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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
1da177e4 | 2 | /* |
f30c2269 | 3 | * mm/page-writeback.c |
1da177e4 LT |
4 | * |
5 | * Copyright (C) 2002, Linus Torvalds. | |
90eec103 | 6 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra |
1da177e4 LT |
7 | * |
8 | * Contains functions related to writing back dirty pages at the | |
9 | * address_space level. | |
10 | * | |
e1f8e874 | 11 | * 10Apr2002 Andrew Morton |
1da177e4 LT |
12 | * Initial version |
13 | */ | |
14 | ||
15 | #include <linux/kernel.h> | |
b95f1b31 | 16 | #include <linux/export.h> |
1da177e4 LT |
17 | #include <linux/spinlock.h> |
18 | #include <linux/fs.h> | |
19 | #include <linux/mm.h> | |
20 | #include <linux/swap.h> | |
21 | #include <linux/slab.h> | |
22 | #include <linux/pagemap.h> | |
23 | #include <linux/writeback.h> | |
24 | #include <linux/init.h> | |
25 | #include <linux/backing-dev.h> | |
55e829af | 26 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
27 | #include <linux/blkdev.h> |
28 | #include <linux/mpage.h> | |
d08b3851 | 29 | #include <linux/rmap.h> |
1da177e4 | 30 | #include <linux/percpu.h> |
1da177e4 LT |
31 | #include <linux/smp.h> |
32 | #include <linux/sysctl.h> | |
33 | #include <linux/cpu.h> | |
34 | #include <linux/syscalls.h> | |
811d736f | 35 | #include <linux/pagevec.h> |
eb608e3a | 36 | #include <linux/timer.h> |
8bd75c77 | 37 | #include <linux/sched/rt.h> |
f361bf4a | 38 | #include <linux/sched/signal.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 | */ |
aa779e51 | 73 | static 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 | */ | |
aa779e51 | 79 | static unsigned long dirty_background_bytes; |
2da02997 | 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 | */ | |
aa779e51 | 85 | static int vm_highmem_is_dirtyable; |
195cf453 | 86 | |
1da177e4 LT |
87 | /* |
88 | * The generator of dirty data starts writeback at this percentage | |
89 | */ | |
aa779e51 | 90 | static 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 | */ | |
aa779e51 | 96 | static unsigned long vm_dirty_bytes; |
2da02997 | 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 | 109 | |
1da177e4 | 110 | /* |
ed5b43f1 BS |
111 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
112 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
113 | */ |
114 | int laptop_mode; | |
115 | ||
116 | EXPORT_SYMBOL(laptop_mode); | |
117 | ||
118 | /* End of sysctl-exported parameters */ | |
119 | ||
dcc25ae7 | 120 | struct wb_domain global_wb_domain; |
1da177e4 | 121 | |
2bc00aef TH |
122 | /* consolidated parameters for balance_dirty_pages() and its subroutines */ |
123 | struct dirty_throttle_control { | |
e9f07dfd TH |
124 | #ifdef CONFIG_CGROUP_WRITEBACK |
125 | struct wb_domain *dom; | |
9fc3a43e | 126 | struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ |
e9f07dfd | 127 | #endif |
2bc00aef | 128 | struct bdi_writeback *wb; |
e9770b34 | 129 | struct fprop_local_percpu *wb_completions; |
eb608e3a | 130 | |
9fc3a43e | 131 | unsigned long avail; /* dirtyable */ |
2bc00aef TH |
132 | unsigned long dirty; /* file_dirty + write + nfs */ |
133 | unsigned long thresh; /* dirty threshold */ | |
134 | unsigned long bg_thresh; /* dirty background threshold */ | |
135 | ||
136 | unsigned long wb_dirty; /* per-wb counterparts */ | |
137 | unsigned long wb_thresh; | |
970fb01a | 138 | unsigned long wb_bg_thresh; |
daddfa3c TH |
139 | |
140 | unsigned long pos_ratio; | |
2bc00aef TH |
141 | }; |
142 | ||
eb608e3a JK |
143 | /* |
144 | * Length of period for aging writeout fractions of bdis. This is an | |
145 | * arbitrarily chosen number. The longer the period, the slower fractions will | |
146 | * reflect changes in current writeout rate. | |
147 | */ | |
148 | #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) | |
04fbfdc1 | 149 | |
693108a8 TH |
150 | #ifdef CONFIG_CGROUP_WRITEBACK |
151 | ||
d60d1bdd TH |
152 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
153 | .dom = &global_wb_domain, \ | |
154 | .wb_completions = &(__wb)->completions | |
155 | ||
9fc3a43e | 156 | #define GDTC_INIT_NO_WB .dom = &global_wb_domain |
d60d1bdd TH |
157 | |
158 | #define MDTC_INIT(__wb, __gdtc) .wb = (__wb), \ | |
159 | .dom = mem_cgroup_wb_domain(__wb), \ | |
160 | .wb_completions = &(__wb)->memcg_completions, \ | |
161 | .gdtc = __gdtc | |
c2aa723a TH |
162 | |
163 | static bool mdtc_valid(struct dirty_throttle_control *dtc) | |
164 | { | |
165 | return dtc->dom; | |
166 | } | |
e9f07dfd TH |
167 | |
168 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) | |
169 | { | |
170 | return dtc->dom; | |
171 | } | |
172 | ||
9fc3a43e TH |
173 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
174 | { | |
175 | return mdtc->gdtc; | |
176 | } | |
177 | ||
841710aa TH |
178 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
179 | { | |
180 | return &wb->memcg_completions; | |
181 | } | |
182 | ||
693108a8 TH |
183 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
184 | unsigned long *minp, unsigned long *maxp) | |
185 | { | |
20792ebf | 186 | unsigned long this_bw = READ_ONCE(wb->avg_write_bandwidth); |
693108a8 TH |
187 | unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); |
188 | unsigned long long min = wb->bdi->min_ratio; | |
189 | unsigned long long max = wb->bdi->max_ratio; | |
190 | ||
191 | /* | |
192 | * @wb may already be clean by the time control reaches here and | |
193 | * the total may not include its bw. | |
194 | */ | |
195 | if (this_bw < tot_bw) { | |
196 | if (min) { | |
197 | min *= this_bw; | |
6d9e8c65 | 198 | min = div64_ul(min, tot_bw); |
693108a8 TH |
199 | } |
200 | if (max < 100) { | |
201 | max *= this_bw; | |
6d9e8c65 | 202 | max = div64_ul(max, tot_bw); |
693108a8 TH |
203 | } |
204 | } | |
205 | ||
206 | *minp = min; | |
207 | *maxp = max; | |
208 | } | |
209 | ||
210 | #else /* CONFIG_CGROUP_WRITEBACK */ | |
211 | ||
d60d1bdd TH |
212 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
213 | .wb_completions = &(__wb)->completions | |
9fc3a43e | 214 | #define GDTC_INIT_NO_WB |
c2aa723a TH |
215 | #define MDTC_INIT(__wb, __gdtc) |
216 | ||
217 | static bool mdtc_valid(struct dirty_throttle_control *dtc) | |
218 | { | |
219 | return false; | |
220 | } | |
e9f07dfd TH |
221 | |
222 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) | |
223 | { | |
224 | return &global_wb_domain; | |
225 | } | |
226 | ||
9fc3a43e TH |
227 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
228 | { | |
229 | return NULL; | |
230 | } | |
231 | ||
841710aa TH |
232 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
233 | { | |
234 | return NULL; | |
235 | } | |
236 | ||
693108a8 TH |
237 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
238 | unsigned long *minp, unsigned long *maxp) | |
239 | { | |
240 | *minp = wb->bdi->min_ratio; | |
241 | *maxp = wb->bdi->max_ratio; | |
242 | } | |
243 | ||
244 | #endif /* CONFIG_CGROUP_WRITEBACK */ | |
245 | ||
a756cf59 JW |
246 | /* |
247 | * In a memory zone, there is a certain amount of pages we consider | |
248 | * available for the page cache, which is essentially the number of | |
249 | * free and reclaimable pages, minus some zone reserves to protect | |
250 | * lowmem and the ability to uphold the zone's watermarks without | |
251 | * requiring writeback. | |
252 | * | |
253 | * This number of dirtyable pages is the base value of which the | |
e0857cf5 | 254 | * user-configurable dirty ratio is the effective number of pages that |
a756cf59 JW |
255 | * are allowed to be actually dirtied. Per individual zone, or |
256 | * globally by using the sum of dirtyable pages over all zones. | |
257 | * | |
258 | * Because the user is allowed to specify the dirty limit globally as | |
259 | * absolute number of bytes, calculating the per-zone dirty limit can | |
260 | * require translating the configured limit into a percentage of | |
261 | * global dirtyable memory first. | |
262 | */ | |
263 | ||
a804552b | 264 | /** |
281e3726 MG |
265 | * node_dirtyable_memory - number of dirtyable pages in a node |
266 | * @pgdat: the node | |
a804552b | 267 | * |
a862f68a | 268 | * Return: the node's number of pages potentially available for dirty |
281e3726 | 269 | * page cache. This is the base value for the per-node dirty limits. |
a804552b | 270 | */ |
281e3726 | 271 | static unsigned long node_dirtyable_memory(struct pglist_data *pgdat) |
a804552b | 272 | { |
281e3726 MG |
273 | unsigned long nr_pages = 0; |
274 | int z; | |
275 | ||
276 | for (z = 0; z < MAX_NR_ZONES; z++) { | |
277 | struct zone *zone = pgdat->node_zones + z; | |
278 | ||
279 | if (!populated_zone(zone)) | |
280 | continue; | |
281 | ||
282 | nr_pages += zone_page_state(zone, NR_FREE_PAGES); | |
283 | } | |
a804552b | 284 | |
a8d01437 JW |
285 | /* |
286 | * Pages reserved for the kernel should not be considered | |
287 | * dirtyable, to prevent a situation where reclaim has to | |
288 | * clean pages in order to balance the zones. | |
289 | */ | |
281e3726 | 290 | nr_pages -= min(nr_pages, pgdat->totalreserve_pages); |
a804552b | 291 | |
281e3726 MG |
292 | nr_pages += node_page_state(pgdat, NR_INACTIVE_FILE); |
293 | nr_pages += node_page_state(pgdat, NR_ACTIVE_FILE); | |
a804552b JW |
294 | |
295 | return nr_pages; | |
296 | } | |
297 | ||
1edf2234 JW |
298 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
299 | { | |
300 | #ifdef CONFIG_HIGHMEM | |
301 | int node; | |
bb4cc2be | 302 | unsigned long x = 0; |
09b4ab3c | 303 | int i; |
1edf2234 JW |
304 | |
305 | for_each_node_state(node, N_HIGH_MEMORY) { | |
281e3726 MG |
306 | for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { |
307 | struct zone *z; | |
9cb937e2 | 308 | unsigned long nr_pages; |
281e3726 MG |
309 | |
310 | if (!is_highmem_idx(i)) | |
311 | continue; | |
312 | ||
313 | z = &NODE_DATA(node)->node_zones[i]; | |
9cb937e2 MK |
314 | if (!populated_zone(z)) |
315 | continue; | |
1edf2234 | 316 | |
9cb937e2 | 317 | nr_pages = zone_page_state(z, NR_FREE_PAGES); |
281e3726 | 318 | /* watch for underflows */ |
9cb937e2 | 319 | nr_pages -= min(nr_pages, high_wmark_pages(z)); |
bb4cc2be MG |
320 | nr_pages += zone_page_state(z, NR_ZONE_INACTIVE_FILE); |
321 | nr_pages += zone_page_state(z, NR_ZONE_ACTIVE_FILE); | |
322 | x += nr_pages; | |
09b4ab3c | 323 | } |
1edf2234 | 324 | } |
281e3726 | 325 | |
1edf2234 JW |
326 | /* |
327 | * Make sure that the number of highmem pages is never larger | |
328 | * than the number of the total dirtyable memory. This can only | |
329 | * occur in very strange VM situations but we want to make sure | |
330 | * that this does not occur. | |
331 | */ | |
332 | return min(x, total); | |
333 | #else | |
334 | return 0; | |
335 | #endif | |
336 | } | |
337 | ||
338 | /** | |
ccafa287 | 339 | * global_dirtyable_memory - number of globally dirtyable pages |
1edf2234 | 340 | * |
a862f68a | 341 | * Return: the global number of pages potentially available for dirty |
ccafa287 | 342 | * page cache. This is the base value for the global dirty limits. |
1edf2234 | 343 | */ |
18cf8cf8 | 344 | static unsigned long global_dirtyable_memory(void) |
1edf2234 JW |
345 | { |
346 | unsigned long x; | |
347 | ||
c41f012a | 348 | x = global_zone_page_state(NR_FREE_PAGES); |
a8d01437 JW |
349 | /* |
350 | * Pages reserved for the kernel should not be considered | |
351 | * dirtyable, to prevent a situation where reclaim has to | |
352 | * clean pages in order to balance the zones. | |
353 | */ | |
354 | x -= min(x, totalreserve_pages); | |
1edf2234 | 355 | |
599d0c95 MG |
356 | x += global_node_page_state(NR_INACTIVE_FILE); |
357 | x += global_node_page_state(NR_ACTIVE_FILE); | |
a804552b | 358 | |
1edf2234 JW |
359 | if (!vm_highmem_is_dirtyable) |
360 | x -= highmem_dirtyable_memory(x); | |
361 | ||
362 | return x + 1; /* Ensure that we never return 0 */ | |
363 | } | |
364 | ||
9fc3a43e TH |
365 | /** |
366 | * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain | |
367 | * @dtc: dirty_throttle_control of interest | |
ccafa287 | 368 | * |
9fc3a43e TH |
369 | * Calculate @dtc->thresh and ->bg_thresh considering |
370 | * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller | |
371 | * must ensure that @dtc->avail is set before calling this function. The | |
a37b0715 | 372 | * dirty limits will be lifted by 1/4 for real-time tasks. |
ccafa287 | 373 | */ |
9fc3a43e | 374 | static void domain_dirty_limits(struct dirty_throttle_control *dtc) |
ccafa287 | 375 | { |
9fc3a43e TH |
376 | const unsigned long available_memory = dtc->avail; |
377 | struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); | |
378 | unsigned long bytes = vm_dirty_bytes; | |
379 | unsigned long bg_bytes = dirty_background_bytes; | |
62a584fe TH |
380 | /* convert ratios to per-PAGE_SIZE for higher precision */ |
381 | unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100; | |
382 | unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100; | |
9fc3a43e TH |
383 | unsigned long thresh; |
384 | unsigned long bg_thresh; | |
ccafa287 JW |
385 | struct task_struct *tsk; |
386 | ||
9fc3a43e TH |
387 | /* gdtc is !NULL iff @dtc is for memcg domain */ |
388 | if (gdtc) { | |
389 | unsigned long global_avail = gdtc->avail; | |
390 | ||
391 | /* | |
392 | * The byte settings can't be applied directly to memcg | |
393 | * domains. Convert them to ratios by scaling against | |
62a584fe TH |
394 | * globally available memory. As the ratios are in |
395 | * per-PAGE_SIZE, they can be obtained by dividing bytes by | |
396 | * number of pages. | |
9fc3a43e TH |
397 | */ |
398 | if (bytes) | |
62a584fe TH |
399 | ratio = min(DIV_ROUND_UP(bytes, global_avail), |
400 | PAGE_SIZE); | |
9fc3a43e | 401 | if (bg_bytes) |
62a584fe TH |
402 | bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail), |
403 | PAGE_SIZE); | |
9fc3a43e TH |
404 | bytes = bg_bytes = 0; |
405 | } | |
406 | ||
407 | if (bytes) | |
408 | thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); | |
ccafa287 | 409 | else |
62a584fe | 410 | thresh = (ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 411 | |
9fc3a43e TH |
412 | if (bg_bytes) |
413 | bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); | |
ccafa287 | 414 | else |
62a584fe | 415 | bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 416 | |
90daf306 | 417 | if (bg_thresh >= thresh) |
9fc3a43e | 418 | bg_thresh = thresh / 2; |
ccafa287 | 419 | tsk = current; |
a37b0715 | 420 | if (rt_task(tsk)) { |
a53eaff8 N |
421 | bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; |
422 | thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; | |
ccafa287 | 423 | } |
9fc3a43e TH |
424 | dtc->thresh = thresh; |
425 | dtc->bg_thresh = bg_thresh; | |
426 | ||
427 | /* we should eventually report the domain in the TP */ | |
428 | if (!gdtc) | |
429 | trace_global_dirty_state(bg_thresh, thresh); | |
430 | } | |
431 | ||
432 | /** | |
433 | * global_dirty_limits - background-writeback and dirty-throttling thresholds | |
434 | * @pbackground: out parameter for bg_thresh | |
435 | * @pdirty: out parameter for thresh | |
436 | * | |
437 | * Calculate bg_thresh and thresh for global_wb_domain. See | |
438 | * domain_dirty_limits() for details. | |
439 | */ | |
440 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) | |
441 | { | |
442 | struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; | |
443 | ||
444 | gdtc.avail = global_dirtyable_memory(); | |
445 | domain_dirty_limits(&gdtc); | |
446 | ||
447 | *pbackground = gdtc.bg_thresh; | |
448 | *pdirty = gdtc.thresh; | |
ccafa287 JW |
449 | } |
450 | ||
a756cf59 | 451 | /** |
281e3726 MG |
452 | * node_dirty_limit - maximum number of dirty pages allowed in a node |
453 | * @pgdat: the node | |
a756cf59 | 454 | * |
a862f68a | 455 | * Return: the maximum number of dirty pages allowed in a node, based |
281e3726 | 456 | * on the node's dirtyable memory. |
a756cf59 | 457 | */ |
281e3726 | 458 | static unsigned long node_dirty_limit(struct pglist_data *pgdat) |
a756cf59 | 459 | { |
281e3726 | 460 | unsigned long node_memory = node_dirtyable_memory(pgdat); |
a756cf59 JW |
461 | struct task_struct *tsk = current; |
462 | unsigned long dirty; | |
463 | ||
464 | if (vm_dirty_bytes) | |
465 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * | |
281e3726 | 466 | node_memory / global_dirtyable_memory(); |
a756cf59 | 467 | else |
281e3726 | 468 | dirty = vm_dirty_ratio * node_memory / 100; |
a756cf59 | 469 | |
a37b0715 | 470 | if (rt_task(tsk)) |
a756cf59 JW |
471 | dirty += dirty / 4; |
472 | ||
473 | return dirty; | |
474 | } | |
475 | ||
476 | /** | |
281e3726 MG |
477 | * node_dirty_ok - tells whether a node is within its dirty limits |
478 | * @pgdat: the node to check | |
a756cf59 | 479 | * |
a862f68a | 480 | * Return: %true when the dirty pages in @pgdat are within the node's |
a756cf59 JW |
481 | * dirty limit, %false if the limit is exceeded. |
482 | */ | |
281e3726 | 483 | bool node_dirty_ok(struct pglist_data *pgdat) |
a756cf59 | 484 | { |
281e3726 MG |
485 | unsigned long limit = node_dirty_limit(pgdat); |
486 | unsigned long nr_pages = 0; | |
487 | ||
11fb9989 | 488 | nr_pages += node_page_state(pgdat, NR_FILE_DIRTY); |
11fb9989 | 489 | nr_pages += node_page_state(pgdat, NR_WRITEBACK); |
a756cf59 | 490 | |
281e3726 | 491 | return nr_pages <= limit; |
a756cf59 JW |
492 | } |
493 | ||
aa779e51 | 494 | #ifdef CONFIG_SYSCTL |
495 | static int dirty_background_ratio_handler(struct ctl_table *table, int write, | |
32927393 | 496 | void *buffer, size_t *lenp, loff_t *ppos) |
2da02997 DR |
497 | { |
498 | int ret; | |
499 | ||
8d65af78 | 500 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
501 | if (ret == 0 && write) |
502 | dirty_background_bytes = 0; | |
503 | return ret; | |
504 | } | |
505 | ||
aa779e51 | 506 | static int dirty_background_bytes_handler(struct ctl_table *table, int write, |
32927393 | 507 | void *buffer, size_t *lenp, loff_t *ppos) |
2da02997 DR |
508 | { |
509 | int ret; | |
510 | ||
8d65af78 | 511 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
512 | if (ret == 0 && write) |
513 | dirty_background_ratio = 0; | |
514 | return ret; | |
515 | } | |
516 | ||
aa779e51 | 517 | static int dirty_ratio_handler(struct ctl_table *table, int write, void *buffer, |
32927393 | 518 | size_t *lenp, loff_t *ppos) |
04fbfdc1 PZ |
519 | { |
520 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
521 | int ret; |
522 | ||
8d65af78 | 523 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 524 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
eb608e3a | 525 | writeback_set_ratelimit(); |
2da02997 DR |
526 | vm_dirty_bytes = 0; |
527 | } | |
528 | return ret; | |
529 | } | |
530 | ||
aa779e51 | 531 | static int dirty_bytes_handler(struct ctl_table *table, int write, |
32927393 | 532 | void *buffer, size_t *lenp, loff_t *ppos) |
2da02997 | 533 | { |
fc3501d4 | 534 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
535 | int ret; |
536 | ||
8d65af78 | 537 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 | 538 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
eb608e3a | 539 | writeback_set_ratelimit(); |
2da02997 | 540 | vm_dirty_ratio = 0; |
04fbfdc1 PZ |
541 | } |
542 | return ret; | |
543 | } | |
aa779e51 | 544 | #endif |
04fbfdc1 | 545 | |
eb608e3a JK |
546 | static unsigned long wp_next_time(unsigned long cur_time) |
547 | { | |
548 | cur_time += VM_COMPLETIONS_PERIOD_LEN; | |
549 | /* 0 has a special meaning... */ | |
550 | if (!cur_time) | |
551 | return 1; | |
552 | return cur_time; | |
553 | } | |
554 | ||
cc24df4c | 555 | static void wb_domain_writeout_add(struct wb_domain *dom, |
c7981433 | 556 | struct fprop_local_percpu *completions, |
cc24df4c | 557 | unsigned int max_prop_frac, long nr) |
04fbfdc1 | 558 | { |
be5f1797 | 559 | __fprop_add_percpu_max(&dom->completions, completions, |
cc24df4c | 560 | max_prop_frac, nr); |
eb608e3a | 561 | /* First event after period switching was turned off? */ |
517663ed | 562 | if (unlikely(!dom->period_time)) { |
eb608e3a JK |
563 | /* |
564 | * We can race with other __bdi_writeout_inc calls here but | |
565 | * it does not cause any harm since the resulting time when | |
566 | * timer will fire and what is in writeout_period_time will be | |
567 | * roughly the same. | |
568 | */ | |
380c27ca TH |
569 | dom->period_time = wp_next_time(jiffies); |
570 | mod_timer(&dom->period_timer, dom->period_time); | |
eb608e3a | 571 | } |
04fbfdc1 PZ |
572 | } |
573 | ||
c7981433 TH |
574 | /* |
575 | * Increment @wb's writeout completion count and the global writeout | |
269ccca3 | 576 | * completion count. Called from __folio_end_writeback(). |
c7981433 | 577 | */ |
cc24df4c | 578 | static inline void __wb_writeout_add(struct bdi_writeback *wb, long nr) |
dd5656e5 | 579 | { |
841710aa | 580 | struct wb_domain *cgdom; |
dd5656e5 | 581 | |
cc24df4c MWO |
582 | wb_stat_mod(wb, WB_WRITTEN, nr); |
583 | wb_domain_writeout_add(&global_wb_domain, &wb->completions, | |
584 | wb->bdi->max_prop_frac, nr); | |
841710aa TH |
585 | |
586 | cgdom = mem_cgroup_wb_domain(wb); | |
587 | if (cgdom) | |
cc24df4c MWO |
588 | wb_domain_writeout_add(cgdom, wb_memcg_completions(wb), |
589 | wb->bdi->max_prop_frac, nr); | |
dd5656e5 | 590 | } |
dd5656e5 | 591 | |
93f78d88 | 592 | void wb_writeout_inc(struct bdi_writeback *wb) |
04fbfdc1 | 593 | { |
dd5656e5 MS |
594 | unsigned long flags; |
595 | ||
596 | local_irq_save(flags); | |
cc24df4c | 597 | __wb_writeout_add(wb, 1); |
dd5656e5 | 598 | local_irq_restore(flags); |
04fbfdc1 | 599 | } |
93f78d88 | 600 | EXPORT_SYMBOL_GPL(wb_writeout_inc); |
04fbfdc1 | 601 | |
eb608e3a JK |
602 | /* |
603 | * On idle system, we can be called long after we scheduled because we use | |
604 | * deferred timers so count with missed periods. | |
605 | */ | |
9823e51b | 606 | static void writeout_period(struct timer_list *t) |
eb608e3a | 607 | { |
9823e51b | 608 | struct wb_domain *dom = from_timer(dom, t, period_timer); |
380c27ca | 609 | int miss_periods = (jiffies - dom->period_time) / |
eb608e3a JK |
610 | VM_COMPLETIONS_PERIOD_LEN; |
611 | ||
380c27ca TH |
612 | if (fprop_new_period(&dom->completions, miss_periods + 1)) { |
613 | dom->period_time = wp_next_time(dom->period_time + | |
eb608e3a | 614 | miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
380c27ca | 615 | mod_timer(&dom->period_timer, dom->period_time); |
eb608e3a JK |
616 | } else { |
617 | /* | |
618 | * Aging has zeroed all fractions. Stop wasting CPU on period | |
619 | * updates. | |
620 | */ | |
380c27ca | 621 | dom->period_time = 0; |
eb608e3a JK |
622 | } |
623 | } | |
624 | ||
380c27ca TH |
625 | int wb_domain_init(struct wb_domain *dom, gfp_t gfp) |
626 | { | |
627 | memset(dom, 0, sizeof(*dom)); | |
dcc25ae7 TH |
628 | |
629 | spin_lock_init(&dom->lock); | |
630 | ||
9823e51b | 631 | timer_setup(&dom->period_timer, writeout_period, TIMER_DEFERRABLE); |
dcc25ae7 TH |
632 | |
633 | dom->dirty_limit_tstamp = jiffies; | |
634 | ||
380c27ca TH |
635 | return fprop_global_init(&dom->completions, gfp); |
636 | } | |
637 | ||
841710aa TH |
638 | #ifdef CONFIG_CGROUP_WRITEBACK |
639 | void wb_domain_exit(struct wb_domain *dom) | |
640 | { | |
641 | del_timer_sync(&dom->period_timer); | |
642 | fprop_global_destroy(&dom->completions); | |
643 | } | |
644 | #endif | |
645 | ||
189d3c4a | 646 | /* |
d08c429b JW |
647 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
648 | * registered backing devices, which, for obvious reasons, can not | |
649 | * exceed 100%. | |
189d3c4a | 650 | */ |
189d3c4a PZ |
651 | static unsigned int bdi_min_ratio; |
652 | ||
653 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
654 | { | |
21f0dd88 | 655 | unsigned int delta; |
189d3c4a | 656 | int ret = 0; |
189d3c4a | 657 | |
cfc4ba53 | 658 | spin_lock_bh(&bdi_lock); |
a42dde04 | 659 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 660 | ret = -EINVAL; |
a42dde04 | 661 | } else { |
21f0dd88 CW |
662 | if (min_ratio < bdi->min_ratio) { |
663 | delta = bdi->min_ratio - min_ratio; | |
664 | bdi_min_ratio -= delta; | |
665 | bdi->min_ratio = min_ratio; | |
a42dde04 | 666 | } else { |
21f0dd88 CW |
667 | delta = min_ratio - bdi->min_ratio; |
668 | if (bdi_min_ratio + delta < 100) { | |
669 | bdi_min_ratio += delta; | |
670 | bdi->min_ratio = min_ratio; | |
671 | } else { | |
672 | ret = -EINVAL; | |
673 | } | |
a42dde04 PZ |
674 | } |
675 | } | |
cfc4ba53 | 676 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
677 | |
678 | return ret; | |
679 | } | |
680 | ||
681 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
682 | { | |
a42dde04 PZ |
683 | int ret = 0; |
684 | ||
685 | if (max_ratio > 100) | |
686 | return -EINVAL; | |
687 | ||
cfc4ba53 | 688 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
689 | if (bdi->min_ratio > max_ratio) { |
690 | ret = -EINVAL; | |
691 | } else { | |
692 | bdi->max_ratio = max_ratio; | |
eb608e3a | 693 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
a42dde04 | 694 | } |
cfc4ba53 | 695 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
696 | |
697 | return ret; | |
698 | } | |
a42dde04 | 699 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 700 | |
6c14ae1e WF |
701 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
702 | unsigned long bg_thresh) | |
703 | { | |
704 | return (thresh + bg_thresh) / 2; | |
705 | } | |
706 | ||
c7981433 TH |
707 | static unsigned long hard_dirty_limit(struct wb_domain *dom, |
708 | unsigned long thresh) | |
ffd1f609 | 709 | { |
dcc25ae7 | 710 | return max(thresh, dom->dirty_limit); |
ffd1f609 WF |
711 | } |
712 | ||
c5edf9cd TH |
713 | /* |
714 | * Memory which can be further allocated to a memcg domain is capped by | |
715 | * system-wide clean memory excluding the amount being used in the domain. | |
716 | */ | |
717 | static void mdtc_calc_avail(struct dirty_throttle_control *mdtc, | |
718 | unsigned long filepages, unsigned long headroom) | |
c2aa723a TH |
719 | { |
720 | struct dirty_throttle_control *gdtc = mdtc_gdtc(mdtc); | |
c5edf9cd TH |
721 | unsigned long clean = filepages - min(filepages, mdtc->dirty); |
722 | unsigned long global_clean = gdtc->avail - min(gdtc->avail, gdtc->dirty); | |
723 | unsigned long other_clean = global_clean - min(global_clean, clean); | |
c2aa723a | 724 | |
c5edf9cd | 725 | mdtc->avail = filepages + min(headroom, other_clean); |
ffd1f609 WF |
726 | } |
727 | ||
6f718656 | 728 | /** |
b1cbc6d4 TH |
729 | * __wb_calc_thresh - @wb's share of dirty throttling threshold |
730 | * @dtc: dirty_throttle_context of interest | |
1babe183 | 731 | * |
aed21ad2 WF |
732 | * Note that balance_dirty_pages() will only seriously take it as a hard limit |
733 | * when sleeping max_pause per page is not enough to keep the dirty pages under | |
734 | * control. For example, when the device is completely stalled due to some error | |
735 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. | |
736 | * In the other normal situations, it acts more gently by throttling the tasks | |
a88a341a | 737 | * more (rather than completely block them) when the wb dirty pages go high. |
1babe183 | 738 | * |
6f718656 | 739 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
740 | * - starving fast devices |
741 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
742 | * | |
a88a341a | 743 | * The wb's share of dirty limit will be adapting to its throughput and |
1babe183 | 744 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
a862f68a MR |
745 | * |
746 | * Return: @wb's dirty limit in pages. The term "dirty" in the context of | |
8d92890b | 747 | * dirty balancing includes all PG_dirty and PG_writeback pages. |
1babe183 | 748 | */ |
b1cbc6d4 | 749 | static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) |
16c4042f | 750 | { |
e9f07dfd | 751 | struct wb_domain *dom = dtc_dom(dtc); |
b1cbc6d4 | 752 | unsigned long thresh = dtc->thresh; |
0d960a38 | 753 | u64 wb_thresh; |
d3ac946e | 754 | unsigned long numerator, denominator; |
693108a8 | 755 | unsigned long wb_min_ratio, wb_max_ratio; |
04fbfdc1 | 756 | |
16c4042f | 757 | /* |
0d960a38 | 758 | * Calculate this BDI's share of the thresh ratio. |
16c4042f | 759 | */ |
e9770b34 | 760 | fprop_fraction_percpu(&dom->completions, dtc->wb_completions, |
380c27ca | 761 | &numerator, &denominator); |
04fbfdc1 | 762 | |
0d960a38 TH |
763 | wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; |
764 | wb_thresh *= numerator; | |
d3ac946e | 765 | wb_thresh = div64_ul(wb_thresh, denominator); |
04fbfdc1 | 766 | |
b1cbc6d4 | 767 | wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); |
04fbfdc1 | 768 | |
0d960a38 TH |
769 | wb_thresh += (thresh * wb_min_ratio) / 100; |
770 | if (wb_thresh > (thresh * wb_max_ratio) / 100) | |
771 | wb_thresh = thresh * wb_max_ratio / 100; | |
16c4042f | 772 | |
0d960a38 | 773 | return wb_thresh; |
1da177e4 LT |
774 | } |
775 | ||
b1cbc6d4 TH |
776 | unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) |
777 | { | |
778 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb), | |
779 | .thresh = thresh }; | |
780 | return __wb_calc_thresh(&gdtc); | |
1da177e4 LT |
781 | } |
782 | ||
5a537485 MP |
783 | /* |
784 | * setpoint - dirty 3 | |
785 | * f(dirty) := 1.0 + (----------------) | |
786 | * limit - setpoint | |
787 | * | |
788 | * it's a 3rd order polynomial that subjects to | |
789 | * | |
790 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
791 | * (2) f(setpoint) = 1.0 => the balance point | |
792 | * (3) f(limit) = 0 => the hard limit | |
793 | * (4) df/dx <= 0 => negative feedback control | |
794 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
795 | * => fast response on large errors; small oscillation near setpoint | |
796 | */ | |
d5c9fde3 | 797 | static long long pos_ratio_polynom(unsigned long setpoint, |
5a537485 MP |
798 | unsigned long dirty, |
799 | unsigned long limit) | |
800 | { | |
801 | long long pos_ratio; | |
802 | long x; | |
803 | ||
d5c9fde3 | 804 | x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, |
464d1387 | 805 | (limit - setpoint) | 1); |
5a537485 MP |
806 | pos_ratio = x; |
807 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
808 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
809 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
810 | ||
811 | return clamp(pos_ratio, 0LL, 2LL << RATELIMIT_CALC_SHIFT); | |
812 | } | |
813 | ||
6c14ae1e WF |
814 | /* |
815 | * Dirty position control. | |
816 | * | |
817 | * (o) global/bdi setpoints | |
818 | * | |
de1fff37 | 819 | * We want the dirty pages be balanced around the global/wb setpoints. |
6c14ae1e WF |
820 | * When the number of dirty pages is higher/lower than the setpoint, the |
821 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
822 | * decreased/increased to bring the dirty pages back to the setpoint. | |
823 | * | |
824 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
825 | * | |
826 | * if (dirty < setpoint) scale up pos_ratio | |
827 | * if (dirty > setpoint) scale down pos_ratio | |
828 | * | |
de1fff37 TH |
829 | * if (wb_dirty < wb_setpoint) scale up pos_ratio |
830 | * if (wb_dirty > wb_setpoint) scale down pos_ratio | |
6c14ae1e WF |
831 | * |
832 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
833 | * | |
834 | * (o) global control line | |
835 | * | |
836 | * ^ pos_ratio | |
837 | * | | |
838 | * | |<===== global dirty control scope ======>| | |
03231554 | 839 | * 2.0 * * * * * * * |
6c14ae1e WF |
840 | * | .* |
841 | * | . * | |
842 | * | . * | |
843 | * | . * | |
844 | * | . * | |
845 | * | . * | |
846 | * 1.0 ................................* | |
847 | * | . . * | |
848 | * | . . * | |
849 | * | . . * | |
850 | * | . . * | |
851 | * | . . * | |
852 | * 0 +------------.------------------.----------------------*-------------> | |
853 | * freerun^ setpoint^ limit^ dirty pages | |
854 | * | |
de1fff37 | 855 | * (o) wb control line |
6c14ae1e WF |
856 | * |
857 | * ^ pos_ratio | |
858 | * | | |
859 | * | * | |
860 | * | * | |
861 | * | * | |
862 | * | * | |
863 | * | * |<=========== span ============>| | |
864 | * 1.0 .......................* | |
865 | * | . * | |
866 | * | . * | |
867 | * | . * | |
868 | * | . * | |
869 | * | . * | |
870 | * | . * | |
871 | * | . * | |
872 | * | . * | |
873 | * | . * | |
874 | * | . * | |
875 | * | . * | |
876 | * 1/4 ...............................................* * * * * * * * * * * * | |
877 | * | . . | |
878 | * | . . | |
879 | * | . . | |
880 | * 0 +----------------------.-------------------------------.-------------> | |
de1fff37 | 881 | * wb_setpoint^ x_intercept^ |
6c14ae1e | 882 | * |
de1fff37 | 883 | * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can |
6c14ae1e WF |
884 | * be smoothly throttled down to normal if it starts high in situations like |
885 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
de1fff37 TH |
886 | * card's wb_dirty may rush to many times higher than wb_setpoint. |
887 | * - the wb dirty thresh drops quickly due to change of JBOD workload | |
6c14ae1e | 888 | */ |
daddfa3c | 889 | static void wb_position_ratio(struct dirty_throttle_control *dtc) |
6c14ae1e | 890 | { |
2bc00aef | 891 | struct bdi_writeback *wb = dtc->wb; |
20792ebf | 892 | unsigned long write_bw = READ_ONCE(wb->avg_write_bandwidth); |
2bc00aef | 893 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
c7981433 | 894 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
2bc00aef | 895 | unsigned long wb_thresh = dtc->wb_thresh; |
6c14ae1e WF |
896 | unsigned long x_intercept; |
897 | unsigned long setpoint; /* dirty pages' target balance point */ | |
de1fff37 | 898 | unsigned long wb_setpoint; |
6c14ae1e WF |
899 | unsigned long span; |
900 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
901 | long x; | |
902 | ||
daddfa3c TH |
903 | dtc->pos_ratio = 0; |
904 | ||
2bc00aef | 905 | if (unlikely(dtc->dirty >= limit)) |
daddfa3c | 906 | return; |
6c14ae1e WF |
907 | |
908 | /* | |
909 | * global setpoint | |
910 | * | |
5a537485 MP |
911 | * See comment for pos_ratio_polynom(). |
912 | */ | |
913 | setpoint = (freerun + limit) / 2; | |
2bc00aef | 914 | pos_ratio = pos_ratio_polynom(setpoint, dtc->dirty, limit); |
5a537485 MP |
915 | |
916 | /* | |
917 | * The strictlimit feature is a tool preventing mistrusted filesystems | |
918 | * from growing a large number of dirty pages before throttling. For | |
de1fff37 TH |
919 | * such filesystems balance_dirty_pages always checks wb counters |
920 | * against wb limits. Even if global "nr_dirty" is under "freerun". | |
5a537485 MP |
921 | * This is especially important for fuse which sets bdi->max_ratio to |
922 | * 1% by default. Without strictlimit feature, fuse writeback may | |
923 | * consume arbitrary amount of RAM because it is accounted in | |
924 | * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". | |
6c14ae1e | 925 | * |
a88a341a | 926 | * Here, in wb_position_ratio(), we calculate pos_ratio based on |
de1fff37 | 927 | * two values: wb_dirty and wb_thresh. Let's consider an example: |
5a537485 MP |
928 | * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global |
929 | * limits are set by default to 10% and 20% (background and throttle). | |
de1fff37 | 930 | * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. |
0d960a38 | 931 | * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is |
de1fff37 | 932 | * about ~6K pages (as the average of background and throttle wb |
5a537485 | 933 | * limits). The 3rd order polynomial will provide positive feedback if |
de1fff37 | 934 | * wb_dirty is under wb_setpoint and vice versa. |
6c14ae1e | 935 | * |
5a537485 | 936 | * Note, that we cannot use global counters in these calculations |
de1fff37 | 937 | * because we want to throttle process writing to a strictlimit wb |
5a537485 MP |
938 | * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB |
939 | * in the example above). | |
6c14ae1e | 940 | */ |
a88a341a | 941 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
de1fff37 | 942 | long long wb_pos_ratio; |
5a537485 | 943 | |
daddfa3c TH |
944 | if (dtc->wb_dirty < 8) { |
945 | dtc->pos_ratio = min_t(long long, pos_ratio * 2, | |
946 | 2 << RATELIMIT_CALC_SHIFT); | |
947 | return; | |
948 | } | |
5a537485 | 949 | |
2bc00aef | 950 | if (dtc->wb_dirty >= wb_thresh) |
daddfa3c | 951 | return; |
5a537485 | 952 | |
970fb01a TH |
953 | wb_setpoint = dirty_freerun_ceiling(wb_thresh, |
954 | dtc->wb_bg_thresh); | |
5a537485 | 955 | |
de1fff37 | 956 | if (wb_setpoint == 0 || wb_setpoint == wb_thresh) |
daddfa3c | 957 | return; |
5a537485 | 958 | |
2bc00aef | 959 | wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, |
de1fff37 | 960 | wb_thresh); |
5a537485 MP |
961 | |
962 | /* | |
de1fff37 TH |
963 | * Typically, for strictlimit case, wb_setpoint << setpoint |
964 | * and pos_ratio >> wb_pos_ratio. In the other words global | |
5a537485 | 965 | * state ("dirty") is not limiting factor and we have to |
de1fff37 | 966 | * make decision based on wb counters. But there is an |
5a537485 MP |
967 | * important case when global pos_ratio should get precedence: |
968 | * global limits are exceeded (e.g. due to activities on other | |
de1fff37 | 969 | * wb's) while given strictlimit wb is below limit. |
5a537485 | 970 | * |
de1fff37 | 971 | * "pos_ratio * wb_pos_ratio" would work for the case above, |
5a537485 | 972 | * but it would look too non-natural for the case of all |
de1fff37 | 973 | * activity in the system coming from a single strictlimit wb |
5a537485 MP |
974 | * with bdi->max_ratio == 100%. |
975 | * | |
976 | * Note that min() below somewhat changes the dynamics of the | |
977 | * control system. Normally, pos_ratio value can be well over 3 | |
de1fff37 | 978 | * (when globally we are at freerun and wb is well below wb |
5a537485 MP |
979 | * setpoint). Now the maximum pos_ratio in the same situation |
980 | * is 2. We might want to tweak this if we observe the control | |
981 | * system is too slow to adapt. | |
982 | */ | |
daddfa3c TH |
983 | dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); |
984 | return; | |
5a537485 | 985 | } |
6c14ae1e WF |
986 | |
987 | /* | |
988 | * We have computed basic pos_ratio above based on global situation. If | |
de1fff37 | 989 | * the wb is over/under its share of dirty pages, we want to scale |
6c14ae1e WF |
990 | * pos_ratio further down/up. That is done by the following mechanism. |
991 | */ | |
992 | ||
993 | /* | |
de1fff37 | 994 | * wb setpoint |
6c14ae1e | 995 | * |
de1fff37 | 996 | * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) |
6c14ae1e | 997 | * |
de1fff37 | 998 | * x_intercept - wb_dirty |
6c14ae1e | 999 | * := -------------------------- |
de1fff37 | 1000 | * x_intercept - wb_setpoint |
6c14ae1e | 1001 | * |
de1fff37 | 1002 | * The main wb control line is a linear function that subjects to |
6c14ae1e | 1003 | * |
de1fff37 TH |
1004 | * (1) f(wb_setpoint) = 1.0 |
1005 | * (2) k = - 1 / (8 * write_bw) (in single wb case) | |
1006 | * or equally: x_intercept = wb_setpoint + 8 * write_bw | |
6c14ae1e | 1007 | * |
de1fff37 | 1008 | * For single wb case, the dirty pages are observed to fluctuate |
6c14ae1e | 1009 | * regularly within range |
de1fff37 | 1010 | * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] |
6c14ae1e WF |
1011 | * for various filesystems, where (2) can yield in a reasonable 12.5% |
1012 | * fluctuation range for pos_ratio. | |
1013 | * | |
de1fff37 | 1014 | * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its |
6c14ae1e | 1015 | * own size, so move the slope over accordingly and choose a slope that |
de1fff37 | 1016 | * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. |
6c14ae1e | 1017 | */ |
2bc00aef TH |
1018 | if (unlikely(wb_thresh > dtc->thresh)) |
1019 | wb_thresh = dtc->thresh; | |
aed21ad2 | 1020 | /* |
de1fff37 | 1021 | * It's very possible that wb_thresh is close to 0 not because the |
aed21ad2 WF |
1022 | * device is slow, but that it has remained inactive for long time. |
1023 | * Honour such devices a reasonable good (hopefully IO efficient) | |
1024 | * threshold, so that the occasional writes won't be blocked and active | |
1025 | * writes can rampup the threshold quickly. | |
1026 | */ | |
2bc00aef | 1027 | wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8); |
6c14ae1e | 1028 | /* |
de1fff37 TH |
1029 | * scale global setpoint to wb's: |
1030 | * wb_setpoint = setpoint * wb_thresh / thresh | |
6c14ae1e | 1031 | */ |
e4bc13ad | 1032 | x = div_u64((u64)wb_thresh << 16, dtc->thresh | 1); |
de1fff37 | 1033 | wb_setpoint = setpoint * (u64)x >> 16; |
6c14ae1e | 1034 | /* |
de1fff37 TH |
1035 | * Use span=(8*write_bw) in single wb case as indicated by |
1036 | * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. | |
6c14ae1e | 1037 | * |
de1fff37 TH |
1038 | * wb_thresh thresh - wb_thresh |
1039 | * span = --------- * (8 * write_bw) + ------------------ * wb_thresh | |
1040 | * thresh thresh | |
6c14ae1e | 1041 | */ |
2bc00aef | 1042 | span = (dtc->thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; |
de1fff37 | 1043 | x_intercept = wb_setpoint + span; |
6c14ae1e | 1044 | |
2bc00aef TH |
1045 | if (dtc->wb_dirty < x_intercept - span / 4) { |
1046 | pos_ratio = div64_u64(pos_ratio * (x_intercept - dtc->wb_dirty), | |
e4bc13ad | 1047 | (x_intercept - wb_setpoint) | 1); |
6c14ae1e WF |
1048 | } else |
1049 | pos_ratio /= 4; | |
1050 | ||
8927f66c | 1051 | /* |
de1fff37 | 1052 | * wb reserve area, safeguard against dirty pool underrun and disk idle |
8927f66c WF |
1053 | * It may push the desired control point of global dirty pages higher |
1054 | * than setpoint. | |
1055 | */ | |
de1fff37 | 1056 | x_intercept = wb_thresh / 2; |
2bc00aef TH |
1057 | if (dtc->wb_dirty < x_intercept) { |
1058 | if (dtc->wb_dirty > x_intercept / 8) | |
1059 | pos_ratio = div_u64(pos_ratio * x_intercept, | |
1060 | dtc->wb_dirty); | |
50657fc4 | 1061 | else |
8927f66c WF |
1062 | pos_ratio *= 8; |
1063 | } | |
1064 | ||
daddfa3c | 1065 | dtc->pos_ratio = pos_ratio; |
6c14ae1e WF |
1066 | } |
1067 | ||
a88a341a TH |
1068 | static void wb_update_write_bandwidth(struct bdi_writeback *wb, |
1069 | unsigned long elapsed, | |
1070 | unsigned long written) | |
e98be2d5 WF |
1071 | { |
1072 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
a88a341a TH |
1073 | unsigned long avg = wb->avg_write_bandwidth; |
1074 | unsigned long old = wb->write_bandwidth; | |
e98be2d5 WF |
1075 | u64 bw; |
1076 | ||
1077 | /* | |
1078 | * bw = written * HZ / elapsed | |
1079 | * | |
1080 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
1081 | * write_bandwidth = --------------------------------------------------- | |
1082 | * period | |
c72efb65 | 1083 | * |
25ff8b15 | 1084 | * @written may have decreased due to folio_account_redirty(). |
c72efb65 | 1085 | * Avoid underflowing @bw calculation. |
e98be2d5 | 1086 | */ |
a88a341a | 1087 | bw = written - min(written, wb->written_stamp); |
e98be2d5 WF |
1088 | bw *= HZ; |
1089 | if (unlikely(elapsed > period)) { | |
0a5d1a7f | 1090 | bw = div64_ul(bw, elapsed); |
e98be2d5 WF |
1091 | avg = bw; |
1092 | goto out; | |
1093 | } | |
a88a341a | 1094 | bw += (u64)wb->write_bandwidth * (period - elapsed); |
e98be2d5 WF |
1095 | bw >>= ilog2(period); |
1096 | ||
1097 | /* | |
1098 | * one more level of smoothing, for filtering out sudden spikes | |
1099 | */ | |
1100 | if (avg > old && old >= (unsigned long)bw) | |
1101 | avg -= (avg - old) >> 3; | |
1102 | ||
1103 | if (avg < old && old <= (unsigned long)bw) | |
1104 | avg += (old - avg) >> 3; | |
1105 | ||
1106 | out: | |
95a46c65 TH |
1107 | /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ |
1108 | avg = max(avg, 1LU); | |
1109 | if (wb_has_dirty_io(wb)) { | |
1110 | long delta = avg - wb->avg_write_bandwidth; | |
1111 | WARN_ON_ONCE(atomic_long_add_return(delta, | |
1112 | &wb->bdi->tot_write_bandwidth) <= 0); | |
1113 | } | |
a88a341a | 1114 | wb->write_bandwidth = bw; |
20792ebf | 1115 | WRITE_ONCE(wb->avg_write_bandwidth, avg); |
e98be2d5 WF |
1116 | } |
1117 | ||
2bc00aef | 1118 | static void update_dirty_limit(struct dirty_throttle_control *dtc) |
c42843f2 | 1119 | { |
e9f07dfd | 1120 | struct wb_domain *dom = dtc_dom(dtc); |
2bc00aef | 1121 | unsigned long thresh = dtc->thresh; |
dcc25ae7 | 1122 | unsigned long limit = dom->dirty_limit; |
c42843f2 WF |
1123 | |
1124 | /* | |
1125 | * Follow up in one step. | |
1126 | */ | |
1127 | if (limit < thresh) { | |
1128 | limit = thresh; | |
1129 | goto update; | |
1130 | } | |
1131 | ||
1132 | /* | |
1133 | * Follow down slowly. Use the higher one as the target, because thresh | |
1134 | * may drop below dirty. This is exactly the reason to introduce | |
dcc25ae7 | 1135 | * dom->dirty_limit which is guaranteed to lie above the dirty pages. |
c42843f2 | 1136 | */ |
2bc00aef | 1137 | thresh = max(thresh, dtc->dirty); |
c42843f2 WF |
1138 | if (limit > thresh) { |
1139 | limit -= (limit - thresh) >> 5; | |
1140 | goto update; | |
1141 | } | |
1142 | return; | |
1143 | update: | |
dcc25ae7 | 1144 | dom->dirty_limit = limit; |
c42843f2 WF |
1145 | } |
1146 | ||
42dd235c JK |
1147 | static void domain_update_dirty_limit(struct dirty_throttle_control *dtc, |
1148 | unsigned long now) | |
c42843f2 | 1149 | { |
e9f07dfd | 1150 | struct wb_domain *dom = dtc_dom(dtc); |
c42843f2 WF |
1151 | |
1152 | /* | |
1153 | * check locklessly first to optimize away locking for the most time | |
1154 | */ | |
dcc25ae7 | 1155 | if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) |
c42843f2 WF |
1156 | return; |
1157 | ||
dcc25ae7 TH |
1158 | spin_lock(&dom->lock); |
1159 | if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) { | |
2bc00aef | 1160 | update_dirty_limit(dtc); |
dcc25ae7 | 1161 | dom->dirty_limit_tstamp = now; |
c42843f2 | 1162 | } |
dcc25ae7 | 1163 | spin_unlock(&dom->lock); |
c42843f2 WF |
1164 | } |
1165 | ||
be3ffa27 | 1166 | /* |
de1fff37 | 1167 | * Maintain wb->dirty_ratelimit, the base dirty throttle rate. |
be3ffa27 | 1168 | * |
de1fff37 | 1169 | * Normal wb tasks will be curbed at or below it in long term. |
be3ffa27 WF |
1170 | * Obviously it should be around (write_bw / N) when there are N dd tasks. |
1171 | */ | |
2bc00aef | 1172 | static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, |
a88a341a TH |
1173 | unsigned long dirtied, |
1174 | unsigned long elapsed) | |
be3ffa27 | 1175 | { |
2bc00aef TH |
1176 | struct bdi_writeback *wb = dtc->wb; |
1177 | unsigned long dirty = dtc->dirty; | |
1178 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); | |
c7981433 | 1179 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
7381131c | 1180 | unsigned long setpoint = (freerun + limit) / 2; |
a88a341a TH |
1181 | unsigned long write_bw = wb->avg_write_bandwidth; |
1182 | unsigned long dirty_ratelimit = wb->dirty_ratelimit; | |
be3ffa27 WF |
1183 | unsigned long dirty_rate; |
1184 | unsigned long task_ratelimit; | |
1185 | unsigned long balanced_dirty_ratelimit; | |
7381131c WF |
1186 | unsigned long step; |
1187 | unsigned long x; | |
d59b1087 | 1188 | unsigned long shift; |
be3ffa27 WF |
1189 | |
1190 | /* | |
1191 | * The dirty rate will match the writeout rate in long term, except | |
1192 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
1193 | */ | |
a88a341a | 1194 | dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; |
be3ffa27 | 1195 | |
be3ffa27 WF |
1196 | /* |
1197 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
1198 | */ | |
1199 | task_ratelimit = (u64)dirty_ratelimit * | |
daddfa3c | 1200 | dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; |
be3ffa27 WF |
1201 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
1202 | ||
1203 | /* | |
1204 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
de1fff37 | 1205 | * if there are N dd tasks, each throttled at task_ratelimit, the wb's |
be3ffa27 WF |
1206 | * dirty_rate will be measured to be (N * task_ratelimit). So the below |
1207 | * formula will yield the balanced rate limit (write_bw / N). | |
1208 | * | |
1209 | * Note that the expanded form is not a pure rate feedback: | |
1210 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
1211 | * but also takes pos_ratio into account: | |
1212 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
1213 | * | |
1214 | * (1) is not realistic because pos_ratio also takes part in balancing | |
1215 | * the dirty rate. Consider the state | |
1216 | * pos_ratio = 0.5 (3) | |
1217 | * rate = 2 * (write_bw / N) (4) | |
1218 | * If (1) is used, it will stuck in that state! Because each dd will | |
1219 | * be throttled at | |
1220 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
1221 | * yielding | |
1222 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
1223 | * put (6) into (1) we get | |
1224 | * rate_(i+1) = rate_(i) (7) | |
1225 | * | |
1226 | * So we end up using (2) to always keep | |
1227 | * rate_(i+1) ~= (write_bw / N) (8) | |
1228 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
1229 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
1230 | * the dirty count meet the setpoint, but also where the slope of | |
1231 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
1232 | */ | |
1233 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
1234 | dirty_rate | 1); | |
bdaac490 WF |
1235 | /* |
1236 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw | |
1237 | */ | |
1238 | if (unlikely(balanced_dirty_ratelimit > write_bw)) | |
1239 | balanced_dirty_ratelimit = write_bw; | |
be3ffa27 | 1240 | |
7381131c WF |
1241 | /* |
1242 | * We could safely do this and return immediately: | |
1243 | * | |
de1fff37 | 1244 | * wb->dirty_ratelimit = balanced_dirty_ratelimit; |
7381131c WF |
1245 | * |
1246 | * However to get a more stable dirty_ratelimit, the below elaborated | |
331cbdee | 1247 | * code makes use of task_ratelimit to filter out singular points and |
7381131c WF |
1248 | * limit the step size. |
1249 | * | |
1250 | * The below code essentially only uses the relative value of | |
1251 | * | |
1252 | * task_ratelimit - dirty_ratelimit | |
1253 | * = (pos_ratio - 1) * dirty_ratelimit | |
1254 | * | |
1255 | * which reflects the direction and size of dirty position error. | |
1256 | */ | |
1257 | ||
1258 | /* | |
1259 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff | |
1260 | * task_ratelimit is on the same side of dirty_ratelimit, too. | |
1261 | * For example, when | |
1262 | * - dirty_ratelimit > balanced_dirty_ratelimit | |
1263 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) | |
1264 | * lowering dirty_ratelimit will help meet both the position and rate | |
1265 | * control targets. Otherwise, don't update dirty_ratelimit if it will | |
1266 | * only help meet the rate target. After all, what the users ultimately | |
1267 | * feel and care are stable dirty rate and small position error. | |
1268 | * | |
1269 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size | |
331cbdee | 1270 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
7381131c WF |
1271 | * keeps jumping around randomly and can even leap far away at times |
1272 | * due to the small 200ms estimation period of dirty_rate (we want to | |
1273 | * keep that period small to reduce time lags). | |
1274 | */ | |
1275 | step = 0; | |
5a537485 MP |
1276 | |
1277 | /* | |
de1fff37 | 1278 | * For strictlimit case, calculations above were based on wb counters |
a88a341a | 1279 | * and limits (starting from pos_ratio = wb_position_ratio() and up to |
5a537485 | 1280 | * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). |
de1fff37 TH |
1281 | * Hence, to calculate "step" properly, we have to use wb_dirty as |
1282 | * "dirty" and wb_setpoint as "setpoint". | |
5a537485 | 1283 | * |
de1fff37 TH |
1284 | * We rampup dirty_ratelimit forcibly if wb_dirty is low because |
1285 | * it's possible that wb_thresh is close to zero due to inactivity | |
970fb01a | 1286 | * of backing device. |
5a537485 | 1287 | */ |
a88a341a | 1288 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
2bc00aef TH |
1289 | dirty = dtc->wb_dirty; |
1290 | if (dtc->wb_dirty < 8) | |
1291 | setpoint = dtc->wb_dirty + 1; | |
5a537485 | 1292 | else |
970fb01a | 1293 | setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; |
5a537485 MP |
1294 | } |
1295 | ||
7381131c | 1296 | if (dirty < setpoint) { |
a88a341a | 1297 | x = min3(wb->balanced_dirty_ratelimit, |
7c809968 | 1298 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1299 | if (dirty_ratelimit < x) |
1300 | step = x - dirty_ratelimit; | |
1301 | } else { | |
a88a341a | 1302 | x = max3(wb->balanced_dirty_ratelimit, |
7c809968 | 1303 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1304 | if (dirty_ratelimit > x) |
1305 | step = dirty_ratelimit - x; | |
1306 | } | |
1307 | ||
1308 | /* | |
1309 | * Don't pursue 100% rate matching. It's impossible since the balanced | |
1310 | * rate itself is constantly fluctuating. So decrease the track speed | |
1311 | * when it gets close to the target. Helps eliminate pointless tremors. | |
1312 | */ | |
d59b1087 AR |
1313 | shift = dirty_ratelimit / (2 * step + 1); |
1314 | if (shift < BITS_PER_LONG) | |
1315 | step = DIV_ROUND_UP(step >> shift, 8); | |
1316 | else | |
1317 | step = 0; | |
7381131c WF |
1318 | |
1319 | if (dirty_ratelimit < balanced_dirty_ratelimit) | |
1320 | dirty_ratelimit += step; | |
1321 | else | |
1322 | dirty_ratelimit -= step; | |
1323 | ||
20792ebf | 1324 | WRITE_ONCE(wb->dirty_ratelimit, max(dirty_ratelimit, 1UL)); |
a88a341a | 1325 | wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit; |
b48c104d | 1326 | |
5634cc2a | 1327 | trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit); |
be3ffa27 WF |
1328 | } |
1329 | ||
c2aa723a TH |
1330 | static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc, |
1331 | struct dirty_throttle_control *mdtc, | |
8a731799 | 1332 | bool update_ratelimit) |
e98be2d5 | 1333 | { |
c2aa723a | 1334 | struct bdi_writeback *wb = gdtc->wb; |
e98be2d5 | 1335 | unsigned long now = jiffies; |
45a2966f | 1336 | unsigned long elapsed; |
be3ffa27 | 1337 | unsigned long dirtied; |
e98be2d5 WF |
1338 | unsigned long written; |
1339 | ||
45a2966f | 1340 | spin_lock(&wb->list_lock); |
8a731799 | 1341 | |
e98be2d5 | 1342 | /* |
45a2966f JK |
1343 | * Lockless checks for elapsed time are racy and delayed update after |
1344 | * IO completion doesn't do it at all (to make sure written pages are | |
1345 | * accounted reasonably quickly). Make sure elapsed >= 1 to avoid | |
1346 | * division errors. | |
e98be2d5 | 1347 | */ |
45a2966f | 1348 | elapsed = max(now - wb->bw_time_stamp, 1UL); |
a88a341a TH |
1349 | dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]); |
1350 | written = percpu_counter_read(&wb->stat[WB_WRITTEN]); | |
e98be2d5 | 1351 | |
8a731799 | 1352 | if (update_ratelimit) { |
42dd235c | 1353 | domain_update_dirty_limit(gdtc, now); |
c2aa723a TH |
1354 | wb_update_dirty_ratelimit(gdtc, dirtied, elapsed); |
1355 | ||
1356 | /* | |
1357 | * @mdtc is always NULL if !CGROUP_WRITEBACK but the | |
1358 | * compiler has no way to figure that out. Help it. | |
1359 | */ | |
1360 | if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { | |
42dd235c | 1361 | domain_update_dirty_limit(mdtc, now); |
c2aa723a TH |
1362 | wb_update_dirty_ratelimit(mdtc, dirtied, elapsed); |
1363 | } | |
be3ffa27 | 1364 | } |
a88a341a | 1365 | wb_update_write_bandwidth(wb, elapsed, written); |
e98be2d5 | 1366 | |
a88a341a TH |
1367 | wb->dirtied_stamp = dirtied; |
1368 | wb->written_stamp = written; | |
20792ebf | 1369 | WRITE_ONCE(wb->bw_time_stamp, now); |
45a2966f | 1370 | spin_unlock(&wb->list_lock); |
e98be2d5 WF |
1371 | } |
1372 | ||
45a2966f | 1373 | void wb_update_bandwidth(struct bdi_writeback *wb) |
e98be2d5 | 1374 | { |
2bc00aef TH |
1375 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb) }; |
1376 | ||
fee468fd | 1377 | __wb_update_bandwidth(&gdtc, NULL, false); |
fee468fd JK |
1378 | } |
1379 | ||
1380 | /* Interval after which we consider wb idle and don't estimate bandwidth */ | |
1381 | #define WB_BANDWIDTH_IDLE_JIF (HZ) | |
1382 | ||
1383 | static void wb_bandwidth_estimate_start(struct bdi_writeback *wb) | |
1384 | { | |
1385 | unsigned long now = jiffies; | |
1386 | unsigned long elapsed = now - READ_ONCE(wb->bw_time_stamp); | |
1387 | ||
1388 | if (elapsed > WB_BANDWIDTH_IDLE_JIF && | |
1389 | !atomic_read(&wb->writeback_inodes)) { | |
1390 | spin_lock(&wb->list_lock); | |
1391 | wb->dirtied_stamp = wb_stat(wb, WB_DIRTIED); | |
1392 | wb->written_stamp = wb_stat(wb, WB_WRITTEN); | |
20792ebf | 1393 | WRITE_ONCE(wb->bw_time_stamp, now); |
fee468fd JK |
1394 | spin_unlock(&wb->list_lock); |
1395 | } | |
e98be2d5 WF |
1396 | } |
1397 | ||
9d823e8f | 1398 | /* |
d0e1d66b | 1399 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
9d823e8f WF |
1400 | * will look to see if it needs to start dirty throttling. |
1401 | * | |
1402 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive | |
c41f012a | 1403 | * global_zone_page_state() too often. So scale it near-sqrt to the safety margin |
9d823e8f WF |
1404 | * (the number of pages we may dirty without exceeding the dirty limits). |
1405 | */ | |
1406 | static unsigned long dirty_poll_interval(unsigned long dirty, | |
1407 | unsigned long thresh) | |
1408 | { | |
1409 | if (thresh > dirty) | |
1410 | return 1UL << (ilog2(thresh - dirty) >> 1); | |
1411 | ||
1412 | return 1; | |
1413 | } | |
1414 | ||
a88a341a | 1415 | static unsigned long wb_max_pause(struct bdi_writeback *wb, |
de1fff37 | 1416 | unsigned long wb_dirty) |
c8462cc9 | 1417 | { |
20792ebf | 1418 | unsigned long bw = READ_ONCE(wb->avg_write_bandwidth); |
e3b6c655 | 1419 | unsigned long t; |
c8462cc9 | 1420 | |
7ccb9ad5 WF |
1421 | /* |
1422 | * Limit pause time for small memory systems. If sleeping for too long | |
1423 | * time, a small pool of dirty/writeback pages may go empty and disk go | |
1424 | * idle. | |
1425 | * | |
1426 | * 8 serves as the safety ratio. | |
1427 | */ | |
de1fff37 | 1428 | t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
7ccb9ad5 WF |
1429 | t++; |
1430 | ||
e3b6c655 | 1431 | return min_t(unsigned long, t, MAX_PAUSE); |
7ccb9ad5 WF |
1432 | } |
1433 | ||
a88a341a TH |
1434 | static long wb_min_pause(struct bdi_writeback *wb, |
1435 | long max_pause, | |
1436 | unsigned long task_ratelimit, | |
1437 | unsigned long dirty_ratelimit, | |
1438 | int *nr_dirtied_pause) | |
c8462cc9 | 1439 | { |
20792ebf JK |
1440 | long hi = ilog2(READ_ONCE(wb->avg_write_bandwidth)); |
1441 | long lo = ilog2(READ_ONCE(wb->dirty_ratelimit)); | |
7ccb9ad5 WF |
1442 | long t; /* target pause */ |
1443 | long pause; /* estimated next pause */ | |
1444 | int pages; /* target nr_dirtied_pause */ | |
c8462cc9 | 1445 | |
7ccb9ad5 WF |
1446 | /* target for 10ms pause on 1-dd case */ |
1447 | t = max(1, HZ / 100); | |
c8462cc9 WF |
1448 | |
1449 | /* | |
1450 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
1451 | * overheads. | |
1452 | * | |
7ccb9ad5 | 1453 | * (N * 10ms) on 2^N concurrent tasks. |
c8462cc9 WF |
1454 | */ |
1455 | if (hi > lo) | |
7ccb9ad5 | 1456 | t += (hi - lo) * (10 * HZ) / 1024; |
c8462cc9 WF |
1457 | |
1458 | /* | |
7ccb9ad5 WF |
1459 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
1460 | * on the much more stable dirty_ratelimit. However the next pause time | |
1461 | * will be computed based on task_ratelimit and the two rate limits may | |
1462 | * depart considerably at some time. Especially if task_ratelimit goes | |
1463 | * below dirty_ratelimit/2 and the target pause is max_pause, the next | |
1464 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a | |
1465 | * result task_ratelimit won't be executed faithfully, which could | |
1466 | * eventually bring down dirty_ratelimit. | |
c8462cc9 | 1467 | * |
7ccb9ad5 WF |
1468 | * We apply two rules to fix it up: |
1469 | * 1) try to estimate the next pause time and if necessary, use a lower | |
1470 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, | |
1471 | * nr_dirtied_pause will be "dancing" with task_ratelimit. | |
1472 | * 2) limit the target pause time to max_pause/2, so that the normal | |
1473 | * small fluctuations of task_ratelimit won't trigger rule (1) and | |
1474 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. | |
c8462cc9 | 1475 | */ |
7ccb9ad5 WF |
1476 | t = min(t, 1 + max_pause / 2); |
1477 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
c8462cc9 WF |
1478 | |
1479 | /* | |
5b9b3574 WF |
1480 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
1481 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. | |
1482 | * When the 16 consecutive reads are often interrupted by some dirty | |
1483 | * throttling pause during the async writes, cfq will go into idles | |
1484 | * (deadline is fine). So push nr_dirtied_pause as high as possible | |
1485 | * until reaches DIRTY_POLL_THRESH=32 pages. | |
c8462cc9 | 1486 | */ |
5b9b3574 WF |
1487 | if (pages < DIRTY_POLL_THRESH) { |
1488 | t = max_pause; | |
1489 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
1490 | if (pages > DIRTY_POLL_THRESH) { | |
1491 | pages = DIRTY_POLL_THRESH; | |
1492 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; | |
1493 | } | |
1494 | } | |
1495 | ||
7ccb9ad5 WF |
1496 | pause = HZ * pages / (task_ratelimit + 1); |
1497 | if (pause > max_pause) { | |
1498 | t = max_pause; | |
1499 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); | |
1500 | } | |
c8462cc9 | 1501 | |
7ccb9ad5 | 1502 | *nr_dirtied_pause = pages; |
c8462cc9 | 1503 | /* |
7ccb9ad5 | 1504 | * The minimal pause time will normally be half the target pause time. |
c8462cc9 | 1505 | */ |
5b9b3574 | 1506 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
c8462cc9 WF |
1507 | } |
1508 | ||
970fb01a | 1509 | static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) |
5a537485 | 1510 | { |
2bc00aef | 1511 | struct bdi_writeback *wb = dtc->wb; |
93f78d88 | 1512 | unsigned long wb_reclaimable; |
5a537485 MP |
1513 | |
1514 | /* | |
de1fff37 | 1515 | * wb_thresh is not treated as some limiting factor as |
5a537485 | 1516 | * dirty_thresh, due to reasons |
de1fff37 | 1517 | * - in JBOD setup, wb_thresh can fluctuate a lot |
5a537485 | 1518 | * - in a system with HDD and USB key, the USB key may somehow |
de1fff37 TH |
1519 | * go into state (wb_dirty >> wb_thresh) either because |
1520 | * wb_dirty starts high, or because wb_thresh drops low. | |
5a537485 | 1521 | * In this case we don't want to hard throttle the USB key |
de1fff37 TH |
1522 | * dirtiers for 100 seconds until wb_dirty drops under |
1523 | * wb_thresh. Instead the auxiliary wb control line in | |
a88a341a | 1524 | * wb_position_ratio() will let the dirtier task progress |
de1fff37 | 1525 | * at some rate <= (write_bw / 2) for bringing down wb_dirty. |
5a537485 | 1526 | */ |
b1cbc6d4 | 1527 | dtc->wb_thresh = __wb_calc_thresh(dtc); |
970fb01a TH |
1528 | dtc->wb_bg_thresh = dtc->thresh ? |
1529 | div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; | |
5a537485 MP |
1530 | |
1531 | /* | |
1532 | * In order to avoid the stacked BDI deadlock we need | |
1533 | * to ensure we accurately count the 'dirty' pages when | |
1534 | * the threshold is low. | |
1535 | * | |
1536 | * Otherwise it would be possible to get thresh+n pages | |
1537 | * reported dirty, even though there are thresh-m pages | |
1538 | * actually dirty; with m+n sitting in the percpu | |
1539 | * deltas. | |
1540 | */ | |
2bce774e | 1541 | if (dtc->wb_thresh < 2 * wb_stat_error()) { |
93f78d88 | 1542 | wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
2bc00aef | 1543 | dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); |
5a537485 | 1544 | } else { |
93f78d88 | 1545 | wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
2bc00aef | 1546 | dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); |
5a537485 MP |
1547 | } |
1548 | } | |
1549 | ||
1da177e4 LT |
1550 | /* |
1551 | * balance_dirty_pages() must be called by processes which are generating dirty | |
1552 | * data. It looks at the number of dirty pages in the machine and will force | |
143dfe86 | 1553 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1554 | * If we're over `background_thresh' then the writeback threads are woken to |
1555 | * perform some writeout. | |
1da177e4 | 1556 | */ |
4c578dce | 1557 | static void balance_dirty_pages(struct bdi_writeback *wb, |
143dfe86 | 1558 | unsigned long pages_dirtied) |
1da177e4 | 1559 | { |
2bc00aef | 1560 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1561 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
2bc00aef | 1562 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1563 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1564 | &mdtc_stor : NULL; | |
1565 | struct dirty_throttle_control *sdtc; | |
8d92890b | 1566 | unsigned long nr_reclaimable; /* = file_dirty */ |
83712358 | 1567 | long period; |
7ccb9ad5 WF |
1568 | long pause; |
1569 | long max_pause; | |
1570 | long min_pause; | |
1571 | int nr_dirtied_pause; | |
e50e3720 | 1572 | bool dirty_exceeded = false; |
143dfe86 | 1573 | unsigned long task_ratelimit; |
7ccb9ad5 | 1574 | unsigned long dirty_ratelimit; |
dfb8ae56 | 1575 | struct backing_dev_info *bdi = wb->bdi; |
5a537485 | 1576 | bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; |
e98be2d5 | 1577 | unsigned long start_time = jiffies; |
1da177e4 LT |
1578 | |
1579 | for (;;) { | |
83712358 | 1580 | unsigned long now = jiffies; |
2bc00aef | 1581 | unsigned long dirty, thresh, bg_thresh; |
50e55bf6 YS |
1582 | unsigned long m_dirty = 0; /* stop bogus uninit warnings */ |
1583 | unsigned long m_thresh = 0; | |
1584 | unsigned long m_bg_thresh = 0; | |
83712358 | 1585 | |
8d92890b | 1586 | nr_reclaimable = global_node_page_state(NR_FILE_DIRTY); |
9fc3a43e | 1587 | gdtc->avail = global_dirtyable_memory(); |
11fb9989 | 1588 | gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK); |
5fce25a9 | 1589 | |
9fc3a43e | 1590 | domain_dirty_limits(gdtc); |
16c4042f | 1591 | |
5a537485 | 1592 | if (unlikely(strictlimit)) { |
970fb01a | 1593 | wb_dirty_limits(gdtc); |
5a537485 | 1594 | |
2bc00aef TH |
1595 | dirty = gdtc->wb_dirty; |
1596 | thresh = gdtc->wb_thresh; | |
970fb01a | 1597 | bg_thresh = gdtc->wb_bg_thresh; |
5a537485 | 1598 | } else { |
2bc00aef TH |
1599 | dirty = gdtc->dirty; |
1600 | thresh = gdtc->thresh; | |
1601 | bg_thresh = gdtc->bg_thresh; | |
5a537485 MP |
1602 | } |
1603 | ||
c2aa723a | 1604 | if (mdtc) { |
c5edf9cd | 1605 | unsigned long filepages, headroom, writeback; |
c2aa723a TH |
1606 | |
1607 | /* | |
1608 | * If @wb belongs to !root memcg, repeat the same | |
1609 | * basic calculations for the memcg domain. | |
1610 | */ | |
c5edf9cd TH |
1611 | mem_cgroup_wb_stats(wb, &filepages, &headroom, |
1612 | &mdtc->dirty, &writeback); | |
c2aa723a | 1613 | mdtc->dirty += writeback; |
c5edf9cd | 1614 | mdtc_calc_avail(mdtc, filepages, headroom); |
c2aa723a TH |
1615 | |
1616 | domain_dirty_limits(mdtc); | |
1617 | ||
1618 | if (unlikely(strictlimit)) { | |
1619 | wb_dirty_limits(mdtc); | |
1620 | m_dirty = mdtc->wb_dirty; | |
1621 | m_thresh = mdtc->wb_thresh; | |
1622 | m_bg_thresh = mdtc->wb_bg_thresh; | |
1623 | } else { | |
1624 | m_dirty = mdtc->dirty; | |
1625 | m_thresh = mdtc->thresh; | |
1626 | m_bg_thresh = mdtc->bg_thresh; | |
1627 | } | |
5a537485 MP |
1628 | } |
1629 | ||
16c4042f WF |
1630 | /* |
1631 | * Throttle it only when the background writeback cannot | |
1632 | * catch-up. This avoids (excessively) small writeouts | |
de1fff37 | 1633 | * when the wb limits are ramping up in case of !strictlimit. |
5a537485 | 1634 | * |
de1fff37 TH |
1635 | * In strictlimit case make decision based on the wb counters |
1636 | * and limits. Small writeouts when the wb limits are ramping | |
5a537485 | 1637 | * up are the price we consciously pay for strictlimit-ing. |
c2aa723a TH |
1638 | * |
1639 | * If memcg domain is in effect, @dirty should be under | |
1640 | * both global and memcg freerun ceilings. | |
16c4042f | 1641 | */ |
c2aa723a TH |
1642 | if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) && |
1643 | (!mdtc || | |
1644 | m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) { | |
a37b0715 N |
1645 | unsigned long intv; |
1646 | unsigned long m_intv; | |
1647 | ||
1648 | free_running: | |
1649 | intv = dirty_poll_interval(dirty, thresh); | |
1650 | m_intv = ULONG_MAX; | |
c2aa723a | 1651 | |
83712358 WF |
1652 | current->dirty_paused_when = now; |
1653 | current->nr_dirtied = 0; | |
c2aa723a TH |
1654 | if (mdtc) |
1655 | m_intv = dirty_poll_interval(m_dirty, m_thresh); | |
1656 | current->nr_dirtied_pause = min(intv, m_intv); | |
16c4042f | 1657 | break; |
83712358 | 1658 | } |
16c4042f | 1659 | |
bc05873d | 1660 | if (unlikely(!writeback_in_progress(wb))) |
9ecf4866 | 1661 | wb_start_background_writeback(wb); |
143dfe86 | 1662 | |
97b27821 TH |
1663 | mem_cgroup_flush_foreign(wb); |
1664 | ||
c2aa723a TH |
1665 | /* |
1666 | * Calculate global domain's pos_ratio and select the | |
1667 | * global dtc by default. | |
1668 | */ | |
a37b0715 | 1669 | if (!strictlimit) { |
970fb01a | 1670 | wb_dirty_limits(gdtc); |
5fce25a9 | 1671 | |
a37b0715 N |
1672 | if ((current->flags & PF_LOCAL_THROTTLE) && |
1673 | gdtc->wb_dirty < | |
1674 | dirty_freerun_ceiling(gdtc->wb_thresh, | |
1675 | gdtc->wb_bg_thresh)) | |
1676 | /* | |
1677 | * LOCAL_THROTTLE tasks must not be throttled | |
1678 | * when below the per-wb freerun ceiling. | |
1679 | */ | |
1680 | goto free_running; | |
1681 | } | |
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 | */ | |
a37b0715 | 1696 | if (!strictlimit) { |
c2aa723a TH |
1697 | wb_dirty_limits(mdtc); |
1698 | ||
a37b0715 N |
1699 | if ((current->flags & PF_LOCAL_THROTTLE) && |
1700 | mdtc->wb_dirty < | |
1701 | dirty_freerun_ceiling(mdtc->wb_thresh, | |
1702 | mdtc->wb_bg_thresh)) | |
1703 | /* | |
1704 | * LOCAL_THROTTLE tasks must not be | |
1705 | * throttled when below the per-wb | |
1706 | * freerun ceiling. | |
1707 | */ | |
1708 | goto free_running; | |
1709 | } | |
c2aa723a TH |
1710 | dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) && |
1711 | ((mdtc->dirty > mdtc->thresh) || strictlimit); | |
1712 | ||
1713 | wb_position_ratio(mdtc); | |
1714 | if (mdtc->pos_ratio < gdtc->pos_ratio) | |
1715 | sdtc = mdtc; | |
1716 | } | |
daddfa3c | 1717 | |
a88a341a TH |
1718 | if (dirty_exceeded && !wb->dirty_exceeded) |
1719 | wb->dirty_exceeded = 1; | |
1da177e4 | 1720 | |
20792ebf | 1721 | if (time_is_before_jiffies(READ_ONCE(wb->bw_time_stamp) + |
45a2966f | 1722 | BANDWIDTH_INTERVAL)) |
fee468fd | 1723 | __wb_update_bandwidth(gdtc, mdtc, true); |
e98be2d5 | 1724 | |
c2aa723a | 1725 | /* throttle according to the chosen dtc */ |
20792ebf | 1726 | dirty_ratelimit = READ_ONCE(wb->dirty_ratelimit); |
c2aa723a | 1727 | task_ratelimit = ((u64)dirty_ratelimit * sdtc->pos_ratio) >> |
3a73dbbc | 1728 | RATELIMIT_CALC_SHIFT; |
c2aa723a | 1729 | max_pause = wb_max_pause(wb, sdtc->wb_dirty); |
a88a341a TH |
1730 | min_pause = wb_min_pause(wb, max_pause, |
1731 | task_ratelimit, dirty_ratelimit, | |
1732 | &nr_dirtied_pause); | |
7ccb9ad5 | 1733 | |
3a73dbbc | 1734 | if (unlikely(task_ratelimit == 0)) { |
83712358 | 1735 | period = max_pause; |
c8462cc9 | 1736 | pause = max_pause; |
143dfe86 | 1737 | goto pause; |
04fbfdc1 | 1738 | } |
83712358 WF |
1739 | period = HZ * pages_dirtied / task_ratelimit; |
1740 | pause = period; | |
1741 | if (current->dirty_paused_when) | |
1742 | pause -= now - current->dirty_paused_when; | |
1743 | /* | |
1744 | * For less than 1s think time (ext3/4 may block the dirtier | |
1745 | * for up to 800ms from time to time on 1-HDD; so does xfs, | |
1746 | * however at much less frequency), try to compensate it in | |
1747 | * future periods by updating the virtual time; otherwise just | |
1748 | * do a reset, as it may be a light dirtier. | |
1749 | */ | |
7ccb9ad5 | 1750 | if (pause < min_pause) { |
5634cc2a | 1751 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1752 | sdtc->thresh, |
1753 | sdtc->bg_thresh, | |
1754 | sdtc->dirty, | |
1755 | sdtc->wb_thresh, | |
1756 | sdtc->wb_dirty, | |
ece13ac3 WF |
1757 | dirty_ratelimit, |
1758 | task_ratelimit, | |
1759 | pages_dirtied, | |
83712358 | 1760 | period, |
7ccb9ad5 | 1761 | min(pause, 0L), |
ece13ac3 | 1762 | start_time); |
83712358 WF |
1763 | if (pause < -HZ) { |
1764 | current->dirty_paused_when = now; | |
1765 | current->nr_dirtied = 0; | |
1766 | } else if (period) { | |
1767 | current->dirty_paused_when += period; | |
1768 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1769 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
1770 | current->nr_dirtied_pause += pages_dirtied; | |
57fc978c | 1771 | break; |
04fbfdc1 | 1772 | } |
7ccb9ad5 WF |
1773 | if (unlikely(pause > max_pause)) { |
1774 | /* for occasional dropped task_ratelimit */ | |
1775 | now += min(pause - max_pause, max_pause); | |
1776 | pause = max_pause; | |
1777 | } | |
143dfe86 WF |
1778 | |
1779 | pause: | |
5634cc2a | 1780 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1781 | sdtc->thresh, |
1782 | sdtc->bg_thresh, | |
1783 | sdtc->dirty, | |
1784 | sdtc->wb_thresh, | |
1785 | sdtc->wb_dirty, | |
ece13ac3 WF |
1786 | dirty_ratelimit, |
1787 | task_ratelimit, | |
1788 | pages_dirtied, | |
83712358 | 1789 | period, |
ece13ac3 WF |
1790 | pause, |
1791 | start_time); | |
499d05ec | 1792 | __set_current_state(TASK_KILLABLE); |
b57d74af | 1793 | wb->dirty_sleep = now; |
d25105e8 | 1794 | io_schedule_timeout(pause); |
87c6a9b2 | 1795 | |
83712358 WF |
1796 | current->dirty_paused_when = now + pause; |
1797 | current->nr_dirtied = 0; | |
7ccb9ad5 | 1798 | current->nr_dirtied_pause = nr_dirtied_pause; |
83712358 | 1799 | |
ffd1f609 | 1800 | /* |
2bc00aef TH |
1801 | * This is typically equal to (dirty < thresh) and can also |
1802 | * keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1803 | */ |
1df64719 | 1804 | if (task_ratelimit) |
ffd1f609 | 1805 | break; |
499d05ec | 1806 | |
c5c6343c | 1807 | /* |
f0953a1b | 1808 | * In the case of an unresponsive NFS server and the NFS dirty |
de1fff37 | 1809 | * pages exceeds dirty_thresh, give the other good wb's a pipe |
c5c6343c WF |
1810 | * to go through, so that tasks on them still remain responsive. |
1811 | * | |
3f8b6fb7 | 1812 | * In theory 1 page is enough to keep the consumer-producer |
c5c6343c | 1813 | * pipe going: the flusher cleans 1 page => the task dirties 1 |
de1fff37 | 1814 | * more page. However wb_dirty has accounting errors. So use |
93f78d88 | 1815 | * the larger and more IO friendly wb_stat_error. |
c5c6343c | 1816 | */ |
2bce774e | 1817 | if (sdtc->wb_dirty <= wb_stat_error()) |
c5c6343c WF |
1818 | break; |
1819 | ||
499d05ec JK |
1820 | if (fatal_signal_pending(current)) |
1821 | break; | |
1da177e4 LT |
1822 | } |
1823 | ||
a88a341a TH |
1824 | if (!dirty_exceeded && wb->dirty_exceeded) |
1825 | wb->dirty_exceeded = 0; | |
1da177e4 | 1826 | |
bc05873d | 1827 | if (writeback_in_progress(wb)) |
5b0830cb | 1828 | return; |
1da177e4 LT |
1829 | |
1830 | /* | |
1831 | * In laptop mode, we wait until hitting the higher threshold before | |
1832 | * starting background writeout, and then write out all the way down | |
1833 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1834 | * | |
1835 | * In normal mode, we start background writeout at the lower | |
1836 | * background_thresh, to keep the amount of dirty memory low. | |
1837 | */ | |
143dfe86 WF |
1838 | if (laptop_mode) |
1839 | return; | |
1840 | ||
2bc00aef | 1841 | if (nr_reclaimable > gdtc->bg_thresh) |
9ecf4866 | 1842 | wb_start_background_writeback(wb); |
1da177e4 LT |
1843 | } |
1844 | ||
9d823e8f | 1845 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1846 | |
54848d73 WF |
1847 | /* |
1848 | * Normal tasks are throttled by | |
1849 | * loop { | |
1850 | * dirty tsk->nr_dirtied_pause pages; | |
1851 | * take a snap in balance_dirty_pages(); | |
1852 | * } | |
1853 | * However there is a worst case. If every task exit immediately when dirtied | |
1854 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be | |
1855 | * called to throttle the page dirties. The solution is to save the not yet | |
1856 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them | |
1857 | * randomly into the running tasks. This works well for the above worst case, | |
1858 | * as the new task will pick up and accumulate the old task's leaked dirty | |
1859 | * count and eventually get throttled. | |
1860 | */ | |
1861 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1862 | ||
1da177e4 | 1863 | /** |
d0e1d66b | 1864 | * balance_dirty_pages_ratelimited - balance dirty memory state |
67be2dd1 | 1865 | * @mapping: address_space which was dirtied |
1da177e4 LT |
1866 | * |
1867 | * Processes which are dirtying memory should call in here once for each page | |
1868 | * which was newly dirtied. The function will periodically check the system's | |
1869 | * dirty state and will initiate writeback if needed. | |
1870 | * | |
5defd497 KW |
1871 | * Once we're over the dirty memory limit we decrease the ratelimiting |
1872 | * by a lot, to prevent individual processes from overshooting the limit | |
1873 | * by (ratelimit_pages) each. | |
1da177e4 | 1874 | */ |
d0e1d66b | 1875 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
1da177e4 | 1876 | { |
dfb8ae56 TH |
1877 | struct inode *inode = mapping->host; |
1878 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1879 | struct bdi_writeback *wb = NULL; | |
9d823e8f WF |
1880 | int ratelimit; |
1881 | int *p; | |
1da177e4 | 1882 | |
f56753ac | 1883 | if (!(bdi->capabilities & BDI_CAP_WRITEBACK)) |
36715cef WF |
1884 | return; |
1885 | ||
dfb8ae56 TH |
1886 | if (inode_cgwb_enabled(inode)) |
1887 | wb = wb_get_create_current(bdi, GFP_KERNEL); | |
1888 | if (!wb) | |
1889 | wb = &bdi->wb; | |
1890 | ||
9d823e8f | 1891 | ratelimit = current->nr_dirtied_pause; |
a88a341a | 1892 | if (wb->dirty_exceeded) |
9d823e8f WF |
1893 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
1894 | ||
9d823e8f | 1895 | preempt_disable(); |
1da177e4 | 1896 | /* |
9d823e8f WF |
1897 | * This prevents one CPU to accumulate too many dirtied pages without |
1898 | * calling into balance_dirty_pages(), which can happen when there are | |
1899 | * 1000+ tasks, all of them start dirtying pages at exactly the same | |
1900 | * time, hence all honoured too large initial task->nr_dirtied_pause. | |
1da177e4 | 1901 | */ |
7c8e0181 | 1902 | p = this_cpu_ptr(&bdp_ratelimits); |
9d823e8f | 1903 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1904 | *p = 0; |
d3bc1fef WF |
1905 | else if (unlikely(*p >= ratelimit_pages)) { |
1906 | *p = 0; | |
1907 | ratelimit = 0; | |
1da177e4 | 1908 | } |
54848d73 WF |
1909 | /* |
1910 | * Pick up the dirtied pages by the exited tasks. This avoids lots of | |
1911 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping | |
1912 | * the dirty throttling and livelock other long-run dirtiers. | |
1913 | */ | |
7c8e0181 | 1914 | p = this_cpu_ptr(&dirty_throttle_leaks); |
54848d73 | 1915 | if (*p > 0 && current->nr_dirtied < ratelimit) { |
d0e1d66b | 1916 | unsigned long nr_pages_dirtied; |
54848d73 WF |
1917 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
1918 | *p -= nr_pages_dirtied; | |
1919 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1920 | } |
fa5a734e | 1921 | preempt_enable(); |
9d823e8f WF |
1922 | |
1923 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
4c578dce | 1924 | balance_dirty_pages(wb, current->nr_dirtied); |
dfb8ae56 TH |
1925 | |
1926 | wb_put(wb); | |
1da177e4 | 1927 | } |
d0e1d66b | 1928 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
1da177e4 | 1929 | |
aa661bbe TH |
1930 | /** |
1931 | * wb_over_bg_thresh - does @wb need to be written back? | |
1932 | * @wb: bdi_writeback of interest | |
1933 | * | |
1934 | * Determines whether background writeback should keep writing @wb or it's | |
a862f68a MR |
1935 | * clean enough. |
1936 | * | |
1937 | * Return: %true if writeback should continue. | |
aa661bbe TH |
1938 | */ |
1939 | bool wb_over_bg_thresh(struct bdi_writeback *wb) | |
1940 | { | |
947e9762 | 1941 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1942 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
947e9762 | 1943 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1944 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1945 | &mdtc_stor : NULL; | |
ab19939a CW |
1946 | unsigned long reclaimable; |
1947 | unsigned long thresh; | |
aa661bbe | 1948 | |
947e9762 TH |
1949 | /* |
1950 | * Similar to balance_dirty_pages() but ignores pages being written | |
1951 | * as we're trying to decide whether to put more under writeback. | |
1952 | */ | |
1953 | gdtc->avail = global_dirtyable_memory(); | |
8d92890b | 1954 | gdtc->dirty = global_node_page_state(NR_FILE_DIRTY); |
947e9762 | 1955 | domain_dirty_limits(gdtc); |
aa661bbe | 1956 | |
947e9762 | 1957 | if (gdtc->dirty > gdtc->bg_thresh) |
aa661bbe TH |
1958 | return true; |
1959 | ||
ab19939a CW |
1960 | thresh = wb_calc_thresh(gdtc->wb, gdtc->bg_thresh); |
1961 | if (thresh < 2 * wb_stat_error()) | |
1962 | reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); | |
1963 | else | |
1964 | reclaimable = wb_stat(wb, WB_RECLAIMABLE); | |
1965 | ||
1966 | if (reclaimable > thresh) | |
aa661bbe TH |
1967 | return true; |
1968 | ||
c2aa723a | 1969 | if (mdtc) { |
c5edf9cd | 1970 | unsigned long filepages, headroom, writeback; |
c2aa723a | 1971 | |
c5edf9cd TH |
1972 | mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, |
1973 | &writeback); | |
1974 | mdtc_calc_avail(mdtc, filepages, headroom); | |
c2aa723a TH |
1975 | domain_dirty_limits(mdtc); /* ditto, ignore writeback */ |
1976 | ||
1977 | if (mdtc->dirty > mdtc->bg_thresh) | |
1978 | return true; | |
1979 | ||
ab19939a CW |
1980 | thresh = wb_calc_thresh(mdtc->wb, mdtc->bg_thresh); |
1981 | if (thresh < 2 * wb_stat_error()) | |
1982 | reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); | |
1983 | else | |
1984 | reclaimable = wb_stat(wb, WB_RECLAIMABLE); | |
1985 | ||
1986 | if (reclaimable > thresh) | |
c2aa723a TH |
1987 | return true; |
1988 | } | |
1989 | ||
aa661bbe TH |
1990 | return false; |
1991 | } | |
1992 | ||
aa779e51 | 1993 | #ifdef CONFIG_SYSCTL |
1da177e4 LT |
1994 | /* |
1995 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1996 | */ | |
aa779e51 | 1997 | static int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, |
32927393 | 1998 | void *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1999 | { |
94af5846 YS |
2000 | unsigned int old_interval = dirty_writeback_interval; |
2001 | int ret; | |
2002 | ||
2003 | ret = proc_dointvec(table, write, buffer, length, ppos); | |
515c24c1 YS |
2004 | |
2005 | /* | |
2006 | * Writing 0 to dirty_writeback_interval will disable periodic writeback | |
2007 | * and a different non-zero value will wakeup the writeback threads. | |
2008 | * wb_wakeup_delayed() would be more appropriate, but it's a pain to | |
2009 | * iterate over all bdis and wbs. | |
2010 | * The reason we do this is to make the change take effect immediately. | |
2011 | */ | |
2012 | if (!ret && write && dirty_writeback_interval && | |
2013 | dirty_writeback_interval != old_interval) | |
94af5846 YS |
2014 | wakeup_flusher_threads(WB_REASON_PERIODIC); |
2015 | ||
2016 | return ret; | |
1da177e4 | 2017 | } |
aa779e51 | 2018 | #endif |
1da177e4 | 2019 | |
bca237a5 | 2020 | void laptop_mode_timer_fn(struct timer_list *t) |
1da177e4 | 2021 | { |
bca237a5 KC |
2022 | struct backing_dev_info *backing_dev_info = |
2023 | from_timer(backing_dev_info, t, laptop_mode_wb_timer); | |
1da177e4 | 2024 | |
bca237a5 | 2025 | wakeup_flusher_threads_bdi(backing_dev_info, WB_REASON_LAPTOP_TIMER); |
1da177e4 LT |
2026 | } |
2027 | ||
2028 | /* | |
2029 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
2030 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
2031 | * then push it back - the user is still using the disk. | |
2032 | */ | |
31373d09 | 2033 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 2034 | { |
31373d09 | 2035 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
2036 | } |
2037 | ||
2038 | /* | |
2039 | * We're in laptop mode and we've just synced. The sync's writes will have | |
2040 | * caused another writeback to be scheduled by laptop_io_completion. | |
2041 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
2042 | */ | |
2043 | void laptop_sync_completion(void) | |
2044 | { | |
31373d09 MG |
2045 | struct backing_dev_info *bdi; |
2046 | ||
2047 | rcu_read_lock(); | |
2048 | ||
2049 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
2050 | del_timer(&bdi->laptop_mode_wb_timer); | |
2051 | ||
2052 | rcu_read_unlock(); | |
1da177e4 LT |
2053 | } |
2054 | ||
2055 | /* | |
2056 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
2057 | * if a large number of processes all perform writes at the same time. | |
1da177e4 LT |
2058 | * |
2059 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
2060 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
9d823e8f | 2061 | * thresholds. |
1da177e4 LT |
2062 | */ |
2063 | ||
2d1d43f6 | 2064 | void writeback_set_ratelimit(void) |
1da177e4 | 2065 | { |
dcc25ae7 | 2066 | struct wb_domain *dom = &global_wb_domain; |
9d823e8f WF |
2067 | unsigned long background_thresh; |
2068 | unsigned long dirty_thresh; | |
dcc25ae7 | 2069 | |
9d823e8f | 2070 | global_dirty_limits(&background_thresh, &dirty_thresh); |
dcc25ae7 | 2071 | dom->dirty_limit = dirty_thresh; |
9d823e8f | 2072 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
1da177e4 LT |
2073 | if (ratelimit_pages < 16) |
2074 | ratelimit_pages = 16; | |
1da177e4 LT |
2075 | } |
2076 | ||
1d7ac6ae | 2077 | static int page_writeback_cpu_online(unsigned int cpu) |
1da177e4 | 2078 | { |
1d7ac6ae SAS |
2079 | writeback_set_ratelimit(); |
2080 | return 0; | |
1da177e4 LT |
2081 | } |
2082 | ||
aa779e51 | 2083 | #ifdef CONFIG_SYSCTL |
3c6a4cba LC |
2084 | |
2085 | /* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */ | |
2086 | static const unsigned long dirty_bytes_min = 2 * PAGE_SIZE; | |
2087 | ||
aa779e51 | 2088 | static struct ctl_table vm_page_writeback_sysctls[] = { |
2089 | { | |
2090 | .procname = "dirty_background_ratio", | |
2091 | .data = &dirty_background_ratio, | |
2092 | .maxlen = sizeof(dirty_background_ratio), | |
2093 | .mode = 0644, | |
2094 | .proc_handler = dirty_background_ratio_handler, | |
2095 | .extra1 = SYSCTL_ZERO, | |
2096 | .extra2 = SYSCTL_ONE_HUNDRED, | |
2097 | }, | |
2098 | { | |
2099 | .procname = "dirty_background_bytes", | |
2100 | .data = &dirty_background_bytes, | |
2101 | .maxlen = sizeof(dirty_background_bytes), | |
2102 | .mode = 0644, | |
2103 | .proc_handler = dirty_background_bytes_handler, | |
2104 | .extra1 = SYSCTL_LONG_ONE, | |
2105 | }, | |
2106 | { | |
2107 | .procname = "dirty_ratio", | |
2108 | .data = &vm_dirty_ratio, | |
2109 | .maxlen = sizeof(vm_dirty_ratio), | |
2110 | .mode = 0644, | |
2111 | .proc_handler = dirty_ratio_handler, | |
2112 | .extra1 = SYSCTL_ZERO, | |
2113 | .extra2 = SYSCTL_ONE_HUNDRED, | |
2114 | }, | |
2115 | { | |
2116 | .procname = "dirty_bytes", | |
2117 | .data = &vm_dirty_bytes, | |
2118 | .maxlen = sizeof(vm_dirty_bytes), | |
2119 | .mode = 0644, | |
2120 | .proc_handler = dirty_bytes_handler, | |
2121 | .extra1 = (void *)&dirty_bytes_min, | |
2122 | }, | |
2123 | { | |
2124 | .procname = "dirty_writeback_centisecs", | |
2125 | .data = &dirty_writeback_interval, | |
2126 | .maxlen = sizeof(dirty_writeback_interval), | |
2127 | .mode = 0644, | |
2128 | .proc_handler = dirty_writeback_centisecs_handler, | |
2129 | }, | |
2130 | { | |
2131 | .procname = "dirty_expire_centisecs", | |
2132 | .data = &dirty_expire_interval, | |
2133 | .maxlen = sizeof(dirty_expire_interval), | |
2134 | .mode = 0644, | |
2135 | .proc_handler = proc_dointvec_minmax, | |
2136 | .extra1 = SYSCTL_ZERO, | |
2137 | }, | |
2138 | #ifdef CONFIG_HIGHMEM | |
2139 | { | |
2140 | .procname = "highmem_is_dirtyable", | |
2141 | .data = &vm_highmem_is_dirtyable, | |
2142 | .maxlen = sizeof(vm_highmem_is_dirtyable), | |
2143 | .mode = 0644, | |
2144 | .proc_handler = proc_dointvec_minmax, | |
2145 | .extra1 = SYSCTL_ZERO, | |
2146 | .extra2 = SYSCTL_ONE, | |
2147 | }, | |
2148 | #endif | |
2149 | { | |
2150 | .procname = "laptop_mode", | |
2151 | .data = &laptop_mode, | |
2152 | .maxlen = sizeof(laptop_mode), | |
2153 | .mode = 0644, | |
2154 | .proc_handler = proc_dointvec_jiffies, | |
2155 | }, | |
2156 | {} | |
2157 | }; | |
2158 | #endif | |
2159 | ||
1da177e4 | 2160 | /* |
dc6e29da LT |
2161 | * Called early on to tune the page writeback dirty limits. |
2162 | * | |
2163 | * We used to scale dirty pages according to how total memory | |
0a18e607 | 2164 | * related to pages that could be allocated for buffers. |
dc6e29da LT |
2165 | * |
2166 | * However, that was when we used "dirty_ratio" to scale with | |
2167 | * all memory, and we don't do that any more. "dirty_ratio" | |
0a18e607 | 2168 | * is now applied to total non-HIGHPAGE memory, and as such we can't |
dc6e29da LT |
2169 | * get into the old insane situation any more where we had |
2170 | * large amounts of dirty pages compared to a small amount of | |
2171 | * non-HIGHMEM memory. | |
2172 | * | |
2173 | * But we might still want to scale the dirty_ratio by how | |
2174 | * much memory the box has.. | |
1da177e4 LT |
2175 | */ |
2176 | void __init page_writeback_init(void) | |
2177 | { | |
a50fcb51 RV |
2178 | BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL)); |
2179 | ||
1d7ac6ae SAS |
2180 | cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online", |
2181 | page_writeback_cpu_online, NULL); | |
2182 | cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL, | |
2183 | page_writeback_cpu_online); | |
aa779e51 | 2184 | #ifdef CONFIG_SYSCTL |
2185 | register_sysctl_init("vm", vm_page_writeback_sysctls); | |
2186 | #endif | |
1da177e4 LT |
2187 | } |
2188 | ||
f446daae JK |
2189 | /** |
2190 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
2191 | * @mapping: address space structure to write | |
2192 | * @start: starting page index | |
2193 | * @end: ending page index (inclusive) | |
2194 | * | |
2195 | * This function scans the page range from @start to @end (inclusive) and tags | |
2196 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
2197 | * that write_cache_pages (or whoever calls this function) will then use | |
2198 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
2199 | * used to avoid livelocking of writeback by a process steadily creating new | |
2200 | * dirty pages in the file (thus it is important for this function to be quick | |
2201 | * so that it can tag pages faster than a dirtying process can create them). | |
2202 | */ | |
f446daae JK |
2203 | void tag_pages_for_writeback(struct address_space *mapping, |
2204 | pgoff_t start, pgoff_t end) | |
2205 | { | |
ff9c745b MW |
2206 | XA_STATE(xas, &mapping->i_pages, start); |
2207 | unsigned int tagged = 0; | |
2208 | void *page; | |
268f42de | 2209 | |
ff9c745b MW |
2210 | xas_lock_irq(&xas); |
2211 | xas_for_each_marked(&xas, page, end, PAGECACHE_TAG_DIRTY) { | |
2212 | xas_set_mark(&xas, PAGECACHE_TAG_TOWRITE); | |
2213 | if (++tagged % XA_CHECK_SCHED) | |
268f42de | 2214 | continue; |
ff9c745b MW |
2215 | |
2216 | xas_pause(&xas); | |
2217 | xas_unlock_irq(&xas); | |
f446daae | 2218 | cond_resched(); |
ff9c745b | 2219 | xas_lock_irq(&xas); |
268f42de | 2220 | } |
ff9c745b | 2221 | xas_unlock_irq(&xas); |
f446daae JK |
2222 | } |
2223 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
2224 | ||
811d736f | 2225 | /** |
0ea97180 | 2226 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
2227 | * @mapping: address space structure to write |
2228 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
2229 | * @writepage: function called for each page |
2230 | * @data: data passed to writepage function | |
811d736f | 2231 | * |
0ea97180 | 2232 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
2233 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
2234 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
2235 | * and msync() need to guarantee that all the data which was dirty at the time | |
2236 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
2237 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
2238 | * existing IO to complete. | |
f446daae JK |
2239 | * |
2240 | * To avoid livelocks (when other process dirties new pages), we first tag | |
2241 | * pages which should be written back with TOWRITE tag and only then start | |
2242 | * writing them. For data-integrity sync we have to be careful so that we do | |
2243 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
2244 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
2245 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
64081362 DC |
2246 | * |
2247 | * To avoid deadlocks between range_cyclic writeback and callers that hold | |
2248 | * pages in PageWriteback to aggregate IO until write_cache_pages() returns, | |
2249 | * we do not loop back to the start of the file. Doing so causes a page | |
2250 | * lock/page writeback access order inversion - we should only ever lock | |
2251 | * multiple pages in ascending page->index order, and looping back to the start | |
2252 | * of the file violates that rule and causes deadlocks. | |
a862f68a MR |
2253 | * |
2254 | * Return: %0 on success, negative error code otherwise | |
811d736f | 2255 | */ |
0ea97180 MS |
2256 | int write_cache_pages(struct address_space *mapping, |
2257 | struct writeback_control *wbc, writepage_t writepage, | |
2258 | void *data) | |
811d736f | 2259 | { |
811d736f DH |
2260 | int ret = 0; |
2261 | int done = 0; | |
3fa750dc | 2262 | int error; |
811d736f DH |
2263 | struct pagevec pvec; |
2264 | int nr_pages; | |
2265 | pgoff_t index; | |
2266 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 2267 | pgoff_t done_index; |
811d736f | 2268 | int range_whole = 0; |
ff9c745b | 2269 | xa_mark_t tag; |
811d736f | 2270 | |
86679820 | 2271 | pagevec_init(&pvec); |
811d736f | 2272 | if (wbc->range_cyclic) { |
28659cc8 | 2273 | index = mapping->writeback_index; /* prev offset */ |
811d736f DH |
2274 | end = -1; |
2275 | } else { | |
09cbfeaf KS |
2276 | index = wbc->range_start >> PAGE_SHIFT; |
2277 | end = wbc->range_end >> PAGE_SHIFT; | |
811d736f DH |
2278 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
2279 | range_whole = 1; | |
811d736f | 2280 | } |
cc7b8f62 MFO |
2281 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) { |
2282 | tag_pages_for_writeback(mapping, index, end); | |
f446daae | 2283 | tag = PAGECACHE_TAG_TOWRITE; |
cc7b8f62 | 2284 | } else { |
f446daae | 2285 | tag = PAGECACHE_TAG_DIRTY; |
cc7b8f62 | 2286 | } |
bd19e012 | 2287 | done_index = index; |
5a3d5c98 NP |
2288 | while (!done && (index <= end)) { |
2289 | int i; | |
2290 | ||
2b9775ae | 2291 | nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end, |
67fd707f | 2292 | tag); |
5a3d5c98 NP |
2293 | if (nr_pages == 0) |
2294 | break; | |
811d736f | 2295 | |
811d736f DH |
2296 | for (i = 0; i < nr_pages; i++) { |
2297 | struct page *page = pvec.pages[i]; | |
2298 | ||
cf15b07c | 2299 | done_index = page->index; |
d5482cdf | 2300 | |
811d736f DH |
2301 | lock_page(page); |
2302 | ||
5a3d5c98 NP |
2303 | /* |
2304 | * Page truncated or invalidated. We can freely skip it | |
2305 | * then, even for data integrity operations: the page | |
2306 | * has disappeared concurrently, so there could be no | |
f0953a1b | 2307 | * real expectation of this data integrity operation |
5a3d5c98 NP |
2308 | * even if there is now a new, dirty page at the same |
2309 | * pagecache address. | |
2310 | */ | |
811d736f | 2311 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 2312 | continue_unlock: |
811d736f DH |
2313 | unlock_page(page); |
2314 | continue; | |
2315 | } | |
2316 | ||
515f4a03 NP |
2317 | if (!PageDirty(page)) { |
2318 | /* someone wrote it for us */ | |
2319 | goto continue_unlock; | |
2320 | } | |
2321 | ||
2322 | if (PageWriteback(page)) { | |
2323 | if (wbc->sync_mode != WB_SYNC_NONE) | |
2324 | wait_on_page_writeback(page); | |
2325 | else | |
2326 | goto continue_unlock; | |
2327 | } | |
811d736f | 2328 | |
515f4a03 NP |
2329 | BUG_ON(PageWriteback(page)); |
2330 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 2331 | goto continue_unlock; |
811d736f | 2332 | |
de1414a6 | 2333 | trace_wbc_writepage(wbc, inode_to_bdi(mapping->host)); |
3fa750dc BF |
2334 | error = (*writepage)(page, wbc, data); |
2335 | if (unlikely(error)) { | |
2336 | /* | |
2337 | * Handle errors according to the type of | |
2338 | * writeback. There's no need to continue for | |
2339 | * background writeback. Just push done_index | |
2340 | * past this page so media errors won't choke | |
2341 | * writeout for the entire file. For integrity | |
2342 | * writeback, we must process the entire dirty | |
2343 | * set regardless of errors because the fs may | |
2344 | * still have state to clear for each page. In | |
2345 | * that case we continue processing and return | |
2346 | * the first error. | |
2347 | */ | |
2348 | if (error == AOP_WRITEPAGE_ACTIVATE) { | |
00266770 | 2349 | unlock_page(page); |
3fa750dc BF |
2350 | error = 0; |
2351 | } else if (wbc->sync_mode != WB_SYNC_ALL) { | |
2352 | ret = error; | |
cf15b07c | 2353 | done_index = page->index + 1; |
00266770 NP |
2354 | done = 1; |
2355 | break; | |
2356 | } | |
3fa750dc BF |
2357 | if (!ret) |
2358 | ret = error; | |
0b564927 | 2359 | } |
00266770 | 2360 | |
546a1924 DC |
2361 | /* |
2362 | * We stop writing back only if we are not doing | |
2363 | * integrity sync. In case of integrity sync we have to | |
2364 | * keep going until we have written all the pages | |
2365 | * we tagged for writeback prior to entering this loop. | |
2366 | */ | |
2367 | if (--wbc->nr_to_write <= 0 && | |
2368 | wbc->sync_mode == WB_SYNC_NONE) { | |
2369 | done = 1; | |
2370 | break; | |
05fe478d | 2371 | } |
811d736f DH |
2372 | } |
2373 | pagevec_release(&pvec); | |
2374 | cond_resched(); | |
2375 | } | |
64081362 DC |
2376 | |
2377 | /* | |
2378 | * If we hit the last page and there is more work to be done: wrap | |
2379 | * back the index back to the start of the file for the next | |
2380 | * time we are called. | |
2381 | */ | |
2382 | if (wbc->range_cyclic && !done) | |
2383 | done_index = 0; | |
0b564927 DC |
2384 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
2385 | mapping->writeback_index = done_index; | |
06d6cf69 | 2386 | |
811d736f DH |
2387 | return ret; |
2388 | } | |
0ea97180 MS |
2389 | EXPORT_SYMBOL(write_cache_pages); |
2390 | ||
2391 | /* | |
2392 | * Function used by generic_writepages to call the real writepage | |
2393 | * function and set the mapping flags on error | |
2394 | */ | |
2395 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
2396 | void *data) | |
2397 | { | |
2398 | struct address_space *mapping = data; | |
2399 | int ret = mapping->a_ops->writepage(page, wbc); | |
2400 | mapping_set_error(mapping, ret); | |
2401 | return ret; | |
2402 | } | |
2403 | ||
2404 | /** | |
2405 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
2406 | * @mapping: address space structure to write | |
2407 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
2408 | * | |
2409 | * This is a library function, which implements the writepages() | |
2410 | * address_space_operation. | |
a862f68a MR |
2411 | * |
2412 | * Return: %0 on success, negative error code otherwise | |
0ea97180 MS |
2413 | */ |
2414 | int generic_writepages(struct address_space *mapping, | |
2415 | struct writeback_control *wbc) | |
2416 | { | |
9b6096a6 SL |
2417 | struct blk_plug plug; |
2418 | int ret; | |
2419 | ||
0ea97180 MS |
2420 | /* deal with chardevs and other special file */ |
2421 | if (!mapping->a_ops->writepage) | |
2422 | return 0; | |
2423 | ||
9b6096a6 SL |
2424 | blk_start_plug(&plug); |
2425 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
2426 | blk_finish_plug(&plug); | |
2427 | return ret; | |
0ea97180 | 2428 | } |
811d736f DH |
2429 | |
2430 | EXPORT_SYMBOL(generic_writepages); | |
2431 | ||
1da177e4 LT |
2432 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
2433 | { | |
22905f77 | 2434 | int ret; |
fee468fd | 2435 | struct bdi_writeback *wb; |
22905f77 | 2436 | |
1da177e4 LT |
2437 | if (wbc->nr_to_write <= 0) |
2438 | return 0; | |
fee468fd JK |
2439 | wb = inode_to_wb_wbc(mapping->host, wbc); |
2440 | wb_bandwidth_estimate_start(wb); | |
80a2ea9f TT |
2441 | while (1) { |
2442 | if (mapping->a_ops->writepages) | |
2443 | ret = mapping->a_ops->writepages(mapping, wbc); | |
2444 | else | |
2445 | ret = generic_writepages(mapping, wbc); | |
2446 | if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL)) | |
2447 | break; | |
8d58802f MG |
2448 | |
2449 | /* | |
2450 | * Lacking an allocation context or the locality or writeback | |
2451 | * state of any of the inode's pages, throttle based on | |
2452 | * writeback activity on the local node. It's as good a | |
2453 | * guess as any. | |
2454 | */ | |
2455 | reclaim_throttle(NODE_DATA(numa_node_id()), | |
c3f4a9a2 | 2456 | VMSCAN_THROTTLE_WRITEBACK); |
80a2ea9f | 2457 | } |
45a2966f JK |
2458 | /* |
2459 | * Usually few pages are written by now from those we've just submitted | |
2460 | * but if there's constant writeback being submitted, this makes sure | |
2461 | * writeback bandwidth is updated once in a while. | |
2462 | */ | |
20792ebf JK |
2463 | if (time_is_before_jiffies(READ_ONCE(wb->bw_time_stamp) + |
2464 | BANDWIDTH_INTERVAL)) | |
45a2966f | 2465 | wb_update_bandwidth(wb); |
22905f77 | 2466 | return ret; |
1da177e4 LT |
2467 | } |
2468 | ||
2469 | /** | |
121703c1 MWO |
2470 | * folio_write_one - write out a single folio and wait on I/O. |
2471 | * @folio: The folio to write. | |
1da177e4 | 2472 | * |
121703c1 | 2473 | * The folio must be locked by the caller and will be unlocked upon return. |
1da177e4 | 2474 | * |
37e51a76 JL |
2475 | * Note that the mapping's AS_EIO/AS_ENOSPC flags will be cleared when this |
2476 | * function returns. | |
a862f68a MR |
2477 | * |
2478 | * Return: %0 on success, negative error code otherwise | |
1da177e4 | 2479 | */ |
121703c1 | 2480 | int folio_write_one(struct folio *folio) |
1da177e4 | 2481 | { |
121703c1 | 2482 | struct address_space *mapping = folio->mapping; |
1da177e4 LT |
2483 | int ret = 0; |
2484 | struct writeback_control wbc = { | |
2485 | .sync_mode = WB_SYNC_ALL, | |
121703c1 | 2486 | .nr_to_write = folio_nr_pages(folio), |
1da177e4 LT |
2487 | }; |
2488 | ||
121703c1 | 2489 | BUG_ON(!folio_test_locked(folio)); |
1da177e4 | 2490 | |
121703c1 | 2491 | folio_wait_writeback(folio); |
1da177e4 | 2492 | |
121703c1 MWO |
2493 | if (folio_clear_dirty_for_io(folio)) { |
2494 | folio_get(folio); | |
2495 | ret = mapping->a_ops->writepage(&folio->page, &wbc); | |
37e51a76 | 2496 | if (ret == 0) |
121703c1 MWO |
2497 | folio_wait_writeback(folio); |
2498 | folio_put(folio); | |
1da177e4 | 2499 | } else { |
121703c1 | 2500 | folio_unlock(folio); |
1da177e4 | 2501 | } |
37e51a76 JL |
2502 | |
2503 | if (!ret) | |
2504 | ret = filemap_check_errors(mapping); | |
1da177e4 LT |
2505 | return ret; |
2506 | } | |
121703c1 | 2507 | EXPORT_SYMBOL(folio_write_one); |
1da177e4 | 2508 | |
76719325 KC |
2509 | /* |
2510 | * For address_spaces which do not use buffers nor write back. | |
2511 | */ | |
46de8b97 | 2512 | bool noop_dirty_folio(struct address_space *mapping, struct folio *folio) |
76719325 | 2513 | { |
46de8b97 MWO |
2514 | if (!folio_test_dirty(folio)) |
2515 | return !folio_test_set_dirty(folio); | |
2516 | return false; | |
76719325 | 2517 | } |
46de8b97 | 2518 | EXPORT_SYMBOL(noop_dirty_folio); |
76719325 | 2519 | |
e3a7cca1 ES |
2520 | /* |
2521 | * Helper function for set_page_dirty family. | |
c4843a75 | 2522 | * |
81f8c3a4 | 2523 | * Caller must hold lock_page_memcg(). |
c4843a75 | 2524 | * |
e3a7cca1 ES |
2525 | * NOTE: This relies on being atomic wrt interrupts. |
2526 | */ | |
203a3151 | 2527 | static void folio_account_dirtied(struct folio *folio, |
6e1cae88 | 2528 | struct address_space *mapping) |
e3a7cca1 | 2529 | { |
52ebea74 TH |
2530 | struct inode *inode = mapping->host; |
2531 | ||
b9b0ff61 | 2532 | trace_writeback_dirty_folio(folio, mapping); |
9fb0a7da | 2533 | |
f56753ac | 2534 | if (mapping_can_writeback(mapping)) { |
52ebea74 | 2535 | struct bdi_writeback *wb; |
203a3151 | 2536 | long nr = folio_nr_pages(folio); |
de1414a6 | 2537 | |
203a3151 | 2538 | inode_attach_wb(inode, &folio->page); |
52ebea74 | 2539 | wb = inode_to_wb(inode); |
de1414a6 | 2540 | |
203a3151 MWO |
2541 | __lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, nr); |
2542 | __zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr); | |
2543 | __node_stat_mod_folio(folio, NR_DIRTIED, nr); | |
2544 | wb_stat_mod(wb, WB_RECLAIMABLE, nr); | |
2545 | wb_stat_mod(wb, WB_DIRTIED, nr); | |
2546 | task_io_account_write(nr * PAGE_SIZE); | |
2547 | current->nr_dirtied += nr; | |
2548 | __this_cpu_add(bdp_ratelimits, nr); | |
97b27821 | 2549 | |
203a3151 | 2550 | mem_cgroup_track_foreign_dirty(folio, wb); |
e3a7cca1 ES |
2551 | } |
2552 | } | |
2553 | ||
b9ea2515 KK |
2554 | /* |
2555 | * Helper function for deaccounting dirty page without writeback. | |
2556 | * | |
81f8c3a4 | 2557 | * Caller must hold lock_page_memcg(). |
b9ea2515 | 2558 | */ |
566d3362 | 2559 | void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb) |
b9ea2515 | 2560 | { |
566d3362 HD |
2561 | long nr = folio_nr_pages(folio); |
2562 | ||
2563 | lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr); | |
2564 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); | |
2565 | wb_stat_mod(wb, WB_RECLAIMABLE, -nr); | |
2566 | task_io_account_cancelled_write(nr * PAGE_SIZE); | |
b9ea2515 | 2567 | } |
b9ea2515 | 2568 | |
6e1cae88 | 2569 | /* |
203a3151 MWO |
2570 | * Mark the folio dirty, and set it dirty in the page cache, and mark |
2571 | * the inode dirty. | |
6e1cae88 | 2572 | * |
203a3151 | 2573 | * If warn is true, then emit a warning if the folio is not uptodate and has |
6e1cae88 MWO |
2574 | * not been truncated. |
2575 | * | |
a229a4f0 MWO |
2576 | * The caller must hold lock_page_memcg(). Most callers have the folio |
2577 | * locked. A few have the folio blocked from truncation through other | |
2578 | * means (eg zap_page_range() has it mapped and is holding the page table | |
2579 | * lock). This can also be called from mark_buffer_dirty(), which I | |
2580 | * cannot prove is always protected against truncate. | |
6e1cae88 | 2581 | */ |
203a3151 | 2582 | void __folio_mark_dirty(struct folio *folio, struct address_space *mapping, |
6e1cae88 MWO |
2583 | int warn) |
2584 | { | |
2585 | unsigned long flags; | |
2586 | ||
2587 | xa_lock_irqsave(&mapping->i_pages, flags); | |
203a3151 MWO |
2588 | if (folio->mapping) { /* Race with truncate? */ |
2589 | WARN_ON_ONCE(warn && !folio_test_uptodate(folio)); | |
2590 | folio_account_dirtied(folio, mapping); | |
2591 | __xa_set_mark(&mapping->i_pages, folio_index(folio), | |
6e1cae88 MWO |
2592 | PAGECACHE_TAG_DIRTY); |
2593 | } | |
2594 | xa_unlock_irqrestore(&mapping->i_pages, flags); | |
2595 | } | |
2596 | ||
85d4d2eb MWO |
2597 | /** |
2598 | * filemap_dirty_folio - Mark a folio dirty for filesystems which do not use buffer_heads. | |
2599 | * @mapping: Address space this folio belongs to. | |
2600 | * @folio: Folio to be marked as dirty. | |
1da177e4 | 2601 | * |
85d4d2eb MWO |
2602 | * Filesystems which do not use buffer heads should call this function |
2603 | * from their set_page_dirty address space operation. It ignores the | |
2604 | * contents of folio_get_private(), so if the filesystem marks individual | |
2605 | * blocks as dirty, the filesystem should handle that itself. | |
1da177e4 | 2606 | * |
85d4d2eb MWO |
2607 | * This is also sometimes used by filesystems which use buffer_heads when |
2608 | * a single buffer is being dirtied: we want to set the folio dirty in | |
2609 | * that case, but not all the buffers. This is a "bottom-up" dirtying, | |
e621900a | 2610 | * whereas block_dirty_folio() is a "top-down" dirtying. |
85d4d2eb MWO |
2611 | * |
2612 | * The caller must ensure this doesn't race with truncation. Most will | |
2613 | * simply hold the folio lock, but e.g. zap_pte_range() calls with the | |
2614 | * folio mapped and the pte lock held, which also locks out truncation. | |
1da177e4 | 2615 | */ |
85d4d2eb | 2616 | bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio) |
1da177e4 | 2617 | { |
85d4d2eb MWO |
2618 | folio_memcg_lock(folio); |
2619 | if (folio_test_set_dirty(folio)) { | |
2620 | folio_memcg_unlock(folio); | |
2621 | return false; | |
2622 | } | |
1da177e4 | 2623 | |
85d4d2eb MWO |
2624 | __folio_mark_dirty(folio, mapping, !folio_test_private(folio)); |
2625 | folio_memcg_unlock(folio); | |
c4843a75 | 2626 | |
85d4d2eb MWO |
2627 | if (mapping->host) { |
2628 | /* !PageAnon && !swapper_space */ | |
2629 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 2630 | } |
85d4d2eb | 2631 | return true; |
1da177e4 | 2632 | } |
85d4d2eb | 2633 | EXPORT_SYMBOL(filemap_dirty_folio); |
1da177e4 | 2634 | |
25ff8b15 MWO |
2635 | /** |
2636 | * folio_account_redirty - Manually account for redirtying a page. | |
2637 | * @folio: The folio which is being redirtied. | |
2638 | * | |
2639 | * Most filesystems should call folio_redirty_for_writepage() instead | |
2640 | * of this fuction. If your filesystem is doing writeback outside the | |
2641 | * context of a writeback_control(), it can call this when redirtying | |
2642 | * a folio, to de-account the dirty counters (NR_DIRTIED, WB_DIRTIED, | |
2643 | * tsk->nr_dirtied), so that they match the written counters (NR_WRITTEN, | |
2644 | * WB_WRITTEN) in long term. The mismatches will lead to systematic errors | |
2645 | * in balanced_dirty_ratelimit and the dirty pages position control. | |
2f800fbd | 2646 | */ |
25ff8b15 | 2647 | void folio_account_redirty(struct folio *folio) |
2f800fbd | 2648 | { |
25ff8b15 | 2649 | struct address_space *mapping = folio->mapping; |
91018134 | 2650 | |
f56753ac | 2651 | if (mapping && mapping_can_writeback(mapping)) { |
682aa8e1 TH |
2652 | struct inode *inode = mapping->host; |
2653 | struct bdi_writeback *wb; | |
2e898e4c | 2654 | struct wb_lock_cookie cookie = {}; |
25ff8b15 | 2655 | long nr = folio_nr_pages(folio); |
91018134 | 2656 | |
2e898e4c | 2657 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
25ff8b15 MWO |
2658 | current->nr_dirtied -= nr; |
2659 | node_stat_mod_folio(folio, NR_DIRTIED, -nr); | |
2660 | wb_stat_mod(wb, WB_DIRTIED, -nr); | |
2e898e4c | 2661 | unlocked_inode_to_wb_end(inode, &cookie); |
2f800fbd WF |
2662 | } |
2663 | } | |
25ff8b15 | 2664 | EXPORT_SYMBOL(folio_account_redirty); |
2f800fbd | 2665 | |
cd78ab11 MWO |
2666 | /** |
2667 | * folio_redirty_for_writepage - Decline to write a dirty folio. | |
2668 | * @wbc: The writeback control. | |
2669 | * @folio: The folio. | |
2670 | * | |
2671 | * When a writepage implementation decides that it doesn't want to write | |
2672 | * @folio for some reason, it should call this function, unlock @folio and | |
2673 | * return 0. | |
2674 | * | |
2675 | * Return: True if we redirtied the folio. False if someone else dirtied | |
2676 | * it first. | |
1da177e4 | 2677 | */ |
cd78ab11 MWO |
2678 | bool folio_redirty_for_writepage(struct writeback_control *wbc, |
2679 | struct folio *folio) | |
1da177e4 | 2680 | { |
cd78ab11 MWO |
2681 | bool ret; |
2682 | long nr = folio_nr_pages(folio); | |
2683 | ||
2684 | wbc->pages_skipped += nr; | |
2685 | ret = filemap_dirty_folio(folio->mapping, folio); | |
2686 | folio_account_redirty(folio); | |
8d38633c | 2687 | |
8d38633c | 2688 | return ret; |
1da177e4 | 2689 | } |
cd78ab11 | 2690 | EXPORT_SYMBOL(folio_redirty_for_writepage); |
1da177e4 | 2691 | |
b5e84594 MWO |
2692 | /** |
2693 | * folio_mark_dirty - Mark a folio as being modified. | |
2694 | * @folio: The folio. | |
6746aff7 | 2695 | * |
2ca456c2 MWO |
2696 | * The folio may not be truncated while this function is running. |
2697 | * Holding the folio lock is sufficient to prevent truncation, but some | |
2698 | * callers cannot acquire a sleeping lock. These callers instead hold | |
2699 | * the page table lock for a page table which contains at least one page | |
2700 | * in this folio. Truncation will block on the page table lock as it | |
2701 | * unmaps pages before removing the folio from its mapping. | |
b5e84594 MWO |
2702 | * |
2703 | * Return: True if the folio was newly dirtied, false if it was already dirty. | |
1da177e4 | 2704 | */ |
b5e84594 | 2705 | bool folio_mark_dirty(struct folio *folio) |
1da177e4 | 2706 | { |
b5e84594 | 2707 | struct address_space *mapping = folio_mapping(folio); |
1da177e4 LT |
2708 | |
2709 | if (likely(mapping)) { | |
278df9f4 MK |
2710 | /* |
2711 | * readahead/lru_deactivate_page could remain | |
6f31a5a2 MWO |
2712 | * PG_readahead/PG_reclaim due to race with folio_end_writeback |
2713 | * About readahead, if the folio is written, the flags would be | |
278df9f4 | 2714 | * reset. So no problem. |
6f31a5a2 MWO |
2715 | * About lru_deactivate_page, if the folio is redirtied, |
2716 | * the flag will be reset. So no problem. but if the | |
2717 | * folio is used by readahead it will confuse readahead | |
2718 | * and make it restart the size rampup process. But it's | |
2719 | * a trivial problem. | |
278df9f4 | 2720 | */ |
b5e84594 MWO |
2721 | if (folio_test_reclaim(folio)) |
2722 | folio_clear_reclaim(folio); | |
3a3bae50 | 2723 | return mapping->a_ops->dirty_folio(mapping, folio); |
4741c9fd | 2724 | } |
3a3bae50 MWO |
2725 | |
2726 | return noop_dirty_folio(mapping, folio); | |
1da177e4 | 2727 | } |
b5e84594 | 2728 | EXPORT_SYMBOL(folio_mark_dirty); |
1da177e4 LT |
2729 | |
2730 | /* | |
2731 | * set_page_dirty() is racy if the caller has no reference against | |
2732 | * page->mapping->host, and if the page is unlocked. This is because another | |
2733 | * CPU could truncate the page off the mapping and then free the mapping. | |
2734 | * | |
2735 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
2736 | * holds a reference on the inode by having an open file. | |
2737 | * | |
2738 | * In other cases, the page should be locked before running set_page_dirty(). | |
2739 | */ | |
2740 | int set_page_dirty_lock(struct page *page) | |
2741 | { | |
2742 | int ret; | |
2743 | ||
7eaceacc | 2744 | lock_page(page); |
1da177e4 LT |
2745 | ret = set_page_dirty(page); |
2746 | unlock_page(page); | |
2747 | return ret; | |
2748 | } | |
2749 | EXPORT_SYMBOL(set_page_dirty_lock); | |
2750 | ||
11f81bec TH |
2751 | /* |
2752 | * This cancels just the dirty bit on the kernel page itself, it does NOT | |
2753 | * actually remove dirty bits on any mmap's that may be around. It also | |
2754 | * leaves the page tagged dirty, so any sync activity will still find it on | |
2755 | * the dirty lists, and in particular, clear_page_dirty_for_io() will still | |
2756 | * look at the dirty bits in the VM. | |
2757 | * | |
2758 | * Doing this should *normally* only ever be done when a page is truncated, | |
2759 | * and is not actually mapped anywhere at all. However, fs/buffer.c does | |
2760 | * this when it notices that somebody has cleaned out all the buffers on a | |
2761 | * page without actually doing it through the VM. Can you say "ext3 is | |
2762 | * horribly ugly"? Thought you could. | |
2763 | */ | |
fdaf532a | 2764 | void __folio_cancel_dirty(struct folio *folio) |
11f81bec | 2765 | { |
fdaf532a | 2766 | struct address_space *mapping = folio_mapping(folio); |
c4843a75 | 2767 | |
f56753ac | 2768 | if (mapping_can_writeback(mapping)) { |
682aa8e1 TH |
2769 | struct inode *inode = mapping->host; |
2770 | struct bdi_writeback *wb; | |
2e898e4c | 2771 | struct wb_lock_cookie cookie = {}; |
c4843a75 | 2772 | |
fdaf532a | 2773 | folio_memcg_lock(folio); |
2e898e4c | 2774 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
c4843a75 | 2775 | |
fdaf532a | 2776 | if (folio_test_clear_dirty(folio)) |
566d3362 | 2777 | folio_account_cleaned(folio, wb); |
c4843a75 | 2778 | |
2e898e4c | 2779 | unlocked_inode_to_wb_end(inode, &cookie); |
fdaf532a | 2780 | folio_memcg_unlock(folio); |
c4843a75 | 2781 | } else { |
fdaf532a | 2782 | folio_clear_dirty(folio); |
c4843a75 | 2783 | } |
11f81bec | 2784 | } |
fdaf532a | 2785 | EXPORT_SYMBOL(__folio_cancel_dirty); |
11f81bec | 2786 | |
1da177e4 | 2787 | /* |
9350f20a MWO |
2788 | * Clear a folio's dirty flag, while caring for dirty memory accounting. |
2789 | * Returns true if the folio was previously dirty. | |
1da177e4 | 2790 | * |
9350f20a MWO |
2791 | * This is for preparing to put the folio under writeout. We leave |
2792 | * the folio tagged as dirty in the xarray so that a concurrent | |
2793 | * write-for-sync can discover it via a PAGECACHE_TAG_DIRTY walk. | |
2794 | * The ->writepage implementation will run either folio_start_writeback() | |
2795 | * or folio_mark_dirty(), at which stage we bring the folio's dirty flag | |
2796 | * and xarray dirty tag back into sync. | |
1da177e4 | 2797 | * |
9350f20a MWO |
2798 | * This incoherency between the folio's dirty flag and xarray tag is |
2799 | * unfortunate, but it only exists while the folio is locked. | |
1da177e4 | 2800 | */ |
9350f20a | 2801 | bool folio_clear_dirty_for_io(struct folio *folio) |
1da177e4 | 2802 | { |
9350f20a MWO |
2803 | struct address_space *mapping = folio_mapping(folio); |
2804 | bool ret = false; | |
1da177e4 | 2805 | |
9350f20a | 2806 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
79352894 | 2807 | |
f56753ac | 2808 | if (mapping && mapping_can_writeback(mapping)) { |
682aa8e1 TH |
2809 | struct inode *inode = mapping->host; |
2810 | struct bdi_writeback *wb; | |
2e898e4c | 2811 | struct wb_lock_cookie cookie = {}; |
682aa8e1 | 2812 | |
7658cc28 LT |
2813 | /* |
2814 | * Yes, Virginia, this is indeed insane. | |
2815 | * | |
2816 | * We use this sequence to make sure that | |
2817 | * (a) we account for dirty stats properly | |
2818 | * (b) we tell the low-level filesystem to | |
9350f20a | 2819 | * mark the whole folio dirty if it was |
7658cc28 | 2820 | * dirty in a pagetable. Only to then |
9350f20a | 2821 | * (c) clean the folio again and return 1 to |
7658cc28 LT |
2822 | * cause the writeback. |
2823 | * | |
2824 | * This way we avoid all nasty races with the | |
2825 | * dirty bit in multiple places and clearing | |
2826 | * them concurrently from different threads. | |
2827 | * | |
9350f20a | 2828 | * Note! Normally the "folio_mark_dirty(folio)" |
7658cc28 LT |
2829 | * has no effect on the actual dirty bit - since |
2830 | * that will already usually be set. But we | |
2831 | * need the side effects, and it can help us | |
2832 | * avoid races. | |
2833 | * | |
9350f20a | 2834 | * We basically use the folio "master dirty bit" |
7658cc28 LT |
2835 | * as a serialization point for all the different |
2836 | * threads doing their things. | |
7658cc28 | 2837 | */ |
9350f20a MWO |
2838 | if (folio_mkclean(folio)) |
2839 | folio_mark_dirty(folio); | |
79352894 NP |
2840 | /* |
2841 | * We carefully synchronise fault handlers against | |
9350f20a | 2842 | * installing a dirty pte and marking the folio dirty |
2d6d7f98 | 2843 | * at this point. We do this by having them hold the |
9350f20a | 2844 | * page lock while dirtying the folio, and folios are |
2d6d7f98 JW |
2845 | * always locked coming in here, so we get the desired |
2846 | * exclusion. | |
79352894 | 2847 | */ |
2e898e4c | 2848 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
9350f20a MWO |
2849 | if (folio_test_clear_dirty(folio)) { |
2850 | long nr = folio_nr_pages(folio); | |
2851 | lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr); | |
2852 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); | |
2853 | wb_stat_mod(wb, WB_RECLAIMABLE, -nr); | |
2854 | ret = true; | |
1da177e4 | 2855 | } |
2e898e4c | 2856 | unlocked_inode_to_wb_end(inode, &cookie); |
c4843a75 | 2857 | return ret; |
1da177e4 | 2858 | } |
9350f20a | 2859 | return folio_test_clear_dirty(folio); |
1da177e4 | 2860 | } |
9350f20a | 2861 | EXPORT_SYMBOL(folio_clear_dirty_for_io); |
1da177e4 | 2862 | |
633a2abb JK |
2863 | static void wb_inode_writeback_start(struct bdi_writeback *wb) |
2864 | { | |
2865 | atomic_inc(&wb->writeback_inodes); | |
2866 | } | |
2867 | ||
2868 | static void wb_inode_writeback_end(struct bdi_writeback *wb) | |
2869 | { | |
2870 | atomic_dec(&wb->writeback_inodes); | |
45a2966f JK |
2871 | /* |
2872 | * Make sure estimate of writeback throughput gets updated after | |
2873 | * writeback completed. We delay the update by BANDWIDTH_INTERVAL | |
2874 | * (which is the interval other bandwidth updates use for batching) so | |
2875 | * that if multiple inodes end writeback at a similar time, they get | |
2876 | * batched into one bandwidth update. | |
2877 | */ | |
2878 | queue_delayed_work(bdi_wq, &wb->bw_dwork, BANDWIDTH_INTERVAL); | |
633a2abb JK |
2879 | } |
2880 | ||
269ccca3 | 2881 | bool __folio_end_writeback(struct folio *folio) |
1da177e4 | 2882 | { |
269ccca3 MWO |
2883 | long nr = folio_nr_pages(folio); |
2884 | struct address_space *mapping = folio_mapping(folio); | |
2885 | bool ret; | |
1da177e4 | 2886 | |
269ccca3 | 2887 | folio_memcg_lock(folio); |
371a096e | 2888 | if (mapping && mapping_use_writeback_tags(mapping)) { |
91018134 TH |
2889 | struct inode *inode = mapping->host; |
2890 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2891 | unsigned long flags; |
2892 | ||
b93b0163 | 2893 | xa_lock_irqsave(&mapping->i_pages, flags); |
269ccca3 | 2894 | ret = folio_test_clear_writeback(folio); |
69cb51d1 | 2895 | if (ret) { |
269ccca3 | 2896 | __xa_clear_mark(&mapping->i_pages, folio_index(folio), |
1da177e4 | 2897 | PAGECACHE_TAG_WRITEBACK); |
823423ef | 2898 | if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) { |
91018134 TH |
2899 | struct bdi_writeback *wb = inode_to_wb(inode); |
2900 | ||
269ccca3 MWO |
2901 | wb_stat_mod(wb, WB_WRITEBACK, -nr); |
2902 | __wb_writeout_add(wb, nr); | |
633a2abb JK |
2903 | if (!mapping_tagged(mapping, |
2904 | PAGECACHE_TAG_WRITEBACK)) | |
2905 | wb_inode_writeback_end(wb); | |
04fbfdc1 | 2906 | } |
69cb51d1 | 2907 | } |
6c60d2b5 DC |
2908 | |
2909 | if (mapping->host && !mapping_tagged(mapping, | |
2910 | PAGECACHE_TAG_WRITEBACK)) | |
2911 | sb_clear_inode_writeback(mapping->host); | |
2912 | ||
b93b0163 | 2913 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
1da177e4 | 2914 | } else { |
269ccca3 | 2915 | ret = folio_test_clear_writeback(folio); |
1da177e4 | 2916 | } |
99b12e3d | 2917 | if (ret) { |
269ccca3 MWO |
2918 | lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr); |
2919 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); | |
2920 | node_stat_mod_folio(folio, NR_WRITTEN, nr); | |
99b12e3d | 2921 | } |
269ccca3 | 2922 | folio_memcg_unlock(folio); |
1da177e4 LT |
2923 | return ret; |
2924 | } | |
2925 | ||
f143f1ea | 2926 | bool __folio_start_writeback(struct folio *folio, bool keep_write) |
1da177e4 | 2927 | { |
f143f1ea MWO |
2928 | long nr = folio_nr_pages(folio); |
2929 | struct address_space *mapping = folio_mapping(folio); | |
2930 | bool ret; | |
2931 | int access_ret; | |
1da177e4 | 2932 | |
f143f1ea | 2933 | folio_memcg_lock(folio); |
371a096e | 2934 | if (mapping && mapping_use_writeback_tags(mapping)) { |
f143f1ea | 2935 | XA_STATE(xas, &mapping->i_pages, folio_index(folio)); |
91018134 TH |
2936 | struct inode *inode = mapping->host; |
2937 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2938 | unsigned long flags; |
2939 | ||
ff9c745b MW |
2940 | xas_lock_irqsave(&xas, flags); |
2941 | xas_load(&xas); | |
f143f1ea | 2942 | ret = folio_test_set_writeback(folio); |
69cb51d1 | 2943 | if (!ret) { |
6c60d2b5 DC |
2944 | bool on_wblist; |
2945 | ||
2946 | on_wblist = mapping_tagged(mapping, | |
2947 | PAGECACHE_TAG_WRITEBACK); | |
2948 | ||
ff9c745b | 2949 | xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK); |
633a2abb JK |
2950 | if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) { |
2951 | struct bdi_writeback *wb = inode_to_wb(inode); | |
2952 | ||
f143f1ea | 2953 | wb_stat_mod(wb, WB_WRITEBACK, nr); |
633a2abb JK |
2954 | if (!on_wblist) |
2955 | wb_inode_writeback_start(wb); | |
2956 | } | |
6c60d2b5 DC |
2957 | |
2958 | /* | |
f143f1ea MWO |
2959 | * We can come through here when swapping |
2960 | * anonymous folios, so we don't necessarily | |
2961 | * have an inode to track for sync. | |
6c60d2b5 DC |
2962 | */ |
2963 | if (mapping->host && !on_wblist) | |
2964 | sb_mark_inode_writeback(mapping->host); | |
69cb51d1 | 2965 | } |
f143f1ea | 2966 | if (!folio_test_dirty(folio)) |
ff9c745b | 2967 | xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); |
1c8349a1 | 2968 | if (!keep_write) |
ff9c745b MW |
2969 | xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE); |
2970 | xas_unlock_irqrestore(&xas, flags); | |
1da177e4 | 2971 | } else { |
f143f1ea | 2972 | ret = folio_test_set_writeback(folio); |
1da177e4 | 2973 | } |
3a3c02ec | 2974 | if (!ret) { |
f143f1ea MWO |
2975 | lruvec_stat_mod_folio(folio, NR_WRITEBACK, nr); |
2976 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr); | |
3a3c02ec | 2977 | } |
f143f1ea MWO |
2978 | folio_memcg_unlock(folio); |
2979 | access_ret = arch_make_folio_accessible(folio); | |
f28d4363 CI |
2980 | /* |
2981 | * If writeback has been triggered on a page that cannot be made | |
2982 | * accessible, it is too late to recover here. | |
2983 | */ | |
f143f1ea | 2984 | VM_BUG_ON_FOLIO(access_ret != 0, folio); |
f28d4363 | 2985 | |
1da177e4 | 2986 | return ret; |
1da177e4 | 2987 | } |
f143f1ea | 2988 | EXPORT_SYMBOL(__folio_start_writeback); |
1da177e4 | 2989 | |
490e016f MWO |
2990 | /** |
2991 | * folio_wait_writeback - Wait for a folio to finish writeback. | |
2992 | * @folio: The folio to wait for. | |
2993 | * | |
2994 | * If the folio is currently being written back to storage, wait for the | |
2995 | * I/O to complete. | |
2996 | * | |
2997 | * Context: Sleeps. Must be called in process context and with | |
2998 | * no spinlocks held. Caller should hold a reference on the folio. | |
2999 | * If the folio is not locked, writeback may start again after writeback | |
3000 | * has finished. | |
19343b5b | 3001 | */ |
490e016f | 3002 | void folio_wait_writeback(struct folio *folio) |
19343b5b | 3003 | { |
490e016f | 3004 | while (folio_test_writeback(folio)) { |
b9b0ff61 | 3005 | trace_folio_wait_writeback(folio, folio_mapping(folio)); |
101c0bf6 | 3006 | folio_wait_bit(folio, PG_writeback); |
19343b5b YS |
3007 | } |
3008 | } | |
490e016f | 3009 | EXPORT_SYMBOL_GPL(folio_wait_writeback); |
19343b5b | 3010 | |
490e016f MWO |
3011 | /** |
3012 | * folio_wait_writeback_killable - Wait for a folio to finish writeback. | |
3013 | * @folio: The folio to wait for. | |
3014 | * | |
3015 | * If the folio is currently being written back to storage, wait for the | |
3016 | * I/O to complete or a fatal signal to arrive. | |
3017 | * | |
3018 | * Context: Sleeps. Must be called in process context and with | |
3019 | * no spinlocks held. Caller should hold a reference on the folio. | |
3020 | * If the folio is not locked, writeback may start again after writeback | |
3021 | * has finished. | |
3022 | * Return: 0 on success, -EINTR if we get a fatal signal while waiting. | |
e5dbd332 | 3023 | */ |
490e016f | 3024 | int folio_wait_writeback_killable(struct folio *folio) |
e5dbd332 | 3025 | { |
490e016f | 3026 | while (folio_test_writeback(folio)) { |
b9b0ff61 | 3027 | trace_folio_wait_writeback(folio, folio_mapping(folio)); |
101c0bf6 | 3028 | if (folio_wait_bit_killable(folio, PG_writeback)) |
e5dbd332 MWO |
3029 | return -EINTR; |
3030 | } | |
3031 | ||
3032 | return 0; | |
3033 | } | |
490e016f | 3034 | EXPORT_SYMBOL_GPL(folio_wait_writeback_killable); |
e5dbd332 | 3035 | |
1d1d1a76 | 3036 | /** |
a49d0c50 MWO |
3037 | * folio_wait_stable() - wait for writeback to finish, if necessary. |
3038 | * @folio: The folio to wait on. | |
1d1d1a76 | 3039 | * |
a49d0c50 MWO |
3040 | * This function determines if the given folio is related to a backing |
3041 | * device that requires folio contents to be held stable during writeback. | |
3042 | * If so, then it will wait for any pending writeback to complete. | |
3043 | * | |
3044 | * Context: Sleeps. Must be called in process context and with | |
3045 | * no spinlocks held. Caller should hold a reference on the folio. | |
3046 | * If the folio is not locked, writeback may start again after writeback | |
3047 | * has finished. | |
1d1d1a76 | 3048 | */ |
a49d0c50 | 3049 | void folio_wait_stable(struct folio *folio) |
1d1d1a76 | 3050 | { |
452c472e | 3051 | if (folio_inode(folio)->i_sb->s_iflags & SB_I_STABLE_WRITES) |
a49d0c50 | 3052 | folio_wait_writeback(folio); |
1d1d1a76 | 3053 | } |
a49d0c50 | 3054 | EXPORT_SYMBOL_GPL(folio_wait_stable); |