Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
Uwe Zeisberger | f30c226 | 2006-10-03 23:01:26 +0200 | [diff] [blame] | 2 | * mm/page-writeback.c |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 3 | * |
| 4 | * Copyright (C) 2002, Linus Torvalds. |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 5 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | * |
| 7 | * Contains functions related to writing back dirty pages at the |
| 8 | * address_space level. |
| 9 | * |
Francois Cami | e1f8e87 | 2008-10-15 22:01:59 -0700 | [diff] [blame] | 10 | * 10Apr2002 Andrew Morton |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 11 | * Initial version |
| 12 | */ |
| 13 | |
| 14 | #include <linux/kernel.h> |
Paul Gortmaker | b95f1b31 | 2011-10-16 02:01:52 -0400 | [diff] [blame] | 15 | #include <linux/export.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 16 | #include <linux/spinlock.h> |
| 17 | #include <linux/fs.h> |
| 18 | #include <linux/mm.h> |
| 19 | #include <linux/swap.h> |
| 20 | #include <linux/slab.h> |
| 21 | #include <linux/pagemap.h> |
| 22 | #include <linux/writeback.h> |
| 23 | #include <linux/init.h> |
| 24 | #include <linux/backing-dev.h> |
Andrew Morton | 55e829a | 2006-12-10 02:19:27 -0800 | [diff] [blame] | 25 | #include <linux/task_io_accounting_ops.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 26 | #include <linux/blkdev.h> |
| 27 | #include <linux/mpage.h> |
Peter Zijlstra | d08b385 | 2006-09-25 23:30:57 -0700 | [diff] [blame] | 28 | #include <linux/rmap.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 29 | #include <linux/percpu.h> |
| 30 | #include <linux/notifier.h> |
| 31 | #include <linux/smp.h> |
| 32 | #include <linux/sysctl.h> |
| 33 | #include <linux/cpu.h> |
| 34 | #include <linux/syscalls.h> |
Al Viro | ff01bb48 | 2011-09-16 02:31:11 -0400 | [diff] [blame] | 35 | #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 36 | #include <linux/pagevec.h> |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 37 | #include <linux/timer.h> |
Dave Chinner | 028c2dd | 2010-07-07 13:24:07 +1000 | [diff] [blame] | 38 | #include <trace/events/writeback.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 39 | |
| 40 | /* |
Wu Fengguang | ffd1f60 | 2011-06-19 22:18:42 -0600 | [diff] [blame] | 41 | * Sleep at most 200ms at a time in balance_dirty_pages(). |
| 42 | */ |
| 43 | #define MAX_PAUSE max(HZ/5, 1) |
| 44 | |
| 45 | /* |
Wu Fengguang | 5b9b357 | 2011-12-06 13:17:17 -0600 | [diff] [blame] | 46 | * Try to keep balance_dirty_pages() call intervals higher than this many pages |
| 47 | * by raising pause time to max_pause when falls below it. |
| 48 | */ |
| 49 | #define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) |
| 50 | |
| 51 | /* |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 52 | * Estimate write bandwidth at 200ms intervals. |
| 53 | */ |
| 54 | #define BANDWIDTH_INTERVAL max(HZ/5, 1) |
| 55 | |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 56 | #define RATELIMIT_CALC_SHIFT 10 |
| 57 | |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 58 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 59 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited |
| 60 | * will look to see if it needs to force writeback or throttling. |
| 61 | */ |
| 62 | static long ratelimit_pages = 32; |
| 63 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 64 | /* The following parameters are exported via /proc/sys/vm */ |
| 65 | |
| 66 | /* |
Jens Axboe | 5b0830c | 2009-09-23 19:37:09 +0200 | [diff] [blame] | 67 | * Start background writeback (via writeback threads) at this percentage |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 68 | */ |
Wu Fengguang | 1b5e62b | 2009-03-23 08:57:38 +0800 | [diff] [blame] | 69 | int dirty_background_ratio = 10; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 70 | |
| 71 | /* |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 72 | * dirty_background_bytes starts at 0 (disabled) so that it is a function of |
| 73 | * dirty_background_ratio * the amount of dirtyable memory |
| 74 | */ |
| 75 | unsigned long dirty_background_bytes; |
| 76 | |
| 77 | /* |
Bron Gondwana | 195cf453 | 2008-02-04 22:29:20 -0800 | [diff] [blame] | 78 | * free highmem will not be subtracted from the total free memory |
| 79 | * for calculating free ratios if vm_highmem_is_dirtyable is true |
| 80 | */ |
| 81 | int vm_highmem_is_dirtyable; |
| 82 | |
| 83 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 84 | * The generator of dirty data starts writeback at this percentage |
| 85 | */ |
Wu Fengguang | 1b5e62b | 2009-03-23 08:57:38 +0800 | [diff] [blame] | 86 | int vm_dirty_ratio = 20; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 87 | |
| 88 | /* |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 89 | * vm_dirty_bytes starts at 0 (disabled) so that it is a function of |
| 90 | * vm_dirty_ratio * the amount of dirtyable memory |
| 91 | */ |
| 92 | unsigned long vm_dirty_bytes; |
| 93 | |
| 94 | /* |
Alexey Dobriyan | 704503d | 2009-03-31 15:23:18 -0700 | [diff] [blame] | 95 | * The interval between `kupdate'-style writebacks |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 96 | */ |
Toshiyuki Okajima | 22ef37e | 2009-05-16 22:56:28 -0700 | [diff] [blame] | 97 | unsigned int dirty_writeback_interval = 5 * 100; /* centiseconds */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 98 | |
Artem Bityutskiy | 91913a2 | 2012-03-21 22:33:00 -0400 | [diff] [blame] | 99 | EXPORT_SYMBOL_GPL(dirty_writeback_interval); |
| 100 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 101 | /* |
Alexey Dobriyan | 704503d | 2009-03-31 15:23:18 -0700 | [diff] [blame] | 102 | * The longest time for which data is allowed to remain dirty |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 103 | */ |
Toshiyuki Okajima | 22ef37e | 2009-05-16 22:56:28 -0700 | [diff] [blame] | 104 | unsigned int dirty_expire_interval = 30 * 100; /* centiseconds */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 105 | |
| 106 | /* |
| 107 | * Flag that makes the machine dump writes/reads and block dirtyings. |
| 108 | */ |
| 109 | int block_dump; |
| 110 | |
| 111 | /* |
Bart Samwel | ed5b43f | 2006-03-24 03:15:49 -0800 | [diff] [blame] | 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. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 114 | */ |
| 115 | int laptop_mode; |
| 116 | |
| 117 | EXPORT_SYMBOL(laptop_mode); |
| 118 | |
| 119 | /* End of sysctl-exported parameters */ |
| 120 | |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 121 | unsigned long global_dirty_limit; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 122 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 123 | /* |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 124 | * Scale the writeback cache size proportional to the relative writeout speeds. |
| 125 | * |
| 126 | * We do this by keeping a floating proportion between BDIs, based on page |
| 127 | * writeback completions [end_page_writeback()]. Those devices that write out |
| 128 | * pages fastest will get the larger share, while the slower will get a smaller |
| 129 | * share. |
| 130 | * |
| 131 | * We use page writeout completions because we are interested in getting rid of |
| 132 | * dirty pages. Having them written out is the primary goal. |
| 133 | * |
| 134 | * We introduce a concept of time, a period over which we measure these events, |
| 135 | * because demand can/will vary over time. The length of this period itself is |
| 136 | * measured in page writeback completions. |
| 137 | * |
| 138 | */ |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 139 | static struct fprop_global writeout_completions; |
| 140 | |
| 141 | static void writeout_period(unsigned long t); |
| 142 | /* Timer for aging of writeout_completions */ |
| 143 | static struct timer_list writeout_period_timer = |
| 144 | TIMER_DEFERRED_INITIALIZER(writeout_period, 0, 0); |
| 145 | static unsigned long writeout_period_time = 0; |
| 146 | |
| 147 | /* |
| 148 | * Length of period for aging writeout fractions of bdis. This is an |
| 149 | * arbitrarily chosen number. The longer the period, the slower fractions will |
| 150 | * reflect changes in current writeout rate. |
| 151 | */ |
| 152 | #define VM_COMPLETIONS_PERIOD_LEN (3*HZ) |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 153 | |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 154 | /* |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 155 | * Work out the current dirty-memory clamping and background writeout |
| 156 | * thresholds. |
| 157 | * |
| 158 | * The main aim here is to lower them aggressively if there is a lot of mapped |
| 159 | * memory around. To avoid stressing page reclaim with lots of unreclaimable |
| 160 | * pages. It is better to clamp down on writers than to start swapping, and |
| 161 | * performing lots of scanning. |
| 162 | * |
| 163 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. |
| 164 | * |
| 165 | * We don't permit the clamping level to fall below 5% - that is getting rather |
| 166 | * excessive. |
| 167 | * |
| 168 | * We make sure that the background writeout level is below the adjusted |
| 169 | * clamping level. |
| 170 | */ |
Johannes Weiner | ccafa28 | 2012-01-10 15:07:44 -0800 | [diff] [blame] | 171 | |
Johannes Weiner | a756cf5 | 2012-01-10 15:07:49 -0800 | [diff] [blame] | 172 | /* |
| 173 | * In a memory zone, there is a certain amount of pages we consider |
| 174 | * available for the page cache, which is essentially the number of |
| 175 | * free and reclaimable pages, minus some zone reserves to protect |
| 176 | * lowmem and the ability to uphold the zone's watermarks without |
| 177 | * requiring writeback. |
| 178 | * |
| 179 | * This number of dirtyable pages is the base value of which the |
| 180 | * user-configurable dirty ratio is the effictive number of pages that |
| 181 | * are allowed to be actually dirtied. Per individual zone, or |
| 182 | * globally by using the sum of dirtyable pages over all zones. |
| 183 | * |
| 184 | * Because the user is allowed to specify the dirty limit globally as |
| 185 | * absolute number of bytes, calculating the per-zone dirty limit can |
| 186 | * require translating the configured limit into a percentage of |
| 187 | * global dirtyable memory first. |
| 188 | */ |
| 189 | |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 190 | static unsigned long highmem_dirtyable_memory(unsigned long total) |
| 191 | { |
| 192 | #ifdef CONFIG_HIGHMEM |
| 193 | int node; |
| 194 | unsigned long x = 0; |
| 195 | |
| 196 | for_each_node_state(node, N_HIGH_MEMORY) { |
| 197 | struct zone *z = |
| 198 | &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; |
| 199 | |
| 200 | x += zone_page_state(z, NR_FREE_PAGES) + |
Johannes Weiner | ab8fabd | 2012-01-10 15:07:42 -0800 | [diff] [blame] | 201 | zone_reclaimable_pages(z) - z->dirty_balance_reserve; |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 202 | } |
| 203 | /* |
| 204 | * Make sure that the number of highmem pages is never larger |
| 205 | * than the number of the total dirtyable memory. This can only |
| 206 | * occur in very strange VM situations but we want to make sure |
| 207 | * that this does not occur. |
| 208 | */ |
| 209 | return min(x, total); |
| 210 | #else |
| 211 | return 0; |
| 212 | #endif |
| 213 | } |
| 214 | |
| 215 | /** |
Johannes Weiner | ccafa28 | 2012-01-10 15:07:44 -0800 | [diff] [blame] | 216 | * global_dirtyable_memory - number of globally dirtyable pages |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 217 | * |
Johannes Weiner | ccafa28 | 2012-01-10 15:07:44 -0800 | [diff] [blame] | 218 | * Returns the global number of pages potentially available for dirty |
| 219 | * page cache. This is the base value for the global dirty limits. |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 220 | */ |
H Hartley Sweeten | 18cf8cf | 2012-04-12 13:44:20 -0700 | [diff] [blame] | 221 | static unsigned long global_dirtyable_memory(void) |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 222 | { |
| 223 | unsigned long x; |
| 224 | |
Johannes Weiner | ab8fabd | 2012-01-10 15:07:42 -0800 | [diff] [blame] | 225 | x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() - |
| 226 | dirty_balance_reserve; |
Johannes Weiner | 1edf223 | 2012-01-10 15:06:57 -0800 | [diff] [blame] | 227 | |
| 228 | if (!vm_highmem_is_dirtyable) |
| 229 | x -= highmem_dirtyable_memory(x); |
| 230 | |
| 231 | return x + 1; /* Ensure that we never return 0 */ |
| 232 | } |
| 233 | |
| 234 | /* |
Johannes Weiner | ccafa28 | 2012-01-10 15:07:44 -0800 | [diff] [blame] | 235 | * global_dirty_limits - background-writeback and dirty-throttling thresholds |
| 236 | * |
| 237 | * Calculate the dirty thresholds based on sysctl parameters |
| 238 | * - vm.dirty_background_ratio or vm.dirty_background_bytes |
| 239 | * - vm.dirty_ratio or vm.dirty_bytes |
| 240 | * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and |
| 241 | * real-time tasks. |
| 242 | */ |
| 243 | void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) |
| 244 | { |
| 245 | unsigned long background; |
| 246 | unsigned long dirty; |
| 247 | unsigned long uninitialized_var(available_memory); |
| 248 | struct task_struct *tsk; |
| 249 | |
| 250 | if (!vm_dirty_bytes || !dirty_background_bytes) |
| 251 | available_memory = global_dirtyable_memory(); |
| 252 | |
| 253 | if (vm_dirty_bytes) |
| 254 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); |
| 255 | else |
| 256 | dirty = (vm_dirty_ratio * available_memory) / 100; |
| 257 | |
| 258 | if (dirty_background_bytes) |
| 259 | background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); |
| 260 | else |
| 261 | background = (dirty_background_ratio * available_memory) / 100; |
| 262 | |
| 263 | if (background >= dirty) |
| 264 | background = dirty / 2; |
| 265 | tsk = current; |
| 266 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { |
| 267 | background += background / 4; |
| 268 | dirty += dirty / 4; |
| 269 | } |
| 270 | *pbackground = background; |
| 271 | *pdirty = dirty; |
| 272 | trace_global_dirty_state(background, dirty); |
| 273 | } |
| 274 | |
Johannes Weiner | a756cf5 | 2012-01-10 15:07:49 -0800 | [diff] [blame] | 275 | /** |
| 276 | * zone_dirtyable_memory - number of dirtyable pages in a zone |
| 277 | * @zone: the zone |
| 278 | * |
| 279 | * Returns the zone's number of pages potentially available for dirty |
| 280 | * page cache. This is the base value for the per-zone dirty limits. |
| 281 | */ |
| 282 | static unsigned long zone_dirtyable_memory(struct zone *zone) |
| 283 | { |
| 284 | /* |
| 285 | * The effective global number of dirtyable pages may exclude |
| 286 | * highmem as a big-picture measure to keep the ratio between |
| 287 | * dirty memory and lowmem reasonable. |
| 288 | * |
| 289 | * But this function is purely about the individual zone and a |
| 290 | * highmem zone can hold its share of dirty pages, so we don't |
| 291 | * care about vm_highmem_is_dirtyable here. |
| 292 | */ |
| 293 | return zone_page_state(zone, NR_FREE_PAGES) + |
| 294 | zone_reclaimable_pages(zone) - |
| 295 | zone->dirty_balance_reserve; |
| 296 | } |
| 297 | |
| 298 | /** |
| 299 | * zone_dirty_limit - maximum number of dirty pages allowed in a zone |
| 300 | * @zone: the zone |
| 301 | * |
| 302 | * Returns the maximum number of dirty pages allowed in a zone, based |
| 303 | * on the zone's dirtyable memory. |
| 304 | */ |
| 305 | static unsigned long zone_dirty_limit(struct zone *zone) |
| 306 | { |
| 307 | unsigned long zone_memory = zone_dirtyable_memory(zone); |
| 308 | struct task_struct *tsk = current; |
| 309 | unsigned long dirty; |
| 310 | |
| 311 | if (vm_dirty_bytes) |
| 312 | dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * |
| 313 | zone_memory / global_dirtyable_memory(); |
| 314 | else |
| 315 | dirty = vm_dirty_ratio * zone_memory / 100; |
| 316 | |
| 317 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) |
| 318 | dirty += dirty / 4; |
| 319 | |
| 320 | return dirty; |
| 321 | } |
| 322 | |
| 323 | /** |
| 324 | * zone_dirty_ok - tells whether a zone is within its dirty limits |
| 325 | * @zone: the zone to check |
| 326 | * |
| 327 | * Returns %true when the dirty pages in @zone are within the zone's |
| 328 | * dirty limit, %false if the limit is exceeded. |
| 329 | */ |
| 330 | bool zone_dirty_ok(struct zone *zone) |
| 331 | { |
| 332 | unsigned long limit = zone_dirty_limit(zone); |
| 333 | |
| 334 | return zone_page_state(zone, NR_FILE_DIRTY) + |
| 335 | zone_page_state(zone, NR_UNSTABLE_NFS) + |
| 336 | zone_page_state(zone, NR_WRITEBACK) <= limit; |
| 337 | } |
| 338 | |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 339 | int dirty_background_ratio_handler(struct ctl_table *table, int write, |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 340 | void __user *buffer, size_t *lenp, |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 341 | loff_t *ppos) |
| 342 | { |
| 343 | int ret; |
| 344 | |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 345 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 346 | if (ret == 0 && write) |
| 347 | dirty_background_bytes = 0; |
| 348 | return ret; |
| 349 | } |
| 350 | |
| 351 | int dirty_background_bytes_handler(struct ctl_table *table, int write, |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 352 | void __user *buffer, size_t *lenp, |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 353 | loff_t *ppos) |
| 354 | { |
| 355 | int ret; |
| 356 | |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 357 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 358 | if (ret == 0 && write) |
| 359 | dirty_background_ratio = 0; |
| 360 | return ret; |
| 361 | } |
| 362 | |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 363 | int dirty_ratio_handler(struct ctl_table *table, int write, |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 364 | void __user *buffer, size_t *lenp, |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 365 | loff_t *ppos) |
| 366 | { |
| 367 | int old_ratio = vm_dirty_ratio; |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 368 | int ret; |
| 369 | |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 370 | ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 371 | if (ret == 0 && write && vm_dirty_ratio != old_ratio) { |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 372 | writeback_set_ratelimit(); |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 373 | vm_dirty_bytes = 0; |
| 374 | } |
| 375 | return ret; |
| 376 | } |
| 377 | |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 378 | int dirty_bytes_handler(struct ctl_table *table, int write, |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 379 | void __user *buffer, size_t *lenp, |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 380 | loff_t *ppos) |
| 381 | { |
Sven Wegener | fc3501d | 2009-02-11 13:04:23 -0800 | [diff] [blame] | 382 | unsigned long old_bytes = vm_dirty_bytes; |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 383 | int ret; |
| 384 | |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 385 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 386 | if (ret == 0 && write && vm_dirty_bytes != old_bytes) { |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 387 | writeback_set_ratelimit(); |
David Rientjes | 2da0299 | 2009-01-06 14:39:31 -0800 | [diff] [blame] | 388 | vm_dirty_ratio = 0; |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 389 | } |
| 390 | return ret; |
| 391 | } |
| 392 | |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 393 | static unsigned long wp_next_time(unsigned long cur_time) |
| 394 | { |
| 395 | cur_time += VM_COMPLETIONS_PERIOD_LEN; |
| 396 | /* 0 has a special meaning... */ |
| 397 | if (!cur_time) |
| 398 | return 1; |
| 399 | return cur_time; |
| 400 | } |
| 401 | |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 402 | /* |
| 403 | * Increment the BDI's writeout completion count and the global writeout |
| 404 | * completion count. Called from test_clear_page_writeback(). |
| 405 | */ |
| 406 | static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) |
| 407 | { |
Jan Kara | f7d2b1e | 2010-12-08 22:44:24 -0600 | [diff] [blame] | 408 | __inc_bdi_stat(bdi, BDI_WRITTEN); |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 409 | __fprop_inc_percpu_max(&writeout_completions, &bdi->completions, |
| 410 | bdi->max_prop_frac); |
| 411 | /* First event after period switching was turned off? */ |
| 412 | if (!unlikely(writeout_period_time)) { |
| 413 | /* |
| 414 | * We can race with other __bdi_writeout_inc calls here but |
| 415 | * it does not cause any harm since the resulting time when |
| 416 | * timer will fire and what is in writeout_period_time will be |
| 417 | * roughly the same. |
| 418 | */ |
| 419 | writeout_period_time = wp_next_time(jiffies); |
| 420 | mod_timer(&writeout_period_timer, writeout_period_time); |
| 421 | } |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 422 | } |
| 423 | |
Miklos Szeredi | dd5656e | 2008-04-30 00:54:37 -0700 | [diff] [blame] | 424 | void bdi_writeout_inc(struct backing_dev_info *bdi) |
| 425 | { |
| 426 | unsigned long flags; |
| 427 | |
| 428 | local_irq_save(flags); |
| 429 | __bdi_writeout_inc(bdi); |
| 430 | local_irq_restore(flags); |
| 431 | } |
| 432 | EXPORT_SYMBOL_GPL(bdi_writeout_inc); |
| 433 | |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 434 | /* |
| 435 | * Obtain an accurate fraction of the BDI's portion. |
| 436 | */ |
| 437 | static void bdi_writeout_fraction(struct backing_dev_info *bdi, |
| 438 | long *numerator, long *denominator) |
| 439 | { |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 440 | fprop_fraction_percpu(&writeout_completions, &bdi->completions, |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 441 | numerator, denominator); |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 442 | } |
| 443 | |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 444 | /* |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 445 | * On idle system, we can be called long after we scheduled because we use |
| 446 | * deferred timers so count with missed periods. |
| 447 | */ |
| 448 | static void writeout_period(unsigned long t) |
| 449 | { |
| 450 | int miss_periods = (jiffies - writeout_period_time) / |
| 451 | VM_COMPLETIONS_PERIOD_LEN; |
| 452 | |
| 453 | if (fprop_new_period(&writeout_completions, miss_periods + 1)) { |
| 454 | writeout_period_time = wp_next_time(writeout_period_time + |
| 455 | miss_periods * VM_COMPLETIONS_PERIOD_LEN); |
| 456 | mod_timer(&writeout_period_timer, writeout_period_time); |
| 457 | } else { |
| 458 | /* |
| 459 | * Aging has zeroed all fractions. Stop wasting CPU on period |
| 460 | * updates. |
| 461 | */ |
| 462 | writeout_period_time = 0; |
| 463 | } |
| 464 | } |
| 465 | |
| 466 | /* |
Johannes Weiner | d08c429 | 2011-10-31 17:07:05 -0700 | [diff] [blame] | 467 | * bdi_min_ratio keeps the sum of the minimum dirty shares of all |
| 468 | * registered backing devices, which, for obvious reasons, can not |
| 469 | * exceed 100%. |
Peter Zijlstra | 189d3c4 | 2008-04-30 00:54:35 -0700 | [diff] [blame] | 470 | */ |
Peter Zijlstra | 189d3c4 | 2008-04-30 00:54:35 -0700 | [diff] [blame] | 471 | static unsigned int bdi_min_ratio; |
| 472 | |
| 473 | int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) |
| 474 | { |
| 475 | int ret = 0; |
Peter Zijlstra | 189d3c4 | 2008-04-30 00:54:35 -0700 | [diff] [blame] | 476 | |
Jens Axboe | cfc4ba5 | 2009-09-14 13:12:40 +0200 | [diff] [blame] | 477 | spin_lock_bh(&bdi_lock); |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 478 | if (min_ratio > bdi->max_ratio) { |
Peter Zijlstra | 189d3c4 | 2008-04-30 00:54:35 -0700 | [diff] [blame] | 479 | ret = -EINVAL; |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 480 | } else { |
| 481 | min_ratio -= bdi->min_ratio; |
| 482 | if (bdi_min_ratio + min_ratio < 100) { |
| 483 | bdi_min_ratio += min_ratio; |
| 484 | bdi->min_ratio += min_ratio; |
| 485 | } else { |
| 486 | ret = -EINVAL; |
| 487 | } |
| 488 | } |
Jens Axboe | cfc4ba5 | 2009-09-14 13:12:40 +0200 | [diff] [blame] | 489 | spin_unlock_bh(&bdi_lock); |
Peter Zijlstra | 189d3c4 | 2008-04-30 00:54:35 -0700 | [diff] [blame] | 490 | |
| 491 | return ret; |
| 492 | } |
| 493 | |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 494 | int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) |
| 495 | { |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 496 | int ret = 0; |
| 497 | |
| 498 | if (max_ratio > 100) |
| 499 | return -EINVAL; |
| 500 | |
Jens Axboe | cfc4ba5 | 2009-09-14 13:12:40 +0200 | [diff] [blame] | 501 | spin_lock_bh(&bdi_lock); |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 502 | if (bdi->min_ratio > max_ratio) { |
| 503 | ret = -EINVAL; |
| 504 | } else { |
| 505 | bdi->max_ratio = max_ratio; |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 506 | bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 507 | } |
Jens Axboe | cfc4ba5 | 2009-09-14 13:12:40 +0200 | [diff] [blame] | 508 | spin_unlock_bh(&bdi_lock); |
Peter Zijlstra | a42dde0 | 2008-04-30 00:54:36 -0700 | [diff] [blame] | 509 | |
| 510 | return ret; |
| 511 | } |
| 512 | EXPORT_SYMBOL(bdi_set_max_ratio); |
| 513 | |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 514 | static unsigned long dirty_freerun_ceiling(unsigned long thresh, |
| 515 | unsigned long bg_thresh) |
| 516 | { |
| 517 | return (thresh + bg_thresh) / 2; |
| 518 | } |
| 519 | |
Wu Fengguang | ffd1f60 | 2011-06-19 22:18:42 -0600 | [diff] [blame] | 520 | static unsigned long hard_dirty_limit(unsigned long thresh) |
| 521 | { |
| 522 | return max(thresh, global_dirty_limit); |
| 523 | } |
| 524 | |
Wu Fengguang | 6f71865 | 2011-03-02 17:14:34 -0600 | [diff] [blame] | 525 | /** |
Wu Fengguang | 1babe18 | 2010-08-11 14:17:40 -0700 | [diff] [blame] | 526 | * bdi_dirty_limit - @bdi's share of dirty throttling threshold |
Wu Fengguang | 6f71865 | 2011-03-02 17:14:34 -0600 | [diff] [blame] | 527 | * @bdi: the backing_dev_info to query |
| 528 | * @dirty: global dirty limit in pages |
Wu Fengguang | 1babe18 | 2010-08-11 14:17:40 -0700 | [diff] [blame] | 529 | * |
Wu Fengguang | 6f71865 | 2011-03-02 17:14:34 -0600 | [diff] [blame] | 530 | * Returns @bdi's dirty limit in pages. The term "dirty" in the context of |
| 531 | * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. |
Wu Fengguang | aed21ad | 2011-11-23 11:44:41 -0600 | [diff] [blame] | 532 | * |
| 533 | * Note that balance_dirty_pages() will only seriously take it as a hard limit |
| 534 | * when sleeping max_pause per page is not enough to keep the dirty pages under |
| 535 | * control. For example, when the device is completely stalled due to some error |
| 536 | * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. |
| 537 | * In the other normal situations, it acts more gently by throttling the tasks |
| 538 | * more (rather than completely block them) when the bdi dirty pages go high. |
Wu Fengguang | 6f71865 | 2011-03-02 17:14:34 -0600 | [diff] [blame] | 539 | * |
| 540 | * It allocates high/low dirty limits to fast/slow devices, in order to prevent |
Wu Fengguang | 1babe18 | 2010-08-11 14:17:40 -0700 | [diff] [blame] | 541 | * - starving fast devices |
| 542 | * - piling up dirty pages (that will take long time to sync) on slow devices |
| 543 | * |
| 544 | * The bdi's share of dirty limit will be adapting to its throughput and |
| 545 | * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set. |
| 546 | */ |
| 547 | unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 548 | { |
| 549 | u64 bdi_dirty; |
| 550 | long numerator, denominator; |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 551 | |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 552 | /* |
| 553 | * Calculate this BDI's share of the dirty ratio. |
| 554 | */ |
| 555 | bdi_writeout_fraction(bdi, &numerator, &denominator); |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 556 | |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 557 | bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100; |
| 558 | bdi_dirty *= numerator; |
| 559 | do_div(bdi_dirty, denominator); |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 560 | |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 561 | bdi_dirty += (dirty * bdi->min_ratio) / 100; |
| 562 | if (bdi_dirty > (dirty * bdi->max_ratio) / 100) |
| 563 | bdi_dirty = dirty * bdi->max_ratio / 100; |
| 564 | |
| 565 | return bdi_dirty; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 566 | } |
| 567 | |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 568 | /* |
| 569 | * Dirty position control. |
| 570 | * |
| 571 | * (o) global/bdi setpoints |
| 572 | * |
| 573 | * We want the dirty pages be balanced around the global/bdi setpoints. |
| 574 | * When the number of dirty pages is higher/lower than the setpoint, the |
| 575 | * dirty position control ratio (and hence task dirty ratelimit) will be |
| 576 | * decreased/increased to bring the dirty pages back to the setpoint. |
| 577 | * |
| 578 | * pos_ratio = 1 << RATELIMIT_CALC_SHIFT |
| 579 | * |
| 580 | * if (dirty < setpoint) scale up pos_ratio |
| 581 | * if (dirty > setpoint) scale down pos_ratio |
| 582 | * |
| 583 | * if (bdi_dirty < bdi_setpoint) scale up pos_ratio |
| 584 | * if (bdi_dirty > bdi_setpoint) scale down pos_ratio |
| 585 | * |
| 586 | * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT |
| 587 | * |
| 588 | * (o) global control line |
| 589 | * |
| 590 | * ^ pos_ratio |
| 591 | * | |
| 592 | * | |<===== global dirty control scope ======>| |
| 593 | * 2.0 .............* |
| 594 | * | .* |
| 595 | * | . * |
| 596 | * | . * |
| 597 | * | . * |
| 598 | * | . * |
| 599 | * | . * |
| 600 | * 1.0 ................................* |
| 601 | * | . . * |
| 602 | * | . . * |
| 603 | * | . . * |
| 604 | * | . . * |
| 605 | * | . . * |
| 606 | * 0 +------------.------------------.----------------------*-------------> |
| 607 | * freerun^ setpoint^ limit^ dirty pages |
| 608 | * |
| 609 | * (o) bdi control line |
| 610 | * |
| 611 | * ^ pos_ratio |
| 612 | * | |
| 613 | * | * |
| 614 | * | * |
| 615 | * | * |
| 616 | * | * |
| 617 | * | * |<=========== span ============>| |
| 618 | * 1.0 .......................* |
| 619 | * | . * |
| 620 | * | . * |
| 621 | * | . * |
| 622 | * | . * |
| 623 | * | . * |
| 624 | * | . * |
| 625 | * | . * |
| 626 | * | . * |
| 627 | * | . * |
| 628 | * | . * |
| 629 | * | . * |
| 630 | * 1/4 ...............................................* * * * * * * * * * * * |
| 631 | * | . . |
| 632 | * | . . |
| 633 | * | . . |
| 634 | * 0 +----------------------.-------------------------------.-------------> |
| 635 | * bdi_setpoint^ x_intercept^ |
| 636 | * |
| 637 | * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can |
| 638 | * be smoothly throttled down to normal if it starts high in situations like |
| 639 | * - start writing to a slow SD card and a fast disk at the same time. The SD |
| 640 | * card's bdi_dirty may rush to many times higher than bdi_setpoint. |
| 641 | * - the bdi dirty thresh drops quickly due to change of JBOD workload |
| 642 | */ |
| 643 | static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, |
| 644 | unsigned long thresh, |
| 645 | unsigned long bg_thresh, |
| 646 | unsigned long dirty, |
| 647 | unsigned long bdi_thresh, |
| 648 | unsigned long bdi_dirty) |
| 649 | { |
| 650 | unsigned long write_bw = bdi->avg_write_bandwidth; |
| 651 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); |
| 652 | unsigned long limit = hard_dirty_limit(thresh); |
| 653 | unsigned long x_intercept; |
| 654 | unsigned long setpoint; /* dirty pages' target balance point */ |
| 655 | unsigned long bdi_setpoint; |
| 656 | unsigned long span; |
| 657 | long long pos_ratio; /* for scaling up/down the rate limit */ |
| 658 | long x; |
| 659 | |
| 660 | if (unlikely(dirty >= limit)) |
| 661 | return 0; |
| 662 | |
| 663 | /* |
| 664 | * global setpoint |
| 665 | * |
| 666 | * setpoint - dirty 3 |
| 667 | * f(dirty) := 1.0 + (----------------) |
| 668 | * limit - setpoint |
| 669 | * |
| 670 | * it's a 3rd order polynomial that subjects to |
| 671 | * |
| 672 | * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast |
| 673 | * (2) f(setpoint) = 1.0 => the balance point |
| 674 | * (3) f(limit) = 0 => the hard limit |
| 675 | * (4) df/dx <= 0 => negative feedback control |
| 676 | * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) |
| 677 | * => fast response on large errors; small oscillation near setpoint |
| 678 | */ |
| 679 | setpoint = (freerun + limit) / 2; |
| 680 | x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT, |
| 681 | limit - setpoint + 1); |
| 682 | pos_ratio = x; |
| 683 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; |
| 684 | pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; |
| 685 | pos_ratio += 1 << RATELIMIT_CALC_SHIFT; |
| 686 | |
| 687 | /* |
| 688 | * We have computed basic pos_ratio above based on global situation. If |
| 689 | * the bdi is over/under its share of dirty pages, we want to scale |
| 690 | * pos_ratio further down/up. That is done by the following mechanism. |
| 691 | */ |
| 692 | |
| 693 | /* |
| 694 | * bdi setpoint |
| 695 | * |
| 696 | * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint) |
| 697 | * |
| 698 | * x_intercept - bdi_dirty |
| 699 | * := -------------------------- |
| 700 | * x_intercept - bdi_setpoint |
| 701 | * |
| 702 | * The main bdi control line is a linear function that subjects to |
| 703 | * |
| 704 | * (1) f(bdi_setpoint) = 1.0 |
| 705 | * (2) k = - 1 / (8 * write_bw) (in single bdi case) |
| 706 | * or equally: x_intercept = bdi_setpoint + 8 * write_bw |
| 707 | * |
| 708 | * For single bdi case, the dirty pages are observed to fluctuate |
| 709 | * regularly within range |
| 710 | * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2] |
| 711 | * for various filesystems, where (2) can yield in a reasonable 12.5% |
| 712 | * fluctuation range for pos_ratio. |
| 713 | * |
| 714 | * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its |
| 715 | * own size, so move the slope over accordingly and choose a slope that |
| 716 | * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh. |
| 717 | */ |
| 718 | if (unlikely(bdi_thresh > thresh)) |
| 719 | bdi_thresh = thresh; |
Wu Fengguang | aed21ad | 2011-11-23 11:44:41 -0600 | [diff] [blame] | 720 | /* |
| 721 | * It's very possible that bdi_thresh is close to 0 not because the |
| 722 | * device is slow, but that it has remained inactive for long time. |
| 723 | * Honour such devices a reasonable good (hopefully IO efficient) |
| 724 | * threshold, so that the occasional writes won't be blocked and active |
| 725 | * writes can rampup the threshold quickly. |
| 726 | */ |
Wu Fengguang | 8927f66 | 2011-08-04 22:16:46 -0600 | [diff] [blame] | 727 | bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 728 | /* |
| 729 | * scale global setpoint to bdi's: |
| 730 | * bdi_setpoint = setpoint * bdi_thresh / thresh |
| 731 | */ |
| 732 | x = div_u64((u64)bdi_thresh << 16, thresh + 1); |
| 733 | bdi_setpoint = setpoint * (u64)x >> 16; |
| 734 | /* |
| 735 | * Use span=(8*write_bw) in single bdi case as indicated by |
| 736 | * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case. |
| 737 | * |
| 738 | * bdi_thresh thresh - bdi_thresh |
| 739 | * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh |
| 740 | * thresh thresh |
| 741 | */ |
| 742 | span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16; |
| 743 | x_intercept = bdi_setpoint + span; |
| 744 | |
| 745 | if (bdi_dirty < x_intercept - span / 4) { |
Wu Fengguang | 50657fc | 2011-10-11 17:06:33 -0600 | [diff] [blame] | 746 | pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), |
| 747 | x_intercept - bdi_setpoint + 1); |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 748 | } else |
| 749 | pos_ratio /= 4; |
| 750 | |
Wu Fengguang | 8927f66 | 2011-08-04 22:16:46 -0600 | [diff] [blame] | 751 | /* |
| 752 | * bdi reserve area, safeguard against dirty pool underrun and disk idle |
| 753 | * It may push the desired control point of global dirty pages higher |
| 754 | * than setpoint. |
| 755 | */ |
| 756 | x_intercept = bdi_thresh / 2; |
| 757 | if (bdi_dirty < x_intercept) { |
Wu Fengguang | 50657fc | 2011-10-11 17:06:33 -0600 | [diff] [blame] | 758 | if (bdi_dirty > x_intercept / 8) |
| 759 | pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty); |
| 760 | else |
Wu Fengguang | 8927f66 | 2011-08-04 22:16:46 -0600 | [diff] [blame] | 761 | pos_ratio *= 8; |
| 762 | } |
| 763 | |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 764 | return pos_ratio; |
| 765 | } |
| 766 | |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 767 | static void bdi_update_write_bandwidth(struct backing_dev_info *bdi, |
| 768 | unsigned long elapsed, |
| 769 | unsigned long written) |
| 770 | { |
| 771 | const unsigned long period = roundup_pow_of_two(3 * HZ); |
| 772 | unsigned long avg = bdi->avg_write_bandwidth; |
| 773 | unsigned long old = bdi->write_bandwidth; |
| 774 | u64 bw; |
| 775 | |
| 776 | /* |
| 777 | * bw = written * HZ / elapsed |
| 778 | * |
| 779 | * bw * elapsed + write_bandwidth * (period - elapsed) |
| 780 | * write_bandwidth = --------------------------------------------------- |
| 781 | * period |
| 782 | */ |
| 783 | bw = written - bdi->written_stamp; |
| 784 | bw *= HZ; |
| 785 | if (unlikely(elapsed > period)) { |
| 786 | do_div(bw, elapsed); |
| 787 | avg = bw; |
| 788 | goto out; |
| 789 | } |
| 790 | bw += (u64)bdi->write_bandwidth * (period - elapsed); |
| 791 | bw >>= ilog2(period); |
| 792 | |
| 793 | /* |
| 794 | * one more level of smoothing, for filtering out sudden spikes |
| 795 | */ |
| 796 | if (avg > old && old >= (unsigned long)bw) |
| 797 | avg -= (avg - old) >> 3; |
| 798 | |
| 799 | if (avg < old && old <= (unsigned long)bw) |
| 800 | avg += (old - avg) >> 3; |
| 801 | |
| 802 | out: |
| 803 | bdi->write_bandwidth = bw; |
| 804 | bdi->avg_write_bandwidth = avg; |
| 805 | } |
| 806 | |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 807 | /* |
| 808 | * The global dirtyable memory and dirty threshold could be suddenly knocked |
| 809 | * down by a large amount (eg. on the startup of KVM in a swapless system). |
| 810 | * This may throw the system into deep dirty exceeded state and throttle |
| 811 | * heavy/light dirtiers alike. To retain good responsiveness, maintain |
| 812 | * global_dirty_limit for tracking slowly down to the knocked down dirty |
| 813 | * threshold. |
| 814 | */ |
| 815 | static void update_dirty_limit(unsigned long thresh, unsigned long dirty) |
| 816 | { |
| 817 | unsigned long limit = global_dirty_limit; |
| 818 | |
| 819 | /* |
| 820 | * Follow up in one step. |
| 821 | */ |
| 822 | if (limit < thresh) { |
| 823 | limit = thresh; |
| 824 | goto update; |
| 825 | } |
| 826 | |
| 827 | /* |
| 828 | * Follow down slowly. Use the higher one as the target, because thresh |
| 829 | * may drop below dirty. This is exactly the reason to introduce |
| 830 | * global_dirty_limit which is guaranteed to lie above the dirty pages. |
| 831 | */ |
| 832 | thresh = max(thresh, dirty); |
| 833 | if (limit > thresh) { |
| 834 | limit -= (limit - thresh) >> 5; |
| 835 | goto update; |
| 836 | } |
| 837 | return; |
| 838 | update: |
| 839 | global_dirty_limit = limit; |
| 840 | } |
| 841 | |
| 842 | static void global_update_bandwidth(unsigned long thresh, |
| 843 | unsigned long dirty, |
| 844 | unsigned long now) |
| 845 | { |
| 846 | static DEFINE_SPINLOCK(dirty_lock); |
| 847 | static unsigned long update_time; |
| 848 | |
| 849 | /* |
| 850 | * check locklessly first to optimize away locking for the most time |
| 851 | */ |
| 852 | if (time_before(now, update_time + BANDWIDTH_INTERVAL)) |
| 853 | return; |
| 854 | |
| 855 | spin_lock(&dirty_lock); |
| 856 | if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) { |
| 857 | update_dirty_limit(thresh, dirty); |
| 858 | update_time = now; |
| 859 | } |
| 860 | spin_unlock(&dirty_lock); |
| 861 | } |
| 862 | |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 863 | /* |
| 864 | * Maintain bdi->dirty_ratelimit, the base dirty throttle rate. |
| 865 | * |
| 866 | * Normal bdi tasks will be curbed at or below it in long term. |
| 867 | * Obviously it should be around (write_bw / N) when there are N dd tasks. |
| 868 | */ |
| 869 | static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, |
| 870 | unsigned long thresh, |
| 871 | unsigned long bg_thresh, |
| 872 | unsigned long dirty, |
| 873 | unsigned long bdi_thresh, |
| 874 | unsigned long bdi_dirty, |
| 875 | unsigned long dirtied, |
| 876 | unsigned long elapsed) |
| 877 | { |
Wu Fengguang | 7381131 | 2011-08-26 15:53:24 -0600 | [diff] [blame] | 878 | unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); |
| 879 | unsigned long limit = hard_dirty_limit(thresh); |
| 880 | unsigned long setpoint = (freerun + limit) / 2; |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 881 | unsigned long write_bw = bdi->avg_write_bandwidth; |
| 882 | unsigned long dirty_ratelimit = bdi->dirty_ratelimit; |
| 883 | unsigned long dirty_rate; |
| 884 | unsigned long task_ratelimit; |
| 885 | unsigned long balanced_dirty_ratelimit; |
| 886 | unsigned long pos_ratio; |
Wu Fengguang | 7381131 | 2011-08-26 15:53:24 -0600 | [diff] [blame] | 887 | unsigned long step; |
| 888 | unsigned long x; |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 889 | |
| 890 | /* |
| 891 | * The dirty rate will match the writeout rate in long term, except |
| 892 | * when dirty pages are truncated by userspace or re-dirtied by FS. |
| 893 | */ |
| 894 | dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; |
| 895 | |
| 896 | pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, |
| 897 | bdi_thresh, bdi_dirty); |
| 898 | /* |
| 899 | * task_ratelimit reflects each dd's dirty rate for the past 200ms. |
| 900 | */ |
| 901 | task_ratelimit = (u64)dirty_ratelimit * |
| 902 | pos_ratio >> RATELIMIT_CALC_SHIFT; |
| 903 | task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */ |
| 904 | |
| 905 | /* |
| 906 | * A linear estimation of the "balanced" throttle rate. The theory is, |
| 907 | * if there are N dd tasks, each throttled at task_ratelimit, the bdi's |
| 908 | * dirty_rate will be measured to be (N * task_ratelimit). So the below |
| 909 | * formula will yield the balanced rate limit (write_bw / N). |
| 910 | * |
| 911 | * Note that the expanded form is not a pure rate feedback: |
| 912 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1) |
| 913 | * but also takes pos_ratio into account: |
| 914 | * rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2) |
| 915 | * |
| 916 | * (1) is not realistic because pos_ratio also takes part in balancing |
| 917 | * the dirty rate. Consider the state |
| 918 | * pos_ratio = 0.5 (3) |
| 919 | * rate = 2 * (write_bw / N) (4) |
| 920 | * If (1) is used, it will stuck in that state! Because each dd will |
| 921 | * be throttled at |
| 922 | * task_ratelimit = pos_ratio * rate = (write_bw / N) (5) |
| 923 | * yielding |
| 924 | * dirty_rate = N * task_ratelimit = write_bw (6) |
| 925 | * put (6) into (1) we get |
| 926 | * rate_(i+1) = rate_(i) (7) |
| 927 | * |
| 928 | * So we end up using (2) to always keep |
| 929 | * rate_(i+1) ~= (write_bw / N) (8) |
| 930 | * regardless of the value of pos_ratio. As long as (8) is satisfied, |
| 931 | * pos_ratio is able to drive itself to 1.0, which is not only where |
| 932 | * the dirty count meet the setpoint, but also where the slope of |
| 933 | * pos_ratio is most flat and hence task_ratelimit is least fluctuated. |
| 934 | */ |
| 935 | balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw, |
| 936 | dirty_rate | 1); |
Wu Fengguang | bdaac49 | 2011-08-03 14:30:36 -0600 | [diff] [blame] | 937 | /* |
| 938 | * balanced_dirty_ratelimit ~= (write_bw / N) <= write_bw |
| 939 | */ |
| 940 | if (unlikely(balanced_dirty_ratelimit > write_bw)) |
| 941 | balanced_dirty_ratelimit = write_bw; |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 942 | |
Wu Fengguang | 7381131 | 2011-08-26 15:53:24 -0600 | [diff] [blame] | 943 | /* |
| 944 | * We could safely do this and return immediately: |
| 945 | * |
| 946 | * bdi->dirty_ratelimit = balanced_dirty_ratelimit; |
| 947 | * |
| 948 | * However to get a more stable dirty_ratelimit, the below elaborated |
Wanpeng Li | 331cbde | 2012-06-09 11:10:55 +0800 | [diff] [blame] | 949 | * code makes use of task_ratelimit to filter out singular points and |
Wu Fengguang | 7381131 | 2011-08-26 15:53:24 -0600 | [diff] [blame] | 950 | * limit the step size. |
| 951 | * |
| 952 | * The below code essentially only uses the relative value of |
| 953 | * |
| 954 | * task_ratelimit - dirty_ratelimit |
| 955 | * = (pos_ratio - 1) * dirty_ratelimit |
| 956 | * |
| 957 | * which reflects the direction and size of dirty position error. |
| 958 | */ |
| 959 | |
| 960 | /* |
| 961 | * dirty_ratelimit will follow balanced_dirty_ratelimit iff |
| 962 | * task_ratelimit is on the same side of dirty_ratelimit, too. |
| 963 | * For example, when |
| 964 | * - dirty_ratelimit > balanced_dirty_ratelimit |
| 965 | * - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint) |
| 966 | * lowering dirty_ratelimit will help meet both the position and rate |
| 967 | * control targets. Otherwise, don't update dirty_ratelimit if it will |
| 968 | * only help meet the rate target. After all, what the users ultimately |
| 969 | * feel and care are stable dirty rate and small position error. |
| 970 | * |
| 971 | * |task_ratelimit - dirty_ratelimit| is used to limit the step size |
Wanpeng Li | 331cbde | 2012-06-09 11:10:55 +0800 | [diff] [blame] | 972 | * and filter out the singular points of balanced_dirty_ratelimit. Which |
Wu Fengguang | 7381131 | 2011-08-26 15:53:24 -0600 | [diff] [blame] | 973 | * keeps jumping around randomly and can even leap far away at times |
| 974 | * due to the small 200ms estimation period of dirty_rate (we want to |
| 975 | * keep that period small to reduce time lags). |
| 976 | */ |
| 977 | step = 0; |
| 978 | if (dirty < setpoint) { |
| 979 | x = min(bdi->balanced_dirty_ratelimit, |
| 980 | min(balanced_dirty_ratelimit, task_ratelimit)); |
| 981 | if (dirty_ratelimit < x) |
| 982 | step = x - dirty_ratelimit; |
| 983 | } else { |
| 984 | x = max(bdi->balanced_dirty_ratelimit, |
| 985 | max(balanced_dirty_ratelimit, task_ratelimit)); |
| 986 | if (dirty_ratelimit > x) |
| 987 | step = dirty_ratelimit - x; |
| 988 | } |
| 989 | |
| 990 | /* |
| 991 | * Don't pursue 100% rate matching. It's impossible since the balanced |
| 992 | * rate itself is constantly fluctuating. So decrease the track speed |
| 993 | * when it gets close to the target. Helps eliminate pointless tremors. |
| 994 | */ |
| 995 | step >>= dirty_ratelimit / (2 * step + 1); |
| 996 | /* |
| 997 | * Limit the tracking speed to avoid overshooting. |
| 998 | */ |
| 999 | step = (step + 7) / 8; |
| 1000 | |
| 1001 | if (dirty_ratelimit < balanced_dirty_ratelimit) |
| 1002 | dirty_ratelimit += step; |
| 1003 | else |
| 1004 | dirty_ratelimit -= step; |
| 1005 | |
| 1006 | bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL); |
| 1007 | bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit; |
Wu Fengguang | b48c104 | 2011-03-02 17:22:49 -0600 | [diff] [blame] | 1008 | |
| 1009 | trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit); |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 1010 | } |
| 1011 | |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1012 | void __bdi_update_bandwidth(struct backing_dev_info *bdi, |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 1013 | unsigned long thresh, |
Wu Fengguang | af6a311 | 2011-10-03 20:46:17 -0600 | [diff] [blame] | 1014 | unsigned long bg_thresh, |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 1015 | unsigned long dirty, |
| 1016 | unsigned long bdi_thresh, |
| 1017 | unsigned long bdi_dirty, |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1018 | unsigned long start_time) |
| 1019 | { |
| 1020 | unsigned long now = jiffies; |
| 1021 | unsigned long elapsed = now - bdi->bw_time_stamp; |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 1022 | unsigned long dirtied; |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1023 | unsigned long written; |
| 1024 | |
| 1025 | /* |
| 1026 | * rate-limit, only update once every 200ms. |
| 1027 | */ |
| 1028 | if (elapsed < BANDWIDTH_INTERVAL) |
| 1029 | return; |
| 1030 | |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 1031 | dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1032 | written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); |
| 1033 | |
| 1034 | /* |
| 1035 | * Skip quiet periods when disk bandwidth is under-utilized. |
| 1036 | * (at least 1s idle time between two flusher runs) |
| 1037 | */ |
| 1038 | if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) |
| 1039 | goto snapshot; |
| 1040 | |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 1041 | if (thresh) { |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 1042 | global_update_bandwidth(thresh, dirty, now); |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 1043 | bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, |
| 1044 | bdi_thresh, bdi_dirty, |
| 1045 | dirtied, elapsed); |
| 1046 | } |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1047 | bdi_update_write_bandwidth(bdi, elapsed, written); |
| 1048 | |
| 1049 | snapshot: |
Wu Fengguang | be3ffa2 | 2011-06-12 10:51:31 -0600 | [diff] [blame] | 1050 | bdi->dirtied_stamp = dirtied; |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1051 | bdi->written_stamp = written; |
| 1052 | bdi->bw_time_stamp = now; |
| 1053 | } |
| 1054 | |
| 1055 | static void bdi_update_bandwidth(struct backing_dev_info *bdi, |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 1056 | unsigned long thresh, |
Wu Fengguang | af6a311 | 2011-10-03 20:46:17 -0600 | [diff] [blame] | 1057 | unsigned long bg_thresh, |
Wu Fengguang | c42843f | 2011-03-02 15:54:09 -0600 | [diff] [blame] | 1058 | unsigned long dirty, |
| 1059 | unsigned long bdi_thresh, |
| 1060 | unsigned long bdi_dirty, |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1061 | unsigned long start_time) |
| 1062 | { |
| 1063 | if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) |
| 1064 | return; |
| 1065 | spin_lock(&bdi->wb.list_lock); |
Wu Fengguang | af6a311 | 2011-10-03 20:46:17 -0600 | [diff] [blame] | 1066 | __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, |
| 1067 | bdi_thresh, bdi_dirty, start_time); |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1068 | spin_unlock(&bdi->wb.list_lock); |
| 1069 | } |
| 1070 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1071 | /* |
Namjae Jeon | d0e1d66 | 2012-12-11 16:00:21 -0800 | [diff] [blame] | 1072 | * After a task dirtied this many pages, balance_dirty_pages_ratelimited() |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1073 | * will look to see if it needs to start dirty throttling. |
| 1074 | * |
| 1075 | * If dirty_poll_interval is too low, big NUMA machines will call the expensive |
| 1076 | * global_page_state() too often. So scale it near-sqrt to the safety margin |
| 1077 | * (the number of pages we may dirty without exceeding the dirty limits). |
| 1078 | */ |
| 1079 | static unsigned long dirty_poll_interval(unsigned long dirty, |
| 1080 | unsigned long thresh) |
| 1081 | { |
| 1082 | if (thresh > dirty) |
| 1083 | return 1UL << (ilog2(thresh - dirty) >> 1); |
| 1084 | |
| 1085 | return 1; |
| 1086 | } |
| 1087 | |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1088 | static long bdi_max_pause(struct backing_dev_info *bdi, |
| 1089 | unsigned long bdi_dirty) |
Wu Fengguang | c8462cc | 2011-06-11 19:21:43 -0600 | [diff] [blame] | 1090 | { |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1091 | long bw = bdi->avg_write_bandwidth; |
| 1092 | long t; |
Wu Fengguang | c8462cc | 2011-06-11 19:21:43 -0600 | [diff] [blame] | 1093 | |
| 1094 | /* |
| 1095 | * Limit pause time for small memory systems. If sleeping for too long |
| 1096 | * time, a small pool of dirty/writeback pages may go empty and disk go |
| 1097 | * idle. |
| 1098 | * |
| 1099 | * 8 serves as the safety ratio. |
| 1100 | */ |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1101 | t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); |
| 1102 | t++; |
| 1103 | |
| 1104 | return min_t(long, t, MAX_PAUSE); |
| 1105 | } |
| 1106 | |
| 1107 | static long bdi_min_pause(struct backing_dev_info *bdi, |
| 1108 | long max_pause, |
| 1109 | unsigned long task_ratelimit, |
| 1110 | unsigned long dirty_ratelimit, |
| 1111 | int *nr_dirtied_pause) |
| 1112 | { |
| 1113 | long hi = ilog2(bdi->avg_write_bandwidth); |
| 1114 | long lo = ilog2(bdi->dirty_ratelimit); |
| 1115 | long t; /* target pause */ |
| 1116 | long pause; /* estimated next pause */ |
| 1117 | int pages; /* target nr_dirtied_pause */ |
| 1118 | |
| 1119 | /* target for 10ms pause on 1-dd case */ |
| 1120 | t = max(1, HZ / 100); |
Wu Fengguang | c8462cc | 2011-06-11 19:21:43 -0600 | [diff] [blame] | 1121 | |
| 1122 | /* |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1123 | * Scale up pause time for concurrent dirtiers in order to reduce CPU |
| 1124 | * overheads. |
| 1125 | * |
| 1126 | * (N * 10ms) on 2^N concurrent tasks. |
Wu Fengguang | c8462cc | 2011-06-11 19:21:43 -0600 | [diff] [blame] | 1127 | */ |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1128 | if (hi > lo) |
| 1129 | t += (hi - lo) * (10 * HZ) / 1024; |
| 1130 | |
| 1131 | /* |
| 1132 | * This is a bit convoluted. We try to base the next nr_dirtied_pause |
| 1133 | * on the much more stable dirty_ratelimit. However the next pause time |
| 1134 | * will be computed based on task_ratelimit and the two rate limits may |
| 1135 | * depart considerably at some time. Especially if task_ratelimit goes |
| 1136 | * below dirty_ratelimit/2 and the target pause is max_pause, the next |
| 1137 | * pause time will be max_pause*2 _trimmed down_ to max_pause. As a |
| 1138 | * result task_ratelimit won't be executed faithfully, which could |
| 1139 | * eventually bring down dirty_ratelimit. |
| 1140 | * |
| 1141 | * We apply two rules to fix it up: |
| 1142 | * 1) try to estimate the next pause time and if necessary, use a lower |
| 1143 | * nr_dirtied_pause so as not to exceed max_pause. When this happens, |
| 1144 | * nr_dirtied_pause will be "dancing" with task_ratelimit. |
| 1145 | * 2) limit the target pause time to max_pause/2, so that the normal |
| 1146 | * small fluctuations of task_ratelimit won't trigger rule (1) and |
| 1147 | * nr_dirtied_pause will remain as stable as dirty_ratelimit. |
| 1148 | */ |
| 1149 | t = min(t, 1 + max_pause / 2); |
| 1150 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); |
| 1151 | |
Wu Fengguang | 5b9b357 | 2011-12-06 13:17:17 -0600 | [diff] [blame] | 1152 | /* |
| 1153 | * Tiny nr_dirtied_pause is found to hurt I/O performance in the test |
| 1154 | * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. |
| 1155 | * When the 16 consecutive reads are often interrupted by some dirty |
| 1156 | * throttling pause during the async writes, cfq will go into idles |
| 1157 | * (deadline is fine). So push nr_dirtied_pause as high as possible |
| 1158 | * until reaches DIRTY_POLL_THRESH=32 pages. |
| 1159 | */ |
| 1160 | if (pages < DIRTY_POLL_THRESH) { |
| 1161 | t = max_pause; |
| 1162 | pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); |
| 1163 | if (pages > DIRTY_POLL_THRESH) { |
| 1164 | pages = DIRTY_POLL_THRESH; |
| 1165 | t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; |
| 1166 | } |
| 1167 | } |
| 1168 | |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1169 | pause = HZ * pages / (task_ratelimit + 1); |
| 1170 | if (pause > max_pause) { |
| 1171 | t = max_pause; |
| 1172 | pages = task_ratelimit * t / roundup_pow_of_two(HZ); |
| 1173 | } |
| 1174 | |
| 1175 | *nr_dirtied_pause = pages; |
| 1176 | /* |
| 1177 | * The minimal pause time will normally be half the target pause time. |
| 1178 | */ |
Wu Fengguang | 5b9b357 | 2011-12-06 13:17:17 -0600 | [diff] [blame] | 1179 | return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; |
Wu Fengguang | c8462cc | 2011-06-11 19:21:43 -0600 | [diff] [blame] | 1180 | } |
| 1181 | |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1182 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1183 | * balance_dirty_pages() must be called by processes which are generating dirty |
| 1184 | * data. It looks at the number of dirty pages in the machine and will force |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1185 | * the caller to wait once crossing the (background_thresh + dirty_thresh) / 2. |
Jens Axboe | 5b0830c | 2009-09-23 19:37:09 +0200 | [diff] [blame] | 1186 | * If we're over `background_thresh' then the writeback threads are woken to |
| 1187 | * perform some writeout. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1188 | */ |
Wu Fengguang | 3a2e9a5 | 2009-09-23 21:56:00 +0800 | [diff] [blame] | 1189 | static void balance_dirty_pages(struct address_space *mapping, |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1190 | unsigned long pages_dirtied) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1191 | { |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1192 | unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */ |
| 1193 | unsigned long bdi_reclaimable; |
Wu Fengguang | 7762741 | 2010-09-12 13:34:05 -0600 | [diff] [blame] | 1194 | unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */ |
| 1195 | unsigned long bdi_dirty; |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 1196 | unsigned long freerun; |
David Rientjes | 364aeb2 | 2009-01-06 14:39:29 -0800 | [diff] [blame] | 1197 | unsigned long background_thresh; |
| 1198 | unsigned long dirty_thresh; |
| 1199 | unsigned long bdi_thresh; |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1200 | long period; |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1201 | long pause; |
| 1202 | long max_pause; |
| 1203 | long min_pause; |
| 1204 | int nr_dirtied_pause; |
Wu Fengguang | e50e372 | 2010-08-11 14:17:37 -0700 | [diff] [blame] | 1205 | bool dirty_exceeded = false; |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1206 | unsigned long task_ratelimit; |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1207 | unsigned long dirty_ratelimit; |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1208 | unsigned long pos_ratio; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1209 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1210 | unsigned long start_time = jiffies; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1211 | |
| 1212 | for (;;) { |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1213 | unsigned long now = jiffies; |
| 1214 | |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1215 | /* |
| 1216 | * Unstable writes are a feature of certain networked |
| 1217 | * filesystems (i.e. NFS) in which data may have been |
| 1218 | * written to the server's write cache, but has not yet |
| 1219 | * been flushed to permanent storage. |
| 1220 | */ |
Peter Zijlstra | 5fce25a | 2007-11-14 16:59:15 -0800 | [diff] [blame] | 1221 | nr_reclaimable = global_page_state(NR_FILE_DIRTY) + |
| 1222 | global_page_state(NR_UNSTABLE_NFS); |
Wu Fengguang | 7762741 | 2010-09-12 13:34:05 -0600 | [diff] [blame] | 1223 | nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK); |
Peter Zijlstra | 5fce25a | 2007-11-14 16:59:15 -0800 | [diff] [blame] | 1224 | |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 1225 | global_dirty_limits(&background_thresh, &dirty_thresh); |
| 1226 | |
| 1227 | /* |
| 1228 | * Throttle it only when the background writeback cannot |
| 1229 | * catch-up. This avoids (excessively) small writeouts |
| 1230 | * when the bdi limits are ramping up. |
| 1231 | */ |
Wu Fengguang | 6c14ae1 | 2011-03-02 16:04:18 -0600 | [diff] [blame] | 1232 | freerun = dirty_freerun_ceiling(dirty_thresh, |
| 1233 | background_thresh); |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1234 | if (nr_dirty <= freerun) { |
| 1235 | current->dirty_paused_when = now; |
| 1236 | current->nr_dirtied = 0; |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1237 | current->nr_dirtied_pause = |
| 1238 | dirty_poll_interval(nr_dirty, dirty_thresh); |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 1239 | break; |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1240 | } |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 1241 | |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1242 | if (unlikely(!writeback_in_progress(bdi))) |
| 1243 | bdi_start_background_writeback(bdi); |
| 1244 | |
| 1245 | /* |
| 1246 | * bdi_thresh is not treated as some limiting factor as |
| 1247 | * dirty_thresh, due to reasons |
| 1248 | * - in JBOD setup, bdi_thresh can fluctuate a lot |
| 1249 | * - in a system with HDD and USB key, the USB key may somehow |
| 1250 | * go into state (bdi_dirty >> bdi_thresh) either because |
| 1251 | * bdi_dirty starts high, or because bdi_thresh drops low. |
| 1252 | * In this case we don't want to hard throttle the USB key |
| 1253 | * dirtiers for 100 seconds until bdi_dirty drops under |
| 1254 | * bdi_thresh. Instead the auxiliary bdi control line in |
| 1255 | * bdi_position_ratio() will let the dirtier task progress |
| 1256 | * at some rate <= (write_bw / 2) for bringing down bdi_dirty. |
| 1257 | */ |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 1258 | bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 1259 | |
Wu Fengguang | e50e372 | 2010-08-11 14:17:37 -0700 | [diff] [blame] | 1260 | /* |
| 1261 | * In order to avoid the stacked BDI deadlock we need |
| 1262 | * to ensure we accurately count the 'dirty' pages when |
| 1263 | * the threshold is low. |
| 1264 | * |
| 1265 | * Otherwise it would be possible to get thresh+n pages |
| 1266 | * reported dirty, even though there are thresh-m pages |
| 1267 | * actually dirty; with m+n sitting in the percpu |
| 1268 | * deltas. |
| 1269 | */ |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1270 | if (bdi_thresh < 2 * bdi_stat_error(bdi)) { |
| 1271 | bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); |
| 1272 | bdi_dirty = bdi_reclaimable + |
Wu Fengguang | 7762741 | 2010-09-12 13:34:05 -0600 | [diff] [blame] | 1273 | bdi_stat_sum(bdi, BDI_WRITEBACK); |
Wu Fengguang | e50e372 | 2010-08-11 14:17:37 -0700 | [diff] [blame] | 1274 | } else { |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1275 | bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); |
| 1276 | bdi_dirty = bdi_reclaimable + |
Wu Fengguang | 7762741 | 2010-09-12 13:34:05 -0600 | [diff] [blame] | 1277 | bdi_stat(bdi, BDI_WRITEBACK); |
Wu Fengguang | e50e372 | 2010-08-11 14:17:37 -0700 | [diff] [blame] | 1278 | } |
Peter Zijlstra | 5fce25a | 2007-11-14 16:59:15 -0800 | [diff] [blame] | 1279 | |
Wu Fengguang | 8279194 | 2011-12-03 21:26:01 -0600 | [diff] [blame] | 1280 | dirty_exceeded = (bdi_dirty > bdi_thresh) && |
Wu Fengguang | 7762741 | 2010-09-12 13:34:05 -0600 | [diff] [blame] | 1281 | (nr_dirty > dirty_thresh); |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1282 | if (dirty_exceeded && !bdi->dirty_exceeded) |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 1283 | bdi->dirty_exceeded = 1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1284 | |
Wu Fengguang | af6a311 | 2011-10-03 20:46:17 -0600 | [diff] [blame] | 1285 | bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, |
| 1286 | nr_dirty, bdi_thresh, bdi_dirty, |
| 1287 | start_time); |
Wu Fengguang | e98be2d | 2010-08-29 11:22:30 -0600 | [diff] [blame] | 1288 | |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1289 | dirty_ratelimit = bdi->dirty_ratelimit; |
| 1290 | pos_ratio = bdi_position_ratio(bdi, dirty_thresh, |
| 1291 | background_thresh, nr_dirty, |
| 1292 | bdi_thresh, bdi_dirty); |
Wu Fengguang | 3a73dbb | 2011-11-07 19:19:28 +0800 | [diff] [blame] | 1293 | task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> |
| 1294 | RATELIMIT_CALC_SHIFT; |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1295 | max_pause = bdi_max_pause(bdi, bdi_dirty); |
| 1296 | min_pause = bdi_min_pause(bdi, max_pause, |
| 1297 | task_ratelimit, dirty_ratelimit, |
| 1298 | &nr_dirtied_pause); |
| 1299 | |
Wu Fengguang | 3a73dbb | 2011-11-07 19:19:28 +0800 | [diff] [blame] | 1300 | if (unlikely(task_ratelimit == 0)) { |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1301 | period = max_pause; |
Wu Fengguang | c8462cc | 2011-06-11 19:21:43 -0600 | [diff] [blame] | 1302 | pause = max_pause; |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1303 | goto pause; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1304 | } |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1305 | period = HZ * pages_dirtied / task_ratelimit; |
| 1306 | pause = period; |
| 1307 | if (current->dirty_paused_when) |
| 1308 | pause -= now - current->dirty_paused_when; |
| 1309 | /* |
| 1310 | * For less than 1s think time (ext3/4 may block the dirtier |
| 1311 | * for up to 800ms from time to time on 1-HDD; so does xfs, |
| 1312 | * however at much less frequency), try to compensate it in |
| 1313 | * future periods by updating the virtual time; otherwise just |
| 1314 | * do a reset, as it may be a light dirtier. |
| 1315 | */ |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1316 | if (pause < min_pause) { |
Wu Fengguang | ece13ac | 2010-08-29 23:33:20 -0600 | [diff] [blame] | 1317 | trace_balance_dirty_pages(bdi, |
| 1318 | dirty_thresh, |
| 1319 | background_thresh, |
| 1320 | nr_dirty, |
| 1321 | bdi_thresh, |
| 1322 | bdi_dirty, |
| 1323 | dirty_ratelimit, |
| 1324 | task_ratelimit, |
| 1325 | pages_dirtied, |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1326 | period, |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1327 | min(pause, 0L), |
Wu Fengguang | ece13ac | 2010-08-29 23:33:20 -0600 | [diff] [blame] | 1328 | start_time); |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1329 | if (pause < -HZ) { |
| 1330 | current->dirty_paused_when = now; |
| 1331 | current->nr_dirtied = 0; |
| 1332 | } else if (period) { |
| 1333 | current->dirty_paused_when += period; |
| 1334 | current->nr_dirtied = 0; |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1335 | } else if (current->nr_dirtied_pause <= pages_dirtied) |
| 1336 | current->nr_dirtied_pause += pages_dirtied; |
Wu Fengguang | 57fc978 | 2011-06-11 19:32:32 -0600 | [diff] [blame] | 1337 | break; |
| 1338 | } |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1339 | if (unlikely(pause > max_pause)) { |
| 1340 | /* for occasional dropped task_ratelimit */ |
| 1341 | now += min(pause - max_pause, max_pause); |
| 1342 | pause = max_pause; |
| 1343 | } |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1344 | |
| 1345 | pause: |
Wu Fengguang | ece13ac | 2010-08-29 23:33:20 -0600 | [diff] [blame] | 1346 | trace_balance_dirty_pages(bdi, |
| 1347 | dirty_thresh, |
| 1348 | background_thresh, |
| 1349 | nr_dirty, |
| 1350 | bdi_thresh, |
| 1351 | bdi_dirty, |
| 1352 | dirty_ratelimit, |
| 1353 | task_ratelimit, |
| 1354 | pages_dirtied, |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1355 | period, |
Wu Fengguang | ece13ac | 2010-08-29 23:33:20 -0600 | [diff] [blame] | 1356 | pause, |
| 1357 | start_time); |
Jan Kara | 499d05e | 2011-11-16 19:34:48 +0800 | [diff] [blame] | 1358 | __set_current_state(TASK_KILLABLE); |
Wu Fengguang | d25105e | 2009-10-09 12:40:42 +0200 | [diff] [blame] | 1359 | io_schedule_timeout(pause); |
Jens Axboe | 87c6a9b | 2009-09-17 19:59:14 +0200 | [diff] [blame] | 1360 | |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1361 | current->dirty_paused_when = now + pause; |
| 1362 | current->nr_dirtied = 0; |
Wu Fengguang | 7ccb9ad | 2011-11-30 11:08:55 -0600 | [diff] [blame] | 1363 | current->nr_dirtied_pause = nr_dirtied_pause; |
Wu Fengguang | 8371235 | 2011-06-11 19:25:42 -0600 | [diff] [blame] | 1364 | |
Wu Fengguang | ffd1f60 | 2011-06-19 22:18:42 -0600 | [diff] [blame] | 1365 | /* |
Wu Fengguang | 1df6471 | 2011-11-13 19:47:32 -0600 | [diff] [blame] | 1366 | * This is typically equal to (nr_dirty < dirty_thresh) and can |
| 1367 | * also keep "1000+ dd on a slow USB stick" under control. |
Wu Fengguang | ffd1f60 | 2011-06-19 22:18:42 -0600 | [diff] [blame] | 1368 | */ |
Wu Fengguang | 1df6471 | 2011-11-13 19:47:32 -0600 | [diff] [blame] | 1369 | if (task_ratelimit) |
Wu Fengguang | ffd1f60 | 2011-06-19 22:18:42 -0600 | [diff] [blame] | 1370 | break; |
Jan Kara | 499d05e | 2011-11-16 19:34:48 +0800 | [diff] [blame] | 1371 | |
Wu Fengguang | c5c6343 | 2011-12-02 10:21:33 -0600 | [diff] [blame] | 1372 | /* |
| 1373 | * In the case of an unresponding NFS server and the NFS dirty |
| 1374 | * pages exceeds dirty_thresh, give the other good bdi's a pipe |
| 1375 | * to go through, so that tasks on them still remain responsive. |
| 1376 | * |
| 1377 | * In theory 1 page is enough to keep the comsumer-producer |
| 1378 | * pipe going: the flusher cleans 1 page => the task dirties 1 |
| 1379 | * more page. However bdi_dirty has accounting errors. So use |
| 1380 | * the larger and more IO friendly bdi_stat_error. |
| 1381 | */ |
| 1382 | if (bdi_dirty <= bdi_stat_error(bdi)) |
| 1383 | break; |
| 1384 | |
Jan Kara | 499d05e | 2011-11-16 19:34:48 +0800 | [diff] [blame] | 1385 | if (fatal_signal_pending(current)) |
| 1386 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1387 | } |
| 1388 | |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1389 | if (!dirty_exceeded && bdi->dirty_exceeded) |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 1390 | bdi->dirty_exceeded = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1391 | |
| 1392 | if (writeback_in_progress(bdi)) |
Jens Axboe | 5b0830c | 2009-09-23 19:37:09 +0200 | [diff] [blame] | 1393 | return; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1394 | |
| 1395 | /* |
| 1396 | * In laptop mode, we wait until hitting the higher threshold before |
| 1397 | * starting background writeout, and then write out all the way down |
| 1398 | * to the lower threshold. So slow writers cause minimal disk activity. |
| 1399 | * |
| 1400 | * In normal mode, we start background writeout at the lower |
| 1401 | * background_thresh, to keep the amount of dirty memory low. |
| 1402 | */ |
Wu Fengguang | 143dfe8 | 2010-08-27 18:45:12 -0600 | [diff] [blame] | 1403 | if (laptop_mode) |
| 1404 | return; |
| 1405 | |
| 1406 | if (nr_reclaimable > background_thresh) |
Christoph Hellwig | c544419 | 2010-06-08 18:15:15 +0200 | [diff] [blame] | 1407 | bdi_start_background_writeback(bdi); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1408 | } |
| 1409 | |
Peter Zijlstra | a200ee1 | 2007-10-08 18:54:37 +0200 | [diff] [blame] | 1410 | void set_page_dirty_balance(struct page *page, int page_mkwrite) |
Peter Zijlstra | edc79b2 | 2006-09-25 23:30:58 -0700 | [diff] [blame] | 1411 | { |
Peter Zijlstra | a200ee1 | 2007-10-08 18:54:37 +0200 | [diff] [blame] | 1412 | if (set_page_dirty(page) || page_mkwrite) { |
Peter Zijlstra | edc79b2 | 2006-09-25 23:30:58 -0700 | [diff] [blame] | 1413 | struct address_space *mapping = page_mapping(page); |
| 1414 | |
| 1415 | if (mapping) |
| 1416 | balance_dirty_pages_ratelimited(mapping); |
| 1417 | } |
| 1418 | } |
| 1419 | |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1420 | static DEFINE_PER_CPU(int, bdp_ratelimits); |
Tejun Heo | 245b2e7 | 2009-06-24 15:13:48 +0900 | [diff] [blame] | 1421 | |
Wu Fengguang | 54848d7 | 2011-04-05 13:21:19 -0600 | [diff] [blame] | 1422 | /* |
| 1423 | * Normal tasks are throttled by |
| 1424 | * loop { |
| 1425 | * dirty tsk->nr_dirtied_pause pages; |
| 1426 | * take a snap in balance_dirty_pages(); |
| 1427 | * } |
| 1428 | * However there is a worst case. If every task exit immediately when dirtied |
| 1429 | * (tsk->nr_dirtied_pause - 1) pages, balance_dirty_pages() will never be |
| 1430 | * called to throttle the page dirties. The solution is to save the not yet |
| 1431 | * throttled page dirties in dirty_throttle_leaks on task exit and charge them |
| 1432 | * randomly into the running tasks. This works well for the above worst case, |
| 1433 | * as the new task will pick up and accumulate the old task's leaked dirty |
| 1434 | * count and eventually get throttled. |
| 1435 | */ |
| 1436 | DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0; |
| 1437 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1438 | /** |
Namjae Jeon | d0e1d66 | 2012-12-11 16:00:21 -0800 | [diff] [blame] | 1439 | * balance_dirty_pages_ratelimited - balance dirty memory state |
Martin Waitz | 67be2dd | 2005-05-01 08:59:26 -0700 | [diff] [blame] | 1440 | * @mapping: address_space which was dirtied |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1441 | * |
| 1442 | * Processes which are dirtying memory should call in here once for each page |
| 1443 | * which was newly dirtied. The function will periodically check the system's |
| 1444 | * dirty state and will initiate writeback if needed. |
| 1445 | * |
| 1446 | * On really big machines, get_writeback_state is expensive, so try to avoid |
| 1447 | * calling it too often (ratelimiting). But once we're over the dirty memory |
| 1448 | * limit we decrease the ratelimiting by a lot, to prevent individual processes |
| 1449 | * from overshooting the limit by (ratelimit_pages) each. |
| 1450 | */ |
Namjae Jeon | d0e1d66 | 2012-12-11 16:00:21 -0800 | [diff] [blame] | 1451 | void balance_dirty_pages_ratelimited(struct address_space *mapping) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1452 | { |
Wu Fengguang | 36715ce | 2011-06-11 17:53:57 -0600 | [diff] [blame] | 1453 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1454 | int ratelimit; |
| 1455 | int *p; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1456 | |
Wu Fengguang | 36715ce | 2011-06-11 17:53:57 -0600 | [diff] [blame] | 1457 | if (!bdi_cap_account_dirty(bdi)) |
| 1458 | return; |
| 1459 | |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1460 | ratelimit = current->nr_dirtied_pause; |
| 1461 | if (bdi->dirty_exceeded) |
| 1462 | ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1463 | |
Andrew Morton | fa5a734 | 2006-03-24 03:18:10 -0800 | [diff] [blame] | 1464 | preempt_disable(); |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1465 | /* |
| 1466 | * This prevents one CPU to accumulate too many dirtied pages without |
| 1467 | * calling into balance_dirty_pages(), which can happen when there are |
| 1468 | * 1000+ tasks, all of them start dirtying pages at exactly the same |
| 1469 | * time, hence all honoured too large initial task->nr_dirtied_pause. |
| 1470 | */ |
Tejun Heo | 245b2e7 | 2009-06-24 15:13:48 +0900 | [diff] [blame] | 1471 | p = &__get_cpu_var(bdp_ratelimits); |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1472 | if (unlikely(current->nr_dirtied >= ratelimit)) |
Andrew Morton | fa5a734 | 2006-03-24 03:18:10 -0800 | [diff] [blame] | 1473 | *p = 0; |
Wu Fengguang | d3bc1fe | 2011-04-14 07:52:37 -0600 | [diff] [blame] | 1474 | else if (unlikely(*p >= ratelimit_pages)) { |
| 1475 | *p = 0; |
| 1476 | ratelimit = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1477 | } |
Wu Fengguang | 54848d7 | 2011-04-05 13:21:19 -0600 | [diff] [blame] | 1478 | /* |
| 1479 | * Pick up the dirtied pages by the exited tasks. This avoids lots of |
| 1480 | * short-lived tasks (eg. gcc invocations in a kernel build) escaping |
| 1481 | * the dirty throttling and livelock other long-run dirtiers. |
| 1482 | */ |
| 1483 | p = &__get_cpu_var(dirty_throttle_leaks); |
| 1484 | if (*p > 0 && current->nr_dirtied < ratelimit) { |
Namjae Jeon | d0e1d66 | 2012-12-11 16:00:21 -0800 | [diff] [blame] | 1485 | unsigned long nr_pages_dirtied; |
Wu Fengguang | 54848d7 | 2011-04-05 13:21:19 -0600 | [diff] [blame] | 1486 | nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); |
| 1487 | *p -= nr_pages_dirtied; |
| 1488 | current->nr_dirtied += nr_pages_dirtied; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1489 | } |
Andrew Morton | fa5a734 | 2006-03-24 03:18:10 -0800 | [diff] [blame] | 1490 | preempt_enable(); |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1491 | |
| 1492 | if (unlikely(current->nr_dirtied >= ratelimit)) |
| 1493 | balance_dirty_pages(mapping, current->nr_dirtied); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1494 | } |
Namjae Jeon | d0e1d66 | 2012-12-11 16:00:21 -0800 | [diff] [blame] | 1495 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1496 | |
Andrew Morton | 232ea4d | 2007-02-28 20:13:21 -0800 | [diff] [blame] | 1497 | void throttle_vm_writeout(gfp_t gfp_mask) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1498 | { |
David Rientjes | 364aeb2 | 2009-01-06 14:39:29 -0800 | [diff] [blame] | 1499 | unsigned long background_thresh; |
| 1500 | unsigned long dirty_thresh; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1501 | |
| 1502 | for ( ; ; ) { |
Wu Fengguang | 16c4042 | 2010-08-11 14:17:39 -0700 | [diff] [blame] | 1503 | global_dirty_limits(&background_thresh, &dirty_thresh); |
Fengguang Wu | 47a1333 | 2012-03-21 16:34:09 -0700 | [diff] [blame] | 1504 | dirty_thresh = hard_dirty_limit(dirty_thresh); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1505 | |
| 1506 | /* |
| 1507 | * Boost the allowable dirty threshold a bit for page |
| 1508 | * allocators so they don't get DoS'ed by heavy writers |
| 1509 | */ |
| 1510 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ |
| 1511 | |
Christoph Lameter | c24f21b | 2006-06-30 01:55:42 -0700 | [diff] [blame] | 1512 | if (global_page_state(NR_UNSTABLE_NFS) + |
| 1513 | global_page_state(NR_WRITEBACK) <= dirty_thresh) |
| 1514 | break; |
Jens Axboe | 8aa7e84 | 2009-07-09 14:52:32 +0200 | [diff] [blame] | 1515 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
Fengguang Wu | 369f238 | 2007-10-16 23:30:45 -0700 | [diff] [blame] | 1516 | |
| 1517 | /* |
| 1518 | * The caller might hold locks which can prevent IO completion |
| 1519 | * or progress in the filesystem. So we cannot just sit here |
| 1520 | * waiting for IO to complete. |
| 1521 | */ |
| 1522 | if ((gfp_mask & (__GFP_FS|__GFP_IO)) != (__GFP_FS|__GFP_IO)) |
| 1523 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1524 | } |
| 1525 | } |
| 1526 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1527 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1528 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs |
| 1529 | */ |
| 1530 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 1531 | void __user *buffer, size_t *length, loff_t *ppos) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1532 | { |
Alexey Dobriyan | 8d65af7 | 2009-09-23 15:57:19 -0700 | [diff] [blame] | 1533 | proc_dointvec(table, write, buffer, length, ppos); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1534 | return 0; |
| 1535 | } |
| 1536 | |
Jens Axboe | c2c4986 | 2010-05-20 09:18:47 +0200 | [diff] [blame] | 1537 | #ifdef CONFIG_BLOCK |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1538 | void laptop_mode_timer_fn(unsigned long data) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1539 | { |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1540 | struct request_queue *q = (struct request_queue *)data; |
| 1541 | int nr_pages = global_page_state(NR_FILE_DIRTY) + |
| 1542 | global_page_state(NR_UNSTABLE_NFS); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1543 | |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1544 | /* |
| 1545 | * We want to write everything out, not just down to the dirty |
| 1546 | * threshold |
| 1547 | */ |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1548 | if (bdi_has_dirty_io(&q->backing_dev_info)) |
Curt Wohlgemuth | 0e175a1 | 2011-10-07 21:54:10 -0600 | [diff] [blame] | 1549 | bdi_start_writeback(&q->backing_dev_info, nr_pages, |
| 1550 | WB_REASON_LAPTOP_TIMER); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1551 | } |
| 1552 | |
| 1553 | /* |
| 1554 | * We've spun up the disk and we're in laptop mode: schedule writeback |
| 1555 | * of all dirty data a few seconds from now. If the flush is already scheduled |
| 1556 | * then push it back - the user is still using the disk. |
| 1557 | */ |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1558 | void laptop_io_completion(struct backing_dev_info *info) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1559 | { |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1560 | mod_timer(&info->laptop_mode_wb_timer, jiffies + laptop_mode); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1561 | } |
| 1562 | |
| 1563 | /* |
| 1564 | * We're in laptop mode and we've just synced. The sync's writes will have |
| 1565 | * caused another writeback to be scheduled by laptop_io_completion. |
| 1566 | * Nothing needs to be written back anymore, so we unschedule the writeback. |
| 1567 | */ |
| 1568 | void laptop_sync_completion(void) |
| 1569 | { |
Matthew Garrett | 31373d0 | 2010-04-06 14:25:14 +0200 | [diff] [blame] | 1570 | struct backing_dev_info *bdi; |
| 1571 | |
| 1572 | rcu_read_lock(); |
| 1573 | |
| 1574 | list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) |
| 1575 | del_timer(&bdi->laptop_mode_wb_timer); |
| 1576 | |
| 1577 | rcu_read_unlock(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1578 | } |
Jens Axboe | c2c4986 | 2010-05-20 09:18:47 +0200 | [diff] [blame] | 1579 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1580 | |
| 1581 | /* |
| 1582 | * If ratelimit_pages is too high then we can get into dirty-data overload |
| 1583 | * if a large number of processes all perform writes at the same time. |
| 1584 | * If it is too low then SMP machines will call the (expensive) |
| 1585 | * get_writeback_state too often. |
| 1586 | * |
| 1587 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are |
| 1588 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1589 | * thresholds. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1590 | */ |
| 1591 | |
Chandra Seetharaman | 2d1d43f | 2006-09-29 02:01:25 -0700 | [diff] [blame] | 1592 | void writeback_set_ratelimit(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1593 | { |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1594 | unsigned long background_thresh; |
| 1595 | unsigned long dirty_thresh; |
| 1596 | global_dirty_limits(&background_thresh, &dirty_thresh); |
Fengguang Wu | 68809c7 | 2012-05-06 13:21:42 +0800 | [diff] [blame] | 1597 | global_dirty_limit = dirty_thresh; |
Wu Fengguang | 9d823e8 | 2011-06-11 18:10:12 -0600 | [diff] [blame] | 1598 | ratelimit_pages = dirty_thresh / (num_online_cpus() * 32); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1599 | if (ratelimit_pages < 16) |
| 1600 | ratelimit_pages = 16; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1601 | } |
| 1602 | |
Chandra Seetharaman | 26c2143 | 2006-06-27 02:54:10 -0700 | [diff] [blame] | 1603 | static int __cpuinit |
Srivatsa S. Bhat | 2f60d62 | 2012-09-28 20:27:49 +0800 | [diff] [blame] | 1604 | ratelimit_handler(struct notifier_block *self, unsigned long action, |
| 1605 | void *hcpu) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1606 | { |
Srivatsa S. Bhat | 2f60d62 | 2012-09-28 20:27:49 +0800 | [diff] [blame] | 1607 | |
| 1608 | switch (action & ~CPU_TASKS_FROZEN) { |
| 1609 | case CPU_ONLINE: |
| 1610 | case CPU_DEAD: |
| 1611 | writeback_set_ratelimit(); |
| 1612 | return NOTIFY_OK; |
| 1613 | default: |
| 1614 | return NOTIFY_DONE; |
| 1615 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1616 | } |
| 1617 | |
Chandra Seetharaman | 74b85f3 | 2006-06-27 02:54:09 -0700 | [diff] [blame] | 1618 | static struct notifier_block __cpuinitdata ratelimit_nb = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1619 | .notifier_call = ratelimit_handler, |
| 1620 | .next = NULL, |
| 1621 | }; |
| 1622 | |
| 1623 | /* |
Linus Torvalds | dc6e29d | 2007-01-29 16:37:38 -0800 | [diff] [blame] | 1624 | * Called early on to tune the page writeback dirty limits. |
| 1625 | * |
| 1626 | * We used to scale dirty pages according to how total memory |
| 1627 | * related to pages that could be allocated for buffers (by |
| 1628 | * comparing nr_free_buffer_pages() to vm_total_pages. |
| 1629 | * |
| 1630 | * However, that was when we used "dirty_ratio" to scale with |
| 1631 | * all memory, and we don't do that any more. "dirty_ratio" |
| 1632 | * is now applied to total non-HIGHPAGE memory (by subtracting |
| 1633 | * totalhigh_pages from vm_total_pages), and as such we can't |
| 1634 | * get into the old insane situation any more where we had |
| 1635 | * large amounts of dirty pages compared to a small amount of |
| 1636 | * non-HIGHMEM memory. |
| 1637 | * |
| 1638 | * But we might still want to scale the dirty_ratio by how |
| 1639 | * much memory the box has.. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1640 | */ |
| 1641 | void __init page_writeback_init(void) |
| 1642 | { |
Chandra Seetharaman | 2d1d43f | 2006-09-29 02:01:25 -0700 | [diff] [blame] | 1643 | writeback_set_ratelimit(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1644 | register_cpu_notifier(&ratelimit_nb); |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 1645 | |
Jan Kara | eb608e3 | 2012-05-24 18:59:11 +0200 | [diff] [blame] | 1646 | fprop_global_init(&writeout_completions); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1647 | } |
| 1648 | |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1649 | /** |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1650 | * tag_pages_for_writeback - tag pages to be written by write_cache_pages |
| 1651 | * @mapping: address space structure to write |
| 1652 | * @start: starting page index |
| 1653 | * @end: ending page index (inclusive) |
| 1654 | * |
| 1655 | * This function scans the page range from @start to @end (inclusive) and tags |
| 1656 | * all pages that have DIRTY tag set with a special TOWRITE tag. The idea is |
| 1657 | * that write_cache_pages (or whoever calls this function) will then use |
| 1658 | * TOWRITE tag to identify pages eligible for writeback. This mechanism is |
| 1659 | * used to avoid livelocking of writeback by a process steadily creating new |
| 1660 | * dirty pages in the file (thus it is important for this function to be quick |
| 1661 | * so that it can tag pages faster than a dirtying process can create them). |
| 1662 | */ |
| 1663 | /* |
| 1664 | * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency. |
| 1665 | */ |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1666 | void tag_pages_for_writeback(struct address_space *mapping, |
| 1667 | pgoff_t start, pgoff_t end) |
| 1668 | { |
Randy Dunlap | 3c111a0 | 2010-08-11 14:17:30 -0700 | [diff] [blame] | 1669 | #define WRITEBACK_TAG_BATCH 4096 |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1670 | unsigned long tagged; |
| 1671 | |
| 1672 | do { |
| 1673 | spin_lock_irq(&mapping->tree_lock); |
| 1674 | tagged = radix_tree_range_tag_if_tagged(&mapping->page_tree, |
| 1675 | &start, end, WRITEBACK_TAG_BATCH, |
| 1676 | PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE); |
| 1677 | spin_unlock_irq(&mapping->tree_lock); |
| 1678 | WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); |
| 1679 | cond_resched(); |
Jan Kara | d5ed3a4 | 2010-08-19 14:13:33 -0700 | [diff] [blame] | 1680 | /* We check 'start' to handle wrapping when end == ~0UL */ |
| 1681 | } while (tagged >= WRITEBACK_TAG_BATCH && start); |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1682 | } |
| 1683 | EXPORT_SYMBOL(tag_pages_for_writeback); |
| 1684 | |
| 1685 | /** |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1686 | * write_cache_pages - walk the list of dirty pages of the given address space and write all of them. |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1687 | * @mapping: address space structure to write |
| 1688 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1689 | * @writepage: function called for each page |
| 1690 | * @data: data passed to writepage function |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1691 | * |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1692 | * If a page is already under I/O, write_cache_pages() skips it, even |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1693 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
| 1694 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() |
| 1695 | * and msync() need to guarantee that all the data which was dirty at the time |
| 1696 | * the call was made get new I/O started against them. If wbc->sync_mode is |
| 1697 | * WB_SYNC_ALL then we were called for data integrity and we must wait for |
| 1698 | * existing IO to complete. |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1699 | * |
| 1700 | * To avoid livelocks (when other process dirties new pages), we first tag |
| 1701 | * pages which should be written back with TOWRITE tag and only then start |
| 1702 | * writing them. For data-integrity sync we have to be careful so that we do |
| 1703 | * not miss some pages (e.g., because some other process has cleared TOWRITE |
| 1704 | * tag we set). The rule we follow is that TOWRITE tag can be cleared only |
| 1705 | * by the process clearing the DIRTY tag (and submitting the page for IO). |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1706 | */ |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1707 | int write_cache_pages(struct address_space *mapping, |
| 1708 | struct writeback_control *wbc, writepage_t writepage, |
| 1709 | void *data) |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1710 | { |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1711 | int ret = 0; |
| 1712 | int done = 0; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1713 | struct pagevec pvec; |
| 1714 | int nr_pages; |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1715 | pgoff_t uninitialized_var(writeback_index); |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1716 | pgoff_t index; |
| 1717 | pgoff_t end; /* Inclusive */ |
Nick Piggin | bd19e01 | 2009-01-06 14:39:06 -0800 | [diff] [blame] | 1718 | pgoff_t done_index; |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1719 | int cycled; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1720 | int range_whole = 0; |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1721 | int tag; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1722 | |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1723 | pagevec_init(&pvec, 0); |
| 1724 | if (wbc->range_cyclic) { |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1725 | writeback_index = mapping->writeback_index; /* prev offset */ |
| 1726 | index = writeback_index; |
| 1727 | if (index == 0) |
| 1728 | cycled = 1; |
| 1729 | else |
| 1730 | cycled = 0; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1731 | end = -1; |
| 1732 | } else { |
| 1733 | index = wbc->range_start >> PAGE_CACHE_SHIFT; |
| 1734 | end = wbc->range_end >> PAGE_CACHE_SHIFT; |
| 1735 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) |
| 1736 | range_whole = 1; |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1737 | cycled = 1; /* ignore range_cyclic tests */ |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1738 | } |
Wu Fengguang | 6e6938b | 2010-06-06 10:38:15 -0600 | [diff] [blame] | 1739 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1740 | tag = PAGECACHE_TAG_TOWRITE; |
| 1741 | else |
| 1742 | tag = PAGECACHE_TAG_DIRTY; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1743 | retry: |
Wu Fengguang | 6e6938b | 2010-06-06 10:38:15 -0600 | [diff] [blame] | 1744 | if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1745 | tag_pages_for_writeback(mapping, index, end); |
Nick Piggin | bd19e01 | 2009-01-06 14:39:06 -0800 | [diff] [blame] | 1746 | done_index = index; |
Nick Piggin | 5a3d5c9 | 2009-01-06 14:39:09 -0800 | [diff] [blame] | 1747 | while (!done && (index <= end)) { |
| 1748 | int i; |
| 1749 | |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 1750 | nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag, |
Nick Piggin | 5a3d5c9 | 2009-01-06 14:39:09 -0800 | [diff] [blame] | 1751 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1); |
| 1752 | if (nr_pages == 0) |
| 1753 | break; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1754 | |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1755 | for (i = 0; i < nr_pages; i++) { |
| 1756 | struct page *page = pvec.pages[i]; |
| 1757 | |
Nick Piggin | d5482cd | 2009-01-06 14:39:11 -0800 | [diff] [blame] | 1758 | /* |
| 1759 | * At this point, the page may be truncated or |
| 1760 | * invalidated (changing page->mapping to NULL), or |
| 1761 | * even swizzled back from swapper_space to tmpfs file |
| 1762 | * mapping. However, page->index will not change |
| 1763 | * because we have a reference on the page. |
| 1764 | */ |
| 1765 | if (page->index > end) { |
| 1766 | /* |
| 1767 | * can't be range_cyclic (1st pass) because |
| 1768 | * end == -1 in that case. |
| 1769 | */ |
| 1770 | done = 1; |
| 1771 | break; |
| 1772 | } |
| 1773 | |
Jun'ichi Nomura | cf15b07 | 2011-03-22 16:33:40 -0700 | [diff] [blame] | 1774 | done_index = page->index; |
Nick Piggin | bd19e01 | 2009-01-06 14:39:06 -0800 | [diff] [blame] | 1775 | |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1776 | lock_page(page); |
| 1777 | |
Nick Piggin | 5a3d5c9 | 2009-01-06 14:39:09 -0800 | [diff] [blame] | 1778 | /* |
| 1779 | * Page truncated or invalidated. We can freely skip it |
| 1780 | * then, even for data integrity operations: the page |
| 1781 | * has disappeared concurrently, so there could be no |
| 1782 | * real expectation of this data interity operation |
| 1783 | * even if there is now a new, dirty page at the same |
| 1784 | * pagecache address. |
| 1785 | */ |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1786 | if (unlikely(page->mapping != mapping)) { |
Nick Piggin | 5a3d5c9 | 2009-01-06 14:39:09 -0800 | [diff] [blame] | 1787 | continue_unlock: |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1788 | unlock_page(page); |
| 1789 | continue; |
| 1790 | } |
| 1791 | |
Nick Piggin | 515f4a0 | 2009-01-06 14:39:10 -0800 | [diff] [blame] | 1792 | if (!PageDirty(page)) { |
| 1793 | /* someone wrote it for us */ |
| 1794 | goto continue_unlock; |
| 1795 | } |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1796 | |
Nick Piggin | 515f4a0 | 2009-01-06 14:39:10 -0800 | [diff] [blame] | 1797 | if (PageWriteback(page)) { |
| 1798 | if (wbc->sync_mode != WB_SYNC_NONE) |
| 1799 | wait_on_page_writeback(page); |
| 1800 | else |
| 1801 | goto continue_unlock; |
| 1802 | } |
| 1803 | |
| 1804 | BUG_ON(PageWriteback(page)); |
| 1805 | if (!clear_page_dirty_for_io(page)) |
Nick Piggin | 5a3d5c9 | 2009-01-06 14:39:09 -0800 | [diff] [blame] | 1806 | goto continue_unlock; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1807 | |
Dave Chinner | 9e09438 | 2010-07-07 13:24:08 +1000 | [diff] [blame] | 1808 | trace_wbc_writepage(wbc, mapping->backing_dev_info); |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1809 | ret = (*writepage)(page, wbc, data); |
Nick Piggin | 0026677 | 2009-01-06 14:39:06 -0800 | [diff] [blame] | 1810 | if (unlikely(ret)) { |
| 1811 | if (ret == AOP_WRITEPAGE_ACTIVATE) { |
| 1812 | unlock_page(page); |
| 1813 | ret = 0; |
| 1814 | } else { |
| 1815 | /* |
| 1816 | * done_index is set past this page, |
| 1817 | * so media errors will not choke |
| 1818 | * background writeout for the entire |
| 1819 | * file. This has consequences for |
| 1820 | * range_cyclic semantics (ie. it may |
| 1821 | * not be suitable for data integrity |
| 1822 | * writeout). |
| 1823 | */ |
Jun'ichi Nomura | cf15b07 | 2011-03-22 16:33:40 -0700 | [diff] [blame] | 1824 | done_index = page->index + 1; |
Nick Piggin | 0026677 | 2009-01-06 14:39:06 -0800 | [diff] [blame] | 1825 | done = 1; |
| 1826 | break; |
| 1827 | } |
Dave Chinner | 0b56492 | 2010-06-09 10:37:18 +1000 | [diff] [blame] | 1828 | } |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1829 | |
Dave Chinner | 546a192 | 2010-08-24 11:44:34 +1000 | [diff] [blame] | 1830 | /* |
| 1831 | * We stop writing back only if we are not doing |
| 1832 | * integrity sync. In case of integrity sync we have to |
| 1833 | * keep going until we have written all the pages |
| 1834 | * we tagged for writeback prior to entering this loop. |
| 1835 | */ |
| 1836 | if (--wbc->nr_to_write <= 0 && |
| 1837 | wbc->sync_mode == WB_SYNC_NONE) { |
| 1838 | done = 1; |
| 1839 | break; |
Nick Piggin | 05fe478 | 2009-01-06 14:39:08 -0800 | [diff] [blame] | 1840 | } |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1841 | } |
| 1842 | pagevec_release(&pvec); |
| 1843 | cond_resched(); |
| 1844 | } |
Nick Piggin | 3a4c680 | 2009-02-12 04:34:23 +0100 | [diff] [blame] | 1845 | if (!cycled && !done) { |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1846 | /* |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1847 | * range_cyclic: |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1848 | * We hit the last page and there is more work to be done: wrap |
| 1849 | * back to the start of the file |
| 1850 | */ |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1851 | cycled = 1; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1852 | index = 0; |
Nick Piggin | 31a1266 | 2009-01-06 14:39:04 -0800 | [diff] [blame] | 1853 | end = writeback_index - 1; |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1854 | goto retry; |
| 1855 | } |
Dave Chinner | 0b56492 | 2010-06-09 10:37:18 +1000 | [diff] [blame] | 1856 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) |
| 1857 | mapping->writeback_index = done_index; |
Aneesh Kumar K.V | 06d6cf6 | 2008-07-11 19:27:31 -0400 | [diff] [blame] | 1858 | |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1859 | return ret; |
| 1860 | } |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1861 | EXPORT_SYMBOL(write_cache_pages); |
| 1862 | |
| 1863 | /* |
| 1864 | * Function used by generic_writepages to call the real writepage |
| 1865 | * function and set the mapping flags on error |
| 1866 | */ |
| 1867 | static int __writepage(struct page *page, struct writeback_control *wbc, |
| 1868 | void *data) |
| 1869 | { |
| 1870 | struct address_space *mapping = data; |
| 1871 | int ret = mapping->a_ops->writepage(page, wbc); |
| 1872 | mapping_set_error(mapping, ret); |
| 1873 | return ret; |
| 1874 | } |
| 1875 | |
| 1876 | /** |
| 1877 | * generic_writepages - walk the list of dirty pages of the given address space and writepage() all of them. |
| 1878 | * @mapping: address space structure to write |
| 1879 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write |
| 1880 | * |
| 1881 | * This is a library function, which implements the writepages() |
| 1882 | * address_space_operation. |
| 1883 | */ |
| 1884 | int generic_writepages(struct address_space *mapping, |
| 1885 | struct writeback_control *wbc) |
| 1886 | { |
Shaohua Li | 9b6096a | 2011-03-17 10:47:06 +0100 | [diff] [blame] | 1887 | struct blk_plug plug; |
| 1888 | int ret; |
| 1889 | |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1890 | /* deal with chardevs and other special file */ |
| 1891 | if (!mapping->a_ops->writepage) |
| 1892 | return 0; |
| 1893 | |
Shaohua Li | 9b6096a | 2011-03-17 10:47:06 +0100 | [diff] [blame] | 1894 | blk_start_plug(&plug); |
| 1895 | ret = write_cache_pages(mapping, wbc, __writepage, mapping); |
| 1896 | blk_finish_plug(&plug); |
| 1897 | return ret; |
Miklos Szeredi | 0ea9718 | 2007-05-10 22:22:51 -0700 | [diff] [blame] | 1898 | } |
David Howells | 811d736 | 2006-08-29 19:06:09 +0100 | [diff] [blame] | 1899 | |
| 1900 | EXPORT_SYMBOL(generic_writepages); |
| 1901 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1902 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) |
| 1903 | { |
Andrew Morton | 22905f7 | 2005-11-16 15:07:01 -0800 | [diff] [blame] | 1904 | int ret; |
| 1905 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1906 | if (wbc->nr_to_write <= 0) |
| 1907 | return 0; |
| 1908 | if (mapping->a_ops->writepages) |
Peter Zijlstra | d08b385 | 2006-09-25 23:30:57 -0700 | [diff] [blame] | 1909 | ret = mapping->a_ops->writepages(mapping, wbc); |
Andrew Morton | 22905f7 | 2005-11-16 15:07:01 -0800 | [diff] [blame] | 1910 | else |
| 1911 | ret = generic_writepages(mapping, wbc); |
Andrew Morton | 22905f7 | 2005-11-16 15:07:01 -0800 | [diff] [blame] | 1912 | return ret; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1913 | } |
| 1914 | |
| 1915 | /** |
| 1916 | * write_one_page - write out a single page and optionally wait on I/O |
Martin Waitz | 67be2dd | 2005-05-01 08:59:26 -0700 | [diff] [blame] | 1917 | * @page: the page to write |
| 1918 | * @wait: if true, wait on writeout |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1919 | * |
| 1920 | * The page must be locked by the caller and will be unlocked upon return. |
| 1921 | * |
| 1922 | * write_one_page() returns a negative error code if I/O failed. |
| 1923 | */ |
| 1924 | int write_one_page(struct page *page, int wait) |
| 1925 | { |
| 1926 | struct address_space *mapping = page->mapping; |
| 1927 | int ret = 0; |
| 1928 | struct writeback_control wbc = { |
| 1929 | .sync_mode = WB_SYNC_ALL, |
| 1930 | .nr_to_write = 1, |
| 1931 | }; |
| 1932 | |
| 1933 | BUG_ON(!PageLocked(page)); |
| 1934 | |
| 1935 | if (wait) |
| 1936 | wait_on_page_writeback(page); |
| 1937 | |
| 1938 | if (clear_page_dirty_for_io(page)) { |
| 1939 | page_cache_get(page); |
| 1940 | ret = mapping->a_ops->writepage(page, &wbc); |
| 1941 | if (ret == 0 && wait) { |
| 1942 | wait_on_page_writeback(page); |
| 1943 | if (PageError(page)) |
| 1944 | ret = -EIO; |
| 1945 | } |
| 1946 | page_cache_release(page); |
| 1947 | } else { |
| 1948 | unlock_page(page); |
| 1949 | } |
| 1950 | return ret; |
| 1951 | } |
| 1952 | EXPORT_SYMBOL(write_one_page); |
| 1953 | |
| 1954 | /* |
Ken Chen | 7671932 | 2007-02-10 01:43:15 -0800 | [diff] [blame] | 1955 | * For address_spaces which do not use buffers nor write back. |
| 1956 | */ |
| 1957 | int __set_page_dirty_no_writeback(struct page *page) |
| 1958 | { |
| 1959 | if (!PageDirty(page)) |
Bob Liu | c3f0da6 | 2011-01-13 15:45:49 -0800 | [diff] [blame] | 1960 | return !TestSetPageDirty(page); |
Ken Chen | 7671932 | 2007-02-10 01:43:15 -0800 | [diff] [blame] | 1961 | return 0; |
| 1962 | } |
| 1963 | |
| 1964 | /* |
Edward Shishkin | e3a7cca | 2009-03-31 15:19:39 -0700 | [diff] [blame] | 1965 | * Helper function for set_page_dirty family. |
| 1966 | * NOTE: This relies on being atomic wrt interrupts. |
| 1967 | */ |
| 1968 | void account_page_dirtied(struct page *page, struct address_space *mapping) |
| 1969 | { |
| 1970 | if (mapping_cap_account_dirty(mapping)) { |
| 1971 | __inc_zone_page_state(page, NR_FILE_DIRTY); |
Michael Rubin | ea941f0 | 2010-10-26 14:21:35 -0700 | [diff] [blame] | 1972 | __inc_zone_page_state(page, NR_DIRTIED); |
Edward Shishkin | e3a7cca | 2009-03-31 15:19:39 -0700 | [diff] [blame] | 1973 | __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
Wu Fengguang | c8e28ce | 2011-01-23 10:07:47 -0600 | [diff] [blame] | 1974 | __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); |
Edward Shishkin | e3a7cca | 2009-03-31 15:19:39 -0700 | [diff] [blame] | 1975 | task_io_account_write(PAGE_CACHE_SIZE); |
Wu Fengguang | d3bc1fe | 2011-04-14 07:52:37 -0600 | [diff] [blame] | 1976 | current->nr_dirtied++; |
| 1977 | this_cpu_inc(bdp_ratelimits); |
Edward Shishkin | e3a7cca | 2009-03-31 15:19:39 -0700 | [diff] [blame] | 1978 | } |
| 1979 | } |
Michael Rubin | 679ceac | 2010-08-20 02:31:26 -0700 | [diff] [blame] | 1980 | EXPORT_SYMBOL(account_page_dirtied); |
Edward Shishkin | e3a7cca | 2009-03-31 15:19:39 -0700 | [diff] [blame] | 1981 | |
| 1982 | /* |
Michael Rubin | f629d1c | 2010-10-26 14:21:33 -0700 | [diff] [blame] | 1983 | * Helper function for set_page_writeback family. |
| 1984 | * NOTE: Unlike account_page_dirtied this does not rely on being atomic |
| 1985 | * wrt interrupts. |
| 1986 | */ |
| 1987 | void account_page_writeback(struct page *page) |
| 1988 | { |
| 1989 | inc_zone_page_state(page, NR_WRITEBACK); |
| 1990 | } |
| 1991 | EXPORT_SYMBOL(account_page_writeback); |
| 1992 | |
| 1993 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1994 | * For address_spaces which do not use buffers. Just tag the page as dirty in |
| 1995 | * its radix tree. |
| 1996 | * |
| 1997 | * This is also used when a single buffer is being dirtied: we want to set the |
| 1998 | * page dirty in that case, but not all the buffers. This is a "bottom-up" |
| 1999 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. |
| 2000 | * |
| 2001 | * Most callers have locked the page, which pins the address_space in memory. |
| 2002 | * But zap_pte_range() does not lock the page, however in that case the |
| 2003 | * mapping is pinned by the vma's ->vm_file reference. |
| 2004 | * |
| 2005 | * We take care to handle the case where the page was truncated from the |
Simon Arlott | 183ff22 | 2007-10-20 01:27:18 +0200 | [diff] [blame] | 2006 | * mapping by re-checking page_mapping() inside tree_lock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2007 | */ |
| 2008 | int __set_page_dirty_nobuffers(struct page *page) |
| 2009 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2010 | if (!TestSetPageDirty(page)) { |
| 2011 | struct address_space *mapping = page_mapping(page); |
| 2012 | struct address_space *mapping2; |
| 2013 | |
Andrew Morton | 8c08540 | 2006-12-10 02:19:24 -0800 | [diff] [blame] | 2014 | if (!mapping) |
| 2015 | return 1; |
| 2016 | |
Nick Piggin | 19fd623 | 2008-07-25 19:45:32 -0700 | [diff] [blame] | 2017 | spin_lock_irq(&mapping->tree_lock); |
Andrew Morton | 8c08540 | 2006-12-10 02:19:24 -0800 | [diff] [blame] | 2018 | mapping2 = page_mapping(page); |
| 2019 | if (mapping2) { /* Race with truncate? */ |
| 2020 | BUG_ON(mapping2 != mapping); |
Nick Piggin | 787d221 | 2007-07-17 04:03:34 -0700 | [diff] [blame] | 2021 | WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page)); |
Edward Shishkin | e3a7cca | 2009-03-31 15:19:39 -0700 | [diff] [blame] | 2022 | account_page_dirtied(page, mapping); |
Andrew Morton | 8c08540 | 2006-12-10 02:19:24 -0800 | [diff] [blame] | 2023 | radix_tree_tag_set(&mapping->page_tree, |
| 2024 | page_index(page), PAGECACHE_TAG_DIRTY); |
| 2025 | } |
Nick Piggin | 19fd623 | 2008-07-25 19:45:32 -0700 | [diff] [blame] | 2026 | spin_unlock_irq(&mapping->tree_lock); |
Andrew Morton | 8c08540 | 2006-12-10 02:19:24 -0800 | [diff] [blame] | 2027 | if (mapping->host) { |
| 2028 | /* !PageAnon && !swapper_space */ |
| 2029 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2030 | } |
Andrew Morton | 4741c9f | 2006-03-24 03:18:11 -0800 | [diff] [blame] | 2031 | return 1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2032 | } |
Andrew Morton | 4741c9f | 2006-03-24 03:18:11 -0800 | [diff] [blame] | 2033 | return 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2034 | } |
| 2035 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); |
| 2036 | |
| 2037 | /* |
Wu Fengguang | 2f800fb | 2011-08-08 15:22:00 -0600 | [diff] [blame] | 2038 | * Call this whenever redirtying a page, to de-account the dirty counters |
| 2039 | * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written |
| 2040 | * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to |
| 2041 | * systematic errors in balanced_dirty_ratelimit and the dirty pages position |
| 2042 | * control. |
| 2043 | */ |
| 2044 | void account_page_redirty(struct page *page) |
| 2045 | { |
| 2046 | struct address_space *mapping = page->mapping; |
| 2047 | if (mapping && mapping_cap_account_dirty(mapping)) { |
| 2048 | current->nr_dirtied--; |
| 2049 | dec_zone_page_state(page, NR_DIRTIED); |
| 2050 | dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); |
| 2051 | } |
| 2052 | } |
| 2053 | EXPORT_SYMBOL(account_page_redirty); |
| 2054 | |
| 2055 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2056 | * When a writepage implementation decides that it doesn't want to write this |
| 2057 | * page for some reason, it should redirty the locked page via |
| 2058 | * redirty_page_for_writepage() and it should then unlock the page and return 0 |
| 2059 | */ |
| 2060 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) |
| 2061 | { |
| 2062 | wbc->pages_skipped++; |
Wu Fengguang | 2f800fb | 2011-08-08 15:22:00 -0600 | [diff] [blame] | 2063 | account_page_redirty(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2064 | return __set_page_dirty_nobuffers(page); |
| 2065 | } |
| 2066 | EXPORT_SYMBOL(redirty_page_for_writepage); |
| 2067 | |
| 2068 | /* |
Wu Fengguang | 6746aff | 2009-09-16 11:50:14 +0200 | [diff] [blame] | 2069 | * Dirty a page. |
| 2070 | * |
| 2071 | * For pages with a mapping this should be done under the page lock |
| 2072 | * for the benefit of asynchronous memory errors who prefer a consistent |
| 2073 | * dirty state. This rule can be broken in some special cases, |
| 2074 | * but should be better not to. |
| 2075 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2076 | * If the mapping doesn't provide a set_page_dirty a_op, then |
| 2077 | * just fall through and assume that it wants buffer_heads. |
| 2078 | */ |
Nick Piggin | 1cf6e7d | 2009-02-18 14:48:18 -0800 | [diff] [blame] | 2079 | int set_page_dirty(struct page *page) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2080 | { |
| 2081 | struct address_space *mapping = page_mapping(page); |
| 2082 | |
| 2083 | if (likely(mapping)) { |
| 2084 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; |
Minchan Kim | 278df9f | 2011-03-22 16:32:54 -0700 | [diff] [blame] | 2085 | /* |
| 2086 | * readahead/lru_deactivate_page could remain |
| 2087 | * PG_readahead/PG_reclaim due to race with end_page_writeback |
| 2088 | * About readahead, if the page is written, the flags would be |
| 2089 | * reset. So no problem. |
| 2090 | * About lru_deactivate_page, if the page is redirty, the flag |
| 2091 | * will be reset. So no problem. but if the page is used by readahead |
| 2092 | * it will confuse readahead and make it restart the size rampup |
| 2093 | * process. But it's a trivial problem. |
| 2094 | */ |
| 2095 | ClearPageReclaim(page); |
David Howells | 9361401 | 2006-09-30 20:45:40 +0200 | [diff] [blame] | 2096 | #ifdef CONFIG_BLOCK |
| 2097 | if (!spd) |
| 2098 | spd = __set_page_dirty_buffers; |
| 2099 | #endif |
| 2100 | return (*spd)(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2101 | } |
Andrew Morton | 4741c9f | 2006-03-24 03:18:11 -0800 | [diff] [blame] | 2102 | if (!PageDirty(page)) { |
| 2103 | if (!TestSetPageDirty(page)) |
| 2104 | return 1; |
| 2105 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2106 | return 0; |
| 2107 | } |
| 2108 | EXPORT_SYMBOL(set_page_dirty); |
| 2109 | |
| 2110 | /* |
| 2111 | * set_page_dirty() is racy if the caller has no reference against |
| 2112 | * page->mapping->host, and if the page is unlocked. This is because another |
| 2113 | * CPU could truncate the page off the mapping and then free the mapping. |
| 2114 | * |
| 2115 | * Usually, the page _is_ locked, or the caller is a user-space process which |
| 2116 | * holds a reference on the inode by having an open file. |
| 2117 | * |
| 2118 | * In other cases, the page should be locked before running set_page_dirty(). |
| 2119 | */ |
| 2120 | int set_page_dirty_lock(struct page *page) |
| 2121 | { |
| 2122 | int ret; |
| 2123 | |
Jens Axboe | 7eaceac | 2011-03-10 08:52:07 +0100 | [diff] [blame] | 2124 | lock_page(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2125 | ret = set_page_dirty(page); |
| 2126 | unlock_page(page); |
| 2127 | return ret; |
| 2128 | } |
| 2129 | EXPORT_SYMBOL(set_page_dirty_lock); |
| 2130 | |
| 2131 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2132 | * Clear a page's dirty flag, while caring for dirty memory accounting. |
| 2133 | * Returns true if the page was previously dirty. |
| 2134 | * |
| 2135 | * This is for preparing to put the page under writeout. We leave the page |
| 2136 | * tagged as dirty in the radix tree so that a concurrent write-for-sync |
| 2137 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage |
| 2138 | * implementation will run either set_page_writeback() or set_page_dirty(), |
| 2139 | * at which stage we bring the page's dirty flag and radix-tree dirty tag |
| 2140 | * back into sync. |
| 2141 | * |
| 2142 | * This incoherency between the page's dirty flag and radix-tree tag is |
| 2143 | * unfortunate, but it only exists while the page is locked. |
| 2144 | */ |
| 2145 | int clear_page_dirty_for_io(struct page *page) |
| 2146 | { |
| 2147 | struct address_space *mapping = page_mapping(page); |
| 2148 | |
Nick Piggin | 7935289 | 2007-07-19 01:47:22 -0700 | [diff] [blame] | 2149 | BUG_ON(!PageLocked(page)); |
| 2150 | |
Linus Torvalds | 7658cc2 | 2006-12-29 10:00:58 -0800 | [diff] [blame] | 2151 | if (mapping && mapping_cap_account_dirty(mapping)) { |
| 2152 | /* |
| 2153 | * Yes, Virginia, this is indeed insane. |
| 2154 | * |
| 2155 | * We use this sequence to make sure that |
| 2156 | * (a) we account for dirty stats properly |
| 2157 | * (b) we tell the low-level filesystem to |
| 2158 | * mark the whole page dirty if it was |
| 2159 | * dirty in a pagetable. Only to then |
| 2160 | * (c) clean the page again and return 1 to |
| 2161 | * cause the writeback. |
| 2162 | * |
| 2163 | * This way we avoid all nasty races with the |
| 2164 | * dirty bit in multiple places and clearing |
| 2165 | * them concurrently from different threads. |
| 2166 | * |
| 2167 | * Note! Normally the "set_page_dirty(page)" |
| 2168 | * has no effect on the actual dirty bit - since |
| 2169 | * that will already usually be set. But we |
| 2170 | * need the side effects, and it can help us |
| 2171 | * avoid races. |
| 2172 | * |
| 2173 | * We basically use the page "master dirty bit" |
| 2174 | * as a serialization point for all the different |
| 2175 | * threads doing their things. |
Linus Torvalds | 7658cc2 | 2006-12-29 10:00:58 -0800 | [diff] [blame] | 2176 | */ |
| 2177 | if (page_mkclean(page)) |
| 2178 | set_page_dirty(page); |
Nick Piggin | 7935289 | 2007-07-19 01:47:22 -0700 | [diff] [blame] | 2179 | /* |
| 2180 | * We carefully synchronise fault handlers against |
| 2181 | * installing a dirty pte and marking the page dirty |
| 2182 | * at this point. We do this by having them hold the |
| 2183 | * page lock at some point after installing their |
| 2184 | * pte, but before marking the page dirty. |
| 2185 | * Pages are always locked coming in here, so we get |
| 2186 | * the desired exclusion. See mm/memory.c:do_wp_page() |
| 2187 | * for more comments. |
| 2188 | */ |
Linus Torvalds | 7658cc2 | 2006-12-29 10:00:58 -0800 | [diff] [blame] | 2189 | if (TestClearPageDirty(page)) { |
Andrew Morton | 8c08540 | 2006-12-10 02:19:24 -0800 | [diff] [blame] | 2190 | dec_zone_page_state(page, NR_FILE_DIRTY); |
Peter Zijlstra | c9e51e4 | 2007-10-16 23:25:47 -0700 | [diff] [blame] | 2191 | dec_bdi_stat(mapping->backing_dev_info, |
| 2192 | BDI_RECLAIMABLE); |
Linus Torvalds | 7658cc2 | 2006-12-29 10:00:58 -0800 | [diff] [blame] | 2193 | return 1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2194 | } |
Linus Torvalds | 7658cc2 | 2006-12-29 10:00:58 -0800 | [diff] [blame] | 2195 | return 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2196 | } |
Linus Torvalds | 7658cc2 | 2006-12-29 10:00:58 -0800 | [diff] [blame] | 2197 | return TestClearPageDirty(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2198 | } |
Hans Reiser | 58bb01a | 2005-11-18 01:10:53 -0800 | [diff] [blame] | 2199 | EXPORT_SYMBOL(clear_page_dirty_for_io); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2200 | |
| 2201 | int test_clear_page_writeback(struct page *page) |
| 2202 | { |
| 2203 | struct address_space *mapping = page_mapping(page); |
| 2204 | int ret; |
| 2205 | |
| 2206 | if (mapping) { |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2207 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2208 | unsigned long flags; |
| 2209 | |
Nick Piggin | 19fd623 | 2008-07-25 19:45:32 -0700 | [diff] [blame] | 2210 | spin_lock_irqsave(&mapping->tree_lock, flags); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2211 | ret = TestClearPageWriteback(page); |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2212 | if (ret) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2213 | radix_tree_tag_clear(&mapping->page_tree, |
| 2214 | page_index(page), |
| 2215 | PAGECACHE_TAG_WRITEBACK); |
Miklos Szeredi | e4ad08f | 2008-04-30 00:54:37 -0700 | [diff] [blame] | 2216 | if (bdi_cap_account_writeback(bdi)) { |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2217 | __dec_bdi_stat(bdi, BDI_WRITEBACK); |
Peter Zijlstra | 04fbfdc | 2007-10-16 23:25:50 -0700 | [diff] [blame] | 2218 | __bdi_writeout_inc(bdi); |
| 2219 | } |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2220 | } |
Nick Piggin | 19fd623 | 2008-07-25 19:45:32 -0700 | [diff] [blame] | 2221 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2222 | } else { |
| 2223 | ret = TestClearPageWriteback(page); |
| 2224 | } |
Wu Fengguang | 99b12e3 | 2011-07-25 17:12:37 -0700 | [diff] [blame] | 2225 | if (ret) { |
Andrew Morton | d688abf | 2007-07-19 01:49:17 -0700 | [diff] [blame] | 2226 | dec_zone_page_state(page, NR_WRITEBACK); |
Wu Fengguang | 99b12e3 | 2011-07-25 17:12:37 -0700 | [diff] [blame] | 2227 | inc_zone_page_state(page, NR_WRITTEN); |
| 2228 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2229 | return ret; |
| 2230 | } |
| 2231 | |
| 2232 | int test_set_page_writeback(struct page *page) |
| 2233 | { |
| 2234 | struct address_space *mapping = page_mapping(page); |
| 2235 | int ret; |
| 2236 | |
| 2237 | if (mapping) { |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2238 | struct backing_dev_info *bdi = mapping->backing_dev_info; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2239 | unsigned long flags; |
| 2240 | |
Nick Piggin | 19fd623 | 2008-07-25 19:45:32 -0700 | [diff] [blame] | 2241 | spin_lock_irqsave(&mapping->tree_lock, flags); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2242 | ret = TestSetPageWriteback(page); |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2243 | if (!ret) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2244 | radix_tree_tag_set(&mapping->page_tree, |
| 2245 | page_index(page), |
| 2246 | PAGECACHE_TAG_WRITEBACK); |
Miklos Szeredi | e4ad08f | 2008-04-30 00:54:37 -0700 | [diff] [blame] | 2247 | if (bdi_cap_account_writeback(bdi)) |
Peter Zijlstra | 69cb51d | 2007-10-16 23:25:48 -0700 | [diff] [blame] | 2248 | __inc_bdi_stat(bdi, BDI_WRITEBACK); |
| 2249 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2250 | if (!PageDirty(page)) |
| 2251 | radix_tree_tag_clear(&mapping->page_tree, |
| 2252 | page_index(page), |
| 2253 | PAGECACHE_TAG_DIRTY); |
Jan Kara | f446daae | 2010-08-09 17:19:12 -0700 | [diff] [blame] | 2254 | radix_tree_tag_clear(&mapping->page_tree, |
| 2255 | page_index(page), |
| 2256 | PAGECACHE_TAG_TOWRITE); |
Nick Piggin | 19fd623 | 2008-07-25 19:45:32 -0700 | [diff] [blame] | 2257 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2258 | } else { |
| 2259 | ret = TestSetPageWriteback(page); |
| 2260 | } |
Andrew Morton | d688abf | 2007-07-19 01:49:17 -0700 | [diff] [blame] | 2261 | if (!ret) |
Michael Rubin | f629d1c | 2010-10-26 14:21:33 -0700 | [diff] [blame] | 2262 | account_page_writeback(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2263 | return ret; |
| 2264 | |
| 2265 | } |
| 2266 | EXPORT_SYMBOL(test_set_page_writeback); |
| 2267 | |
| 2268 | /* |
Nick Piggin | 0012818 | 2007-10-16 01:24:40 -0700 | [diff] [blame] | 2269 | * Return true if any of the pages in the mapping are marked with the |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2270 | * passed tag. |
| 2271 | */ |
| 2272 | int mapping_tagged(struct address_space *mapping, int tag) |
| 2273 | { |
Konstantin Khlebnikov | 72c4783 | 2011-07-25 17:12:31 -0700 | [diff] [blame] | 2274 | return radix_tree_tagged(&mapping->page_tree, tag); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2275 | } |
| 2276 | EXPORT_SYMBOL(mapping_tagged); |