1 files changed, 218 insertions, 241 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index a6a7743ee98f..cf25b00f03c8 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -364,7 +364,7 @@ static int expected_page_refs(struct address_space *mapping, struct page *page)
 	 */
 	expected_count += is_device_private_page(page);
 	if (mapping)
-		expected_count += thp_nr_pages(page) + page_has_private(page);
+		expected_count += compound_nr(page) + page_has_private(page);
 
 	return expected_count;
 }
@@ -377,74 +377,69 @@ static int expected_page_refs(struct address_space *mapping, struct page *page)
  * 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)
+int folio_migrate_mapping(struct address_space *mapping,
+		struct folio *newfolio, struct folio *folio, int extra_count)
 {
-	XA_STATE(xas, &mapping->i_pages, page_index(page));
+	XA_STATE(xas, &mapping->i_pages, folio_index(folio));
 	struct zone *oldzone, *newzone;
 	int dirty;
-	int expected_count = expected_page_refs(mapping, page) + extra_count;
-	int nr = thp_nr_pages(page);
+	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
+	long nr = folio_nr_pages(folio);
 
 	if (!mapping) {
 		/* Anonymous page without mapping */
-		if (page_count(page) != expected_count)
+		if (folio_ref_count(folio) != expected_count)
 			return -EAGAIN;
 
 		/* No turning back from here */
-		newpage->index = page->index;
-		newpage->mapping = page->mapping;
-		if (PageSwapBacked(page))
-			__SetPageSwapBacked(newpage);
+		newfolio->index = folio->index;
+		newfolio->mapping = folio->mapping;
+		if (folio_test_swapbacked(folio))
+			__folio_set_swapbacked(newfolio);
 
 		return MIGRATEPAGE_SUCCESS;
 	}
 
-	oldzone = page_zone(page);
-	newzone = page_zone(newpage);
+	oldzone = folio_zone(folio);
+	newzone = folio_zone(newfolio);
 
 	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)) {
+	if (!folio_ref_freeze(folio, expected_count)) {
 		xas_unlock_irq(&xas);
 		return -EAGAIN;
 	}
 
 	/*
-	 * Now we know that no one else is looking at the page:
+	 * Now we know that no one else is looking at the folio:
 	 * 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)) {
-			SetPageSwapCache(newpage);
-			set_page_private(newpage, page_private(page));
+	newfolio->index = folio->index;
+	newfolio->mapping = folio->mapping;
+	folio_ref_add(newfolio, nr); /* add cache reference */
+	if (folio_test_swapbacked(folio)) {
+		__folio_set_swapbacked(newfolio);
+		if (folio_test_swapcache(folio)) {
+			folio_set_swapcache(newfolio);
+			newfolio->private = folio_get_private(folio);
 		}
 	} else {
-		VM_BUG_ON_PAGE(PageSwapCache(page), page);
+		VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
 	}
 
 	/* Move dirty while page refs frozen and newpage not yet exposed */
-	dirty = PageDirty(page);
+	dirty = folio_test_dirty(folio);
 	if (dirty) {
-		ClearPageDirty(page);
-		SetPageDirty(newpage);
+		folio_clear_dirty(folio);
+		folio_set_dirty(newfolio);
 	}
 
-	xas_store(&xas, newpage);
-	if (PageTransHuge(page)) {
+	xas_store(&xas, newfolio);
+	if (nr > 1) {
 		int i;
 
 		for (i = 1; i < nr; i++) {
 			xas_next(&xas);
-			xas_store(&xas, newpage);
+			xas_store(&xas, newfolio);
 		}
 	}
 
@@ -453,7 +448,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	 * to one less reference.
 	 * We know this isn't the last reference.
 	 */
-	page_ref_unfreeze(page, expected_count - nr);
+	folio_ref_unfreeze(folio, expected_count - nr);
 
 	xas_unlock(&xas);
 	/* Leave irq disabled to prevent preemption while updating stats */
@@ -472,18 +467,18 @@ int migrate_page_move_mapping(struct address_space *mapping,
 		struct lruvec *old_lruvec, *new_lruvec;
 		struct mem_cgroup *memcg;
 
-		memcg = page_memcg(page);
+		memcg = folio_memcg(folio);
 		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)) {
+		if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) {
 			__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
 			__mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
 		}
 #ifdef CONFIG_SWAP
-		if (PageSwapCache(page)) {
+		if (folio_test_swapcache(folio)) {
 			__mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr);
 			__mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr);
 		}
@@ -499,11 +494,11 @@ int migrate_page_move_mapping(struct address_space *mapping,
 
 	return MIGRATEPAGE_SUCCESS;
 }
-EXPORT_SYMBOL(migrate_page_move_mapping);
+EXPORT_SYMBOL(folio_migrate_mapping);
 
 /*
  * The expected number of remaining references is the same as that
- * of migrate_page_move_mapping().
+ * of folio_migrate_mapping().
  */
 int migrate_huge_page_move_mapping(struct address_space *mapping,
 				   struct page *newpage, struct page *page)
@@ -538,91 +533,87 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 }
 
 /*
- * Copy the page to its new location
+ * Copy the flags and some other ancillary information
  */
-void migrate_page_states(struct page *newpage, struct page *page)
+void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
 {
 	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);
+	if (folio_test_error(folio))
+		folio_set_error(newfolio);
+	if (folio_test_referenced(folio))
+		folio_set_referenced(newfolio);
+	if (folio_test_uptodate(folio))
+		folio_mark_uptodate(newfolio);
+	if (folio_test_clear_active(folio)) {
+		VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio);
+		folio_set_active(newfolio);
+	} else if (folio_test_clear_unevictable(folio))
+		folio_set_unevictable(newfolio);
+	if (folio_test_workingset(folio))
+		folio_set_workingset(newfolio);
+	if (folio_test_checked(folio))
+		folio_set_checked(newfolio);
+	if (folio_test_mappedtodisk(folio))
+		folio_set_mappedtodisk(newfolio);
+
+	/* Move dirty on pages not done by folio_migrate_mapping() */
+	if (folio_test_dirty(folio))
+		folio_set_dirty(newfolio);
+
+	if (folio_test_young(folio))
+		folio_set_young(newfolio);
+	if (folio_test_idle(folio))
+		folio_set_idle(newfolio);
 
 	/*
 	 * 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);
+	cpupid = page_cpupid_xchg_last(&folio->page, -1);
+	page_cpupid_xchg_last(&newfolio->page, cpupid);
 
-	ksm_migrate_page(newpage, page);
+	folio_migrate_ksm(newfolio, folio);
 	/*
 	 * 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);
+	if (folio_test_swapcache(folio))
+		folio_clear_swapcache(folio);
+	folio_clear_private(folio);
 
 	/* page->private contains hugetlb specific flags */
-	if (!PageHuge(page))
-		set_page_private(page, 0);
+	if (!folio_test_hugetlb(folio))
+		folio->private = NULL;
 
 	/*
 	 * If any waiters have accumulated on the new page then
 	 * wake them up.
 	 */
-	if (PageWriteback(newpage))
-		end_page_writeback(newpage);
+	if (folio_test_writeback(newfolio))
+		folio_end_writeback(newfolio);
 
 	/*
 	 * 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);
+	if (folio_test_readahead(folio))
+		folio_set_readahead(newfolio);
 
-	copy_page_owner(page, newpage);
+	folio_copy_owner(newfolio, folio);
 
-	if (!PageHuge(page))
-		mem_cgroup_migrate(page, newpage);
+	if (!folio_test_hugetlb(folio))
+		mem_cgroup_migrate(folio, newfolio);
 }
-EXPORT_SYMBOL(migrate_page_states);
+EXPORT_SYMBOL(folio_migrate_flags);
 
-void migrate_page_copy(struct page *newpage, struct page *page)
+void folio_migrate_copy(struct folio *newfolio, struct folio *folio)
 {
-	if (PageHuge(page) || PageTransHuge(page))
-		copy_huge_page(newpage, page);
-	else
-		copy_highpage(newpage, page);
-
-	migrate_page_states(newpage, page);
+	folio_copy(newfolio, folio);
+	folio_migrate_flags(newfolio, folio);
 }
-EXPORT_SYMBOL(migrate_page_copy);
+EXPORT_SYMBOL(folio_migrate_copy);
 
 /************************************************************
  *                    Migration functions
@@ -638,19 +629,21 @@ int migrate_page(struct address_space *mapping,
 		struct page *newpage, struct page *page,
 		enum migrate_mode mode)
 {
+	struct folio *newfolio = page_folio(newpage);
+	struct folio *folio = page_folio(page);
 	int rc;
 
-	BUG_ON(PageWriteback(page));	/* Writeback must be complete */
+	BUG_ON(folio_test_writeback(folio));	/* Writeback must be complete */
 
-	rc = migrate_page_move_mapping(mapping, newpage, page, 0);
+	rc = folio_migrate_mapping(mapping, newfolio, folio, 0);
 
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
+		folio_migrate_copy(newfolio, folio);
 	else
-		migrate_page_states(newpage, page);
+		folio_migrate_flags(newfolio, folio);
 	return MIGRATEPAGE_SUCCESS;
 }
 EXPORT_SYMBOL(migrate_page);
@@ -2369,7 +2362,6 @@ again:
 		 * can't be dropped from it).
 		 */
 		get_page(page);
-		migrate->cpages++;
 
 		/*
 		 * Optimize for the common case where page is only mapped once
@@ -2379,7 +2371,7 @@ again:
 		if (trylock_page(page)) {
 			pte_t swp_pte;
 
-			mpfn |= MIGRATE_PFN_LOCKED;
+			migrate->cpages++;
 			ptep_get_and_clear(mm, addr, ptep);
 
 			/* Setup special migration page table entry */
@@ -2413,6 +2405,9 @@ again:
 
 			if (pte_present(pte))
 				unmapped++;
+		} else {
+			put_page(page);
+			mpfn = 0;
 		}
 
 next:
@@ -2468,7 +2463,7 @@ static void migrate_vma_collect(struct migrate_vma *migrate)
  * @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
+ * folio_migrate_mapping(), except that here we allow migration of a
  * ZONE_DEVICE page.
  */
 static bool migrate_vma_check_page(struct page *page)
@@ -2517,15 +2512,17 @@ static bool migrate_vma_check_page(struct page *page)
 }
 
 /*
- * migrate_vma_prepare() - lock pages and isolate them from the lru
+ * migrate_vma_unmap() - replace page mapping with special migration pte entry
  * @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.
+ * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
+ * special migration pte entry and check 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_prepare(struct migrate_vma *migrate)
+static void migrate_vma_unmap(struct migrate_vma *migrate)
 {
 	const unsigned long npages = migrate->npages;
 	const unsigned long start = migrate->start;
@@ -2534,32 +2531,12 @@ static void migrate_vma_prepare(struct migrate_vma *migrate)
 
 	lru_add_drain();
 
-	for (i = 0; (i < npages) && migrate->cpages; i++) {
+	for (i = 0; i < npages; 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) {
@@ -2569,16 +2546,9 @@ static void migrate_vma_prepare(struct migrate_vma *migrate)
 			}
 
 			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);
-				}
+				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+				migrate->cpages--;
+				restore++;
 				continue;
 			}
 
@@ -2586,80 +2556,20 @@ static void migrate_vma_prepare(struct migrate_vma *migrate)
 			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 (page_mapped(page))
+			try_to_migrate(page, 0);
 
-				if (!is_zone_device_page(page))
-					putback_lru_page(page);
-				else
-					put_page(page);
+		if (page_mapped(page) || !migrate_vma_check_page(page)) {
+			if (!is_zone_device_page(page)) {
+				get_page(page);
+				putback_lru_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))
+			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+			migrate->cpages--;
+			restore++;
 			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++) {
@@ -2672,12 +2582,8 @@ restore:
 
 		migrate->src[i] = 0;
 		unlock_page(page);
+		put_page(page);
 		restore--;
-
-		if (is_zone_device_page(page))
-			put_page(page);
-		else
-			putback_lru_page(page);
 	}
 }
 
@@ -2700,8 +2606,8 @@ restore:
  * 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()).
+ * page and with MIGRATE_PFN_VALID. Destination pages must be 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
@@ -2771,8 +2677,6 @@ int migrate_vma_setup(struct migrate_vma *args)
 	migrate_vma_collect(args);
 
 	if (args->cpages)
-		migrate_vma_prepare(args);
-	if (args->cpages)
 		migrate_vma_unmap(args);
 
 	/*
@@ -2846,7 +2750,7 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
 
 	if (unlikely(anon_vma_prepare(vma)))
 		goto abort;
-	if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
+	if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
 		goto abort;
 
 	/*
@@ -3066,7 +2970,7 @@ void migrate_vma_finalize(struct migrate_vma *migrate)
 EXPORT_SYMBOL(migrate_vma_finalize);
 #endif /* CONFIG_DEVICE_PRIVATE */
 
-#if defined(CONFIG_MEMORY_HOTPLUG)
+#if defined(CONFIG_HOTPLUG_CPU)
 /* Disable reclaim-based migration. */
 static void __disable_all_migrate_targets(void)
 {
@@ -3209,25 +3113,6 @@ static void set_migration_target_nodes(void)
 }
 
 /*
- * 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;
-}
-
-/*
  * 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
@@ -3239,8 +3124,18 @@ static int migration_offline_cpu(unsigned int cpu)
  * set_migration_target_nodes().
  */
 static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
-						 unsigned long action, void *arg)
+						 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:
 		/*
@@ -3274,13 +3169,31 @@ static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
 	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(CPUHP_AP_ONLINE_DYN, "migrate on reclaim",
-				migration_online_cpu,
-				migration_offline_cpu);
+	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
@@ -3288,9 +3201,73 @@ static int __init migrate_on_reclaim_init(void)
 	 * 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_MEMORY_HOTPLUG */
+#endif /* CONFIG_HOTPLUG_CPU */
+
+bool numa_demotion_enabled = false;
+
+#ifdef CONFIG_SYSFS
+static ssize_t numa_demotion_enabled_show(struct kobject *kobj,
+					  struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n",
+			  numa_demotion_enabled ? "true" : "false");
+}
+
+static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
+					   struct kobj_attribute *attr,
+					   const char *buf, size_t count)
+{
+	if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
+		numa_demotion_enabled = true;
+	else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
+		numa_demotion_enabled = false;
+	else
+		return -EINVAL;
+
+	return count;
+}
+
+static struct kobj_attribute numa_demotion_enabled_attr =
+	__ATTR(demotion_enabled, 0644, numa_demotion_enabled_show,
+	       numa_demotion_enabled_store);
+
+static struct attribute *numa_attrs[] = {
+	&numa_demotion_enabled_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group numa_attr_group = {
+	.attrs = numa_attrs,
+};
+
+static int __init numa_init_sysfs(void)
+{
+	int err;
+	struct kobject *numa_kobj;
+
+	numa_kobj = kobject_create_and_add("numa", mm_kobj);
+	if (!numa_kobj) {
+		pr_err("failed to create numa kobject\n");
+		return -ENOMEM;
+	}
+	err = sysfs_create_group(numa_kobj, &numa_attr_group);
+	if (err) {
+		pr_err("failed to register numa group\n");
+		goto delete_obj;
+	}
+	return 0;
+
+delete_obj:
+	kobject_put(numa_kobj);
+	return err;
+}
+subsys_initcall(numa_init_sysfs);
+#endif