diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 5361ebec3361..007ba86aef78 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1334,7 +1334,7 @@ PAGE_SIZE multiple when read back.
 
 	  pgdeactivate
 
-		Amount of pages moved to the inactive LRU lis
+		Amount of pages moved to the inactive LRU list
 
 	  pglazyfree
 
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 6ebae6bbe6a5..b2d9f79c4a7c 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -508,10 +508,6 @@ void kernfs_put(struct kernfs_node *kn)
 	struct kernfs_node *parent;
 	struct kernfs_root *root;
 
-	/*
-	 * kernfs_node is freed with ->count 0, kernfs_find_and_get_node_by_ino
-	 * depends on this to filter reused stale node
-	 */
 	if (!kn || !atomic_dec_and_test(&kn->count))
 		return;
 	root = kernfs_root(kn);
@@ -536,7 +532,7 @@ void kernfs_put(struct kernfs_node *kn)
 		kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
 	}
 	spin_lock(&kernfs_idr_lock);
-	idr_remove(&root->ino_idr, kn->id.ino);
+	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
 	spin_unlock(&kernfs_idr_lock);
 	kmem_cache_free(kernfs_node_cache, kn);
 
@@ -621,8 +617,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 					     unsigned flags)
 {
 	struct kernfs_node *kn;
-	u32 gen;
-	int cursor;
+	u32 id_highbits;
 	int ret;
 
 	name = kstrdup_const(name, GFP_KERNEL);
@@ -635,23 +630,19 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 
 	idr_preload(GFP_KERNEL);
 	spin_lock(&kernfs_idr_lock);
-	cursor = idr_get_cursor(&root->ino_idr);
 	ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
-	if (ret >= 0 && ret < cursor)
-		root->next_generation++;
-	gen = root->next_generation;
+	if (ret >= 0 && ret < root->last_id_lowbits)
+		root->id_highbits++;
+	id_highbits = root->id_highbits;
+	root->last_id_lowbits = ret;
 	spin_unlock(&kernfs_idr_lock);
 	idr_preload_end();
 	if (ret < 0)
 		goto err_out2;
-	kn->id.ino = ret;
-	kn->id.generation = gen;
 
-	/*
-	 * set ino first. This RELEASE is paired with atomic_inc_not_zero in
-	 * kernfs_find_and_get_node_by_ino
-	 */
-	atomic_set_release(&kn->count, 1);
+	kn->id = (u64)id_highbits << 32 | ret;
+
+	atomic_set(&kn->count, 1);
 	atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
 	RB_CLEAR_NODE(&kn->rb);
 
@@ -680,7 +671,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	return kn;
 
  err_out3:
-	idr_remove(&root->ino_idr, kn->id.ino);
+	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
  err_out2:
 	kmem_cache_free(kernfs_node_cache, kn);
  err_out1:
@@ -705,50 +696,52 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
 }
 
 /*
- * kernfs_find_and_get_node_by_ino - get kernfs_node from inode number
+ * kernfs_find_and_get_node_by_id - get kernfs_node from node id
  * @root: the kernfs root
- * @ino: inode number
+ * @id: the target node id
+ *
+ * @id's lower 32bits encode ino and upper gen.  If the gen portion is
+ * zero, all generations are matched.
  *
  * RETURNS:
  * NULL on failure. Return a kernfs node with reference counter incremented
  */
-struct kernfs_node *kernfs_find_and_get_node_by_ino(struct kernfs_root *root,
-						    unsigned int ino)
+struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
+						   u64 id)
 {
 	struct kernfs_node *kn;
+	ino_t ino = kernfs_id_ino(id);
+	u32 gen = kernfs_id_gen(id);
 
-	rcu_read_lock();
-	kn = idr_find(&root->ino_idr, ino);
+	spin_lock(&kernfs_idr_lock);
+
+	kn = idr_find(&root->ino_idr, (u32)ino);
 	if (!kn)
-		goto out;
+		goto err_unlock;
 
-	/*
-	 * Since kernfs_node is freed in RCU, it's possible an old node for ino
-	 * is freed, but reused before RCU grace period. But a freed node (see
-	 * kernfs_put) or an incompletedly initialized node (see
-	 * __kernfs_new_node) should have 'count' 0. We can use this fact to
-	 * filter out such node.
-	 */
-	if (!atomic_inc_not_zero(&kn->count)) {
-		kn = NULL;
-		goto out;
+	if (sizeof(ino_t) >= sizeof(u64)) {
+		/* we looked up with the low 32bits, compare the whole */
+		if (kernfs_ino(kn) != ino)
+			goto err_unlock;
+	} else {
+		/* 0 matches all generations */
+		if (unlikely(gen && kernfs_gen(kn) != gen))
+			goto err_unlock;
 	}
 
 	/*
-	 * The node could be a new node or a reused node. If it's a new node,
-	 * we are ok. If it's reused because of RCU (because of
-	 * SLAB_TYPESAFE_BY_RCU), the __kernfs_new_node always sets its 'ino'
-	 * before 'count'. So if 'count' is uptodate, 'ino' should be uptodate,
-	 * hence we can use 'ino' to filter stale node.
+	 * ACTIVATED is protected with kernfs_mutex but it was clear when
+	 * @kn was added to idr and we just wanna see it set.  No need to
+	 * grab kernfs_mutex.
 	 */
-	if (kn->id.ino != ino)
-		goto out;
-	rcu_read_unlock();
+	if (unlikely(!(kn->flags & KERNFS_ACTIVATED) ||
+		     !atomic_inc_not_zero(&kn->count)))
+		goto err_unlock;
 
+	spin_unlock(&kernfs_idr_lock);
 	return kn;
-out:
-	rcu_read_unlock();
-	kernfs_put(kn);
+err_unlock:
+	spin_unlock(&kernfs_idr_lock);
 	return NULL;
 }
 
@@ -962,7 +955,17 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
 
 	idr_init(&root->ino_idr);
 	INIT_LIST_HEAD(&root->supers);
-	root->next_generation = 1;
+
+	/*
+	 * On 64bit ino setups, id is ino.  On 32bit, low 32bits are ino.
+	 * High bits generation.  The starting value for both ino and
+	 * genenration is 1.  Initialize upper 32bit allocation
+	 * accordingly.
+	 */
+	if (sizeof(ino_t) >= sizeof(u64))
+		root->id_highbits = 0;
+	else
+		root->id_highbits = 1;
 
 	kn = __kernfs_new_node(root, NULL, "", S_IFDIR | S_IRUGO | S_IXUGO,
 			       GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
@@ -1678,7 +1681,7 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
 		const char *name = pos->name;
 		unsigned int type = dt_type(pos);
 		int len = strlen(name);
-		ino_t ino = pos->id.ino;
+		ino_t ino = kernfs_ino(pos);
 
 		ctx->pos = pos->hash;
 		file->private_data = pos;
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index e8c792b49616..34366db3620d 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -892,7 +892,7 @@ repeat:
 		 * have the matching @file available.  Look up the inodes
 		 * and generate the events manually.
 		 */
-		inode = ilookup(info->sb, kn->id.ino);
+		inode = ilookup(info->sb, kernfs_ino(kn));
 		if (!inode)
 			continue;
 
@@ -901,7 +901,7 @@ repeat:
 		if (parent) {
 			struct inode *p_inode;
 
-			p_inode = ilookup(info->sb, parent->id.ino);
+			p_inode = ilookup(info->sb, kernfs_ino(parent));
 			if (p_inode) {
 				fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
 					 inode, FSNOTIFY_EVENT_INODE, &name, 0);
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index f3eaa8869f42..eac277c63d42 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -201,7 +201,7 @@ static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 	inode->i_private = kn;
 	inode->i_mapping->a_ops = &kernfs_aops;
 	inode->i_op = &kernfs_iops;
-	inode->i_generation = kn->id.generation;
+	inode->i_generation = kernfs_gen(kn);
 
 	set_default_inode_attr(inode, kn->mode);
 	kernfs_refresh_inode(kn, inode);
@@ -247,7 +247,7 @@ struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 {
 	struct inode *inode;
 
-	inode = iget_locked(sb, kn->id.ino);
+	inode = iget_locked(sb, kernfs_ino(kn));
 	if (inode && (inode->i_state & I_NEW))
 		kernfs_init_inode(kn, inode);
 
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 02ce570a9a3c..2f3c51d55261 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -109,8 +109,6 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
 				    const char *name, umode_t mode,
 				    kuid_t uid, kgid_t gid,
 				    unsigned flags);
-struct kernfs_node *kernfs_find_and_get_node_by_ino(struct kernfs_root *root,
-						    unsigned int ino);
 
 /*
  * file.c
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 6c12fac2c287..4d31503abaee 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -53,63 +53,85 @@ const struct super_operations kernfs_sops = {
 	.show_path	= kernfs_sop_show_path,
 };
 
-/*
- * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
- * number and generation
- */
-struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
-	const union kernfs_node_id *id)
+static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
+			    struct inode *parent)
 {
-	struct kernfs_node *kn;
+	struct kernfs_node *kn = inode->i_private;
 
-	kn = kernfs_find_and_get_node_by_ino(root, id->ino);
-	if (!kn)
-		return NULL;
-	if (kn->id.generation != id->generation) {
-		kernfs_put(kn);
-		return NULL;
+	if (*max_len < 2) {
+		*max_len = 2;
+		return FILEID_INVALID;
 	}
-	return kn;
+
+	*max_len = 2;
+	*(u64 *)fh = kn->id;
+	return FILEID_KERNFS;
 }
 
-static struct inode *kernfs_fh_get_inode(struct super_block *sb,
-		u64 ino, u32 generation)
+static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb,
+					    struct fid *fid, int fh_len,
+					    int fh_type, bool get_parent)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);
-	struct inode *inode;
 	struct kernfs_node *kn;
+	struct inode *inode;
+	u64 id;
 
-	if (ino == 0)
-		return ERR_PTR(-ESTALE);
+	if (fh_len < 2)
+		return NULL;
 
-	kn = kernfs_find_and_get_node_by_ino(info->root, ino);
+	switch (fh_type) {
+	case FILEID_KERNFS:
+		id = *(u64 *)fid;
+		break;
+	case FILEID_INO32_GEN:
+	case FILEID_INO32_GEN_PARENT:
+		/*
+		 * blk_log_action() exposes "LOW32,HIGH32" pair without
+		 * type and userland can call us with generic fid
+		 * constructed from them.  Combine it back to ID.  See
+		 * blk_log_action().
+		 */
+		id = ((u64)fid->i32.gen << 32) | fid->i32.ino;
+		break;
+	default:
+		return NULL;
+	}
+
+	kn = kernfs_find_and_get_node_by_id(info->root, id);
 	if (!kn)
 		return ERR_PTR(-ESTALE);
+
+	if (get_parent) {
+		struct kernfs_node *parent;
+
+		parent = kernfs_get_parent(kn);
+		kernfs_put(kn);
+		kn = parent;
+		if (!kn)
+			return ERR_PTR(-ESTALE);
+	}
+
 	inode = kernfs_get_inode(sb, kn);
 	kernfs_put(kn);
 	if (!inode)
 		return ERR_PTR(-ESTALE);
 
-	if (generation && inode->i_generation != generation) {
-		/* we didn't find the right inode.. */
-		iput(inode);
-		return ERR_PTR(-ESTALE);
-	}
-	return inode;
+	return d_obtain_alias(inode);
 }
 
-static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
-		int fh_len, int fh_type)
+static struct dentry *kernfs_fh_to_dentry(struct super_block *sb,
+					  struct fid *fid, int fh_len,
+					  int fh_type)
 {
-	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
-				    kernfs_fh_get_inode);
+	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
 }
 
-static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
-		int fh_len, int fh_type)
+static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
+					  struct fid *fid, int fh_len,
+					  int fh_type)
 {
-	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
-				    kernfs_fh_get_inode);
+	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
 }
 
 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
@@ -120,6 +142,7 @@ static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
 }
 
 static const struct export_operations kernfs_export_ops = {
+	.encode_fh	= kernfs_encode_fh,
 	.fh_to_dentry	= kernfs_fh_to_dentry,
 	.fh_to_parent	= kernfs_fh_to_parent,
 	.get_parent	= kernfs_get_parent_dentry,
@@ -363,18 +386,9 @@ void kernfs_kill_sb(struct super_block *sb)
 
 void __init kernfs_init(void)
 {
-
-	/*
-	 * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
-	 * can access the slab lock free. This could introduce stale nodes,
-	 * please see how kernfs_find_and_get_node_by_ino filters out stale
-	 * nodes.
-	 */
 	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
 					      sizeof(struct kernfs_node),
-					      0,
-					      SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
-					      NULL);
+					      0, SLAB_PANIC, NULL);
 
 	/* Creates slab cache for kernfs inode attributes */
 	kernfs_iattrs_cache  = kmem_cache_create("kernfs_iattrs_cache",
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 430e219e3aba..63097cb243cb 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -354,16 +354,6 @@ struct cgroup {
 
 	unsigned long flags;		/* "unsigned long" so bitops work */
 
-	/*
-	 * idr allocated in-hierarchy ID.
-	 *
-	 * ID 0 is not used, the ID of the root cgroup is always 1, and a
-	 * new cgroup will be assigned with a smallest available ID.
-	 *
-	 * Allocating/Removing ID must be protected by cgroup_mutex.
-	 */
-	int id;
-
 	/*
 	 * The depth this cgroup is at.  The root is at depth zero and each
 	 * step down the hierarchy increments the level.  This along with
@@ -458,7 +448,7 @@ struct cgroup {
 	struct list_head rstat_css_list;
 
 	/* cgroup basic resource statistics */
-	struct cgroup_base_stat pending_bstat;	/* pending from children */
+	struct cgroup_base_stat last_bstat;
 	struct cgroup_base_stat bstat;
 	struct prev_cputime prev_cputime;	/* for printing out cputime */
 
@@ -488,7 +478,7 @@ struct cgroup {
 	struct cgroup_freezer_state freezer;
 
 	/* ids of the ancestors at each level including self */
-	int ancestor_ids[];
+	u64 ancestor_ids[];
 };
 
 /*
@@ -509,7 +499,7 @@ struct cgroup_root {
 	struct cgroup cgrp;
 
 	/* for cgrp->ancestor_ids[0] */
-	int cgrp_ancestor_id_storage;
+	u64 cgrp_ancestor_id_storage;
 
 	/* Number of cgroups in the hierarchy, used only for /proc/cgroups */
 	atomic_t nr_cgrps;
@@ -520,9 +510,6 @@ struct cgroup_root {
 	/* Hierarchy-specific flags */
 	unsigned int flags;
 
-	/* IDs for cgroups in this hierarchy */
-	struct idr cgroup_idr;
-
 	/* The path to use for release notifications. */
 	char release_agent_path[PATH_MAX];
 
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 3ba3e6da13a6..d7ddebd0cdec 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -150,7 +150,6 @@ struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
 					struct cgroup_subsys_state **dst_cssp);
 
-void cgroup_enable_task_cg_lists(void);
 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
 			 struct css_task_iter *it);
 struct task_struct *css_task_iter_next(struct css_task_iter *it);
@@ -305,6 +304,11 @@ void css_task_iter_end(struct css_task_iter *it);
  * Inline functions.
  */
 
+static inline u64 cgroup_id(struct cgroup *cgrp)
+{
+	return cgrp->kn->id;
+}
+
 /**
  * css_get - obtain a reference on the specified css
  * @css: target css
@@ -566,7 +570,7 @@ static inline bool cgroup_is_descendant(struct cgroup *cgrp,
 {
 	if (cgrp->root != ancestor->root || cgrp->level < ancestor->level)
 		return false;
-	return cgrp->ancestor_ids[ancestor->level] == ancestor->id;
+	return cgrp->ancestor_ids[ancestor->level] == cgroup_id(ancestor);
 }
 
 /**
@@ -617,7 +621,7 @@ static inline bool cgroup_is_populated(struct cgroup *cgrp)
 /* returns ino associated with a cgroup */
 static inline ino_t cgroup_ino(struct cgroup *cgrp)
 {
-	return cgrp->kn->id.ino;
+	return kernfs_ino(cgrp->kn);
 }
 
 /* cft/css accessors for cftype->write() operation */
@@ -688,18 +692,13 @@ static inline void cgroup_kthread_ready(void)
 	current->no_cgroup_migration = 0;
 }
 
-static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
-{
-	return &cgrp->kn->id;
-}
-
-void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
-					char *buf, size_t buflen);
+void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen);
 #else /* !CONFIG_CGROUPS */
 
 struct cgroup_subsys_state;
 struct cgroup;
 
+static inline u64 cgroup_id(struct cgroup *cgrp) { return 1; }
 static inline void css_get(struct cgroup_subsys_state *css) {}
 static inline void css_put(struct cgroup_subsys_state *css) {}
 static inline int cgroup_attach_task_all(struct task_struct *from,
@@ -719,10 +718,6 @@ static inline int cgroup_init_early(void) { return 0; }
 static inline int cgroup_init(void) { return 0; }
 static inline void cgroup_init_kthreadd(void) {}
 static inline void cgroup_kthread_ready(void) {}
-static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
-{
-	return NULL;
-}
 
 static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
 {
@@ -740,8 +735,8 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
 	return true;
 }
 
-static inline void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
-	char *buf, size_t buflen) {}
+static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
+{}
 #endif /* !CONFIG_CGROUPS */
 
 #ifdef CONFIG_CGROUPS
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index cf6571fc9c01..d896b8657085 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -104,6 +104,11 @@ enum fid_type {
 	 */
 	FILEID_LUSTRE = 0x97,
 
+	/*
+	 * 64 bit unique kernfs id
+	 */
+	FILEID_KERNFS = 0xfe,
+
 	/*
 	 * Filesystems must not use 0xff file ID.
 	 */
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 936b61bd504e..dded2e5a9f42 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -104,21 +104,6 @@ struct kernfs_elem_attr {
 	struct kernfs_node	*notify_next;	/* for kernfs_notify() */
 };
 
-/* represent a kernfs node */
-union kernfs_node_id {
-	struct {
-		/*
-		 * blktrace will export this struct as a simplified 'struct
-		 * fid' (which is a big data struction), so userspace can use
-		 * it to find kernfs node. The layout must match the first two
-		 * fields of 'struct fid' exactly.
-		 */
-		u32		ino;
-		u32		generation;
-	};
-	u64			id;
-};
-
 /*
  * kernfs_node - the building block of kernfs hierarchy.  Each and every
  * kernfs node is represented by single kernfs_node.  Most fields are
@@ -155,7 +140,12 @@ struct kernfs_node {
 
 	void			*priv;
 
-	union kernfs_node_id	id;
+	/*
+	 * 64bit unique ID.  On 64bit ino setups, id is the ino.  On 32bit,
+	 * the low 32bits are ino and upper generation.
+	 */
+	u64			id;
+
 	unsigned short		flags;
 	umode_t			mode;
 	struct kernfs_iattrs	*iattr;
@@ -187,7 +177,8 @@ struct kernfs_root {
 
 	/* private fields, do not use outside kernfs proper */
 	struct idr		ino_idr;
-	u32			next_generation;
+	u32			last_id_lowbits;
+	u32			id_highbits;
 	struct kernfs_syscall_ops *syscall_ops;
 
 	/* list of kernfs_super_info of this root, protected by kernfs_mutex */
@@ -291,6 +282,34 @@ static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
 	return kn->flags & KERNFS_TYPE_MASK;
 }
 
+static inline ino_t kernfs_id_ino(u64 id)
+{
+	/* id is ino if ino_t is 64bit; otherwise, low 32bits */
+	if (sizeof(ino_t) >= sizeof(u64))
+		return id;
+	else
+		return (u32)id;
+}
+
+static inline u32 kernfs_id_gen(u64 id)
+{
+	/* gen is fixed at 1 if ino_t is 64bit; otherwise, high 32bits */
+	if (sizeof(ino_t) >= sizeof(u64))
+		return 1;
+	else
+		return id >> 32;
+}
+
+static inline ino_t kernfs_ino(struct kernfs_node *kn)
+{
+	return kernfs_id_ino(kn->id);
+}
+
+static inline ino_t kernfs_gen(struct kernfs_node *kn)
+{
+	return kernfs_id_gen(kn->id);
+}
+
 /**
  * kernfs_enable_ns - enable namespace under a directory
  * @kn: directory of interest, should be empty
@@ -382,8 +401,8 @@ void kernfs_kill_sb(struct super_block *sb);
 
 void kernfs_init(void);
 
-struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
-	const union kernfs_node_id *id);
+struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
+						   u64 id);
 #else	/* CONFIG_KERNFS */
 
 static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
index cfc9441ef074..dec7522b6ce1 100644
--- a/include/net/netprio_cgroup.h
+++ b/include/net/netprio_cgroup.h
@@ -26,7 +26,7 @@ static inline u32 task_netprioidx(struct task_struct *p)
 
 	rcu_read_lock();
 	css = task_css(p, net_prio_cgrp_id);
-	idx = css->cgroup->id;
+	idx = css->id;
 	rcu_read_unlock();
 	return idx;
 }
diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
index a566cc521476..7f42a3de59e6 100644
--- a/include/trace/events/cgroup.h
+++ b/include/trace/events/cgroup.h
@@ -66,7 +66,7 @@ DECLARE_EVENT_CLASS(cgroup,
 
 	TP_fast_assign(
 		__entry->root = cgrp->root->hierarchy_id;
-		__entry->id = cgrp->id;
+		__entry->id = cgroup_id(cgrp);
 		__entry->level = cgrp->level;
 		__assign_str(path, path);
 	),
@@ -135,7 +135,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
 
 	TP_fast_assign(
 		__entry->dst_root = dst_cgrp->root->hierarchy_id;
-		__entry->dst_id = dst_cgrp->id;
+		__entry->dst_id = cgroup_id(dst_cgrp);
 		__entry->dst_level = dst_cgrp->level;
 		__assign_str(dst_path, path);
 		__entry->pid = task->pid;
@@ -179,7 +179,7 @@ DECLARE_EVENT_CLASS(cgroup_event,
 
 	TP_fast_assign(
 		__entry->root = cgrp->root->hierarchy_id;
-		__entry->id = cgrp->id;
+		__entry->id = cgroup_id(cgrp);
 		__entry->level = cgrp->level;
 		__assign_str(path, path);
 		__entry->val = val;
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index c2ce6480b4b1..ef50be4e5e6c 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -61,7 +61,7 @@ DECLARE_EVENT_CLASS(writeback_page_template,
 
 	TP_STRUCT__entry (
 		__array(char, name, 32)
-		__field(unsigned long, ino)
+		__field(ino_t, ino)
 		__field(pgoff_t, index)
 	),
 
@@ -75,7 +75,7 @@ DECLARE_EVENT_CLASS(writeback_page_template,
 
 	TP_printk("bdi %s: ino=%lu index=%lu",
 		__entry->name,
-		__entry->ino,
+		(unsigned long)__entry->ino,
 		__entry->index
 	)
 );
@@ -102,7 +102,7 @@ DECLARE_EVENT_CLASS(writeback_dirty_inode_template,
 
 	TP_STRUCT__entry (
 		__array(char, name, 32)
-		__field(unsigned long, ino)
+		__field(ino_t, ino)
 		__field(unsigned long, state)
 		__field(unsigned long, flags)
 	),
@@ -120,7 +120,7 @@ DECLARE_EVENT_CLASS(writeback_dirty_inode_template,
 
 	TP_printk("bdi %s: ino=%lu state=%s flags=%s",
 		__entry->name,
-		__entry->ino,
+		(unsigned long)__entry->ino,
 		show_inode_state(__entry->state),
 		show_inode_state(__entry->flags)
 	)
@@ -150,28 +150,28 @@ DEFINE_EVENT(writeback_dirty_inode_template, writeback_dirty_inode,
 #ifdef CREATE_TRACE_POINTS
 #ifdef CONFIG_CGROUP_WRITEBACK
 
-static inline unsigned int __trace_wb_assign_cgroup(struct bdi_writeback *wb)
+static inline ino_t __trace_wb_assign_cgroup(struct bdi_writeback *wb)
 {
-	return wb->memcg_css->cgroup->kn->id.ino;
+	return cgroup_ino(wb->memcg_css->cgroup);
 }
 
-static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *wbc)
+static inline ino_t __trace_wbc_assign_cgroup(struct writeback_control *wbc)
 {
 	if (wbc->wb)
 		return __trace_wb_assign_cgroup(wbc->wb);
 	else
-		return -1U;
+		return 1;
 }
 #else	/* CONFIG_CGROUP_WRITEBACK */
 
-static inline unsigned int __trace_wb_assign_cgroup(struct bdi_writeback *wb)
+static inline ino_t __trace_wb_assign_cgroup(struct bdi_writeback *wb)
 {
-	return -1U;
+	return 1;
 }
 
-static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *wbc)
+static inline ino_t __trace_wbc_assign_cgroup(struct writeback_control *wbc)
 {
-	return -1U;
+	return 1;
 }
 
 #endif	/* CONFIG_CGROUP_WRITEBACK */
@@ -187,8 +187,8 @@ TRACE_EVENT(inode_foreign_history,
 
 	TP_STRUCT__entry(
 		__array(char,		name, 32)
-		__field(unsigned long,	ino)
-		__field(unsigned int,	cgroup_ino)
+		__field(ino_t,		ino)
+		__field(ino_t,		cgroup_ino)
 		__field(unsigned int,	history)
 	),
 
@@ -199,10 +199,10 @@ TRACE_EVENT(inode_foreign_history,
 		__entry->history	= history;
 	),
 
-	TP_printk("bdi %s: ino=%lu cgroup_ino=%u history=0x%x",
+	TP_printk("bdi %s: ino=%lu cgroup_ino=%lu history=0x%x",
 		__entry->name,
-		__entry->ino,
-		__entry->cgroup_ino,
+		(unsigned long)__entry->ino,
+		(unsigned long)__entry->cgroup_ino,
 		__entry->history
 	)
 );
@@ -216,9 +216,9 @@ TRACE_EVENT(inode_switch_wbs,
 
 	TP_STRUCT__entry(
 		__array(char,		name, 32)
-		__field(unsigned long,	ino)
-		__field(unsigned int,	old_cgroup_ino)
-		__field(unsigned int,	new_cgroup_ino)
+		__field(ino_t,		ino)
+		__field(ino_t,		old_cgroup_ino)
+		__field(ino_t,		new_cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -228,11 +228,11 @@ TRACE_EVENT(inode_switch_wbs,
 		__entry->new_cgroup_ino	= __trace_wb_assign_cgroup(new_wb);
 	),
 
-	TP_printk("bdi %s: ino=%lu old_cgroup_ino=%u new_cgroup_ino=%u",
+	TP_printk("bdi %s: ino=%lu old_cgroup_ino=%lu new_cgroup_ino=%lu",
 		__entry->name,
-		__entry->ino,
-		__entry->old_cgroup_ino,
-		__entry->new_cgroup_ino
+		(unsigned long)__entry->ino,
+		(unsigned long)__entry->old_cgroup_ino,
+		(unsigned long)__entry->new_cgroup_ino
 	)
 );
 
@@ -245,10 +245,10 @@ TRACE_EVENT(track_foreign_dirty,
 	TP_STRUCT__entry(
 		__array(char,		name, 32)
 		__field(u64,		bdi_id)
-		__field(unsigned long,	ino)
+		__field(ino_t,		ino)
 		__field(unsigned int,	memcg_id)
-		__field(unsigned int,	cgroup_ino)
-		__field(unsigned int,	page_cgroup_ino)
+		__field(ino_t,		cgroup_ino)
+		__field(ino_t,		page_cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -260,16 +260,16 @@ TRACE_EVENT(track_foreign_dirty,
 		__entry->ino		= inode ? inode->i_ino : 0;
 		__entry->memcg_id	= wb->memcg_css->id;
 		__entry->cgroup_ino	= __trace_wb_assign_cgroup(wb);
-		__entry->page_cgroup_ino = page->mem_cgroup->css.cgroup->kn->id.ino;
+		__entry->page_cgroup_ino = cgroup_ino(page->mem_cgroup->css.cgroup);
 	),
 
-	TP_printk("bdi %s[%llu]: ino=%lu memcg_id=%u cgroup_ino=%u page_cgroup_ino=%u",
+	TP_printk("bdi %s[%llu]: ino=%lu memcg_id=%u cgroup_ino=%lu page_cgroup_ino=%lu",
 		__entry->name,
 		__entry->bdi_id,
-		__entry->ino,
+		(unsigned long)__entry->ino,
 		__entry->memcg_id,
-		__entry->cgroup_ino,
-		__entry->page_cgroup_ino
+		(unsigned long)__entry->cgroup_ino,
+		(unsigned long)__entry->page_cgroup_ino
 	)
 );
 
@@ -282,7 +282,7 @@ TRACE_EVENT(flush_foreign,
 
 	TP_STRUCT__entry(
 		__array(char,		name, 32)
-		__field(unsigned int,	cgroup_ino)
+		__field(ino_t,		cgroup_ino)
 		__field(unsigned int,	frn_bdi_id)
 		__field(unsigned int,	frn_memcg_id)
 	),
@@ -294,9 +294,9 @@ TRACE_EVENT(flush_foreign,
 		__entry->frn_memcg_id	= frn_memcg_id;
 	),
 
-	TP_printk("bdi %s: cgroup_ino=%u frn_bdi_id=%u frn_memcg_id=%u",
+	TP_printk("bdi %s: cgroup_ino=%lu frn_bdi_id=%u frn_memcg_id=%u",
 		__entry->name,
-		__entry->cgroup_ino,
+		(unsigned long)__entry->cgroup_ino,
 		__entry->frn_bdi_id,
 		__entry->frn_memcg_id
 	)
@@ -311,9 +311,9 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
 
 	TP_STRUCT__entry (
 		__array(char, name, 32)
-		__field(unsigned long, ino)
+		__field(ino_t, ino)
 		__field(int, sync_mode)
-		__field(unsigned int, cgroup_ino)
+		__field(ino_t, cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -324,11 +324,11 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
 		__entry->cgroup_ino	= __trace_wbc_assign_cgroup(wbc);
 	),
 
-	TP_printk("bdi %s: ino=%lu sync_mode=%d cgroup_ino=%u",
+	TP_printk("bdi %s: ino=%lu sync_mode=%d cgroup_ino=%lu",
 		__entry->name,
-		__entry->ino,
+		(unsigned long)__entry->ino,
 		__entry->sync_mode,
-		__entry->cgroup_ino
+		(unsigned long)__entry->cgroup_ino
 	)
 );
 
@@ -358,7 +358,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
 		__field(int, range_cyclic)
 		__field(int, for_background)
 		__field(int, reason)
-		__field(unsigned int, cgroup_ino)
+		__field(ino_t, cgroup_ino)
 	),
 	TP_fast_assign(
 		strscpy_pad(__entry->name,
@@ -374,7 +374,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
 		__entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
 	),
 	TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d "
-		  "kupdate=%d range_cyclic=%d background=%d reason=%s cgroup_ino=%u",
+		  "kupdate=%d range_cyclic=%d background=%d reason=%s cgroup_ino=%lu",
 		  __entry->name,
 		  MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev),
 		  __entry->nr_pages,
@@ -383,7 +383,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
 		  __entry->range_cyclic,
 		  __entry->for_background,
 		  __print_symbolic(__entry->reason, WB_WORK_REASON),
-		  __entry->cgroup_ino
+		  (unsigned long)__entry->cgroup_ino
 	)
 );
 #define DEFINE_WRITEBACK_WORK_EVENT(name) \
@@ -413,15 +413,15 @@ DECLARE_EVENT_CLASS(writeback_class,
 	TP_ARGS(wb),
 	TP_STRUCT__entry(
 		__array(char, name, 32)
-		__field(unsigned int, cgroup_ino)
+		__field(ino_t, cgroup_ino)
 	),
 	TP_fast_assign(
 		strscpy_pad(__entry->name, dev_name(wb->bdi->dev), 32);
 		__entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
 	),
-	TP_printk("bdi %s: cgroup_ino=%u",
+	TP_printk("bdi %s: cgroup_ino=%lu",
 		  __entry->name,
-		  __entry->cgroup_ino
+		  (unsigned long)__entry->cgroup_ino
 	)
 );
 #define DEFINE_WRITEBACK_EVENT(name) \
@@ -459,7 +459,7 @@ DECLARE_EVENT_CLASS(wbc_class,
 		__field(int, range_cyclic)
 		__field(long, range_start)
 		__field(long, range_end)
-		__field(unsigned int, cgroup_ino)
+		__field(ino_t, cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -478,7 +478,7 @@ DECLARE_EVENT_CLASS(wbc_class,
 
 	TP_printk("bdi %s: towrt=%ld skip=%ld mode=%d kupd=%d "
 		"bgrd=%d reclm=%d cyclic=%d "
-		"start=0x%lx end=0x%lx cgroup_ino=%u",
+		"start=0x%lx end=0x%lx cgroup_ino=%lu",
 		__entry->name,
 		__entry->nr_to_write,
 		__entry->pages_skipped,
@@ -489,7 +489,7 @@ DECLARE_EVENT_CLASS(wbc_class,
 		__entry->range_cyclic,
 		__entry->range_start,
 		__entry->range_end,
-		__entry->cgroup_ino
+		(unsigned long)__entry->cgroup_ino
 	)
 )
 
@@ -510,7 +510,7 @@ TRACE_EVENT(writeback_queue_io,
 		__field(long,		age)
 		__field(int,		moved)
 		__field(int,		reason)
-		__field(unsigned int,	cgroup_ino)
+		__field(ino_t,		cgroup_ino)
 	),
 	TP_fast_assign(
 		unsigned long *older_than_this = work->older_than_this;
@@ -522,13 +522,13 @@ TRACE_EVENT(writeback_queue_io,
 		__entry->reason	= work->reason;
 		__entry->cgroup_ino	= __trace_wb_assign_cgroup(wb);
 	),
-	TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s cgroup_ino=%u",
+	TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s cgroup_ino=%lu",
 		__entry->name,
 		__entry->older,	/* older_than_this in jiffies */
 		__entry->age,	/* older_than_this in relative milliseconds */
 		__entry->moved,
 		__print_symbolic(__entry->reason, WB_WORK_REASON),
-		__entry->cgroup_ino
+		(unsigned long)__entry->cgroup_ino
 	)
 );
 
@@ -596,7 +596,7 @@ TRACE_EVENT(bdi_dirty_ratelimit,
 		__field(unsigned long,	dirty_ratelimit)
 		__field(unsigned long,	task_ratelimit)
 		__field(unsigned long,	balanced_dirty_ratelimit)
-		__field(unsigned int,	cgroup_ino)
+		__field(ino_t,		cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -614,7 +614,7 @@ TRACE_EVENT(bdi_dirty_ratelimit,
 	TP_printk("bdi %s: "
 		  "write_bw=%lu awrite_bw=%lu dirty_rate=%lu "
 		  "dirty_ratelimit=%lu task_ratelimit=%lu "
-		  "balanced_dirty_ratelimit=%lu cgroup_ino=%u",
+		  "balanced_dirty_ratelimit=%lu cgroup_ino=%lu",
 		  __entry->bdi,
 		  __entry->write_bw,		/* write bandwidth */
 		  __entry->avg_write_bw,	/* avg write bandwidth */
@@ -622,7 +622,7 @@ TRACE_EVENT(bdi_dirty_ratelimit,
 		  __entry->dirty_ratelimit,	/* base ratelimit */
 		  __entry->task_ratelimit, /* ratelimit with position control */
 		  __entry->balanced_dirty_ratelimit, /* the balanced ratelimit */
-		  __entry->cgroup_ino
+		  (unsigned long)__entry->cgroup_ino
 	)
 );
 
@@ -660,7 +660,7 @@ TRACE_EVENT(balance_dirty_pages,
 		__field(	 long,	pause)
 		__field(unsigned long,	period)
 		__field(	 long,	think)
-		__field(unsigned int,	cgroup_ino)
+		__field(ino_t,		cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -692,7 +692,7 @@ TRACE_EVENT(balance_dirty_pages,
 		  "bdi_setpoint=%lu bdi_dirty=%lu "
 		  "dirty_ratelimit=%lu task_ratelimit=%lu "
 		  "dirtied=%u dirtied_pause=%u "
-		  "paused=%lu pause=%ld period=%lu think=%ld cgroup_ino=%u",
+		  "paused=%lu pause=%ld period=%lu think=%ld cgroup_ino=%lu",
 		  __entry->bdi,
 		  __entry->limit,
 		  __entry->setpoint,
@@ -707,7 +707,7 @@ TRACE_EVENT(balance_dirty_pages,
 		  __entry->pause,	/* ms */
 		  __entry->period,	/* ms */
 		  __entry->think,	/* ms */
-		  __entry->cgroup_ino
+		  (unsigned long)__entry->cgroup_ino
 	  )
 );
 
@@ -718,10 +718,10 @@ TRACE_EVENT(writeback_sb_inodes_requeue,
 
 	TP_STRUCT__entry(
 		__array(char, name, 32)
-		__field(unsigned long, ino)
+		__field(ino_t, ino)
 		__field(unsigned long, state)
 		__field(unsigned long, dirtied_when)
-		__field(unsigned int, cgroup_ino)
+		__field(ino_t, cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -733,13 +733,13 @@ TRACE_EVENT(writeback_sb_inodes_requeue,
 		__entry->cgroup_ino	= __trace_wb_assign_cgroup(inode_to_wb(inode));
 	),
 
-	TP_printk("bdi %s: ino=%lu state=%s dirtied_when=%lu age=%lu cgroup_ino=%u",
+	TP_printk("bdi %s: ino=%lu state=%s dirtied_when=%lu age=%lu cgroup_ino=%lu",
 		  __entry->name,
-		  __entry->ino,
+		  (unsigned long)__entry->ino,
 		  show_inode_state(__entry->state),
 		  __entry->dirtied_when,
 		  (jiffies - __entry->dirtied_when) / HZ,
-		  __entry->cgroup_ino
+		  (unsigned long)__entry->cgroup_ino
 	)
 );
 
@@ -789,13 +789,13 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
 
 	TP_STRUCT__entry(
 		__array(char, name, 32)
-		__field(unsigned long, ino)
+		__field(ino_t, ino)
 		__field(unsigned long, state)
 		__field(unsigned long, dirtied_when)
 		__field(unsigned long, writeback_index)
 		__field(long, nr_to_write)
 		__field(unsigned long, wrote)
-		__field(unsigned int, cgroup_ino)
+		__field(ino_t, cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -811,16 +811,16 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
 	),
 
 	TP_printk("bdi %s: ino=%lu state=%s dirtied_when=%lu age=%lu "
-		  "index=%lu to_write=%ld wrote=%lu cgroup_ino=%u",
+		  "index=%lu to_write=%ld wrote=%lu cgroup_ino=%lu",
 		  __entry->name,
-		  __entry->ino,
+		  (unsigned long)__entry->ino,
 		  show_inode_state(__entry->state),
 		  __entry->dirtied_when,
 		  (jiffies - __entry->dirtied_when) / HZ,
 		  __entry->writeback_index,
 		  __entry->nr_to_write,
 		  __entry->wrote,
-		  __entry->cgroup_ino
+		  (unsigned long)__entry->cgroup_ino
 	)
 );
 
@@ -845,7 +845,7 @@ DECLARE_EVENT_CLASS(writeback_inode_template,
 
 	TP_STRUCT__entry(
 		__field(	dev_t,	dev			)
-		__field(unsigned long,	ino			)
+		__field(	ino_t,	ino			)
 		__field(unsigned long,	state			)
 		__field(	__u16, mode			)
 		__field(unsigned long, dirtied_when		)
@@ -861,7 +861,7 @@ DECLARE_EVENT_CLASS(writeback_inode_template,
 
 	TP_printk("dev %d,%d ino %lu dirtied %lu state %s mode 0%o",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
-		  __entry->ino, __entry->dirtied_when,
+		  (unsigned long)__entry->ino, __entry->dirtied_when,
 		  show_inode_state(__entry->state), __entry->mode)
 );
 
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 5e28718928ca..cada974c9f4e 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -317,7 +317,7 @@ BPF_CALL_0(bpf_get_current_cgroup_id)
 {
 	struct cgroup *cgrp = task_dfl_cgroup(current);
 
-	return cgrp->kn->id.id;
+	return cgroup_id(cgrp);
 }
 
 const struct bpf_func_proto bpf_get_current_cgroup_id_proto = {
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index addd6fdceec8..2ba750725cb2 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -569,7 +569,7 @@ void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
 		return;
 
 	storage->key.attach_type = type;
-	storage->key.cgroup_inode_id = cgroup->kn->id.id;
+	storage->key.cgroup_inode_id = cgroup_id(cgroup);
 
 	map = storage->map;
 
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 809e34a3c017..90d1710fef6c 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -231,9 +231,10 @@ int cgroup_migrate(struct task_struct *leader, bool threadgroup,
 
 int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
 		       bool threadgroup);
-struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup)
+struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
+					     bool *locked)
 	__acquires(&cgroup_threadgroup_rwsem);
-void cgroup_procs_write_finish(struct task_struct *task)
+void cgroup_procs_write_finish(struct task_struct *task, bool locked)
 	__releases(&cgroup_threadgroup_rwsem);
 
 void cgroup_lock_and_drain_offline(struct cgroup *cgrp);
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 7f83f4121d8d..09f3a413f6f8 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -495,12 +495,13 @@ static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of,
 	struct task_struct *task;
 	const struct cred *cred, *tcred;
 	ssize_t ret;
+	bool locked;
 
 	cgrp = cgroup_kn_lock_live(of->kn, false);
 	if (!cgrp)
 		return -ENODEV;
 
-	task = cgroup_procs_write_start(buf, threadgroup);
+	task = cgroup_procs_write_start(buf, threadgroup, &locked);
 	ret = PTR_ERR_OR_ZERO(task);
 	if (ret)
 		goto out_unlock;
@@ -522,7 +523,7 @@ static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of,
 	ret = cgroup_attach_task(cgrp, task, threadgroup);
 
 out_finish:
-	cgroup_procs_write_finish(task);
+	cgroup_procs_write_finish(task, locked);
 out_unlock:
 	cgroup_kn_unlock(of->kn);
 
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index ef4242e5d4bc..735af8f15f95 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -899,8 +899,7 @@ static void css_set_move_task(struct task_struct *task,
 		/*
 		 * We are synchronized through cgroup_threadgroup_rwsem
 		 * against PF_EXITING setting such that we can't race
-		 * against cgroup_exit() changing the css_set to
-		 * init_css_set and dropping the old one.
+		 * against cgroup_exit()/cgroup_free() dropping the css_set.
 		 */
 		WARN_ON_ONCE(task->flags & PF_EXITING);
 
@@ -1309,10 +1308,7 @@ static void cgroup_exit_root_id(struct cgroup_root *root)
 
 void cgroup_free_root(struct cgroup_root *root)
 {
-	if (root) {
-		idr_destroy(&root->cgroup_idr);
-		kfree(root);
-	}
+	kfree(root);
 }
 
 static void cgroup_destroy_root(struct cgroup_root *root)
@@ -1374,6 +1370,8 @@ current_cgns_cgroup_from_root(struct cgroup_root *root)
 	cset = current->nsproxy->cgroup_ns->root_cset;
 	if (cset == &init_css_set) {
 		res = &root->cgrp;
+	} else if (root == &cgrp_dfl_root) {
+		res = cset->dfl_cgrp;
 	} else {
 		struct cgrp_cset_link *link;
 
@@ -1430,9 +1428,8 @@ struct cgroup *task_cgroup_from_root(struct task_struct *task,
 				     struct cgroup_root *root)
 {
 	/*
-	 * No need to lock the task - since we hold cgroup_mutex the
-	 * task can't change groups, so the only thing that can happen
-	 * is that it exits and its css is set back to init_css_set.
+	 * No need to lock the task - since we hold css_set_lock the
+	 * task can't change groups.
 	 */
 	return cset_cgroup_from_root(task_css_set(task), root);
 }
@@ -1883,65 +1880,6 @@ static int cgroup_reconfigure(struct fs_context *fc)
 	return 0;
 }
 
-/*
- * To reduce the fork() overhead for systems that are not actually using
- * their cgroups capability, we don't maintain the lists running through
- * each css_set to its tasks until we see the list actually used - in other
- * words after the first mount.
- */
-static bool use_task_css_set_links __read_mostly;
-
-void cgroup_enable_task_cg_lists(void)
-{
-	struct task_struct *p, *g;
-
-	/*
-	 * We need tasklist_lock because RCU is not safe against
-	 * while_each_thread(). Besides, a forking task that has passed
-	 * cgroup_post_fork() without seeing use_task_css_set_links = 1
-	 * is not guaranteed to have its child immediately visible in the
-	 * tasklist if we walk through it with RCU.
-	 */
-	read_lock(&tasklist_lock);
-	spin_lock_irq(&css_set_lock);
-
-	if (use_task_css_set_links)
-		goto out_unlock;
-
-	use_task_css_set_links = true;
-
-	do_each_thread(g, p) {
-		WARN_ON_ONCE(!list_empty(&p->cg_list) ||
-			     task_css_set(p) != &init_css_set);
-
-		/*
-		 * We should check if the process is exiting, otherwise
-		 * it will race with cgroup_exit() in that the list
-		 * entry won't be deleted though the process has exited.
-		 * Do it while holding siglock so that we don't end up
-		 * racing against cgroup_exit().
-		 *
-		 * Interrupts were already disabled while acquiring
-		 * the css_set_lock, so we do not need to disable it
-		 * again when acquiring the sighand->siglock here.
-		 */
-		spin_lock(&p->sighand->siglock);
-		if (!(p->flags & PF_EXITING)) {
-			struct css_set *cset = task_css_set(p);
-
-			if (!css_set_populated(cset))
-				css_set_update_populated(cset, true);
-			list_add_tail(&p->cg_list, &cset->tasks);
-			get_css_set(cset);
-			cset->nr_tasks++;
-		}
-		spin_unlock(&p->sighand->siglock);
-	} while_each_thread(g, p);
-out_unlock:
-	spin_unlock_irq(&css_set_lock);
-	read_unlock(&tasklist_lock);
-}
-
 static void init_cgroup_housekeeping(struct cgroup *cgrp)
 {
 	struct cgroup_subsys *ss;
@@ -1976,7 +1914,6 @@ void init_cgroup_root(struct cgroup_fs_context *ctx)
 	atomic_set(&root->nr_cgrps, 1);
 	cgrp->root = root;
 	init_cgroup_housekeeping(cgrp);
-	idr_init(&root->cgroup_idr);
 
 	root->flags = ctx->flags;
 	if (ctx->release_agent)
@@ -1997,12 +1934,6 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 
 	lockdep_assert_held(&cgroup_mutex);
 
-	ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_KERNEL);
-	if (ret < 0)
-		goto out;
-	root_cgrp->id = ret;
-	root_cgrp->ancestor_ids[0] = ret;
-
 	ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
 			      0, GFP_KERNEL);
 	if (ret)
@@ -2035,6 +1966,8 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 		goto exit_root_id;
 	}
 	root_cgrp->kn = root->kf_root->kn;
+	WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1);
+	root_cgrp->ancestor_ids[0] = cgroup_id(root_cgrp);
 
 	ret = css_populate_dir(&root_cgrp->self);
 	if (ret)
@@ -2188,13 +2121,6 @@ static int cgroup_init_fs_context(struct fs_context *fc)
 	if (!ctx)
 		return -ENOMEM;
 
-	/*
-	 * The first time anyone tries to mount a cgroup, enable the list
-	 * linking each css_set to its tasks and fix up all existing tasks.
-	 */
-	if (!use_task_css_set_links)
-		cgroup_enable_task_cg_lists();
-
 	ctx->ns = current->nsproxy->cgroup_ns;
 	get_cgroup_ns(ctx->ns);
 	fc->fs_private = &ctx->kfc;
@@ -2372,9 +2298,8 @@ static void cgroup_migrate_add_task(struct task_struct *task,
 	if (task->flags & PF_EXITING)
 		return;
 
-	/* leave @task alone if post_fork() hasn't linked it yet */
-	if (list_empty(&task->cg_list))
-		return;
+	/* cgroup_threadgroup_rwsem protects racing against forks */
+	WARN_ON_ONCE(list_empty(&task->cg_list));
 
 	cset = task_css_set(task);
 	if (!cset->mg_src_cgrp)
@@ -2825,7 +2750,8 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
 	return ret;
 }
 
-struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup)
+struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
+					     bool *locked)
 	__acquires(&cgroup_threadgroup_rwsem)
 {
 	struct task_struct *tsk;
@@ -2834,7 +2760,21 @@ struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup)
 	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
 		return ERR_PTR(-EINVAL);
 
-	percpu_down_write(&cgroup_threadgroup_rwsem);
+	/*
+	 * If we migrate a single thread, we don't care about threadgroup
+	 * stability. If the thread is `current`, it won't exit(2) under our
+	 * hands or change PID through exec(2). We exclude
+	 * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write
+	 * callers by cgroup_mutex.
+	 * Therefore, we can skip the global lock.
+	 */
+	lockdep_assert_held(&cgroup_mutex);
+	if (pid || threadgroup) {
+		percpu_down_write(&cgroup_threadgroup_rwsem);
+		*locked = true;
+	} else {
+		*locked = false;
+	}
 
 	rcu_read_lock();
 	if (pid) {
@@ -2865,13 +2805,16 @@ struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup)
 	goto out_unlock_rcu;
 
 out_unlock_threadgroup:
-	percpu_up_write(&cgroup_threadgroup_rwsem);
+	if (*locked) {
+		percpu_up_write(&cgroup_threadgroup_rwsem);
+		*locked = false;
+	}
 out_unlock_rcu:
 	rcu_read_unlock();
 	return tsk;
 }
 
-void cgroup_procs_write_finish(struct task_struct *task)
+void cgroup_procs_write_finish(struct task_struct *task, bool locked)
 	__releases(&cgroup_threadgroup_rwsem)
 {
 	struct cgroup_subsys *ss;
@@ -2880,7 +2823,8 @@ void cgroup_procs_write_finish(struct task_struct *task)
 	/* release reference from cgroup_procs_write_start() */
 	put_task_struct(task);
 
-	percpu_up_write(&cgroup_threadgroup_rwsem);
+	if (locked)
+		percpu_up_write(&cgroup_threadgroup_rwsem);
 	for_each_subsys(ss, ssid)
 		if (ss->post_attach)
 			ss->post_attach();
@@ -3601,22 +3545,22 @@ static int cpu_stat_show(struct seq_file *seq, void *v)
 #ifdef CONFIG_PSI
 static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
 {
-	struct cgroup *cgroup = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup->id == 1 ? &psi_system : &cgroup->psi;
+	struct cgroup *cgrp = seq_css(seq)->cgroup;
+	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_IO);
 }
 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
 {
-	struct cgroup *cgroup = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup->id == 1 ? &psi_system : &cgroup->psi;
+	struct cgroup *cgrp = seq_css(seq)->cgroup;
+	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_MEM);
 }
 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
 {
-	struct cgroup *cgroup = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup->id == 1 ? &psi_system : &cgroup->psi;
+	struct cgroup *cgrp = seq_css(seq)->cgroup;
+	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_CPU);
 }
@@ -4568,9 +4512,6 @@ repeat:
 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
 			 struct css_task_iter *it)
 {
-	/* no one should try to iterate before mounting cgroups */
-	WARN_ON_ONCE(!use_task_css_set_links);
-
 	memset(it, 0, sizeof(*it));
 
 	spin_lock_irq(&css_set_lock);
@@ -4755,12 +4696,13 @@ static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
 	struct cgroup *src_cgrp, *dst_cgrp;
 	struct task_struct *task;
 	ssize_t ret;
+	bool locked;
 
 	dst_cgrp = cgroup_kn_lock_live(of->kn, false);
 	if (!dst_cgrp)
 		return -ENODEV;
 
-	task = cgroup_procs_write_start(buf, true);
+	task = cgroup_procs_write_start(buf, true, &locked);
 	ret = PTR_ERR_OR_ZERO(task);
 	if (ret)
 		goto out_unlock;
@@ -4778,7 +4720,7 @@ static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
 	ret = cgroup_attach_task(dst_cgrp, task, true);
 
 out_finish:
-	cgroup_procs_write_finish(task);
+	cgroup_procs_write_finish(task, locked);
 out_unlock:
 	cgroup_kn_unlock(of->kn);
 
@@ -4796,6 +4738,7 @@ static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
 	struct cgroup *src_cgrp, *dst_cgrp;
 	struct task_struct *task;
 	ssize_t ret;
+	bool locked;
 
 	buf = strstrip(buf);
 
@@ -4803,7 +4746,7 @@ static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
 	if (!dst_cgrp)
 		return -ENODEV;
 
-	task = cgroup_procs_write_start(buf, false);
+	task = cgroup_procs_write_start(buf, false, &locked);
 	ret = PTR_ERR_OR_ZERO(task);
 	if (ret)
 		goto out_unlock;
@@ -4827,7 +4770,7 @@ static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
 	ret = cgroup_attach_task(dst_cgrp, task, false);
 
 out_finish:
-	cgroup_procs_write_finish(task);
+	cgroup_procs_write_finish(task, locked);
 out_unlock:
 	cgroup_kn_unlock(of->kn);
 
@@ -5037,9 +4980,6 @@ static void css_release_work_fn(struct work_struct *work)
 			tcgrp->nr_dying_descendants--;
 		spin_unlock_irq(&css_set_lock);
 
-		cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
-		cgrp->id = -1;
-
 		/*
 		 * There are two control paths which try to determine
 		 * cgroup from dentry without going through kernfs -
@@ -5204,10 +5144,12 @@ err_free_css:
  * it isn't associated with its kernfs_node and doesn't have the control
  * mask applied.
  */
-static struct cgroup *cgroup_create(struct cgroup *parent)
+static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
+				    umode_t mode)
 {
 	struct cgroup_root *root = parent->root;
 	struct cgroup *cgrp, *tcgrp;
+	struct kernfs_node *kn;
 	int level = parent->level + 1;
 	int ret;
 
@@ -5227,15 +5169,13 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 			goto out_cancel_ref;
 	}
 
-	/*
-	 * Temporarily set the pointer to NULL, so idr_find() won't return
-	 * a half-baked cgroup.
-	 */
-	cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_KERNEL);
-	if (cgrp->id < 0) {
-		ret = -ENOMEM;
+	/* create the directory */
+	kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
+	if (IS_ERR(kn)) {
+		ret = PTR_ERR(kn);
 		goto out_stat_exit;
 	}
+	cgrp->kn = kn;
 
 	init_cgroup_housekeeping(cgrp);
 
@@ -5245,7 +5185,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 
 	ret = psi_cgroup_alloc(cgrp);
 	if (ret)
-		goto out_idr_free;
+		goto out_kernfs_remove;
 
 	ret = cgroup_bpf_inherit(cgrp);
 	if (ret)
@@ -5269,7 +5209,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 
 	spin_lock_irq(&css_set_lock);
 	for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
-		cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
+		cgrp->ancestor_ids[tcgrp->level] = cgroup_id(tcgrp);
 
 		if (tcgrp != cgrp) {
 			tcgrp->nr_descendants++;
@@ -5298,12 +5238,6 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 	atomic_inc(&root->nr_cgrps);
 	cgroup_get_live(parent);
 
-	/*
-	 * @cgrp is now fully operational.  If something fails after this
-	 * point, it'll be released via the normal destruction path.
-	 */
-	cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
-
 	/*
 	 * On the default hierarchy, a child doesn't automatically inherit
 	 * subtree_control from the parent.  Each is configured manually.
@@ -5317,8 +5251,8 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 
 out_psi_free:
 	psi_cgroup_free(cgrp);
-out_idr_free:
-	cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
+out_kernfs_remove:
+	kernfs_remove(cgrp->kn);
 out_stat_exit:
 	if (cgroup_on_dfl(parent))
 		cgroup_rstat_exit(cgrp);
@@ -5355,7 +5289,6 @@ fail:
 int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
 {
 	struct cgroup *parent, *cgrp;
-	struct kernfs_node *kn;
 	int ret;
 
 	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
@@ -5371,27 +5304,19 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
 		goto out_unlock;
 	}
 
-	cgrp = cgroup_create(parent);
+	cgrp = cgroup_create(parent, name, mode);
 	if (IS_ERR(cgrp)) {
 		ret = PTR_ERR(cgrp);
 		goto out_unlock;
 	}
 
-	/* create the directory */
-	kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
-	if (IS_ERR(kn)) {
-		ret = PTR_ERR(kn);
-		goto out_destroy;
-	}
-	cgrp->kn = kn;
-
 	/*
 	 * This extra ref will be put in cgroup_free_fn() and guarantees
 	 * that @cgrp->kn is always accessible.
 	 */
-	kernfs_get(kn);
+	kernfs_get(cgrp->kn);
 
-	ret = cgroup_kn_set_ugid(kn);
+	ret = cgroup_kn_set_ugid(cgrp->kn);
 	if (ret)
 		goto out_destroy;
 
@@ -5406,7 +5331,7 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
 	TRACE_CGROUP_PATH(mkdir, cgrp);
 
 	/* let's create and online css's */
-	kernfs_activate(kn);
+	kernfs_activate(cgrp->kn);
 
 	ret = 0;
 	goto out_unlock;
@@ -5836,12 +5761,11 @@ static int __init cgroup_wq_init(void)
 }
 core_initcall(cgroup_wq_init);
 
-void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
-					char *buf, size_t buflen)
+void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 {
 	struct kernfs_node *kn;
 
-	kn = kernfs_get_node_by_id(cgrp_dfl_root.kf_root, id);
+	kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
 	if (!kn)
 		return;
 	kernfs_path(kn, buf, buflen);
@@ -6002,62 +5926,38 @@ void cgroup_cancel_fork(struct task_struct *child)
 void cgroup_post_fork(struct task_struct *child)
 {
 	struct cgroup_subsys *ss;
+	struct css_set *cset;
 	int i;
 
-	/*
-	 * This may race against cgroup_enable_task_cg_lists().  As that
-	 * function sets use_task_css_set_links before grabbing
-	 * tasklist_lock and we just went through tasklist_lock to add
-	 * @child, it's guaranteed that either we see the set
-	 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
-	 * @child during its iteration.
-	 *
-	 * If we won the race, @child is associated with %current's
-	 * css_set.  Grabbing css_set_lock guarantees both that the
-	 * association is stable, and, on completion of the parent's
-	 * migration, @child is visible in the source of migration or
-	 * already in the destination cgroup.  This guarantee is necessary
-	 * when implementing operations which need to migrate all tasks of
-	 * a cgroup to another.
-	 *
-	 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
-	 * will remain in init_css_set.  This is safe because all tasks are
-	 * in the init_css_set before cg_links is enabled and there's no
-	 * operation which transfers all tasks out of init_css_set.
-	 */
-	if (use_task_css_set_links) {
-		struct css_set *cset;
+	spin_lock_irq(&css_set_lock);
 
-		spin_lock_irq(&css_set_lock);
-		cset = task_css_set(current);
-		if (list_empty(&child->cg_list)) {
-			get_css_set(cset);
-			cset->nr_tasks++;
-			css_set_move_task(child, NULL, cset, false);
-		}
+	WARN_ON_ONCE(!list_empty(&child->cg_list));
+	cset = task_css_set(current); /* current is @child's parent */
+	get_css_set(cset);
+	cset->nr_tasks++;
+	css_set_move_task(child, NULL, cset, false);
+
+	/*
+	 * If the cgroup has to be frozen, the new task has too.  Let's set
+	 * the JOBCTL_TRAP_FREEZE jobctl bit to get the task into the
+	 * frozen state.
+	 */
+	if (unlikely(cgroup_task_freeze(child))) {
+		spin_lock(&child->sighand->siglock);
+		WARN_ON_ONCE(child->frozen);
+		child->jobctl |= JOBCTL_TRAP_FREEZE;
+		spin_unlock(&child->sighand->siglock);
 
 		/*
-		 * If the cgroup has to be frozen, the new task has too.
-		 * Let's set the JOBCTL_TRAP_FREEZE jobctl bit to get
-		 * the task into the frozen state.
+		 * Calling cgroup_update_frozen() isn't required here,
+		 * because it will be called anyway a bit later from
+		 * do_freezer_trap(). So we avoid cgroup's transient switch
+		 * from the frozen state and back.
 		 */
-		if (unlikely(cgroup_task_freeze(child))) {
-			spin_lock(&child->sighand->siglock);
-			WARN_ON_ONCE(child->frozen);
-			child->jobctl |= JOBCTL_TRAP_FREEZE;
-			spin_unlock(&child->sighand->siglock);
-
-			/*
-			 * Calling cgroup_update_frozen() isn't required here,
-			 * because it will be called anyway a bit later
-			 * from do_freezer_trap(). So we avoid cgroup's
-			 * transient switch from the frozen state and back.
-			 */
-		}
-
-		spin_unlock_irq(&css_set_lock);
 	}
 
+	spin_unlock_irq(&css_set_lock);
+
 	/*
 	 * Call ss->fork().  This must happen after @child is linked on
 	 * css_set; otherwise, @child might change state between ->fork()
@@ -6072,20 +5972,8 @@ void cgroup_post_fork(struct task_struct *child)
  * cgroup_exit - detach cgroup from exiting task
  * @tsk: pointer to task_struct of exiting process
  *
- * Description: Detach cgroup from @tsk and release it.
+ * Description: Detach cgroup from @tsk.
  *
- * Note that cgroups marked notify_on_release force every task in
- * them to take the global cgroup_mutex mutex when exiting.
- * This could impact scaling on very large systems.  Be reluctant to
- * use notify_on_release cgroups where very high task exit scaling
- * is required on large systems.
- *
- * We set the exiting tasks cgroup to the root cgroup (top_cgroup).  We
- * call cgroup_exit() while the task is still competent to handle
- * notify_on_release(), then leave the task attached to the root cgroup in
- * each hierarchy for the remainder of its exit.  No need to bother with
- * init_css_set refcnting.  init_css_set never goes away and we can't race
- * with migration path - PF_EXITING is visible to migration path.
  */
 void cgroup_exit(struct task_struct *tsk)
 {
@@ -6093,26 +5981,19 @@ void cgroup_exit(struct task_struct *tsk)
 	struct css_set *cset;
 	int i;
 
-	/*
-	 * Unlink from @tsk from its css_set.  As migration path can't race
-	 * with us, we can check css_set and cg_list without synchronization.
-	 */
+	spin_lock_irq(&css_set_lock);
+
+	WARN_ON_ONCE(list_empty(&tsk->cg_list));
 	cset = task_css_set(tsk);
+	css_set_move_task(tsk, cset, NULL, false);
+	list_add_tail(&tsk->cg_list, &cset->dying_tasks);
+	cset->nr_tasks--;
 
-	if (!list_empty(&tsk->cg_list)) {
-		spin_lock_irq(&css_set_lock);
-		css_set_move_task(tsk, cset, NULL, false);
-		list_add_tail(&tsk->cg_list, &cset->dying_tasks);
-		cset->nr_tasks--;
+	WARN_ON_ONCE(cgroup_task_frozen(tsk));
+	if (unlikely(cgroup_task_freeze(tsk)))
+		cgroup_update_frozen(task_dfl_cgroup(tsk));
 
-		WARN_ON_ONCE(cgroup_task_frozen(tsk));
-		if (unlikely(cgroup_task_freeze(tsk)))
-			cgroup_update_frozen(task_dfl_cgroup(tsk));
-
-		spin_unlock_irq(&css_set_lock);
-	} else {
-		get_css_set(cset);
-	}
+	spin_unlock_irq(&css_set_lock);
 
 	/* see cgroup_post_fork() for details */
 	do_each_subsys_mask(ss, i, have_exit_callback) {
@@ -6129,12 +6010,10 @@ void cgroup_release(struct task_struct *task)
 		ss->release(task);
 	} while_each_subsys_mask();
 
-	if (use_task_css_set_links) {
-		spin_lock_irq(&css_set_lock);
-		css_set_skip_task_iters(task_css_set(task), task);
-		list_del_init(&task->cg_list);
-		spin_unlock_irq(&css_set_lock);
-	}
+	spin_lock_irq(&css_set_lock);
+	css_set_skip_task_iters(task_css_set(task), task);
+	list_del_init(&task->cg_list);
+	spin_unlock_irq(&css_set_lock);
 }
 
 void cgroup_free(struct task_struct *task)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index c87ee6412b36..58f5073acff7 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -929,8 +929,6 @@ static void rebuild_root_domains(void)
 	lockdep_assert_cpus_held();
 	lockdep_assert_held(&sched_domains_mutex);
 
-	cgroup_enable_task_cg_lists();
-
 	rcu_read_lock();
 
 	/*
diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
index 8cf010680678..3984dd6b8ddb 100644
--- a/kernel/cgroup/freezer.c
+++ b/kernel/cgroup/freezer.c
@@ -230,6 +230,15 @@ void cgroup_freezer_migrate_task(struct task_struct *task,
 	if (task->flags & PF_KTHREAD)
 		return;
 
+	/*
+	 * It's not necessary to do changes if both of the src and dst cgroups
+	 * are not freezing and task is not frozen.
+	 */
+	if (!test_bit(CGRP_FREEZE, &src->flags) &&
+	    !test_bit(CGRP_FREEZE, &dst->flags) &&
+	    !task->frozen)
+		return;
+
 	/*
 	 * Adjust counters of freezing and frozen tasks.
 	 * Note, that if the task is frozen, but the destination cgroup is not
diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c
index 8e513a573fe9..138059eb730d 100644
--- a/kernel/cgroup/pids.c
+++ b/kernel/cgroup/pids.c
@@ -45,7 +45,7 @@ struct pids_cgroup {
 	 * %PIDS_MAX = (%PID_MAX_LIMIT + 1).
 	 */
 	atomic64_t			counter;
-	int64_t				limit;
+	atomic64_t			limit;
 
 	/* Handle for "pids.events" */
 	struct cgroup_file		events_file;
@@ -73,8 +73,8 @@ pids_css_alloc(struct cgroup_subsys_state *parent)
 	if (!pids)
 		return ERR_PTR(-ENOMEM);
 
-	pids->limit = PIDS_MAX;
 	atomic64_set(&pids->counter, 0);
+	atomic64_set(&pids->limit, PIDS_MAX);
 	atomic64_set(&pids->events_limit, 0);
 	return &pids->css;
 }
@@ -146,13 +146,14 @@ static int pids_try_charge(struct pids_cgroup *pids, int num)
 
 	for (p = pids; parent_pids(p); p = parent_pids(p)) {
 		int64_t new = atomic64_add_return(num, &p->counter);
+		int64_t limit = atomic64_read(&p->limit);
 
 		/*
 		 * Since new is capped to the maximum number of pid_t, if
 		 * p->limit is %PIDS_MAX then we know that this test will never
 		 * fail.
 		 */
-		if (new > p->limit)
+		if (new > limit)
 			goto revert;
 	}
 
@@ -277,7 +278,7 @@ set_limit:
 	 * Limit updates don't need to be mutex'd, since it isn't
 	 * critical that any racing fork()s follow the new limit.
 	 */
-	pids->limit = limit;
+	atomic64_set(&pids->limit, limit);
 	return nbytes;
 }
 
@@ -285,7 +286,7 @@ static int pids_max_show(struct seq_file *sf, void *v)
 {
 	struct cgroup_subsys_state *css = seq_css(sf);
 	struct pids_cgroup *pids = css_pids(css);
-	int64_t limit = pids->limit;
+	int64_t limit = atomic64_read(&pids->limit);
 
 	if (limit >= PIDS_MAX)
 		seq_printf(sf, "%s\n", PIDS_MAX_STR);
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index ca19b4c8acf5..b48b22d4deb6 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -304,44 +304,48 @@ void __init cgroup_rstat_boot(void)
  * Functions for cgroup basic resource statistics implemented on top of
  * rstat.
  */
-static void cgroup_base_stat_accumulate(struct cgroup_base_stat *dst_bstat,
-					struct cgroup_base_stat *src_bstat)
+static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat,
+				 struct cgroup_base_stat *src_bstat)
 {
 	dst_bstat->cputime.utime += src_bstat->cputime.utime;
 	dst_bstat->cputime.stime += src_bstat->cputime.stime;
 	dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime;
 }
 
+static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
+				 struct cgroup_base_stat *src_bstat)
+{
+	dst_bstat->cputime.utime -= src_bstat->cputime.utime;
+	dst_bstat->cputime.stime -= src_bstat->cputime.stime;
+	dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime;
+}
+
 static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
 {
 	struct cgroup *parent = cgroup_parent(cgrp);
 	struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
-	struct task_cputime *last_cputime = &rstatc->last_bstat.cputime;
-	struct task_cputime cputime;
-	struct cgroup_base_stat delta;
+	struct cgroup_base_stat cur, delta;
 	unsigned seq;
 
 	/* fetch the current per-cpu values */
 	do {
 		seq = __u64_stats_fetch_begin(&rstatc->bsync);
-		cputime = rstatc->bstat.cputime;
+		cur.cputime = rstatc->bstat.cputime;
 	} while (__u64_stats_fetch_retry(&rstatc->bsync, seq));
 
-	/* calculate the delta to propgate */
-	delta.cputime.utime = cputime.utime - last_cputime->utime;
-	delta.cputime.stime = cputime.stime - last_cputime->stime;
-	delta.cputime.sum_exec_runtime = cputime.sum_exec_runtime -
-					 last_cputime->sum_exec_runtime;
-	*last_cputime = cputime;
+	/* propagate percpu delta to global */
+	delta = cur;
+	cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
+	cgroup_base_stat_add(&cgrp->bstat, &delta);
+	cgroup_base_stat_add(&rstatc->last_bstat, &delta);
 
-	/* transfer the pending stat into delta */
-	cgroup_base_stat_accumulate(&delta, &cgrp->pending_bstat);
-	memset(&cgrp->pending_bstat, 0, sizeof(cgrp->pending_bstat));
-
-	/* propagate delta into the global stat and the parent's pending */
-	cgroup_base_stat_accumulate(&cgrp->bstat, &delta);
-	if (parent)
-		cgroup_base_stat_accumulate(&parent->pending_bstat, &delta);
+	/* propagate global delta to parent */
+	if (parent) {
+		delta = cgrp->bstat;
+		cgroup_base_stat_sub(&delta, &cgrp->last_bstat);
+		cgroup_base_stat_add(&parent->bstat, &delta);
+		cgroup_base_stat_add(&cgrp->last_bstat, &delta);
+	}
 }
 
 static struct cgroup_rstat_cpu *
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 2d6e93ab0478..475e29498bca 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -64,8 +64,7 @@ static void blk_unregister_tracepoints(void);
  * Send out a notify message.
  */
 static void trace_note(struct blk_trace *bt, pid_t pid, int action,
-		       const void *data, size_t len,
-		       union kernfs_node_id *cgid)
+		       const void *data, size_t len, u64 cgid)
 {
 	struct blk_io_trace *t;
 	struct ring_buffer_event *event = NULL;
@@ -73,7 +72,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action,
 	int pc = 0;
 	int cpu = smp_processor_id();
 	bool blk_tracer = blk_tracer_enabled;
-	ssize_t cgid_len = cgid ? sizeof(*cgid) : 0;
+	ssize_t cgid_len = cgid ? sizeof(cgid) : 0;
 
 	if (blk_tracer) {
 		buffer = blk_tr->trace_buffer.buffer;
@@ -100,8 +99,8 @@ record_it:
 		t->pid = pid;
 		t->cpu = cpu;
 		t->pdu_len = len + cgid_len;
-		if (cgid)
-			memcpy((void *)t + sizeof(*t), cgid, cgid_len);
+		if (cgid_len)
+			memcpy((void *)t + sizeof(*t), &cgid, cgid_len);
 		memcpy((void *) t + sizeof(*t) + cgid_len, data, len);
 
 		if (blk_tracer)
@@ -122,7 +121,7 @@ static void trace_note_tsk(struct task_struct *tsk)
 	spin_lock_irqsave(&running_trace_lock, flags);
 	list_for_each_entry(bt, &running_trace_list, running_list) {
 		trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm,
-			   sizeof(tsk->comm), NULL);
+			   sizeof(tsk->comm), 0);
 	}
 	spin_unlock_irqrestore(&running_trace_lock, flags);
 }
@@ -139,7 +138,7 @@ static void trace_note_time(struct blk_trace *bt)
 	words[1] = now.tv_nsec;
 
 	local_irq_save(flags);
-	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words), NULL);
+	trace_note(bt, 0, BLK_TN_TIMESTAMP, words, sizeof(words), 0);
 	local_irq_restore(flags);
 }
 
@@ -172,9 +171,9 @@ void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
 		blkcg = NULL;
 #ifdef CONFIG_BLK_CGROUP
 	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n,
-		blkcg ? cgroup_get_kernfs_id(blkcg->css.cgroup) : NULL);
+		   blkcg ? cgroup_id(blkcg->css.cgroup) : 1);
 #else
-	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n, NULL);
+	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n, 0);
 #endif
 	local_irq_restore(flags);
 }
@@ -212,7 +211,7 @@ static const u32 ddir_act[2] = { BLK_TC_ACT(BLK_TC_READ),
  */
 static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 		     int op, int op_flags, u32 what, int error, int pdu_len,
-		     void *pdu_data, union kernfs_node_id *cgid)
+		     void *pdu_data, u64 cgid)
 {
 	struct task_struct *tsk = current;
 	struct ring_buffer_event *event = NULL;
@@ -223,7 +222,7 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 	pid_t pid;
 	int cpu, pc = 0;
 	bool blk_tracer = blk_tracer_enabled;
-	ssize_t cgid_len = cgid ? sizeof(*cgid) : 0;
+	ssize_t cgid_len = cgid ? sizeof(cgid) : 0;
 
 	if (unlikely(bt->trace_state != Blktrace_running && !blk_tracer))
 		return;
@@ -294,7 +293,7 @@ record_it:
 		t->pdu_len = pdu_len + cgid_len;
 
 		if (cgid_len)
-			memcpy((void *)t + sizeof(*t), cgid, cgid_len);
+			memcpy((void *)t + sizeof(*t), &cgid, cgid_len);
 		if (pdu_len)
 			memcpy((void *)t + sizeof(*t) + cgid_len, pdu_data, pdu_len);
 
@@ -751,31 +750,29 @@ void blk_trace_shutdown(struct request_queue *q)
 }
 
 #ifdef CONFIG_BLK_CGROUP
-static union kernfs_node_id *
-blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
+static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
 {
 	struct blk_trace *bt = q->blk_trace;
 
 	if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
-		return NULL;
+		return 0;
 
 	if (!bio->bi_blkg)
-		return NULL;
-	return cgroup_get_kernfs_id(bio_blkcg(bio)->css.cgroup);
+		return 0;
+	return cgroup_id(bio_blkcg(bio)->css.cgroup);
 }
 #else
-static union kernfs_node_id *
-blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
+u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
 {
-	return NULL;
+	return 0;
 }
 #endif
 
-static union kernfs_node_id *
+static u64
 blk_trace_request_get_cgid(struct request_queue *q, struct request *rq)
 {
 	if (!rq->bio)
-		return NULL;
+		return 0;
 	/* Use the first bio */
 	return blk_trace_bio_get_cgid(q, rq->bio);
 }
@@ -797,8 +794,7 @@ blk_trace_request_get_cgid(struct request_queue *q, struct request *rq)
  *
  **/
 static void blk_add_trace_rq(struct request *rq, int error,
-			     unsigned int nr_bytes, u32 what,
-			     union kernfs_node_id *cgid)
+			     unsigned int nr_bytes, u32 what, u64 cgid)
 {
 	struct blk_trace *bt = rq->q->blk_trace;
 
@@ -913,7 +909,7 @@ static void blk_add_trace_getrq(void *ignore,
 
 		if (bt)
 			__blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_GETRQ, 0, 0,
-					NULL, NULL);
+					NULL, 0);
 	}
 }
 
@@ -929,7 +925,7 @@ static void blk_add_trace_sleeprq(void *ignore,
 
 		if (bt)
 			__blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_SLEEPRQ,
-					0, 0, NULL, NULL);
+					0, 0, NULL, 0);
 	}
 }
 
@@ -938,7 +934,7 @@ static void blk_add_trace_plug(void *ignore, struct request_queue *q)
 	struct blk_trace *bt = q->blk_trace;
 
 	if (bt)
-		__blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, NULL);
+		__blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, 0);
 }
 
 static void blk_add_trace_unplug(void *ignore, struct request_queue *q,
@@ -955,7 +951,7 @@ static void blk_add_trace_unplug(void *ignore, struct request_queue *q,
 		else
 			what = BLK_TA_UNPLUG_TIMER;
 
-		__blk_add_trace(bt, 0, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu, NULL);
+		__blk_add_trace(bt, 0, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu, 0);
 	}
 }
 
@@ -1172,19 +1168,17 @@ const struct blk_io_trace *te_blk_io_trace(const struct trace_entry *ent)
 
 static inline const void *pdu_start(const struct trace_entry *ent, bool has_cg)
 {
-	return (void *)(te_blk_io_trace(ent) + 1) +
-		(has_cg ? sizeof(union kernfs_node_id) : 0);
+	return (void *)(te_blk_io_trace(ent) + 1) + (has_cg ? sizeof(u64) : 0);
 }
 
-static inline const void *cgid_start(const struct trace_entry *ent)
+static inline u64 t_cgid(const struct trace_entry *ent)
 {
-	return (void *)(te_blk_io_trace(ent) + 1);
+	return *(u64 *)(te_blk_io_trace(ent) + 1);
 }
 
 static inline int pdu_real_len(const struct trace_entry *ent, bool has_cg)
 {
-	return te_blk_io_trace(ent)->pdu_len -
-			(has_cg ? sizeof(union kernfs_node_id) : 0);
+	return te_blk_io_trace(ent)->pdu_len - (has_cg ? sizeof(u64) : 0);
 }
 
 static inline u32 t_action(const struct trace_entry *ent)
@@ -1257,7 +1251,7 @@ static void blk_log_action(struct trace_iterator *iter, const char *act,
 
 	fill_rwbs(rwbs, t);
 	if (has_cg) {
-		const union kernfs_node_id *id = cgid_start(iter->ent);
+		u64 id = t_cgid(iter->ent);
 
 		if (blk_tracer_flags.val & TRACE_BLK_OPT_CGNAME) {
 			char blkcg_name_buf[NAME_MAX + 1] = "<...>";
@@ -1267,11 +1261,25 @@ static void blk_log_action(struct trace_iterator *iter, const char *act,
 			trace_seq_printf(&iter->seq, "%3d,%-3d %s %2s %3s ",
 				 MAJOR(t->device), MINOR(t->device),
 				 blkcg_name_buf, act, rwbs);
-		} else
+		} else {
+			/*
+			 * The cgid portion used to be "INO,GEN".  Userland
+			 * builds a FILEID_INO32_GEN fid out of them and
+			 * opens the cgroup using open_by_handle_at(2).
+			 * While 32bit ino setups are still the same, 64bit
+			 * ones now use the 64bit ino as the whole ID and
+			 * no longer use generation.
+			 *
+			 * Regarldess of the content, always output
+			 * "LOW32,HIGH32" so that FILEID_INO32_GEN fid can
+			 * be mapped back to @id on both 64 and 32bit ino
+			 * setups.  See __kernfs_fh_to_dentry().
+			 */
 			trace_seq_printf(&iter->seq,
-				 "%3d,%-3d %x,%-x %2s %3s ",
+				 "%3d,%-3d %llx,%-llx %2s %3s ",
 				 MAJOR(t->device), MINOR(t->device),
-				 id->ino, id->generation, act, rwbs);
+				 id & U32_MAX, id >> 32, act, rwbs);
+		}
 	} else
 		trace_seq_printf(&iter->seq, "%3d,%-3d %2s %3s ",
 				 MAJOR(t->device), MINOR(t->device), act, rwbs);
diff --git a/net/core/filter.c b/net/core/filter.c
index 3fed5755494b..9ad29f576f1a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4089,7 +4089,7 @@ BPF_CALL_1(bpf_skb_cgroup_id, const struct sk_buff *, skb)
 		return 0;
 
 	cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
-	return cgrp->kn->id.id;
+	return cgroup_id(cgrp);
 }
 
 static const struct bpf_func_proto bpf_skb_cgroup_id_proto = {
@@ -4114,7 +4114,7 @@ BPF_CALL_2(bpf_skb_ancestor_cgroup_id, const struct sk_buff *, skb, int,
 	if (!ancestor)
 		return 0;
 
-	return ancestor->kn->id.id;
+	return cgroup_id(ancestor);
 }
 
 static const struct bpf_func_proto bpf_skb_ancestor_cgroup_id_proto = {
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 256b7954b720..8881dd943dd0 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -93,7 +93,7 @@ static int extend_netdev_table(struct net_device *dev, u32 target_idx)
 static u32 netprio_prio(struct cgroup_subsys_state *css, struct net_device *dev)
 {
 	struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
-	int id = css->cgroup->id;
+	int id = css->id;
 
 	if (map && id < map->priomap_len)
 		return map->priomap[id];
@@ -113,7 +113,7 @@ static int netprio_set_prio(struct cgroup_subsys_state *css,
 			    struct net_device *dev, u32 prio)
 {
 	struct netprio_map *map;
-	int id = css->cgroup->id;
+	int id = css->id;
 	int ret;
 
 	/* avoid extending priomap for zero writes */
@@ -177,7 +177,7 @@ static void cgrp_css_free(struct cgroup_subsys_state *css)
 
 static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
 {
-	return css->cgroup->id;
+	return css->id;
 }
 
 static int read_priomap(struct seq_file *sf, void *v)
@@ -237,7 +237,7 @@ static void net_prio_attach(struct cgroup_taskset *tset)
 	struct cgroup_subsys_state *css;
 
 	cgroup_taskset_for_each(p, css, tset) {
-		void *v = (void *)(unsigned long)css->cgroup->id;
+		void *v = (void *)(unsigned long)css->id;
 
 		task_lock(p);
 		iterate_fd(p->files, 0, update_netprio, v);
diff --git a/tools/testing/selftests/cgroup/Makefile b/tools/testing/selftests/cgroup/Makefile
index 8d369b6a2069..66aafe1f5746 100644
--- a/tools/testing/selftests/cgroup/Makefile
+++ b/tools/testing/selftests/cgroup/Makefile
@@ -1,8 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
-CFLAGS += -Wall
+CFLAGS += -Wall -pthread
 
 all:
 
+TEST_FILES     := with_stress.sh
+TEST_PROGS     := test_stress.sh
 TEST_GEN_PROGS = test_memcontrol
 TEST_GEN_PROGS += test_core
 TEST_GEN_PROGS += test_freezer
diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
index bdb69599c4bd..8f7131dcf1ff 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/cgroup_util.c
@@ -158,6 +158,22 @@ long cg_read_key_long(const char *cgroup, const char *control, const char *key)
 	return atol(ptr + strlen(key));
 }
 
+long cg_read_lc(const char *cgroup, const char *control)
+{
+	char buf[PAGE_SIZE];
+	const char delim[] = "\n";
+	char *line;
+	long cnt = 0;
+
+	if (cg_read(cgroup, control, buf, sizeof(buf)))
+		return -1;
+
+	for (line = strtok(buf, delim); line; line = strtok(NULL, delim))
+		cnt++;
+
+	return cnt;
+}
+
 int cg_write(const char *cgroup, const char *control, char *buf)
 {
 	char path[PATH_MAX];
@@ -282,10 +298,12 @@ int cg_enter(const char *cgroup, int pid)
 
 int cg_enter_current(const char *cgroup)
 {
-	char pidbuf[64];
+	return cg_write(cgroup, "cgroup.procs", "0");
+}
 
-	snprintf(pidbuf, sizeof(pidbuf), "%d", getpid());
-	return cg_write(cgroup, "cgroup.procs", pidbuf);
+int cg_enter_current_thread(const char *cgroup)
+{
+	return cg_write(cgroup, "cgroup.threads", "0");
 }
 
 int cg_run(const char *cgroup,
@@ -410,11 +428,25 @@ int set_oom_adj_score(int pid, int score)
 	return 0;
 }
 
-char proc_read_text(int pid, const char *item, char *buf, size_t size)
+ssize_t proc_read_text(int pid, bool thread, const char *item, char *buf, size_t size)
 {
 	char path[PATH_MAX];
 
-	snprintf(path, sizeof(path), "/proc/%d/%s", pid, item);
+	if (!pid)
+		snprintf(path, sizeof(path), "/proc/%s/%s",
+			 thread ? "thread-self" : "self", item);
+	else
+		snprintf(path, sizeof(path), "/proc/%d/%s", pid, item);
 
 	return read_text(path, buf, size);
 }
+
+int proc_read_strstr(int pid, bool thread, const char *item, const char *needle)
+{
+	char buf[PAGE_SIZE];
+
+	if (proc_read_text(pid, thread, item, buf, sizeof(buf)) < 0)
+		return -1;
+
+	return strstr(buf, needle) ? 0 : -1;
+}
diff --git a/tools/testing/selftests/cgroup/cgroup_util.h b/tools/testing/selftests/cgroup/cgroup_util.h
index c72f28046bfa..49c54fbdb229 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.h
+++ b/tools/testing/selftests/cgroup/cgroup_util.h
@@ -1,4 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#include <stdbool.h>
 #include <stdlib.h>
 
 #define PAGE_SIZE 4096
@@ -29,12 +30,14 @@ extern int cg_read_strstr(const char *cgroup, const char *control,
 			  const char *needle);
 extern long cg_read_long(const char *cgroup, const char *control);
 long cg_read_key_long(const char *cgroup, const char *control, const char *key);
+extern long cg_read_lc(const char *cgroup, const char *control);
 extern int cg_write(const char *cgroup, const char *control, char *buf);
 extern int cg_run(const char *cgroup,
 		  int (*fn)(const char *cgroup, void *arg),
 		  void *arg);
 extern int cg_enter(const char *cgroup, int pid);
 extern int cg_enter_current(const char *cgroup);
+extern int cg_enter_current_thread(const char *cgroup);
 extern int cg_run_nowait(const char *cgroup,
 			 int (*fn)(const char *cgroup, void *arg),
 			 void *arg);
@@ -45,4 +48,5 @@ extern int is_swap_enabled(void);
 extern int set_oom_adj_score(int pid, int score);
 extern int cg_wait_for_proc_count(const char *cgroup, int count);
 extern int cg_killall(const char *cgroup);
-extern char proc_read_text(int pid, const char *item, char *buf, size_t size);
+extern ssize_t proc_read_text(int pid, bool thread, const char *item, char *buf, size_t size);
+extern int proc_read_strstr(int pid, bool thread, const char *item, const char *needle);
diff --git a/tools/testing/selftests/cgroup/test_core.c b/tools/testing/selftests/cgroup/test_core.c
index 79053a4f4783..c5ca669feb2b 100644
--- a/tools/testing/selftests/cgroup/test_core.c
+++ b/tools/testing/selftests/cgroup/test_core.c
@@ -5,6 +5,9 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
+#include <signal.h>
+#include <string.h>
+#include <pthread.h>
 
 #include "../kselftest.h"
 #include "cgroup_util.h"
@@ -354,6 +357,147 @@ cleanup:
 	return ret;
 }
 
+static void *dummy_thread_fn(void *arg)
+{
+	return (void *)(size_t)pause();
+}
+
+/*
+ * Test threadgroup migration.
+ * All threads of a process are migrated together.
+ */
+static int test_cgcore_proc_migration(const char *root)
+{
+	int ret = KSFT_FAIL;
+	int t, c_threads, n_threads = 13;
+	char *src = NULL, *dst = NULL;
+	pthread_t threads[n_threads];
+
+	src = cg_name(root, "cg_src");
+	dst = cg_name(root, "cg_dst");
+	if (!src || !dst)
+		goto cleanup;
+
+	if (cg_create(src))
+		goto cleanup;
+	if (cg_create(dst))
+		goto cleanup;
+
+	if (cg_enter_current(src))
+		goto cleanup;
+
+	for (c_threads = 0; c_threads < n_threads; ++c_threads) {
+		if (pthread_create(&threads[c_threads], NULL, dummy_thread_fn, NULL))
+			goto cleanup;
+	}
+
+	cg_enter_current(dst);
+	if (cg_read_lc(dst, "cgroup.threads") != n_threads + 1)
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	for (t = 0; t < c_threads; ++t) {
+		pthread_cancel(threads[t]);
+	}
+
+	for (t = 0; t < c_threads; ++t) {
+		pthread_join(threads[t], NULL);
+	}
+
+	cg_enter_current(root);
+
+	if (dst)
+		cg_destroy(dst);
+	if (src)
+		cg_destroy(src);
+	free(dst);
+	free(src);
+	return ret;
+}
+
+static void *migrating_thread_fn(void *arg)
+{
+	int g, i, n_iterations = 1000;
+	char **grps = arg;
+	char lines[3][PATH_MAX];
+
+	for (g = 1; g < 3; ++g)
+		snprintf(lines[g], sizeof(lines[g]), "0::%s", grps[g] + strlen(grps[0]));
+
+	for (i = 0; i < n_iterations; ++i) {
+		cg_enter_current_thread(grps[(i % 2) + 1]);
+
+		if (proc_read_strstr(0, 1, "cgroup", lines[(i % 2) + 1]))
+			return (void *)-1;
+	}
+	return NULL;
+}
+
+/*
+ * Test single thread migration.
+ * Threaded cgroups allow successful migration of a thread.
+ */
+static int test_cgcore_thread_migration(const char *root)
+{
+	int ret = KSFT_FAIL;
+	char *dom = NULL;
+	char line[PATH_MAX];
+	char *grps[3] = { (char *)root, NULL, NULL };
+	pthread_t thr;
+	void *retval;
+
+	dom = cg_name(root, "cg_dom");
+	grps[1] = cg_name(root, "cg_dom/cg_src");
+	grps[2] = cg_name(root, "cg_dom/cg_dst");
+	if (!grps[1] || !grps[2] || !dom)
+		goto cleanup;
+
+	if (cg_create(dom))
+		goto cleanup;
+	if (cg_create(grps[1]))
+		goto cleanup;
+	if (cg_create(grps[2]))
+		goto cleanup;
+
+	if (cg_write(grps[1], "cgroup.type", "threaded"))
+		goto cleanup;
+	if (cg_write(grps[2], "cgroup.type", "threaded"))
+		goto cleanup;
+
+	if (cg_enter_current(grps[1]))
+		goto cleanup;
+
+	if (pthread_create(&thr, NULL, migrating_thread_fn, grps))
+		goto cleanup;
+
+	if (pthread_join(thr, &retval))
+		goto cleanup;
+
+	if (retval)
+		goto cleanup;
+
+	snprintf(line, sizeof(line), "0::%s", grps[1] + strlen(grps[0]));
+	if (proc_read_strstr(0, 1, "cgroup", line))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_enter_current(root);
+	if (grps[2])
+		cg_destroy(grps[2]);
+	if (grps[1])
+		cg_destroy(grps[1]);
+	if (dom)
+		cg_destroy(dom);
+	free(grps[2]);
+	free(grps[1]);
+	free(dom);
+	return ret;
+}
+
 #define T(x) { x, #x }
 struct corecg_test {
 	int (*fn)(const char *root);
@@ -366,6 +510,8 @@ struct corecg_test {
 	T(test_cgcore_parent_becomes_threaded),
 	T(test_cgcore_invalid_domain),
 	T(test_cgcore_populated),
+	T(test_cgcore_proc_migration),
+	T(test_cgcore_thread_migration),
 };
 #undef T
 
diff --git a/tools/testing/selftests/cgroup/test_freezer.c b/tools/testing/selftests/cgroup/test_freezer.c
index 0fc1b6d4b0f9..23d8fa4a3e4e 100644
--- a/tools/testing/selftests/cgroup/test_freezer.c
+++ b/tools/testing/selftests/cgroup/test_freezer.c
@@ -72,6 +72,7 @@ static int cg_prepare_for_wait(const char *cgroup)
 	if (ret == -1) {
 		debug("Error: inotify_add_watch() failed\n");
 		close(fd);
+		fd = -1;
 	}
 
 	return fd;
@@ -701,7 +702,7 @@ static int proc_check_stopped(int pid)
 	char buf[PAGE_SIZE];
 	int len;
 
-	len = proc_read_text(pid, "stat", buf, sizeof(buf));
+	len = proc_read_text(pid, 0, "stat", buf, sizeof(buf));
 	if (len == -1) {
 		debug("Can't get %d stat\n", pid);
 		return -1;
diff --git a/tools/testing/selftests/cgroup/test_stress.sh b/tools/testing/selftests/cgroup/test_stress.sh
new file mode 100755
index 000000000000..15d9d5896394
--- /dev/null
+++ b/tools/testing/selftests/cgroup/test_stress.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+./with_stress.sh -s subsys -s fork ./test_core
diff --git a/tools/testing/selftests/cgroup/with_stress.sh b/tools/testing/selftests/cgroup/with_stress.sh
new file mode 100755
index 000000000000..e28c35008f5b
--- /dev/null
+++ b/tools/testing/selftests/cgroup/with_stress.sh
@@ -0,0 +1,101 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+stress_fork()
+{
+	while true ; do
+		/usr/bin/true
+		sleep 0.01
+	done
+}
+
+stress_subsys()
+{
+	local verb=+
+	while true ; do
+		echo $verb$subsys_ctrl >$sysfs/cgroup.subtree_control
+		[ $verb = "+" ] && verb=- || verb=+
+		# incommensurable period with other stresses
+		sleep 0.011
+	done
+}
+
+init_and_check()
+{
+	sysfs=`mount -t cgroup2 | head -1 | awk '{ print $3 }'`
+	if [ ! -d "$sysfs" ]; then
+		echo "Skipping: cgroup2 is not mounted" >&2
+		exit $ksft_skip
+	fi
+
+	if ! echo +$subsys_ctrl >$sysfs/cgroup.subtree_control ; then
+		echo "Skipping: cannot enable $subsys_ctrl in $sysfs" >&2
+		exit $ksft_skip
+	fi
+
+	if ! echo -$subsys_ctrl >$sysfs/cgroup.subtree_control ; then
+		echo "Skipping: cannot disable $subsys_ctrl in $sysfs" >&2
+		exit $ksft_skip
+	fi
+}
+
+declare -a stresses
+declare -a stress_pids
+duration=5
+rc=0
+subsys_ctrl=cpuset
+sysfs=
+
+while getopts c:d:hs: opt; do
+	case $opt in
+	c)
+		subsys_ctrl=$OPTARG
+		;;
+	d)
+		duration=$OPTARG
+		;;
+	h)
+		echo "Usage $0 [ -s stress ] ... [ -d duration ] [-c controller] cmd args .."
+		echo -e "\t default duration $duration seconds"
+		echo -e "\t default controller $subsys_ctrl"
+		exit
+		;;
+	s)
+		func=stress_$OPTARG
+		if [ "x$(type -t $func)" != "xfunction" ] ; then
+			echo "Unknown stress $OPTARG"
+			exit 1
+		fi
+		stresses+=($func)
+		;;
+	esac
+done
+shift $((OPTIND - 1))
+
+init_and_check
+
+for s in ${stresses[*]} ; do
+	$s &
+	stress_pids+=($!)
+done
+
+
+time=0
+start=$(date +%s)
+
+while [ $time -lt $duration ] ; do
+	$*
+	rc=$?
+	[ $rc -eq 0 ] || break
+	time=$(($(date +%s) - $start))
+done
+
+for pid in ${stress_pids[*]} ; do
+	kill -SIGTERM $pid
+	wait $pid
+done
+
+exit $rc