migrate.c revision e78bbfa8262424417a29349a8064a535053912b9
1/* 2 * Memory Migration functionality - linux/mm/migration.c 3 * 4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter 5 * 6 * Page migration was first developed in the context of the memory hotplug 7 * project. The main authors of the migration code are: 8 * 9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> 10 * Hirokazu Takahashi <taka@valinux.co.jp> 11 * Dave Hansen <haveblue@us.ibm.com> 12 * Christoph Lameter 13 */ 14 15#include <linux/migrate.h> 16#include <linux/module.h> 17#include <linux/swap.h> 18#include <linux/swapops.h> 19#include <linux/pagemap.h> 20#include <linux/buffer_head.h> 21#include <linux/mm_inline.h> 22#include <linux/nsproxy.h> 23#include <linux/pagevec.h> 24#include <linux/rmap.h> 25#include <linux/topology.h> 26#include <linux/cpu.h> 27#include <linux/cpuset.h> 28#include <linux/writeback.h> 29#include <linux/mempolicy.h> 30#include <linux/vmalloc.h> 31#include <linux/security.h> 32#include <linux/memcontrol.h> 33#include <linux/syscalls.h> 34 35#include "internal.h" 36 37#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 38 39/* 40 * migrate_prep() needs to be called before we start compiling a list of pages 41 * to be migrated using isolate_lru_page(). 42 */ 43int migrate_prep(void) 44{ 45 /* 46 * Clear the LRU lists so pages can be isolated. 47 * Note that pages may be moved off the LRU after we have 48 * drained them. Those pages will fail to migrate like other 49 * pages that may be busy. 50 */ 51 lru_add_drain_all(); 52 53 return 0; 54} 55 56/* 57 * Add isolated pages on the list back to the LRU under page lock 58 * to avoid leaking evictable pages back onto unevictable list. 59 * 60 * returns the number of pages put back. 61 */ 62int putback_lru_pages(struct list_head *l) 63{ 64 struct page *page; 65 struct page *page2; 66 int count = 0; 67 68 list_for_each_entry_safe(page, page2, l, lru) { 69 list_del(&page->lru); 70 putback_lru_page(page); 71 count++; 72 } 73 return count; 74} 75 76/* 77 * Restore a potential migration pte to a working pte entry 78 */ 79static void remove_migration_pte(struct vm_area_struct *vma, 80 struct page *old, struct page *new) 81{ 82 struct mm_struct *mm = vma->vm_mm; 83 swp_entry_t entry; 84 pgd_t *pgd; 85 pud_t *pud; 86 pmd_t *pmd; 87 pte_t *ptep, pte; 88 spinlock_t *ptl; 89 unsigned long addr = page_address_in_vma(new, vma); 90 91 if (addr == -EFAULT) 92 return; 93 94 pgd = pgd_offset(mm, addr); 95 if (!pgd_present(*pgd)) 96 return; 97 98 pud = pud_offset(pgd, addr); 99 if (!pud_present(*pud)) 100 return; 101 102 pmd = pmd_offset(pud, addr); 103 if (!pmd_present(*pmd)) 104 return; 105 106 ptep = pte_offset_map(pmd, addr); 107 108 if (!is_swap_pte(*ptep)) { 109 pte_unmap(ptep); 110 return; 111 } 112 113 ptl = pte_lockptr(mm, pmd); 114 spin_lock(ptl); 115 pte = *ptep; 116 if (!is_swap_pte(pte)) 117 goto out; 118 119 entry = pte_to_swp_entry(pte); 120 121 if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) 122 goto out; 123 124 /* 125 * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge. 126 * Failure is not an option here: we're now expected to remove every 127 * migration pte, and will cause crashes otherwise. Normally this 128 * is not an issue: mem_cgroup_prepare_migration bumped up the old 129 * page_cgroup count for safety, that's now attached to the new page, 130 * so this charge should just be another incrementation of the count, 131 * to keep in balance with rmap.c's mem_cgroup_uncharging. But if 132 * there's been a force_empty, those reference counts may no longer 133 * be reliable, and this charge can actually fail: oh well, we don't 134 * make the situation any worse by proceeding as if it had succeeded. 135 */ 136 mem_cgroup_charge(new, mm, GFP_ATOMIC); 137 138 get_page(new); 139 pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); 140 if (is_write_migration_entry(entry)) 141 pte = pte_mkwrite(pte); 142 flush_cache_page(vma, addr, pte_pfn(pte)); 143 set_pte_at(mm, addr, ptep, pte); 144 145 if (PageAnon(new)) 146 page_add_anon_rmap(new, vma, addr); 147 else 148 page_add_file_rmap(new); 149 150 /* No need to invalidate - it was non-present before */ 151 update_mmu_cache(vma, addr, pte); 152 153out: 154 pte_unmap_unlock(ptep, ptl); 155} 156 157/* 158 * Note that remove_file_migration_ptes will only work on regular mappings, 159 * Nonlinear mappings do not use migration entries. 160 */ 161static void remove_file_migration_ptes(struct page *old, struct page *new) 162{ 163 struct vm_area_struct *vma; 164 struct address_space *mapping = page_mapping(new); 165 struct prio_tree_iter iter; 166 pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 167 168 if (!mapping) 169 return; 170 171 spin_lock(&mapping->i_mmap_lock); 172 173 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) 174 remove_migration_pte(vma, old, new); 175 176 spin_unlock(&mapping->i_mmap_lock); 177} 178 179/* 180 * Must hold mmap_sem lock on at least one of the vmas containing 181 * the page so that the anon_vma cannot vanish. 182 */ 183static void remove_anon_migration_ptes(struct page *old, struct page *new) 184{ 185 struct anon_vma *anon_vma; 186 struct vm_area_struct *vma; 187 unsigned long mapping; 188 189 mapping = (unsigned long)new->mapping; 190 191 if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0) 192 return; 193 194 /* 195 * We hold the mmap_sem lock. So no need to call page_lock_anon_vma. 196 */ 197 anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON); 198 spin_lock(&anon_vma->lock); 199 200 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) 201 remove_migration_pte(vma, old, new); 202 203 spin_unlock(&anon_vma->lock); 204} 205 206/* 207 * Get rid of all migration entries and replace them by 208 * references to the indicated page. 209 */ 210static void remove_migration_ptes(struct page *old, struct page *new) 211{ 212 if (PageAnon(new)) 213 remove_anon_migration_ptes(old, new); 214 else 215 remove_file_migration_ptes(old, new); 216} 217 218/* 219 * Something used the pte of a page under migration. We need to 220 * get to the page and wait until migration is finished. 221 * When we return from this function the fault will be retried. 222 * 223 * This function is called from do_swap_page(). 224 */ 225void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 226 unsigned long address) 227{ 228 pte_t *ptep, pte; 229 spinlock_t *ptl; 230 swp_entry_t entry; 231 struct page *page; 232 233 ptep = pte_offset_map_lock(mm, pmd, address, &ptl); 234 pte = *ptep; 235 if (!is_swap_pte(pte)) 236 goto out; 237 238 entry = pte_to_swp_entry(pte); 239 if (!is_migration_entry(entry)) 240 goto out; 241 242 page = migration_entry_to_page(entry); 243 244 /* 245 * Once radix-tree replacement of page migration started, page_count 246 * *must* be zero. And, we don't want to call wait_on_page_locked() 247 * against a page without get_page(). 248 * So, we use get_page_unless_zero(), here. Even failed, page fault 249 * will occur again. 250 */ 251 if (!get_page_unless_zero(page)) 252 goto out; 253 pte_unmap_unlock(ptep, ptl); 254 wait_on_page_locked(page); 255 put_page(page); 256 return; 257out: 258 pte_unmap_unlock(ptep, ptl); 259} 260 261/* 262 * Replace the page in the mapping. 263 * 264 * The number of remaining references must be: 265 * 1 for anonymous pages without a mapping 266 * 2 for pages with a mapping 267 * 3 for pages with a mapping and PagePrivate set. 268 */ 269static int migrate_page_move_mapping(struct address_space *mapping, 270 struct page *newpage, struct page *page) 271{ 272 int expected_count; 273 void **pslot; 274 275 if (!mapping) { 276 /* Anonymous page without mapping */ 277 if (page_count(page) != 1) 278 return -EAGAIN; 279 return 0; 280 } 281 282 spin_lock_irq(&mapping->tree_lock); 283 284 pslot = radix_tree_lookup_slot(&mapping->page_tree, 285 page_index(page)); 286 287 expected_count = 2 + !!PagePrivate(page); 288 if (page_count(page) != expected_count || 289 (struct page *)radix_tree_deref_slot(pslot) != page) { 290 spin_unlock_irq(&mapping->tree_lock); 291 return -EAGAIN; 292 } 293 294 if (!page_freeze_refs(page, expected_count)) { 295 spin_unlock_irq(&mapping->tree_lock); 296 return -EAGAIN; 297 } 298 299 /* 300 * Now we know that no one else is looking at the page. 301 */ 302 get_page(newpage); /* add cache reference */ 303#ifdef CONFIG_SWAP 304 if (PageSwapCache(page)) { 305 SetPageSwapCache(newpage); 306 set_page_private(newpage, page_private(page)); 307 } 308#endif 309 310 radix_tree_replace_slot(pslot, newpage); 311 312 page_unfreeze_refs(page, expected_count); 313 /* 314 * Drop cache reference from old page. 315 * We know this isn't the last reference. 316 */ 317 __put_page(page); 318 319 /* 320 * If moved to a different zone then also account 321 * the page for that zone. Other VM counters will be 322 * taken care of when we establish references to the 323 * new page and drop references to the old page. 324 * 325 * Note that anonymous pages are accounted for 326 * via NR_FILE_PAGES and NR_ANON_PAGES if they 327 * are mapped to swap space. 328 */ 329 __dec_zone_page_state(page, NR_FILE_PAGES); 330 __inc_zone_page_state(newpage, NR_FILE_PAGES); 331 332 spin_unlock_irq(&mapping->tree_lock); 333 if (!PageSwapCache(newpage)) 334 mem_cgroup_uncharge_cache_page(page); 335 336 return 0; 337} 338 339/* 340 * Copy the page to its new location 341 */ 342static void migrate_page_copy(struct page *newpage, struct page *page) 343{ 344 copy_highpage(newpage, page); 345 346 if (PageError(page)) 347 SetPageError(newpage); 348 if (PageReferenced(page)) 349 SetPageReferenced(newpage); 350 if (PageUptodate(page)) 351 SetPageUptodate(newpage); 352 if (TestClearPageActive(page)) { 353 VM_BUG_ON(PageUnevictable(page)); 354 SetPageActive(newpage); 355 } else 356 unevictable_migrate_page(newpage, page); 357 if (PageChecked(page)) 358 SetPageChecked(newpage); 359 if (PageMappedToDisk(page)) 360 SetPageMappedToDisk(newpage); 361 362 if (PageDirty(page)) { 363 clear_page_dirty_for_io(page); 364 /* 365 * Want to mark the page and the radix tree as dirty, and 366 * redo the accounting that clear_page_dirty_for_io undid, 367 * but we can't use set_page_dirty because that function 368 * is actually a signal that all of the page has become dirty. 369 * Wheras only part of our page may be dirty. 370 */ 371 __set_page_dirty_nobuffers(newpage); 372 } 373 374 mlock_migrate_page(newpage, page); 375 376#ifdef CONFIG_SWAP 377 ClearPageSwapCache(page); 378#endif 379 ClearPagePrivate(page); 380 set_page_private(page, 0); 381 page->mapping = NULL; 382 383 /* 384 * If any waiters have accumulated on the new page then 385 * wake them up. 386 */ 387 if (PageWriteback(newpage)) 388 end_page_writeback(newpage); 389} 390 391/************************************************************ 392 * Migration functions 393 ***********************************************************/ 394 395/* Always fail migration. Used for mappings that are not movable */ 396int fail_migrate_page(struct address_space *mapping, 397 struct page *newpage, struct page *page) 398{ 399 return -EIO; 400} 401EXPORT_SYMBOL(fail_migrate_page); 402 403/* 404 * Common logic to directly migrate a single page suitable for 405 * pages that do not use PagePrivate. 406 * 407 * Pages are locked upon entry and exit. 408 */ 409int migrate_page(struct address_space *mapping, 410 struct page *newpage, struct page *page) 411{ 412 int rc; 413 414 BUG_ON(PageWriteback(page)); /* Writeback must be complete */ 415 416 rc = migrate_page_move_mapping(mapping, newpage, page); 417 418 if (rc) 419 return rc; 420 421 migrate_page_copy(newpage, page); 422 return 0; 423} 424EXPORT_SYMBOL(migrate_page); 425 426#ifdef CONFIG_BLOCK 427/* 428 * Migration function for pages with buffers. This function can only be used 429 * if the underlying filesystem guarantees that no other references to "page" 430 * exist. 431 */ 432int buffer_migrate_page(struct address_space *mapping, 433 struct page *newpage, struct page *page) 434{ 435 struct buffer_head *bh, *head; 436 int rc; 437 438 if (!page_has_buffers(page)) 439 return migrate_page(mapping, newpage, page); 440 441 head = page_buffers(page); 442 443 rc = migrate_page_move_mapping(mapping, newpage, page); 444 445 if (rc) 446 return rc; 447 448 bh = head; 449 do { 450 get_bh(bh); 451 lock_buffer(bh); 452 bh = bh->b_this_page; 453 454 } while (bh != head); 455 456 ClearPagePrivate(page); 457 set_page_private(newpage, page_private(page)); 458 set_page_private(page, 0); 459 put_page(page); 460 get_page(newpage); 461 462 bh = head; 463 do { 464 set_bh_page(bh, newpage, bh_offset(bh)); 465 bh = bh->b_this_page; 466 467 } while (bh != head); 468 469 SetPagePrivate(newpage); 470 471 migrate_page_copy(newpage, page); 472 473 bh = head; 474 do { 475 unlock_buffer(bh); 476 put_bh(bh); 477 bh = bh->b_this_page; 478 479 } while (bh != head); 480 481 return 0; 482} 483EXPORT_SYMBOL(buffer_migrate_page); 484#endif 485 486/* 487 * Writeback a page to clean the dirty state 488 */ 489static int writeout(struct address_space *mapping, struct page *page) 490{ 491 struct writeback_control wbc = { 492 .sync_mode = WB_SYNC_NONE, 493 .nr_to_write = 1, 494 .range_start = 0, 495 .range_end = LLONG_MAX, 496 .nonblocking = 1, 497 .for_reclaim = 1 498 }; 499 int rc; 500 501 if (!mapping->a_ops->writepage) 502 /* No write method for the address space */ 503 return -EINVAL; 504 505 if (!clear_page_dirty_for_io(page)) 506 /* Someone else already triggered a write */ 507 return -EAGAIN; 508 509 /* 510 * A dirty page may imply that the underlying filesystem has 511 * the page on some queue. So the page must be clean for 512 * migration. Writeout may mean we loose the lock and the 513 * page state is no longer what we checked for earlier. 514 * At this point we know that the migration attempt cannot 515 * be successful. 516 */ 517 remove_migration_ptes(page, page); 518 519 rc = mapping->a_ops->writepage(page, &wbc); 520 if (rc < 0) 521 /* I/O Error writing */ 522 return -EIO; 523 524 if (rc != AOP_WRITEPAGE_ACTIVATE) 525 /* unlocked. Relock */ 526 lock_page(page); 527 528 return -EAGAIN; 529} 530 531/* 532 * Default handling if a filesystem does not provide a migration function. 533 */ 534static int fallback_migrate_page(struct address_space *mapping, 535 struct page *newpage, struct page *page) 536{ 537 if (PageDirty(page)) 538 return writeout(mapping, page); 539 540 /* 541 * Buffers may be managed in a filesystem specific way. 542 * We must have no buffers or drop them. 543 */ 544 if (PagePrivate(page) && 545 !try_to_release_page(page, GFP_KERNEL)) 546 return -EAGAIN; 547 548 return migrate_page(mapping, newpage, page); 549} 550 551/* 552 * Move a page to a newly allocated page 553 * The page is locked and all ptes have been successfully removed. 554 * 555 * The new page will have replaced the old page if this function 556 * is successful. 557 * 558 * Return value: 559 * < 0 - error code 560 * == 0 - success 561 */ 562static int move_to_new_page(struct page *newpage, struct page *page) 563{ 564 struct address_space *mapping; 565 int rc; 566 567 /* 568 * Block others from accessing the page when we get around to 569 * establishing additional references. We are the only one 570 * holding a reference to the new page at this point. 571 */ 572 if (!trylock_page(newpage)) 573 BUG(); 574 575 /* Prepare mapping for the new page.*/ 576 newpage->index = page->index; 577 newpage->mapping = page->mapping; 578 if (PageSwapBacked(page)) 579 SetPageSwapBacked(newpage); 580 581 mapping = page_mapping(page); 582 if (!mapping) 583 rc = migrate_page(mapping, newpage, page); 584 else if (mapping->a_ops->migratepage) 585 /* 586 * Most pages have a mapping and most filesystems 587 * should provide a migration function. Anonymous 588 * pages are part of swap space which also has its 589 * own migration function. This is the most common 590 * path for page migration. 591 */ 592 rc = mapping->a_ops->migratepage(mapping, 593 newpage, page); 594 else 595 rc = fallback_migrate_page(mapping, newpage, page); 596 597 if (!rc) { 598 remove_migration_ptes(page, newpage); 599 } else 600 newpage->mapping = NULL; 601 602 unlock_page(newpage); 603 604 return rc; 605} 606 607/* 608 * Obtain the lock on page, remove all ptes and migrate the page 609 * to the newly allocated page in newpage. 610 */ 611static int unmap_and_move(new_page_t get_new_page, unsigned long private, 612 struct page *page, int force) 613{ 614 int rc = 0; 615 int *result = NULL; 616 struct page *newpage = get_new_page(page, private, &result); 617 int rcu_locked = 0; 618 int charge = 0; 619 620 if (!newpage) 621 return -ENOMEM; 622 623 if (page_count(page) == 1) { 624 /* page was freed from under us. So we are done. */ 625 goto move_newpage; 626 } 627 628 charge = mem_cgroup_prepare_migration(page, newpage); 629 if (charge == -ENOMEM) { 630 rc = -ENOMEM; 631 goto move_newpage; 632 } 633 /* prepare cgroup just returns 0 or -ENOMEM */ 634 BUG_ON(charge); 635 636 rc = -EAGAIN; 637 if (!trylock_page(page)) { 638 if (!force) 639 goto move_newpage; 640 lock_page(page); 641 } 642 643 if (PageWriteback(page)) { 644 if (!force) 645 goto unlock; 646 wait_on_page_writeback(page); 647 } 648 /* 649 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, 650 * we cannot notice that anon_vma is freed while we migrates a page. 651 * This rcu_read_lock() delays freeing anon_vma pointer until the end 652 * of migration. File cache pages are no problem because of page_lock() 653 * File Caches may use write_page() or lock_page() in migration, then, 654 * just care Anon page here. 655 */ 656 if (PageAnon(page)) { 657 rcu_read_lock(); 658 rcu_locked = 1; 659 } 660 661 /* 662 * Corner case handling: 663 * 1. When a new swap-cache page is read into, it is added to the LRU 664 * and treated as swapcache but it has no rmap yet. 665 * Calling try_to_unmap() against a page->mapping==NULL page will 666 * trigger a BUG. So handle it here. 667 * 2. An orphaned page (see truncate_complete_page) might have 668 * fs-private metadata. The page can be picked up due to memory 669 * offlining. Everywhere else except page reclaim, the page is 670 * invisible to the vm, so the page can not be migrated. So try to 671 * free the metadata, so the page can be freed. 672 */ 673 if (!page->mapping) { 674 if (!PageAnon(page) && PagePrivate(page)) { 675 /* 676 * Go direct to try_to_free_buffers() here because 677 * a) that's what try_to_release_page() would do anyway 678 * b) we may be under rcu_read_lock() here, so we can't 679 * use GFP_KERNEL which is what try_to_release_page() 680 * needs to be effective. 681 */ 682 try_to_free_buffers(page); 683 } 684 goto rcu_unlock; 685 } 686 687 /* Establish migration ptes or remove ptes */ 688 try_to_unmap(page, 1); 689 690 if (!page_mapped(page)) 691 rc = move_to_new_page(newpage, page); 692 693 if (rc) 694 remove_migration_ptes(page, page); 695rcu_unlock: 696 if (rcu_locked) 697 rcu_read_unlock(); 698 699unlock: 700 unlock_page(page); 701 702 if (rc != -EAGAIN) { 703 /* 704 * A page that has been migrated has all references 705 * removed and will be freed. A page that has not been 706 * migrated will have kepts its references and be 707 * restored. 708 */ 709 list_del(&page->lru); 710 putback_lru_page(page); 711 } 712 713move_newpage: 714 if (!charge) 715 mem_cgroup_end_migration(newpage); 716 717 /* 718 * Move the new page to the LRU. If migration was not successful 719 * then this will free the page. 720 */ 721 putback_lru_page(newpage); 722 723 if (result) { 724 if (rc) 725 *result = rc; 726 else 727 *result = page_to_nid(newpage); 728 } 729 return rc; 730} 731 732/* 733 * migrate_pages 734 * 735 * The function takes one list of pages to migrate and a function 736 * that determines from the page to be migrated and the private data 737 * the target of the move and allocates the page. 738 * 739 * The function returns after 10 attempts or if no pages 740 * are movable anymore because to has become empty 741 * or no retryable pages exist anymore. All pages will be 742 * returned to the LRU or freed. 743 * 744 * Return: Number of pages not migrated or error code. 745 */ 746int migrate_pages(struct list_head *from, 747 new_page_t get_new_page, unsigned long private) 748{ 749 int retry = 1; 750 int nr_failed = 0; 751 int pass = 0; 752 struct page *page; 753 struct page *page2; 754 int swapwrite = current->flags & PF_SWAPWRITE; 755 int rc; 756 757 if (!swapwrite) 758 current->flags |= PF_SWAPWRITE; 759 760 for(pass = 0; pass < 10 && retry; pass++) { 761 retry = 0; 762 763 list_for_each_entry_safe(page, page2, from, lru) { 764 cond_resched(); 765 766 rc = unmap_and_move(get_new_page, private, 767 page, pass > 2); 768 769 switch(rc) { 770 case -ENOMEM: 771 goto out; 772 case -EAGAIN: 773 retry++; 774 break; 775 case 0: 776 break; 777 default: 778 /* Permanent failure */ 779 nr_failed++; 780 break; 781 } 782 } 783 } 784 rc = 0; 785out: 786 if (!swapwrite) 787 current->flags &= ~PF_SWAPWRITE; 788 789 putback_lru_pages(from); 790 791 if (rc) 792 return rc; 793 794 return nr_failed + retry; 795} 796 797#ifdef CONFIG_NUMA 798/* 799 * Move a list of individual pages 800 */ 801struct page_to_node { 802 unsigned long addr; 803 struct page *page; 804 int node; 805 int status; 806}; 807 808static struct page *new_page_node(struct page *p, unsigned long private, 809 int **result) 810{ 811 struct page_to_node *pm = (struct page_to_node *)private; 812 813 while (pm->node != MAX_NUMNODES && pm->page != p) 814 pm++; 815 816 if (pm->node == MAX_NUMNODES) 817 return NULL; 818 819 *result = &pm->status; 820 821 return alloc_pages_node(pm->node, 822 GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); 823} 824 825/* 826 * Move a set of pages as indicated in the pm array. The addr 827 * field must be set to the virtual address of the page to be moved 828 * and the node number must contain a valid target node. 829 */ 830static int do_move_pages(struct mm_struct *mm, struct page_to_node *pm, 831 int migrate_all) 832{ 833 int err; 834 struct page_to_node *pp; 835 LIST_HEAD(pagelist); 836 837 down_read(&mm->mmap_sem); 838 839 /* 840 * Build a list of pages to migrate 841 */ 842 migrate_prep(); 843 for (pp = pm; pp->node != MAX_NUMNODES; pp++) { 844 struct vm_area_struct *vma; 845 struct page *page; 846 847 /* 848 * A valid page pointer that will not match any of the 849 * pages that will be moved. 850 */ 851 pp->page = ZERO_PAGE(0); 852 853 err = -EFAULT; 854 vma = find_vma(mm, pp->addr); 855 if (!vma || !vma_migratable(vma)) 856 goto set_status; 857 858 page = follow_page(vma, pp->addr, FOLL_GET); 859 860 err = PTR_ERR(page); 861 if (IS_ERR(page)) 862 goto set_status; 863 864 err = -ENOENT; 865 if (!page) 866 goto set_status; 867 868 if (PageReserved(page)) /* Check for zero page */ 869 goto put_and_set; 870 871 pp->page = page; 872 err = page_to_nid(page); 873 874 if (err == pp->node) 875 /* 876 * Node already in the right place 877 */ 878 goto put_and_set; 879 880 err = -EACCES; 881 if (page_mapcount(page) > 1 && 882 !migrate_all) 883 goto put_and_set; 884 885 err = isolate_lru_page(page); 886 if (!err) 887 list_add_tail(&page->lru, &pagelist); 888put_and_set: 889 /* 890 * Either remove the duplicate refcount from 891 * isolate_lru_page() or drop the page ref if it was 892 * not isolated. 893 */ 894 put_page(page); 895set_status: 896 pp->status = err; 897 } 898 899 err = 0; 900 if (!list_empty(&pagelist)) 901 err = migrate_pages(&pagelist, new_page_node, 902 (unsigned long)pm); 903 904 up_read(&mm->mmap_sem); 905 return err; 906} 907 908/* 909 * Determine the nodes of a list of pages. The addr in the pm array 910 * must have been set to the virtual address of which we want to determine 911 * the node number. 912 */ 913static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm) 914{ 915 down_read(&mm->mmap_sem); 916 917 for ( ; pm->node != MAX_NUMNODES; pm++) { 918 struct vm_area_struct *vma; 919 struct page *page; 920 int err; 921 922 err = -EFAULT; 923 vma = find_vma(mm, pm->addr); 924 if (!vma) 925 goto set_status; 926 927 page = follow_page(vma, pm->addr, 0); 928 929 err = PTR_ERR(page); 930 if (IS_ERR(page)) 931 goto set_status; 932 933 err = -ENOENT; 934 /* Use PageReserved to check for zero page */ 935 if (!page || PageReserved(page)) 936 goto set_status; 937 938 err = page_to_nid(page); 939set_status: 940 pm->status = err; 941 } 942 943 up_read(&mm->mmap_sem); 944 return 0; 945} 946 947/* 948 * Move a list of pages in the address space of the currently executing 949 * process. 950 */ 951asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages, 952 const void __user * __user *pages, 953 const int __user *nodes, 954 int __user *status, int flags) 955{ 956 int err = 0; 957 int i; 958 struct task_struct *task; 959 nodemask_t task_nodes; 960 struct mm_struct *mm; 961 struct page_to_node *pm = NULL; 962 963 /* Check flags */ 964 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) 965 return -EINVAL; 966 967 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) 968 return -EPERM; 969 970 /* Find the mm_struct */ 971 read_lock(&tasklist_lock); 972 task = pid ? find_task_by_vpid(pid) : current; 973 if (!task) { 974 read_unlock(&tasklist_lock); 975 return -ESRCH; 976 } 977 mm = get_task_mm(task); 978 read_unlock(&tasklist_lock); 979 980 if (!mm) 981 return -EINVAL; 982 983 /* 984 * Check if this process has the right to modify the specified 985 * process. The right exists if the process has administrative 986 * capabilities, superuser privileges or the same 987 * userid as the target process. 988 */ 989 if ((current->euid != task->suid) && (current->euid != task->uid) && 990 (current->uid != task->suid) && (current->uid != task->uid) && 991 !capable(CAP_SYS_NICE)) { 992 err = -EPERM; 993 goto out2; 994 } 995 996 err = security_task_movememory(task); 997 if (err) 998 goto out2; 999 1000 1001 task_nodes = cpuset_mems_allowed(task); 1002 1003 /* Limit nr_pages so that the multiplication may not overflow */ 1004 if (nr_pages >= ULONG_MAX / sizeof(struct page_to_node) - 1) { 1005 err = -E2BIG; 1006 goto out2; 1007 } 1008 1009 pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node)); 1010 if (!pm) { 1011 err = -ENOMEM; 1012 goto out2; 1013 } 1014 1015 /* 1016 * Get parameters from user space and initialize the pm 1017 * array. Return various errors if the user did something wrong. 1018 */ 1019 for (i = 0; i < nr_pages; i++) { 1020 const void __user *p; 1021 1022 err = -EFAULT; 1023 if (get_user(p, pages + i)) 1024 goto out; 1025 1026 pm[i].addr = (unsigned long)p; 1027 if (nodes) { 1028 int node; 1029 1030 if (get_user(node, nodes + i)) 1031 goto out; 1032 1033 err = -ENODEV; 1034 if (!node_state(node, N_HIGH_MEMORY)) 1035 goto out; 1036 1037 err = -EACCES; 1038 if (!node_isset(node, task_nodes)) 1039 goto out; 1040 1041 pm[i].node = node; 1042 } else 1043 pm[i].node = 0; /* anything to not match MAX_NUMNODES */ 1044 } 1045 /* End marker */ 1046 pm[nr_pages].node = MAX_NUMNODES; 1047 1048 if (nodes) 1049 err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL); 1050 else 1051 err = do_pages_stat(mm, pm); 1052 1053 if (err >= 0) 1054 /* Return status information */ 1055 for (i = 0; i < nr_pages; i++) 1056 if (put_user(pm[i].status, status + i)) 1057 err = -EFAULT; 1058 1059out: 1060 vfree(pm); 1061out2: 1062 mmput(mm); 1063 return err; 1064} 1065 1066/* 1067 * Call migration functions in the vma_ops that may prepare 1068 * memory in a vm for migration. migration functions may perform 1069 * the migration for vmas that do not have an underlying page struct. 1070 */ 1071int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, 1072 const nodemask_t *from, unsigned long flags) 1073{ 1074 struct vm_area_struct *vma; 1075 int err = 0; 1076 1077 for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) { 1078 if (vma->vm_ops && vma->vm_ops->migrate) { 1079 err = vma->vm_ops->migrate(vma, to, from, flags); 1080 if (err) 1081 break; 1082 } 1083 } 1084 return err; 1085} 1086#endif 1087