ClabureDB: Classified Bug-Reports Database

   /*
    * Memory Migration functionality - linux/mm/migration.c
    *
    * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
    *
    * Page migration was first developed in the context of the memory hotplug
    * project. The main authors of the migration code are:
    *
    * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
   * Hirokazu Takahashi <taka@valinux.co.jp>
   * Dave Hansen <haveblue@us.ibm.com>
   * Christoph Lameter
   */
  
  #include <linux/migrate.h>
  #include <linux/module.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/pagemap.h>
  #include <linux/buffer_head.h>
  #include <linux/mm_inline.h>
  #include <linux/nsproxy.h>
  #include <linux/pagevec.h>
  #include <linux/rmap.h>
  #include <linux/topology.h>
  #include <linux/cpu.h>
  #include <linux/cpuset.h>
  #include <linux/writeback.h>
  #include <linux/mempolicy.h>
  #include <linux/vmalloc.h>
  #include <linux/security.h>
  #include <linux/memcontrol.h>
  #include <linux/syscalls.h>
  
  #include "internal.h"
  
  #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
  
  /*
   * migrate_prep() needs to be called before we start compiling a list of pages
   * to be migrated using isolate_lru_page().
   */
  int migrate_prep(void)
  {
          /*
           * Clear the LRU lists so pages can be isolated.
           * Note that pages may be moved off the LRU after we have
           * drained them. Those pages will fail to migrate like other
           * pages that may be busy.
           */
          lru_add_drain_all();
  
          return 0;
  }
  
  /*
   * Add isolated pages on the list back to the LRU under page lock
   * to avoid leaking evictable pages back onto unevictable list.
   *
   * returns the number of pages put back.
   */
  int putback_lru_pages(struct list_head *l)
  {
          struct page *page;
          struct page *page2;
          int count = 0;
  
          list_for_each_entry_safe(page, page2, l, lru) {
                  list_del(&page->lru);
                  putback_lru_page(page);
                  count++;
          }
          return count;
  }
  
  /*
   * Restore a potential migration pte to a working pte entry
   */
  static void remove_migration_pte(struct vm_area_struct *vma,
                  struct page *old, struct page *new)
  {
          struct mm_struct *mm = vma->vm_mm;
          swp_entry_t entry;
           pgd_t *pgd;
           pud_t *pud;
           pmd_t *pmd;
          pte_t *ptep, pte;
           spinlock_t *ptl;
          unsigned long addr = page_address_in_vma(new, vma);
  
          if (addr == -EFAULT)
                  return;
  
           pgd = pgd_offset(mm, addr);
          if (!pgd_present(*pgd))
                  return;
  
          pud = pud_offset(pgd, addr);
          if (!pud_present(*pud))
                 return;
 
         pmd = pmd_offset(pud, addr);
         if (!pmd_present(*pmd))
                 return;
 
         ptep = pte_offset_map(pmd, addr);
 
         if (!is_swap_pte(*ptep)) {
                 pte_unmap(ptep);
                  return;
          }
 
          ptl = pte_lockptr(mm, pmd);
          spin_lock(ptl);
         pte = *ptep;
         if (!is_swap_pte(pte))
                 goto out;
 
         entry = pte_to_swp_entry(pte);
 
         if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)
                 goto out;
 
         /*
          * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge.
          * Failure is not an option here: we're now expected to remove every
          * migration pte, and will cause crashes otherwise.  Normally this
          * is not an issue: mem_cgroup_prepare_migration bumped up the old
          * page_cgroup count for safety, that's now attached to the new page,
          * so this charge should just be another incrementation of the count,
          * to keep in balance with rmap.c's mem_cgroup_uncharging.  But if
          * there's been a force_empty, those reference counts may no longer
          * be reliable, and this charge can actually fail: oh well, we don't
          * make the situation any worse by proceeding as if it had succeeded.
          */
         mem_cgroup_charge(new, mm, GFP_ATOMIC);
 
         get_page(new);
         pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
         if (is_write_migration_entry(entry))
                 pte = pte_mkwrite(pte);
         flush_cache_page(vma, addr, pte_pfn(pte));
         set_pte_at(mm, addr, ptep, pte);
 
         if (PageAnon(new))
                 page_add_anon_rmap(new, vma, addr);
         else
                 page_add_file_rmap(new);
 
         /* No need to invalidate - it was non-present before */
         update_mmu_cache(vma, addr, pte);
 
 out:
         pte_unmap_unlock(ptep, ptl);
 }
 
 /*
  * Note that remove_file_migration_ptes will only work on regular mappings,
  * Nonlinear mappings do not use migration entries.
  */
 static void remove_file_migration_ptes(struct page *old, struct page *new)
 {
         struct vm_area_struct *vma;
         struct address_space *mapping = page_mapping(new);
         struct prio_tree_iter iter;
         pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 
         if (!mapping)
                 return;
 
         spin_lock(&mapping->i_mmap_lock);
 
         vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
                 remove_migration_pte(vma, old, new);
 
         spin_unlock(&mapping->i_mmap_lock);
 }
 
 /*
  * Must hold mmap_sem lock on at least one of the vmas containing
  * the page so that the anon_vma cannot vanish.
  */
 static void remove_anon_migration_ptes(struct page *old, struct page *new)
 {
         struct anon_vma *anon_vma;
         struct vm_area_struct *vma;
         unsigned long mapping;
 
         mapping = (unsigned long)new->mapping;
 
         if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
                 return;
 
         /*
          * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
          */
         anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
         spin_lock(&anon_vma->lock);
 
         list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
                 remove_migration_pte(vma, old, new);
 
         spin_unlock(&anon_vma->lock);
 }
 
 /*
  * Get rid of all migration entries and replace them by
  * references to the indicated page.
  */
 static void remove_migration_ptes(struct page *old, struct page *new)
 {
         if (PageAnon(new))
                 remove_anon_migration_ptes(old, new);
         else
                 remove_file_migration_ptes(old, new);
 }
 
 /*
  * Something used the pte of a page under migration. We need to
  * get to the page and wait until migration is finished.
  * When we return from this function the fault will be retried.
  *
  * This function is called from do_swap_page().
  */
 void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
                                 unsigned long address)
 {
         pte_t *ptep, pte;
         spinlock_t *ptl;
         swp_entry_t entry;
         struct page *page;
 
         ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
         pte = *ptep;
         if (!is_swap_pte(pte))
                 goto out;
 
         entry = pte_to_swp_entry(pte);
         if (!is_migration_entry(entry))
                 goto out;
 
         page = migration_entry_to_page(entry);
 
         /*
          * Once radix-tree replacement of page migration started, page_count
          * *must* be zero. And, we don't want to call wait_on_page_locked()
          * against a page without get_page().
          * So, we use get_page_unless_zero(), here. Even failed, page fault
          * will occur again.
          */
         if (!get_page_unless_zero(page))
                 goto out;
         pte_unmap_unlock(ptep, ptl);
         wait_on_page_locked(page);
         put_page(page);
         return;
 out:
         pte_unmap_unlock(ptep, ptl);
 }
 
 /*
  * Replace the page in the mapping.
  *
  * The number of remaining references must be:
  * 1 for anonymous pages without a mapping
  * 2 for pages with a mapping
  * 3 for pages with a mapping and PagePrivate set.
  */
 static int migrate_page_move_mapping(struct address_space *mapping,
                 struct page *newpage, struct page *page)
 {
         int expected_count;
         void **pslot;
 
         if (!mapping) {
                 /* Anonymous page without mapping */
                 if (page_count(page) != 1)
                         return -EAGAIN;
                 return 0;
         }
 
         spin_lock_irq(&mapping->tree_lock);
 
         pslot = radix_tree_lookup_slot(&mapping->page_tree,
                                          page_index(page));
 
         expected_count = 2 + !!PagePrivate(page);
         if (page_count(page) != expected_count ||
                         (struct page *)radix_tree_deref_slot(pslot) != page) {
                 spin_unlock_irq(&mapping->tree_lock);
                 return -EAGAIN;
         }
 
         if (!page_freeze_refs(page, expected_count)) {
                 spin_unlock_irq(&mapping->tree_lock);
                 return -EAGAIN;
         }
 
         /*
          * Now we know that no one else is looking at the page.
          */
         get_page(newpage);        /* add cache reference */
 #ifdef CONFIG_SWAP
         if (PageSwapCache(page)) {
                 SetPageSwapCache(newpage);
                 set_page_private(newpage, page_private(page));
         }
 #endif
 
         radix_tree_replace_slot(pslot, newpage);
 
         page_unfreeze_refs(page, expected_count);
         /*
          * Drop cache reference from old page.
          * We know this isn't the last reference.
          */
         __put_page(page);
 
         /*
          * If moved to a different zone then also account
          * the page for that zone. Other VM counters will be
          * taken care of when we establish references to the
          * new page and drop references to the old page.
          *
          * Note that anonymous pages are accounted for
          * via NR_FILE_PAGES and NR_ANON_PAGES if they
          * are mapped to swap space.
          */
         __dec_zone_page_state(page, NR_FILE_PAGES);
         __inc_zone_page_state(newpage, NR_FILE_PAGES);
 
         spin_unlock_irq(&mapping->tree_lock);
 
         return 0;
 }
 
 /*
  * Copy the page to its new location
  */
 static void migrate_page_copy(struct page *newpage, struct page *page)
 {
         int anon;
 
         copy_highpage(newpage, page);
 
         if (PageError(page))
                 SetPageError(newpage);
         if (PageReferenced(page))
                 SetPageReferenced(newpage);
         if (PageUptodate(page))
                 SetPageUptodate(newpage);
         if (TestClearPageActive(page)) {
                 VM_BUG_ON(PageUnevictable(page));
                 SetPageActive(newpage);
         } else
                 unevictable_migrate_page(newpage, page);
         if (PageChecked(page))
                 SetPageChecked(newpage);
         if (PageMappedToDisk(page))
                 SetPageMappedToDisk(newpage);
 
         if (PageDirty(page)) {
                 clear_page_dirty_for_io(page);
                 /*
                  * Want to mark the page and the radix tree as dirty, and
                  * redo the accounting that clear_page_dirty_for_io undid,
                  * but we can't use set_page_dirty because that function
                  * is actually a signal that all of the page has become dirty.
                  * Wheras only part of our page may be dirty.
                  */
                 __set_page_dirty_nobuffers(newpage);
          }
 
         mlock_migrate_page(newpage, page);
 
 #ifdef CONFIG_SWAP
         ClearPageSwapCache(page);
 #endif
         ClearPagePrivate(page);
         set_page_private(page, 0);
         /* page->mapping contains a flag for PageAnon() */
         anon = PageAnon(page);
         page->mapping = NULL;
 
         if (!anon) /* This page was removed from radix-tree. */
                 mem_cgroup_uncharge_cache_page(page);
 
         /*
          * If any waiters have accumulated on the new page then
          * wake them up.
          */
         if (PageWriteback(newpage))
                 end_page_writeback(newpage);
 }
 
 /************************************************************
  *                    Migration functions
  ***********************************************************/
 
 /* Always fail migration. Used for mappings that are not movable */
 int fail_migrate_page(struct address_space *mapping,
                         struct page *newpage, struct page *page)
 {
         return -EIO;
 }
 EXPORT_SYMBOL(fail_migrate_page);
 
 /*
  * Common logic to directly migrate a single page suitable for
  * pages that do not use PagePrivate.
  *
  * Pages are locked upon entry and exit.
  */
 int migrate_page(struct address_space *mapping,
                 struct page *newpage, struct page *page)
 {
         int rc;
 
         BUG_ON(PageWriteback(page));        /* Writeback must be complete */
 
         rc = migrate_page_move_mapping(mapping, newpage, page);
 
         if (rc)
                 return rc;
 
         migrate_page_copy(newpage, page);
         return 0;
 }
 EXPORT_SYMBOL(migrate_page);
 
 #ifdef CONFIG_BLOCK
 /*
  * Migration function for pages with buffers. This function can only be used
  * if the underlying filesystem guarantees that no other references to "page"
  * exist.
  */
 int buffer_migrate_page(struct address_space *mapping,
                 struct page *newpage, struct page *page)
 {
         struct buffer_head *bh, *head;
         int rc;
 
         if (!page_has_buffers(page))
                 return migrate_page(mapping, newpage, page);
 
         head = page_buffers(page);
 
         rc = migrate_page_move_mapping(mapping, newpage, page);
 
         if (rc)
                 return rc;
 
         bh = head;
         do {
                 get_bh(bh);
                 lock_buffer(bh);
                 bh = bh->b_this_page;
 
         } while (bh != head);
 
         ClearPagePrivate(page);
         set_page_private(newpage, page_private(page));
         set_page_private(page, 0);
         put_page(page);
         get_page(newpage);
 
         bh = head;
         do {
                 set_bh_page(bh, newpage, bh_offset(bh));
                 bh = bh->b_this_page;
 
         } while (bh != head);
 
         SetPagePrivate(newpage);
 
         migrate_page_copy(newpage, page);
 
         bh = head;
         do {
                 unlock_buffer(bh);
                  put_bh(bh);
                 bh = bh->b_this_page;
 
         } while (bh != head);
 
         return 0;
 }
 EXPORT_SYMBOL(buffer_migrate_page);
 #endif
 
 /*
  * Writeback a page to clean the dirty state
  */
 static int writeout(struct address_space *mapping, struct page *page)
 {
         struct writeback_control wbc = {
                 .sync_mode = WB_SYNC_NONE,
                 .nr_to_write = 1,
                 .range_start = 0,
                 .range_end = LLONG_MAX,
                 .nonblocking = 1,
                 .for_reclaim = 1
         };
         int rc;
 
         if (!mapping->a_ops->writepage)
                 /* No write method for the address space */
                 return -EINVAL;
 
         if (!clear_page_dirty_for_io(page))
                 /* Someone else already triggered a write */
                 return -EAGAIN;
 
         /*
          * A dirty page may imply that the underlying filesystem has
          * the page on some queue. So the page must be clean for
          * migration. Writeout may mean we loose the lock and the
          * page state is no longer what we checked for earlier.
          * At this point we know that the migration attempt cannot
          * be successful.
          */
         remove_migration_ptes(page, page);
 
         rc = mapping->a_ops->writepage(page, &wbc);
 
         if (rc != AOP_WRITEPAGE_ACTIVATE)
                 /* unlocked. Relock */
                 lock_page(page);
 
         return (rc < 0) ? -EIO : -EAGAIN;
 }
 
 /*
  * Default handling if a filesystem does not provide a migration function.
  */
 static int fallback_migrate_page(struct address_space *mapping,
         struct page *newpage, struct page *page)
 {
         if (PageDirty(page))
                 return writeout(mapping, page);
 
         /*
          * Buffers may be managed in a filesystem specific way.
          * We must have no buffers or drop them.
          */
         if (PagePrivate(page) &&
             !try_to_release_page(page, GFP_KERNEL))
                 return -EAGAIN;
 
         return migrate_page(mapping, newpage, page);
 }
 
 /*
  * Move a page to a newly allocated page
  * The page is locked and all ptes have been successfully removed.
  *
  * The new page will have replaced the old page if this function
  * is successful.
  *
  * Return value:
  *   < 0 - error code
  *  == 0 - success
  */
 static int move_to_new_page(struct page *newpage, struct page *page)
 {
         struct address_space *mapping;
         int rc;
 
         /*
          * Block others from accessing the page when we get around to
          * establishing additional references. We are the only one
          * holding a reference to the new page at this point.
          */
         if (!trylock_page(newpage))
                 BUG();
 
         /* Prepare mapping for the new page.*/
         newpage->index = page->index;
         newpage->mapping = page->mapping;
         if (PageSwapBacked(page))
                 SetPageSwapBacked(newpage);
 
         mapping = page_mapping(page);
         if (!mapping)
                 rc = migrate_page(mapping, newpage, page);
         else if (mapping->a_ops->migratepage)
                 /*
                  * Most pages have a mapping and most filesystems
                  * should provide a migration function. Anonymous
                  * pages are part of swap space which also has its
                  * own migration function. This is the most common
                  * path for page migration.
                  */
                 rc = mapping->a_ops->migratepage(mapping,
                                                 newpage, page);
         else
                 rc = fallback_migrate_page(mapping, newpage, page);
 
         if (!rc) {
                 remove_migration_ptes(page, newpage);
         } else
                 newpage->mapping = NULL;
 
         unlock_page(newpage);
 
         return rc;
 }
 
 /*
  * Obtain the lock on page, remove all ptes and migrate the page
  * to the newly allocated page in newpage.
  */
 static int unmap_and_move(new_page_t get_new_page, unsigned long private,
                         struct page *page, int force)
 {
         int rc = 0;
         int *result = NULL;
         struct page *newpage = get_new_page(page, private, &result);
         int rcu_locked = 0;
         int charge = 0;
 
         if (!newpage)
                 return -ENOMEM;
 
         if (page_count(page) == 1) {
                 /* page was freed from under us. So we are done. */
                 goto move_newpage;
         }
 
         charge = mem_cgroup_prepare_migration(page, newpage);
         if (charge == -ENOMEM) {
                 rc = -ENOMEM;
                 goto move_newpage;
         }
         /* prepare cgroup just returns 0 or -ENOMEM */
         BUG_ON(charge);
 
         rc = -EAGAIN;
         if (!trylock_page(page)) {
                 if (!force)
                         goto move_newpage;
                 lock_page(page);
         }
 
         if (PageWriteback(page)) {
                 if (!force)
                         goto unlock;
                 wait_on_page_writeback(page);
         }
         /*
          * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
          * we cannot notice that anon_vma is freed while we migrates a page.
          * This rcu_read_lock() delays freeing anon_vma pointer until the end
          * of migration. File cache pages are no problem because of page_lock()
          * File Caches may use write_page() or lock_page() in migration, then,
          * just care Anon page here.
          */
         if (PageAnon(page)) {
                 rcu_read_lock();
                 rcu_locked = 1;
         }
 
         /*
          * Corner case handling:
          * 1. When a new swap-cache page is read into, it is added to the LRU
          * and treated as swapcache but it has no rmap yet.
          * Calling try_to_unmap() against a page->mapping==NULL page will
          * trigger a BUG.  So handle it here.
          * 2. An orphaned page (see truncate_complete_page) might have
          * fs-private metadata. The page can be picked up due to memory
          * offlining.  Everywhere else except page reclaim, the page is
          * invisible to the vm, so the page can not be migrated.  So try to
          * free the metadata, so the page can be freed.
          */
         if (!page->mapping) {
                 if (!PageAnon(page) && PagePrivate(page)) {
                         /*
                          * Go direct to try_to_free_buffers() here because
                          * a) that's what try_to_release_page() would do anyway
                          * b) we may be under rcu_read_lock() here, so we can't
                          *    use GFP_KERNEL which is what try_to_release_page()
                          *    needs to be effective.
                          */
                         try_to_free_buffers(page);
                 }
                 goto rcu_unlock;
         }
 
         /* Establish migration ptes or remove ptes */
         try_to_unmap(page, 1);
 
         if (!page_mapped(page))
                 rc = move_to_new_page(newpage, page);
 
         if (rc)
                 remove_migration_ptes(page, page);
 rcu_unlock:
         if (rcu_locked)
                 rcu_read_unlock();
 
 unlock:
         unlock_page(page);
 
         if (rc != -EAGAIN) {
                  /*
                   * A page that has been migrated has all references
                   * removed and will be freed. A page that has not been
                   * migrated will have kepts its references and be
                   * restored.
                   */
                  list_del(&page->lru);
                 putback_lru_page(page);
         }
 
 move_newpage:
         if (!charge)
                 mem_cgroup_end_migration(newpage);
 
         /*
          * Move the new page to the LRU. If migration was not successful
          * then this will free the page.
          */
         putback_lru_page(newpage);
 
         if (result) {
                 if (rc)
                         *result = rc;
                 else
                         *result = page_to_nid(newpage);
         }
         return rc;
 }
 
 /*
  * migrate_pages
  *
  * The function takes one list of pages to migrate and a function
  * that determines from the page to be migrated and the private data
  * the target of the move and allocates the page.
  *
  * The function returns after 10 attempts or if no pages
  * are movable anymore because to has become empty
  * or no retryable pages exist anymore. All pages will be
  * returned to the LRU or freed.
  *
  * Return: Number of pages not migrated or error code.
  */
 int migrate_pages(struct list_head *from,
                 new_page_t get_new_page, unsigned long private)
 {
         int retry = 1;
         int nr_failed = 0;
         int pass = 0;
         struct page *page;
         struct page *page2;
         int swapwrite = current->flags & PF_SWAPWRITE;
         int rc;
 
         if (!swapwrite)
                 current->flags |= PF_SWAPWRITE;
 
         for(pass = 0; pass < 10 && retry; pass++) {
                 retry = 0;
 
                 list_for_each_entry_safe(page, page2, from, lru) {
                         cond_resched();
 
                         rc = unmap_and_move(get_new_page, private,
                                                 page, pass > 2);
 
                         switch(rc) {
                         case -ENOMEM:
                                 goto out;
                         case -EAGAIN:
                                 retry++;
                                 break;
                         case 0:
                                 break;
                         default:
                                 /* Permanent failure */
                                 nr_failed++;
                                 break;
                         }
                 }
         }
         rc = 0;
 out:
         if (!swapwrite)
                 current->flags &= ~PF_SWAPWRITE;
 
         putback_lru_pages(from);
 
         if (rc)
                 return rc;
 
         return nr_failed + retry;
 }
 
 #ifdef CONFIG_NUMA
 /*
  * Move a list of individual pages
  */
 struct page_to_node {
         unsigned long addr;
         struct page *page;
         int node;
         int status;
 };
 
 static struct page *new_page_node(struct page *p, unsigned long private,
                 int **result)
 {
         struct page_to_node *pm = (struct page_to_node *)private;
 
         while (pm->node != MAX_NUMNODES && pm->page != p)
                 pm++;
 
         if (pm->node == MAX_NUMNODES)
                 return NULL;
 
         *result = &pm->status;
 
         return alloc_pages_node(pm->node,
                                 GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
 }
 
 /*
  * Move a set of pages as indicated in the pm array. The addr
  * field must be set to the virtual address of the page to be moved
  * and the node number must contain a valid target node.
  * The pm array ends with node = MAX_NUMNODES.
  */
 static int do_move_page_to_node_array(struct mm_struct *mm,
                                       struct page_to_node *pm,
                                       int migrate_all)
 {
         int err;
         struct page_to_node *pp;
         LIST_HEAD(pagelist);
 
         migrate_prep();
         down_read(&mm->mmap_sem);
 
         /*
          * Build a list of pages to migrate
          */
         for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
                 struct vm_area_struct *vma;
                 struct page *page;
 
                 /*
                  * A valid page pointer that will not match any of the
                  * pages that will be moved.
                  */
                 pp->page = ZERO_PAGE(0);
 
                 err = -EFAULT;
                 vma = find_vma(mm, pp->addr);
                 if (!vma || !vma_migratable(vma))
                         goto set_status;
 
                 page = follow_page(vma, pp->addr, FOLL_GET);
 
                 err = PTR_ERR(page);
                 if (IS_ERR(page))
                         goto set_status;
 
                 err = -ENOENT;
                 if (!page)
                         goto set_status;
 
                 if (PageReserved(page))                /* Check for zero page */
                         goto put_and_set;
 
                 pp->page = page;
                 err = page_to_nid(page);
 
                 if (err == pp->node)
                         /*
                          * Node already in the right place
                          */
                         goto put_and_set;
 
                 err = -EACCES;
                 if (page_mapcount(page) > 1 &&
                                 !migrate_all)
                         goto put_and_set;
 
                 err = isolate_lru_page(page);
                 if (!err)
                         list_add_tail(&page->lru, &pagelist);
 put_and_set:
                 /*
                  * Either remove the duplicate refcount from
                  * isolate_lru_page() or drop the page ref if it was
                  * not isolated.
                  */
                 put_page(page);
 set_status:
                 pp->status = err;
         }
 
         err = 0;
         if (!list_empty(&pagelist))
                 err = migrate_pages(&pagelist, new_page_node,
                                 (unsigned long)pm);
 
         up_read(&mm->mmap_sem);
         return err;
 }
 
 /*
  * Migrate an array of page address onto an array of nodes and fill
  * the corresponding array of status.
  */
 static int do_pages_move(struct mm_struct *mm, struct task_struct *task,
                          unsigned long nr_pages,
                          const void __user * __user *pages,
                          const int __user *nodes,
                          int __user *status, int flags)
 {
         struct page_to_node *pm = NULL;
         nodemask_t task_nodes;
         int err = 0;
         int i;
 
         task_nodes = cpuset_mems_allowed(task);
 
         /* Limit nr_pages so that the multiplication may not overflow */
         if (nr_pages >= ULONG_MAX / sizeof(struct page_to_node) - 1) {
                 err = -E2BIG;
                 goto out;
         }
 
         pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node));
         if (!pm) {
                 err = -ENOMEM;
                 goto out;
         }
 
         /*
          * Get parameters from user space and initialize the pm
          * array. Return various errors if the user did something wrong.
          */
         for (i = 0; i < nr_pages; i++) {
                 const void __user *p;
 
                 err = -EFAULT;
                 if (get_user(p, pages + i))
                         goto out_pm;
 
                 pm[i].addr = (unsigned long)p;
                 if (nodes) {
                         int node;
 
                         if (get_user(node, nodes + i))
                                 goto out_pm;
 
                         err = -ENODEV;
                         if (!node_state(node, N_HIGH_MEMORY))
                                 goto out_pm;
 
                         err = -EACCES;
                         if (!node_isset(node, task_nodes))
                                 goto out_pm;
 
                         pm[i].node = node;
                 } else
                         pm[i].node = 0;        /* anything to not match MAX_NUMNODES */
         }
         /* End marker */
         pm[nr_pages].node = MAX_NUMNODES;
 
         err = do_move_page_to_node_array(mm, pm, flags & MPOL_MF_MOVE_ALL);
         if (err >= 0)
                 /* Return status information */
                 for (i = 0; i < nr_pages; i++)
                         if (put_user(pm[i].status, status + i))
                                 err = -EFAULT;
 
 out_pm:
         vfree(pm);
 out:
         return err;
 }
 
 /*
  * Determine the nodes of an array of pages and store it in an array of status.
  */
 static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
                                 const void __user **pages, int *status)
 {
         unsigned long i;
 
         down_read(&mm->mmap_sem);
 
         for (i = 0; i < nr_pages; i++) {
                 unsigned long addr = (unsigned long)(*pages);
                 struct vm_area_struct *vma;
                struct page *page;
                int err = -EFAULT;

                vma = find_vma(mm, addr);
                if (!vma)
                        goto set_status;

                page = follow_page(vma, addr, 0);

                err = PTR_ERR(page);
                if (IS_ERR(page))
                        goto set_status;

                err = -ENOENT;
                /* Use PageReserved to check for zero page */
                if (!page || PageReserved(page))
                        goto set_status;

                err = page_to_nid(page);
set_status:
                *status = err;

                pages++;
                status++;
        }

        up_read(&mm->mmap_sem);
}

/*
 * Determine the nodes of a user array of pages and store it in
 * a user array of status.
 */
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
                         const void __user * __user *pages,
                         int __user *status)
{
#define DO_PAGES_STAT_CHUNK_NR 16
        const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
        int chunk_status[DO_PAGES_STAT_CHUNK_NR];
        unsigned long i, chunk_nr = DO_PAGES_STAT_CHUNK_NR;
        int err;

        for (i = 0; i < nr_pages; i += chunk_nr) {
                if (chunk_nr + i > nr_pages)
                        chunk_nr = nr_pages - i;

                err = copy_from_user(chunk_pages, &pages[i],
                                     chunk_nr * sizeof(*chunk_pages));
                if (err) {
                        err = -EFAULT;
                        goto out;
                }

                do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);

                err = copy_to_user(&status[i], chunk_status,
                                   chunk_nr * sizeof(*chunk_status));
                if (err) {
                        err = -EFAULT;
                        goto out;
                }
        }
        err = 0;

out:
        return err;
}

/*
 * Move a list of pages in the address space of the currently executing
 * process.
 */
asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
                        const void __user * __user *pages,
                        const int __user *nodes,
                        int __user *status, int flags)
{
        struct task_struct *task;
        struct mm_struct *mm;
        int err;

        /* Check flags */
        if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
                return -EINVAL;

        if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
                return -EPERM;

        /* Find the mm_struct */
        read_lock(&tasklist_lock);
        task = pid ? find_task_by_vpid(pid) : current;
        if (!task) {
                read_unlock(&tasklist_lock);
                return -ESRCH;
        }
        mm = get_task_mm(task);
        read_unlock(&tasklist_lock);

        if (!mm)
                return -EINVAL;

        /*
         * Check if this process has the right to modify the specified
         * process. The right exists if the process has administrative
         * capabilities, superuser privileges or the same
         * userid as the target process.
         */
        if ((current->euid != task->suid) && (current->euid != task->uid) &&
            (current->uid != task->suid) && (current->uid != task->uid) &&
            !capable(CAP_SYS_NICE)) {
                err = -EPERM;
                goto out;
        }

         err = security_task_movememory(task);
         if (err)
                goto out;

        if (nodes) {
                err = do_pages_move(mm, task, nr_pages, pages, nodes, status,
                                    flags);
        } else {
                err = do_pages_stat(mm, nr_pages, pages, status);
        }

out:
        mmput(mm);
        return err;
}

/*
 * Call migration functions in the vma_ops that may prepare
 * memory in a vm for migration. migration functions may perform
 * the migration for vmas that do not have an underlying page struct.
 */
int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
        const nodemask_t *from, unsigned long flags)
{
         struct vm_area_struct *vma;
         int err = 0;

         for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) {
                 if (vma->vm_ops && vma->vm_ops->migrate) {
                         err = vma->vm_ops->migrate(vma, to, from, flags);
                         if (err)
                                 break;
                 }
         }
         return err;
}
#endif