Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * mm/page-writeback.c. | |
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> | |
24 | #include <linux/blkdev.h> | |
25 | #include <linux/mpage.h> | |
d08b3851 | 26 | #include <linux/rmap.h> |
1da177e4 LT |
27 | #include <linux/percpu.h> |
28 | #include <linux/notifier.h> | |
29 | #include <linux/smp.h> | |
30 | #include <linux/sysctl.h> | |
31 | #include <linux/cpu.h> | |
32 | #include <linux/syscalls.h> | |
33 | ||
34 | /* | |
35 | * The maximum number of pages to writeout in a single bdflush/kupdate | |
36 | * operation. We do this so we don't hold I_LOCK against an inode for | |
37 | * enormous amounts of time, which would block a userspace task which has | |
38 | * been forced to throttle against that inode. Also, the code reevaluates | |
39 | * the dirty each time it has written this many pages. | |
40 | */ | |
41 | #define MAX_WRITEBACK_PAGES 1024 | |
42 | ||
43 | /* | |
44 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
45 | * will look to see if it needs to force writeback or throttling. | |
46 | */ | |
47 | static long ratelimit_pages = 32; | |
48 | ||
e236a166 | 49 | static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */ |
1da177e4 LT |
50 | |
51 | /* | |
52 | * When balance_dirty_pages decides that the caller needs to perform some | |
53 | * non-background writeback, this is how many pages it will attempt to write. | |
54 | * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably | |
55 | * large amounts of I/O are submitted. | |
56 | */ | |
57 | static inline long sync_writeback_pages(void) | |
58 | { | |
59 | return ratelimit_pages + ratelimit_pages / 2; | |
60 | } | |
61 | ||
62 | /* The following parameters are exported via /proc/sys/vm */ | |
63 | ||
64 | /* | |
65 | * Start background writeback (via pdflush) at this percentage | |
66 | */ | |
67 | int dirty_background_ratio = 10; | |
68 | ||
69 | /* | |
70 | * The generator of dirty data starts writeback at this percentage | |
71 | */ | |
72 | int vm_dirty_ratio = 40; | |
73 | ||
74 | /* | |
fd5403c7 | 75 | * The interval between `kupdate'-style writebacks, in jiffies |
1da177e4 | 76 | */ |
f6ef9438 | 77 | int dirty_writeback_interval = 5 * HZ; |
1da177e4 LT |
78 | |
79 | /* | |
fd5403c7 | 80 | * The longest number of jiffies for which data is allowed to remain dirty |
1da177e4 | 81 | */ |
f6ef9438 | 82 | int dirty_expire_interval = 30 * HZ; |
1da177e4 LT |
83 | |
84 | /* | |
85 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
86 | */ | |
87 | int block_dump; | |
88 | ||
89 | /* | |
ed5b43f1 BS |
90 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
91 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
92 | */ |
93 | int laptop_mode; | |
94 | ||
95 | EXPORT_SYMBOL(laptop_mode); | |
96 | ||
97 | /* End of sysctl-exported parameters */ | |
98 | ||
99 | ||
100 | static void background_writeout(unsigned long _min_pages); | |
101 | ||
1da177e4 LT |
102 | /* |
103 | * Work out the current dirty-memory clamping and background writeout | |
104 | * thresholds. | |
105 | * | |
106 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
107 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
108 | * pages. It is better to clamp down on writers than to start swapping, and | |
109 | * performing lots of scanning. | |
110 | * | |
111 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
112 | * | |
113 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
114 | * excessive. | |
115 | * | |
116 | * We make sure that the background writeout level is below the adjusted | |
117 | * clamping level. | |
118 | */ | |
119 | static void | |
c24f21bd CL |
120 | get_dirty_limits(long *pbackground, long *pdirty, |
121 | struct address_space *mapping) | |
1da177e4 LT |
122 | { |
123 | int background_ratio; /* Percentages */ | |
124 | int dirty_ratio; | |
125 | int unmapped_ratio; | |
126 | long background; | |
127 | long dirty; | |
40c99aae | 128 | unsigned long available_memory = vm_total_pages; |
1da177e4 LT |
129 | struct task_struct *tsk; |
130 | ||
1da177e4 LT |
131 | #ifdef CONFIG_HIGHMEM |
132 | /* | |
133 | * If this mapping can only allocate from low memory, | |
134 | * we exclude high memory from our count. | |
135 | */ | |
136 | if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM)) | |
137 | available_memory -= totalhigh_pages; | |
138 | #endif | |
139 | ||
140 | ||
c24f21bd CL |
141 | unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) + |
142 | global_page_state(NR_ANON_PAGES)) * 100) / | |
40c99aae | 143 | vm_total_pages; |
1da177e4 LT |
144 | |
145 | dirty_ratio = vm_dirty_ratio; | |
146 | if (dirty_ratio > unmapped_ratio / 2) | |
147 | dirty_ratio = unmapped_ratio / 2; | |
148 | ||
149 | if (dirty_ratio < 5) | |
150 | dirty_ratio = 5; | |
151 | ||
152 | background_ratio = dirty_background_ratio; | |
153 | if (background_ratio >= dirty_ratio) | |
154 | background_ratio = dirty_ratio / 2; | |
155 | ||
156 | background = (background_ratio * available_memory) / 100; | |
157 | dirty = (dirty_ratio * available_memory) / 100; | |
158 | tsk = current; | |
159 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
160 | background += background / 4; | |
161 | dirty += dirty / 4; | |
162 | } | |
163 | *pbackground = background; | |
164 | *pdirty = dirty; | |
165 | } | |
166 | ||
167 | /* | |
168 | * balance_dirty_pages() must be called by processes which are generating dirty | |
169 | * data. It looks at the number of dirty pages in the machine and will force | |
170 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
171 | * If we're over `background_thresh' then pdflush is woken to perform some | |
172 | * writeout. | |
173 | */ | |
174 | static void balance_dirty_pages(struct address_space *mapping) | |
175 | { | |
1da177e4 LT |
176 | long nr_reclaimable; |
177 | long background_thresh; | |
178 | long dirty_thresh; | |
179 | unsigned long pages_written = 0; | |
180 | unsigned long write_chunk = sync_writeback_pages(); | |
181 | ||
182 | struct backing_dev_info *bdi = mapping->backing_dev_info; | |
183 | ||
184 | for (;;) { | |
185 | struct writeback_control wbc = { | |
186 | .bdi = bdi, | |
187 | .sync_mode = WB_SYNC_NONE, | |
188 | .older_than_this = NULL, | |
189 | .nr_to_write = write_chunk, | |
111ebb6e | 190 | .range_cyclic = 1, |
1da177e4 LT |
191 | }; |
192 | ||
c24f21bd CL |
193 | get_dirty_limits(&background_thresh, &dirty_thresh, mapping); |
194 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + | |
195 | global_page_state(NR_UNSTABLE_NFS); | |
196 | if (nr_reclaimable + global_page_state(NR_WRITEBACK) <= | |
197 | dirty_thresh) | |
198 | break; | |
1da177e4 | 199 | |
e236a166 AM |
200 | if (!dirty_exceeded) |
201 | dirty_exceeded = 1; | |
1da177e4 LT |
202 | |
203 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. | |
204 | * Unstable writes are a feature of certain networked | |
205 | * filesystems (i.e. NFS) in which data may have been | |
206 | * written to the server's write cache, but has not yet | |
207 | * been flushed to permanent storage. | |
208 | */ | |
209 | if (nr_reclaimable) { | |
210 | writeback_inodes(&wbc); | |
c24f21bd CL |
211 | get_dirty_limits(&background_thresh, |
212 | &dirty_thresh, mapping); | |
213 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + | |
214 | global_page_state(NR_UNSTABLE_NFS); | |
215 | if (nr_reclaimable + | |
216 | global_page_state(NR_WRITEBACK) | |
217 | <= dirty_thresh) | |
218 | break; | |
1da177e4 LT |
219 | pages_written += write_chunk - wbc.nr_to_write; |
220 | if (pages_written >= write_chunk) | |
221 | break; /* We've done our duty */ | |
222 | } | |
223 | blk_congestion_wait(WRITE, HZ/10); | |
224 | } | |
225 | ||
c24f21bd CL |
226 | if (nr_reclaimable + global_page_state(NR_WRITEBACK) |
227 | <= dirty_thresh && dirty_exceeded) | |
228 | dirty_exceeded = 0; | |
1da177e4 LT |
229 | |
230 | if (writeback_in_progress(bdi)) | |
231 | return; /* pdflush is already working this queue */ | |
232 | ||
233 | /* | |
234 | * In laptop mode, we wait until hitting the higher threshold before | |
235 | * starting background writeout, and then write out all the way down | |
236 | * to the lower threshold. So slow writers cause minimal disk activity. | |
237 | * | |
238 | * In normal mode, we start background writeout at the lower | |
239 | * background_thresh, to keep the amount of dirty memory low. | |
240 | */ | |
241 | if ((laptop_mode && pages_written) || | |
242 | (!laptop_mode && (nr_reclaimable > background_thresh))) | |
243 | pdflush_operation(background_writeout, 0); | |
244 | } | |
245 | ||
edc79b2a PZ |
246 | void set_page_dirty_balance(struct page *page) |
247 | { | |
248 | if (set_page_dirty(page)) { | |
249 | struct address_space *mapping = page_mapping(page); | |
250 | ||
251 | if (mapping) | |
252 | balance_dirty_pages_ratelimited(mapping); | |
253 | } | |
254 | } | |
255 | ||
1da177e4 | 256 | /** |
fa5a734e | 257 | * balance_dirty_pages_ratelimited_nr - balance dirty memory state |
67be2dd1 | 258 | * @mapping: address_space which was dirtied |
a580290c | 259 | * @nr_pages_dirtied: number of pages which the caller has just dirtied |
1da177e4 LT |
260 | * |
261 | * Processes which are dirtying memory should call in here once for each page | |
262 | * which was newly dirtied. The function will periodically check the system's | |
263 | * dirty state and will initiate writeback if needed. | |
264 | * | |
265 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
266 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
267 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
268 | * from overshooting the limit by (ratelimit_pages) each. | |
269 | */ | |
fa5a734e AM |
270 | void balance_dirty_pages_ratelimited_nr(struct address_space *mapping, |
271 | unsigned long nr_pages_dirtied) | |
1da177e4 | 272 | { |
fa5a734e AM |
273 | static DEFINE_PER_CPU(unsigned long, ratelimits) = 0; |
274 | unsigned long ratelimit; | |
275 | unsigned long *p; | |
1da177e4 LT |
276 | |
277 | ratelimit = ratelimit_pages; | |
278 | if (dirty_exceeded) | |
279 | ratelimit = 8; | |
280 | ||
281 | /* | |
282 | * Check the rate limiting. Also, we do not want to throttle real-time | |
283 | * tasks in balance_dirty_pages(). Period. | |
284 | */ | |
fa5a734e AM |
285 | preempt_disable(); |
286 | p = &__get_cpu_var(ratelimits); | |
287 | *p += nr_pages_dirtied; | |
288 | if (unlikely(*p >= ratelimit)) { | |
289 | *p = 0; | |
290 | preempt_enable(); | |
1da177e4 LT |
291 | balance_dirty_pages(mapping); |
292 | return; | |
293 | } | |
fa5a734e | 294 | preempt_enable(); |
1da177e4 | 295 | } |
fa5a734e | 296 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr); |
1da177e4 LT |
297 | |
298 | void throttle_vm_writeout(void) | |
299 | { | |
1da177e4 LT |
300 | long background_thresh; |
301 | long dirty_thresh; | |
302 | ||
303 | for ( ; ; ) { | |
c24f21bd | 304 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL); |
1da177e4 LT |
305 | |
306 | /* | |
307 | * Boost the allowable dirty threshold a bit for page | |
308 | * allocators so they don't get DoS'ed by heavy writers | |
309 | */ | |
310 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
311 | ||
c24f21bd CL |
312 | if (global_page_state(NR_UNSTABLE_NFS) + |
313 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
314 | break; | |
1da177e4 LT |
315 | blk_congestion_wait(WRITE, HZ/10); |
316 | } | |
317 | } | |
318 | ||
319 | ||
320 | /* | |
321 | * writeback at least _min_pages, and keep writing until the amount of dirty | |
322 | * memory is less than the background threshold, or until we're all clean. | |
323 | */ | |
324 | static void background_writeout(unsigned long _min_pages) | |
325 | { | |
326 | long min_pages = _min_pages; | |
327 | struct writeback_control wbc = { | |
328 | .bdi = NULL, | |
329 | .sync_mode = WB_SYNC_NONE, | |
330 | .older_than_this = NULL, | |
331 | .nr_to_write = 0, | |
332 | .nonblocking = 1, | |
111ebb6e | 333 | .range_cyclic = 1, |
1da177e4 LT |
334 | }; |
335 | ||
336 | for ( ; ; ) { | |
1da177e4 LT |
337 | long background_thresh; |
338 | long dirty_thresh; | |
339 | ||
c24f21bd CL |
340 | get_dirty_limits(&background_thresh, &dirty_thresh, NULL); |
341 | if (global_page_state(NR_FILE_DIRTY) + | |
342 | global_page_state(NR_UNSTABLE_NFS) < background_thresh | |
1da177e4 LT |
343 | && min_pages <= 0) |
344 | break; | |
345 | wbc.encountered_congestion = 0; | |
346 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
347 | wbc.pages_skipped = 0; | |
348 | writeback_inodes(&wbc); | |
349 | min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
350 | if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { | |
351 | /* Wrote less than expected */ | |
352 | blk_congestion_wait(WRITE, HZ/10); | |
353 | if (!wbc.encountered_congestion) | |
354 | break; | |
355 | } | |
356 | } | |
357 | } | |
358 | ||
359 | /* | |
360 | * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back | |
361 | * the whole world. Returns 0 if a pdflush thread was dispatched. Returns | |
362 | * -1 if all pdflush threads were busy. | |
363 | */ | |
687a21ce | 364 | int wakeup_pdflush(long nr_pages) |
1da177e4 | 365 | { |
c24f21bd CL |
366 | if (nr_pages == 0) |
367 | nr_pages = global_page_state(NR_FILE_DIRTY) + | |
368 | global_page_state(NR_UNSTABLE_NFS); | |
1da177e4 LT |
369 | return pdflush_operation(background_writeout, nr_pages); |
370 | } | |
371 | ||
372 | static void wb_timer_fn(unsigned long unused); | |
373 | static void laptop_timer_fn(unsigned long unused); | |
374 | ||
8d06afab IM |
375 | static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0); |
376 | static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0); | |
1da177e4 LT |
377 | |
378 | /* | |
379 | * Periodic writeback of "old" data. | |
380 | * | |
381 | * Define "old": the first time one of an inode's pages is dirtied, we mark the | |
382 | * dirtying-time in the inode's address_space. So this periodic writeback code | |
383 | * just walks the superblock inode list, writing back any inodes which are | |
384 | * older than a specific point in time. | |
385 | * | |
f6ef9438 BS |
386 | * Try to run once per dirty_writeback_interval. But if a writeback event |
387 | * takes longer than a dirty_writeback_interval interval, then leave a | |
1da177e4 LT |
388 | * one-second gap. |
389 | * | |
390 | * older_than_this takes precedence over nr_to_write. So we'll only write back | |
391 | * all dirty pages if they are all attached to "old" mappings. | |
392 | */ | |
393 | static void wb_kupdate(unsigned long arg) | |
394 | { | |
395 | unsigned long oldest_jif; | |
396 | unsigned long start_jif; | |
397 | unsigned long next_jif; | |
398 | long nr_to_write; | |
1da177e4 LT |
399 | struct writeback_control wbc = { |
400 | .bdi = NULL, | |
401 | .sync_mode = WB_SYNC_NONE, | |
402 | .older_than_this = &oldest_jif, | |
403 | .nr_to_write = 0, | |
404 | .nonblocking = 1, | |
405 | .for_kupdate = 1, | |
111ebb6e | 406 | .range_cyclic = 1, |
1da177e4 LT |
407 | }; |
408 | ||
409 | sync_supers(); | |
410 | ||
f6ef9438 | 411 | oldest_jif = jiffies - dirty_expire_interval; |
1da177e4 | 412 | start_jif = jiffies; |
f6ef9438 | 413 | next_jif = start_jif + dirty_writeback_interval; |
c24f21bd CL |
414 | nr_to_write = global_page_state(NR_FILE_DIRTY) + |
415 | global_page_state(NR_UNSTABLE_NFS) + | |
1da177e4 LT |
416 | (inodes_stat.nr_inodes - inodes_stat.nr_unused); |
417 | while (nr_to_write > 0) { | |
418 | wbc.encountered_congestion = 0; | |
419 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
420 | writeback_inodes(&wbc); | |
421 | if (wbc.nr_to_write > 0) { | |
422 | if (wbc.encountered_congestion) | |
423 | blk_congestion_wait(WRITE, HZ/10); | |
424 | else | |
425 | break; /* All the old data is written */ | |
426 | } | |
427 | nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
428 | } | |
429 | if (time_before(next_jif, jiffies + HZ)) | |
430 | next_jif = jiffies + HZ; | |
f6ef9438 | 431 | if (dirty_writeback_interval) |
1da177e4 LT |
432 | mod_timer(&wb_timer, next_jif); |
433 | } | |
434 | ||
435 | /* | |
436 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
437 | */ | |
438 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
439 | struct file *file, void __user *buffer, size_t *length, loff_t *ppos) | |
440 | { | |
f6ef9438 BS |
441 | proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos); |
442 | if (dirty_writeback_interval) { | |
1da177e4 | 443 | mod_timer(&wb_timer, |
f6ef9438 BS |
444 | jiffies + dirty_writeback_interval); |
445 | } else { | |
1da177e4 LT |
446 | del_timer(&wb_timer); |
447 | } | |
448 | return 0; | |
449 | } | |
450 | ||
451 | static void wb_timer_fn(unsigned long unused) | |
452 | { | |
453 | if (pdflush_operation(wb_kupdate, 0) < 0) | |
454 | mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */ | |
455 | } | |
456 | ||
457 | static void laptop_flush(unsigned long unused) | |
458 | { | |
459 | sys_sync(); | |
460 | } | |
461 | ||
462 | static void laptop_timer_fn(unsigned long unused) | |
463 | { | |
464 | pdflush_operation(laptop_flush, 0); | |
465 | } | |
466 | ||
467 | /* | |
468 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
469 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
470 | * then push it back - the user is still using the disk. | |
471 | */ | |
472 | void laptop_io_completion(void) | |
473 | { | |
ed5b43f1 | 474 | mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
475 | } |
476 | ||
477 | /* | |
478 | * We're in laptop mode and we've just synced. The sync's writes will have | |
479 | * caused another writeback to be scheduled by laptop_io_completion. | |
480 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
481 | */ | |
482 | void laptop_sync_completion(void) | |
483 | { | |
484 | del_timer(&laptop_mode_wb_timer); | |
485 | } | |
486 | ||
487 | /* | |
488 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
489 | * if a large number of processes all perform writes at the same time. | |
490 | * If it is too low then SMP machines will call the (expensive) | |
491 | * get_writeback_state too often. | |
492 | * | |
493 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
494 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
495 | * thresholds before writeback cuts in. | |
496 | * | |
497 | * But the limit should not be set too high. Because it also controls the | |
498 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
499 | * If this is too large then the caller will block on the IO queue all the | |
500 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
501 | * will write six megabyte chunks, max. | |
502 | */ | |
503 | ||
2d1d43f6 | 504 | void writeback_set_ratelimit(void) |
1da177e4 | 505 | { |
40c99aae | 506 | ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); |
1da177e4 LT |
507 | if (ratelimit_pages < 16) |
508 | ratelimit_pages = 16; | |
509 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
510 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
511 | } | |
512 | ||
26c2143b | 513 | static int __cpuinit |
1da177e4 LT |
514 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) |
515 | { | |
2d1d43f6 | 516 | writeback_set_ratelimit(); |
1da177e4 LT |
517 | return 0; |
518 | } | |
519 | ||
74b85f37 | 520 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
1da177e4 LT |
521 | .notifier_call = ratelimit_handler, |
522 | .next = NULL, | |
523 | }; | |
524 | ||
525 | /* | |
526 | * If the machine has a large highmem:lowmem ratio then scale back the default | |
527 | * dirty memory thresholds: allowing too much dirty highmem pins an excessive | |
528 | * number of buffer_heads. | |
529 | */ | |
530 | void __init page_writeback_init(void) | |
531 | { | |
532 | long buffer_pages = nr_free_buffer_pages(); | |
533 | long correction; | |
534 | ||
40c99aae | 535 | correction = (100 * 4 * buffer_pages) / vm_total_pages; |
1da177e4 LT |
536 | |
537 | if (correction < 100) { | |
538 | dirty_background_ratio *= correction; | |
539 | dirty_background_ratio /= 100; | |
540 | vm_dirty_ratio *= correction; | |
541 | vm_dirty_ratio /= 100; | |
542 | ||
543 | if (dirty_background_ratio <= 0) | |
544 | dirty_background_ratio = 1; | |
545 | if (vm_dirty_ratio <= 0) | |
546 | vm_dirty_ratio = 1; | |
547 | } | |
f6ef9438 | 548 | mod_timer(&wb_timer, jiffies + dirty_writeback_interval); |
2d1d43f6 | 549 | writeback_set_ratelimit(); |
1da177e4 LT |
550 | register_cpu_notifier(&ratelimit_nb); |
551 | } | |
552 | ||
553 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) | |
554 | { | |
22905f77 AM |
555 | int ret; |
556 | ||
1da177e4 LT |
557 | if (wbc->nr_to_write <= 0) |
558 | return 0; | |
22905f77 | 559 | wbc->for_writepages = 1; |
1da177e4 | 560 | if (mapping->a_ops->writepages) |
d08b3851 | 561 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
562 | else |
563 | ret = generic_writepages(mapping, wbc); | |
564 | wbc->for_writepages = 0; | |
565 | return ret; | |
1da177e4 LT |
566 | } |
567 | ||
568 | /** | |
569 | * write_one_page - write out a single page and optionally wait on I/O | |
570 | * | |
67be2dd1 MW |
571 | * @page: the page to write |
572 | * @wait: if true, wait on writeout | |
1da177e4 LT |
573 | * |
574 | * The page must be locked by the caller and will be unlocked upon return. | |
575 | * | |
576 | * write_one_page() returns a negative error code if I/O failed. | |
577 | */ | |
578 | int write_one_page(struct page *page, int wait) | |
579 | { | |
580 | struct address_space *mapping = page->mapping; | |
581 | int ret = 0; | |
582 | struct writeback_control wbc = { | |
583 | .sync_mode = WB_SYNC_ALL, | |
584 | .nr_to_write = 1, | |
585 | }; | |
586 | ||
587 | BUG_ON(!PageLocked(page)); | |
588 | ||
589 | if (wait) | |
590 | wait_on_page_writeback(page); | |
591 | ||
592 | if (clear_page_dirty_for_io(page)) { | |
593 | page_cache_get(page); | |
594 | ret = mapping->a_ops->writepage(page, &wbc); | |
595 | if (ret == 0 && wait) { | |
596 | wait_on_page_writeback(page); | |
597 | if (PageError(page)) | |
598 | ret = -EIO; | |
599 | } | |
600 | page_cache_release(page); | |
601 | } else { | |
602 | unlock_page(page); | |
603 | } | |
604 | return ret; | |
605 | } | |
606 | EXPORT_SYMBOL(write_one_page); | |
607 | ||
608 | /* | |
609 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
610 | * its radix tree. | |
611 | * | |
612 | * This is also used when a single buffer is being dirtied: we want to set the | |
613 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
614 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
615 | * | |
616 | * Most callers have locked the page, which pins the address_space in memory. | |
617 | * But zap_pte_range() does not lock the page, however in that case the | |
618 | * mapping is pinned by the vma's ->vm_file reference. | |
619 | * | |
620 | * We take care to handle the case where the page was truncated from the | |
621 | * mapping by re-checking page_mapping() insode tree_lock. | |
622 | */ | |
623 | int __set_page_dirty_nobuffers(struct page *page) | |
624 | { | |
1da177e4 LT |
625 | if (!TestSetPageDirty(page)) { |
626 | struct address_space *mapping = page_mapping(page); | |
627 | struct address_space *mapping2; | |
628 | ||
629 | if (mapping) { | |
630 | write_lock_irq(&mapping->tree_lock); | |
631 | mapping2 = page_mapping(page); | |
632 | if (mapping2) { /* Race with truncate? */ | |
633 | BUG_ON(mapping2 != mapping); | |
634 | if (mapping_cap_account_dirty(mapping)) | |
b1e7a8fd CL |
635 | __inc_zone_page_state(page, |
636 | NR_FILE_DIRTY); | |
1da177e4 LT |
637 | radix_tree_tag_set(&mapping->page_tree, |
638 | page_index(page), PAGECACHE_TAG_DIRTY); | |
639 | } | |
640 | write_unlock_irq(&mapping->tree_lock); | |
641 | if (mapping->host) { | |
642 | /* !PageAnon && !swapper_space */ | |
643 | __mark_inode_dirty(mapping->host, | |
644 | I_DIRTY_PAGES); | |
645 | } | |
646 | } | |
4741c9fd | 647 | return 1; |
1da177e4 | 648 | } |
4741c9fd | 649 | return 0; |
1da177e4 LT |
650 | } |
651 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
652 | ||
653 | /* | |
654 | * When a writepage implementation decides that it doesn't want to write this | |
655 | * page for some reason, it should redirty the locked page via | |
656 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
657 | */ | |
658 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
659 | { | |
660 | wbc->pages_skipped++; | |
661 | return __set_page_dirty_nobuffers(page); | |
662 | } | |
663 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
664 | ||
665 | /* | |
666 | * If the mapping doesn't provide a set_page_dirty a_op, then | |
667 | * just fall through and assume that it wants buffer_heads. | |
668 | */ | |
669 | int fastcall set_page_dirty(struct page *page) | |
670 | { | |
671 | struct address_space *mapping = page_mapping(page); | |
672 | ||
673 | if (likely(mapping)) { | |
674 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
675 | if (spd) | |
676 | return (*spd)(page); | |
677 | return __set_page_dirty_buffers(page); | |
678 | } | |
4741c9fd AM |
679 | if (!PageDirty(page)) { |
680 | if (!TestSetPageDirty(page)) | |
681 | return 1; | |
682 | } | |
1da177e4 LT |
683 | return 0; |
684 | } | |
685 | EXPORT_SYMBOL(set_page_dirty); | |
686 | ||
687 | /* | |
688 | * set_page_dirty() is racy if the caller has no reference against | |
689 | * page->mapping->host, and if the page is unlocked. This is because another | |
690 | * CPU could truncate the page off the mapping and then free the mapping. | |
691 | * | |
692 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
693 | * holds a reference on the inode by having an open file. | |
694 | * | |
695 | * In other cases, the page should be locked before running set_page_dirty(). | |
696 | */ | |
697 | int set_page_dirty_lock(struct page *page) | |
698 | { | |
699 | int ret; | |
700 | ||
db37648c | 701 | lock_page_nosync(page); |
1da177e4 LT |
702 | ret = set_page_dirty(page); |
703 | unlock_page(page); | |
704 | return ret; | |
705 | } | |
706 | EXPORT_SYMBOL(set_page_dirty_lock); | |
707 | ||
708 | /* | |
709 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
710 | * Returns true if the page was previously dirty. | |
711 | */ | |
712 | int test_clear_page_dirty(struct page *page) | |
713 | { | |
714 | struct address_space *mapping = page_mapping(page); | |
715 | unsigned long flags; | |
716 | ||
717 | if (mapping) { | |
718 | write_lock_irqsave(&mapping->tree_lock, flags); | |
719 | if (TestClearPageDirty(page)) { | |
720 | radix_tree_tag_clear(&mapping->page_tree, | |
721 | page_index(page), | |
722 | PAGECACHE_TAG_DIRTY); | |
b1e7a8fd | 723 | write_unlock_irqrestore(&mapping->tree_lock, flags); |
d08b3851 PZ |
724 | /* |
725 | * We can continue to use `mapping' here because the | |
726 | * page is locked, which pins the address_space | |
727 | */ | |
728 | if (mapping_cap_account_dirty(mapping)) { | |
729 | page_mkclean(page); | |
730 | dec_zone_page_state(page, NR_FILE_DIRTY); | |
731 | } | |
1da177e4 LT |
732 | return 1; |
733 | } | |
734 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
735 | return 0; | |
736 | } | |
737 | return TestClearPageDirty(page); | |
738 | } | |
739 | EXPORT_SYMBOL(test_clear_page_dirty); | |
740 | ||
741 | /* | |
742 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
743 | * Returns true if the page was previously dirty. | |
744 | * | |
745 | * This is for preparing to put the page under writeout. We leave the page | |
746 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
747 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
748 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
749 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
750 | * back into sync. | |
751 | * | |
752 | * This incoherency between the page's dirty flag and radix-tree tag is | |
753 | * unfortunate, but it only exists while the page is locked. | |
754 | */ | |
755 | int clear_page_dirty_for_io(struct page *page) | |
756 | { | |
757 | struct address_space *mapping = page_mapping(page); | |
758 | ||
759 | if (mapping) { | |
760 | if (TestClearPageDirty(page)) { | |
d08b3851 PZ |
761 | if (mapping_cap_account_dirty(mapping)) { |
762 | page_mkclean(page); | |
b1e7a8fd | 763 | dec_zone_page_state(page, NR_FILE_DIRTY); |
d08b3851 | 764 | } |
1da177e4 LT |
765 | return 1; |
766 | } | |
767 | return 0; | |
768 | } | |
769 | return TestClearPageDirty(page); | |
770 | } | |
58bb01a9 | 771 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
772 | |
773 | int test_clear_page_writeback(struct page *page) | |
774 | { | |
775 | struct address_space *mapping = page_mapping(page); | |
776 | int ret; | |
777 | ||
778 | if (mapping) { | |
779 | unsigned long flags; | |
780 | ||
781 | write_lock_irqsave(&mapping->tree_lock, flags); | |
782 | ret = TestClearPageWriteback(page); | |
783 | if (ret) | |
784 | radix_tree_tag_clear(&mapping->page_tree, | |
785 | page_index(page), | |
786 | PAGECACHE_TAG_WRITEBACK); | |
787 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
788 | } else { | |
789 | ret = TestClearPageWriteback(page); | |
790 | } | |
791 | return ret; | |
792 | } | |
793 | ||
794 | int test_set_page_writeback(struct page *page) | |
795 | { | |
796 | struct address_space *mapping = page_mapping(page); | |
797 | int ret; | |
798 | ||
799 | if (mapping) { | |
800 | unsigned long flags; | |
801 | ||
802 | write_lock_irqsave(&mapping->tree_lock, flags); | |
803 | ret = TestSetPageWriteback(page); | |
804 | if (!ret) | |
805 | radix_tree_tag_set(&mapping->page_tree, | |
806 | page_index(page), | |
807 | PAGECACHE_TAG_WRITEBACK); | |
808 | if (!PageDirty(page)) | |
809 | radix_tree_tag_clear(&mapping->page_tree, | |
810 | page_index(page), | |
811 | PAGECACHE_TAG_DIRTY); | |
812 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
813 | } else { | |
814 | ret = TestSetPageWriteback(page); | |
815 | } | |
816 | return ret; | |
817 | ||
818 | } | |
819 | EXPORT_SYMBOL(test_set_page_writeback); | |
820 | ||
275a082f TM |
821 | /* |
822 | * Wakes up tasks that are being throttled due to writeback congestion | |
823 | */ | |
824 | void writeback_congestion_end(void) | |
825 | { | |
826 | blk_congestion_end(WRITE); | |
827 | } | |
828 | EXPORT_SYMBOL(writeback_congestion_end); | |
829 | ||
1da177e4 LT |
830 | /* |
831 | * Return true if any of the pages in the mapping are marged with the | |
832 | * passed tag. | |
833 | */ | |
834 | int mapping_tagged(struct address_space *mapping, int tag) | |
835 | { | |
836 | unsigned long flags; | |
837 | int ret; | |
838 | ||
839 | read_lock_irqsave(&mapping->tree_lock, flags); | |
840 | ret = radix_tree_tagged(&mapping->page_tree, tag); | |
841 | read_unlock_irqrestore(&mapping->tree_lock, flags); | |
842 | return ret; | |
843 | } | |
844 | EXPORT_SYMBOL(mapping_tagged); |