| 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 operation 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/export.h> |
| 25 | #include <linux/mm_inline.h> |
| 26 | #include <linux/percpu_counter.h> |
| 27 | #include <linux/percpu.h> |
| 28 | #include <linux/cpu.h> |
| 29 | #include <linux/notifier.h> |
| 30 | #include <linux/backing-dev.h> |
| 31 | #include <linux/memcontrol.h> |
| 32 | #include <linux/gfp.h> |
| 33 | #include <linux/uio.h> |
| 34 | |
| 35 | #include "internal.h" |
| 36 | |
| 37 | #define CREATE_TRACE_POINTS |
| 38 | #include <trace/events/pagemap.h> |
| 39 | |
| 40 | /* How many pages do we try to swap or page in/out together? */ |
| 41 | int page_cluster; |
| 42 | |
| 43 | static DEFINE_PER_CPU(struct pagevec, lru_add_pvec); |
| 44 | static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs); |
| 45 | static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs); |
| 46 | |
| 47 | /* |
| 48 | * This path almost never happens for VM activity - pages are normally |
| 49 | * freed via pagevecs. But it gets used by networking. |
| 50 | */ |
| 51 | static void __page_cache_release(struct page *page) |
| 52 | { |
| 53 | if (PageLRU(page)) { |
| 54 | struct zone *zone = page_zone(page); |
| 55 | struct lruvec *lruvec; |
| 56 | unsigned long flags; |
| 57 | |
| 58 | spin_lock_irqsave(&zone->lru_lock, flags); |
| 59 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 60 | VM_BUG_ON_PAGE(!PageLRU(page), page); |
| 61 | __ClearPageLRU(page); |
| 62 | del_page_from_lru_list(page, lruvec, page_off_lru(page)); |
| 63 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 64 | } |
| 65 | mem_cgroup_uncharge(page); |
| 66 | } |
| 67 | |
| 68 | static void __put_single_page(struct page *page) |
| 69 | { |
| 70 | __page_cache_release(page); |
| 71 | free_hot_cold_page(page, false); |
| 72 | } |
| 73 | |
| 74 | static void __put_compound_page(struct page *page) |
| 75 | { |
| 76 | compound_page_dtor *dtor; |
| 77 | |
| 78 | __page_cache_release(page); |
| 79 | dtor = get_compound_page_dtor(page); |
| 80 | (*dtor)(page); |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Two special cases here: we could avoid taking compound_lock_irqsave |
| 85 | * and could skip the tail refcounting(in _mapcount). |
| 86 | * |
| 87 | * 1. Hugetlbfs page: |
| 88 | * |
| 89 | * PageHeadHuge will remain true until the compound page |
| 90 | * is released and enters the buddy allocator, and it could |
| 91 | * not be split by __split_huge_page_refcount(). |
| 92 | * |
| 93 | * So if we see PageHeadHuge set, and we have the tail page pin, |
| 94 | * then we could safely put head page. |
| 95 | * |
| 96 | * 2. Slab THP page: |
| 97 | * |
| 98 | * PG_slab is cleared before the slab frees the head page, and |
| 99 | * tail pin cannot be the last reference left on the head page, |
| 100 | * because the slab code is free to reuse the compound page |
| 101 | * after a kfree/kmem_cache_free without having to check if |
| 102 | * there's any tail pin left. In turn all tail pinsmust be always |
| 103 | * released while the head is still pinned by the slab code |
| 104 | * and so we know PG_slab will be still set too. |
| 105 | * |
| 106 | * So if we see PageSlab set, and we have the tail page pin, |
| 107 | * then we could safely put head page. |
| 108 | */ |
| 109 | static __always_inline |
| 110 | void put_unrefcounted_compound_page(struct page *page_head, struct page *page) |
| 111 | { |
| 112 | /* |
| 113 | * If @page is a THP tail, we must read the tail page |
| 114 | * flags after the head page flags. The |
| 115 | * __split_huge_page_refcount side enforces write memory barriers |
| 116 | * between clearing PageTail and before the head page |
| 117 | * can be freed and reallocated. |
| 118 | */ |
| 119 | smp_rmb(); |
| 120 | if (likely(PageTail(page))) { |
| 121 | /* |
| 122 | * __split_huge_page_refcount cannot race |
| 123 | * here, see the comment above this function. |
| 124 | */ |
| 125 | VM_BUG_ON_PAGE(!PageHead(page_head), page_head); |
| 126 | VM_BUG_ON_PAGE(page_mapcount(page) != 0, page); |
| 127 | if (put_page_testzero(page_head)) { |
| 128 | /* |
| 129 | * If this is the tail of a slab THP page, |
| 130 | * the tail pin must not be the last reference |
| 131 | * held on the page, because the PG_slab cannot |
| 132 | * be cleared before all tail pins (which skips |
| 133 | * the _mapcount tail refcounting) have been |
| 134 | * released. |
| 135 | * |
| 136 | * If this is the tail of a hugetlbfs page, |
| 137 | * the tail pin may be the last reference on |
| 138 | * the page instead, because PageHeadHuge will |
| 139 | * not go away until the compound page enters |
| 140 | * the buddy allocator. |
| 141 | */ |
| 142 | VM_BUG_ON_PAGE(PageSlab(page_head), page_head); |
| 143 | __put_compound_page(page_head); |
| 144 | } |
| 145 | } else |
| 146 | /* |
| 147 | * __split_huge_page_refcount run before us, |
| 148 | * @page was a THP tail. The split @page_head |
| 149 | * has been freed and reallocated as slab or |
| 150 | * hugetlbfs page of smaller order (only |
| 151 | * possible if reallocated as slab on x86). |
| 152 | */ |
| 153 | if (put_page_testzero(page)) |
| 154 | __put_single_page(page); |
| 155 | } |
| 156 | |
| 157 | static __always_inline |
| 158 | void put_refcounted_compound_page(struct page *page_head, struct page *page) |
| 159 | { |
| 160 | if (likely(page != page_head && get_page_unless_zero(page_head))) { |
| 161 | unsigned long flags; |
| 162 | |
| 163 | /* |
| 164 | * @page_head wasn't a dangling pointer but it may not |
| 165 | * be a head page anymore by the time we obtain the |
| 166 | * lock. That is ok as long as it can't be freed from |
| 167 | * under us. |
| 168 | */ |
| 169 | flags = compound_lock_irqsave(page_head); |
| 170 | if (unlikely(!PageTail(page))) { |
| 171 | /* __split_huge_page_refcount run before us */ |
| 172 | compound_unlock_irqrestore(page_head, flags); |
| 173 | if (put_page_testzero(page_head)) { |
| 174 | /* |
| 175 | * The @page_head may have been freed |
| 176 | * and reallocated as a compound page |
| 177 | * of smaller order and then freed |
| 178 | * again. All we know is that it |
| 179 | * cannot have become: a THP page, a |
| 180 | * compound page of higher order, a |
| 181 | * tail page. That is because we |
| 182 | * still hold the refcount of the |
| 183 | * split THP tail and page_head was |
| 184 | * the THP head before the split. |
| 185 | */ |
| 186 | if (PageHead(page_head)) |
| 187 | __put_compound_page(page_head); |
| 188 | else |
| 189 | __put_single_page(page_head); |
| 190 | } |
| 191 | out_put_single: |
| 192 | if (put_page_testzero(page)) |
| 193 | __put_single_page(page); |
| 194 | return; |
| 195 | } |
| 196 | VM_BUG_ON_PAGE(page_head != page->first_page, page); |
| 197 | /* |
| 198 | * We can release the refcount taken by |
| 199 | * get_page_unless_zero() now that |
| 200 | * __split_huge_page_refcount() is blocked on the |
| 201 | * compound_lock. |
| 202 | */ |
| 203 | if (put_page_testzero(page_head)) |
| 204 | VM_BUG_ON_PAGE(1, page_head); |
| 205 | /* __split_huge_page_refcount will wait now */ |
| 206 | VM_BUG_ON_PAGE(page_mapcount(page) <= 0, page); |
| 207 | atomic_dec(&page->_mapcount); |
| 208 | VM_BUG_ON_PAGE(atomic_read(&page_head->_count) <= 0, page_head); |
| 209 | VM_BUG_ON_PAGE(atomic_read(&page->_count) != 0, page); |
| 210 | compound_unlock_irqrestore(page_head, flags); |
| 211 | |
| 212 | if (put_page_testzero(page_head)) { |
| 213 | if (PageHead(page_head)) |
| 214 | __put_compound_page(page_head); |
| 215 | else |
| 216 | __put_single_page(page_head); |
| 217 | } |
| 218 | } else { |
| 219 | /* @page_head is a dangling pointer */ |
| 220 | VM_BUG_ON_PAGE(PageTail(page), page); |
| 221 | goto out_put_single; |
| 222 | } |
| 223 | } |
| 224 | |
| 225 | static void put_compound_page(struct page *page) |
| 226 | { |
| 227 | struct page *page_head; |
| 228 | |
| 229 | /* |
| 230 | * We see the PageCompound set and PageTail not set, so @page maybe: |
| 231 | * 1. hugetlbfs head page, or |
| 232 | * 2. THP head page. |
| 233 | */ |
| 234 | if (likely(!PageTail(page))) { |
| 235 | if (put_page_testzero(page)) { |
| 236 | /* |
| 237 | * By the time all refcounts have been released |
| 238 | * split_huge_page cannot run anymore from under us. |
| 239 | */ |
| 240 | if (PageHead(page)) |
| 241 | __put_compound_page(page); |
| 242 | else |
| 243 | __put_single_page(page); |
| 244 | } |
| 245 | return; |
| 246 | } |
| 247 | |
| 248 | /* |
| 249 | * We see the PageCompound set and PageTail set, so @page maybe: |
| 250 | * 1. a tail hugetlbfs page, or |
| 251 | * 2. a tail THP page, or |
| 252 | * 3. a split THP page. |
| 253 | * |
| 254 | * Case 3 is possible, as we may race with |
| 255 | * __split_huge_page_refcount tearing down a THP page. |
| 256 | */ |
| 257 | page_head = compound_head_by_tail(page); |
| 258 | if (!__compound_tail_refcounted(page_head)) |
| 259 | put_unrefcounted_compound_page(page_head, page); |
| 260 | else |
| 261 | put_refcounted_compound_page(page_head, page); |
| 262 | } |
| 263 | |
| 264 | void put_page(struct page *page) |
| 265 | { |
| 266 | if (unlikely(PageCompound(page))) |
| 267 | put_compound_page(page); |
| 268 | else if (put_page_testzero(page)) |
| 269 | __put_single_page(page); |
| 270 | } |
| 271 | EXPORT_SYMBOL(put_page); |
| 272 | |
| 273 | /* |
| 274 | * This function is exported but must not be called by anything other |
| 275 | * than get_page(). It implements the slow path of get_page(). |
| 276 | */ |
| 277 | bool __get_page_tail(struct page *page) |
| 278 | { |
| 279 | /* |
| 280 | * This takes care of get_page() if run on a tail page |
| 281 | * returned by one of the get_user_pages/follow_page variants. |
| 282 | * get_user_pages/follow_page itself doesn't need the compound |
| 283 | * lock because it runs __get_page_tail_foll() under the |
| 284 | * proper PT lock that already serializes against |
| 285 | * split_huge_page(). |
| 286 | */ |
| 287 | unsigned long flags; |
| 288 | bool got; |
| 289 | struct page *page_head = compound_head(page); |
| 290 | |
| 291 | /* Ref to put_compound_page() comment. */ |
| 292 | if (!__compound_tail_refcounted(page_head)) { |
| 293 | smp_rmb(); |
| 294 | if (likely(PageTail(page))) { |
| 295 | /* |
| 296 | * This is a hugetlbfs page or a slab |
| 297 | * page. __split_huge_page_refcount |
| 298 | * cannot race here. |
| 299 | */ |
| 300 | VM_BUG_ON_PAGE(!PageHead(page_head), page_head); |
| 301 | __get_page_tail_foll(page, true); |
| 302 | return true; |
| 303 | } else { |
| 304 | /* |
| 305 | * __split_huge_page_refcount run |
| 306 | * before us, "page" was a THP |
| 307 | * tail. The split page_head has been |
| 308 | * freed and reallocated as slab or |
| 309 | * hugetlbfs page of smaller order |
| 310 | * (only possible if reallocated as |
| 311 | * slab on x86). |
| 312 | */ |
| 313 | return false; |
| 314 | } |
| 315 | } |
| 316 | |
| 317 | got = false; |
| 318 | if (likely(page != page_head && get_page_unless_zero(page_head))) { |
| 319 | /* |
| 320 | * page_head wasn't a dangling pointer but it |
| 321 | * may not be a head page anymore by the time |
| 322 | * we obtain the lock. That is ok as long as it |
| 323 | * can't be freed from under us. |
| 324 | */ |
| 325 | flags = compound_lock_irqsave(page_head); |
| 326 | /* here __split_huge_page_refcount won't run anymore */ |
| 327 | if (likely(PageTail(page))) { |
| 328 | __get_page_tail_foll(page, false); |
| 329 | got = true; |
| 330 | } |
| 331 | compound_unlock_irqrestore(page_head, flags); |
| 332 | if (unlikely(!got)) |
| 333 | put_page(page_head); |
| 334 | } |
| 335 | return got; |
| 336 | } |
| 337 | EXPORT_SYMBOL(__get_page_tail); |
| 338 | |
| 339 | /** |
| 340 | * put_pages_list() - release a list of pages |
| 341 | * @pages: list of pages threaded on page->lru |
| 342 | * |
| 343 | * Release a list of pages which are strung together on page.lru. Currently |
| 344 | * used by read_cache_pages() and related error recovery code. |
| 345 | */ |
| 346 | void put_pages_list(struct list_head *pages) |
| 347 | { |
| 348 | while (!list_empty(pages)) { |
| 349 | struct page *victim; |
| 350 | |
| 351 | victim = list_entry(pages->prev, struct page, lru); |
| 352 | list_del(&victim->lru); |
| 353 | page_cache_release(victim); |
| 354 | } |
| 355 | } |
| 356 | EXPORT_SYMBOL(put_pages_list); |
| 357 | |
| 358 | /* |
| 359 | * get_kernel_pages() - pin kernel pages in memory |
| 360 | * @kiov: An array of struct kvec structures |
| 361 | * @nr_segs: number of segments to pin |
| 362 | * @write: pinning for read/write, currently ignored |
| 363 | * @pages: array that receives pointers to the pages pinned. |
| 364 | * Should be at least nr_segs long. |
| 365 | * |
| 366 | * Returns number of pages pinned. This may be fewer than the number |
| 367 | * requested. If nr_pages is 0 or negative, returns 0. If no pages |
| 368 | * were pinned, returns -errno. Each page returned must be released |
| 369 | * with a put_page() call when it is finished with. |
| 370 | */ |
| 371 | int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write, |
| 372 | struct page **pages) |
| 373 | { |
| 374 | int seg; |
| 375 | |
| 376 | for (seg = 0; seg < nr_segs; seg++) { |
| 377 | if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE)) |
| 378 | return seg; |
| 379 | |
| 380 | pages[seg] = kmap_to_page(kiov[seg].iov_base); |
| 381 | page_cache_get(pages[seg]); |
| 382 | } |
| 383 | |
| 384 | return seg; |
| 385 | } |
| 386 | EXPORT_SYMBOL_GPL(get_kernel_pages); |
| 387 | |
| 388 | /* |
| 389 | * get_kernel_page() - pin a kernel page in memory |
| 390 | * @start: starting kernel address |
| 391 | * @write: pinning for read/write, currently ignored |
| 392 | * @pages: array that receives pointer to the page pinned. |
| 393 | * Must be at least nr_segs long. |
| 394 | * |
| 395 | * Returns 1 if page is pinned. If the page was not pinned, returns |
| 396 | * -errno. The page returned must be released with a put_page() call |
| 397 | * when it is finished with. |
| 398 | */ |
| 399 | int get_kernel_page(unsigned long start, int write, struct page **pages) |
| 400 | { |
| 401 | const struct kvec kiov = { |
| 402 | .iov_base = (void *)start, |
| 403 | .iov_len = PAGE_SIZE |
| 404 | }; |
| 405 | |
| 406 | return get_kernel_pages(&kiov, 1, write, pages); |
| 407 | } |
| 408 | EXPORT_SYMBOL_GPL(get_kernel_page); |
| 409 | |
| 410 | static void pagevec_lru_move_fn(struct pagevec *pvec, |
| 411 | void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg), |
| 412 | void *arg) |
| 413 | { |
| 414 | int i; |
| 415 | struct zone *zone = NULL; |
| 416 | struct lruvec *lruvec; |
| 417 | unsigned long flags = 0; |
| 418 | |
| 419 | for (i = 0; i < pagevec_count(pvec); i++) { |
| 420 | struct page *page = pvec->pages[i]; |
| 421 | struct zone *pagezone = page_zone(page); |
| 422 | |
| 423 | if (pagezone != zone) { |
| 424 | if (zone) |
| 425 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 426 | zone = pagezone; |
| 427 | spin_lock_irqsave(&zone->lru_lock, flags); |
| 428 | } |
| 429 | |
| 430 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 431 | (*move_fn)(page, lruvec, arg); |
| 432 | } |
| 433 | if (zone) |
| 434 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 435 | release_pages(pvec->pages, pvec->nr, pvec->cold); |
| 436 | pagevec_reinit(pvec); |
| 437 | } |
| 438 | |
| 439 | static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec, |
| 440 | void *arg) |
| 441 | { |
| 442 | int *pgmoved = arg; |
| 443 | |
| 444 | if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { |
| 445 | enum lru_list lru = page_lru_base_type(page); |
| 446 | list_move_tail(&page->lru, &lruvec->lists[lru]); |
| 447 | (*pgmoved)++; |
| 448 | } |
| 449 | } |
| 450 | |
| 451 | /* |
| 452 | * pagevec_move_tail() must be called with IRQ disabled. |
| 453 | * Otherwise this may cause nasty races. |
| 454 | */ |
| 455 | static void pagevec_move_tail(struct pagevec *pvec) |
| 456 | { |
| 457 | int pgmoved = 0; |
| 458 | |
| 459 | pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved); |
| 460 | __count_vm_events(PGROTATED, pgmoved); |
| 461 | } |
| 462 | |
| 463 | /* |
| 464 | * Writeback is about to end against a page which has been marked for immediate |
| 465 | * reclaim. If it still appears to be reclaimable, move it to the tail of the |
| 466 | * inactive list. |
| 467 | */ |
| 468 | void rotate_reclaimable_page(struct page *page) |
| 469 | { |
| 470 | if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) && |
| 471 | !PageUnevictable(page) && PageLRU(page)) { |
| 472 | struct pagevec *pvec; |
| 473 | unsigned long flags; |
| 474 | |
| 475 | page_cache_get(page); |
| 476 | local_irq_save(flags); |
| 477 | pvec = this_cpu_ptr(&lru_rotate_pvecs); |
| 478 | if (!pagevec_add(pvec, page)) |
| 479 | pagevec_move_tail(pvec); |
| 480 | local_irq_restore(flags); |
| 481 | } |
| 482 | } |
| 483 | |
| 484 | static void update_page_reclaim_stat(struct lruvec *lruvec, |
| 485 | int file, int rotated) |
| 486 | { |
| 487 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 488 | |
| 489 | reclaim_stat->recent_scanned[file]++; |
| 490 | if (rotated) |
| 491 | reclaim_stat->recent_rotated[file]++; |
| 492 | } |
| 493 | |
| 494 | static void __activate_page(struct page *page, struct lruvec *lruvec, |
| 495 | void *arg) |
| 496 | { |
| 497 | if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { |
| 498 | int file = page_is_file_cache(page); |
| 499 | int lru = page_lru_base_type(page); |
| 500 | |
| 501 | del_page_from_lru_list(page, lruvec, lru); |
| 502 | SetPageActive(page); |
| 503 | lru += LRU_ACTIVE; |
| 504 | add_page_to_lru_list(page, lruvec, lru); |
| 505 | trace_mm_lru_activate(page); |
| 506 | |
| 507 | __count_vm_event(PGACTIVATE); |
| 508 | update_page_reclaim_stat(lruvec, file, 1); |
| 509 | } |
| 510 | } |
| 511 | |
| 512 | #ifdef CONFIG_SMP |
| 513 | static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs); |
| 514 | |
| 515 | static void activate_page_drain(int cpu) |
| 516 | { |
| 517 | struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu); |
| 518 | |
| 519 | if (pagevec_count(pvec)) |
| 520 | pagevec_lru_move_fn(pvec, __activate_page, NULL); |
| 521 | } |
| 522 | |
| 523 | static bool need_activate_page_drain(int cpu) |
| 524 | { |
| 525 | return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0; |
| 526 | } |
| 527 | |
| 528 | void activate_page(struct page *page) |
| 529 | { |
| 530 | if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { |
| 531 | struct pagevec *pvec = &get_cpu_var(activate_page_pvecs); |
| 532 | |
| 533 | page_cache_get(page); |
| 534 | if (!pagevec_add(pvec, page)) |
| 535 | pagevec_lru_move_fn(pvec, __activate_page, NULL); |
| 536 | put_cpu_var(activate_page_pvecs); |
| 537 | } |
| 538 | } |
| 539 | |
| 540 | #else |
| 541 | static inline void activate_page_drain(int cpu) |
| 542 | { |
| 543 | } |
| 544 | |
| 545 | static bool need_activate_page_drain(int cpu) |
| 546 | { |
| 547 | return false; |
| 548 | } |
| 549 | |
| 550 | void activate_page(struct page *page) |
| 551 | { |
| 552 | struct zone *zone = page_zone(page); |
| 553 | |
| 554 | spin_lock_irq(&zone->lru_lock); |
| 555 | __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL); |
| 556 | spin_unlock_irq(&zone->lru_lock); |
| 557 | } |
| 558 | #endif |
| 559 | |
| 560 | static void __lru_cache_activate_page(struct page *page) |
| 561 | { |
| 562 | struct pagevec *pvec = &get_cpu_var(lru_add_pvec); |
| 563 | int i; |
| 564 | |
| 565 | /* |
| 566 | * Search backwards on the optimistic assumption that the page being |
| 567 | * activated has just been added to this pagevec. Note that only |
| 568 | * the local pagevec is examined as a !PageLRU page could be in the |
| 569 | * process of being released, reclaimed, migrated or on a remote |
| 570 | * pagevec that is currently being drained. Furthermore, marking |
| 571 | * a remote pagevec's page PageActive potentially hits a race where |
| 572 | * a page is marked PageActive just after it is added to the inactive |
| 573 | * list causing accounting errors and BUG_ON checks to trigger. |
| 574 | */ |
| 575 | for (i = pagevec_count(pvec) - 1; i >= 0; i--) { |
| 576 | struct page *pagevec_page = pvec->pages[i]; |
| 577 | |
| 578 | if (pagevec_page == page) { |
| 579 | SetPageActive(page); |
| 580 | break; |
| 581 | } |
| 582 | } |
| 583 | |
| 584 | put_cpu_var(lru_add_pvec); |
| 585 | } |
| 586 | |
| 587 | /* |
| 588 | * Mark a page as having seen activity. |
| 589 | * |
| 590 | * inactive,unreferenced -> inactive,referenced |
| 591 | * inactive,referenced -> active,unreferenced |
| 592 | * active,unreferenced -> active,referenced |
| 593 | * |
| 594 | * When a newly allocated page is not yet visible, so safe for non-atomic ops, |
| 595 | * __SetPageReferenced(page) may be substituted for mark_page_accessed(page). |
| 596 | */ |
| 597 | void mark_page_accessed(struct page *page) |
| 598 | { |
| 599 | if (!PageActive(page) && !PageUnevictable(page) && |
| 600 | PageReferenced(page)) { |
| 601 | |
| 602 | /* |
| 603 | * If the page is on the LRU, queue it for activation via |
| 604 | * activate_page_pvecs. Otherwise, assume the page is on a |
| 605 | * pagevec, mark it active and it'll be moved to the active |
| 606 | * LRU on the next drain. |
| 607 | */ |
| 608 | if (PageLRU(page)) |
| 609 | activate_page(page); |
| 610 | else |
| 611 | __lru_cache_activate_page(page); |
| 612 | ClearPageReferenced(page); |
| 613 | if (page_is_file_cache(page)) |
| 614 | workingset_activation(page); |
| 615 | } else if (!PageReferenced(page)) { |
| 616 | SetPageReferenced(page); |
| 617 | } |
| 618 | } |
| 619 | EXPORT_SYMBOL(mark_page_accessed); |
| 620 | |
| 621 | static void __lru_cache_add(struct page *page) |
| 622 | { |
| 623 | struct pagevec *pvec = &get_cpu_var(lru_add_pvec); |
| 624 | |
| 625 | page_cache_get(page); |
| 626 | if (!pagevec_space(pvec)) |
| 627 | __pagevec_lru_add(pvec); |
| 628 | pagevec_add(pvec, page); |
| 629 | put_cpu_var(lru_add_pvec); |
| 630 | } |
| 631 | |
| 632 | /** |
| 633 | * lru_cache_add: add a page to the page lists |
| 634 | * @page: the page to add |
| 635 | */ |
| 636 | void lru_cache_add_anon(struct page *page) |
| 637 | { |
| 638 | if (PageActive(page)) |
| 639 | ClearPageActive(page); |
| 640 | __lru_cache_add(page); |
| 641 | } |
| 642 | |
| 643 | void lru_cache_add_file(struct page *page) |
| 644 | { |
| 645 | if (PageActive(page)) |
| 646 | ClearPageActive(page); |
| 647 | __lru_cache_add(page); |
| 648 | } |
| 649 | EXPORT_SYMBOL(lru_cache_add_file); |
| 650 | |
| 651 | /** |
| 652 | * lru_cache_add - add a page to a page list |
| 653 | * @page: the page to be added to the LRU. |
| 654 | * |
| 655 | * Queue the page for addition to the LRU via pagevec. The decision on whether |
| 656 | * to add the page to the [in]active [file|anon] list is deferred until the |
| 657 | * pagevec is drained. This gives a chance for the caller of lru_cache_add() |
| 658 | * have the page added to the active list using mark_page_accessed(). |
| 659 | */ |
| 660 | void lru_cache_add(struct page *page) |
| 661 | { |
| 662 | VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page); |
| 663 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 664 | __lru_cache_add(page); |
| 665 | } |
| 666 | |
| 667 | /** |
| 668 | * add_page_to_unevictable_list - add a page to the unevictable list |
| 669 | * @page: the page to be added to the unevictable list |
| 670 | * |
| 671 | * Add page directly to its zone's unevictable list. To avoid races with |
| 672 | * tasks that might be making the page evictable, through eg. munlock, |
| 673 | * munmap or exit, while it's not on the lru, we want to add the page |
| 674 | * while it's locked or otherwise "invisible" to other tasks. This is |
| 675 | * difficult to do when using the pagevec cache, so bypass that. |
| 676 | */ |
| 677 | void add_page_to_unevictable_list(struct page *page) |
| 678 | { |
| 679 | struct zone *zone = page_zone(page); |
| 680 | struct lruvec *lruvec; |
| 681 | |
| 682 | spin_lock_irq(&zone->lru_lock); |
| 683 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 684 | ClearPageActive(page); |
| 685 | SetPageUnevictable(page); |
| 686 | SetPageLRU(page); |
| 687 | add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE); |
| 688 | spin_unlock_irq(&zone->lru_lock); |
| 689 | } |
| 690 | |
| 691 | /** |
| 692 | * lru_cache_add_active_or_unevictable |
| 693 | * @page: the page to be added to LRU |
| 694 | * @vma: vma in which page is mapped for determining reclaimability |
| 695 | * |
| 696 | * Place @page on the active or unevictable LRU list, depending on its |
| 697 | * evictability. Note that if the page is not evictable, it goes |
| 698 | * directly back onto it's zone's unevictable list, it does NOT use a |
| 699 | * per cpu pagevec. |
| 700 | */ |
| 701 | void lru_cache_add_active_or_unevictable(struct page *page, |
| 702 | struct vm_area_struct *vma) |
| 703 | { |
| 704 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 705 | |
| 706 | if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED)) { |
| 707 | SetPageActive(page); |
| 708 | lru_cache_add(page); |
| 709 | return; |
| 710 | } |
| 711 | |
| 712 | if (!TestSetPageMlocked(page)) { |
| 713 | /* |
| 714 | * We use the irq-unsafe __mod_zone_page_stat because this |
| 715 | * counter is not modified from interrupt context, and the pte |
| 716 | * lock is held(spinlock), which implies preemption disabled. |
| 717 | */ |
| 718 | __mod_zone_page_state(page_zone(page), NR_MLOCK, |
| 719 | hpage_nr_pages(page)); |
| 720 | count_vm_event(UNEVICTABLE_PGMLOCKED); |
| 721 | } |
| 722 | add_page_to_unevictable_list(page); |
| 723 | } |
| 724 | |
| 725 | /* |
| 726 | * If the page can not be invalidated, it is moved to the |
| 727 | * inactive list to speed up its reclaim. It is moved to the |
| 728 | * head of the list, rather than the tail, to give the flusher |
| 729 | * threads some time to write it out, as this is much more |
| 730 | * effective than the single-page writeout from reclaim. |
| 731 | * |
| 732 | * If the page isn't page_mapped and dirty/writeback, the page |
| 733 | * could reclaim asap using PG_reclaim. |
| 734 | * |
| 735 | * 1. active, mapped page -> none |
| 736 | * 2. active, dirty/writeback page -> inactive, head, PG_reclaim |
| 737 | * 3. inactive, mapped page -> none |
| 738 | * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim |
| 739 | * 5. inactive, clean -> inactive, tail |
| 740 | * 6. Others -> none |
| 741 | * |
| 742 | * In 4, why it moves inactive's head, the VM expects the page would |
| 743 | * be write it out by flusher threads as this is much more effective |
| 744 | * than the single-page writeout from reclaim. |
| 745 | */ |
| 746 | static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec, |
| 747 | void *arg) |
| 748 | { |
| 749 | int lru, file; |
| 750 | bool active; |
| 751 | |
| 752 | if (!PageLRU(page)) |
| 753 | return; |
| 754 | |
| 755 | if (PageUnevictable(page)) |
| 756 | return; |
| 757 | |
| 758 | /* Some processes are using the page */ |
| 759 | if (page_mapped(page)) |
| 760 | return; |
| 761 | |
| 762 | active = PageActive(page); |
| 763 | file = page_is_file_cache(page); |
| 764 | lru = page_lru_base_type(page); |
| 765 | |
| 766 | del_page_from_lru_list(page, lruvec, lru + active); |
| 767 | ClearPageActive(page); |
| 768 | ClearPageReferenced(page); |
| 769 | add_page_to_lru_list(page, lruvec, lru); |
| 770 | |
| 771 | if (PageWriteback(page) || PageDirty(page)) { |
| 772 | /* |
| 773 | * PG_reclaim could be raced with end_page_writeback |
| 774 | * It can make readahead confusing. But race window |
| 775 | * is _really_ small and it's non-critical problem. |
| 776 | */ |
| 777 | SetPageReclaim(page); |
| 778 | } else { |
| 779 | /* |
| 780 | * The page's writeback ends up during pagevec |
| 781 | * We moves tha page into tail of inactive. |
| 782 | */ |
| 783 | list_move_tail(&page->lru, &lruvec->lists[lru]); |
| 784 | __count_vm_event(PGROTATED); |
| 785 | } |
| 786 | |
| 787 | if (active) |
| 788 | __count_vm_event(PGDEACTIVATE); |
| 789 | update_page_reclaim_stat(lruvec, file, 0); |
| 790 | } |
| 791 | |
| 792 | /* |
| 793 | * Drain pages out of the cpu's pagevecs. |
| 794 | * Either "cpu" is the current CPU, and preemption has already been |
| 795 | * disabled; or "cpu" is being hot-unplugged, and is already dead. |
| 796 | */ |
| 797 | void lru_add_drain_cpu(int cpu) |
| 798 | { |
| 799 | struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu); |
| 800 | |
| 801 | if (pagevec_count(pvec)) |
| 802 | __pagevec_lru_add(pvec); |
| 803 | |
| 804 | pvec = &per_cpu(lru_rotate_pvecs, cpu); |
| 805 | if (pagevec_count(pvec)) { |
| 806 | unsigned long flags; |
| 807 | |
| 808 | /* No harm done if a racing interrupt already did this */ |
| 809 | local_irq_save(flags); |
| 810 | pagevec_move_tail(pvec); |
| 811 | local_irq_restore(flags); |
| 812 | } |
| 813 | |
| 814 | pvec = &per_cpu(lru_deactivate_pvecs, cpu); |
| 815 | if (pagevec_count(pvec)) |
| 816 | pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL); |
| 817 | |
| 818 | activate_page_drain(cpu); |
| 819 | } |
| 820 | |
| 821 | /** |
| 822 | * deactivate_page - forcefully deactivate a page |
| 823 | * @page: page to deactivate |
| 824 | * |
| 825 | * This function hints the VM that @page is a good reclaim candidate, |
| 826 | * for example if its invalidation fails due to the page being dirty |
| 827 | * or under writeback. |
| 828 | */ |
| 829 | void deactivate_page(struct page *page) |
| 830 | { |
| 831 | /* |
| 832 | * In a workload with many unevictable page such as mprotect, unevictable |
| 833 | * page deactivation for accelerating reclaim is pointless. |
| 834 | */ |
| 835 | if (PageUnevictable(page)) |
| 836 | return; |
| 837 | |
| 838 | if (likely(get_page_unless_zero(page))) { |
| 839 | struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs); |
| 840 | |
| 841 | if (!pagevec_add(pvec, page)) |
| 842 | pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL); |
| 843 | put_cpu_var(lru_deactivate_pvecs); |
| 844 | } |
| 845 | } |
| 846 | |
| 847 | void lru_add_drain(void) |
| 848 | { |
| 849 | lru_add_drain_cpu(get_cpu()); |
| 850 | put_cpu(); |
| 851 | } |
| 852 | |
| 853 | static void lru_add_drain_per_cpu(struct work_struct *dummy) |
| 854 | { |
| 855 | lru_add_drain(); |
| 856 | } |
| 857 | |
| 858 | static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); |
| 859 | |
| 860 | void lru_add_drain_all(void) |
| 861 | { |
| 862 | static DEFINE_MUTEX(lock); |
| 863 | static struct cpumask has_work; |
| 864 | int cpu; |
| 865 | |
| 866 | mutex_lock(&lock); |
| 867 | get_online_cpus(); |
| 868 | cpumask_clear(&has_work); |
| 869 | |
| 870 | for_each_online_cpu(cpu) { |
| 871 | struct work_struct *work = &per_cpu(lru_add_drain_work, cpu); |
| 872 | |
| 873 | if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) || |
| 874 | pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) || |
| 875 | pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) || |
| 876 | need_activate_page_drain(cpu)) { |
| 877 | INIT_WORK(work, lru_add_drain_per_cpu); |
| 878 | schedule_work_on(cpu, work); |
| 879 | cpumask_set_cpu(cpu, &has_work); |
| 880 | } |
| 881 | } |
| 882 | |
| 883 | for_each_cpu(cpu, &has_work) |
| 884 | flush_work(&per_cpu(lru_add_drain_work, cpu)); |
| 885 | |
| 886 | put_online_cpus(); |
| 887 | mutex_unlock(&lock); |
| 888 | } |
| 889 | |
| 890 | /** |
| 891 | * release_pages - batched page_cache_release() |
| 892 | * @pages: array of pages to release |
| 893 | * @nr: number of pages |
| 894 | * @cold: whether the pages are cache cold |
| 895 | * |
| 896 | * Decrement the reference count on all the pages in @pages. If it |
| 897 | * fell to zero, remove the page from the LRU and free it. |
| 898 | */ |
| 899 | void release_pages(struct page **pages, int nr, bool cold) |
| 900 | { |
| 901 | int i; |
| 902 | LIST_HEAD(pages_to_free); |
| 903 | struct zone *zone = NULL; |
| 904 | struct lruvec *lruvec; |
| 905 | unsigned long uninitialized_var(flags); |
| 906 | unsigned int uninitialized_var(lock_batch); |
| 907 | |
| 908 | for (i = 0; i < nr; i++) { |
| 909 | struct page *page = pages[i]; |
| 910 | |
| 911 | if (unlikely(PageCompound(page))) { |
| 912 | if (zone) { |
| 913 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 914 | zone = NULL; |
| 915 | } |
| 916 | put_compound_page(page); |
| 917 | continue; |
| 918 | } |
| 919 | |
| 920 | /* |
| 921 | * Make sure the IRQ-safe lock-holding time does not get |
| 922 | * excessive with a continuous string of pages from the |
| 923 | * same zone. The lock is held only if zone != NULL. |
| 924 | */ |
| 925 | if (zone && ++lock_batch == SWAP_CLUSTER_MAX) { |
| 926 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 927 | zone = NULL; |
| 928 | } |
| 929 | |
| 930 | if (!put_page_testzero(page)) |
| 931 | continue; |
| 932 | |
| 933 | if (PageLRU(page)) { |
| 934 | struct zone *pagezone = page_zone(page); |
| 935 | |
| 936 | if (pagezone != zone) { |
| 937 | if (zone) |
| 938 | spin_unlock_irqrestore(&zone->lru_lock, |
| 939 | flags); |
| 940 | lock_batch = 0; |
| 941 | zone = pagezone; |
| 942 | spin_lock_irqsave(&zone->lru_lock, flags); |
| 943 | } |
| 944 | |
| 945 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 946 | VM_BUG_ON_PAGE(!PageLRU(page), page); |
| 947 | __ClearPageLRU(page); |
| 948 | del_page_from_lru_list(page, lruvec, page_off_lru(page)); |
| 949 | } |
| 950 | |
| 951 | /* Clear Active bit in case of parallel mark_page_accessed */ |
| 952 | __ClearPageActive(page); |
| 953 | |
| 954 | list_add(&page->lru, &pages_to_free); |
| 955 | } |
| 956 | if (zone) |
| 957 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 958 | |
| 959 | mem_cgroup_uncharge_list(&pages_to_free); |
| 960 | free_hot_cold_page_list(&pages_to_free, cold); |
| 961 | } |
| 962 | EXPORT_SYMBOL(release_pages); |
| 963 | |
| 964 | /* |
| 965 | * The pages which we're about to release may be in the deferred lru-addition |
| 966 | * queues. That would prevent them from really being freed right now. That's |
| 967 | * OK from a correctness point of view but is inefficient - those pages may be |
| 968 | * cache-warm and we want to give them back to the page allocator ASAP. |
| 969 | * |
| 970 | * So __pagevec_release() will drain those queues here. __pagevec_lru_add() |
| 971 | * and __pagevec_lru_add_active() call release_pages() directly to avoid |
| 972 | * mutual recursion. |
| 973 | */ |
| 974 | void __pagevec_release(struct pagevec *pvec) |
| 975 | { |
| 976 | lru_add_drain(); |
| 977 | release_pages(pvec->pages, pagevec_count(pvec), pvec->cold); |
| 978 | pagevec_reinit(pvec); |
| 979 | } |
| 980 | EXPORT_SYMBOL(__pagevec_release); |
| 981 | |
| 982 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 983 | /* used by __split_huge_page_refcount() */ |
| 984 | void lru_add_page_tail(struct page *page, struct page *page_tail, |
| 985 | struct lruvec *lruvec, struct list_head *list) |
| 986 | { |
| 987 | const int file = 0; |
| 988 | |
| 989 | VM_BUG_ON_PAGE(!PageHead(page), page); |
| 990 | VM_BUG_ON_PAGE(PageCompound(page_tail), page); |
| 991 | VM_BUG_ON_PAGE(PageLRU(page_tail), page); |
| 992 | VM_BUG_ON(NR_CPUS != 1 && |
| 993 | !spin_is_locked(&lruvec_zone(lruvec)->lru_lock)); |
| 994 | |
| 995 | if (!list) |
| 996 | SetPageLRU(page_tail); |
| 997 | |
| 998 | if (likely(PageLRU(page))) |
| 999 | list_add_tail(&page_tail->lru, &page->lru); |
| 1000 | else if (list) { |
| 1001 | /* page reclaim is reclaiming a huge page */ |
| 1002 | get_page(page_tail); |
| 1003 | list_add_tail(&page_tail->lru, list); |
| 1004 | } else { |
| 1005 | struct list_head *list_head; |
| 1006 | /* |
| 1007 | * Head page has not yet been counted, as an hpage, |
| 1008 | * so we must account for each subpage individually. |
| 1009 | * |
| 1010 | * Use the standard add function to put page_tail on the list, |
| 1011 | * but then correct its position so they all end up in order. |
| 1012 | */ |
| 1013 | add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail)); |
| 1014 | list_head = page_tail->lru.prev; |
| 1015 | list_move_tail(&page_tail->lru, list_head); |
| 1016 | } |
| 1017 | |
| 1018 | if (!PageUnevictable(page)) |
| 1019 | update_page_reclaim_stat(lruvec, file, PageActive(page_tail)); |
| 1020 | } |
| 1021 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
| 1022 | |
| 1023 | static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec, |
| 1024 | void *arg) |
| 1025 | { |
| 1026 | int file = page_is_file_cache(page); |
| 1027 | int active = PageActive(page); |
| 1028 | enum lru_list lru = page_lru(page); |
| 1029 | |
| 1030 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 1031 | |
| 1032 | SetPageLRU(page); |
| 1033 | add_page_to_lru_list(page, lruvec, lru); |
| 1034 | update_page_reclaim_stat(lruvec, file, active); |
| 1035 | trace_mm_lru_insertion(page, lru); |
| 1036 | } |
| 1037 | |
| 1038 | /* |
| 1039 | * Add the passed pages to the LRU, then drop the caller's refcount |
| 1040 | * on them. Reinitialises the caller's pagevec. |
| 1041 | */ |
| 1042 | void __pagevec_lru_add(struct pagevec *pvec) |
| 1043 | { |
| 1044 | pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL); |
| 1045 | } |
| 1046 | EXPORT_SYMBOL(__pagevec_lru_add); |
| 1047 | |
| 1048 | /** |
| 1049 | * pagevec_lookup_entries - gang pagecache lookup |
| 1050 | * @pvec: Where the resulting entries are placed |
| 1051 | * @mapping: The address_space to search |
| 1052 | * @start: The starting entry index |
| 1053 | * @nr_entries: The maximum number of entries |
| 1054 | * @indices: The cache indices corresponding to the entries in @pvec |
| 1055 | * |
| 1056 | * pagevec_lookup_entries() will search for and return a group of up |
| 1057 | * to @nr_entries pages and shadow entries in the mapping. All |
| 1058 | * entries are placed in @pvec. pagevec_lookup_entries() takes a |
| 1059 | * reference against actual pages in @pvec. |
| 1060 | * |
| 1061 | * The search returns a group of mapping-contiguous entries with |
| 1062 | * ascending indexes. There may be holes in the indices due to |
| 1063 | * not-present entries. |
| 1064 | * |
| 1065 | * pagevec_lookup_entries() returns the number of entries which were |
| 1066 | * found. |
| 1067 | */ |
| 1068 | unsigned pagevec_lookup_entries(struct pagevec *pvec, |
| 1069 | struct address_space *mapping, |
| 1070 | pgoff_t start, unsigned nr_pages, |
| 1071 | pgoff_t *indices) |
| 1072 | { |
| 1073 | pvec->nr = find_get_entries(mapping, start, nr_pages, |
| 1074 | pvec->pages, indices); |
| 1075 | return pagevec_count(pvec); |
| 1076 | } |
| 1077 | |
| 1078 | /** |
| 1079 | * pagevec_remove_exceptionals - pagevec exceptionals pruning |
| 1080 | * @pvec: The pagevec to prune |
| 1081 | * |
| 1082 | * pagevec_lookup_entries() fills both pages and exceptional radix |
| 1083 | * tree entries into the pagevec. This function prunes all |
| 1084 | * exceptionals from @pvec without leaving holes, so that it can be |
| 1085 | * passed on to page-only pagevec operations. |
| 1086 | */ |
| 1087 | void pagevec_remove_exceptionals(struct pagevec *pvec) |
| 1088 | { |
| 1089 | int i, j; |
| 1090 | |
| 1091 | for (i = 0, j = 0; i < pagevec_count(pvec); i++) { |
| 1092 | struct page *page = pvec->pages[i]; |
| 1093 | if (!radix_tree_exceptional_entry(page)) |
| 1094 | pvec->pages[j++] = page; |
| 1095 | } |
| 1096 | pvec->nr = j; |
| 1097 | } |
| 1098 | |
| 1099 | /** |
| 1100 | * pagevec_lookup - gang pagecache lookup |
| 1101 | * @pvec: Where the resulting pages are placed |
| 1102 | * @mapping: The address_space to search |
| 1103 | * @start: The starting page index |
| 1104 | * @nr_pages: The maximum number of pages |
| 1105 | * |
| 1106 | * pagevec_lookup() will search for and return a group of up to @nr_pages pages |
| 1107 | * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a |
| 1108 | * reference against the pages in @pvec. |
| 1109 | * |
| 1110 | * The search returns a group of mapping-contiguous pages with ascending |
| 1111 | * indexes. There may be holes in the indices due to not-present pages. |
| 1112 | * |
| 1113 | * pagevec_lookup() returns the number of pages which were found. |
| 1114 | */ |
| 1115 | unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping, |
| 1116 | pgoff_t start, unsigned nr_pages) |
| 1117 | { |
| 1118 | pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages); |
| 1119 | return pagevec_count(pvec); |
| 1120 | } |
| 1121 | EXPORT_SYMBOL(pagevec_lookup); |
| 1122 | |
| 1123 | unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping, |
| 1124 | pgoff_t *index, int tag, unsigned nr_pages) |
| 1125 | { |
| 1126 | pvec->nr = find_get_pages_tag(mapping, index, tag, |
| 1127 | nr_pages, pvec->pages); |
| 1128 | return pagevec_count(pvec); |
| 1129 | } |
| 1130 | EXPORT_SYMBOL(pagevec_lookup_tag); |
| 1131 | |
| 1132 | /* |
| 1133 | * Perform any setup for the swap system |
| 1134 | */ |
| 1135 | void __init swap_setup(void) |
| 1136 | { |
| 1137 | unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT); |
| 1138 | #ifdef CONFIG_SWAP |
| 1139 | int i; |
| 1140 | |
| 1141 | for (i = 0; i < MAX_SWAPFILES; i++) |
| 1142 | spin_lock_init(&swapper_spaces[i].tree_lock); |
| 1143 | #endif |
| 1144 | |
| 1145 | /* Use a smaller cluster for small-memory machines */ |
| 1146 | if (megs < 16) |
| 1147 | page_cluster = 2; |
| 1148 | else |
| 1149 | page_cluster = 3; |
| 1150 | /* |
| 1151 | * Right now other parts of the system means that we |
| 1152 | * _really_ don't want to cluster much more |
| 1153 | */ |
| 1154 | } |