Commit | Line | Data |
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1da177e4 | 1 | /* |
f30c2269 | 2 | * mm/page-writeback.c |
1da177e4 LT |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. | |
5 | * | |
6 | * Contains functions related to writing back dirty pages at the | |
7 | * address_space level. | |
8 | * | |
9 | * 10Apr2002 akpm@zip.com.au | |
10 | * Initial version | |
11 | */ | |
12 | ||
13 | #include <linux/kernel.h> | |
14 | #include <linux/module.h> | |
15 | #include <linux/spinlock.h> | |
16 | #include <linux/fs.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/swap.h> | |
19 | #include <linux/slab.h> | |
20 | #include <linux/pagemap.h> | |
21 | #include <linux/writeback.h> | |
22 | #include <linux/init.h> | |
23 | #include <linux/backing-dev.h> | |
55e829af | 24 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
25 | #include <linux/blkdev.h> |
26 | #include <linux/mpage.h> | |
d08b3851 | 27 | #include <linux/rmap.h> |
1da177e4 LT |
28 | #include <linux/percpu.h> |
29 | #include <linux/notifier.h> | |
30 | #include <linux/smp.h> | |
31 | #include <linux/sysctl.h> | |
32 | #include <linux/cpu.h> | |
33 | #include <linux/syscalls.h> | |
cf9a2ae8 | 34 | #include <linux/buffer_head.h> |
811d736f | 35 | #include <linux/pagevec.h> |
1da177e4 LT |
36 | |
37 | /* | |
38 | * The maximum number of pages to writeout in a single bdflush/kupdate | |
39 | * operation. We do this so we don't hold I_LOCK against an inode for | |
40 | * enormous amounts of time, which would block a userspace task which has | |
41 | * been forced to throttle against that inode. Also, the code reevaluates | |
42 | * the dirty each time it has written this many pages. | |
43 | */ | |
44 | #define MAX_WRITEBACK_PAGES 1024 | |
45 | ||
46 | /* | |
47 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
48 | * will look to see if it needs to force writeback or throttling. | |
49 | */ | |
50 | static long ratelimit_pages = 32; | |
51 | ||
e236a166 | 52 | static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */ |
1da177e4 LT |
53 | |
54 | /* | |
55 | * When balance_dirty_pages decides that the caller needs to perform some | |
56 | * non-background writeback, this is how many pages it will attempt to write. | |
57 | * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably | |
58 | * large amounts of I/O are submitted. | |
59 | */ | |
60 | static inline long sync_writeback_pages(void) | |
61 | { | |
62 | return ratelimit_pages + ratelimit_pages / 2; | |
63 | } | |
64 | ||
65 | /* The following parameters are exported via /proc/sys/vm */ | |
66 | ||
67 | /* | |
68 | * Start background writeback (via pdflush) at this percentage | |
69 | */ | |
70 | int dirty_background_ratio = 10; | |
71 | ||
72 | /* | |
73 | * The generator of dirty data starts writeback at this percentage | |
74 | */ | |
75 | int vm_dirty_ratio = 40; | |
76 | ||
77 | /* | |
fd5403c7 | 78 | * The interval between `kupdate'-style writebacks, in jiffies |
1da177e4 | 79 | */ |
f6ef9438 | 80 | int dirty_writeback_interval = 5 * HZ; |
1da177e4 LT |
81 | |
82 | /* | |
fd5403c7 | 83 | * The longest number of jiffies for which data is allowed to remain dirty |
1da177e4 | 84 | */ |
f6ef9438 | 85 | int dirty_expire_interval = 30 * HZ; |
1da177e4 LT |
86 | |
87 | /* | |
88 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
89 | */ | |
90 | int block_dump; | |
91 | ||
92 | /* | |
ed5b43f1 BS |
93 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
94 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
95 | */ |
96 | int laptop_mode; | |
97 | ||
98 | EXPORT_SYMBOL(laptop_mode); | |
99 | ||
100 | /* End of sysctl-exported parameters */ | |
101 | ||
102 | ||
103 | static void background_writeout(unsigned long _min_pages); | |
104 | ||
1da177e4 LT |
105 | /* |
106 | * Work out the current dirty-memory clamping and background writeout | |
107 | * thresholds. | |
108 | * | |
109 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
110 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
111 | * pages. It is better to clamp down on writers than to start swapping, and | |
112 | * performing lots of scanning. | |
113 | * | |
114 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
115 | * | |
116 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
117 | * excessive. | |
118 | * | |
119 | * We make sure that the background writeout level is below the adjusted | |
120 | * clamping level. | |
121 | */ | |
122 | static void | |
c24f21bd CL |
123 | get_dirty_limits(long *pbackground, long *pdirty, |
124 | struct address_space *mapping) | |
1da177e4 LT |
125 | { |
126 | int background_ratio; /* Percentages */ | |
127 | int dirty_ratio; | |
128 | int unmapped_ratio; | |
129 | long background; | |
130 | long dirty; | |
40c99aae | 131 | unsigned long available_memory = vm_total_pages; |
1da177e4 LT |
132 | struct task_struct *tsk; |
133 | ||
1da177e4 LT |
134 | #ifdef CONFIG_HIGHMEM |
135 | /* | |
dc6e29da | 136 | * We always exclude high memory from our count. |
1da177e4 | 137 | */ |
dc6e29da | 138 | available_memory -= totalhigh_pages; |
1da177e4 LT |
139 | #endif |
140 | ||
141 | ||
c24f21bd CL |
142 | unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) + |
143 | global_page_state(NR_ANON_PAGES)) * 100) / | |
40c99aae | 144 | vm_total_pages; |
1da177e4 LT |
145 | |
146 | dirty_ratio = vm_dirty_ratio; | |
147 | if (dirty_ratio > unmapped_ratio / 2) | |
148 | dirty_ratio = unmapped_ratio / 2; | |
149 | ||
150 | if (dirty_ratio < 5) | |
151 | dirty_ratio = 5; | |
152 | ||
153 | background_ratio = dirty_background_ratio; | |
154 | if (background_ratio >= dirty_ratio) | |
155 | background_ratio = dirty_ratio / 2; | |
156 | ||
157 | background = (background_ratio * available_memory) / 100; | |
158 | dirty = (dirty_ratio * available_memory) / 100; | |
159 | tsk = current; | |
160 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
161 | background += background / 4; | |
162 | dirty += dirty / 4; | |
163 | } | |
164 | *pbackground = background; | |
165 | *pdirty = dirty; | |
166 | } | |
167 | ||
168 | /* | |
169 | * balance_dirty_pages() must be called by processes which are generating dirty | |
170 | * data. It looks at the number of dirty pages in the machine and will force | |
171 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
172 | * If we're over `background_thresh' then pdflush is woken to perform some | |
173 | * writeout. | |
174 | */ | |
175 | static void balance_dirty_pages(struct address_space *mapping) | |
176 | { | |
1da177e4 LT |
177 | long nr_reclaimable; |
178 | long background_thresh; | |
179 | long dirty_thresh; | |
180 | unsigned long pages_written = 0; | |
181 | unsigned long write_chunk = sync_writeback_pages(); | |
182 | ||
183 | struct backing_dev_info *bdi = mapping->backing_dev_info; | |
184 | ||
185 | for (;;) { | |
186 | struct writeback_control wbc = { | |
187 | .bdi = bdi, | |
188 | .sync_mode = WB_SYNC_NONE, | |
189 | .older_than_this = NULL, | |
190 | .nr_to_write = write_chunk, | |
111ebb6e | 191 | .range_cyclic = 1, |
1da177e4 LT |
192 | }; |
193 | ||
c24f21bd CL |
194 | get_dirty_limits(&background_thresh, &dirty_thresh, mapping); |
195 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + | |
196 | global_page_state(NR_UNSTABLE_NFS); | |
197 | if (nr_reclaimable + global_page_state(NR_WRITEBACK) <= | |
198 | dirty_thresh) | |
199 | break; | |
1da177e4 | 200 | |
e236a166 AM |
201 | if (!dirty_exceeded) |
202 | dirty_exceeded = 1; | |
1da177e4 LT |
203 | |
204 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. | |
205 | * Unstable writes are a feature of certain networked | |
206 | * filesystems (i.e. NFS) in which data may have been | |
207 | * written to the server's write cache, but has not yet | |
208 | * been flushed to permanent storage. | |
209 | */ | |
210 | if (nr_reclaimable) { | |
211 | writeback_inodes(&wbc); | |
c24f21bd CL |
212 | get_dirty_limits(&background_thresh, |
213 | &dirty_thresh, mapping); | |
214 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + | |
215 | global_page_state(NR_UNSTABLE_NFS); | |
216 | if (nr_reclaimable + | |
217 | global_page_state(NR_WRITEBACK) | |
218 | <= dirty_thresh) | |
219 | break; | |
1da177e4 LT |
220 | pages_written += write_chunk - wbc.nr_to_write; |
221 | if (pages_written >= write_chunk) | |
222 | break; /* We've done our duty */ | |
223 | } | |
3fcfab16 | 224 | congestion_wait(WRITE, HZ/10); |
1da177e4 LT |
225 | } |
226 | ||
c24f21bd CL |
227 | if (nr_reclaimable + global_page_state(NR_WRITEBACK) |
228 | <= dirty_thresh && dirty_exceeded) | |
229 | dirty_exceeded = 0; | |
1da177e4 LT |
230 | |
231 | if (writeback_in_progress(bdi)) | |
232 | return; /* pdflush is already working this queue */ | |
233 | ||
234 | /* | |
235 | * In laptop mode, we wait until hitting the higher threshold before | |
236 | * starting background writeout, and then write out all the way down | |
237 | * to the lower threshold. So slow writers cause minimal disk activity. | |
238 | * | |
239 | * In normal mode, we start background writeout at the lower | |
240 | * background_thresh, to keep the amount of dirty memory low. | |
241 | */ | |
242 | if ((laptop_mode && pages_written) || | |
243 | (!laptop_mode && (nr_reclaimable > background_thresh))) | |
244 | pdflush_operation(background_writeout, 0); | |
245 | } | |
246 | ||
edc79b2a PZ |
247 | void set_page_dirty_balance(struct page *page) |
248 | { | |
249 | if (set_page_dirty(page)) { | |
250 | struct address_space *mapping = page_mapping(page); | |
251 | ||
252 | if (mapping) | |
253 | balance_dirty_pages_ratelimited(mapping); | |
254 | } | |
255 | } | |
256 | ||
1da177e4 | 257 | /** |
fa5a734e | 258 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 259 | * @mapping: address_space which was dirtied |
a580290c | 260 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
261 | * |
262 | * Processes which are dirtying memory should call in here once for each page | |
263 | * which was newly dirtied. The function will periodically check the system's | |
264 | * dirty state and will initiate writeback if needed. | |
265 | * | |
266 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
267 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
268 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
269 | * from overshooting the limit by (ratelimit_pages) each. | |
270 | */ | |
fa5a734e AM |
271 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
272 | unsigned long nr_pages_dirtied) | |
1da177e4 | 273 | { |
fa5a734e AM |
274 | static DEFINE_PER_CPU(unsigned long, ratelimits) = 0; |
275 | unsigned long ratelimit; | |
276 | unsigned long *p; | |
1da177e4 LT |
277 | |
278 | ratelimit = ratelimit_pages; | |
279 | if (dirty_exceeded) | |
280 | ratelimit = 8; | |
281 | ||
282 | /* | |
283 | * Check the rate limiting. Also, we do not want to throttle real-time | |
284 | * tasks in balance_dirty_pages(). Period. | |
285 | */ | |
fa5a734e AM |
286 | preempt_disable(); |
287 | p = &__get_cpu_var(ratelimits); | |
288 | *p += nr_pages_dirtied; | |
289 | if (unlikely(*p >= ratelimit)) { | |
290 | *p = 0; | |
291 | preempt_enable(); | |
1da177e4 LT |
292 | balance_dirty_pages(mapping); |
293 | return; | |
294 | } | |
fa5a734e | 295 | preempt_enable(); |
1da177e4 | 296 | } |
fa5a734e | 297 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 | 298 | |
232ea4d6 | 299 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 300 | { |
1da177e4 LT |
301 | long background_thresh; |
302 | long dirty_thresh; | |
303 | ||
232ea4d6 AM |
304 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) { |
305 | /* | |
306 | * The caller might hold locks which can prevent IO completion | |
307 | * or progress in the filesystem. So we cannot just sit here | |
308 | * waiting for IO to complete. | |
309 | */ | |
310 | congestion_wait(WRITE, HZ/10); | |
311 | return; | |
312 | } | |
313 | ||
1da177e4 | 314 | for ( ; ; ) { |
c24f21bd | 315 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL); |
1da177e4 LT |
316 | |
317 | /* | |
318 | * Boost the allowable dirty threshold a bit for page | |
319 | * allocators so they don't get DoS'ed by heavy writers | |
320 | */ | |
321 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
322 | ||
c24f21bd CL |
323 | if (global_page_state(NR_UNSTABLE_NFS) + |
324 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
325 | break; | |
3fcfab16 | 326 | congestion_wait(WRITE, HZ/10); |
1da177e4 LT |
327 | } |
328 | } | |
329 | ||
1da177e4 LT |
330 | /* |
331 | * writeback at least _min_pages, and keep writing until the amount of dirty | |
332 | * memory is less than the background threshold, or until we're all clean. | |
333 | */ | |
334 | static void background_writeout(unsigned long _min_pages) | |
335 | { | |
336 | long min_pages = _min_pages; | |
337 | struct writeback_control wbc = { | |
338 | .bdi = NULL, | |
339 | .sync_mode = WB_SYNC_NONE, | |
340 | .older_than_this = NULL, | |
341 | .nr_to_write = 0, | |
342 | .nonblocking = 1, | |
111ebb6e | 343 | .range_cyclic = 1, |
1da177e4 LT |
344 | }; |
345 | ||
346 | for ( ; ; ) { | |
1da177e4 LT |
347 | long background_thresh; |
348 | long dirty_thresh; | |
349 | ||
c24f21bd CL |
350 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL); |
351 | if (global_page_state(NR_FILE_DIRTY) + | |
352 | global_page_state(NR_UNSTABLE_NFS) < background_thresh | |
1da177e4 LT |
353 | && min_pages <= 0) |
354 | break; | |
355 | wbc.encountered_congestion = 0; | |
356 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
357 | wbc.pages_skipped = 0; | |
358 | writeback_inodes(&wbc); | |
359 | min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
360 | if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { | |
361 | /* Wrote less than expected */ | |
3fcfab16 | 362 | congestion_wait(WRITE, HZ/10); |
1da177e4 LT |
363 | if (!wbc.encountered_congestion) |
364 | break; | |
365 | } | |
366 | } | |
367 | } | |
368 | ||
369 | /* | |
370 | * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back | |
371 | * the whole world. Returns 0 if a pdflush thread was dispatched. Returns | |
372 | * -1 if all pdflush threads were busy. | |
373 | */ | |
687a21ce | 374 | int wakeup_pdflush(long nr_pages) |
1da177e4 | 375 | { |
c24f21bd CL |
376 | if (nr_pages == 0) |
377 | nr_pages = global_page_state(NR_FILE_DIRTY) + | |
378 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 LT |
379 | return pdflush_operation(background_writeout, nr_pages); |
380 | } | |
381 | ||
382 | static void wb_timer_fn(unsigned long unused); | |
383 | static void laptop_timer_fn(unsigned long unused); | |
384 | ||
8d06afab IM |
385 | static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0); |
386 | static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0); | |
1da177e4 LT |
387 | |
388 | /* | |
389 | * Periodic writeback of "old" data. | |
390 | * | |
391 | * Define "old": the first time one of an inode's pages is dirtied, we mark the | |
392 | * dirtying-time in the inode's address_space. So this periodic writeback code | |
393 | * just walks the superblock inode list, writing back any inodes which are | |
394 | * older than a specific point in time. | |
395 | * | |
f6ef9438 BS |
396 | * Try to run once per dirty_writeback_interval. But if a writeback event |
397 | * takes longer than a dirty_writeback_interval interval, then leave a | |
1da177e4 LT |
398 | * one-second gap. |
399 | * | |
400 | * older_than_this takes precedence over nr_to_write. So we'll only write back | |
401 | * all dirty pages if they are all attached to "old" mappings. | |
402 | */ | |
403 | static void wb_kupdate(unsigned long arg) | |
404 | { | |
405 | unsigned long oldest_jif; | |
406 | unsigned long start_jif; | |
407 | unsigned long next_jif; | |
408 | long nr_to_write; | |
1da177e4 LT |
409 | struct writeback_control wbc = { |
410 | .bdi = NULL, | |
411 | .sync_mode = WB_SYNC_NONE, | |
412 | .older_than_this = &oldest_jif, | |
413 | .nr_to_write = 0, | |
414 | .nonblocking = 1, | |
415 | .for_kupdate = 1, | |
111ebb6e | 416 | .range_cyclic = 1, |
1da177e4 LT |
417 | }; |
418 | ||
419 | sync_supers(); | |
420 | ||
f6ef9438 | 421 | oldest_jif = jiffies - dirty_expire_interval; |
1da177e4 | 422 | start_jif = jiffies; |
f6ef9438 | 423 | next_jif = start_jif + dirty_writeback_interval; |
c24f21bd CL |
424 | nr_to_write = global_page_state(NR_FILE_DIRTY) + |
425 | global_page_state(NR_UNSTABLE_NFS) + | |
1da177e4 LT |
426 | (inodes_stat.nr_inodes - inodes_stat.nr_unused); |
427 | while (nr_to_write > 0) { | |
428 | wbc.encountered_congestion = 0; | |
429 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
430 | writeback_inodes(&wbc); | |
431 | if (wbc.nr_to_write > 0) { | |
432 | if (wbc.encountered_congestion) | |
3fcfab16 | 433 | congestion_wait(WRITE, HZ/10); |
1da177e4 LT |
434 | else |
435 | break; /* All the old data is written */ | |
436 | } | |
437 | nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
438 | } | |
439 | if (time_before(next_jif, jiffies + HZ)) | |
440 | next_jif = jiffies + HZ; | |
f6ef9438 | 441 | if (dirty_writeback_interval) |
1da177e4 LT |
442 | mod_timer(&wb_timer, next_jif); |
443 | } | |
444 | ||
445 | /* | |
446 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
447 | */ | |
448 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
449 | struct file *file, void __user *buffer, size_t *length, loff_t *ppos) | |
450 | { | |
f6ef9438 BS |
451 | proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos); |
452 | if (dirty_writeback_interval) { | |
1da177e4 | 453 | mod_timer(&wb_timer, |
f6ef9438 BS |
454 | jiffies + dirty_writeback_interval); |
455 | } else { | |
1da177e4 LT |
456 | del_timer(&wb_timer); |
457 | } | |
458 | return 0; | |
459 | } | |
460 | ||
461 | static void wb_timer_fn(unsigned long unused) | |
462 | { | |
463 | if (pdflush_operation(wb_kupdate, 0) < 0) | |
464 | mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */ | |
465 | } | |
466 | ||
467 | static void laptop_flush(unsigned long unused) | |
468 | { | |
469 | sys_sync(); | |
470 | } | |
471 | ||
472 | static void laptop_timer_fn(unsigned long unused) | |
473 | { | |
474 | pdflush_operation(laptop_flush, 0); | |
475 | } | |
476 | ||
477 | /* | |
478 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
479 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
480 | * then push it back - the user is still using the disk. | |
481 | */ | |
482 | void laptop_io_completion(void) | |
483 | { | |
ed5b43f1 | 484 | mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
485 | } |
486 | ||
487 | /* | |
488 | * We're in laptop mode and we've just synced. The sync's writes will have | |
489 | * caused another writeback to be scheduled by laptop_io_completion. | |
490 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
491 | */ | |
492 | void laptop_sync_completion(void) | |
493 | { | |
494 | del_timer(&laptop_mode_wb_timer); | |
495 | } | |
496 | ||
497 | /* | |
498 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
499 | * if a large number of processes all perform writes at the same time. | |
500 | * If it is too low then SMP machines will call the (expensive) | |
501 | * get_writeback_state too often. | |
502 | * | |
503 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
504 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
505 | * thresholds before writeback cuts in. | |
506 | * | |
507 | * But the limit should not be set too high. Because it also controls the | |
508 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
509 | * If this is too large then the caller will block on the IO queue all the | |
510 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
511 | * will write six megabyte chunks, max. | |
512 | */ | |
513 | ||
2d1d43f6 | 514 | void writeback_set_ratelimit(void) |
1da177e4 | 515 | { |
40c99aae | 516 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
517 | if (ratelimit_pages < 16) |
518 | ratelimit_pages = 16; | |
519 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
520 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
521 | } | |
522 | ||
26c2143b | 523 | static int __cpuinit |
1da177e4 LT |
524 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
525 | { | |
2d1d43f6 | 526 | writeback_set_ratelimit(); |
aa0f0303 | 527 | return NOTIFY_DONE; |
1da177e4 LT |
528 | } |
529 | ||
74b85f37 | 530 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
531 | .notifier_call = ratelimit_handler, |
532 | .next = NULL, | |
533 | }; | |
534 | ||
535 | /* | |
dc6e29da LT |
536 | * Called early on to tune the page writeback dirty limits. |
537 | * | |
538 | * We used to scale dirty pages according to how total memory | |
539 | * related to pages that could be allocated for buffers (by | |
540 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
541 | * | |
542 | * However, that was when we used "dirty_ratio" to scale with | |
543 | * all memory, and we don't do that any more. "dirty_ratio" | |
544 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
545 | * totalhigh_pages from vm_total_pages), and as such we can't | |
546 | * get into the old insane situation any more where we had | |
547 | * large amounts of dirty pages compared to a small amount of | |
548 | * non-HIGHMEM memory. | |
549 | * | |
550 | * But we might still want to scale the dirty_ratio by how | |
551 | * much memory the box has.. | |
1da177e4 LT |
552 | */ |
553 | void __init page_writeback_init(void) | |
554 | { | |
f6ef9438 | 555 | mod_timer(&wb_timer, jiffies + dirty_writeback_interval); |
2d1d43f6 | 556 | writeback_set_ratelimit(); |
1da177e4 LT |
557 | register_cpu_notifier(&ratelimit_nb); |
558 | } | |
559 | ||
811d736f | 560 | /** |
72fd4a35 | 561 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. |
811d736f DH |
562 | * @mapping: address space structure to write |
563 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
564 | * | |
565 | * This is a library function, which implements the writepages() | |
566 | * address_space_operation. | |
567 | * | |
568 | * If a page is already under I/O, generic_writepages() skips it, even | |
569 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, | |
570 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
571 | * and msync() need to guarantee that all the data which was dirty at the time | |
572 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
573 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
574 | * existing IO to complete. | |
575 | * | |
576 | * Derived from mpage_writepages() - if you fix this you should check that | |
577 | * also! | |
578 | */ | |
579 | int generic_writepages(struct address_space *mapping, | |
580 | struct writeback_control *wbc) | |
581 | { | |
582 | struct backing_dev_info *bdi = mapping->backing_dev_info; | |
583 | int ret = 0; | |
584 | int done = 0; | |
585 | int (*writepage)(struct page *page, struct writeback_control *wbc); | |
586 | struct pagevec pvec; | |
587 | int nr_pages; | |
588 | pgoff_t index; | |
589 | pgoff_t end; /* Inclusive */ | |
590 | int scanned = 0; | |
591 | int range_whole = 0; | |
592 | ||
593 | if (wbc->nonblocking && bdi_write_congested(bdi)) { | |
594 | wbc->encountered_congestion = 1; | |
595 | return 0; | |
596 | } | |
597 | ||
598 | writepage = mapping->a_ops->writepage; | |
599 | ||
600 | /* deal with chardevs and other special file */ | |
601 | if (!writepage) | |
602 | return 0; | |
603 | ||
604 | pagevec_init(&pvec, 0); | |
605 | if (wbc->range_cyclic) { | |
606 | index = mapping->writeback_index; /* Start from prev offset */ | |
607 | end = -1; | |
608 | } else { | |
609 | index = wbc->range_start >> PAGE_CACHE_SHIFT; | |
610 | end = wbc->range_end >> PAGE_CACHE_SHIFT; | |
611 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) | |
612 | range_whole = 1; | |
613 | scanned = 1; | |
614 | } | |
615 | retry: | |
616 | while (!done && (index <= end) && | |
617 | (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, | |
618 | PAGECACHE_TAG_DIRTY, | |
619 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) { | |
620 | unsigned i; | |
621 | ||
622 | scanned = 1; | |
623 | for (i = 0; i < nr_pages; i++) { | |
624 | struct page *page = pvec.pages[i]; | |
625 | ||
626 | /* | |
627 | * At this point we hold neither mapping->tree_lock nor | |
628 | * lock on the page itself: the page may be truncated or | |
629 | * invalidated (changing page->mapping to NULL), or even | |
630 | * swizzled back from swapper_space to tmpfs file | |
631 | * mapping | |
632 | */ | |
633 | lock_page(page); | |
634 | ||
635 | if (unlikely(page->mapping != mapping)) { | |
636 | unlock_page(page); | |
637 | continue; | |
638 | } | |
639 | ||
640 | if (!wbc->range_cyclic && page->index > end) { | |
641 | done = 1; | |
642 | unlock_page(page); | |
643 | continue; | |
644 | } | |
645 | ||
646 | if (wbc->sync_mode != WB_SYNC_NONE) | |
647 | wait_on_page_writeback(page); | |
648 | ||
649 | if (PageWriteback(page) || | |
650 | !clear_page_dirty_for_io(page)) { | |
651 | unlock_page(page); | |
652 | continue; | |
653 | } | |
654 | ||
655 | ret = (*writepage)(page, wbc); | |
656 | if (ret) { | |
657 | if (ret == -ENOSPC) | |
658 | set_bit(AS_ENOSPC, &mapping->flags); | |
659 | else | |
660 | set_bit(AS_EIO, &mapping->flags); | |
661 | } | |
662 | ||
663 | if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) | |
664 | unlock_page(page); | |
665 | if (ret || (--(wbc->nr_to_write) <= 0)) | |
666 | done = 1; | |
667 | if (wbc->nonblocking && bdi_write_congested(bdi)) { | |
668 | wbc->encountered_congestion = 1; | |
669 | done = 1; | |
670 | } | |
671 | } | |
672 | pagevec_release(&pvec); | |
673 | cond_resched(); | |
674 | } | |
675 | if (!scanned && !done) { | |
676 | /* | |
677 | * We hit the last page and there is more work to be done: wrap | |
678 | * back to the start of the file | |
679 | */ | |
680 | scanned = 1; | |
681 | index = 0; | |
682 | goto retry; | |
683 | } | |
684 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) | |
685 | mapping->writeback_index = index; | |
686 | return ret; | |
687 | } | |
688 | ||
689 | EXPORT_SYMBOL(generic_writepages); | |
690 | ||
1da177e4 LT |
691 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
692 | { | |
22905f77 AM |
693 | int ret; |
694 | ||
1da177e4 LT |
695 | if (wbc->nr_to_write <= 0) |
696 | return 0; | |
22905f77 | 697 | wbc->for_writepages = 1; |
1da177e4 | 698 | if (mapping->a_ops->writepages) |
d08b3851 | 699 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
700 | else |
701 | ret = generic_writepages(mapping, wbc); | |
702 | wbc->for_writepages = 0; | |
703 | return ret; | |
1da177e4 LT |
704 | } |
705 | ||
706 | /** | |
707 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
708 | * @page: the page to write |
709 | * @wait: if true, wait on writeout | |
1da177e4 LT |
710 | * |
711 | * The page must be locked by the caller and will be unlocked upon return. | |
712 | * | |
713 | * write_one_page() returns a negative error code if I/O failed. | |
714 | */ | |
715 | int write_one_page(struct page *page, int wait) | |
716 | { | |
717 | struct address_space *mapping = page->mapping; | |
718 | int ret = 0; | |
719 | struct writeback_control wbc = { | |
720 | .sync_mode = WB_SYNC_ALL, | |
721 | .nr_to_write = 1, | |
722 | }; | |
723 | ||
724 | BUG_ON(!PageLocked(page)); | |
725 | ||
726 | if (wait) | |
727 | wait_on_page_writeback(page); | |
728 | ||
729 | if (clear_page_dirty_for_io(page)) { | |
730 | page_cache_get(page); | |
731 | ret = mapping->a_ops->writepage(page, &wbc); | |
732 | if (ret == 0 && wait) { | |
733 | wait_on_page_writeback(page); | |
734 | if (PageError(page)) | |
735 | ret = -EIO; | |
736 | } | |
737 | page_cache_release(page); | |
738 | } else { | |
739 | unlock_page(page); | |
740 | } | |
741 | return ret; | |
742 | } | |
743 | EXPORT_SYMBOL(write_one_page); | |
744 | ||
76719325 KC |
745 | /* |
746 | * For address_spaces which do not use buffers nor write back. | |
747 | */ | |
748 | int __set_page_dirty_no_writeback(struct page *page) | |
749 | { | |
750 | if (!PageDirty(page)) | |
751 | SetPageDirty(page); | |
752 | return 0; | |
753 | } | |
754 | ||
1da177e4 LT |
755 | /* |
756 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
757 | * its radix tree. | |
758 | * | |
759 | * This is also used when a single buffer is being dirtied: we want to set the | |
760 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
761 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
762 | * | |
763 | * Most callers have locked the page, which pins the address_space in memory. | |
764 | * But zap_pte_range() does not lock the page, however in that case the | |
765 | * mapping is pinned by the vma's ->vm_file reference. | |
766 | * | |
767 | * We take care to handle the case where the page was truncated from the | |
768 | * mapping by re-checking page_mapping() insode tree_lock. | |
769 | */ | |
770 | int __set_page_dirty_nobuffers(struct page *page) | |
771 | { | |
1da177e4 LT |
772 | if (!TestSetPageDirty(page)) { |
773 | struct address_space *mapping = page_mapping(page); | |
774 | struct address_space *mapping2; | |
775 | ||
8c08540f AM |
776 | if (!mapping) |
777 | return 1; | |
778 | ||
779 | write_lock_irq(&mapping->tree_lock); | |
780 | mapping2 = page_mapping(page); | |
781 | if (mapping2) { /* Race with truncate? */ | |
782 | BUG_ON(mapping2 != mapping); | |
55e829af | 783 | if (mapping_cap_account_dirty(mapping)) { |
8c08540f | 784 | __inc_zone_page_state(page, NR_FILE_DIRTY); |
55e829af AM |
785 | task_io_account_write(PAGE_CACHE_SIZE); |
786 | } | |
8c08540f AM |
787 | radix_tree_tag_set(&mapping->page_tree, |
788 | page_index(page), PAGECACHE_TAG_DIRTY); | |
789 | } | |
790 | write_unlock_irq(&mapping->tree_lock); | |
791 | if (mapping->host) { | |
792 | /* !PageAnon && !swapper_space */ | |
793 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 794 | } |
4741c9fd | 795 | return 1; |
1da177e4 | 796 | } |
4741c9fd | 797 | return 0; |
1da177e4 LT |
798 | } |
799 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
800 | ||
801 | /* | |
802 | * When a writepage implementation decides that it doesn't want to write this | |
803 | * page for some reason, it should redirty the locked page via | |
804 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
805 | */ | |
806 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
807 | { | |
808 | wbc->pages_skipped++; | |
809 | return __set_page_dirty_nobuffers(page); | |
810 | } | |
811 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
812 | ||
813 | /* | |
814 | * If the mapping doesn't provide a set_page_dirty a_op, then | |
815 | * just fall through and assume that it wants buffer_heads. | |
816 | */ | |
817 | int fastcall set_page_dirty(struct page *page) | |
818 | { | |
819 | struct address_space *mapping = page_mapping(page); | |
820 | ||
821 | if (likely(mapping)) { | |
822 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
9361401e DH |
823 | #ifdef CONFIG_BLOCK |
824 | if (!spd) | |
825 | spd = __set_page_dirty_buffers; | |
826 | #endif | |
827 | return (*spd)(page); | |
1da177e4 | 828 | } |
4741c9fd AM |
829 | if (!PageDirty(page)) { |
830 | if (!TestSetPageDirty(page)) | |
831 | return 1; | |
832 | } | |
1da177e4 LT |
833 | return 0; |
834 | } | |
835 | EXPORT_SYMBOL(set_page_dirty); | |
836 | ||
837 | /* | |
838 | * set_page_dirty() is racy if the caller has no reference against | |
839 | * page->mapping->host, and if the page is unlocked. This is because another | |
840 | * CPU could truncate the page off the mapping and then free the mapping. | |
841 | * | |
842 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
843 | * holds a reference on the inode by having an open file. | |
844 | * | |
845 | * In other cases, the page should be locked before running set_page_dirty(). | |
846 | */ | |
847 | int set_page_dirty_lock(struct page *page) | |
848 | { | |
849 | int ret; | |
850 | ||
db37648c | 851 | lock_page_nosync(page); |
1da177e4 LT |
852 | ret = set_page_dirty(page); |
853 | unlock_page(page); | |
854 | return ret; | |
855 | } | |
856 | EXPORT_SYMBOL(set_page_dirty_lock); | |
857 | ||
1da177e4 LT |
858 | /* |
859 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
860 | * Returns true if the page was previously dirty. | |
861 | * | |
862 | * This is for preparing to put the page under writeout. We leave the page | |
863 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
864 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
865 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
866 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
867 | * back into sync. | |
868 | * | |
869 | * This incoherency between the page's dirty flag and radix-tree tag is | |
870 | * unfortunate, but it only exists while the page is locked. | |
871 | */ | |
872 | int clear_page_dirty_for_io(struct page *page) | |
873 | { | |
874 | struct address_space *mapping = page_mapping(page); | |
875 | ||
7658cc28 LT |
876 | if (mapping && mapping_cap_account_dirty(mapping)) { |
877 | /* | |
878 | * Yes, Virginia, this is indeed insane. | |
879 | * | |
880 | * We use this sequence to make sure that | |
881 | * (a) we account for dirty stats properly | |
882 | * (b) we tell the low-level filesystem to | |
883 | * mark the whole page dirty if it was | |
884 | * dirty in a pagetable. Only to then | |
885 | * (c) clean the page again and return 1 to | |
886 | * cause the writeback. | |
887 | * | |
888 | * This way we avoid all nasty races with the | |
889 | * dirty bit in multiple places and clearing | |
890 | * them concurrently from different threads. | |
891 | * | |
892 | * Note! Normally the "set_page_dirty(page)" | |
893 | * has no effect on the actual dirty bit - since | |
894 | * that will already usually be set. But we | |
895 | * need the side effects, and it can help us | |
896 | * avoid races. | |
897 | * | |
898 | * We basically use the page "master dirty bit" | |
899 | * as a serialization point for all the different | |
900 | * threads doing their things. | |
901 | * | |
902 | * FIXME! We still have a race here: if somebody | |
903 | * adds the page back to the page tables in | |
904 | * between the "page_mkclean()" and the "TestClearPageDirty()", | |
905 | * we might have it mapped without the dirty bit set. | |
906 | */ | |
907 | if (page_mkclean(page)) | |
908 | set_page_dirty(page); | |
909 | if (TestClearPageDirty(page)) { | |
8c08540f | 910 | dec_zone_page_state(page, NR_FILE_DIRTY); |
7658cc28 | 911 | return 1; |
1da177e4 | 912 | } |
7658cc28 | 913 | return 0; |
1da177e4 | 914 | } |
7658cc28 | 915 | return TestClearPageDirty(page); |
1da177e4 | 916 | } |
58bb01a9 | 917 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
918 | |
919 | int test_clear_page_writeback(struct page *page) | |
920 | { | |
921 | struct address_space *mapping = page_mapping(page); | |
922 | int ret; | |
923 | ||
924 | if (mapping) { | |
925 | unsigned long flags; | |
926 | ||
927 | write_lock_irqsave(&mapping->tree_lock, flags); | |
928 | ret = TestClearPageWriteback(page); | |
929 | if (ret) | |
930 | radix_tree_tag_clear(&mapping->page_tree, | |
931 | page_index(page), | |
932 | PAGECACHE_TAG_WRITEBACK); | |
933 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
934 | } else { | |
935 | ret = TestClearPageWriteback(page); | |
936 | } | |
937 | return ret; | |
938 | } | |
939 | ||
940 | int test_set_page_writeback(struct page *page) | |
941 | { | |
942 | struct address_space *mapping = page_mapping(page); | |
943 | int ret; | |
944 | ||
945 | if (mapping) { | |
946 | unsigned long flags; | |
947 | ||
948 | write_lock_irqsave(&mapping->tree_lock, flags); | |
949 | ret = TestSetPageWriteback(page); | |
950 | if (!ret) | |
951 | radix_tree_tag_set(&mapping->page_tree, | |
952 | page_index(page), | |
953 | PAGECACHE_TAG_WRITEBACK); | |
954 | if (!PageDirty(page)) | |
955 | radix_tree_tag_clear(&mapping->page_tree, | |
956 | page_index(page), | |
957 | PAGECACHE_TAG_DIRTY); | |
958 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
959 | } else { | |
960 | ret = TestSetPageWriteback(page); | |
961 | } | |
962 | return ret; | |
963 | ||
964 | } | |
965 | EXPORT_SYMBOL(test_set_page_writeback); | |
966 | ||
967 | /* | |
968 | * Return true if any of the pages in the mapping are marged with the | |
969 | * passed tag. | |
970 | */ | |
971 | int mapping_tagged(struct address_space *mapping, int tag) | |
972 | { | |
973 | unsigned long flags; | |
974 | int ret; | |
975 | ||
976 | read_lock_irqsave(&mapping->tree_lock, flags); | |
977 | ret = radix_tree_tagged(&mapping->page_tree, tag); | |
978 | read_unlock_irqrestore(&mapping->tree_lock, flags); | |
979 | return ret; | |
980 | } | |
981 | EXPORT_SYMBOL(mapping_tagged); |