mm/migrate.c

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