mm/swap.c

   1 /*
   2  *  linux/mm/swap.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   5  */
   6
   7 /*
   8  * This file contains the default values for the opereation of the
   9  * Linux VM subsystem. Fine-tuning documentation can be found in
  10  * Documentation/sysctl/vm.txt.
  11  * Started 18.12.91
  12  * Swap aging added 23.2.95, Stephen Tweedie.
  13  * Buffermem limits added 12.3.98, Rik van Riel.
  14  */
  15
  16 #include <linux/mm.h>
  17 #include <linux/sched.h>
  18 #include <linux/kernel_stat.h>
  19 #include <linux/swap.h>
  20 #include <linux/mman.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/pagevec.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/mm_inline.h>
  26 #include <linux/buffer_head.h>  /* for try_to_release_page() */
  27 #include <linux/module.h>
  28 #include <linux/percpu_counter.h>
  29 #include <linux/percpu.h>
  30 #include <linux/cpu.h>
  31 #include <linux/notifier.h>
  32 #include <linux/init.h>
  33
  34 /* How many pages do we try to swap or page in/out together? */
  35 int page_cluster;
  36
  37 /*
  38  * This path almost never happens for VM activity - pages are normally
  39  * freed via pagevecs.  But it gets used by networking.
  40  */
  41 static void fastcall __page_cache_release(struct page *page)
  42 {
  43         if (PageLRU(page)) {
  44                 unsigned long flags;
  45                 struct zone *zone = page_zone(page);
  46
  47                 spin_lock_irqsave(&zone->lru_lock, flags);
  48                 VM_BUG_ON(!PageLRU(page));
  49                 __ClearPageLRU(page);
  50                 del_page_from_lru(zone, page);
  51                 spin_unlock_irqrestore(&zone->lru_lock, flags);
  52         }
  53         free_hot_page(page);
  54 }
  55
  56 static void put_compound_page(struct page *page)
  57 {
  58         page = (struct page *)page_private(page);
  59         if (put_page_testzero(page)) {
  60                 compound_page_dtor *dtor;
  61
  62                 dtor = get_compound_page_dtor(page);
  63                 (*dtor)(page);
  64         }
  65 }
  66
  67 void put_page(struct page *page)
  68 {
  69         if (unlikely(PageCompound(page)))
  70                 put_compound_page(page);
  71         else if (put_page_testzero(page))
  72                 __page_cache_release(page);
  73 }
  74 EXPORT_SYMBOL(put_page);
  75
  76 /**
  77  * put_pages_list(): release a list of pages
  78  *
  79  * Release a list of pages which are strung together on page.lru.  Currently
  80  * used by read_cache_pages() and related error recovery code.
  81  *
  82  * @pages: list of pages threaded on page->lru
  83  */
  84 void put_pages_list(struct list_head *pages)
  85 {
  86         while (!list_empty(pages)) {
  87                 struct page *victim;
  88
  89                 victim = list_entry(pages->prev, struct page, lru);
  90                 list_del(&victim->lru);
  91                 page_cache_release(victim);
  92         }
  93 }
  94 EXPORT_SYMBOL(put_pages_list);
  95
  96 /*
  97  * Writeback is about to end against a page which has been marked for immediate
  98  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
  99  * inactive list.  The page still has PageWriteback set, which will pin it.
 100  *
 101  * We don't expect many pages to come through here, so don't bother batching
 102  * things up.
 103  *
 104  * To avoid placing the page at the tail of the LRU while PG_writeback is still
 105  * set, this function will clear PG_writeback before performing the page
 106  * motion.  Do that inside the lru lock because once PG_writeback is cleared
 107  * we may not touch the page.
 108  *
 109  * Returns zero if it cleared PG_writeback.
 110  */
 111 int rotate_reclaimable_page(struct page *page)
 112 {
 113         struct zone *zone;
 114         unsigned long flags;
 115
 116         if (PageLocked(page))
 117                 return 1;
 118         if (PageDirty(page))
 119                 return 1;
 120         if (PageActive(page))
 121                 return 1;
 122         if (!PageLRU(page))
 123                 return 1;
 124
 125         zone = page_zone(page);
 126         spin_lock_irqsave(&zone->lru_lock, flags);
 127         if (PageLRU(page) && !PageActive(page)) {
 128                 list_move_tail(&page->lru, &zone->inactive_list);
 129                 __count_vm_event(PGROTATED);
 130         }
 131         if (!test_clear_page_writeback(page))
 132                 BUG();
 133         spin_unlock_irqrestore(&zone->lru_lock, flags);
 134         return 0;
 135 }
 136
 137 /*
 138  * FIXME: speed this up?
 139  */
 140 void fastcall activate_page(struct page *page)
 141 {
 142         struct zone *zone = page_zone(page);
 143
 144         spin_lock_irq(&zone->lru_lock);
 145         if (PageLRU(page) && !PageActive(page)) {
 146                 del_page_from_inactive_list(zone, page);
 147                 SetPageActive(page);
 148                 add_page_to_active_list(zone, page);
 149                 __count_vm_event(PGACTIVATE);
 150         }
 151         spin_unlock_irq(&zone->lru_lock);
 152 }
 153
 154 /*
 155  * Mark a page as having seen activity.
 156  *
 157  * inactive,unreferenced        ->      inactive,referenced
 158  * inactive,referenced          ->      active,unreferenced
 159  * active,unreferenced          ->      active,referenced
 160  */
 161 void fastcall mark_page_accessed(struct page *page)
 162 {
 163         if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
 164                 activate_page(page);
 165                 ClearPageReferenced(page);
 166         } else if (!PageReferenced(page)) {
 167                 SetPageReferenced(page);
 168         }
 169 }
 170
 171 EXPORT_SYMBOL(mark_page_accessed);
 172
 173 /**
 174  * lru_cache_add: add a page to the page lists
 175  * @page: the page to add
 176  */
 177 static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
 178 static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
 179
 180 void fastcall lru_cache_add(struct page *page)
 181 {
 182         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
 183
 184         page_cache_get(page);
 185         if (!pagevec_add(pvec, page))
 186                 __pagevec_lru_add(pvec);
 187         put_cpu_var(lru_add_pvecs);
 188 }
 189
 190 void fastcall lru_cache_add_active(struct page *page)
 191 {
 192         struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
 193
 194         page_cache_get(page);
 195         if (!pagevec_add(pvec, page))
 196                 __pagevec_lru_add_active(pvec);
 197         put_cpu_var(lru_add_active_pvecs);
 198 }
 199
 200 static void __lru_add_drain(int cpu)
 201 {
 202         struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
 203
 204         /* CPU is dead, so no locking needed. */
 205         if (pagevec_count(pvec))
 206                 __pagevec_lru_add(pvec);
 207         pvec = &per_cpu(lru_add_active_pvecs, cpu);
 208         if (pagevec_count(pvec))
 209                 __pagevec_lru_add_active(pvec);
 210 }
 211
 212 void lru_add_drain(void)
 213 {
 214         __lru_add_drain(get_cpu());
 215         put_cpu();
 216 }
 217
 218 #ifdef CONFIG_NUMA
 219 static void lru_add_drain_per_cpu(struct work_struct *dummy)
 220 {
 221         lru_add_drain();
 222 }
 223
 224 /*
 225  * Returns 0 for success
 226  */
 227 int lru_add_drain_all(void)
 228 {
 229         return schedule_on_each_cpu(lru_add_drain_per_cpu);
 230 }
 231
 232 #else
 233
 234 /*
 235  * Returns 0 for success
 236  */
 237 int lru_add_drain_all(void)
 238 {
 239         lru_add_drain();
 240         return 0;
 241 }
 242 #endif
 243
 244 /*
 245  * Batched page_cache_release().  Decrement the reference count on all the
 246  * passed pages.  If it fell to zero then remove the page from the LRU and
 247  * free it.
 248  *
 249  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 250  * for the remainder of the operation.
 251  *
 252  * The locking in this function is against shrink_cache(): we recheck the
 253  * page count inside the lock to see whether shrink_cache grabbed the page
 254  * via the LRU.  If it did, give up: shrink_cache will free it.
 255  */
 256 void release_pages(struct page **pages, int nr, int cold)
 257 {
 258         int i;
 259         struct pagevec pages_to_free;
 260         struct zone *zone = NULL;
 261
 262         pagevec_init(&pages_to_free, cold);
 263         for (i = 0; i < nr; i++) {
 264                 struct page *page = pages[i];
 265
 266                 if (unlikely(PageCompound(page))) {
 267                         if (zone) {
 268                                 spin_unlock_irq(&zone->lru_lock);
 269                                 zone = NULL;
 270                         }
 271                         put_compound_page(page);
 272                         continue;
 273                 }
 274
 275                 if (!put_page_testzero(page))
 276                         continue;
 277
 278                 if (PageLRU(page)) {
 279                         struct zone *pagezone = page_zone(page);
 280                         if (pagezone != zone) {
 281                                 if (zone)
 282                                         spin_unlock_irq(&zone->lru_lock);
 283                                 zone = pagezone;
 284                                 spin_lock_irq(&zone->lru_lock);
 285                         }
 286                         VM_BUG_ON(!PageLRU(page));
 287                         __ClearPageLRU(page);
 288                         del_page_from_lru(zone, page);
 289                 }
 290
 291                 if (!pagevec_add(&pages_to_free, page)) {
 292                         if (zone) {
 293                                 spin_unlock_irq(&zone->lru_lock);
 294                                 zone = NULL;
 295                         }
 296                         __pagevec_free(&pages_to_free);
 297                         pagevec_reinit(&pages_to_free);
 298                 }
 299         }
 300         if (zone)
 301                 spin_unlock_irq(&zone->lru_lock);
 302
 303         pagevec_free(&pages_to_free);
 304 }
 305
 306 /*
 307  * The pages which we're about to release may be in the deferred lru-addition
 308  * queues.  That would prevent them from really being freed right now.  That's
 309  * OK from a correctness point of view but is inefficient - those pages may be
 310  * cache-warm and we want to give them back to the page allocator ASAP.
 311  *
 312  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 313  * and __pagevec_lru_add_active() call release_pages() directly to avoid
 314  * mutual recursion.
 315  */
 316 void __pagevec_release(struct pagevec *pvec)
 317 {
 318         lru_add_drain();
 319         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 320         pagevec_reinit(pvec);
 321 }
 322
 323 EXPORT_SYMBOL(__pagevec_release);
 324
 325 /*
 326  * pagevec_release() for pages which are known to not be on the LRU
 327  *
 328  * This function reinitialises the caller's pagevec.
 329  */
 330 void __pagevec_release_nonlru(struct pagevec *pvec)
 331 {
 332         int i;
 333         struct pagevec pages_to_free;
 334
 335         pagevec_init(&pages_to_free, pvec->cold);
 336         for (i = 0; i < pagevec_count(pvec); i++) {
 337                 struct page *page = pvec->pages[i];
 338
 339                 VM_BUG_ON(PageLRU(page));
 340                 if (put_page_testzero(page))
 341                         pagevec_add(&pages_to_free, page);
 342         }
 343         pagevec_free(&pages_to_free);
 344         pagevec_reinit(pvec);
 345 }
 346
 347 /*
 348  * Add the passed pages to the LRU, then drop the caller's refcount
 349  * on them.  Reinitialises the caller's pagevec.
 350  */
 351 void __pagevec_lru_add(struct pagevec *pvec)
 352 {
 353         int i;
 354         struct zone *zone = NULL;
 355
 356         for (i = 0; i < pagevec_count(pvec); i++) {
 357                 struct page *page = pvec->pages[i];
 358                 struct zone *pagezone = page_zone(page);
 359
 360                 if (pagezone != zone) {
 361                         if (zone)
 362                                 spin_unlock_irq(&zone->lru_lock);
 363                         zone = pagezone;
 364                         spin_lock_irq(&zone->lru_lock);
 365                 }
 366                 VM_BUG_ON(PageLRU(page));
 367                 SetPageLRU(page);
 368                 add_page_to_inactive_list(zone, page);
 369         }
 370         if (zone)
 371                 spin_unlock_irq(&zone->lru_lock);
 372         release_pages(pvec->pages, pvec->nr, pvec->cold);
 373         pagevec_reinit(pvec);
 374 }
 375
 376 EXPORT_SYMBOL(__pagevec_lru_add);
 377
 378 void __pagevec_lru_add_active(struct pagevec *pvec)
 379 {
 380         int i;
 381         struct zone *zone = NULL;
 382
 383         for (i = 0; i < pagevec_count(pvec); i++) {
 384                 struct page *page = pvec->pages[i];
 385                 struct zone *pagezone = page_zone(page);
 386
 387                 if (pagezone != zone) {
 388                         if (zone)
 389                                 spin_unlock_irq(&zone->lru_lock);
 390                         zone = pagezone;
 391                         spin_lock_irq(&zone->lru_lock);
 392                 }
 393                 VM_BUG_ON(PageLRU(page));
 394                 SetPageLRU(page);
 395                 VM_BUG_ON(PageActive(page));
 396                 SetPageActive(page);
 397                 add_page_to_active_list(zone, page);
 398         }
 399         if (zone)
 400                 spin_unlock_irq(&zone->lru_lock);
 401         release_pages(pvec->pages, pvec->nr, pvec->cold);
 402         pagevec_reinit(pvec);
 403 }
 404
 405 /*
 406  * Try to drop buffers from the pages in a pagevec
 407  */
 408 void pagevec_strip(struct pagevec *pvec)
 409 {
 410         int i;
 411
 412         for (i = 0; i < pagevec_count(pvec); i++) {
 413                 struct page *page = pvec->pages[i];
 414
 415                 if (PagePrivate(page) && !TestSetPageLocked(page)) {
 416                         if (PagePrivate(page))
 417                                 try_to_release_page(page, 0);
 418                         unlock_page(page);
 419                 }
 420         }
 421 }
 422
 423 /**
 424  * pagevec_lookup - gang pagecache lookup
 425  * @pvec:       Where the resulting pages are placed
 426  * @mapping:    The address_space to search
 427  * @start:      The starting page index
 428  * @nr_pages:   The maximum number of pages
 429  *
 430  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 431  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 432  * reference against the pages in @pvec.
 433  *
 434  * The search returns a group of mapping-contiguous pages with ascending
 435  * indexes.  There may be holes in the indices due to not-present pages.
 436  *
 437  * pagevec_lookup() returns the number of pages which were found.
 438  */
 439 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 440                 pgoff_t start, unsigned nr_pages)
 441 {
 442         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 443         return pagevec_count(pvec);
 444 }
 445
 446 EXPORT_SYMBOL(pagevec_lookup);
 447
 448 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 449                 pgoff_t *index, int tag, unsigned nr_pages)
 450 {
 451         pvec->nr = find_get_pages_tag(mapping, index, tag,
 452                                         nr_pages, pvec->pages);
 453         return pagevec_count(pvec);
 454 }
 455
 456 EXPORT_SYMBOL(pagevec_lookup_tag);
 457
 458 #ifdef CONFIG_SMP
 459 /*
 460  * We tolerate a little inaccuracy to avoid ping-ponging the counter between
 461  * CPUs
 462  */
 463 #define ACCT_THRESHOLD  max(16, NR_CPUS * 2)
 464
 465 static DEFINE_PER_CPU(long, committed_space) = 0;
 466
 467 void vm_acct_memory(long pages)
 468 {
 469         long *local;
 470
 471         preempt_disable();
 472         local = &__get_cpu_var(committed_space);
 473         *local += pages;
 474         if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
 475                 atomic_add(*local, &vm_committed_space);
 476                 *local = 0;
 477         }
 478         preempt_enable();
 479 }
 480
 481 #ifdef CONFIG_HOTPLUG_CPU
 482
 483 /* Drop the CPU's cached committed space back into the central pool. */
 484 static int cpu_swap_callback(struct notifier_block *nfb,
 485                              unsigned long action,
 486                              void *hcpu)
 487 {
 488         long *committed;
 489
 490         committed = &per_cpu(committed_space, (long)hcpu);
 491         if (action == CPU_DEAD) {
 492                 atomic_add(*committed, &vm_committed_space);
 493                 *committed = 0;
 494                 __lru_add_drain((long)hcpu);
 495         }
 496         return NOTIFY_OK;
 497 }
 498 #endif /* CONFIG_HOTPLUG_CPU */
 499 #endif /* CONFIG_SMP */
 500
 501 /*
 502  * Perform any setup for the swap system
 503  */
 504 void __init swap_setup(void)
 505 {
 506         unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
 507
 508         /* Use a smaller cluster for small-memory machines */
 509         if (megs < 16)
 510                 page_cluster = 2;
 511         else
 512                 page_cluster = 3;
 513         /*
 514          * Right now other parts of the system means that we
 515          * _really_ don't want to cluster much more
 516          */
 517 #ifdef CONFIG_HOTPLUG_CPU
 518         hotcpu_notifier(cpu_swap_callback, 0);
 519 #endif
 520 }