3 files changed, 282 insertions, 159 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 63dbdef60cbd..744cde2b2368 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -392,8 +392,6 @@ enum page_memcg_data_flags {
 
 #define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1)
 
-static inline bool folio_memcg_kmem(struct folio *folio);
-
 /*
  * After the initialization objcg->memcg is always pointing at
  * a valid memcg, but can be atomically swapped to the parent memcg.
@@ -407,43 +405,19 @@ static inline struct mem_cgroup *obj_cgroup_memcg(struct obj_cgroup *objcg)
 }
 
 /*
- * __folio_memcg - Get the memory cgroup associated with a non-kmem folio
- * @folio: Pointer to the folio.
- *
- * Returns a pointer to the memory cgroup associated with the folio,
- * or NULL. This function assumes that the folio is known to have a
- * proper memory cgroup pointer. It's not safe to call this function
- * against some type of folios, e.g. slab folios or ex-slab folios or
- * kmem folios.
- */
-static inline struct mem_cgroup *__folio_memcg(struct folio *folio)
-{
-	unsigned long memcg_data = folio->memcg_data;
-
-	VM_BUG_ON_FOLIO(folio_test_slab(folio), folio);
-	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_OBJCGS, folio);
-	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_KMEM, folio);
-
-	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
-}
-
-/*
- * __folio_objcg - get the object cgroup associated with a kmem folio.
+ * folio_objcg - get the object cgroup associated with a folio.
  * @folio: Pointer to the folio.
  *
  * Returns a pointer to the object cgroup associated with the folio,
  * or NULL. This function assumes that the folio is known to have a
- * proper object cgroup pointer. It's not safe to call this function
- * against some type of folios, e.g. slab folios or ex-slab folios or
- * LRU folios.
+ * proper object cgroup pointer.
  */
-static inline struct obj_cgroup *__folio_objcg(struct folio *folio)
+static inline struct obj_cgroup *folio_objcg(struct folio *folio)
 {
 	unsigned long memcg_data = folio->memcg_data;
 
 	VM_BUG_ON_FOLIO(folio_test_slab(folio), folio);
 	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_OBJCGS, folio);
-	VM_BUG_ON_FOLIO(!(memcg_data & MEMCG_DATA_KMEM), folio);
 
 	return (struct obj_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
 }
@@ -457,22 +431,33 @@ static inline struct obj_cgroup *__folio_objcg(struct folio *folio)
  * proper memory cgroup pointer. It's not safe to call this function
  * against some type of folios, e.g. slab folios or ex-slab folios.
  *
- * For a non-kmem folio any of the following ensures folio and memcg binding
- * stability:
+ * For a folio any of the following ensures folio and objcg binding stability:
  *
  * - the folio lock
  * - LRU isolation
  * - lock_page_memcg()
  * - exclusive reference
  *
+ * Based on the stable binding of folio and objcg, for a folio any of the
+ * following ensures folio and memcg binding stability:
+ *
+ * - objcg_lock
+ * - cgroup_mutex
+ * - the lruvec lock
+ * - the split queue lock (only THP page)
+ *
+ * If the caller only want to ensure that the page counters of memcg are
+ * updated correctly, ensure that the binding stability of folio and objcg
+ * is sufficient.
+ *
  * Note: The caller should hold an rcu read lock to protect memcg associated
  * with a folio from being released.
  */
 static inline struct mem_cgroup *folio_memcg(struct folio *folio)
 {
-	if (folio_memcg_kmem(folio))
-		return obj_cgroup_memcg(__folio_objcg(folio));
-	return __folio_memcg(folio);
+	struct obj_cgroup *objcg = folio_objcg(folio);
+
+	return objcg ? obj_cgroup_memcg(objcg) : NULL;
 }
 
 /*
@@ -496,6 +481,8 @@ static inline struct mem_cgroup *page_memcg(struct page *page)
  * folio is known to have a proper memory cgroup pointer. It's not safe
  * to call this function against some type of pages, e.g. slab pages or
  * ex-slab pages.
+ *
+ * The page and objcg or memcg binding rules can refer to folio_memcg().
  */
 static inline struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio)
 {
@@ -526,22 +513,20 @@ static inline struct mem_cgroup *get_mem_cgroup_from_page(struct page *page)
  *
  * Return: A pointer to the memory cgroup associated with the folio,
  * or NULL.
+ *
+ * The folio and objcg or memcg binding rules can refer to folio_memcg().
  */
 static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
 {
 	unsigned long memcg_data = READ_ONCE(folio->memcg_data);
+	struct obj_cgroup *objcg;
 
 	VM_BUG_ON_FOLIO(folio_test_slab(folio), folio);
 	WARN_ON_ONCE(!rcu_read_lock_held());
 
-	if (memcg_data & MEMCG_DATA_KMEM) {
-		struct obj_cgroup *objcg;
+	objcg = (void *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
 
-		objcg = (void *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
-		return obj_cgroup_memcg(objcg);
-	}
-
-	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+	return objcg ? obj_cgroup_memcg(objcg) : NULL;
 }
 
 /*
@@ -554,16 +539,10 @@ static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
  * has an associated memory cgroup pointer or an object cgroups vector or
  * an object cgroup.
  *
- * For a non-kmem page any of the following ensures page and memcg binding
- * stability:
+ * The page and objcg or memcg binding rules can refer to page_memcg().
  *
- * - the page lock
- * - LRU isolation
- * - lock_page_memcg()
- * - exclusive reference
- *
- * For a kmem page a caller should hold an rcu read lock to protect memcg
- * associated with a kmem page from being released.
+ * A caller should hold an rcu read lock to protect memcg associated with a
+ * page from being released.
  */
 static inline struct mem_cgroup *page_memcg_check(struct page *page)
 {
@@ -572,18 +551,14 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
 	 * for slab pages, READ_ONCE() should be used here.
 	 */
 	unsigned long memcg_data = READ_ONCE(page->memcg_data);
+	struct obj_cgroup *objcg;
 
 	if (memcg_data & MEMCG_DATA_OBJCGS)
 		return NULL;
 
-	if (memcg_data & MEMCG_DATA_KMEM) {
-		struct obj_cgroup *objcg;
-
-		objcg = (void *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
-		return obj_cgroup_memcg(objcg);
-	}
+	objcg = (void *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
 
-	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+	return objcg ? obj_cgroup_memcg(objcg) : NULL;
 }
 
 static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 613dfe65b8c8..ae8384f3bb82 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -561,6 +561,8 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 }
 
 #ifdef CONFIG_MEMCG
+static struct shrinker deferred_split_shrinker;
+
 static inline struct mem_cgroup *folio_split_queue_memcg(struct folio *folio,
 		struct deferred_split *queue)
 {
@@ -577,6 +579,39 @@ static inline struct deferred_split *folio_memcg_split_queue(struct folio *folio
 
 	return memcg ? &memcg->deferred_split_queue : NULL;
 }
+
+static void thp_sq_reparent_lock(struct mem_cgroup *src, struct mem_cgroup *dst)
+{
+	spin_lock(&src->deferred_split_queue.split_queue_lock);
+	spin_lock_nested(&dst->deferred_split_queue.split_queue_lock,
+			 SINGLE_DEPTH_NESTING);
+}
+
+static void thp_sq_reparent_relocate(struct mem_cgroup *src, struct mem_cgroup *dst)
+{
+	int nid;
+	struct deferred_split *src_queue, *dst_queue;
+
+	src_queue = &src->deferred_split_queue;
+	dst_queue = &dst->deferred_split_queue;
+
+	if (!src_queue->split_queue_len)
+		return;
+
+	list_splice_tail_init(&src_queue->split_queue, &dst_queue->split_queue);
+	dst_queue->split_queue_len += src_queue->split_queue_len;
+	src_queue->split_queue_len = 0;
+
+	for_each_node(nid)
+		set_shrinker_bit(dst, nid, deferred_split_shrinker.id);
+}
+
+static void thp_sq_reparent_unlock(struct mem_cgroup *src, struct mem_cgroup *dst)
+{
+	spin_unlock(&dst->deferred_split_queue.split_queue_lock);
+	spin_unlock(&src->deferred_split_queue.split_queue_lock);
+}
+DEFINE_MEMCG_REPARENT_OPS(thp_sq);
 #else
 static inline struct mem_cgroup *folio_split_queue_memcg(struct folio *folio,
 		struct deferred_split *queue)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6ef3a264054e..803dbdf5f233 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -77,6 +77,7 @@ struct cgroup_subsys memory_cgrp_subsys __read_mostly;
 EXPORT_SYMBOL(memory_cgrp_subsys);
 
 struct mem_cgroup *root_mem_cgroup __read_mostly;
+static struct obj_cgroup *root_obj_cgroup __read_mostly;
 
 /* Active memory cgroup to use from an interrupt context */
 DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
@@ -254,6 +255,11 @@ struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr)
 
 static DEFINE_SPINLOCK(objcg_lock);
 
+static inline bool obj_cgroup_is_root(struct obj_cgroup *objcg)
+{
+	return objcg == root_obj_cgroup;
+}
+
 #ifdef CONFIG_MEMCG_KMEM
 bool mem_cgroup_kmem_disabled(void)
 {
@@ -361,8 +367,78 @@ static void objcg_reparent_unlock(struct mem_cgroup *src, struct mem_cgroup *dst
 
 static DEFINE_MEMCG_REPARENT_OPS(objcg);
 
+static void lruvec_reparent_lock(struct mem_cgroup *src, struct mem_cgroup *dst)
+{
+	int nid, nest = 0;
+
+	for_each_node(nid) {
+		spin_lock_nested(&mem_cgroup_lruvec(src,
+				 NODE_DATA(nid))->lru_lock, nest++);
+		spin_lock_nested(&mem_cgroup_lruvec(dst,
+				 NODE_DATA(nid))->lru_lock, nest++);
+	}
+}
+
+static void lruvec_reparent_lru(struct lruvec *src, struct lruvec *dst,
+				enum lru_list lru)
+{
+	int zid;
+	struct mem_cgroup_per_node *mz_src, *mz_dst;
+
+	mz_src = container_of(src, struct mem_cgroup_per_node, lruvec);
+	mz_dst = container_of(dst, struct mem_cgroup_per_node, lruvec);
+
+	if (lru != LRU_UNEVICTABLE)
+		list_splice_tail_init(&src->lists[lru], &dst->lists[lru]);
+
+	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+		mz_dst->lru_zone_size[zid][lru] += mz_src->lru_zone_size[zid][lru];
+		mz_src->lru_zone_size[zid][lru] = 0;
+	}
+}
+
+static void lruvec_reparent_relocate(struct mem_cgroup *src, struct mem_cgroup *dst)
+{
+	int nid;
+
+	for_each_node(nid) {
+		enum lru_list lru;
+		struct lruvec *src_lruvec, *dst_lruvec;
+
+		src_lruvec = mem_cgroup_lruvec(src, NODE_DATA(nid));
+		dst_lruvec = mem_cgroup_lruvec(dst, NODE_DATA(nid));
+
+		dst_lruvec->anon_cost += src_lruvec->anon_cost;
+		dst_lruvec->file_cost += src_lruvec->file_cost;
+
+		for_each_lru(lru)
+			lruvec_reparent_lru(src_lruvec, dst_lruvec, lru);
+	}
+}
+
+static void lruvec_reparent_unlock(struct mem_cgroup *src, struct mem_cgroup *dst)
+{
+	int nid;
+
+	for_each_node(nid) {
+		spin_unlock(&mem_cgroup_lruvec(dst, NODE_DATA(nid))->lru_lock);
+		spin_unlock(&mem_cgroup_lruvec(src, NODE_DATA(nid))->lru_lock);
+	}
+}
+
+static DEFINE_MEMCG_REPARENT_OPS(lruvec);
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+DECLARE_MEMCG_REPARENT_OPS(thp_sq);
+#endif
+
+/* The lock order depends on the order of elements in this array. */
 static const struct memcg_reparent_ops *memcg_reparent_ops[] = {
 	&memcg_objcg_reparent_ops,
+	&memcg_lruvec_reparent_ops,
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	&memcg_thp_sq_reparent_ops,
+#endif
 };
 
 #define DEFINE_MEMCG_REPARENT_FUNC(phase)				\
@@ -2825,18 +2901,33 @@ static inline void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages
 		page_counter_uncharge(&memcg->memsw, nr_pages);
 }
 
-static void commit_charge(struct folio *folio, struct mem_cgroup *memcg)
+static void commit_charge(struct folio *folio, struct obj_cgroup *objcg)
 {
-	VM_BUG_ON_FOLIO(folio_memcg(folio), folio);
+	VM_BUG_ON_FOLIO(folio_objcg(folio), folio);
 	/*
-	 * Any of the following ensures page's memcg stability:
+	 * Any of the following ensures page's objcg stability:
 	 *
 	 * - the page lock
 	 * - LRU isolation
 	 * - lock_page_memcg()
 	 * - exclusive reference
 	 */
-	folio->memcg_data = (unsigned long)memcg;
+	folio->memcg_data = (unsigned long)objcg;
+}
+
+static struct obj_cgroup *get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
+{
+	struct obj_cgroup *objcg = NULL;
+
+	rcu_read_lock();
+	for (; memcg; memcg = parent_mem_cgroup(memcg)) {
+		objcg = rcu_dereference(memcg->objcg);
+		if (objcg && obj_cgroup_tryget(objcg))
+			break;
+	}
+	rcu_read_unlock();
+
+	return objcg;
 }
 
 #ifdef CONFIG_MEMCG_KMEM
@@ -2982,19 +3073,6 @@ struct mem_cgroup *mem_cgroup_from_slab_obj(void *p)
 	return mem_cgroup_from_obj_folio(virt_to_folio(p), p);
 }
 
-static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
-{
-	struct obj_cgroup *objcg = NULL;
-
-	for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) {
-		objcg = rcu_dereference(memcg->objcg);
-		if (objcg && obj_cgroup_tryget(objcg))
-			break;
-		objcg = NULL;
-	}
-	return objcg;
-}
-
 __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
 {
 	struct obj_cgroup *objcg = NULL;
@@ -3008,7 +3086,16 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
 		memcg = active_memcg();
 	else
 		memcg = mem_cgroup_from_task(current);
-	objcg = __get_obj_cgroup_from_memcg(memcg);
+
+	if (mem_cgroup_is_root(memcg))
+		goto out;
+
+	objcg = get_obj_cgroup_from_memcg(memcg);
+	if (obj_cgroup_is_root(objcg)) {
+		obj_cgroup_put(objcg);
+		objcg = NULL;
+	}
+out:
 	rcu_read_unlock();
 	return objcg;
 }
@@ -3020,20 +3107,10 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
 	if (!memcg_kmem_enabled() || memcg_kmem_bypass())
 		return NULL;
 
-	if (PageMemcgKmem(page)) {
-		objcg = __folio_objcg(page_folio(page));
+	objcg = folio_objcg(page_folio(page));
+	if (objcg)
 		obj_cgroup_get(objcg);
-	} else {
-		struct mem_cgroup *memcg;
 
-		rcu_read_lock();
-		memcg = __folio_memcg(page_folio(page));
-		if (memcg)
-			objcg = __get_obj_cgroup_from_memcg(memcg);
-		else
-			objcg = NULL;
-		rcu_read_unlock();
-	}
 	return objcg;
 }
 
@@ -3128,13 +3205,13 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
 void __memcg_kmem_uncharge_page(struct page *page, int order)
 {
 	struct folio *folio = page_folio(page);
-	struct obj_cgroup *objcg;
+	struct obj_cgroup *objcg = folio_objcg(folio);
 	unsigned int nr_pages = 1 << order;
 
-	if (!folio_memcg_kmem(folio))
+	if (!objcg)
 		return;
 
-	objcg = __folio_objcg(folio);
+	VM_BUG_ON_FOLIO(!folio_memcg_kmem(folio), folio);
 	obj_cgroup_uncharge_pages(objcg, nr_pages);
 	folio->memcg_data = 0;
 	obj_cgroup_put(objcg);
@@ -3388,26 +3465,21 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
 #endif /* CONFIG_MEMCG_KMEM */
 
 /*
- * Because page_memcg(head) is not set on tails, set it now.
+ * Because page_objcg(head) is not set on tails, set it now.
  */
 void split_page_memcg(struct page *head, unsigned int nr)
 {
 	struct folio *folio = page_folio(head);
-	struct mem_cgroup *memcg = get_mem_cgroup_from_folio(folio);
+	struct obj_cgroup *objcg = folio_objcg(folio);
 	int i;
 
-	if (mem_cgroup_disabled() || !memcg)
+	if (mem_cgroup_disabled() || !objcg)
 		return;
 
 	for (i = 1; i < nr; i++)
 		folio_page(folio, i)->memcg_data = folio->memcg_data;
 
-	if (folio_memcg_kmem(folio))
-		obj_cgroup_get_many(__folio_objcg(folio), nr - 1);
-	else
-		css_get_many(&memcg->css, nr - 1);
-
-	css_put(&memcg->css);
+	obj_cgroup_get_many(objcg, nr - 1);
 }
 
 #ifdef CONFIG_MEMCG_SWAP
@@ -5325,6 +5397,9 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
 	objcg->memcg = memcg;
 	rcu_assign_pointer(memcg->objcg, objcg);
 
+	if (unlikely(mem_cgroup_is_root(memcg)))
+		root_obj_cgroup = objcg;
+
 	/* Online state pins memcg ID, memcg ID pins CSS */
 	refcount_set(&memcg->id.ref, 1);
 	css_get(css);
@@ -5729,10 +5804,12 @@ static int mem_cgroup_move_account(struct page *page,
 	 */
 	smp_mb();
 
-	css_get(&to->css);
-	css_put(&from->css);
+	rcu_read_lock();
+	obj_cgroup_get(rcu_dereference(to->objcg));
+	obj_cgroup_put(rcu_dereference(from->objcg));
+	rcu_read_unlock();
 
-	folio->memcg_data = (unsigned long)to;
+	folio->memcg_data = (unsigned long)rcu_access_pointer(to->objcg);
 
 	__folio_memcg_unlock(from);
 
@@ -6208,6 +6285,42 @@ retry:
 	walk_page_range(mc.mm, 0, ULONG_MAX, &charge_walk_ops, NULL);
 	mmap_read_unlock(mc.mm);
 	atomic_dec(&mc.from->moving_account);
+
+	/*
+	 * Moving its pages to another memcg is finished. Wait for already
+	 * started RCU-only updates to finish to make sure that the caller
+	 * of lock_page_memcg() can unlock the correct move_lock. The
+	 * possible bad scenario would like:
+	 *
+	 * CPU0:				CPU1:
+	 * mem_cgroup_move_charge()
+	 *     walk_page_range()
+	 *
+	 *					lock_page_memcg(page)
+	 *					    memcg = folio_memcg()
+	 *					    spin_lock_irqsave(&memcg->move_lock)
+	 *					    memcg->move_lock_task = current
+	 *
+	 *     atomic_dec(&mc.from->moving_account)
+	 *
+	 * mem_cgroup_css_offline()
+	 *     memcg_offline_kmem()
+	 *         memcg_reparent_objcgs() <== reparented
+	 *
+	 *					unlock_page_memcg(page)
+	 *					    memcg = folio_memcg() <== memcg has been changed
+	 *					    if (memcg->move_lock_task == current) <== false
+	 *					        spin_unlock_irqrestore(&memcg->move_lock)
+	 *
+	 * Once mem_cgroup_move_charge() returns (it means that the cgroup_mutex
+	 * would be released soon), the page can be reparented to its parent
+	 * memcg. When the unlock_page_memcg() is called for the page, we will
+	 * miss unlock the move_lock. So using synchronize_rcu to wait for
+	 * already started RCU-only updates to finish before this function
+	 * returns (mem_cgroup_move_charge() and mem_cgroup_css_offline() are
+	 * serialized by cgroup_mutex).
+	 */
+	synchronize_rcu();
 }
 
 /*
@@ -6822,21 +6935,26 @@ void mem_cgroup_calculate_protection(struct mem_cgroup *root,
 static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg,
 			gfp_t gfp)
 {
+	struct obj_cgroup *objcg;
 	long nr_pages = folio_nr_pages(folio);
-	int ret;
+	int ret = 0;
 
-	ret = try_charge(memcg, gfp, nr_pages);
+	objcg = get_obj_cgroup_from_memcg(memcg);
+	/* Do not account at the root objcg level. */
+	if (!obj_cgroup_is_root(objcg))
+		ret = try_charge(memcg, gfp, nr_pages);
 	if (ret)
 		goto out;
 
-	css_get(&memcg->css);
-	commit_charge(folio, memcg);
+	obj_cgroup_get(objcg);
+	commit_charge(folio, objcg);
 
 	local_irq_disable();
 	mem_cgroup_charge_statistics(memcg, nr_pages);
 	memcg_check_events(memcg, folio_nid(folio));
 	local_irq_enable();
 out:
+	obj_cgroup_put(objcg);
 	return ret;
 }
 
@@ -6922,7 +7040,7 @@ void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
 }
 
 struct uncharge_gather {
-	struct mem_cgroup *memcg;
+	struct obj_cgroup *objcg;
 	unsigned long nr_memory;
 	unsigned long pgpgout;
 	unsigned long nr_kmem;
@@ -6937,63 +7055,56 @@ static inline void uncharge_gather_clear(struct uncharge_gather *ug)
 static void uncharge_batch(const struct uncharge_gather *ug)
 {
 	unsigned long flags;
+	struct mem_cgroup *memcg;
 
+	rcu_read_lock();
+	memcg = obj_cgroup_memcg(ug->objcg);
 	if (ug->nr_memory) {
-		page_counter_uncharge(&ug->memcg->memory, ug->nr_memory);
+		page_counter_uncharge(&memcg->memory, ug->nr_memory);
 		if (do_memsw_account())
-			page_counter_uncharge(&ug->memcg->memsw, ug->nr_memory);
+			page_counter_uncharge(&memcg->memsw, ug->nr_memory);
 		if (ug->nr_kmem)
-			memcg_account_kmem(ug->memcg, -ug->nr_kmem);
-		memcg_oom_recover(ug->memcg);
+			memcg_account_kmem(memcg, -ug->nr_kmem);
+		memcg_oom_recover(memcg);
 	}
 
 	local_irq_save(flags);
-	__count_memcg_events(ug->memcg, PGPGOUT, ug->pgpgout);
-	__this_cpu_add(ug->memcg->vmstats_percpu->nr_page_events, ug->nr_memory);
-	memcg_check_events(ug->memcg, ug->nid);
+	__count_memcg_events(memcg, PGPGOUT, ug->pgpgout);
+	__this_cpu_add(memcg->vmstats_percpu->nr_page_events, ug->nr_memory);
+	memcg_check_events(memcg, ug->nid);
 	local_irq_restore(flags);
+	rcu_read_unlock();
 
 	/* drop reference from uncharge_folio */
-	css_put(&ug->memcg->css);
+	obj_cgroup_put(ug->objcg);
 }
 
 static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
 {
 	long nr_pages;
-	struct mem_cgroup *memcg;
 	struct obj_cgroup *objcg;
 
 	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 
 	/*
 	 * Nobody should be changing or seriously looking at
-	 * folio memcg or objcg at this point, we have fully
-	 * exclusive access to the folio.
+	 * folio objcg at this point, we have fully exclusive
+	 * access to the folio.
 	 */
-	if (folio_memcg_kmem(folio)) {
-		objcg = __folio_objcg(folio);
-		/*
-		 * This get matches the put at the end of the function and
-		 * kmem pages do not hold memcg references anymore.
-		 */
-		memcg = get_mem_cgroup_from_objcg(objcg);
-	} else {
-		memcg = __folio_memcg(folio);
-	}
-
-	if (!memcg)
+	objcg = folio_objcg(folio);
+	if (!objcg)
 		return;
 
-	if (ug->memcg != memcg) {
-		if (ug->memcg) {
+	if (ug->objcg != objcg) {
+		if (ug->objcg) {
 			uncharge_batch(ug);
 			uncharge_gather_clear(ug);
 		}
-		ug->memcg = memcg;
+		ug->objcg = objcg;
 		ug->nid = folio_nid(folio);
 
-		/* pairs with css_put in uncharge_batch */
-		css_get(&memcg->css);
+		/* pairs with obj_cgroup_put in uncharge_batch */
+		obj_cgroup_get(objcg);
 	}
 
 	nr_pages = folio_nr_pages(folio);
@@ -7001,19 +7112,15 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
 	if (folio_memcg_kmem(folio)) {
 		ug->nr_memory += nr_pages;
 		ug->nr_kmem += nr_pages;
-
-		folio->memcg_data = 0;
-		obj_cgroup_put(objcg);
 	} else {
 		/* LRU pages aren't accounted at the root level */
-		if (!mem_cgroup_is_root(memcg))
+		if (!obj_cgroup_is_root(objcg))
 			ug->nr_memory += nr_pages;
 		ug->pgpgout++;
-
-		folio->memcg_data = 0;
 	}
 
-	css_put(&memcg->css);
+	folio->memcg_data = 0;
+	obj_cgroup_put(objcg);
 }
 
 void __mem_cgroup_uncharge(struct folio *folio)
@@ -7021,7 +7128,7 @@ void __mem_cgroup_uncharge(struct folio *folio)
 	struct uncharge_gather ug;
 
 	/* Don't touch folio->lru of any random page, pre-check: */
-	if (!folio_memcg(folio))
+	if (!folio_objcg(folio))
 		return;
 
 	uncharge_gather_clear(&ug);
@@ -7044,7 +7151,7 @@ void __mem_cgroup_uncharge_list(struct list_head *page_list)
 	uncharge_gather_clear(&ug);
 	list_for_each_entry(folio, page_list, lru)
 		uncharge_folio(folio, &ug);
-	if (ug.memcg)
+	if (ug.objcg)
 		uncharge_batch(&ug);
 }
 
@@ -7061,6 +7168,7 @@ void __mem_cgroup_uncharge_list(struct list_head *page_list)
 void mem_cgroup_migrate(struct folio *old, struct folio *new)
 {
 	struct mem_cgroup *memcg;
+	struct obj_cgroup *objcg;
 	long nr_pages = folio_nr_pages(new);
 	unsigned long flags;
 
@@ -7073,30 +7181,33 @@ void mem_cgroup_migrate(struct folio *old, struct folio *new)
 		return;
 
 	/* Page cache replacement: new folio already charged? */
-	if (folio_memcg(new))
+	if (folio_objcg(new))
 		return;
 
-	memcg = get_mem_cgroup_from_folio(old);
-	VM_WARN_ON_ONCE_FOLIO(!memcg, old);
-	if (!memcg)
+	objcg = folio_objcg(old);
+	VM_WARN_ON_ONCE_FOLIO(!objcg, old);
+	if (!objcg)
 		return;
 
+	rcu_read_lock();
+	memcg = obj_cgroup_memcg(objcg);
+
 	/* Force-charge the new page. The old one will be freed soon */
-	if (!mem_cgroup_is_root(memcg)) {
+	if (!obj_cgroup_is_root(objcg)) {
 		page_counter_charge(&memcg->memory, nr_pages);
 		if (do_memsw_account())
 			page_counter_charge(&memcg->memsw, nr_pages);
 	}
 
-	css_get(&memcg->css);
-	commit_charge(new, memcg);
+	obj_cgroup_get(objcg);
+	commit_charge(new, objcg);
 
 	local_irq_save(flags);
 	mem_cgroup_charge_statistics(memcg, nr_pages);
 	memcg_check_events(memcg, folio_nid(new));
 	local_irq_restore(flags);
 
-	css_put(&memcg->css);
+	rcu_read_unlock();
 }
 
 DEFINE_STATIC_KEY_FALSE(memcg_sockets_enabled_key);
@@ -7269,6 +7380,7 @@ static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
 void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 {
 	struct mem_cgroup *memcg, *swap_memcg;
+	struct obj_cgroup *objcg;
 	unsigned int nr_entries;
 	unsigned short oldid;
 
@@ -7281,15 +7393,16 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return;
 
+	objcg = folio_objcg(folio);
+	VM_WARN_ON_ONCE_FOLIO(!objcg, folio);
+	if (!objcg)
+		return;
+
 	/*
 	 * Interrupts should be disabled by the caller (see the comments below),
 	 * which can serve as RCU read-side critical sections.
 	 */
-	memcg = folio_memcg(folio);
-
-	VM_WARN_ON_ONCE_FOLIO(!memcg, folio);
-	if (!memcg)
-		return;
+	memcg = obj_cgroup_memcg(objcg);
 
 	/*
 	 * In case the memcg owning these pages has been offlined and doesn't
@@ -7308,7 +7421,7 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 
 	folio->memcg_data = 0;
 
-	if (!mem_cgroup_is_root(memcg))
+	if (!obj_cgroup_is_root(objcg))
 		page_counter_uncharge(&memcg->memory, nr_entries);
 
 	if (!cgroup_memory_noswap && memcg != swap_memcg) {
@@ -7328,7 +7441,7 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 	memcg_stats_unlock();
 	memcg_check_events(memcg, folio_nid(folio));
 
-	css_put(&memcg->css);
+	obj_cgroup_put(objcg);
 }
 
 /**