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