlock; | |
1023 | } | |
1024 | ||
1025 | if (PageWriteback(page)) { | |
1026 | if (wbc->sync_mode != WB_SYNC_NONE) | |
1027 | wait_on_page_writeback(page); | |
1028 | else | |
1029 | goto continue_unlock; | |
1030 | } | |
811d736f | 1031 | |
515f4a03 NP |
1032 | BUG_ON(PageWriteback(page)); |
1033 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 1034 | goto continue_unlock; |
811d736f | 1035 | |
0ea97180 | 1036 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
1037 | if (unlikely(ret)) { |
1038 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
1039 | unlock_page(page); | |
1040 | ret = 0; | |
1041 | } else { | |
1042 | /* | |
1043 | * done_index is set past this page, | |
1044 | * so media errors will not choke | |
1045 | * background writeout for the entire | |
1046 | * file. This has consequences for | |
1047 | * range_cyclic semantics (ie. it may | |
1048 | * not be suitable for data integrity | |
1049 | * writeout). | |
1050 | */ | |
1051 | done = 1; | |
1052 | break; | |
1053 | } | |
1054 | } | |
1055 | ||
89e12190 | 1056 | if (nr_to_write > 0) { |
dcf6a79d | 1057 | nr_to_write--; |
89e12190 FC |
1058 | if (nr_to_write == 0 && |
1059 | wbc->sync_mode == WB_SYNC_NONE) { | |
1060 | /* | |
1061 | * We stop writing back only if we are | |
1062 | * not doing integrity sync. In case of | |
1063 | * integrity sync we have to keep going | |
1064 | * because someone may be concurrently | |
1065 | * dirtying pages, and we might have | |
1066 | * synced a lot of newly appeared dirty | |
1067 | * pages, but have not synced all of the | |
1068 | * old dirty pages. | |
1069 | */ | |
1070 | done = 1; | |
1071 | break; | |
1072 | } | |
05fe478d | 1073 | } |
dcf6a79d | 1074 | |
811d736f DH |
1075 | if (wbc->nonblocking && bdi_write_congested(bdi)) { |
1076 | wbc->encountered_congestion = 1; | |
1077 | done = 1; | |
82fd1a9a | 1078 | break; |
811d736f DH |
1079 | } |
1080 | } | |
1081 | pagevec_release(&pvec); | |
1082 | cond_resched(); | |
1083 | } | |
3a4c6800 | 1084 | if (!cycled && !done) { |
811d736f | 1085 | /* |
31a12666 | 1086 | * range_cyclic: |
811d736f DH |
1087 | * We hit the last page and there is more work to be done: wrap |
1088 | * back to the start of the file | |
1089 | */ | |
31a12666 | 1090 | cycled = 1; |
811d736f | 1091 | index = 0; |
31a12666 | 1092 | end = writeback_index - 1; |
811d736f DH |
1093 | goto retry; |
1094 | } | |
17bc6c30 AK |
1095 | if (!wbc->no_nrwrite_index_update) { |
1096 | if (wbc->range_cyclic || (range_whole && nr_to_write > 0)) | |
bd19e012 | 1097 | mapping->writeback_index = done_index; |
17bc6c30 AK |
1098 | wbc->nr_to_write = nr_to_write; |
1099 | } | |
06d6cf69 | 1100 | |
811d736f DH |
1101 | return ret; |
1102 | } | |
0ea97180 MS |
1103 | EXPORT_SYMBOL(write_cache_pages); |
1104 | ||
1105 | /* | |
1106 | * Function used by generic_writepages to call the real writepage | |
1107 | * function and set the mapping flags on error | |
1108 | */ | |
1109 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
1110 | void *data) | |
1111 | { | |
1112 | struct address_space *mapping = data; | |
1113 | int ret = mapping->a_ops->writepage(page, wbc); | |
1114 | mapping_set_error(mapping, ret); | |
1115 | return ret; | |
1116 | } | |
1117 | ||
1118 | /** | |
1119 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
1120 | * @mapping: address space structure to write | |
1121 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
1122 | * | |
1123 | * This is a library function, which implements the writepages() | |
1124 | * address_space_operation. | |
1125 | */ | |
1126 | int generic_writepages(struct address_space *mapping, | |
1127 | struct writeback_control *wbc) | |
1128 | { | |
1129 | /* deal with chardevs and other special file */ | |
1130 | if (!mapping->a_ops->writepage) | |
1131 | return 0; | |
1132 | ||
1133 | return write_cache_pages(mapping, wbc, __writepage, mapping); | |
1134 | } | |
811d736f DH |
1135 | |
1136 | EXPORT_SYMBOL(generic_writepages); | |
1137 | ||
1da177e4 LT |
1138 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
1139 | { | |
22905f77 AM |
1140 | int ret; |
1141 | ||
1da177e4 LT |
1142 | if (wbc->nr_to_write <= 0) |
1143 | return 0; | |
22905f77 | 1144 | wbc->for_writepages = 1; |
1da177e4 | 1145 | if (mapping->a_ops->writepages) |
d08b3851 | 1146 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
1147 | else |
1148 | ret = generic_writepages(mapping, wbc); | |
1149 | wbc->for_writepages = 0; | |
1150 | return ret; | |
1da177e4 LT |
1151 | } |
1152 | ||
1153 | /** | |
1154 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
1155 | * @page: the page to write |
1156 | * @wait: if true, wait on writeout | |
1da177e4 LT |
1157 | * |
1158 | * The page must be locked by the caller and will be unlocked upon return. | |
1159 | * | |
1160 | * write_one_page() returns a negative error code if I/O failed. | |
1161 | */ | |
1162 | int write_one_page(struct page *page, int wait) | |
1163 | { | |
1164 | struct address_space *mapping = page->mapping; | |
1165 | int ret = 0; | |
1166 | struct writeback_control wbc = { | |
1167 | .sync_mode = WB_SYNC_ALL, | |
1168 | .nr_to_write = 1, | |
1169 | }; | |
1170 | ||
1171 | BUG_ON(!PageLocked(page)); | |
1172 | ||
1173 | if (wait) | |
1174 | wait_on_page_writeback(page); | |
1175 | ||
1176 | if (clear_page_dirty_for_io(page)) { | |
1177 | page_cache_get(page); | |
1178 | ret = mapping->a_ops->writepage(page, &wbc); | |
1179 | if (ret == 0 && wait) { | |
1180 | wait_on_page_writeback(page); | |
1181 | if (PageError(page)) | |
1182 | ret = -EIO; | |
1183 | } | |
1184 | page_cache_release(page); | |
1185 | } else { | |
1186 | unlock_page(page); | |
1187 | } | |
1188 | return ret; | |
1189 | } | |
1190 | EXPORT_SYMBOL(write_one_page); | |
1191 | ||
76719325 KC |
1192 | /* |
1193 | * For address_spaces which do not use buffers nor write back. | |
1194 | */ | |
1195 | int __set_page_dirty_no_writeback(struct page *page) | |
1196 | { | |
1197 | if (!PageDirty(page)) | |
1198 | SetPageDirty(page); | |
1199 | return 0; | |
1200 | } | |
1201 | ||
e3a7cca1 ES |
1202 | /* |
1203 | * Helper function for set_page_dirty family. | |
1204 | * NOTE: This relies on being atomic wrt interrupts. | |
1205 | */ | |
1206 | void account_page_dirtied(struct page *page, struct address_space *mapping) | |
1207 | { | |
1208 | if (mapping_cap_account_dirty(mapping)) { | |
1209 | __inc_zone_page_state(page, NR_FILE_DIRTY); | |
1210 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); | |
1211 | task_dirty_inc(current); | |
1212 | task_io_account_write(PAGE_CACHE_SIZE); | |
1213 | } | |
1214 | } | |
1215 | ||
1da177e4 LT |
1216 | /* |
1217 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
1218 | * its radix tree. | |
1219 | * | |
1220 | * This is also used when a single buffer is being dirtied: we want to set the | |
1221 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
1222 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
1223 | * | |
1224 | * Most callers have locked the page, which pins the address_space in memory. | |
1225 | * But zap_pte_range() does not lock the page, however in that case the | |
1226 | * mapping is pinned by the vma's ->vm_file reference. | |
1227 | * | |
1228 | * We take care to handle the case where the page was truncated from the | |
183ff22b | 1229 | * mapping by re-checking page_mapping() inside tree_lock. |
1da177e4 LT |
1230 | */ |
1231 | int __set_page_dirty_nobuffers(struct page *page) | |
1232 | { | |
1da177e4 LT |
1233 | if (!TestSetPageDirty(page)) { |
1234 | struct address_space *mapping = page_mapping(page); | |
1235 | struct address_space *mapping2; | |
1236 | ||
8c08540f AM |
1237 | if (!mapping) |
1238 | return 1; | |
1239 | ||
19fd6231 | 1240 | spin_lock_irq(&mapping->tree_lock); |
8c08540f AM |
1241 | mapping2 = page_mapping(page); |
1242 | if (mapping2) { /* Race with truncate? */ | |
1243 | BUG_ON(mapping2 != mapping); | |
787d2214 | 1244 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
e3a7cca1 | 1245 | account_page_dirtied(page, mapping); |
8c08540f AM |
1246 | radix_tree_tag_set(&mapping->page_tree, |
1247 | page_index(page), PAGECACHE_TAG_DIRTY); | |
1248 | } | |
19fd6231 | 1249 | spin_unlock_irq(&mapping->tree_lock); |
8c08540f AM |
1250 | if (mapping->host) { |
1251 | /* !PageAnon && !swapper_space */ | |
1252 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 1253 | } |
4741c9fd | 1254 | return 1; |
1da177e4 | 1255 | } |
4741c9fd | 1256 | return 0; |
1da177e4 LT |
1257 | } |
1258 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
1259 | ||
1260 | /* | |
1261 | * When a writepage implementation decides that it doesn't want to write this | |
1262 | * page for some reason, it should redirty the locked page via | |
1263 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
1264 | */ | |
1265 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
1266 | { | |
1267 | wbc->pages_skipped++; | |
1268 | return __set_page_dirty_nobuffers(page); | |
1269 | } | |
1270 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
1271 | ||
1272 | /* | |
1273 | * If the mapping doesn't provide a set_page_dirty a_op, then | |
1274 | * just fall through and assume that it wants buffer_heads. | |
1275 | */ | |
1cf6e7d8 | 1276 | int set_page_dirty(struct page *page) |
1da177e4 LT |
1277 | { |
1278 | struct address_space *mapping = page_mapping(page); | |
1279 | ||
1280 | if (likely(mapping)) { | |
1281 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
9361401e DH |
1282 | #ifdef CONFIG_BLOCK |
1283 | if (!spd) | |
1284 | spd = __set_page_dirty_buffers; | |
1285 | #endif | |
1286 | return (*spd)(page); | |
1da177e4 | 1287 | } |
4741c9fd AM |
1288 | if (!PageDirty(page)) { |
1289 | if (!TestSetPageDirty(page)) | |
1290 | return 1; | |
1291 | } | |
1da177e4 LT |
1292 | return 0; |
1293 | } | |
1294 | EXPORT_SYMBOL(set_page_dirty); | |
1295 | ||
1296 | /* | |
1297 | * set_page_dirty() is racy if the caller has no reference against | |
1298 | * page->mapping->host, and if the page is unlocked. This is because another | |
1299 | * CPU could truncate the page off the mapping and then free the mapping. | |
1300 | * | |
1301 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
1302 | * holds a reference on the inode by having an open file. | |
1303 | * | |
1304 | * In other cases, the page should be locked before running set_page_dirty(). | |
1305 | */ | |
1306 | int set_page_dirty_lock(struct page *page) | |
1307 | { | |
1308 | int ret; | |
1309 | ||
db37648c | 1310 | lock_page_nosync(page); |
1da177e4 LT |
1311 | ret = set_page_dirty(page); |
1312 | unlock_page(page); | |
1313 | return ret; | |
1314 | } | |
1315 | EXPORT_SYMBOL(set_page_dirty_lock); | |
1316 | ||
1da177e4 LT |
1317 | /* |
1318 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
1319 | * Returns true if the page was previously dirty. | |
1320 | * | |
1321 | * This is for preparing to put the page under writeout. We leave the page | |
1322 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
1323 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
1324 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
1325 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
1326 | * back into sync. | |
1327 | * | |
1328 | * This incoherency between the page's dirty flag and radix-tree tag is | |
1329 | * unfortunate, but it only exists while the page is locked. | |
1330 | */ | |
1331 | int clear_page_dirty_for_io(struct page *page) | |
1332 | { | |
1333 | struct address_space *mapping = page_mapping(page); | |
1334 | ||
79352894 NP |
1335 | BUG_ON(!PageLocked(page)); |
1336 | ||
fe3cba17 | 1337 | ClearPageReclaim(page); |
7658cc28 LT |
1338 | if (mapping && mapping_cap_account_dirty(mapping)) { |
1339 | /* | |
1340 | * Yes, Virginia, this is indeed insane. | |
1341 | * | |
1342 | * We use this sequence to make sure that | |
1343 | * (a) we account for dirty stats properly | |
1344 | * (b) we tell the low-level filesystem to | |
1345 | * mark the whole page dirty if it was | |
1346 | * dirty in a pagetable. Only to then | |
1347 | * (c) clean the page again and return 1 to | |
1348 | * cause the writeback. | |
1349 | * | |
1350 | * This way we avoid all nasty races with the | |
1351 | * dirty bit in multiple places and clearing | |
1352 | * them concurrently from different threads. | |
1353 | * | |
1354 | * Note! Normally the "set_page_dirty(page)" | |
1355 | * has no effect on the actual dirty bit - since | |
1356 | * that will already usually be set. But we | |
1357 | * need the side effects, and it can help us | |
1358 | * avoid races. | |
1359 | * | |
1360 | * We basically use the page "master dirty bit" | |
1361 | * as a serialization point for all the different | |
1362 | * threads doing their things. | |
7658cc28 LT |
1363 | */ |
1364 | if (page_mkclean(page)) | |
1365 | set_page_dirty(page); | |
79352894 NP |
1366 | /* |
1367 | * We carefully synchronise fault handlers against | |
1368 | * installing a dirty pte and marking the page dirty | |
1369 | * at this point. We do this by having them hold the | |
1370 | * page lock at some point after installing their | |
1371 | * pte, but before marking the page dirty. | |
1372 | * Pages are always locked coming in here, so we get | |
1373 | * the desired exclusion. See mm/memory.c:do_wp_page() | |
1374 | * for more comments. | |
1375 | */ | |
7658cc28 | 1376 | if (TestClearPageDirty(page)) { |
8c08540f | 1377 | dec_zone_page_state(page, NR_FILE_DIRTY); |
c9e51e41 PZ |
1378 | dec_bdi_stat(mapping->backing_dev_info, |
1379 | BDI_RECLAIMABLE); | |
7658cc28 | 1380 | return 1; |
1da177e4 | 1381 | } |
7658cc28 | 1382 | return 0; |
1da177e4 | 1383 | } |
7658cc28 | 1384 | return TestClearPageDirty(page); |
1da177e4 | 1385 | } |
58bb01a9 | 1386 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
1387 | |
1388 | int test_clear_page_writeback(struct page *page) | |
1389 | { | |
1390 | struct address_space *mapping = page_mapping(page); | |
1391 | int ret; | |
1392 | ||
1393 | if (mapping) { | |
69cb51d1 | 1394 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1395 | unsigned long flags; |
1396 | ||
19fd6231 | 1397 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1398 | ret = TestClearPageWriteback(page); |
69cb51d1 | 1399 | if (ret) { |
1da177e4 LT |
1400 | radix_tree_tag_clear(&mapping->page_tree, |
1401 | page_index(page), | |
1402 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1403 | if (bdi_cap_account_writeback(bdi)) { |
69cb51d1 | 1404 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
04fbfdc1 PZ |
1405 | __bdi_writeout_inc(bdi); |
1406 | } | |
69cb51d1 | 1407 | } |
19fd6231 | 1408 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1409 | } else { |
1410 | ret = TestClearPageWriteback(page); | |
1411 | } | |
d688abf5 AM |
1412 | if (ret) |
1413 | dec_zone_page_state(page, NR_WRITEBACK); | |
1da177e4 LT |
1414 | return ret; |
1415 | } | |
1416 | ||
1417 | int test_set_page_writeback(struct page *page) | |
1418 | { | |
1419 | struct address_space *mapping = page_mapping(page); | |
1420 | int ret; | |
1421 | ||
1422 | if (mapping) { | |
69cb51d1 | 1423 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
1da177e4 LT |
1424 | unsigned long flags; |
1425 | ||
19fd6231 | 1426 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 1427 | ret = TestSetPageWriteback(page); |
69cb51d1 | 1428 | if (!ret) { |
1da177e4 LT |
1429 | radix_tree_tag_set(&mapping->page_tree, |
1430 | page_index(page), | |
1431 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 1432 | if (bdi_cap_account_writeback(bdi)) |
69cb51d1 PZ |
1433 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
1434 | } | |
1da177e4 LT |
1435 | if (!PageDirty(page)) |
1436 | radix_tree_tag_clear(&mapping->page_tree, | |
1437 | page_index(page), | |
1438 | PAGECACHE_TAG_DIRTY); | |
19fd6231 | 1439 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
1440 | } else { |
1441 | ret = TestSetPageWriteback(page); | |
1442 | } | |
d688abf5 AM |
1443 | if (!ret) |
1444 | inc_zone_page_state(page, NR_WRITEBACK); | |
1da177e4 LT |
1445 | return ret; |
1446 | ||
1447 | } | |
1448 | EXPORT_SYMBOL(test_set_page_writeback); | |
1449 | ||
1450 | /* | |
00128188 | 1451 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
1452 | * passed tag. |
1453 | */ | |
1454 | int mapping_tagged(struct address_space *mapping, int tag) | |
1455 | { | |
1da177e4 | 1456 | int ret; |
00128188 | 1457 | rcu_read_lock(); |
1da177e4 | 1458 | ret = radix_tree_tagged(&mapping->page_tree, tag); |
00128188 | 1459 | rcu_read_unlock(); |
1da177e4 LT |
1460 | return ret; |
1461 | } | |
1462 | EXPORT_SYMBOL(mapping_tagged); |