Commit | Line | Data |
---|---|---|
1da177e4 | 1 | /* |
f30c2269 | 2 | * mm/page-writeback.c |
1da177e4 LT |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. | |
90eec103 | 5 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra |
1da177e4 LT |
6 | * |
7 | * Contains functions related to writing back dirty pages at the | |
8 | * address_space level. | |
9 | * | |
e1f8e874 | 10 | * 10Apr2002 Andrew Morton |
1da177e4 LT |
11 | * Initial version |
12 | */ | |
13 | ||
14 | #include <linux/kernel.h> | |
b95f1b31 | 15 | #include <linux/export.h> |
1da177e4 LT |
16 | #include <linux/spinlock.h> |
17 | #include <linux/fs.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/swap.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/pagemap.h> | |
22 | #include <linux/writeback.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/backing-dev.h> | |
55e829af | 25 | #include <linux/task_io_accounting_ops.h> |
1da177e4 LT |
26 | #include <linux/blkdev.h> |
27 | #include <linux/mpage.h> | |
d08b3851 | 28 | #include <linux/rmap.h> |
1da177e4 | 29 | #include <linux/percpu.h> |
1da177e4 LT |
30 | #include <linux/smp.h> |
31 | #include <linux/sysctl.h> | |
32 | #include <linux/cpu.h> | |
33 | #include <linux/syscalls.h> | |
ff01bb48 | 34 | #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ |
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 | */ |
1b5e62b4 | 73 | int dirty_background_ratio = 10; |
1da177e4 | 74 | |
2da02997 DR |
75 | /* |
76 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of | |
77 | * dirty_background_ratio * the amount of dirtyable memory | |
78 | */ | |
79 | unsigned long dirty_background_bytes; | |
80 | ||
195cf453 BG |
81 | /* |
82 | * free highmem will not be subtracted from the total free memory | |
83 | * for calculating free ratios if vm_highmem_is_dirtyable is true | |
84 | */ | |
85 | int vm_highmem_is_dirtyable; | |
86 | ||
1da177e4 LT |
87 | /* |
88 | * The generator of dirty data starts writeback at this percentage | |
89 | */ | |
1b5e62b4 | 90 | int vm_dirty_ratio = 20; |
1da177e4 | 91 | |
2da02997 DR |
92 | /* |
93 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of | |
94 | * vm_dirty_ratio * the amount of dirtyable memory | |
95 | */ | |
96 | unsigned long vm_dirty_bytes; | |
97 | ||
1da177e4 | 98 | /* |
704503d8 | 99 | * The interval between `kupdate'-style writebacks |
1da177e4 | 100 | */ |
22ef37ee | 101 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
1da177e4 | 102 | |
91913a29 AB |
103 | EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
104 | ||
1da177e4 | 105 | /* |
704503d8 | 106 | * The longest time for which data is allowed to remain dirty |
1da177e4 | 107 | */ |
22ef37ee | 108 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
1da177e4 LT |
109 | |
110 | /* | |
111 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
112 | */ | |
113 | int block_dump; | |
114 | ||
115 | /* | |
ed5b43f1 BS |
116 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
117 | * a full sync is triggered after this time elapses without any disk activity. | |
1da177e4 LT |
118 | */ |
119 | int laptop_mode; | |
120 | ||
121 | EXPORT_SYMBOL(laptop_mode); | |
122 | ||
123 | /* End of sysctl-exported parameters */ | |
124 | ||
dcc25ae7 | 125 | struct wb_domain global_wb_domain; |
1da177e4 | 126 | |
2bc00aef TH |
127 | /* consolidated parameters for balance_dirty_pages() and its subroutines */ |
128 | struct dirty_throttle_control { | |
e9f07dfd TH |
129 | #ifdef CONFIG_CGROUP_WRITEBACK |
130 | struct wb_domain *dom; | |
9fc3a43e | 131 | struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ |
e9f07dfd | 132 | #endif |
2bc00aef | 133 | struct bdi_writeback *wb; |
e9770b34 | 134 | struct fprop_local_percpu *wb_completions; |
eb608e3a | 135 | |
9fc3a43e | 136 | unsigned long avail; /* dirtyable */ |
2bc00aef TH |
137 | unsigned long dirty; /* file_dirty + write + nfs */ |
138 | unsigned long thresh; /* dirty threshold */ | |
139 | unsigned long bg_thresh; /* dirty background threshold */ | |
140 | ||
141 | unsigned long wb_dirty; /* per-wb counterparts */ | |
142 | unsigned long wb_thresh; | |
970fb01a | 143 | unsigned long wb_bg_thresh; |
daddfa3c TH |
144 | |
145 | unsigned long pos_ratio; | |
2bc00aef TH |
146 | }; |
147 | ||
eb608e3a JK |
148 | /* |
149 | * Length of period for aging writeout fractions of bdis. This is an | |
150 | * arbitrarily chosen number. The longer the period, the slower fractions will | |
151 | * reflect changes in current writeout rate. | |
152 | */ | |
153 | #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) | |
04fbfdc1 | 154 | |
693108a8 TH |
155 | #ifdef CONFIG_CGROUP_WRITEBACK |
156 | ||
d60d1bdd TH |
157 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
158 | .dom = &global_wb_domain, \ | |
159 | .wb_completions = &(__wb)->completions | |
160 | ||
9fc3a43e | 161 | #define GDTC_INIT_NO_WB .dom = &global_wb_domain |
d60d1bdd TH |
162 | |
163 | #define MDTC_INIT(__wb, __gdtc) .wb = (__wb), \ | |
164 | .dom = mem_cgroup_wb_domain(__wb), \ | |
165 | .wb_completions = &(__wb)->memcg_completions, \ | |
166 | .gdtc = __gdtc | |
c2aa723a TH |
167 | |
168 | static bool mdtc_valid(struct dirty_throttle_control *dtc) | |
169 | { | |
170 | return dtc->dom; | |
171 | } | |
e9f07dfd TH |
172 | |
173 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) | |
174 | { | |
175 | return dtc->dom; | |
176 | } | |
177 | ||
9fc3a43e TH |
178 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
179 | { | |
180 | return mdtc->gdtc; | |
181 | } | |
182 | ||
841710aa TH |
183 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
184 | { | |
185 | return &wb->memcg_completions; | |
186 | } | |
187 | ||
693108a8 TH |
188 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
189 | unsigned long *minp, unsigned long *maxp) | |
190 | { | |
191 | unsigned long this_bw = wb->avg_write_bandwidth; | |
192 | unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); | |
193 | unsigned long long min = wb->bdi->min_ratio; | |
194 | unsigned long long max = wb->bdi->max_ratio; | |
195 | ||
196 | /* | |
197 | * @wb may already be clean by the time control reaches here and | |
198 | * the total may not include its bw. | |
199 | */ | |
200 | if (this_bw < tot_bw) { | |
201 | if (min) { | |
202 | min *= this_bw; | |
203 | do_div(min, tot_bw); | |
204 | } | |
205 | if (max < 100) { | |
206 | max *= this_bw; | |
207 | do_div(max, tot_bw); | |
208 | } | |
209 | } | |
210 | ||
211 | *minp = min; | |
212 | *maxp = max; | |
213 | } | |
214 | ||
215 | #else /* CONFIG_CGROUP_WRITEBACK */ | |
216 | ||
d60d1bdd TH |
217 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
218 | .wb_completions = &(__wb)->completions | |
9fc3a43e | 219 | #define GDTC_INIT_NO_WB |
c2aa723a TH |
220 | #define MDTC_INIT(__wb, __gdtc) |
221 | ||
222 | static bool mdtc_valid(struct dirty_throttle_control *dtc) | |
223 | { | |
224 | return false; | |
225 | } | |
e9f07dfd TH |
226 | |
227 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) | |
228 | { | |
229 | return &global_wb_domain; | |
230 | } | |
231 | ||
9fc3a43e TH |
232 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
233 | { | |
234 | return NULL; | |
235 | } | |
236 | ||
841710aa TH |
237 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
238 | { | |
239 | return NULL; | |
240 | } | |
241 | ||
693108a8 TH |
242 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
243 | unsigned long *minp, unsigned long *maxp) | |
244 | { | |
245 | *minp = wb->bdi->min_ratio; | |
246 | *maxp = wb->bdi->max_ratio; | |
247 | } | |
248 | ||
249 | #endif /* CONFIG_CGROUP_WRITEBACK */ | |
250 | ||
a756cf59 JW |
251 | /* |
252 | * In a memory zone, there is a certain amount of pages we consider | |
253 | * available for the page cache, which is essentially the number of | |
254 | * free and reclaimable pages, minus some zone reserves to protect | |
255 | * lowmem and the ability to uphold the zone's watermarks without | |
256 | * requiring writeback. | |
257 | * | |
258 | * This number of dirtyable pages is the base value of which the | |
259 | * user-configurable dirty ratio is the effictive number of pages that | |
260 | * are allowed to be actually dirtied. Per individual zone, or | |
261 | * globally by using the sum of dirtyable pages over all zones. | |
262 | * | |
263 | * Because the user is allowed to specify the dirty limit globally as | |
264 | * absolute number of bytes, calculating the per-zone dirty limit can | |
265 | * require translating the configured limit into a percentage of | |
266 | * global dirtyable memory first. | |
267 | */ | |
268 | ||
a804552b | 269 | /** |
281e3726 MG |
270 | * node_dirtyable_memory - number of dirtyable pages in a node |
271 | * @pgdat: the node | |
a804552b | 272 | * |
a862f68a | 273 | * Return: the node's number of pages potentially available for dirty |
281e3726 | 274 | * page cache. This is the base value for the per-node dirty limits. |
a804552b | 275 | */ |
281e3726 | 276 | static unsigned long node_dirtyable_memory(struct pglist_data *pgdat) |
a804552b | 277 | { |
281e3726 MG |
278 | unsigned long nr_pages = 0; |
279 | int z; | |
280 | ||
281 | for (z = 0; z < MAX_NR_ZONES; z++) { | |
282 | struct zone *zone = pgdat->node_zones + z; | |
283 | ||
284 | if (!populated_zone(zone)) | |
285 | continue; | |
286 | ||
287 | nr_pages += zone_page_state(zone, NR_FREE_PAGES); | |
288 | } | |
a804552b | 289 | |
a8d01437 JW |
290 | /* |
291 | * Pages reserved for the kernel should not be considered | |
292 | * dirtyable, to prevent a situation where reclaim has to | |
293 | * clean pages in order to balance the zones. | |
294 | */ | |
281e3726 | 295 | nr_pages -= min(nr_pages, pgdat->totalreserve_pages); |
a804552b | 296 | |
281e3726 MG |
297 | nr_pages += node_page_state(pgdat, NR_INACTIVE_FILE); |
298 | nr_pages += node_page_state(pgdat, NR_ACTIVE_FILE); | |
a804552b JW |
299 | |
300 | return nr_pages; | |
301 | } | |
302 | ||
1edf2234 JW |
303 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
304 | { | |
305 | #ifdef CONFIG_HIGHMEM | |
306 | int node; | |
bb4cc2be | 307 | unsigned long x = 0; |
09b4ab3c | 308 | int i; |
1edf2234 JW |
309 | |
310 | for_each_node_state(node, N_HIGH_MEMORY) { | |
281e3726 MG |
311 | for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { |
312 | struct zone *z; | |
9cb937e2 | 313 | unsigned long nr_pages; |
281e3726 MG |
314 | |
315 | if (!is_highmem_idx(i)) | |
316 | continue; | |
317 | ||
318 | z = &NODE_DATA(node)->node_zones[i]; | |
9cb937e2 MK |
319 | if (!populated_zone(z)) |
320 | continue; | |
1edf2234 | 321 | |
9cb937e2 | 322 | nr_pages = zone_page_state(z, NR_FREE_PAGES); |
281e3726 | 323 | /* watch for underflows */ |
9cb937e2 | 324 | nr_pages -= min(nr_pages, high_wmark_pages(z)); |
bb4cc2be MG |
325 | nr_pages += zone_page_state(z, NR_ZONE_INACTIVE_FILE); |
326 | nr_pages += zone_page_state(z, NR_ZONE_ACTIVE_FILE); | |
327 | x += nr_pages; | |
09b4ab3c | 328 | } |
1edf2234 | 329 | } |
281e3726 | 330 | |
c8b74c2f SR |
331 | /* |
332 | * Unreclaimable memory (kernel memory or anonymous memory | |
333 | * without swap) can bring down the dirtyable pages below | |
334 | * the zone's dirty balance reserve and the above calculation | |
335 | * will underflow. However we still want to add in nodes | |
336 | * which are below threshold (negative values) to get a more | |
337 | * accurate calculation but make sure that the total never | |
338 | * underflows. | |
339 | */ | |
340 | if ((long)x < 0) | |
341 | x = 0; | |
342 | ||
1edf2234 JW |
343 | /* |
344 | * Make sure that the number of highmem pages is never larger | |
345 | * than the number of the total dirtyable memory. This can only | |
346 | * occur in very strange VM situations but we want to make sure | |
347 | * that this does not occur. | |
348 | */ | |
349 | return min(x, total); | |
350 | #else | |
351 | return 0; | |
352 | #endif | |
353 | } | |
354 | ||
355 | /** | |
ccafa287 | 356 | * global_dirtyable_memory - number of globally dirtyable pages |
1edf2234 | 357 | * |
a862f68a | 358 | * Return: the global number of pages potentially available for dirty |
ccafa287 | 359 | * page cache. This is the base value for the global dirty limits. |
1edf2234 | 360 | */ |
18cf8cf8 | 361 | static unsigned long global_dirtyable_memory(void) |
1edf2234 JW |
362 | { |
363 | unsigned long x; | |
364 | ||
c41f012a | 365 | x = global_zone_page_state(NR_FREE_PAGES); |
a8d01437 JW |
366 | /* |
367 | * Pages reserved for the kernel should not be considered | |
368 | * dirtyable, to prevent a situation where reclaim has to | |
369 | * clean pages in order to balance the zones. | |
370 | */ | |
371 | x -= min(x, totalreserve_pages); | |
1edf2234 | 372 | |
599d0c95 MG |
373 | x += global_node_page_state(NR_INACTIVE_FILE); |
374 | x += global_node_page_state(NR_ACTIVE_FILE); | |
a804552b | 375 | |
1edf2234 JW |
376 | if (!vm_highmem_is_dirtyable) |
377 | x -= highmem_dirtyable_memory(x); | |
378 | ||
379 | return x + 1; /* Ensure that we never return 0 */ | |
380 | } | |
381 | ||
9fc3a43e TH |
382 | /** |
383 | * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain | |
384 | * @dtc: dirty_throttle_control of interest | |
ccafa287 | 385 | * |
9fc3a43e TH |
386 | * Calculate @dtc->thresh and ->bg_thresh considering |
387 | * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller | |
388 | * must ensure that @dtc->avail is set before calling this function. The | |
389 | * dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and | |
ccafa287 JW |
390 | * real-time tasks. |
391 | */ | |
9fc3a43e | 392 | static void domain_dirty_limits(struct dirty_throttle_control *dtc) |
ccafa287 | 393 | { |
9fc3a43e TH |
394 | const unsigned long available_memory = dtc->avail; |
395 | struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); | |
396 | unsigned long bytes = vm_dirty_bytes; | |
397 | unsigned long bg_bytes = dirty_background_bytes; | |
62a584fe TH |
398 | /* convert ratios to per-PAGE_SIZE for higher precision */ |
399 | unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100; | |
400 | unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100; | |
9fc3a43e TH |
401 | unsigned long thresh; |
402 | unsigned long bg_thresh; | |
ccafa287 JW |
403 | struct task_struct *tsk; |
404 | ||
9fc3a43e TH |
405 | /* gdtc is !NULL iff @dtc is for memcg domain */ |
406 | if (gdtc) { | |
407 | unsigned long global_avail = gdtc->avail; | |
408 | ||
409 | /* | |
410 | * The byte settings can't be applied directly to memcg | |
411 | * domains. Convert them to ratios by scaling against | |
62a584fe TH |
412 | * globally available memory. As the ratios are in |
413 | * per-PAGE_SIZE, they can be obtained by dividing bytes by | |
414 | * number of pages. | |
9fc3a43e TH |
415 | */ |
416 | if (bytes) | |
62a584fe TH |
417 | ratio = min(DIV_ROUND_UP(bytes, global_avail), |
418 | PAGE_SIZE); | |
9fc3a43e | 419 | if (bg_bytes) |
62a584fe TH |
420 | bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail), |
421 | PAGE_SIZE); | |
9fc3a43e TH |
422 | bytes = bg_bytes = 0; |
423 | } | |
424 | ||
425 | if (bytes) | |
426 | thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); | |
ccafa287 | 427 | else |
62a584fe | 428 | thresh = (ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 429 | |
9fc3a43e TH |
430 | if (bg_bytes) |
431 | bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); | |
ccafa287 | 432 | else |
62a584fe | 433 | bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE; |
ccafa287 | 434 | |
90daf306 | 435 | if (bg_thresh >= thresh) |
9fc3a43e | 436 | bg_thresh = thresh / 2; |
ccafa287 JW |
437 | tsk = current; |
438 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
a53eaff8 N |
439 | bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; |
440 | thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; | |
ccafa287 | 441 | } |
9fc3a43e TH |
442 | dtc->thresh = thresh; |
443 | dtc->bg_thresh = bg_thresh; | |
444 | ||
445 | /* we should eventually report the domain in the TP */ | |
446 | if (!gdtc) | |
447 | trace_global_dirty_state(bg_thresh, thresh); | |
448 | } | |
449 | ||
450 | /** | |
451 | * global_dirty_limits - background-writeback and dirty-throttling thresholds | |
452 | * @pbackground: out parameter for bg_thresh | |
453 | * @pdirty: out parameter for thresh | |
454 | * | |
455 | * Calculate bg_thresh and thresh for global_wb_domain. See | |
456 | * domain_dirty_limits() for details. | |
457 | */ | |
458 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) | |
459 | { | |
460 | struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; | |
461 | ||
462 | gdtc.avail = global_dirtyable_memory(); | |
463 | domain_dirty_limits(&gdtc); | |
464 | ||
465 | *pbackground = gdtc.bg_thresh; | |
466 | *pdirty = gdtc.thresh; | |
ccafa287 JW |
467 | } |
468 | ||
a756cf59 | 469 | /** |
281e3726 MG |
470 | * node_dirty_limit - maximum number of dirty pages allowed in a node |
471 | * @pgdat: the node | |
a756cf59 | 472 | * |
a862f68a | 473 | * Return: the maximum number of dirty pages allowed in a node, based |
281e3726 | 474 | * on the node's dirtyable memory. |
a756cf59 | 475 | */ |
281e3726 | 476 | static unsigned long node_dirty_limit(struct pglist_data *pgdat) |
a756cf59 | 477 | { |
281e3726 | 478 | unsigned long node_memory = node_dirtyable_memory(pgdat); |
a756cf59 JW |
479 | struct task_struct *tsk = current; |
480 | unsigned long dirty; | |
481 | ||
482 | if (vm_dirty_bytes) | |
483 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * | |
281e3726 | 484 | node_memory / global_dirtyable_memory(); |
a756cf59 | 485 | else |
281e3726 | 486 | dirty = vm_dirty_ratio * node_memory / 100; |
a756cf59 JW |
487 | |
488 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) | |
489 | dirty += dirty / 4; | |
490 | ||
491 | return dirty; | |
492 | } | |
493 | ||
494 | /** | |
281e3726 MG |
495 | * node_dirty_ok - tells whether a node is within its dirty limits |
496 | * @pgdat: the node to check | |
a756cf59 | 497 | * |
a862f68a | 498 | * Return: %true when the dirty pages in @pgdat are within the node's |
a756cf59 JW |
499 | * dirty limit, %false if the limit is exceeded. |
500 | */ | |
281e3726 | 501 | bool node_dirty_ok(struct pglist_data *pgdat) |
a756cf59 | 502 | { |
281e3726 MG |
503 | unsigned long limit = node_dirty_limit(pgdat); |
504 | unsigned long nr_pages = 0; | |
505 | ||
11fb9989 MG |
506 | nr_pages += node_page_state(pgdat, NR_FILE_DIRTY); |
507 | nr_pages += node_page_state(pgdat, NR_UNSTABLE_NFS); | |
508 | nr_pages += node_page_state(pgdat, NR_WRITEBACK); | |
a756cf59 | 509 | |
281e3726 | 510 | return nr_pages <= limit; |
a756cf59 JW |
511 | } |
512 | ||
2da02997 | 513 | int dirty_background_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 514 | void __user *buffer, size_t *lenp, |
2da02997 DR |
515 | loff_t *ppos) |
516 | { | |
517 | int ret; | |
518 | ||
8d65af78 | 519 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
520 | if (ret == 0 && write) |
521 | dirty_background_bytes = 0; | |
522 | return ret; | |
523 | } | |
524 | ||
525 | int dirty_background_bytes_handler(struct ctl_table *table, int write, | |
8d65af78 | 526 | void __user *buffer, size_t *lenp, |
2da02997 DR |
527 | loff_t *ppos) |
528 | { | |
529 | int ret; | |
530 | ||
8d65af78 | 531 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 DR |
532 | if (ret == 0 && write) |
533 | dirty_background_ratio = 0; | |
534 | return ret; | |
535 | } | |
536 | ||
04fbfdc1 | 537 | int dirty_ratio_handler(struct ctl_table *table, int write, |
8d65af78 | 538 | void __user *buffer, size_t *lenp, |
04fbfdc1 PZ |
539 | loff_t *ppos) |
540 | { | |
541 | int old_ratio = vm_dirty_ratio; | |
2da02997 DR |
542 | int ret; |
543 | ||
8d65af78 | 544 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
04fbfdc1 | 545 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
eb608e3a | 546 | writeback_set_ratelimit(); |
2da02997 DR |
547 | vm_dirty_bytes = 0; |
548 | } | |
549 | return ret; | |
550 | } | |
551 | ||
2da02997 | 552 | int dirty_bytes_handler(struct ctl_table *table, int write, |
8d65af78 | 553 | void __user *buffer, size_t *lenp, |
2da02997 DR |
554 | loff_t *ppos) |
555 | { | |
fc3501d4 | 556 | unsigned long old_bytes = vm_dirty_bytes; |
2da02997 DR |
557 | int ret; |
558 | ||
8d65af78 | 559 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
2da02997 | 560 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
eb608e3a | 561 | writeback_set_ratelimit(); |
2da02997 | 562 | vm_dirty_ratio = 0; |
04fbfdc1 PZ |
563 | } |
564 | return ret; | |
565 | } | |
566 | ||
eb608e3a JK |
567 | static unsigned long wp_next_time(unsigned long cur_time) |
568 | { | |
569 | cur_time += VM_COMPLETIONS_PERIOD_LEN; | |
570 | /* 0 has a special meaning... */ | |
571 | if (!cur_time) | |
572 | return 1; | |
573 | return cur_time; | |
574 | } | |
575 | ||
c7981433 TH |
576 | static void wb_domain_writeout_inc(struct wb_domain *dom, |
577 | struct fprop_local_percpu *completions, | |
578 | unsigned int max_prop_frac) | |
04fbfdc1 | 579 | { |
c7981433 TH |
580 | __fprop_inc_percpu_max(&dom->completions, completions, |
581 | max_prop_frac); | |
eb608e3a | 582 | /* First event after period switching was turned off? */ |
517663ed | 583 | if (unlikely(!dom->period_time)) { |
eb608e3a JK |
584 | /* |
585 | * We can race with other __bdi_writeout_inc calls here but | |
586 | * it does not cause any harm since the resulting time when | |
587 | * timer will fire and what is in writeout_period_time will be | |
588 | * roughly the same. | |
589 | */ | |
380c27ca TH |
590 | dom->period_time = wp_next_time(jiffies); |
591 | mod_timer(&dom->period_timer, dom->period_time); | |
eb608e3a | 592 | } |
04fbfdc1 PZ |
593 | } |
594 | ||
c7981433 TH |
595 | /* |
596 | * Increment @wb's writeout completion count and the global writeout | |
597 | * completion count. Called from test_clear_page_writeback(). | |
598 | */ | |
599 | static inline void __wb_writeout_inc(struct bdi_writeback *wb) | |
dd5656e5 | 600 | { |
841710aa | 601 | struct wb_domain *cgdom; |
dd5656e5 | 602 | |
3e8f399d | 603 | inc_wb_stat(wb, WB_WRITTEN); |
c7981433 TH |
604 | wb_domain_writeout_inc(&global_wb_domain, &wb->completions, |
605 | wb->bdi->max_prop_frac); | |
841710aa TH |
606 | |
607 | cgdom = mem_cgroup_wb_domain(wb); | |
608 | if (cgdom) | |
609 | wb_domain_writeout_inc(cgdom, wb_memcg_completions(wb), | |
610 | wb->bdi->max_prop_frac); | |
dd5656e5 | 611 | } |
dd5656e5 | 612 | |
93f78d88 | 613 | void wb_writeout_inc(struct bdi_writeback *wb) |
04fbfdc1 | 614 | { |
dd5656e5 MS |
615 | unsigned long flags; |
616 | ||
617 | local_irq_save(flags); | |
93f78d88 | 618 | __wb_writeout_inc(wb); |
dd5656e5 | 619 | local_irq_restore(flags); |
04fbfdc1 | 620 | } |
93f78d88 | 621 | EXPORT_SYMBOL_GPL(wb_writeout_inc); |
04fbfdc1 | 622 | |
eb608e3a JK |
623 | /* |
624 | * On idle system, we can be called long after we scheduled because we use | |
625 | * deferred timers so count with missed periods. | |
626 | */ | |
9823e51b | 627 | static void writeout_period(struct timer_list *t) |
eb608e3a | 628 | { |
9823e51b | 629 | struct wb_domain *dom = from_timer(dom, t, period_timer); |
380c27ca | 630 | int miss_periods = (jiffies - dom->period_time) / |
eb608e3a JK |
631 | VM_COMPLETIONS_PERIOD_LEN; |
632 | ||
380c27ca TH |
633 | if (fprop_new_period(&dom->completions, miss_periods + 1)) { |
634 | dom->period_time = wp_next_time(dom->period_time + | |
eb608e3a | 635 | miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
380c27ca | 636 | mod_timer(&dom->period_timer, dom->period_time); |
eb608e3a JK |
637 | } else { |
638 | /* | |
639 | * Aging has zeroed all fractions. Stop wasting CPU on period | |
640 | * updates. | |
641 | */ | |
380c27ca | 642 | dom->period_time = 0; |
eb608e3a JK |
643 | } |
644 | } | |
645 | ||
380c27ca TH |
646 | int wb_domain_init(struct wb_domain *dom, gfp_t gfp) |
647 | { | |
648 | memset(dom, 0, sizeof(*dom)); | |
dcc25ae7 TH |
649 | |
650 | spin_lock_init(&dom->lock); | |
651 | ||
9823e51b | 652 | timer_setup(&dom->period_timer, writeout_period, TIMER_DEFERRABLE); |
dcc25ae7 TH |
653 | |
654 | dom->dirty_limit_tstamp = jiffies; | |
655 | ||
380c27ca TH |
656 | return fprop_global_init(&dom->completions, gfp); |
657 | } | |
658 | ||
841710aa TH |
659 | #ifdef CONFIG_CGROUP_WRITEBACK |
660 | void wb_domain_exit(struct wb_domain *dom) | |
661 | { | |
662 | del_timer_sync(&dom->period_timer); | |
663 | fprop_global_destroy(&dom->completions); | |
664 | } | |
665 | #endif | |
666 | ||
189d3c4a | 667 | /* |
d08c429b JW |
668 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
669 | * registered backing devices, which, for obvious reasons, can not | |
670 | * exceed 100%. | |
189d3c4a | 671 | */ |
189d3c4a PZ |
672 | static unsigned int bdi_min_ratio; |
673 | ||
674 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) | |
675 | { | |
676 | int ret = 0; | |
189d3c4a | 677 | |
cfc4ba53 | 678 | spin_lock_bh(&bdi_lock); |
a42dde04 | 679 | if (min_ratio > bdi->max_ratio) { |
189d3c4a | 680 | ret = -EINVAL; |
a42dde04 PZ |
681 | } else { |
682 | min_ratio -= bdi->min_ratio; | |
683 | if (bdi_min_ratio + min_ratio < 100) { | |
684 | bdi_min_ratio += min_ratio; | |
685 | bdi->min_ratio += min_ratio; | |
686 | } else { | |
687 | ret = -EINVAL; | |
688 | } | |
689 | } | |
cfc4ba53 | 690 | spin_unlock_bh(&bdi_lock); |
a42dde04 PZ |
691 | |
692 | return ret; | |
693 | } | |
694 | ||
695 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) | |
696 | { | |
a42dde04 PZ |
697 | int ret = 0; |
698 | ||
699 | if (max_ratio > 100) | |
700 | return -EINVAL; | |
701 | ||
cfc4ba53 | 702 | spin_lock_bh(&bdi_lock); |
a42dde04 PZ |
703 | if (bdi->min_ratio > max_ratio) { |
704 | ret = -EINVAL; | |
705 | } else { | |
706 | bdi->max_ratio = max_ratio; | |
eb608e3a | 707 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
a42dde04 | 708 | } |
cfc4ba53 | 709 | spin_unlock_bh(&bdi_lock); |
189d3c4a PZ |
710 | |
711 | return ret; | |
712 | } | |
a42dde04 | 713 | EXPORT_SYMBOL(bdi_set_max_ratio); |
189d3c4a | 714 | |
6c14ae1e WF |
715 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
716 | unsigned long bg_thresh) | |
717 | { | |
718 | return (thresh + bg_thresh) / 2; | |
719 | } | |
720 | ||
c7981433 TH |
721 | static unsigned long hard_dirty_limit(struct wb_domain *dom, |
722 | unsigned long thresh) | |
ffd1f609 | 723 | { |
dcc25ae7 | 724 | return max(thresh, dom->dirty_limit); |
ffd1f609 WF |
725 | } |
726 | ||
c5edf9cd TH |
727 | /* |
728 | * Memory which can be further allocated to a memcg domain is capped by | |
729 | * system-wide clean memory excluding the amount being used in the domain. | |
730 | */ | |
731 | static void mdtc_calc_avail(struct dirty_throttle_control *mdtc, | |
732 | unsigned long filepages, unsigned long headroom) | |
c2aa723a TH |
733 | { |
734 | struct dirty_throttle_control *gdtc = mdtc_gdtc(mdtc); | |
c5edf9cd TH |
735 | unsigned long clean = filepages - min(filepages, mdtc->dirty); |
736 | unsigned long global_clean = gdtc->avail - min(gdtc->avail, gdtc->dirty); | |
737 | unsigned long other_clean = global_clean - min(global_clean, clean); | |
c2aa723a | 738 | |
c5edf9cd | 739 | mdtc->avail = filepages + min(headroom, other_clean); |
ffd1f609 WF |
740 | } |
741 | ||
6f718656 | 742 | /** |
b1cbc6d4 TH |
743 | * __wb_calc_thresh - @wb's share of dirty throttling threshold |
744 | * @dtc: dirty_throttle_context of interest | |
1babe183 | 745 | * |
aed21ad2 WF |
746 | * Note that balance_dirty_pages() will only seriously take it as a hard limit |
747 | * when sleeping max_pause per page is not enough to keep the dirty pages under | |
748 | * control. For example, when the device is completely stalled due to some error | |
749 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. | |
750 | * In the other normal situations, it acts more gently by throttling the tasks | |
a88a341a | 751 | * more (rather than completely block them) when the wb dirty pages go high. |
1babe183 | 752 | * |
6f718656 | 753 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
1babe183 WF |
754 | * - starving fast devices |
755 | * - piling up dirty pages (that will take long time to sync) on slow devices | |
756 | * | |
a88a341a | 757 | * The wb's share of dirty limit will be adapting to its throughput and |
1babe183 | 758 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
a862f68a MR |
759 | * |
760 | * Return: @wb's dirty limit in pages. The term "dirty" in the context of | |
761 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. | |
1babe183 | 762 | */ |
b1cbc6d4 | 763 | static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) |
16c4042f | 764 | { |
e9f07dfd | 765 | struct wb_domain *dom = dtc_dom(dtc); |
b1cbc6d4 | 766 | unsigned long thresh = dtc->thresh; |
0d960a38 | 767 | u64 wb_thresh; |
16c4042f | 768 | long numerator, denominator; |
693108a8 | 769 | unsigned long wb_min_ratio, wb_max_ratio; |
04fbfdc1 | 770 | |
16c4042f | 771 | /* |
0d960a38 | 772 | * Calculate this BDI's share of the thresh ratio. |
16c4042f | 773 | */ |
e9770b34 | 774 | fprop_fraction_percpu(&dom->completions, dtc->wb_completions, |
380c27ca | 775 | &numerator, &denominator); |
04fbfdc1 | 776 | |
0d960a38 TH |
777 | wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; |
778 | wb_thresh *= numerator; | |
779 | do_div(wb_thresh, denominator); | |
04fbfdc1 | 780 | |
b1cbc6d4 | 781 | wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); |
04fbfdc1 | 782 | |
0d960a38 TH |
783 | wb_thresh += (thresh * wb_min_ratio) / 100; |
784 | if (wb_thresh > (thresh * wb_max_ratio) / 100) | |
785 | wb_thresh = thresh * wb_max_ratio / 100; | |
16c4042f | 786 | |
0d960a38 | 787 | return wb_thresh; |
1da177e4 LT |
788 | } |
789 | ||
b1cbc6d4 TH |
790 | unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) |
791 | { | |
792 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb), | |
793 | .thresh = thresh }; | |
794 | return __wb_calc_thresh(&gdtc); | |
1da177e4 LT |
795 | } |
796 | ||
5a537485 MP |
797 | /* |
798 | * setpoint - dirty 3 | |
799 | * f(dirty) := 1.0 + (----------------) | |
800 | * limit - setpoint | |
801 | * | |
802 | * it's a 3rd order polynomial that subjects to | |
803 | * | |
804 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast | |
805 | * (2) f(setpoint) = 1.0 => the balance point | |
806 | * (3) f(limit) = 0 => the hard limit | |
807 | * (4) df/dx <= 0 => negative feedback control | |
808 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) | |
809 | * => fast response on large errors; small oscillation near setpoint | |
810 | */ | |
d5c9fde3 | 811 | static long long pos_ratio_polynom(unsigned long setpoint, |
5a537485 MP |
812 | unsigned long dirty, |
813 | unsigned long limit) | |
814 | { | |
815 | long long pos_ratio; | |
816 | long x; | |
817 | ||
d5c9fde3 | 818 | x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, |
464d1387 | 819 | (limit - setpoint) | 1); |
5a537485 MP |
820 | pos_ratio = x; |
821 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
822 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; | |
823 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; | |
824 | ||
825 | return clamp(pos_ratio, 0LL, 2LL << RATELIMIT_CALC_SHIFT); | |
826 | } | |
827 | ||
6c14ae1e WF |
828 | /* |
829 | * Dirty position control. | |
830 | * | |
831 | * (o) global/bdi setpoints | |
832 | * | |
de1fff37 | 833 | * We want the dirty pages be balanced around the global/wb setpoints. |
6c14ae1e WF |
834 | * When the number of dirty pages is higher/lower than the setpoint, the |
835 | * dirty position control ratio (and hence task dirty ratelimit) will be | |
836 | * decreased/increased to bring the dirty pages back to the setpoint. | |
837 | * | |
838 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT | |
839 | * | |
840 | * if (dirty < setpoint) scale up pos_ratio | |
841 | * if (dirty > setpoint) scale down pos_ratio | |
842 | * | |
de1fff37 TH |
843 | * if (wb_dirty < wb_setpoint) scale up pos_ratio |
844 | * if (wb_dirty > wb_setpoint) scale down pos_ratio | |
6c14ae1e WF |
845 | * |
846 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT | |
847 | * | |
848 | * (o) global control line | |
849 | * | |
850 | * ^ pos_ratio | |
851 | * | | |
852 | * | |<===== global dirty control scope ======>| | |
853 | * 2.0 .............* | |
854 | * | .* | |
855 | * | . * | |
856 | * | . * | |
857 | * | . * | |
858 | * | . * | |
859 | * | . * | |
860 | * 1.0 ................................* | |
861 | * | . . * | |
862 | * | . . * | |
863 | * | . . * | |
864 | * | . . * | |
865 | * | . . * | |
866 | * 0 +------------.------------------.----------------------*-------------> | |
867 | * freerun^ setpoint^ limit^ dirty pages | |
868 | * | |
de1fff37 | 869 | * (o) wb control line |
6c14ae1e WF |
870 | * |
871 | * ^ pos_ratio | |
872 | * | | |
873 | * | * | |
874 | * | * | |
875 | * | * | |
876 | * | * | |
877 | * | * |<=========== span ============>| | |
878 | * 1.0 .......................* | |
879 | * | . * | |
880 | * | . * | |
881 | * | . * | |
882 | * | . * | |
883 | * | . * | |
884 | * | . * | |
885 | * | . * | |
886 | * | . * | |
887 | * | . * | |
888 | * | . * | |
889 | * | . * | |
890 | * 1/4 ...............................................* * * * * * * * * * * * | |
891 | * | . . | |
892 | * | . . | |
893 | * | . . | |
894 | * 0 +----------------------.-------------------------------.-------------> | |
de1fff37 | 895 | * wb_setpoint^ x_intercept^ |
6c14ae1e | 896 | * |
de1fff37 | 897 | * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can |
6c14ae1e WF |
898 | * be smoothly throttled down to normal if it starts high in situations like |
899 | * - start writing to a slow SD card and a fast disk at the same time. The SD | |
de1fff37 TH |
900 | * card's wb_dirty may rush to many times higher than wb_setpoint. |
901 | * - the wb dirty thresh drops quickly due to change of JBOD workload | |
6c14ae1e | 902 | */ |
daddfa3c | 903 | static void wb_position_ratio(struct dirty_throttle_control *dtc) |
6c14ae1e | 904 | { |
2bc00aef | 905 | struct bdi_writeback *wb = dtc->wb; |
a88a341a | 906 | unsigned long write_bw = wb->avg_write_bandwidth; |
2bc00aef | 907 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
c7981433 | 908 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
2bc00aef | 909 | unsigned long wb_thresh = dtc->wb_thresh; |
6c14ae1e WF |
910 | unsigned long x_intercept; |
911 | unsigned long setpoint; /* dirty pages' target balance point */ | |
de1fff37 | 912 | unsigned long wb_setpoint; |
6c14ae1e WF |
913 | unsigned long span; |
914 | long long pos_ratio; /* for scaling up/down the rate limit */ | |
915 | long x; | |
916 | ||
daddfa3c TH |
917 | dtc->pos_ratio = 0; |
918 | ||
2bc00aef | 919 | if (unlikely(dtc->dirty >= limit)) |
daddfa3c | 920 | return; |
6c14ae1e WF |
921 | |
922 | /* | |
923 | * global setpoint | |
924 | * | |
5a537485 MP |
925 | * See comment for pos_ratio_polynom(). |
926 | */ | |
927 | setpoint = (freerun + limit) / 2; | |
2bc00aef | 928 | pos_ratio = pos_ratio_polynom(setpoint, dtc->dirty, limit); |
5a537485 MP |
929 | |
930 | /* | |
931 | * The strictlimit feature is a tool preventing mistrusted filesystems | |
932 | * from growing a large number of dirty pages before throttling. For | |
de1fff37 TH |
933 | * such filesystems balance_dirty_pages always checks wb counters |
934 | * against wb limits. Even if global "nr_dirty" is under "freerun". | |
5a537485 MP |
935 | * This is especially important for fuse which sets bdi->max_ratio to |
936 | * 1% by default. Without strictlimit feature, fuse writeback may | |
937 | * consume arbitrary amount of RAM because it is accounted in | |
938 | * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". | |
6c14ae1e | 939 | * |
a88a341a | 940 | * Here, in wb_position_ratio(), we calculate pos_ratio based on |
de1fff37 | 941 | * two values: wb_dirty and wb_thresh. Let's consider an example: |
5a537485 MP |
942 | * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global |
943 | * limits are set by default to 10% and 20% (background and throttle). | |
de1fff37 | 944 | * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. |
0d960a38 | 945 | * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is |
de1fff37 | 946 | * about ~6K pages (as the average of background and throttle wb |
5a537485 | 947 | * limits). The 3rd order polynomial will provide positive feedback if |
de1fff37 | 948 | * wb_dirty is under wb_setpoint and vice versa. |
6c14ae1e | 949 | * |
5a537485 | 950 | * Note, that we cannot use global counters in these calculations |
de1fff37 | 951 | * because we want to throttle process writing to a strictlimit wb |
5a537485 MP |
952 | * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB |
953 | * in the example above). | |
6c14ae1e | 954 | */ |
a88a341a | 955 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
de1fff37 | 956 | long long wb_pos_ratio; |
5a537485 | 957 | |
daddfa3c TH |
958 | if (dtc->wb_dirty < 8) { |
959 | dtc->pos_ratio = min_t(long long, pos_ratio * 2, | |
960 | 2 << RATELIMIT_CALC_SHIFT); | |
961 | return; | |
962 | } | |
5a537485 | 963 | |
2bc00aef | 964 | if (dtc->wb_dirty >= wb_thresh) |
daddfa3c | 965 | return; |
5a537485 | 966 | |
970fb01a TH |
967 | wb_setpoint = dirty_freerun_ceiling(wb_thresh, |
968 | dtc->wb_bg_thresh); | |
5a537485 | 969 | |
de1fff37 | 970 | if (wb_setpoint == 0 || wb_setpoint == wb_thresh) |
daddfa3c | 971 | return; |
5a537485 | 972 | |
2bc00aef | 973 | wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, |
de1fff37 | 974 | wb_thresh); |
5a537485 MP |
975 | |
976 | /* | |
de1fff37 TH |
977 | * Typically, for strictlimit case, wb_setpoint << setpoint |
978 | * and pos_ratio >> wb_pos_ratio. In the other words global | |
5a537485 | 979 | * state ("dirty") is not limiting factor and we have to |
de1fff37 | 980 | * make decision based on wb counters. But there is an |
5a537485 MP |
981 | * important case when global pos_ratio should get precedence: |
982 | * global limits are exceeded (e.g. due to activities on other | |
de1fff37 | 983 | * wb's) while given strictlimit wb is below limit. |
5a537485 | 984 | * |
de1fff37 | 985 | * "pos_ratio * wb_pos_ratio" would work for the case above, |
5a537485 | 986 | * but it would look too non-natural for the case of all |
de1fff37 | 987 | * activity in the system coming from a single strictlimit wb |
5a537485 MP |
988 | * with bdi->max_ratio == 100%. |
989 | * | |
990 | * Note that min() below somewhat changes the dynamics of the | |
991 | * control system. Normally, pos_ratio value can be well over 3 | |
de1fff37 | 992 | * (when globally we are at freerun and wb is well below wb |
5a537485 MP |
993 | * setpoint). Now the maximum pos_ratio in the same situation |
994 | * is 2. We might want to tweak this if we observe the control | |
995 | * system is too slow to adapt. | |
996 | */ | |
daddfa3c TH |
997 | dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); |
998 | return; | |
5a537485 | 999 | } |
6c14ae1e WF |
1000 | |
1001 | /* | |
1002 | * We have computed basic pos_ratio above based on global situation. If | |
de1fff37 | 1003 | * the wb is over/under its share of dirty pages, we want to scale |
6c14ae1e WF |
1004 | * pos_ratio further down/up. That is done by the following mechanism. |
1005 | */ | |
1006 | ||
1007 | /* | |
de1fff37 | 1008 | * wb setpoint |
6c14ae1e | 1009 | * |
de1fff37 | 1010 | * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) |
6c14ae1e | 1011 | * |
de1fff37 | 1012 | * x_intercept - wb_dirty |
6c14ae1e | 1013 | * := -------------------------- |
de1fff37 | 1014 | * x_intercept - wb_setpoint |
6c14ae1e | 1015 | * |
de1fff37 | 1016 | * The main wb control line is a linear function that subjects to |
6c14ae1e | 1017 | * |
de1fff37 TH |
1018 | * (1) f(wb_setpoint) = 1.0 |
1019 | * (2) k = - 1 / (8 * write_bw) (in single wb case) | |
1020 | * or equally: x_intercept = wb_setpoint + 8 * write_bw | |
6c14ae1e | 1021 | * |
de1fff37 | 1022 | * For single wb case, the dirty pages are observed to fluctuate |
6c14ae1e | 1023 | * regularly within range |
de1fff37 | 1024 | * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] |
6c14ae1e WF |
1025 | * for various filesystems, where (2) can yield in a reasonable 12.5% |
1026 | * fluctuation range for pos_ratio. | |
1027 | * | |
de1fff37 | 1028 | * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its |
6c14ae1e | 1029 | * own size, so move the slope over accordingly and choose a slope that |
de1fff37 | 1030 | * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. |
6c14ae1e | 1031 | */ |
2bc00aef TH |
1032 | if (unlikely(wb_thresh > dtc->thresh)) |
1033 | wb_thresh = dtc->thresh; | |
aed21ad2 | 1034 | /* |
de1fff37 | 1035 | * It's very possible that wb_thresh is close to 0 not because the |
aed21ad2 WF |
1036 | * device is slow, but that it has remained inactive for long time. |
1037 | * Honour such devices a reasonable good (hopefully IO efficient) | |
1038 | * threshold, so that the occasional writes won't be blocked and active | |
1039 | * writes can rampup the threshold quickly. | |
1040 | */ | |
2bc00aef | 1041 | wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8); |
6c14ae1e | 1042 | /* |
de1fff37 TH |
1043 | * scale global setpoint to wb's: |
1044 | * wb_setpoint = setpoint * wb_thresh / thresh | |
6c14ae1e | 1045 | */ |
e4bc13ad | 1046 | x = div_u64((u64)wb_thresh << 16, dtc->thresh | 1); |
de1fff37 | 1047 | wb_setpoint = setpoint * (u64)x >> 16; |
6c14ae1e | 1048 | /* |
de1fff37 TH |
1049 | * Use span=(8*write_bw) in single wb case as indicated by |
1050 | * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. | |
6c14ae1e | 1051 | * |
de1fff37 TH |
1052 | * wb_thresh thresh - wb_thresh |
1053 | * span = --------- * (8 * write_bw) + ------------------ * wb_thresh | |
1054 | * thresh thresh | |
6c14ae1e | 1055 | */ |
2bc00aef | 1056 | span = (dtc->thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; |
de1fff37 | 1057 | x_intercept = wb_setpoint + span; |
6c14ae1e | 1058 | |
2bc00aef TH |
1059 | if (dtc->wb_dirty < x_intercept - span / 4) { |
1060 | pos_ratio = div64_u64(pos_ratio * (x_intercept - dtc->wb_dirty), | |
e4bc13ad | 1061 | (x_intercept - wb_setpoint) | 1); |
6c14ae1e WF |
1062 | } else |
1063 | pos_ratio /= 4; | |
1064 | ||
8927f66c | 1065 | /* |
de1fff37 | 1066 | * wb reserve area, safeguard against dirty pool underrun and disk idle |
8927f66c WF |
1067 | * It may push the desired control point of global dirty pages higher |
1068 | * than setpoint. | |
1069 | */ | |
de1fff37 | 1070 | x_intercept = wb_thresh / 2; |
2bc00aef TH |
1071 | if (dtc->wb_dirty < x_intercept) { |
1072 | if (dtc->wb_dirty > x_intercept / 8) | |
1073 | pos_ratio = div_u64(pos_ratio * x_intercept, | |
1074 | dtc->wb_dirty); | |
50657fc4 | 1075 | else |
8927f66c WF |
1076 | pos_ratio *= 8; |
1077 | } | |
1078 | ||
daddfa3c | 1079 | dtc->pos_ratio = pos_ratio; |
6c14ae1e WF |
1080 | } |
1081 | ||
a88a341a TH |
1082 | static void wb_update_write_bandwidth(struct bdi_writeback *wb, |
1083 | unsigned long elapsed, | |
1084 | unsigned long written) | |
e98be2d5 WF |
1085 | { |
1086 | const unsigned long period = roundup_pow_of_two(3 * HZ); | |
a88a341a TH |
1087 | unsigned long avg = wb->avg_write_bandwidth; |
1088 | unsigned long old = wb->write_bandwidth; | |
e98be2d5 WF |
1089 | u64 bw; |
1090 | ||
1091 | /* | |
1092 | * bw = written * HZ / elapsed | |
1093 | * | |
1094 | * bw * elapsed + write_bandwidth * (period - elapsed) | |
1095 | * write_bandwidth = --------------------------------------------------- | |
1096 | * period | |
c72efb65 TH |
1097 | * |
1098 | * @written may have decreased due to account_page_redirty(). | |
1099 | * Avoid underflowing @bw calculation. | |
e98be2d5 | 1100 | */ |
a88a341a | 1101 | bw = written - min(written, wb->written_stamp); |
e98be2d5 WF |
1102 | bw *= HZ; |
1103 | if (unlikely(elapsed > period)) { | |
1104 | do_div(bw, elapsed); | |
1105 | avg = bw; | |
1106 | goto out; | |
1107 | } | |
a88a341a | 1108 | bw += (u64)wb->write_bandwidth * (period - elapsed); |
e98be2d5 WF |
1109 | bw >>= ilog2(period); |
1110 | ||
1111 | /* | |
1112 | * one more level of smoothing, for filtering out sudden spikes | |
1113 | */ | |
1114 | if (avg > old && old >= (unsigned long)bw) | |
1115 | avg -= (avg - old) >> 3; | |
1116 | ||
1117 | if (avg < old && old <= (unsigned long)bw) | |
1118 | avg += (old - avg) >> 3; | |
1119 | ||
1120 | out: | |
95a46c65 TH |
1121 | /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ |
1122 | avg = max(avg, 1LU); | |
1123 | if (wb_has_dirty_io(wb)) { | |
1124 | long delta = avg - wb->avg_write_bandwidth; | |
1125 | WARN_ON_ONCE(atomic_long_add_return(delta, | |
1126 | &wb->bdi->tot_write_bandwidth) <= 0); | |
1127 | } | |
a88a341a TH |
1128 | wb->write_bandwidth = bw; |
1129 | wb->avg_write_bandwidth = avg; | |
e98be2d5 WF |
1130 | } |
1131 | ||
2bc00aef | 1132 | static void update_dirty_limit(struct dirty_throttle_control *dtc) |
c42843f2 | 1133 | { |
e9f07dfd | 1134 | struct wb_domain *dom = dtc_dom(dtc); |
2bc00aef | 1135 | unsigned long thresh = dtc->thresh; |
dcc25ae7 | 1136 | unsigned long limit = dom->dirty_limit; |
c42843f2 WF |
1137 | |
1138 | /* | |
1139 | * Follow up in one step. | |
1140 | */ | |
1141 | if (limit < thresh) { | |
1142 | limit = thresh; | |
1143 | goto update; | |
1144 | } | |
1145 | ||
1146 | /* | |
1147 | * Follow down slowly. Use the higher one as the target, because thresh | |
1148 | * may drop below dirty. This is exactly the reason to introduce | |
dcc25ae7 | 1149 | * dom->dirty_limit which is guaranteed to lie above the dirty pages. |
c42843f2 | 1150 | */ |
2bc00aef | 1151 | thresh = max(thresh, dtc->dirty); |
c42843f2 WF |
1152 | if (limit > thresh) { |
1153 | limit -= (limit - thresh) >> 5; | |
1154 | goto update; | |
1155 | } | |
1156 | return; | |
1157 | update: | |
dcc25ae7 | 1158 | dom->dirty_limit = limit; |
c42843f2 WF |
1159 | } |
1160 | ||
e9f07dfd | 1161 | static void domain_update_bandwidth(struct dirty_throttle_control *dtc, |
c42843f2 WF |
1162 | unsigned long now) |
1163 | { | |
e9f07dfd | 1164 | struct wb_domain *dom = dtc_dom(dtc); |
c42843f2 WF |
1165 | |
1166 | /* | |
1167 | * check locklessly first to optimize away locking for the most time | |
1168 | */ | |
dcc25ae7 | 1169 | if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) |
c42843f2 WF |
1170 | return; |
1171 | ||
dcc25ae7 TH |
1172 | spin_lock(&dom->lock); |
1173 | if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) { | |
2bc00aef | 1174 | update_dirty_limit(dtc); |
dcc25ae7 | 1175 | dom->dirty_limit_tstamp = now; |
c42843f2 | 1176 | } |
dcc25ae7 | 1177 | spin_unlock(&dom->lock); |
c42843f2 WF |
1178 | } |
1179 | ||
be3ffa27 | 1180 | /* |
de1fff37 | 1181 | * Maintain wb->dirty_ratelimit, the base dirty throttle rate. |
be3ffa27 | 1182 | * |
de1fff37 | 1183 | * Normal wb tasks will be curbed at or below it in long term. |
be3ffa27 WF |
1184 | * Obviously it should be around (write_bw / N) when there are N dd tasks. |
1185 | */ | |
2bc00aef | 1186 | static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, |
a88a341a TH |
1187 | unsigned long dirtied, |
1188 | unsigned long elapsed) | |
be3ffa27 | 1189 | { |
2bc00aef TH |
1190 | struct bdi_writeback *wb = dtc->wb; |
1191 | unsigned long dirty = dtc->dirty; | |
1192 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); | |
c7981433 | 1193 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
7381131c | 1194 | unsigned long setpoint = (freerun + limit) / 2; |
a88a341a TH |
1195 | unsigned long write_bw = wb->avg_write_bandwidth; |
1196 | unsigned long dirty_ratelimit = wb->dirty_ratelimit; | |
be3ffa27 WF |
1197 | unsigned long dirty_rate; |
1198 | unsigned long task_ratelimit; | |
1199 | unsigned long balanced_dirty_ratelimit; | |
7381131c WF |
1200 | unsigned long step; |
1201 | unsigned long x; | |
d59b1087 | 1202 | unsigned long shift; |
be3ffa27 WF |
1203 | |
1204 | /* | |
1205 | * The dirty rate will match the writeout rate in long term, except | |
1206 | * when dirty pages are truncated by userspace or re-dirtied by FS. | |
1207 | */ | |
a88a341a | 1208 | dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; |
be3ffa27 | 1209 | |
be3ffa27 WF |
1210 | /* |
1211 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. | |
1212 | */ | |
1213 | task_ratelimit = (u64)dirty_ratelimit * | |
daddfa3c | 1214 | dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; |
be3ffa27 WF |
1215 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
1216 | ||
1217 | /* | |
1218 | * A linear estimation of the "balanced" throttle rate. The theory is, | |
de1fff37 | 1219 | * if there are N dd tasks, each throttled at task_ratelimit, the wb's |
be3ffa27 WF |
1220 | * dirty_rate will be measured to be (N * task_ratelimit). So the below |
1221 | * formula will yield the balanced rate limit (write_bw / N). | |
1222 | * | |
1223 | * Note that the expanded form is not a pure rate feedback: | |
1224 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) | |
1225 | * but also takes pos_ratio into account: | |
1226 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) | |
1227 | * | |
1228 | * (1) is not realistic because pos_ratio also takes part in balancing | |
1229 | * the dirty rate. Consider the state | |
1230 | * pos_ratio = 0.5 (3) | |
1231 | * rate = 2 * (write_bw / N) (4) | |
1232 | * If (1) is used, it will stuck in that state! Because each dd will | |
1233 | * be throttled at | |
1234 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) | |
1235 | * yielding | |
1236 | * dirty_rate = N * task_ratelimit = write_bw (6) | |
1237 | * put (6) into (1) we get | |
1238 | * rate_(i+1) = rate_(i) (7) | |
1239 | * | |
1240 | * So we end up using (2) to always keep | |
1241 | * rate_(i+1) ~= (write_bw / N) (8) | |
1242 | * regardless of the value of pos_ratio. As long as (8) is satisfied, | |
1243 | * pos_ratio is able to drive itself to 1.0, which is not only where | |
1244 | * the dirty count meet the setpoint, but also where the slope of | |
1245 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. | |
1246 | */ | |
1247 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, | |
1248 | dirty_rate | 1); | |
bdaac490 WF |
1249 | /* |
1250 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw | |
1251 | */ | |
1252 | if (unlikely(balanced_dirty_ratelimit > write_bw)) | |
1253 | balanced_dirty_ratelimit = write_bw; | |
be3ffa27 | 1254 | |
7381131c WF |
1255 | /* |
1256 | * We could safely do this and return immediately: | |
1257 | * | |
de1fff37 | 1258 | * wb->dirty_ratelimit = balanced_dirty_ratelimit; |
7381131c WF |
1259 | * |
1260 | * However to get a more stable dirty_ratelimit, the below elaborated | |
331cbdee | 1261 | * code makes use of task_ratelimit to filter out singular points and |
7381131c WF |
1262 | * limit the step size. |
1263 | * | |
1264 | * The below code essentially only uses the relative value of | |
1265 | * | |
1266 | * task_ratelimit - dirty_ratelimit | |
1267 | * = (pos_ratio - 1) * dirty_ratelimit | |
1268 | * | |
1269 | * which reflects the direction and size of dirty position error. | |
1270 | */ | |
1271 | ||
1272 | /* | |
1273 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff | |
1274 | * task_ratelimit is on the same side of dirty_ratelimit, too. | |
1275 | * For example, when | |
1276 | * - dirty_ratelimit > balanced_dirty_ratelimit | |
1277 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) | |
1278 | * lowering dirty_ratelimit will help meet both the position and rate | |
1279 | * control targets. Otherwise, don't update dirty_ratelimit if it will | |
1280 | * only help meet the rate target. After all, what the users ultimately | |
1281 | * feel and care are stable dirty rate and small position error. | |
1282 | * | |
1283 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size | |
331cbdee | 1284 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
7381131c WF |
1285 | * keeps jumping around randomly and can even leap far away at times |
1286 | * due to the small 200ms estimation period of dirty_rate (we want to | |
1287 | * keep that period small to reduce time lags). | |
1288 | */ | |
1289 | step = 0; | |
5a537485 MP |
1290 | |
1291 | /* | |
de1fff37 | 1292 | * For strictlimit case, calculations above were based on wb counters |
a88a341a | 1293 | * and limits (starting from pos_ratio = wb_position_ratio() and up to |
5a537485 | 1294 | * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). |
de1fff37 TH |
1295 | * Hence, to calculate "step" properly, we have to use wb_dirty as |
1296 | * "dirty" and wb_setpoint as "setpoint". | |
5a537485 | 1297 | * |
de1fff37 TH |
1298 | * We rampup dirty_ratelimit forcibly if wb_dirty is low because |
1299 | * it's possible that wb_thresh is close to zero due to inactivity | |
970fb01a | 1300 | * of backing device. |
5a537485 | 1301 | */ |
a88a341a | 1302 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
2bc00aef TH |
1303 | dirty = dtc->wb_dirty; |
1304 | if (dtc->wb_dirty < 8) | |
1305 | setpoint = dtc->wb_dirty + 1; | |
5a537485 | 1306 | else |
970fb01a | 1307 | setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; |
5a537485 MP |
1308 | } |
1309 | ||
7381131c | 1310 | if (dirty < setpoint) { |
a88a341a | 1311 | x = min3(wb->balanced_dirty_ratelimit, |
7c809968 | 1312 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1313 | if (dirty_ratelimit < x) |
1314 | step = x - dirty_ratelimit; | |
1315 | } else { | |
a88a341a | 1316 | x = max3(wb->balanced_dirty_ratelimit, |
7c809968 | 1317 | balanced_dirty_ratelimit, task_ratelimit); |
7381131c WF |
1318 | if (dirty_ratelimit > x) |
1319 | step = dirty_ratelimit - x; | |
1320 | } | |
1321 | ||
1322 | /* | |
1323 | * Don't pursue 100% rate matching. It's impossible since the balanced | |
1324 | * rate itself is constantly fluctuating. So decrease the track speed | |
1325 | * when it gets close to the target. Helps eliminate pointless tremors. | |
1326 | */ | |
d59b1087 AR |
1327 | shift = dirty_ratelimit / (2 * step + 1); |
1328 | if (shift < BITS_PER_LONG) | |
1329 | step = DIV_ROUND_UP(step >> shift, 8); | |
1330 | else | |
1331 | step = 0; | |
7381131c WF |
1332 | |
1333 | if (dirty_ratelimit < balanced_dirty_ratelimit) | |
1334 | dirty_ratelimit += step; | |
1335 | else | |
1336 | dirty_ratelimit -= step; | |
1337 | ||
a88a341a TH |
1338 | wb->dirty_ratelimit = max(dirty_ratelimit, 1UL); |
1339 | wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit; | |
b48c104d | 1340 | |
5634cc2a | 1341 | trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit); |
be3ffa27 WF |
1342 | } |
1343 | ||
c2aa723a TH |
1344 | static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc, |
1345 | struct dirty_throttle_control *mdtc, | |
8a731799 TH |
1346 | unsigned long start_time, |
1347 | bool update_ratelimit) | |
e98be2d5 | 1348 | { |
c2aa723a | 1349 | struct bdi_writeback *wb = gdtc->wb; |
e98be2d5 | 1350 | unsigned long now = jiffies; |
a88a341a | 1351 | unsigned long elapsed = now - wb->bw_time_stamp; |
be3ffa27 | 1352 | unsigned long dirtied; |
e98be2d5 WF |
1353 | unsigned long written; |
1354 | ||
8a731799 TH |
1355 | lockdep_assert_held(&wb->list_lock); |
1356 | ||
e98be2d5 WF |
1357 | /* |
1358 | * rate-limit, only update once every 200ms. | |
1359 | */ | |
1360 | if (elapsed < BANDWIDTH_INTERVAL) | |
1361 | return; | |
1362 | ||
a88a341a TH |
1363 | dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]); |
1364 | written = percpu_counter_read(&wb->stat[WB_WRITTEN]); | |
e98be2d5 WF |
1365 | |
1366 | /* | |
1367 | * Skip quiet periods when disk bandwidth is under-utilized. | |
1368 | * (at least 1s idle time between two flusher runs) | |
1369 | */ | |
a88a341a | 1370 | if (elapsed > HZ && time_before(wb->bw_time_stamp, start_time)) |
e98be2d5 WF |
1371 | goto snapshot; |
1372 | ||
8a731799 | 1373 | if (update_ratelimit) { |
c2aa723a TH |
1374 | domain_update_bandwidth(gdtc, now); |
1375 | wb_update_dirty_ratelimit(gdtc, dirtied, elapsed); | |
1376 | ||
1377 | /* | |
1378 | * @mdtc is always NULL if !CGROUP_WRITEBACK but the | |
1379 | * compiler has no way to figure that out. Help it. | |
1380 | */ | |
1381 | if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { | |
1382 | domain_update_bandwidth(mdtc, now); | |
1383 | wb_update_dirty_ratelimit(mdtc, dirtied, elapsed); | |
1384 | } | |
be3ffa27 | 1385 | } |
a88a341a | 1386 | wb_update_write_bandwidth(wb, elapsed, written); |
e98be2d5 WF |
1387 | |
1388 | snapshot: | |
a88a341a TH |
1389 | wb->dirtied_stamp = dirtied; |
1390 | wb->written_stamp = written; | |
1391 | wb->bw_time_stamp = now; | |
e98be2d5 WF |
1392 | } |
1393 | ||
8a731799 | 1394 | void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time) |
e98be2d5 | 1395 | { |
2bc00aef TH |
1396 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb) }; |
1397 | ||
c2aa723a | 1398 | __wb_update_bandwidth(&gdtc, NULL, start_time, false); |
e98be2d5 WF |
1399 | } |
1400 | ||
9d823e8f | 1401 | /* |
d0e1d66b | 1402 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
9d823e8f WF |
1403 | * will look to see if it needs to start dirty throttling. |
1404 | * | |
1405 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive | |
c41f012a | 1406 | * global_zone_page_state() too often. So scale it near-sqrt to the safety margin |
9d823e8f WF |
1407 | * (the number of pages we may dirty without exceeding the dirty limits). |
1408 | */ | |
1409 | static unsigned long dirty_poll_interval(unsigned long dirty, | |
1410 | unsigned long thresh) | |
1411 | { | |
1412 | if (thresh > dirty) | |
1413 | return 1UL << (ilog2(thresh - dirty) >> 1); | |
1414 | ||
1415 | return 1; | |
1416 | } | |
1417 | ||
a88a341a | 1418 | static unsigned long wb_max_pause(struct bdi_writeback *wb, |
de1fff37 | 1419 | unsigned long wb_dirty) |
c8462cc9 | 1420 | { |
a88a341a | 1421 | unsigned long bw = wb->avg_write_bandwidth; |
e3b6c655 | 1422 | unsigned long t; |
c8462cc9 | 1423 | |
7ccb9ad5 WF |
1424 | /* |
1425 | * Limit pause time for small memory systems. If sleeping for too long | |
1426 | * time, a small pool of dirty/writeback pages may go empty and disk go | |
1427 | * idle. | |
1428 | * | |
1429 | * 8 serves as the safety ratio. | |
1430 | */ | |
de1fff37 | 1431 | t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
7ccb9ad5 WF |
1432 | t++; |
1433 | ||
e3b6c655 | 1434 | return min_t(unsigned long, t, MAX_PAUSE); |
7ccb9ad5 WF |
1435 | } |
1436 | ||
a88a341a TH |
1437 | static long wb_min_pause(struct bdi_writeback *wb, |
1438 | long max_pause, | |
1439 | unsigned long task_ratelimit, | |
1440 | unsigned long dirty_ratelimit, | |
1441 | int *nr_dirtied_pause) | |
c8462cc9 | 1442 | { |
a88a341a TH |
1443 | long hi = ilog2(wb->avg_write_bandwidth); |
1444 | long lo = ilog2(wb->dirty_ratelimit); | |
7ccb9ad5 WF |
1445 | long t; /* target pause */ |
1446 | long pause; /* estimated next pause */ | |
1447 | int pages; /* target nr_dirtied_pause */ | |
c8462cc9 | 1448 | |
7ccb9ad5 WF |
1449 | /* target for 10ms pause on 1-dd case */ |
1450 | t = max(1, HZ / 100); | |
c8462cc9 WF |
1451 | |
1452 | /* | |
1453 | * Scale up pause time for concurrent dirtiers in order to reduce CPU | |
1454 | * overheads. | |
1455 | * | |
7ccb9ad5 | 1456 | * (N * 10ms) on 2^N concurrent tasks. |
c8462cc9 WF |
1457 | */ |
1458 | if (hi > lo) | |
7ccb9ad5 | 1459 | t += (hi - lo) * (10 * HZ) / 1024; |
c8462cc9 WF |
1460 | |
1461 | /* | |
7ccb9ad5 WF |
1462 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
1463 | * on the much more stable dirty_ratelimit. However the next pause time | |
1464 | * will be computed based on task_ratelimit and the two rate limits may | |
1465 | * depart considerably at some time. Especially if task_ratelimit goes | |
1466 | * below dirty_ratelimit/2 and the target pause is max_pause, the next | |
1467 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a | |
1468 | * result task_ratelimit won't be executed faithfully, which could | |
1469 | * eventually bring down dirty_ratelimit. | |
c8462cc9 | 1470 | * |
7ccb9ad5 WF |
1471 | * We apply two rules to fix it up: |
1472 | * 1) try to estimate the next pause time and if necessary, use a lower | |
1473 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, | |
1474 | * nr_dirtied_pause will be "dancing" with task_ratelimit. | |
1475 | * 2) limit the target pause time to max_pause/2, so that the normal | |
1476 | * small fluctuations of task_ratelimit won't trigger rule (1) and | |
1477 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. | |
c8462cc9 | 1478 | */ |
7ccb9ad5 WF |
1479 | t = min(t, 1 + max_pause / 2); |
1480 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
c8462cc9 WF |
1481 | |
1482 | /* | |
5b9b3574 WF |
1483 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
1484 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. | |
1485 | * When the 16 consecutive reads are often interrupted by some dirty | |
1486 | * throttling pause during the async writes, cfq will go into idles | |
1487 | * (deadline is fine). So push nr_dirtied_pause as high as possible | |
1488 | * until reaches DIRTY_POLL_THRESH=32 pages. | |
c8462cc9 | 1489 | */ |
5b9b3574 WF |
1490 | if (pages < DIRTY_POLL_THRESH) { |
1491 | t = max_pause; | |
1492 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); | |
1493 | if (pages > DIRTY_POLL_THRESH) { | |
1494 | pages = DIRTY_POLL_THRESH; | |
1495 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; | |
1496 | } | |
1497 | } | |
1498 | ||
7ccb9ad5 WF |
1499 | pause = HZ * pages / (task_ratelimit + 1); |
1500 | if (pause > max_pause) { | |
1501 | t = max_pause; | |
1502 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); | |
1503 | } | |
c8462cc9 | 1504 | |
7ccb9ad5 | 1505 | *nr_dirtied_pause = pages; |
c8462cc9 | 1506 | /* |
7ccb9ad5 | 1507 | * The minimal pause time will normally be half the target pause time. |
c8462cc9 | 1508 | */ |
5b9b3574 | 1509 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
c8462cc9 WF |
1510 | } |
1511 | ||
970fb01a | 1512 | static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) |
5a537485 | 1513 | { |
2bc00aef | 1514 | struct bdi_writeback *wb = dtc->wb; |
93f78d88 | 1515 | unsigned long wb_reclaimable; |
5a537485 MP |
1516 | |
1517 | /* | |
de1fff37 | 1518 | * wb_thresh is not treated as some limiting factor as |
5a537485 | 1519 | * dirty_thresh, due to reasons |
de1fff37 | 1520 | * - in JBOD setup, wb_thresh can fluctuate a lot |
5a537485 | 1521 | * - in a system with HDD and USB key, the USB key may somehow |
de1fff37 TH |
1522 | * go into state (wb_dirty >> wb_thresh) either because |
1523 | * wb_dirty starts high, or because wb_thresh drops low. | |
5a537485 | 1524 | * In this case we don't want to hard throttle the USB key |
de1fff37 TH |
1525 | * dirtiers for 100 seconds until wb_dirty drops under |
1526 | * wb_thresh. Instead the auxiliary wb control line in | |
a88a341a | 1527 | * wb_position_ratio() will let the dirtier task progress |
de1fff37 | 1528 | * at some rate <= (write_bw / 2) for bringing down wb_dirty. |
5a537485 | 1529 | */ |
b1cbc6d4 | 1530 | dtc->wb_thresh = __wb_calc_thresh(dtc); |
970fb01a TH |
1531 | dtc->wb_bg_thresh = dtc->thresh ? |
1532 | div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; | |
5a537485 MP |
1533 | |
1534 | /* | |
1535 | * In order to avoid the stacked BDI deadlock we need | |
1536 | * to ensure we accurately count the 'dirty' pages when | |
1537 | * the threshold is low. | |
1538 | * | |
1539 | * Otherwise it would be possible to get thresh+n pages | |
1540 | * reported dirty, even though there are thresh-m pages | |
1541 | * actually dirty; with m+n sitting in the percpu | |
1542 | * deltas. | |
1543 | */ | |
2bce774e | 1544 | if (dtc->wb_thresh < 2 * wb_stat_error()) { |
93f78d88 | 1545 | wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
2bc00aef | 1546 | dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); |
5a537485 | 1547 | } else { |
93f78d88 | 1548 | wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
2bc00aef | 1549 | dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); |
5a537485 MP |
1550 | } |
1551 | } | |
1552 | ||
1da177e4 LT |
1553 | /* |
1554 | * balance_dirty_pages() must be called by processes which are generating dirty | |
1555 | * data. It looks at the number of dirty pages in the machine and will force | |
143dfe86 | 1556 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
5b0830cb JA |
1557 | * If we're over `background_thresh' then the writeback threads are woken to |
1558 | * perform some writeout. | |
1da177e4 | 1559 | */ |
4c578dce | 1560 | static void balance_dirty_pages(struct bdi_writeback *wb, |
143dfe86 | 1561 | unsigned long pages_dirtied) |
1da177e4 | 1562 | { |
2bc00aef | 1563 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1564 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
2bc00aef | 1565 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1566 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1567 | &mdtc_stor : NULL; | |
1568 | struct dirty_throttle_control *sdtc; | |
143dfe86 | 1569 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
83712358 | 1570 | long period; |
7ccb9ad5 WF |
1571 | long pause; |
1572 | long max_pause; | |
1573 | long min_pause; | |
1574 | int nr_dirtied_pause; | |
e50e3720 | 1575 | bool dirty_exceeded = false; |
143dfe86 | 1576 | unsigned long task_ratelimit; |
7ccb9ad5 | 1577 | unsigned long dirty_ratelimit; |
dfb8ae56 | 1578 | struct backing_dev_info *bdi = wb->bdi; |
5a537485 | 1579 | bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; |
e98be2d5 | 1580 | unsigned long start_time = jiffies; |
1da177e4 LT |
1581 | |
1582 | for (;;) { | |
83712358 | 1583 | unsigned long now = jiffies; |
2bc00aef | 1584 | unsigned long dirty, thresh, bg_thresh; |
50e55bf6 YS |
1585 | unsigned long m_dirty = 0; /* stop bogus uninit warnings */ |
1586 | unsigned long m_thresh = 0; | |
1587 | unsigned long m_bg_thresh = 0; | |
83712358 | 1588 | |
143dfe86 WF |
1589 | /* |
1590 | * Unstable writes are a feature of certain networked | |
1591 | * filesystems (i.e. NFS) in which data may have been | |
1592 | * written to the server's write cache, but has not yet | |
1593 | * been flushed to permanent storage. | |
1594 | */ | |
11fb9989 MG |
1595 | nr_reclaimable = global_node_page_state(NR_FILE_DIRTY) + |
1596 | global_node_page_state(NR_UNSTABLE_NFS); | |
9fc3a43e | 1597 | gdtc->avail = global_dirtyable_memory(); |
11fb9989 | 1598 | gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK); |
5fce25a9 | 1599 | |
9fc3a43e | 1600 | domain_dirty_limits(gdtc); |
16c4042f | 1601 | |
5a537485 | 1602 | if (unlikely(strictlimit)) { |
970fb01a | 1603 | wb_dirty_limits(gdtc); |
5a537485 | 1604 | |
2bc00aef TH |
1605 | dirty = gdtc->wb_dirty; |
1606 | thresh = gdtc->wb_thresh; | |
970fb01a | 1607 | bg_thresh = gdtc->wb_bg_thresh; |
5a537485 | 1608 | } else { |
2bc00aef TH |
1609 | dirty = gdtc->dirty; |
1610 | thresh = gdtc->thresh; | |
1611 | bg_thresh = gdtc->bg_thresh; | |
5a537485 MP |
1612 | } |
1613 | ||
c2aa723a | 1614 | if (mdtc) { |
c5edf9cd | 1615 | unsigned long filepages, headroom, writeback; |
c2aa723a TH |
1616 | |
1617 | /* | |
1618 | * If @wb belongs to !root memcg, repeat the same | |
1619 | * basic calculations for the memcg domain. | |
1620 | */ | |
c5edf9cd TH |
1621 | mem_cgroup_wb_stats(wb, &filepages, &headroom, |
1622 | &mdtc->dirty, &writeback); | |
c2aa723a | 1623 | mdtc->dirty += writeback; |
c5edf9cd | 1624 | mdtc_calc_avail(mdtc, filepages, headroom); |
c2aa723a TH |
1625 | |
1626 | domain_dirty_limits(mdtc); | |
1627 | ||
1628 | if (unlikely(strictlimit)) { | |
1629 | wb_dirty_limits(mdtc); | |
1630 | m_dirty = mdtc->wb_dirty; | |
1631 | m_thresh = mdtc->wb_thresh; | |
1632 | m_bg_thresh = mdtc->wb_bg_thresh; | |
1633 | } else { | |
1634 | m_dirty = mdtc->dirty; | |
1635 | m_thresh = mdtc->thresh; | |
1636 | m_bg_thresh = mdtc->bg_thresh; | |
1637 | } | |
5a537485 MP |
1638 | } |
1639 | ||
16c4042f WF |
1640 | /* |
1641 | * Throttle it only when the background writeback cannot | |
1642 | * catch-up. This avoids (excessively) small writeouts | |
de1fff37 | 1643 | * when the wb limits are ramping up in case of !strictlimit. |
5a537485 | 1644 | * |
de1fff37 TH |
1645 | * In strictlimit case make decision based on the wb counters |
1646 | * and limits. Small writeouts when the wb limits are ramping | |
5a537485 | 1647 | * up are the price we consciously pay for strictlimit-ing. |
c2aa723a TH |
1648 | * |
1649 | * If memcg domain is in effect, @dirty should be under | |
1650 | * both global and memcg freerun ceilings. | |
16c4042f | 1651 | */ |
c2aa723a TH |
1652 | if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) && |
1653 | (!mdtc || | |
1654 | m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) { | |
1655 | unsigned long intv = dirty_poll_interval(dirty, thresh); | |
1656 | unsigned long m_intv = ULONG_MAX; | |
1657 | ||
83712358 WF |
1658 | current->dirty_paused_when = now; |
1659 | current->nr_dirtied = 0; | |
c2aa723a TH |
1660 | if (mdtc) |
1661 | m_intv = dirty_poll_interval(m_dirty, m_thresh); | |
1662 | current->nr_dirtied_pause = min(intv, m_intv); | |
16c4042f | 1663 | break; |
83712358 | 1664 | } |
16c4042f | 1665 | |
bc05873d | 1666 | if (unlikely(!writeback_in_progress(wb))) |
9ecf4866 | 1667 | wb_start_background_writeback(wb); |
143dfe86 | 1668 | |
c2aa723a TH |
1669 | /* |
1670 | * Calculate global domain's pos_ratio and select the | |
1671 | * global dtc by default. | |
1672 | */ | |
5a537485 | 1673 | if (!strictlimit) |
970fb01a | 1674 | wb_dirty_limits(gdtc); |
5fce25a9 | 1675 | |
2bc00aef TH |
1676 | dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && |
1677 | ((gdtc->dirty > gdtc->thresh) || strictlimit); | |
daddfa3c TH |
1678 | |
1679 | wb_position_ratio(gdtc); | |
c2aa723a TH |
1680 | sdtc = gdtc; |
1681 | ||
1682 | if (mdtc) { | |
1683 | /* | |
1684 | * If memcg domain is in effect, calculate its | |
1685 | * pos_ratio. @wb should satisfy constraints from | |
1686 | * both global and memcg domains. Choose the one | |
1687 | * w/ lower pos_ratio. | |
1688 | */ | |
1689 | if (!strictlimit) | |
1690 | wb_dirty_limits(mdtc); | |
1691 | ||
1692 | dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) && | |
1693 | ((mdtc->dirty > mdtc->thresh) || strictlimit); | |
1694 | ||
1695 | wb_position_ratio(mdtc); | |
1696 | if (mdtc->pos_ratio < gdtc->pos_ratio) | |
1697 | sdtc = mdtc; | |
1698 | } | |
daddfa3c | 1699 | |
a88a341a TH |
1700 | if (dirty_exceeded && !wb->dirty_exceeded) |
1701 | wb->dirty_exceeded = 1; | |
1da177e4 | 1702 | |
8a731799 TH |
1703 | if (time_is_before_jiffies(wb->bw_time_stamp + |
1704 | BANDWIDTH_INTERVAL)) { | |
1705 | spin_lock(&wb->list_lock); | |
c2aa723a | 1706 | __wb_update_bandwidth(gdtc, mdtc, start_time, true); |
8a731799 TH |
1707 | spin_unlock(&wb->list_lock); |
1708 | } | |
e98be2d5 | 1709 | |
c2aa723a | 1710 | /* throttle according to the chosen dtc */ |
a88a341a | 1711 | dirty_ratelimit = wb->dirty_ratelimit; |
c2aa723a | 1712 | task_ratelimit = ((u64)dirty_ratelimit * sdtc->pos_ratio) >> |
3a73dbbc | 1713 | RATELIMIT_CALC_SHIFT; |
c2aa723a | 1714 | max_pause = wb_max_pause(wb, sdtc->wb_dirty); |
a88a341a TH |
1715 | min_pause = wb_min_pause(wb, max_pause, |
1716 | task_ratelimit, dirty_ratelimit, | |
1717 | &nr_dirtied_pause); | |
7ccb9ad5 | 1718 | |
3a73dbbc | 1719 | if (unlikely(task_ratelimit == 0)) { |
83712358 | 1720 | period = max_pause; |
c8462cc9 | 1721 | pause = max_pause; |
143dfe86 | 1722 | goto pause; |
04fbfdc1 | 1723 | } |
83712358 WF |
1724 | period = HZ * pages_dirtied / task_ratelimit; |
1725 | pause = period; | |
1726 | if (current->dirty_paused_when) | |
1727 | pause -= now - current->dirty_paused_when; | |
1728 | /* | |
1729 | * For less than 1s think time (ext3/4 may block the dirtier | |
1730 | * for up to 800ms from time to time on 1-HDD; so does xfs, | |
1731 | * however at much less frequency), try to compensate it in | |
1732 | * future periods by updating the virtual time; otherwise just | |
1733 | * do a reset, as it may be a light dirtier. | |
1734 | */ | |
7ccb9ad5 | 1735 | if (pause < min_pause) { |
5634cc2a | 1736 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1737 | sdtc->thresh, |
1738 | sdtc->bg_thresh, | |
1739 | sdtc->dirty, | |
1740 | sdtc->wb_thresh, | |
1741 | sdtc->wb_dirty, | |
ece13ac3 WF |
1742 | dirty_ratelimit, |
1743 | task_ratelimit, | |
1744 | pages_dirtied, | |
83712358 | 1745 | period, |
7ccb9ad5 | 1746 | min(pause, 0L), |
ece13ac3 | 1747 | start_time); |
83712358 WF |
1748 | if (pause < -HZ) { |
1749 | current->dirty_paused_when = now; | |
1750 | current->nr_dirtied = 0; | |
1751 | } else if (period) { | |
1752 | current->dirty_paused_when += period; | |
1753 | current->nr_dirtied = 0; | |
7ccb9ad5 WF |
1754 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
1755 | current->nr_dirtied_pause += pages_dirtied; | |
57fc978c | 1756 | break; |
04fbfdc1 | 1757 | } |
7ccb9ad5 WF |
1758 | if (unlikely(pause > max_pause)) { |
1759 | /* for occasional dropped task_ratelimit */ | |
1760 | now += min(pause - max_pause, max_pause); | |
1761 | pause = max_pause; | |
1762 | } | |
143dfe86 WF |
1763 | |
1764 | pause: | |
5634cc2a | 1765 | trace_balance_dirty_pages(wb, |
c2aa723a TH |
1766 | sdtc->thresh, |
1767 | sdtc->bg_thresh, | |
1768 | sdtc->dirty, | |
1769 | sdtc->wb_thresh, | |
1770 | sdtc->wb_dirty, | |
ece13ac3 WF |
1771 | dirty_ratelimit, |
1772 | task_ratelimit, | |
1773 | pages_dirtied, | |
83712358 | 1774 | period, |
ece13ac3 WF |
1775 | pause, |
1776 | start_time); | |
499d05ec | 1777 | __set_current_state(TASK_KILLABLE); |
b57d74af | 1778 | wb->dirty_sleep = now; |
d25105e8 | 1779 | io_schedule_timeout(pause); |
87c6a9b2 | 1780 | |
83712358 WF |
1781 | current->dirty_paused_when = now + pause; |
1782 | current->nr_dirtied = 0; | |
7ccb9ad5 | 1783 | current->nr_dirtied_pause = nr_dirtied_pause; |
83712358 | 1784 | |
ffd1f609 | 1785 | /* |
2bc00aef TH |
1786 | * This is typically equal to (dirty < thresh) and can also |
1787 | * keep "1000+ dd on a slow USB stick" under control. | |
ffd1f609 | 1788 | */ |
1df64719 | 1789 | if (task_ratelimit) |
ffd1f609 | 1790 | break; |
499d05ec | 1791 | |
c5c6343c WF |
1792 | /* |
1793 | * In the case of an unresponding NFS server and the NFS dirty | |
de1fff37 | 1794 | * pages exceeds dirty_thresh, give the other good wb's a pipe |
c5c6343c WF |
1795 | * to go through, so that tasks on them still remain responsive. |
1796 | * | |
3f8b6fb7 | 1797 | * In theory 1 page is enough to keep the consumer-producer |
c5c6343c | 1798 | * pipe going: the flusher cleans 1 page => the task dirties 1 |
de1fff37 | 1799 | * more page. However wb_dirty has accounting errors. So use |
93f78d88 | 1800 | * the larger and more IO friendly wb_stat_error. |
c5c6343c | 1801 | */ |
2bce774e | 1802 | if (sdtc->wb_dirty <= wb_stat_error()) |
c5c6343c WF |
1803 | break; |
1804 | ||
499d05ec JK |
1805 | if (fatal_signal_pending(current)) |
1806 | break; | |
1da177e4 LT |
1807 | } |
1808 | ||
a88a341a TH |
1809 | if (!dirty_exceeded && wb->dirty_exceeded) |
1810 | wb->dirty_exceeded = 0; | |
1da177e4 | 1811 | |
bc05873d | 1812 | if (writeback_in_progress(wb)) |
5b0830cb | 1813 | return; |
1da177e4 LT |
1814 | |
1815 | /* | |
1816 | * In laptop mode, we wait until hitting the higher threshold before | |
1817 | * starting background writeout, and then write out all the way down | |
1818 | * to the lower threshold. So slow writers cause minimal disk activity. | |
1819 | * | |
1820 | * In normal mode, we start background writeout at the lower | |
1821 | * background_thresh, to keep the amount of dirty memory low. | |
1822 | */ | |
143dfe86 WF |
1823 | if (laptop_mode) |
1824 | return; | |
1825 | ||
2bc00aef | 1826 | if (nr_reclaimable > gdtc->bg_thresh) |
9ecf4866 | 1827 | wb_start_background_writeback(wb); |
1da177e4 LT |
1828 | } |
1829 | ||
9d823e8f | 1830 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
245b2e70 | 1831 | |
54848d73 WF |
1832 | /* |
1833 | * Normal tasks are throttled by | |
1834 | * loop { | |
1835 | * dirty tsk->nr_dirtied_pause pages; | |
1836 | * take a snap in balance_dirty_pages(); | |
1837 | * } | |
1838 | * However there is a worst case. If every task exit immediately when dirtied | |
1839 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be | |
1840 | * called to throttle the page dirties. The solution is to save the not yet | |
1841 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them | |
1842 | * randomly into the running tasks. This works well for the above worst case, | |
1843 | * as the new task will pick up and accumulate the old task's leaked dirty | |
1844 | * count and eventually get throttled. | |
1845 | */ | |
1846 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; | |
1847 | ||
1da177e4 | 1848 | /** |
d0e1d66b | 1849 | * balance_dirty_pages_ratelimited - balance dirty memory state |
67be2dd1 | 1850 | * @mapping: address_space which was dirtied |
1da177e4 LT |
1851 | * |
1852 | * Processes which are dirtying memory should call in here once for each page | |
1853 | * which was newly dirtied. The function will periodically check the system's | |
1854 | * dirty state and will initiate writeback if needed. | |
1855 | * | |
1856 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
1857 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
1858 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
1859 | * from overshooting the limit by (ratelimit_pages) each. | |
1860 | */ | |
d0e1d66b | 1861 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
1da177e4 | 1862 | { |
dfb8ae56 TH |
1863 | struct inode *inode = mapping->host; |
1864 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1865 | struct bdi_writeback *wb = NULL; | |
9d823e8f WF |
1866 | int ratelimit; |
1867 | int *p; | |
1da177e4 | 1868 | |
36715cef WF |
1869 | if (!bdi_cap_account_dirty(bdi)) |
1870 | return; | |
1871 | ||
dfb8ae56 TH |
1872 | if (inode_cgwb_enabled(inode)) |
1873 | wb = wb_get_create_current(bdi, GFP_KERNEL); | |
1874 | if (!wb) | |
1875 | wb = &bdi->wb; | |
1876 | ||
9d823e8f | 1877 | ratelimit = current->nr_dirtied_pause; |
a88a341a | 1878 | if (wb->dirty_exceeded) |
9d823e8f WF |
1879 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
1880 | ||
9d823e8f | 1881 | preempt_disable(); |
1da177e4 | 1882 | /* |
9d823e8f WF |
1883 | * This prevents one CPU to accumulate too many dirtied pages without |
1884 | * calling into balance_dirty_pages(), which can happen when there are | |
1885 | * 1000+ tasks, all of them start dirtying pages at exactly the same | |
1886 | * time, hence all honoured too large initial task->nr_dirtied_pause. | |
1da177e4 | 1887 | */ |
7c8e0181 | 1888 | p = this_cpu_ptr(&bdp_ratelimits); |
9d823e8f | 1889 | if (unlikely(current->nr_dirtied >= ratelimit)) |
fa5a734e | 1890 | *p = 0; |
d3bc1fef WF |
1891 | else if (unlikely(*p >= ratelimit_pages)) { |
1892 | *p = 0; | |
1893 | ratelimit = 0; | |
1da177e4 | 1894 | } |
54848d73 WF |
1895 | /* |
1896 | * Pick up the dirtied pages by the exited tasks. This avoids lots of | |
1897 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping | |
1898 | * the dirty throttling and livelock other long-run dirtiers. | |
1899 | */ | |
7c8e0181 | 1900 | p = this_cpu_ptr(&dirty_throttle_leaks); |
54848d73 | 1901 | if (*p > 0 && current->nr_dirtied < ratelimit) { |
d0e1d66b | 1902 | unsigned long nr_pages_dirtied; |
54848d73 WF |
1903 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
1904 | *p -= nr_pages_dirtied; | |
1905 | current->nr_dirtied += nr_pages_dirtied; | |
1da177e4 | 1906 | } |
fa5a734e | 1907 | preempt_enable(); |
9d823e8f WF |
1908 | |
1909 | if (unlikely(current->nr_dirtied >= ratelimit)) | |
4c578dce | 1910 | balance_dirty_pages(wb, current->nr_dirtied); |
dfb8ae56 TH |
1911 | |
1912 | wb_put(wb); | |
1da177e4 | 1913 | } |
d0e1d66b | 1914 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
1da177e4 | 1915 | |
aa661bbe TH |
1916 | /** |
1917 | * wb_over_bg_thresh - does @wb need to be written back? | |
1918 | * @wb: bdi_writeback of interest | |
1919 | * | |
1920 | * Determines whether background writeback should keep writing @wb or it's | |
a862f68a MR |
1921 | * clean enough. |
1922 | * | |
1923 | * Return: %true if writeback should continue. | |
aa661bbe TH |
1924 | */ |
1925 | bool wb_over_bg_thresh(struct bdi_writeback *wb) | |
1926 | { | |
947e9762 | 1927 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
c2aa723a | 1928 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
947e9762 | 1929 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
c2aa723a TH |
1930 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
1931 | &mdtc_stor : NULL; | |
aa661bbe | 1932 | |
947e9762 TH |
1933 | /* |
1934 | * Similar to balance_dirty_pages() but ignores pages being written | |
1935 | * as we're trying to decide whether to put more under writeback. | |
1936 | */ | |
1937 | gdtc->avail = global_dirtyable_memory(); | |
11fb9989 MG |
1938 | gdtc->dirty = global_node_page_state(NR_FILE_DIRTY) + |
1939 | global_node_page_state(NR_UNSTABLE_NFS); | |
947e9762 | 1940 | domain_dirty_limits(gdtc); |
aa661bbe | 1941 | |
947e9762 | 1942 | if (gdtc->dirty > gdtc->bg_thresh) |
aa661bbe TH |
1943 | return true; |
1944 | ||
74d36944 HC |
1945 | if (wb_stat(wb, WB_RECLAIMABLE) > |
1946 | wb_calc_thresh(gdtc->wb, gdtc->bg_thresh)) | |
aa661bbe TH |
1947 | return true; |
1948 | ||
c2aa723a | 1949 | if (mdtc) { |
c5edf9cd | 1950 | unsigned long filepages, headroom, writeback; |
c2aa723a | 1951 | |
c5edf9cd TH |
1952 | mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, |
1953 | &writeback); | |
1954 | mdtc_calc_avail(mdtc, filepages, headroom); | |
c2aa723a TH |
1955 | domain_dirty_limits(mdtc); /* ditto, ignore writeback */ |
1956 | ||
1957 | if (mdtc->dirty > mdtc->bg_thresh) | |
1958 | return true; | |
1959 | ||
74d36944 HC |
1960 | if (wb_stat(wb, WB_RECLAIMABLE) > |
1961 | wb_calc_thresh(mdtc->wb, mdtc->bg_thresh)) | |
c2aa723a TH |
1962 | return true; |
1963 | } | |
1964 | ||
aa661bbe TH |
1965 | return false; |
1966 | } | |
1967 | ||
1da177e4 LT |
1968 | /* |
1969 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
1970 | */ | |
cccad5b9 | 1971 | int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, |
8d65af78 | 1972 | void __user *buffer, size_t *length, loff_t *ppos) |
1da177e4 | 1973 | { |
94af5846 YS |
1974 | unsigned int old_interval = dirty_writeback_interval; |
1975 | int ret; | |
1976 | ||
1977 | ret = proc_dointvec(table, write, buffer, length, ppos); | |
515c24c1 YS |
1978 | |
1979 | /* | |
1980 | * Writing 0 to dirty_writeback_interval will disable periodic writeback | |
1981 | * and a different non-zero value will wakeup the writeback threads. | |
1982 | * wb_wakeup_delayed() would be more appropriate, but it's a pain to | |
1983 | * iterate over all bdis and wbs. | |
1984 | * The reason we do this is to make the change take effect immediately. | |
1985 | */ | |
1986 | if (!ret && write && dirty_writeback_interval && | |
1987 | dirty_writeback_interval != old_interval) | |
94af5846 YS |
1988 | wakeup_flusher_threads(WB_REASON_PERIODIC); |
1989 | ||
1990 | return ret; | |
1da177e4 LT |
1991 | } |
1992 | ||
c2c4986e | 1993 | #ifdef CONFIG_BLOCK |
bca237a5 | 1994 | void laptop_mode_timer_fn(struct timer_list *t) |
1da177e4 | 1995 | { |
bca237a5 KC |
1996 | struct backing_dev_info *backing_dev_info = |
1997 | from_timer(backing_dev_info, t, laptop_mode_wb_timer); | |
1da177e4 | 1998 | |
bca237a5 | 1999 | wakeup_flusher_threads_bdi(backing_dev_info, WB_REASON_LAPTOP_TIMER); |
1da177e4 LT |
2000 | } |
2001 | ||
2002 | /* | |
2003 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
2004 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
2005 | * then push it back - the user is still using the disk. | |
2006 | */ | |
31373d09 | 2007 | void laptop_io_completion(struct backing_dev_info *info) |
1da177e4 | 2008 | { |
31373d09 | 2009 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
1da177e4 LT |
2010 | } |
2011 | ||
2012 | /* | |
2013 | * We're in laptop mode and we've just synced. The sync's writes will have | |
2014 | * caused another writeback to be scheduled by laptop_io_completion. | |
2015 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
2016 | */ | |
2017 | void laptop_sync_completion(void) | |
2018 | { | |
31373d09 MG |
2019 | struct backing_dev_info *bdi; |
2020 | ||
2021 | rcu_read_lock(); | |
2022 | ||
2023 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) | |
2024 | del_timer(&bdi->laptop_mode_wb_timer); | |
2025 | ||
2026 | rcu_read_unlock(); | |
1da177e4 | 2027 | } |
c2c4986e | 2028 | #endif |
1da177e4 LT |
2029 | |
2030 | /* | |
2031 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
2032 | * if a large number of processes all perform writes at the same time. | |
2033 | * If it is too low then SMP machines will call the (expensive) | |
2034 | * get_writeback_state too often. | |
2035 | * | |
2036 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
2037 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
9d823e8f | 2038 | * thresholds. |
1da177e4 LT |
2039 | */ |
2040 | ||
2d1d43f6 | 2041 | void writeback_set_ratelimit(void) |
1da177e4 | 2042 | { |
dcc25ae7 | 2043 | struct wb_domain *dom = &global_wb_domain; |
9d823e8f WF |
2044 | unsigned long background_thresh; |
2045 | unsigned long dirty_thresh; | |
dcc25ae7 | 2046 | |
9d823e8f | 2047 | global_dirty_limits(&background_thresh, &dirty_thresh); |
dcc25ae7 | 2048 | dom->dirty_limit = dirty_thresh; |
9d823e8f | 2049 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
1da177e4 LT |
2050 | if (ratelimit_pages < 16) |
2051 | ratelimit_pages = 16; | |
1da177e4 LT |
2052 | } |
2053 | ||
1d7ac6ae | 2054 | static int page_writeback_cpu_online(unsigned int cpu) |
1da177e4 | 2055 | { |
1d7ac6ae SAS |
2056 | writeback_set_ratelimit(); |
2057 | return 0; | |
1da177e4 LT |
2058 | } |
2059 | ||
1da177e4 | 2060 | /* |
dc6e29da LT |
2061 | * Called early on to tune the page writeback dirty limits. |
2062 | * | |
2063 | * We used to scale dirty pages according to how total memory | |
2064 | * related to pages that could be allocated for buffers (by | |
2065 | * comparing nr_free_buffer_pages() to vm_total_pages. | |
2066 | * | |
2067 | * However, that was when we used "dirty_ratio" to scale with | |
2068 | * all memory, and we don't do that any more. "dirty_ratio" | |
2069 | * is now applied to total non-HIGHPAGE memory (by subtracting | |
2070 | * totalhigh_pages from vm_total_pages), and as such we can't | |
2071 | * get into the old insane situation any more where we had | |
2072 | * large amounts of dirty pages compared to a small amount of | |
2073 | * non-HIGHMEM memory. | |
2074 | * | |
2075 | * But we might still want to scale the dirty_ratio by how | |
2076 | * much memory the box has.. | |
1da177e4 LT |
2077 | */ |
2078 | void __init page_writeback_init(void) | |
2079 | { | |
a50fcb51 RV |
2080 | BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL)); |
2081 | ||
1d7ac6ae SAS |
2082 | cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online", |
2083 | page_writeback_cpu_online, NULL); | |
2084 | cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL, | |
2085 | page_writeback_cpu_online); | |
1da177e4 LT |
2086 | } |
2087 | ||
f446daae JK |
2088 | /** |
2089 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages | |
2090 | * @mapping: address space structure to write | |
2091 | * @start: starting page index | |
2092 | * @end: ending page index (inclusive) | |
2093 | * | |
2094 | * This function scans the page range from @start to @end (inclusive) and tags | |
2095 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is | |
2096 | * that write_cache_pages (or whoever calls this function) will then use | |
2097 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is | |
2098 | * used to avoid livelocking of writeback by a process steadily creating new | |
2099 | * dirty pages in the file (thus it is important for this function to be quick | |
2100 | * so that it can tag pages faster than a dirtying process can create them). | |
2101 | */ | |
f446daae JK |
2102 | void tag_pages_for_writeback(struct address_space *mapping, |
2103 | pgoff_t start, pgoff_t end) | |
2104 | { | |
ff9c745b MW |
2105 | XA_STATE(xas, &mapping->i_pages, start); |
2106 | unsigned int tagged = 0; | |
2107 | void *page; | |
268f42de | 2108 | |
ff9c745b MW |
2109 | xas_lock_irq(&xas); |
2110 | xas_for_each_marked(&xas, page, end, PAGECACHE_TAG_DIRTY) { | |
2111 | xas_set_mark(&xas, PAGECACHE_TAG_TOWRITE); | |
2112 | if (++tagged % XA_CHECK_SCHED) | |
268f42de | 2113 | continue; |
ff9c745b MW |
2114 | |
2115 | xas_pause(&xas); | |
2116 | xas_unlock_irq(&xas); | |
f446daae | 2117 | cond_resched(); |
ff9c745b | 2118 | xas_lock_irq(&xas); |
268f42de | 2119 | } |
ff9c745b | 2120 | xas_unlock_irq(&xas); |
f446daae JK |
2121 | } |
2122 | EXPORT_SYMBOL(tag_pages_for_writeback); | |
2123 | ||
811d736f | 2124 | /** |
0ea97180 | 2125 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
811d736f DH |
2126 | * @mapping: address space structure to write |
2127 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
0ea97180 MS |
2128 | * @writepage: function called for each page |
2129 | * @data: data passed to writepage function | |
811d736f | 2130 | * |
0ea97180 | 2131 | * If a page is already under I/O, write_cache_pages() skips it, even |
811d736f DH |
2132 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
2133 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
2134 | * and msync() need to guarantee that all the data which was dirty at the time | |
2135 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
2136 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
2137 | * existing IO to complete. | |
f446daae JK |
2138 | * |
2139 | * To avoid livelocks (when other process dirties new pages), we first tag | |
2140 | * pages which should be written back with TOWRITE tag and only then start | |
2141 | * writing them. For data-integrity sync we have to be careful so that we do | |
2142 | * not miss some pages (e.g., because some other process has cleared TOWRITE | |
2143 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only | |
2144 | * by the process clearing the DIRTY tag (and submitting the page for IO). | |
64081362 DC |
2145 | * |
2146 | * To avoid deadlocks between range_cyclic writeback and callers that hold | |
2147 | * pages in PageWriteback to aggregate IO until write_cache_pages() returns, | |
2148 | * we do not loop back to the start of the file. Doing so causes a page | |
2149 | * lock/page writeback access order inversion - we should only ever lock | |
2150 | * multiple pages in ascending page->index order, and looping back to the start | |
2151 | * of the file violates that rule and causes deadlocks. | |
a862f68a MR |
2152 | * |
2153 | * Return: %0 on success, negative error code otherwise | |
811d736f | 2154 | */ |
0ea97180 MS |
2155 | int write_cache_pages(struct address_space *mapping, |
2156 | struct writeback_control *wbc, writepage_t writepage, | |
2157 | void *data) | |
811d736f | 2158 | { |
811d736f DH |
2159 | int ret = 0; |
2160 | int done = 0; | |
3fa750dc | 2161 | int error; |
811d736f DH |
2162 | struct pagevec pvec; |
2163 | int nr_pages; | |
31a12666 | 2164 | pgoff_t uninitialized_var(writeback_index); |
811d736f DH |
2165 | pgoff_t index; |
2166 | pgoff_t end; /* Inclusive */ | |
bd19e012 | 2167 | pgoff_t done_index; |
811d736f | 2168 | int range_whole = 0; |
ff9c745b | 2169 | xa_mark_t tag; |
811d736f | 2170 | |
86679820 | 2171 | pagevec_init(&pvec); |
811d736f | 2172 | if (wbc->range_cyclic) { |
31a12666 NP |
2173 | writeback_index = mapping->writeback_index; /* prev offset */ |
2174 | index = writeback_index; | |
811d736f DH |
2175 | end = -1; |
2176 | } else { | |
09cbfeaf KS |
2177 | index = wbc->range_start >> PAGE_SHIFT; |
2178 | end = wbc->range_end >> PAGE_SHIFT; | |
811d736f DH |
2179 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
2180 | range_whole = 1; | |
811d736f | 2181 | } |
6e6938b6 | 2182 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae JK |
2183 | tag = PAGECACHE_TAG_TOWRITE; |
2184 | else | |
2185 | tag = PAGECACHE_TAG_DIRTY; | |
6e6938b6 | 2186 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
f446daae | 2187 | tag_pages_for_writeback(mapping, index, end); |
bd19e012 | 2188 | done_index = index; |
5a3d5c98 NP |
2189 | while (!done && (index <= end)) { |
2190 | int i; | |
2191 | ||
2b9775ae | 2192 | nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end, |
67fd707f | 2193 | tag); |
5a3d5c98 NP |
2194 | if (nr_pages == 0) |
2195 | break; | |
811d736f | 2196 | |
811d736f DH |
2197 | for (i = 0; i < nr_pages; i++) { |
2198 | struct page *page = pvec.pages[i]; | |
2199 | ||
cf15b07c | 2200 | done_index = page->index; |
d5482cdf | 2201 | |
811d736f DH |
2202 | lock_page(page); |
2203 | ||
5a3d5c98 NP |
2204 | /* |
2205 | * Page truncated or invalidated. We can freely skip it | |
2206 | * then, even for data integrity operations: the page | |
2207 | * has disappeared concurrently, so there could be no | |
2208 | * real expectation of this data interity operation | |
2209 | * even if there is now a new, dirty page at the same | |
2210 | * pagecache address. | |
2211 | */ | |
811d736f | 2212 | if (unlikely(page->mapping != mapping)) { |
5a3d5c98 | 2213 | continue_unlock: |
811d736f DH |
2214 | unlock_page(page); |
2215 | continue; | |
2216 | } | |
2217 | ||
515f4a03 NP |
2218 | if (!PageDirty(page)) { |
2219 | /* someone wrote it for us */ | |
2220 | goto continue_unlock; | |
2221 | } | |
2222 | ||
2223 | if (PageWriteback(page)) { | |
2224 | if (wbc->sync_mode != WB_SYNC_NONE) | |
2225 | wait_on_page_writeback(page); | |
2226 | else | |
2227 | goto continue_unlock; | |
2228 | } | |
811d736f | 2229 | |
515f4a03 NP |
2230 | BUG_ON(PageWriteback(page)); |
2231 | if (!clear_page_dirty_for_io(page)) | |
5a3d5c98 | 2232 | goto continue_unlock; |
811d736f | 2233 | |
de1414a6 | 2234 | trace_wbc_writepage(wbc, inode_to_bdi(mapping->host)); |
3fa750dc BF |
2235 | error = (*writepage)(page, wbc, data); |
2236 | if (unlikely(error)) { | |
2237 | /* | |
2238 | * Handle errors according to the type of | |
2239 | * writeback. There's no need to continue for | |
2240 | * background writeback. Just push done_index | |
2241 | * past this page so media errors won't choke | |
2242 | * writeout for the entire file. For integrity | |
2243 | * writeback, we must process the entire dirty | |
2244 | * set regardless of errors because the fs may | |
2245 | * still have state to clear for each page. In | |
2246 | * that case we continue processing and return | |
2247 | * the first error. | |
2248 | */ | |
2249 | if (error == AOP_WRITEPAGE_ACTIVATE) { | |
00266770 | 2250 | unlock_page(page); |
3fa750dc BF |
2251 | error = 0; |
2252 | } else if (wbc->sync_mode != WB_SYNC_ALL) { | |
2253 | ret = error; | |
cf15b07c | 2254 | done_index = page->index + 1; |
00266770 NP |
2255 | done = 1; |
2256 | break; | |
2257 | } | |
3fa750dc BF |
2258 | if (!ret) |
2259 | ret = error; | |
0b564927 | 2260 | } |
00266770 | 2261 | |
546a1924 DC |
2262 | /* |
2263 | * We stop writing back only if we are not doing | |
2264 | * integrity sync. In case of integrity sync we have to | |
2265 | * keep going until we have written all the pages | |
2266 | * we tagged for writeback prior to entering this loop. | |
2267 | */ | |
2268 | if (--wbc->nr_to_write <= 0 && | |
2269 | wbc->sync_mode == WB_SYNC_NONE) { | |
2270 | done = 1; | |
2271 | break; | |
05fe478d | 2272 | } |
811d736f DH |
2273 | } |
2274 | pagevec_release(&pvec); | |
2275 | cond_resched(); | |
2276 | } | |
64081362 DC |
2277 | |
2278 | /* | |
2279 | * If we hit the last page and there is more work to be done: wrap | |
2280 | * back the index back to the start of the file for the next | |
2281 | * time we are called. | |
2282 | */ | |
2283 | if (wbc->range_cyclic && !done) | |
2284 | done_index = 0; | |
0b564927 DC |
2285 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
2286 | mapping->writeback_index = done_index; | |
06d6cf69 | 2287 | |
811d736f DH |
2288 | return ret; |
2289 | } | |
0ea97180 MS |
2290 | EXPORT_SYMBOL(write_cache_pages); |
2291 | ||
2292 | /* | |
2293 | * Function used by generic_writepages to call the real writepage | |
2294 | * function and set the mapping flags on error | |
2295 | */ | |
2296 | static int __writepage(struct page *page, struct writeback_control *wbc, | |
2297 | void *data) | |
2298 | { | |
2299 | struct address_space *mapping = data; | |
2300 | int ret = mapping->a_ops->writepage(page, wbc); | |
2301 | mapping_set_error(mapping, ret); | |
2302 | return ret; | |
2303 | } | |
2304 | ||
2305 | /** | |
2306 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. | |
2307 | * @mapping: address space structure to write | |
2308 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
2309 | * | |
2310 | * This is a library function, which implements the writepages() | |
2311 | * address_space_operation. | |
a862f68a MR |
2312 | * |
2313 | * Return: %0 on success, negative error code otherwise | |
0ea97180 MS |
2314 | */ |
2315 | int generic_writepages(struct address_space *mapping, | |
2316 | struct writeback_control *wbc) | |
2317 | { | |
9b6096a6 SL |
2318 | struct blk_plug plug; |
2319 | int ret; | |
2320 | ||
0ea97180 MS |
2321 | /* deal with chardevs and other special file */ |
2322 | if (!mapping->a_ops->writepage) | |
2323 | return 0; | |
2324 | ||
9b6096a6 SL |
2325 | blk_start_plug(&plug); |
2326 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); | |
2327 | blk_finish_plug(&plug); | |
2328 | return ret; | |
0ea97180 | 2329 | } |
811d736f DH |
2330 | |
2331 | EXPORT_SYMBOL(generic_writepages); | |
2332 | ||
1da177e4 LT |
2333 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
2334 | { | |
22905f77 AM |
2335 | int ret; |
2336 | ||
1da177e4 LT |
2337 | if (wbc->nr_to_write <= 0) |
2338 | return 0; | |
80a2ea9f TT |
2339 | while (1) { |
2340 | if (mapping->a_ops->writepages) | |
2341 | ret = mapping->a_ops->writepages(mapping, wbc); | |
2342 | else | |
2343 | ret = generic_writepages(mapping, wbc); | |
2344 | if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL)) | |
2345 | break; | |
2346 | cond_resched(); | |
2347 | congestion_wait(BLK_RW_ASYNC, HZ/50); | |
2348 | } | |
22905f77 | 2349 | return ret; |
1da177e4 LT |
2350 | } |
2351 | ||
2352 | /** | |
2b69c828 | 2353 | * write_one_page - write out a single page and wait on I/O |
67be2dd1 | 2354 | * @page: the page to write |
1da177e4 LT |
2355 | * |
2356 | * The page must be locked by the caller and will be unlocked upon return. | |
2357 | * | |
37e51a76 JL |
2358 | * Note that the mapping's AS_EIO/AS_ENOSPC flags will be cleared when this |
2359 | * function returns. | |
a862f68a MR |
2360 | * |
2361 | * Return: %0 on success, negative error code otherwise | |
1da177e4 | 2362 | */ |
2b69c828 | 2363 | int write_one_page(struct page *page) |
1da177e4 LT |
2364 | { |
2365 | struct address_space *mapping = page->mapping; | |
2366 | int ret = 0; | |
2367 | struct writeback_control wbc = { | |
2368 | .sync_mode = WB_SYNC_ALL, | |
2369 | .nr_to_write = 1, | |
2370 | }; | |
2371 | ||
2372 | BUG_ON(!PageLocked(page)); | |
2373 | ||
2b69c828 | 2374 | wait_on_page_writeback(page); |
1da177e4 LT |
2375 | |
2376 | if (clear_page_dirty_for_io(page)) { | |
09cbfeaf | 2377 | get_page(page); |
1da177e4 | 2378 | ret = mapping->a_ops->writepage(page, &wbc); |
37e51a76 | 2379 | if (ret == 0) |
1da177e4 | 2380 | wait_on_page_writeback(page); |
09cbfeaf | 2381 | put_page(page); |
1da177e4 LT |
2382 | } else { |
2383 | unlock_page(page); | |
2384 | } | |
37e51a76 JL |
2385 | |
2386 | if (!ret) | |
2387 | ret = filemap_check_errors(mapping); | |
1da177e4 LT |
2388 | return ret; |
2389 | } | |
2390 | EXPORT_SYMBOL(write_one_page); | |
2391 | ||
76719325 KC |
2392 | /* |
2393 | * For address_spaces which do not use buffers nor write back. | |
2394 | */ | |
2395 | int __set_page_dirty_no_writeback(struct page *page) | |
2396 | { | |
2397 | if (!PageDirty(page)) | |
c3f0da63 | 2398 | return !TestSetPageDirty(page); |
76719325 KC |
2399 | return 0; |
2400 | } | |
2401 | ||
e3a7cca1 ES |
2402 | /* |
2403 | * Helper function for set_page_dirty family. | |
c4843a75 | 2404 | * |
81f8c3a4 | 2405 | * Caller must hold lock_page_memcg(). |
c4843a75 | 2406 | * |
e3a7cca1 ES |
2407 | * NOTE: This relies on being atomic wrt interrupts. |
2408 | */ | |
62cccb8c | 2409 | void account_page_dirtied(struct page *page, struct address_space *mapping) |
e3a7cca1 | 2410 | { |
52ebea74 TH |
2411 | struct inode *inode = mapping->host; |
2412 | ||
9fb0a7da TH |
2413 | trace_writeback_dirty_page(page, mapping); |
2414 | ||
e3a7cca1 | 2415 | if (mapping_cap_account_dirty(mapping)) { |
52ebea74 | 2416 | struct bdi_writeback *wb; |
de1414a6 | 2417 | |
52ebea74 TH |
2418 | inode_attach_wb(inode, page); |
2419 | wb = inode_to_wb(inode); | |
de1414a6 | 2420 | |
00f3ca2c | 2421 | __inc_lruvec_page_state(page, NR_FILE_DIRTY); |
5a1c84b4 | 2422 | __inc_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
c4a25635 | 2423 | __inc_node_page_state(page, NR_DIRTIED); |
3e8f399d NB |
2424 | inc_wb_stat(wb, WB_RECLAIMABLE); |
2425 | inc_wb_stat(wb, WB_DIRTIED); | |
09cbfeaf | 2426 | task_io_account_write(PAGE_SIZE); |
d3bc1fef WF |
2427 | current->nr_dirtied++; |
2428 | this_cpu_inc(bdp_ratelimits); | |
e3a7cca1 ES |
2429 | } |
2430 | } | |
679ceace | 2431 | EXPORT_SYMBOL(account_page_dirtied); |
e3a7cca1 | 2432 | |
b9ea2515 KK |
2433 | /* |
2434 | * Helper function for deaccounting dirty page without writeback. | |
2435 | * | |
81f8c3a4 | 2436 | * Caller must hold lock_page_memcg(). |
b9ea2515 | 2437 | */ |
c4843a75 | 2438 | void account_page_cleaned(struct page *page, struct address_space *mapping, |
62cccb8c | 2439 | struct bdi_writeback *wb) |
b9ea2515 KK |
2440 | { |
2441 | if (mapping_cap_account_dirty(mapping)) { | |
00f3ca2c | 2442 | dec_lruvec_page_state(page, NR_FILE_DIRTY); |
5a1c84b4 | 2443 | dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
682aa8e1 | 2444 | dec_wb_stat(wb, WB_RECLAIMABLE); |
09cbfeaf | 2445 | task_io_account_cancelled_write(PAGE_SIZE); |
b9ea2515 KK |
2446 | } |
2447 | } | |
b9ea2515 | 2448 | |
1da177e4 LT |
2449 | /* |
2450 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
ff9c745b | 2451 | * the xarray. |
1da177e4 LT |
2452 | * |
2453 | * This is also used when a single buffer is being dirtied: we want to set the | |
2454 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
2455 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
2456 | * | |
2d6d7f98 JW |
2457 | * The caller must ensure this doesn't race with truncation. Most will simply |
2458 | * hold the page lock, but e.g. zap_pte_range() calls with the page mapped and | |
2459 | * the pte lock held, which also locks out truncation. | |
1da177e4 LT |
2460 | */ |
2461 | int __set_page_dirty_nobuffers(struct page *page) | |
2462 | { | |
62cccb8c | 2463 | lock_page_memcg(page); |
1da177e4 LT |
2464 | if (!TestSetPageDirty(page)) { |
2465 | struct address_space *mapping = page_mapping(page); | |
a85d9df1 | 2466 | unsigned long flags; |
1da177e4 | 2467 | |
c4843a75 | 2468 | if (!mapping) { |
62cccb8c | 2469 | unlock_page_memcg(page); |
8c08540f | 2470 | return 1; |
c4843a75 | 2471 | } |
8c08540f | 2472 | |
b93b0163 | 2473 | xa_lock_irqsave(&mapping->i_pages, flags); |
2d6d7f98 JW |
2474 | BUG_ON(page_mapping(page) != mapping); |
2475 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); | |
62cccb8c | 2476 | account_page_dirtied(page, mapping); |
ff9c745b | 2477 | __xa_set_mark(&mapping->i_pages, page_index(page), |
2d6d7f98 | 2478 | PAGECACHE_TAG_DIRTY); |
b93b0163 | 2479 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
62cccb8c | 2480 | unlock_page_memcg(page); |
c4843a75 | 2481 | |
8c08540f AM |
2482 | if (mapping->host) { |
2483 | /* !PageAnon && !swapper_space */ | |
2484 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); | |
1da177e4 | 2485 | } |
4741c9fd | 2486 | return 1; |
1da177e4 | 2487 | } |
62cccb8c | 2488 | unlock_page_memcg(page); |
4741c9fd | 2489 | return 0; |
1da177e4 LT |
2490 | } |
2491 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
2492 | ||
2f800fbd WF |
2493 | /* |
2494 | * Call this whenever redirtying a page, to de-account the dirty counters | |
dcfe4df3 GT |
2495 | * (NR_DIRTIED, WB_DIRTIED, tsk->nr_dirtied), so that they match the written |
2496 | * counters (NR_WRITTEN, WB_WRITTEN) in long term. The mismatches will lead to | |
2f800fbd WF |
2497 | * systematic errors in balanced_dirty_ratelimit and the dirty pages position |
2498 | * control. | |
2499 | */ | |
2500 | void account_page_redirty(struct page *page) | |
2501 | { | |
2502 | struct address_space *mapping = page->mapping; | |
91018134 | 2503 | |
2f800fbd | 2504 | if (mapping && mapping_cap_account_dirty(mapping)) { |
682aa8e1 TH |
2505 | struct inode *inode = mapping->host; |
2506 | struct bdi_writeback *wb; | |
2e898e4c | 2507 | struct wb_lock_cookie cookie = {}; |
91018134 | 2508 | |
2e898e4c | 2509 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
2f800fbd | 2510 | current->nr_dirtied--; |
c4a25635 | 2511 | dec_node_page_state(page, NR_DIRTIED); |
91018134 | 2512 | dec_wb_stat(wb, WB_DIRTIED); |
2e898e4c | 2513 | unlocked_inode_to_wb_end(inode, &cookie); |
2f800fbd WF |
2514 | } |
2515 | } | |
2516 | EXPORT_SYMBOL(account_page_redirty); | |
2517 | ||
1da177e4 LT |
2518 | /* |
2519 | * When a writepage implementation decides that it doesn't want to write this | |
2520 | * page for some reason, it should redirty the locked page via | |
2521 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
2522 | */ | |
2523 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
2524 | { | |
8d38633c KK |
2525 | int ret; |
2526 | ||
1da177e4 | 2527 | wbc->pages_skipped++; |
8d38633c | 2528 | ret = __set_page_dirty_nobuffers(page); |
2f800fbd | 2529 | account_page_redirty(page); |
8d38633c | 2530 | return ret; |
1da177e4 LT |
2531 | } |
2532 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
2533 | ||
2534 | /* | |
6746aff7 WF |
2535 | * Dirty a page. |
2536 | * | |
2537 | * For pages with a mapping this should be done under the page lock | |
2538 | * for the benefit of asynchronous memory errors who prefer a consistent | |
2539 | * dirty state. This rule can be broken in some special cases, | |
2540 | * but should be better not to. | |
2541 | * | |
1da177e4 LT |
2542 | * If the mapping doesn't provide a set_page_dirty a_op, then |
2543 | * just fall through and assume that it wants buffer_heads. | |
2544 | */ | |
1cf6e7d8 | 2545 | int set_page_dirty(struct page *page) |
1da177e4 LT |
2546 | { |
2547 | struct address_space *mapping = page_mapping(page); | |
2548 | ||
800d8c63 | 2549 | page = compound_head(page); |
1da177e4 LT |
2550 | if (likely(mapping)) { |
2551 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
278df9f4 MK |
2552 | /* |
2553 | * readahead/lru_deactivate_page could remain | |
2554 | * PG_readahead/PG_reclaim due to race with end_page_writeback | |
2555 | * About readahead, if the page is written, the flags would be | |
2556 | * reset. So no problem. | |
2557 | * About lru_deactivate_page, if the page is redirty, the flag | |
2558 | * will be reset. So no problem. but if the page is used by readahead | |
2559 | * it will confuse readahead and make it restart the size rampup | |
2560 | * process. But it's a trivial problem. | |
2561 | */ | |
a4bb3ecd NH |
2562 | if (PageReclaim(page)) |
2563 | ClearPageReclaim(page); | |
9361401e DH |
2564 | #ifdef CONFIG_BLOCK |
2565 | if (!spd) | |
2566 | spd = __set_page_dirty_buffers; | |
2567 | #endif | |
2568 | return (*spd)(page); | |
1da177e4 | 2569 | } |
4741c9fd AM |
2570 | if (!PageDirty(page)) { |
2571 | if (!TestSetPageDirty(page)) | |
2572 | return 1; | |
2573 | } | |
1da177e4 LT |
2574 | return 0; |
2575 | } | |
2576 | EXPORT_SYMBOL(set_page_dirty); | |
2577 | ||
2578 | /* | |
2579 | * set_page_dirty() is racy if the caller has no reference against | |
2580 | * page->mapping->host, and if the page is unlocked. This is because another | |
2581 | * CPU could truncate the page off the mapping and then free the mapping. | |
2582 | * | |
2583 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
2584 | * holds a reference on the inode by having an open file. | |
2585 | * | |
2586 | * In other cases, the page should be locked before running set_page_dirty(). | |
2587 | */ | |
2588 | int set_page_dirty_lock(struct page *page) | |
2589 | { | |
2590 | int ret; | |
2591 | ||
7eaceacc | 2592 | lock_page(page); |
1da177e4 LT |
2593 | ret = set_page_dirty(page); |
2594 | unlock_page(page); | |
2595 | return ret; | |
2596 | } | |
2597 | EXPORT_SYMBOL(set_page_dirty_lock); | |
2598 | ||
11f81bec TH |
2599 | /* |
2600 | * This cancels just the dirty bit on the kernel page itself, it does NOT | |
2601 | * actually remove dirty bits on any mmap's that may be around. It also | |
2602 | * leaves the page tagged dirty, so any sync activity will still find it on | |
2603 | * the dirty lists, and in particular, clear_page_dirty_for_io() will still | |
2604 | * look at the dirty bits in the VM. | |
2605 | * | |
2606 | * Doing this should *normally* only ever be done when a page is truncated, | |
2607 | * and is not actually mapped anywhere at all. However, fs/buffer.c does | |
2608 | * this when it notices that somebody has cleaned out all the buffers on a | |
2609 | * page without actually doing it through the VM. Can you say "ext3 is | |
2610 | * horribly ugly"? Thought you could. | |
2611 | */ | |
736304f3 | 2612 | void __cancel_dirty_page(struct page *page) |
11f81bec | 2613 | { |
c4843a75 GT |
2614 | struct address_space *mapping = page_mapping(page); |
2615 | ||
2616 | if (mapping_cap_account_dirty(mapping)) { | |
682aa8e1 TH |
2617 | struct inode *inode = mapping->host; |
2618 | struct bdi_writeback *wb; | |
2e898e4c | 2619 | struct wb_lock_cookie cookie = {}; |
c4843a75 | 2620 | |
62cccb8c | 2621 | lock_page_memcg(page); |
2e898e4c | 2622 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
c4843a75 GT |
2623 | |
2624 | if (TestClearPageDirty(page)) | |
62cccb8c | 2625 | account_page_cleaned(page, mapping, wb); |
c4843a75 | 2626 | |
2e898e4c | 2627 | unlocked_inode_to_wb_end(inode, &cookie); |
62cccb8c | 2628 | unlock_page_memcg(page); |
c4843a75 GT |
2629 | } else { |
2630 | ClearPageDirty(page); | |
2631 | } | |
11f81bec | 2632 | } |
736304f3 | 2633 | EXPORT_SYMBOL(__cancel_dirty_page); |
11f81bec | 2634 | |
1da177e4 LT |
2635 | /* |
2636 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
2637 | * Returns true if the page was previously dirty. | |
2638 | * | |
2639 | * This is for preparing to put the page under writeout. We leave the page | |
ff9c745b | 2640 | * tagged as dirty in the xarray so that a concurrent write-for-sync |
1da177e4 LT |
2641 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage |
2642 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
ff9c745b | 2643 | * at which stage we bring the page's dirty flag and xarray dirty tag |
1da177e4 LT |
2644 | * back into sync. |
2645 | * | |
ff9c745b | 2646 | * This incoherency between the page's dirty flag and xarray tag is |
1da177e4 LT |
2647 | * unfortunate, but it only exists while the page is locked. |
2648 | */ | |
2649 | int clear_page_dirty_for_io(struct page *page) | |
2650 | { | |
2651 | struct address_space *mapping = page_mapping(page); | |
c4843a75 | 2652 | int ret = 0; |
1da177e4 | 2653 | |
79352894 NP |
2654 | BUG_ON(!PageLocked(page)); |
2655 | ||
7658cc28 | 2656 | if (mapping && mapping_cap_account_dirty(mapping)) { |
682aa8e1 TH |
2657 | struct inode *inode = mapping->host; |
2658 | struct bdi_writeback *wb; | |
2e898e4c | 2659 | struct wb_lock_cookie cookie = {}; |
682aa8e1 | 2660 | |
7658cc28 LT |
2661 | /* |
2662 | * Yes, Virginia, this is indeed insane. | |
2663 | * | |
2664 | * We use this sequence to make sure that | |
2665 | * (a) we account for dirty stats properly | |
2666 | * (b) we tell the low-level filesystem to | |
2667 | * mark the whole page dirty if it was | |
2668 | * dirty in a pagetable. Only to then | |
2669 | * (c) clean the page again and return 1 to | |
2670 | * cause the writeback. | |
2671 | * | |
2672 | * This way we avoid all nasty races with the | |
2673 | * dirty bit in multiple places and clearing | |
2674 | * them concurrently from different threads. | |
2675 | * | |
2676 | * Note! Normally the "set_page_dirty(page)" | |
2677 | * has no effect on the actual dirty bit - since | |
2678 | * that will already usually be set. But we | |
2679 | * need the side effects, and it can help us | |
2680 | * avoid races. | |
2681 | * | |
2682 | * We basically use the page "master dirty bit" | |
2683 | * as a serialization point for all the different | |
2684 | * threads doing their things. | |
7658cc28 LT |
2685 | */ |
2686 | if (page_mkclean(page)) | |
2687 | set_page_dirty(page); | |
79352894 NP |
2688 | /* |
2689 | * We carefully synchronise fault handlers against | |
2690 | * installing a dirty pte and marking the page dirty | |
2d6d7f98 JW |
2691 | * at this point. We do this by having them hold the |
2692 | * page lock while dirtying the page, and pages are | |
2693 | * always locked coming in here, so we get the desired | |
2694 | * exclusion. | |
79352894 | 2695 | */ |
2e898e4c | 2696 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
7658cc28 | 2697 | if (TestClearPageDirty(page)) { |
00f3ca2c | 2698 | dec_lruvec_page_state(page, NR_FILE_DIRTY); |
5a1c84b4 | 2699 | dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
682aa8e1 | 2700 | dec_wb_stat(wb, WB_RECLAIMABLE); |
c4843a75 | 2701 | ret = 1; |
1da177e4 | 2702 | } |
2e898e4c | 2703 | unlocked_inode_to_wb_end(inode, &cookie); |
c4843a75 | 2704 | return ret; |
1da177e4 | 2705 | } |
7658cc28 | 2706 | return TestClearPageDirty(page); |
1da177e4 | 2707 | } |
58bb01a9 | 2708 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
1da177e4 LT |
2709 | |
2710 | int test_clear_page_writeback(struct page *page) | |
2711 | { | |
2712 | struct address_space *mapping = page_mapping(page); | |
739f79fc JW |
2713 | struct mem_cgroup *memcg; |
2714 | struct lruvec *lruvec; | |
d7365e78 | 2715 | int ret; |
1da177e4 | 2716 | |
739f79fc JW |
2717 | memcg = lock_page_memcg(page); |
2718 | lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page)); | |
371a096e | 2719 | if (mapping && mapping_use_writeback_tags(mapping)) { |
91018134 TH |
2720 | struct inode *inode = mapping->host; |
2721 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2722 | unsigned long flags; |
2723 | ||
b93b0163 | 2724 | xa_lock_irqsave(&mapping->i_pages, flags); |
1da177e4 | 2725 | ret = TestClearPageWriteback(page); |
69cb51d1 | 2726 | if (ret) { |
ff9c745b | 2727 | __xa_clear_mark(&mapping->i_pages, page_index(page), |
1da177e4 | 2728 | PAGECACHE_TAG_WRITEBACK); |
e4ad08fe | 2729 | if (bdi_cap_account_writeback(bdi)) { |
91018134 TH |
2730 | struct bdi_writeback *wb = inode_to_wb(inode); |
2731 | ||
3e8f399d | 2732 | dec_wb_stat(wb, WB_WRITEBACK); |
91018134 | 2733 | __wb_writeout_inc(wb); |
04fbfdc1 | 2734 | } |
69cb51d1 | 2735 | } |
6c60d2b5 DC |
2736 | |
2737 | if (mapping->host && !mapping_tagged(mapping, | |
2738 | PAGECACHE_TAG_WRITEBACK)) | |
2739 | sb_clear_inode_writeback(mapping->host); | |
2740 | ||
b93b0163 | 2741 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
1da177e4 LT |
2742 | } else { |
2743 | ret = TestClearPageWriteback(page); | |
2744 | } | |
739f79fc JW |
2745 | /* |
2746 | * NOTE: Page might be free now! Writeback doesn't hold a page | |
2747 | * reference on its own, it relies on truncation to wait for | |
2748 | * the clearing of PG_writeback. The below can only access | |
2749 | * page state that is static across allocation cycles. | |
2750 | */ | |
99b12e3d | 2751 | if (ret) { |
739f79fc | 2752 | dec_lruvec_state(lruvec, NR_WRITEBACK); |
5a1c84b4 | 2753 | dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
c4a25635 | 2754 | inc_node_page_state(page, NR_WRITTEN); |
99b12e3d | 2755 | } |
739f79fc | 2756 | __unlock_page_memcg(memcg); |
1da177e4 LT |
2757 | return ret; |
2758 | } | |
2759 | ||
1c8349a1 | 2760 | int __test_set_page_writeback(struct page *page, bool keep_write) |
1da177e4 LT |
2761 | { |
2762 | struct address_space *mapping = page_mapping(page); | |
d7365e78 | 2763 | int ret; |
1da177e4 | 2764 | |
62cccb8c | 2765 | lock_page_memcg(page); |
371a096e | 2766 | if (mapping && mapping_use_writeback_tags(mapping)) { |
ff9c745b | 2767 | XA_STATE(xas, &mapping->i_pages, page_index(page)); |
91018134 TH |
2768 | struct inode *inode = mapping->host; |
2769 | struct backing_dev_info *bdi = inode_to_bdi(inode); | |
1da177e4 LT |
2770 | unsigned long flags; |
2771 | ||
ff9c745b MW |
2772 | xas_lock_irqsave(&xas, flags); |
2773 | xas_load(&xas); | |
1da177e4 | 2774 | ret = TestSetPageWriteback(page); |
69cb51d1 | 2775 | if (!ret) { |
6c60d2b5 DC |
2776 | bool on_wblist; |
2777 | ||
2778 | on_wblist = mapping_tagged(mapping, | |
2779 | PAGECACHE_TAG_WRITEBACK); | |
2780 | ||
ff9c745b | 2781 | xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK); |
e4ad08fe | 2782 | if (bdi_cap_account_writeback(bdi)) |
3e8f399d | 2783 | inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK); |
6c60d2b5 DC |
2784 | |
2785 | /* | |
2786 | * We can come through here when swapping anonymous | |
2787 | * pages, so we don't necessarily have an inode to track | |
2788 | * for sync. | |
2789 | */ | |
2790 | if (mapping->host && !on_wblist) | |
2791 | sb_mark_inode_writeback(mapping->host); | |
69cb51d1 | 2792 | } |
1da177e4 | 2793 | if (!PageDirty(page)) |
ff9c745b | 2794 | xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); |
1c8349a1 | 2795 | if (!keep_write) |
ff9c745b MW |
2796 | xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE); |
2797 | xas_unlock_irqrestore(&xas, flags); | |
1da177e4 LT |
2798 | } else { |
2799 | ret = TestSetPageWriteback(page); | |
2800 | } | |
3a3c02ec | 2801 | if (!ret) { |
00f3ca2c | 2802 | inc_lruvec_page_state(page, NR_WRITEBACK); |
5a1c84b4 | 2803 | inc_zone_page_state(page, NR_ZONE_WRITE_PENDING); |
3a3c02ec | 2804 | } |
62cccb8c | 2805 | unlock_page_memcg(page); |
1da177e4 LT |
2806 | return ret; |
2807 | ||
2808 | } | |
1c8349a1 | 2809 | EXPORT_SYMBOL(__test_set_page_writeback); |
1da177e4 | 2810 | |
1d1d1a76 DW |
2811 | /** |
2812 | * wait_for_stable_page() - wait for writeback to finish, if necessary. | |
2813 | * @page: The page to wait on. | |
2814 | * | |
2815 | * This function determines if the given page is related to a backing device | |
2816 | * that requires page contents to be held stable during writeback. If so, then | |
2817 | * it will wait for any pending writeback to complete. | |
2818 | */ | |
2819 | void wait_for_stable_page(struct page *page) | |
2820 | { | |
de1414a6 CH |
2821 | if (bdi_cap_stable_pages_required(inode_to_bdi(page->mapping->host))) |
2822 | wait_on_page_writeback(page); | |
1d1d1a76 DW |
2823 | } |
2824 | EXPORT_SYMBOL_GPL(wait_for_stable_page); |