| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * mm/page-writeback.c |
| 4 | * |
| 5 | * Copyright (C) 2002, Linus Torvalds. |
| 6 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra |
| 7 | * |
| 8 | * Contains functions related to writing back dirty pages at the |
| 9 | * address_space level. |
| 10 | * |
| 11 | * 10Apr2002 Andrew Morton |
| 12 | * Initial version |
| 13 | */ |
| 14 | |
| 15 | #include <linux/kernel.h> |
| 16 | #include <linux/math64.h> |
| 17 | #include <linux/export.h> |
| 18 | #include <linux/spinlock.h> |
| 19 | #include <linux/fs.h> |
| 20 | #include <linux/mm.h> |
| 21 | #include <linux/swap.h> |
| 22 | #include <linux/slab.h> |
| 23 | #include <linux/pagemap.h> |
| 24 | #include <linux/writeback.h> |
| 25 | #include <linux/init.h> |
| 26 | #include <linux/backing-dev.h> |
| 27 | #include <linux/task_io_accounting_ops.h> |
| 28 | #include <linux/blkdev.h> |
| 29 | #include <linux/mpage.h> |
| 30 | #include <linux/rmap.h> |
| 31 | #include <linux/percpu.h> |
| 32 | #include <linux/smp.h> |
| 33 | #include <linux/sysctl.h> |
| 34 | #include <linux/cpu.h> |
| 35 | #include <linux/syscalls.h> |
| 36 | #include <linux/pagevec.h> |
| 37 | #include <linux/timer.h> |
| 38 | #include <linux/sched/rt.h> |
| 39 | #include <linux/sched/signal.h> |
| 40 | #include <linux/mm_inline.h> |
| 41 | #include <trace/events/writeback.h> |
| 42 | |
| 43 | #include "internal.h" |
| 44 | |
| 45 | /* |
| 46 | * Sleep at most 200ms at a time in balance_dirty_pages(). |
| 47 | */ |
| 48 | #define MAX_PAUSE max(HZ/5, 1) |
| 49 | |
| 50 | /* |
| 51 | * Try to keep balance_dirty_pages() call intervals higher than this many pages |
| 52 | * by raising pause time to max_pause when falls below it. |
| 53 | */ |
| 54 | #define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) |
| 55 | |
| 56 | /* |
| 57 | * Estimate write bandwidth at 200ms intervals. |
| 58 | */ |
| 59 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) |
| 60 | |
| 61 | #define RATELIMIT_CALC_SHIFT 10 |
| 62 | |
| 63 | /* |
| 64 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited |
| 65 | * will look to see if it needs to force writeback or throttling. |
| 66 | */ |
| 67 | static long ratelimit_pages = 32; |
| 68 | |
| 69 | /* The following parameters are exported via /proc/sys/vm */ |
| 70 | |
| 71 | /* |
| 72 | * Start background writeback (via writeback threads) at this percentage |
| 73 | */ |
| 74 | static int dirty_background_ratio = 10; |
| 75 | |
| 76 | /* |
| 77 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of |
| 78 | * dirty_background_ratio * the amount of dirtyable memory |
| 79 | */ |
| 80 | static unsigned long dirty_background_bytes; |
| 81 | |
| 82 | /* |
| 83 | * free highmem will not be subtracted from the total free memory |
| 84 | * for calculating free ratios if vm_highmem_is_dirtyable is true |
| 85 | */ |
| 86 | static int vm_highmem_is_dirtyable; |
| 87 | |
| 88 | /* |
| 89 | * The generator of dirty data starts writeback at this percentage |
| 90 | */ |
| 91 | static int vm_dirty_ratio = 20; |
| 92 | |
| 93 | /* |
| 94 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of |
| 95 | * vm_dirty_ratio * the amount of dirtyable memory |
| 96 | */ |
| 97 | static unsigned long vm_dirty_bytes; |
| 98 | |
| 99 | /* |
| 100 | * The interval between `kupdate'-style writebacks |
| 101 | */ |
| 102 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
| 103 | |
| 104 | EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
| 105 | |
| 106 | /* |
| 107 | * The longest time for which data is allowed to remain dirty |
| 108 | */ |
| 109 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
| 110 | |
| 111 | /* |
| 112 | * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies: |
| 113 | * a full sync is triggered after this time elapses without any disk activity. |
| 114 | */ |
| 115 | int laptop_mode; |
| 116 | |
| 117 | EXPORT_SYMBOL(laptop_mode); |
| 118 | |
| 119 | /* End of sysctl-exported parameters */ |
| 120 | |
| 121 | struct wb_domain global_wb_domain; |
| 122 | |
| 123 | /* consolidated parameters for balance_dirty_pages() and its subroutines */ |
| 124 | struct dirty_throttle_control { |
| 125 | #ifdef CONFIG_CGROUP_WRITEBACK |
| 126 | struct wb_domain *dom; |
| 127 | struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ |
| 128 | #endif |
| 129 | struct bdi_writeback *wb; |
| 130 | struct fprop_local_percpu *wb_completions; |
| 131 | |
| 132 | unsigned long avail; /* dirtyable */ |
| 133 | unsigned long dirty; /* file_dirty + write + nfs */ |
| 134 | unsigned long thresh; /* dirty threshold */ |
| 135 | unsigned long bg_thresh; /* dirty background threshold */ |
| 136 | |
| 137 | unsigned long wb_dirty; /* per-wb counterparts */ |
| 138 | unsigned long wb_thresh; |
| 139 | unsigned long wb_bg_thresh; |
| 140 | |
| 141 | unsigned long pos_ratio; |
| 142 | }; |
| 143 | |
| 144 | /* |
| 145 | * Length of period for aging writeout fractions of bdis. This is an |
| 146 | * arbitrarily chosen number. The longer the period, the slower fractions will |
| 147 | * reflect changes in current writeout rate. |
| 148 | */ |
| 149 | #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) |
| 150 | |
| 151 | #ifdef CONFIG_CGROUP_WRITEBACK |
| 152 | |
| 153 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
| 154 | .dom = &global_wb_domain, \ |
| 155 | .wb_completions = &(__wb)->completions |
| 156 | |
| 157 | #define GDTC_INIT_NO_WB .dom = &global_wb_domain |
| 158 | |
| 159 | #define MDTC_INIT(__wb, __gdtc) .wb = (__wb), \ |
| 160 | .dom = mem_cgroup_wb_domain(__wb), \ |
| 161 | .wb_completions = &(__wb)->memcg_completions, \ |
| 162 | .gdtc = __gdtc |
| 163 | |
| 164 | static bool mdtc_valid(struct dirty_throttle_control *dtc) |
| 165 | { |
| 166 | return dtc->dom; |
| 167 | } |
| 168 | |
| 169 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) |
| 170 | { |
| 171 | return dtc->dom; |
| 172 | } |
| 173 | |
| 174 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
| 175 | { |
| 176 | return mdtc->gdtc; |
| 177 | } |
| 178 | |
| 179 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
| 180 | { |
| 181 | return &wb->memcg_completions; |
| 182 | } |
| 183 | |
| 184 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
| 185 | unsigned long *minp, unsigned long *maxp) |
| 186 | { |
| 187 | unsigned long this_bw = READ_ONCE(wb->avg_write_bandwidth); |
| 188 | unsigned long tot_bw = atomic_long_read(&wb->bdi->tot_write_bandwidth); |
| 189 | unsigned long long min = wb->bdi->min_ratio; |
| 190 | unsigned long long max = wb->bdi->max_ratio; |
| 191 | |
| 192 | /* |
| 193 | * @wb may already be clean by the time control reaches here and |
| 194 | * the total may not include its bw. |
| 195 | */ |
| 196 | if (this_bw < tot_bw) { |
| 197 | if (min) { |
| 198 | min *= this_bw; |
| 199 | min = div64_ul(min, tot_bw); |
| 200 | } |
| 201 | if (max < 100 * BDI_RATIO_SCALE) { |
| 202 | max *= this_bw; |
| 203 | max = div64_ul(max, tot_bw); |
| 204 | } |
| 205 | } |
| 206 | |
| 207 | *minp = min; |
| 208 | *maxp = max; |
| 209 | } |
| 210 | |
| 211 | #else /* CONFIG_CGROUP_WRITEBACK */ |
| 212 | |
| 213 | #define GDTC_INIT(__wb) .wb = (__wb), \ |
| 214 | .wb_completions = &(__wb)->completions |
| 215 | #define GDTC_INIT_NO_WB |
| 216 | #define MDTC_INIT(__wb, __gdtc) |
| 217 | |
| 218 | static bool mdtc_valid(struct dirty_throttle_control *dtc) |
| 219 | { |
| 220 | return false; |
| 221 | } |
| 222 | |
| 223 | static struct wb_domain *dtc_dom(struct dirty_throttle_control *dtc) |
| 224 | { |
| 225 | return &global_wb_domain; |
| 226 | } |
| 227 | |
| 228 | static struct dirty_throttle_control *mdtc_gdtc(struct dirty_throttle_control *mdtc) |
| 229 | { |
| 230 | return NULL; |
| 231 | } |
| 232 | |
| 233 | static struct fprop_local_percpu *wb_memcg_completions(struct bdi_writeback *wb) |
| 234 | { |
| 235 | return NULL; |
| 236 | } |
| 237 | |
| 238 | static void wb_min_max_ratio(struct bdi_writeback *wb, |
| 239 | unsigned long *minp, unsigned long *maxp) |
| 240 | { |
| 241 | *minp = wb->bdi->min_ratio; |
| 242 | *maxp = wb->bdi->max_ratio; |
| 243 | } |
| 244 | |
| 245 | #endif /* CONFIG_CGROUP_WRITEBACK */ |
| 246 | |
| 247 | /* |
| 248 | * In a memory zone, there is a certain amount of pages we consider |
| 249 | * available for the page cache, which is essentially the number of |
| 250 | * free and reclaimable pages, minus some zone reserves to protect |
| 251 | * lowmem and the ability to uphold the zone's watermarks without |
| 252 | * requiring writeback. |
| 253 | * |
| 254 | * This number of dirtyable pages is the base value of which the |
| 255 | * user-configurable dirty ratio is the effective number of pages that |
| 256 | * are allowed to be actually dirtied. Per individual zone, or |
| 257 | * globally by using the sum of dirtyable pages over all zones. |
| 258 | * |
| 259 | * Because the user is allowed to specify the dirty limit globally as |
| 260 | * absolute number of bytes, calculating the per-zone dirty limit can |
| 261 | * require translating the configured limit into a percentage of |
| 262 | * global dirtyable memory first. |
| 263 | */ |
| 264 | |
| 265 | /** |
| 266 | * node_dirtyable_memory - number of dirtyable pages in a node |
| 267 | * @pgdat: the node |
| 268 | * |
| 269 | * Return: the node's number of pages potentially available for dirty |
| 270 | * page cache. This is the base value for the per-node dirty limits. |
| 271 | */ |
| 272 | static unsigned long node_dirtyable_memory(struct pglist_data *pgdat) |
| 273 | { |
| 274 | unsigned long nr_pages = 0; |
| 275 | int z; |
| 276 | |
| 277 | for (z = 0; z < MAX_NR_ZONES; z++) { |
| 278 | struct zone *zone = pgdat->node_zones + z; |
| 279 | |
| 280 | if (!populated_zone(zone)) |
| 281 | continue; |
| 282 | |
| 283 | nr_pages += zone_page_state(zone, NR_FREE_PAGES); |
| 284 | } |
| 285 | |
| 286 | /* |
| 287 | * Pages reserved for the kernel should not be considered |
| 288 | * dirtyable, to prevent a situation where reclaim has to |
| 289 | * clean pages in order to balance the zones. |
| 290 | */ |
| 291 | nr_pages -= min(nr_pages, pgdat->totalreserve_pages); |
| 292 | |
| 293 | nr_pages += node_page_state(pgdat, NR_INACTIVE_FILE); |
| 294 | nr_pages += node_page_state(pgdat, NR_ACTIVE_FILE); |
| 295 | |
| 296 | return nr_pages; |
| 297 | } |
| 298 | |
| 299 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
| 300 | { |
| 301 | #ifdef CONFIG_HIGHMEM |
| 302 | int node; |
| 303 | unsigned long x = 0; |
| 304 | int i; |
| 305 | |
| 306 | for_each_node_state(node, N_HIGH_MEMORY) { |
| 307 | for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { |
| 308 | struct zone *z; |
| 309 | unsigned long nr_pages; |
| 310 | |
| 311 | if (!is_highmem_idx(i)) |
| 312 | continue; |
| 313 | |
| 314 | z = &NODE_DATA(node)->node_zones[i]; |
| 315 | if (!populated_zone(z)) |
| 316 | continue; |
| 317 | |
| 318 | nr_pages = zone_page_state(z, NR_FREE_PAGES); |
| 319 | /* watch for underflows */ |
| 320 | nr_pages -= min(nr_pages, high_wmark_pages(z)); |
| 321 | nr_pages += zone_page_state(z, NR_ZONE_INACTIVE_FILE); |
| 322 | nr_pages += zone_page_state(z, NR_ZONE_ACTIVE_FILE); |
| 323 | x += nr_pages; |
| 324 | } |
| 325 | } |
| 326 | |
| 327 | /* |
| 328 | * Make sure that the number of highmem pages is never larger |
| 329 | * than the number of the total dirtyable memory. This can only |
| 330 | * occur in very strange VM situations but we want to make sure |
| 331 | * that this does not occur. |
| 332 | */ |
| 333 | return min(x, total); |
| 334 | #else |
| 335 | return 0; |
| 336 | #endif |
| 337 | } |
| 338 | |
| 339 | /** |
| 340 | * global_dirtyable_memory - number of globally dirtyable pages |
| 341 | * |
| 342 | * Return: the global number of pages potentially available for dirty |
| 343 | * page cache. This is the base value for the global dirty limits. |
| 344 | */ |
| 345 | static unsigned long global_dirtyable_memory(void) |
| 346 | { |
| 347 | unsigned long x; |
| 348 | |
| 349 | x = global_zone_page_state(NR_FREE_PAGES); |
| 350 | /* |
| 351 | * Pages reserved for the kernel should not be considered |
| 352 | * dirtyable, to prevent a situation where reclaim has to |
| 353 | * clean pages in order to balance the zones. |
| 354 | */ |
| 355 | x -= min(x, totalreserve_pages); |
| 356 | |
| 357 | x += global_node_page_state(NR_INACTIVE_FILE); |
| 358 | x += global_node_page_state(NR_ACTIVE_FILE); |
| 359 | |
| 360 | if (!vm_highmem_is_dirtyable) |
| 361 | x -= highmem_dirtyable_memory(x); |
| 362 | |
| 363 | return x + 1; /* Ensure that we never return 0 */ |
| 364 | } |
| 365 | |
| 366 | /** |
| 367 | * domain_dirty_limits - calculate thresh and bg_thresh for a wb_domain |
| 368 | * @dtc: dirty_throttle_control of interest |
| 369 | * |
| 370 | * Calculate @dtc->thresh and ->bg_thresh considering |
| 371 | * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. The caller |
| 372 | * must ensure that @dtc->avail is set before calling this function. The |
| 373 | * dirty limits will be lifted by 1/4 for real-time tasks. |
| 374 | */ |
| 375 | static void domain_dirty_limits(struct dirty_throttle_control *dtc) |
| 376 | { |
| 377 | const unsigned long available_memory = dtc->avail; |
| 378 | struct dirty_throttle_control *gdtc = mdtc_gdtc(dtc); |
| 379 | unsigned long bytes = vm_dirty_bytes; |
| 380 | unsigned long bg_bytes = dirty_background_bytes; |
| 381 | /* convert ratios to per-PAGE_SIZE for higher precision */ |
| 382 | unsigned long ratio = (vm_dirty_ratio * PAGE_SIZE) / 100; |
| 383 | unsigned long bg_ratio = (dirty_background_ratio * PAGE_SIZE) / 100; |
| 384 | unsigned long thresh; |
| 385 | unsigned long bg_thresh; |
| 386 | struct task_struct *tsk; |
| 387 | |
| 388 | /* gdtc is !NULL iff @dtc is for memcg domain */ |
| 389 | if (gdtc) { |
| 390 | unsigned long global_avail = gdtc->avail; |
| 391 | |
| 392 | /* |
| 393 | * The byte settings can't be applied directly to memcg |
| 394 | * domains. Convert them to ratios by scaling against |
| 395 | * globally available memory. As the ratios are in |
| 396 | * per-PAGE_SIZE, they can be obtained by dividing bytes by |
| 397 | * number of pages. |
| 398 | */ |
| 399 | if (bytes) |
| 400 | ratio = min(DIV_ROUND_UP(bytes, global_avail), |
| 401 | PAGE_SIZE); |
| 402 | if (bg_bytes) |
| 403 | bg_ratio = min(DIV_ROUND_UP(bg_bytes, global_avail), |
| 404 | PAGE_SIZE); |
| 405 | bytes = bg_bytes = 0; |
| 406 | } |
| 407 | |
| 408 | if (bytes) |
| 409 | thresh = DIV_ROUND_UP(bytes, PAGE_SIZE); |
| 410 | else |
| 411 | thresh = (ratio * available_memory) / PAGE_SIZE; |
| 412 | |
| 413 | if (bg_bytes) |
| 414 | bg_thresh = DIV_ROUND_UP(bg_bytes, PAGE_SIZE); |
| 415 | else |
| 416 | bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE; |
| 417 | |
| 418 | if (bg_thresh >= thresh) |
| 419 | bg_thresh = thresh / 2; |
| 420 | tsk = current; |
| 421 | if (rt_task(tsk)) { |
| 422 | bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32; |
| 423 | thresh += thresh / 4 + global_wb_domain.dirty_limit / 32; |
| 424 | } |
| 425 | dtc->thresh = thresh; |
| 426 | dtc->bg_thresh = bg_thresh; |
| 427 | |
| 428 | /* we should eventually report the domain in the TP */ |
| 429 | if (!gdtc) |
| 430 | trace_global_dirty_state(bg_thresh, thresh); |
| 431 | } |
| 432 | |
| 433 | /** |
| 434 | * global_dirty_limits - background-writeback and dirty-throttling thresholds |
| 435 | * @pbackground: out parameter for bg_thresh |
| 436 | * @pdirty: out parameter for thresh |
| 437 | * |
| 438 | * Calculate bg_thresh and thresh for global_wb_domain. See |
| 439 | * domain_dirty_limits() for details. |
| 440 | */ |
| 441 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
| 442 | { |
| 443 | struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB }; |
| 444 | |
| 445 | gdtc.avail = global_dirtyable_memory(); |
| 446 | domain_dirty_limits(&gdtc); |
| 447 | |
| 448 | *pbackground = gdtc.bg_thresh; |
| 449 | *pdirty = gdtc.thresh; |
| 450 | } |
| 451 | |
| 452 | /** |
| 453 | * node_dirty_limit - maximum number of dirty pages allowed in a node |
| 454 | * @pgdat: the node |
| 455 | * |
| 456 | * Return: the maximum number of dirty pages allowed in a node, based |
| 457 | * on the node's dirtyable memory. |
| 458 | */ |
| 459 | static unsigned long node_dirty_limit(struct pglist_data *pgdat) |
| 460 | { |
| 461 | unsigned long node_memory = node_dirtyable_memory(pgdat); |
| 462 | struct task_struct *tsk = current; |
| 463 | unsigned long dirty; |
| 464 | |
| 465 | if (vm_dirty_bytes) |
| 466 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * |
| 467 | node_memory / global_dirtyable_memory(); |
| 468 | else |
| 469 | dirty = vm_dirty_ratio * node_memory / 100; |
| 470 | |
| 471 | if (rt_task(tsk)) |
| 472 | dirty += dirty / 4; |
| 473 | |
| 474 | return dirty; |
| 475 | } |
| 476 | |
| 477 | /** |
| 478 | * node_dirty_ok - tells whether a node is within its dirty limits |
| 479 | * @pgdat: the node to check |
| 480 | * |
| 481 | * Return: %true when the dirty pages in @pgdat are within the node's |
| 482 | * dirty limit, %false if the limit is exceeded. |
| 483 | */ |
| 484 | bool node_dirty_ok(struct pglist_data *pgdat) |
| 485 | { |
| 486 | unsigned long limit = node_dirty_limit(pgdat); |
| 487 | unsigned long nr_pages = 0; |
| 488 | |
| 489 | nr_pages += node_page_state(pgdat, NR_FILE_DIRTY); |
| 490 | nr_pages += node_page_state(pgdat, NR_WRITEBACK); |
| 491 | |
| 492 | return nr_pages <= limit; |
| 493 | } |
| 494 | |
| 495 | #ifdef CONFIG_SYSCTL |
| 496 | static int dirty_background_ratio_handler(struct ctl_table *table, int write, |
| 497 | void *buffer, size_t *lenp, loff_t *ppos) |
| 498 | { |
| 499 | int ret; |
| 500 | |
| 501 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
| 502 | if (ret == 0 && write) |
| 503 | dirty_background_bytes = 0; |
| 504 | return ret; |
| 505 | } |
| 506 | |
| 507 | static int dirty_background_bytes_handler(struct ctl_table *table, int write, |
| 508 | void *buffer, size_t *lenp, loff_t *ppos) |
| 509 | { |
| 510 | int ret; |
| 511 | |
| 512 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| 513 | if (ret == 0 && write) |
| 514 | dirty_background_ratio = 0; |
| 515 | return ret; |
| 516 | } |
| 517 | |
| 518 | static int dirty_ratio_handler(struct ctl_table *table, int write, void *buffer, |
| 519 | size_t *lenp, loff_t *ppos) |
| 520 | { |
| 521 | int old_ratio = vm_dirty_ratio; |
| 522 | int ret; |
| 523 | |
| 524 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
| 525 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
| 526 | writeback_set_ratelimit(); |
| 527 | vm_dirty_bytes = 0; |
| 528 | } |
| 529 | return ret; |
| 530 | } |
| 531 | |
| 532 | static int dirty_bytes_handler(struct ctl_table *table, int write, |
| 533 | void *buffer, size_t *lenp, loff_t *ppos) |
| 534 | { |
| 535 | unsigned long old_bytes = vm_dirty_bytes; |
| 536 | int ret; |
| 537 | |
| 538 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| 539 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
| 540 | writeback_set_ratelimit(); |
| 541 | vm_dirty_ratio = 0; |
| 542 | } |
| 543 | return ret; |
| 544 | } |
| 545 | #endif |
| 546 | |
| 547 | static unsigned long wp_next_time(unsigned long cur_time) |
| 548 | { |
| 549 | cur_time += VM_COMPLETIONS_PERIOD_LEN; |
| 550 | /* 0 has a special meaning... */ |
| 551 | if (!cur_time) |
| 552 | return 1; |
| 553 | return cur_time; |
| 554 | } |
| 555 | |
| 556 | static void wb_domain_writeout_add(struct wb_domain *dom, |
| 557 | struct fprop_local_percpu *completions, |
| 558 | unsigned int max_prop_frac, long nr) |
| 559 | { |
| 560 | __fprop_add_percpu_max(&dom->completions, completions, |
| 561 | max_prop_frac, nr); |
| 562 | /* First event after period switching was turned off? */ |
| 563 | if (unlikely(!dom->period_time)) { |
| 564 | /* |
| 565 | * We can race with other __bdi_writeout_inc calls here but |
| 566 | * it does not cause any harm since the resulting time when |
| 567 | * timer will fire and what is in writeout_period_time will be |
| 568 | * roughly the same. |
| 569 | */ |
| 570 | dom->period_time = wp_next_time(jiffies); |
| 571 | mod_timer(&dom->period_timer, dom->period_time); |
| 572 | } |
| 573 | } |
| 574 | |
| 575 | /* |
| 576 | * Increment @wb's writeout completion count and the global writeout |
| 577 | * completion count. Called from __folio_end_writeback(). |
| 578 | */ |
| 579 | static inline void __wb_writeout_add(struct bdi_writeback *wb, long nr) |
| 580 | { |
| 581 | struct wb_domain *cgdom; |
| 582 | |
| 583 | wb_stat_mod(wb, WB_WRITTEN, nr); |
| 584 | wb_domain_writeout_add(&global_wb_domain, &wb->completions, |
| 585 | wb->bdi->max_prop_frac, nr); |
| 586 | |
| 587 | cgdom = mem_cgroup_wb_domain(wb); |
| 588 | if (cgdom) |
| 589 | wb_domain_writeout_add(cgdom, wb_memcg_completions(wb), |
| 590 | wb->bdi->max_prop_frac, nr); |
| 591 | } |
| 592 | |
| 593 | void wb_writeout_inc(struct bdi_writeback *wb) |
| 594 | { |
| 595 | unsigned long flags; |
| 596 | |
| 597 | local_irq_save(flags); |
| 598 | __wb_writeout_add(wb, 1); |
| 599 | local_irq_restore(flags); |
| 600 | } |
| 601 | EXPORT_SYMBOL_GPL(wb_writeout_inc); |
| 602 | |
| 603 | /* |
| 604 | * On idle system, we can be called long after we scheduled because we use |
| 605 | * deferred timers so count with missed periods. |
| 606 | */ |
| 607 | static void writeout_period(struct timer_list *t) |
| 608 | { |
| 609 | struct wb_domain *dom = from_timer(dom, t, period_timer); |
| 610 | int miss_periods = (jiffies - dom->period_time) / |
| 611 | VM_COMPLETIONS_PERIOD_LEN; |
| 612 | |
| 613 | if (fprop_new_period(&dom->completions, miss_periods + 1)) { |
| 614 | dom->period_time = wp_next_time(dom->period_time + |
| 615 | miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
| 616 | mod_timer(&dom->period_timer, dom->period_time); |
| 617 | } else { |
| 618 | /* |
| 619 | * Aging has zeroed all fractions. Stop wasting CPU on period |
| 620 | * updates. |
| 621 | */ |
| 622 | dom->period_time = 0; |
| 623 | } |
| 624 | } |
| 625 | |
| 626 | int wb_domain_init(struct wb_domain *dom, gfp_t gfp) |
| 627 | { |
| 628 | memset(dom, 0, sizeof(*dom)); |
| 629 | |
| 630 | spin_lock_init(&dom->lock); |
| 631 | |
| 632 | timer_setup(&dom->period_timer, writeout_period, TIMER_DEFERRABLE); |
| 633 | |
| 634 | dom->dirty_limit_tstamp = jiffies; |
| 635 | |
| 636 | return fprop_global_init(&dom->completions, gfp); |
| 637 | } |
| 638 | |
| 639 | #ifdef CONFIG_CGROUP_WRITEBACK |
| 640 | void wb_domain_exit(struct wb_domain *dom) |
| 641 | { |
| 642 | del_timer_sync(&dom->period_timer); |
| 643 | fprop_global_destroy(&dom->completions); |
| 644 | } |
| 645 | #endif |
| 646 | |
| 647 | /* |
| 648 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
| 649 | * registered backing devices, which, for obvious reasons, can not |
| 650 | * exceed 100%. |
| 651 | */ |
| 652 | static unsigned int bdi_min_ratio; |
| 653 | |
| 654 | static int bdi_check_pages_limit(unsigned long pages) |
| 655 | { |
| 656 | unsigned long max_dirty_pages = global_dirtyable_memory(); |
| 657 | |
| 658 | if (pages > max_dirty_pages) |
| 659 | return -EINVAL; |
| 660 | |
| 661 | return 0; |
| 662 | } |
| 663 | |
| 664 | static unsigned long bdi_ratio_from_pages(unsigned long pages) |
| 665 | { |
| 666 | unsigned long background_thresh; |
| 667 | unsigned long dirty_thresh; |
| 668 | unsigned long ratio; |
| 669 | |
| 670 | global_dirty_limits(&background_thresh, &dirty_thresh); |
| 671 | ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); |
| 672 | |
| 673 | return ratio; |
| 674 | } |
| 675 | |
| 676 | static u64 bdi_get_bytes(unsigned int ratio) |
| 677 | { |
| 678 | unsigned long background_thresh; |
| 679 | unsigned long dirty_thresh; |
| 680 | u64 bytes; |
| 681 | |
| 682 | global_dirty_limits(&background_thresh, &dirty_thresh); |
| 683 | bytes = (dirty_thresh * PAGE_SIZE * ratio) / BDI_RATIO_SCALE / 100; |
| 684 | |
| 685 | return bytes; |
| 686 | } |
| 687 | |
| 688 | static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) |
| 689 | { |
| 690 | unsigned int delta; |
| 691 | int ret = 0; |
| 692 | |
| 693 | if (min_ratio > 100 * BDI_RATIO_SCALE) |
| 694 | return -EINVAL; |
| 695 | min_ratio *= BDI_RATIO_SCALE; |
| 696 | |
| 697 | spin_lock_bh(&bdi_lock); |
| 698 | if (min_ratio > bdi->max_ratio) { |
| 699 | ret = -EINVAL; |
| 700 | } else { |
| 701 | if (min_ratio < bdi->min_ratio) { |
| 702 | delta = bdi->min_ratio - min_ratio; |
| 703 | bdi_min_ratio -= delta; |
| 704 | bdi->min_ratio = min_ratio; |
| 705 | } else { |
| 706 | delta = min_ratio - bdi->min_ratio; |
| 707 | if (bdi_min_ratio + delta < 100 * BDI_RATIO_SCALE) { |
| 708 | bdi_min_ratio += delta; |
| 709 | bdi->min_ratio = min_ratio; |
| 710 | } else { |
| 711 | ret = -EINVAL; |
| 712 | } |
| 713 | } |
| 714 | } |
| 715 | spin_unlock_bh(&bdi_lock); |
| 716 | |
| 717 | return ret; |
| 718 | } |
| 719 | |
| 720 | static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio) |
| 721 | { |
| 722 | int ret = 0; |
| 723 | |
| 724 | if (max_ratio > 100 * BDI_RATIO_SCALE) |
| 725 | return -EINVAL; |
| 726 | |
| 727 | spin_lock_bh(&bdi_lock); |
| 728 | if (bdi->min_ratio > max_ratio) { |
| 729 | ret = -EINVAL; |
| 730 | } else { |
| 731 | bdi->max_ratio = max_ratio; |
| 732 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
| 733 | } |
| 734 | spin_unlock_bh(&bdi_lock); |
| 735 | |
| 736 | return ret; |
| 737 | } |
| 738 | |
| 739 | int bdi_set_min_ratio_no_scale(struct backing_dev_info *bdi, unsigned int min_ratio) |
| 740 | { |
| 741 | return __bdi_set_min_ratio(bdi, min_ratio); |
| 742 | } |
| 743 | |
| 744 | int bdi_set_max_ratio_no_scale(struct backing_dev_info *bdi, unsigned int max_ratio) |
| 745 | { |
| 746 | return __bdi_set_max_ratio(bdi, max_ratio); |
| 747 | } |
| 748 | |
| 749 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) |
| 750 | { |
| 751 | return __bdi_set_min_ratio(bdi, min_ratio * BDI_RATIO_SCALE); |
| 752 | } |
| 753 | |
| 754 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio) |
| 755 | { |
| 756 | return __bdi_set_max_ratio(bdi, max_ratio * BDI_RATIO_SCALE); |
| 757 | } |
| 758 | EXPORT_SYMBOL(bdi_set_max_ratio); |
| 759 | |
| 760 | u64 bdi_get_min_bytes(struct backing_dev_info *bdi) |
| 761 | { |
| 762 | return bdi_get_bytes(bdi->min_ratio); |
| 763 | } |
| 764 | |
| 765 | int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes) |
| 766 | { |
| 767 | int ret; |
| 768 | unsigned long pages = min_bytes >> PAGE_SHIFT; |
| 769 | unsigned long min_ratio; |
| 770 | |
| 771 | ret = bdi_check_pages_limit(pages); |
| 772 | if (ret) |
| 773 | return ret; |
| 774 | |
| 775 | min_ratio = bdi_ratio_from_pages(pages); |
| 776 | return __bdi_set_min_ratio(bdi, min_ratio); |
| 777 | } |
| 778 | |
| 779 | u64 bdi_get_max_bytes(struct backing_dev_info *bdi) |
| 780 | { |
| 781 | return bdi_get_bytes(bdi->max_ratio); |
| 782 | } |
| 783 | |
| 784 | int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 max_bytes) |
| 785 | { |
| 786 | int ret; |
| 787 | unsigned long pages = max_bytes >> PAGE_SHIFT; |
| 788 | unsigned long max_ratio; |
| 789 | |
| 790 | ret = bdi_check_pages_limit(pages); |
| 791 | if (ret) |
| 792 | return ret; |
| 793 | |
| 794 | max_ratio = bdi_ratio_from_pages(pages); |
| 795 | return __bdi_set_max_ratio(bdi, max_ratio); |
| 796 | } |
| 797 | |
| 798 | int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit) |
| 799 | { |
| 800 | if (strict_limit > 1) |
| 801 | return -EINVAL; |
| 802 | |
| 803 | spin_lock_bh(&bdi_lock); |
| 804 | if (strict_limit) |
| 805 | bdi->capabilities |= BDI_CAP_STRICTLIMIT; |
| 806 | else |
| 807 | bdi->capabilities &= ~BDI_CAP_STRICTLIMIT; |
| 808 | spin_unlock_bh(&bdi_lock); |
| 809 | |
| 810 | return 0; |
| 811 | } |
| 812 | |
| 813 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
| 814 | unsigned long bg_thresh) |
| 815 | { |
| 816 | return (thresh + bg_thresh) / 2; |
| 817 | } |
| 818 | |
| 819 | static unsigned long hard_dirty_limit(struct wb_domain *dom, |
| 820 | unsigned long thresh) |
| 821 | { |
| 822 | return max(thresh, dom->dirty_limit); |
| 823 | } |
| 824 | |
| 825 | /* |
| 826 | * Memory which can be further allocated to a memcg domain is capped by |
| 827 | * system-wide clean memory excluding the amount being used in the domain. |
| 828 | */ |
| 829 | static void mdtc_calc_avail(struct dirty_throttle_control *mdtc, |
| 830 | unsigned long filepages, unsigned long headroom) |
| 831 | { |
| 832 | struct dirty_throttle_control *gdtc = mdtc_gdtc(mdtc); |
| 833 | unsigned long clean = filepages - min(filepages, mdtc->dirty); |
| 834 | unsigned long global_clean = gdtc->avail - min(gdtc->avail, gdtc->dirty); |
| 835 | unsigned long other_clean = global_clean - min(global_clean, clean); |
| 836 | |
| 837 | mdtc->avail = filepages + min(headroom, other_clean); |
| 838 | } |
| 839 | |
| 840 | /** |
| 841 | * __wb_calc_thresh - @wb's share of dirty throttling threshold |
| 842 | * @dtc: dirty_throttle_context of interest |
| 843 | * |
| 844 | * Note that balance_dirty_pages() will only seriously take it as a hard limit |
| 845 | * when sleeping max_pause per page is not enough to keep the dirty pages under |
| 846 | * control. For example, when the device is completely stalled due to some error |
| 847 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. |
| 848 | * In the other normal situations, it acts more gently by throttling the tasks |
| 849 | * more (rather than completely block them) when the wb dirty pages go high. |
| 850 | * |
| 851 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
| 852 | * - starving fast devices |
| 853 | * - piling up dirty pages (that will take long time to sync) on slow devices |
| 854 | * |
| 855 | * The wb's share of dirty limit will be adapting to its throughput and |
| 856 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
| 857 | * |
| 858 | * Return: @wb's dirty limit in pages. The term "dirty" in the context of |
| 859 | * dirty balancing includes all PG_dirty and PG_writeback pages. |
| 860 | */ |
| 861 | static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) |
| 862 | { |
| 863 | struct wb_domain *dom = dtc_dom(dtc); |
| 864 | unsigned long thresh = dtc->thresh; |
| 865 | u64 wb_thresh; |
| 866 | unsigned long numerator, denominator; |
| 867 | unsigned long wb_min_ratio, wb_max_ratio; |
| 868 | |
| 869 | /* |
| 870 | * Calculate this BDI's share of the thresh ratio. |
| 871 | */ |
| 872 | fprop_fraction_percpu(&dom->completions, dtc->wb_completions, |
| 873 | &numerator, &denominator); |
| 874 | |
| 875 | wb_thresh = (thresh * (100 * BDI_RATIO_SCALE - bdi_min_ratio)) / (100 * BDI_RATIO_SCALE); |
| 876 | wb_thresh *= numerator; |
| 877 | wb_thresh = div64_ul(wb_thresh, denominator); |
| 878 | |
| 879 | wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); |
| 880 | |
| 881 | wb_thresh += (thresh * wb_min_ratio) / (100 * BDI_RATIO_SCALE); |
| 882 | if (wb_thresh > (thresh * wb_max_ratio) / (100 * BDI_RATIO_SCALE)) |
| 883 | wb_thresh = thresh * wb_max_ratio / (100 * BDI_RATIO_SCALE); |
| 884 | |
| 885 | return wb_thresh; |
| 886 | } |
| 887 | |
| 888 | unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) |
| 889 | { |
| 890 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb), |
| 891 | .thresh = thresh }; |
| 892 | return __wb_calc_thresh(&gdtc); |
| 893 | } |
| 894 | |
| 895 | /* |
| 896 | * setpoint - dirty 3 |
| 897 | * f(dirty) := 1.0 + (----------------) |
| 898 | * limit - setpoint |
| 899 | * |
| 900 | * it's a 3rd order polynomial that subjects to |
| 901 | * |
| 902 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast |
| 903 | * (2) f(setpoint) = 1.0 => the balance point |
| 904 | * (3) f(limit) = 0 => the hard limit |
| 905 | * (4) df/dx <= 0 => negative feedback control |
| 906 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) |
| 907 | * => fast response on large errors; small oscillation near setpoint |
| 908 | */ |
| 909 | static long long pos_ratio_polynom(unsigned long setpoint, |
| 910 | unsigned long dirty, |
| 911 | unsigned long limit) |
| 912 | { |
| 913 | long long pos_ratio; |
| 914 | long x; |
| 915 | |
| 916 | x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, |
| 917 | (limit - setpoint) | 1); |
| 918 | pos_ratio = x; |
| 919 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; |
| 920 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; |
| 921 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; |
| 922 | |
| 923 | return clamp(pos_ratio, 0LL, 2LL << RATELIMIT_CALC_SHIFT); |
| 924 | } |
| 925 | |
| 926 | /* |
| 927 | * Dirty position control. |
| 928 | * |
| 929 | * (o) global/bdi setpoints |
| 930 | * |
| 931 | * We want the dirty pages be balanced around the global/wb setpoints. |
| 932 | * When the number of dirty pages is higher/lower than the setpoint, the |
| 933 | * dirty position control ratio (and hence task dirty ratelimit) will be |
| 934 | * decreased/increased to bring the dirty pages back to the setpoint. |
| 935 | * |
| 936 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT |
| 937 | * |
| 938 | * if (dirty < setpoint) scale up pos_ratio |
| 939 | * if (dirty > setpoint) scale down pos_ratio |
| 940 | * |
| 941 | * if (wb_dirty < wb_setpoint) scale up pos_ratio |
| 942 | * if (wb_dirty > wb_setpoint) scale down pos_ratio |
| 943 | * |
| 944 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT |
| 945 | * |
| 946 | * (o) global control line |
| 947 | * |
| 948 | * ^ pos_ratio |
| 949 | * | |
| 950 | * | |<===== global dirty control scope ======>| |
| 951 | * 2.0 * * * * * * * |
| 952 | * | .* |
| 953 | * | . * |
| 954 | * | . * |
| 955 | * | . * |
| 956 | * | . * |
| 957 | * | . * |
| 958 | * 1.0 ................................* |
| 959 | * | . . * |
| 960 | * | . . * |
| 961 | * | . . * |
| 962 | * | . . * |
| 963 | * | . . * |
| 964 | * 0 +------------.------------------.----------------------*-------------> |
| 965 | * freerun^ setpoint^ limit^ dirty pages |
| 966 | * |
| 967 | * (o) wb control line |
| 968 | * |
| 969 | * ^ pos_ratio |
| 970 | * | |
| 971 | * | * |
| 972 | * | * |
| 973 | * | * |
| 974 | * | * |
| 975 | * | * |<=========== span ============>| |
| 976 | * 1.0 .......................* |
| 977 | * | . * |
| 978 | * | . * |
| 979 | * | . * |
| 980 | * | . * |
| 981 | * | . * |
| 982 | * | . * |
| 983 | * | . * |
| 984 | * | . * |
| 985 | * | . * |
| 986 | * | . * |
| 987 | * | . * |
| 988 | * 1/4 ...............................................* * * * * * * * * * * * |
| 989 | * | . . |
| 990 | * | . . |
| 991 | * | . . |
| 992 | * 0 +----------------------.-------------------------------.-------------> |
| 993 | * wb_setpoint^ x_intercept^ |
| 994 | * |
| 995 | * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can |
| 996 | * be smoothly throttled down to normal if it starts high in situations like |
| 997 | * - start writing to a slow SD card and a fast disk at the same time. The SD |
| 998 | * card's wb_dirty may rush to many times higher than wb_setpoint. |
| 999 | * - the wb dirty thresh drops quickly due to change of JBOD workload |
| 1000 | */ |
| 1001 | static void wb_position_ratio(struct dirty_throttle_control *dtc) |
| 1002 | { |
| 1003 | struct bdi_writeback *wb = dtc->wb; |
| 1004 | unsigned long write_bw = READ_ONCE(wb->avg_write_bandwidth); |
| 1005 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
| 1006 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
| 1007 | unsigned long wb_thresh = dtc->wb_thresh; |
| 1008 | unsigned long x_intercept; |
| 1009 | unsigned long setpoint; /* dirty pages' target balance point */ |
| 1010 | unsigned long wb_setpoint; |
| 1011 | unsigned long span; |
| 1012 | long long pos_ratio; /* for scaling up/down the rate limit */ |
| 1013 | long x; |
| 1014 | |
| 1015 | dtc->pos_ratio = 0; |
| 1016 | |
| 1017 | if (unlikely(dtc->dirty >= limit)) |
| 1018 | return; |
| 1019 | |
| 1020 | /* |
| 1021 | * global setpoint |
| 1022 | * |
| 1023 | * See comment for pos_ratio_polynom(). |
| 1024 | */ |
| 1025 | setpoint = (freerun + limit) / 2; |
| 1026 | pos_ratio = pos_ratio_polynom(setpoint, dtc->dirty, limit); |
| 1027 | |
| 1028 | /* |
| 1029 | * The strictlimit feature is a tool preventing mistrusted filesystems |
| 1030 | * from growing a large number of dirty pages before throttling. For |
| 1031 | * such filesystems balance_dirty_pages always checks wb counters |
| 1032 | * against wb limits. Even if global "nr_dirty" is under "freerun". |
| 1033 | * This is especially important for fuse which sets bdi->max_ratio to |
| 1034 | * 1% by default. Without strictlimit feature, fuse writeback may |
| 1035 | * consume arbitrary amount of RAM because it is accounted in |
| 1036 | * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". |
| 1037 | * |
| 1038 | * Here, in wb_position_ratio(), we calculate pos_ratio based on |
| 1039 | * two values: wb_dirty and wb_thresh. Let's consider an example: |
| 1040 | * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global |
| 1041 | * limits are set by default to 10% and 20% (background and throttle). |
| 1042 | * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. |
| 1043 | * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is |
| 1044 | * about ~6K pages (as the average of background and throttle wb |
| 1045 | * limits). The 3rd order polynomial will provide positive feedback if |
| 1046 | * wb_dirty is under wb_setpoint and vice versa. |
| 1047 | * |
| 1048 | * Note, that we cannot use global counters in these calculations |
| 1049 | * because we want to throttle process writing to a strictlimit wb |
| 1050 | * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB |
| 1051 | * in the example above). |
| 1052 | */ |
| 1053 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
| 1054 | long long wb_pos_ratio; |
| 1055 | |
| 1056 | if (dtc->wb_dirty < 8) { |
| 1057 | dtc->pos_ratio = min_t(long long, pos_ratio * 2, |
| 1058 | 2 << RATELIMIT_CALC_SHIFT); |
| 1059 | return; |
| 1060 | } |
| 1061 | |
| 1062 | if (dtc->wb_dirty >= wb_thresh) |
| 1063 | return; |
| 1064 | |
| 1065 | wb_setpoint = dirty_freerun_ceiling(wb_thresh, |
| 1066 | dtc->wb_bg_thresh); |
| 1067 | |
| 1068 | if (wb_setpoint == 0 || wb_setpoint == wb_thresh) |
| 1069 | return; |
| 1070 | |
| 1071 | wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, |
| 1072 | wb_thresh); |
| 1073 | |
| 1074 | /* |
| 1075 | * Typically, for strictlimit case, wb_setpoint << setpoint |
| 1076 | * and pos_ratio >> wb_pos_ratio. In the other words global |
| 1077 | * state ("dirty") is not limiting factor and we have to |
| 1078 | * make decision based on wb counters. But there is an |
| 1079 | * important case when global pos_ratio should get precedence: |
| 1080 | * global limits are exceeded (e.g. due to activities on other |
| 1081 | * wb's) while given strictlimit wb is below limit. |
| 1082 | * |
| 1083 | * "pos_ratio * wb_pos_ratio" would work for the case above, |
| 1084 | * but it would look too non-natural for the case of all |
| 1085 | * activity in the system coming from a single strictlimit wb |
| 1086 | * with bdi->max_ratio == 100%. |
| 1087 | * |
| 1088 | * Note that min() below somewhat changes the dynamics of the |
| 1089 | * control system. Normally, pos_ratio value can be well over 3 |
| 1090 | * (when globally we are at freerun and wb is well below wb |
| 1091 | * setpoint). Now the maximum pos_ratio in the same situation |
| 1092 | * is 2. We might want to tweak this if we observe the control |
| 1093 | * system is too slow to adapt. |
| 1094 | */ |
| 1095 | dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); |
| 1096 | return; |
| 1097 | } |
| 1098 | |
| 1099 | /* |
| 1100 | * We have computed basic pos_ratio above based on global situation. If |
| 1101 | * the wb is over/under its share of dirty pages, we want to scale |
| 1102 | * pos_ratio further down/up. That is done by the following mechanism. |
| 1103 | */ |
| 1104 | |
| 1105 | /* |
| 1106 | * wb setpoint |
| 1107 | * |
| 1108 | * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) |
| 1109 | * |
| 1110 | * x_intercept - wb_dirty |
| 1111 | * := -------------------------- |
| 1112 | * x_intercept - wb_setpoint |
| 1113 | * |
| 1114 | * The main wb control line is a linear function that subjects to |
| 1115 | * |
| 1116 | * (1) f(wb_setpoint) = 1.0 |
| 1117 | * (2) k = - 1 / (8 * write_bw) (in single wb case) |
| 1118 | * or equally: x_intercept = wb_setpoint + 8 * write_bw |
| 1119 | * |
| 1120 | * For single wb case, the dirty pages are observed to fluctuate |
| 1121 | * regularly within range |
| 1122 | * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] |
| 1123 | * for various filesystems, where (2) can yield in a reasonable 12.5% |
| 1124 | * fluctuation range for pos_ratio. |
| 1125 | * |
| 1126 | * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its |
| 1127 | * own size, so move the slope over accordingly and choose a slope that |
| 1128 | * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. |
| 1129 | */ |
| 1130 | if (unlikely(wb_thresh > dtc->thresh)) |
| 1131 | wb_thresh = dtc->thresh; |
| 1132 | /* |
| 1133 | * It's very possible that wb_thresh is close to 0 not because the |
| 1134 | * device is slow, but that it has remained inactive for long time. |
| 1135 | * Honour such devices a reasonable good (hopefully IO efficient) |
| 1136 | * threshold, so that the occasional writes won't be blocked and active |
| 1137 | * writes can rampup the threshold quickly. |
| 1138 | */ |
| 1139 | wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8); |
| 1140 | /* |
| 1141 | * scale global setpoint to wb's: |
| 1142 | * wb_setpoint = setpoint * wb_thresh / thresh |
| 1143 | */ |
| 1144 | x = div_u64((u64)wb_thresh << 16, dtc->thresh | 1); |
| 1145 | wb_setpoint = setpoint * (u64)x >> 16; |
| 1146 | /* |
| 1147 | * Use span=(8*write_bw) in single wb case as indicated by |
| 1148 | * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. |
| 1149 | * |
| 1150 | * wb_thresh thresh - wb_thresh |
| 1151 | * span = --------- * (8 * write_bw) + ------------------ * wb_thresh |
| 1152 | * thresh thresh |
| 1153 | */ |
| 1154 | span = (dtc->thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; |
| 1155 | x_intercept = wb_setpoint + span; |
| 1156 | |
| 1157 | if (dtc->wb_dirty < x_intercept - span / 4) { |
| 1158 | pos_ratio = div64_u64(pos_ratio * (x_intercept - dtc->wb_dirty), |
| 1159 | (x_intercept - wb_setpoint) | 1); |
| 1160 | } else |
| 1161 | pos_ratio /= 4; |
| 1162 | |
| 1163 | /* |
| 1164 | * wb reserve area, safeguard against dirty pool underrun and disk idle |
| 1165 | * It may push the desired control point of global dirty pages higher |
| 1166 | * than setpoint. |
| 1167 | */ |
| 1168 | x_intercept = wb_thresh / 2; |
| 1169 | if (dtc->wb_dirty < x_intercept) { |
| 1170 | if (dtc->wb_dirty > x_intercept / 8) |
| 1171 | pos_ratio = div_u64(pos_ratio * x_intercept, |
| 1172 | dtc->wb_dirty); |
| 1173 | else |
| 1174 | pos_ratio *= 8; |
| 1175 | } |
| 1176 | |
| 1177 | dtc->pos_ratio = pos_ratio; |
| 1178 | } |
| 1179 | |
| 1180 | static void wb_update_write_bandwidth(struct bdi_writeback *wb, |
| 1181 | unsigned long elapsed, |
| 1182 | unsigned long written) |
| 1183 | { |
| 1184 | const unsigned long period = roundup_pow_of_two(3 * HZ); |
| 1185 | unsigned long avg = wb->avg_write_bandwidth; |
| 1186 | unsigned long old = wb->write_bandwidth; |
| 1187 | u64 bw; |
| 1188 | |
| 1189 | /* |
| 1190 | * bw = written * HZ / elapsed |
| 1191 | * |
| 1192 | * bw * elapsed + write_bandwidth * (period - elapsed) |
| 1193 | * write_bandwidth = --------------------------------------------------- |
| 1194 | * period |
| 1195 | * |
| 1196 | * @written may have decreased due to folio_account_redirty(). |
| 1197 | * Avoid underflowing @bw calculation. |
| 1198 | */ |
| 1199 | bw = written - min(written, wb->written_stamp); |
| 1200 | bw *= HZ; |
| 1201 | if (unlikely(elapsed > period)) { |
| 1202 | bw = div64_ul(bw, elapsed); |
| 1203 | avg = bw; |
| 1204 | goto out; |
| 1205 | } |
| 1206 | bw += (u64)wb->write_bandwidth * (period - elapsed); |
| 1207 | bw >>= ilog2(period); |
| 1208 | |
| 1209 | /* |
| 1210 | * one more level of smoothing, for filtering out sudden spikes |
| 1211 | */ |
| 1212 | if (avg > old && old >= (unsigned long)bw) |
| 1213 | avg -= (avg - old) >> 3; |
| 1214 | |
| 1215 | if (avg < old && old <= (unsigned long)bw) |
| 1216 | avg += (old - avg) >> 3; |
| 1217 | |
| 1218 | out: |
| 1219 | /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ |
| 1220 | avg = max(avg, 1LU); |
| 1221 | if (wb_has_dirty_io(wb)) { |
| 1222 | long delta = avg - wb->avg_write_bandwidth; |
| 1223 | WARN_ON_ONCE(atomic_long_add_return(delta, |
| 1224 | &wb->bdi->tot_write_bandwidth) <= 0); |
| 1225 | } |
| 1226 | wb->write_bandwidth = bw; |
| 1227 | WRITE_ONCE(wb->avg_write_bandwidth, avg); |
| 1228 | } |
| 1229 | |
| 1230 | static void update_dirty_limit(struct dirty_throttle_control *dtc) |
| 1231 | { |
| 1232 | struct wb_domain *dom = dtc_dom(dtc); |
| 1233 | unsigned long thresh = dtc->thresh; |
| 1234 | unsigned long limit = dom->dirty_limit; |
| 1235 | |
| 1236 | /* |
| 1237 | * Follow up in one step. |
| 1238 | */ |
| 1239 | if (limit < thresh) { |
| 1240 | limit = thresh; |
| 1241 | goto update; |
| 1242 | } |
| 1243 | |
| 1244 | /* |
| 1245 | * Follow down slowly. Use the higher one as the target, because thresh |
| 1246 | * may drop below dirty. This is exactly the reason to introduce |
| 1247 | * dom->dirty_limit which is guaranteed to lie above the dirty pages. |
| 1248 | */ |
| 1249 | thresh = max(thresh, dtc->dirty); |
| 1250 | if (limit > thresh) { |
| 1251 | limit -= (limit - thresh) >> 5; |
| 1252 | goto update; |
| 1253 | } |
| 1254 | return; |
| 1255 | update: |
| 1256 | dom->dirty_limit = limit; |
| 1257 | } |
| 1258 | |
| 1259 | static void domain_update_dirty_limit(struct dirty_throttle_control *dtc, |
| 1260 | unsigned long now) |
| 1261 | { |
| 1262 | struct wb_domain *dom = dtc_dom(dtc); |
| 1263 | |
| 1264 | /* |
| 1265 | * check locklessly first to optimize away locking for the most time |
| 1266 | */ |
| 1267 | if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) |
| 1268 | return; |
| 1269 | |
| 1270 | spin_lock(&dom->lock); |
| 1271 | if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) { |
| 1272 | update_dirty_limit(dtc); |
| 1273 | dom->dirty_limit_tstamp = now; |
| 1274 | } |
| 1275 | spin_unlock(&dom->lock); |
| 1276 | } |
| 1277 | |
| 1278 | /* |
| 1279 | * Maintain wb->dirty_ratelimit, the base dirty throttle rate. |
| 1280 | * |
| 1281 | * Normal wb tasks will be curbed at or below it in long term. |
| 1282 | * Obviously it should be around (write_bw / N) when there are N dd tasks. |
| 1283 | */ |
| 1284 | static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, |
| 1285 | unsigned long dirtied, |
| 1286 | unsigned long elapsed) |
| 1287 | { |
| 1288 | struct bdi_writeback *wb = dtc->wb; |
| 1289 | unsigned long dirty = dtc->dirty; |
| 1290 | unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh); |
| 1291 | unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh); |
| 1292 | unsigned long setpoint = (freerun + limit) / 2; |
| 1293 | unsigned long write_bw = wb->avg_write_bandwidth; |
| 1294 | unsigned long dirty_ratelimit = wb->dirty_ratelimit; |
| 1295 | unsigned long dirty_rate; |
| 1296 | unsigned long task_ratelimit; |
| 1297 | unsigned long balanced_dirty_ratelimit; |
| 1298 | unsigned long step; |
| 1299 | unsigned long x; |
| 1300 | unsigned long shift; |
| 1301 | |
| 1302 | /* |
| 1303 | * The dirty rate will match the writeout rate in long term, except |
| 1304 | * when dirty pages are truncated by userspace or re-dirtied by FS. |
| 1305 | */ |
| 1306 | dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; |
| 1307 | |
| 1308 | /* |
| 1309 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. |
| 1310 | */ |
| 1311 | task_ratelimit = (u64)dirty_ratelimit * |
| 1312 | dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; |
| 1313 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
| 1314 | |
| 1315 | /* |
| 1316 | * A linear estimation of the "balanced" throttle rate. The theory is, |
| 1317 | * if there are N dd tasks, each throttled at task_ratelimit, the wb's |
| 1318 | * dirty_rate will be measured to be (N * task_ratelimit). So the below |
| 1319 | * formula will yield the balanced rate limit (write_bw / N). |
| 1320 | * |
| 1321 | * Note that the expanded form is not a pure rate feedback: |
| 1322 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) |
| 1323 | * but also takes pos_ratio into account: |
| 1324 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) |
| 1325 | * |
| 1326 | * (1) is not realistic because pos_ratio also takes part in balancing |
| 1327 | * the dirty rate. Consider the state |
| 1328 | * pos_ratio = 0.5 (3) |
| 1329 | * rate = 2 * (write_bw / N) (4) |
| 1330 | * If (1) is used, it will stuck in that state! Because each dd will |
| 1331 | * be throttled at |
| 1332 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) |
| 1333 | * yielding |
| 1334 | * dirty_rate = N * task_ratelimit = write_bw (6) |
| 1335 | * put (6) into (1) we get |
| 1336 | * rate_(i+1) = rate_(i) (7) |
| 1337 | * |
| 1338 | * So we end up using (2) to always keep |
| 1339 | * rate_(i+1) ~= (write_bw / N) (8) |
| 1340 | * regardless of the value of pos_ratio. As long as (8) is satisfied, |
| 1341 | * pos_ratio is able to drive itself to 1.0, which is not only where |
| 1342 | * the dirty count meet the setpoint, but also where the slope of |
| 1343 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. |
| 1344 | */ |
| 1345 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, |
| 1346 | dirty_rate | 1); |
| 1347 | /* |
| 1348 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw |
| 1349 | */ |
| 1350 | if (unlikely(balanced_dirty_ratelimit > write_bw)) |
| 1351 | balanced_dirty_ratelimit = write_bw; |
| 1352 | |
| 1353 | /* |
| 1354 | * We could safely do this and return immediately: |
| 1355 | * |
| 1356 | * wb->dirty_ratelimit = balanced_dirty_ratelimit; |
| 1357 | * |
| 1358 | * However to get a more stable dirty_ratelimit, the below elaborated |
| 1359 | * code makes use of task_ratelimit to filter out singular points and |
| 1360 | * limit the step size. |
| 1361 | * |
| 1362 | * The below code essentially only uses the relative value of |
| 1363 | * |
| 1364 | * task_ratelimit - dirty_ratelimit |
| 1365 | * = (pos_ratio - 1) * dirty_ratelimit |
| 1366 | * |
| 1367 | * which reflects the direction and size of dirty position error. |
| 1368 | */ |
| 1369 | |
| 1370 | /* |
| 1371 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff |
| 1372 | * task_ratelimit is on the same side of dirty_ratelimit, too. |
| 1373 | * For example, when |
| 1374 | * - dirty_ratelimit > balanced_dirty_ratelimit |
| 1375 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) |
| 1376 | * lowering dirty_ratelimit will help meet both the position and rate |
| 1377 | * control targets. Otherwise, don't update dirty_ratelimit if it will |
| 1378 | * only help meet the rate target. After all, what the users ultimately |
| 1379 | * feel and care are stable dirty rate and small position error. |
| 1380 | * |
| 1381 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size |
| 1382 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
| 1383 | * keeps jumping around randomly and can even leap far away at times |
| 1384 | * due to the small 200ms estimation period of dirty_rate (we want to |
| 1385 | * keep that period small to reduce time lags). |
| 1386 | */ |
| 1387 | step = 0; |
| 1388 | |
| 1389 | /* |
| 1390 | * For strictlimit case, calculations above were based on wb counters |
| 1391 | * and limits (starting from pos_ratio = wb_position_ratio() and up to |
| 1392 | * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). |
| 1393 | * Hence, to calculate "step" properly, we have to use wb_dirty as |
| 1394 | * "dirty" and wb_setpoint as "setpoint". |
| 1395 | * |
| 1396 | * We rampup dirty_ratelimit forcibly if wb_dirty is low because |
| 1397 | * it's possible that wb_thresh is close to zero due to inactivity |
| 1398 | * of backing device. |
| 1399 | */ |
| 1400 | if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { |
| 1401 | dirty = dtc->wb_dirty; |
| 1402 | if (dtc->wb_dirty < 8) |
| 1403 | setpoint = dtc->wb_dirty + 1; |
| 1404 | else |
| 1405 | setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; |
| 1406 | } |
| 1407 | |
| 1408 | if (dirty < setpoint) { |
| 1409 | x = min3(wb->balanced_dirty_ratelimit, |
| 1410 | balanced_dirty_ratelimit, task_ratelimit); |
| 1411 | if (dirty_ratelimit < x) |
| 1412 | step = x - dirty_ratelimit; |
| 1413 | } else { |
| 1414 | x = max3(wb->balanced_dirty_ratelimit, |
| 1415 | balanced_dirty_ratelimit, task_ratelimit); |
| 1416 | if (dirty_ratelimit > x) |
| 1417 | step = dirty_ratelimit - x; |
| 1418 | } |
| 1419 | |
| 1420 | /* |
| 1421 | * Don't pursue 100% rate matching. It's impossible since the balanced |
| 1422 | * rate itself is constantly fluctuating. So decrease the track speed |
| 1423 | * when it gets close to the target. Helps eliminate pointless tremors. |
| 1424 | */ |
| 1425 | shift = dirty_ratelimit / (2 * step + 1); |
| 1426 | if (shift < BITS_PER_LONG) |
| 1427 | step = DIV_ROUND_UP(step >> shift, 8); |
| 1428 | else |
| 1429 | step = 0; |
| 1430 | |
| 1431 | if (dirty_ratelimit < balanced_dirty_ratelimit) |
| 1432 | dirty_ratelimit += step; |
| 1433 | else |
| 1434 | dirty_ratelimit -= step; |
| 1435 | |
| 1436 | WRITE_ONCE(wb->dirty_ratelimit, max(dirty_ratelimit, 1UL)); |
| 1437 | wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit; |
| 1438 | |
| 1439 | trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit); |
| 1440 | } |
| 1441 | |
| 1442 | static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc, |
| 1443 | struct dirty_throttle_control *mdtc, |
| 1444 | bool update_ratelimit) |
| 1445 | { |
| 1446 | struct bdi_writeback *wb = gdtc->wb; |
| 1447 | unsigned long now = jiffies; |
| 1448 | unsigned long elapsed; |
| 1449 | unsigned long dirtied; |
| 1450 | unsigned long written; |
| 1451 | |
| 1452 | spin_lock(&wb->list_lock); |
| 1453 | |
| 1454 | /* |
| 1455 | * Lockless checks for elapsed time are racy and delayed update after |
| 1456 | * IO completion doesn't do it at all (to make sure written pages are |
| 1457 | * accounted reasonably quickly). Make sure elapsed >= 1 to avoid |
| 1458 | * division errors. |
| 1459 | */ |
| 1460 | elapsed = max(now - wb->bw_time_stamp, 1UL); |
| 1461 | dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]); |
| 1462 | written = percpu_counter_read(&wb->stat[WB_WRITTEN]); |
| 1463 | |
| 1464 | if (update_ratelimit) { |
| 1465 | domain_update_dirty_limit(gdtc, now); |
| 1466 | wb_update_dirty_ratelimit(gdtc, dirtied, elapsed); |
| 1467 | |
| 1468 | /* |
| 1469 | * @mdtc is always NULL if !CGROUP_WRITEBACK but the |
| 1470 | * compiler has no way to figure that out. Help it. |
| 1471 | */ |
| 1472 | if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { |
| 1473 | domain_update_dirty_limit(mdtc, now); |
| 1474 | wb_update_dirty_ratelimit(mdtc, dirtied, elapsed); |
| 1475 | } |
| 1476 | } |
| 1477 | wb_update_write_bandwidth(wb, elapsed, written); |
| 1478 | |
| 1479 | wb->dirtied_stamp = dirtied; |
| 1480 | wb->written_stamp = written; |
| 1481 | WRITE_ONCE(wb->bw_time_stamp, now); |
| 1482 | spin_unlock(&wb->list_lock); |
| 1483 | } |
| 1484 | |
| 1485 | void wb_update_bandwidth(struct bdi_writeback *wb) |
| 1486 | { |
| 1487 | struct dirty_throttle_control gdtc = { GDTC_INIT(wb) }; |
| 1488 | |
| 1489 | __wb_update_bandwidth(&gdtc, NULL, false); |
| 1490 | } |
| 1491 | |
| 1492 | /* Interval after which we consider wb idle and don't estimate bandwidth */ |
| 1493 | #define WB_BANDWIDTH_IDLE_JIF (HZ) |
| 1494 | |
| 1495 | static void wb_bandwidth_estimate_start(struct bdi_writeback *wb) |
| 1496 | { |
| 1497 | unsigned long now = jiffies; |
| 1498 | unsigned long elapsed = now - READ_ONCE(wb->bw_time_stamp); |
| 1499 | |
| 1500 | if (elapsed > WB_BANDWIDTH_IDLE_JIF && |
| 1501 | !atomic_read(&wb->writeback_inodes)) { |
| 1502 | spin_lock(&wb->list_lock); |
| 1503 | wb->dirtied_stamp = wb_stat(wb, WB_DIRTIED); |
| 1504 | wb->written_stamp = wb_stat(wb, WB_WRITTEN); |
| 1505 | WRITE_ONCE(wb->bw_time_stamp, now); |
| 1506 | spin_unlock(&wb->list_lock); |
| 1507 | } |
| 1508 | } |
| 1509 | |
| 1510 | /* |
| 1511 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
| 1512 | * will look to see if it needs to start dirty throttling. |
| 1513 | * |
| 1514 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive |
| 1515 | * global_zone_page_state() too often. So scale it near-sqrt to the safety margin |
| 1516 | * (the number of pages we may dirty without exceeding the dirty limits). |
| 1517 | */ |
| 1518 | static unsigned long dirty_poll_interval(unsigned long dirty, |
| 1519 | unsigned long thresh) |
| 1520 | { |
| 1521 | if (thresh > dirty) |
| 1522 | return 1UL << (ilog2(thresh - dirty) >> 1); |
| 1523 | |
| 1524 | return 1; |
| 1525 | } |
| 1526 | |
| 1527 | static unsigned long wb_max_pause(struct bdi_writeback *wb, |
| 1528 | unsigned long wb_dirty) |
| 1529 | { |
| 1530 | unsigned long bw = READ_ONCE(wb->avg_write_bandwidth); |
| 1531 | unsigned long t; |
| 1532 | |
| 1533 | /* |
| 1534 | * Limit pause time for small memory systems. If sleeping for too long |
| 1535 | * time, a small pool of dirty/writeback pages may go empty and disk go |
| 1536 | * idle. |
| 1537 | * |
| 1538 | * 8 serves as the safety ratio. |
| 1539 | */ |
| 1540 | t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
| 1541 | t++; |
| 1542 | |
| 1543 | return min_t(unsigned long, t, MAX_PAUSE); |
| 1544 | } |
| 1545 | |
| 1546 | static long wb_min_pause(struct bdi_writeback *wb, |
| 1547 | long max_pause, |
| 1548 | unsigned long task_ratelimit, |
| 1549 | unsigned long dirty_ratelimit, |
| 1550 | int *nr_dirtied_pause) |
| 1551 | { |
| 1552 | long hi = ilog2(READ_ONCE(wb->avg_write_bandwidth)); |
| 1553 | long lo = ilog2(READ_ONCE(wb->dirty_ratelimit)); |
| 1554 | long t; /* target pause */ |
| 1555 | long pause; /* estimated next pause */ |
| 1556 | int pages; /* target nr_dirtied_pause */ |
| 1557 | |
| 1558 | /* target for 10ms pause on 1-dd case */ |
| 1559 | t = max(1, HZ / 100); |
| 1560 | |
| 1561 | /* |
| 1562 | * Scale up pause time for concurrent dirtiers in order to reduce CPU |
| 1563 | * overheads. |
| 1564 | * |
| 1565 | * (N * 10ms) on 2^N concurrent tasks. |
| 1566 | */ |
| 1567 | if (hi > lo) |
| 1568 | t += (hi - lo) * (10 * HZ) / 1024; |
| 1569 | |
| 1570 | /* |
| 1571 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
| 1572 | * on the much more stable dirty_ratelimit. However the next pause time |
| 1573 | * will be computed based on task_ratelimit and the two rate limits may |
| 1574 | * depart considerably at some time. Especially if task_ratelimit goes |
| 1575 | * below dirty_ratelimit/2 and the target pause is max_pause, the next |
| 1576 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a |
| 1577 | * result task_ratelimit won't be executed faithfully, which could |
| 1578 | * eventually bring down dirty_ratelimit. |
| 1579 | * |
| 1580 | * We apply two rules to fix it up: |
| 1581 | * 1) try to estimate the next pause time and if necessary, use a lower |
| 1582 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, |
| 1583 | * nr_dirtied_pause will be "dancing" with task_ratelimit. |
| 1584 | * 2) limit the target pause time to max_pause/2, so that the normal |
| 1585 | * small fluctuations of task_ratelimit won't trigger rule (1) and |
| 1586 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. |
| 1587 | */ |
| 1588 | t = min(t, 1 + max_pause / 2); |
| 1589 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); |
| 1590 | |
| 1591 | /* |
| 1592 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
| 1593 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. |
| 1594 | * When the 16 consecutive reads are often interrupted by some dirty |
| 1595 | * throttling pause during the async writes, cfq will go into idles |
| 1596 | * (deadline is fine). So push nr_dirtied_pause as high as possible |
| 1597 | * until reaches DIRTY_POLL_THRESH=32 pages. |
| 1598 | */ |
| 1599 | if (pages < DIRTY_POLL_THRESH) { |
| 1600 | t = max_pause; |
| 1601 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); |
| 1602 | if (pages > DIRTY_POLL_THRESH) { |
| 1603 | pages = DIRTY_POLL_THRESH; |
| 1604 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; |
| 1605 | } |
| 1606 | } |
| 1607 | |
| 1608 | pause = HZ * pages / (task_ratelimit + 1); |
| 1609 | if (pause > max_pause) { |
| 1610 | t = max_pause; |
| 1611 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); |
| 1612 | } |
| 1613 | |
| 1614 | *nr_dirtied_pause = pages; |
| 1615 | /* |
| 1616 | * The minimal pause time will normally be half the target pause time. |
| 1617 | */ |
| 1618 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
| 1619 | } |
| 1620 | |
| 1621 | static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) |
| 1622 | { |
| 1623 | struct bdi_writeback *wb = dtc->wb; |
| 1624 | unsigned long wb_reclaimable; |
| 1625 | |
| 1626 | /* |
| 1627 | * wb_thresh is not treated as some limiting factor as |
| 1628 | * dirty_thresh, due to reasons |
| 1629 | * - in JBOD setup, wb_thresh can fluctuate a lot |
| 1630 | * - in a system with HDD and USB key, the USB key may somehow |
| 1631 | * go into state (wb_dirty >> wb_thresh) either because |
| 1632 | * wb_dirty starts high, or because wb_thresh drops low. |
| 1633 | * In this case we don't want to hard throttle the USB key |
| 1634 | * dirtiers for 100 seconds until wb_dirty drops under |
| 1635 | * wb_thresh. Instead the auxiliary wb control line in |
| 1636 | * wb_position_ratio() will let the dirtier task progress |
| 1637 | * at some rate <= (write_bw / 2) for bringing down wb_dirty. |
| 1638 | */ |
| 1639 | dtc->wb_thresh = __wb_calc_thresh(dtc); |
| 1640 | dtc->wb_bg_thresh = dtc->thresh ? |
| 1641 | div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; |
| 1642 | |
| 1643 | /* |
| 1644 | * In order to avoid the stacked BDI deadlock we need |
| 1645 | * to ensure we accurately count the 'dirty' pages when |
| 1646 | * the threshold is low. |
| 1647 | * |
| 1648 | * Otherwise it would be possible to get thresh+n pages |
| 1649 | * reported dirty, even though there are thresh-m pages |
| 1650 | * actually dirty; with m+n sitting in the percpu |
| 1651 | * deltas. |
| 1652 | */ |
| 1653 | if (dtc->wb_thresh < 2 * wb_stat_error()) { |
| 1654 | wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
| 1655 | dtc->wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); |
| 1656 | } else { |
| 1657 | wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
| 1658 | dtc->wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); |
| 1659 | } |
| 1660 | } |
| 1661 | |
| 1662 | /* |
| 1663 | * balance_dirty_pages() must be called by processes which are generating dirty |
| 1664 | * data. It looks at the number of dirty pages in the machine and will force |
| 1665 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
| 1666 | * If we're over `background_thresh' then the writeback threads are woken to |
| 1667 | * perform some writeout. |
| 1668 | */ |
| 1669 | static int balance_dirty_pages(struct bdi_writeback *wb, |
| 1670 | unsigned long pages_dirtied, unsigned int flags) |
| 1671 | { |
| 1672 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
| 1673 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
| 1674 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
| 1675 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
| 1676 | &mdtc_stor : NULL; |
| 1677 | struct dirty_throttle_control *sdtc; |
| 1678 | unsigned long nr_reclaimable; /* = file_dirty */ |
| 1679 | long period; |
| 1680 | long pause; |
| 1681 | long max_pause; |
| 1682 | long min_pause; |
| 1683 | int nr_dirtied_pause; |
| 1684 | bool dirty_exceeded = false; |
| 1685 | unsigned long task_ratelimit; |
| 1686 | unsigned long dirty_ratelimit; |
| 1687 | struct backing_dev_info *bdi = wb->bdi; |
| 1688 | bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT; |
| 1689 | unsigned long start_time = jiffies; |
| 1690 | int ret = 0; |
| 1691 | |
| 1692 | for (;;) { |
| 1693 | unsigned long now = jiffies; |
| 1694 | unsigned long dirty, thresh, bg_thresh; |
| 1695 | unsigned long m_dirty = 0; /* stop bogus uninit warnings */ |
| 1696 | unsigned long m_thresh = 0; |
| 1697 | unsigned long m_bg_thresh = 0; |
| 1698 | |
| 1699 | nr_reclaimable = global_node_page_state(NR_FILE_DIRTY); |
| 1700 | gdtc->avail = global_dirtyable_memory(); |
| 1701 | gdtc->dirty = nr_reclaimable + global_node_page_state(NR_WRITEBACK); |
| 1702 | |
| 1703 | domain_dirty_limits(gdtc); |
| 1704 | |
| 1705 | if (unlikely(strictlimit)) { |
| 1706 | wb_dirty_limits(gdtc); |
| 1707 | |
| 1708 | dirty = gdtc->wb_dirty; |
| 1709 | thresh = gdtc->wb_thresh; |
| 1710 | bg_thresh = gdtc->wb_bg_thresh; |
| 1711 | } else { |
| 1712 | dirty = gdtc->dirty; |
| 1713 | thresh = gdtc->thresh; |
| 1714 | bg_thresh = gdtc->bg_thresh; |
| 1715 | } |
| 1716 | |
| 1717 | if (mdtc) { |
| 1718 | unsigned long filepages, headroom, writeback; |
| 1719 | |
| 1720 | /* |
| 1721 | * If @wb belongs to !root memcg, repeat the same |
| 1722 | * basic calculations for the memcg domain. |
| 1723 | */ |
| 1724 | mem_cgroup_wb_stats(wb, &filepages, &headroom, |
| 1725 | &mdtc->dirty, &writeback); |
| 1726 | mdtc->dirty += writeback; |
| 1727 | mdtc_calc_avail(mdtc, filepages, headroom); |
| 1728 | |
| 1729 | domain_dirty_limits(mdtc); |
| 1730 | |
| 1731 | if (unlikely(strictlimit)) { |
| 1732 | wb_dirty_limits(mdtc); |
| 1733 | m_dirty = mdtc->wb_dirty; |
| 1734 | m_thresh = mdtc->wb_thresh; |
| 1735 | m_bg_thresh = mdtc->wb_bg_thresh; |
| 1736 | } else { |
| 1737 | m_dirty = mdtc->dirty; |
| 1738 | m_thresh = mdtc->thresh; |
| 1739 | m_bg_thresh = mdtc->bg_thresh; |
| 1740 | } |
| 1741 | } |
| 1742 | |
| 1743 | /* |
| 1744 | * In laptop mode, we wait until hitting the higher threshold |
| 1745 | * before starting background writeout, and then write out all |
| 1746 | * the way down to the lower threshold. So slow writers cause |
| 1747 | * minimal disk activity. |
| 1748 | * |
| 1749 | * In normal mode, we start background writeout at the lower |
| 1750 | * background_thresh, to keep the amount of dirty memory low. |
| 1751 | */ |
| 1752 | if (!laptop_mode && nr_reclaimable > gdtc->bg_thresh && |
| 1753 | !writeback_in_progress(wb)) |
| 1754 | wb_start_background_writeback(wb); |
| 1755 | |
| 1756 | /* |
| 1757 | * Throttle it only when the background writeback cannot |
| 1758 | * catch-up. This avoids (excessively) small writeouts |
| 1759 | * when the wb limits are ramping up in case of !strictlimit. |
| 1760 | * |
| 1761 | * In strictlimit case make decision based on the wb counters |
| 1762 | * and limits. Small writeouts when the wb limits are ramping |
| 1763 | * up are the price we consciously pay for strictlimit-ing. |
| 1764 | * |
| 1765 | * If memcg domain is in effect, @dirty should be under |
| 1766 | * both global and memcg freerun ceilings. |
| 1767 | */ |
| 1768 | if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) && |
| 1769 | (!mdtc || |
| 1770 | m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) { |
| 1771 | unsigned long intv; |
| 1772 | unsigned long m_intv; |
| 1773 | |
| 1774 | free_running: |
| 1775 | intv = dirty_poll_interval(dirty, thresh); |
| 1776 | m_intv = ULONG_MAX; |
| 1777 | |
| 1778 | current->dirty_paused_when = now; |
| 1779 | current->nr_dirtied = 0; |
| 1780 | if (mdtc) |
| 1781 | m_intv = dirty_poll_interval(m_dirty, m_thresh); |
| 1782 | current->nr_dirtied_pause = min(intv, m_intv); |
| 1783 | break; |
| 1784 | } |
| 1785 | |
| 1786 | /* Start writeback even when in laptop mode */ |
| 1787 | if (unlikely(!writeback_in_progress(wb))) |
| 1788 | wb_start_background_writeback(wb); |
| 1789 | |
| 1790 | mem_cgroup_flush_foreign(wb); |
| 1791 | |
| 1792 | /* |
| 1793 | * Calculate global domain's pos_ratio and select the |
| 1794 | * global dtc by default. |
| 1795 | */ |
| 1796 | if (!strictlimit) { |
| 1797 | wb_dirty_limits(gdtc); |
| 1798 | |
| 1799 | if ((current->flags & PF_LOCAL_THROTTLE) && |
| 1800 | gdtc->wb_dirty < |
| 1801 | dirty_freerun_ceiling(gdtc->wb_thresh, |
| 1802 | gdtc->wb_bg_thresh)) |
| 1803 | /* |
| 1804 | * LOCAL_THROTTLE tasks must not be throttled |
| 1805 | * when below the per-wb freerun ceiling. |
| 1806 | */ |
| 1807 | goto free_running; |
| 1808 | } |
| 1809 | |
| 1810 | dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && |
| 1811 | ((gdtc->dirty > gdtc->thresh) || strictlimit); |
| 1812 | |
| 1813 | wb_position_ratio(gdtc); |
| 1814 | sdtc = gdtc; |
| 1815 | |
| 1816 | if (mdtc) { |
| 1817 | /* |
| 1818 | * If memcg domain is in effect, calculate its |
| 1819 | * pos_ratio. @wb should satisfy constraints from |
| 1820 | * both global and memcg domains. Choose the one |
| 1821 | * w/ lower pos_ratio. |
| 1822 | */ |
| 1823 | if (!strictlimit) { |
| 1824 | wb_dirty_limits(mdtc); |
| 1825 | |
| 1826 | if ((current->flags & PF_LOCAL_THROTTLE) && |
| 1827 | mdtc->wb_dirty < |
| 1828 | dirty_freerun_ceiling(mdtc->wb_thresh, |
| 1829 | mdtc->wb_bg_thresh)) |
| 1830 | /* |
| 1831 | * LOCAL_THROTTLE tasks must not be |
| 1832 | * throttled when below the per-wb |
| 1833 | * freerun ceiling. |
| 1834 | */ |
| 1835 | goto free_running; |
| 1836 | } |
| 1837 | dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) && |
| 1838 | ((mdtc->dirty > mdtc->thresh) || strictlimit); |
| 1839 | |
| 1840 | wb_position_ratio(mdtc); |
| 1841 | if (mdtc->pos_ratio < gdtc->pos_ratio) |
| 1842 | sdtc = mdtc; |
| 1843 | } |
| 1844 | |
| 1845 | if (dirty_exceeded != wb->dirty_exceeded) |
| 1846 | wb->dirty_exceeded = dirty_exceeded; |
| 1847 | |
| 1848 | if (time_is_before_jiffies(READ_ONCE(wb->bw_time_stamp) + |
| 1849 | BANDWIDTH_INTERVAL)) |
| 1850 | __wb_update_bandwidth(gdtc, mdtc, true); |
| 1851 | |
| 1852 | /* throttle according to the chosen dtc */ |
| 1853 | dirty_ratelimit = READ_ONCE(wb->dirty_ratelimit); |
| 1854 | task_ratelimit = ((u64)dirty_ratelimit * sdtc->pos_ratio) >> |
| 1855 | RATELIMIT_CALC_SHIFT; |
| 1856 | max_pause = wb_max_pause(wb, sdtc->wb_dirty); |
| 1857 | min_pause = wb_min_pause(wb, max_pause, |
| 1858 | task_ratelimit, dirty_ratelimit, |
| 1859 | &nr_dirtied_pause); |
| 1860 | |
| 1861 | if (unlikely(task_ratelimit == 0)) { |
| 1862 | period = max_pause; |
| 1863 | pause = max_pause; |
| 1864 | goto pause; |
| 1865 | } |
| 1866 | period = HZ * pages_dirtied / task_ratelimit; |
| 1867 | pause = period; |
| 1868 | if (current->dirty_paused_when) |
| 1869 | pause -= now - current->dirty_paused_when; |
| 1870 | /* |
| 1871 | * For less than 1s think time (ext3/4 may block the dirtier |
| 1872 | * for up to 800ms from time to time on 1-HDD; so does xfs, |
| 1873 | * however at much less frequency), try to compensate it in |
| 1874 | * future periods by updating the virtual time; otherwise just |
| 1875 | * do a reset, as it may be a light dirtier. |
| 1876 | */ |
| 1877 | if (pause < min_pause) { |
| 1878 | trace_balance_dirty_pages(wb, |
| 1879 | sdtc->thresh, |
| 1880 | sdtc->bg_thresh, |
| 1881 | sdtc->dirty, |
| 1882 | sdtc->wb_thresh, |
| 1883 | sdtc->wb_dirty, |
| 1884 | dirty_ratelimit, |
| 1885 | task_ratelimit, |
| 1886 | pages_dirtied, |
| 1887 | period, |
| 1888 | min(pause, 0L), |
| 1889 | start_time); |
| 1890 | if (pause < -HZ) { |
| 1891 | current->dirty_paused_when = now; |
| 1892 | current->nr_dirtied = 0; |
| 1893 | } else if (period) { |
| 1894 | current->dirty_paused_when += period; |
| 1895 | current->nr_dirtied = 0; |
| 1896 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
| 1897 | current->nr_dirtied_pause += pages_dirtied; |
| 1898 | break; |
| 1899 | } |
| 1900 | if (unlikely(pause > max_pause)) { |
| 1901 | /* for occasional dropped task_ratelimit */ |
| 1902 | now += min(pause - max_pause, max_pause); |
| 1903 | pause = max_pause; |
| 1904 | } |
| 1905 | |
| 1906 | pause: |
| 1907 | trace_balance_dirty_pages(wb, |
| 1908 | sdtc->thresh, |
| 1909 | sdtc->bg_thresh, |
| 1910 | sdtc->dirty, |
| 1911 | sdtc->wb_thresh, |
| 1912 | sdtc->wb_dirty, |
| 1913 | dirty_ratelimit, |
| 1914 | task_ratelimit, |
| 1915 | pages_dirtied, |
| 1916 | period, |
| 1917 | pause, |
| 1918 | start_time); |
| 1919 | if (flags & BDP_ASYNC) { |
| 1920 | ret = -EAGAIN; |
| 1921 | break; |
| 1922 | } |
| 1923 | __set_current_state(TASK_KILLABLE); |
| 1924 | wb->dirty_sleep = now; |
| 1925 | io_schedule_timeout(pause); |
| 1926 | |
| 1927 | current->dirty_paused_when = now + pause; |
| 1928 | current->nr_dirtied = 0; |
| 1929 | current->nr_dirtied_pause = nr_dirtied_pause; |
| 1930 | |
| 1931 | /* |
| 1932 | * This is typically equal to (dirty < thresh) and can also |
| 1933 | * keep "1000+ dd on a slow USB stick" under control. |
| 1934 | */ |
| 1935 | if (task_ratelimit) |
| 1936 | break; |
| 1937 | |
| 1938 | /* |
| 1939 | * In the case of an unresponsive NFS server and the NFS dirty |
| 1940 | * pages exceeds dirty_thresh, give the other good wb's a pipe |
| 1941 | * to go through, so that tasks on them still remain responsive. |
| 1942 | * |
| 1943 | * In theory 1 page is enough to keep the consumer-producer |
| 1944 | * pipe going: the flusher cleans 1 page => the task dirties 1 |
| 1945 | * more page. However wb_dirty has accounting errors. So use |
| 1946 | * the larger and more IO friendly wb_stat_error. |
| 1947 | */ |
| 1948 | if (sdtc->wb_dirty <= wb_stat_error()) |
| 1949 | break; |
| 1950 | |
| 1951 | if (fatal_signal_pending(current)) |
| 1952 | break; |
| 1953 | } |
| 1954 | return ret; |
| 1955 | } |
| 1956 | |
| 1957 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
| 1958 | |
| 1959 | /* |
| 1960 | * Normal tasks are throttled by |
| 1961 | * loop { |
| 1962 | * dirty tsk->nr_dirtied_pause pages; |
| 1963 | * take a snap in balance_dirty_pages(); |
| 1964 | * } |
| 1965 | * However there is a worst case. If every task exit immediately when dirtied |
| 1966 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be |
| 1967 | * called to throttle the page dirties. The solution is to save the not yet |
| 1968 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them |
| 1969 | * randomly into the running tasks. This works well for the above worst case, |
| 1970 | * as the new task will pick up and accumulate the old task's leaked dirty |
| 1971 | * count and eventually get throttled. |
| 1972 | */ |
| 1973 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; |
| 1974 | |
| 1975 | /** |
| 1976 | * balance_dirty_pages_ratelimited_flags - Balance dirty memory state. |
| 1977 | * @mapping: address_space which was dirtied. |
| 1978 | * @flags: BDP flags. |
| 1979 | * |
| 1980 | * Processes which are dirtying memory should call in here once for each page |
| 1981 | * which was newly dirtied. The function will periodically check the system's |
| 1982 | * dirty state and will initiate writeback if needed. |
| 1983 | * |
| 1984 | * See balance_dirty_pages_ratelimited() for details. |
| 1985 | * |
| 1986 | * Return: If @flags contains BDP_ASYNC, it may return -EAGAIN to |
| 1987 | * indicate that memory is out of balance and the caller must wait |
| 1988 | * for I/O to complete. Otherwise, it will return 0 to indicate |
| 1989 | * that either memory was already in balance, or it was able to sleep |
| 1990 | * until the amount of dirty memory returned to balance. |
| 1991 | */ |
| 1992 | int balance_dirty_pages_ratelimited_flags(struct address_space *mapping, |
| 1993 | unsigned int flags) |
| 1994 | { |
| 1995 | struct inode *inode = mapping->host; |
| 1996 | struct backing_dev_info *bdi = inode_to_bdi(inode); |
| 1997 | struct bdi_writeback *wb = NULL; |
| 1998 | int ratelimit; |
| 1999 | int ret = 0; |
| 2000 | int *p; |
| 2001 | |
| 2002 | if (!(bdi->capabilities & BDI_CAP_WRITEBACK)) |
| 2003 | return ret; |
| 2004 | |
| 2005 | if (inode_cgwb_enabled(inode)) |
| 2006 | wb = wb_get_create_current(bdi, GFP_KERNEL); |
| 2007 | if (!wb) |
| 2008 | wb = &bdi->wb; |
| 2009 | |
| 2010 | ratelimit = current->nr_dirtied_pause; |
| 2011 | if (wb->dirty_exceeded) |
| 2012 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
| 2013 | |
| 2014 | preempt_disable(); |
| 2015 | /* |
| 2016 | * This prevents one CPU to accumulate too many dirtied pages without |
| 2017 | * calling into balance_dirty_pages(), which can happen when there are |
| 2018 | * 1000+ tasks, all of them start dirtying pages at exactly the same |
| 2019 | * time, hence all honoured too large initial task->nr_dirtied_pause. |
| 2020 | */ |
| 2021 | p = this_cpu_ptr(&bdp_ratelimits); |
| 2022 | if (unlikely(current->nr_dirtied >= ratelimit)) |
| 2023 | *p = 0; |
| 2024 | else if (unlikely(*p >= ratelimit_pages)) { |
| 2025 | *p = 0; |
| 2026 | ratelimit = 0; |
| 2027 | } |
| 2028 | /* |
| 2029 | * Pick up the dirtied pages by the exited tasks. This avoids lots of |
| 2030 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping |
| 2031 | * the dirty throttling and livelock other long-run dirtiers. |
| 2032 | */ |
| 2033 | p = this_cpu_ptr(&dirty_throttle_leaks); |
| 2034 | if (*p > 0 && current->nr_dirtied < ratelimit) { |
| 2035 | unsigned long nr_pages_dirtied; |
| 2036 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
| 2037 | *p -= nr_pages_dirtied; |
| 2038 | current->nr_dirtied += nr_pages_dirtied; |
| 2039 | } |
| 2040 | preempt_enable(); |
| 2041 | |
| 2042 | if (unlikely(current->nr_dirtied >= ratelimit)) |
| 2043 | ret = balance_dirty_pages(wb, current->nr_dirtied, flags); |
| 2044 | |
| 2045 | wb_put(wb); |
| 2046 | return ret; |
| 2047 | } |
| 2048 | EXPORT_SYMBOL_GPL(balance_dirty_pages_ratelimited_flags); |
| 2049 | |
| 2050 | /** |
| 2051 | * balance_dirty_pages_ratelimited - balance dirty memory state. |
| 2052 | * @mapping: address_space which was dirtied. |
| 2053 | * |
| 2054 | * Processes which are dirtying memory should call in here once for each page |
| 2055 | * which was newly dirtied. The function will periodically check the system's |
| 2056 | * dirty state and will initiate writeback if needed. |
| 2057 | * |
| 2058 | * Once we're over the dirty memory limit we decrease the ratelimiting |
| 2059 | * by a lot, to prevent individual processes from overshooting the limit |
| 2060 | * by (ratelimit_pages) each. |
| 2061 | */ |
| 2062 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
| 2063 | { |
| 2064 | balance_dirty_pages_ratelimited_flags(mapping, 0); |
| 2065 | } |
| 2066 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
| 2067 | |
| 2068 | /** |
| 2069 | * wb_over_bg_thresh - does @wb need to be written back? |
| 2070 | * @wb: bdi_writeback of interest |
| 2071 | * |
| 2072 | * Determines whether background writeback should keep writing @wb or it's |
| 2073 | * clean enough. |
| 2074 | * |
| 2075 | * Return: %true if writeback should continue. |
| 2076 | */ |
| 2077 | bool wb_over_bg_thresh(struct bdi_writeback *wb) |
| 2078 | { |
| 2079 | struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) }; |
| 2080 | struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) }; |
| 2081 | struct dirty_throttle_control * const gdtc = &gdtc_stor; |
| 2082 | struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ? |
| 2083 | &mdtc_stor : NULL; |
| 2084 | unsigned long reclaimable; |
| 2085 | unsigned long thresh; |
| 2086 | |
| 2087 | /* |
| 2088 | * Similar to balance_dirty_pages() but ignores pages being written |
| 2089 | * as we're trying to decide whether to put more under writeback. |
| 2090 | */ |
| 2091 | gdtc->avail = global_dirtyable_memory(); |
| 2092 | gdtc->dirty = global_node_page_state(NR_FILE_DIRTY); |
| 2093 | domain_dirty_limits(gdtc); |
| 2094 | |
| 2095 | if (gdtc->dirty > gdtc->bg_thresh) |
| 2096 | return true; |
| 2097 | |
| 2098 | thresh = wb_calc_thresh(gdtc->wb, gdtc->bg_thresh); |
| 2099 | if (thresh < 2 * wb_stat_error()) |
| 2100 | reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
| 2101 | else |
| 2102 | reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
| 2103 | |
| 2104 | if (reclaimable > thresh) |
| 2105 | return true; |
| 2106 | |
| 2107 | if (mdtc) { |
| 2108 | unsigned long filepages, headroom, writeback; |
| 2109 | |
| 2110 | mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, |
| 2111 | &writeback); |
| 2112 | mdtc_calc_avail(mdtc, filepages, headroom); |
| 2113 | domain_dirty_limits(mdtc); /* ditto, ignore writeback */ |
| 2114 | |
| 2115 | if (mdtc->dirty > mdtc->bg_thresh) |
| 2116 | return true; |
| 2117 | |
| 2118 | thresh = wb_calc_thresh(mdtc->wb, mdtc->bg_thresh); |
| 2119 | if (thresh < 2 * wb_stat_error()) |
| 2120 | reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); |
| 2121 | else |
| 2122 | reclaimable = wb_stat(wb, WB_RECLAIMABLE); |
| 2123 | |
| 2124 | if (reclaimable > thresh) |
| 2125 | return true; |
| 2126 | } |
| 2127 | |
| 2128 | return false; |
| 2129 | } |
| 2130 | |
| 2131 | #ifdef CONFIG_SYSCTL |
| 2132 | /* |
| 2133 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs |
| 2134 | */ |
| 2135 | static int dirty_writeback_centisecs_handler(struct ctl_table *table, int write, |
| 2136 | void *buffer, size_t *length, loff_t *ppos) |
| 2137 | { |
| 2138 | unsigned int old_interval = dirty_writeback_interval; |
| 2139 | int ret; |
| 2140 | |
| 2141 | ret = proc_dointvec(table, write, buffer, length, ppos); |
| 2142 | |
| 2143 | /* |
| 2144 | * Writing 0 to dirty_writeback_interval will disable periodic writeback |
| 2145 | * and a different non-zero value will wakeup the writeback threads. |
| 2146 | * wb_wakeup_delayed() would be more appropriate, but it's a pain to |
| 2147 | * iterate over all bdis and wbs. |
| 2148 | * The reason we do this is to make the change take effect immediately. |
| 2149 | */ |
| 2150 | if (!ret && write && dirty_writeback_interval && |
| 2151 | dirty_writeback_interval != old_interval) |
| 2152 | wakeup_flusher_threads(WB_REASON_PERIODIC); |
| 2153 | |
| 2154 | return ret; |
| 2155 | } |
| 2156 | #endif |
| 2157 | |
| 2158 | void laptop_mode_timer_fn(struct timer_list *t) |
| 2159 | { |
| 2160 | struct backing_dev_info *backing_dev_info = |
| 2161 | from_timer(backing_dev_info, t, laptop_mode_wb_timer); |
| 2162 | |
| 2163 | wakeup_flusher_threads_bdi(backing_dev_info, WB_REASON_LAPTOP_TIMER); |
| 2164 | } |
| 2165 | |
| 2166 | /* |
| 2167 | * We've spun up the disk and we're in laptop mode: schedule writeback |
| 2168 | * of all dirty data a few seconds from now. If the flush is already scheduled |
| 2169 | * then push it back - the user is still using the disk. |
| 2170 | */ |
| 2171 | void laptop_io_completion(struct backing_dev_info *info) |
| 2172 | { |
| 2173 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
| 2174 | } |
| 2175 | |
| 2176 | /* |
| 2177 | * We're in laptop mode and we've just synced. The sync's writes will have |
| 2178 | * caused another writeback to be scheduled by laptop_io_completion. |
| 2179 | * Nothing needs to be written back anymore, so we unschedule the writeback. |
| 2180 | */ |
| 2181 | void laptop_sync_completion(void) |
| 2182 | { |
| 2183 | struct backing_dev_info *bdi; |
| 2184 | |
| 2185 | rcu_read_lock(); |
| 2186 | |
| 2187 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) |
| 2188 | del_timer(&bdi->laptop_mode_wb_timer); |
| 2189 | |
| 2190 | rcu_read_unlock(); |
| 2191 | } |
| 2192 | |
| 2193 | /* |
| 2194 | * If ratelimit_pages is too high then we can get into dirty-data overload |
| 2195 | * if a large number of processes all perform writes at the same time. |
| 2196 | * |
| 2197 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are |
| 2198 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory |
| 2199 | * thresholds. |
| 2200 | */ |
| 2201 | |
| 2202 | void writeback_set_ratelimit(void) |
| 2203 | { |
| 2204 | struct wb_domain *dom = &global_wb_domain; |
| 2205 | unsigned long background_thresh; |
| 2206 | unsigned long dirty_thresh; |
| 2207 | |
| 2208 | global_dirty_limits(&background_thresh, &dirty_thresh); |
| 2209 | dom->dirty_limit = dirty_thresh; |
| 2210 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
| 2211 | if (ratelimit_pages < 16) |
| 2212 | ratelimit_pages = 16; |
| 2213 | } |
| 2214 | |
| 2215 | static int page_writeback_cpu_online(unsigned int cpu) |
| 2216 | { |
| 2217 | writeback_set_ratelimit(); |
| 2218 | return 0; |
| 2219 | } |
| 2220 | |
| 2221 | #ifdef CONFIG_SYSCTL |
| 2222 | |
| 2223 | /* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */ |
| 2224 | static const unsigned long dirty_bytes_min = 2 * PAGE_SIZE; |
| 2225 | |
| 2226 | static struct ctl_table vm_page_writeback_sysctls[] = { |
| 2227 | { |
| 2228 | .procname = "dirty_background_ratio", |
| 2229 | .data = &dirty_background_ratio, |
| 2230 | .maxlen = sizeof(dirty_background_ratio), |
| 2231 | .mode = 0644, |
| 2232 | .proc_handler = dirty_background_ratio_handler, |
| 2233 | .extra1 = SYSCTL_ZERO, |
| 2234 | .extra2 = SYSCTL_ONE_HUNDRED, |
| 2235 | }, |
| 2236 | { |
| 2237 | .procname = "dirty_background_bytes", |
| 2238 | .data = &dirty_background_bytes, |
| 2239 | .maxlen = sizeof(dirty_background_bytes), |
| 2240 | .mode = 0644, |
| 2241 | .proc_handler = dirty_background_bytes_handler, |
| 2242 | .extra1 = SYSCTL_LONG_ONE, |
| 2243 | }, |
| 2244 | { |
| 2245 | .procname = "dirty_ratio", |
| 2246 | .data = &vm_dirty_ratio, |
| 2247 | .maxlen = sizeof(vm_dirty_ratio), |
| 2248 | .mode = 0644, |
| 2249 | .proc_handler = dirty_ratio_handler, |
| 2250 | .extra1 = SYSCTL_ZERO, |
| 2251 | .extra2 = SYSCTL_ONE_HUNDRED, |
| 2252 | }, |
| 2253 | { |
| 2254 | .procname = "dirty_bytes", |
| 2255 | .data = &vm_dirty_bytes, |
| 2256 | .maxlen = sizeof(vm_dirty_bytes), |
| 2257 | .mode = 0644, |
| 2258 | .proc_handler = dirty_bytes_handler, |
| 2259 | .extra1 = (void *)&dirty_bytes_min, |
| 2260 | }, |
| 2261 | { |
| 2262 | .procname = "dirty_writeback_centisecs", |
| 2263 | .data = &dirty_writeback_interval, |
| 2264 | .maxlen = sizeof(dirty_writeback_interval), |
| 2265 | .mode = 0644, |
| 2266 | .proc_handler = dirty_writeback_centisecs_handler, |
| 2267 | }, |
| 2268 | { |
| 2269 | .procname = "dirty_expire_centisecs", |
| 2270 | .data = &dirty_expire_interval, |
| 2271 | .maxlen = sizeof(dirty_expire_interval), |
| 2272 | .mode = 0644, |
| 2273 | .proc_handler = proc_dointvec_minmax, |
| 2274 | .extra1 = SYSCTL_ZERO, |
| 2275 | }, |
| 2276 | #ifdef CONFIG_HIGHMEM |
| 2277 | { |
| 2278 | .procname = "highmem_is_dirtyable", |
| 2279 | .data = &vm_highmem_is_dirtyable, |
| 2280 | .maxlen = sizeof(vm_highmem_is_dirtyable), |
| 2281 | .mode = 0644, |
| 2282 | .proc_handler = proc_dointvec_minmax, |
| 2283 | .extra1 = SYSCTL_ZERO, |
| 2284 | .extra2 = SYSCTL_ONE, |
| 2285 | }, |
| 2286 | #endif |
| 2287 | { |
| 2288 | .procname = "laptop_mode", |
| 2289 | .data = &laptop_mode, |
| 2290 | .maxlen = sizeof(laptop_mode), |
| 2291 | .mode = 0644, |
| 2292 | .proc_handler = proc_dointvec_jiffies, |
| 2293 | }, |
| 2294 | {} |
| 2295 | }; |
| 2296 | #endif |
| 2297 | |
| 2298 | /* |
| 2299 | * Called early on to tune the page writeback dirty limits. |
| 2300 | * |
| 2301 | * We used to scale dirty pages according to how total memory |
| 2302 | * related to pages that could be allocated for buffers. |
| 2303 | * |
| 2304 | * However, that was when we used "dirty_ratio" to scale with |
| 2305 | * all memory, and we don't do that any more. "dirty_ratio" |
| 2306 | * is now applied to total non-HIGHPAGE memory, and as such we can't |
| 2307 | * get into the old insane situation any more where we had |
| 2308 | * large amounts of dirty pages compared to a small amount of |
| 2309 | * non-HIGHMEM memory. |
| 2310 | * |
| 2311 | * But we might still want to scale the dirty_ratio by how |
| 2312 | * much memory the box has.. |
| 2313 | */ |
| 2314 | void __init page_writeback_init(void) |
| 2315 | { |
| 2316 | BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL)); |
| 2317 | |
| 2318 | cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online", |
| 2319 | page_writeback_cpu_online, NULL); |
| 2320 | cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL, |
| 2321 | page_writeback_cpu_online); |
| 2322 | #ifdef CONFIG_SYSCTL |
| 2323 | register_sysctl_init("vm", vm_page_writeback_sysctls); |
| 2324 | #endif |
| 2325 | } |
| 2326 | |
| 2327 | /** |
| 2328 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages |
| 2329 | * @mapping: address space structure to write |
| 2330 | * @start: starting page index |
| 2331 | * @end: ending page index (inclusive) |
| 2332 | * |
| 2333 | * This function scans the page range from @start to @end (inclusive) and tags |
| 2334 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is |
| 2335 | * that write_cache_pages (or whoever calls this function) will then use |
| 2336 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is |
| 2337 | * used to avoid livelocking of writeback by a process steadily creating new |
| 2338 | * dirty pages in the file (thus it is important for this function to be quick |
| 2339 | * so that it can tag pages faster than a dirtying process can create them). |
| 2340 | */ |
| 2341 | void tag_pages_for_writeback(struct address_space *mapping, |
| 2342 | pgoff_t start, pgoff_t end) |
| 2343 | { |
| 2344 | XA_STATE(xas, &mapping->i_pages, start); |
| 2345 | unsigned int tagged = 0; |
| 2346 | void *page; |
| 2347 | |
| 2348 | xas_lock_irq(&xas); |
| 2349 | xas_for_each_marked(&xas, page, end, PAGECACHE_TAG_DIRTY) { |
| 2350 | xas_set_mark(&xas, PAGECACHE_TAG_TOWRITE); |
| 2351 | if (++tagged % XA_CHECK_SCHED) |
| 2352 | continue; |
| 2353 | |
| 2354 | xas_pause(&xas); |
| 2355 | xas_unlock_irq(&xas); |
| 2356 | cond_resched(); |
| 2357 | xas_lock_irq(&xas); |
| 2358 | } |
| 2359 | xas_unlock_irq(&xas); |
| 2360 | } |
| 2361 | EXPORT_SYMBOL(tag_pages_for_writeback); |
| 2362 | |
| 2363 | /** |
| 2364 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
| 2365 | * @mapping: address space structure to write |
| 2366 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write |
| 2367 | * @writepage: function called for each page |
| 2368 | * @data: data passed to writepage function |
| 2369 | * |
| 2370 | * If a page is already under I/O, write_cache_pages() skips it, even |
| 2371 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
| 2372 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() |
| 2373 | * and msync() need to guarantee that all the data which was dirty at the time |
| 2374 | * the call was made get new I/O started against them. If wbc->sync_mode is |
| 2375 | * WB_SYNC_ALL then we were called for data integrity and we must wait for |
| 2376 | * existing IO to complete. |
| 2377 | * |
| 2378 | * To avoid livelocks (when other process dirties new pages), we first tag |
| 2379 | * pages which should be written back with TOWRITE tag and only then start |
| 2380 | * writing them. For data-integrity sync we have to be careful so that we do |
| 2381 | * not miss some pages (e.g., because some other process has cleared TOWRITE |
| 2382 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only |
| 2383 | * by the process clearing the DIRTY tag (and submitting the page for IO). |
| 2384 | * |
| 2385 | * To avoid deadlocks between range_cyclic writeback and callers that hold |
| 2386 | * pages in PageWriteback to aggregate IO until write_cache_pages() returns, |
| 2387 | * we do not loop back to the start of the file. Doing so causes a page |
| 2388 | * lock/page writeback access order inversion - we should only ever lock |
| 2389 | * multiple pages in ascending page->index order, and looping back to the start |
| 2390 | * of the file violates that rule and causes deadlocks. |
| 2391 | * |
| 2392 | * Return: %0 on success, negative error code otherwise |
| 2393 | */ |
| 2394 | int write_cache_pages(struct address_space *mapping, |
| 2395 | struct writeback_control *wbc, writepage_t writepage, |
| 2396 | void *data) |
| 2397 | { |
| 2398 | int ret = 0; |
| 2399 | int done = 0; |
| 2400 | int error; |
| 2401 | struct folio_batch fbatch; |
| 2402 | int nr_folios; |
| 2403 | pgoff_t index; |
| 2404 | pgoff_t end; /* Inclusive */ |
| 2405 | pgoff_t done_index; |
| 2406 | int range_whole = 0; |
| 2407 | xa_mark_t tag; |
| 2408 | |
| 2409 | folio_batch_init(&fbatch); |
| 2410 | if (wbc->range_cyclic) { |
| 2411 | index = mapping->writeback_index; /* prev offset */ |
| 2412 | end = -1; |
| 2413 | } else { |
| 2414 | index = wbc->range_start >> PAGE_SHIFT; |
| 2415 | end = wbc->range_end >> PAGE_SHIFT; |
| 2416 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
| 2417 | range_whole = 1; |
| 2418 | } |
| 2419 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) { |
| 2420 | tag_pages_for_writeback(mapping, index, end); |
| 2421 | tag = PAGECACHE_TAG_TOWRITE; |
| 2422 | } else { |
| 2423 | tag = PAGECACHE_TAG_DIRTY; |
| 2424 | } |
| 2425 | done_index = index; |
| 2426 | while (!done && (index <= end)) { |
| 2427 | int i; |
| 2428 | |
| 2429 | nr_folios = filemap_get_folios_tag(mapping, &index, end, |
| 2430 | tag, &fbatch); |
| 2431 | |
| 2432 | if (nr_folios == 0) |
| 2433 | break; |
| 2434 | |
| 2435 | for (i = 0; i < nr_folios; i++) { |
| 2436 | struct folio *folio = fbatch.folios[i]; |
| 2437 | |
| 2438 | done_index = folio->index; |
| 2439 | |
| 2440 | folio_lock(folio); |
| 2441 | |
| 2442 | /* |
| 2443 | * Page truncated or invalidated. We can freely skip it |
| 2444 | * then, even for data integrity operations: the page |
| 2445 | * has disappeared concurrently, so there could be no |
| 2446 | * real expectation of this data integrity operation |
| 2447 | * even if there is now a new, dirty page at the same |
| 2448 | * pagecache address. |
| 2449 | */ |
| 2450 | if (unlikely(folio->mapping != mapping)) { |
| 2451 | continue_unlock: |
| 2452 | folio_unlock(folio); |
| 2453 | continue; |
| 2454 | } |
| 2455 | |
| 2456 | if (!folio_test_dirty(folio)) { |
| 2457 | /* someone wrote it for us */ |
| 2458 | goto continue_unlock; |
| 2459 | } |
| 2460 | |
| 2461 | if (folio_test_writeback(folio)) { |
| 2462 | if (wbc->sync_mode != WB_SYNC_NONE) |
| 2463 | folio_wait_writeback(folio); |
| 2464 | else |
| 2465 | goto continue_unlock; |
| 2466 | } |
| 2467 | |
| 2468 | BUG_ON(folio_test_writeback(folio)); |
| 2469 | if (!folio_clear_dirty_for_io(folio)) |
| 2470 | goto continue_unlock; |
| 2471 | |
| 2472 | trace_wbc_writepage(wbc, inode_to_bdi(mapping->host)); |
| 2473 | error = writepage(folio, wbc, data); |
| 2474 | if (unlikely(error)) { |
| 2475 | /* |
| 2476 | * Handle errors according to the type of |
| 2477 | * writeback. There's no need to continue for |
| 2478 | * background writeback. Just push done_index |
| 2479 | * past this page so media errors won't choke |
| 2480 | * writeout for the entire file. For integrity |
| 2481 | * writeback, we must process the entire dirty |
| 2482 | * set regardless of errors because the fs may |
| 2483 | * still have state to clear for each page. In |
| 2484 | * that case we continue processing and return |
| 2485 | * the first error. |
| 2486 | */ |
| 2487 | if (error == AOP_WRITEPAGE_ACTIVATE) { |
| 2488 | folio_unlock(folio); |
| 2489 | error = 0; |
| 2490 | } else if (wbc->sync_mode != WB_SYNC_ALL) { |
| 2491 | ret = error; |
| 2492 | done_index = folio->index + |
| 2493 | folio_nr_pages(folio); |
| 2494 | done = 1; |
| 2495 | break; |
| 2496 | } |
| 2497 | if (!ret) |
| 2498 | ret = error; |
| 2499 | } |
| 2500 | |
| 2501 | /* |
| 2502 | * We stop writing back only if we are not doing |
| 2503 | * integrity sync. In case of integrity sync we have to |
| 2504 | * keep going until we have written all the pages |
| 2505 | * we tagged for writeback prior to entering this loop. |
| 2506 | */ |
| 2507 | if (--wbc->nr_to_write <= 0 && |
| 2508 | wbc->sync_mode == WB_SYNC_NONE) { |
| 2509 | done = 1; |
| 2510 | break; |
| 2511 | } |
| 2512 | } |
| 2513 | folio_batch_release(&fbatch); |
| 2514 | cond_resched(); |
| 2515 | } |
| 2516 | |
| 2517 | /* |
| 2518 | * If we hit the last page and there is more work to be done: wrap |
| 2519 | * back the index back to the start of the file for the next |
| 2520 | * time we are called. |
| 2521 | */ |
| 2522 | if (wbc->range_cyclic && !done) |
| 2523 | done_index = 0; |
| 2524 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
| 2525 | mapping->writeback_index = done_index; |
| 2526 | |
| 2527 | return ret; |
| 2528 | } |
| 2529 | EXPORT_SYMBOL(write_cache_pages); |
| 2530 | |
| 2531 | static int writepage_cb(struct folio *folio, struct writeback_control *wbc, |
| 2532 | void *data) |
| 2533 | { |
| 2534 | struct address_space *mapping = data; |
| 2535 | int ret = mapping->a_ops->writepage(&folio->page, wbc); |
| 2536 | mapping_set_error(mapping, ret); |
| 2537 | return ret; |
| 2538 | } |
| 2539 | |
| 2540 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
| 2541 | { |
| 2542 | int ret; |
| 2543 | struct bdi_writeback *wb; |
| 2544 | |
| 2545 | if (wbc->nr_to_write <= 0) |
| 2546 | return 0; |
| 2547 | wb = inode_to_wb_wbc(mapping->host, wbc); |
| 2548 | wb_bandwidth_estimate_start(wb); |
| 2549 | while (1) { |
| 2550 | if (mapping->a_ops->writepages) { |
| 2551 | ret = mapping->a_ops->writepages(mapping, wbc); |
| 2552 | } else if (mapping->a_ops->writepage) { |
| 2553 | struct blk_plug plug; |
| 2554 | |
| 2555 | blk_start_plug(&plug); |
| 2556 | ret = write_cache_pages(mapping, wbc, writepage_cb, |
| 2557 | mapping); |
| 2558 | blk_finish_plug(&plug); |
| 2559 | } else { |
| 2560 | /* deal with chardevs and other special files */ |
| 2561 | ret = 0; |
| 2562 | } |
| 2563 | if (ret != -ENOMEM || wbc->sync_mode != WB_SYNC_ALL) |
| 2564 | break; |
| 2565 | |
| 2566 | /* |
| 2567 | * Lacking an allocation context or the locality or writeback |
| 2568 | * state of any of the inode's pages, throttle based on |
| 2569 | * writeback activity on the local node. It's as good a |
| 2570 | * guess as any. |
| 2571 | */ |
| 2572 | reclaim_throttle(NODE_DATA(numa_node_id()), |
| 2573 | VMSCAN_THROTTLE_WRITEBACK); |
| 2574 | } |
| 2575 | /* |
| 2576 | * Usually few pages are written by now from those we've just submitted |
| 2577 | * but if there's constant writeback being submitted, this makes sure |
| 2578 | * writeback bandwidth is updated once in a while. |
| 2579 | */ |
| 2580 | if (time_is_before_jiffies(READ_ONCE(wb->bw_time_stamp) + |
| 2581 | BANDWIDTH_INTERVAL)) |
| 2582 | wb_update_bandwidth(wb); |
| 2583 | return ret; |
| 2584 | } |
| 2585 | |
| 2586 | /* |
| 2587 | * For address_spaces which do not use buffers nor write back. |
| 2588 | */ |
| 2589 | bool noop_dirty_folio(struct address_space *mapping, struct folio *folio) |
| 2590 | { |
| 2591 | if (!folio_test_dirty(folio)) |
| 2592 | return !folio_test_set_dirty(folio); |
| 2593 | return false; |
| 2594 | } |
| 2595 | EXPORT_SYMBOL(noop_dirty_folio); |
| 2596 | |
| 2597 | /* |
| 2598 | * Helper function for set_page_dirty family. |
| 2599 | * |
| 2600 | * Caller must hold lock_page_memcg(). |
| 2601 | * |
| 2602 | * NOTE: This relies on being atomic wrt interrupts. |
| 2603 | */ |
| 2604 | static void folio_account_dirtied(struct folio *folio, |
| 2605 | struct address_space *mapping) |
| 2606 | { |
| 2607 | struct inode *inode = mapping->host; |
| 2608 | |
| 2609 | trace_writeback_dirty_folio(folio, mapping); |
| 2610 | |
| 2611 | if (mapping_can_writeback(mapping)) { |
| 2612 | struct bdi_writeback *wb; |
| 2613 | long nr = folio_nr_pages(folio); |
| 2614 | |
| 2615 | inode_attach_wb(inode, folio); |
| 2616 | wb = inode_to_wb(inode); |
| 2617 | |
| 2618 | __lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, nr); |
| 2619 | __zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr); |
| 2620 | __node_stat_mod_folio(folio, NR_DIRTIED, nr); |
| 2621 | wb_stat_mod(wb, WB_RECLAIMABLE, nr); |
| 2622 | wb_stat_mod(wb, WB_DIRTIED, nr); |
| 2623 | task_io_account_write(nr * PAGE_SIZE); |
| 2624 | current->nr_dirtied += nr; |
| 2625 | __this_cpu_add(bdp_ratelimits, nr); |
| 2626 | |
| 2627 | mem_cgroup_track_foreign_dirty(folio, wb); |
| 2628 | } |
| 2629 | } |
| 2630 | |
| 2631 | /* |
| 2632 | * Helper function for deaccounting dirty page without writeback. |
| 2633 | * |
| 2634 | * Caller must hold lock_page_memcg(). |
| 2635 | */ |
| 2636 | void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb) |
| 2637 | { |
| 2638 | long nr = folio_nr_pages(folio); |
| 2639 | |
| 2640 | lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr); |
| 2641 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); |
| 2642 | wb_stat_mod(wb, WB_RECLAIMABLE, -nr); |
| 2643 | task_io_account_cancelled_write(nr * PAGE_SIZE); |
| 2644 | } |
| 2645 | |
| 2646 | /* |
| 2647 | * Mark the folio dirty, and set it dirty in the page cache, and mark |
| 2648 | * the inode dirty. |
| 2649 | * |
| 2650 | * If warn is true, then emit a warning if the folio is not uptodate and has |
| 2651 | * not been truncated. |
| 2652 | * |
| 2653 | * The caller must hold lock_page_memcg(). Most callers have the folio |
| 2654 | * locked. A few have the folio blocked from truncation through other |
| 2655 | * means (eg zap_vma_pages() has it mapped and is holding the page table |
| 2656 | * lock). This can also be called from mark_buffer_dirty(), which I |
| 2657 | * cannot prove is always protected against truncate. |
| 2658 | */ |
| 2659 | void __folio_mark_dirty(struct folio *folio, struct address_space *mapping, |
| 2660 | int warn) |
| 2661 | { |
| 2662 | unsigned long flags; |
| 2663 | |
| 2664 | xa_lock_irqsave(&mapping->i_pages, flags); |
| 2665 | if (folio->mapping) { /* Race with truncate? */ |
| 2666 | WARN_ON_ONCE(warn && !folio_test_uptodate(folio)); |
| 2667 | folio_account_dirtied(folio, mapping); |
| 2668 | __xa_set_mark(&mapping->i_pages, folio_index(folio), |
| 2669 | PAGECACHE_TAG_DIRTY); |
| 2670 | } |
| 2671 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
| 2672 | } |
| 2673 | |
| 2674 | /** |
| 2675 | * filemap_dirty_folio - Mark a folio dirty for filesystems which do not use buffer_heads. |
| 2676 | * @mapping: Address space this folio belongs to. |
| 2677 | * @folio: Folio to be marked as dirty. |
| 2678 | * |
| 2679 | * Filesystems which do not use buffer heads should call this function |
| 2680 | * from their set_page_dirty address space operation. It ignores the |
| 2681 | * contents of folio_get_private(), so if the filesystem marks individual |
| 2682 | * blocks as dirty, the filesystem should handle that itself. |
| 2683 | * |
| 2684 | * This is also sometimes used by filesystems which use buffer_heads when |
| 2685 | * a single buffer is being dirtied: we want to set the folio dirty in |
| 2686 | * that case, but not all the buffers. This is a "bottom-up" dirtying, |
| 2687 | * whereas block_dirty_folio() is a "top-down" dirtying. |
| 2688 | * |
| 2689 | * The caller must ensure this doesn't race with truncation. Most will |
| 2690 | * simply hold the folio lock, but e.g. zap_pte_range() calls with the |
| 2691 | * folio mapped and the pte lock held, which also locks out truncation. |
| 2692 | */ |
| 2693 | bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio) |
| 2694 | { |
| 2695 | folio_memcg_lock(folio); |
| 2696 | if (folio_test_set_dirty(folio)) { |
| 2697 | folio_memcg_unlock(folio); |
| 2698 | return false; |
| 2699 | } |
| 2700 | |
| 2701 | __folio_mark_dirty(folio, mapping, !folio_test_private(folio)); |
| 2702 | folio_memcg_unlock(folio); |
| 2703 | |
| 2704 | if (mapping->host) { |
| 2705 | /* !PageAnon && !swapper_space */ |
| 2706 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| 2707 | } |
| 2708 | return true; |
| 2709 | } |
| 2710 | EXPORT_SYMBOL(filemap_dirty_folio); |
| 2711 | |
| 2712 | /** |
| 2713 | * folio_account_redirty - Manually account for redirtying a page. |
| 2714 | * @folio: The folio which is being redirtied. |
| 2715 | * |
| 2716 | * Most filesystems should call folio_redirty_for_writepage() instead |
| 2717 | * of this fuction. If your filesystem is doing writeback outside the |
| 2718 | * context of a writeback_control(), it can call this when redirtying |
| 2719 | * a folio, to de-account the dirty counters (NR_DIRTIED, WB_DIRTIED, |
| 2720 | * tsk->nr_dirtied), so that they match the written counters (NR_WRITTEN, |
| 2721 | * WB_WRITTEN) in long term. The mismatches will lead to systematic errors |
| 2722 | * in balanced_dirty_ratelimit and the dirty pages position control. |
| 2723 | */ |
| 2724 | void folio_account_redirty(struct folio *folio) |
| 2725 | { |
| 2726 | struct address_space *mapping = folio->mapping; |
| 2727 | |
| 2728 | if (mapping && mapping_can_writeback(mapping)) { |
| 2729 | struct inode *inode = mapping->host; |
| 2730 | struct bdi_writeback *wb; |
| 2731 | struct wb_lock_cookie cookie = {}; |
| 2732 | long nr = folio_nr_pages(folio); |
| 2733 | |
| 2734 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
| 2735 | current->nr_dirtied -= nr; |
| 2736 | node_stat_mod_folio(folio, NR_DIRTIED, -nr); |
| 2737 | wb_stat_mod(wb, WB_DIRTIED, -nr); |
| 2738 | unlocked_inode_to_wb_end(inode, &cookie); |
| 2739 | } |
| 2740 | } |
| 2741 | EXPORT_SYMBOL(folio_account_redirty); |
| 2742 | |
| 2743 | /** |
| 2744 | * folio_redirty_for_writepage - Decline to write a dirty folio. |
| 2745 | * @wbc: The writeback control. |
| 2746 | * @folio: The folio. |
| 2747 | * |
| 2748 | * When a writepage implementation decides that it doesn't want to write |
| 2749 | * @folio for some reason, it should call this function, unlock @folio and |
| 2750 | * return 0. |
| 2751 | * |
| 2752 | * Return: True if we redirtied the folio. False if someone else dirtied |
| 2753 | * it first. |
| 2754 | */ |
| 2755 | bool folio_redirty_for_writepage(struct writeback_control *wbc, |
| 2756 | struct folio *folio) |
| 2757 | { |
| 2758 | bool ret; |
| 2759 | long nr = folio_nr_pages(folio); |
| 2760 | |
| 2761 | wbc->pages_skipped += nr; |
| 2762 | ret = filemap_dirty_folio(folio->mapping, folio); |
| 2763 | folio_account_redirty(folio); |
| 2764 | |
| 2765 | return ret; |
| 2766 | } |
| 2767 | EXPORT_SYMBOL(folio_redirty_for_writepage); |
| 2768 | |
| 2769 | /** |
| 2770 | * folio_mark_dirty - Mark a folio as being modified. |
| 2771 | * @folio: The folio. |
| 2772 | * |
| 2773 | * The folio may not be truncated while this function is running. |
| 2774 | * Holding the folio lock is sufficient to prevent truncation, but some |
| 2775 | * callers cannot acquire a sleeping lock. These callers instead hold |
| 2776 | * the page table lock for a page table which contains at least one page |
| 2777 | * in this folio. Truncation will block on the page table lock as it |
| 2778 | * unmaps pages before removing the folio from its mapping. |
| 2779 | * |
| 2780 | * Return: True if the folio was newly dirtied, false if it was already dirty. |
| 2781 | */ |
| 2782 | bool folio_mark_dirty(struct folio *folio) |
| 2783 | { |
| 2784 | struct address_space *mapping = folio_mapping(folio); |
| 2785 | |
| 2786 | if (likely(mapping)) { |
| 2787 | /* |
| 2788 | * readahead/folio_deactivate could remain |
| 2789 | * PG_readahead/PG_reclaim due to race with folio_end_writeback |
| 2790 | * About readahead, if the folio is written, the flags would be |
| 2791 | * reset. So no problem. |
| 2792 | * About folio_deactivate, if the folio is redirtied, |
| 2793 | * the flag will be reset. So no problem. but if the |
| 2794 | * folio is used by readahead it will confuse readahead |
| 2795 | * and make it restart the size rampup process. But it's |
| 2796 | * a trivial problem. |
| 2797 | */ |
| 2798 | if (folio_test_reclaim(folio)) |
| 2799 | folio_clear_reclaim(folio); |
| 2800 | return mapping->a_ops->dirty_folio(mapping, folio); |
| 2801 | } |
| 2802 | |
| 2803 | return noop_dirty_folio(mapping, folio); |
| 2804 | } |
| 2805 | EXPORT_SYMBOL(folio_mark_dirty); |
| 2806 | |
| 2807 | /* |
| 2808 | * set_page_dirty() is racy if the caller has no reference against |
| 2809 | * page->mapping->host, and if the page is unlocked. This is because another |
| 2810 | * CPU could truncate the page off the mapping and then free the mapping. |
| 2811 | * |
| 2812 | * Usually, the page _is_ locked, or the caller is a user-space process which |
| 2813 | * holds a reference on the inode by having an open file. |
| 2814 | * |
| 2815 | * In other cases, the page should be locked before running set_page_dirty(). |
| 2816 | */ |
| 2817 | int set_page_dirty_lock(struct page *page) |
| 2818 | { |
| 2819 | int ret; |
| 2820 | |
| 2821 | lock_page(page); |
| 2822 | ret = set_page_dirty(page); |
| 2823 | unlock_page(page); |
| 2824 | return ret; |
| 2825 | } |
| 2826 | EXPORT_SYMBOL(set_page_dirty_lock); |
| 2827 | |
| 2828 | /* |
| 2829 | * This cancels just the dirty bit on the kernel page itself, it does NOT |
| 2830 | * actually remove dirty bits on any mmap's that may be around. It also |
| 2831 | * leaves the page tagged dirty, so any sync activity will still find it on |
| 2832 | * the dirty lists, and in particular, clear_page_dirty_for_io() will still |
| 2833 | * look at the dirty bits in the VM. |
| 2834 | * |
| 2835 | * Doing this should *normally* only ever be done when a page is truncated, |
| 2836 | * and is not actually mapped anywhere at all. However, fs/buffer.c does |
| 2837 | * this when it notices that somebody has cleaned out all the buffers on a |
| 2838 | * page without actually doing it through the VM. Can you say "ext3 is |
| 2839 | * horribly ugly"? Thought you could. |
| 2840 | */ |
| 2841 | void __folio_cancel_dirty(struct folio *folio) |
| 2842 | { |
| 2843 | struct address_space *mapping = folio_mapping(folio); |
| 2844 | |
| 2845 | if (mapping_can_writeback(mapping)) { |
| 2846 | struct inode *inode = mapping->host; |
| 2847 | struct bdi_writeback *wb; |
| 2848 | struct wb_lock_cookie cookie = {}; |
| 2849 | |
| 2850 | folio_memcg_lock(folio); |
| 2851 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
| 2852 | |
| 2853 | if (folio_test_clear_dirty(folio)) |
| 2854 | folio_account_cleaned(folio, wb); |
| 2855 | |
| 2856 | unlocked_inode_to_wb_end(inode, &cookie); |
| 2857 | folio_memcg_unlock(folio); |
| 2858 | } else { |
| 2859 | folio_clear_dirty(folio); |
| 2860 | } |
| 2861 | } |
| 2862 | EXPORT_SYMBOL(__folio_cancel_dirty); |
| 2863 | |
| 2864 | /* |
| 2865 | * Clear a folio's dirty flag, while caring for dirty memory accounting. |
| 2866 | * Returns true if the folio was previously dirty. |
| 2867 | * |
| 2868 | * This is for preparing to put the folio under writeout. We leave |
| 2869 | * the folio tagged as dirty in the xarray so that a concurrent |
| 2870 | * write-for-sync can discover it via a PAGECACHE_TAG_DIRTY walk. |
| 2871 | * The ->writepage implementation will run either folio_start_writeback() |
| 2872 | * or folio_mark_dirty(), at which stage we bring the folio's dirty flag |
| 2873 | * and xarray dirty tag back into sync. |
| 2874 | * |
| 2875 | * This incoherency between the folio's dirty flag and xarray tag is |
| 2876 | * unfortunate, but it only exists while the folio is locked. |
| 2877 | */ |
| 2878 | bool folio_clear_dirty_for_io(struct folio *folio) |
| 2879 | { |
| 2880 | struct address_space *mapping = folio_mapping(folio); |
| 2881 | bool ret = false; |
| 2882 | |
| 2883 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| 2884 | |
| 2885 | if (mapping && mapping_can_writeback(mapping)) { |
| 2886 | struct inode *inode = mapping->host; |
| 2887 | struct bdi_writeback *wb; |
| 2888 | struct wb_lock_cookie cookie = {}; |
| 2889 | |
| 2890 | /* |
| 2891 | * Yes, Virginia, this is indeed insane. |
| 2892 | * |
| 2893 | * We use this sequence to make sure that |
| 2894 | * (a) we account for dirty stats properly |
| 2895 | * (b) we tell the low-level filesystem to |
| 2896 | * mark the whole folio dirty if it was |
| 2897 | * dirty in a pagetable. Only to then |
| 2898 | * (c) clean the folio again and return 1 to |
| 2899 | * cause the writeback. |
| 2900 | * |
| 2901 | * This way we avoid all nasty races with the |
| 2902 | * dirty bit in multiple places and clearing |
| 2903 | * them concurrently from different threads. |
| 2904 | * |
| 2905 | * Note! Normally the "folio_mark_dirty(folio)" |
| 2906 | * has no effect on the actual dirty bit - since |
| 2907 | * that will already usually be set. But we |
| 2908 | * need the side effects, and it can help us |
| 2909 | * avoid races. |
| 2910 | * |
| 2911 | * We basically use the folio "master dirty bit" |
| 2912 | * as a serialization point for all the different |
| 2913 | * threads doing their things. |
| 2914 | */ |
| 2915 | if (folio_mkclean(folio)) |
| 2916 | folio_mark_dirty(folio); |
| 2917 | /* |
| 2918 | * We carefully synchronise fault handlers against |
| 2919 | * installing a dirty pte and marking the folio dirty |
| 2920 | * at this point. We do this by having them hold the |
| 2921 | * page lock while dirtying the folio, and folios are |
| 2922 | * always locked coming in here, so we get the desired |
| 2923 | * exclusion. |
| 2924 | */ |
| 2925 | wb = unlocked_inode_to_wb_begin(inode, &cookie); |
| 2926 | if (folio_test_clear_dirty(folio)) { |
| 2927 | long nr = folio_nr_pages(folio); |
| 2928 | lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr); |
| 2929 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); |
| 2930 | wb_stat_mod(wb, WB_RECLAIMABLE, -nr); |
| 2931 | ret = true; |
| 2932 | } |
| 2933 | unlocked_inode_to_wb_end(inode, &cookie); |
| 2934 | return ret; |
| 2935 | } |
| 2936 | return folio_test_clear_dirty(folio); |
| 2937 | } |
| 2938 | EXPORT_SYMBOL(folio_clear_dirty_for_io); |
| 2939 | |
| 2940 | static void wb_inode_writeback_start(struct bdi_writeback *wb) |
| 2941 | { |
| 2942 | atomic_inc(&wb->writeback_inodes); |
| 2943 | } |
| 2944 | |
| 2945 | static void wb_inode_writeback_end(struct bdi_writeback *wb) |
| 2946 | { |
| 2947 | unsigned long flags; |
| 2948 | atomic_dec(&wb->writeback_inodes); |
| 2949 | /* |
| 2950 | * Make sure estimate of writeback throughput gets updated after |
| 2951 | * writeback completed. We delay the update by BANDWIDTH_INTERVAL |
| 2952 | * (which is the interval other bandwidth updates use for batching) so |
| 2953 | * that if multiple inodes end writeback at a similar time, they get |
| 2954 | * batched into one bandwidth update. |
| 2955 | */ |
| 2956 | spin_lock_irqsave(&wb->work_lock, flags); |
| 2957 | if (test_bit(WB_registered, &wb->state)) |
| 2958 | queue_delayed_work(bdi_wq, &wb->bw_dwork, BANDWIDTH_INTERVAL); |
| 2959 | spin_unlock_irqrestore(&wb->work_lock, flags); |
| 2960 | } |
| 2961 | |
| 2962 | bool __folio_end_writeback(struct folio *folio) |
| 2963 | { |
| 2964 | long nr = folio_nr_pages(folio); |
| 2965 | struct address_space *mapping = folio_mapping(folio); |
| 2966 | bool ret; |
| 2967 | |
| 2968 | folio_memcg_lock(folio); |
| 2969 | if (mapping && mapping_use_writeback_tags(mapping)) { |
| 2970 | struct inode *inode = mapping->host; |
| 2971 | struct backing_dev_info *bdi = inode_to_bdi(inode); |
| 2972 | unsigned long flags; |
| 2973 | |
| 2974 | xa_lock_irqsave(&mapping->i_pages, flags); |
| 2975 | ret = folio_test_clear_writeback(folio); |
| 2976 | if (ret) { |
| 2977 | __xa_clear_mark(&mapping->i_pages, folio_index(folio), |
| 2978 | PAGECACHE_TAG_WRITEBACK); |
| 2979 | if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) { |
| 2980 | struct bdi_writeback *wb = inode_to_wb(inode); |
| 2981 | |
| 2982 | wb_stat_mod(wb, WB_WRITEBACK, -nr); |
| 2983 | __wb_writeout_add(wb, nr); |
| 2984 | if (!mapping_tagged(mapping, |
| 2985 | PAGECACHE_TAG_WRITEBACK)) |
| 2986 | wb_inode_writeback_end(wb); |
| 2987 | } |
| 2988 | } |
| 2989 | |
| 2990 | if (mapping->host && !mapping_tagged(mapping, |
| 2991 | PAGECACHE_TAG_WRITEBACK)) |
| 2992 | sb_clear_inode_writeback(mapping->host); |
| 2993 | |
| 2994 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
| 2995 | } else { |
| 2996 | ret = folio_test_clear_writeback(folio); |
| 2997 | } |
| 2998 | if (ret) { |
| 2999 | lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr); |
| 3000 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); |
| 3001 | node_stat_mod_folio(folio, NR_WRITTEN, nr); |
| 3002 | } |
| 3003 | folio_memcg_unlock(folio); |
| 3004 | return ret; |
| 3005 | } |
| 3006 | |
| 3007 | bool __folio_start_writeback(struct folio *folio, bool keep_write) |
| 3008 | { |
| 3009 | long nr = folio_nr_pages(folio); |
| 3010 | struct address_space *mapping = folio_mapping(folio); |
| 3011 | bool ret; |
| 3012 | int access_ret; |
| 3013 | |
| 3014 | folio_memcg_lock(folio); |
| 3015 | if (mapping && mapping_use_writeback_tags(mapping)) { |
| 3016 | XA_STATE(xas, &mapping->i_pages, folio_index(folio)); |
| 3017 | struct inode *inode = mapping->host; |
| 3018 | struct backing_dev_info *bdi = inode_to_bdi(inode); |
| 3019 | unsigned long flags; |
| 3020 | |
| 3021 | xas_lock_irqsave(&xas, flags); |
| 3022 | xas_load(&xas); |
| 3023 | ret = folio_test_set_writeback(folio); |
| 3024 | if (!ret) { |
| 3025 | bool on_wblist; |
| 3026 | |
| 3027 | on_wblist = mapping_tagged(mapping, |
| 3028 | PAGECACHE_TAG_WRITEBACK); |
| 3029 | |
| 3030 | xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK); |
| 3031 | if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) { |
| 3032 | struct bdi_writeback *wb = inode_to_wb(inode); |
| 3033 | |
| 3034 | wb_stat_mod(wb, WB_WRITEBACK, nr); |
| 3035 | if (!on_wblist) |
| 3036 | wb_inode_writeback_start(wb); |
| 3037 | } |
| 3038 | |
| 3039 | /* |
| 3040 | * We can come through here when swapping |
| 3041 | * anonymous folios, so we don't necessarily |
| 3042 | * have an inode to track for sync. |
| 3043 | */ |
| 3044 | if (mapping->host && !on_wblist) |
| 3045 | sb_mark_inode_writeback(mapping->host); |
| 3046 | } |
| 3047 | if (!folio_test_dirty(folio)) |
| 3048 | xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); |
| 3049 | if (!keep_write) |
| 3050 | xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE); |
| 3051 | xas_unlock_irqrestore(&xas, flags); |
| 3052 | } else { |
| 3053 | ret = folio_test_set_writeback(folio); |
| 3054 | } |
| 3055 | if (!ret) { |
| 3056 | lruvec_stat_mod_folio(folio, NR_WRITEBACK, nr); |
| 3057 | zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr); |
| 3058 | } |
| 3059 | folio_memcg_unlock(folio); |
| 3060 | access_ret = arch_make_folio_accessible(folio); |
| 3061 | /* |
| 3062 | * If writeback has been triggered on a page that cannot be made |
| 3063 | * accessible, it is too late to recover here. |
| 3064 | */ |
| 3065 | VM_BUG_ON_FOLIO(access_ret != 0, folio); |
| 3066 | |
| 3067 | return ret; |
| 3068 | } |
| 3069 | EXPORT_SYMBOL(__folio_start_writeback); |
| 3070 | |
| 3071 | /** |
| 3072 | * folio_wait_writeback - Wait for a folio to finish writeback. |
| 3073 | * @folio: The folio to wait for. |
| 3074 | * |
| 3075 | * If the folio is currently being written back to storage, wait for the |
| 3076 | * I/O to complete. |
| 3077 | * |
| 3078 | * Context: Sleeps. Must be called in process context and with |
| 3079 | * no spinlocks held. Caller should hold a reference on the folio. |
| 3080 | * If the folio is not locked, writeback may start again after writeback |
| 3081 | * has finished. |
| 3082 | */ |
| 3083 | void folio_wait_writeback(struct folio *folio) |
| 3084 | { |
| 3085 | while (folio_test_writeback(folio)) { |
| 3086 | trace_folio_wait_writeback(folio, folio_mapping(folio)); |
| 3087 | folio_wait_bit(folio, PG_writeback); |
| 3088 | } |
| 3089 | } |
| 3090 | EXPORT_SYMBOL_GPL(folio_wait_writeback); |
| 3091 | |
| 3092 | /** |
| 3093 | * folio_wait_writeback_killable - Wait for a folio to finish writeback. |
| 3094 | * @folio: The folio to wait for. |
| 3095 | * |
| 3096 | * If the folio is currently being written back to storage, wait for the |
| 3097 | * I/O to complete or a fatal signal to arrive. |
| 3098 | * |
| 3099 | * Context: Sleeps. Must be called in process context and with |
| 3100 | * no spinlocks held. Caller should hold a reference on the folio. |
| 3101 | * If the folio is not locked, writeback may start again after writeback |
| 3102 | * has finished. |
| 3103 | * Return: 0 on success, -EINTR if we get a fatal signal while waiting. |
| 3104 | */ |
| 3105 | int folio_wait_writeback_killable(struct folio *folio) |
| 3106 | { |
| 3107 | while (folio_test_writeback(folio)) { |
| 3108 | trace_folio_wait_writeback(folio, folio_mapping(folio)); |
| 3109 | if (folio_wait_bit_killable(folio, PG_writeback)) |
| 3110 | return -EINTR; |
| 3111 | } |
| 3112 | |
| 3113 | return 0; |
| 3114 | } |
| 3115 | EXPORT_SYMBOL_GPL(folio_wait_writeback_killable); |
| 3116 | |
| 3117 | /** |
| 3118 | * folio_wait_stable() - wait for writeback to finish, if necessary. |
| 3119 | * @folio: The folio to wait on. |
| 3120 | * |
| 3121 | * This function determines if the given folio is related to a backing |
| 3122 | * device that requires folio contents to be held stable during writeback. |
| 3123 | * If so, then it will wait for any pending writeback to complete. |
| 3124 | * |
| 3125 | * Context: Sleeps. Must be called in process context and with |
| 3126 | * no spinlocks held. Caller should hold a reference on the folio. |
| 3127 | * If the folio is not locked, writeback may start again after writeback |
| 3128 | * has finished. |
| 3129 | */ |
| 3130 | void folio_wait_stable(struct folio *folio) |
| 3131 | { |
| 3132 | if (folio_inode(folio)->i_sb->s_iflags & SB_I_STABLE_WRITES) |
| 3133 | folio_wait_writeback(folio); |
| 3134 | } |
| 3135 | EXPORT_SYMBOL_GPL(folio_wait_stable); |