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 or pte_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 60 kmem_cache_t *anon_vma_cachep; 61 62 static 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. */ 81 int 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 } 119 120 void __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 } 125 126 void __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 } 135 136 void 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 } 147 148 void 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 } 167 168 static 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 } 178 179 void __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 */ 189 static 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); 203 out: 204 rcu_read_unlock(); 205 return anon_vma; 206 } 207 208 /* 209 * At what user virtual address is page expected in vma? 210 */ 211 static inline unsigned long 212 vma_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 */ 230 unsigned 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 pte mapped and locked. 248 */ 249 pte_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 */ 291 static 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); 319 out: 320 return referenced; 321 } 322 323 static 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 */ 356 static 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 */ 412 int 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 pte lock. 449 */ 450 void 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 pte lock. 472 */ 473 void 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 * The caller needs to hold the pte lock. 487 */ 488 void 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 */ 511 static 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 if (list_empty(&mm->mmlist)) 563 list_add(&mm->mmlist, &init_mm.mmlist); 564 spin_unlock(&mmlist_lock); 565 } 566 set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); 567 BUG_ON(pte_file(*pte)); 568 dec_mm_counter(mm, anon_rss); 569 } else 570 dec_mm_counter(mm, file_rss); 571 572 page_remove_rmap(page); 573 page_cache_release(page); 574 575 out_unmap: 576 pte_unmap_unlock(pte, ptl); 577 out: 578 return ret; 579 } 580 581 /* 582 * objrmap doesn't work for nonlinear VMAs because the assumption that 583 * offset-into-file correlates with offset-into-virtual-addresses does not hold. 584 * Consequently, given a particular page and its ->index, we cannot locate the 585 * ptes which are mapping that page without an exhaustive linear search. 586 * 587 * So what this code does is a mini "virtual scan" of each nonlinear VMA which 588 * maps the file to which the target page belongs. The ->vm_private_data field 589 * holds the current cursor into that scan. Successive searches will circulate 590 * around the vma's virtual address space. 591 * 592 * So as more replacement pressure is applied to the pages in a nonlinear VMA, 593 * more scanning pressure is placed against them as well. Eventually pages 594 * will become fully unmapped and are eligible for eviction. 595 * 596 * For very sparsely populated VMAs this is a little inefficient - chances are 597 * there there won't be many ptes located within the scan cluster. In this case 598 * maybe we could scan further - to the end of the pte page, perhaps. 599 */ 600 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) 601 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) 602 603 static void try_to_unmap_cluster(unsigned long cursor, 604 unsigned int *mapcount, struct vm_area_struct *vma) 605 { 606 struct mm_struct *mm = vma->vm_mm; 607 pgd_t *pgd; 608 pud_t *pud; 609 pmd_t *pmd; 610 pte_t *pte; 611 pte_t pteval; 612 spinlock_t *ptl; 613 struct page *page; 614 unsigned long address; 615 unsigned long end; 616 unsigned long pfn; 617 618 address = (vma->vm_start + cursor) & CLUSTER_MASK; 619 end = address + CLUSTER_SIZE; 620 if (address < vma->vm_start) 621 address = vma->vm_start; 622 if (end > vma->vm_end) 623 end = vma->vm_end; 624 625 pgd = pgd_offset(mm, address); 626 if (!pgd_present(*pgd)) 627 return; 628 629 pud = pud_offset(pgd, address); 630 if (!pud_present(*pud)) 631 return; 632 633 pmd = pmd_offset(pud, address); 634 if (!pmd_present(*pmd)) 635 return; 636 637 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 638 639 /* Update high watermark before we lower rss */ 640 update_hiwater_rss(mm); 641 642 for (; address < end; pte++, address += PAGE_SIZE) { 643 if (!pte_present(*pte)) 644 continue; 645 646 pfn = pte_pfn(*pte); 647 if (unlikely(!pfn_valid(pfn))) { 648 print_bad_pte(vma, *pte, address); 649 continue; 650 } 651 652 page = pfn_to_page(pfn); 653 BUG_ON(PageAnon(page)); 654 655 if (ptep_clear_flush_young(vma, address, pte)) 656 continue; 657 658 /* Nuke the page table entry. */ 659 flush_cache_page(vma, address, pfn); 660 pteval = ptep_clear_flush(vma, address, pte); 661 662 /* If nonlinear, store the file page offset in the pte. */ 663 if (page->index != linear_page_index(vma, address)) 664 set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); 665 666 /* Move the dirty bit to the physical page now the pte is gone. */ 667 if (pte_dirty(pteval)) 668 set_page_dirty(page); 669 670 page_remove_rmap(page); 671 page_cache_release(page); 672 dec_mm_counter(mm, file_rss); 673 (*mapcount)--; 674 } 675 pte_unmap_unlock(pte - 1, ptl); 676 } 677 678 static int try_to_unmap_anon(struct page *page) 679 { 680 struct anon_vma *anon_vma; 681 struct vm_area_struct *vma; 682 int ret = SWAP_AGAIN; 683 684 anon_vma = page_lock_anon_vma(page); 685 if (!anon_vma) 686 return ret; 687 688 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { 689 ret = try_to_unmap_one(page, vma); 690 if (ret == SWAP_FAIL || !page_mapped(page)) 691 break; 692 } 693 spin_unlock(&anon_vma->lock); 694 return ret; 695 } 696 697 /** 698 * try_to_unmap_file - unmap file page using the object-based rmap method 699 * @page: the page to unmap 700 * 701 * Find all the mappings of a page using the mapping pointer and the vma chains 702 * contained in the address_space struct it points to. 703 * 704 * This function is only called from try_to_unmap for object-based pages. 705 */ 706 static int try_to_unmap_file(struct page *page) 707 { 708 struct address_space *mapping = page->mapping; 709 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 710 struct vm_area_struct *vma; 711 struct prio_tree_iter iter; 712 int ret = SWAP_AGAIN; 713 unsigned long cursor; 714 unsigned long max_nl_cursor = 0; 715 unsigned long max_nl_size = 0; 716 unsigned int mapcount; 717 718 spin_lock(&mapping->i_mmap_lock); 719 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { 720 ret = try_to_unmap_one(page, vma); 721 if (ret == SWAP_FAIL || !page_mapped(page)) 722 goto out; 723 } 724 725 if (list_empty(&mapping->i_mmap_nonlinear)) 726 goto out; 727 728 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, 729 shared.vm_set.list) { 730 if (vma->vm_flags & (VM_LOCKED|VM_RESERVED)) 731 continue; 732 cursor = (unsigned long) vma->vm_private_data; 733 if (cursor > max_nl_cursor) 734 max_nl_cursor = cursor; 735 cursor = vma->vm_end - vma->vm_start; 736 if (cursor > max_nl_size) 737 max_nl_size = cursor; 738 } 739 740 if (max_nl_size == 0) { /* any nonlinears locked or reserved */ 741 ret = SWAP_FAIL; 742 goto out; 743 } 744 745 /* 746 * We don't try to search for this page in the nonlinear vmas, 747 * and page_referenced wouldn't have found it anyway. Instead 748 * just walk the nonlinear vmas trying to age and unmap some. 749 * The mapcount of the page we came in with is irrelevant, 750 * but even so use it as a guide to how hard we should try? 751 */ 752 mapcount = page_mapcount(page); 753 if (!mapcount) 754 goto out; 755 cond_resched_lock(&mapping->i_mmap_lock); 756 757 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; 758 if (max_nl_cursor == 0) 759 max_nl_cursor = CLUSTER_SIZE; 760 761 do { 762 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, 763 shared.vm_set.list) { 764 if (vma->vm_flags & (VM_LOCKED|VM_RESERVED)) 765 continue; 766 cursor = (unsigned long) vma->vm_private_data; 767 while ( cursor < max_nl_cursor && 768 cursor < vma->vm_end - vma->vm_start) { 769 try_to_unmap_cluster(cursor, &mapcount, vma); 770 cursor += CLUSTER_SIZE; 771 vma->vm_private_data = (void *) cursor; 772 if ((int)mapcount <= 0) 773 goto out; 774 } 775 vma->vm_private_data = (void *) max_nl_cursor; 776 } 777 cond_resched_lock(&mapping->i_mmap_lock); 778 max_nl_cursor += CLUSTER_SIZE; 779 } while (max_nl_cursor <= max_nl_size); 780 781 /* 782 * Don't loop forever (perhaps all the remaining pages are 783 * in locked vmas). Reset cursor on all unreserved nonlinear 784 * vmas, now forgetting on which ones it had fallen behind. 785 */ 786 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, 787 shared.vm_set.list) { 788 if (!(vma->vm_flags & VM_RESERVED)) 789 vma->vm_private_data = NULL; 790 } 791 out: 792 spin_unlock(&mapping->i_mmap_lock); 793 return ret; 794 } 795 796 /** 797 * try_to_unmap - try to remove all page table mappings to a page 798 * @page: the page to get unmapped 799 * 800 * Tries to remove all the page table entries which are mapping this 801 * page, used in the pageout path. Caller must hold the page lock. 802 * Return values are: 803 * 804 * SWAP_SUCCESS - we succeeded in removing all mappings 805 * SWAP_AGAIN - we missed a mapping, try again later 806 * SWAP_FAIL - the page is unswappable 807 */ 808 int try_to_unmap(struct page *page) 809 { 810 int ret; 811 812 BUG_ON(!PageLocked(page)); 813 814 if (PageAnon(page)) 815 ret = try_to_unmap_anon(page); 816 else 817 ret = try_to_unmap_file(page); 818 819 if (!page_mapped(page)) 820 ret = SWAP_SUCCESS; 821 return ret; 822 } 823 824