/* * Memory Migration functionality - linux/mm/migrate.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 * Hirokazu Takahashi * Dave Hansen * Christoph Lameter */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define CREATE_TRACE_POINTS #include #include "internal.h" /* * 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; } /* * Put previously isolated pages back onto the appropriate lists * from where they were once taken off for compaction/migration. * * This function shall be used whenever the isolated pageset has been * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() * and isolate_huge_page(). */ void putback_movable_pages(struct list_head *l) { struct page *page; struct page *page2; list_for_each_entry_safe(page, page2, l, lru) { if (unlikely(PageHuge(page))) { putback_active_hugepage(page); continue; } list_del(&page->lru); dec_zone_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); if (unlikely(isolated_balloon_page(page))) balloon_page_putback(page); else 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; 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 = huge_pte_lockptr(hstate_vma(vma), mm, ptep); } else { pmd = mm_find_pmd(mm, addr); if (!pmd) goto out; ptep = pte_offset_map(pmd, addr); /* * Peek to check is_swap_pte() before taking ptlock? No, we * can race mremap's move_ptes(), which skips anon_vma lock. */ 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 (pte_swp_soft_dirty(*ptep)) pte = pte_mksoft_dirty(pte); /* Recheck VMA as permissions can change since migration started */ if (is_write_migration_entry(entry)) pte = maybe_mkwrite(pte, vma); #ifdef CONFIG_HUGETLB_PAGE if (PageHuge(new)) { pte = pte_mkhuge(pte); pte = arch_make_huge_pte(pte, vma, new, 0); } #endif flush_dcache_page(new); 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, true); } else if (PageAnon(new)) page_add_anon_rmap(new, vma, addr, false); else page_add_file_rmap(new); if (vma->vm_flags & VM_LOCKED) mlock_vma_page(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) { struct rmap_walk_control rwc = { .rmap_one = remove_migration_pte, .arg = old, }; rmap_walk(new, &rwc); } /* * 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. */ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, spinlock_t *ptl) { pte_t pte; swp_entry_t entry; struct page *page; spin_lock(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); } void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, unsigned long address) { spinlock_t *ptl = pte_lockptr(mm, pmd); pte_t *ptep = pte_offset_map(pmd, address); __migration_entry_wait(mm, ptep, ptl); } void migration_entry_wait_huge(struct vm_area_struct *vma, struct mm_struct *mm, pte_t *pte) { spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte); __migration_entry_wait(mm, pte, ptl); } #ifdef CONFIG_BLOCK /* Returns true if all buffers are successfully locked */ static bool buffer_migrate_lock_buffers(struct buffer_head *head, enum migrate_mode mode) { struct buffer_head *bh = head; /* Simple case, sync compaction */ if (mode != MIGRATE_ASYNC) { do { get_bh(bh); lock_buffer(bh); bh = bh->b_this_page; } while (bh != head); return true; } /* async case, we cannot block on lock_buffer so use trylock_buffer */ do { get_bh(bh); if (!trylock_buffer(bh)) { /* * We failed to lock the buffer and cannot stall in * async migration. Release the taken locks */ struct buffer_head *failed_bh = bh; put_bh(failed_bh); bh = head; while (bh != failed_bh) { unlock_buffer(bh); put_bh(bh); bh = bh->b_this_page; } return false; } bh = bh->b_this_page; } while (bh != head); return true; } #else static inline bool buffer_migrate_lock_buffers(struct buffer_head *head, enum migrate_mode mode) { return true; } #endif /* CONFIG_BLOCK */ /* * 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. */ int migrate_page_move_mapping(struct address_space *mapping, struct page *newpage, struct page *page, struct buffer_head *head, enum migrate_mode mode, int extra_count) { struct zone *oldzone, *newzone; int dirty; int expected_count = 1 + extra_count; void **pslot; if (!mapping) { /* Anonymous page without mapping */ if (page_count(page) != expected_count) return -EAGAIN; /* No turning back from here */ newpage->index = page->index; newpage->mapping = page->mapping; if (PageSwapBacked(page)) SetPageSwapBacked(newpage); return MIGRATEPAGE_SUCCESS; } oldzone = page_zone(page); newzone = page_zone(newpage); spin_lock_irq(&mapping->tree_lock); pslot = radix_tree_lookup_slot(&mapping->page_tree, page_index(page)); expected_count += 1 + page_has_private(page); if (page_count(page) != expected_count || radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } if (!page_freeze_refs(page, expected_count)) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } /* * In the async migration case of moving a page with buffers, lock the * buffers using trylock before the mapping is moved. If the mapping * was moved, we later failed to lock the buffers and could not move * the mapping back due to an elevated page count, we would have to * block waiting on other references to be dropped. */ if (mode == MIGRATE_ASYNC && head && !buffer_migrate_lock_buffers(head, mode)) { page_unfreeze_refs(page, expected_count); spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } /* * Now we know that no one else is looking at the page: * no turning back from here. */ newpage->index = page->index; newpage->mapping = page->mapping; if (PageSwapBacked(page)) SetPageSwapBacked(newpage); get_page(newpage); /* add cache reference */ if (PageSwapCache(page)) { SetPageSwapCache(newpage); set_page_private(newpage, page_private(page)); } /* Move dirty while page refs frozen and newpage not yet exposed */ dirty = PageDirty(page); if (dirty) { ClearPageDirty(page); SetPageDirty(newpage); } radix_tree_replace_slot(pslot, newpage); /* * Drop cache reference from old page by unfreezing * to one less reference. * We know this isn't the last reference. */ page_unfreeze_refs(page, expected_count - 1); spin_unlock(&mapping->tree_lock); /* Leave irq disabled to prevent preemption while updating stats */ /* * 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. */ if (newzone != oldzone) { __dec_zone_state(oldzone, NR_FILE_PAGES); __inc_zone_state(newzone, NR_FILE_PAGES); if (PageSwapBacked(page) && !PageSwapCache(page)) { __dec_zone_state(oldzone, NR_SHMEM); __inc_zone_state(newzone, NR_SHMEM); } if (dirty && mapping_cap_account_dirty(mapping)) { __dec_zone_state(oldzone, NR_FILE_DIRTY); __inc_zone_state(newzone, NR_FILE_DIRTY); } } local_irq_enable(); return MIGRATEPAGE_SUCCESS; } /* * 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; 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 || radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } if (!page_freeze_refs(page, expected_count)) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } newpage->index = page->index; newpage->mapping = page->mapping; get_page(newpage); radix_tree_replace_slot(pslot, newpage); page_unfreeze_refs(page, expected_count - 1); spin_unlock_irq(&mapping->tree_lock); return MIGRATEPAGE_SUCCESS; } /* * Gigantic pages are so large that we do not guarantee that page++ pointer * arithmetic will work across the entire page. We need something more * specialized. */ static void __copy_gigantic_page(struct page *dst, struct page *src, int nr_pages) { int i; struct page *dst_base = dst; struct page *src_base = src; for (i = 0; i < nr_pages; ) { cond_resched(); copy_highpage(dst, src); i++; dst = mem_map_next(dst, dst_base, i); src = mem_map_next(src, src_base, i); } } static void copy_huge_page(struct page *dst, struct page *src) { int i; int nr_pages; if (PageHuge(src)) { /* hugetlbfs page */ struct hstate *h = page_hstate(src); nr_pages = pages_per_huge_page(h); if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) { __copy_gigantic_page(dst, src, nr_pages); return; } } else { /* thp page */ BUG_ON(!PageTransHuge(src)); nr_pages = hpage_nr_pages(src); } for (i = 0; i < nr_pages; i++) { cond_resched(); copy_highpage(dst + i, src + i); } } /* * Copy the page to its new location */ void migrate_page_copy(struct page *newpage, struct page *page) { int cpupid; if (PageHuge(page) || PageTransHuge(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_PAGE(PageUnevictable(page), page); SetPageActive(newpage); } else if (TestClearPageUnevictable(page)) SetPageUnevictable(newpage); if (PageChecked(page)) SetPageChecked(newpage); if (PageMappedToDisk(page)) SetPageMappedToDisk(newpage); /* Move dirty on pages not done by migrate_page_move_mapping() */ if (PageDirty(page)) SetPageDirty(newpage); if (page_is_young(page)) set_page_young(newpage); if (page_is_idle(page)) set_page_idle(newpage); /* * Copy NUMA information to the new page, to prevent over-eager * future migrations of this same page. */ cpupid = page_cpupid_xchg_last(page, -1); page_cpupid_xchg_last(newpage, cpupid); ksm_migrate_page(newpage, page); /* * Please do not reorder this without considering how mm/ksm.c's * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). */ if (PageSwapCache(page)) ClearPageSwapCache(page); ClearPagePrivate(page); set_page_private(page, 0); /* * If any waiters have accumulated on the new page then * wake them up. */ if (PageWriteback(newpage)) end_page_writeback(newpage); copy_page_owner(page, newpage); mem_cgroup_migrate(page, newpage); } /************************************************************ * Migration functions ***********************************************************/ /* * 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, enum migrate_mode mode) { int rc; BUG_ON(PageWriteback(page)); /* Writeback must be complete */ rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0); if (rc != MIGRATEPAGE_SUCCESS) return rc; migrate_page_copy(newpage, page); return MIGRATEPAGE_SUCCESS; } 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, enum migrate_mode mode) { struct buffer_head *bh, *head; int rc; if (!page_has_buffers(page)) return migrate_page(mapping, newpage, page, mode); head = page_buffers(page); rc = migrate_page_move_mapping(mapping, newpage, page, head, mode, 0); if (rc != MIGRATEPAGE_SUCCESS) return rc; /* * In the async case, migrate_page_move_mapping locked the buffers * with an IRQ-safe spinlock held. In the sync case, the buffers * need to be locked now */ if (mode != MIGRATE_ASYNC) BUG_ON(!buffer_migrate_lock_buffers(head, mode)); 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 MIGRATEPAGE_SUCCESS; } 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, enum migrate_mode mode) { if (PageDirty(page)) { /* Only writeback pages in full synchronous migration */ if (mode != MIGRATE_SYNC) return -EBUSY; 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, mode); } /* * 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 * MIGRATEPAGE_SUCCESS - success */ static int move_to_new_page(struct page *newpage, struct page *page, enum migrate_mode mode) { struct address_space *mapping; int rc; VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); mapping = page_mapping(page); if (!mapping) rc = migrate_page(mapping, newpage, page, mode); else if (mapping->a_ops->migratepage) /* * Most pages have a mapping and most filesystems provide a * migratepage callback. Anonymous pages are part of swap * space which also has its own migratepage callback. This * is the most common path for page migration. */ rc = mapping->a_ops->migratepage(mapping, newpage, page, mode); else rc = fallback_migrate_page(mapping, newpage, page, mode); /* * When successful, old pagecache page->mapping must be cleared before * page is freed; but stats require that PageAnon be left as PageAnon. */ if (rc == MIGRATEPAGE_SUCCESS) { if (!PageAnon(page)) page->mapping = NULL; } return rc; } static int __unmap_and_move(struct page *page, struct page *newpage, int force, enum migrate_mode mode) { int rc = -EAGAIN; int page_was_mapped = 0; struct anon_vma *anon_vma = NULL; if (!trylock_page(page)) { if (!force || mode == MIGRATE_ASYNC) goto out; /* * 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 out; lock_page(page); } if (PageWriteback(page)) { /* * Only in the case of a full synchronous migration is it * necessary to wait for PageWriteback. In the async case, * the retry loop is too short and in the sync-light case, * the overhead of stalling is too much */ if (mode != MIGRATE_SYNC) { rc = -EBUSY; goto out_unlock; } if (!force) goto out_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 get_anon_vma() 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. * * Only page_get_anon_vma() understands the subtleties of * getting a hold on an anon_vma from outside one of its mms. * But if we cannot get anon_vma, then we won't need it anyway, * because that implies that the anon page is no longer mapped * (and cannot be remapped so long as we hold the page lock). */ if (PageAnon(page) && !PageKsm(page)) anon_vma = page_get_anon_vma(page); /* * Block others from accessing the new page when we get around to * establishing additional references. We are usually the only one * holding a reference to newpage at this point. We used to have a BUG * here if trylock_page(newpage) fails, but would like to allow for * cases where there might be a race with the previous use of newpage. * This is much like races on refcount of oldpage: just don't BUG(). */ if (unlikely(!trylock_page(newpage))) goto out_unlock; if (unlikely(isolated_balloon_page(page))) { /* * A ballooned page does not need any special attention from * physical to virtual reverse mapping procedures. * Skip any attempt to unmap PTEs or to remap swap cache, * in order to avoid burning cycles at rmap level, and perform * the page migration right away (proteced by page lock). */ rc = balloon_page_migrate(newpage, page, mode); goto out_unlock_both; } /* * 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) { VM_BUG_ON_PAGE(PageAnon(page), page); if (page_has_private(page)) { try_to_free_buffers(page); goto out_unlock_both; } } else if (page_mapped(page)) { /* Establish migration ptes */ VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, page); try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); page_was_mapped = 1; } if (!page_mapped(page)) rc = move_to_new_page(newpage, page, mode); if (page_was_mapped) remove_migration_ptes(page, rc == MIGRATEPAGE_SUCCESS ? newpage : page); out_unlock_both: unlock_page(newpage); out_unlock: /* Drop an anon_vma reference if we took one */ if (anon_vma) put_anon_vma(anon_vma); unlock_page(page); out: return rc; } /* * gcc 4.7 and 4.8 on arm get an ICEs when inlining unmap_and_move(). Work * around it. */ #if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM) #define ICE_noinline noinline #else #define ICE_noinline #endif /* * Obtain the lock on page, remove all ptes and migrate the page * to the newly allocated page in newpage. */ static ICE_noinline int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page, unsigned long private, struct page *page, int force, enum migrate_mode mode, enum migrate_reason reason) { int rc = MIGRATEPAGE_SUCCESS; int *result = NULL; struct page *newpage; newpage = get_new_page(page, private, &result); if (!newpage) return -ENOMEM; if (page_count(page) == 1) { /* page was freed from under us. So we are done. */ goto out; } if (unlikely(PageTransHuge(page))) { lock_page(page); rc = split_huge_page(page); unlock_page(page); if (rc) goto out; } rc = __unmap_and_move(page, newpage, force, mode); if (rc == MIGRATEPAGE_SUCCESS) { put_new_page = NULL; set_page_owner_migrate_reason(newpage, reason); } out: 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)); /* Soft-offlined page shouldn't go through lru cache list */ if (reason == MR_MEMORY_FAILURE) { put_page(page); if (!test_set_page_hwpoison(page)) num_poisoned_pages_inc(); } else putback_lru_page(page); } /* * If migration was not successful and there's a freeing callback, use * it. Otherwise, putback_lru_page() will drop the reference grabbed * during isolation. */ if (put_new_page) put_new_page(newpage, private); else if (unlikely(__is_movable_balloon_page(newpage))) { /* drop our reference, page already in the balloon */ put_page(newpage); } else 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, free_page_t put_new_page, unsigned long private, struct page *hpage, int force, enum migrate_mode mode, int reason) { int rc = -EAGAIN; int *result = NULL; int page_was_mapped = 0; struct page *new_hpage; struct anon_vma *anon_vma = NULL; /* * Movability of hugepages depends on architectures and hugepage size. * This check is necessary because some callers of hugepage migration * like soft offline and memory hotremove don't walk through page * tables or check whether the hugepage is pmd-based or not before * kicking migration. */ if (!hugepage_migration_supported(page_hstate(hpage))) { putback_active_hugepage(hpage); return -ENOSYS; } new_hpage = get_new_page(hpage, private, &result); if (!new_hpage) return -ENOMEM; if (!trylock_page(hpage)) { if (!force || mode != MIGRATE_SYNC) goto out; lock_page(hpage); } if (PageAnon(hpage)) anon_vma = page_get_anon_vma(hpage); if (unlikely(!trylock_page(new_hpage))) goto put_anon; if (page_mapped(hpage)) { try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); page_was_mapped = 1; } if (!page_mapped(hpage)) rc = move_to_new_page(new_hpage, hpage, mode); if (page_was_mapped) remove_migration_ptes(hpage, rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage); unlock_page(new_hpage); put_anon: if (anon_vma) put_anon_vma(anon_vma); if (rc == MIGRATEPAGE_SUCCESS) { hugetlb_cgroup_migrate(hpage, new_hpage); put_new_page = NULL; set_page_owner_migrate_reason(new_hpage, reason); } unlock_page(hpage); out: if (rc != -EAGAIN) putback_active_hugepage(hpage); /* * If migration was not successful and there's a freeing callback, use * it. Otherwise, put_page() will drop the reference grabbed during * isolation. */ if (put_new_page) put_new_page(new_hpage, private); else putback_active_hugepage(new_hpage); if (result) { if (rc) *result = rc; else *result = page_to_nid(new_hpage); } return rc; } /* * migrate_pages - migrate the pages specified in a list, to the free pages * supplied as the target for the page migration * * @from: The list of pages to be migrated. * @get_new_page: The function used to allocate free pages to be used * as the target of the page migration. * @put_new_page: The function used to free target pages if migration * fails, or NULL if no special handling is necessary. * @private: Private data to be passed on to get_new_page() * @mode: The migration mode that specifies the constraints for * page migration, if any. * @reason: The reason for page migration. * * The function returns after 10 attempts or if no pages are movable any more * because the list has become empty or no retryable pages exist any more. * The caller should call putback_movable_pages() to return pages to the LRU * or free list only if ret != 0. * * Returns the number of pages that were not migrated, or an error code. */ int migrate_pages(struct list_head *from, new_page_t get_new_page, free_page_t put_new_page, unsigned long private, enum migrate_mode mode, int reason) { int retry = 1; int nr_failed = 0; int nr_succeeded = 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(); if (PageHuge(page)) rc = unmap_and_move_huge_page(get_new_page, put_new_page, private, page, pass > 2, mode, reason); else rc = unmap_and_move(get_new_page, put_new_page, private, page, pass > 2, mode, reason); switch(rc) { case -ENOMEM: goto out; case -EAGAIN: retry++; break; case MIGRATEPAGE_SUCCESS: nr_succeeded++; break; default: /* * Permanent failure (-EBUSY, -ENOSYS, etc.): * unlike -EAGAIN case, the failed page is * removed from migration page list and not * retried in the next outer loop. */ nr_failed++; break; } } } nr_failed += retry; rc = nr_failed; out: if (nr_succeeded) count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); if (nr_failed) count_vm_events(PGMIGRATE_FAIL, nr_failed); trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason); if (!swapwrite) current->flags &= ~PF_SWAPWRITE; return rc; } #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; if (PageHuge(p)) return alloc_huge_page_node(page_hstate(compound_head(p)), pm->node); else 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); 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; /* FOLL_DUMP to ignore special (like zero) pages */ page = follow_page(vma, pp->addr, FOLL_GET | FOLL_SPLIT | FOLL_DUMP); err = PTR_ERR(page); if (IS_ERR(page)) goto set_status; err = -ENOENT; if (!page) goto set_status; 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; if (PageHuge(page)) { if (PageHead(page)) isolate_huge_page(page, &pagelist); 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, NULL, (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL); if (err) putback_movable_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, nodemask_t task_nodes, unsigned long nr_pages, const void __user * __user *pages, const int __user *nodes, int __user *status, int flags) { struct page_to_node *pm; unsigned long chunk_nr_pages; unsigned long chunk_start; int err; 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_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; /* FOLL_DUMP to ignore special (like zero) pages */ page = follow_page(vma, addr, FOLL_DUMP); err = PTR_ERR(page); if (IS_ERR(page)) goto set_status; err = page ? page_to_nid(page) : -ENOENT; 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; nodemask_t task_nodes; /* 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 */ rcu_read_lock(); task = pid ? find_task_by_vpid(pid) : current; if (!task) { rcu_read_unlock(); return -ESRCH; } get_task_struct(task); /* * 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. */ tcred = __task_cred(task); if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) && !uid_eq(cred->uid, tcred->suid) && !uid_eq(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; task_nodes = cpuset_mems_allowed(task); mm = get_task_mm(task); put_task_struct(task); if (!mm) return -EINVAL; if (nodes) err = do_pages_move(mm, task_nodes, nr_pages, pages, nodes, status, flags); else err = do_pages_stat(mm, nr_pages, pages, status); mmput(mm); return err; out: put_task_struct(task); return err; } #ifdef CONFIG_NUMA_BALANCING /* * Returns true if this is a safe migration target node for misplaced NUMA * pages. Currently it only checks the watermarks which crude */ static bool migrate_balanced_pgdat(struct pglist_data *pgdat, unsigned long nr_migrate_pages) { int z; for (z = pgdat->nr_zones - 1; z >= 0; z--) { struct zone *zone = pgdat->node_zones + z; if (!populated_zone(zone)) continue; if (!zone_reclaimable(zone)) continue; /* Avoid waking kswapd by allocating pages_to_migrate pages. */ if (!zone_watermark_ok(zone, 0, high_wmark_pages(zone) + nr_migrate_pages, 0, 0)) continue; return true; } return false; } static struct page *alloc_misplaced_dst_page(struct page *page, unsigned long data, int **result) { int nid = (int) data; struct page *newpage; newpage = __alloc_pages_node(nid, (GFP_HIGHUSER_MOVABLE | __GFP_THISNODE | __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN) & ~__GFP_RECLAIM, 0); return newpage; } /* * page migration rate limiting control. * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs * window of time. Default here says do not migrate more than 1280M per second. */ static unsigned int migrate_interval_millisecs __read_mostly = 100; static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT); /* Returns true if the node is migrate rate-limited after the update */ static bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages) { /* * Rate-limit the amount of data that is being migrated to a node. * Optimal placement is no good if the memory bus is saturated and * all the time is being spent migrating! */ if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) { spin_lock(&pgdat->numabalancing_migrate_lock); pgdat->numabalancing_migrate_nr_pages = 0; pgdat->numabalancing_migrate_next_window = jiffies + msecs_to_jiffies(migrate_interval_millisecs); spin_unlock(&pgdat->numabalancing_migrate_lock); } if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) { trace_mm_numa_migrate_ratelimit(current, pgdat->node_id, nr_pages); return true; } /* * This is an unlocked non-atomic update so errors are possible. * The consequences are failing to migrate when we potentiall should * have which is not severe enough to warrant locking. If it is ever * a problem, it can be converted to a per-cpu counter. */ pgdat->numabalancing_migrate_nr_pages += nr_pages; return false; } static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) { int page_lru; VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); /* Avoid migrating to a node that is nearly full */ if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) return 0; if (isolate_lru_page(page)) return 0; /* * migrate_misplaced_transhuge_page() skips page migration's usual * check on page_count(), so we must do it here, now that the page * has been isolated: a GUP pin, or any other pin, prevents migration. * The expected page count is 3: 1 for page's mapcount and 1 for the * caller's pin and 1 for the reference taken by isolate_lru_page(). */ if (PageTransHuge(page) && page_count(page) != 3) { putback_lru_page(page); return 0; } page_lru = page_is_file_cache(page); mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, hpage_nr_pages(page)); /* * Isolating the page has taken another reference, so the * caller's reference can be safely dropped without the page * disappearing underneath us during migration. */ put_page(page); return 1; } bool pmd_trans_migrating(pmd_t pmd) { struct page *page = pmd_page(pmd); return PageLocked(page); } /* * Attempt to migrate a misplaced page to the specified destination * node. Caller is expected to have an elevated reference count on * the page that will be dropped by this function before returning. */ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma, int node) { pg_data_t *pgdat = NODE_DATA(node); int isolated; int nr_remaining; LIST_HEAD(migratepages); /* * Don't migrate file pages that are mapped in multiple processes * with execute permissions as they are probably shared libraries. */ if (page_mapcount(page) != 1 && page_is_file_cache(page) && (vma->vm_flags & VM_EXEC)) goto out; /* * Rate-limit the amount of data that is being migrated to a node. * Optimal placement is no good if the memory bus is saturated and * all the time is being spent migrating! */ if (numamigrate_update_ratelimit(pgdat, 1)) goto out; isolated = numamigrate_isolate_page(pgdat, page); if (!isolated) goto out; list_add(&page->lru, &migratepages); nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page, NULL, node, MIGRATE_ASYNC, MR_NUMA_MISPLACED); if (nr_remaining) { if (!list_empty(&migratepages)) { list_del(&page->lru); dec_zone_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); putback_lru_page(page); } isolated = 0; } else count_vm_numa_event(NUMA_PAGE_MIGRATE); BUG_ON(!list_empty(&migratepages)); return isolated; out: put_page(page); return 0; } #endif /* CONFIG_NUMA_BALANCING */ #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE) /* * Migrates a THP to a given target node. page must be locked and is unlocked * before returning. */ int migrate_misplaced_transhuge_page(struct mm_struct *mm, struct vm_area_struct *vma, pmd_t *pmd, pmd_t entry, unsigned long address, struct page *page, int node) { spinlock_t *ptl; pg_data_t *pgdat = NODE_DATA(node); int isolated = 0; struct page *new_page = NULL; int page_lru = page_is_file_cache(page); unsigned long mmun_start = address & HPAGE_PMD_MASK; unsigned long mmun_end = mmun_start + HPAGE_PMD_SIZE; pmd_t orig_entry; /* * Rate-limit the amount of data that is being migrated to a node. * Optimal placement is no good if the memory bus is saturated and * all the time is being spent migrating! */ if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR)) goto out_dropref; new_page = alloc_pages_node(node, (GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM, HPAGE_PMD_ORDER); if (!new_page) goto out_fail; prep_transhuge_page(new_page); isolated = numamigrate_isolate_page(pgdat, page); if (!isolated) { put_page(new_page); goto out_fail; } /* * We are not sure a pending tlb flush here is for a huge page * mapping or not. Hence use the tlb range variant */ if (mm_tlb_flush_pending(mm)) flush_tlb_range(vma, mmun_start, mmun_end); /* Prepare a page as a migration target */ __SetPageLocked(new_page); SetPageSwapBacked(new_page); /* anon mapping, we can simply copy page->mapping to the new page: */ new_page->mapping = page->mapping; new_page->index = page->index; migrate_page_copy(new_page, page); WARN_ON(PageLRU(new_page)); /* Recheck the target PMD */ mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); ptl = pmd_lock(mm, pmd); if (unlikely(!pmd_same(*pmd, entry) || page_count(page) != 2)) { fail_putback: spin_unlock(ptl); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); /* Reverse changes made by migrate_page_copy() */ if (TestClearPageActive(new_page)) SetPageActive(page); if (TestClearPageUnevictable(new_page)) SetPageUnevictable(page); unlock_page(new_page); put_page(new_page); /* Free it */ /* Retake the callers reference and putback on LRU */ get_page(page); putback_lru_page(page); mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR); goto out_unlock; } orig_entry = *pmd; entry = mk_pmd(new_page, vma->vm_page_prot); entry = pmd_mkhuge(entry); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); /* * Clear the old entry under pagetable lock and establish the new PTE. * Any parallel GUP will either observe the old page blocking on the * page lock, block on the page table lock or observe the new page. * The SetPageUptodate on the new page and page_add_new_anon_rmap * guarantee the copy is visible before the pagetable update. */ flush_cache_range(vma, mmun_start, mmun_end); page_add_anon_rmap(new_page, vma, mmun_start, true); pmdp_huge_clear_flush_notify(vma, mmun_start, pmd); set_pmd_at(mm, mmun_start, pmd, entry); update_mmu_cache_pmd(vma, address, &entry); if (page_count(page) != 2) { set_pmd_at(mm, mmun_start, pmd, orig_entry); flush_pmd_tlb_range(vma, mmun_start, mmun_end); mmu_notifier_invalidate_range(mm, mmun_start, mmun_end); update_mmu_cache_pmd(vma, address, &entry); page_remove_rmap(new_page, true); goto fail_putback; } mlock_migrate_page(new_page, page); page_remove_rmap(page, true); set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED); spin_unlock(ptl); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); /* Take an "isolate" reference and put new page on the LRU. */ get_page(new_page); putback_lru_page(new_page); unlock_page(new_page); unlock_page(page); put_page(page); /* Drop the rmap reference */ put_page(page); /* Drop the LRU isolation reference */ count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR); count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR); mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR); return isolated; out_fail: count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); out_dropref: ptl = pmd_lock(mm, pmd); if (pmd_same(*pmd, entry)) { entry = pmd_modify(entry, vma->vm_page_prot); set_pmd_at(mm, mmun_start, pmd, entry); update_mmu_cache_pmd(vma, address, &entry); } spin_unlock(ptl); out_unlock: unlock_page(page); put_page(page); return 0; } #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_NUMA */