| /* |
| * 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/ksm.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 <linux/hugetlb.h> |
| #include <linux/gfp.h> |
| |
| #include <asm/tlbflush.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(). If scheduling work on other CPUs is |
| * undesirable, use migrate_prep_local() |
| */ |
| 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; |
| } |
| |
| /* Do the necessary work of migrate_prep but not if it involves other CPUs */ |
| int migrate_prep_local(void) |
| { |
| lru_add_drain(); |
| |
| return 0; |
| } |
| |
| /* |
| * Add isolated pages on the list back to the LRU under page lock |
| * to avoid leaking evictable pages back onto unevictable list. |
| */ |
| void putback_lru_pages(struct list_head *l) |
| { |
| struct page *page; |
| struct page *page2; |
| |
| list_for_each_entry_safe(page, page2, l, lru) { |
| list_del(&page->lru); |
| dec_zone_page_state(page, NR_ISOLATED_ANON + |
| page_is_file_cache(page)); |
| putback_lru_page(page); |
| } |
| } |
| |
| /* |
| * Restore a potential migration pte to a working pte entry |
| */ |
| static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, |
| unsigned long addr, void *old) |
| { |
| 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; |
| |
| if (unlikely(PageHuge(new))) { |
| ptep = huge_pte_offset(mm, addr); |
| if (!ptep) |
| goto out; |
| ptl = &mm->page_table_lock; |
| } else { |
| pgd = pgd_offset(mm, addr); |
| if (!pgd_present(*pgd)) |
| goto out; |
| |
| pud = pud_offset(pgd, addr); |
| if (!pud_present(*pud)) |
| goto out; |
| |
| pmd = pmd_offset(pud, addr); |
| if (pmd_trans_huge(*pmd)) |
| goto out; |
| if (!pmd_present(*pmd)) |
| goto out; |
| |
| ptep = pte_offset_map(pmd, addr); |
| |
| if (!is_swap_pte(*ptep)) { |
| pte_unmap(ptep); |
| goto out; |
| } |
| |
| ptl = pte_lockptr(mm, pmd); |
| } |
| |
| spin_lock(ptl); |
| pte = *ptep; |
| if (!is_swap_pte(pte)) |
| goto unlock; |
| |
| entry = pte_to_swp_entry(pte); |
| |
| if (!is_migration_entry(entry) || |
| migration_entry_to_page(entry) != old) |
| goto unlock; |
| |
| get_page(new); |
| pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); |
| if (is_write_migration_entry(entry)) |
| pte = pte_mkwrite(pte); |
| #ifdef CONFIG_HUGETLB_PAGE |
| if (PageHuge(new)) |
| pte = pte_mkhuge(pte); |
| #endif |
| flush_cache_page(vma, addr, pte_pfn(pte)); |
| set_pte_at(mm, addr, ptep, pte); |
| |
| if (PageHuge(new)) { |
| if (PageAnon(new)) |
| hugepage_add_anon_rmap(new, vma, addr); |
| else |
| page_dup_rmap(new); |
| } else 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, ptep); |
| unlock: |
| pte_unmap_unlock(ptep, ptl); |
| out: |
| return SWAP_AGAIN; |
| } |
| |
| /* |
| * 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) |
| { |
| rmap_walk(new, remove_migration_pte, old); |
| } |
| |
| /* |
| * 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/PagePrivate2 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 + page_has_private(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 */ |
| if (PageSwapCache(page)) { |
| SetPageSwapCache(newpage); |
| set_page_private(newpage, page_private(page)); |
| } |
| |
| 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); |
| if (PageSwapBacked(page)) { |
| __dec_zone_page_state(page, NR_SHMEM); |
| __inc_zone_page_state(newpage, NR_SHMEM); |
| } |
| spin_unlock_irq(&mapping->tree_lock); |
| |
| return 0; |
| } |
| |
| /* |
| * The expected number of remaining references is the same as that |
| * of migrate_page_move_mapping(). |
| */ |
| int migrate_huge_page_move_mapping(struct address_space *mapping, |
| struct page *newpage, struct page *page) |
| { |
| int expected_count; |
| void **pslot; |
| |
| if (!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 + page_has_private(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; |
| } |
| |
| get_page(newpage); |
| |
| radix_tree_replace_slot(pslot, newpage); |
| |
| page_unfreeze_refs(page, expected_count); |
| |
| __put_page(page); |
| |
| spin_unlock_irq(&mapping->tree_lock); |
| return 0; |
| } |
| |
| /* |
| * Copy the page to its new location |
| */ |
| void migrate_page_copy(struct page *newpage, struct page *page) |
| { |
| if (PageHuge(page)) |
| copy_huge_page(newpage, page); |
| else |
| 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 if (TestClearPageUnevictable(page)) |
| SetPageUnevictable(newpage); |
| 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); |
| ksm_migrate_page(newpage, page); |
| |
| ClearPageSwapCache(page); |
| ClearPagePrivate(page); |
| set_page_private(page, 0); |
| page->mapping = NULL; |
| |
| /* |
| * 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/PagePrivate2. |
| * |
| * 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, |
| .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 (page_has_private(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, |
| int remap_swapcache) |
| { |
| 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) { |
| newpage->mapping = NULL; |
| } else { |
| if (remap_swapcache) |
| remove_migration_ptes(page, newpage); |
| } |
| |
| 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, bool offlining, bool sync) |
| { |
| int rc = 0; |
| int *result = NULL; |
| struct page *newpage = get_new_page(page, private, &result); |
| int remap_swapcache = 1; |
| int rcu_locked = 0; |
| int charge = 0; |
| struct mem_cgroup *mem = NULL; |
| struct anon_vma *anon_vma = NULL; |
| |
| if (!newpage) |
| return -ENOMEM; |
| |
| if (page_count(page) == 1) { |
| /* page was freed from under us. So we are done. */ |
| goto move_newpage; |
| } |
| if (unlikely(PageTransHuge(page))) |
| if (unlikely(split_huge_page(page))) |
| goto move_newpage; |
| |
| /* prepare cgroup just returns 0 or -ENOMEM */ |
| rc = -EAGAIN; |
| |
| if (!trylock_page(page)) { |
| if (!force) |
| goto move_newpage; |
| |
| /* |
| * It's not safe for direct compaction to call lock_page. |
| * For example, during page readahead pages are added locked |
| * to the LRU. Later, when the IO completes the pages are |
| * marked uptodate and unlocked. However, the queueing |
| * could be merging multiple pages for one bio (e.g. |
| * mpage_readpages). If an allocation happens for the |
| * second or third page, the process can end up locking |
| * the same page twice and deadlocking. Rather than |
| * trying to be clever about what pages can be locked, |
| * avoid the use of lock_page for direct compaction |
| * altogether. |
| */ |
| if (current->flags & PF_MEMALLOC) |
| goto move_newpage; |
| |
| lock_page(page); |
| } |
| |
| /* |
| * Only memory hotplug's offline_pages() caller has locked out KSM, |
| * and can safely migrate a KSM page. The other cases have skipped |
| * PageKsm along with PageReserved - but it is only now when we have |
| * the page lock that we can be certain it will not go KSM beneath us |
| * (KSM will not upgrade a page from PageAnon to PageKsm when it sees |
| * its pagecount raised, but only here do we take the page lock which |
| * serializes that). |
| */ |
| if (PageKsm(page) && !offlining) { |
| rc = -EBUSY; |
| goto unlock; |
| } |
| |
| /* charge against new page */ |
| charge = mem_cgroup_prepare_migration(page, newpage, &mem); |
| if (charge == -ENOMEM) { |
| rc = -ENOMEM; |
| goto unlock; |
| } |
| BUG_ON(charge); |
| |
| if (PageWriteback(page)) { |
| if (!force || !sync) |
| goto uncharge; |
| 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; |
| |
| /* Determine how to safely use anon_vma */ |
| if (!page_mapped(page)) { |
| if (!PageSwapCache(page)) |
| goto rcu_unlock; |
| |
| /* |
| * We cannot be sure that the anon_vma of an unmapped |
| * swapcache page is safe to use because we don't |
| * know in advance if the VMA that this page belonged |
| * to still exists. If the VMA and others sharing the |
| * data have been freed, then the anon_vma could |
| * already be invalid. |
| * |
| * To avoid this possibility, swapcache pages get |
| * migrated but are not remapped when migration |
| * completes |
| */ |
| remap_swapcache = 0; |
| } else { |
| /* |
| * Take a reference count on the anon_vma if the |
| * page is mapped so that it is guaranteed to |
| * exist when the page is remapped later |
| */ |
| anon_vma = page_anon_vma(page); |
| get_anon_vma(anon_vma); |
| } |
| } |
| |
| /* |
| * 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) && page_has_private(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; |
| } |
| goto skip_unmap; |
| } |
| |
| /* Establish migration ptes or remove ptes */ |
| try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); |
| |
| skip_unmap: |
| if (!page_mapped(page)) |
| rc = move_to_new_page(newpage, page, remap_swapcache); |
| |
| if (rc && remap_swapcache) |
| remove_migration_ptes(page, page); |
| rcu_unlock: |
| |
| /* Drop an anon_vma reference if we took one */ |
| if (anon_vma) |
| drop_anon_vma(anon_vma); |
| |
| if (rcu_locked) |
| rcu_read_unlock(); |
| uncharge: |
| if (!charge) |
| mem_cgroup_end_migration(mem, page, newpage); |
| 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); |
| dec_zone_page_state(page, NR_ISOLATED_ANON + |
| page_is_file_cache(page)); |
| putback_lru_page(page); |
| } |
| |
| move_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; |
| } |
| |
| /* |
| * Counterpart of unmap_and_move_page() for hugepage migration. |
| * |
| * This function doesn't wait the completion of hugepage I/O |
| * because there is no race between I/O and migration for hugepage. |
| * Note that currently hugepage I/O occurs only in direct I/O |
| * where no lock is held and PG_writeback is irrelevant, |
| * and writeback status of all subpages are counted in the reference |
| * count of the head page (i.e. if all subpages of a 2MB hugepage are |
| * under direct I/O, the reference of the head page is 512 and a bit more.) |
| * This means that when we try to migrate hugepage whose subpages are |
| * doing direct I/O, some references remain after try_to_unmap() and |
| * hugepage migration fails without data corruption. |
| * |
| * There is also no race when direct I/O is issued on the page under migration, |
| * because then pte is replaced with migration swap entry and direct I/O code |
| * will wait in the page fault for migration to complete. |
| */ |
| static int unmap_and_move_huge_page(new_page_t get_new_page, |
| unsigned long private, struct page *hpage, |
| int force, bool offlining, bool sync) |
| { |
| int rc = 0; |
| int *result = NULL; |
| struct page *new_hpage = get_new_page(hpage, private, &result); |
| int rcu_locked = 0; |
| struct anon_vma *anon_vma = NULL; |
| |
| if (!new_hpage) |
| return -ENOMEM; |
| |
| rc = -EAGAIN; |
| |
| if (!trylock_page(hpage)) { |
| if (!force || !sync) |
| goto out; |
| lock_page(hpage); |
| } |
| |
| if (PageAnon(hpage)) { |
| rcu_read_lock(); |
| rcu_locked = 1; |
| |
| if (page_mapped(hpage)) { |
| anon_vma = page_anon_vma(hpage); |
| atomic_inc(&anon_vma->external_refcount); |
| } |
| } |
| |
| try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); |
| |
| if (!page_mapped(hpage)) |
| rc = move_to_new_page(new_hpage, hpage, 1); |
| |
| if (rc) |
| remove_migration_ptes(hpage, hpage); |
| |
| if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, |
| &anon_vma->lock)) { |
| int empty = list_empty(&anon_vma->head); |
| spin_unlock(&anon_vma->lock); |
| if (empty) |
| anon_vma_free(anon_vma); |
| } |
| |
| if (rcu_locked) |
| rcu_read_unlock(); |
| out: |
| unlock_page(hpage); |
| |
| if (rc != -EAGAIN) { |
| list_del(&hpage->lru); |
| put_page(hpage); |
| } |
| |
| put_page(new_hpage); |
| |
| if (result) { |
| if (rc) |
| *result = rc; |
| else |
| *result = page_to_nid(new_hpage); |
| } |
| 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. |
| * Caller should call putback_lru_pages to return pages to the LRU |
| * or free list. |
| * |
| * 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, bool offlining, |
| bool sync) |
| { |
| 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, offlining, |
| sync); |
| |
| 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; |
| |
| if (rc) |
| return rc; |
| |
| return nr_failed + retry; |
| } |
| |
| int migrate_huge_pages(struct list_head *from, |
| new_page_t get_new_page, unsigned long private, bool offlining, |
| bool sync) |
| { |
| int retry = 1; |
| int nr_failed = 0; |
| int pass = 0; |
| struct page *page; |
| struct page *page2; |
| int rc; |
| |
| for (pass = 0; pass < 10 && retry; pass++) { |
| retry = 0; |
| |
| list_for_each_entry_safe(page, page2, from, lru) { |
| cond_resched(); |
| |
| rc = unmap_and_move_huge_page(get_new_page, |
| private, page, pass > 2, offlining, |
| sync); |
| |
| switch(rc) { |
| case -ENOMEM: |
| goto out; |
| case -EAGAIN: |
| retry++; |
| break; |
| case 0: |
| break; |
| default: |
| /* Permanent failure */ |
| nr_failed++; |
| break; |
| } |
| } |
| } |
| rc = 0; |
| out: |
| |
| list_for_each_entry_safe(page, page2, from, lru) |
| put_page(page); |
| |
| 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_exact_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); |
| |
| 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; |
| |
| err = -EFAULT; |
| vma = find_vma(mm, pp->addr); |
| if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma)) |
| goto set_status; |
| |
| page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT); |
| |
| err = PTR_ERR(page); |
| if (IS_ERR(page)) |
| goto set_status; |
| |
| err = -ENOENT; |
| if (!page) |
| goto set_status; |
| |
| /* Use PageReserved to check for zero page */ |
| if (PageReserved(page) || PageKsm(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); |
| inc_zone_page_state(page, NR_ISOLATED_ANON + |
| page_is_file_cache(page)); |
| } |
| 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, 0, true); |
| if (err) |
| putback_lru_pages(&pagelist); |
| } |
| |
| 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; |
| nodemask_t task_nodes; |
| unsigned long chunk_nr_pages; |
| unsigned long chunk_start; |
| int err; |
| |
| task_nodes = cpuset_mems_allowed(task); |
| |
| err = -ENOMEM; |
| pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); |
| if (!pm) |
| goto out; |
| |
| migrate_prep(); |
| |
| /* |
| * Store a chunk of page_to_node array in a page, |
| * but keep the last one as a marker |
| */ |
| chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; |
| |
| for (chunk_start = 0; |
| chunk_start < nr_pages; |
| chunk_start += chunk_nr_pages) { |
| int j; |
| |
| if (chunk_start + chunk_nr_pages > nr_pages) |
| chunk_nr_pages = nr_pages - chunk_start; |
| |
| /* fill the chunk pm with addrs and nodes from user-space */ |
| for (j = 0; j < chunk_nr_pages; j++) { |
| const void __user *p; |
| int node; |
| |
| err = -EFAULT; |
| if (get_user(p, pages + j + chunk_start)) |
| goto out_pm; |
| pm[j].addr = (unsigned long) p; |
| |
| if (get_user(node, nodes + j + chunk_start)) |
| goto out_pm; |
| |
| err = -ENODEV; |
| if (node < 0 || node >= MAX_NUMNODES) |
| goto out_pm; |
| |
| if (!node_state(node, N_HIGH_MEMORY)) |
| goto out_pm; |
| |
| err = -EACCES; |
| if (!node_isset(node, task_nodes)) |
| goto out_pm; |
| |
| pm[j].node = node; |
| } |
| |
| /* End marker for this chunk */ |
| pm[chunk_nr_pages].node = MAX_NUMNODES; |
| |
| /* Migrate this chunk */ |
| err = do_move_page_to_node_array(mm, pm, |
| flags & MPOL_MF_MOVE_ALL); |
| if (err < 0) |
| goto out_pm; |
| |
| /* Return status information */ |
| for (j = 0; j < chunk_nr_pages; j++) |
| if (put_user(pm[j].status, status + j + chunk_start)) { |
| err = -EFAULT; |
| goto out_pm; |
| } |
| } |
| err = 0; |
| |
| out_pm: |
| free_page((unsigned long)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 || addr < vma->vm_start) |
| 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) || PageKsm(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]; |
| |
| while (nr_pages) { |
| unsigned long chunk_nr; |
| |
| chunk_nr = nr_pages; |
| if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) |
| chunk_nr = DO_PAGES_STAT_CHUNK_NR; |
| |
| if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages))) |
| break; |
| |
| do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); |
| |
| if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) |
| break; |
| |
| pages += chunk_nr; |
| status += chunk_nr; |
| nr_pages -= chunk_nr; |
| } |
| return nr_pages ? -EFAULT : 0; |
| } |
| |
| /* |
| * Move a list of pages in the address space of the currently executing |
| * process. |
| */ |
| SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, |
| const void __user * __user *, pages, |
| const int __user *, nodes, |
| int __user *, status, int, flags) |
| { |
| const struct cred *cred = current_cred(), *tcred; |
| 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. |
| */ |
| rcu_read_lock(); |
| tcred = __task_cred(task); |
| if (cred->euid != tcred->suid && cred->euid != tcred->uid && |
| cred->uid != tcred->suid && cred->uid != tcred->uid && |
| !capable(CAP_SYS_NICE)) { |
| rcu_read_unlock(); |
| err = -EPERM; |
| goto out; |
| } |
| rcu_read_unlock(); |
| |
| 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 && !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 |