Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
f30c2269 | 2 | * mm/page-writeback.c |
1da177e4 LT |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. | |
90eec103 | 5 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra |
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> | |
b95f1b31 | 15 | #include <linux/export.h> |
1da177e4 LT |
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> | |
ff01bb48 | 35 | #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ |
811d736f | 36 | #include <linux/pagevec.h> |
eb608e3a | 37 | #include <linux/timer.h> |
8bd75c77 | 38 | #include <linux/sched/rt.h> |
6e543d57 | 39 | #include <linux/mm_inline.h> |
028c2dd1 | 40 | #include <trace/events/writeback.h> |
1da177e4 | 41 | |
6e543d57 LD |
42 | #include "internal.h" |
43 | ||
ffd1f609 WF |
44 | /* |
45 | * Sleep at most 200ms at a time in balance_dirty_pages(). | |
46 | */ | |
47 | #define MAX_PAUSE max(HZ/5, 1) | |
48 | ||
5b9b3574 WF |
49 | /* |
50 | * Try to keep balance_dirty_pages() call intervals higher than this many pages | |
51 | * by raising pause time to max_pause when falls below it. | |
52 | */ | |
53 | #define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) | |
54 | ||
e98be2d5 WF |
55 | /* |
56 | * Estimate write bandwidth at 200ms intervals. | |
57 | */ | |
58 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) | |
59 | ||
6c14ae1e WF |
60 | #define RATELIMIT_CALC_SHIFT 10 |
61 | ||
1da177e4 LT |
62 | /* |
63 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
64 | * will look to see if it needs to force writeback or throttling. | |
65 | */ | |
66 | static long ratelimit_pages = 32; | |
67 | ||
1da177e4 LT |
68 | /* The following parameters are exported via /proc/sys/vm */ |
69 | ||
70 | /* | |
5b0830cb | 71 | * Start background writeback (via writeback threads) at this percentage |
1da177e4 | 72 | */ |
1b5e62b4 | 73 | int dirty_background_ratio = 10; |
1da177e4 | 74 | |
2da02997 DR |
75 | /* |
76 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
77 | * dirty_background_ratio * the amount of dirtyable memory | |
78 | */ | |
79 | unsigned long dirty_background_bytes; | |
80 | ||
195cf453 BG |
81 | /* |
82 | * free highmem will not be subtracted from the total free memory | |
83 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
84 | */ | |
85 | int vm_highmem_is_dirtyable; | |
86 | ||
1da177e4 LT |
87 | /* |
88 | * The generator of dirty data starts writeback at this percentage | |
89 | */ | |
1b5e62b4 | 90 | int vm_dirty_ratio = 20; |
1da177e4 | 91 | |
2da02997 DR |
92 | /* |
93 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
94 | * vm_dirty_ratio * the amount of dirtyable memory | |
95 | */ | |
96 | unsigned long vm_dirty_bytes; | |
97 | ||
1da177e4 | 98 | /* |
704503d8 | 99 | * The interval between `kupdate'-style writebacks |
1da177e4 | 100 | */ |
22ef37ee | 101 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 | 102 | |
91913a29 AB |
103 | EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
104 | ||
1da177e4 | 105 | /* |
704503d8 | 106 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 107 | */ |
22ef37ee | 108 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
109 | |
110 | /* | |
111 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
112 | */ | |
113 | int block_dump; | |
114 | ||
115 | /* | |
ed5b43f1 BS |
116 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
117 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
118 | */ |
119 | int laptop_mode; | |
120 | ||
121 | EXPORT_SYMBOL(laptop_mode); | |
122 | ||
123 | /* End of sysctl-exported parameters */ | |
124 | ||
dcc25ae7 | 125 | struct wb_domain global_wb_domain; |
1da177e4 | 126 | |
2bc00aef TH |
127 | /* consolidated parameters for balance_dirty_pages() and its subroutines */ |
128 | struct dirty_throttle_control { | |
e9f07dfd TH |
129 | #ifdef CONFIG_CGROUP_WRITEBACK |
130 | struct wb_domain *dom; | |
9fc3a43e | 131 | struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ |
e9f07dfd | 132 | #endif |
2bc00aef | 133 | struct bdi_writeback *wb; |
e9770b34 | 134 | struct fprop_local_percpu *wb_completions; |
eb608e3a | 135 | |
9fc3a43e | 136 | unsigned long avail; /* dirtyable */ |
2bc00aef TH |
137 | unsigned long dirty; /* file_dirty + write + nfs */ |
138 | unsigned long thresh; /* dirty threshold */ | |
139 | unsigned long bg_thresh; /* dirty background threshold */ | |
140 | ||
141 | unsigned long wb_dirty; /* per-wb counterparts */ | |
142 | unsigned long wb_thresh; | |
970fb01a | 143 | unsigned long wb_bg_thresh; |
daddfa3c TH |
144 | |
145 | unsigned long pos_ratio; | |
2bc00aef TH |
146 | }; |
147 | ||
eb608e3a JK |
148 | /* |
149 | * Length of period for aging writeout fractions of bdis. This is an | |
150 | * arbitrarily chosen number. The longer the period, the slower fractions will | |
151 | * reflect changes in current writeout rate. | |
152 | */ | |
153 | #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) | |
04fbfdc1 | 154 | |
693108a8 TH |
155 | #ifdef CONFIG_CGROUP_WRITEBACK |
156 | ||
d60d1bdd TH |
157 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
158 | .dom = &global_wb_domain, \ | |
159 | .wb_completions = &(__wb)->completions | |
160 | ||
9fc3a43e | 161 | #define GDTC_INIT_NO_WB .dom = &global_wb_domain |
d60d1bdd TH |
162 | |
163 | #define MDTC_INIT(__wb, __gdtc) .wb = (__wb), \ | |
164 | .dom = mem_cgroup_wb_domain(__wb), \ | |
165 | .wb_completions = &(__wb)->memcg_completions, \ | |
166 | .gdtc = __gdtc | |
c2aa723a TH |
167 | |
168 | static bool mdtc_valid(struct dirty_throttle_control *dtc) | |
169 | { | |
170 | return dtc->dom; | |
171 | } | |
e9f07dfd TH |
172 | |
173 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) | |
174 | { | |
175 | return dtc->dom; | |
176 | } | |
177 | ||
9fc3a43e TH |
178 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
179 | { | |
180 | return mdtc->gdtc; | |
181 | } | |
182 | ||
841710aa TH |
183 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
184 | { | |
185 | return &wb->memcg_completions; | |
186 | } | |
187 | ||
693108a8 TH |
188 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
189 | unsigned long *minp, unsigned long *maxp) | |
190 | { | |
191 | unsigned long this_bw = wb->avg_write_bandwidth; | |
192 | unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); | |
193 | unsigned long long min = wb->bdi->min_ratio; | |
194 | unsigned long long max = wb->bdi->max_ratio; | |
195 | ||
196 | /* | |
197 | * @wb may already be clean by the time control reaches here and | |
198 | * the total may not include its bw. | |
199 | */ | |
200 | if (this_bw < tot_bw) { | |
201 | if (min) { | |
202 | min *= this_bw; | |
203 | do_div(min, tot_bw); | |
204 | } | |
205 | if (max < 100) { | |
206 | max *= this_bw; | |
207 | do_div(max, tot_bw); | |
208 | } | |
209 | } | |
210 | ||
211 | *minp = min; | |
212 | *maxp = max; | |
213 | } | |
214 | ||
215 | #else /* CONFIG_CGROUP_WRITEBACK */ | |
216 | ||
d60d1bdd TH |
217 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
218 | .wb_completions = &(__wb)->completions | |
9fc3a43e | 219 | #define GDTC_INIT_NO_WB |
c2aa723a TH |
220 | #define MDTC_INIT(__wb, __gdtc) |
221 | ||
222 | static bool mdtc_valid(struct dirty_throttle_control *dtc) | |
223 | { | |
224 | return false; | |
225 | } | |
e9f07dfd TH |
226 | |
227 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) | |
228 | { | |
229 | return &global_wb_domain; | |
230 | } | |
231 | ||
9fc3a43e TH |
232 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
233 | { | |
234 | return NULL; | |
235 | } | |
236 | ||
841710aa TH |
237 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
238 | { | |
239 | return NULL; | |
240 | } | |
241 | ||
693108a8 TH |
242 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
243 | unsigned long *minp, unsigned long *maxp) | |
244 | { | |
245 | *minp = wb->bdi->min_ratio; | |
246 | *maxp = wb->bdi->max_ratio; | |
247 | } | |
248 | ||
249 | #endif /* CONFIG_CGROUP_WRITEBACK */ | |
250 | ||
a756cf59 JW |
251 | /* |
252 | * In a memory zone, there is a certain amount of pages we consider | |
253 | * available for the page cache, which is essentially the number of | |
254 | * free and reclaimable pages, minus some zone reserves to protect | |
255 | * lowmem and the ability to uphold the zone's watermarks without | |
256 | * requiring writeback. | |
257 | * | |
258 | * This number of dirtyable pages is the base value of which the | |
259 | * user-configurable dirty ratio is the effictive number of pages that | |
260 | * are allowed to be actually dirtied. Per individual zone, or | |
261 | * globally by using the sum of dirtyable pages over all zones. | |
262 | * | |
263 | * Because the user is allowed to specify the dirty limit globally as | |
264 | * absolute number of bytes, calculating the per-zone dirty limit can | |
265 | * require translating the configured limit into a percentage of | |
266 | * global dirtyable memory first. | |
267 | */ | |
268 | ||
a804552b JW |
269 | /** |
270 | * zone_dirtyable_memory - number of dirtyable pages in a zone | |
271 | * @zone: the zone | |
272 | * | |
273 | * Returns the zone's number of pages potentially available for dirty | |
274 | * page cache. This is the base value for the per-zone dirty limits. | |
275 | */ | |
276 | static unsigned long zone_dirtyable_memory(struct zone *zone) | |
277 | { | |
278 | unsigned long nr_pages; | |
279 | ||
280 | nr_pages = zone_page_state(zone, NR_FREE_PAGES); | |
a8d01437 JW |
281 | /* |
282 | * Pages reserved for the kernel should not be considered | |
283 | * dirtyable, to prevent a situation where reclaim has to | |
284 | * clean pages in order to balance the zones. | |
285 | */ | |
286 | nr_pages -= min(nr_pages, zone->totalreserve_pages); | |
a804552b | 287 | |
a1c3bfb2 JW |
288 | nr_pages += zone_page_state(zone, NR_INACTIVE_FILE); |
289 | nr_pages += zone_page_state(zone, NR_ACTIVE_FILE); | |
a804552b JW |
290 | |
291 | return nr_pages; | |
292 | } | |
293 | ||
1edf2234 JW |
294 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
295 | { | |
296 | #ifdef CONFIG_HIGHMEM | |
297 | int node; | |
298 | unsigned long x = 0; | |
09b4ab3c | 299 | int i; |
1edf2234 JW |
300 | |
301 | for_each_node_state(node, N_HIGH_MEMORY) { | |
09b4ab3c JK |
302 | for (i = 0; i < MAX_NR_ZONES; i++) { |
303 | struct zone *z = &NODE_DATA(node)->node_zones[i]; | |
1edf2234 | 304 | |
09b4ab3c JK |
305 | if (is_highmem(z)) |
306 | x += zone_dirtyable_memory(z); | |
307 | } | |
1edf2234 | 308 | } |
c8b74c2f SR |
309 | /* |
310 | * Unreclaimable memory (kernel memory or anonymous memory | |
311 | * without swap) can bring down the dirtyable pages below | |
312 | * the zone's dirty balance reserve and the above calculation | |
313 | * will underflow. However we still want to add in nodes | |
314 | * which are below threshold (negative values) to get a more | |
315 | * accurate calculation but make sure that the total never | |
316 | * underflows. | |
317 | */ | |
318 | if ((long)x < 0) | |
319 | x = 0; | |
320 | ||
1edf2234 JW |
321 | /* |
322 | * Make sure that the number of highmem pages is never larger | |
323 | * than the number of the total dirtyable memory. This can only | |
324 | * occur in very strange VM situations but we want to make sure | |
325 | * that this does not occur. | |
326 | */ | |
327 | return min(x, total); | |
328 | #else | |
329 | return 0; | |
330 | #endif | |
331 | } | |
332 | ||
333 | /** | |
ccafa287 | 334 | * global_dirtyable_memory - number of globally dirtyable pages |
1edf2234 | 335 | * |
ccafa287 JW |
336 | * Returns the global number of pages potentially available for dirty |
337 | * page cache. This is the base value for the global dirty limits. | |
1edf2234 | 338 | */ |
18cf8cf8 | 339 | static unsigned long global_dirtyable_memory(void) |
1edf2234 JW |
340 | { |
341 | unsigned long x; | |
342 | ||
a804552b | 343 | x = global_page_state(NR_FREE_PAGES); |
a8d01437 JW |
344 | /* |
345 | * Pages reserved for the kernel should not be considered | |
346 | * dirtyable, to prevent a situation where reclaim has to | |
347 | * clean pages in order to balance the zones. | |
348 | */ | |
349 | x -= min(x, totalreserve_pages); | |
1edf2234 | 350 | |
a1c3bfb2 JW |
351 | x += global_page_state(NR_INACTIVE_FILE); |
352 | x += global_page_state(NR_ACTIVE_FILE); | |
a804552b | 353 | |
1edf2234 JW |
354 | if (!vm_highmem_is_dirtyable) |
355 | x -= highmem_dirtyable_memory(x); | |
356 | ||
357 | return x + 1; /* Ensure that we never return 0 */ | |
358 | } | |
359 | ||
9fc3a43e TH |
360 | /** |
361 | * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain | |
362 | * @dtc: dirty_throttle_control of interest | |
ccafa287 | 363 | * |
9fc3a43e TH |
364 | * Calculate @dtc->thresh and ->bg_thresh considering |
365 | * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller | |
366 | * must ensure that @dtc->avail is set before calling this function. The | |
367 | * dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ccafa287 JW |
368 | * real-time tasks. |
369 | */ | |
9fc3a43e | 370 | static void domain_dirty_limits(struct dirty_throttle_control *dtc) |
ccafa287 | 371 | { |
9fc3a43e TH |
372 | const unsigned long available_memory = dtc->avail; |
373 | struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); | |
374 | unsigned long bytes = vm_dirty_bytes; | |
375 | unsigned long bg_bytes = dirty_background_bytes; | |
62a584fe TH |
376 | /* convert ratios to per-PAGE_SIZE for higher precision */ |
377 | unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100; | |
378 | unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100; | |
9fc3a43e TH |
379 | unsigned long thresh; |
380 | unsigned long bg_thresh; | |
ccafa287 JW |
381 | struct task_struct *tsk; |
382 | ||
9fc3a43e TH |
383 | /* gdtc is !NULL iff @dtc is for memcg domain */ |
384 | if (gdtc) { | |
385 | unsigned long global_avail = gdtc->avail; | |
386 | ||
387 | /* | |
388 | * The byte settings can't be applied directly to memcg | |
389 | * domains. Convert them to ratios by scaling against | |
62a584fe TH |
390 | * globally available memory. As the ratios are in |
391 | * per-PAGE_SIZE, they can be obtained by dividing bytes by | |
392 | * number of pages. | |
9fc3a43e TH |
393 | */ |
394 | if (bytes) | |
62a584fe TH |
395 | ratio = min(DIV_ROUND_UP(bytes, global_avail), |
396 | PAGE_SIZE); | |
9fc3a43e | 397 | if (bg_bytes) |
62a584fe TH |
398 | bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail), |
399 | PAGE_SIZE); | |
9fc3a43e TH |
400 | bytes = bg_bytes = 0; |
401 | } | |
402 | ||
403 | if (bytes) | |
404 | thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); | |
ccafa287 | 405 | else |
62a584fe | 406 | thresh = (ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 407 | |
9fc3a43e TH |
408 | if (bg_bytes) |
409 | bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); | |
ccafa287 | 410 | else |
62a584fe | 411 | bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 412 | |
9fc3a43e TH |
413 | if (bg_thresh >= thresh) |
414 | bg_thresh = thresh / 2; | |
ccafa287 JW |
415 | tsk = current; |
416 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
a53eaff8 N |
417 | bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; |
418 | thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; | |
ccafa287 | 419 | } |
9fc3a43e TH |
420 | dtc->thresh = thresh; |
421 | dtc->bg_thresh = bg_thresh; | |
422 | ||
423 | /* we should eventually report the domain in the TP */ | |
424 | if (!gdtc) | |
425 | trace_global_dirty_state(bg_thresh, thresh); | |
426 | } | |
427 | ||
428 | /** | |
429 | * global_dirty_limits - background-writeback and dirty-throttling thresholds | |
430 | * @pbackground: out parameter for bg_thresh | |
431 | * @pdirty: out parameter for thresh | |
432 | * | |
433 | * Calculate bg_thresh and thresh for global_wb_domain. See | |
434 | * domain_dirty_limits() for details. | |
435 | */ | |
436 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) | |
437 | { | |
438 | struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; | |
439 | ||
440 | gdtc.avail = global_dirtyable_memory(); | |
441 | domain_dirty_limits(&gdtc); | |
442 | ||
443 | *pbackground = gdtc.bg_thresh; | |
444 | *pdirty = gdtc.thresh; | |
ccafa287 JW |
445 | } |
446 | ||
a756cf59 JW |
447 | /** |
448 | * zone_dirty_limit - maximum number of dirty pages allowed in a zone | |
449 | * @zone: the zone | |
450 | * | |
451 | * Returns the maximum number of dirty pages allowed in a zone, based | |
452 | * on the zone's dirtyable memory. | |
453 | */ | |
454 | static unsigned long zone_dirty_limit(struct zone *zone) | |
455 | { | |
456 | unsigned long zone_memory = zone_dirtyable_memory(zone); | |
457 | struct task_struct *tsk = current; | |
458 | unsigned long dirty; | |
459 | ||
460 | if (vm_dirty_bytes) | |
461 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * | |
462 | zone_memory / global_dirtyable_memory(); | |
463 | else | |
464 | dirty = vm_dirty_ratio * zone_memory / 100; | |
465 | ||
466 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) | |
467 | dirty += dirty / 4; | |
468 | ||
469 | return dirty; | |
470 | } | |
471 | ||
472 | /** | |
473 | * zone_dirty_ok - tells whether a zone is within its dirty limits | |
474 | * @zone: the zone to check | |
475 | * | |
476 | * Returns %true when the dirty pages in @zone are within the zone's | |
477 | * dirty limit, %false if the limit is exceeded. | |
478 | */ | |
479 | bool zone_dirty_ok(struct zone *zone) | |
480 | { | |
481 | unsigned long limit = zone_dirty_limit(zone); | |
482 | ||
483 | return zone_page_state(zone, NR_FILE_DIRTY) + | |
484 | zone_page_state(zone, NR_UNSTABLE_NFS) + | |
485 | zone_page_state(zone, NR_WRITEBACK) <= limit; | |
486 | } | |
487 | ||
2da02997 | 488 | int dirty_background_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 489 | void __user *buffer, size_t *lenp, |
2da02997 DR |
490 | loff_t *ppos) |
491 | { | |
492 | int ret; | |
493 | ||
8d65af78 | 494 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
495 | if (ret == 0 && write) |
496 | dirty_background_bytes = 0; | |
497 | return ret; | |
498 | } | |
499 | ||
500 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 501 | void __user *buffer, size_t *lenp, |
2da02997 DR |
502 | loff_t *ppos) |
503 | { | |
504 | int ret; | |
505 | ||
8d65af78 | 506 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
507 | if (ret == 0 && write) |
508 | dirty_background_ratio = 0; | |
509 | return ret; | |
510 | } | |
511 | ||
04fbfdc1 | 512 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 513 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
514 | loff_t *ppos) |
515 | { | |
516 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
517 | int ret; |
518 | ||
8d65af78 | 519 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 520 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
eb608e3a | 521 | writeback_set_ratelimit(); |
2da02997 DR |
522 | vm_dirty_bytes = 0; |
523 | } | |
524 | return ret; | |
525 | } | |
526 | ||
2da02997 | 527 | int dirty_bytes_handler(struct ctl_table *table, int write, |
8d65af78 | 528 | void __user *buffer, size_t *lenp, |
2da02997 DR |
529 | loff_t *ppos) |
530 | { | |
fc3501d4 | 531 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
532 | int ret; |
533 | ||
8d65af78 | 534 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 | 535 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
eb608e3a | 536 | writeback_set_ratelimit(); |
2da02997 | 537 | vm_dirty_ratio = 0; |
04fbfdc1 PZ |
538 | } |
539 | return ret; | |
540 | } | |
541 | ||
eb608e3a JK |
542 | static unsigned long wp_next_time(unsigned long cur_time) |
543 | { | |
544 | cur_time += VM_COMPLETIONS_PERIOD_LEN; | |
545 | /* 0 has a special meaning... */ | |
546 | if (!cur_time) | |
547 | return 1; | |
548 | return cur_time; | |
549 | } | |
550 | ||
c7981433 TH |
551 | static void wb_domain_writeout_inc(struct wb_domain *dom, |
552 | struct fprop_local_percpu *completions, | |
553 | unsigned int max_prop_frac) | |
04fbfdc1 | 554 | { |
c7981433 TH |
555 | __fprop_inc_percpu_max(&dom->completions, completions, |
556 | max_prop_frac); | |
eb608e3a | 557 | /* First event after period switching was turned off? */ |
380c27ca | 558 | if (!unlikely(dom->period_time)) { |
eb608e3a JK |
559 | /* |
560 | * We can race with other __bdi_writeout_inc calls here but | |
561 | * it does not cause any harm since the resulting time when | |
562 | * timer will fire and what is in writeout_period_time will be | |
563 | * roughly the same. | |
564 | */ | |
380c27ca TH |
565 | dom->period_time = wp_next_time(jiffies); |
566 | mod_timer(&dom->period_timer, dom->period_time); | |
eb608e3a | 567 | } |
04fbfdc1 PZ |
568 | } |
569 | ||
c7981433 TH |
570 | /* |
571 | * Increment @wb's writeout completion count and the global writeout | |
572 | * completion count. Called from test_clear_page_writeback(). | |
573 | */ | |
574 | static inline void __wb_writeout_inc(struct bdi_writeback *wb) | |
dd5656e5 | 575 | { |
841710aa | 576 | struct wb_domain *cgdom; |
dd5656e5 | 577 | |
c7981433 TH |
578 | __inc_wb_stat(wb, WB_WRITTEN); |
579 | wb_domain_writeout_inc(&global_wb_domain, &wb->completions, | |
580 | wb->bdi->max_prop_frac); | |
841710aa TH |
581 | |
582 | cgdom = mem_cgroup_wb_domain(wb); | |
583 | if (cgdom) | |
584 | wb_domain_writeout_inc(cgdom, wb_memcg_completions(wb), | |
585 | wb->bdi->max_prop_frac); | |
dd5656e5 | 586 | } |
dd5656e5 | 587 | |
93f78d88 | 588 | void wb_writeout_inc(struct bdi_writeback *wb) |
04fbfdc1 | 589 | { |
dd5656e5 MS |
590 | unsigned long flags; |
591 | ||
592 | local_irq_save(flags); | |
93f78d88 | 593 | __wb_writeout_inc(wb); |
dd5656e5 | 594 | local_irq_restore(flags); |
04fbfdc1 | 595 | } |
93f78d88 | 596 | EXPORT_SYMBOL_GPL(wb_writeout_inc); |
04fbfdc1 | 597 | |
eb608e3a JK |
598 | /* |
599 | * On idle system, we can be called long after we scheduled because we use | |
600 | * deferred timers so count with missed periods. | |
601 | */ | |
602 | static void writeout_period(unsigned long t) | |
603 | { | |
380c27ca TH |
604 | struct wb_domain *dom = (void *)t; |
605 | int miss_periods = (jiffies - dom->period_time) / | |
eb608e3a JK |
606 | VM_COMPLETIONS_PERIOD_LEN; |
607 | ||
380c27ca TH |
608 | if (fprop_new_period(&dom->completions, miss_periods + 1)) { |
609 | dom->period_time = wp_next_time(dom->period_time + | |
eb608e3a | 610 | miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
380c27ca | 611 | mod_timer(&dom->period_timer, dom->period_time); |
eb608e3a JK |
612 | } else { |
613 | /* | |
614 | * Aging has zeroed all fractions. Stop wasting CPU on period | |
615 | * updates. | |
616 | */ | |
380c27ca | 617 | dom->period_time = 0; |
eb608e3a JK |
618 | } |
619 | } | |
620 | ||
380c27ca TH |
621 | int wb_domain_init(struct wb_domain *dom, gfp_t gfp) |
622 | { | |
623 | memset(dom, 0, sizeof(*dom)); | |
dcc25ae7 TH |
624 | |
625 | spin_lock_init(&dom->lock); | |
626 | ||
380c27ca TH |
627 | init_timer_deferrable(&dom->period_timer); |
628 | dom->period_timer.function = writeout_period; | |
629 | dom->period_timer.data = (unsigned long)dom; | |
dcc25ae7 TH |
630 | |
631 | dom->dirty_limit_tstamp = jiffies; | |
632 | ||
380c27ca TH |
633 | return fprop_global_init(&dom->completions, gfp); |
634 | } | |
635 | ||
841710aa TH |
636 | #ifdef CONFIG_CGROUP_WRITEBACK |
637 | void wb_domain_exit(struct wb_domain *dom) | |
638 | { | |
639 | del_timer_sync(&dom->period_timer); | |
640 | fprop_global_destroy(&dom->completions); | |
641 | } | |
642 | #endif | |
643 | ||
189d3c4a | 644 | /* |
d08c429b JW |
645 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
646 | * registered backing devices, which, for obvious reasons, can not | |
647 | * exceed 100%. | |
189d3c4a | 648 | */ |
189d3c4a PZ |
649 | static unsigned int bdi_min_ratio; |
650 | ||
651 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
652 | { | |
653 | int ret = 0; | |
189d3c4a | 654 | |
cfc4ba53 | 655 | spin_lock_bh(&bdi_lock); |
a42dde04 | 656 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 657 | ret = -EINVAL; |
a42dde04 PZ |
658 | } else { |
659 | min_ratio -= bdi->min_ratio; | |
660 | if (bdi_min_ratio + min_ratio < 100) { | |
661 | bdi_min_ratio += min_ratio; | |
662 | bdi->min_ratio += min_ratio; | |
663 | } else { | |
664 | ret = -EINVAL; | |
665 | } | |
666 | } | |
cfc4ba53 | 667 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
668 | |
669 | return ret; | |
670 | } | |
671 | ||
672 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
673 | { | |
a42dde04 PZ |
674 | int ret = 0; |
675 | ||
676 | if (max_ratio > 100) | |
677 | return -EINVAL; | |
678 | ||
cfc4ba53 | 679 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
680 | if (bdi->min_ratio > max_ratio) { |
681 | ret = -EINVAL; | |
682 | } else { | |
683 | bdi->max_ratio = max_ratio; | |
eb608e3a | 684 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
a42dde04 | 685 | } |
cfc4ba53 | 686 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
687 | |
688 | return ret; | |
689 | } | |
a42dde04 | 690 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 691 | |
6c14ae1e WF |
692 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
693 | unsigned long bg_thresh) | |
694 | { | |
695 | return (thresh + bg_thresh) / 2; | |
696 | } | |
697 | ||
c7981433 TH |
698 | static unsigned long hard_dirty_limit(struct wb_domain *dom, |
699 | unsigned long thresh) | |
ffd1f609 | 700 | { |
dcc25ae7 | 701 | return max(thresh, dom->dirty_limit); |
ffd1f609 WF |
702 | } |
703 | ||
c5edf9cd TH |
704 | /* |
705 | * Memory which can be further allocated to a memcg domain is capped by | |
706 | * system-wide clean memory excluding the amount being used in the domain. | |
707 | */ | |
708 | static void mdtc_calc_avail(struct dirty_throttle_control *mdtc, | |
709 | unsigned long filepages, unsigned long headroom) | |
c2aa723a TH |
710 | { |
711 | struct dirty_throttle_control *gdtc = mdtc_gdtc(mdtc); | |
c5edf9cd TH |
712 | unsigned long clean = filepages - min(filepages, mdtc->dirty); |
713 | unsigned long global_clean = gdtc->avail - min(gdtc->avail, gdtc->dirty); | |
714 | unsigned long other_clean = global_clean - min(global_clean, clean); | |
c2aa723a | 715 | |
c5edf9cd | 716 | mdtc->avail = filepages + min(headroom, other_clean); |
ffd1f609 WF |
717 | } |
718 | ||
6f718656 | 719 | /** |
b1cbc6d4 TH |
720 | * __wb_calc_thresh - @wb's share of dirty throttling threshold |
721 | * @dtc: dirty_throttle_context of interest | |
1babe183 | 722 | * |
a88a341a | 723 | * Returns @wb's dirty limit in pages. The term "dirty" in the context of |
6f718656 | 724 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. |
aed21ad2 WF |
725 | * |
726 | * Note that balance_dirty_pages() will only seriously take it as a hard limit | |
727 | * when sleeping max_pause per page is not enough to keep the dirty pages under | |
728 | * control. For example, when the device is completely stalled due to some error | |
729 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. | |
730 | * In the other normal situations, it acts more gently by throttling the tasks | |
a88a341a | 731 | * more (rather than completely block them) when the wb dirty pages go high. |
1babe183 | 732 | * |
6f718656 | 733 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
734 | * - starving fast devices |
735 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
736 | * | |
a88a341a | 737 | * The wb's share of dirty limit will be adapting to its throughput and |
1babe183 WF |
738 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
739 | */ | |
b1cbc6d4 | 740 | static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) |
16c4042f | 741 | { |
e9f07dfd | 742 | struct wb_domain *dom = dtc_dom(dtc); |
b1cbc6d4 | 743 | unsigned long thresh = dtc->thresh; |
0d960a38 | 744 | u64 wb_thresh; |
16c4042f | 745 | long numerator, denominator; |
693108a8 | 746 | unsigned long wb_min_ratio, wb_max_ratio; |
04fbfdc1 | 747 | |
16c4042f | 748 | /* |
0d960a38 | 749 | * Calculate this BDI's share of the thresh ratio. |
16c4042f | 750 | */ |
e9770b34 | 751 | fprop_fraction_percpu(&dom->completions, dtc->wb_completions, |
380c27ca | 752 | &numerator, &denominator); |
04fbfdc1 | 753 | |
0d960a38 TH |
754 | wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; |
755 | wb_thresh *= numerator; | |
756 | do_div(wb_thresh, denominator); | |
04fbfdc1 | 757 | |
b1cbc6d4 | 758 | wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); |
04fbfdc1 | 759 | |
0d960a38 TH |
760 | wb_thresh += (thresh * wb_min_ratio) / 100; |
761 | if (wb_thresh > (thresh * wb_max_ratio) / 100) | |
762 | wb_thresh = thresh * wb_max_ratio / 100; | |
16c4042f | 763 | |
0d960a38 | 764 | return wb_thresh; |
1da177e4 LT |
765 | } |
766 | ||
b1cbc6d4 TH |
767 | unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) |
768 | { | |
769 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb), | |
770 | .thresh = thresh }; | |
771 | return __wb_calc_thresh(&gdtc); | |
1da177e4 LT |
772 | } |
773 | ||
5a537485 MP |
774 | /* |
775 | * setpoint - dirty 3 | |
776 | * f(dirty) := 1.0 + (----------------) | |
777 | * limit - setpoint | |
778 | * | |
779 | * it's a 3rd order polynomial that subjects to | |
780 | * | |
781 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
782 | * (2) f(setpoint) = 1.0 => the balance point | |
783 | * (3) f(limit) = 0 => the hard limit | |
784 | * (4) df/dx <= 0 => negative feedback control | |
785 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
786 | * => fast response on large errors; small oscillation near setpoint | |
787 | */ | |
d5c9fde3 | 788 | static long long pos_ratio_polynom(unsigned long setpoint, |
5a537485 MP |
789 | unsigned long dirty, |
790 | unsigned long limit) | |
791 | { | |
792 | long long pos_ratio; | |
793 | long x; | |
794 | ||
d5c9fde3 | 795 | x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, |
464d1387 | 796 | (limit - setpoint) | 1); |
5a537485 MP |
797 | pos_ratio = x; |
798 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
799 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
800 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
801 | ||
802 | return clamp(pos_ratio, 0LL, 2LL << RATELIMIT_CALC_SHIFT); | |
803 | } | |
804 | ||
6c14ae1e WF |
805 | /* |
806 | * Dirty position control. | |
807 | * | |
808 | * (o) global/bdi setpoints | |
809 | * | |
de1fff37 | 810 | * We want the dirty pages be balanced around the global/wb setpoints. |
6c14ae1e WF |
811 | * When the number of dirty pages is higher/lower than the setpoint, the |
812 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
813 | * decreased/increased to bring the dirty pages back to the setpoint. | |
814 | * | |
815 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
816 | * | |
817 | * if (dirty < setpoint) scale up pos_ratio | |
818 | * if (dirty > setpoint) scale down pos_ratio | |
819 | * | |
de1fff37 TH |
820 | * if (wb_dirty < wb_setpoint) scale up pos_ratio |
821 | * if (wb_dirty > wb_setpoint) scale down pos_ratio | |
6c14ae1e WF |
822 | * |
823 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
824 | * | |
825 | * (o) global control line | |
826 | * | |
827 | * ^ pos_ratio | |
828 | * | | |
829 | * | |<===== global dirty control scope ======>| | |
830 | * 2.0 .............* | |
831 | * | .* | |
832 | * | . * | |
833 | * | . * | |
834 | * | . * | |
835 | * | . * | |
836 | * | . * | |
837 | * 1.0 ................................* | |
838 | * | . . * | |
839 | * | . . * | |
840 | * | . . * | |
841 | * | . . * | |
842 | * | . . * | |
843 | * 0 +------------.------------------.----------------------*-------------> | |
844 | * freerun^ setpoint^ limit^ dirty pages | |
845 | * | |
de1fff37 | 846 | * (o) wb control line |
6c14ae1e WF |
847 | * |
848 | * ^ pos_ratio | |
849 | * | | |
850 | * | * | |
851 | * | * | |
852 | * | * | |
853 | * | * | |
854 | * | * |<=========== span ============>| | |
855 | * 1.0 .......................* | |
856 | * | . * | |
857 | * | . * | |
858 | * | . * | |
859 | * | . * | |
860 | * | . * | |
861 | * | . * | |
862 | * | . * | |
863 | * | . * | |
864 | * | . * | |
865 | * | . * | |
866 | * | . * | |
867 | * 1/4 ...............................................* * * * * * * * * * * * | |
868 | * | . . | |
869 | * | . . | |
870 | * | . . | |
871 | * 0 +----------------------.-------------------------------.-------------> | |
de1fff37 | 872 | * wb_setpoint^ x_intercept^ |
6c14ae1e | 873 | * |
de1fff37 | 874 | * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can |
6c14ae1e WF |
875 | * be smoothly throttled down to normal if it starts high in situations like |
876 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
de1fff37 TH |
877 | * card's wb_dirty may rush to many times higher than wb_setpoint. |
878 | * - the wb dirty thresh drops quickly due to change of JBOD workload | |
6c14ae1e | 879 | */ |
daddfa3c | 880 | static void wb_position_ratio(struct dirty_throttle_control *dtc) |
6c14ae1e | 881 | { |
2bc00aef | 882 | struct bdi_writeback *wb = dtc->wb; |
a88a341a | 883 | unsigned long write_bw = wb->avg_write_bandwidth; |
2bc00aef | 884 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
c7981433 | 885 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
2bc00aef | 886 | unsigned long wb_thresh = dtc->wb_thresh; |
6c14ae1e WF |
887 | unsigned long x_intercept; |
888 | unsigned long setpoint; /* dirty pages' target balance point */ | |
de1fff37 | 889 | unsigned long wb_setpoint; |
6c14ae1e WF |
890 | unsigned long span; |
891 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
892 | long x; | |
893 | ||
daddfa3c TH |
894 | dtc->pos_ratio = 0; |
895 | ||
2bc00aef | 896 | if (unlikely(dtc->dirty >= limit)) |
daddfa3c | 897 | return; |
6c14ae1e WF |
898 | |
899 | /* | |
900 | * global setpoint | |
901 | * | |
5a537485 MP |
902 | * See comment for pos_ratio_polynom(). |
903 | */ | |
904 | setpoint = (freerun + limit) / 2; | |
2bc00aef | 905 | pos_ratio = pos_ratio_polynom(setpoint, dtc->dirty, limit); |
5a537485 MP |
906 | |
907 | /* | |
908 | * The strictlimit feature is a tool preventing mistrusted filesystems | |
909 | * from growing a large number of dirty pages before throttling. For | |
de1fff37 TH |
910 | * such filesystems balance_dirty_pages always checks wb counters |
911 | * against wb limits. Even if global "nr_dirty" is under "freerun". | |
5a537485 MP |
912 | * This is especially important for fuse which sets bdi->max_ratio to |
913 | * 1% by default. Without strictlimit feature, fuse writeback may | |
914 | * consume arbitrary amount of RAM because it is accounted in | |
915 | * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". | |
6c14ae1e | 916 | * |
a88a341a | 917 | * Here, in wb_position_ratio(), we calculate pos_ratio based on |
de1fff37 | 918 | * two values: wb_dirty and wb_thresh. Let's consider an example: |
5a537485 MP |
919 | * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global |
920 | * limits are set by default to 10% and 20% (background and throttle). | |
de1fff37 | 921 | * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. |
0d960a38 | 922 | * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is |
de1fff37 | 923 | * about ~6K pages (as the average of background and throttle wb |
5a537485 | 924 | * limits). The 3rd order polynomial will provide positive feedback if |
de1fff37 | 925 | * wb_dirty is under wb_setpoint and vice versa. |
6c14ae1e | 926 | * |
5a537485 | 927 | * Note, that we cannot use global counters in these calculations |
de1fff37 | 928 | * because we want to throttle process writing to a strictlimit wb |
5a537485 MP |
929 | * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB |
930 | * in the example above). | |
6c14ae1e | 931 | */ |
a88a341a | 932 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
de1fff37 | 933 | long long wb_pos_ratio; |
5a537485 | 934 | |
daddfa3c TH |
935 | if (dtc->wb_dirty < 8) { |
936 | dtc->pos_ratio = min_t(long long, pos_ratio * 2, | |
937 | 2 << RATELIMIT_CALC_SHIFT); | |
938 | return; | |
939 | } | |
5a537485 | 940 | |
2bc00aef | 941 | if (dtc->wb_dirty >= wb_thresh) |
daddfa3c | 942 | return; |
5a537485 | 943 | |
970fb01a TH |
944 | wb_setpoint = dirty_freerun_ceiling(wb_thresh, |
945 | dtc->wb_bg_thresh); | |
5a537485 | 946 | |
de1fff37 | 947 | if (wb_setpoint == 0 || wb_setpoint == wb_thresh) |
daddfa3c | 948 | return; |
5a537485 | 949 | |
2bc00aef | 950 | wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, |
de1fff37 | 951 | wb_thresh); |
5a537485 MP |
952 | |
953 | /* | |
de1fff37 TH |
954 | * Typically, for strictlimit case, wb_setpoint << setpoint |
955 | * and pos_ratio >> wb_pos_ratio. In the other words global | |
5a537485 | 956 | * state ("dirty") is not limiting factor and we have to |
de1fff37 | 957 | * make decision based on wb counters. But there is an |
5a537485 MP |
958 | * important case when global pos_ratio should get precedence: |
959 | * global limits are exceeded (e.g. due to activities on other | |
de1fff37 | 960 | * wb's) while given strictlimit wb is below limit. |
5a537485 | 961 | * |
de1fff37 | 962 | * "pos_ratio * wb_pos_ratio" would work for the case above, |
5a537485 | 963 | * but it would look too non-natural for the case of all |
de1fff37 | 964 | * activity in the system coming from a single strictlimit wb |
5a537485 MP |
965 | * with bdi->max_ratio == 100%. |
966 | * | |
967 | * Note that min() below somewhat changes the dynamics of the | |
968 | * control system. Normally, pos_ratio value can be well over 3 | |
de1fff37 | 969 | * (when globally we are at freerun and wb is well below wb |
5a537485 MP |
970 | * setpoint). Now the maximum pos_ratio in the same situation |
971 | * is 2. We might want to tweak this if we observe the control | |
972 | * system is too slow to adapt. | |
973 | */ | |
daddfa3c TH |
974 | dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); |
975 | return; | |
5a537485 | 976 | } |
6c14ae1e WF |
977 | |
978 | /* | |
979 | * We have computed basic pos_ratio above based on global situation. If | |
de1fff37 | 980 | * the wb is over/under its share of dirty pages, we want to scale |
6c14ae1e WF |
981 | * pos_ratio further down/up. That is done by the following mechanism. |
982 | */ | |
983 | ||
984 | /* | |
de1fff37 | 985 | * wb setpoint |
6c14ae1e | 986 | * |
de1fff37 | 987 | * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) |
6c14ae1e | 988 | * |
de1fff37 | 989 | * x_intercept - wb_dirty |
6c14ae1e | 990 | * := -------------------------- |
de1fff37 | 991 | * x_intercept - wb_setpoint |
6c14ae1e | 992 | * |
de1fff37 | 993 | * The main wb control line is a linear function that subjects to |
6c14ae1e | 994 | * |
de1fff37 TH |
995 | * (1) f(wb_setpoint) = 1.0 |
996 | * (2) k = - 1 / (8 * write_bw) (in single wb case) | |
997 | * or equally: x_intercept = wb_setpoint + 8 * write_bw | |
6c14ae1e | 998 | * |
de1fff37 | 999 | * For single wb case, the dirty pages are observed to fluctuate |
6c14ae1e | 1000 | * regularly within range |
de1fff37 | 1001 | * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] |
6c14ae1e WF |
1002 | * for various filesystems, where (2) can yield in a reasonable 12.5% |
1003 | * fluctuation range for pos_ratio. | |
1004 | * | |
de1fff37 | 1005 | * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its |
6c14ae1e | 1006 | * own size, so move the slope over accordingly and choose a slope that |
de1fff37 | 1007 | * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. |
6c14ae1e | 1008 | */ |
2bc00aef TH |
1009 | if (unlikely(wb_thresh > dtc->thresh)) |
1010 | wb_thresh = dtc->thresh; | |
aed21ad2 | 1011 | /* |
de1fff37 | 1012 | * It's very possible that wb_thresh is close to 0 not because the |
aed21ad2 WF |
1013 | * device is slow, but that it has remained inactive for long time. |
1014 | * Honour such devices a reasonable good (hopefully IO efficient) | |
1015 | * threshold, so that the occasional writes won't be blocked and active | |
1016 | * writes can rampup the threshold quickly. | |
1017 | */ | |
2bc00aef | 1018 | wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8); |
6c14ae1e | 1019 | /* |
de1fff37 TH |
1020 | * scale global setpoint to wb's: |
1021 | * wb_setpoint = setpoint * wb_thresh / thresh | |
6c14ae1e | 1022 | */ |
e4bc13ad | 1023 | x = div_u64((u64)wb_thresh << 16, dtc->thresh | 1); |
de1fff37 | 1024 | wb_setpoint = setpoint * (u64)x >> 16; |
6c14ae1e | 1025 | /* |
de1fff37 TH |
1026 | * Use span=(8*write_bw) in single wb case as indicated by |
1027 | * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. | |
6c14ae1e | 1028 | * |
de1fff37 TH |
1029 | * wb_thresh thresh - wb_thresh |
1030 | * span = --------- * (8 * write_bw) + ------------------ * wb_thresh | |
1031 | * thresh thresh | |
6c14ae1e | 1032 | */ |
2bc00aef | 1033 | span = (dtc->thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; |
de1fff37 | 1034 | x_intercept = wb_setpoint + span; |
6c14ae1e | 1035 | |
2bc00aef TH |
1036 | if (dtc->wb_dirty < x_intercept - span / 4) { |
1037 | pos_ratio = div64_u64(pos_ratio * (x_intercept - dtc->wb_dirty), | |
e4bc13ad | 1038 | (x_intercept - wb_setpoint) | 1); |
6c14ae1e WF |
1039 | } else |
1040 | pos_ratio /= 4; | |
1041 | ||
8927f66c | 1042 | /* |
de1fff37 | 1043 | * wb reserve area, safeguard against dirty pool underrun and disk idle |
8927f66c WF |
1044 | * It may push the desired control point of global dirty pages higher |
1045 | * than setpoint. | |
1046 | */ | |
de1fff37 | 1047 | x_intercept = wb_thresh / 2; |
2bc00aef TH |
1048 | if (dtc->wb_dirty < x_intercept) { |
1049 | if (dtc->wb_dirty > x_intercept / 8) | |
1050 | pos_ratio = div_u64(pos_ratio * x_intercept, | |
1051 | dtc->wb_dirty); | |
50657fc4 | 1052 | else |
8927f66c WF |
1053 | pos_ratio *= 8; |
1054 | } | |
1055 | ||
daddfa3c | 1056 | dtc->pos_ratio = pos_ratio; |
6c14ae1e WF |
1057 | } |
1058 | ||
a88a341a TH |
1059 | static void wb_update_write_bandwidth(struct bdi_writeback *wb, |
1060 | unsigned long elapsed, | |
1061 | unsigned long written) | |
e98be2d5 WF |
1062 | { |
1063 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
a88a341a TH |
1064 | unsigned long avg = wb->avg_write_bandwidth; |
1065 | unsigned long old = wb->write_bandwidth; | |
e98be2d5 WF |
1066 | u64 bw; |
1067 | ||
1068 | /* | |
1069 | * bw = written * HZ / elapsed | |
1070 | * | |
1071 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
1072 | * write_bandwidth = --------------------------------------------------- | |
1073 | * period | |
c72efb65 TH |
1074 | * |
1075 | * @written may have decreased due to account_page_redirty(). | |
1076 | * Avoid underflowing @bw calculation. | |
e98be2d5 | 1077 | */ |
a88a341a | 1078 | bw = written - min(written, wb->written_stamp); |
e98be2d5 WF |
1079 | bw *= HZ; |
1080 | if (unlikely(elapsed > period)) { | |
1081 | do_div(bw, elapsed); | |
1082 | avg = bw; | |
1083 | goto out; | |
1084 | } | |
a88a341a | 1085 | bw += (u64)wb->write_bandwidth * (period - elapsed); |
e98be2d5 WF |
1086 | bw >>= ilog2(period); |
1087 | ||
1088 | /* | |
1089 | * one more level of smoothing, for filtering out sudden spikes | |
1090 | */ | |
1091 | if (avg > old && old >= (unsigned long)bw) | |
1092 | avg -= (avg - old) >> 3; | |
1093 | ||
1094 | if (avg < old && old <= (unsigned long)bw) | |
1095 | avg += (old - avg) >> 3; | |
1096 | ||
1097 | out: | |
95a46c65 TH |
1098 | /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ |
1099 | avg = max(avg, 1LU); | |
1100 | if (wb_has_dirty_io(wb)) { | |
1101 | long delta = avg - wb->avg_write_bandwidth; | |
1102 | WARN_ON_ONCE(atomic_long_add_return(delta, | |
1103 | &wb->bdi->tot_write_bandwidth) <= 0); | |
1104 | } | |
a88a341a TH |
1105 | wb->write_bandwidth = bw; |
1106 | wb->avg_write_bandwidth = avg; | |
e98be2d5 WF |
1107 | } |
1108 | ||
2bc00aef | 1109 | static void update_dirty_limit(struct dirty_throttle_control *dtc) |
c42843f2 | 1110 | { |
e9f07dfd | 1111 | struct wb_domain *dom = dtc_dom(dtc); |
2bc00aef | 1112 | unsigned long thresh = dtc->thresh; |
dcc25ae7 | 1113 | unsigned long limit = dom->dirty_limit; |
c42843f2 WF |
1114 | |
1115 | /* | |
1116 | * Follow up in one step. | |
1117 | */ | |
1118 | if (limit < thresh) { | |
1119 | limit = thresh; | |
1120 | goto update; | |
1121 | } | |
1122 | ||
1123 | /* | |
1124 | * Follow down slowly. Use the higher one as the target, because thresh | |
1125 | * may drop below dirty. This is exactly the reason to introduce | |
dcc25ae7 | 1126 | * dom->dirty_limit which is guaranteed to lie above the dirty pages. |
c42843f2 | 1127 | */ |
2bc00aef | 1128 | thresh = max(thresh, dtc->dirty); |
c42843f2 WF |
1129 | if (limit > thresh) { |
1130 | limit -= (limit - thresh) >> 5; | |
1131 | goto update; | |
1132 | } | |
1133 | return; | |
1134 | update: | |
dcc25ae7 | 1135 | dom->dirty_limit = limit; |
c42843f2 WF |
1136 | } |
1137 | ||
e9f07dfd | 1138 | static void domain_update_bandwidth(struct dirty_throttle_control *dtc, |
c42843f2 WF |
1139 | unsigned long now) |
1140 | { | |
e9f07dfd | 1141 | struct wb_domain *dom = dtc_dom(dtc); |
c42843f2 WF |
1142 | |
1143 | /* | |
1144 | * check locklessly first to optimize away locking for the most time | |
1145 | */ | |
dcc25ae7 | 1146 | if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) |
c42843f2 WF |
1147 | return; |
1148 | ||
dcc25ae7 TH |
1149 | spin_lock(&dom->lock); |
1150 | if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) { | |
2bc00aef | 1151 | update_dirty_limit(dtc); |
dcc25ae7 | 1152 | dom->dirty_limit_tstamp = now; |
c42843f2 | 1153 | } |
dcc25ae7 | 1154 | spin_unlock(&dom->lock); |
c42843f2 WF |
1155 | } |
1156 | ||
be3ffa27 | 1157 | /* |
de1fff37 | 1158 | * Maintain wb->dirty_ratelimit, the base dirty throttle rate. |
be3ffa27 | 1159 | * |
de1fff37 | 1160 | * Normal wb tasks will be curbed at or below it in long term. |
be3ffa27 WF |
1161 | * Obviously it should be around (write_bw / N) when there are N dd tasks. |
1162 | */ | |
2bc00aef | 1163 | static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, |
a88a341a TH |
1164 | unsigned long dirtied, |
1165 | unsigned long elapsed) | |
be3ffa27 | 1166 | { |
2bc00aef TH |
1167 | struct bdi_writeback *wb = dtc->wb; |
1168 | unsigned long dirty = dtc->dirty; | |
1169 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); | |
c7981433 | 1170 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
7381131c | 1171 | unsigned long setpoint = (freerun + limit) / 2; |
a88a341a TH |
1172 | unsigned long write_bw = wb->avg_write_bandwidth; |
1173 | unsigned long dirty_ratelimit = wb->dirty_ratelimit; | |
be3ffa27 WF |
1174 | unsigned long dirty_rate; |
1175 | unsigned long task_ratelimit; | |
1176 | unsigned long balanced_dirty_ratelimit; | |
7381131c WF |
1177 | unsigned long step; |
1178 | unsigned long x; | |
d59b1087 | 1179 | unsigned long shift; |
be3ffa27 WF |
1180 | |
1181 | /* | |
1182 | * The dirty rate will match the writeout rate in long term, except | |
1183 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
1184 | */ | |
a88a341a | 1185 | dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; |
be3ffa27 | 1186 | |
be3ffa27 WF |
1187 | /* |
1188 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
1189 | */ | |
1190 | task_ratelimit = (u64)dirty_ratelimit * | |
daddfa3c | 1191 | dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; |
be3ffa27 WF |
1192 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
1193 | ||
1194 | /* | |
1195 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
de1fff37 | 1196 | * if there are N dd tasks, each throttled at task_ratelimit, the wb's |
be3ffa27 WF |
1197 | * dirty_rate will be measured to be (N * task_ratelimit). So the below |
1198 | * formula will yield the balanced rate limit (write_bw / N). | |
1199 | * | |
1200 | * Note that the expanded form is not a pure rate feedback: | |
1201 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
1202 | * but also takes pos_ratio into account: | |
1203 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
1204 | * | |
1205 | * (1) is not realistic because pos_ratio also takes part in balancing | |
1206 | * the dirty rate. Consider the state | |
1207 | * pos_ratio = 0.5 (3) | |
1208 | * rate = 2 * (write_bw / N) (4) | |
1209 | * If (1) is used, it will stuck in that state! Because each dd will | |
1210 | * be throttled at | |
1211 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
1212 | * yielding | |
1213 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
1214 | * put (6) into (1) we get | |
1215 | * rate_(i+1) = rate_(i) (7) | |
1216 | * | |
1217 | * So we end up using (2) to always keep | |
1218 | * rate_(i+1) ~= (write_bw / N) (8) | |
1219 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
1220 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
1221 | * the dirty count meet the setpoint, but also where the slope of | |
1222 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
1223 | */ | |
1224 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
1225 | dirty_rate | 1); | |
bdaac490 WF |
1226 | /* |
1227 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw | |
1228 | */ | |
1229 | if (unlikely(balanced_dirty_ratelimit > write_bw)) | |
1230 | balanced_dirty_ratelimit = write_bw; | |
be3ffa27 | 1231 | |
7381131c WF |
1232 | /* |
1233 | * We could safely do this and return immediately: | |
1234 | * | |
de1fff37 | 1235 | * wb->dirty_ratelimit = balanced_dirty_ratelimit; |
7381131c WF |
1236 | * |
1237 | * However to get a more stable dirty_ratelimit, the below elaborated | |
331cbdee | 1238 | * code makes use of task_ratelimit to filter out singular points and |
7381131c WF |
1239 | * limit the step size. |
1240 | * | |
1241 | * The below code essentially only uses the relative value of | |
1242 | * | |
1243 | * task_ratelimit - dirty_ratelimit | |
1244 | * = (pos_ratio - 1) * dirty_ratelimit | |
1245 | * | |
1246 | * which reflects the direction and size of dirty position error. | |
1247 | */ | |
1248 | ||
1249 | /* | |
1250 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff | |
1251 | * task_ratelimit is on the same side of dirty_ratelimit, too. | |
1252 | * For example, when | |
1253 | * - dirty_ratelimit > balanced_dirty_ratelimit | |
1254 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) | |
1255 | * lowering dirty_ratelimit will help meet both the position and rate | |
1256 | * control targets. Otherwise, don't update dirty_ratelimit if it will | |
1257 | * only help meet the rate target. After all, what the users ultimately | |
1258 | * feel and care are stable dirty rate and small position error. | |
1259 | * | |
1260 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size | |
331cbdee | 1261 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
7381131c WF |
1262 | * keeps jumping around randomly and can even leap far away at times |
1263 | * due to the small 200ms estimation period of dirty_rate (we want to | |
1264 | * keep that period small to reduce time lags). | |
1265 | */ | |
1266 | step = 0; | |
5a537485 MP |
1267 | |
1268 | /* | |
de1fff37 | 1269 | * For strictlimit case, calculations above were based on wb counters |
a88a341a | 1270 | * and limits (starting from pos_ratio = wb_position_ratio() and up to |
5a537485 | 1271 | * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). |
de1fff37 TH |
1272 | * Hence, to calculate "step" properly, we have to use wb_dirty as |
1273 | * "dirty" and wb_setpoint as "setpoint". | |
5a537485 | 1274 | * |
de1fff37 TH |
1275 | * We rampup dirty_ratelimit forcibly if wb_dirty is low because |
1276 | * it's possible that wb_thresh is close to zero due to inactivity | |
970fb01a | 1277 | * of backing device. |
5a537485 | 1278 | */ |
a88a341a | 1279 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
2bc00aef TH |
1280 | dirty = dtc->wb_dirty; |
1281 | if (dtc->wb_dirty < 8) | |
1282 | setpoint = dtc->wb_dirty + 1; | |
5a537485 | 1283 | else |
970fb01a | 1284 | setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; |
5a537485 MP |
1285 | } |
1286 | ||
7381131c | 1287 | if (dirty < setpoint) { |
a88a341a | 1288 | x = min3(wb->balanced_dirty_ratelimit, |
7c809968 | 1289 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1290 | if (dirty_ratelimit < x) |
1291 | step = x - dirty_ratelimit; | |
1292 | } else { | |
a88a341a | 1293 | x = max3(wb->balanced_dirty_ratelimit, |
7c809968 | 1294 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1295 | if (dirty_ratelimit > x) |
1296 | step = dirty_ratelimit - x; | |
1297 | } | |
1298 | ||
1299 | /* | |
1300 | * Don't pursue 100% rate matching. It's impossible since the balanced | |
1301 | * rate itself is constantly fluctuating. So decrease the track speed | |
1302 | * when it gets close to the target. Helps eliminate pointless tremors. | |
1303 | */ | |
d59b1087 AR |
1304 | shift = dirty_ratelimit / (2 * step + 1); |
1305 | if (shift < BITS_PER_LONG) | |
1306 | step = DIV_ROUND_UP(step >> shift, 8); | |
1307 | else | |
1308 | step = 0; | |
7381131c WF |
1309 | |
1310 | if (dirty_ratelimit < balanced_dirty_ratelimit) | |
1311 | dirty_ratelimit += step; | |
1312 | else | |
1313 | dirty_ratelimit -= step; | |
1314 | ||
a88a341a TH |
1315 | wb->dirty_ratelimit = max(dirty_ratelimit, 1UL); |
1316 | wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit; | |
b48c104d | 1317 | |
5634cc2a | 1318 | trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit); |
be3ffa27 WF |
1319 | } |
1320 | ||
c2aa723a TH |
1321 | static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc, |
1322 | struct dirty_throttle_control *mdtc, | |
8a731799 TH |
1323 | unsigned long start_time, |
1324 | bool update_ratelimit) | |
e98be2d5 | 1325 | { |
c2aa723a | 1326 | struct bdi_writeback *wb = gdtc->wb; |
e98be2d5 | 1327 | unsigned long now = jiffies; |
a88a341a | 1328 | unsigned long elapsed = now - wb->bw_time_stamp; |
be3ffa27 | 1329 | unsigned long dirtied; |
e98be2d5 WF |
1330 | unsigned long written; |
1331 | ||
8a731799 TH |
1332 | lockdep_assert_held(&wb->list_lock); |
1333 | ||
e98be2d5 WF |
1334 | /* |
1335 | * rate-limit, only update once every 200ms. | |
1336 | */ | |
1337 | if (elapsed < BANDWIDTH_INTERVAL) | |
1338 | return; | |
1339 | ||
a88a341a TH |
1340 | dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]); |
1341 | written = percpu_counter_read(&wb->stat[WB_WRITTEN]); | |
e98be2d5 WF |
1342 | |
1343 | /* | |
1344 | * Skip quiet periods when disk bandwidth is under-utilized. | |
1345 | * (at least 1s idle time between two flusher runs) | |
1346 | */ | |
a88a341a | 1347 | if (elapsed > HZ && time_before(wb->bw_time_stamp, start_time)) |
e98be2d5 WF |
1348 | goto snapshot; |
1349 | ||
8a731799 | 1350 | if (update_ratelimit) { |
c2aa723a TH |
1351 | domain_update_bandwidth(gdtc, now); |
1352 | wb_update_dirty_ratelimit(gdtc, dirtied, elapsed); | |
1353 | ||
1354 | /* | |
1355 | * @mdtc is always NULL if !CGROUP_WRITEBACK but the | |
1356 | * compiler has no way to figure that out. Help it. | |
1357 | */ | |
1358 | if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { | |
1359 | domain_update_bandwidth(mdtc, now); | |
1360 | wb_update_dirty_ratelimit(mdtc, dirtied, elapsed); | |
1361 | } | |
be3ffa27 | 1362 | } |
a88a341a | 1363 | wb_update_write_bandwidth(wb, elapsed, written); |
e98be2d5 WF |
1364 | |
1365 | snapshot: | |
a88a341a TH |
1366 | wb->dirtied_stamp = dirtied; |
1367 | wb->written_stamp = written; | |
1368 | wb->bw_time_stamp = now; | |
e98be2d5 WF |
1369 | } |
1370 | ||
8a731799 | 1371 | void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time) |
e98be2d5 | 1372 | { |
2bc00aef TH |
1373 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb) }; |
1374 | ||
c2aa723a | 1375 | __wb_update_bandwidth(&gdtc, NULL, start_time, false); |
e98be2d5 WF |
1376 | } |
1377 | ||
9d823e8f | 1378 | /* |
d0e1d66b | 1379 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
9d823e8f WF |
1380 | * will look to see if it needs to start dirty throttling. |
1381 | * | |
1382 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive | |
1383 | * global_page_state() too often. So scale it near-sqrt to the safety margin | |
1384 | * (the number of pages we may dirty without exceeding the dirty limits). | |
1385 | */ | |
1386 | static unsigned long dirty_poll_interval(unsigned long dirty, | |
1387 | unsigned long thresh) | |
1388 | { | |
1389 | if (thresh > dirty) | |
1390 | return 1UL << (ilog2(thresh - dirty) >> 1); | |
1391 | ||
1392 | return 1; | |
1393 | } | |
1394 | ||
a88a341a | 1395 | static unsigned long wb_max_pause(struct bdi_writeback *wb, |
de1fff37 | 1396 | unsigned long wb_dirty) |
c8462cc9 | 1397 | { |
a88a341a | 1398 | unsigned long bw = wb->avg_write_bandwidth; |
e3b6c655 | 1399 | unsigned long t; |
c8462cc9 | 1400 | |
7ccb9ad5 WF |
1401 | /* |
1402 | * Limit pause time for small memory systems. If sleeping for too long | |
1403 | * time, a small pool of dirty/writeback pages may go empty and disk go | |
1404 | * idle. | |
1405 | * | |
1406 | * 8 serves as the safety ratio. | |
1407 | */ | |
de1fff37 | 1408 | t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
7ccb9ad5 WF |
1409 | t++; |
1410 | ||
e3b6c655 | 1411 | return min_t(unsigned long, t, MAX_PAUSE); |
7ccb9ad5 WF |
1412 | } |
1413 | ||
a88a341a TH |
1414 | static long wb_min_pause(struct bdi_writeback *wb, |
1415 | long max_pause, | |
1416 | unsigned long task_ratelimit, | |
1417 | unsigned long dirty_ratelimit, | |
1418 | int *nr_dirtied_pause) | |
c8462cc9 | 1419 | { |
a88a341a TH |
1420 | long hi = ilog2(wb->avg_write_bandwidth); |
1421 | long lo = ilog2(wb->dirty_ratelimit); | |
7ccb9ad5 WF |
1422 | long t; /* target pause */ |
1423 | long pause; /* estimated next pause */ | |
1424 | int pages; /* target nr_dirtied_pause */ | |
c8462cc9 | 1425 | |
7ccb9ad5 WF |
1426 | /* target for 10ms pause on 1-dd case */ |
1427 | t = max(1, HZ / 100); | |
c8462cc9 WF |
1428 | |
1429 | /* | |
1430 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
1431 | * overheads. | |
1432 | * | |
7ccb9ad5 | 1433 | * (N * 10ms) on 2^N concurrent tasks. |
c8462cc9 WF |
1434 | */ |
1435 | if (hi > lo) | |
7ccb9ad5 | 1436 | t += (hi - lo) * (10 * HZ) / 1024; |
c8462cc9 WF |
1437 | |
1438 | /* | |
7ccb9ad5 WF |
1439 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
1440 | * on the much more stable dirty_ratelimit. However the next pause time | |
1441 | * will be computed based on task_ratelimit and the two rate limits may | |
1442 | * depart considerably at some time. Especially if task_ratelimit goes | |
1443 | * below dirty_ratelimit/2 and the target pause is max_pause, the next | |
1444 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a | |
1445 | * result task_ratelimit won't be executed faithfully, which could | |
1446 | * eventually bring down dirty_ratelimit. | |
c8462cc9 | 1447 | * |
7ccb9ad5 WF |
1448 | * We apply two rules to fix it up: |
1449 | * 1) try to estimate the next pause time and if necessary, use a lower | |
1450 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, | |
1451 | * nr_dirtied_pause will be "dancing" with task_ratelimit. | |
1452 | * 2) limit the target pause time to max_pause/2, so that the normal | |
1453 | * small fluctuations of task_ratelimit won't trigger rule (1) and | |
1454 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. | |
c8462cc9 | 1455 | */ |
7ccb9ad5 WF |
1456 | t = min(t, 1 + max_pause / 2); |
1457 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
c8462cc9 WF |
1458 | |
1459 | /* | |
5b9b3574 WF |
1460 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
1461 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. | |
1462 | * When the 16 consecutive reads are often interrupted by some dirty | |
1463 | * throttling pause during the async writes, cfq will go into idles | |
1464 | * (deadline is fine). So push nr_dirtied_pause as high as possible | |
1465 | * until reaches DIRTY_POLL_THRESH=32 pages. | |
c8462cc9 | 1466 | */ |
5b9b3574 WF |
1467 | if (pages < DIRTY_POLL_THRESH) { |
1468 | t = max_pause; | |
1469 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
1470 | if (pages > DIRTY_POLL_THRESH) { | |
1471 | pages = DIRTY_POLL_THRESH; | |
1472 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; | |
1473 | } | |
1474 | } | |
1475 | ||
7ccb9ad5 WF |
1476 | pause = HZ * pages / (task_ratelimit + 1); |
1477 | if (pause > max_pause) { | |
1478 | t = max_pause; | |
1479 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); | |
1480 | } | |
c8462cc9 | 1481 | |
7ccb9ad5 | 1482 | *nr_dirtied_pause = pages; |
c8462cc9 | 1483 | /* |
7ccb9ad5 | 1484 | * The minimal pause time will normally be half the target pause time. |
c8462cc9 | 1485 | */ |
5b9b3574 | 1486 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
c8462cc9 WF |
1487 | } |
1488 | ||
970fb01a | 1489 | static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) |
5a537485 | 1490 | { |
2bc00aef | 1491 | struct bdi_writeback *wb = dtc->wb; |
93f78d88 | 1492 | unsigned long wb_reclaimable; |
5a537485 MP |
1493 | |
1494 | /* | |
de1fff37 | 1495 | * wb_thresh is not treated as some limiting factor as |
5a537485 | 1496 | * dirty_thresh, due to reasons |
de1fff37 | 1497 | * - in JBOD setup, wb_thresh can fluctuate a lot |
5a537485 | 1498 | * - in a system with HDD and USB key, the USB key may somehow |
de1fff37 TH |
1499 | * go into state (wb_dirty >> wb_thresh) either because |
1500 | * wb_dirty starts high, or because wb_thresh drops low. | |
5a537485 | 1501 | * In this case we don't want to hard throttle the USB key |
de1fff37 TH |
1502 | * dirtiers for 100 seconds until wb_dirty drops under |
1503 | * wb_thresh. Instead the auxiliary wb control line in | |
a88a341a | 1504 | * wb_position_ratio() will let the dirtier task progress |
de1fff37 | 1505 | * at some rate <= (write_bw / 2) for bringing down wb_dirty. |
5a537485 | 1506 | */ |
b1cbc6d4 | 1507 | dtc->wb_thresh = __wb_calc_thresh(dtc); |
970fb01a TH |
1508 | dtc->wb_bg_thresh = dtc->thresh ? |
1509 | div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; | |
5a537485 MP |
1510 | |
1511 | /* | |
1512 | * In order to avoid the stacked BDI deadlock we need | |
1513 | * to ensure we accurately count the 'dirty' pages when | |
1514 | * the threshold is low. | |
1515 | * | |
1516 | * Otherwise it would be possible to get thresh+n pages | |
1517 | * reported dirty, even though there are thresh-m pages | |
1518 | * actually dirty; with m+n sitting in the percpu | |
1519 | * deltas. | |
1520 | */ | |
2bc00aef | 1521 | if (dtc->wb_thresh < 2 * wb_stat_error(wb)) { |
93f78d88 | 1522 | wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
2bc00aef | 1523 | dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); |
5a537485 | 1524 | } else { |
93f78d88 | 1525 | wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
2bc00aef | 1526 | dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); |
5a537485 MP |
1527 | } |
1528 | } | |
1529 | ||
1da177e4 LT |
1530 | /* |
1531 | * balance_dirty_pages() must be called by processes which are generating dirty | |
1532 | * data. It looks at the number of dirty pages in the machine and will force | |
143dfe86 | 1533 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1534 | * If we're over `background_thresh' then the writeback threads are woken to |
1535 | * perform some writeout. | |
1da177e4 | 1536 | */ |
3a2e9a5a | 1537 | static void balance_dirty_pages(struct address_space *mapping, |
dfb8ae56 | 1538 | struct bdi_writeback *wb, |
143dfe86 | 1539 | unsigned long pages_dirtied) |
1da177e4 | 1540 | { |
2bc00aef | 1541 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1542 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
2bc00aef | 1543 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1544 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1545 | &mdtc_stor : NULL; | |
1546 | struct dirty_throttle_control *sdtc; | |
143dfe86 | 1547 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
83712358 | 1548 | long period; |
7ccb9ad5 WF |
1549 | long pause; |
1550 | long max_pause; | |
1551 | long min_pause; | |
1552 | int nr_dirtied_pause; | |
e50e3720 | 1553 | bool dirty_exceeded = false; |
143dfe86 | 1554 | unsigned long task_ratelimit; |
7ccb9ad5 | 1555 | unsigned long dirty_ratelimit; |
dfb8ae56 | 1556 | struct backing_dev_info *bdi = wb->bdi; |
5a537485 | 1557 | bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; |
e98be2d5 | 1558 | unsigned long start_time = jiffies; |
1da177e4 LT |
1559 | |
1560 | for (;;) { | |
83712358 | 1561 | unsigned long now = jiffies; |
2bc00aef | 1562 | unsigned long dirty, thresh, bg_thresh; |
50e55bf6 YS |
1563 | unsigned long m_dirty = 0; /* stop bogus uninit warnings */ |
1564 | unsigned long m_thresh = 0; | |
1565 | unsigned long m_bg_thresh = 0; | |
83712358 | 1566 | |
143dfe86 WF |
1567 | /* |
1568 | * Unstable writes are a feature of certain networked | |
1569 | * filesystems (i.e. NFS) in which data may have been | |
1570 | * written to the server's write cache, but has not yet | |
1571 | * been flushed to permanent storage. | |
1572 | */ | |
5fce25a9 PZ |
1573 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
1574 | global_page_state(NR_UNSTABLE_NFS); | |
9fc3a43e | 1575 | gdtc->avail = global_dirtyable_memory(); |
2bc00aef | 1576 | gdtc->dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
5fce25a9 | 1577 | |
9fc3a43e | 1578 | domain_dirty_limits(gdtc); |
16c4042f | 1579 | |
5a537485 | 1580 | if (unlikely(strictlimit)) { |
970fb01a | 1581 | wb_dirty_limits(gdtc); |
5a537485 | 1582 | |
2bc00aef TH |
1583 | dirty = gdtc->wb_dirty; |
1584 | thresh = gdtc->wb_thresh; | |
970fb01a | 1585 | bg_thresh = gdtc->wb_bg_thresh; |
5a537485 | 1586 | } else { |
2bc00aef TH |
1587 | dirty = gdtc->dirty; |
1588 | thresh = gdtc->thresh; | |
1589 | bg_thresh = gdtc->bg_thresh; | |
5a537485 MP |
1590 | } |
1591 | ||
c2aa723a | 1592 | if (mdtc) { |
c5edf9cd | 1593 | unsigned long filepages, headroom, writeback; |
c2aa723a TH |
1594 | |
1595 | /* | |
1596 | * If @wb belongs to !root memcg, repeat the same | |
1597 | * basic calculations for the memcg domain. | |
1598 | */ | |
c5edf9cd TH |
1599 | mem_cgroup_wb_stats(wb, &filepages, &headroom, |
1600 | &mdtc->dirty, &writeback); | |
c2aa723a | 1601 | mdtc->dirty += writeback; |
c5edf9cd | 1602 | mdtc_calc_avail(mdtc, filepages, headroom); |
c2aa723a TH |
1603 | |
1604 | domain_dirty_limits(mdtc); | |
1605 | ||
1606 | if (unlikely(strictlimit)) { | |
1607 | wb_dirty_limits(mdtc); | |
1608 | m_dirty = mdtc->wb_dirty; | |
1609 | m_thresh = mdtc->wb_thresh; | |
1610 | m_bg_thresh = mdtc->wb_bg_thresh; | |
1611 | } else { | |
1612 | m_dirty = mdtc->dirty; | |
1613 | m_thresh = mdtc->thresh; | |
1614 | m_bg_thresh = mdtc->bg_thresh; | |
1615 | } | |
5a537485 MP |
1616 | } |
1617 | ||
16c4042f WF |
1618 | /* |
1619 | * Throttle it only when the background writeback cannot | |
1620 | * catch-up. This avoids (excessively) small writeouts | |
de1fff37 | 1621 | * when the wb limits are ramping up in case of !strictlimit. |
5a537485 | 1622 | * |
de1fff37 TH |
1623 | * In strictlimit case make decision based on the wb counters |
1624 | * and limits. Small writeouts when the wb limits are ramping | |
5a537485 | 1625 | * up are the price we consciously pay for strictlimit-ing. |
c2aa723a TH |
1626 | * |
1627 | * If memcg domain is in effect, @dirty should be under | |
1628 | * both global and memcg freerun ceilings. | |
16c4042f | 1629 | */ |
c2aa723a TH |
1630 | if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) && |
1631 | (!mdtc || | |
1632 | m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) { | |
1633 | unsigned long intv = dirty_poll_interval(dirty, thresh); | |
1634 | unsigned long m_intv = ULONG_MAX; | |
1635 | ||
83712358 WF |
1636 | current->dirty_paused_when = now; |
1637 | current->nr_dirtied = 0; | |
c2aa723a TH |
1638 | if (mdtc) |
1639 | m_intv = dirty_poll_interval(m_dirty, m_thresh); | |
1640 | current->nr_dirtied_pause = min(intv, m_intv); | |
16c4042f | 1641 | break; |
83712358 | 1642 | } |
16c4042f | 1643 | |
bc05873d | 1644 | if (unlikely(!writeback_in_progress(wb))) |
9ecf4866 | 1645 | wb_start_background_writeback(wb); |
143dfe86 | 1646 | |
c2aa723a TH |
1647 | /* |
1648 | * Calculate global domain's pos_ratio and select the | |
1649 | * global dtc by default. | |
1650 | */ | |
5a537485 | 1651 | if (!strictlimit) |
970fb01a | 1652 | wb_dirty_limits(gdtc); |
5fce25a9 | 1653 | |
2bc00aef TH |
1654 | dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && |
1655 | ((gdtc->dirty > gdtc->thresh) || strictlimit); | |
daddfa3c TH |
1656 | |
1657 | wb_position_ratio(gdtc); | |
c2aa723a TH |
1658 | sdtc = gdtc; |
1659 | ||
1660 | if (mdtc) { | |
1661 | /* | |
1662 | * If memcg domain is in effect, calculate its | |
1663 | * pos_ratio. @wb should satisfy constraints from | |
1664 | * both global and memcg domains. Choose the one | |
1665 | * w/ lower pos_ratio. | |
1666 | */ | |
1667 | if (!strictlimit) | |
1668 | wb_dirty_limits(mdtc); | |
1669 | ||
1670 | dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) && | |
1671 | ((mdtc->dirty > mdtc->thresh) || strictlimit); | |
1672 | ||
1673 | wb_position_ratio(mdtc); | |
1674 | if (mdtc->pos_ratio < gdtc->pos_ratio) | |
1675 | sdtc = mdtc; | |
1676 | } | |
daddfa3c | 1677 | |
a88a341a TH |
1678 | if (dirty_exceeded && !wb->dirty_exceeded) |
1679 | wb->dirty_exceeded = 1; | |
1da177e4 | 1680 | |
8a731799 TH |
1681 | if (time_is_before_jiffies(wb->bw_time_stamp + |
1682 | BANDWIDTH_INTERVAL)) { | |
1683 | spin_lock(&wb->list_lock); | |
c2aa723a | 1684 | __wb_update_bandwidth(gdtc, mdtc, start_time, true); |
8a731799 TH |
1685 | spin_unlock(&wb->list_lock); |
1686 | } | |
e98be2d5 | 1687 | |
c2aa723a | 1688 | /* throttle according to the chosen dtc */ |
a88a341a | 1689 | dirty_ratelimit = wb->dirty_ratelimit; |
c2aa723a | 1690 | task_ratelimit = ((u64)dirty_ratelimit * sdtc->pos_ratio) >> |
3a73dbbc | 1691 | RATELIMIT_CALC_SHIFT; |
c2aa723a | 1692 | max_pause = wb_max_pause(wb, sdtc->wb_dirty); |
a88a341a TH |
1693 | min_pause = wb_min_pause(wb, max_pause, |
1694 | task_ratelimit, dirty_ratelimit, | |
1695 | &nr_dirtied_pause); | |
7ccb9ad5 | 1696 | |
3a73dbbc | 1697 | if (unlikely(task_ratelimit == 0)) { |
83712358 | 1698 | period = max_pause; |
c8462cc9 | 1699 | pause = max_pause; |
143dfe86 | 1700 | goto pause; |
04fbfdc1 | 1701 | } |
83712358 WF |
1702 | period = HZ * pages_dirtied / task_ratelimit; |
1703 | pause = period; | |
1704 | if (current->dirty_paused_when) | |
1705 | pause -= now - current->dirty_paused_when; | |
1706 | /* | |
1707 | * For less than 1s think time (ext3/4 may block the dirtier | |
1708 | * for up to 800ms from time to time on 1-HDD; so does xfs, | |
1709 | * however at much less frequency), try to compensate it in | |
1710 | * future periods by updating the virtual time; otherwise just | |
1711 | * do a reset, as it may be a light dirtier. | |
1712 | */ | |
7ccb9ad5 | 1713 | if (pause < min_pause) { |
5634cc2a | 1714 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1715 | sdtc->thresh, |
1716 | sdtc->bg_thresh, | |
1717 | sdtc->dirty, | |
1718 | sdtc->wb_thresh, | |
1719 | sdtc->wb_dirty, | |
ece13ac3 WF |
1720 | dirty_ratelimit, |
1721 | task_ratelimit, | |
1722 | pages_dirtied, | |
83712358 | 1723 | period, |
7ccb9ad5 | 1724 | min(pause, 0L), |
ece13ac3 | 1725 | start_time); |
83712358 WF |
1726 | if (pause < -HZ) { |
1727 | current->dirty_paused_when = now; | |
1728 | current->nr_dirtied = 0; | |
1729 | } else if (period) { | |
1730 | current->dirty_paused_when += period; | |
1731 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1732 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
1733 | current->nr_dirtied_pause += pages_dirtied; | |
57fc978c | 1734 | break; |
04fbfdc1 | 1735 | } |
7ccb9ad5 WF |
1736 | if (unlikely(pause > max_pause)) { |
1737 | /* for occasional dropped task_ratelimit */ | |
1738 | now += min(pause - max_pause, max_pause); | |
1739 | pause = max_pause; | |
1740 | } | |
143dfe86 WF |
1741 | |
1742 | pause: | |
5634cc2a | 1743 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1744 | sdtc->thresh, |
1745 | sdtc->bg_thresh, | |
1746 | sdtc->dirty, | |
1747 | sdtc->wb_thresh, | |
1748 | sdtc->wb_dirty, | |
ece13ac3 WF |
1749 | dirty_ratelimit, |
1750 | task_ratelimit, | |
1751 | pages_dirtied, | |
83712358 | 1752 | period, |
ece13ac3 WF |
1753 | pause, |
1754 | start_time); | |
499d05ec | 1755 | __set_current_state(TASK_KILLABLE); |
d25105e8 | 1756 | io_schedule_timeout(pause); |
87c6a9b2 | 1757 | |
83712358 WF |
1758 | current->dirty_paused_when = now + pause; |
1759 | current->nr_dirtied = 0; | |
7ccb9ad5 | 1760 | current->nr_dirtied_pause = nr_dirtied_pause; |
83712358 | 1761 | |
ffd1f609 | 1762 | /* |
2bc00aef TH |
1763 | * This is typically equal to (dirty < thresh) and can also |
1764 | * keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1765 | */ |
1df64719 | 1766 | if (task_ratelimit) |
ffd1f609 | 1767 | break; |
499d05ec | 1768 | |
c5c6343c WF |
1769 | /* |
1770 | * In the case of an unresponding NFS server and the NFS dirty | |
de1fff37 | 1771 | * pages exceeds dirty_thresh, give the other good wb's a pipe |
c5c6343c WF |
1772 | * to go through, so that tasks on them still remain responsive. |
1773 | * | |
1774 | * In theory 1 page is enough to keep the comsumer-producer | |
1775 | * pipe going: the flusher cleans 1 page => the task dirties 1 | |
de1fff37 | 1776 | * more page. However wb_dirty has accounting errors. So use |
93f78d88 | 1777 | * the larger and more IO friendly wb_stat_error. |
c5c6343c | 1778 | */ |
c2aa723a | 1779 | if (sdtc->wb_dirty <= wb_stat_error(wb)) |
c5c6343c WF |
1780 | break; |
1781 | ||
499d05ec JK |
1782 | if (fatal_signal_pending(current)) |
1783 | break; | |
1da177e4 LT |
1784 | } |
1785 | ||
a88a341a TH |
1786 | if (!dirty_exceeded && wb->dirty_exceeded) |
1787 | wb->dirty_exceeded = 0; | |
1da177e4 | 1788 | |
bc05873d | 1789 | if (writeback_in_progress(wb)) |
5b0830cb | 1790 | return; |
1da177e4 LT |
1791 | |
1792 | /* | |
1793 | * In laptop mode, we wait until hitting the higher threshold before | |
1794 | * starting background writeout, and then write out all the way down | |
1795 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1796 | * | |
1797 | * In normal mode, we start background writeout at the lower | |
1798 | * background_thresh, to keep the amount of dirty memory low. | |
1799 | */ | |
143dfe86 WF |
1800 | if (laptop_mode) |
1801 | return; | |
1802 | ||
2bc00aef | 1803 | if (nr_reclaimable > gdtc->bg_thresh) |
9ecf4866 | 1804 | wb_start_background_writeback(wb); |
1da177e4 LT |
1805 | } |
1806 | ||
9d823e8f | 1807 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1808 | |
54848d73 WF |
1809 | /* |
1810 | * Normal tasks are throttled by | |
1811 | * loop { | |
1812 | * dirty tsk->nr_dirtied_pause pages; | |
1813 | * take a snap in balance_dirty_pages(); | |
1814 | * } | |
1815 | * However there is a worst case. If every task exit immediately when dirtied | |
1816 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be | |
1817 | * called to throttle the page dirties. The solution is to save the not yet | |
1818 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them | |
1819 | * randomly into the running tasks. This works well for the above worst case, | |
1820 | * as the new task will pick up and accumulate the old task's leaked dirty | |
1821 | * count and eventually get throttled. | |
1822 | */ | |
1823 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1824 | ||
1da177e4 | 1825 | /** |
d0e1d66b | 1826 | * balance_dirty_pages_ratelimited - balance dirty memory state |
67be2dd1 | 1827 | * @mapping: address_space which was dirtied |
1da177e4 LT |
1828 | * |
1829 | * Processes which are dirtying memory should call in here once for each page | |
1830 | * which was newly dirtied. The function will periodically check the system's | |
1831 | * dirty state and will initiate writeback if needed. | |
1832 | * | |
1833 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
1834 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
1835 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
1836 | * from overshooting the limit by (ratelimit_pages) each. | |
1837 | */ | |
d0e1d66b | 1838 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
1da177e4 | 1839 | { |
dfb8ae56 TH |
1840 | struct inode *inode = mapping->host; |
1841 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1842 | struct bdi_writeback *wb = NULL; | |
9d823e8f WF |
1843 | int ratelimit; |
1844 | int *p; | |
1da177e4 | 1845 | |
36715cef WF |
1846 | if (!bdi_cap_account_dirty(bdi)) |
1847 | return; | |
1848 | ||
dfb8ae56 TH |
1849 | if (inode_cgwb_enabled(inode)) |
1850 | wb = wb_get_create_current(bdi, GFP_KERNEL); | |
1851 | if (!wb) | |
1852 | wb = &bdi->wb; | |
1853 | ||
9d823e8f | 1854 | ratelimit = current->nr_dirtied_pause; |
a88a341a | 1855 | if (wb->dirty_exceeded) |
9d823e8f WF |
1856 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
1857 | ||
9d823e8f | 1858 | preempt_disable(); |
1da177e4 | 1859 | /* |
9d823e8f WF |
1860 | * This prevents one CPU to accumulate too many dirtied pages without |
1861 | * calling into balance_dirty_pages(), which can happen when there are | |
1862 | * 1000+ tasks, all of them start dirtying pages at exactly the same | |
1863 | * time, hence all honoured too large initial task->nr_dirtied_pause. | |
1da177e4 | 1864 | */ |
7c8e0181 | 1865 | p = this_cpu_ptr(&bdp_ratelimits); |
9d823e8f | 1866 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1867 | *p = 0; |
d3bc1fef WF |
1868 | else if (unlikely(*p >= ratelimit_pages)) { |
1869 | *p = 0; | |
1870 | ratelimit = 0; | |
1da177e4 | 1871 | } |
54848d73 WF |
1872 | /* |
1873 | * Pick up the dirtied pages by the exited tasks. This avoids lots of | |
1874 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping | |
1875 | * the dirty throttling and livelock other long-run dirtiers. | |
1876 | */ | |
7c8e0181 | 1877 | p = this_cpu_ptr(&dirty_throttle_leaks); |
54848d73 | 1878 | if (*p > 0 && current->nr_dirtied < ratelimit) { |
d0e1d66b | 1879 | unsigned long nr_pages_dirtied; |
54848d73 WF |
1880 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
1881 | *p -= nr_pages_dirtied; | |
1882 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1883 | } |
fa5a734e | 1884 | preempt_enable(); |
9d823e8f WF |
1885 | |
1886 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
dfb8ae56 TH |
1887 | balance_dirty_pages(mapping, wb, current->nr_dirtied); |
1888 | ||
1889 | wb_put(wb); | |
1da177e4 | 1890 | } |
d0e1d66b | 1891 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
1da177e4 | 1892 | |
aa661bbe TH |
1893 | /** |
1894 | * wb_over_bg_thresh - does @wb need to be written back? | |
1895 | * @wb: bdi_writeback of interest | |
1896 | * | |
1897 | * Determines whether background writeback should keep writing @wb or it's | |
1898 | * clean enough. Returns %true if writeback should continue. | |
1899 | */ | |
1900 | bool wb_over_bg_thresh(struct bdi_writeback *wb) | |
1901 | { | |
947e9762 | 1902 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1903 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
947e9762 | 1904 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1905 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1906 | &mdtc_stor : NULL; | |
aa661bbe | 1907 | |
947e9762 TH |
1908 | /* |
1909 | * Similar to balance_dirty_pages() but ignores pages being written | |
1910 | * as we're trying to decide whether to put more under writeback. | |
1911 | */ | |
1912 | gdtc->avail = global_dirtyable_memory(); | |
1913 | gdtc->dirty = global_page_state(NR_FILE_DIRTY) + | |
1914 | global_page_state(NR_UNSTABLE_NFS); | |
1915 | domain_dirty_limits(gdtc); | |
aa661bbe | 1916 | |
947e9762 | 1917 | if (gdtc->dirty > gdtc->bg_thresh) |
aa661bbe TH |
1918 | return true; |
1919 | ||
74d36944 HC |
1920 | if (wb_stat(wb, WB_RECLAIMABLE) > |
1921 | wb_calc_thresh(gdtc->wb, gdtc->bg_thresh)) | |
aa661bbe TH |
1922 | return true; |
1923 | ||
c2aa723a | 1924 | if (mdtc) { |
c5edf9cd | 1925 | unsigned long filepages, headroom, writeback; |
c2aa723a | 1926 | |
c5edf9cd TH |
1927 | mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, |
1928 | &writeback); | |
1929 | mdtc_calc_avail(mdtc, filepages, headroom); | |
c2aa723a TH |
1930 | domain_dirty_limits(mdtc); /* ditto, ignore writeback */ |
1931 | ||
1932 | if (mdtc->dirty > mdtc->bg_thresh) | |
1933 | return true; | |
1934 | ||
74d36944 HC |
1935 | if (wb_stat(wb, WB_RECLAIMABLE) > |
1936 | wb_calc_thresh(mdtc->wb, mdtc->bg_thresh)) | |
c2aa723a TH |
1937 | return true; |
1938 | } | |
1939 | ||
aa661bbe TH |
1940 | return false; |
1941 | } | |
1942 | ||
232ea4d6 | 1943 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 1944 | { |
364aeb28 DR |
1945 | unsigned long background_thresh; |
1946 | unsigned long dirty_thresh; | |
1da177e4 LT |
1947 | |
1948 | for ( ; ; ) { | |
16c4042f | 1949 | global_dirty_limits(&background_thresh, &dirty_thresh); |
c7981433 | 1950 | dirty_thresh = hard_dirty_limit(&global_wb_domain, dirty_thresh); |
1da177e4 LT |
1951 | |
1952 | /* | |
1953 | * Boost the allowable dirty threshold a bit for page | |
1954 | * allocators so they don't get DoS'ed by heavy writers | |
1955 | */ | |
1956 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
1957 | ||
c24f21bd CL |
1958 | if (global_page_state(NR_UNSTABLE_NFS) + |
1959 | global_page_state(NR_WRITEBACK) <= dirty_thresh) | |
1960 | break; | |
8aa7e847 | 1961 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
1962 | |
1963 | /* | |
1964 | * The caller might hold locks which can prevent IO completion | |
1965 | * or progress in the filesystem. So we cannot just sit here | |
1966 | * waiting for IO to complete. | |
1967 | */ | |
1968 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
1969 | break; | |
1da177e4 LT |
1970 | } |
1971 | } | |
1972 | ||
1da177e4 LT |
1973 | /* |
1974 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1975 | */ | |
cccad5b9 | 1976 | int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, |
8d65af78 | 1977 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1978 | { |
8d65af78 | 1979 | proc_dointvec(table, write, buffer, length, ppos); |
1da177e4 LT |
1980 | return 0; |
1981 | } | |
1982 | ||
c2c4986e | 1983 | #ifdef CONFIG_BLOCK |
31373d09 | 1984 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 1985 | { |
31373d09 MG |
1986 | struct request_queue *q = (struct request_queue *)data; |
1987 | int nr_pages = global_page_state(NR_FILE_DIRTY) + | |
1988 | global_page_state(NR_UNSTABLE_NFS); | |
a06fd6b1 | 1989 | struct bdi_writeback *wb; |
1da177e4 | 1990 | |
31373d09 MG |
1991 | /* |
1992 | * We want to write everything out, not just down to the dirty | |
1993 | * threshold | |
1994 | */ | |
a06fd6b1 TH |
1995 | if (!bdi_has_dirty_io(&q->backing_dev_info)) |
1996 | return; | |
1997 | ||
9ad18ab9 | 1998 | rcu_read_lock(); |
b817525a | 1999 | list_for_each_entry_rcu(wb, &q->backing_dev_info.wb_list, bdi_node) |
a06fd6b1 TH |
2000 | if (wb_has_dirty_io(wb)) |
2001 | wb_start_writeback(wb, nr_pages, true, | |
2002 | WB_REASON_LAPTOP_TIMER); | |
9ad18ab9 | 2003 | rcu_read_unlock(); |
1da177e4 LT |
2004 | } |
2005 | ||
2006 | /* | |
2007 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
2008 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
2009 | * then push it back - the user is still using the disk. | |
2010 | */ | |
31373d09 | 2011 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 2012 | { |
31373d09 | 2013 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
2014 | } |
2015 | ||
2016 | /* | |
2017 | * We're in laptop mode and we've just synced. The sync's writes will have | |
2018 | * caused another writeback to be scheduled by laptop_io_completion. | |
2019 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
2020 | */ | |
2021 | void laptop_sync_completion(void) | |
2022 | { | |
31373d09 MG |
2023 | struct backing_dev_info *bdi; |
2024 | ||
2025 | rcu_read_lock(); | |
2026 | ||
2027 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
2028 | del_timer(&bdi->laptop_mode_wb_timer); | |
2029 | ||
2030 | rcu_read_unlock(); | |
1da177e4 | 2031 | } |
c2c4986e | 2032 | #endif |
1da177e4 LT |
2033 | |
2034 | /* | |
2035 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
2036 | * if a large number of processes all perform writes at the same time. | |
2037 | * If it is too low then SMP machines will call the (expensive) | |
2038 | * get_writeback_state too often. | |
2039 | * | |
2040 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
2041 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
9d823e8f | 2042 | * thresholds. |
1da177e4 LT |
2043 | */ |
2044 | ||
2d1d43f6 | 2045 | void writeback_set_ratelimit(void) |
1da177e4 | 2046 | { |
dcc25ae7 | 2047 | struct wb_domain *dom = &global_wb_domain; |
9d823e8f WF |
2048 | unsigned long background_thresh; |
2049 | unsigned long dirty_thresh; | |
dcc25ae7 | 2050 | |
9d823e8f | 2051 | global_dirty_limits(&background_thresh, &dirty_thresh); |
dcc25ae7 | 2052 | dom->dirty_limit = dirty_thresh; |
9d823e8f | 2053 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
1da177e4 LT |
2054 | if (ratelimit_pages < 16) |
2055 | ratelimit_pages = 16; | |
1da177e4 LT |
2056 | } |
2057 | ||
0db0628d | 2058 | static int |
2f60d628 SB |
2059 | ratelimit_handler(struct notifier_block *self, unsigned long action, |
2060 | void *hcpu) | |
1da177e4 | 2061 | { |
2f60d628 SB |
2062 | |
2063 | switch (action & ~CPU_TASKS_FROZEN) { | |
2064 | case CPU_ONLINE: | |
2065 | case CPU_DEAD: | |
2066 | writeback_set_ratelimit(); | |
2067 | return NOTIFY_OK; | |
2068 | default: | |
2069 | return NOTIFY_DONE; | |
2070 | } | |
1da177e4 LT |
2071 | } |
2072 | ||
0db0628d | 2073 | static struct notifier_block ratelimit_nb = { |
1da177e4 LT |
2074 | .notifier_call = ratelimit_handler, |
2075 | .next = NULL, | |
2076 | }; | |
2077 | ||
2078 | /* | |
dc6e29da LT |
2079 | * Called early on to tune the page writeback dirty limits. |
2080 | * | |
2081 | * We used to scale dirty pages according to how total memory | |
2082 | * related to pages that could be allocated for buffers (by | |
2083 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
2084 | * | |
2085 | * However, that was when we used "dirty_ratio" to scale with | |
2086 | * all memory, and we don't do that any more. "dirty_ratio" | |
2087 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
2088 | * totalhigh_pages from vm_total_pages), and as such we can't | |
2089 | * get into the old insane situation any more where we had | |
2090 | * large amounts of dirty pages compared to a small amount of | |
2091 | * non-HIGHMEM memory. | |
2092 | * | |
2093 | * But we might still want to scale the dirty_ratio by how | |
2094 | * much memory the box has.. | |
1da177e4 LT |
2095 | */ |
2096 | void __init page_writeback_init(void) | |
2097 | { | |
a50fcb51 RV |
2098 | BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL)); |
2099 | ||
2d1d43f6 | 2100 | writeback_set_ratelimit(); |
1da177e4 LT |
2101 | register_cpu_notifier(&ratelimit_nb); |
2102 | } | |
2103 | ||
f446daae JK |
2104 | /** |
2105 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
2106 | * @mapping: address space structure to write | |
2107 | * @start: starting page index | |
2108 | * @end: ending page index (inclusive) | |
2109 | * | |
2110 | * This function scans the page range from @start to @end (inclusive) and tags | |
2111 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
2112 | * that write_cache_pages (or whoever calls this function) will then use | |
2113 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
2114 | * used to avoid livelocking of writeback by a process steadily creating new | |
2115 | * dirty pages in the file (thus it is important for this function to be quick | |
2116 | * so that it can tag pages faster than a dirtying process can create them). | |
2117 | */ | |
2118 | /* | |
2119 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
2120 | */ | |
f446daae JK |
2121 | void tag_pages_for_writeback(struct address_space *mapping, |
2122 | pgoff_t start, pgoff_t end) | |
2123 | { | |
3c111a07 | 2124 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
2125 | unsigned long tagged; |
2126 | ||
2127 | do { | |
2128 | spin_lock_irq(&mapping->tree_lock); | |
2129 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
2130 | &start, end, WRITEBACK_TAG_BATCH, | |
2131 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
2132 | spin_unlock_irq(&mapping->tree_lock); | |
2133 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
2134 | cond_resched(); | |
d5ed3a4a JK |
2135 | /* We check 'start' to handle wrapping when end == ~0UL */ |
2136 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
2137 | } |
2138 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
2139 | ||
811d736f | 2140 | /** |
0ea97180 | 2141 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
2142 | * @mapping: address space structure to write |
2143 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
2144 | * @writepage: function called for each page |
2145 | * @data: data passed to writepage function | |
811d736f | 2146 | * |
0ea97180 | 2147 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
2148 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
2149 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
2150 | * and msync() need to guarantee that all the data which was dirty at the time | |
2151 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
2152 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
2153 | * existing IO to complete. | |
f446daae JK |
2154 | * |
2155 | * To avoid livelocks (when other process dirties new pages), we first tag | |
2156 | * pages which should be written back with TOWRITE tag and only then start | |
2157 | * writing them. For data-integrity sync we have to be careful so that we do | |
2158 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
2159 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
2160 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 2161 | */ |
0ea97180 MS |
2162 | int write_cache_pages(struct address_space *mapping, |
2163 | struct writeback_control *wbc, writepage_t writepage, | |
2164 | void *data) | |
811d736f | 2165 | { |
811d736f DH |
2166 | int ret = 0; |
2167 | int done = 0; | |
811d736f DH |
2168 | struct pagevec pvec; |
2169 | int nr_pages; | |
31a12666 | 2170 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
2171 | pgoff_t index; |
2172 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 2173 | pgoff_t done_index; |
31a12666 | 2174 | int cycled; |
811d736f | 2175 | int range_whole = 0; |
f446daae | 2176 | int tag; |
811d736f | 2177 | |
811d736f DH |
2178 | pagevec_init(&pvec, 0); |
2179 | if (wbc->range_cyclic) { | |
31a12666 NP |
2180 | writeback_index = mapping->writeback_index; /* prev offset */ |
2181 | index = writeback_index; | |
2182 | if (index == 0) | |
2183 | cycled = 1; | |
2184 | else | |
2185 | cycled = 0; | |
811d736f DH |
2186 | end = -1; |
2187 | } else { | |
09cbfeaf KS |
2188 | index = wbc->range_start >> PAGE_SHIFT; |
2189 | end = wbc->range_end >> PAGE_SHIFT; | |
811d736f DH |
2190 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
2191 | range_whole = 1; | |
31a12666 | 2192 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 2193 | } |
6e6938b6 | 2194 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
2195 | tag = PAGECACHE_TAG_TOWRITE; |
2196 | else | |
2197 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 2198 | retry: |
6e6938b6 | 2199 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 2200 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 2201 | done_index = index; |
5a3d5c98 NP |
2202 | while (!done && (index <= end)) { |
2203 | int i; | |
2204 | ||
f446daae | 2205 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
2206 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
2207 | if (nr_pages == 0) | |
2208 | break; | |
811d736f | 2209 | |
811d736f DH |
2210 | for (i = 0; i < nr_pages; i++) { |
2211 | struct page *page = pvec.pages[i]; | |
2212 | ||
2213 | /* | |
d5482cdf NP |
2214 | * At this point, the page may be truncated or |
2215 | * invalidated (changing page->mapping to NULL), or | |
2216 | * even swizzled back from swapper_space to tmpfs file | |
2217 | * mapping. However, page->index will not change | |
2218 | * because we have a reference on the page. | |
811d736f | 2219 | */ |
d5482cdf NP |
2220 | if (page->index > end) { |
2221 | /* | |
2222 | * can't be range_cyclic (1st pass) because | |
2223 | * end == -1 in that case. | |
2224 | */ | |
2225 | done = 1; | |
2226 | break; | |
2227 | } | |
2228 | ||
cf15b07c | 2229 | done_index = page->index; |
d5482cdf | 2230 | |
811d736f DH |
2231 | lock_page(page); |
2232 | ||
5a3d5c98 NP |
2233 | /* |
2234 | * Page truncated or invalidated. We can freely skip it | |
2235 | * then, even for data integrity operations: the page | |
2236 | * has disappeared concurrently, so there could be no | |
2237 | * real expectation of this data interity operation | |
2238 | * even if there is now a new, dirty page at the same | |
2239 | * pagecache address. | |
2240 | */ | |
811d736f | 2241 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 2242 | continue_unlock: |
811d736f DH |
2243 | unlock_page(page); |
2244 | continue; | |
2245 | } | |
2246 | ||
515f4a03 NP |
2247 | if (!PageDirty(page)) { |
2248 | /* someone wrote it for us */ | |
2249 | goto continue_unlock; | |
2250 | } | |
2251 | ||
2252 | if (PageWriteback(page)) { | |
2253 | if (wbc->sync_mode != WB_SYNC_NONE) | |
2254 | wait_on_page_writeback(page); | |
2255 | else | |
2256 | goto continue_unlock; | |
2257 | } | |
811d736f | 2258 | |
515f4a03 NP |
2259 | BUG_ON(PageWriteback(page)); |
2260 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 2261 | goto continue_unlock; |
811d736f | 2262 | |
de1414a6 | 2263 | trace_wbc_writepage(wbc, inode_to_bdi(mapping->host)); |
0ea97180 | 2264 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
2265 | if (unlikely(ret)) { |
2266 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
2267 | unlock_page(page); | |
2268 | ret = 0; | |
2269 | } else { | |
2270 | /* | |
2271 | * done_index is set past this page, | |
2272 | * so media errors will not choke | |
2273 | * background writeout for the entire | |
2274 | * file. This has consequences for | |
2275 | * range_cyclic semantics (ie. it may | |
2276 | * not be suitable for data integrity | |
2277 | * writeout). | |
2278 | */ | |
cf15b07c | 2279 | done_index = page->index + 1; |
00266770 NP |
2280 | done = 1; |
2281 | break; | |
2282 | } | |
0b564927 | 2283 | } |
00266770 | 2284 | |
546a1924 DC |
2285 | /* |
2286 | * We stop writing back only if we are not doing | |
2287 | * integrity sync. In case of integrity sync we have to | |
2288 | * keep going until we have written all the pages | |
2289 | * we tagged for writeback prior to entering this loop. | |
2290 | */ | |
2291 | if (--wbc->nr_to_write <= 0 && | |
2292 | wbc->sync_mode == WB_SYNC_NONE) { | |
2293 | done = 1; | |
2294 | break; | |
05fe478d | 2295 | } |
811d736f DH |
2296 | } |
2297 | pagevec_release(&pvec); | |
2298 | cond_resched(); | |
2299 | } | |
3a4c6800 | 2300 | if (!cycled && !done) { |
811d736f | 2301 | /* |
31a12666 | 2302 | * range_cyclic: |
811d736f DH |
2303 | * We hit the last page and there is more work to be done: wrap |
2304 | * back to the start of the file | |
2305 | */ | |
31a12666 | 2306 | cycled = 1; |
811d736f | 2307 | index = 0; |
31a12666 | 2308 | end = writeback_index - 1; |
811d736f DH |
2309 | goto retry; |
2310 | } | |
0b564927 DC |
2311 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
2312 | mapping->writeback_index = done_index; | |
06d6cf69 | 2313 | |
811d736f DH |
2314 | return ret; |
2315 | } | |
0ea97180 MS |
2316 | EXPORT_SYMBOL(write_cache_pages); |
2317 | ||
2318 | /* | |
2319 | * Function used by generic_writepages to call the real writepage | |
2320 | * function and set the mapping flags on error | |
2321 | */ | |
2322 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
2323 | void *data) | |
2324 | { | |
2325 | struct address_space *mapping = data; | |
2326 | int ret = mapping->a_ops->writepage(page, wbc); | |
2327 | mapping_set_error(mapping, ret); | |
2328 | return ret; | |
2329 | } | |
2330 | ||
2331 | /** | |
2332 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
2333 | * @mapping: address space structure to write | |
2334 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
2335 | * | |
2336 | * This is a library function, which implements the writepages() | |
2337 | * address_space_operation. | |
2338 | */ | |
2339 | int generic_writepages(struct address_space *mapping, | |
2340 | struct writeback_control *wbc) | |
2341 | { | |
9b6096a6 SL |
2342 | struct blk_plug plug; |
2343 | int ret; | |
2344 | ||
0ea97180 MS |
2345 | /* deal with chardevs and other special file */ |
2346 | if (!mapping->a_ops->writepage) | |
2347 | return 0; | |
2348 | ||
9b6096a6 SL |
2349 | blk_start_plug(&plug); |
2350 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
2351 | blk_finish_plug(&plug); | |
2352 | return ret; | |
0ea97180 | 2353 | } |
811d736f DH |
2354 | |
2355 | EXPORT_SYMBOL(generic_writepages); | |
2356 | ||
1da177e4 LT |
2357 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
2358 | { | |
22905f77 AM |
2359 | int ret; |
2360 | ||
1da177e4 LT |
2361 | if (wbc->nr_to_write <= 0) |
2362 | return 0; | |
2363 | if (mapping->a_ops->writepages) | |
d08b3851 | 2364 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
2365 | else |
2366 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 2367 | return ret; |
1da177e4 LT |
2368 | } |
2369 | ||
2370 | /** | |
2371 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
2372 | * @page: the page to write |
2373 | * @wait: if true, wait on writeout | |
1da177e4 LT |
2374 | * |
2375 | * The page must be locked by the caller and will be unlocked upon return. | |
2376 | * | |
2377 | * write_one_page() returns a negative error code if I/O failed. | |
2378 | */ | |
2379 | int write_one_page(struct page *page, int wait) | |
2380 | { | |
2381 | struct address_space *mapping = page->mapping; | |
2382 | int ret = 0; | |
2383 | struct writeback_control wbc = { | |
2384 | .sync_mode = WB_SYNC_ALL, | |
2385 | .nr_to_write = 1, | |
2386 | }; | |
2387 | ||
2388 | BUG_ON(!PageLocked(page)); | |
2389 | ||
2390 | if (wait) | |
2391 | wait_on_page_writeback(page); | |
2392 | ||
2393 | if (clear_page_dirty_for_io(page)) { | |
09cbfeaf | 2394 | get_page(page); |
1da177e4 LT |
2395 | ret = mapping->a_ops->writepage(page, &wbc); |
2396 | if (ret == 0 && wait) { | |
2397 | wait_on_page_writeback(page); | |
2398 | if (PageError(page)) | |
2399 | ret = -EIO; | |
2400 | } | |
09cbfeaf | 2401 | put_page(page); |
1da177e4 LT |
2402 | } else { |
2403 | unlock_page(page); | |
2404 | } | |
2405 | return ret; | |
2406 | } | |
2407 | EXPORT_SYMBOL(write_one_page); | |
2408 | ||
76719325 KC |
2409 | /* |
2410 | * For address_spaces which do not use buffers nor write back. | |
2411 | */ | |
2412 | int __set_page_dirty_no_writeback(struct page *page) | |
2413 | { | |
2414 | if (!PageDirty(page)) | |
c3f0da63 | 2415 | return !TestSetPageDirty(page); |
76719325 KC |
2416 | return 0; |
2417 | } | |
2418 | ||
e3a7cca1 ES |
2419 | /* |
2420 | * Helper function for set_page_dirty family. | |
c4843a75 | 2421 | * |
81f8c3a4 | 2422 | * Caller must hold lock_page_memcg(). |
c4843a75 | 2423 | * |
e3a7cca1 ES |
2424 | * NOTE: This relies on being atomic wrt interrupts. |
2425 | */ | |
62cccb8c | 2426 | void account_page_dirtied(struct page *page, struct address_space *mapping) |
e3a7cca1 | 2427 | { |
52ebea74 TH |
2428 | struct inode *inode = mapping->host; |
2429 | ||
9fb0a7da TH |
2430 | trace_writeback_dirty_page(page, mapping); |
2431 | ||
e3a7cca1 | 2432 | if (mapping_cap_account_dirty(mapping)) { |
52ebea74 | 2433 | struct bdi_writeback *wb; |
de1414a6 | 2434 | |
52ebea74 TH |
2435 | inode_attach_wb(inode, page); |
2436 | wb = inode_to_wb(inode); | |
de1414a6 | 2437 | |
62cccb8c | 2438 | mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_DIRTY); |
e3a7cca1 | 2439 | __inc_zone_page_state(page, NR_FILE_DIRTY); |
ea941f0e | 2440 | __inc_zone_page_state(page, NR_DIRTIED); |
52ebea74 TH |
2441 | __inc_wb_stat(wb, WB_RECLAIMABLE); |
2442 | __inc_wb_stat(wb, WB_DIRTIED); | |
09cbfeaf | 2443 | task_io_account_write(PAGE_SIZE); |
d3bc1fef WF |
2444 | current->nr_dirtied++; |
2445 | this_cpu_inc(bdp_ratelimits); | |
e3a7cca1 ES |
2446 | } |
2447 | } | |
679ceace | 2448 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 2449 | |
b9ea2515 KK |
2450 | /* |
2451 | * Helper function for deaccounting dirty page without writeback. | |
2452 | * | |
81f8c3a4 | 2453 | * Caller must hold lock_page_memcg(). |
b9ea2515 | 2454 | */ |
c4843a75 | 2455 | void account_page_cleaned(struct page *page, struct address_space *mapping, |
62cccb8c | 2456 | struct bdi_writeback *wb) |
b9ea2515 KK |
2457 | { |
2458 | if (mapping_cap_account_dirty(mapping)) { | |
62cccb8c | 2459 | mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY); |
b9ea2515 | 2460 | dec_zone_page_state(page, NR_FILE_DIRTY); |
682aa8e1 | 2461 | dec_wb_stat(wb, WB_RECLAIMABLE); |
09cbfeaf | 2462 | task_io_account_cancelled_write(PAGE_SIZE); |
b9ea2515 KK |
2463 | } |
2464 | } | |
b9ea2515 | 2465 | |
1da177e4 LT |
2466 | /* |
2467 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
2468 | * its radix tree. | |
2469 | * | |
2470 | * This is also used when a single buffer is being dirtied: we want to set the | |
2471 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
2472 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
2473 | * | |
2d6d7f98 JW |
2474 | * The caller must ensure this doesn't race with truncation. Most will simply |
2475 | * hold the page lock, but e.g. zap_pte_range() calls with the page mapped and | |
2476 | * the pte lock held, which also locks out truncation. | |
1da177e4 LT |
2477 | */ |
2478 | int __set_page_dirty_nobuffers(struct page *page) | |
2479 | { | |
62cccb8c | 2480 | lock_page_memcg(page); |
1da177e4 LT |
2481 | if (!TestSetPageDirty(page)) { |
2482 | struct address_space *mapping = page_mapping(page); | |
a85d9df1 | 2483 | unsigned long flags; |
1da177e4 | 2484 | |
c4843a75 | 2485 | if (!mapping) { |
62cccb8c | 2486 | unlock_page_memcg(page); |
8c08540f | 2487 | return 1; |
c4843a75 | 2488 | } |
8c08540f | 2489 | |
a85d9df1 | 2490 | spin_lock_irqsave(&mapping->tree_lock, flags); |
2d6d7f98 JW |
2491 | BUG_ON(page_mapping(page) != mapping); |
2492 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); | |
62cccb8c | 2493 | account_page_dirtied(page, mapping); |
2d6d7f98 JW |
2494 | radix_tree_tag_set(&mapping->page_tree, page_index(page), |
2495 | PAGECACHE_TAG_DIRTY); | |
a85d9df1 | 2496 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
62cccb8c | 2497 | unlock_page_memcg(page); |
c4843a75 | 2498 | |
8c08540f AM |
2499 | if (mapping->host) { |
2500 | /* !PageAnon && !swapper_space */ | |
2501 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 2502 | } |
4741c9fd | 2503 | return 1; |
1da177e4 | 2504 | } |
62cccb8c | 2505 | unlock_page_memcg(page); |
4741c9fd | 2506 | return 0; |
1da177e4 LT |
2507 | } |
2508 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
2509 | ||
2f800fbd WF |
2510 | /* |
2511 | * Call this whenever redirtying a page, to de-account the dirty counters | |
2512 | * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written | |
2513 | * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to | |
2514 | * systematic errors in balanced_dirty_ratelimit and the dirty pages position | |
2515 | * control. | |
2516 | */ | |
2517 | void account_page_redirty(struct page *page) | |
2518 | { | |
2519 | struct address_space *mapping = page->mapping; | |
91018134 | 2520 | |
2f800fbd | 2521 | if (mapping && mapping_cap_account_dirty(mapping)) { |
682aa8e1 TH |
2522 | struct inode *inode = mapping->host; |
2523 | struct bdi_writeback *wb; | |
2524 | bool locked; | |
91018134 | 2525 | |
682aa8e1 | 2526 | wb = unlocked_inode_to_wb_begin(inode, &locked); |
2f800fbd WF |
2527 | current->nr_dirtied--; |
2528 | dec_zone_page_state(page, NR_DIRTIED); | |
91018134 | 2529 | dec_wb_stat(wb, WB_DIRTIED); |
682aa8e1 | 2530 | unlocked_inode_to_wb_end(inode, locked); |
2f800fbd WF |
2531 | } |
2532 | } | |
2533 | EXPORT_SYMBOL(account_page_redirty); | |
2534 | ||
1da177e4 LT |
2535 | /* |
2536 | * When a writepage implementation decides that it doesn't want to write this | |
2537 | * page for some reason, it should redirty the locked page via | |
2538 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
2539 | */ | |
2540 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
2541 | { | |
8d38633c KK |
2542 | int ret; |
2543 | ||
1da177e4 | 2544 | wbc->pages_skipped++; |
8d38633c | 2545 | ret = __set_page_dirty_nobuffers(page); |
2f800fbd | 2546 | account_page_redirty(page); |
8d38633c | 2547 | return ret; |
1da177e4 LT |
2548 | } |
2549 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
2550 | ||
2551 | /* | |
6746aff7 WF |
2552 | * Dirty a page. |
2553 | * | |
2554 | * For pages with a mapping this should be done under the page lock | |
2555 | * for the benefit of asynchronous memory errors who prefer a consistent | |
2556 | * dirty state. This rule can be broken in some special cases, | |
2557 | * but should be better not to. | |
2558 | * | |
1da177e4 LT |
2559 | * If the mapping doesn't provide a set_page_dirty a_op, then |
2560 | * just fall through and assume that it wants buffer_heads. | |
2561 | */ | |
1cf6e7d8 | 2562 | int set_page_dirty(struct page *page) |
1da177e4 LT |
2563 | { |
2564 | struct address_space *mapping = page_mapping(page); | |
2565 | ||
2566 | if (likely(mapping)) { | |
2567 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
2568 | /* |
2569 | * readahead/lru_deactivate_page could remain | |
2570 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
2571 | * About readahead, if the page is written, the flags would be | |
2572 | * reset. So no problem. | |
2573 | * About lru_deactivate_page, if the page is redirty, the flag | |
2574 | * will be reset. So no problem. but if the page is used by readahead | |
2575 | * it will confuse readahead and make it restart the size rampup | |
2576 | * process. But it's a trivial problem. | |
2577 | */ | |
a4bb3ecd NH |
2578 | if (PageReclaim(page)) |
2579 | ClearPageReclaim(page); | |
9361401e DH |
2580 | #ifdef CONFIG_BLOCK |
2581 | if (!spd) | |
2582 | spd = __set_page_dirty_buffers; | |
2583 | #endif | |
2584 | return (*spd)(page); | |
1da177e4 | 2585 | } |
4741c9fd AM |
2586 | if (!PageDirty(page)) { |
2587 | if (!TestSetPageDirty(page)) | |
2588 | return 1; | |
2589 | } | |
1da177e4 LT |
2590 | return 0; |
2591 | } | |
2592 | EXPORT_SYMBOL(set_page_dirty); | |
2593 | ||
2594 | /* | |
2595 | * set_page_dirty() is racy if the caller has no reference against | |
2596 | * page->mapping->host, and if the page is unlocked. This is because another | |
2597 | * CPU could truncate the page off the mapping and then free the mapping. | |
2598 | * | |
2599 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
2600 | * holds a reference on the inode by having an open file. | |
2601 | * | |
2602 | * In other cases, the page should be locked before running set_page_dirty(). | |
2603 | */ | |
2604 | int set_page_dirty_lock(struct page *page) | |
2605 | { | |
2606 | int ret; | |
2607 | ||
7eaceacc | 2608 | lock_page(page); |
1da177e4 LT |
2609 | ret = set_page_dirty(page); |
2610 | unlock_page(page); | |
2611 | return ret; | |
2612 | } | |
2613 | EXPORT_SYMBOL(set_page_dirty_lock); | |
2614 | ||
11f81bec TH |
2615 | /* |
2616 | * This cancels just the dirty bit on the kernel page itself, it does NOT | |
2617 | * actually remove dirty bits on any mmap's that may be around. It also | |
2618 | * leaves the page tagged dirty, so any sync activity will still find it on | |
2619 | * the dirty lists, and in particular, clear_page_dirty_for_io() will still | |
2620 | * look at the dirty bits in the VM. | |
2621 | * | |
2622 | * Doing this should *normally* only ever be done when a page is truncated, | |
2623 | * and is not actually mapped anywhere at all. However, fs/buffer.c does | |
2624 | * this when it notices that somebody has cleaned out all the buffers on a | |
2625 | * page without actually doing it through the VM. Can you say "ext3 is | |
2626 | * horribly ugly"? Thought you could. | |
2627 | */ | |
2628 | void cancel_dirty_page(struct page *page) | |
2629 | { | |
c4843a75 GT |
2630 | struct address_space *mapping = page_mapping(page); |
2631 | ||
2632 | if (mapping_cap_account_dirty(mapping)) { | |
682aa8e1 TH |
2633 | struct inode *inode = mapping->host; |
2634 | struct bdi_writeback *wb; | |
682aa8e1 | 2635 | bool locked; |
c4843a75 | 2636 | |
62cccb8c | 2637 | lock_page_memcg(page); |
682aa8e1 | 2638 | wb = unlocked_inode_to_wb_begin(inode, &locked); |
c4843a75 GT |
2639 | |
2640 | if (TestClearPageDirty(page)) | |
62cccb8c | 2641 | account_page_cleaned(page, mapping, wb); |
c4843a75 | 2642 | |
682aa8e1 | 2643 | unlocked_inode_to_wb_end(inode, locked); |
62cccb8c | 2644 | unlock_page_memcg(page); |
c4843a75 GT |
2645 | } else { |
2646 | ClearPageDirty(page); | |
2647 | } | |
11f81bec TH |
2648 | } |
2649 | EXPORT_SYMBOL(cancel_dirty_page); | |
2650 | ||
1da177e4 LT |
2651 | /* |
2652 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
2653 | * Returns true if the page was previously dirty. | |
2654 | * | |
2655 | * This is for preparing to put the page under writeout. We leave the page | |
2656 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
2657 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
2658 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
2659 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
2660 | * back into sync. | |
2661 | * | |
2662 | * This incoherency between the page's dirty flag and radix-tree tag is | |
2663 | * unfortunate, but it only exists while the page is locked. | |
2664 | */ | |
2665 | int clear_page_dirty_for_io(struct page *page) | |
2666 | { | |
2667 | struct address_space *mapping = page_mapping(page); | |
c4843a75 | 2668 | int ret = 0; |
1da177e4 | 2669 | |
79352894 NP |
2670 | BUG_ON(!PageLocked(page)); |
2671 | ||
7658cc28 | 2672 | if (mapping && mapping_cap_account_dirty(mapping)) { |
682aa8e1 TH |
2673 | struct inode *inode = mapping->host; |
2674 | struct bdi_writeback *wb; | |
682aa8e1 TH |
2675 | bool locked; |
2676 | ||
7658cc28 LT |
2677 | /* |
2678 | * Yes, Virginia, this is indeed insane. | |
2679 | * | |
2680 | * We use this sequence to make sure that | |
2681 | * (a) we account for dirty stats properly | |
2682 | * (b) we tell the low-level filesystem to | |
2683 | * mark the whole page dirty if it was | |
2684 | * dirty in a pagetable. Only to then | |
2685 | * (c) clean the page again and return 1 to | |
2686 | * cause the writeback. | |
2687 | * | |
2688 | * This way we avoid all nasty races with the | |
2689 | * dirty bit in multiple places and clearing | |
2690 | * them concurrently from different threads. | |
2691 | * | |
2692 | * Note! Normally the "set_page_dirty(page)" | |
2693 | * has no effect on the actual dirty bit - since | |
2694 | * that will already usually be set. But we | |
2695 | * need the side effects, and it can help us | |
2696 | * avoid races. | |
2697 | * | |
2698 | * We basically use the page "master dirty bit" | |
2699 | * as a serialization point for all the different | |
2700 | * threads doing their things. | |
7658cc28 LT |
2701 | */ |
2702 | if (page_mkclean(page)) | |
2703 | set_page_dirty(page); | |
79352894 NP |
2704 | /* |
2705 | * We carefully synchronise fault handlers against | |
2706 | * installing a dirty pte and marking the page dirty | |
2d6d7f98 JW |
2707 | * at this point. We do this by having them hold the |
2708 | * page lock while dirtying the page, and pages are | |
2709 | * always locked coming in here, so we get the desired | |
2710 | * exclusion. | |
79352894 | 2711 | */ |
682aa8e1 | 2712 | wb = unlocked_inode_to_wb_begin(inode, &locked); |
7658cc28 | 2713 | if (TestClearPageDirty(page)) { |
62cccb8c | 2714 | mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY); |
8c08540f | 2715 | dec_zone_page_state(page, NR_FILE_DIRTY); |
682aa8e1 | 2716 | dec_wb_stat(wb, WB_RECLAIMABLE); |
c4843a75 | 2717 | ret = 1; |
1da177e4 | 2718 | } |
682aa8e1 | 2719 | unlocked_inode_to_wb_end(inode, locked); |
c4843a75 | 2720 | return ret; |
1da177e4 | 2721 | } |
7658cc28 | 2722 | return TestClearPageDirty(page); |
1da177e4 | 2723 | } |
58bb01a9 | 2724 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
2725 | |
2726 | int test_clear_page_writeback(struct page *page) | |
2727 | { | |
2728 | struct address_space *mapping = page_mapping(page); | |
d7365e78 | 2729 | int ret; |
1da177e4 | 2730 | |
62cccb8c | 2731 | lock_page_memcg(page); |
1da177e4 | 2732 | if (mapping) { |
91018134 TH |
2733 | struct inode *inode = mapping->host; |
2734 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2735 | unsigned long flags; |
2736 | ||
19fd6231 | 2737 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2738 | ret = TestClearPageWriteback(page); |
69cb51d1 | 2739 | if (ret) { |
1da177e4 LT |
2740 | radix_tree_tag_clear(&mapping->page_tree, |
2741 | page_index(page), | |
2742 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2743 | if (bdi_cap_account_writeback(bdi)) { |
91018134 TH |
2744 | struct bdi_writeback *wb = inode_to_wb(inode); |
2745 | ||
2746 | __dec_wb_stat(wb, WB_WRITEBACK); | |
2747 | __wb_writeout_inc(wb); | |
04fbfdc1 | 2748 | } |
69cb51d1 | 2749 | } |
6c60d2b5 DC |
2750 | |
2751 | if (mapping->host && !mapping_tagged(mapping, | |
2752 | PAGECACHE_TAG_WRITEBACK)) | |
2753 | sb_clear_inode_writeback(mapping->host); | |
2754 | ||
19fd6231 | 2755 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2756 | } else { |
2757 | ret = TestClearPageWriteback(page); | |
2758 | } | |
99b12e3d | 2759 | if (ret) { |
62cccb8c | 2760 | mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); |
d688abf5 | 2761 | dec_zone_page_state(page, NR_WRITEBACK); |
99b12e3d WF |
2762 | inc_zone_page_state(page, NR_WRITTEN); |
2763 | } | |
62cccb8c | 2764 | unlock_page_memcg(page); |
1da177e4 LT |
2765 | return ret; |
2766 | } | |
2767 | ||
1c8349a1 | 2768 | int __test_set_page_writeback(struct page *page, bool keep_write) |
1da177e4 LT |
2769 | { |
2770 | struct address_space *mapping = page_mapping(page); | |
d7365e78 | 2771 | int ret; |
1da177e4 | 2772 | |
62cccb8c | 2773 | lock_page_memcg(page); |
1da177e4 | 2774 | if (mapping) { |
91018134 TH |
2775 | struct inode *inode = mapping->host; |
2776 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2777 | unsigned long flags; |
2778 | ||
19fd6231 | 2779 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2780 | ret = TestSetPageWriteback(page); |
69cb51d1 | 2781 | if (!ret) { |
6c60d2b5 DC |
2782 | bool on_wblist; |
2783 | ||
2784 | on_wblist = mapping_tagged(mapping, | |
2785 | PAGECACHE_TAG_WRITEBACK); | |
2786 | ||
1da177e4 LT |
2787 | radix_tree_tag_set(&mapping->page_tree, |
2788 | page_index(page), | |
2789 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2790 | if (bdi_cap_account_writeback(bdi)) |
91018134 | 2791 | __inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK); |
6c60d2b5 DC |
2792 | |
2793 | /* | |
2794 | * We can come through here when swapping anonymous | |
2795 | * pages, so we don't necessarily have an inode to track | |
2796 | * for sync. | |
2797 | */ | |
2798 | if (mapping->host && !on_wblist) | |
2799 | sb_mark_inode_writeback(mapping->host); | |
69cb51d1 | 2800 | } |
1da177e4 LT |
2801 | if (!PageDirty(page)) |
2802 | radix_tree_tag_clear(&mapping->page_tree, | |
2803 | page_index(page), | |
2804 | PAGECACHE_TAG_DIRTY); | |
1c8349a1 NJ |
2805 | if (!keep_write) |
2806 | radix_tree_tag_clear(&mapping->page_tree, | |
2807 | page_index(page), | |
2808 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 2809 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2810 | } else { |
2811 | ret = TestSetPageWriteback(page); | |
2812 | } | |
3a3c02ec | 2813 | if (!ret) { |
62cccb8c | 2814 | mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); |
3a3c02ec JW |
2815 | inc_zone_page_state(page, NR_WRITEBACK); |
2816 | } | |
62cccb8c | 2817 | unlock_page_memcg(page); |
1da177e4 LT |
2818 | return ret; |
2819 | ||
2820 | } | |
1c8349a1 | 2821 | EXPORT_SYMBOL(__test_set_page_writeback); |
1da177e4 LT |
2822 | |
2823 | /* | |
00128188 | 2824 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
2825 | * passed tag. |
2826 | */ | |
2827 | int mapping_tagged(struct address_space *mapping, int tag) | |
2828 | { | |
72c47832 | 2829 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
2830 | } |
2831 | EXPORT_SYMBOL(mapping_tagged); | |
1d1d1a76 DW |
2832 | |
2833 | /** | |
2834 | * wait_for_stable_page() - wait for writeback to finish, if necessary. | |
2835 | * @page: The page to wait on. | |
2836 | * | |
2837 | * This function determines if the given page is related to a backing device | |
2838 | * that requires page contents to be held stable during writeback. If so, then | |
2839 | * it will wait for any pending writeback to complete. | |
2840 | */ | |
2841 | void wait_for_stable_page(struct page *page) | |
2842 | { | |
de1414a6 CH |
2843 | if (bdi_cap_stable_pages_required(inode_to_bdi(page->mapping->host))) |
2844 | wait_on_page_writeback(page); | |
1d1d1a76 DW |
2845 | } |
2846 | EXPORT_SYMBOL_GPL(wait_for_stable_page); |