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Commit | Line | Data |
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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 | 269 | /** |
281e3726 MG |
270 | * node_dirtyable_memory - number of dirtyable pages in a node |
271 | * @pgdat: the node | |
a804552b | 272 | * |
281e3726 MG |
273 | * Returns the node's number of pages potentially available for dirty |
274 | * page cache. This is the base value for the per-node dirty limits. | |
a804552b | 275 | */ |
281e3726 | 276 | static unsigned long node_dirtyable_memory(struct pglist_data *pgdat) |
a804552b | 277 | { |
281e3726 MG |
278 | unsigned long nr_pages = 0; |
279 | int z; | |
280 | ||
281 | for (z = 0; z < MAX_NR_ZONES; z++) { | |
282 | struct zone *zone = pgdat->node_zones + z; | |
283 | ||
284 | if (!populated_zone(zone)) | |
285 | continue; | |
286 | ||
287 | nr_pages += zone_page_state(zone, NR_FREE_PAGES); | |
288 | } | |
a804552b | 289 | |
a8d01437 JW |
290 | /* |
291 | * Pages reserved for the kernel should not be considered | |
292 | * dirtyable, to prevent a situation where reclaim has to | |
293 | * clean pages in order to balance the zones. | |
294 | */ | |
281e3726 | 295 | nr_pages -= min(nr_pages, pgdat->totalreserve_pages); |
a804552b | 296 | |
281e3726 MG |
297 | nr_pages += node_page_state(pgdat, NR_INACTIVE_FILE); |
298 | nr_pages += node_page_state(pgdat, NR_ACTIVE_FILE); | |
a804552b JW |
299 | |
300 | return nr_pages; | |
301 | } | |
bca67592 MG |
302 | #ifdef CONFIG_HIGHMEM |
303 | atomic_t highmem_file_pages; | |
304 | #endif | |
a804552b | 305 | |
1edf2234 JW |
306 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
307 | { | |
308 | #ifdef CONFIG_HIGHMEM | |
309 | int node; | |
9cb937e2 | 310 | unsigned long x; |
09b4ab3c | 311 | int i; |
9cb937e2 | 312 | unsigned long dirtyable = 0; |
1edf2234 JW |
313 | |
314 | for_each_node_state(node, N_HIGH_MEMORY) { | |
281e3726 MG |
315 | for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { |
316 | struct zone *z; | |
9cb937e2 | 317 | unsigned long nr_pages; |
281e3726 MG |
318 | |
319 | if (!is_highmem_idx(i)) | |
320 | continue; | |
321 | ||
322 | z = &NODE_DATA(node)->node_zones[i]; | |
9cb937e2 MK |
323 | if (!populated_zone(z)) |
324 | continue; | |
1edf2234 | 325 | |
9cb937e2 | 326 | nr_pages = zone_page_state(z, NR_FREE_PAGES); |
281e3726 | 327 | /* watch for underflows */ |
9cb937e2 MK |
328 | nr_pages -= min(nr_pages, high_wmark_pages(z)); |
329 | dirtyable += nr_pages; | |
09b4ab3c | 330 | } |
1edf2234 | 331 | } |
281e3726 | 332 | |
9cb937e2 MK |
333 | x = dirtyable + atomic_read(&highmem_file_pages); |
334 | ||
c8b74c2f SR |
335 | /* |
336 | * Unreclaimable memory (kernel memory or anonymous memory | |
337 | * without swap) can bring down the dirtyable pages below | |
338 | * the zone's dirty balance reserve and the above calculation | |
339 | * will underflow. However we still want to add in nodes | |
340 | * which are below threshold (negative values) to get a more | |
341 | * accurate calculation but make sure that the total never | |
342 | * underflows. | |
343 | */ | |
344 | if ((long)x < 0) | |
345 | x = 0; | |
346 | ||
1edf2234 JW |
347 | /* |
348 | * Make sure that the number of highmem pages is never larger | |
349 | * than the number of the total dirtyable memory. This can only | |
350 | * occur in very strange VM situations but we want to make sure | |
351 | * that this does not occur. | |
352 | */ | |
353 | return min(x, total); | |
354 | #else | |
355 | return 0; | |
356 | #endif | |
357 | } | |
358 | ||
359 | /** | |
ccafa287 | 360 | * global_dirtyable_memory - number of globally dirtyable pages |
1edf2234 | 361 | * |
ccafa287 JW |
362 | * Returns the global number of pages potentially available for dirty |
363 | * page cache. This is the base value for the global dirty limits. | |
1edf2234 | 364 | */ |
18cf8cf8 | 365 | static unsigned long global_dirtyable_memory(void) |
1edf2234 JW |
366 | { |
367 | unsigned long x; | |
368 | ||
a804552b | 369 | x = global_page_state(NR_FREE_PAGES); |
a8d01437 JW |
370 | /* |
371 | * Pages reserved for the kernel should not be considered | |
372 | * dirtyable, to prevent a situation where reclaim has to | |
373 | * clean pages in order to balance the zones. | |
374 | */ | |
375 | x -= min(x, totalreserve_pages); | |
1edf2234 | 376 | |
599d0c95 MG |
377 | x += global_node_page_state(NR_INACTIVE_FILE); |
378 | x += global_node_page_state(NR_ACTIVE_FILE); | |
a804552b | 379 | |
1edf2234 JW |
380 | if (!vm_highmem_is_dirtyable) |
381 | x -= highmem_dirtyable_memory(x); | |
382 | ||
383 | return x + 1; /* Ensure that we never return 0 */ | |
384 | } | |
385 | ||
9fc3a43e TH |
386 | /** |
387 | * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain | |
388 | * @dtc: dirty_throttle_control of interest | |
ccafa287 | 389 | * |
9fc3a43e TH |
390 | * Calculate @dtc->thresh and ->bg_thresh considering |
391 | * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller | |
392 | * must ensure that @dtc->avail is set before calling this function. The | |
393 | * dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ccafa287 JW |
394 | * real-time tasks. |
395 | */ | |
9fc3a43e | 396 | static void domain_dirty_limits(struct dirty_throttle_control *dtc) |
ccafa287 | 397 | { |
9fc3a43e TH |
398 | const unsigned long available_memory = dtc->avail; |
399 | struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); | |
400 | unsigned long bytes = vm_dirty_bytes; | |
401 | unsigned long bg_bytes = dirty_background_bytes; | |
62a584fe TH |
402 | /* convert ratios to per-PAGE_SIZE for higher precision */ |
403 | unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100; | |
404 | unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100; | |
9fc3a43e TH |
405 | unsigned long thresh; |
406 | unsigned long bg_thresh; | |
ccafa287 JW |
407 | struct task_struct *tsk; |
408 | ||
9fc3a43e TH |
409 | /* gdtc is !NULL iff @dtc is for memcg domain */ |
410 | if (gdtc) { | |
411 | unsigned long global_avail = gdtc->avail; | |
412 | ||
413 | /* | |
414 | * The byte settings can't be applied directly to memcg | |
415 | * domains. Convert them to ratios by scaling against | |
62a584fe TH |
416 | * globally available memory. As the ratios are in |
417 | * per-PAGE_SIZE, they can be obtained by dividing bytes by | |
418 | * number of pages. | |
9fc3a43e TH |
419 | */ |
420 | if (bytes) | |
62a584fe TH |
421 | ratio = min(DIV_ROUND_UP(bytes, global_avail), |
422 | PAGE_SIZE); | |
9fc3a43e | 423 | if (bg_bytes) |
62a584fe TH |
424 | bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail), |
425 | PAGE_SIZE); | |
9fc3a43e TH |
426 | bytes = bg_bytes = 0; |
427 | } | |
428 | ||
429 | if (bytes) | |
430 | thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); | |
ccafa287 | 431 | else |
62a584fe | 432 | thresh = (ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 433 | |
9fc3a43e TH |
434 | if (bg_bytes) |
435 | bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); | |
ccafa287 | 436 | else |
62a584fe | 437 | bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 438 | |
9fc3a43e TH |
439 | if (bg_thresh >= thresh) |
440 | bg_thresh = thresh / 2; | |
ccafa287 JW |
441 | tsk = current; |
442 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
a53eaff8 N |
443 | bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; |
444 | thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; | |
ccafa287 | 445 | } |
9fc3a43e TH |
446 | dtc->thresh = thresh; |
447 | dtc->bg_thresh = bg_thresh; | |
448 | ||
449 | /* we should eventually report the domain in the TP */ | |
450 | if (!gdtc) | |
451 | trace_global_dirty_state(bg_thresh, thresh); | |
452 | } | |
453 | ||
454 | /** | |
455 | * global_dirty_limits - background-writeback and dirty-throttling thresholds | |
456 | * @pbackground: out parameter for bg_thresh | |
457 | * @pdirty: out parameter for thresh | |
458 | * | |
459 | * Calculate bg_thresh and thresh for global_wb_domain. See | |
460 | * domain_dirty_limits() for details. | |
461 | */ | |
462 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) | |
463 | { | |
464 | struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; | |
465 | ||
466 | gdtc.avail = global_dirtyable_memory(); | |
467 | domain_dirty_limits(&gdtc); | |
468 | ||
469 | *pbackground = gdtc.bg_thresh; | |
470 | *pdirty = gdtc.thresh; | |
ccafa287 JW |
471 | } |
472 | ||
a756cf59 | 473 | /** |
281e3726 MG |
474 | * node_dirty_limit - maximum number of dirty pages allowed in a node |
475 | * @pgdat: the node | |
a756cf59 | 476 | * |
281e3726 MG |
477 | * Returns the maximum number of dirty pages allowed in a node, based |
478 | * on the node's dirtyable memory. | |
a756cf59 | 479 | */ |
281e3726 | 480 | static unsigned long node_dirty_limit(struct pglist_data *pgdat) |
a756cf59 | 481 | { |
281e3726 | 482 | unsigned long node_memory = node_dirtyable_memory(pgdat); |
a756cf59 JW |
483 | struct task_struct *tsk = current; |
484 | unsigned long dirty; | |
485 | ||
486 | if (vm_dirty_bytes) | |
487 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * | |
281e3726 | 488 | node_memory / global_dirtyable_memory(); |
a756cf59 | 489 | else |
281e3726 | 490 | dirty = vm_dirty_ratio * node_memory / 100; |
a756cf59 JW |
491 | |
492 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) | |
493 | dirty += dirty / 4; | |
494 | ||
495 | return dirty; | |
496 | } | |
497 | ||
498 | /** | |
281e3726 MG |
499 | * node_dirty_ok - tells whether a node is within its dirty limits |
500 | * @pgdat: the node to check | |
a756cf59 | 501 | * |
281e3726 | 502 | * Returns %true when the dirty pages in @pgdat are within the node's |
a756cf59 JW |
503 | * dirty limit, %false if the limit is exceeded. |
504 | */ | |
281e3726 | 505 | bool node_dirty_ok(struct pglist_data *pgdat) |
a756cf59 | 506 | { |
281e3726 MG |
507 | unsigned long limit = node_dirty_limit(pgdat); |
508 | unsigned long nr_pages = 0; | |
509 | ||
11fb9989 MG |
510 | nr_pages += node_page_state(pgdat, NR_FILE_DIRTY); |
511 | nr_pages += node_page_state(pgdat, NR_UNSTABLE_NFS); | |
512 | nr_pages += node_page_state(pgdat, NR_WRITEBACK); | |
a756cf59 | 513 | |
281e3726 | 514 | return nr_pages <= limit; |
a756cf59 JW |
515 | } |
516 | ||
2da02997 | 517 | int dirty_background_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 518 | void __user *buffer, size_t *lenp, |
2da02997 DR |
519 | loff_t *ppos) |
520 | { | |
521 | int ret; | |
522 | ||
8d65af78 | 523 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
524 | if (ret == 0 && write) |
525 | dirty_background_bytes = 0; | |
526 | return ret; | |
527 | } | |
528 | ||
529 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 530 | void __user *buffer, size_t *lenp, |
2da02997 DR |
531 | loff_t *ppos) |
532 | { | |
533 | int ret; | |
534 | ||
8d65af78 | 535 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
536 | if (ret == 0 && write) |
537 | dirty_background_ratio = 0; | |
538 | return ret; | |
539 | } | |
540 | ||
04fbfdc1 | 541 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 542 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
543 | loff_t *ppos) |
544 | { | |
545 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
546 | int ret; |
547 | ||
8d65af78 | 548 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 549 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
eb608e3a | 550 | writeback_set_ratelimit(); |
2da02997 DR |
551 | vm_dirty_bytes = 0; |
552 | } | |
553 | return ret; | |
554 | } | |
555 | ||
2da02997 | 556 | int dirty_bytes_handler(struct ctl_table *table, int write, |
8d65af78 | 557 | void __user *buffer, size_t *lenp, |
2da02997 DR |
558 | loff_t *ppos) |
559 | { | |
fc3501d4 | 560 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
561 | int ret; |
562 | ||
8d65af78 | 563 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 | 564 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
eb608e3a | 565 | writeback_set_ratelimit(); |
2da02997 | 566 | vm_dirty_ratio = 0; |
04fbfdc1 PZ |
567 | } |
568 | return ret; | |
569 | } | |
570 | ||
eb608e3a JK |
571 | static unsigned long wp_next_time(unsigned long cur_time) |
572 | { | |
573 | cur_time += VM_COMPLETIONS_PERIOD_LEN; | |
574 | /* 0 has a special meaning... */ | |
575 | if (!cur_time) | |
576 | return 1; | |
577 | return cur_time; | |
578 | } | |
579 | ||
c7981433 TH |
580 | static void wb_domain_writeout_inc(struct wb_domain *dom, |
581 | struct fprop_local_percpu *completions, | |
582 | unsigned int max_prop_frac) | |
04fbfdc1 | 583 | { |
c7981433 TH |
584 | __fprop_inc_percpu_max(&dom->completions, completions, |
585 | max_prop_frac); | |
eb608e3a | 586 | /* First event after period switching was turned off? */ |
380c27ca | 587 | if (!unlikely(dom->period_time)) { |
eb608e3a JK |
588 | /* |
589 | * We can race with other __bdi_writeout_inc calls here but | |
590 | * it does not cause any harm since the resulting time when | |
591 | * timer will fire and what is in writeout_period_time will be | |
592 | * roughly the same. | |
593 | */ | |
380c27ca TH |
594 | dom->period_time = wp_next_time(jiffies); |
595 | mod_timer(&dom->period_timer, dom->period_time); | |
eb608e3a | 596 | } |
04fbfdc1 PZ |
597 | } |
598 | ||
c7981433 TH |
599 | /* |
600 | * Increment @wb's writeout completion count and the global writeout | |
601 | * completion count. Called from test_clear_page_writeback(). | |
602 | */ | |
603 | static inline void __wb_writeout_inc(struct bdi_writeback *wb) | |
dd5656e5 | 604 | { |
841710aa | 605 | struct wb_domain *cgdom; |
dd5656e5 | 606 | |
c7981433 TH |
607 | __inc_wb_stat(wb, WB_WRITTEN); |
608 | wb_domain_writeout_inc(&global_wb_domain, &wb->completions, | |
609 | wb->bdi->max_prop_frac); | |
841710aa TH |
610 | |
611 | cgdom = mem_cgroup_wb_domain(wb); | |
612 | if (cgdom) | |
613 | wb_domain_writeout_inc(cgdom, wb_memcg_completions(wb), | |
614 | wb->bdi->max_prop_frac); | |
dd5656e5 | 615 | } |
dd5656e5 | 616 | |
93f78d88 | 617 | void wb_writeout_inc(struct bdi_writeback *wb) |
04fbfdc1 | 618 | { |
dd5656e5 MS |
619 | unsigned long flags; |
620 | ||
621 | local_irq_save(flags); | |
93f78d88 | 622 | __wb_writeout_inc(wb); |
dd5656e5 | 623 | local_irq_restore(flags); |
04fbfdc1 | 624 | } |
93f78d88 | 625 | EXPORT_SYMBOL_GPL(wb_writeout_inc); |
04fbfdc1 | 626 | |
eb608e3a JK |
627 | /* |
628 | * On idle system, we can be called long after we scheduled because we use | |
629 | * deferred timers so count with missed periods. | |
630 | */ | |
631 | static void writeout_period(unsigned long t) | |
632 | { | |
380c27ca TH |
633 | struct wb_domain *dom = (void *)t; |
634 | int miss_periods = (jiffies - dom->period_time) / | |
eb608e3a JK |
635 | VM_COMPLETIONS_PERIOD_LEN; |
636 | ||
380c27ca TH |
637 | if (fprop_new_period(&dom->completions, miss_periods + 1)) { |
638 | dom->period_time = wp_next_time(dom->period_time + | |
eb608e3a | 639 | miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
380c27ca | 640 | mod_timer(&dom->period_timer, dom->period_time); |
eb608e3a JK |
641 | } else { |
642 | /* | |
643 | * Aging has zeroed all fractions. Stop wasting CPU on period | |
644 | * updates. | |
645 | */ | |
380c27ca | 646 | dom->period_time = 0; |
eb608e3a JK |
647 | } |
648 | } | |
649 | ||
380c27ca TH |
650 | int wb_domain_init(struct wb_domain *dom, gfp_t gfp) |
651 | { | |
652 | memset(dom, 0, sizeof(*dom)); | |
dcc25ae7 TH |
653 | |
654 | spin_lock_init(&dom->lock); | |
655 | ||
380c27ca TH |
656 | init_timer_deferrable(&dom->period_timer); |
657 | dom->period_timer.function = writeout_period; | |
658 | dom->period_timer.data = (unsigned long)dom; | |
dcc25ae7 TH |
659 | |
660 | dom->dirty_limit_tstamp = jiffies; | |
661 | ||
380c27ca TH |
662 | return fprop_global_init(&dom->completions, gfp); |
663 | } | |
664 | ||
841710aa TH |
665 | #ifdef CONFIG_CGROUP_WRITEBACK |
666 | void wb_domain_exit(struct wb_domain *dom) | |
667 | { | |
668 | del_timer_sync(&dom->period_timer); | |
669 | fprop_global_destroy(&dom->completions); | |
670 | } | |
671 | #endif | |
672 | ||
189d3c4a | 673 | /* |
d08c429b JW |
674 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
675 | * registered backing devices, which, for obvious reasons, can not | |
676 | * exceed 100%. | |
189d3c4a | 677 | */ |
189d3c4a PZ |
678 | static unsigned int bdi_min_ratio; |
679 | ||
680 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
681 | { | |
682 | int ret = 0; | |
189d3c4a | 683 | |
cfc4ba53 | 684 | spin_lock_bh(&bdi_lock); |
a42dde04 | 685 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 686 | ret = -EINVAL; |
a42dde04 PZ |
687 | } else { |
688 | min_ratio -= bdi->min_ratio; | |
689 | if (bdi_min_ratio + min_ratio < 100) { | |
690 | bdi_min_ratio += min_ratio; | |
691 | bdi->min_ratio += min_ratio; | |
692 | } else { | |
693 | ret = -EINVAL; | |
694 | } | |
695 | } | |
cfc4ba53 | 696 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
697 | |
698 | return ret; | |
699 | } | |
700 | ||
701 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
702 | { | |
a42dde04 PZ |
703 | int ret = 0; |
704 | ||
705 | if (max_ratio > 100) | |
706 | return -EINVAL; | |
707 | ||
cfc4ba53 | 708 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
709 | if (bdi->min_ratio > max_ratio) { |
710 | ret = -EINVAL; | |
711 | } else { | |
712 | bdi->max_ratio = max_ratio; | |
eb608e3a | 713 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
a42dde04 | 714 | } |
cfc4ba53 | 715 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
716 | |
717 | return ret; | |
718 | } | |
a42dde04 | 719 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 720 | |
6c14ae1e WF |
721 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
722 | unsigned long bg_thresh) | |
723 | { | |
724 | return (thresh + bg_thresh) / 2; | |
725 | } | |
726 | ||
c7981433 TH |
727 | static unsigned long hard_dirty_limit(struct wb_domain *dom, |
728 | unsigned long thresh) | |
ffd1f609 | 729 | { |
dcc25ae7 | 730 | return max(thresh, dom->dirty_limit); |
ffd1f609 WF |
731 | } |
732 | ||
c5edf9cd TH |
733 | /* |
734 | * Memory which can be further allocated to a memcg domain is capped by | |
735 | * system-wide clean memory excluding the amount being used in the domain. | |
736 | */ | |
737 | static void mdtc_calc_avail(struct dirty_throttle_control *mdtc, | |
738 | unsigned long filepages, unsigned long headroom) | |
c2aa723a TH |
739 | { |
740 | struct dirty_throttle_control *gdtc = mdtc_gdtc(mdtc); | |
c5edf9cd TH |
741 | unsigned long clean = filepages - min(filepages, mdtc->dirty); |
742 | unsigned long global_clean = gdtc->avail - min(gdtc->avail, gdtc->dirty); | |
743 | unsigned long other_clean = global_clean - min(global_clean, clean); | |
c2aa723a | 744 | |
c5edf9cd | 745 | mdtc->avail = filepages + min(headroom, other_clean); |
ffd1f609 WF |
746 | } |
747 | ||
6f718656 | 748 | /** |
b1cbc6d4 TH |
749 | * __wb_calc_thresh - @wb's share of dirty throttling threshold |
750 | * @dtc: dirty_throttle_context of interest | |
1babe183 | 751 | * |
a88a341a | 752 | * Returns @wb's dirty limit in pages. The term "dirty" in the context of |
6f718656 | 753 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. |
aed21ad2 WF |
754 | * |
755 | * Note that balance_dirty_pages() will only seriously take it as a hard limit | |
756 | * when sleeping max_pause per page is not enough to keep the dirty pages under | |
757 | * control. For example, when the device is completely stalled due to some error | |
758 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. | |
759 | * In the other normal situations, it acts more gently by throttling the tasks | |
a88a341a | 760 | * more (rather than completely block them) when the wb dirty pages go high. |
1babe183 | 761 | * |
6f718656 | 762 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
763 | * - starving fast devices |
764 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
765 | * | |
a88a341a | 766 | * The wb's share of dirty limit will be adapting to its throughput and |
1babe183 WF |
767 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
768 | */ | |
b1cbc6d4 | 769 | static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) |
16c4042f | 770 | { |
e9f07dfd | 771 | struct wb_domain *dom = dtc_dom(dtc); |
b1cbc6d4 | 772 | unsigned long thresh = dtc->thresh; |
0d960a38 | 773 | u64 wb_thresh; |
16c4042f | 774 | long numerator, denominator; |
693108a8 | 775 | unsigned long wb_min_ratio, wb_max_ratio; |
04fbfdc1 | 776 | |
16c4042f | 777 | /* |
0d960a38 | 778 | * Calculate this BDI's share of the thresh ratio. |
16c4042f | 779 | */ |
e9770b34 | 780 | fprop_fraction_percpu(&dom->completions, dtc->wb_completions, |
380c27ca | 781 | &numerator, &denominator); |
04fbfdc1 | 782 | |
0d960a38 TH |
783 | wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; |
784 | wb_thresh *= numerator; | |
785 | do_div(wb_thresh, denominator); | |
04fbfdc1 | 786 | |
b1cbc6d4 | 787 | wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); |
04fbfdc1 | 788 | |
0d960a38 TH |
789 | wb_thresh += (thresh * wb_min_ratio) / 100; |
790 | if (wb_thresh > (thresh * wb_max_ratio) / 100) | |
791 | wb_thresh = thresh * wb_max_ratio / 100; | |
16c4042f | 792 | |
0d960a38 | 793 | return wb_thresh; |
1da177e4 LT |
794 | } |
795 | ||
b1cbc6d4 TH |
796 | unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) |
797 | { | |
798 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb), | |
799 | .thresh = thresh }; | |
800 | return __wb_calc_thresh(&gdtc); | |
1da177e4 LT |
801 | } |
802 | ||
5a537485 MP |
803 | /* |
804 | * setpoint - dirty 3 | |
805 | * f(dirty) := 1.0 + (----------------) | |
806 | * limit - setpoint | |
807 | * | |
808 | * it's a 3rd order polynomial that subjects to | |
809 | * | |
810 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
811 | * (2) f(setpoint) = 1.0 => the balance point | |
812 | * (3) f(limit) = 0 => the hard limit | |
813 | * (4) df/dx <= 0 => negative feedback control | |
814 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
815 | * => fast response on large errors; small oscillation near setpoint | |
816 | */ | |
d5c9fde3 | 817 | static long long pos_ratio_polynom(unsigned long setpoint, |
5a537485 MP |
818 | unsigned long dirty, |
819 | unsigned long limit) | |
820 | { | |
821 | long long pos_ratio; | |
822 | long x; | |
823 | ||
d5c9fde3 | 824 | x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, |
464d1387 | 825 | (limit - setpoint) | 1); |
5a537485 MP |
826 | pos_ratio = x; |
827 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
828 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
829 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
830 | ||
831 | return clamp(pos_ratio, 0LL, 2LL << RATELIMIT_CALC_SHIFT); | |
832 | } | |
833 | ||
6c14ae1e WF |
834 | /* |
835 | * Dirty position control. | |
836 | * | |
837 | * (o) global/bdi setpoints | |
838 | * | |
de1fff37 | 839 | * We want the dirty pages be balanced around the global/wb setpoints. |
6c14ae1e WF |
840 | * When the number of dirty pages is higher/lower than the setpoint, the |
841 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
842 | * decreased/increased to bring the dirty pages back to the setpoint. | |
843 | * | |
844 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
845 | * | |
846 | * if (dirty < setpoint) scale up pos_ratio | |
847 | * if (dirty > setpoint) scale down pos_ratio | |
848 | * | |
de1fff37 TH |
849 | * if (wb_dirty < wb_setpoint) scale up pos_ratio |
850 | * if (wb_dirty > wb_setpoint) scale down pos_ratio | |
6c14ae1e WF |
851 | * |
852 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
853 | * | |
854 | * (o) global control line | |
855 | * | |
856 | * ^ pos_ratio | |
857 | * | | |
858 | * | |<===== global dirty control scope ======>| | |
859 | * 2.0 .............* | |
860 | * | .* | |
861 | * | . * | |
862 | * | . * | |
863 | * | . * | |
864 | * | . * | |
865 | * | . * | |
866 | * 1.0 ................................* | |
867 | * | . . * | |
868 | * | . . * | |
869 | * | . . * | |
870 | * | . . * | |
871 | * | . . * | |
872 | * 0 +------------.------------------.----------------------*-------------> | |
873 | * freerun^ setpoint^ limit^ dirty pages | |
874 | * | |
de1fff37 | 875 | * (o) wb control line |
6c14ae1e WF |
876 | * |
877 | * ^ pos_ratio | |
878 | * | | |
879 | * | * | |
880 | * | * | |
881 | * | * | |
882 | * | * | |
883 | * | * |<=========== span ============>| | |
884 | * 1.0 .......................* | |
885 | * | . * | |
886 | * | . * | |
887 | * | . * | |
888 | * | . * | |
889 | * | . * | |
890 | * | . * | |
891 | * | . * | |
892 | * | . * | |
893 | * | . * | |
894 | * | . * | |
895 | * | . * | |
896 | * 1/4 ...............................................* * * * * * * * * * * * | |
897 | * | . . | |
898 | * | . . | |
899 | * | . . | |
900 | * 0 +----------------------.-------------------------------.-------------> | |
de1fff37 | 901 | * wb_setpoint^ x_intercept^ |
6c14ae1e | 902 | * |
de1fff37 | 903 | * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can |
6c14ae1e WF |
904 | * be smoothly throttled down to normal if it starts high in situations like |
905 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
de1fff37 TH |
906 | * card's wb_dirty may rush to many times higher than wb_setpoint. |
907 | * - the wb dirty thresh drops quickly due to change of JBOD workload | |
6c14ae1e | 908 | */ |
daddfa3c | 909 | static void wb_position_ratio(struct dirty_throttle_control *dtc) |
6c14ae1e | 910 | { |
2bc00aef | 911 | struct bdi_writeback *wb = dtc->wb; |
a88a341a | 912 | unsigned long write_bw = wb->avg_write_bandwidth; |
2bc00aef | 913 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
c7981433 | 914 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
2bc00aef | 915 | unsigned long wb_thresh = dtc->wb_thresh; |
6c14ae1e WF |
916 | unsigned long x_intercept; |
917 | unsigned long setpoint; /* dirty pages' target balance point */ | |
de1fff37 | 918 | unsigned long wb_setpoint; |
6c14ae1e WF |
919 | unsigned long span; |
920 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
921 | long x; | |
922 | ||
daddfa3c TH |
923 | dtc->pos_ratio = 0; |
924 | ||
2bc00aef | 925 | if (unlikely(dtc->dirty >= limit)) |
daddfa3c | 926 | return; |
6c14ae1e WF |
927 | |
928 | /* | |
929 | * global setpoint | |
930 | * | |
5a537485 MP |
931 | * See comment for pos_ratio_polynom(). |
932 | */ | |
933 | setpoint = (freerun + limit) / 2; | |
2bc00aef | 934 | pos_ratio = pos_ratio_polynom(setpoint, dtc->dirty, limit); |
5a537485 MP |
935 | |
936 | /* | |
937 | * The strictlimit feature is a tool preventing mistrusted filesystems | |
938 | * from growing a large number of dirty pages before throttling. For | |
de1fff37 TH |
939 | * such filesystems balance_dirty_pages always checks wb counters |
940 | * against wb limits. Even if global "nr_dirty" is under "freerun". | |
5a537485 MP |
941 | * This is especially important for fuse which sets bdi->max_ratio to |
942 | * 1% by default. Without strictlimit feature, fuse writeback may | |
943 | * consume arbitrary amount of RAM because it is accounted in | |
944 | * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". | |
6c14ae1e | 945 | * |
a88a341a | 946 | * Here, in wb_position_ratio(), we calculate pos_ratio based on |
de1fff37 | 947 | * two values: wb_dirty and wb_thresh. Let's consider an example: |
5a537485 MP |
948 | * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global |
949 | * limits are set by default to 10% and 20% (background and throttle). | |
de1fff37 | 950 | * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. |
0d960a38 | 951 | * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is |
de1fff37 | 952 | * about ~6K pages (as the average of background and throttle wb |
5a537485 | 953 | * limits). The 3rd order polynomial will provide positive feedback if |
de1fff37 | 954 | * wb_dirty is under wb_setpoint and vice versa. |
6c14ae1e | 955 | * |
5a537485 | 956 | * Note, that we cannot use global counters in these calculations |
de1fff37 | 957 | * because we want to throttle process writing to a strictlimit wb |
5a537485 MP |
958 | * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB |
959 | * in the example above). | |
6c14ae1e | 960 | */ |
a88a341a | 961 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
de1fff37 | 962 | long long wb_pos_ratio; |
5a537485 | 963 | |
daddfa3c TH |
964 | if (dtc->wb_dirty < 8) { |
965 | dtc->pos_ratio = min_t(long long, pos_ratio * 2, | |
966 | 2 << RATELIMIT_CALC_SHIFT); | |
967 | return; | |
968 | } | |
5a537485 | 969 | |
2bc00aef | 970 | if (dtc->wb_dirty >= wb_thresh) |
daddfa3c | 971 | return; |
5a537485 | 972 | |
970fb01a TH |
973 | wb_setpoint = dirty_freerun_ceiling(wb_thresh, |
974 | dtc->wb_bg_thresh); | |
5a537485 | 975 | |
de1fff37 | 976 | if (wb_setpoint == 0 || wb_setpoint == wb_thresh) |
daddfa3c | 977 | return; |
5a537485 | 978 | |
2bc00aef | 979 | wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, |
de1fff37 | 980 | wb_thresh); |
5a537485 MP |
981 | |
982 | /* | |
de1fff37 TH |
983 | * Typically, for strictlimit case, wb_setpoint << setpoint |
984 | * and pos_ratio >> wb_pos_ratio. In the other words global | |
5a537485 | 985 | * state ("dirty") is not limiting factor and we have to |
de1fff37 | 986 | * make decision based on wb counters. But there is an |
5a537485 MP |
987 | * important case when global pos_ratio should get precedence: |
988 | * global limits are exceeded (e.g. due to activities on other | |
de1fff37 | 989 | * wb's) while given strictlimit wb is below limit. |
5a537485 | 990 | * |
de1fff37 | 991 | * "pos_ratio * wb_pos_ratio" would work for the case above, |
5a537485 | 992 | * but it would look too non-natural for the case of all |
de1fff37 | 993 | * activity in the system coming from a single strictlimit wb |
5a537485 MP |
994 | * with bdi->max_ratio == 100%. |
995 | * | |
996 | * Note that min() below somewhat changes the dynamics of the | |
997 | * control system. Normally, pos_ratio value can be well over 3 | |
de1fff37 | 998 | * (when globally we are at freerun and wb is well below wb |
5a537485 MP |
999 | * setpoint). Now the maximum pos_ratio in the same situation |
1000 | * is 2. We might want to tweak this if we observe the control | |
1001 | * system is too slow to adapt. | |
1002 | */ | |
daddfa3c TH |
1003 | dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); |
1004 | return; | |
5a537485 | 1005 | } |
6c14ae1e WF |
1006 | |
1007 | /* | |
1008 | * We have computed basic pos_ratio above based on global situation. If | |
de1fff37 | 1009 | * the wb is over/under its share of dirty pages, we want to scale |
6c14ae1e WF |
1010 | * pos_ratio further down/up. That is done by the following mechanism. |
1011 | */ | |
1012 | ||
1013 | /* | |
de1fff37 | 1014 | * wb setpoint |
6c14ae1e | 1015 | * |
de1fff37 | 1016 | * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) |
6c14ae1e | 1017 | * |
de1fff37 | 1018 | * x_intercept - wb_dirty |
6c14ae1e | 1019 | * := -------------------------- |
de1fff37 | 1020 | * x_intercept - wb_setpoint |
6c14ae1e | 1021 | * |
de1fff37 | 1022 | * The main wb control line is a linear function that subjects to |
6c14ae1e | 1023 | * |
de1fff37 TH |
1024 | * (1) f(wb_setpoint) = 1.0 |
1025 | * (2) k = - 1 / (8 * write_bw) (in single wb case) | |
1026 | * or equally: x_intercept = wb_setpoint + 8 * write_bw | |
6c14ae1e | 1027 | * |
de1fff37 | 1028 | * For single wb case, the dirty pages are observed to fluctuate |
6c14ae1e | 1029 | * regularly within range |
de1fff37 | 1030 | * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] |
6c14ae1e WF |
1031 | * for various filesystems, where (2) can yield in a reasonable 12.5% |
1032 | * fluctuation range for pos_ratio. | |
1033 | * | |
de1fff37 | 1034 | * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its |
6c14ae1e | 1035 | * own size, so move the slope over accordingly and choose a slope that |
de1fff37 | 1036 | * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. |
6c14ae1e | 1037 | */ |
2bc00aef TH |
1038 | if (unlikely(wb_thresh > dtc->thresh)) |
1039 | wb_thresh = dtc->thresh; | |
aed21ad2 | 1040 | /* |
de1fff37 | 1041 | * It's very possible that wb_thresh is close to 0 not because the |
aed21ad2 WF |
1042 | * device is slow, but that it has remained inactive for long time. |
1043 | * Honour such devices a reasonable good (hopefully IO efficient) | |
1044 | * threshold, so that the occasional writes won't be blocked and active | |
1045 | * writes can rampup the threshold quickly. | |
1046 | */ | |
2bc00aef | 1047 | wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8); |
6c14ae1e | 1048 | /* |
de1fff37 TH |
1049 | * scale global setpoint to wb's: |
1050 | * wb_setpoint = setpoint * wb_thresh / thresh | |
6c14ae1e | 1051 | */ |
e4bc13ad | 1052 | x = div_u64((u64)wb_thresh << 16, dtc->thresh | 1); |
de1fff37 | 1053 | wb_setpoint = setpoint * (u64)x >> 16; |
6c14ae1e | 1054 | /* |
de1fff37 TH |
1055 | * Use span=(8*write_bw) in single wb case as indicated by |
1056 | * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. | |
6c14ae1e | 1057 | * |
de1fff37 TH |
1058 | * wb_thresh thresh - wb_thresh |
1059 | * span = --------- * (8 * write_bw) + ------------------ * wb_thresh | |
1060 | * thresh thresh | |
6c14ae1e | 1061 | */ |
2bc00aef | 1062 | span = (dtc->thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; |
de1fff37 | 1063 | x_intercept = wb_setpoint + span; |
6c14ae1e | 1064 | |
2bc00aef TH |
1065 | if (dtc->wb_dirty < x_intercept - span / 4) { |
1066 | pos_ratio = div64_u64(pos_ratio * (x_intercept - dtc->wb_dirty), | |
e4bc13ad | 1067 | (x_intercept - wb_setpoint) | 1); |
6c14ae1e WF |
1068 | } else |
1069 | pos_ratio /= 4; | |
1070 | ||
8927f66c | 1071 | /* |
de1fff37 | 1072 | * wb reserve area, safeguard against dirty pool underrun and disk idle |
8927f66c WF |
1073 | * It may push the desired control point of global dirty pages higher |
1074 | * than setpoint. | |
1075 | */ | |
de1fff37 | 1076 | x_intercept = wb_thresh / 2; |
2bc00aef TH |
1077 | if (dtc->wb_dirty < x_intercept) { |
1078 | if (dtc->wb_dirty > x_intercept / 8) | |
1079 | pos_ratio = div_u64(pos_ratio * x_intercept, | |
1080 | dtc->wb_dirty); | |
50657fc4 | 1081 | else |
8927f66c WF |
1082 | pos_ratio *= 8; |
1083 | } | |
1084 | ||
daddfa3c | 1085 | dtc->pos_ratio = pos_ratio; |
6c14ae1e WF |
1086 | } |
1087 | ||
a88a341a TH |
1088 | static void wb_update_write_bandwidth(struct bdi_writeback *wb, |
1089 | unsigned long elapsed, | |
1090 | unsigned long written) | |
e98be2d5 WF |
1091 | { |
1092 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
a88a341a TH |
1093 | unsigned long avg = wb->avg_write_bandwidth; |
1094 | unsigned long old = wb->write_bandwidth; | |
e98be2d5 WF |
1095 | u64 bw; |
1096 | ||
1097 | /* | |
1098 | * bw = written * HZ / elapsed | |
1099 | * | |
1100 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
1101 | * write_bandwidth = --------------------------------------------------- | |
1102 | * period | |
c72efb65 TH |
1103 | * |
1104 | * @written may have decreased due to account_page_redirty(). | |
1105 | * Avoid underflowing @bw calculation. | |
e98be2d5 | 1106 | */ |
a88a341a | 1107 | bw = written - min(written, wb->written_stamp); |
e98be2d5 WF |
1108 | bw *= HZ; |
1109 | if (unlikely(elapsed > period)) { | |
1110 | do_div(bw, elapsed); | |
1111 | avg = bw; | |
1112 | goto out; | |
1113 | } | |
a88a341a | 1114 | bw += (u64)wb->write_bandwidth * (period - elapsed); |
e98be2d5 WF |
1115 | bw >>= ilog2(period); |
1116 | ||
1117 | /* | |
1118 | * one more level of smoothing, for filtering out sudden spikes | |
1119 | */ | |
1120 | if (avg > old && old >= (unsigned long)bw) | |
1121 | avg -= (avg - old) >> 3; | |
1122 | ||
1123 | if (avg < old && old <= (unsigned long)bw) | |
1124 | avg += (old - avg) >> 3; | |
1125 | ||
1126 | out: | |
95a46c65 TH |
1127 | /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ |
1128 | avg = max(avg, 1LU); | |
1129 | if (wb_has_dirty_io(wb)) { | |
1130 | long delta = avg - wb->avg_write_bandwidth; | |
1131 | WARN_ON_ONCE(atomic_long_add_return(delta, | |
1132 | &wb->bdi->tot_write_bandwidth) <= 0); | |
1133 | } | |
a88a341a TH |
1134 | wb->write_bandwidth = bw; |
1135 | wb->avg_write_bandwidth = avg; | |
e98be2d5 WF |
1136 | } |
1137 | ||
2bc00aef | 1138 | static void update_dirty_limit(struct dirty_throttle_control *dtc) |
c42843f2 | 1139 | { |
e9f07dfd | 1140 | struct wb_domain *dom = dtc_dom(dtc); |
2bc00aef | 1141 | unsigned long thresh = dtc->thresh; |
dcc25ae7 | 1142 | unsigned long limit = dom->dirty_limit; |
c42843f2 WF |
1143 | |
1144 | /* | |
1145 | * Follow up in one step. | |
1146 | */ | |
1147 | if (limit < thresh) { | |
1148 | limit = thresh; | |
1149 | goto update; | |
1150 | } | |
1151 | ||
1152 | /* | |
1153 | * Follow down slowly. Use the higher one as the target, because thresh | |
1154 | * may drop below dirty. This is exactly the reason to introduce | |
dcc25ae7 | 1155 | * dom->dirty_limit which is guaranteed to lie above the dirty pages. |
c42843f2 | 1156 | */ |
2bc00aef | 1157 | thresh = max(thresh, dtc->dirty); |
c42843f2 WF |
1158 | if (limit > thresh) { |
1159 | limit -= (limit - thresh) >> 5; | |
1160 | goto update; | |
1161 | } | |
1162 | return; | |
1163 | update: | |
dcc25ae7 | 1164 | dom->dirty_limit = limit; |
c42843f2 WF |
1165 | } |
1166 | ||
e9f07dfd | 1167 | static void domain_update_bandwidth(struct dirty_throttle_control *dtc, |
c42843f2 WF |
1168 | unsigned long now) |
1169 | { | |
e9f07dfd | 1170 | struct wb_domain *dom = dtc_dom(dtc); |
c42843f2 WF |
1171 | |
1172 | /* | |
1173 | * check locklessly first to optimize away locking for the most time | |
1174 | */ | |
dcc25ae7 | 1175 | if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) |
c42843f2 WF |
1176 | return; |
1177 | ||
dcc25ae7 TH |
1178 | spin_lock(&dom->lock); |
1179 | if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) { | |
2bc00aef | 1180 | update_dirty_limit(dtc); |
dcc25ae7 | 1181 | dom->dirty_limit_tstamp = now; |
c42843f2 | 1182 | } |
dcc25ae7 | 1183 | spin_unlock(&dom->lock); |
c42843f2 WF |
1184 | } |
1185 | ||
be3ffa27 | 1186 | /* |
de1fff37 | 1187 | * Maintain wb->dirty_ratelimit, the base dirty throttle rate. |
be3ffa27 | 1188 | * |
de1fff37 | 1189 | * Normal wb tasks will be curbed at or below it in long term. |
be3ffa27 WF |
1190 | * Obviously it should be around (write_bw / N) when there are N dd tasks. |
1191 | */ | |
2bc00aef | 1192 | static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, |
a88a341a TH |
1193 | unsigned long dirtied, |
1194 | unsigned long elapsed) | |
be3ffa27 | 1195 | { |
2bc00aef TH |
1196 | struct bdi_writeback *wb = dtc->wb; |
1197 | unsigned long dirty = dtc->dirty; | |
1198 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); | |
c7981433 | 1199 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
7381131c | 1200 | unsigned long setpoint = (freerun + limit) / 2; |
a88a341a TH |
1201 | unsigned long write_bw = wb->avg_write_bandwidth; |
1202 | unsigned long dirty_ratelimit = wb->dirty_ratelimit; | |
be3ffa27 WF |
1203 | unsigned long dirty_rate; |
1204 | unsigned long task_ratelimit; | |
1205 | unsigned long balanced_dirty_ratelimit; | |
7381131c WF |
1206 | unsigned long step; |
1207 | unsigned long x; | |
d59b1087 | 1208 | unsigned long shift; |
be3ffa27 WF |
1209 | |
1210 | /* | |
1211 | * The dirty rate will match the writeout rate in long term, except | |
1212 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
1213 | */ | |
a88a341a | 1214 | dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; |
be3ffa27 | 1215 | |
be3ffa27 WF |
1216 | /* |
1217 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
1218 | */ | |
1219 | task_ratelimit = (u64)dirty_ratelimit * | |
daddfa3c | 1220 | dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; |
be3ffa27 WF |
1221 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
1222 | ||
1223 | /* | |
1224 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
de1fff37 | 1225 | * if there are N dd tasks, each throttled at task_ratelimit, the wb's |
be3ffa27 WF |
1226 | * dirty_rate will be measured to be (N * task_ratelimit). So the below |
1227 | * formula will yield the balanced rate limit (write_bw / N). | |
1228 | * | |
1229 | * Note that the expanded form is not a pure rate feedback: | |
1230 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
1231 | * but also takes pos_ratio into account: | |
1232 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
1233 | * | |
1234 | * (1) is not realistic because pos_ratio also takes part in balancing | |
1235 | * the dirty rate. Consider the state | |
1236 | * pos_ratio = 0.5 (3) | |
1237 | * rate = 2 * (write_bw / N) (4) | |
1238 | * If (1) is used, it will stuck in that state! Because each dd will | |
1239 | * be throttled at | |
1240 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
1241 | * yielding | |
1242 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
1243 | * put (6) into (1) we get | |
1244 | * rate_(i+1) = rate_(i) (7) | |
1245 | * | |
1246 | * So we end up using (2) to always keep | |
1247 | * rate_(i+1) ~= (write_bw / N) (8) | |
1248 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
1249 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
1250 | * the dirty count meet the setpoint, but also where the slope of | |
1251 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
1252 | */ | |
1253 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
1254 | dirty_rate | 1); | |
bdaac490 WF |
1255 | /* |
1256 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw | |
1257 | */ | |
1258 | if (unlikely(balanced_dirty_ratelimit > write_bw)) | |
1259 | balanced_dirty_ratelimit = write_bw; | |
be3ffa27 | 1260 | |
7381131c WF |
1261 | /* |
1262 | * We could safely do this and return immediately: | |
1263 | * | |
de1fff37 | 1264 | * wb->dirty_ratelimit = balanced_dirty_ratelimit; |
7381131c WF |
1265 | * |
1266 | * However to get a more stable dirty_ratelimit, the below elaborated | |
331cbdee | 1267 | * code makes use of task_ratelimit to filter out singular points and |
7381131c WF |
1268 | * limit the step size. |
1269 | * | |
1270 | * The below code essentially only uses the relative value of | |
1271 | * | |
1272 | * task_ratelimit - dirty_ratelimit | |
1273 | * = (pos_ratio - 1) * dirty_ratelimit | |
1274 | * | |
1275 | * which reflects the direction and size of dirty position error. | |
1276 | */ | |
1277 | ||
1278 | /* | |
1279 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff | |
1280 | * task_ratelimit is on the same side of dirty_ratelimit, too. | |
1281 | * For example, when | |
1282 | * - dirty_ratelimit > balanced_dirty_ratelimit | |
1283 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) | |
1284 | * lowering dirty_ratelimit will help meet both the position and rate | |
1285 | * control targets. Otherwise, don't update dirty_ratelimit if it will | |
1286 | * only help meet the rate target. After all, what the users ultimately | |
1287 | * feel and care are stable dirty rate and small position error. | |
1288 | * | |
1289 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size | |
331cbdee | 1290 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
7381131c WF |
1291 | * keeps jumping around randomly and can even leap far away at times |
1292 | * due to the small 200ms estimation period of dirty_rate (we want to | |
1293 | * keep that period small to reduce time lags). | |
1294 | */ | |
1295 | step = 0; | |
5a537485 MP |
1296 | |
1297 | /* | |
de1fff37 | 1298 | * For strictlimit case, calculations above were based on wb counters |
a88a341a | 1299 | * and limits (starting from pos_ratio = wb_position_ratio() and up to |
5a537485 | 1300 | * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). |
de1fff37 TH |
1301 | * Hence, to calculate "step" properly, we have to use wb_dirty as |
1302 | * "dirty" and wb_setpoint as "setpoint". | |
5a537485 | 1303 | * |
de1fff37 TH |
1304 | * We rampup dirty_ratelimit forcibly if wb_dirty is low because |
1305 | * it's possible that wb_thresh is close to zero due to inactivity | |
970fb01a | 1306 | * of backing device. |
5a537485 | 1307 | */ |
a88a341a | 1308 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
2bc00aef TH |
1309 | dirty = dtc->wb_dirty; |
1310 | if (dtc->wb_dirty < 8) | |
1311 | setpoint = dtc->wb_dirty + 1; | |
5a537485 | 1312 | else |
970fb01a | 1313 | setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; |
5a537485 MP |
1314 | } |
1315 | ||
7381131c | 1316 | if (dirty < setpoint) { |
a88a341a | 1317 | x = min3(wb->balanced_dirty_ratelimit, |
7c809968 | 1318 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1319 | if (dirty_ratelimit < x) |
1320 | step = x - dirty_ratelimit; | |
1321 | } else { | |
a88a341a | 1322 | x = max3(wb->balanced_dirty_ratelimit, |
7c809968 | 1323 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1324 | if (dirty_ratelimit > x) |
1325 | step = dirty_ratelimit - x; | |
1326 | } | |
1327 | ||
1328 | /* | |
1329 | * Don't pursue 100% rate matching. It's impossible since the balanced | |
1330 | * rate itself is constantly fluctuating. So decrease the track speed | |
1331 | * when it gets close to the target. Helps eliminate pointless tremors. | |
1332 | */ | |
d59b1087 AR |
1333 | shift = dirty_ratelimit / (2 * step + 1); |
1334 | if (shift < BITS_PER_LONG) | |
1335 | step = DIV_ROUND_UP(step >> shift, 8); | |
1336 | else | |
1337 | step = 0; | |
7381131c WF |
1338 | |
1339 | if (dirty_ratelimit < balanced_dirty_ratelimit) | |
1340 | dirty_ratelimit += step; | |
1341 | else | |
1342 | dirty_ratelimit -= step; | |
1343 | ||
a88a341a TH |
1344 | wb->dirty_ratelimit = max(dirty_ratelimit, 1UL); |
1345 | wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit; | |
b48c104d | 1346 | |
5634cc2a | 1347 | trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit); |
be3ffa27 WF |
1348 | } |
1349 | ||
c2aa723a TH |
1350 | static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc, |
1351 | struct dirty_throttle_control *mdtc, | |
8a731799 TH |
1352 | unsigned long start_time, |
1353 | bool update_ratelimit) | |
e98be2d5 | 1354 | { |
c2aa723a | 1355 | struct bdi_writeback *wb = gdtc->wb; |
e98be2d5 | 1356 | unsigned long now = jiffies; |
a88a341a | 1357 | unsigned long elapsed = now - wb->bw_time_stamp; |
be3ffa27 | 1358 | unsigned long dirtied; |
e98be2d5 WF |
1359 | unsigned long written; |
1360 | ||
8a731799 TH |
1361 | lockdep_assert_held(&wb->list_lock); |
1362 | ||
e98be2d5 WF |
1363 | /* |
1364 | * rate-limit, only update once every 200ms. | |
1365 | */ | |
1366 | if (elapsed < BANDWIDTH_INTERVAL) | |
1367 | return; | |
1368 | ||
a88a341a TH |
1369 | dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]); |
1370 | written = percpu_counter_read(&wb->stat[WB_WRITTEN]); | |
e98be2d5 WF |
1371 | |
1372 | /* | |
1373 | * Skip quiet periods when disk bandwidth is under-utilized. | |
1374 | * (at least 1s idle time between two flusher runs) | |
1375 | */ | |
a88a341a | 1376 | if (elapsed > HZ && time_before(wb->bw_time_stamp, start_time)) |
e98be2d5 WF |
1377 | goto snapshot; |
1378 | ||
8a731799 | 1379 | if (update_ratelimit) { |
c2aa723a TH |
1380 | domain_update_bandwidth(gdtc, now); |
1381 | wb_update_dirty_ratelimit(gdtc, dirtied, elapsed); | |
1382 | ||
1383 | /* | |
1384 | * @mdtc is always NULL if !CGROUP_WRITEBACK but the | |
1385 | * compiler has no way to figure that out. Help it. | |
1386 | */ | |
1387 | if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { | |
1388 | domain_update_bandwidth(mdtc, now); | |
1389 | wb_update_dirty_ratelimit(mdtc, dirtied, elapsed); | |
1390 | } | |
be3ffa27 | 1391 | } |
a88a341a | 1392 | wb_update_write_bandwidth(wb, elapsed, written); |
e98be2d5 WF |
1393 | |
1394 | snapshot: | |
a88a341a TH |
1395 | wb->dirtied_stamp = dirtied; |
1396 | wb->written_stamp = written; | |
1397 | wb->bw_time_stamp = now; | |
e98be2d5 WF |
1398 | } |
1399 | ||
8a731799 | 1400 | void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time) |
e98be2d5 | 1401 | { |
2bc00aef TH |
1402 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb) }; |
1403 | ||
c2aa723a | 1404 | __wb_update_bandwidth(&gdtc, NULL, start_time, false); |
e98be2d5 WF |
1405 | } |
1406 | ||
9d823e8f | 1407 | /* |
d0e1d66b | 1408 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
9d823e8f WF |
1409 | * will look to see if it needs to start dirty throttling. |
1410 | * | |
1411 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive | |
1412 | * global_page_state() too often. So scale it near-sqrt to the safety margin | |
1413 | * (the number of pages we may dirty without exceeding the dirty limits). | |
1414 | */ | |
1415 | static unsigned long dirty_poll_interval(unsigned long dirty, | |
1416 | unsigned long thresh) | |
1417 | { | |
1418 | if (thresh > dirty) | |
1419 | return 1UL << (ilog2(thresh - dirty) >> 1); | |
1420 | ||
1421 | return 1; | |
1422 | } | |
1423 | ||
a88a341a | 1424 | static unsigned long wb_max_pause(struct bdi_writeback *wb, |
de1fff37 | 1425 | unsigned long wb_dirty) |
c8462cc9 | 1426 | { |
a88a341a | 1427 | unsigned long bw = wb->avg_write_bandwidth; |
e3b6c655 | 1428 | unsigned long t; |
c8462cc9 | 1429 | |
7ccb9ad5 WF |
1430 | /* |
1431 | * Limit pause time for small memory systems. If sleeping for too long | |
1432 | * time, a small pool of dirty/writeback pages may go empty and disk go | |
1433 | * idle. | |
1434 | * | |
1435 | * 8 serves as the safety ratio. | |
1436 | */ | |
de1fff37 | 1437 | t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
7ccb9ad5 WF |
1438 | t++; |
1439 | ||
e3b6c655 | 1440 | return min_t(unsigned long, t, MAX_PAUSE); |
7ccb9ad5 WF |
1441 | } |
1442 | ||
a88a341a TH |
1443 | static long wb_min_pause(struct bdi_writeback *wb, |
1444 | long max_pause, | |
1445 | unsigned long task_ratelimit, | |
1446 | unsigned long dirty_ratelimit, | |
1447 | int *nr_dirtied_pause) | |
c8462cc9 | 1448 | { |
a88a341a TH |
1449 | long hi = ilog2(wb->avg_write_bandwidth); |
1450 | long lo = ilog2(wb->dirty_ratelimit); | |
7ccb9ad5 WF |
1451 | long t; /* target pause */ |
1452 | long pause; /* estimated next pause */ | |
1453 | int pages; /* target nr_dirtied_pause */ | |
c8462cc9 | 1454 | |
7ccb9ad5 WF |
1455 | /* target for 10ms pause on 1-dd case */ |
1456 | t = max(1, HZ / 100); | |
c8462cc9 WF |
1457 | |
1458 | /* | |
1459 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
1460 | * overheads. | |
1461 | * | |
7ccb9ad5 | 1462 | * (N * 10ms) on 2^N concurrent tasks. |
c8462cc9 WF |
1463 | */ |
1464 | if (hi > lo) | |
7ccb9ad5 | 1465 | t += (hi - lo) * (10 * HZ) / 1024; |
c8462cc9 WF |
1466 | |
1467 | /* | |
7ccb9ad5 WF |
1468 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
1469 | * on the much more stable dirty_ratelimit. However the next pause time | |
1470 | * will be computed based on task_ratelimit and the two rate limits may | |
1471 | * depart considerably at some time. Especially if task_ratelimit goes | |
1472 | * below dirty_ratelimit/2 and the target pause is max_pause, the next | |
1473 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a | |
1474 | * result task_ratelimit won't be executed faithfully, which could | |
1475 | * eventually bring down dirty_ratelimit. | |
c8462cc9 | 1476 | * |
7ccb9ad5 WF |
1477 | * We apply two rules to fix it up: |
1478 | * 1) try to estimate the next pause time and if necessary, use a lower | |
1479 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, | |
1480 | * nr_dirtied_pause will be "dancing" with task_ratelimit. | |
1481 | * 2) limit the target pause time to max_pause/2, so that the normal | |
1482 | * small fluctuations of task_ratelimit won't trigger rule (1) and | |
1483 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. | |
c8462cc9 | 1484 | */ |
7ccb9ad5 WF |
1485 | t = min(t, 1 + max_pause / 2); |
1486 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
c8462cc9 WF |
1487 | |
1488 | /* | |
5b9b3574 WF |
1489 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
1490 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. | |
1491 | * When the 16 consecutive reads are often interrupted by some dirty | |
1492 | * throttling pause during the async writes, cfq will go into idles | |
1493 | * (deadline is fine). So push nr_dirtied_pause as high as possible | |
1494 | * until reaches DIRTY_POLL_THRESH=32 pages. | |
c8462cc9 | 1495 | */ |
5b9b3574 WF |
1496 | if (pages < DIRTY_POLL_THRESH) { |
1497 | t = max_pause; | |
1498 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
1499 | if (pages > DIRTY_POLL_THRESH) { | |
1500 | pages = DIRTY_POLL_THRESH; | |
1501 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; | |
1502 | } | |
1503 | } | |
1504 | ||
7ccb9ad5 WF |
1505 | pause = HZ * pages / (task_ratelimit + 1); |
1506 | if (pause > max_pause) { | |
1507 | t = max_pause; | |
1508 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); | |
1509 | } | |
c8462cc9 | 1510 | |
7ccb9ad5 | 1511 | *nr_dirtied_pause = pages; |
c8462cc9 | 1512 | /* |
7ccb9ad5 | 1513 | * The minimal pause time will normally be half the target pause time. |
c8462cc9 | 1514 | */ |
5b9b3574 | 1515 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
c8462cc9 WF |
1516 | } |
1517 | ||
970fb01a | 1518 | static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) |
5a537485 | 1519 | { |
2bc00aef | 1520 | struct bdi_writeback *wb = dtc->wb; |
93f78d88 | 1521 | unsigned long wb_reclaimable; |
5a537485 MP |
1522 | |
1523 | /* | |
de1fff37 | 1524 | * wb_thresh is not treated as some limiting factor as |
5a537485 | 1525 | * dirty_thresh, due to reasons |
de1fff37 | 1526 | * - in JBOD setup, wb_thresh can fluctuate a lot |
5a537485 | 1527 | * - in a system with HDD and USB key, the USB key may somehow |
de1fff37 TH |
1528 | * go into state (wb_dirty >> wb_thresh) either because |
1529 | * wb_dirty starts high, or because wb_thresh drops low. | |
5a537485 | 1530 | * In this case we don't want to hard throttle the USB key |
de1fff37 TH |
1531 | * dirtiers for 100 seconds until wb_dirty drops under |
1532 | * wb_thresh. Instead the auxiliary wb control line in | |
a88a341a | 1533 | * wb_position_ratio() will let the dirtier task progress |
de1fff37 | 1534 | * at some rate <= (write_bw / 2) for bringing down wb_dirty. |
5a537485 | 1535 | */ |
b1cbc6d4 | 1536 | dtc->wb_thresh = __wb_calc_thresh(dtc); |
970fb01a TH |
1537 | dtc->wb_bg_thresh = dtc->thresh ? |
1538 | div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; | |
5a537485 MP |
1539 | |
1540 | /* | |
1541 | * In order to avoid the stacked BDI deadlock we need | |
1542 | * to ensure we accurately count the 'dirty' pages when | |
1543 | * the threshold is low. | |
1544 | * | |
1545 | * Otherwise it would be possible to get thresh+n pages | |
1546 | * reported dirty, even though there are thresh-m pages | |
1547 | * actually dirty; with m+n sitting in the percpu | |
1548 | * deltas. | |
1549 | */ | |
2bc00aef | 1550 | if (dtc->wb_thresh < 2 * wb_stat_error(wb)) { |
93f78d88 | 1551 | wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
2bc00aef | 1552 | dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); |
5a537485 | 1553 | } else { |
93f78d88 | 1554 | wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
2bc00aef | 1555 | dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); |
5a537485 MP |
1556 | } |
1557 | } | |
1558 | ||
1da177e4 LT |
1559 | /* |
1560 | * balance_dirty_pages() must be called by processes which are generating dirty | |
1561 | * data. It looks at the number of dirty pages in the machine and will force | |
143dfe86 | 1562 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1563 | * If we're over `background_thresh' then the writeback threads are woken to |
1564 | * perform some writeout. | |
1da177e4 | 1565 | */ |
3a2e9a5a | 1566 | static void balance_dirty_pages(struct address_space *mapping, |
dfb8ae56 | 1567 | struct bdi_writeback *wb, |
143dfe86 | 1568 | unsigned long pages_dirtied) |
1da177e4 | 1569 | { |
2bc00aef | 1570 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1571 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
2bc00aef | 1572 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1573 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1574 | &mdtc_stor : NULL; | |
1575 | struct dirty_throttle_control *sdtc; | |
143dfe86 | 1576 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
83712358 | 1577 | long period; |
7ccb9ad5 WF |
1578 | long pause; |
1579 | long max_pause; | |
1580 | long min_pause; | |
1581 | int nr_dirtied_pause; | |
e50e3720 | 1582 | bool dirty_exceeded = false; |
143dfe86 | 1583 | unsigned long task_ratelimit; |
7ccb9ad5 | 1584 | unsigned long dirty_ratelimit; |
dfb8ae56 | 1585 | struct backing_dev_info *bdi = wb->bdi; |
5a537485 | 1586 | bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; |
e98be2d5 | 1587 | unsigned long start_time = jiffies; |
1da177e4 LT |
1588 | |
1589 | for (;;) { | |
83712358 | 1590 | unsigned long now = jiffies; |
2bc00aef | 1591 | unsigned long dirty, thresh, bg_thresh; |
50e55bf6 YS |
1592 | unsigned long m_dirty = 0; /* stop bogus uninit warnings */ |
1593 | unsigned long m_thresh = 0; | |
1594 | unsigned long m_bg_thresh = 0; | |
83712358 | 1595 | |
143dfe86 WF |
1596 | /* |
1597 | * Unstable writes are a feature of certain networked | |
1598 | * filesystems (i.e. NFS) in which data may have been | |
1599 | * written to the server's write cache, but has not yet | |
1600 | * been flushed to permanent storage. | |
1601 | */ | |
11fb9989 MG |
1602 | nr_reclaimable = global_node_page_state(NR_FILE_DIRTY) + |
1603 | global_node_page_state(NR_UNSTABLE_NFS); | |
9fc3a43e | 1604 | gdtc->avail = global_dirtyable_memory(); |
11fb9989 | 1605 | gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK); |
5fce25a9 | 1606 | |
9fc3a43e | 1607 | domain_dirty_limits(gdtc); |
16c4042f | 1608 | |
5a537485 | 1609 | if (unlikely(strictlimit)) { |
970fb01a | 1610 | wb_dirty_limits(gdtc); |
5a537485 | 1611 | |
2bc00aef TH |
1612 | dirty = gdtc->wb_dirty; |
1613 | thresh = gdtc->wb_thresh; | |
970fb01a | 1614 | bg_thresh = gdtc->wb_bg_thresh; |
5a537485 | 1615 | } else { |
2bc00aef TH |
1616 | dirty = gdtc->dirty; |
1617 | thresh = gdtc->thresh; | |
1618 | bg_thresh = gdtc->bg_thresh; | |
5a537485 MP |
1619 | } |
1620 | ||
c2aa723a | 1621 | if (mdtc) { |
c5edf9cd | 1622 | unsigned long filepages, headroom, writeback; |
c2aa723a TH |
1623 | |
1624 | /* | |
1625 | * If @wb belongs to !root memcg, repeat the same | |
1626 | * basic calculations for the memcg domain. | |
1627 | */ | |
c5edf9cd TH |
1628 | mem_cgroup_wb_stats(wb, &filepages, &headroom, |
1629 | &mdtc->dirty, &writeback); | |
c2aa723a | 1630 | mdtc->dirty += writeback; |
c5edf9cd | 1631 | mdtc_calc_avail(mdtc, filepages, headroom); |
c2aa723a TH |
1632 | |
1633 | domain_dirty_limits(mdtc); | |
1634 | ||
1635 | if (unlikely(strictlimit)) { | |
1636 | wb_dirty_limits(mdtc); | |
1637 | m_dirty = mdtc->wb_dirty; | |
1638 | m_thresh = mdtc->wb_thresh; | |
1639 | m_bg_thresh = mdtc->wb_bg_thresh; | |
1640 | } else { | |
1641 | m_dirty = mdtc->dirty; | |
1642 | m_thresh = mdtc->thresh; | |
1643 | m_bg_thresh = mdtc->bg_thresh; | |
1644 | } | |
5a537485 MP |
1645 | } |
1646 | ||
16c4042f WF |
1647 | /* |
1648 | * Throttle it only when the background writeback cannot | |
1649 | * catch-up. This avoids (excessively) small writeouts | |
de1fff37 | 1650 | * when the wb limits are ramping up in case of !strictlimit. |
5a537485 | 1651 | * |
de1fff37 TH |
1652 | * In strictlimit case make decision based on the wb counters |
1653 | * and limits. Small writeouts when the wb limits are ramping | |
5a537485 | 1654 | * up are the price we consciously pay for strictlimit-ing. |
c2aa723a TH |
1655 | * |
1656 | * If memcg domain is in effect, @dirty should be under | |
1657 | * both global and memcg freerun ceilings. | |
16c4042f | 1658 | */ |
c2aa723a TH |
1659 | if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) && |
1660 | (!mdtc || | |
1661 | m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) { | |
1662 | unsigned long intv = dirty_poll_interval(dirty, thresh); | |
1663 | unsigned long m_intv = ULONG_MAX; | |
1664 | ||
83712358 WF |
1665 | current->dirty_paused_when = now; |
1666 | current->nr_dirtied = 0; | |
c2aa723a TH |
1667 | if (mdtc) |
1668 | m_intv = dirty_poll_interval(m_dirty, m_thresh); | |
1669 | current->nr_dirtied_pause = min(intv, m_intv); | |
16c4042f | 1670 | break; |
83712358 | 1671 | } |
16c4042f | 1672 | |
bc05873d | 1673 | if (unlikely(!writeback_in_progress(wb))) |
9ecf4866 | 1674 | wb_start_background_writeback(wb); |
143dfe86 | 1675 | |
c2aa723a TH |
1676 | /* |
1677 | * Calculate global domain's pos_ratio and select the | |
1678 | * global dtc by default. | |
1679 | */ | |
5a537485 | 1680 | if (!strictlimit) |
970fb01a | 1681 | wb_dirty_limits(gdtc); |
5fce25a9 | 1682 | |
2bc00aef TH |
1683 | dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && |
1684 | ((gdtc->dirty > gdtc->thresh) || strictlimit); | |
daddfa3c TH |
1685 | |
1686 | wb_position_ratio(gdtc); | |
c2aa723a TH |
1687 | sdtc = gdtc; |
1688 | ||
1689 | if (mdtc) { | |
1690 | /* | |
1691 | * If memcg domain is in effect, calculate its | |
1692 | * pos_ratio. @wb should satisfy constraints from | |
1693 | * both global and memcg domains. Choose the one | |
1694 | * w/ lower pos_ratio. | |
1695 | */ | |
1696 | if (!strictlimit) | |
1697 | wb_dirty_limits(mdtc); | |
1698 | ||
1699 | dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) && | |
1700 | ((mdtc->dirty > mdtc->thresh) || strictlimit); | |
1701 | ||
1702 | wb_position_ratio(mdtc); | |
1703 | if (mdtc->pos_ratio < gdtc->pos_ratio) | |
1704 | sdtc = mdtc; | |
1705 | } | |
daddfa3c | 1706 | |
a88a341a TH |
1707 | if (dirty_exceeded && !wb->dirty_exceeded) |
1708 | wb->dirty_exceeded = 1; | |
1da177e4 | 1709 | |
8a731799 TH |
1710 | if (time_is_before_jiffies(wb->bw_time_stamp + |
1711 | BANDWIDTH_INTERVAL)) { | |
1712 | spin_lock(&wb->list_lock); | |
c2aa723a | 1713 | __wb_update_bandwidth(gdtc, mdtc, start_time, true); |
8a731799 TH |
1714 | spin_unlock(&wb->list_lock); |
1715 | } | |
e98be2d5 | 1716 | |
c2aa723a | 1717 | /* throttle according to the chosen dtc */ |
a88a341a | 1718 | dirty_ratelimit = wb->dirty_ratelimit; |
c2aa723a | 1719 | task_ratelimit = ((u64)dirty_ratelimit * sdtc->pos_ratio) >> |
3a73dbbc | 1720 | RATELIMIT_CALC_SHIFT; |
c2aa723a | 1721 | max_pause = wb_max_pause(wb, sdtc->wb_dirty); |
a88a341a TH |
1722 | min_pause = wb_min_pause(wb, max_pause, |
1723 | task_ratelimit, dirty_ratelimit, | |
1724 | &nr_dirtied_pause); | |
7ccb9ad5 | 1725 | |
3a73dbbc | 1726 | if (unlikely(task_ratelimit == 0)) { |
83712358 | 1727 | period = max_pause; |
c8462cc9 | 1728 | pause = max_pause; |
143dfe86 | 1729 | goto pause; |
04fbfdc1 | 1730 | } |
83712358 WF |
1731 | period = HZ * pages_dirtied / task_ratelimit; |
1732 | pause = period; | |
1733 | if (current->dirty_paused_when) | |
1734 | pause -= now - current->dirty_paused_when; | |
1735 | /* | |
1736 | * For less than 1s think time (ext3/4 may block the dirtier | |
1737 | * for up to 800ms from time to time on 1-HDD; so does xfs, | |
1738 | * however at much less frequency), try to compensate it in | |
1739 | * future periods by updating the virtual time; otherwise just | |
1740 | * do a reset, as it may be a light dirtier. | |
1741 | */ | |
7ccb9ad5 | 1742 | if (pause < min_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, |
7ccb9ad5 | 1753 | min(pause, 0L), |
ece13ac3 | 1754 | start_time); |
83712358 WF |
1755 | if (pause < -HZ) { |
1756 | current->dirty_paused_when = now; | |
1757 | current->nr_dirtied = 0; | |
1758 | } else if (period) { | |
1759 | current->dirty_paused_when += period; | |
1760 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1761 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
1762 | current->nr_dirtied_pause += pages_dirtied; | |
57fc978c | 1763 | break; |
04fbfdc1 | 1764 | } |
7ccb9ad5 WF |
1765 | if (unlikely(pause > max_pause)) { |
1766 | /* for occasional dropped task_ratelimit */ | |
1767 | now += min(pause - max_pause, max_pause); | |
1768 | pause = max_pause; | |
1769 | } | |
143dfe86 WF |
1770 | |
1771 | pause: | |
5634cc2a | 1772 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1773 | sdtc->thresh, |
1774 | sdtc->bg_thresh, | |
1775 | sdtc->dirty, | |
1776 | sdtc->wb_thresh, | |
1777 | sdtc->wb_dirty, | |
ece13ac3 WF |
1778 | dirty_ratelimit, |
1779 | task_ratelimit, | |
1780 | pages_dirtied, | |
83712358 | 1781 | period, |
ece13ac3 WF |
1782 | pause, |
1783 | start_time); | |
499d05ec | 1784 | __set_current_state(TASK_KILLABLE); |
d25105e8 | 1785 | io_schedule_timeout(pause); |
87c6a9b2 | 1786 | |
83712358 WF |
1787 | current->dirty_paused_when = now + pause; |
1788 | current->nr_dirtied = 0; | |
7ccb9ad5 | 1789 | current->nr_dirtied_pause = nr_dirtied_pause; |
83712358 | 1790 | |
ffd1f609 | 1791 | /* |
2bc00aef TH |
1792 | * This is typically equal to (dirty < thresh) and can also |
1793 | * keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1794 | */ |
1df64719 | 1795 | if (task_ratelimit) |
ffd1f609 | 1796 | break; |
499d05ec | 1797 | |
c5c6343c WF |
1798 | /* |
1799 | * In the case of an unresponding NFS server and the NFS dirty | |
de1fff37 | 1800 | * pages exceeds dirty_thresh, give the other good wb's a pipe |
c5c6343c WF |
1801 | * to go through, so that tasks on them still remain responsive. |
1802 | * | |
1803 | * In theory 1 page is enough to keep the comsumer-producer | |
1804 | * pipe going: the flusher cleans 1 page => the task dirties 1 | |
de1fff37 | 1805 | * more page. However wb_dirty has accounting errors. So use |
93f78d88 | 1806 | * the larger and more IO friendly wb_stat_error. |
c5c6343c | 1807 | */ |
c2aa723a | 1808 | if (sdtc->wb_dirty <= wb_stat_error(wb)) |
c5c6343c WF |
1809 | break; |
1810 | ||
499d05ec JK |
1811 | if (fatal_signal_pending(current)) |
1812 | break; | |
1da177e4 LT |
1813 | } |
1814 | ||
a88a341a TH |
1815 | if (!dirty_exceeded && wb->dirty_exceeded) |
1816 | wb->dirty_exceeded = 0; | |
1da177e4 | 1817 | |
bc05873d | 1818 | if (writeback_in_progress(wb)) |
5b0830cb | 1819 | return; |
1da177e4 LT |
1820 | |
1821 | /* | |
1822 | * In laptop mode, we wait until hitting the higher threshold before | |
1823 | * starting background writeout, and then write out all the way down | |
1824 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1825 | * | |
1826 | * In normal mode, we start background writeout at the lower | |
1827 | * background_thresh, to keep the amount of dirty memory low. | |
1828 | */ | |
143dfe86 WF |
1829 | if (laptop_mode) |
1830 | return; | |
1831 | ||
2bc00aef | 1832 | if (nr_reclaimable > gdtc->bg_thresh) |
9ecf4866 | 1833 | wb_start_background_writeback(wb); |
1da177e4 LT |
1834 | } |
1835 | ||
9d823e8f | 1836 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1837 | |
54848d73 WF |
1838 | /* |
1839 | * Normal tasks are throttled by | |
1840 | * loop { | |
1841 | * dirty tsk->nr_dirtied_pause pages; | |
1842 | * take a snap in balance_dirty_pages(); | |
1843 | * } | |
1844 | * However there is a worst case. If every task exit immediately when dirtied | |
1845 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be | |
1846 | * called to throttle the page dirties. The solution is to save the not yet | |
1847 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them | |
1848 | * randomly into the running tasks. This works well for the above worst case, | |
1849 | * as the new task will pick up and accumulate the old task's leaked dirty | |
1850 | * count and eventually get throttled. | |
1851 | */ | |
1852 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1853 | ||
1da177e4 | 1854 | /** |
d0e1d66b | 1855 | * balance_dirty_pages_ratelimited - balance dirty memory state |
67be2dd1 | 1856 | * @mapping: address_space which was dirtied |
1da177e4 LT |
1857 | * |
1858 | * Processes which are dirtying memory should call in here once for each page | |
1859 | * which was newly dirtied. The function will periodically check the system's | |
1860 | * dirty state and will initiate writeback if needed. | |
1861 | * | |
1862 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
1863 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
1864 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
1865 | * from overshooting the limit by (ratelimit_pages) each. | |
1866 | */ | |
d0e1d66b | 1867 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
1da177e4 | 1868 | { |
dfb8ae56 TH |
1869 | struct inode *inode = mapping->host; |
1870 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1871 | struct bdi_writeback *wb = NULL; | |
9d823e8f WF |
1872 | int ratelimit; |
1873 | int *p; | |
1da177e4 | 1874 | |
36715cef WF |
1875 | if (!bdi_cap_account_dirty(bdi)) |
1876 | return; | |
1877 | ||
dfb8ae56 TH |
1878 | if (inode_cgwb_enabled(inode)) |
1879 | wb = wb_get_create_current(bdi, GFP_KERNEL); | |
1880 | if (!wb) | |
1881 | wb = &bdi->wb; | |
1882 | ||
9d823e8f | 1883 | ratelimit = current->nr_dirtied_pause; |
a88a341a | 1884 | if (wb->dirty_exceeded) |
9d823e8f WF |
1885 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
1886 | ||
9d823e8f | 1887 | preempt_disable(); |
1da177e4 | 1888 | /* |
9d823e8f WF |
1889 | * This prevents one CPU to accumulate too many dirtied pages without |
1890 | * calling into balance_dirty_pages(), which can happen when there are | |
1891 | * 1000+ tasks, all of them start dirtying pages at exactly the same | |
1892 | * time, hence all honoured too large initial task->nr_dirtied_pause. | |
1da177e4 | 1893 | */ |
7c8e0181 | 1894 | p = this_cpu_ptr(&bdp_ratelimits); |
9d823e8f | 1895 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1896 | *p = 0; |
d3bc1fef WF |
1897 | else if (unlikely(*p >= ratelimit_pages)) { |
1898 | *p = 0; | |
1899 | ratelimit = 0; | |
1da177e4 | 1900 | } |
54848d73 WF |
1901 | /* |
1902 | * Pick up the dirtied pages by the exited tasks. This avoids lots of | |
1903 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping | |
1904 | * the dirty throttling and livelock other long-run dirtiers. | |
1905 | */ | |
7c8e0181 | 1906 | p = this_cpu_ptr(&dirty_throttle_leaks); |
54848d73 | 1907 | if (*p > 0 && current->nr_dirtied < ratelimit) { |
d0e1d66b | 1908 | unsigned long nr_pages_dirtied; |
54848d73 WF |
1909 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
1910 | *p -= nr_pages_dirtied; | |
1911 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1912 | } |
fa5a734e | 1913 | preempt_enable(); |
9d823e8f WF |
1914 | |
1915 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
dfb8ae56 TH |
1916 | balance_dirty_pages(mapping, wb, current->nr_dirtied); |
1917 | ||
1918 | wb_put(wb); | |
1da177e4 | 1919 | } |
d0e1d66b | 1920 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
1da177e4 | 1921 | |
aa661bbe TH |
1922 | /** |
1923 | * wb_over_bg_thresh - does @wb need to be written back? | |
1924 | * @wb: bdi_writeback of interest | |
1925 | * | |
1926 | * Determines whether background writeback should keep writing @wb or it's | |
1927 | * clean enough. Returns %true if writeback should continue. | |
1928 | */ | |
1929 | bool wb_over_bg_thresh(struct bdi_writeback *wb) | |
1930 | { | |
947e9762 | 1931 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1932 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
947e9762 | 1933 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1934 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1935 | &mdtc_stor : NULL; | |
aa661bbe | 1936 | |
947e9762 TH |
1937 | /* |
1938 | * Similar to balance_dirty_pages() but ignores pages being written | |
1939 | * as we're trying to decide whether to put more under writeback. | |
1940 | */ | |
1941 | gdtc->avail = global_dirtyable_memory(); | |
11fb9989 MG |
1942 | gdtc->dirty = global_node_page_state(NR_FILE_DIRTY) + |
1943 | global_node_page_state(NR_UNSTABLE_NFS); | |
947e9762 | 1944 | domain_dirty_limits(gdtc); |
aa661bbe | 1945 | |
947e9762 | 1946 | if (gdtc->dirty > gdtc->bg_thresh) |
aa661bbe TH |
1947 | return true; |
1948 | ||
74d36944 HC |
1949 | if (wb_stat(wb, WB_RECLAIMABLE) > |
1950 | wb_calc_thresh(gdtc->wb, gdtc->bg_thresh)) | |
aa661bbe TH |
1951 | return true; |
1952 | ||
c2aa723a | 1953 | if (mdtc) { |
c5edf9cd | 1954 | unsigned long filepages, headroom, writeback; |
c2aa723a | 1955 | |
c5edf9cd TH |
1956 | mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, |
1957 | &writeback); | |
1958 | mdtc_calc_avail(mdtc, filepages, headroom); | |
c2aa723a TH |
1959 | domain_dirty_limits(mdtc); /* ditto, ignore writeback */ |
1960 | ||
1961 | if (mdtc->dirty > mdtc->bg_thresh) | |
1962 | return true; | |
1963 | ||
74d36944 HC |
1964 | if (wb_stat(wb, WB_RECLAIMABLE) > |
1965 | wb_calc_thresh(mdtc->wb, mdtc->bg_thresh)) | |
c2aa723a TH |
1966 | return true; |
1967 | } | |
1968 | ||
aa661bbe TH |
1969 | return false; |
1970 | } | |
1971 | ||
232ea4d6 | 1972 | void throttle_vm_writeout(gfp_t gfp_mask) |
1da177e4 | 1973 | { |
364aeb28 DR |
1974 | unsigned long background_thresh; |
1975 | unsigned long dirty_thresh; | |
1da177e4 LT |
1976 | |
1977 | for ( ; ; ) { | |
16c4042f | 1978 | global_dirty_limits(&background_thresh, &dirty_thresh); |
c7981433 | 1979 | dirty_thresh = hard_dirty_limit(&global_wb_domain, dirty_thresh); |
1da177e4 LT |
1980 | |
1981 | /* | |
1982 | * Boost the allowable dirty threshold a bit for page | |
1983 | * allocators so they don't get DoS'ed by heavy writers | |
1984 | */ | |
1985 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
1986 | ||
11fb9989 MG |
1987 | if (global_node_page_state(NR_UNSTABLE_NFS) + |
1988 | global_node_page_state(NR_WRITEBACK) <= dirty_thresh) | |
c24f21bd | 1989 | break; |
8aa7e847 | 1990 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
369f2389 FW |
1991 | |
1992 | /* | |
1993 | * The caller might hold locks which can prevent IO completion | |
1994 | * or progress in the filesystem. So we cannot just sit here | |
1995 | * waiting for IO to complete. | |
1996 | */ | |
1997 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) | |
1998 | break; | |
1da177e4 LT |
1999 | } |
2000 | } | |
2001 | ||
1da177e4 LT |
2002 | /* |
2003 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
2004 | */ | |
cccad5b9 | 2005 | int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, |
8d65af78 | 2006 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 2007 | { |
8d65af78 | 2008 | proc_dointvec(table, write, buffer, length, ppos); |
1da177e4 LT |
2009 | return 0; |
2010 | } | |
2011 | ||
c2c4986e | 2012 | #ifdef CONFIG_BLOCK |
31373d09 | 2013 | void laptop_mode_timer_fn(unsigned long data) |
1da177e4 | 2014 | { |
31373d09 | 2015 | struct request_queue *q = (struct request_queue *)data; |
11fb9989 MG |
2016 | int nr_pages = global_node_page_state(NR_FILE_DIRTY) + |
2017 | global_node_page_state(NR_UNSTABLE_NFS); | |
a06fd6b1 | 2018 | struct bdi_writeback *wb; |
1da177e4 | 2019 | |
31373d09 MG |
2020 | /* |
2021 | * We want to write everything out, not just down to the dirty | |
2022 | * threshold | |
2023 | */ | |
a06fd6b1 TH |
2024 | if (!bdi_has_dirty_io(&q->backing_dev_info)) |
2025 | return; | |
2026 | ||
9ad18ab9 | 2027 | rcu_read_lock(); |
b817525a | 2028 | list_for_each_entry_rcu(wb, &q->backing_dev_info.wb_list, bdi_node) |
a06fd6b1 TH |
2029 | if (wb_has_dirty_io(wb)) |
2030 | wb_start_writeback(wb, nr_pages, true, | |
2031 | WB_REASON_LAPTOP_TIMER); | |
9ad18ab9 | 2032 | rcu_read_unlock(); |
1da177e4 LT |
2033 | } |
2034 | ||
2035 | /* | |
2036 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
2037 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
2038 | * then push it back - the user is still using the disk. | |
2039 | */ | |
31373d09 | 2040 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 2041 | { |
31373d09 | 2042 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
2043 | } |
2044 | ||
2045 | /* | |
2046 | * We're in laptop mode and we've just synced. The sync's writes will have | |
2047 | * caused another writeback to be scheduled by laptop_io_completion. | |
2048 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
2049 | */ | |
2050 | void laptop_sync_completion(void) | |
2051 | { | |
31373d09 MG |
2052 | struct backing_dev_info *bdi; |
2053 | ||
2054 | rcu_read_lock(); | |
2055 | ||
2056 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
2057 | del_timer(&bdi->laptop_mode_wb_timer); | |
2058 | ||
2059 | rcu_read_unlock(); | |
1da177e4 | 2060 | } |
c2c4986e | 2061 | #endif |
1da177e4 LT |
2062 | |
2063 | /* | |
2064 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
2065 | * if a large number of processes all perform writes at the same time. | |
2066 | * If it is too low then SMP machines will call the (expensive) | |
2067 | * get_writeback_state too often. | |
2068 | * | |
2069 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
2070 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
9d823e8f | 2071 | * thresholds. |
1da177e4 LT |
2072 | */ |
2073 | ||
2d1d43f6 | 2074 | void writeback_set_ratelimit(void) |
1da177e4 | 2075 | { |
dcc25ae7 | 2076 | struct wb_domain *dom = &global_wb_domain; |
9d823e8f WF |
2077 | unsigned long background_thresh; |
2078 | unsigned long dirty_thresh; | |
dcc25ae7 | 2079 | |
9d823e8f | 2080 | global_dirty_limits(&background_thresh, &dirty_thresh); |
dcc25ae7 | 2081 | dom->dirty_limit = dirty_thresh; |
9d823e8f | 2082 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
1da177e4 LT |
2083 | if (ratelimit_pages < 16) |
2084 | ratelimit_pages = 16; | |
1da177e4 LT |
2085 | } |
2086 | ||
0db0628d | 2087 | static int |
2f60d628 SB |
2088 | ratelimit_handler(struct notifier_block *self, unsigned long action, |
2089 | void *hcpu) | |
1da177e4 | 2090 | { |
2f60d628 SB |
2091 | |
2092 | switch (action & ~CPU_TASKS_FROZEN) { | |
2093 | case CPU_ONLINE: | |
2094 | case CPU_DEAD: | |
2095 | writeback_set_ratelimit(); | |
2096 | return NOTIFY_OK; | |
2097 | default: | |
2098 | return NOTIFY_DONE; | |
2099 | } | |
1da177e4 LT |
2100 | } |
2101 | ||
0db0628d | 2102 | static struct notifier_block ratelimit_nb = { |
1da177e4 LT |
2103 | .notifier_call = ratelimit_handler, |
2104 | .next = NULL, | |
2105 | }; | |
2106 | ||
2107 | /* | |
dc6e29da LT |
2108 | * Called early on to tune the page writeback dirty limits. |
2109 | * | |
2110 | * We used to scale dirty pages according to how total memory | |
2111 | * related to pages that could be allocated for buffers (by | |
2112 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
2113 | * | |
2114 | * However, that was when we used "dirty_ratio" to scale with | |
2115 | * all memory, and we don't do that any more. "dirty_ratio" | |
2116 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
2117 | * totalhigh_pages from vm_total_pages), and as such we can't | |
2118 | * get into the old insane situation any more where we had | |
2119 | * large amounts of dirty pages compared to a small amount of | |
2120 | * non-HIGHMEM memory. | |
2121 | * | |
2122 | * But we might still want to scale the dirty_ratio by how | |
2123 | * much memory the box has.. | |
1da177e4 LT |
2124 | */ |
2125 | void __init page_writeback_init(void) | |
2126 | { | |
a50fcb51 RV |
2127 | BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL)); |
2128 | ||
2d1d43f6 | 2129 | writeback_set_ratelimit(); |
1da177e4 LT |
2130 | register_cpu_notifier(&ratelimit_nb); |
2131 | } | |
2132 | ||
f446daae JK |
2133 | /** |
2134 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
2135 | * @mapping: address space structure to write | |
2136 | * @start: starting page index | |
2137 | * @end: ending page index (inclusive) | |
2138 | * | |
2139 | * This function scans the page range from @start to @end (inclusive) and tags | |
2140 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
2141 | * that write_cache_pages (or whoever calls this function) will then use | |
2142 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
2143 | * used to avoid livelocking of writeback by a process steadily creating new | |
2144 | * dirty pages in the file (thus it is important for this function to be quick | |
2145 | * so that it can tag pages faster than a dirtying process can create them). | |
2146 | */ | |
2147 | /* | |
2148 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. | |
2149 | */ | |
f446daae JK |
2150 | void tag_pages_for_writeback(struct address_space *mapping, |
2151 | pgoff_t start, pgoff_t end) | |
2152 | { | |
3c111a07 | 2153 | #define WRITEBACK_TAG_BATCH 4096 |
f446daae JK |
2154 | unsigned long tagged; |
2155 | ||
2156 | do { | |
2157 | spin_lock_irq(&mapping->tree_lock); | |
2158 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, | |
2159 | &start, end, WRITEBACK_TAG_BATCH, | |
2160 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); | |
2161 | spin_unlock_irq(&mapping->tree_lock); | |
2162 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); | |
2163 | cond_resched(); | |
d5ed3a4a JK |
2164 | /* We check 'start' to handle wrapping when end == ~0UL */ |
2165 | } while (tagged >= WRITEBACK_TAG_BATCH && start); | |
f446daae JK |
2166 | } |
2167 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
2168 | ||
811d736f | 2169 | /** |
0ea97180 | 2170 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
2171 | * @mapping: address space structure to write |
2172 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
2173 | * @writepage: function called for each page |
2174 | * @data: data passed to writepage function | |
811d736f | 2175 | * |
0ea97180 | 2176 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
2177 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
2178 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
2179 | * and msync() need to guarantee that all the data which was dirty at the time | |
2180 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
2181 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
2182 | * existing IO to complete. | |
f446daae JK |
2183 | * |
2184 | * To avoid livelocks (when other process dirties new pages), we first tag | |
2185 | * pages which should be written back with TOWRITE tag and only then start | |
2186 | * writing them. For data-integrity sync we have to be careful so that we do | |
2187 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
2188 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
2189 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
811d736f | 2190 | */ |
0ea97180 MS |
2191 | int write_cache_pages(struct address_space *mapping, |
2192 | struct writeback_control *wbc, writepage_t writepage, | |
2193 | void *data) | |
811d736f | 2194 | { |
811d736f DH |
2195 | int ret = 0; |
2196 | int done = 0; | |
811d736f DH |
2197 | struct pagevec pvec; |
2198 | int nr_pages; | |
31a12666 | 2199 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
2200 | pgoff_t index; |
2201 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 2202 | pgoff_t done_index; |
31a12666 | 2203 | int cycled; |
811d736f | 2204 | int range_whole = 0; |
f446daae | 2205 | int tag; |
811d736f | 2206 | |
811d736f DH |
2207 | pagevec_init(&pvec, 0); |
2208 | if (wbc->range_cyclic) { | |
31a12666 NP |
2209 | writeback_index = mapping->writeback_index; /* prev offset */ |
2210 | index = writeback_index; | |
2211 | if (index == 0) | |
2212 | cycled = 1; | |
2213 | else | |
2214 | cycled = 0; | |
811d736f DH |
2215 | end = -1; |
2216 | } else { | |
09cbfeaf KS |
2217 | index = wbc->range_start >> PAGE_SHIFT; |
2218 | end = wbc->range_end >> PAGE_SHIFT; | |
811d736f DH |
2219 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
2220 | range_whole = 1; | |
31a12666 | 2221 | cycled = 1; /* ignore range_cyclic tests */ |
811d736f | 2222 | } |
6e6938b6 | 2223 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
2224 | tag = PAGECACHE_TAG_TOWRITE; |
2225 | else | |
2226 | tag = PAGECACHE_TAG_DIRTY; | |
811d736f | 2227 | retry: |
6e6938b6 | 2228 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 2229 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 2230 | done_index = index; |
5a3d5c98 NP |
2231 | while (!done && (index <= end)) { |
2232 | int i; | |
2233 | ||
f446daae | 2234 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
5a3d5c98 NP |
2235 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
2236 | if (nr_pages == 0) | |
2237 | break; | |
811d736f | 2238 | |
811d736f DH |
2239 | for (i = 0; i < nr_pages; i++) { |
2240 | struct page *page = pvec.pages[i]; | |
2241 | ||
2242 | /* | |
d5482cdf NP |
2243 | * At this point, the page may be truncated or |
2244 | * invalidated (changing page->mapping to NULL), or | |
2245 | * even swizzled back from swapper_space to tmpfs file | |
2246 | * mapping. However, page->index will not change | |
2247 | * because we have a reference on the page. | |
811d736f | 2248 | */ |
d5482cdf NP |
2249 | if (page->index > end) { |
2250 | /* | |
2251 | * can't be range_cyclic (1st pass) because | |
2252 | * end == -1 in that case. | |
2253 | */ | |
2254 | done = 1; | |
2255 | break; | |
2256 | } | |
2257 | ||
cf15b07c | 2258 | done_index = page->index; |
d5482cdf | 2259 | |
811d736f DH |
2260 | lock_page(page); |
2261 | ||
5a3d5c98 NP |
2262 | /* |
2263 | * Page truncated or invalidated. We can freely skip it | |
2264 | * then, even for data integrity operations: the page | |
2265 | * has disappeared concurrently, so there could be no | |
2266 | * real expectation of this data interity operation | |
2267 | * even if there is now a new, dirty page at the same | |
2268 | * pagecache address. | |
2269 | */ | |
811d736f | 2270 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 2271 | continue_unlock: |
811d736f DH |
2272 | unlock_page(page); |
2273 | continue; | |
2274 | } | |
2275 | ||
515f4a03 NP |
2276 | if (!PageDirty(page)) { |
2277 | /* someone wrote it for us */ | |
2278 | goto continue_unlock; | |
2279 | } | |
2280 | ||
2281 | if (PageWriteback(page)) { | |
2282 | if (wbc->sync_mode != WB_SYNC_NONE) | |
2283 | wait_on_page_writeback(page); | |
2284 | else | |
2285 | goto continue_unlock; | |
2286 | } | |
811d736f | 2287 | |
515f4a03 NP |
2288 | BUG_ON(PageWriteback(page)); |
2289 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 2290 | goto continue_unlock; |
811d736f | 2291 | |
de1414a6 | 2292 | trace_wbc_writepage(wbc, inode_to_bdi(mapping->host)); |
0ea97180 | 2293 | ret = (*writepage)(page, wbc, data); |
00266770 NP |
2294 | if (unlikely(ret)) { |
2295 | if (ret == AOP_WRITEPAGE_ACTIVATE) { | |
2296 | unlock_page(page); | |
2297 | ret = 0; | |
2298 | } else { | |
2299 | /* | |
2300 | * done_index is set past this page, | |
2301 | * so media errors will not choke | |
2302 | * background writeout for the entire | |
2303 | * file. This has consequences for | |
2304 | * range_cyclic semantics (ie. it may | |
2305 | * not be suitable for data integrity | |
2306 | * writeout). | |
2307 | */ | |
cf15b07c | 2308 | done_index = page->index + 1; |
00266770 NP |
2309 | done = 1; |
2310 | break; | |
2311 | } | |
0b564927 | 2312 | } |
00266770 | 2313 | |
546a1924 DC |
2314 | /* |
2315 | * We stop writing back only if we are not doing | |
2316 | * integrity sync. In case of integrity sync we have to | |
2317 | * keep going until we have written all the pages | |
2318 | * we tagged for writeback prior to entering this loop. | |
2319 | */ | |
2320 | if (--wbc->nr_to_write <= 0 && | |
2321 | wbc->sync_mode == WB_SYNC_NONE) { | |
2322 | done = 1; | |
2323 | break; | |
05fe478d | 2324 | } |
811d736f DH |
2325 | } |
2326 | pagevec_release(&pvec); | |
2327 | cond_resched(); | |
2328 | } | |
3a4c6800 | 2329 | if (!cycled && !done) { |
811d736f | 2330 | /* |
31a12666 | 2331 | * range_cyclic: |
811d736f DH |
2332 | * We hit the last page and there is more work to be done: wrap |
2333 | * back to the start of the file | |
2334 | */ | |
31a12666 | 2335 | cycled = 1; |
811d736f | 2336 | index = 0; |
31a12666 | 2337 | end = writeback_index - 1; |
811d736f DH |
2338 | goto retry; |
2339 | } | |
0b564927 DC |
2340 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
2341 | mapping->writeback_index = done_index; | |
06d6cf69 | 2342 | |
811d736f DH |
2343 | return ret; |
2344 | } | |
0ea97180 MS |
2345 | EXPORT_SYMBOL(write_cache_pages); |
2346 | ||
2347 | /* | |
2348 | * Function used by generic_writepages to call the real writepage | |
2349 | * function and set the mapping flags on error | |
2350 | */ | |
2351 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
2352 | void *data) | |
2353 | { | |
2354 | struct address_space *mapping = data; | |
2355 | int ret = mapping->a_ops->writepage(page, wbc); | |
2356 | mapping_set_error(mapping, ret); | |
2357 | return ret; | |
2358 | } | |
2359 | ||
2360 | /** | |
2361 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
2362 | * @mapping: address space structure to write | |
2363 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
2364 | * | |
2365 | * This is a library function, which implements the writepages() | |
2366 | * address_space_operation. | |
2367 | */ | |
2368 | int generic_writepages(struct address_space *mapping, | |
2369 | struct writeback_control *wbc) | |
2370 | { | |
9b6096a6 SL |
2371 | struct blk_plug plug; |
2372 | int ret; | |
2373 | ||
0ea97180 MS |
2374 | /* deal with chardevs and other special file */ |
2375 | if (!mapping->a_ops->writepage) | |
2376 | return 0; | |
2377 | ||
9b6096a6 SL |
2378 | blk_start_plug(&plug); |
2379 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
2380 | blk_finish_plug(&plug); | |
2381 | return ret; | |
0ea97180 | 2382 | } |
811d736f DH |
2383 | |
2384 | EXPORT_SYMBOL(generic_writepages); | |
2385 | ||
1da177e4 LT |
2386 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
2387 | { | |
22905f77 AM |
2388 | int ret; |
2389 | ||
1da177e4 LT |
2390 | if (wbc->nr_to_write <= 0) |
2391 | return 0; | |
2392 | if (mapping->a_ops->writepages) | |
d08b3851 | 2393 | ret = mapping->a_ops->writepages(mapping, wbc); |
22905f77 AM |
2394 | else |
2395 | ret = generic_writepages(mapping, wbc); | |
22905f77 | 2396 | return ret; |
1da177e4 LT |
2397 | } |
2398 | ||
2399 | /** | |
2400 | * write_one_page - write out a single page and optionally wait on I/O | |
67be2dd1 MW |
2401 | * @page: the page to write |
2402 | * @wait: if true, wait on writeout | |
1da177e4 LT |
2403 | * |
2404 | * The page must be locked by the caller and will be unlocked upon return. | |
2405 | * | |
2406 | * write_one_page() returns a negative error code if I/O failed. | |
2407 | */ | |
2408 | int write_one_page(struct page *page, int wait) | |
2409 | { | |
2410 | struct address_space *mapping = page->mapping; | |
2411 | int ret = 0; | |
2412 | struct writeback_control wbc = { | |
2413 | .sync_mode = WB_SYNC_ALL, | |
2414 | .nr_to_write = 1, | |
2415 | }; | |
2416 | ||
2417 | BUG_ON(!PageLocked(page)); | |
2418 | ||
2419 | if (wait) | |
2420 | wait_on_page_writeback(page); | |
2421 | ||
2422 | if (clear_page_dirty_for_io(page)) { | |
09cbfeaf | 2423 | get_page(page); |
1da177e4 LT |
2424 | ret = mapping->a_ops->writepage(page, &wbc); |
2425 | if (ret == 0 && wait) { | |
2426 | wait_on_page_writeback(page); | |
2427 | if (PageError(page)) | |
2428 | ret = -EIO; | |
2429 | } | |
09cbfeaf | 2430 | put_page(page); |
1da177e4 LT |
2431 | } else { |
2432 | unlock_page(page); | |
2433 | } | |
2434 | return ret; | |
2435 | } | |
2436 | EXPORT_SYMBOL(write_one_page); | |
2437 | ||
76719325 KC |
2438 | /* |
2439 | * For address_spaces which do not use buffers nor write back. | |
2440 | */ | |
2441 | int __set_page_dirty_no_writeback(struct page *page) | |
2442 | { | |
2443 | if (!PageDirty(page)) | |
c3f0da63 | 2444 | return !TestSetPageDirty(page); |
76719325 KC |
2445 | return 0; |
2446 | } | |
2447 | ||
e3a7cca1 ES |
2448 | /* |
2449 | * Helper function for set_page_dirty family. | |
c4843a75 | 2450 | * |
81f8c3a4 | 2451 | * Caller must hold lock_page_memcg(). |
c4843a75 | 2452 | * |
e3a7cca1 ES |
2453 | * NOTE: This relies on being atomic wrt interrupts. |
2454 | */ | |
62cccb8c | 2455 | void account_page_dirtied(struct page *page, struct address_space *mapping) |
e3a7cca1 | 2456 | { |
52ebea74 TH |
2457 | struct inode *inode = mapping->host; |
2458 | ||
9fb0a7da TH |
2459 | trace_writeback_dirty_page(page, mapping); |
2460 | ||
e3a7cca1 | 2461 | if (mapping_cap_account_dirty(mapping)) { |
52ebea74 | 2462 | struct bdi_writeback *wb; |
de1414a6 | 2463 | |
52ebea74 TH |
2464 | inode_attach_wb(inode, page); |
2465 | wb = inode_to_wb(inode); | |
de1414a6 | 2466 | |
62cccb8c | 2467 | mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_DIRTY); |
11fb9989 | 2468 | __inc_node_page_state(page, NR_FILE_DIRTY); |
c4a25635 | 2469 | __inc_node_page_state(page, NR_DIRTIED); |
52ebea74 TH |
2470 | __inc_wb_stat(wb, WB_RECLAIMABLE); |
2471 | __inc_wb_stat(wb, WB_DIRTIED); | |
09cbfeaf | 2472 | task_io_account_write(PAGE_SIZE); |
d3bc1fef WF |
2473 | current->nr_dirtied++; |
2474 | this_cpu_inc(bdp_ratelimits); | |
e3a7cca1 ES |
2475 | } |
2476 | } | |
679ceace | 2477 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 2478 | |
b9ea2515 KK |
2479 | /* |
2480 | * Helper function for deaccounting dirty page without writeback. | |
2481 | * | |
81f8c3a4 | 2482 | * Caller must hold lock_page_memcg(). |
b9ea2515 | 2483 | */ |
c4843a75 | 2484 | void account_page_cleaned(struct page *page, struct address_space *mapping, |
62cccb8c | 2485 | struct bdi_writeback *wb) |
b9ea2515 KK |
2486 | { |
2487 | if (mapping_cap_account_dirty(mapping)) { | |
62cccb8c | 2488 | mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY); |
11fb9989 | 2489 | dec_node_page_state(page, NR_FILE_DIRTY); |
682aa8e1 | 2490 | dec_wb_stat(wb, WB_RECLAIMABLE); |
09cbfeaf | 2491 | task_io_account_cancelled_write(PAGE_SIZE); |
b9ea2515 KK |
2492 | } |
2493 | } | |
b9ea2515 | 2494 | |
1da177e4 LT |
2495 | /* |
2496 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
2497 | * its radix tree. | |
2498 | * | |
2499 | * This is also used when a single buffer is being dirtied: we want to set the | |
2500 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
2501 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
2502 | * | |
2d6d7f98 JW |
2503 | * The caller must ensure this doesn't race with truncation. Most will simply |
2504 | * hold the page lock, but e.g. zap_pte_range() calls with the page mapped and | |
2505 | * the pte lock held, which also locks out truncation. | |
1da177e4 LT |
2506 | */ |
2507 | int __set_page_dirty_nobuffers(struct page *page) | |
2508 | { | |
62cccb8c | 2509 | lock_page_memcg(page); |
1da177e4 LT |
2510 | if (!TestSetPageDirty(page)) { |
2511 | struct address_space *mapping = page_mapping(page); | |
a85d9df1 | 2512 | unsigned long flags; |
1da177e4 | 2513 | |
c4843a75 | 2514 | if (!mapping) { |
62cccb8c | 2515 | unlock_page_memcg(page); |
8c08540f | 2516 | return 1; |
c4843a75 | 2517 | } |
8c08540f | 2518 | |
a85d9df1 | 2519 | spin_lock_irqsave(&mapping->tree_lock, flags); |
2d6d7f98 JW |
2520 | BUG_ON(page_mapping(page) != mapping); |
2521 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); | |
62cccb8c | 2522 | account_page_dirtied(page, mapping); |
2d6d7f98 JW |
2523 | radix_tree_tag_set(&mapping->page_tree, page_index(page), |
2524 | PAGECACHE_TAG_DIRTY); | |
a85d9df1 | 2525 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
62cccb8c | 2526 | unlock_page_memcg(page); |
c4843a75 | 2527 | |
8c08540f AM |
2528 | if (mapping->host) { |
2529 | /* !PageAnon && !swapper_space */ | |
2530 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 2531 | } |
4741c9fd | 2532 | return 1; |
1da177e4 | 2533 | } |
62cccb8c | 2534 | unlock_page_memcg(page); |
4741c9fd | 2535 | return 0; |
1da177e4 LT |
2536 | } |
2537 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
2538 | ||
2f800fbd WF |
2539 | /* |
2540 | * Call this whenever redirtying a page, to de-account the dirty counters | |
2541 | * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written | |
2542 | * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to | |
2543 | * systematic errors in balanced_dirty_ratelimit and the dirty pages position | |
2544 | * control. | |
2545 | */ | |
2546 | void account_page_redirty(struct page *page) | |
2547 | { | |
2548 | struct address_space *mapping = page->mapping; | |
91018134 | 2549 | |
2f800fbd | 2550 | if (mapping && mapping_cap_account_dirty(mapping)) { |
682aa8e1 TH |
2551 | struct inode *inode = mapping->host; |
2552 | struct bdi_writeback *wb; | |
2553 | bool locked; | |
91018134 | 2554 | |
682aa8e1 | 2555 | wb = unlocked_inode_to_wb_begin(inode, &locked); |
2f800fbd | 2556 | current->nr_dirtied--; |
c4a25635 | 2557 | dec_node_page_state(page, NR_DIRTIED); |
91018134 | 2558 | dec_wb_stat(wb, WB_DIRTIED); |
682aa8e1 | 2559 | unlocked_inode_to_wb_end(inode, locked); |
2f800fbd WF |
2560 | } |
2561 | } | |
2562 | EXPORT_SYMBOL(account_page_redirty); | |
2563 | ||
1da177e4 LT |
2564 | /* |
2565 | * When a writepage implementation decides that it doesn't want to write this | |
2566 | * page for some reason, it should redirty the locked page via | |
2567 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
2568 | */ | |
2569 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
2570 | { | |
8d38633c KK |
2571 | int ret; |
2572 | ||
1da177e4 | 2573 | wbc->pages_skipped++; |
8d38633c | 2574 | ret = __set_page_dirty_nobuffers(page); |
2f800fbd | 2575 | account_page_redirty(page); |
8d38633c | 2576 | return ret; |
1da177e4 LT |
2577 | } |
2578 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
2579 | ||
2580 | /* | |
6746aff7 WF |
2581 | * Dirty a page. |
2582 | * | |
2583 | * For pages with a mapping this should be done under the page lock | |
2584 | * for the benefit of asynchronous memory errors who prefer a consistent | |
2585 | * dirty state. This rule can be broken in some special cases, | |
2586 | * but should be better not to. | |
2587 | * | |
1da177e4 LT |
2588 | * If the mapping doesn't provide a set_page_dirty a_op, then |
2589 | * just fall through and assume that it wants buffer_heads. | |
2590 | */ | |
1cf6e7d8 | 2591 | int set_page_dirty(struct page *page) |
1da177e4 LT |
2592 | { |
2593 | struct address_space *mapping = page_mapping(page); | |
2594 | ||
800d8c63 | 2595 | page = compound_head(page); |
1da177e4 LT |
2596 | if (likely(mapping)) { |
2597 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
2598 | /* |
2599 | * readahead/lru_deactivate_page could remain | |
2600 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
2601 | * About readahead, if the page is written, the flags would be | |
2602 | * reset. So no problem. | |
2603 | * About lru_deactivate_page, if the page is redirty, the flag | |
2604 | * will be reset. So no problem. but if the page is used by readahead | |
2605 | * it will confuse readahead and make it restart the size rampup | |
2606 | * process. But it's a trivial problem. | |
2607 | */ | |
a4bb3ecd NH |
2608 | if (PageReclaim(page)) |
2609 | ClearPageReclaim(page); | |
9361401e DH |
2610 | #ifdef CONFIG_BLOCK |
2611 | if (!spd) | |
2612 | spd = __set_page_dirty_buffers; | |
2613 | #endif | |
2614 | return (*spd)(page); | |
1da177e4 | 2615 | } |
4741c9fd AM |
2616 | if (!PageDirty(page)) { |
2617 | if (!TestSetPageDirty(page)) | |
2618 | return 1; | |
2619 | } | |
1da177e4 LT |
2620 | return 0; |
2621 | } | |
2622 | EXPORT_SYMBOL(set_page_dirty); | |
2623 | ||
2624 | /* | |
2625 | * set_page_dirty() is racy if the caller has no reference against | |
2626 | * page->mapping->host, and if the page is unlocked. This is because another | |
2627 | * CPU could truncate the page off the mapping and then free the mapping. | |
2628 | * | |
2629 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
2630 | * holds a reference on the inode by having an open file. | |
2631 | * | |
2632 | * In other cases, the page should be locked before running set_page_dirty(). | |
2633 | */ | |
2634 | int set_page_dirty_lock(struct page *page) | |
2635 | { | |
2636 | int ret; | |
2637 | ||
7eaceacc | 2638 | lock_page(page); |
1da177e4 LT |
2639 | ret = set_page_dirty(page); |
2640 | unlock_page(page); | |
2641 | return ret; | |
2642 | } | |
2643 | EXPORT_SYMBOL(set_page_dirty_lock); | |
2644 | ||
11f81bec TH |
2645 | /* |
2646 | * This cancels just the dirty bit on the kernel page itself, it does NOT | |
2647 | * actually remove dirty bits on any mmap's that may be around. It also | |
2648 | * leaves the page tagged dirty, so any sync activity will still find it on | |
2649 | * the dirty lists, and in particular, clear_page_dirty_for_io() will still | |
2650 | * look at the dirty bits in the VM. | |
2651 | * | |
2652 | * Doing this should *normally* only ever be done when a page is truncated, | |
2653 | * and is not actually mapped anywhere at all. However, fs/buffer.c does | |
2654 | * this when it notices that somebody has cleaned out all the buffers on a | |
2655 | * page without actually doing it through the VM. Can you say "ext3 is | |
2656 | * horribly ugly"? Thought you could. | |
2657 | */ | |
2658 | void cancel_dirty_page(struct page *page) | |
2659 | { | |
c4843a75 GT |
2660 | struct address_space *mapping = page_mapping(page); |
2661 | ||
2662 | if (mapping_cap_account_dirty(mapping)) { | |
682aa8e1 TH |
2663 | struct inode *inode = mapping->host; |
2664 | struct bdi_writeback *wb; | |
682aa8e1 | 2665 | bool locked; |
c4843a75 | 2666 | |
62cccb8c | 2667 | lock_page_memcg(page); |
682aa8e1 | 2668 | wb = unlocked_inode_to_wb_begin(inode, &locked); |
c4843a75 GT |
2669 | |
2670 | if (TestClearPageDirty(page)) | |
62cccb8c | 2671 | account_page_cleaned(page, mapping, wb); |
c4843a75 | 2672 | |
682aa8e1 | 2673 | unlocked_inode_to_wb_end(inode, locked); |
62cccb8c | 2674 | unlock_page_memcg(page); |
c4843a75 GT |
2675 | } else { |
2676 | ClearPageDirty(page); | |
2677 | } | |
11f81bec TH |
2678 | } |
2679 | EXPORT_SYMBOL(cancel_dirty_page); | |
2680 | ||
1da177e4 LT |
2681 | /* |
2682 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
2683 | * Returns true if the page was previously dirty. | |
2684 | * | |
2685 | * This is for preparing to put the page under writeout. We leave the page | |
2686 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
2687 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
2688 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
2689 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
2690 | * back into sync. | |
2691 | * | |
2692 | * This incoherency between the page's dirty flag and radix-tree tag is | |
2693 | * unfortunate, but it only exists while the page is locked. | |
2694 | */ | |
2695 | int clear_page_dirty_for_io(struct page *page) | |
2696 | { | |
2697 | struct address_space *mapping = page_mapping(page); | |
c4843a75 | 2698 | int ret = 0; |
1da177e4 | 2699 | |
79352894 NP |
2700 | BUG_ON(!PageLocked(page)); |
2701 | ||
7658cc28 | 2702 | if (mapping && mapping_cap_account_dirty(mapping)) { |
682aa8e1 TH |
2703 | struct inode *inode = mapping->host; |
2704 | struct bdi_writeback *wb; | |
682aa8e1 TH |
2705 | bool locked; |
2706 | ||
7658cc28 LT |
2707 | /* |
2708 | * Yes, Virginia, this is indeed insane. | |
2709 | * | |
2710 | * We use this sequence to make sure that | |
2711 | * (a) we account for dirty stats properly | |
2712 | * (b) we tell the low-level filesystem to | |
2713 | * mark the whole page dirty if it was | |
2714 | * dirty in a pagetable. Only to then | |
2715 | * (c) clean the page again and return 1 to | |
2716 | * cause the writeback. | |
2717 | * | |
2718 | * This way we avoid all nasty races with the | |
2719 | * dirty bit in multiple places and clearing | |
2720 | * them concurrently from different threads. | |
2721 | * | |
2722 | * Note! Normally the "set_page_dirty(page)" | |
2723 | * has no effect on the actual dirty bit - since | |
2724 | * that will already usually be set. But we | |
2725 | * need the side effects, and it can help us | |
2726 | * avoid races. | |
2727 | * | |
2728 | * We basically use the page "master dirty bit" | |
2729 | * as a serialization point for all the different | |
2730 | * threads doing their things. | |
7658cc28 LT |
2731 | */ |
2732 | if (page_mkclean(page)) | |
2733 | set_page_dirty(page); | |
79352894 NP |
2734 | /* |
2735 | * We carefully synchronise fault handlers against | |
2736 | * installing a dirty pte and marking the page dirty | |
2d6d7f98 JW |
2737 | * at this point. We do this by having them hold the |
2738 | * page lock while dirtying the page, and pages are | |
2739 | * always locked coming in here, so we get the desired | |
2740 | * exclusion. | |
79352894 | 2741 | */ |
682aa8e1 | 2742 | wb = unlocked_inode_to_wb_begin(inode, &locked); |
7658cc28 | 2743 | if (TestClearPageDirty(page)) { |
62cccb8c | 2744 | mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY); |
11fb9989 | 2745 | dec_node_page_state(page, NR_FILE_DIRTY); |
682aa8e1 | 2746 | dec_wb_stat(wb, WB_RECLAIMABLE); |
c4843a75 | 2747 | ret = 1; |
1da177e4 | 2748 | } |
682aa8e1 | 2749 | unlocked_inode_to_wb_end(inode, locked); |
c4843a75 | 2750 | return ret; |
1da177e4 | 2751 | } |
7658cc28 | 2752 | return TestClearPageDirty(page); |
1da177e4 | 2753 | } |
58bb01a9 | 2754 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
2755 | |
2756 | int test_clear_page_writeback(struct page *page) | |
2757 | { | |
2758 | struct address_space *mapping = page_mapping(page); | |
d7365e78 | 2759 | int ret; |
1da177e4 | 2760 | |
62cccb8c | 2761 | lock_page_memcg(page); |
1da177e4 | 2762 | if (mapping) { |
91018134 TH |
2763 | struct inode *inode = mapping->host; |
2764 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2765 | unsigned long flags; |
2766 | ||
19fd6231 | 2767 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2768 | ret = TestClearPageWriteback(page); |
69cb51d1 | 2769 | if (ret) { |
1da177e4 LT |
2770 | radix_tree_tag_clear(&mapping->page_tree, |
2771 | page_index(page), | |
2772 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2773 | if (bdi_cap_account_writeback(bdi)) { |
91018134 TH |
2774 | struct bdi_writeback *wb = inode_to_wb(inode); |
2775 | ||
2776 | __dec_wb_stat(wb, WB_WRITEBACK); | |
2777 | __wb_writeout_inc(wb); | |
04fbfdc1 | 2778 | } |
69cb51d1 | 2779 | } |
6c60d2b5 DC |
2780 | |
2781 | if (mapping->host && !mapping_tagged(mapping, | |
2782 | PAGECACHE_TAG_WRITEBACK)) | |
2783 | sb_clear_inode_writeback(mapping->host); | |
2784 | ||
19fd6231 | 2785 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2786 | } else { |
2787 | ret = TestClearPageWriteback(page); | |
2788 | } | |
99b12e3d | 2789 | if (ret) { |
62cccb8c | 2790 | mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); |
11fb9989 | 2791 | dec_node_page_state(page, NR_WRITEBACK); |
c4a25635 | 2792 | inc_node_page_state(page, NR_WRITTEN); |
99b12e3d | 2793 | } |
62cccb8c | 2794 | unlock_page_memcg(page); |
1da177e4 LT |
2795 | return ret; |
2796 | } | |
2797 | ||
1c8349a1 | 2798 | int __test_set_page_writeback(struct page *page, bool keep_write) |
1da177e4 LT |
2799 | { |
2800 | struct address_space *mapping = page_mapping(page); | |
d7365e78 | 2801 | int ret; |
1da177e4 | 2802 | |
62cccb8c | 2803 | lock_page_memcg(page); |
1da177e4 | 2804 | if (mapping) { |
91018134 TH |
2805 | struct inode *inode = mapping->host; |
2806 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2807 | unsigned long flags; |
2808 | ||
19fd6231 | 2809 | spin_lock_irqsave(&mapping->tree_lock, flags); |
1da177e4 | 2810 | ret = TestSetPageWriteback(page); |
69cb51d1 | 2811 | if (!ret) { |
6c60d2b5 DC |
2812 | bool on_wblist; |
2813 | ||
2814 | on_wblist = mapping_tagged(mapping, | |
2815 | PAGECACHE_TAG_WRITEBACK); | |
2816 | ||
1da177e4 LT |
2817 | radix_tree_tag_set(&mapping->page_tree, |
2818 | page_index(page), | |
2819 | PAGECACHE_TAG_WRITEBACK); | |
e4ad08fe | 2820 | if (bdi_cap_account_writeback(bdi)) |
91018134 | 2821 | __inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK); |
6c60d2b5 DC |
2822 | |
2823 | /* | |
2824 | * We can come through here when swapping anonymous | |
2825 | * pages, so we don't necessarily have an inode to track | |
2826 | * for sync. | |
2827 | */ | |
2828 | if (mapping->host && !on_wblist) | |
2829 | sb_mark_inode_writeback(mapping->host); | |
69cb51d1 | 2830 | } |
1da177e4 LT |
2831 | if (!PageDirty(page)) |
2832 | radix_tree_tag_clear(&mapping->page_tree, | |
2833 | page_index(page), | |
2834 | PAGECACHE_TAG_DIRTY); | |
1c8349a1 NJ |
2835 | if (!keep_write) |
2836 | radix_tree_tag_clear(&mapping->page_tree, | |
2837 | page_index(page), | |
2838 | PAGECACHE_TAG_TOWRITE); | |
19fd6231 | 2839 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
1da177e4 LT |
2840 | } else { |
2841 | ret = TestSetPageWriteback(page); | |
2842 | } | |
3a3c02ec | 2843 | if (!ret) { |
62cccb8c | 2844 | mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); |
11fb9989 | 2845 | inc_node_page_state(page, NR_WRITEBACK); |
3a3c02ec | 2846 | } |
62cccb8c | 2847 | unlock_page_memcg(page); |
1da177e4 LT |
2848 | return ret; |
2849 | ||
2850 | } | |
1c8349a1 | 2851 | EXPORT_SYMBOL(__test_set_page_writeback); |
1da177e4 LT |
2852 | |
2853 | /* | |
00128188 | 2854 | * Return true if any of the pages in the mapping are marked with the |
1da177e4 LT |
2855 | * passed tag. |
2856 | */ | |
2857 | int mapping_tagged(struct address_space *mapping, int tag) | |
2858 | { | |
72c47832 | 2859 | return radix_tree_tagged(&mapping->page_tree, tag); |
1da177e4 LT |
2860 | } |
2861 | EXPORT_SYMBOL(mapping_tagged); | |
1d1d1a76 DW |
2862 | |
2863 | /** | |
2864 | * wait_for_stable_page() - wait for writeback to finish, if necessary. | |
2865 | * @page: The page to wait on. | |
2866 | * | |
2867 | * This function determines if the given page is related to a backing device | |
2868 | * that requires page contents to be held stable during writeback. If so, then | |
2869 | * it will wait for any pending writeback to complete. | |
2870 | */ | |
2871 | void wait_for_stable_page(struct page *page) | |
2872 | { | |
de1414a6 CH |
2873 | if (bdi_cap_stable_pages_required(inode_to_bdi(page->mapping->host))) |
2874 | wait_on_page_writeback(page); | |
1d1d1a76 DW |
2875 | } |
2876 | EXPORT_SYMBOL_GPL(wait_for_stable_page); |