rmap.c revision 4c21e2f2441dc5fbb957b030333f5a3f2d02dea7
1/* 2 * mm/rmap.c - physical to virtual reverse mappings 3 * 4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br> 5 * Released under the General Public License (GPL). 6 * 7 * Simple, low overhead reverse mapping scheme. 8 * Please try to keep this thing as modular as possible. 9 * 10 * Provides methods for unmapping each kind of mapped page: 11 * the anon methods track anonymous pages, and 12 * the file methods track pages belonging to an inode. 13 * 14 * Original design by Rik van Riel <riel@conectiva.com.br> 2001 15 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004 16 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004 17 * Contributions by Hugh Dickins <hugh@veritas.com> 2003, 2004 18 */ 19 20/* 21 * Lock ordering in mm: 22 * 23 * inode->i_sem (while writing or truncating, not reading or faulting) 24 * inode->i_alloc_sem 25 * 26 * When a page fault occurs in writing from user to file, down_read 27 * of mmap_sem nests within i_sem; in sys_msync, i_sem nests within 28 * down_read of mmap_sem; i_sem and down_write of mmap_sem are never 29 * taken together; in truncation, i_sem is taken outermost. 30 * 31 * mm->mmap_sem 32 * page->flags PG_locked (lock_page) 33 * mapping->i_mmap_lock 34 * anon_vma->lock 35 * mm->page_table_lock 36 * zone->lru_lock (in mark_page_accessed) 37 * swap_lock (in swap_duplicate, swap_info_get) 38 * mmlist_lock (in mmput, drain_mmlist and others) 39 * mapping->private_lock (in __set_page_dirty_buffers) 40 * inode_lock (in set_page_dirty's __mark_inode_dirty) 41 * sb_lock (within inode_lock in fs/fs-writeback.c) 42 * mapping->tree_lock (widely used, in set_page_dirty, 43 * in arch-dependent flush_dcache_mmap_lock, 44 * within inode_lock in __sync_single_inode) 45 */ 46 47#include <linux/mm.h> 48#include <linux/pagemap.h> 49#include <linux/swap.h> 50#include <linux/swapops.h> 51#include <linux/slab.h> 52#include <linux/init.h> 53#include <linux/rmap.h> 54#include <linux/rcupdate.h> 55 56#include <asm/tlbflush.h> 57 58//#define RMAP_DEBUG /* can be enabled only for debugging */ 59 60kmem_cache_t *anon_vma_cachep; 61 62static inline void validate_anon_vma(struct vm_area_struct *find_vma) 63{ 64#ifdef RMAP_DEBUG 65 struct anon_vma *anon_vma = find_vma->anon_vma; 66 struct vm_area_struct *vma; 67 unsigned int mapcount = 0; 68 int found = 0; 69 70 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { 71 mapcount++; 72 BUG_ON(mapcount > 100000); 73 if (vma == find_vma) 74 found = 1; 75 } 76 BUG_ON(!found); 77#endif 78} 79 80/* This must be called under the mmap_sem. */ 81int anon_vma_prepare(struct vm_area_struct *vma) 82{ 83 struct anon_vma *anon_vma = vma->anon_vma; 84 85 might_sleep(); 86 if (unlikely(!anon_vma)) { 87 struct mm_struct *mm = vma->vm_mm; 88 struct anon_vma *allocated, *locked; 89 90 anon_vma = find_mergeable_anon_vma(vma); 91 if (anon_vma) { 92 allocated = NULL; 93 locked = anon_vma; 94 spin_lock(&locked->lock); 95 } else { 96 anon_vma = anon_vma_alloc(); 97 if (unlikely(!anon_vma)) 98 return -ENOMEM; 99 allocated = anon_vma; 100 locked = NULL; 101 } 102 103 /* page_table_lock to protect against threads */ 104 spin_lock(&mm->page_table_lock); 105 if (likely(!vma->anon_vma)) { 106 vma->anon_vma = anon_vma; 107 list_add(&vma->anon_vma_node, &anon_vma->head); 108 allocated = NULL; 109 } 110 spin_unlock(&mm->page_table_lock); 111 112 if (locked) 113 spin_unlock(&locked->lock); 114 if (unlikely(allocated)) 115 anon_vma_free(allocated); 116 } 117 return 0; 118} 119 120void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next) 121{ 122 BUG_ON(vma->anon_vma != next->anon_vma); 123 list_del(&next->anon_vma_node); 124} 125 126void __anon_vma_link(struct vm_area_struct *vma) 127{ 128 struct anon_vma *anon_vma = vma->anon_vma; 129 130 if (anon_vma) { 131 list_add(&vma->anon_vma_node, &anon_vma->head); 132 validate_anon_vma(vma); 133 } 134} 135 136void anon_vma_link(struct vm_area_struct *vma) 137{ 138 struct anon_vma *anon_vma = vma->anon_vma; 139 140 if (anon_vma) { 141 spin_lock(&anon_vma->lock); 142 list_add(&vma->anon_vma_node, &anon_vma->head); 143 validate_anon_vma(vma); 144 spin_unlock(&anon_vma->lock); 145 } 146} 147 148void anon_vma_unlink(struct vm_area_struct *vma) 149{ 150 struct anon_vma *anon_vma = vma->anon_vma; 151 int empty; 152 153 if (!anon_vma) 154 return; 155 156 spin_lock(&anon_vma->lock); 157 validate_anon_vma(vma); 158 list_del(&vma->anon_vma_node); 159 160 /* We must garbage collect the anon_vma if it's empty */ 161 empty = list_empty(&anon_vma->head); 162 spin_unlock(&anon_vma->lock); 163 164 if (empty) 165 anon_vma_free(anon_vma); 166} 167 168static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags) 169{ 170 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == 171 SLAB_CTOR_CONSTRUCTOR) { 172 struct anon_vma *anon_vma = data; 173 174 spin_lock_init(&anon_vma->lock); 175 INIT_LIST_HEAD(&anon_vma->head); 176 } 177} 178 179void __init anon_vma_init(void) 180{ 181 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), 182 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL); 183} 184 185/* 186 * Getting a lock on a stable anon_vma from a page off the LRU is 187 * tricky: page_lock_anon_vma rely on RCU to guard against the races. 188 */ 189static struct anon_vma *page_lock_anon_vma(struct page *page) 190{ 191 struct anon_vma *anon_vma = NULL; 192 unsigned long anon_mapping; 193 194 rcu_read_lock(); 195 anon_mapping = (unsigned long) page->mapping; 196 if (!(anon_mapping & PAGE_MAPPING_ANON)) 197 goto out; 198 if (!page_mapped(page)) 199 goto out; 200 201 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); 202 spin_lock(&anon_vma->lock); 203out: 204 rcu_read_unlock(); 205 return anon_vma; 206} 207 208/* 209 * At what user virtual address is page expected in vma? 210 */ 211static inline unsigned long 212vma_address(struct page *page, struct vm_area_struct *vma) 213{ 214 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 215 unsigned long address; 216 217 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); 218 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { 219 /* page should be within any vma from prio_tree_next */ 220 BUG_ON(!PageAnon(page)); 221 return -EFAULT; 222 } 223 return address; 224} 225 226/* 227 * At what user virtual address is page expected in vma? checking that the 228 * page matches the vma: currently only used by unuse_process, on anon pages. 229 */ 230unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) 231{ 232 if (PageAnon(page)) { 233 if ((void *)vma->anon_vma != 234 (void *)page->mapping - PAGE_MAPPING_ANON) 235 return -EFAULT; 236 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { 237 if (vma->vm_file->f_mapping != page->mapping) 238 return -EFAULT; 239 } else 240 return -EFAULT; 241 return vma_address(page, vma); 242} 243 244/* 245 * Check that @page is mapped at @address into @mm. 246 * 247 * On success returns with mapped pte and locked mm->page_table_lock. 248 */ 249pte_t *page_check_address(struct page *page, struct mm_struct *mm, 250 unsigned long address, spinlock_t **ptlp) 251{ 252 pgd_t *pgd; 253 pud_t *pud; 254 pmd_t *pmd; 255 pte_t *pte; 256 spinlock_t *ptl; 257 258 pgd = pgd_offset(mm, address); 259 if (!pgd_present(*pgd)) 260 return NULL; 261 262 pud = pud_offset(pgd, address); 263 if (!pud_present(*pud)) 264 return NULL; 265 266 pmd = pmd_offset(pud, address); 267 if (!pmd_present(*pmd)) 268 return NULL; 269 270 pte = pte_offset_map(pmd, address); 271 /* Make a quick check before getting the lock */ 272 if (!pte_present(*pte)) { 273 pte_unmap(pte); 274 return NULL; 275 } 276 277 ptl = pte_lockptr(mm, pmd); 278 spin_lock(ptl); 279 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { 280 *ptlp = ptl; 281 return pte; 282 } 283 pte_unmap_unlock(pte, ptl); 284 return NULL; 285} 286 287/* 288 * Subfunctions of page_referenced: page_referenced_one called 289 * repeatedly from either page_referenced_anon or page_referenced_file. 290 */ 291static int page_referenced_one(struct page *page, 292 struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token) 293{ 294 struct mm_struct *mm = vma->vm_mm; 295 unsigned long address; 296 pte_t *pte; 297 spinlock_t *ptl; 298 int referenced = 0; 299 300 address = vma_address(page, vma); 301 if (address == -EFAULT) 302 goto out; 303 304 pte = page_check_address(page, mm, address, &ptl); 305 if (!pte) 306 goto out; 307 308 if (ptep_clear_flush_young(vma, address, pte)) 309 referenced++; 310 311 /* Pretend the page is referenced if the task has the 312 swap token and is in the middle of a page fault. */ 313 if (mm != current->mm && !ignore_token && has_swap_token(mm) && 314 rwsem_is_locked(&mm->mmap_sem)) 315 referenced++; 316 317 (*mapcount)--; 318 pte_unmap_unlock(pte, ptl); 319out: 320 return referenced; 321} 322 323static int page_referenced_anon(struct page *page, int ignore_token) 324{ 325 unsigned int mapcount; 326 struct anon_vma *anon_vma; 327 struct vm_area_struct *vma; 328 int referenced = 0; 329 330 anon_vma = page_lock_anon_vma(page); 331 if (!anon_vma) 332 return referenced; 333 334 mapcount = page_mapcount(page); 335 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { 336 referenced += page_referenced_one(page, vma, &mapcount, 337 ignore_token); 338 if (!mapcount) 339 break; 340 } 341 spin_unlock(&anon_vma->lock); 342 return referenced; 343} 344 345/** 346 * page_referenced_file - referenced check for object-based rmap 347 * @page: the page we're checking references on. 348 * 349 * For an object-based mapped page, find all the places it is mapped and 350 * check/clear the referenced flag. This is done by following the page->mapping 351 * pointer, then walking the chain of vmas it holds. It returns the number 352 * of references it found. 353 * 354 * This function is only called from page_referenced for object-based pages. 355 */ 356static int page_referenced_file(struct page *page, int ignore_token) 357{ 358 unsigned int mapcount; 359 struct address_space *mapping = page->mapping; 360 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 361 struct vm_area_struct *vma; 362 struct prio_tree_iter iter; 363 int referenced = 0; 364 365 /* 366 * The caller's checks on page->mapping and !PageAnon have made 367 * sure that this is a file page: the check for page->mapping 368 * excludes the case just before it gets set on an anon page. 369 */ 370 BUG_ON(PageAnon(page)); 371 372 /* 373 * The page lock not only makes sure that page->mapping cannot 374 * suddenly be NULLified by truncation, it makes sure that the 375 * structure at mapping cannot be freed and reused yet, 376 * so we can safely take mapping->i_mmap_lock. 377 */ 378 BUG_ON(!PageLocked(page)); 379 380 spin_lock(&mapping->i_mmap_lock); 381 382 /* 383 * i_mmap_lock does not stabilize mapcount at all, but mapcount 384 * is more likely to be accurate if we note it after spinning. 385 */ 386 mapcount = page_mapcount(page); 387 388 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { 389 if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE)) 390 == (VM_LOCKED|VM_MAYSHARE)) { 391 referenced++; 392 break; 393 } 394 referenced += page_referenced_one(page, vma, &mapcount, 395 ignore_token); 396 if (!mapcount) 397 break; 398 } 399 400 spin_unlock(&mapping->i_mmap_lock); 401 return referenced; 402} 403 404/** 405 * page_referenced - test if the page was referenced 406 * @page: the page to test 407 * @is_locked: caller holds lock on the page 408 * 409 * Quick test_and_clear_referenced for all mappings to a page, 410 * returns the number of ptes which referenced the page. 411 */ 412int page_referenced(struct page *page, int is_locked, int ignore_token) 413{ 414 int referenced = 0; 415 416 if (!swap_token_default_timeout) 417 ignore_token = 1; 418 419 if (page_test_and_clear_young(page)) 420 referenced++; 421 422 if (TestClearPageReferenced(page)) 423 referenced++; 424 425 if (page_mapped(page) && page->mapping) { 426 if (PageAnon(page)) 427 referenced += page_referenced_anon(page, ignore_token); 428 else if (is_locked) 429 referenced += page_referenced_file(page, ignore_token); 430 else if (TestSetPageLocked(page)) 431 referenced++; 432 else { 433 if (page->mapping) 434 referenced += page_referenced_file(page, 435 ignore_token); 436 unlock_page(page); 437 } 438 } 439 return referenced; 440} 441 442/** 443 * page_add_anon_rmap - add pte mapping to an anonymous page 444 * @page: the page to add the mapping to 445 * @vma: the vm area in which the mapping is added 446 * @address: the user virtual address mapped 447 * 448 * The caller needs to hold the mm->page_table_lock. 449 */ 450void page_add_anon_rmap(struct page *page, 451 struct vm_area_struct *vma, unsigned long address) 452{ 453 if (atomic_inc_and_test(&page->_mapcount)) { 454 struct anon_vma *anon_vma = vma->anon_vma; 455 456 BUG_ON(!anon_vma); 457 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; 458 page->mapping = (struct address_space *) anon_vma; 459 460 page->index = linear_page_index(vma, address); 461 462 inc_page_state(nr_mapped); 463 } 464 /* else checking page index and mapping is racy */ 465} 466 467/** 468 * page_add_file_rmap - add pte mapping to a file page 469 * @page: the page to add the mapping to 470 * 471 * The caller needs to hold the mm->page_table_lock. 472 */ 473void page_add_file_rmap(struct page *page) 474{ 475 BUG_ON(PageAnon(page)); 476 BUG_ON(!pfn_valid(page_to_pfn(page))); 477 478 if (atomic_inc_and_test(&page->_mapcount)) 479 inc_page_state(nr_mapped); 480} 481 482/** 483 * page_remove_rmap - take down pte mapping from a page 484 * @page: page to remove mapping from 485 * 486 * Caller needs to hold the mm->page_table_lock. 487 */ 488void page_remove_rmap(struct page *page) 489{ 490 if (atomic_add_negative(-1, &page->_mapcount)) { 491 BUG_ON(page_mapcount(page) < 0); 492 /* 493 * It would be tidy to reset the PageAnon mapping here, 494 * but that might overwrite a racing page_add_anon_rmap 495 * which increments mapcount after us but sets mapping 496 * before us: so leave the reset to free_hot_cold_page, 497 * and remember that it's only reliable while mapped. 498 * Leaving it set also helps swapoff to reinstate ptes 499 * faster for those pages still in swapcache. 500 */ 501 if (page_test_and_clear_dirty(page)) 502 set_page_dirty(page); 503 dec_page_state(nr_mapped); 504 } 505} 506 507/* 508 * Subfunctions of try_to_unmap: try_to_unmap_one called 509 * repeatedly from either try_to_unmap_anon or try_to_unmap_file. 510 */ 511static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma) 512{ 513 struct mm_struct *mm = vma->vm_mm; 514 unsigned long address; 515 pte_t *pte; 516 pte_t pteval; 517 spinlock_t *ptl; 518 int ret = SWAP_AGAIN; 519 520 address = vma_address(page, vma); 521 if (address == -EFAULT) 522 goto out; 523 524 pte = page_check_address(page, mm, address, &ptl); 525 if (!pte) 526 goto out; 527 528 /* 529 * If the page is mlock()d, we cannot swap it out. 530 * If it's recently referenced (perhaps page_referenced 531 * skipped over this mm) then we should reactivate it. 532 * 533 * Pages belonging to VM_RESERVED regions should not happen here. 534 */ 535 if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) || 536 ptep_clear_flush_young(vma, address, pte)) { 537 ret = SWAP_FAIL; 538 goto out_unmap; 539 } 540 541 /* Nuke the page table entry. */ 542 flush_cache_page(vma, address, page_to_pfn(page)); 543 pteval = ptep_clear_flush(vma, address, pte); 544 545 /* Move the dirty bit to the physical page now the pte is gone. */ 546 if (pte_dirty(pteval)) 547 set_page_dirty(page); 548 549 /* Update high watermark before we lower rss */ 550 update_hiwater_rss(mm); 551 552 if (PageAnon(page)) { 553 swp_entry_t entry = { .val = page_private(page) }; 554 /* 555 * Store the swap location in the pte. 556 * See handle_pte_fault() ... 557 */ 558 BUG_ON(!PageSwapCache(page)); 559 swap_duplicate(entry); 560 if (list_empty(&mm->mmlist)) { 561 spin_lock(&mmlist_lock); 562 list_add(&mm->mmlist, &init_mm.mmlist); 563 spin_unlock(&mmlist_lock); 564 } 565 set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); 566 BUG_ON(pte_file(*pte)); 567 dec_mm_counter(mm, anon_rss); 568 } else 569 dec_mm_counter(mm, file_rss); 570 571 page_remove_rmap(page); 572 page_cache_release(page); 573 574out_unmap: 575 pte_unmap_unlock(pte, ptl); 576out: 577 return ret; 578} 579 580/* 581 * objrmap doesn't work for nonlinear VMAs because the assumption that 582 * offset-into-file correlates with offset-into-virtual-addresses does not hold. 583 * Consequently, given a particular page and its ->index, we cannot locate the 584 * ptes which are mapping that page without an exhaustive linear search. 585 * 586 * So what this code does is a mini "virtual scan" of each nonlinear VMA which 587 * maps the file to which the target page belongs. The ->vm_private_data field 588 * holds the current cursor into that scan. Successive searches will circulate 589 * around the vma's virtual address space. 590 * 591 * So as more replacement pressure is applied to the pages in a nonlinear VMA, 592 * more scanning pressure is placed against them as well. Eventually pages 593 * will become fully unmapped and are eligible for eviction. 594 * 595 * For very sparsely populated VMAs this is a little inefficient - chances are 596 * there there won't be many ptes located within the scan cluster. In this case 597 * maybe we could scan further - to the end of the pte page, perhaps. 598 */ 599#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) 600#define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) 601 602static void try_to_unmap_cluster(unsigned long cursor, 603 unsigned int *mapcount, struct vm_area_struct *vma) 604{ 605 struct mm_struct *mm = vma->vm_mm; 606 pgd_t *pgd; 607 pud_t *pud; 608 pmd_t *pmd; 609 pte_t *pte; 610 pte_t pteval; 611 spinlock_t *ptl; 612 struct page *page; 613 unsigned long address; 614 unsigned long end; 615 unsigned long pfn; 616 617 address = (vma->vm_start + cursor) & CLUSTER_MASK; 618 end = address + CLUSTER_SIZE; 619 if (address < vma->vm_start) 620 address = vma->vm_start; 621 if (end > vma->vm_end) 622 end = vma->vm_end; 623 624 pgd = pgd_offset(mm, address); 625 if (!pgd_present(*pgd)) 626 return; 627 628 pud = pud_offset(pgd, address); 629 if (!pud_present(*pud)) 630 return; 631 632 pmd = pmd_offset(pud, address); 633 if (!pmd_present(*pmd)) 634 return; 635 636 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 637 638 /* Update high watermark before we lower rss */ 639 update_hiwater_rss(mm); 640 641 for (; address < end; pte++, address += PAGE_SIZE) { 642 if (!pte_present(*pte)) 643 continue; 644 645 pfn = pte_pfn(*pte); 646 if (unlikely(!pfn_valid(pfn))) { 647 print_bad_pte(vma, *pte, address); 648 continue; 649 } 650 651 page = pfn_to_page(pfn); 652 BUG_ON(PageAnon(page)); 653 654 if (ptep_clear_flush_young(vma, address, pte)) 655 continue; 656 657 /* Nuke the page table entry. */ 658 flush_cache_page(vma, address, pfn); 659 pteval = ptep_clear_flush(vma, address, pte); 660 661 /* If nonlinear, store the file page offset in the pte. */ 662 if (page->index != linear_page_index(vma, address)) 663 set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); 664 665 /* Move the dirty bit to the physical page now the pte is gone. */ 666 if (pte_dirty(pteval)) 667 set_page_dirty(page); 668 669 page_remove_rmap(page); 670 page_cache_release(page); 671 dec_mm_counter(mm, file_rss); 672 (*mapcount)--; 673 } 674 pte_unmap_unlock(pte - 1, ptl); 675} 676 677static int try_to_unmap_anon(struct page *page) 678{ 679 struct anon_vma *anon_vma; 680 struct vm_area_struct *vma; 681 int ret = SWAP_AGAIN; 682 683 anon_vma = page_lock_anon_vma(page); 684 if (!anon_vma) 685 return ret; 686 687 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { 688 ret = try_to_unmap_one(page, vma); 689 if (ret == SWAP_FAIL || !page_mapped(page)) 690 break; 691 } 692 spin_unlock(&anon_vma->lock); 693 return ret; 694} 695 696/** 697 * try_to_unmap_file - unmap file page using the object-based rmap method 698 * @page: the page to unmap 699 * 700 * Find all the mappings of a page using the mapping pointer and the vma chains 701 * contained in the address_space struct it points to. 702 * 703 * This function is only called from try_to_unmap for object-based pages. 704 */ 705static int try_to_unmap_file(struct page *page) 706{ 707 struct address_space *mapping = page->mapping; 708 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 709 struct vm_area_struct *vma; 710 struct prio_tree_iter iter; 711 int ret = SWAP_AGAIN; 712 unsigned long cursor; 713 unsigned long max_nl_cursor = 0; 714 unsigned long max_nl_size = 0; 715 unsigned int mapcount; 716 717 spin_lock(&mapping->i_mmap_lock); 718 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { 719 ret = try_to_unmap_one(page, vma); 720 if (ret == SWAP_FAIL || !page_mapped(page)) 721 goto out; 722 } 723 724 if (list_empty(&mapping->i_mmap_nonlinear)) 725 goto out; 726 727 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, 728 shared.vm_set.list) { 729 if (vma->vm_flags & (VM_LOCKED|VM_RESERVED)) 730 continue; 731 cursor = (unsigned long) vma->vm_private_data; 732 if (cursor > max_nl_cursor) 733 max_nl_cursor = cursor; 734 cursor = vma->vm_end - vma->vm_start; 735 if (cursor > max_nl_size) 736 max_nl_size = cursor; 737 } 738 739 if (max_nl_size == 0) { /* any nonlinears locked or reserved */ 740 ret = SWAP_FAIL; 741 goto out; 742 } 743 744 /* 745 * We don't try to search for this page in the nonlinear vmas, 746 * and page_referenced wouldn't have found it anyway. Instead 747 * just walk the nonlinear vmas trying to age and unmap some. 748 * The mapcount of the page we came in with is irrelevant, 749 * but even so use it as a guide to how hard we should try? 750 */ 751 mapcount = page_mapcount(page); 752 if (!mapcount) 753 goto out; 754 cond_resched_lock(&mapping->i_mmap_lock); 755 756 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; 757 if (max_nl_cursor == 0) 758 max_nl_cursor = CLUSTER_SIZE; 759 760 do { 761 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, 762 shared.vm_set.list) { 763 if (vma->vm_flags & (VM_LOCKED|VM_RESERVED)) 764 continue; 765 cursor = (unsigned long) vma->vm_private_data; 766 while ( cursor < max_nl_cursor && 767 cursor < vma->vm_end - vma->vm_start) { 768 try_to_unmap_cluster(cursor, &mapcount, vma); 769 cursor += CLUSTER_SIZE; 770 vma->vm_private_data = (void *) cursor; 771 if ((int)mapcount <= 0) 772 goto out; 773 } 774 vma->vm_private_data = (void *) max_nl_cursor; 775 } 776 cond_resched_lock(&mapping->i_mmap_lock); 777 max_nl_cursor += CLUSTER_SIZE; 778 } while (max_nl_cursor <= max_nl_size); 779 780 /* 781 * Don't loop forever (perhaps all the remaining pages are 782 * in locked vmas). Reset cursor on all unreserved nonlinear 783 * vmas, now forgetting on which ones it had fallen behind. 784 */ 785 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, 786 shared.vm_set.list) { 787 if (!(vma->vm_flags & VM_RESERVED)) 788 vma->vm_private_data = NULL; 789 } 790out: 791 spin_unlock(&mapping->i_mmap_lock); 792 return ret; 793} 794 795/** 796 * try_to_unmap - try to remove all page table mappings to a page 797 * @page: the page to get unmapped 798 * 799 * Tries to remove all the page table entries which are mapping this 800 * page, used in the pageout path. Caller must hold the page lock. 801 * Return values are: 802 * 803 * SWAP_SUCCESS - we succeeded in removing all mappings 804 * SWAP_AGAIN - we missed a mapping, try again later 805 * SWAP_FAIL - the page is unswappable 806 */ 807int try_to_unmap(struct page *page) 808{ 809 int ret; 810 811 BUG_ON(!PageLocked(page)); 812 813 if (PageAnon(page)) 814 ret = try_to_unmap_anon(page); 815 else 816 ret = try_to_unmap_file(page); 817 818 if (!page_mapped(page)) 819 ret = SWAP_SUCCESS; 820 return ret; 821} 822 823