/* * 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); if (!PageSwapCache(newpage)) mem_cgroup_uncharge_cache_page(page); return 0; } /* * Copy the page to its new location */ static void migrate_page_copy(struct page *newpage, struct page *page) { 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); } #ifdef CONFIG_SWAP ClearPageSwapCache(page); #endif 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. * * 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 < 0) /* I/O Error writing */ return -EIO; if (rc != AOP_WRITEPAGE_ACTIVATE) /* unlocked. Relock */ lock_page(page); return -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. */ static int do_move_pages(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 */ migrate_prep(); 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; } if (!list_empty(&pagelist)) err = migrate_pages(&pagelist, new_page_node, (unsigned long)pm); else err = -ENOENT; up_read(&mm->mmap_sem); return err; } /* * Determine the nodes of a list of pages. The addr in the pm array * must have been set to the virtual address of which we want to determine * the node number. */ static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm) { down_read(&mm->mmap_sem); for ( ; pm->node != MAX_NUMNODES; pm++) { struct vm_area_struct *vma; struct page *page; int err; err = -EFAULT; vma = find_vma(mm, pm->addr); if (!vma) goto set_status; page = follow_page(vma, pm->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: pm->status = err; } up_read(&mm->mmap_sem); return 0; } /* * 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) { int err = 0; int i; struct task_struct *task; nodemask_t task_nodes; struct mm_struct *mm; struct page_to_node *pm = NULL; /* 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 out2; } err = security_task_movememory(task); if (err) goto out2; 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 out2; } pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node)); if (!pm) { err = -ENOMEM; goto out2; } /* * 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[i].addr = (unsigned long)p; if (nodes) { int node; if (get_user(node, nodes + i)) goto out; err = -ENODEV; if (!node_state(node, N_HIGH_MEMORY)) goto out; err = -EACCES; if (!node_isset(node, task_nodes)) goto out; pm[i].node = node; } else pm[i].node = 0; /* anything to not match MAX_NUMNODES */ } /* End marker */ pm[nr_pages].node = MAX_NUMNODES; if (nodes) err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL); else err = do_pages_stat(mm, pm); if (err >= 0) /* Return status information */ for (i = 0; i < nr_pages; i++) if (put_user(pm[i].status, status + i)) err = -EFAULT; out: vfree(pm); out2: 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