// SPDX-License-Identifier: GPL-2.0 /* * 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 #include #include #include #include #include #include #include #include #include #include #define CREATE_TRACE_POINTS #include #include "internal.h" int isolate_movable_page(struct page *page, isolate_mode_t mode) { struct address_space *mapping; /* * Avoid burning cycles with pages that are yet under __free_pages(), * or just got freed under us. * * In case we 'win' a race for a movable page being freed under us and * raise its refcount preventing __free_pages() from doing its job * the put_page() at the end of this block will take care of * release this page, thus avoiding a nasty leakage. */ if (unlikely(!get_page_unless_zero(page))) goto out; /* * Check PageMovable before holding a PG_lock because page's owner * assumes anybody doesn't touch PG_lock of newly allocated page * so unconditionally grabbing the lock ruins page's owner side. */ if (unlikely(!__PageMovable(page))) goto out_putpage; /* * As movable pages are not isolated from LRU lists, concurrent * compaction threads can race against page migration functions * as well as race against the releasing a page. * * In order to avoid having an already isolated movable page * being (wrongly) re-isolated while it is under migration, * or to avoid attempting to isolate pages being released, * lets be sure we have the page lock * before proceeding with the movable page isolation steps. */ if (unlikely(!trylock_page(page))) goto out_putpage; if (!PageMovable(page) || PageIsolated(page)) goto out_no_isolated; mapping = page_mapping(page); VM_BUG_ON_PAGE(!mapping, page); if (!mapping->a_ops->isolate_page(page, mode)) goto out_no_isolated; /* Driver shouldn't use PG_isolated bit of page->flags */ WARN_ON_ONCE(PageIsolated(page)); __SetPageIsolated(page); unlock_page(page); return 0; out_no_isolated: unlock_page(page); out_putpage: put_page(page); out: return -EBUSY; } static void putback_movable_page(struct page *page) { struct address_space *mapping; mapping = page_mapping(page); mapping->a_ops->putback_page(page); __ClearPageIsolated(page); } /* * 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_hugetlb(). */ 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); /* * We isolated non-lru movable page so here we can use * __PageMovable because LRU page's mapping cannot have * PAGE_MAPPING_MOVABLE. */ if (unlikely(__PageMovable(page))) { VM_BUG_ON_PAGE(!PageIsolated(page), page); lock_page(page); if (PageMovable(page)) putback_movable_page(page); else __ClearPageIsolated(page); unlock_page(page); put_page(page); } else { mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page), -thp_nr_pages(page)); putback_lru_page(page); } } } /* * Restore a potential migration pte to a working pte entry */ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, unsigned long addr, void *old) { struct page_vma_mapped_walk pvmw = { .page = old, .vma = vma, .address = addr, .flags = PVMW_SYNC | PVMW_MIGRATION, }; struct page *new; pte_t pte; swp_entry_t entry; VM_BUG_ON_PAGE(PageTail(page), page); while (page_vma_mapped_walk(&pvmw)) { if (PageKsm(page)) new = page; else new = page - pvmw.page->index + linear_page_index(vma, pvmw.address); #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION /* PMD-mapped THP migration entry */ if (!pvmw.pte) { VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page); remove_migration_pmd(&pvmw, new); continue; } #endif get_page(new); pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot))); if (pte_swp_soft_dirty(*pvmw.pte)) pte = pte_mksoft_dirty(pte); /* * Recheck VMA as permissions can change since migration started */ entry = pte_to_swp_entry(*pvmw.pte); if (is_writable_migration_entry(entry)) pte = maybe_mkwrite(pte, vma); else if (pte_swp_uffd_wp(*pvmw.pte)) pte = pte_mkuffd_wp(pte); if (unlikely(is_device_private_page(new))) { if (pte_write(pte)) entry = make_writable_device_private_entry( page_to_pfn(new)); else entry = make_readable_device_private_entry( page_to_pfn(new)); pte = swp_entry_to_pte(entry); if (pte_swp_soft_dirty(*pvmw.pte)) pte = pte_swp_mksoft_dirty(pte); if (pte_swp_uffd_wp(*pvmw.pte)) pte = pte_swp_mkuffd_wp(pte); } #ifdef CONFIG_HUGETLB_PAGE if (PageHuge(new)) { unsigned int shift = huge_page_shift(hstate_vma(vma)); pte = pte_mkhuge(pte); pte = arch_make_huge_pte(pte, shift, vma->vm_flags); set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); if (PageAnon(new)) hugepage_add_anon_rmap(new, vma, pvmw.address); else page_dup_rmap(new, true); } else #endif { set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); if (PageAnon(new)) page_add_anon_rmap(new, vma, pvmw.address, false); else page_add_file_rmap(new, false); } if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new)) mlock_vma_page(new); if (PageTransHuge(page) && PageMlocked(page)) clear_page_mlock(page); /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, pvmw.address, pvmw.pte); } return true; } /* * Get rid of all migration entries and replace them by * references to the indicated page. */ void remove_migration_ptes(struct page *old, struct page *new, bool locked) { struct rmap_walk_control rwc = { .rmap_one = remove_migration_pte, .arg = old, }; if (locked) rmap_walk_locked(new, &rwc); else 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 = pfn_swap_entry_to_page(entry); page = compound_head(page); /* * Once page cache replacement of page migration started, page_count * is zero; but we must not call put_and_wait_on_page_locked() without * a ref. Use get_page_unless_zero(), and just fault again if it fails. */ if (!get_page_unless_zero(page)) goto out; pte_unmap_unlock(ptep, ptl); put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); 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_ARCH_ENABLE_THP_MIGRATION void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd) { spinlock_t *ptl; struct page *page; ptl = pmd_lock(mm, pmd); if (!is_pmd_migration_entry(*pmd)) goto unlock; page = pfn_swap_entry_to_page(pmd_to_swp_entry(*pmd)); if (!get_page_unless_zero(page)) goto unlock; spin_unlock(ptl); put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); return; unlock: spin_unlock(ptl); } #endif static int expected_page_refs(struct address_space *mapping, struct page *page) { int expected_count = 1; /* * Device private pages have an extra refcount as they are * ZONE_DEVICE pages. */ expected_count += is_device_private_page(page); if (mapping) expected_count += thp_nr_pages(page) + page_has_private(page); return expected_count; } /* * 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, int extra_count) { XA_STATE(xas, &mapping->i_pages, page_index(page)); struct zone *oldzone, *newzone; int dirty; int expected_count = expected_page_refs(mapping, page) + extra_count; int nr = thp_nr_pages(page); 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); xas_lock_irq(&xas); if (page_count(page) != expected_count || xas_load(&xas) != page) { xas_unlock_irq(&xas); return -EAGAIN; } if (!page_ref_freeze(page, expected_count)) { xas_unlock_irq(&xas); 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; page_ref_add(newpage, nr); /* add cache reference */ if (PageSwapBacked(page)) { __SetPageSwapBacked(newpage); if (PageSwapCache(page)) { int i; SetPageSwapCache(newpage); for (i = 0; i < (1 << compound_order(page)); i++) set_page_private(newpage + i, page_private(page + i)); } } else { VM_BUG_ON_PAGE(PageSwapCache(page), page); } /* Move dirty while page refs frozen and newpage not yet exposed */ dirty = PageDirty(page); if (dirty) { ClearPageDirty(page); SetPageDirty(newpage); } xas_store(&xas, newpage); if (PageTransHuge(page)) { int i; for (i = 1; i < nr; i++) { xas_next(&xas); xas_store(&xas, newpage); } } /* * Drop cache reference from old page by unfreezing * to one less reference. * We know this isn't the last reference. */ page_ref_unfreeze(page, expected_count - nr); xas_unlock(&xas); /* 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_MAPPED if they * are mapped to swap space. */ if (newzone != oldzone) { struct lruvec *old_lruvec, *new_lruvec; struct mem_cgroup *memcg; memcg = page_memcg(page); old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat); new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat); __mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr); __mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr); if (PageSwapBacked(page) && !PageSwapCache(page)) { __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr); __mod_lruvec_state(new_lruvec, NR_SHMEM, nr); } #ifdef CONFIG_SWAP if (PageSwapCache(page)) { __mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr); __mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr); } #endif if (dirty && mapping_can_writeback(mapping)) { __mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr); __mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr); __mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr); __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr); } } local_irq_enable(); return MIGRATEPAGE_SUCCESS; } EXPORT_SYMBOL(migrate_page_move_mapping); /* * 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) { XA_STATE(xas, &mapping->i_pages, page_index(page)); int expected_count; xas_lock_irq(&xas); expected_count = 2 + page_has_private(page); if (page_count(page) != expected_count || xas_load(&xas) != page) { xas_unlock_irq(&xas); return -EAGAIN; } if (!page_ref_freeze(page, expected_count)) { xas_unlock_irq(&xas); return -EAGAIN; } newpage->index = page->index; newpage->mapping = page->mapping; get_page(newpage); xas_store(&xas, newpage); page_ref_unfreeze(page, expected_count - 1); xas_unlock_irq(&xas); return MIGRATEPAGE_SUCCESS; } /* * Copy the page to its new location */ void migrate_page_states(struct page *newpage, struct page *page) { int cpupid; 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 (PageWorkingset(page)) SetPageWorkingset(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); /* page->private contains hugetlb specific flags */ if (!PageHuge(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); /* * PG_readahead shares the same bit with PG_reclaim. The above * end_page_writeback() may clear PG_readahead mistakenly, so set the * bit after that. */ if (PageReadahead(page)) SetPageReadahead(newpage); copy_page_owner(page, newpage); if (!PageHuge(page)) mem_cgroup_migrate(page, newpage); } EXPORT_SYMBOL(migrate_page_states); void migrate_page_copy(struct page *newpage, struct page *page) { if (PageHuge(page) || PageTransHuge(page)) copy_huge_page(newpage, page); else copy_highpage(newpage, page); migrate_page_states(newpage, page); } EXPORT_SYMBOL(migrate_page_copy); /************************************************************ * Migration functions ***********************************************************/ /* * Common logic to directly migrate a single LRU 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, 0); if (rc != MIGRATEPAGE_SUCCESS) return rc; if (mode != MIGRATE_SYNC_NO_COPY) migrate_page_copy(newpage, page); else migrate_page_states(newpage, page); return MIGRATEPAGE_SUCCESS; } EXPORT_SYMBOL(migrate_page); #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 { 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 { 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; bh = head; while (bh != failed_bh) { unlock_buffer(bh); bh = bh->b_this_page; } return false; } bh = bh->b_this_page; } while (bh != head); return true; } static int __buffer_migrate_page(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode, bool check_refs) { struct buffer_head *bh, *head; int rc; int expected_count; if (!page_has_buffers(page)) return migrate_page(mapping, newpage, page, mode); /* Check whether page does not have extra refs before we do more work */ expected_count = expected_page_refs(mapping, page); if (page_count(page) != expected_count) return -EAGAIN; head = page_buffers(page); if (!buffer_migrate_lock_buffers(head, mode)) return -EAGAIN; if (check_refs) { bool busy; bool invalidated = false; recheck_buffers: busy = false; spin_lock(&mapping->private_lock); bh = head; do { if (atomic_read(&bh->b_count)) { busy = true; break; } bh = bh->b_this_page; } while (bh != head); if (busy) { if (invalidated) { rc = -EAGAIN; goto unlock_buffers; } spin_unlock(&mapping->private_lock); invalidate_bh_lrus(); invalidated = true; goto recheck_buffers; } } rc = migrate_page_move_mapping(mapping, newpage, page, 0); if (rc != MIGRATEPAGE_SUCCESS) goto unlock_buffers; attach_page_private(newpage, detach_page_private(page)); bh = head; do { set_bh_page(bh, newpage, bh_offset(bh)); bh = bh->b_this_page; } while (bh != head); if (mode != MIGRATE_SYNC_NO_COPY) migrate_page_copy(newpage, page); else migrate_page_states(newpage, page); rc = MIGRATEPAGE_SUCCESS; unlock_buffers: if (check_refs) spin_unlock(&mapping->private_lock); bh = head; do { unlock_buffer(bh); bh = bh->b_this_page; } while (bh != head); return rc; } /* * Migration function for pages with buffers. This function can only be used * if the underlying filesystem guarantees that no other references to "page" * exist. For example attached buffer heads are accessed only under page lock. */ int buffer_migrate_page(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode) { return __buffer_migrate_page(mapping, newpage, page, mode, false); } EXPORT_SYMBOL(buffer_migrate_page); /* * Same as above except that this variant is more careful and checks that there * are also no buffer head references. This function is the right one for * mappings where buffer heads are directly looked up and referenced (such as * block device mappings). */ int buffer_migrate_page_norefs(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode) { return __buffer_migrate_page(mapping, newpage, page, mode, true); } #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, false); 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 */ switch (mode) { case MIGRATE_SYNC: case MIGRATE_SYNC_NO_COPY: break; default: 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 mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY; 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 = -EAGAIN; bool is_lru = !__PageMovable(page); VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); mapping = page_mapping(page); if (likely(is_lru)) { 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); } else { /* * In case of non-lru page, it could be released after * isolation step. In that case, we shouldn't try migration. */ VM_BUG_ON_PAGE(!PageIsolated(page), page); if (!PageMovable(page)) { rc = MIGRATEPAGE_SUCCESS; __ClearPageIsolated(page); goto out; } rc = mapping->a_ops->migratepage(mapping, newpage, page, mode); WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS && !PageIsolated(page)); } /* * 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 (__PageMovable(page)) { VM_BUG_ON_PAGE(!PageIsolated(page), page); /* * We clear PG_movable under page_lock so any compactor * cannot try to migrate this page. */ __ClearPageIsolated(page); } /* * Anonymous and movable page->mapping will be cleared by * free_pages_prepare so don't reset it here for keeping * the type to work PageAnon, for example. */ if (!PageMappingFlags(page)) page->mapping = NULL; if (likely(!is_zone_device_page(newpage))) { int i, nr = compound_nr(newpage); for (i = 0; i < nr; i++) flush_dcache_page(newpage + i); } } out: return rc; } static int __unmap_and_move(struct page *page, struct page *newpage, int force, enum migrate_mode mode) { int rc = -EAGAIN; bool page_was_mapped = false; struct anon_vma *anon_vma = NULL; bool is_lru = !__PageMovable(page); 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_readahead). 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 */ switch (mode) { case MIGRATE_SYNC: case MIGRATE_SYNC_NO_COPY: break; default: rc = -EBUSY; goto out_unlock; } if (!force) goto out_unlock; wait_on_page_writeback(page); } /* * By try_to_migrate(), 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(!is_lru)) { rc = move_to_new_page(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_cleanup_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_migrate(page, 0); page_was_mapped = true; } 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, false); 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: /* * If migration is successful, decrease refcount of the newpage * which will not free the page because new page owner increased * refcounter. As well, if it is LRU page, add the page to LRU * list in here. Use the old state of the isolated source page to * determine if we migrated a LRU page. newpage was already unlocked * and possibly modified by its owner - don't rely on the page * state. */ if (rc == MIGRATEPAGE_SUCCESS) { if (unlikely(!is_lru)) put_page(newpage); else putback_lru_page(newpage); } return rc; } /* * node_demotion[] example: * * Consider a system with two sockets. Each socket has * three classes of memory attached: fast, medium and slow. * Each memory class is placed in its own NUMA node. The * CPUs are placed in the node with the "fast" memory. The * 6 NUMA nodes (0-5) might be split among the sockets like * this: * * Socket A: 0, 1, 2 * Socket B: 3, 4, 5 * * When Node 0 fills up, its memory should be migrated to * Node 1. When Node 1 fills up, it should be migrated to * Node 2. The migration path start on the nodes with the * processors (since allocations default to this node) and * fast memory, progress through medium and end with the * slow memory: * * 0 -> 1 -> 2 -> stop * 3 -> 4 -> 5 -> stop * * This is represented in the node_demotion[] like this: * * { 1, // Node 0 migrates to 1 * 2, // Node 1 migrates to 2 * -1, // Node 2 does not migrate * 4, // Node 3 migrates to 4 * 5, // Node 4 migrates to 5 * -1} // Node 5 does not migrate */ /* * Writes to this array occur without locking. Cycles are * not allowed: Node X demotes to Y which demotes to X... * * If multiple reads are performed, a single rcu_read_lock() * must be held over all reads to ensure that no cycles are * observed. */ static int node_demotion[MAX_NUMNODES] __read_mostly = {[0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE}; /** * next_demotion_node() - Get the next node in the demotion path * @node: The starting node to lookup the next node * * Return: node id for next memory node in the demotion path hierarchy * from @node; NUMA_NO_NODE if @node is terminal. This does not keep * @node online or guarantee that it *continues* to be the next demotion * target. */ int next_demotion_node(int node) { int target; /* * node_demotion[] is updated without excluding this * function from running. RCU doesn't provide any * compiler barriers, so the READ_ONCE() is required * to avoid compiler reordering or read merging. * * Make sure to use RCU over entire code blocks if * node_demotion[] reads need to be consistent. */ rcu_read_lock(); target = READ_ONCE(node_demotion[node]); rcu_read_unlock(); return target; } /* * 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, free_page_t put_new_page, unsigned long private, struct page *page, int force, enum migrate_mode mode, enum migrate_reason reason, struct list_head *ret) { int rc = MIGRATEPAGE_SUCCESS; struct page *newpage = NULL; if (!thp_migration_supported() && PageTransHuge(page)) return -ENOSYS; if (page_count(page) == 1) { /* page was freed from under us. So we are done. */ ClearPageActive(page); ClearPageUnevictable(page); if (unlikely(__PageMovable(page))) { lock_page(page); if (!PageMovable(page)) __ClearPageIsolated(page); unlock_page(page); } goto out; } newpage = get_new_page(page, private); if (!newpage) return -ENOMEM; rc = __unmap_and_move(page, newpage, force, mode); if (rc == MIGRATEPAGE_SUCCESS) 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 kept its references and be restored. */ list_del(&page->lru); } /* * If migration is successful, releases reference grabbed during * isolation. Otherwise, restore the page to right list unless * we want to retry. */ if (rc == MIGRATEPAGE_SUCCESS) { /* * Compaction can migrate also non-LRU pages which are * not accounted to NR_ISOLATED_*. They can be recognized * as __PageMovable */ if (likely(!__PageMovable(page))) mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page), -thp_nr_pages(page)); if (reason != MR_MEMORY_FAILURE) /* * We release the page in page_handle_poison. */ put_page(page); } else { if (rc != -EAGAIN) list_add_tail(&page->lru, ret); if (put_new_page) put_new_page(newpage, private); else put_page(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, struct list_head *ret) { int rc = -EAGAIN; int page_was_mapped = 0; struct page *new_hpage; struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; /* * Migratability of hugepages depends on architectures and their 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))) { list_move_tail(&hpage->lru, ret); return -ENOSYS; } if (page_count(hpage) == 1) { /* page was freed from under us. So we are done. */ putback_active_hugepage(hpage); return MIGRATEPAGE_SUCCESS; } new_hpage = get_new_page(hpage, private); if (!new_hpage) return -ENOMEM; if (!trylock_page(hpage)) { if (!force) goto out; switch (mode) { case MIGRATE_SYNC: case MIGRATE_SYNC_NO_COPY: break; default: goto out; } lock_page(hpage); } /* * Check for pages which are in the process of being freed. Without * page_mapping() set, hugetlbfs specific move page routine will not * be called and we could leak usage counts for subpools. */ if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) { rc = -EBUSY; goto out_unlock; } if (PageAnon(hpage)) anon_vma = page_get_anon_vma(hpage); if (unlikely(!trylock_page(new_hpage))) goto put_anon; if (page_mapped(hpage)) { bool mapping_locked = false; enum ttu_flags ttu = 0; if (!PageAnon(hpage)) { /* * In shared mappings, try_to_unmap could potentially * call huge_pmd_unshare. Because of this, take * semaphore in write mode here and set TTU_RMAP_LOCKED * to let lower levels know we have taken the lock. */ mapping = hugetlb_page_mapping_lock_write(hpage); if (unlikely(!mapping)) goto unlock_put_anon; mapping_locked = true; ttu |= TTU_RMAP_LOCKED; } try_to_migrate(hpage, ttu); page_was_mapped = 1; if (mapping_locked) i_mmap_unlock_write(mapping); } 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, false); unlock_put_anon: unlock_page(new_hpage); put_anon: if (anon_vma) put_anon_vma(anon_vma); if (rc == MIGRATEPAGE_SUCCESS) { move_hugetlb_state(hpage, new_hpage, reason); put_new_page = NULL; } out_unlock: unlock_page(hpage); out: if (rc == MIGRATEPAGE_SUCCESS) putback_active_hugepage(hpage); else if (rc != -EAGAIN) list_move_tail(&hpage->lru, ret); /* * 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); return rc; } static inline int try_split_thp(struct page *page, struct page **page2, struct list_head *from) { int rc = 0; lock_page(page); rc = split_huge_page_to_list(page, from); unlock_page(page); if (!rc) list_safe_reset_next(page, *page2, lru); 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. * @ret_succeeded: Set to the number of pages migrated successfully if * the caller passes a non-NULL pointer. * * 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. * It is caller's responsibility to 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, unsigned int *ret_succeeded) { int retry = 1; int thp_retry = 1; int nr_failed = 0; int nr_succeeded = 0; int nr_thp_succeeded = 0; int nr_thp_failed = 0; int nr_thp_split = 0; int pass = 0; bool is_thp = false; struct page *page; struct page *page2; int swapwrite = current->flags & PF_SWAPWRITE; int rc, nr_subpages; LIST_HEAD(ret_pages); bool nosplit = (reason == MR_NUMA_MISPLACED); trace_mm_migrate_pages_start(mode, reason); if (!swapwrite) current->flags |= PF_SWAPWRITE; for (pass = 0; pass < 10 && (retry || thp_retry); pass++) { retry = 0; thp_retry = 0; list_for_each_entry_safe(page, page2, from, lru) { retry: /* * THP statistics is based on the source huge page. * Capture required information that might get lost * during migration. */ is_thp = PageTransHuge(page) && !PageHuge(page); nr_subpages = thp_nr_pages(page); cond_resched(); if (PageHuge(page)) rc = unmap_and_move_huge_page(get_new_page, put_new_page, private, page, pass > 2, mode, reason, &ret_pages); else rc = unmap_and_move(get_new_page, put_new_page, private, page, pass > 2, mode, reason, &ret_pages); /* * The rules are: * Success: non hugetlb page will be freed, hugetlb * page will be put back * -EAGAIN: stay on the from list * -ENOMEM: stay on the from list * Other errno: put on ret_pages list then splice to * from list */ switch(rc) { /* * THP migration might be unsupported or the * allocation could've failed so we should * retry on the same page with the THP split * to base pages. * * Head page is retried immediately and tail * pages are added to the tail of the list so * we encounter them after the rest of the list * is processed. */ case -ENOSYS: /* THP migration is unsupported */ if (is_thp) { if (!try_split_thp(page, &page2, from)) { nr_thp_split++; goto retry; } nr_thp_failed++; nr_failed += nr_subpages; break; } /* Hugetlb migration is unsupported */ nr_failed++; break; case -ENOMEM: /* * When memory is low, don't bother to try to migrate * other pages, just exit. * THP NUMA faulting doesn't split THP to retry. */ if (is_thp && !nosplit) { if (!try_split_thp(page, &page2, from)) { nr_thp_split++; goto retry; } nr_thp_failed++; nr_failed += nr_subpages; goto out; } nr_failed++; goto out; case -EAGAIN: if (is_thp) { thp_retry++; break; } retry++; break; case MIGRATEPAGE_SUCCESS: if (is_thp) { nr_thp_succeeded++; nr_succeeded += nr_subpages; break; } nr_succeeded++; break; default: /* * Permanent failure (-EBUSY, etc.): * unlike -EAGAIN case, the failed page is * removed from migration page list and not * retried in the next outer loop. */ if (is_thp) { nr_thp_failed++; nr_failed += nr_subpages; break; } nr_failed++; break; } } } nr_failed += retry + thp_retry; nr_thp_failed += thp_retry; rc = nr_failed; out: /* * Put the permanent failure page back to migration list, they * will be put back to the right list by the caller. */ list_splice(&ret_pages, from); count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); count_vm_events(PGMIGRATE_FAIL, nr_failed); count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded); count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed); count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split); trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded, nr_thp_failed, nr_thp_split, mode, reason); if (!swapwrite) current->flags &= ~PF_SWAPWRITE; if (ret_succeeded) *ret_succeeded = nr_succeeded; return rc; } struct page *alloc_migration_target(struct page *page, unsigned long private) { struct migration_target_control *mtc; gfp_t gfp_mask; unsigned int order = 0; struct page *new_page = NULL; int nid; int zidx; mtc = (struct migration_target_control *)private; gfp_mask = mtc->gfp_mask; nid = mtc->nid; if (nid == NUMA_NO_NODE) nid = page_to_nid(page); if (PageHuge(page)) { struct hstate *h = page_hstate(compound_head(page)); gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); return alloc_huge_page_nodemask(h, nid, mtc->nmask, gfp_mask); } if (PageTransHuge(page)) { /* * clear __GFP_RECLAIM to make the migration callback * consistent with regular THP allocations. */ gfp_mask &= ~__GFP_RECLAIM; gfp_mask |= GFP_TRANSHUGE; order = HPAGE_PMD_ORDER; } zidx = zone_idx(page_zone(page)); if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE) gfp_mask |= __GFP_HIGHMEM; new_page = __alloc_pages(gfp_mask, order, nid, mtc->nmask); if (new_page && PageTransHuge(new_page)) prep_transhuge_page(new_page); return new_page; } #ifdef CONFIG_NUMA static int store_status(int __user *status, int start, int value, int nr) { while (nr-- > 0) { if (put_user(value, status + start)) return -EFAULT; start++; } return 0; } static int do_move_pages_to_node(struct mm_struct *mm, struct list_head *pagelist, int node) { int err; struct migration_target_control mtc = { .nid = node, .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, }; err = migrate_pages(pagelist, alloc_migration_target, NULL, (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL); if (err) putback_movable_pages(pagelist); return err; } /* * Resolves the given address to a struct page, isolates it from the LRU and * puts it to the given pagelist. * Returns: * errno - if the page cannot be found/isolated * 0 - when it doesn't have to be migrated because it is already on the * target node * 1 - when it has been queued */ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, int node, struct list_head *pagelist, bool migrate_all) { struct vm_area_struct *vma; struct page *page; unsigned int follflags; int err; mmap_read_lock(mm); err = -EFAULT; vma = find_vma(mm, addr); if (!vma || addr < vma->vm_start || !vma_migratable(vma)) goto out; /* FOLL_DUMP to ignore special (like zero) pages */ follflags = FOLL_GET | FOLL_DUMP; page = follow_page(vma, addr, follflags); err = PTR_ERR(page); if (IS_ERR(page)) goto out; err = -ENOENT; if (!page) goto out; err = 0; if (page_to_nid(page) == node) goto out_putpage; err = -EACCES; if (page_mapcount(page) > 1 && !migrate_all) goto out_putpage; if (PageHuge(page)) { if (PageHead(page)) { err = isolate_hugetlb(page, pagelist); if (!err) err = 1; } } else { struct page *head; head = compound_head(page); err = isolate_lru_page(head); if (err) goto out_putpage; err = 1; list_add_tail(&head->lru, pagelist); mod_node_page_state(page_pgdat(head), NR_ISOLATED_ANON + page_is_file_lru(head), thp_nr_pages(head)); } out_putpage: /* * Either remove the duplicate refcount from * isolate_lru_page() or drop the page ref if it was * not isolated. */ put_page(page); out: mmap_read_unlock(mm); return err; } static int move_pages_and_store_status(struct mm_struct *mm, int node, struct list_head *pagelist, int __user *status, int start, int i, unsigned long nr_pages) { int err; if (list_empty(pagelist)) return 0; err = do_move_pages_to_node(mm, pagelist, node); if (err) { /* * Positive err means the number of failed * pages to migrate. Since we are going to * abort and return the number of non-migrated * pages, so need to include the rest of the * nr_pages that have not been attempted as * well. */ if (err > 0) err += nr_pages - i - 1; return err; } return store_status(status, start, node, i - start); } /* * 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) { compat_uptr_t __user *compat_pages = (void __user *)pages; int current_node = NUMA_NO_NODE; LIST_HEAD(pagelist); int start, i; int err = 0, err1; lru_cache_disable(); for (i = start = 0; i < nr_pages; i++) { const void __user *p; unsigned long addr; int node; err = -EFAULT; if (in_compat_syscall()) { compat_uptr_t cp; if (get_user(cp, compat_pages + i)) goto out_flush; p = compat_ptr(cp); } else { if (get_user(p, pages + i)) goto out_flush; } if (get_user(node, nodes + i)) goto out_flush; addr = (unsigned long)untagged_addr(p); err = -ENODEV; if (node < 0 || node >= MAX_NUMNODES) goto out_flush; if (!node_state(node, N_MEMORY)) goto out_flush; err = -EACCES; if (!node_isset(node, task_nodes)) goto out_flush; if (current_node == NUMA_NO_NODE) { current_node = node; start = i; } else if (node != current_node) { err = move_pages_and_store_status(mm, current_node, &pagelist, status, start, i, nr_pages); if (err) goto out; start = i; current_node = node; } /* * Errors in the page lookup or isolation are not fatal and we simply * report them via status */ err = add_page_for_migration(mm, addr, current_node, &pagelist, flags & MPOL_MF_MOVE_ALL); if (err > 0) { /* The page is successfully queued for migration */ continue; } /* * If the page is already on the target node (!err), store the * node, otherwise, store the err. */ err = store_status(status, i, err ? : current_node, 1); if (err) goto out_flush; err = move_pages_and_store_status(mm, current_node, &pagelist, status, start, i, nr_pages); if (err) goto out; current_node = NUMA_NO_NODE; } out_flush: /* Make sure we do not overwrite the existing error */ err1 = move_pages_and_store_status(mm, current_node, &pagelist, status, start, i, nr_pages); if (err >= 0) err = err1; out: lru_cache_enable(); 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; mmap_read_lock(mm); 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 = vma_lookup(mm, addr); if (!vma) 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++; } mmap_read_unlock(mm); } static int get_compat_pages_array(const void __user *chunk_pages[], const void __user * __user *pages, unsigned long chunk_nr) { compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; compat_uptr_t p; int i; for (i = 0; i < chunk_nr; i++) { if (get_user(p, pages32 + i)) return -EFAULT; chunk_pages[i] = compat_ptr(p); } return 0; } /* * 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 (in_compat_syscall()) { if (get_compat_pages_array(chunk_pages, pages, chunk_nr)) break; } else { 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; } static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes) { struct task_struct *task; struct mm_struct *mm; /* * There is no need to check if current process has the right to modify * the specified process when they are same. */ if (!pid) { mmget(current->mm); *mem_nodes = cpuset_mems_allowed(current); return current->mm; } /* Find the mm_struct */ rcu_read_lock(); task = find_task_by_vpid(pid); if (!task) { rcu_read_unlock(); return ERR_PTR(-ESRCH); } get_task_struct(task); /* * Check if this process has the right to modify the specified * process. Use the regular "ptrace_may_access()" checks. */ if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { rcu_read_unlock(); mm = ERR_PTR(-EPERM); goto out; } rcu_read_unlock(); mm = ERR_PTR(security_task_movememory(task)); if (IS_ERR(mm)) goto out; *mem_nodes = cpuset_mems_allowed(task); mm = get_task_mm(task); out: put_task_struct(task); if (!mm) mm = ERR_PTR(-EINVAL); return mm; } /* * Move a list of pages in the address space of the currently executing * process. */ static int kernel_move_pages(pid_t pid, unsigned long nr_pages, const void __user * __user *pages, const int __user *nodes, int __user *status, int flags) { 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; mm = find_mm_struct(pid, &task_nodes); if (IS_ERR(mm)) return PTR_ERR(mm); 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; } 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) { return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags); } #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; /* Avoid waking kswapd by allocating pages_to_migrate pages. */ if (!zone_watermark_ok(zone, 0, high_wmark_pages(zone) + nr_migrate_pages, ZONE_MOVABLE, 0)) continue; return true; } return false; } static struct page *alloc_misplaced_dst_page(struct page *page, unsigned long data) { 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; } static struct page *alloc_misplaced_dst_page_thp(struct page *page, unsigned long data) { int nid = (int) data; struct page *newpage; newpage = alloc_pages_node(nid, (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE), HPAGE_PMD_ORDER); if (!newpage) goto out; prep_transhuge_page(newpage); out: return newpage; } static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) { int page_lru; int nr_pages = thp_nr_pages(page); VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); /* Do not migrate THP mapped by multiple processes */ if (PageTransHuge(page) && total_mapcount(page) > 1) return 0; /* Avoid migrating to a node that is nearly full */ if (!migrate_balanced_pgdat(pgdat, nr_pages)) return 0; if (isolate_lru_page(page)) return 0; page_lru = page_is_file_lru(page); mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru, nr_pages); /* * 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; } /* * 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); new_page_t *new; bool compound; int nr_pages = thp_nr_pages(page); /* * PTE mapped THP or HugeTLB page can't reach here so the page could * be either base page or THP. And it must be head page if it is * THP. */ compound = PageTransHuge(page); if (compound) new = alloc_misplaced_dst_page_thp; else new = alloc_misplaced_dst_page; /* * 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_lru(page) && (vma->vm_flags & VM_EXEC)) goto out; /* * Also do not migrate dirty pages as not all filesystems can move * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles. */ if (page_is_file_lru(page) && PageDirty(page)) goto out; isolated = numamigrate_isolate_page(pgdat, page); if (!isolated) goto out; list_add(&page->lru, &migratepages); nr_remaining = migrate_pages(&migratepages, *new, NULL, node, MIGRATE_ASYNC, MR_NUMA_MISPLACED, NULL); if (nr_remaining) { if (!list_empty(&migratepages)) { list_del(&page->lru); mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page), -nr_pages); putback_lru_page(page); } isolated = 0; } else count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_pages); BUG_ON(!list_empty(&migratepages)); return isolated; out: put_page(page); return 0; } #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_NUMA */ #ifdef CONFIG_DEVICE_PRIVATE static int migrate_vma_collect_skip(unsigned long start, unsigned long end, struct mm_walk *walk) { struct migrate_vma *migrate = walk->private; unsigned long addr; for (addr = start; addr < end; addr += PAGE_SIZE) { migrate->dst[migrate->npages] = 0; migrate->src[migrate->npages++] = 0; } return 0; } static int migrate_vma_collect_hole(unsigned long start, unsigned long end, __always_unused int depth, struct mm_walk *walk) { struct migrate_vma *migrate = walk->private; unsigned long addr; /* Only allow populating anonymous memory. */ if (!vma_is_anonymous(walk->vma)) return migrate_vma_collect_skip(start, end, walk); for (addr = start; addr < end; addr += PAGE_SIZE) { migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE; migrate->dst[migrate->npages] = 0; migrate->npages++; migrate->cpages++; } return 0; } static int migrate_vma_collect_pmd(pmd_t *pmdp, unsigned long start, unsigned long end, struct mm_walk *walk) { struct migrate_vma *migrate = walk->private; struct vm_area_struct *vma = walk->vma; struct mm_struct *mm = vma->vm_mm; unsigned long addr = start, unmapped = 0; spinlock_t *ptl; pte_t *ptep; again: if (pmd_none(*pmdp)) return migrate_vma_collect_hole(start, end, -1, walk); if (pmd_trans_huge(*pmdp)) { struct page *page; ptl = pmd_lock(mm, pmdp); if (unlikely(!pmd_trans_huge(*pmdp))) { spin_unlock(ptl); goto again; } page = pmd_page(*pmdp); if (is_huge_zero_page(page)) { spin_unlock(ptl); split_huge_pmd(vma, pmdp, addr); if (pmd_trans_unstable(pmdp)) return migrate_vma_collect_skip(start, end, walk); } else { int ret; get_page(page); spin_unlock(ptl); if (unlikely(!trylock_page(page))) return migrate_vma_collect_skip(start, end, walk); ret = split_huge_page(page); unlock_page(page); put_page(page); if (ret) return migrate_vma_collect_skip(start, end, walk); if (pmd_none(*pmdp)) return migrate_vma_collect_hole(start, end, -1, walk); } } if (unlikely(pmd_bad(*pmdp))) return migrate_vma_collect_skip(start, end, walk); ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); arch_enter_lazy_mmu_mode(); for (; addr < end; addr += PAGE_SIZE, ptep++) { unsigned long mpfn = 0, pfn; struct page *page; swp_entry_t entry; pte_t pte; pte = *ptep; if (pte_none(pte)) { if (vma_is_anonymous(vma)) { mpfn = MIGRATE_PFN_MIGRATE; migrate->cpages++; } goto next; } if (!pte_present(pte)) { /* * Only care about unaddressable device page special * page table entry. Other special swap entries are not * migratable, and we ignore regular swapped page. */ entry = pte_to_swp_entry(pte); if (!is_device_private_entry(entry)) goto next; page = pfn_swap_entry_to_page(entry); if (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_PRIVATE) || page->pgmap->owner != migrate->pgmap_owner) goto next; mpfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE; if (is_writable_device_private_entry(entry)) mpfn |= MIGRATE_PFN_WRITE; } else { if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) goto next; pfn = pte_pfn(pte); if (is_zero_pfn(pfn)) { mpfn = MIGRATE_PFN_MIGRATE; migrate->cpages++; goto next; } page = vm_normal_page(migrate->vma, addr, pte); mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE; mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0; } /* FIXME support THP */ if (!page || !page->mapping || PageTransCompound(page)) { mpfn = 0; goto next; } /* * By getting a reference on the page we pin it and that blocks * any kind of migration. Side effect is that it "freezes" the * pte. * * We drop this reference after isolating the page from the lru * for non device page (device page are not on the lru and thus * can't be dropped from it). */ get_page(page); migrate->cpages++; /* * Optimize for the common case where page is only mapped once * in one process. If we can lock the page, then we can safely * set up a special migration page table entry now. */ if (trylock_page(page)) { pte_t swp_pte; mpfn |= MIGRATE_PFN_LOCKED; ptep_get_and_clear(mm, addr, ptep); /* Setup special migration page table entry */ if (mpfn & MIGRATE_PFN_WRITE) entry = make_writable_migration_entry( page_to_pfn(page)); else entry = make_readable_migration_entry( page_to_pfn(page)); swp_pte = swp_entry_to_pte(entry); if (pte_present(pte)) { if (pte_soft_dirty(pte)) swp_pte = pte_swp_mksoft_dirty(swp_pte); if (pte_uffd_wp(pte)) swp_pte = pte_swp_mkuffd_wp(swp_pte); } else { if (pte_swp_soft_dirty(pte)) swp_pte = pte_swp_mksoft_dirty(swp_pte); if (pte_swp_uffd_wp(pte)) swp_pte = pte_swp_mkuffd_wp(swp_pte); } set_pte_at(mm, addr, ptep, swp_pte); /* * This is like regular unmap: we remove the rmap and * drop page refcount. Page won't be freed, as we took * a reference just above. */ page_remove_rmap(page, false); put_page(page); if (pte_present(pte)) unmapped++; } next: migrate->dst[migrate->npages] = 0; migrate->src[migrate->npages++] = mpfn; } /* Only flush the TLB if we actually modified any entries */ if (unmapped) flush_tlb_range(walk->vma, start, end); arch_leave_lazy_mmu_mode(); pte_unmap_unlock(ptep - 1, ptl); return 0; } static const struct mm_walk_ops migrate_vma_walk_ops = { .pmd_entry = migrate_vma_collect_pmd, .pte_hole = migrate_vma_collect_hole, }; /* * migrate_vma_collect() - collect pages over a range of virtual addresses * @migrate: migrate struct containing all migration information * * This will walk the CPU page table. For each virtual address backed by a * valid page, it updates the src array and takes a reference on the page, in * order to pin the page until we lock it and unmap it. */ static void migrate_vma_collect(struct migrate_vma *migrate) { struct mmu_notifier_range range; /* * Note that the pgmap_owner is passed to the mmu notifier callback so * that the registered device driver can skip invalidating device * private page mappings that won't be migrated. */ mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0, migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end, migrate->pgmap_owner); mmu_notifier_invalidate_range_start(&range); walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end, &migrate_vma_walk_ops, migrate); mmu_notifier_invalidate_range_end(&range); migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT); } /* * migrate_vma_check_page() - check if page is pinned or not * @page: struct page to check * * Pinned pages cannot be migrated. This is the same test as in * migrate_page_move_mapping(), except that here we allow migration of a * ZONE_DEVICE page. */ static bool migrate_vma_check_page(struct page *page) { /* * One extra ref because caller holds an extra reference, either from * isolate_lru_page() for a regular page, or migrate_vma_collect() for * a device page. */ int extra = 1; /* * FIXME support THP (transparent huge page), it is bit more complex to * check them than regular pages, because they can be mapped with a pmd * or with a pte (split pte mapping). */ if (PageCompound(page)) return false; /* Page from ZONE_DEVICE have one extra reference */ if (is_zone_device_page(page)) { /* * Private page can never be pin as they have no valid pte and * GUP will fail for those. Yet if there is a pending migration * a thread might try to wait on the pte migration entry and * will bump the page reference count. Sadly there is no way to * differentiate a regular pin from migration wait. Hence to * avoid 2 racing thread trying to migrate back to CPU to enter * infinite loop (one stopping migration because the other is * waiting on pte migration entry). We always return true here. * * FIXME proper solution is to rework migration_entry_wait() so * it does not need to take a reference on page. */ return is_device_private_page(page); } /* For file back page */ if (page_mapping(page)) extra += 1 + page_has_private(page); if ((page_count(page) - extra) > page_mapcount(page)) return false; return true; } /* * migrate_vma_prepare() - lock pages and isolate them from the lru * @migrate: migrate struct containing all migration information * * This locks pages that have been collected by migrate_vma_collect(). Once each * page is locked it is isolated from the lru (for non-device pages). Finally, * the ref taken by migrate_vma_collect() is dropped, as locked pages cannot be * migrated by concurrent kernel threads. */ static void migrate_vma_prepare(struct migrate_vma *migrate) { const unsigned long npages = migrate->npages; const unsigned long start = migrate->start; unsigned long addr, i, restore = 0; bool allow_drain = true; lru_add_drain(); for (i = 0; (i < npages) && migrate->cpages; i++) { struct page *page = migrate_pfn_to_page(migrate->src[i]); bool remap = true; if (!page) continue; if (!(migrate->src[i] & MIGRATE_PFN_LOCKED)) { /* * Because we are migrating several pages there can be * a deadlock between 2 concurrent migration where each * are waiting on each other page lock. * * Make migrate_vma() a best effort thing and backoff * for any page we can not lock right away. */ if (!trylock_page(page)) { migrate->src[i] = 0; migrate->cpages--; put_page(page); continue; } remap = false; migrate->src[i] |= MIGRATE_PFN_LOCKED; } /* ZONE_DEVICE pages are not on LRU */ if (!is_zone_device_page(page)) { if (!PageLRU(page) && allow_drain) { /* Drain CPU's pagevec */ lru_add_drain_all(); allow_drain = false; } if (isolate_lru_page(page)) { if (remap) { migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; migrate->cpages--; restore++; } else { migrate->src[i] = 0; unlock_page(page); migrate->cpages--; put_page(page); } continue; } /* Drop the reference we took in collect */ put_page(page); } if (!migrate_vma_check_page(page)) { if (remap) { migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; migrate->cpages--; restore++; if (!is_zone_device_page(page)) { get_page(page); putback_lru_page(page); } } else { migrate->src[i] = 0; unlock_page(page); migrate->cpages--; if (!is_zone_device_page(page)) putback_lru_page(page); else put_page(page); } } } for (i = 0, addr = start; i < npages && restore; i++, addr += PAGE_SIZE) { struct page *page = migrate_pfn_to_page(migrate->src[i]); if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) continue; remove_migration_pte(page, migrate->vma, addr, page); migrate->src[i] = 0; unlock_page(page); put_page(page); restore--; } } /* * migrate_vma_unmap() - replace page mapping with special migration pte entry * @migrate: migrate struct containing all migration information * * Replace page mapping (CPU page table pte) with a special migration pte entry * and check again if it has been pinned. Pinned pages are restored because we * cannot migrate them. * * This is the last step before we call the device driver callback to allocate * destination memory and copy contents of original page over to new page. */ static void migrate_vma_unmap(struct migrate_vma *migrate) { const unsigned long npages = migrate->npages; const unsigned long start = migrate->start; unsigned long addr, i, restore = 0; for (i = 0; i < npages; i++) { struct page *page = migrate_pfn_to_page(migrate->src[i]); if (!page || !(migrate->src[i] & MIGRATE_PFN_MIGRATE)) continue; if (page_mapped(page)) { try_to_migrate(page, 0); if (page_mapped(page)) goto restore; } if (migrate_vma_check_page(page)) continue; restore: migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; migrate->cpages--; restore++; } for (addr = start, i = 0; i < npages && restore; addr += PAGE_SIZE, i++) { struct page *page = migrate_pfn_to_page(migrate->src[i]); if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE)) continue; remove_migration_ptes(page, page, false); migrate->src[i] = 0; unlock_page(page); restore--; if (is_zone_device_page(page)) put_page(page); else putback_lru_page(page); } } /** * migrate_vma_setup() - prepare to migrate a range of memory * @args: contains the vma, start, and pfns arrays for the migration * * Returns: negative errno on failures, 0 when 0 or more pages were migrated * without an error. * * Prepare to migrate a range of memory virtual address range by collecting all * the pages backing each virtual address in the range, saving them inside the * src array. Then lock those pages and unmap them. Once the pages are locked * and unmapped, check whether each page is pinned or not. Pages that aren't * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the * corresponding src array entry. Then restores any pages that are pinned, by * remapping and unlocking those pages. * * The caller should then allocate destination memory and copy source memory to * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE * flag set). Once these are allocated and copied, the caller must update each * corresponding entry in the dst array with the pfn value of the destination * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_LOCKED flags set * (destination pages must have their struct pages locked, via lock_page()). * * Note that the caller does not have to migrate all the pages that are marked * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from * device memory to system memory. If the caller cannot migrate a device page * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe * consequences for the userspace process, so it must be avoided if at all * possible. * * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus * allowing the caller to allocate device memory for those unbacked virtual * addresses. For this the caller simply has to allocate device memory and * properly set the destination entry like for regular migration. Note that * this can still fail, and thus inside the device driver you must check if the * migration was successful for those entries after calling migrate_vma_pages(), * just like for regular migration. * * After that, the callers must call migrate_vma_pages() to go over each entry * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set, * then migrate_vma_pages() to migrate struct page information from the source * struct page to the destination struct page. If it fails to migrate the * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the * src array. * * At this point all successfully migrated pages have an entry in the src * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst * array entry with MIGRATE_PFN_VALID flag set. * * Once migrate_vma_pages() returns the caller may inspect which pages were * successfully migrated, and which were not. Successfully migrated pages will * have the MIGRATE_PFN_MIGRATE flag set for their src array entry. * * It is safe to update device page table after migrate_vma_pages() because * both destination and source page are still locked, and the mmap_lock is held * in read mode (hence no one can unmap the range being migrated). * * Once the caller is done cleaning up things and updating its page table (if it * chose to do so, this is not an obligation) it finally calls * migrate_vma_finalize() to update the CPU page table to point to new pages * for successfully migrated pages or otherwise restore the CPU page table to * point to the original source pages. */ int migrate_vma_setup(struct migrate_vma *args) { long nr_pages = (args->end - args->start) >> PAGE_SHIFT; args->start &= PAGE_MASK; args->end &= PAGE_MASK; if (!args->vma || is_vm_hugetlb_page(args->vma) || (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma)) return -EINVAL; if (nr_pages <= 0) return -EINVAL; if (args->start < args->vma->vm_start || args->start >= args->vma->vm_end) return -EINVAL; if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end) return -EINVAL; if (!args->src || !args->dst) return -EINVAL; memset(args->src, 0, sizeof(*args->src) * nr_pages); args->cpages = 0; args->npages = 0; migrate_vma_collect(args); if (args->cpages) migrate_vma_prepare(args); if (args->cpages) migrate_vma_unmap(args); /* * At this point pages are locked and unmapped, and thus they have * stable content and can safely be copied to destination memory that * is allocated by the drivers. */ return 0; } EXPORT_SYMBOL(migrate_vma_setup); /* * This code closely matches the code in: * __handle_mm_fault() * handle_pte_fault() * do_anonymous_page() * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE * private page. */ static void migrate_vma_insert_page(struct migrate_vma *migrate, unsigned long addr, struct page *page, unsigned long *src) { struct vm_area_struct *vma = migrate->vma; struct mm_struct *mm = vma->vm_mm; bool flush = false; spinlock_t *ptl; pte_t entry; pgd_t *pgdp; p4d_t *p4dp; pud_t *pudp; pmd_t *pmdp; pte_t *ptep; /* Only allow populating anonymous memory */ if (!vma_is_anonymous(vma)) goto abort; pgdp = pgd_offset(mm, addr); p4dp = p4d_alloc(mm, pgdp, addr); if (!p4dp) goto abort; pudp = pud_alloc(mm, p4dp, addr); if (!pudp) goto abort; pmdp = pmd_alloc(mm, pudp, addr); if (!pmdp) goto abort; if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp)) goto abort; /* * Use pte_alloc() instead of pte_alloc_map(). We can't run * pte_offset_map() on pmds where a huge pmd might be created * from a different thread. * * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when * parallel threads are excluded by other means. * * Here we only have mmap_read_lock(mm). */ if (pte_alloc(mm, pmdp)) goto abort; /* See the comment in pte_alloc_one_map() */ if (unlikely(pmd_trans_unstable(pmdp))) goto abort; if (unlikely(anon_vma_prepare(vma))) goto abort; if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL)) goto abort; /* * The memory barrier inside __SetPageUptodate makes sure that * preceding stores to the page contents become visible before * the set_pte_at() write. */ __SetPageUptodate(page); if (is_zone_device_page(page)) { if (is_device_private_page(page)) { swp_entry_t swp_entry; if (vma->vm_flags & VM_WRITE) swp_entry = make_writable_device_private_entry( page_to_pfn(page)); else swp_entry = make_readable_device_private_entry( page_to_pfn(page)); entry = swp_entry_to_pte(swp_entry); } else { /* * For now we only support migrating to un-addressable * device memory. */ pr_warn_once("Unsupported ZONE_DEVICE page type.\n"); goto abort; } } else { entry = mk_pte(page, vma->vm_page_prot); if (vma->vm_flags & VM_WRITE) entry = pte_mkwrite(pte_mkdirty(entry)); } ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); if (check_stable_address_space(mm)) goto unlock_abort; if (pte_present(*ptep)) { unsigned long pfn = pte_pfn(*ptep); if (!is_zero_pfn(pfn)) goto unlock_abort; flush = true; } else if (!pte_none(*ptep)) goto unlock_abort; /* * Check for userfaultfd but do not deliver the fault. Instead, * just back off. */ if (userfaultfd_missing(vma)) goto unlock_abort; inc_mm_counter(mm, MM_ANONPAGES); page_add_new_anon_rmap(page, vma, addr, false); if (!is_zone_device_page(page)) lru_cache_add_inactive_or_unevictable(page, vma); get_page(page); if (flush) { flush_cache_page(vma, addr, pte_pfn(*ptep)); ptep_clear_flush_notify(vma, addr, ptep); set_pte_at_notify(mm, addr, ptep, entry); update_mmu_cache(vma, addr, ptep); } else { /* No need to invalidate - it was non-present before */ set_pte_at(mm, addr, ptep, entry); update_mmu_cache(vma, addr, ptep); } pte_unmap_unlock(ptep, ptl); *src = MIGRATE_PFN_MIGRATE; return; unlock_abort: pte_unmap_unlock(ptep, ptl); abort: *src &= ~MIGRATE_PFN_MIGRATE; } /** * migrate_vma_pages() - migrate meta-data from src page to dst page * @migrate: migrate struct containing all migration information * * This migrates struct page meta-data from source struct page to destination * struct page. This effectively finishes the migration from source page to the * destination page. */ void migrate_vma_pages(struct migrate_vma *migrate) { const unsigned long npages = migrate->npages; const unsigned long start = migrate->start; struct mmu_notifier_range range; unsigned long addr, i; bool notified = false; for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) { struct page *newpage = migrate_pfn_to_page(migrate->dst[i]); struct page *page = migrate_pfn_to_page(migrate->src[i]); struct address_space *mapping; int r; if (!newpage) { migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; continue; } if (!page) { if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE)) continue; if (!notified) { notified = true; mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0, migrate->vma, migrate->vma->vm_mm, addr, migrate->end, migrate->pgmap_owner); mmu_notifier_invalidate_range_start(&range); } migrate_vma_insert_page(migrate, addr, newpage, &migrate->src[i]); continue; } mapping = page_mapping(page); if (is_zone_device_page(newpage)) { if (is_device_private_page(newpage)) { /* * For now only support private anonymous when * migrating to un-addressable device memory. */ if (mapping) { migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; continue; } } else { /* * Other types of ZONE_DEVICE page are not * supported. */ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; continue; } } r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY); if (r != MIGRATEPAGE_SUCCESS) migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; } /* * No need to double call mmu_notifier->invalidate_range() callback as * the above ptep_clear_flush_notify() inside migrate_vma_insert_page() * did already call it. */ if (notified) mmu_notifier_invalidate_range_only_end(&range); } EXPORT_SYMBOL(migrate_vma_pages); /** * migrate_vma_finalize() - restore CPU page table entry * @migrate: migrate struct containing all migration information * * This replaces the special migration pte entry with either a mapping to the * new page if migration was successful for that page, or to the original page * otherwise. * * This also unlocks the pages and puts them back on the lru, or drops the extra * refcount, for device pages. */ void migrate_vma_finalize(struct migrate_vma *migrate) { const unsigned long npages = migrate->npages; unsigned long i; for (i = 0; i < npages; i++) { struct page *newpage = migrate_pfn_to_page(migrate->dst[i]); struct page *page = migrate_pfn_to_page(migrate->src[i]); if (!page) { if (newpage) { unlock_page(newpage); put_page(newpage); } continue; } if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) { if (newpage) { unlock_page(newpage); put_page(newpage); } newpage = page; } remove_migration_ptes(page, newpage, false); unlock_page(page); if (is_zone_device_page(page)) put_page(page); else putback_lru_page(page); if (newpage != page) { unlock_page(newpage); if (is_zone_device_page(newpage)) put_page(newpage); else putback_lru_page(newpage); } } } EXPORT_SYMBOL(migrate_vma_finalize); #endif /* CONFIG_DEVICE_PRIVATE */ #if defined(CONFIG_HOTPLUG_CPU) /* Disable reclaim-based migration. */ static void __disable_all_migrate_targets(void) { int node; for_each_online_node(node) node_demotion[node] = NUMA_NO_NODE; } static void disable_all_migrate_targets(void) { __disable_all_migrate_targets(); /* * Ensure that the "disable" is visible across the system. * Readers will see either a combination of before+disable * state or disable+after. They will never see before and * after state together. * * The before+after state together might have cycles and * could cause readers to do things like loop until this * function finishes. This ensures they can only see a * single "bad" read and would, for instance, only loop * once. */ synchronize_rcu(); } /* * Find an automatic demotion target for 'node'. * Failing here is OK. It might just indicate * being at the end of a chain. */ static int establish_migrate_target(int node, nodemask_t *used) { int migration_target; /* * Can not set a migration target on a * node with it already set. * * No need for READ_ONCE() here since this * in the write path for node_demotion[]. * This should be the only thread writing. */ if (node_demotion[node] != NUMA_NO_NODE) return NUMA_NO_NODE; migration_target = find_next_best_node(node, used); if (migration_target == NUMA_NO_NODE) return NUMA_NO_NODE; node_demotion[node] = migration_target; return migration_target; } /* * When memory fills up on a node, memory contents can be * automatically migrated to another node instead of * discarded at reclaim. * * Establish a "migration path" which will start at nodes * with CPUs and will follow the priorities used to build the * page allocator zonelists. * * The difference here is that cycles must be avoided. If * node0 migrates to node1, then neither node1, nor anything * node1 migrates to can migrate to node0. * * This function can run simultaneously with readers of * node_demotion[]. However, it can not run simultaneously * with itself. Exclusion is provided by memory hotplug events * being single-threaded. */ static void __set_migration_target_nodes(void) { nodemask_t next_pass = NODE_MASK_NONE; nodemask_t this_pass = NODE_MASK_NONE; nodemask_t used_targets = NODE_MASK_NONE; int node; /* * Avoid any oddities like cycles that could occur * from changes in the topology. This will leave * a momentary gap when migration is disabled. */ disable_all_migrate_targets(); /* * Allocations go close to CPUs, first. Assume that * the migration path starts at the nodes with CPUs. */ next_pass = node_states[N_CPU]; again: this_pass = next_pass; next_pass = NODE_MASK_NONE; /* * To avoid cycles in the migration "graph", ensure * that migration sources are not future targets by * setting them in 'used_targets'. Do this only * once per pass so that multiple source nodes can * share a target node. * * 'used_targets' will become unavailable in future * passes. This limits some opportunities for * multiple source nodes to share a destination. */ nodes_or(used_targets, used_targets, this_pass); for_each_node_mask(node, this_pass) { int target_node = establish_migrate_target(node, &used_targets); if (target_node == NUMA_NO_NODE) continue; /* * Visit targets from this pass in the next pass. * Eventually, every node will have been part of * a pass, and will become set in 'used_targets'. */ node_set(target_node, next_pass); } /* * 'next_pass' contains nodes which became migration * targets in this pass. Make additional passes until * no more migrations targets are available. */ if (!nodes_empty(next_pass)) goto again; } /* * For callers that do not hold get_online_mems() already. */ static void set_migration_target_nodes(void) { get_online_mems(); __set_migration_target_nodes(); put_online_mems(); } /* * This leaves migrate-on-reclaim transiently disabled between * the MEM_GOING_OFFLINE and MEM_OFFLINE events. This runs * whether reclaim-based migration is enabled or not, which * ensures that the user can turn reclaim-based migration at * any time without needing to recalculate migration targets. * * These callbacks already hold get_online_mems(). That is why * __set_migration_target_nodes() can be used as opposed to * set_migration_target_nodes(). */ static int __meminit migrate_on_reclaim_callback(struct notifier_block *self, unsigned long action, void *_arg) { struct memory_notify *arg = _arg; /* * Only update the node migration order when a node is * changing status, like online->offline. This avoids * the overhead of synchronize_rcu() in most cases. */ if (arg->status_change_nid < 0) return notifier_from_errno(0); switch (action) { case MEM_GOING_OFFLINE: /* * Make sure there are not transient states where * an offline node is a migration target. This * will leave migration disabled until the offline * completes and the MEM_OFFLINE case below runs. */ disable_all_migrate_targets(); break; case MEM_OFFLINE: case MEM_ONLINE: /* * Recalculate the target nodes once the node * reaches its final state (online or offline). */ __set_migration_target_nodes(); break; case MEM_CANCEL_OFFLINE: /* * MEM_GOING_OFFLINE disabled all the migration * targets. Reenable them. */ __set_migration_target_nodes(); break; case MEM_GOING_ONLINE: case MEM_CANCEL_ONLINE: break; } return notifier_from_errno(0); } /* * React to hotplug events that might affect the migration targets * like events that online or offline NUMA nodes. * * The ordering is also currently dependent on which nodes have * CPUs. That means we need CPU on/offline notification too. */ static int migration_online_cpu(unsigned int cpu) { set_migration_target_nodes(); return 0; } static int migration_offline_cpu(unsigned int cpu) { set_migration_target_nodes(); return 0; } static int __init migrate_on_reclaim_init(void) { int ret; ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline", NULL, migration_offline_cpu); /* * In the unlikely case that this fails, the automatic * migration targets may become suboptimal for nodes * where N_CPU changes. With such a small impact in a * rare case, do not bother trying to do anything special. */ WARN_ON(ret < 0); ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online", migration_online_cpu, NULL); WARN_ON(ret < 0); hotplug_memory_notifier(migrate_on_reclaim_callback, 100); return 0; } late_initcall(migrate_on_reclaim_init); #endif /* CONFIG_HOTPLUG_CPU */