Merge remote-tracking branch 'cgroup/for-next'

30 files changed, 1240 insertions, 2337 deletions

diff --git a/arch/sparc/kernel/leon_pci_grpci2.c b/arch/sparc/kernel/leon_pci_grpci2.c
index 5f0402aab7fb..24d6a4446349 100644
--- a/arch/sparc/kernel/leon_pci_grpci2.c
+++ b/arch/sparc/kernel/leon_pci_grpci2.c
@@ -8,6 +8,7 @@
 #include <linux/of_device.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
+#include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/export.h>
 #include <asm/io.h>
diff --git a/arch/sparc/kernel/sun4m_irq.c b/arch/sparc/kernel/sun4m_irq.c
index c5ade9d27a1d..8bb3b3fddea7 100644
--- a/arch/sparc/kernel/sun4m_irq.c
+++ b/arch/sparc/kernel/sun4m_irq.c
@@ -9,6 +9,8 @@
  *  Copyright (C) 1996 Dave Redman (djhr@tadpole.co.uk)
  */
 
+#include <linux/slab.h>
+
 #include <asm/timer.h>
 #include <asm/traps.h>
 #include <asm/pgalloc.h>
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b6e95b5e262f..e4a4145926f6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -894,7 +894,7 @@ static int blkcg_can_attach(struct cgroup_subsys_state *css,
 	int ret = 0;
 
 	/* task_lock() is needed to avoid races with exit_io_context() */
-	cgroup_taskset_for_each(task, css, tset) {
+	cgroup_taskset_for_each(task, tset) {
 		task_lock(task);
 		ioc = task->io_context;
 		if (ioc && atomic_read(&ioc->nr_tasks) > 1)
@@ -906,17 +906,14 @@ static int blkcg_can_attach(struct cgroup_subsys_state *css,
 	return ret;
 }
 
-struct cgroup_subsys blkio_subsys = {
-	.name = "blkio",
+struct cgroup_subsys blkio_cgrp_subsys = {
 	.css_alloc = blkcg_css_alloc,
 	.css_offline = blkcg_css_offline,
 	.css_free = blkcg_css_free,
 	.can_attach = blkcg_can_attach,
-	.subsys_id = blkio_subsys_id,
 	.base_cftypes = blkcg_files,
-	.module = THIS_MODULE,
 };
-EXPORT_SYMBOL_GPL(blkio_subsys);
+EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);
 
 /**
  * blkcg_activate_policy - activate a blkcg policy on a request_queue
@@ -1106,7 +1103,7 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 
 	/* everything is in place, add intf files for the new policy */
 	if (pol->cftypes)
-		WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
+		WARN_ON(cgroup_add_cftypes(&blkio_cgrp_subsys, pol->cftypes));
 	ret = 0;
 out_unlock:
 	mutex_unlock(&blkcg_pol_mutex);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 86154eab9523..15a8d640de57 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -186,7 +186,7 @@ static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 
 static inline struct blkcg *task_blkcg(struct task_struct *tsk)
 {
-	return css_to_blkcg(task_css(tsk, blkio_subsys_id));
+	return css_to_blkcg(task_css(tsk, blkio_cgrp_id));
 }
 
 static inline struct blkcg *bio_blkcg(struct bio *bio)
@@ -241,12 +241,16 @@ static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
  */
 static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
 {
-	int ret;
+	char *p;
 
-	ret = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
-	if (ret)
+	p = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
+	if (!p) {
 		strncpy(buf, "<unavailable>", buflen);
-	return ret;
+		return -ENAMETOOLONG;
+	}
+
+	memmove(buf, p, buf + buflen - p);
+	return 0;
 }
 
 /**
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 1474c3ab7e72..861c363e4129 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1425,28 +1425,24 @@ static struct cftype throtl_files[] = {
 		.private = offsetof(struct throtl_grp, bps[READ]),
 		.seq_show = tg_print_conf_u64,
 		.write_string = tg_set_conf_u64,
-		.max_write_len = 256,
 	},
 	{
 		.name = "throttle.write_bps_device",
 		.private = offsetof(struct throtl_grp, bps[WRITE]),
 		.seq_show = tg_print_conf_u64,
 		.write_string = tg_set_conf_u64,
-		.max_write_len = 256,
 	},
 	{
 		.name = "throttle.read_iops_device",
 		.private = offsetof(struct throtl_grp, iops[READ]),
 		.seq_show = tg_print_conf_uint,
 		.write_string = tg_set_conf_uint,
-		.max_write_len = 256,
 	},
 	{
 		.name = "throttle.write_iops_device",
 		.private = offsetof(struct throtl_grp, iops[WRITE]),
 		.seq_show = tg_print_conf_uint,
 		.write_string = tg_set_conf_uint,
-		.max_write_len = 256,
 	},
 	{
 		.name = "throttle.io_service_bytes",
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 744833b630c6..461187943392 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1838,7 +1838,6 @@ static struct cftype cfq_blkcg_files[] = {
 		.flags = CFTYPE_ONLY_ON_ROOT,
 		.seq_show = cfqg_print_leaf_weight_device,
 		.write_string = cfqg_set_leaf_weight_device,
-		.max_write_len = 256,
 	},
 	{
 		.name = "weight",
@@ -1853,7 +1852,6 @@ static struct cftype cfq_blkcg_files[] = {
 		.flags = CFTYPE_NOT_ON_ROOT,
 		.seq_show = cfqg_print_weight_device,
 		.write_string = cfqg_set_weight_device,
-		.max_write_len = 256,
 	},
 	{
 		.name = "weight",
@@ -1866,7 +1864,6 @@ static struct cftype cfq_blkcg_files[] = {
 		.name = "leaf_weight_device",
 		.seq_show = cfqg_print_leaf_weight_device,
 		.write_string = cfqg_set_leaf_weight_device,
-		.max_write_len = 256,
 	},
 	{
 		.name = "leaf_weight",
diff --git a/fs/bio.c b/fs/bio.c
index b2dd42ed9edd..b1bc722b89aa 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1969,7 +1969,7 @@ int bio_associate_current(struct bio *bio)
 
 	/* associate blkcg if exists */
 	rcu_read_lock();
-	css = task_css(current, blkio_subsys_id);
+	css = task_css(current, blkio_cgrp_id);
 	if (css && css_tryget(css))
 		bio->bi_css = css;
 	rcu_read_unlock();
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8245d3b34894..5a398c0c3d99 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -112,6 +112,7 @@ char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
 	spin_unlock_irqrestore(&kernfs_rename_lock, flags);
 	return p;
 }
+EXPORT_SYMBOL_GPL(kernfs_path);
 
 /**
  * pr_cont_kernfs_name - pr_cont name of a kernfs_node
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 9450f025fe0c..8c283a910b91 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -14,14 +14,13 @@
 #include <linux/rcupdate.h>
 #include <linux/rculist.h>
 #include <linux/cgroupstats.h>
-#include <linux/prio_heap.h>
 #include <linux/rwsem.h>
 #include <linux/idr.h>
 #include <linux/workqueue.h>
-#include <linux/xattr.h>
 #include <linux/fs.h>
 #include <linux/percpu-refcount.h>
 #include <linux/seq_file.h>
+#include <linux/kernfs.h>
 
 #ifdef CONFIG_CGROUPS
 
@@ -37,28 +36,13 @@ extern void cgroup_post_fork(struct task_struct *p);
 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
 extern int cgroupstats_build(struct cgroupstats *stats,
 				struct dentry *dentry);
-extern int cgroup_load_subsys(struct cgroup_subsys *ss);
-extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
 
 extern int proc_cgroup_show(struct seq_file *, void *);
 
-/*
- * Define the enumeration of all cgroup subsystems.
- *
- * We define ids for builtin subsystems and then modular ones.
- */
-#define SUBSYS(_x) _x ## _subsys_id,
+/* define the enumeration of all cgroup subsystems */
+#define SUBSYS(_x) _x ## _cgrp_id,
 enum cgroup_subsys_id {
-#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
 #include <linux/cgroup_subsys.h>
-#undef IS_SUBSYS_ENABLED
-	CGROUP_BUILTIN_SUBSYS_COUNT,
-
-	__CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1,
-
-#define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
-#include <linux/cgroup_subsys.h>
-#undef IS_SUBSYS_ENABLED
 	CGROUP_SUBSYS_COUNT,
 };
 #undef SUBSYS
@@ -153,11 +137,6 @@ enum {
 	CGRP_SANE_BEHAVIOR,
 };
 
-struct cgroup_name {
-	struct rcu_head rcu_head;
-	char name[];
-};
-
 struct cgroup {
 	unsigned long flags;		/* "unsigned long" so bitops work */
 
@@ -174,16 +153,17 @@ struct cgroup {
 	/* the number of attached css's */
 	int nr_css;
 
+	atomic_t refcnt;
+
 	/*
 	 * We link our 'sibling' struct into our parent's 'children'.
 	 * Our children link their 'sibling' into our 'children'.
 	 */
 	struct list_head sibling;	/* my parent's children */
 	struct list_head children;	/* my children */
-	struct list_head files;		/* my files */
 
 	struct cgroup *parent;		/* my parent */
-	struct dentry *dentry;		/* cgroup fs entry, RCU protected */
+	struct kernfs_node *kn;		/* cgroup kernfs entry */
 
 	/*
 	 * Monotonically increasing unique serial number which defines a
@@ -193,19 +173,6 @@ struct cgroup {
 	 */
 	u64 serial_nr;
 
-	/*
-	 * This is a copy of dentry->d_name, and it's needed because
-	 * we can't use dentry->d_name in cgroup_path().
-	 *
-	 * You must acquire rcu_read_lock() to access cgrp->name, and
-	 * the only place that can change it is rename(), which is
-	 * protected by parent dir's i_mutex.
-	 *
-	 * Normally you should use cgroup_name() wrapper rather than
-	 * access it directly.
-	 */
-	struct cgroup_name __rcu *name;
-
 	/* Private pointers for each registered subsystem */
 	struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
 
@@ -237,9 +204,6 @@ struct cgroup {
 	/* For css percpu_ref killing and RCU-protected deletion */
 	struct rcu_head rcu_head;
 	struct work_struct destroy_work;
-
-	/* directory xattrs */
-	struct simple_xattrs xattrs;
 };
 
 #define MAX_CGROUP_ROOT_NAMELEN 64
@@ -262,8 +226,8 @@ enum {
 	 *
 	 * The followings are the behaviors currently affected this flag.
 	 *
-	 * - Mount options "noprefix" and "clone_children" are disallowed.
-	 *   Also, cgroupfs file cgroup.clone_children is not created.
+	 * - Mount options "noprefix", "xattr", "clone_children",
+	 *   "release_agent" and "name" are disallowed.
 	 *
 	 * - When mounting an existing superblock, mount options should
 	 *   match.
@@ -281,6 +245,8 @@ enum {
 	 * - "release_agent" and "notify_on_release" are removed.
 	 *   Replacement notification mechanism will be implemented.
 	 *
+	 * - "cgroup.clone_children" is removed.
+	 *
 	 * - cpuset: tasks will be kept in empty cpusets when hotplug happens
 	 *   and take masks of ancestors with non-empty cpus/mems, instead of
 	 *   being moved to an ancestor.
@@ -300,17 +266,15 @@ enum {
 
 	/* mount options live below bit 16 */
 	CGRP_ROOT_OPTION_MASK	= (1 << 16) - 1,
-
-	CGRP_ROOT_SUBSYS_BOUND	= (1 << 16), /* subsystems finished binding */
 };
 
 /*
  * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
- * associated with a superblock to form an active hierarchy.  This is
+ * associated with a kernfs_root to form an active hierarchy.  This is
  * internal to cgroup core.  Don't access directly from controllers.
  */
 struct cgroupfs_root {
-	struct super_block *sb;
+	struct kernfs_root *kf_root;
 
 	/* The bitmask of subsystems attached to this hierarchy */
 	unsigned long subsys_mask;
@@ -318,11 +282,11 @@ struct cgroupfs_root {
 	/* Unique id for this hierarchy. */
 	int hierarchy_id;
 
-	/* The root cgroup for this hierarchy */
+	/* The root cgroup.  Root is destroyed on its release. */
 	struct cgroup top_cgroup;
 
-	/* Tracks how many cgroups are currently defined in hierarchy.*/
-	int number_of_cgroups;
+	/* Number of cgroups in the hierarchy, used only for /proc/cgroups */
+	atomic_t nr_cgrps;
 
 	/* A list running through the active hierarchies */
 	struct list_head root_list;
@@ -372,10 +336,9 @@ struct css_set {
 	struct list_head cgrp_links;
 
 	/*
-	 * Set of subsystem states, one for each subsystem. This array
-	 * is immutable after creation apart from the init_css_set
-	 * during subsystem registration (at boot time) and modular subsystem
-	 * loading/unloading.
+	 * Set of subsystem states, one for each subsystem. This array is
+	 * immutable after creation apart from the init_css_set during
+	 * subsystem registration (at boot time).
 	 */
 	struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 
@@ -416,8 +379,9 @@ struct cftype {
 	umode_t mode;
 
 	/*
-	 * If non-zero, defines the maximum length of string that can
-	 * be passed to write_string; defaults to 64
+	 * The maximum length of string, excluding trailing nul, that can
+	 * be passed to write_string.  If < PAGE_SIZE-1, PAGE_SIZE-1 is
+	 * assumed.
 	 */
 	size_t max_write_len;
 
@@ -425,10 +389,12 @@ struct cftype {
 	unsigned int flags;
 
 	/*
-	 * The subsys this file belongs to.  Initialized automatically
-	 * during registration.  NULL for cgroup core files.
+	 * Fields used for internal bookkeeping.  Initialized automatically
+	 * during registration.
 	 */
-	struct cgroup_subsys *ss;
+	struct cgroup_subsys *ss;	/* NULL for cgroup core files */
+	struct list_head node;		/* anchored at ss->cfts */
+	struct kernfs_ops *kf_ops;
 
 	/*
 	 * read_u64() is a shortcut for the common case of returning a
@@ -475,36 +441,10 @@ struct cftype {
 	 * kick type for multiplexing.
 	 */
 	int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
-};
-
-/*
- * cftype_sets describe cftypes belonging to a subsystem and are chained at
- * cgroup_subsys->cftsets.  Each cftset points to an array of cftypes
- * terminated by zero length name.
- */
-struct cftype_set {
-	struct list_head		node;	/* chained at subsys->cftsets */
-	struct cftype			*cfts;
-};
-
-/*
- * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.  Don't
- * access directly.
- */
-struct cfent {
-	struct list_head		node;
-	struct dentry			*dentry;
-	struct cftype			*type;
-	struct cgroup_subsys_state	*css;
-
-	/* file xattrs */
-	struct simple_xattrs		xattrs;
-};
 
-/* seq_file->private points to the following, only ->priv is public */
-struct cgroup_open_file {
-	struct cfent			*cfe;
-	void				*priv;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lock_class_key	lockdep_key;
+#endif
 };
 
 /*
@@ -516,34 +456,79 @@ static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
 	return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
 }
 
-/* Caller should hold rcu_read_lock() */
-static inline const char *cgroup_name(const struct cgroup *cgrp)
+/* no synchronization, the result can only be used as a hint */
+static inline bool cgroup_has_tasks(struct cgroup *cgrp)
 {
-	return rcu_dereference(cgrp->name)->name;
+	return !list_empty(&cgrp->cset_links);
 }
 
-static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
+/* returns ino associated with a cgroup, 0 indicates unmounted root */
+static inline ino_t cgroup_ino(struct cgroup *cgrp)
 {
-	struct cgroup_open_file *of = seq->private;
-	return of->cfe->css;
+	if (cgrp->kn)
+		return cgrp->kn->ino;
+	else
+		return 0;
 }
 
 static inline struct cftype *seq_cft(struct seq_file *seq)
 {
-	struct cgroup_open_file *of = seq->private;
-	return of->cfe->type;
+	struct kernfs_open_file *of = seq->private;
+
+	return of->kn->priv;
+}
+
+struct cgroup_subsys_state *seq_css(struct seq_file *seq);
+
+/*
+ * Name / path handling functions.  All are thin wrappers around the kernfs
+ * counterparts and can be called under any context.
+ */
+
+static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
+{
+	/* dummy_top doesn't have a kn associated */
+	if (cgrp->kn)
+		return kernfs_name(cgrp->kn, buf, buflen);
+	else
+		return strlcpy(buf, "/", buflen);
 }
 
+static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
+					      size_t buflen)
+{
+	/* dummy_top doesn't have a kn associated */
+	if (cgrp->kn)
+		return kernfs_path(cgrp->kn, buf, buflen);
+	strlcpy(buf, "/", buflen);
+	return (buflen <= 2) ? NULL : buf;
+}
+
+static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
+{
+	/* dummy_top doesn't have a kn associated */
+	if (cgrp->kn)
+		pr_cont_kernfs_name(cgrp->kn);
+	else
+		pr_cont("/");
+}
+
+static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
+{
+	/* dummy_top doesn't have a kn associated */
+	if (cgrp->kn)
+		pr_cont_kernfs_path(cgrp->kn);
+	else
+		pr_cont("/");
+}
+
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
+
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
 int cgroup_rm_cftypes(struct cftype *cfts);
 
 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
 
-int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
-int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
-
-int cgroup_task_count(const struct cgroup *cgrp);
-
 /*
  * Control Group taskset, used to pass around set of tasks to cgroup_subsys
  * methods.
@@ -551,22 +536,15 @@ int cgroup_task_count(const struct cgroup *cgrp);
 struct cgroup_taskset;
 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
-struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
-						   int subsys_id);
-int cgroup_taskset_size(struct cgroup_taskset *tset);
 
 /**
  * cgroup_taskset_for_each - iterate cgroup_taskset
  * @task: the loop cursor
- * @skip_css: skip if task's css matches this, %NULL to iterate through all
  * @tset: taskset to iterate
  */
-#define cgroup_taskset_for_each(task, skip_css, tset)			\
+#define cgroup_taskset_for_each(task, tset)				\
 	for ((task) = cgroup_taskset_first((tset)); (task);		\
-	     (task) = cgroup_taskset_next((tset)))			\
-		if (!(skip_css) ||					\
-		    cgroup_taskset_cur_css((tset),			\
-			(skip_css)->ss->subsys_id) != (skip_css))
+	     (task) = cgroup_taskset_next((tset)))
 
 /*
  * Control Group subsystem type.
@@ -591,7 +569,6 @@ struct cgroup_subsys {
 		     struct task_struct *task);
 	void (*bind)(struct cgroup_subsys_state *root_css);
 
-	int subsys_id;
 	int disabled;
 	int early_init;
 
@@ -610,27 +587,26 @@ struct cgroup_subsys {
 	bool broken_hierarchy;
 	bool warned_broken_hierarchy;
 
+	/* the following two fields are initialized automtically during boot */
+	int id;
 #define MAX_CGROUP_TYPE_NAMELEN 32
 	const char *name;
 
 	/* link to parent, protected by cgroup_lock() */
 	struct cgroupfs_root *root;
 
-	/* list of cftype_sets */
-	struct list_head cftsets;
+	/*
+	 * List of cftypes.  Each entry is the first entry of an array
+	 * terminated by zero length name.
+	 */
+	struct list_head cfts;
 
-	/* base cftypes, automatically [de]registered with subsys itself */
+	/* base cftypes, automatically registered with subsys itself */
 	struct cftype *base_cftypes;
-	struct cftype_set base_cftset;
-
-	/* should be defined only by modular subsystems */
-	struct module *module;
 };
 
-#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
-#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
+#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
 #include <linux/cgroup_subsys.h>
-#undef IS_SUBSYS_ENABLED
 #undef SUBSYS
 
 /**
@@ -837,16 +813,11 @@ void css_task_iter_start(struct cgroup_subsys_state *css,
 struct task_struct *css_task_iter_next(struct css_task_iter *it);
 void css_task_iter_end(struct css_task_iter *it);
 
-int css_scan_tasks(struct cgroup_subsys_state *css,
-		   bool (*test)(struct task_struct *, void *),
-		   void (*process)(struct task_struct *, void *),
-		   void *data, struct ptr_heap *heap);
-
 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
 
-struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
-					 struct cgroup_subsys *ss);
+struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry,
+						struct cgroup_subsys *ss);
 
 #else /* !CONFIG_CGROUPS */
 
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 7b99d717411d..768fe44e19f0 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -3,51 +3,51 @@
  *
  * DO NOT ADD ANY SUBSYSTEM WITHOUT EXPLICIT ACKS FROM CGROUP MAINTAINERS.
  */
-#if IS_SUBSYS_ENABLED(CONFIG_CPUSETS)
+#if IS_ENABLED(CONFIG_CPUSETS)
 SUBSYS(cpuset)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEBUG)
+#if IS_ENABLED(CONFIG_CGROUP_DEBUG)
 SUBSYS(debug)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_SCHED)
-SUBSYS(cpu_cgroup)
+#if IS_ENABLED(CONFIG_CGROUP_SCHED)
+SUBSYS(cpu)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_CPUACCT)
+#if IS_ENABLED(CONFIG_CGROUP_CPUACCT)
 SUBSYS(cpuacct)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_MEMCG)
-SUBSYS(mem_cgroup)
+#if IS_ENABLED(CONFIG_MEMCG)
+SUBSYS(memory)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEVICE)
+#if IS_ENABLED(CONFIG_CGROUP_DEVICE)
 SUBSYS(devices)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_FREEZER)
+#if IS_ENABLED(CONFIG_CGROUP_FREEZER)
 SUBSYS(freezer)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_NET_CLASSID)
+#if IS_ENABLED(CONFIG_CGROUP_NET_CLASSID)
 SUBSYS(net_cls)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_BLK_CGROUP)
+#if IS_ENABLED(CONFIG_BLK_CGROUP)
 SUBSYS(blkio)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_PERF)
-SUBSYS(perf)
+#if IS_ENABLED(CONFIG_CGROUP_PERF)
+SUBSYS(perf_event)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_NET_PRIO)
+#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
 SUBSYS(net_prio)
 #endif
 
-#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_HUGETLB)
+#if IS_ENABLED(CONFIG_CGROUP_HUGETLB)
 SUBSYS(hugetlb)
 #endif
 /*
diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
index 787bba3bf552..0129f89cf98d 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -49,7 +49,7 @@ int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
 
 static inline bool hugetlb_cgroup_disabled(void)
 {
-	if (hugetlb_subsys.disabled)
+	if (hugetlb_cgrp_subsys.disabled)
 		return true;
 	return false;
 }
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index abd0113b6620..eccfb4a4b379 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -162,7 +162,7 @@ extern int do_swap_account;
 
 static inline bool mem_cgroup_disabled(void)
 {
-	if (mem_cgroup_subsys.disabled)
+	if (memory_cgrp_subsys.disabled)
 		return true;
 	return false;
 }
diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index 9cf2d5ef38d9..c15d39456e14 100644
--- a/include/net/cls_cgroup.h
+++ b/include/net/cls_cgroup.h
@@ -34,7 +34,7 @@ static inline u32 task_cls_classid(struct task_struct *p)
 		return 0;
 
 	rcu_read_lock();
-	classid = container_of(task_css(p, net_cls_subsys_id),
+	classid = container_of(task_css(p, net_cls_cgrp_id),
 			       struct cgroup_cls_state, css)->classid;
 	rcu_read_unlock();
 
diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
index dafc09f0fdbc..f2a9597ff53c 100644
--- a/include/net/netprio_cgroup.h
+++ b/include/net/netprio_cgroup.h
@@ -27,32 +27,17 @@ struct netprio_map {
 
 void sock_update_netprioidx(struct sock *sk);
 
-#if IS_BUILTIN(CONFIG_CGROUP_NET_PRIO)
 static inline u32 task_netprioidx(struct task_struct *p)
 {
 	struct cgroup_subsys_state *css;
 	u32 idx;
 
 	rcu_read_lock();
-	css = task_css(p, net_prio_subsys_id);
+	css = task_css(p, net_prio_cgrp_id);
 	idx = css->cgroup->id;
 	rcu_read_unlock();
 	return idx;
 }
-#elif IS_MODULE(CONFIG_CGROUP_NET_PRIO)
-static inline u32 task_netprioidx(struct task_struct *p)
-{
-	struct cgroup_subsys_state *css;
-	u32 idx = 0;
-
-	rcu_read_lock();
-	css = task_css(p, net_prio_subsys_id);
-	if (css)
-		idx = css->cgroup->id;
-	rcu_read_unlock();
-	return idx;
-}
-#endif
 #else /* !CONFIG_CGROUP_NET_PRIO */
 static inline u32 task_netprioidx(struct task_struct *p)
 {
diff --git a/init/Kconfig b/init/Kconfig
index 009a797dd242..3f74784560a5 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -854,6 +854,7 @@ config NUMA_BALANCING
 
 menuconfig CGROUPS
 	boolean "Control Group support"
+	select KERNFS
 	help
 	  This option adds support for grouping sets of processes together, for
 	  use with process control subsystems such as Cpusets, CFS, memory
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 105f273b6f86..8ab800c7bac0 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -40,23 +40,21 @@
 #include <linux/proc_fs.h>
 #include <linux/rcupdate.h>
 #include <linux/sched.h>
-#include <linux/backing-dev.h>
 #include <linux/slab.h>
-#include <linux/magic.h>
 #include <linux/spinlock.h>
+#include <linux/rwsem.h>
 #include <linux/string.h>
 #include <linux/sort.h>
 #include <linux/kmod.h>
-#include <linux/module.h>
 #include <linux/delayacct.h>
 #include <linux/cgroupstats.h>
 #include <linux/hashtable.h>
-#include <linux/namei.h>
 #include <linux/pid_namespace.h>
 #include <linux/idr.h>
 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
 #include <linux/flex_array.h> /* used in cgroup_attach_task */
 #include <linux/kthread.h>
+#include <linux/delay.h>
 
 #include <linux/atomic.h>
 
@@ -68,21 +66,21 @@
  */
 #define CGROUP_PIDLIST_DESTROY_DELAY	HZ
 
+#define CGROUP_FILE_NAME_MAX		(MAX_CGROUP_TYPE_NAMELEN +	\
+					 MAX_CFTYPE_NAME + 2)
+
+/*
+ * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file
+ * creation/removal and hierarchy changing operations including cgroup
+ * creation, removal, css association and controller rebinding.  This outer
+ * lock is needed mainly to resolve the circular dependency between kernfs
+ * active ref and cgroup_mutex.  cgroup_tree_mutex nests above both.
+ */
+static DEFINE_MUTEX(cgroup_tree_mutex);
+
 /*
  * cgroup_mutex is the master lock.  Any modification to cgroup or its
  * hierarchy must be performed while holding it.
- *
- * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
- * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
- * release_agent_path and so on.  Modifying requires both cgroup_mutex and
- * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
- * break the following locking order cycle.
- *
- *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
- *  B. namespace_sem -> cgroup_mutex
- *
- * B happens only through cgroup_show_options() and using cgroup_root_mutex
- * breaks it.
  */
 #ifdef CONFIG_PROVE_RCU
 DEFINE_MUTEX(cgroup_mutex);
@@ -91,20 +89,17 @@ EXPORT_SYMBOL_GPL(cgroup_mutex);	/* only for lockdep */
 static DEFINE_MUTEX(cgroup_mutex);
 #endif
 
-static DEFINE_MUTEX(cgroup_root_mutex);
+/*
+ * Protects cgroup_subsys->release_agent_path.  Modifying it also requires
+ * cgroup_mutex.  Reading requires either cgroup_mutex or this spinlock.
+ */
+static DEFINE_SPINLOCK(release_agent_path_lock);
 
-#define cgroup_assert_mutex_or_rcu_locked()				\
+#define cgroup_assert_mutexes_or_rcu_locked()				\
 	rcu_lockdep_assert(rcu_read_lock_held() ||			\
+			   lockdep_is_held(&cgroup_tree_mutex) ||	\
 			   lockdep_is_held(&cgroup_mutex),		\
-			   "cgroup_mutex or RCU read lock required");
-
-#ifdef CONFIG_LOCKDEP
-#define cgroup_assert_mutex_or_root_locked()				\
-	WARN_ON_ONCE(debug_locks && (!lockdep_is_held(&cgroup_mutex) &&	\
-				     !lockdep_is_held(&cgroup_root_mutex)))
-#else
-#define cgroup_assert_mutex_or_root_locked()	do { } while (0)
-#endif
+			   "cgroup_[tree_]mutex or RCU read lock required");
 
 /*
  * cgroup destruction makes heavy use of work items and there can be a lot
@@ -120,17 +115,19 @@ static struct workqueue_struct *cgroup_destroy_wq;
  */
 static struct workqueue_struct *cgroup_pidlist_destroy_wq;
 
-/*
- * Generate an array of cgroup subsystem pointers. At boot time, this is
- * populated with the built in subsystems, and modular subsystems are
- * registered after that. The mutable section of this array is protected by
- * cgroup_mutex.
- */
-#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
-#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
-static struct cgroup_subsys *cgroup_subsys[CGROUP_SUBSYS_COUNT] = {
+/* generate an array of cgroup subsystem pointers */
+#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
+static struct cgroup_subsys *cgroup_subsys[] = {
+#include <linux/cgroup_subsys.h>
+};
+#undef SUBSYS
+
+/* array of cgroup subsystem names */
+#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
+static const char *cgroup_subsys_name[] = {
 #include <linux/cgroup_subsys.h>
 };
+#undef SUBSYS
 
 /*
  * The dummy hierarchy, reserved for the subsystems that are otherwise
@@ -147,15 +144,9 @@ static struct cgroup * const cgroup_dummy_top = &cgroup_dummy_root.top_cgroup;
 static LIST_HEAD(cgroup_roots);
 static int cgroup_root_count;
 
-/*
- * Hierarchy ID allocation and mapping.  It follows the same exclusion
- * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
- * writes, either for reads.
- */
+/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
 static DEFINE_IDR(cgroup_hierarchy_idr);
 
-static struct cgroup_name root_cgroup_name = { .name = "/" };
-
 /*
  * Assign a monotonically increasing serial number to cgroups.  It
  * guarantees cgroups with bigger numbers are newer than those with smaller
@@ -175,11 +166,13 @@ static int need_forkexit_callback __read_mostly;
 
 static struct cftype cgroup_base_files[];
 
+static void cgroup_put(struct cgroup *cgrp);
+static int rebind_subsystems(struct cgroupfs_root *root,
+			     unsigned long added_mask, unsigned removed_mask);
 static void cgroup_destroy_css_killed(struct cgroup *cgrp);
 static int cgroup_destroy_locked(struct cgroup *cgrp);
 static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
 			      bool is_add);
-static int cgroup_file_release(struct inode *inode, struct file *file);
 static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
 
 /**
@@ -197,8 +190,9 @@ static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
 					      struct cgroup_subsys *ss)
 {
 	if (ss)
-		return rcu_dereference_check(cgrp->subsys[ss->subsys_id],
-					     lockdep_is_held(&cgroup_mutex));
+		return rcu_dereference_check(cgrp->subsys[ss->id],
+					lockdep_is_held(&cgroup_tree_mutex) ||
+					lockdep_is_held(&cgroup_mutex));
 	else
 		return &cgrp->dummy_css;
 }
@@ -209,6 +203,27 @@ static inline bool cgroup_is_dead(const struct cgroup *cgrp)
 	return test_bit(CGRP_DEAD, &cgrp->flags);
 }
 
+struct cgroup_subsys_state *seq_css(struct seq_file *seq)
+{
+	struct kernfs_open_file *of = seq->private;
+	struct cgroup *cgrp = of->kn->parent->priv;
+	struct cftype *cft = seq_cft(seq);
+
+	/*
+	 * This is open and unprotected implementation of cgroup_css().
+	 * seq_css() is only called from a kernfs file operation which has
+	 * an active reference on the file.  Because all the subsystem
+	 * files are drained before a css is disassociated with a cgroup,
+	 * the matching css from the cgroup's subsys table is guaranteed to
+	 * be and stay valid until the enclosing operation is complete.
+	 */
+	if (cft->ss)
+		return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
+	else
+		return &cgrp->dummy_css;
+}
+EXPORT_SYMBOL_GPL(seq_css);
+
 /**
  * cgroup_is_descendant - test ancestry
  * @cgrp: the cgroup to be tested
@@ -227,7 +242,6 @@ bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
 	}
 	return false;
 }
-EXPORT_SYMBOL_GPL(cgroup_is_descendant);
 
 static int cgroup_is_releasable(const struct cgroup *cgrp)
 {
@@ -254,54 +268,23 @@ static int notify_on_release(const struct cgroup *cgrp)
 	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)	\
 		if (!((css) = rcu_dereference_check(			\
 				(cgrp)->subsys[(ssid)],			\
+				lockdep_is_held(&cgroup_tree_mutex) ||	\
 				lockdep_is_held(&cgroup_mutex)))) { }	\
 		else
 
 /**
- * for_each_subsys - iterate all loaded cgroup subsystems
+ * for_each_subsys - iterate all enabled cgroup subsystems
  * @ss: the iteration cursor
  * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
- *
- * Iterates through all loaded subsystems.  Should be called under
- * cgroup_mutex or cgroup_root_mutex.
  */
 #define for_each_subsys(ss, ssid)					\
-	for (({ cgroup_assert_mutex_or_root_locked(); (ssid) = 0; });	\
-	     (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)			\
-		if (!((ss) = cgroup_subsys[(ssid)])) { }		\
-		else
-
-/**
- * for_each_builtin_subsys - iterate all built-in cgroup subsystems
- * @ss: the iteration cursor
- * @i: the index of @ss, CGROUP_BUILTIN_SUBSYS_COUNT after reaching the end
- *
- * Bulit-in subsystems are always present and iteration itself doesn't
- * require any synchronization.
- */
-#define for_each_builtin_subsys(ss, i)					\
-	for ((i) = 0; (i) < CGROUP_BUILTIN_SUBSYS_COUNT &&		\
-	     (((ss) = cgroup_subsys[i]) || true); (i)++)
+	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\
+	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
 
 /* iterate across the active hierarchies */
 #define for_each_active_root(root)					\
 	list_for_each_entry((root), &cgroup_roots, root_list)
 
-static inline struct cgroup *__d_cgrp(struct dentry *dentry)
-{
-	return dentry->d_fsdata;
-}
-
-static inline struct cfent *__d_cfe(struct dentry *dentry)
-{
-	return dentry->d_fsdata;
-}
-
-static inline struct cftype *__d_cft(struct dentry *dentry)
-{
-	return __d_cfe(dentry)->type;
-}
-
 /**
  * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
  * @cgrp: the cgroup to be checked for liveness
@@ -358,11 +341,10 @@ static struct css_set init_css_set;
 static struct cgrp_cset_link init_cgrp_cset_link;
 
 /*
- * css_set_lock protects the list of css_set objects, and the chain of
- * tasks off each css_set.  Nests outside task->alloc_lock due to
- * css_task_iter_start().
+ * css_set_rwsem protects the list of css_set objects, and the chain of
+ * tasks off each css_set.
  */
-static DEFINE_RWLOCK(css_set_lock);
+static DECLARE_RWSEM(css_set_rwsem);
 static int css_set_count;
 
 /*
@@ -386,30 +368,14 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
 	return key;
 }
 
-/*
- * We don't maintain the lists running through each css_set to its task
- * until after the first call to css_task_iter_start().  This reduces the
- * fork()/exit() overhead for people who have cgroups compiled into their
- * kernel but not actually in use.
- */
-static int use_task_css_set_links __read_mostly;
-
-static void __put_css_set(struct css_set *cset, int taskexit)
+static void put_css_set_locked(struct css_set *cset, bool taskexit)
 {
 	struct cgrp_cset_link *link, *tmp_link;
 
-	/*
-	 * Ensure that the refcount doesn't hit zero while any readers
-	 * can see it. Similar to atomic_dec_and_lock(), but for an
-	 * rwlock
-	 */
-	if (atomic_add_unless(&cset->refcount, -1, 1))
-		return;
-	write_lock(&css_set_lock);
-	if (!atomic_dec_and_test(&cset->refcount)) {
-		write_unlock(&css_set_lock);
+	lockdep_assert_held(&css_set_rwsem);
+
+	if (!atomic_dec_and_test(&cset->refcount))
 		return;
-	}
 
 	/* This css_set is dead. unlink it and release cgroup refcounts */
 	hash_del(&cset->hlist);
@@ -421,7 +387,7 @@ static void __put_css_set(struct css_set *cset, int taskexit)
 		list_del(&link->cset_link);
 		list_del(&link->cgrp_link);
 
-		/* @cgrp can't go away while we're holding css_set_lock */
+		/* @cgrp can't go away while we're holding css_set_rwsem */
 		if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
 			if (taskexit)
 				set_bit(CGRP_RELEASABLE, &cgrp->flags);
@@ -431,10 +397,24 @@ static void __put_css_set(struct css_set *cset, int taskexit)
 		kfree(link);
 	}
 
-	write_unlock(&css_set_lock);
 	kfree_rcu(cset, rcu_head);
 }
 
+static void put_css_set(struct css_set *cset, bool taskexit)
+{
+	/*
+	 * Ensure that the refcount doesn't hit zero while any readers
+	 * can see it. Similar to atomic_dec_and_lock(), but for an
+	 * rwlock
+	 */
+	if (atomic_add_unless(&cset->refcount, -1, 1))
+		return;
+
+	down_write(&css_set_rwsem);
+	put_css_set_locked(cset, taskexit);
+	up_write(&css_set_rwsem);
+}
+
 /*
  * refcounted get/put for css_set objects
  */
@@ -443,16 +423,6 @@ static inline void get_css_set(struct css_set *cset)
 	atomic_inc(&cset->refcount);
 }
 
-static inline void put_css_set(struct css_set *cset)
-{
-	__put_css_set(cset, 0);
-}
-
-static inline void put_css_set_taskexit(struct css_set *cset)
-{
-	__put_css_set(cset, 1);
-}
-
 /**
  * compare_css_sets - helper function for find_existing_css_set().
  * @cset: candidate css_set being tested
@@ -652,11 +622,11 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 
 	/* First see if we already have a cgroup group that matches
 	 * the desired set */
-	read_lock(&css_set_lock);
+	down_read(&css_set_rwsem);
 	cset = find_existing_css_set(old_cset, cgrp, template);
 	if (cset)
 		get_css_set(cset);
-	read_unlock(&css_set_lock);
+	up_read(&css_set_rwsem);
 
 	if (cset)
 		return cset;
@@ -680,7 +650,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	 * find_existing_css_set() */
 	memcpy(cset->subsys, template, sizeof(cset->subsys));
 
-	write_lock(&css_set_lock);
+	down_write(&css_set_rwsem);
 	/* Add reference counts and links from the new css_set. */
 	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
 		struct cgroup *c = link->cgrp;
@@ -698,14 +668,98 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	key = css_set_hash(cset->subsys);
 	hash_add(css_set_table, &cset->hlist, key);
 
-	write_unlock(&css_set_lock);
+	up_write(&css_set_rwsem);
 
 	return cset;
 }
 
+static struct cgroupfs_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
+{
+	struct cgroup *top_cgrp = kf_root->kn->priv;
+
+	return top_cgrp->root;
+}
+
+static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
+{
+	int id;
+
+	lockdep_assert_held(&cgroup_mutex);
+
+	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, start, end,
+			      GFP_KERNEL);
+	if (id < 0)
+		return id;
+
+	root->hierarchy_id = id;
+	return 0;
+}
+
+static void cgroup_exit_root_id(struct cgroupfs_root *root)
+{
+	lockdep_assert_held(&cgroup_mutex);
+
+	if (root->hierarchy_id) {
+		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
+		root->hierarchy_id = 0;
+	}
+}
+
+static void cgroup_free_root(struct cgroupfs_root *root)
+{
+	if (root) {
+		/* hierarhcy ID shoulid already have been released */
+		WARN_ON_ONCE(root->hierarchy_id);
+
+		idr_destroy(&root->cgroup_idr);
+		kfree(root);
+	}
+}
+
+static void cgroup_destroy_root(struct cgroupfs_root *root)
+{
+	struct cgroup *cgrp = &root->top_cgroup;
+	struct cgrp_cset_link *link, *tmp_link;
+
+	mutex_lock(&cgroup_tree_mutex);
+	mutex_lock(&cgroup_mutex);
+
+	BUG_ON(atomic_read(&root->nr_cgrps));
+	BUG_ON(!list_empty(&cgrp->children));
+
+	/* Rebind all subsystems back to the default hierarchy */
+	WARN_ON(rebind_subsystems(root, 0, root->subsys_mask));
+
+	/*
+	 * Release all the links from cset_links to this hierarchy's
+	 * root cgroup
+	 */
+	down_write(&css_set_rwsem);
+
+	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
+		list_del(&link->cset_link);
+		list_del(&link->cgrp_link);
+		kfree(link);
+	}
+	up_write(&css_set_rwsem);
+
+	if (!list_empty(&root->root_list)) {
+		list_del(&root->root_list);
+		cgroup_root_count--;
+	}
+
+	cgroup_exit_root_id(root);
+
+	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
+
+	kernfs_destroy_root(root->kf_root);
+	cgroup_free_root(root);
+}
+
 /*
  * Return the cgroup for "task" from the given hierarchy. Must be
- * called with cgroup_mutex held.
+ * called with cgroup_mutex and css_set_rwsem held.
  */
 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
 					    struct cgroupfs_root *root)
@@ -713,8 +767,9 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
 	struct css_set *cset;
 	struct cgroup *res = NULL;
 
-	BUG_ON(!mutex_is_locked(&cgroup_mutex));
-	read_lock(&css_set_lock);
+	lockdep_assert_held(&cgroup_mutex);
+	lockdep_assert_held(&css_set_rwsem);
+
 	/*
 	 * No need to lock the task - since we hold cgroup_mutex the
 	 * task can't change groups, so the only thing that can happen
@@ -735,7 +790,7 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
 			}
 		}
 	}
-	read_unlock(&css_set_lock);
+
 	BUG_ON(!res);
 	return res;
 }
@@ -790,78 +845,71 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
  * update of a tasks cgroup pointer by cgroup_attach_task()
  */
 
-/*
- * A couple of forward declarations required, due to cyclic reference loop:
- * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
- * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
- * -> cgroup_mkdir.
- */
-
-static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
-static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
 static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask);
-static const struct inode_operations cgroup_dir_inode_operations;
+static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
 static const struct file_operations proc_cgroupstats_operations;
 
-static struct backing_dev_info cgroup_backing_dev_info = {
-	.name		= "cgroup",
-	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
-};
-
-static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
+static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
+			      char *buf)
 {
-	struct inode *inode = new_inode(sb);
-
-	if (inode) {
-		inode->i_ino = get_next_ino();
-		inode->i_mode = mode;
-		inode->i_uid = current_fsuid();
-		inode->i_gid = current_fsgid();
-		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
-		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
-	}
-	return inode;
+	if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
+	    !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
+		snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
+			 cft->ss->name, cft->name);
+	else
+		strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
+	return buf;
 }
 
-static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry)
+/**
+ * cgroup_file_mode - deduce file mode of a control file
+ * @cft: the control file in question
+ *
+ * returns cft->mode if ->mode is not 0
+ * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
+ * returns S_IRUGO if it has only a read handler
+ * returns S_IWUSR if it has only a write hander
+ */
+static umode_t cgroup_file_mode(const struct cftype *cft)
 {
-	struct cgroup_name *name;
+	umode_t mode = 0;
 
-	name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
-	if (!name)
-		return NULL;
-	strcpy(name->name, dentry->d_name.name);
-	return name;
+	if (cft->mode)
+		return cft->mode;
+
+	if (cft->read_u64 || cft->read_s64 || cft->seq_show)
+		mode |= S_IRUGO;
+
+	if (cft->write_u64 || cft->write_s64 || cft->write_string ||
+	    cft->trigger)
+		mode |= S_IWUSR;
+
+	return mode;
 }
 
 static void cgroup_free_fn(struct work_struct *work)
 {
 	struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
 
-	mutex_lock(&cgroup_mutex);
-	cgrp->root->number_of_cgroups--;
-	mutex_unlock(&cgroup_mutex);
-
-	/*
-	 * We get a ref to the parent's dentry, and put the ref when
-	 * this cgroup is being freed, so it's guaranteed that the
-	 * parent won't be destroyed before its children.
-	 */
-	dput(cgrp->parent->dentry);
-
-	/*
-	 * Drop the active superblock reference that we took when we
-	 * created the cgroup. This will free cgrp->root, if we are
-	 * holding the last reference to @sb.
-	 */
-	deactivate_super(cgrp->root->sb);
-
+	atomic_dec(&cgrp->root->nr_cgrps);
 	cgroup_pidlist_destroy_all(cgrp);
 
-	simple_xattrs_free(&cgrp->xattrs);
-
-	kfree(rcu_dereference_raw(cgrp->name));
-	kfree(cgrp);
+	if (cgrp->parent) {
+		/*
+		 * We get a ref to the parent, and put the ref when this
+		 * cgroup is being freed, so it's guaranteed that the
+		 * parent won't be destroyed before its children.
+		 */
+		cgroup_put(cgrp->parent);
+		kernfs_put(cgrp->kn);
+		kfree(cgrp);
+	} else {
+		/*
+		 * This is top cgroup's refcnt reaching zero, which
+		 * indicates that the root should be released.
+		 */
+		cgroup_destroy_root(cgrp->root);
+	}
 }
 
 static void cgroup_free_rcu(struct rcu_head *head)
@@ -872,73 +920,40 @@ static void cgroup_free_rcu(struct rcu_head *head)
 	queue_work(cgroup_destroy_wq, &cgrp->destroy_work);
 }
 
-static void cgroup_diput(struct dentry *dentry, struct inode *inode)
-{
-	/* is dentry a directory ? if so, kfree() associated cgroup */
-	if (S_ISDIR(inode->i_mode)) {
-		struct cgroup *cgrp = dentry->d_fsdata;
-
-		BUG_ON(!(cgroup_is_dead(cgrp)));
-
-		/*
-		 * XXX: cgrp->id is only used to look up css's.  As cgroup
-		 * and css's lifetimes will be decoupled, it should be made
-		 * per-subsystem and moved to css->id so that lookups are
-		 * successful until the target css is released.
-		 */
-		mutex_lock(&cgroup_mutex);
-		idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
-		mutex_unlock(&cgroup_mutex);
-		cgrp->id = -1;
-
-		call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
-	} else {
-		struct cfent *cfe = __d_cfe(dentry);
-		struct cgroup *cgrp = dentry->d_parent->d_fsdata;
-
-		WARN_ONCE(!list_empty(&cfe->node) &&
-			  cgrp != &cgrp->root->top_cgroup,
-			  "cfe still linked for %s\n", cfe->type->name);
-		simple_xattrs_free(&cfe->xattrs);
-		kfree(cfe);
-	}
-	iput(inode);
-}
-
-static void remove_dir(struct dentry *d)
+static void cgroup_get(struct cgroup *cgrp)
 {
-	struct dentry *parent = dget(d->d_parent);
-
-	d_delete(d);
-	simple_rmdir(parent->d_inode, d);
-	dput(parent);
+	WARN_ON_ONCE(cgroup_is_dead(cgrp));
+	WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0);
+	atomic_inc(&cgrp->refcnt);
 }
 
-static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
+static void cgroup_put(struct cgroup *cgrp)
 {
-	struct cfent *cfe;
-
-	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
-	lockdep_assert_held(&cgroup_mutex);
+	if (!atomic_dec_and_test(&cgrp->refcnt))
+		return;
+	if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp)))
+		return;
 
 	/*
-	 * If we're doing cleanup due to failure of cgroup_create(),
-	 * the corresponding @cfe may not exist.
+	 * XXX: cgrp->id is only used to look up css's.  As cgroup and
+	 * css's lifetimes will be decoupled, it should be made
+	 * per-subsystem and moved to css->id so that lookups are
+	 * successful until the target css is released.
 	 */
-	list_for_each_entry(cfe, &cgrp->files, node) {
-		struct dentry *d = cfe->dentry;
+	mutex_lock(&cgroup_mutex);
+	idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
+	mutex_unlock(&cgroup_mutex);
+	cgrp->id = -1;
 
-		if (cft && cfe->type != cft)
-			continue;
+	call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
+}
 
-		dget(d);
-		d_delete(d);
-		simple_unlink(cgrp->dentry->d_inode, d);
-		list_del_init(&cfe->node);
-		dput(d);
+static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
+{
+	char name[CGROUP_FILE_NAME_MAX];
 
-		break;
-	}
+	lockdep_assert_held(&cgroup_tree_mutex);
+	kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
 }
 
 /**
@@ -952,81 +967,41 @@ static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 	int i;
 
 	for_each_subsys(ss, i) {
-		struct cftype_set *set;
+		struct cftype *cfts;
 
 		if (!test_bit(i, &subsys_mask))
 			continue;
-		list_for_each_entry(set, &ss->cftsets, node)
-			cgroup_addrm_files(cgrp, set->cfts, false);
+		list_for_each_entry(cfts, &ss->cfts, node)
+			cgroup_addrm_files(cgrp, cfts, false);
 	}
 }
 
-/*
- * NOTE : the dentry must have been dget()'ed
- */
-static void cgroup_d_remove_dir(struct dentry *dentry)
-{
-	struct dentry *parent;
-
-	parent = dentry->d_parent;
-	spin_lock(&parent->d_lock);
-	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-	list_del_init(&dentry->d_u.d_child);
-	spin_unlock(&dentry->d_lock);
-	spin_unlock(&parent->d_lock);
-	remove_dir(dentry);
-}
-
-/*
- * Call with cgroup_mutex held. Drops reference counts on modules, including
- * any duplicate ones that parse_cgroupfs_options took. If this function
- * returns an error, no reference counts are touched.
- */
 static int rebind_subsystems(struct cgroupfs_root *root,
 			     unsigned long added_mask, unsigned removed_mask)
 {
 	struct cgroup *cgrp = &root->top_cgroup;
 	struct cgroup_subsys *ss;
-	unsigned long pinned = 0;
 	int i, ret;
 
-	BUG_ON(!mutex_is_locked(&cgroup_mutex));
-	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
+	lockdep_assert_held(&cgroup_tree_mutex);
+	lockdep_assert_held(&cgroup_mutex);
 
 	/* Check that any added subsystems are currently free */
-	for_each_subsys(ss, i) {
-		if (!(added_mask & (1 << i)))
-			continue;
-
-		/* is the subsystem mounted elsewhere? */
-		if (ss->root != &cgroup_dummy_root) {
-			ret = -EBUSY;
-			goto out_put;
-		}
-
-		/* pin the module */
-		if (!try_module_get(ss->module)) {
-			ret = -ENOENT;
-			goto out_put;
-		}
-		pinned |= 1 << i;
-	}
-
-	/* subsys could be missing if unloaded between parsing and here */
-	if (added_mask != pinned) {
-		ret = -ENOENT;
-		goto out_put;
-	}
+	for_each_subsys(ss, i)
+		if ((added_mask & (1 << i)) && ss->root != &cgroup_dummy_root)
+			return -EBUSY;
 
 	ret = cgroup_populate_dir(cgrp, added_mask);
 	if (ret)
-		goto out_put;
+		return ret;
 
 	/*
 	 * Nothing can fail from this point on.  Remove files for the
 	 * removed subsystems and rebind each subsystem.
 	 */
+	mutex_unlock(&cgroup_mutex);
 	cgroup_clear_dir(cgrp, removed_mask);
+	mutex_lock(&cgroup_mutex);
 
 	for_each_subsys(ss, i) {
 		unsigned long bit = 1UL << i;
@@ -1059,35 +1034,21 @@ static int rebind_subsystems(struct cgroupfs_root *root,
 			RCU_INIT_POINTER(cgrp->subsys[i], NULL);
 
 			cgroup_subsys[i]->root = &cgroup_dummy_root;
-
-			/* subsystem is now free - drop reference on module */
-			module_put(ss->module);
 			root->subsys_mask &= ~bit;
 		}
 	}
 
-	/*
-	 * Mark @root has finished binding subsystems.  @root->subsys_mask
-	 * now matches the bound subsystems.
-	 */
-	root->flags |= CGRP_ROOT_SUBSYS_BOUND;
-
+	kernfs_activate(cgrp->kn);
 	return 0;
-
-out_put:
-	for_each_subsys(ss, i)
-		if (pinned & (1 << i))
-			module_put(ss->module);
-	return ret;
 }
 
-static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
+static int cgroup_show_options(struct seq_file *seq,
+			       struct kernfs_root *kf_root)
 {
-	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
+	struct cgroupfs_root *root = cgroup_root_from_kf(kf_root);
 	struct cgroup_subsys *ss;
 	int ssid;
 
-	mutex_lock(&cgroup_root_mutex);
 	for_each_subsys(ss, ssid)
 		if (root->subsys_mask & (1 << ssid))
 			seq_printf(seq, ",%s", ss->name);
@@ -1097,13 +1058,16 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",noprefix");
 	if (root->flags & CGRP_ROOT_XATTR)
 		seq_puts(seq, ",xattr");
+
+	spin_lock(&release_agent_path_lock);
 	if (strlen(root->release_agent_path))
 		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
+	spin_unlock(&release_agent_path_lock);
+
 	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
 		seq_puts(seq, ",clone_children");
 	if (strlen(root->name))
 		seq_printf(seq, ",name=%s", root->name);
-	mutex_unlock(&cgroup_root_mutex);
 	return 0;
 }
 
@@ -1115,9 +1079,6 @@ struct cgroup_sb_opts {
 	char *name;
 	/* User explicitly requested empty subsystem */
 	bool none;
-
-	struct cgroupfs_root *new_root;
-
 };
 
 /*
@@ -1137,7 +1098,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 	BUG_ON(!mutex_is_locked(&cgroup_mutex));
 
 #ifdef CONFIG_CPUSETS
-	mask = ~(1UL << cpuset_subsys_id);
+	mask = ~(1UL << cpuset_cgrp_id);
 #endif
 
 	memset(opts, 0, sizeof(*opts));
@@ -1242,13 +1203,10 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 	if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
 		pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
 
-		if (opts->flags & CGRP_ROOT_NOPREFIX) {
-			pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
-			return -EINVAL;
-		}
-
-		if (opts->cpuset_clone_children) {
-			pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
+		if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) ||
+		    opts->cpuset_clone_children || opts->release_agent ||
+		    opts->name) {
+			pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
 			return -EINVAL;
 		}
 	}
@@ -1276,11 +1234,10 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 	return 0;
 }
 
-static int cgroup_remount(struct super_block *sb, int *flags, char *data)
+static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
 {
 	int ret = 0;
-	struct cgroupfs_root *root = sb->s_fs_info;
-	struct cgroup *cgrp = &root->top_cgroup;
+	struct cgroupfs_root *root = cgroup_root_from_kf(kf_root);
 	struct cgroup_sb_opts opts;
 	unsigned long added_mask, removed_mask;
 
@@ -1289,9 +1246,8 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 		return -EINVAL;
 	}
 
-	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
+	mutex_lock(&cgroup_tree_mutex);
 	mutex_lock(&cgroup_mutex);
-	mutex_lock(&cgroup_root_mutex);
 
 	/* See what subsystems are wanted */
 	ret = parse_cgroupfs_options(data, &opts);
@@ -1316,7 +1272,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 	}
 
 	/* remounting is not allowed for populated hierarchies */
-	if (root->number_of_cgroups > 1) {
+	if (!list_empty(&root->top_cgroup.children)) {
 		ret = -EBUSY;
 		goto out_unlock;
 	}
@@ -1325,35 +1281,81 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 	if (ret)
 		goto out_unlock;
 
-	if (opts.release_agent)
+	if (opts.release_agent) {
+		spin_lock(&release_agent_path_lock);
 		strcpy(root->release_agent_path, opts.release_agent);
+		spin_unlock(&release_agent_path_lock);
+	}
  out_unlock:
 	kfree(opts.release_agent);
 	kfree(opts.name);
-	mutex_unlock(&cgroup_root_mutex);
 	mutex_unlock(&cgroup_mutex);
-	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 	return ret;
 }
 
-static const struct super_operations cgroup_ops = {
-	.statfs = simple_statfs,
-	.drop_inode = generic_delete_inode,
-	.show_options = cgroup_show_options,
-	.remount_fs = cgroup_remount,
-};
+/*
+ * 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;
+
+static void cgroup_enable_task_cg_lists(void)
+{
+	struct task_struct *p, *g;
+
+	down_write(&css_set_rwsem);
+
+	if (use_task_css_set_links)
+		goto out_unlock;
+
+	use_task_css_set_links = true;
+
+	/*
+	 * 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);
+	do_each_thread(g, p) {
+		task_lock(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().
+		 */
+		spin_lock_irq(&p->sighand->siglock);
+		if (!(p->flags & PF_EXITING))
+			list_add(&p->cg_list, &task_css_set(p)->tasks);
+		spin_unlock_irq(&p->sighand->siglock);
+
+		task_unlock(p);
+	} while_each_thread(g, p);
+	read_unlock(&tasklist_lock);
+out_unlock:
+	up_write(&css_set_rwsem);
+}
 
 static void init_cgroup_housekeeping(struct cgroup *cgrp)
 {
+	atomic_set(&cgrp->refcnt, 1);
 	INIT_LIST_HEAD(&cgrp->sibling);
 	INIT_LIST_HEAD(&cgrp->children);
-	INIT_LIST_HEAD(&cgrp->files);
 	INIT_LIST_HEAD(&cgrp->cset_links);
 	INIT_LIST_HEAD(&cgrp->release_list);
 	INIT_LIST_HEAD(&cgrp->pidlists);
 	mutex_init(&cgrp->pidlist_mutex);
 	cgrp->dummy_css.cgroup = cgrp;
-	simple_xattrs_init(&cgrp->xattrs);
 }
 
 static void init_cgroup_root(struct cgroupfs_root *root)
@@ -1361,66 +1363,18 @@ static void init_cgroup_root(struct cgroupfs_root *root)
 	struct cgroup *cgrp = &root->top_cgroup;
 
 	INIT_LIST_HEAD(&root->root_list);
-	root->number_of_cgroups = 1;
+	atomic_set(&root->nr_cgrps, 1);
 	cgrp->root = root;
-	RCU_INIT_POINTER(cgrp->name, &root_cgroup_name);
 	init_cgroup_housekeeping(cgrp);
 	idr_init(&root->cgroup_idr);
 }
 
-static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
-{
-	int id;
-
-	lockdep_assert_held(&cgroup_mutex);
-	lockdep_assert_held(&cgroup_root_mutex);
-
-	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, start, end,
-			      GFP_KERNEL);
-	if (id < 0)
-		return id;
-
-	root->hierarchy_id = id;
-	return 0;
-}
-
-static void cgroup_exit_root_id(struct cgroupfs_root *root)
-{
-	lockdep_assert_held(&cgroup_mutex);
-	lockdep_assert_held(&cgroup_root_mutex);
-
-	if (root->hierarchy_id) {
-		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
-		root->hierarchy_id = 0;
-	}
-}
-
-static int cgroup_test_super(struct super_block *sb, void *data)
-{
-	struct cgroup_sb_opts *opts = data;
-	struct cgroupfs_root *root = sb->s_fs_info;
-
-	/* If we asked for a name then it must match */
-	if (opts->name && strcmp(opts->name, root->name))
-		return 0;
-
-	/*
-	 * If we asked for subsystems (or explicitly for no
-	 * subsystems) then they must match
-	 */
-	if ((opts->subsys_mask || opts->none)
-	    && (opts->subsys_mask != root->subsys_mask))
-		return 0;
-
-	return 1;
-}
-
 static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 {
 	struct cgroupfs_root *root;
 
 	if (!opts->subsys_mask && !opts->none)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	root = kzalloc(sizeof(*root), GFP_KERNEL);
 	if (!root)
@@ -1428,15 +1382,6 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 
 	init_cgroup_root(root);
 
-	/*
-	 * We need to set @root->subsys_mask now so that @root can be
-	 * matched by cgroup_test_super() before it finishes
-	 * initialization; otherwise, competing mounts with the same
-	 * options may try to bind the same subsystems instead of waiting
-	 * for the first one leading to unexpected mount errors.
-	 * SUBSYS_BOUND will be set once actual binding is complete.
-	 */
-	root->subsys_mask = opts->subsys_mask;
 	root->flags = opts->flags;
 	if (opts->release_agent)
 		strcpy(root->release_agent_path, opts->release_agent);
@@ -1447,291 +1392,202 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 	return root;
 }
 
-static void cgroup_free_root(struct cgroupfs_root *root)
+static int cgroup_setup_root(struct cgroupfs_root *root, unsigned long ss_mask)
 {
-	if (root) {
-		/* hierarhcy ID shoulid already have been released */
-		WARN_ON_ONCE(root->hierarchy_id);
-
-		idr_destroy(&root->cgroup_idr);
-		kfree(root);
-	}
-}
+	LIST_HEAD(tmp_links);
+	struct cgroup *root_cgrp = &root->top_cgroup;
+	struct css_set *cset;
+	int i, ret;
 
-static int cgroup_set_super(struct super_block *sb, void *data)
-{
-	int ret;
-	struct cgroup_sb_opts *opts = data;
+	lockdep_assert_held(&cgroup_tree_mutex);
+	lockdep_assert_held(&cgroup_mutex);
 
-	/* If we don't have a new root, we can't set up a new sb */
-	if (!opts->new_root)
-		return -EINVAL;
+	ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
+	if (ret < 0)
+		goto out;
+	root_cgrp->id = ret;
 
-	BUG_ON(!opts->subsys_mask && !opts->none);
+	/*
+	 * We're accessing css_set_count without locking css_set_rwsem here,
+	 * but that's OK - it can only be increased by someone holding
+	 * cgroup_lock, and that's us. The worst that can happen is that we
+	 * have some link structures left over
+	 */
+	ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
+	if (ret)
+		goto out;
 
-	ret = set_anon_super(sb, NULL);
+	/* ID 0 is reserved for dummy root, 1 for unified hierarchy */
+	ret = cgroup_init_root_id(root, 2, 0);
 	if (ret)
-		return ret;
+		goto out;
 
-	sb->s_fs_info = opts->new_root;
-	opts->new_root->sb = sb;
+	root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
+					   KERNFS_ROOT_CREATE_DEACTIVATED,
+					   root_cgrp);
+	if (IS_ERR(root->kf_root)) {
+		ret = PTR_ERR(root->kf_root);
+		goto exit_root_id;
+	}
+	root_cgrp->kn = root->kf_root->kn;
 
-	sb->s_blocksize = PAGE_CACHE_SIZE;
-	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
-	sb->s_magic = CGROUP_SUPER_MAGIC;
-	sb->s_op = &cgroup_ops;
+	ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
+	if (ret)
+		goto destroy_root;
 
-	return 0;
-}
+	ret = rebind_subsystems(root, ss_mask, 0);
+	if (ret)
+		goto destroy_root;
 
-static int cgroup_get_rootdir(struct super_block *sb)
-{
-	static const struct dentry_operations cgroup_dops = {
-		.d_iput = cgroup_diput,
-		.d_delete = always_delete_dentry,
-	};
+	/*
+	 * There must be no failure case after here, since rebinding takes
+	 * care of subsystems' refcounts, which are explicitly dropped in
+	 * the failure exit path.
+	 */
+	list_add(&root->root_list, &cgroup_roots);
+	cgroup_root_count++;
 
-	struct inode *inode =
-		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
+	/*
+	 * Link the top cgroup in this hierarchy into all the css_set
+	 * objects.
+	 */
+	down_write(&css_set_rwsem);
+	hash_for_each(css_set_table, i, cset, hlist)
+		link_css_set(&tmp_links, cset, root_cgrp);
+	up_write(&css_set_rwsem);
 
-	if (!inode)
-		return -ENOMEM;
+	BUG_ON(!list_empty(&root_cgrp->children));
+	BUG_ON(atomic_read(&root->nr_cgrps) != 1);
 
-	inode->i_fop = &simple_dir_operations;
-	inode->i_op = &cgroup_dir_inode_operations;
-	/* directories start off with i_nlink == 2 (for "." entry) */
-	inc_nlink(inode);
-	sb->s_root = d_make_root(inode);
-	if (!sb->s_root)
-		return -ENOMEM;
-	/* for everything else we want ->d_op set */
-	sb->s_d_op = &cgroup_dops;
-	return 0;
+	kernfs_activate(root_cgrp->kn);
+	ret = 0;
+	goto out;
+
+destroy_root:
+	kernfs_destroy_root(root->kf_root);
+	root->kf_root = NULL;
+exit_root_id:
+	cgroup_exit_root_id(root);
+out:
+	free_cgrp_cset_links(&tmp_links);
+	return ret;
 }
 
 static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 			 int flags, const char *unused_dev_name,
 			 void *data)
 {
-	struct cgroup_sb_opts opts;
 	struct cgroupfs_root *root;
-	int ret = 0;
-	struct super_block *sb;
-	struct cgroupfs_root *new_root;
-	struct list_head tmp_links;
-	struct inode *inode;
-	const struct cred *cred;
-
-	/* First find the desired set of subsystems */
-	mutex_lock(&cgroup_mutex);
-	ret = parse_cgroupfs_options(data, &opts);
-	mutex_unlock(&cgroup_mutex);
-	if (ret)
-		goto out_err;
+	struct cgroup_sb_opts opts;
+	struct dentry *dentry;
+	int ret;
 
 	/*
-	 * Allocate a new cgroup root. We may not need it if we're
-	 * reusing an existing hierarchy.
+	 * 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.
 	 */
-	new_root = cgroup_root_from_opts(&opts);
-	if (IS_ERR(new_root)) {
-		ret = PTR_ERR(new_root);
-		goto out_err;
-	}
-	opts.new_root = new_root;
-
-	/* Locate an existing or new sb for this hierarchy */
-	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
-	if (IS_ERR(sb)) {
-		ret = PTR_ERR(sb);
-		cgroup_free_root(opts.new_root);
-		goto out_err;
-	}
-
-	root = sb->s_fs_info;
-	BUG_ON(!root);
-	if (root == opts.new_root) {
-		/* We used the new root structure, so this is a new hierarchy */
-		struct cgroup *root_cgrp = &root->top_cgroup;
-		struct cgroupfs_root *existing_root;
-		int i;
-		struct css_set *cset;
-
-		BUG_ON(sb->s_root != NULL);
-
-		ret = cgroup_get_rootdir(sb);
-		if (ret)
-			goto drop_new_super;
-		inode = sb->s_root->d_inode;
-
-		mutex_lock(&inode->i_mutex);
-		mutex_lock(&cgroup_mutex);
-		mutex_lock(&cgroup_root_mutex);
-
-		ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
-		if (ret < 0)
-			goto unlock_drop;
-		root_cgrp->id = ret;
-
-		/* Check for name clashes with existing mounts */
-		ret = -EBUSY;
-		if (strlen(root->name))
-			for_each_active_root(existing_root)
-				if (!strcmp(existing_root->name, root->name))
-					goto unlock_drop;
-
-		/*
-		 * We're accessing css_set_count without locking
-		 * css_set_lock here, but that's OK - it can only be
-		 * increased by someone holding cgroup_lock, and
-		 * that's us. The worst that can happen is that we
-		 * have some link structures left over
-		 */
-		ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
-		if (ret)
-			goto unlock_drop;
-
-		/* ID 0 is reserved for dummy root, 1 for unified hierarchy */
-		ret = cgroup_init_root_id(root, 2, 0);
-		if (ret)
-			goto unlock_drop;
-
-		sb->s_root->d_fsdata = root_cgrp;
-		root_cgrp->dentry = sb->s_root;
-
-		/*
-		 * We're inside get_sb() and will call lookup_one_len() to
-		 * create the root files, which doesn't work if SELinux is
-		 * in use.  The following cred dancing somehow works around
-		 * it.  See 2ce9738ba ("cgroupfs: use init_cred when
-		 * populating new cgroupfs mount") for more details.
-		 */
-		cred = override_creds(&init_cred);
-
-		ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
-		if (ret)
-			goto rm_base_files;
+	if (!use_task_css_set_links)
+		cgroup_enable_task_cg_lists();
+retry:
+	mutex_lock(&cgroup_tree_mutex);
+	mutex_lock(&cgroup_mutex);
 
-		ret = rebind_subsystems(root, root->subsys_mask, 0);
-		if (ret)
-			goto rm_base_files;
+	/* First find the desired set of subsystems */
+	ret = parse_cgroupfs_options(data, &opts);
+	if (ret)
+		goto out_unlock;
 
-		revert_creds(cred);
+	/* look for a matching existing root */
+	for_each_active_root(root) {
+		bool name_match = false;
 
 		/*
-		 * There must be no failure case after here, since rebinding
-		 * takes care of subsystems' refcounts, which are explicitly
-		 * dropped in the failure exit path.
+		 * If we asked for a name then it must match.  Also, if
+		 * name matches but sybsys_mask doesn't, we should fail.
+		 * Remember whether name matched.
 		 */
+		if (opts.name) {
+			if (strcmp(opts.name, root->name))
+				continue;
+			name_match = true;
+		}
 
-		list_add(&root->root_list, &cgroup_roots);
-		cgroup_root_count++;
-
-		/* Link the top cgroup in this hierarchy into all
-		 * the css_set objects */
-		write_lock(&css_set_lock);
-		hash_for_each(css_set_table, i, cset, hlist)
-			link_css_set(&tmp_links, cset, root_cgrp);
-		write_unlock(&css_set_lock);
-
-		free_cgrp_cset_links(&tmp_links);
-
-		BUG_ON(!list_empty(&root_cgrp->children));
-		BUG_ON(root->number_of_cgroups != 1);
-
-		mutex_unlock(&cgroup_root_mutex);
-		mutex_unlock(&cgroup_mutex);
-		mutex_unlock(&inode->i_mutex);
-	} else {
 		/*
-		 * We re-used an existing hierarchy - the new root (if
-		 * any) is not needed
+		 * If we asked for subsystems (or explicitly for no
+		 * subsystems) then they must match.
 		 */
-		cgroup_free_root(opts.new_root);
+		if ((opts.subsys_mask || opts.none) &&
+		    (opts.subsys_mask != root->subsys_mask)) {
+			if (!name_match)
+				continue;
+			ret = -EBUSY;
+			goto out_unlock;
+		}
 
 		if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
 			if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
 				pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
 				ret = -EINVAL;
-				goto drop_new_super;
+				goto out_unlock;
 			} else {
 				pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
 			}
 		}
-	}
 
-	kfree(opts.release_agent);
-	kfree(opts.name);
-	return dget(sb->s_root);
-
- rm_base_files:
-	free_cgrp_cset_links(&tmp_links);
-	cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);
-	revert_creds(cred);
- unlock_drop:
-	cgroup_exit_root_id(root);
-	mutex_unlock(&cgroup_root_mutex);
-	mutex_unlock(&cgroup_mutex);
-	mutex_unlock(&inode->i_mutex);
- drop_new_super:
-	deactivate_locked_super(sb);
- out_err:
-	kfree(opts.release_agent);
-	kfree(opts.name);
-	return ERR_PTR(ret);
-}
-
-static void cgroup_kill_sb(struct super_block *sb)
-{
-	struct cgroupfs_root *root = sb->s_fs_info;
-	struct cgroup *cgrp = &root->top_cgroup;
-	struct cgrp_cset_link *link, *tmp_link;
-	int ret;
-
-	BUG_ON(!root);
-
-	BUG_ON(root->number_of_cgroups != 1);
-	BUG_ON(!list_empty(&cgrp->children));
+		/*
+		 * A root's lifetime is governed by its top cgroup.  Zero
+		 * ref indicate that the root is being destroyed.  Wait for
+		 * destruction to complete so that the subsystems are free.
+		 * We can use wait_queue for the wait but this path is
+		 * super cold.  Let's just sleep for a bit and retry.
+		 */
+		if (!atomic_inc_not_zero(&root->top_cgroup.refcnt)) {
+			mutex_unlock(&cgroup_mutex);
+			mutex_unlock(&cgroup_tree_mutex);
+			kfree(opts.release_agent);
+			kfree(opts.name);
+			msleep(10);
+			goto retry;
+		}
 
-	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
-	mutex_lock(&cgroup_mutex);
-	mutex_lock(&cgroup_root_mutex);
+		ret = 0;
+		goto out_unlock;
+	}
 
-	/* Rebind all subsystems back to the default hierarchy */
-	if (root->flags & CGRP_ROOT_SUBSYS_BOUND) {
-		ret = rebind_subsystems(root, 0, root->subsys_mask);
-		/* Shouldn't be able to fail ... */
-		BUG_ON(ret);
+	/* no such thing, create a new one */
+	root = cgroup_root_from_opts(&opts);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out_unlock;
 	}
 
-	/*
-	 * Release all the links from cset_links to this hierarchy's
-	 * root cgroup
-	 */
-	write_lock(&css_set_lock);
+	ret = cgroup_setup_root(root, opts.subsys_mask);
+	if (ret)
+		cgroup_free_root(root);
 
-	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
-		list_del(&link->cset_link);
-		list_del(&link->cgrp_link);
-		kfree(link);
-	}
-	write_unlock(&css_set_lock);
+out_unlock:
+	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 
-	if (!list_empty(&root->root_list)) {
-		list_del(&root->root_list);
-		cgroup_root_count--;
-	}
+	kfree(opts.release_agent);
+	kfree(opts.name);
 
-	cgroup_exit_root_id(root);
+	if (ret)
+		return ERR_PTR(ret);
 
-	mutex_unlock(&cgroup_root_mutex);
-	mutex_unlock(&cgroup_mutex);
-	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
+	dentry = kernfs_mount(fs_type, flags, root->kf_root);
+	if (IS_ERR(dentry))
+		cgroup_put(&root->top_cgroup);
+	return dentry;
+}
 
-	simple_xattrs_free(&cgrp->xattrs);
+static void cgroup_kill_sb(struct super_block *sb)
+{
+	struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
+	struct cgroupfs_root *root = cgroup_root_from_kf(kf_root);
 
-	kill_litter_super(sb);
-	cgroup_free_root(root);
+	cgroup_put(&root->top_cgroup);
+	kernfs_kill_sb(sb);
 }
 
 static struct file_system_type cgroup_fs_type = {
@@ -1743,57 +1599,6 @@ static struct file_system_type cgroup_fs_type = {
 static struct kobject *cgroup_kobj;
 
 /**
- * cgroup_path - generate the path of a cgroup
- * @cgrp: the cgroup in question
- * @buf: the buffer to write the path into
- * @buflen: the length of the buffer
- *
- * Writes path of cgroup into buf.  Returns 0 on success, -errno on error.
- *
- * We can't generate cgroup path using dentry->d_name, as accessing
- * dentry->name must be protected by irq-unsafe dentry->d_lock or parent
- * inode's i_mutex, while on the other hand cgroup_path() can be called
- * with some irq-safe spinlocks held.
- */
-int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
-{
-	int ret = -ENAMETOOLONG;
-	char *start;
-
-	if (!cgrp->parent) {
-		if (strlcpy(buf, "/", buflen) >= buflen)
-			return -ENAMETOOLONG;
-		return 0;
-	}
-
-	start = buf + buflen - 1;
-	*start = '\0';
-
-	rcu_read_lock();
-	do {
-		const char *name = cgroup_name(cgrp);
-		int len;
-
-		len = strlen(name);
-		if ((start -= len) < buf)
-			goto out;
-		memcpy(start, name, len);
-
-		if (--start < buf)
-			goto out;
-		*start = '/';
-
-		cgrp = cgrp->parent;
-	} while (cgrp->parent);
-	ret = 0;
-	memmove(buf, start, buf + buflen - start);
-out:
-	rcu_read_unlock();
-	return ret;
-}
-EXPORT_SYMBOL_GPL(cgroup_path);
-
-/**
  * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
  * @task: target task
  * @buf: the buffer to write the path into
@@ -1804,31 +1609,32 @@ EXPORT_SYMBOL_GPL(cgroup_path);
  * function grabs cgroup_mutex and shouldn't be used inside locks used by
  * cgroup controller callbacks.
  *
- * Returns 0 on success, fails with -%ENAMETOOLONG if @buflen is too short.
+ * Return value is the same as kernfs_path().
  */
-int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
 {
 	struct cgroupfs_root *root;
 	struct cgroup *cgrp;
-	int hierarchy_id = 1, ret = 0;
-
-	if (buflen < 2)
-		return -ENAMETOOLONG;
+	int hierarchy_id = 1;
+	char *path = NULL;
 
 	mutex_lock(&cgroup_mutex);
+	down_read(&css_set_rwsem);
 
 	root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
 
 	if (root) {
 		cgrp = task_cgroup_from_root(task, root);
-		ret = cgroup_path(cgrp, buf, buflen);
+		path = cgroup_path(cgrp, buf, buflen);
 	} else {
 		/* if no hierarchy exists, everyone is in "/" */
-		memcpy(buf, "/", 2);
+		if (strlcpy(buf, "/", buflen) < buflen)
+			path = buf;
 	}
 
+	up_read(&css_set_rwsem);
 	mutex_unlock(&cgroup_mutex);
-	return ret;
+	return path;
 }
 EXPORT_SYMBOL_GPL(task_cgroup_path);
 
@@ -1846,7 +1652,6 @@ struct cgroup_taskset {
 	struct flex_array	*tc_array;
 	int			tc_array_len;
 	int			idx;
-	struct cgroup		*cur_cgrp;
 };
 
 /**
@@ -1861,11 +1666,9 @@ struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
 		tset->idx = 0;
 		return cgroup_taskset_next(tset);
 	} else {
-		tset->cur_cgrp = tset->single.cgrp;
 		return tset->single.task;
 	}
 }
-EXPORT_SYMBOL_GPL(cgroup_taskset_first);
 
 /**
  * cgroup_taskset_next - iterate to the next task in taskset
@@ -1882,42 +1685,16 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
 		return NULL;
 
 	tc = flex_array_get(tset->tc_array, tset->idx++);
-	tset->cur_cgrp = tc->cgrp;
 	return tc->task;
 }
-EXPORT_SYMBOL_GPL(cgroup_taskset_next);
 
 /**
- * cgroup_taskset_cur_css - return the matching css for the current task
- * @tset: taskset of interest
- * @subsys_id: the ID of the target subsystem
- *
- * Return the css for the current (last returned) task of @tset for
- * subsystem specified by @subsys_id.  This function must be preceded by
- * either cgroup_taskset_first() or cgroup_taskset_next().
- */
-struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
-						   int subsys_id)
-{
-	return cgroup_css(tset->cur_cgrp, cgroup_subsys[subsys_id]);
-}
-EXPORT_SYMBOL_GPL(cgroup_taskset_cur_css);
-
-/**
- * cgroup_taskset_size - return the number of tasks in taskset
- * @tset: taskset of interest
- */
-int cgroup_taskset_size(struct cgroup_taskset *tset)
-{
-	return tset->tc_array ? tset->tc_array_len : 1;
-}
-EXPORT_SYMBOL_GPL(cgroup_taskset_size);
-
-
-/*
  * cgroup_task_migrate - move a task from one cgroup to another.
+ * @old_cgrp; the cgroup @tsk is being migrated from
+ * @tsk: the task being migrated
+ * @new_cset: the new css_set @tsk is being attached to
  *
- * Must be called with cgroup_mutex and threadgroup locked.
+ * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
  */
 static void cgroup_task_migrate(struct cgroup *old_cgrp,
 				struct task_struct *tsk,
@@ -1925,6 +1702,9 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
 {
 	struct css_set *old_cset;
 
+	lockdep_assert_held(&cgroup_mutex);
+	lockdep_assert_held(&css_set_rwsem);
+
 	/*
 	 * We are synchronized through threadgroup_lock() against PF_EXITING
 	 * setting such that we can't race against cgroup_exit() changing the
@@ -1937,11 +1717,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
 	rcu_assign_pointer(tsk->cgroups, new_cset);
 	task_unlock(tsk);
 
-	/* Update the css_set linked lists if we're using them */
-	write_lock(&css_set_lock);
-	if (!list_empty(&tsk->cg_list))
-		list_move(&tsk->cg_list, &new_cset->tasks);
-	write_unlock(&css_set_lock);
+	list_move(&tsk->cg_list, &new_cset->tasks);
 
 	/*
 	 * We just gained a reference on old_cset by taking it from the
@@ -1949,26 +1725,26 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
 	 * we're safe to drop it here; it will be freed under RCU.
 	 */
 	set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
-	put_css_set(old_cset);
+	put_css_set_locked(old_cset, false);
 }
 
 /**
  * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
  * @cgrp: the cgroup to attach to
- * @tsk: the task or the leader of the threadgroup to be attached
+ * @leader: the task or the leader of the threadgroup to be attached
  * @threadgroup: attach the whole threadgroup?
  *
  * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
  * task_lock of @tsk or each thread in the threadgroup individually in turn.
  */
-static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
+static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *leader,
 			      bool threadgroup)
 {
-	int retval, i, group_size;
+	int ret, i, group_size;
 	struct cgroupfs_root *root = cgrp->root;
 	struct cgroup_subsys_state *css, *failed_css = NULL;
 	/* threadgroup list cursor and array */
-	struct task_struct *leader = tsk;
+	struct task_struct *task;
 	struct task_and_cgroup *tc;
 	struct flex_array *group;
 	struct cgroup_taskset tset = { };
@@ -1981,7 +1757,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 	 * threads exit, this will just be an over-estimate.
 	 */
 	if (threadgroup)
-		group_size = get_nr_threads(tsk);
+		group_size = get_nr_threads(leader);
 	else
 		group_size = 1;
 	/* flex_array supports very large thread-groups better than kmalloc. */
@@ -1989,8 +1765,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 	if (!group)
 		return -ENOMEM;
 	/* pre-allocate to guarantee space while iterating in rcu read-side. */
-	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
-	if (retval)
+	ret = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
+	if (ret)
 		goto out_free_group_list;
 
 	i = 0;
@@ -1999,18 +1775,20 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 	 * already PF_EXITING could be freed from underneath us unless we
 	 * take an rcu_read_lock.
 	 */
+	down_read(&css_set_rwsem);
 	rcu_read_lock();
+	task = leader;
 	do {
 		struct task_and_cgroup ent;
 
-		/* @tsk either already exited or can't exit until the end */
-		if (tsk->flags & PF_EXITING)
+		/* @task either already exited or can't exit until the end */
+		if (task->flags & PF_EXITING)
 			goto next;
 
 		/* as per above, nr_threads may decrease, but not increase. */
 		BUG_ON(i >= group_size);
-		ent.task = tsk;
-		ent.cgrp = task_cgroup_from_root(tsk, root);
+		ent.task = task;
+		ent.cgrp = task_cgroup_from_root(task, root);
 		/* nothing to do if this task is already in the cgroup */
 		if (ent.cgrp == cgrp)
 			goto next;
@@ -2018,21 +1796,22 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 		 * saying GFP_ATOMIC has no effect here because we did prealloc
 		 * earlier, but it's good form to communicate our expectations.
 		 */
-		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
-		BUG_ON(retval != 0);
+		ret = flex_array_put(group, i, &ent, GFP_ATOMIC);
+		BUG_ON(ret != 0);
 		i++;
 	next:
 		if (!threadgroup)
 			break;
-	} while_each_thread(leader, tsk);
+	} while_each_thread(leader, task);
 	rcu_read_unlock();
+	up_read(&css_set_rwsem);
 	/* remember the number of threads in the array for later. */
 	group_size = i;
 	tset.tc_array = group;
 	tset.tc_array_len = group_size;
 
 	/* methods shouldn't be called if no task is actually migrating */
-	retval = 0;
+	ret = 0;
 	if (!group_size)
 		goto out_free_group_list;
 
@@ -2041,8 +1820,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 	 */
 	for_each_css(css, i, cgrp) {
 		if (css->ss->can_attach) {
-			retval = css->ss->can_attach(css, &tset);
-			if (retval) {
+			ret = css->ss->can_attach(css, &tset);
+			if (ret) {
 				failed_css = css;
 				goto out_cancel_attach;
 			}
@@ -2060,7 +1839,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 		old_cset = task_css_set(tc->task);
 		tc->cset = find_css_set(old_cset, cgrp);
 		if (!tc->cset) {
-			retval = -ENOMEM;
+			ret = -ENOMEM;
 			goto out_put_css_set_refs;
 		}
 	}
@@ -2070,10 +1849,12 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 	 * proceed to move all tasks to the new cgroup.  There are no
 	 * failure cases after here, so this is the commit point.
 	 */
+	down_write(&css_set_rwsem);
 	for (i = 0; i < group_size; i++) {
 		tc = flex_array_get(group, i);
 		cgroup_task_migrate(tc->cgrp, tc->task, tc->cset);
 	}
+	up_write(&css_set_rwsem);
 	/* nothing is sensitive to fork() after this point. */
 
 	/*
@@ -2086,18 +1867,18 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
 	/*
 	 * step 5: success! and cleanup
 	 */
-	retval = 0;
+	ret = 0;
 out_put_css_set_refs:
-	if (retval) {
+	if (ret) {
 		for (i = 0; i < group_size; i++) {
 			tc = flex_array_get(group, i);
 			if (!tc->cset)
 				break;
-			put_css_set(tc->cset);
+			put_css_set(tc->cset, false);
 		}
 	}
 out_cancel_attach:
-	if (retval) {
+	if (ret) {
 		for_each_css(css, i, cgrp) {
 			if (css == failed_css)
 				break;
@@ -2107,7 +1888,7 @@ out_cancel_attach:
 	}
 out_free_group_list:
 	flex_array_free(group);
-	return retval;
+	return ret;
 }
 
 /*
@@ -2203,7 +1984,11 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
 
 	mutex_lock(&cgroup_mutex);
 	for_each_active_root(root) {
-		struct cgroup *from_cgrp = task_cgroup_from_root(from, root);
+		struct cgroup *from_cgrp;
+
+		down_read(&css_set_rwsem);
+		from_cgrp = task_cgroup_from_root(from, root);
+		up_read(&css_set_rwsem);
 
 		retval = cgroup_attach_task(from_cgrp, tsk, false);
 		if (retval)
@@ -2230,14 +2015,15 @@ static int cgroup_procs_write(struct cgroup_subsys_state *css,
 static int cgroup_release_agent_write(struct cgroup_subsys_state *css,
 				      struct cftype *cft, const char *buffer)
 {
-	BUILD_BUG_ON(sizeof(css->cgroup->root->release_agent_path) < PATH_MAX);
-	if (strlen(buffer) >= PATH_MAX)
-		return -EINVAL;
+	struct cgroupfs_root *root = css->cgroup->root;
+
+	BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX);
 	if (!cgroup_lock_live_group(css->cgroup))
 		return -ENODEV;
-	mutex_lock(&cgroup_root_mutex);
-	strcpy(css->cgroup->root->release_agent_path, buffer);
-	mutex_unlock(&cgroup_root_mutex);
+	spin_lock(&release_agent_path_lock);
+	strlcpy(root->release_agent_path, buffer,
+		sizeof(root->release_agent_path));
+	spin_unlock(&release_agent_path_lock);
 	mutex_unlock(&cgroup_mutex);
 	return 0;
 }
@@ -2262,32 +2048,23 @@ static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
 	return 0;
 }
 
-/* A buffer size big enough for numbers or short strings */
-#define CGROUP_LOCAL_BUFFER_SIZE 64
-
-static ssize_t cgroup_file_write(struct file *file, const char __user *userbuf,
-				 size_t nbytes, loff_t *ppos)
+static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
+				 size_t nbytes, loff_t off)
 {
-	struct cfent *cfe = __d_cfe(file->f_dentry);
-	struct cftype *cft = __d_cft(file->f_dentry);
-	struct cgroup_subsys_state *css = cfe->css;
-	size_t max_bytes = cft->max_write_len ?: CGROUP_LOCAL_BUFFER_SIZE - 1;
-	char *buf;
+	struct cgroup *cgrp = of->kn->parent->priv;
+	struct cftype *cft = of->kn->priv;
+	struct cgroup_subsys_state *css;
 	int ret;
 
-	if (nbytes >= max_bytes)
-		return -E2BIG;
-
-	buf = kmalloc(nbytes + 1, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	if (copy_from_user(buf, userbuf, nbytes)) {
-		ret = -EFAULT;
-		goto out_free;
-	}
-
-	buf[nbytes] = '\0';
+	/*
+	 * kernfs guarantees that a file isn't deleted with operations in
+	 * flight, which means that the matching css is and stays alive and
+	 * doesn't need to be pinned.  The RCU locking is not necessary
+	 * either.  It's just for the convenience of using cgroup_css().
+	 */
+	rcu_read_lock();
+	css = cgroup_css(cgrp, cft->ss);
+	rcu_read_unlock();
 
 	if (cft->write_string) {
 		ret = cft->write_string(css, cft, strstrip(buf));
@@ -2306,53 +2083,23 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *userbuf,
 	} else {
 		ret = -EINVAL;
 	}
-out_free:
-	kfree(buf);
+
 	return ret ?: nbytes;
 }
 
-/*
- * seqfile ops/methods for returning structured data. Currently just
- * supports string->u64 maps, but can be extended in future.
- */
-
 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
 {
-	struct cftype *cft = seq_cft(seq);
-
-	if (cft->seq_start) {
-		return cft->seq_start(seq, ppos);
-	} else {
-		/*
-		 * The same behavior and code as single_open().  Returns
-		 * !NULL if pos is at the beginning; otherwise, NULL.
-		 */
-		return NULL + !*ppos;
-	}
+	return seq_cft(seq)->seq_start(seq, ppos);
 }
 
 static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
 {
-	struct cftype *cft = seq_cft(seq);
-
-	if (cft->seq_next) {
-		return cft->seq_next(seq, v, ppos);
-	} else {
-		/*
-		 * The same behavior and code as single_open(), always
-		 * terminate after the initial read.
-		 */
-		++*ppos;
-		return NULL;
-	}
+	return seq_cft(seq)->seq_next(seq, v, ppos);
 }
 
 static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
 {
-	struct cftype *cft = seq_cft(seq);
-
-	if (cft->seq_stop)
-		cft->seq_stop(seq, v);
+	seq_cft(seq)->seq_stop(seq, v);
 }
 
 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
@@ -2372,96 +2119,35 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)
 	return 0;
 }
 
-static struct seq_operations cgroup_seq_operations = {
-	.start		= cgroup_seqfile_start,
-	.next		= cgroup_seqfile_next,
-	.stop		= cgroup_seqfile_stop,
-	.show		= cgroup_seqfile_show,
+static struct kernfs_ops cgroup_kf_single_ops = {
+	.atomic_write_len	= PAGE_SIZE,
+	.write			= cgroup_file_write,
+	.seq_show		= cgroup_seqfile_show,
 };
 
-static int cgroup_file_open(struct inode *inode, struct file *file)
-{
-	struct cfent *cfe = __d_cfe(file->f_dentry);
-	struct cftype *cft = __d_cft(file->f_dentry);
-	struct cgroup *cgrp = __d_cgrp(cfe->dentry->d_parent);
-	struct cgroup_subsys_state *css;
-	struct cgroup_open_file *of;
-	int err;
-
-	err = generic_file_open(inode, file);
-	if (err)
-		return err;
-
-	/*
-	 * If the file belongs to a subsystem, pin the css.  Will be
-	 * unpinned either on open failure or release.  This ensures that
-	 * @css stays alive for all file operations.
-	 */
-	rcu_read_lock();
-	css = cgroup_css(cgrp, cft->ss);
-	if (cft->ss && !css_tryget(css))
-		css = NULL;
-	rcu_read_unlock();
-
-	if (!css)
-		return -ENODEV;
-
-	/*
-	 * @cfe->css is used by read/write/close to determine the
-	 * associated css.  @file->private_data would be a better place but
-	 * that's already used by seqfile.  Multiple accessors may use it
-	 * simultaneously which is okay as the association never changes.
-	 */
-	WARN_ON_ONCE(cfe->css && cfe->css != css);
-	cfe->css = css;
-
-	of = __seq_open_private(file, &cgroup_seq_operations,
-				sizeof(struct cgroup_open_file));
-	if (of) {
-		of->cfe = cfe;
-		return 0;
-	}
-
-	if (css->ss)
-		css_put(css);
-	return -ENOMEM;
-}
-
-static int cgroup_file_release(struct inode *inode, struct file *file)
-{
-	struct cfent *cfe = __d_cfe(file->f_dentry);
-	struct cgroup_subsys_state *css = cfe->css;
-
-	if (css->ss)
-		css_put(css);
-	return seq_release_private(inode, file);
-}
+static struct kernfs_ops cgroup_kf_ops = {
+	.atomic_write_len	= PAGE_SIZE,
+	.write			= cgroup_file_write,
+	.seq_start		= cgroup_seqfile_start,
+	.seq_next		= cgroup_seqfile_next,
+	.seq_stop		= cgroup_seqfile_stop,
+	.seq_show		= cgroup_seqfile_show,
+};
 
 /*
  * cgroup_rename - Only allow simple rename of directories in place.
  */
-static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
-			    struct inode *new_dir, struct dentry *new_dentry)
+static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
+			 const char *new_name_str)
 {
+	struct cgroup *cgrp = kn->priv;
 	int ret;
-	struct cgroup_name *name, *old_name;
-	struct cgroup *cgrp;
-
-	/*
-	 * It's convinient to use parent dir's i_mutex to protected
-	 * cgrp->name.
-	 */
-	lockdep_assert_held(&old_dir->i_mutex);
 
-	if (!S_ISDIR(old_dentry->d_inode->i_mode))
+	if (kernfs_type(kn) != KERNFS_DIR)
 		return -ENOTDIR;
-	if (new_dentry->d_inode)
-		return -EEXIST;
-	if (old_dir != new_dir)
+	if (kn->parent != new_parent)
 		return -EIO;
 
-	cgrp = __d_cgrp(old_dentry);
-
 	/*
 	 * This isn't a proper migration and its usefulness is very
 	 * limited.  Disallow if sane_behavior.
@@ -2469,218 +2155,29 @@ static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (cgroup_sane_behavior(cgrp))
 		return -EPERM;
 
-	name = cgroup_alloc_name(new_dentry);
-	if (!name)
-		return -ENOMEM;
-
-	ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry);
-	if (ret) {
-		kfree(name);
-		return ret;
-	}
-
-	old_name = rcu_dereference_protected(cgrp->name, true);
-	rcu_assign_pointer(cgrp->name, name);
-
-	kfree_rcu(old_name, rcu_head);
-	return 0;
-}
-
-static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
-{
-	if (S_ISDIR(dentry->d_inode->i_mode))
-		return &__d_cgrp(dentry)->xattrs;
-	else
-		return &__d_cfe(dentry)->xattrs;
-}
-
-static inline int xattr_enabled(struct dentry *dentry)
-{
-	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
-	return root->flags & CGRP_ROOT_XATTR;
-}
-
-static bool is_valid_xattr(const char *name)
-{
-	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
-	    !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
-		return true;
-	return false;
-}
-
-static int cgroup_setxattr(struct dentry *dentry, const char *name,
-			   const void *val, size_t size, int flags)
-{
-	if (!xattr_enabled(dentry))
-		return -EOPNOTSUPP;
-	if (!is_valid_xattr(name))
-		return -EINVAL;
-	return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
-}
-
-static int cgroup_removexattr(struct dentry *dentry, const char *name)
-{
-	if (!xattr_enabled(dentry))
-		return -EOPNOTSUPP;
-	if (!is_valid_xattr(name))
-		return -EINVAL;
-	return simple_xattr_remove(__d_xattrs(dentry), name);
-}
-
-static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
-			       void *buf, size_t size)
-{
-	if (!xattr_enabled(dentry))
-		return -EOPNOTSUPP;
-	if (!is_valid_xattr(name))
-		return -EINVAL;
-	return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
-}
-
-static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
-{
-	if (!xattr_enabled(dentry))
-		return -EOPNOTSUPP;
-	return simple_xattr_list(__d_xattrs(dentry), buf, size);
-}
-
-static const struct file_operations cgroup_file_operations = {
-	.read = seq_read,
-	.write = cgroup_file_write,
-	.llseek = generic_file_llseek,
-	.open = cgroup_file_open,
-	.release = cgroup_file_release,
-};
-
-static const struct inode_operations cgroup_file_inode_operations = {
-	.setxattr = cgroup_setxattr,
-	.getxattr = cgroup_getxattr,
-	.listxattr = cgroup_listxattr,
-	.removexattr = cgroup_removexattr,
-};
-
-static const struct inode_operations cgroup_dir_inode_operations = {
-	.lookup = simple_lookup,
-	.mkdir = cgroup_mkdir,
-	.rmdir = cgroup_rmdir,
-	.rename = cgroup_rename,
-	.setxattr = cgroup_setxattr,
-	.getxattr = cgroup_getxattr,
-	.listxattr = cgroup_listxattr,
-	.removexattr = cgroup_removexattr,
-};
-
-static int cgroup_create_file(struct dentry *dentry, umode_t mode,
-				struct super_block *sb)
-{
-	struct inode *inode;
-
-	if (!dentry)
-		return -ENOENT;
-	if (dentry->d_inode)
-		return -EEXIST;
-
-	inode = cgroup_new_inode(mode, sb);
-	if (!inode)
-		return -ENOMEM;
-
-	if (S_ISDIR(mode)) {
-		inode->i_op = &cgroup_dir_inode_operations;
-		inode->i_fop = &simple_dir_operations;
-
-		/* start off with i_nlink == 2 (for "." entry) */
-		inc_nlink(inode);
-		inc_nlink(dentry->d_parent->d_inode);
-
-		/*
-		 * Control reaches here with cgroup_mutex held.
-		 * @inode->i_mutex should nest outside cgroup_mutex but we
-		 * want to populate it immediately without releasing
-		 * cgroup_mutex.  As @inode isn't visible to anyone else
-		 * yet, trylock will always succeed without affecting
-		 * lockdep checks.
-		 */
-		WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
-	} else if (S_ISREG(mode)) {
-		inode->i_size = 0;
-		inode->i_fop = &cgroup_file_operations;
-		inode->i_op = &cgroup_file_inode_operations;
-	}
-	d_instantiate(dentry, inode);
-	dget(dentry);	/* Extra count - pin the dentry in core */
-	return 0;
-}
-
-/**
- * cgroup_file_mode - deduce file mode of a control file
- * @cft: the control file in question
- *
- * returns cft->mode if ->mode is not 0
- * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
- * returns S_IRUGO if it has only a read handler
- * returns S_IWUSR if it has only a write hander
- */
-static umode_t cgroup_file_mode(const struct cftype *cft)
-{
-	umode_t mode = 0;
-
-	if (cft->mode)
-		return cft->mode;
-
-	if (cft->read_u64 || cft->read_s64 || cft->seq_show)
-		mode |= S_IRUGO;
+	mutex_lock(&cgroup_tree_mutex);
+	mutex_lock(&cgroup_mutex);
 
-	if (cft->write_u64 || cft->write_s64 || cft->write_string ||
-	    cft->trigger)
-		mode |= S_IWUSR;
+	ret = kernfs_rename(kn, new_parent, new_name_str);
 
-	return mode;
+	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
+	return ret;
 }
 
 static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
 {
-	struct dentry *dir = cgrp->dentry;
-	struct cgroup *parent = __d_cgrp(dir);
-	struct dentry *dentry;
-	struct cfent *cfe;
-	int error;
-	umode_t mode;
-	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
-
-	if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
-	    !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
-		strcpy(name, cft->ss->name);
-		strcat(name, ".");
-	}
-	strcat(name, cft->name);
+	char name[CGROUP_FILE_NAME_MAX];
+	struct kernfs_node *kn;
+	struct lock_class_key *key = NULL;
 
-	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
-
-	cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
-	if (!cfe)
-		return -ENOMEM;
-
-	dentry = lookup_one_len(name, dir, strlen(name));
-	if (IS_ERR(dentry)) {
-		error = PTR_ERR(dentry);
-		goto out;
-	}
-
-	cfe->type = (void *)cft;
-	cfe->dentry = dentry;
-	dentry->d_fsdata = cfe;
-	simple_xattrs_init(&cfe->xattrs);
-
-	mode = cgroup_file_mode(cft);
-	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
-	if (!error) {
-		list_add_tail(&cfe->node, &parent->files);
-		cfe = NULL;
-	}
-	dput(dentry);
-out:
-	kfree(cfe);
-	return error;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	key = &cft->lockdep_key;
+#endif
+	kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
+				  cgroup_file_mode(cft), 0, cft->kf_ops, cft,
+				  NULL, false, key);
+	return PTR_ERR_OR_ZERO(kn);
 }
 
 /**
@@ -2700,8 +2197,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
 	struct cftype *cft;
 	int ret;
 
-	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
-	lockdep_assert_held(&cgroup_mutex);
+	lockdep_assert_held(&cgroup_tree_mutex);
 
 	for (cft = cfts; cft->name[0] != '\0'; cft++) {
 		/* does cft->flags tell us to skip this file on @cgrp? */
@@ -2726,44 +2222,19 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
 	return 0;
 }
 
-static void cgroup_cfts_prepare(void)
-	__acquires(&cgroup_mutex)
-{
-	/*
-	 * Thanks to the entanglement with vfs inode locking, we can't walk
-	 * the existing cgroups under cgroup_mutex and create files.
-	 * Instead, we use css_for_each_descendant_pre() and drop RCU read
-	 * lock before calling cgroup_addrm_files().
-	 */
-	mutex_lock(&cgroup_mutex);
-}
-
-static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
-	__releases(&cgroup_mutex)
+static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
 {
 	LIST_HEAD(pending);
 	struct cgroup_subsys *ss = cfts[0].ss;
 	struct cgroup *root = &ss->root->top_cgroup;
-	struct super_block *sb = ss->root->sb;
-	struct dentry *prev = NULL;
-	struct inode *inode;
 	struct cgroup_subsys_state *css;
-	u64 update_before;
 	int ret = 0;
 
-	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
-	if (!cfts || ss->root == &cgroup_dummy_root ||
-	    !atomic_inc_not_zero(&sb->s_active)) {
-		mutex_unlock(&cgroup_mutex);
-		return 0;
-	}
+	lockdep_assert_held(&cgroup_tree_mutex);
 
-	/*
-	 * All cgroups which are created after we drop cgroup_mutex will
-	 * have the updated set of files, so we only need to update the
-	 * cgroups created before the current @cgroup_serial_nr_next.
-	 */
-	update_before = cgroup_serial_nr_next;
+	/* don't bother if @ss isn't attached */
+	if (ss->root == &cgroup_dummy_root)
+		return 0;
 
 	/* add/rm files for all cgroups created before */
 	css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
@@ -2772,62 +2243,75 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
 		if (cgroup_is_dead(cgrp))
 			continue;
 
-		inode = cgrp->dentry->d_inode;
-		dget(cgrp->dentry);
-		dput(prev);
-		prev = cgrp->dentry;
-
-		mutex_unlock(&cgroup_mutex);
-		mutex_lock(&inode->i_mutex);
-		mutex_lock(&cgroup_mutex);
-		if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp))
-			ret = cgroup_addrm_files(cgrp, cfts, is_add);
-		mutex_unlock(&inode->i_mutex);
+		ret = cgroup_addrm_files(cgrp, cfts, is_add);
 		if (ret)
 			break;
 	}
-	mutex_unlock(&cgroup_mutex);
-	dput(prev);
-	deactivate_super(sb);
+
+	if (is_add && !ret)
+		kernfs_activate(root->kn);
 	return ret;
 }
 
-/**
- * cgroup_add_cftypes - add an array of cftypes to a subsystem
- * @ss: target cgroup subsystem
- * @cfts: zero-length name terminated array of cftypes
- *
- * Register @cfts to @ss.  Files described by @cfts are created for all
- * existing cgroups to which @ss is attached and all future cgroups will
- * have them too.  This function can be called anytime whether @ss is
- * attached or not.
- *
- * Returns 0 on successful registration, -errno on failure.  Note that this
- * function currently returns 0 as long as @cfts registration is successful
- * even if some file creation attempts on existing cgroups fail.
- */
-int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+static void cgroup_exit_cftypes(struct cftype *cfts)
 {
-	struct cftype_set *set;
 	struct cftype *cft;
-	int ret;
 
-	set = kzalloc(sizeof(*set), GFP_KERNEL);
-	if (!set)
-		return -ENOMEM;
+	for (cft = cfts; cft->name[0] != '\0'; cft++) {
+		/* free copy for custom atomic_write_len, see init_cftypes() */
+		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
+			kfree(cft->kf_ops);
+		cft->kf_ops = NULL;
+		cft->ss = NULL;
+	}
+}
+
+static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+{
+	struct cftype *cft;
 
-	for (cft = cfts; cft->name[0] != '\0'; cft++)
+	for (cft = cfts; cft->name[0] != '\0'; cft++) {
+		struct kernfs_ops *kf_ops;
+
+		WARN_ON(cft->ss || cft->kf_ops);
+
+		if (cft->seq_start)
+			kf_ops = &cgroup_kf_ops;
+		else
+			kf_ops = &cgroup_kf_single_ops;
+
+		/*
+		 * Ugh... if @cft wants a custom max_write_len, we need to
+		 * make a copy of kf_ops to set its atomic_write_len.
+		 */
+		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
+			kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
+			if (!kf_ops) {
+				cgroup_exit_cftypes(cfts);
+				return -ENOMEM;
+			}
+			kf_ops->atomic_write_len = cft->max_write_len;
+		}
+
+		cft->kf_ops = kf_ops;
 		cft->ss = ss;
+	}
 
-	cgroup_cfts_prepare();
-	set->cfts = cfts;
-	list_add_tail(&set->node, &ss->cftsets);
-	ret = cgroup_cfts_commit(cfts, true);
-	if (ret)
-		cgroup_rm_cftypes(cfts);
-	return ret;
+	return 0;
+}
+
+static int cgroup_rm_cftypes_locked(struct cftype *cfts)
+{
+	lockdep_assert_held(&cgroup_tree_mutex);
+
+	if (!cfts || !cfts[0].ss)
+		return -ENOENT;
+
+	list_del(&cfts->node);
+	cgroup_apply_cftypes(cfts, false);
+	cgroup_exit_cftypes(cfts);
+	return 0;
 }
-EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
 
 /**
  * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
@@ -2842,24 +2326,48 @@ EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
  */
 int cgroup_rm_cftypes(struct cftype *cfts)
 {
-	struct cftype_set *set;
+	int ret;
 
-	if (!cfts || !cfts[0].ss)
-		return -ENOENT;
+	mutex_lock(&cgroup_tree_mutex);
+	ret = cgroup_rm_cftypes_locked(cfts);
+	mutex_unlock(&cgroup_tree_mutex);
+	return ret;
+}
 
-	cgroup_cfts_prepare();
+/**
+ * cgroup_add_cftypes - add an array of cftypes to a subsystem
+ * @ss: target cgroup subsystem
+ * @cfts: zero-length name terminated array of cftypes
+ *
+ * Register @cfts to @ss.  Files described by @cfts are created for all
+ * existing cgroups to which @ss is attached and all future cgroups will
+ * have them too.  This function can be called anytime whether @ss is
+ * attached or not.
+ *
+ * Returns 0 on successful registration, -errno on failure.  Note that this
+ * function currently returns 0 as long as @cfts registration is successful
+ * even if some file creation attempts on existing cgroups fail.
+ */
+int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+{
+	int ret;
 
-	list_for_each_entry(set, &cfts[0].ss->cftsets, node) {
-		if (set->cfts == cfts) {
-			list_del(&set->node);
-			kfree(set);
-			cgroup_cfts_commit(cfts, false);
-			return 0;
-		}
-	}
+	if (!cfts || cfts[0].name[0] == '\0')
+		return 0;
+
+	ret = cgroup_init_cftypes(ss, cfts);
+	if (ret)
+		return ret;
+
+	mutex_lock(&cgroup_tree_mutex);
 
-	cgroup_cfts_commit(NULL, false);
-	return -ENOENT;
+	list_add_tail(&cfts->node, &ss->cfts);
+	ret = cgroup_apply_cftypes(cfts, true);
+	if (ret)
+		cgroup_rm_cftypes_locked(cfts);
+
+	mutex_unlock(&cgroup_tree_mutex);
+	return ret;
 }
 
 /**
@@ -2868,57 +2376,18 @@ int cgroup_rm_cftypes(struct cftype *cfts)
  *
  * Return the number of tasks in the cgroup.
  */
-int cgroup_task_count(const struct cgroup *cgrp)
+static int cgroup_task_count(const struct cgroup *cgrp)
 {
 	int count = 0;
 	struct cgrp_cset_link *link;
 
-	read_lock(&css_set_lock);
+	down_read(&css_set_rwsem);
 	list_for_each_entry(link, &cgrp->cset_links, cset_link)
 		count += atomic_read(&link->cset->refcount);
-	read_unlock(&css_set_lock);
+	up_read(&css_set_rwsem);
 	return count;
 }
 
-/*
- * 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 call to css_task_iter_start().
- */
-static void cgroup_enable_task_cg_lists(void)
-{
-	struct task_struct *p, *g;
-	write_lock(&css_set_lock);
-	use_task_css_set_links = 1;
-	/*
-	 * 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);
-	do_each_thread(g, p) {
-		task_lock(p);
-		/*
-		 * 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().
-		 */
-		spin_lock_irq(&p->sighand->siglock);
-		if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
-			list_add(&p->cg_list, &task_css_set(p)->tasks);
-		spin_unlock_irq(&p->sighand->siglock);
-
-		task_unlock(p);
-	} while_each_thread(g, p);
-	read_unlock(&tasklist_lock);
-	write_unlock(&css_set_lock);
-}
-
 /**
  * css_next_child - find the next child of a given css
  * @pos_css: the current position (%NULL to initiate traversal)
@@ -2937,7 +2406,7 @@ css_next_child(struct cgroup_subsys_state *pos_css,
 	struct cgroup *cgrp = parent_css->cgroup;
 	struct cgroup *next;
 
-	cgroup_assert_mutex_or_rcu_locked();
+	cgroup_assert_mutexes_or_rcu_locked();
 
 	/*
 	 * @pos could already have been removed.  Once a cgroup is removed,
@@ -2973,7 +2442,6 @@ css_next_child(struct cgroup_subsys_state *pos_css,
 
 	return cgroup_css(next, parent_css->ss);
 }
-EXPORT_SYMBOL_GPL(css_next_child);
 
 /**
  * css_next_descendant_pre - find the next descendant for pre-order walk
@@ -2995,7 +2463,7 @@ css_next_descendant_pre(struct cgroup_subsys_state *pos,
 {
 	struct cgroup_subsys_state *next;
 
-	cgroup_assert_mutex_or_rcu_locked();
+	cgroup_assert_mutexes_or_rcu_locked();
 
 	/* if first iteration, visit @root */
 	if (!pos)
@@ -3016,7 +2484,6 @@ css_next_descendant_pre(struct cgroup_subsys_state *pos,
 
 	return NULL;
 }
-EXPORT_SYMBOL_GPL(css_next_descendant_pre);
 
 /**
  * css_rightmost_descendant - return the rightmost descendant of a css
@@ -3036,7 +2503,7 @@ css_rightmost_descendant(struct cgroup_subsys_state *pos)
 {
 	struct cgroup_subsys_state *last, *tmp;
 
-	cgroup_assert_mutex_or_rcu_locked();
+	cgroup_assert_mutexes_or_rcu_locked();
 
 	do {
 		last = pos;
@@ -3048,7 +2515,6 @@ css_rightmost_descendant(struct cgroup_subsys_state *pos)
 
 	return last;
 }
-EXPORT_SYMBOL_GPL(css_rightmost_descendant);
 
 static struct cgroup_subsys_state *
 css_leftmost_descendant(struct cgroup_subsys_state *pos)
@@ -3084,7 +2550,7 @@ css_next_descendant_post(struct cgroup_subsys_state *pos,
 {
 	struct cgroup_subsys_state *next;
 
-	cgroup_assert_mutex_or_rcu_locked();
+	cgroup_assert_mutexes_or_rcu_locked();
 
 	/* if first iteration, visit leftmost descendant which may be @root */
 	if (!pos)
@@ -3102,7 +2568,6 @@ css_next_descendant_post(struct cgroup_subsys_state *pos,
 	/* no sibling left, visit parent */
 	return css_parent(pos);
 }
-EXPORT_SYMBOL_GPL(css_next_descendant_post);
 
 /**
  * css_advance_task_iter - advance a task itererator to the next css_set
@@ -3146,17 +2611,12 @@ static void css_advance_task_iter(struct css_task_iter *it)
  */
 void css_task_iter_start(struct cgroup_subsys_state *css,
 			 struct css_task_iter *it)
-	__acquires(css_set_lock)
+	__acquires(css_set_rwsem)
 {
-	/*
-	 * The first time anyone tries to iterate across a css, we need to
-	 * 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();
+	/* no one should try to iterate before mounting cgroups */
+	WARN_ON_ONCE(!use_task_css_set_links);
 
-	read_lock(&css_set_lock);
+	down_read(&css_set_rwsem);
 
 	it->origin_css = css;
 	it->cset_link = &css->cgroup->cset_links;
@@ -3204,180 +2664,9 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it)
  * Finish task iteration started by css_task_iter_start().
  */
 void css_task_iter_end(struct css_task_iter *it)
-	__releases(css_set_lock)
-{
-	read_unlock(&css_set_lock);
-}
-
-static inline int started_after_time(struct task_struct *t1,
-				     struct timespec *time,
-				     struct task_struct *t2)
-{
-	int start_diff = timespec_compare(&t1->start_time, time);
-	if (start_diff > 0) {
-		return 1;
-	} else if (start_diff < 0) {
-		return 0;
-	} else {
-		/*
-		 * Arbitrarily, if two processes started at the same
-		 * time, we'll say that the lower pointer value
-		 * started first. Note that t2 may have exited by now
-		 * so this may not be a valid pointer any longer, but
-		 * that's fine - it still serves to distinguish
-		 * between two tasks started (effectively) simultaneously.
-		 */
-		return t1 > t2;
-	}
-}
-
-/*
- * This function is a callback from heap_insert() and is used to order
- * the heap.
- * In this case we order the heap in descending task start time.
- */
-static inline int started_after(void *p1, void *p2)
-{
-	struct task_struct *t1 = p1;
-	struct task_struct *t2 = p2;
-	return started_after_time(t1, &t2->start_time, t2);
-}
-
-/**
- * css_scan_tasks - iterate though all the tasks in a css
- * @css: the css to iterate tasks of
- * @test: optional test callback
- * @process: process callback
- * @data: data passed to @test and @process
- * @heap: optional pre-allocated heap used for task iteration
- *
- * Iterate through all the tasks in @css, calling @test for each, and if it
- * returns %true, call @process for it also.
- *
- * @test may be NULL, meaning always true (select all tasks), which
- * effectively duplicates css_task_iter_{start,next,end}() but does not
- * lock css_set_lock for the call to @process.
- *
- * It is guaranteed that @process will act on every task that is a member
- * of @css for the duration of this call.  This function may or may not
- * call @process for tasks that exit or move to a different css during the
- * call, or are forked or move into the css during the call.
- *
- * Note that @test may be called with locks held, and may in some
- * situations be called multiple times for the same task, so it should be
- * cheap.
- *
- * If @heap is non-NULL, a heap has been pre-allocated and will be used for
- * heap operations (and its "gt" member will be overwritten), else a
- * temporary heap will be used (allocation of which may cause this function
- * to fail).
- */
-int css_scan_tasks(struct cgroup_subsys_state *css,
-		   bool (*test)(struct task_struct *, void *),
-		   void (*process)(struct task_struct *, void *),
-		   void *data, struct ptr_heap *heap)
-{
-	int retval, i;
-	struct css_task_iter it;
-	struct task_struct *p, *dropped;
-	/* Never dereference latest_task, since it's not refcounted */
-	struct task_struct *latest_task = NULL;
-	struct ptr_heap tmp_heap;
-	struct timespec latest_time = { 0, 0 };
-
-	if (heap) {
-		/* The caller supplied our heap and pre-allocated its memory */
-		heap->gt = &started_after;
-	} else {
-		/* We need to allocate our own heap memory */
-		heap = &tmp_heap;
-		retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
-		if (retval)
-			/* cannot allocate the heap */
-			return retval;
-	}
-
- again:
-	/*
-	 * Scan tasks in the css, using the @test callback to determine
-	 * which are of interest, and invoking @process callback on the
-	 * ones which need an update.  Since we don't want to hold any
-	 * locks during the task updates, gather tasks to be processed in a
-	 * heap structure.  The heap is sorted by descending task start
-	 * time.  If the statically-sized heap fills up, we overflow tasks
-	 * that started later, and in future iterations only consider tasks
-	 * that started after the latest task in the previous pass. This
-	 * guarantees forward progress and that we don't miss any tasks.
-	 */
-	heap->size = 0;
-	css_task_iter_start(css, &it);
-	while ((p = css_task_iter_next(&it))) {
-		/*
-		 * Only affect tasks that qualify per the caller's callback,
-		 * if he provided one
-		 */
-		if (test && !test(p, data))
-			continue;
-		/*
-		 * Only process tasks that started after the last task
-		 * we processed
-		 */
-		if (!started_after_time(p, &latest_time, latest_task))
-			continue;
-		dropped = heap_insert(heap, p);
-		if (dropped == NULL) {
-			/*
-			 * The new task was inserted; the heap wasn't
-			 * previously full
-			 */
-			get_task_struct(p);
-		} else if (dropped != p) {
-			/*
-			 * The new task was inserted, and pushed out a
-			 * different task
-			 */
-			get_task_struct(p);
-			put_task_struct(dropped);
-		}
-		/*
-		 * Else the new task was newer than anything already in
-		 * the heap and wasn't inserted
-		 */
-	}
-	css_task_iter_end(&it);
-
-	if (heap->size) {
-		for (i = 0; i < heap->size; i++) {
-			struct task_struct *q = heap->ptrs[i];
-			if (i == 0) {
-				latest_time = q->start_time;
-				latest_task = q;
-			}
-			/* Process the task per the caller's callback */
-			process(q, data);
-			put_task_struct(q);
-		}
-		/*
-		 * If we had to process any tasks at all, scan again
-		 * in case some of them were in the middle of forking
-		 * children that didn't get processed.
-		 * Not the most efficient way to do it, but it avoids
-		 * having to take callback_mutex in the fork path
-		 */
-		goto again;
-	}
-	if (heap == &tmp_heap)
-		heap_free(&tmp_heap);
-	return 0;
-}
-
-static void cgroup_transfer_one_task(struct task_struct *task, void *data)
+	__releases(css_set_rwsem)
 {
-	struct cgroup *new_cgroup = data;
-
-	mutex_lock(&cgroup_mutex);
-	cgroup_attach_task(new_cgroup, task, false);
-	mutex_unlock(&cgroup_mutex);
+	up_read(&css_set_rwsem);
 }
 
 /**
@@ -3387,8 +2676,26 @@ static void cgroup_transfer_one_task(struct task_struct *task, void *data)
  */
 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 {
-	return css_scan_tasks(&from->dummy_css, NULL, cgroup_transfer_one_task,
-			      to, NULL);
+	struct css_task_iter it;
+	struct task_struct *task;
+	int ret = 0;
+
+	do {
+		css_task_iter_start(&from->dummy_css, &it);
+		task = css_task_iter_next(&it);
+		if (task)
+			get_task_struct(task);
+		css_task_iter_end(&it);
+
+		if (task) {
+			mutex_lock(&cgroup_mutex);
+			ret = cgroup_attach_task(to, task, false);
+			mutex_unlock(&cgroup_mutex);
+			put_task_struct(task);
+		}
+	} while (task && !ret);
+
+	return ret;
 }
 
 /*
@@ -3687,21 +2994,31 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
  */
 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
 {
-	int ret = -EINVAL;
+	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
 	struct cgroup *cgrp;
 	struct css_task_iter it;
 	struct task_struct *tsk;
 
+	/* it should be kernfs_node belonging to cgroupfs and is a directory */
+	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
+	    kernfs_type(kn) != KERNFS_DIR)
+		return -EINVAL;
+
+	mutex_lock(&cgroup_mutex);
+
 	/*
-	 * Validate dentry by checking the superblock operations,
-	 * and make sure it's a directory.
+	 * We aren't being called from kernfs and there's no guarantee on
+	 * @kn->priv's validity.  For this and css_tryget_from_dir(),
+	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
 	 */
-	if (dentry->d_sb->s_op != &cgroup_ops ||
-	    !S_ISDIR(dentry->d_inode->i_mode))
-		 goto err;
-
-	ret = 0;
-	cgrp = dentry->d_fsdata;
+	rcu_read_lock();
+	cgrp = rcu_dereference(kn->priv);
+	if (!cgrp || cgroup_is_dead(cgrp)) {
+		rcu_read_unlock();
+		mutex_unlock(&cgroup_mutex);
+		return -ENOENT;
+	}
+	rcu_read_unlock();
 
 	css_task_iter_start(&cgrp->dummy_css, &it);
 	while ((tsk = css_task_iter_next(&it))) {
@@ -3726,8 +3043,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
 	}
 	css_task_iter_end(&it);
 
-err:
-	return ret;
+	mutex_unlock(&cgroup_mutex);
+	return 0;
 }
 
 
@@ -3745,7 +3062,7 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
 	 * after a seek to the start). Use a binary-search to find the
 	 * next pid to display, if any
 	 */
-	struct cgroup_open_file *of = s->private;
+	struct kernfs_open_file *of = s->private;
 	struct cgroup *cgrp = seq_css(s)->cgroup;
 	struct cgroup_pidlist *l;
 	enum cgroup_filetype type = seq_cft(s)->private;
@@ -3800,7 +3117,7 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
 
 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
 {
-	struct cgroup_open_file *of = s->private;
+	struct kernfs_open_file *of = s->private;
 	struct cgroup_pidlist *l = of->priv;
 
 	if (l)
@@ -3811,7 +3128,7 @@ static void cgroup_pidlist_stop(struct seq_file *s, void *v)
 
 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
 {
-	struct cgroup_open_file *of = s->private;
+	struct kernfs_open_file *of = s->private;
 	struct cgroup_pidlist *l = of->priv;
 	pid_t *p = v;
 	pid_t *end = l->list + l->length;
@@ -3861,23 +3178,6 @@ static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
 	return 0;
 }
 
-/*
- * When dput() is called asynchronously, if umount has been done and
- * then deactivate_super() in cgroup_free_fn() kills the superblock,
- * there's a small window that vfs will see the root dentry with non-zero
- * refcnt and trigger BUG().
- *
- * That's why we hold a reference before dput() and drop it right after.
- */
-static void cgroup_dput(struct cgroup *cgrp)
-{
-	struct super_block *sb = cgrp->root->sb;
-
-	atomic_inc(&sb->s_active);
-	dput(cgrp->dentry);
-	deactivate_super(sb);
-}
-
 static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
 				      struct cftype *cft)
 {
@@ -3944,7 +3244,7 @@ static struct cftype cgroup_base_files[] = {
 		.flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
 		.seq_show = cgroup_release_agent_show,
 		.write_string = cgroup_release_agent_write,
-		.max_write_len = PATH_MAX,
+		.max_write_len = PATH_MAX - 1,
 	},
 	{ }	/* terminate */
 };
@@ -3963,13 +3263,13 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 
 	/* process cftsets of each subsystem */
 	for_each_subsys(ss, i) {
-		struct cftype_set *set;
+		struct cftype *cfts;
 
 		if (!test_bit(i, &subsys_mask))
 			continue;
 
-		list_for_each_entry(set, &ss->cftsets, node) {
-			ret = cgroup_addrm_files(cgrp, set->cfts, true);
+		list_for_each_entry(cfts, &ss->cfts, node) {
+			ret = cgroup_addrm_files(cgrp, cfts, true);
 			if (ret < 0)
 				goto err;
 		}
@@ -4012,7 +3312,7 @@ static void css_free_work_fn(struct work_struct *work)
 		css_put(css->parent);
 
 	css->ss->css_free(css);
-	cgroup_dput(cgrp);
+	cgroup_put(cgrp);
 }
 
 static void css_free_rcu_fn(struct rcu_head *rcu_head)
@@ -4020,10 +3320,6 @@ static void css_free_rcu_fn(struct rcu_head *rcu_head)
 	struct cgroup_subsys_state *css =
 		container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
 
-	/*
-	 * css holds an extra ref to @cgrp->dentry which is put on the last
-	 * css_put().  dput() requires process context which we don't have.
-	 */
 	INIT_WORK(&css->destroy_work, css_free_work_fn);
 	queue_work(cgroup_destroy_wq, &css->destroy_work);
 }
@@ -4033,7 +3329,7 @@ static void css_release(struct percpu_ref *ref)
 	struct cgroup_subsys_state *css =
 		container_of(ref, struct cgroup_subsys_state, refcnt);
 
-	rcu_assign_pointer(css->cgroup->subsys[css->ss->subsys_id], NULL);
+	rcu_assign_pointer(css->cgroup->subsys[css->ss->id], NULL);
 	call_rcu(&css->rcu_head, css_free_rcu_fn);
 }
 
@@ -4058,6 +3354,7 @@ static int online_css(struct cgroup_subsys_state *css)
 	struct cgroup_subsys *ss = css->ss;
 	int ret = 0;
 
+	lockdep_assert_held(&cgroup_tree_mutex);
 	lockdep_assert_held(&cgroup_mutex);
 
 	if (ss->css_online)
@@ -4065,7 +3362,7 @@ static int online_css(struct cgroup_subsys_state *css)
 	if (!ret) {
 		css->flags |= CSS_ONLINE;
 		css->cgroup->nr_css++;
-		rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css);
+		rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
 	}
 	return ret;
 }
@@ -4075,6 +3372,7 @@ static void offline_css(struct cgroup_subsys_state *css)
 {
 	struct cgroup_subsys *ss = css->ss;
 
+	lockdep_assert_held(&cgroup_tree_mutex);
 	lockdep_assert_held(&cgroup_mutex);
 
 	if (!(css->flags & CSS_ONLINE))
@@ -4085,7 +3383,7 @@ static void offline_css(struct cgroup_subsys_state *css)
 
 	css->flags &= ~CSS_ONLINE;
 	css->cgroup->nr_css--;
-	RCU_INIT_POINTER(css->cgroup->subsys[ss->subsys_id], css);
+	RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css);
 }
 
 /**
@@ -4103,7 +3401,6 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
 	struct cgroup_subsys_state *css;
 	int err;
 
-	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
 	lockdep_assert_held(&cgroup_mutex);
 
 	css = ss->css_alloc(cgroup_css(parent, ss));
@@ -4116,7 +3413,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
 
 	init_css(css, ss, cgrp);
 
-	err = cgroup_populate_dir(cgrp, 1 << ss->subsys_id);
+	err = cgroup_populate_dir(cgrp, 1 << ss->id);
 	if (err)
 		goto err_free;
 
@@ -4124,7 +3421,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
 	if (err)
 		goto err_free;
 
-	dget(cgrp->dentry);
+	cgroup_get(cgrp);
 	css_get(css->parent);
 
 	if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
@@ -4144,35 +3441,27 @@ err_free:
 	return err;
 }
 
-/*
+/**
  * cgroup_create - create a cgroup
  * @parent: cgroup that will be parent of the new cgroup
- * @dentry: dentry of the new cgroup
- * @mode: mode to set on new inode
- *
- * Must be called with the mutex on the parent inode held
+ * @name: name of the new cgroup
+ * @mode: mode to set on new cgroup
  */
-static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
-			     umode_t mode)
+static long cgroup_create(struct cgroup *parent, const char *name,
+			  umode_t mode)
 {
 	struct cgroup *cgrp;
-	struct cgroup_name *name;
 	struct cgroupfs_root *root = parent->root;
 	int ssid, err;
 	struct cgroup_subsys *ss;
-	struct super_block *sb = root->sb;
+	struct kernfs_node *kn;
 
 	/* allocate the cgroup and its ID, 0 is reserved for the root */
 	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
 	if (!cgrp)
 		return -ENOMEM;
 
-	name = cgroup_alloc_name(dentry);
-	if (!name) {
-		err = -ENOMEM;
-		goto err_free_cgrp;
-	}
-	rcu_assign_pointer(cgrp->name, name);
+	mutex_lock(&cgroup_tree_mutex);
 
 	/*
 	 * Only live parents can have children.  Note that the liveliness
@@ -4183,7 +3472,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	 */
 	if (!cgroup_lock_live_group(parent)) {
 		err = -ENODEV;
-		goto err_free_name;
+		goto err_unlock_tree;
 	}
 
 	/*
@@ -4196,18 +3485,8 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 		goto err_unlock;
 	}
 
-	/* Grab a reference on the superblock so the hierarchy doesn't
-	 * get deleted on unmount if there are child cgroups.  This
-	 * can be done outside cgroup_mutex, since the sb can't
-	 * disappear while someone has an open control file on the
-	 * fs */
-	atomic_inc(&sb->s_active);
-
 	init_cgroup_housekeeping(cgrp);
 
-	dentry->d_fsdata = cgrp;
-	cgrp->dentry = dentry;
-
 	cgrp->parent = parent;
 	cgrp->dummy_css.parent = &parent->dummy_css;
 	cgrp->root = parent->root;
@@ -4218,24 +3497,26 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
 		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
 
+	/* create the directory */
+	kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
+	if (IS_ERR(kn)) {
+		err = PTR_ERR(kn);
+		goto err_free_id;
+	}
+	cgrp->kn = kn;
+
 	/*
-	 * Create directory.  cgroup_create_file() returns with the new
-	 * directory locked on success so that it can be populated without
-	 * dropping cgroup_mutex.
+	 * This extra ref will be put in cgroup_free_fn() and guarantees
+	 * that @cgrp->kn is always accessible.
 	 */
-	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
-	if (err < 0)
-		goto err_free_id;
-	lockdep_assert_held(&dentry->d_inode->i_mutex);
+	kernfs_get(kn);
 
 	cgrp->serial_nr = cgroup_serial_nr_next++;
 
 	/* allocation complete, commit to creation */
 	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
-	root->number_of_cgroups++;
-
-	/* hold a ref to the parent's dentry */
-	dget(parent->dentry);
+	atomic_inc(&root->nr_cgrps);
+	cgroup_get(parent);
 
 	/*
 	 * @cgrp is now fully operational.  If something fails after this
@@ -4256,36 +3537,35 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 		}
 	}
 
+	kernfs_activate(kn);
+
 	mutex_unlock(&cgroup_mutex);
-	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 
 	return 0;
 
 err_free_id:
 	idr_remove(&root->cgroup_idr, cgrp->id);
-	/* Release the reference count that we took on the superblock */
-	deactivate_super(sb);
 err_unlock:
 	mutex_unlock(&cgroup_mutex);
-err_free_name:
-	kfree(rcu_dereference_raw(cgrp->name));
-err_free_cgrp:
+err_unlock_tree:
+	mutex_unlock(&cgroup_tree_mutex);
 	kfree(cgrp);
 	return err;
 
 err_destroy:
 	cgroup_destroy_locked(cgrp);
 	mutex_unlock(&cgroup_mutex);
-	mutex_unlock(&dentry->d_inode->i_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 	return err;
 }
 
-static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
+			umode_t mode)
 {
-	struct cgroup *c_parent = dentry->d_parent->d_fsdata;
+	struct cgroup *parent = parent_kn->priv;
 
-	/* the vfs holds inode->i_mutex already */
-	return cgroup_create(c_parent, dentry, mode | S_IFDIR);
+	return cgroup_create(parent, name, mode);
 }
 
 /*
@@ -4298,6 +3578,7 @@ static void css_killed_work_fn(struct work_struct *work)
 		container_of(work, struct cgroup_subsys_state, destroy_work);
 	struct cgroup *cgrp = css->cgroup;
 
+	mutex_lock(&cgroup_tree_mutex);
 	mutex_lock(&cgroup_mutex);
 
 	/*
@@ -4315,6 +3596,7 @@ static void css_killed_work_fn(struct work_struct *work)
 		cgroup_destroy_css_killed(cgrp);
 
 	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 
 	/*
 	 * Put the css refs from kill_css().  Each css holds an extra
@@ -4347,7 +3629,11 @@ static void css_killed_ref_fn(struct percpu_ref *ref)
  */
 static void kill_css(struct cgroup_subsys_state *css)
 {
-	cgroup_clear_dir(css->cgroup, 1 << css->ss->subsys_id);
+	/*
+	 * This must happen before css is disassociated with its cgroup.
+	 * See seq_css() for details.
+	 */
+	cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
 
 	/*
 	 * Killing would put the base ref, but we need to keep it alive
@@ -4395,22 +3681,21 @@ static void kill_css(struct cgroup_subsys_state *css)
 static int cgroup_destroy_locked(struct cgroup *cgrp)
 	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
 {
-	struct dentry *d = cgrp->dentry;
-	struct cgroup_subsys_state *css;
 	struct cgroup *child;
+	struct cgroup_subsys_state *css;
 	bool empty;
 	int ssid;
 
-	lockdep_assert_held(&d->d_inode->i_mutex);
+	lockdep_assert_held(&cgroup_tree_mutex);
 	lockdep_assert_held(&cgroup_mutex);
 
 	/*
-	 * css_set_lock synchronizes access to ->cset_links and prevents
-	 * @cgrp from being removed while __put_css_set() is in progress.
+	 * css_set_rwsem synchronizes access to ->cset_links and prevents
+	 * @cgrp from being removed while put_css_set() is in progress.
 	 */
-	read_lock(&css_set_lock);
+	down_read(&css_set_rwsem);
 	empty = list_empty(&cgrp->cset_links);
-	read_unlock(&css_set_lock);
+	up_read(&css_set_rwsem);
 	if (!empty)
 		return -EBUSY;
 
@@ -4433,10 +3718,13 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 	/*
 	 * Initiate massacre of all css's.  cgroup_destroy_css_killed()
 	 * will be invoked to perform the rest of destruction once the
-	 * percpu refs of all css's are confirmed to be killed.
+	 * percpu refs of all css's are confirmed to be killed.  This
+	 * involves removing the subsystem's files, drop cgroup_mutex.
 	 */
+	mutex_unlock(&cgroup_mutex);
 	for_each_css(css, ssid, cgrp)
 		kill_css(css);
+	mutex_lock(&cgroup_mutex);
 
 	/*
 	 * Mark @cgrp dead.  This prevents further task migration and child
@@ -4462,14 +3750,20 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 	if (!cgrp->nr_css)
 		cgroup_destroy_css_killed(cgrp);
 
+	/* remove @cgrp directory along with the base files */
+	mutex_unlock(&cgroup_mutex);
+
 	/*
-	 * Clear the base files and remove @cgrp directory.  The removal
-	 * puts the base ref but we aren't quite done with @cgrp yet, so
-	 * hold onto it.
+	 * There are two control paths which try to determine cgroup from
+	 * dentry without going through kernfs - cgroupstats_build() and
+	 * css_tryget_from_dir().  Those are supported by RCU protecting
+	 * clearing of cgrp->kn->priv backpointer, which should happen
+	 * after all files under it have been removed.
 	 */
-	cgroup_addrm_files(cgrp, cgroup_base_files, false);
-	dget(d);
-	cgroup_d_remove_dir(d);
+	kernfs_remove(cgrp->kn);	/* @cgrp has an extra ref on its kn */
+	RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
+
+	mutex_lock(&cgroup_mutex);
 
 	return 0;
 };
@@ -4486,59 +3780,69 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 static void cgroup_destroy_css_killed(struct cgroup *cgrp)
 {
 	struct cgroup *parent = cgrp->parent;
-	struct dentry *d = cgrp->dentry;
 
+	lockdep_assert_held(&cgroup_tree_mutex);
 	lockdep_assert_held(&cgroup_mutex);
 
 	/* delete this cgroup from parent->children */
 	list_del_rcu(&cgrp->sibling);
 
-	dput(d);
+	cgroup_put(cgrp);
 
 	set_bit(CGRP_RELEASABLE, &parent->flags);
 	check_for_release(parent);
 }
 
-static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
+static int cgroup_rmdir(struct kernfs_node *kn)
 {
-	int ret;
-
-	mutex_lock(&cgroup_mutex);
-	ret = cgroup_destroy_locked(dentry->d_fsdata);
-	mutex_unlock(&cgroup_mutex);
+	struct cgroup *cgrp = kn->priv;
+	int ret = 0;
 
-	return ret;
-}
+	/*
+	 * This is self-destruction but @kn can't be removed while this
+	 * callback is in progress.  Let's break active protection.  Once
+	 * the protection is broken, @cgrp can be destroyed at any point.
+	 * Pin it so that it stays accessible.
+	 */
+	cgroup_get(cgrp);
+	kernfs_break_active_protection(kn);
 
-static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
-{
-	INIT_LIST_HEAD(&ss->cftsets);
+	mutex_lock(&cgroup_tree_mutex);
+	mutex_lock(&cgroup_mutex);
 
 	/*
-	 * base_cftset is embedded in subsys itself, no need to worry about
-	 * deregistration.
+	 * @cgrp might already have been destroyed while we're trying to
+	 * grab the mutexes.
 	 */
-	if (ss->base_cftypes) {
-		struct cftype *cft;
+	if (!cgroup_is_dead(cgrp))
+		ret = cgroup_destroy_locked(cgrp);
 
-		for (cft = ss->base_cftypes; cft->name[0] != '\0'; cft++)
-			cft->ss = ss;
+	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 
-		ss->base_cftset.cfts = ss->base_cftypes;
-		list_add_tail(&ss->base_cftset.node, &ss->cftsets);
-	}
+	kernfs_unbreak_active_protection(kn);
+	cgroup_put(cgrp);
+	return ret;
 }
 
+static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
+	.remount_fs		= cgroup_remount,
+	.show_options		= cgroup_show_options,
+	.mkdir			= cgroup_mkdir,
+	.rmdir			= cgroup_rmdir,
+	.rename			= cgroup_rename,
+};
+
 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 {
 	struct cgroup_subsys_state *css;
 
 	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
 
+	mutex_lock(&cgroup_tree_mutex);
 	mutex_lock(&cgroup_mutex);
 
-	/* init base cftset */
-	cgroup_init_cftsets(ss);
+	INIT_LIST_HEAD(&ss->cfts);
 
 	/* Create the top cgroup state for this subsystem */
 	ss->root = &cgroup_dummy_root;
@@ -4551,7 +3855,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 	 * pointer to this state - since the subsystem is
 	 * newly registered, all tasks and hence the
 	 * init_css_set is in the subsystem's top cgroup. */
-	init_css_set.subsys[ss->subsys_id] = css;
+	init_css_set.subsys[ss->id] = css;
 
 	need_forkexit_callback |= ss->fork || ss->exit;
 
@@ -4563,184 +3867,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 	BUG_ON(online_css(css));
 
 	mutex_unlock(&cgroup_mutex);
-
-	/* this function shouldn't be used with modular subsystems, since they
-	 * need to register a subsys_id, among other things */
-	BUG_ON(ss->module);
-}
-
-/**
- * cgroup_load_subsys: load and register a modular subsystem at runtime
- * @ss: the subsystem to load
- *
- * This function should be called in a modular subsystem's initcall. If the
- * subsystem is built as a module, it will be assigned a new subsys_id and set
- * up for use. If the subsystem is built-in anyway, work is delegated to the
- * simpler cgroup_init_subsys.
- */
-int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
-{
-	struct cgroup_subsys_state *css;
-	int i, ret;
-	struct hlist_node *tmp;
-	struct css_set *cset;
-	unsigned long key;
-
-	/* check name and function validity */
-	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
-	    ss->css_alloc == NULL || ss->css_free == NULL)
-		return -EINVAL;
-
-	/*
-	 * we don't support callbacks in modular subsystems. this check is
-	 * before the ss->module check for consistency; a subsystem that could
-	 * be a module should still have no callbacks even if the user isn't
-	 * compiling it as one.
-	 */
-	if (ss->fork || ss->exit)
-		return -EINVAL;
-
-	/*
-	 * an optionally modular subsystem is built-in: we want to do nothing,
-	 * since cgroup_init_subsys will have already taken care of it.
-	 */
-	if (ss->module == NULL) {
-		/* a sanity check */
-		BUG_ON(cgroup_subsys[ss->subsys_id] != ss);
-		return 0;
-	}
-
-	/* init base cftset */
-	cgroup_init_cftsets(ss);
-
-	mutex_lock(&cgroup_mutex);
-	mutex_lock(&cgroup_root_mutex);
-	cgroup_subsys[ss->subsys_id] = ss;
-
-	/*
-	 * no ss->css_alloc seems to need anything important in the ss
-	 * struct, so this can happen first (i.e. before the dummy root
-	 * attachment).
-	 */
-	css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss));
-	if (IS_ERR(css)) {
-		/* failure case - need to deassign the cgroup_subsys[] slot. */
-		cgroup_subsys[ss->subsys_id] = NULL;
-		mutex_unlock(&cgroup_root_mutex);
-		mutex_unlock(&cgroup_mutex);
-		return PTR_ERR(css);
-	}
-
-	ss->root = &cgroup_dummy_root;
-
-	/* our new subsystem will be attached to the dummy hierarchy. */
-	init_css(css, ss, cgroup_dummy_top);
-
-	/*
-	 * Now we need to entangle the css into the existing css_sets. unlike
-	 * in cgroup_init_subsys, there are now multiple css_sets, so each one
-	 * will need a new pointer to it; done by iterating the css_set_table.
-	 * furthermore, modifying the existing css_sets will corrupt the hash
-	 * table state, so each changed css_set will need its hash recomputed.
-	 * this is all done under the css_set_lock.
-	 */
-	write_lock(&css_set_lock);
-	hash_for_each_safe(css_set_table, i, tmp, cset, hlist) {
-		/* skip entries that we already rehashed */
-		if (cset->subsys[ss->subsys_id])
-			continue;
-		/* remove existing entry */
-		hash_del(&cset->hlist);
-		/* set new value */
-		cset->subsys[ss->subsys_id] = css;
-		/* recompute hash and restore entry */
-		key = css_set_hash(cset->subsys);
-		hash_add(css_set_table, &cset->hlist, key);
-	}
-	write_unlock(&css_set_lock);
-
-	ret = online_css(css);
-	if (ret) {
-		ss->css_free(css);
-		goto err_unload;
-	}
-
-	/* success! */
-	mutex_unlock(&cgroup_root_mutex);
-	mutex_unlock(&cgroup_mutex);
-	return 0;
-
-err_unload:
-	mutex_unlock(&cgroup_root_mutex);
-	mutex_unlock(&cgroup_mutex);
-	/* @ss can't be mounted here as try_module_get() would fail */
-	cgroup_unload_subsys(ss);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(cgroup_load_subsys);
-
-/**
- * cgroup_unload_subsys: unload a modular subsystem
- * @ss: the subsystem to unload
- *
- * This function should be called in a modular subsystem's exitcall. When this
- * function is invoked, the refcount on the subsystem's module will be 0, so
- * the subsystem will not be attached to any hierarchy.
- */
-void cgroup_unload_subsys(struct cgroup_subsys *ss)
-{
-	struct cgrp_cset_link *link;
-	struct cgroup_subsys_state *css;
-
-	BUG_ON(ss->module == NULL);
-
-	/*
-	 * we shouldn't be called if the subsystem is in use, and the use of
-	 * try_module_get() in rebind_subsystems() should ensure that it
-	 * doesn't start being used while we're killing it off.
-	 */
-	BUG_ON(ss->root != &cgroup_dummy_root);
-
-	mutex_lock(&cgroup_mutex);
-	mutex_lock(&cgroup_root_mutex);
-
-	css = cgroup_css(cgroup_dummy_top, ss);
-	if (css)
-		offline_css(css);
-
-	/* deassign the subsys_id */
-	cgroup_subsys[ss->subsys_id] = NULL;
-
-	/*
-	 * disentangle the css from all css_sets attached to the dummy
-	 * top. as in loading, we need to pay our respects to the hashtable
-	 * gods.
-	 */
-	write_lock(&css_set_lock);
-	list_for_each_entry(link, &cgroup_dummy_top->cset_links, cset_link) {
-		struct css_set *cset = link->cset;
-		unsigned long key;
-
-		hash_del(&cset->hlist);
-		cset->subsys[ss->subsys_id] = NULL;
-		key = css_set_hash(cset->subsys);
-		hash_add(css_set_table, &cset->hlist, key);
-	}
-	write_unlock(&css_set_lock);
-
-	/*
-	 * remove subsystem's css from the cgroup_dummy_top and free it -
-	 * need to free before marking as null because ss->css_free needs
-	 * the cgrp->subsys pointer to find their state.
-	 */
-	if (css)
-		ss->css_free(css);
-	RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL);
-
-	mutex_unlock(&cgroup_root_mutex);
-	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&cgroup_tree_mutex);
 }
-EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
 
 /**
  * cgroup_init_early - cgroup initialization at system boot
@@ -4767,17 +3895,16 @@ int __init cgroup_init_early(void)
 	list_add(&init_cgrp_cset_link.cset_link, &cgroup_dummy_top->cset_links);
 	list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);
 
-	/* at bootup time, we don't worry about modular subsystems */
-	for_each_builtin_subsys(ss, i) {
-		BUG_ON(!ss->name);
-		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
-		BUG_ON(!ss->css_alloc);
-		BUG_ON(!ss->css_free);
-		if (ss->subsys_id != i) {
-			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
-			       ss->name, ss->subsys_id);
-			BUG();
-		}
+	for_each_subsys(ss, i) {
+		WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
+		     "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
+		     i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
+		     ss->id, ss->name);
+		WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
+		     "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
+
+		ss->id = i;
+		ss->name = cgroup_subsys_name[i];
 
 		if (ss->early_init)
 			cgroup_init_subsys(ss);
@@ -4797,18 +3924,22 @@ int __init cgroup_init(void)
 	unsigned long key;
 	int i, err;
 
-	err = bdi_init(&cgroup_backing_dev_info);
-	if (err)
-		return err;
+	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
 
-	for_each_builtin_subsys(ss, i) {
+	for_each_subsys(ss, i) {
 		if (!ss->early_init)
 			cgroup_init_subsys(ss);
+
+		/*
+		 * cftype registration needs kmalloc and can't be done
+		 * during early_init.  Register base cftypes separately.
+		 */
+		if (ss->base_cftypes)
+			WARN_ON(cgroup_add_cftypes(ss, ss->base_cftypes));
 	}
 
 	/* allocate id for the dummy hierarchy */
 	mutex_lock(&cgroup_mutex);
-	mutex_lock(&cgroup_root_mutex);
 
 	/* Add init_css_set to the hash table */
 	key = css_set_hash(init_css_set.subsys);
@@ -4820,28 +3951,20 @@ int __init cgroup_init(void)
 			0, 1, GFP_KERNEL);
 	BUG_ON(err < 0);
 
-	mutex_unlock(&cgroup_root_mutex);
 	mutex_unlock(&cgroup_mutex);
 
 	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
-	if (!cgroup_kobj) {
-		err = -ENOMEM;
-		goto out;
-	}
+	if (!cgroup_kobj)
+		return -ENOMEM;
 
 	err = register_filesystem(&cgroup_fs_type);
 	if (err < 0) {
 		kobject_put(cgroup_kobj);
-		goto out;
+		return err;
 	}
 
 	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
-
-out:
-	if (err)
-		bdi_destroy(&cgroup_backing_dev_info);
-
-	return err;
+	return 0;
 }
 
 static int __init cgroup_wq_init(void)
@@ -4886,12 +4009,12 @@ int proc_cgroup_show(struct seq_file *m, void *v)
 {
 	struct pid *pid;
 	struct task_struct *tsk;
-	char *buf;
+	char *buf, *path;
 	int retval;
 	struct cgroupfs_root *root;
 
 	retval = -ENOMEM;
-	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	buf = kmalloc(PATH_MAX, GFP_KERNEL);
 	if (!buf)
 		goto out;
 
@@ -4904,6 +4027,7 @@ int proc_cgroup_show(struct seq_file *m, void *v)
 	retval = 0;
 
 	mutex_lock(&cgroup_mutex);
+	down_read(&css_set_rwsem);
 
 	for_each_active_root(root) {
 		struct cgroup_subsys *ss;
@@ -4919,14 +4043,17 @@ int proc_cgroup_show(struct seq_file *m, void *v)
 				   root->name);
 		seq_putc(m, ':');
 		cgrp = task_cgroup_from_root(tsk, root);
-		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
-		if (retval < 0)
+		path = cgroup_path(cgrp, buf, PATH_MAX);
+		if (!path) {
+			retval = -ENAMETOOLONG;
 			goto out_unlock;
-		seq_puts(m, buf);
+		}
+		seq_puts(m, path);
 		seq_putc(m, '\n');
 	}
 
 out_unlock:
+	up_read(&css_set_rwsem);
 	mutex_unlock(&cgroup_mutex);
 	put_task_struct(tsk);
 out_free:
@@ -4952,7 +4079,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
 	for_each_subsys(ss, i)
 		seq_printf(m, "%s\t%d\t%d\t%d\n",
 			   ss->name, ss->root->hierarchy_id,
-			   ss->root->number_of_cgroups, !ss->disabled);
+			   atomic_read(&ss->root->nr_cgrps), !ss->disabled);
 
 	mutex_unlock(&cgroup_mutex);
 	return 0;
@@ -5022,12 +4149,12 @@ void cgroup_post_fork(struct task_struct *child)
 	 * lock on fork.
 	 */
 	if (use_task_css_set_links) {
-		write_lock(&css_set_lock);
+		down_write(&css_set_rwsem);
 		task_lock(child);
 		if (list_empty(&child->cg_list))
 			list_add(&child->cg_list, &task_css_set(child)->tasks);
 		task_unlock(child);
-		write_unlock(&css_set_lock);
+		up_write(&css_set_rwsem);
 	}
 
 	/*
@@ -5036,15 +4163,7 @@ void cgroup_post_fork(struct task_struct *child)
 	 * and addition to css_set.
 	 */
 	if (need_forkexit_callback) {
-		/*
-		 * fork/exit callbacks are supported only for builtin
-		 * subsystems, and the builtin section of the subsys
-		 * array is immutable, so we don't need to lock the
-		 * subsys array here. On the other hand, modular section
-		 * of the array can be freed at module unload, so we
-		 * can't touch that.
-		 */
-		for_each_builtin_subsys(ss, i)
+		for_each_subsys(ss, i)
 			if (ss->fork)
 				ss->fork(child);
 	}
@@ -5092,15 +4211,14 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 	int i;
 
 	/*
-	 * Unlink from the css_set task list if necessary.
-	 * Optimistically check cg_list before taking
-	 * css_set_lock
+	 * Unlink from the css_set task list if necessary.  Optimistically
+	 * check cg_list before taking css_set_rwsem.
 	 */
 	if (!list_empty(&tsk->cg_list)) {
-		write_lock(&css_set_lock);
+		down_write(&css_set_rwsem);
 		if (!list_empty(&tsk->cg_list))
 			list_del_init(&tsk->cg_list);
-		write_unlock(&css_set_lock);
+		up_write(&css_set_rwsem);
 	}
 
 	/* Reassign the task to the init_css_set. */
@@ -5109,11 +4227,8 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 	RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
 
 	if (run_callbacks && need_forkexit_callback) {
-		/*
-		 * fork/exit callbacks are supported only for builtin
-		 * subsystems, see cgroup_post_fork() for details.
-		 */
-		for_each_builtin_subsys(ss, i) {
+		/* see cgroup_post_fork() for details */
+		for_each_subsys(ss, i) {
 			if (ss->exit) {
 				struct cgroup_subsys_state *old_css = cset->subsys[i];
 				struct cgroup_subsys_state *css = task_css(tsk, i);
@@ -5124,7 +4239,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 	}
 	task_unlock(tsk);
 
-	put_css_set_taskexit(cset);
+	put_css_set(cset, true);
 }
 
 static void check_for_release(struct cgroup *cgrp)
@@ -5181,16 +4296,17 @@ static void cgroup_release_agent(struct work_struct *work)
 	while (!list_empty(&release_list)) {
 		char *argv[3], *envp[3];
 		int i;
-		char *pathbuf = NULL, *agentbuf = NULL;
+		char *pathbuf = NULL, *agentbuf = NULL, *path;
 		struct cgroup *cgrp = list_entry(release_list.next,
 						    struct cgroup,
 						    release_list);
 		list_del_init(&cgrp->release_list);
 		raw_spin_unlock(&release_list_lock);
-		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+		pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 		if (!pathbuf)
 			goto continue_free;
-		if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
+		path = cgroup_path(cgrp, pathbuf, PATH_MAX);
+		if (!path)
 			goto continue_free;
 		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
 		if (!agentbuf)
@@ -5198,7 +4314,7 @@ static void cgroup_release_agent(struct work_struct *work)
 
 		i = 0;
 		argv[i++] = agentbuf;
-		argv[i++] = pathbuf;
+		argv[i++] = path;
 		argv[i] = NULL;
 
 		i = 0;
@@ -5232,11 +4348,7 @@ static int __init cgroup_disable(char *str)
 		if (!*token)
 			continue;
 
-		/*
-		 * cgroup_disable, being at boot time, can't know about
-		 * module subsystems, so we don't worry about them.
-		 */
-		for_each_builtin_subsys(ss, i) {
+		for_each_subsys(ss, i) {
 			if (!strcmp(token, ss->name)) {
 				ss->disabled = 1;
 				printk(KERN_INFO "Disabling %s control group"
@@ -5250,28 +4362,42 @@ static int __init cgroup_disable(char *str)
 __setup("cgroup_disable=", cgroup_disable);
 
 /**
- * css_from_dir - get corresponding css from the dentry of a cgroup dir
+ * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir
  * @dentry: directory dentry of interest
  * @ss: subsystem of interest
  *
- * Must be called under cgroup_mutex or RCU read lock.  The caller is
- * responsible for pinning the returned css if it needs to be accessed
- * outside the critical section.
+ * If @dentry is a directory for a cgroup which has @ss enabled on it, try
+ * to get the corresponding css and return it.  If such css doesn't exist
+ * or can't be pinned, an ERR_PTR value is returned.
  */
-struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
-					 struct cgroup_subsys *ss)
+struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry,
+						struct cgroup_subsys *ss)
 {
+	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
+	struct cgroup_subsys_state *css = NULL;
 	struct cgroup *cgrp;
 
-	cgroup_assert_mutex_or_rcu_locked();
-
 	/* is @dentry a cgroup dir? */
-	if (!dentry->d_inode ||
-	    dentry->d_inode->i_op != &cgroup_dir_inode_operations)
+	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
+	    kernfs_type(kn) != KERNFS_DIR)
 		return ERR_PTR(-EBADF);
 
-	cgrp = __d_cgrp(dentry);
-	return cgroup_css(cgrp, ss) ?: ERR_PTR(-ENOENT);
+	rcu_read_lock();
+
+	/*
+	 * This path doesn't originate from kernfs and @kn could already
+	 * have been or be removed at any point.  @kn->priv is RCU
+	 * protected for this access.  See destroy_locked() for details.
+	 */
+	cgrp = rcu_dereference(kn->priv);
+	if (cgrp)
+		css = cgroup_css(cgrp, ss);
+
+	if (!css || !css_tryget(css))
+		css = ERR_PTR(-ENOENT);
+
+	rcu_read_unlock();
+	return css;
 }
 
 /**
@@ -5286,7 +4412,7 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
 {
 	struct cgroup *cgrp;
 
-	cgroup_assert_mutex_or_rcu_locked();
+	cgroup_assert_mutexes_or_rcu_locked();
 
 	cgrp = idr_find(&ss->root->cgroup_idr, id);
 	if (cgrp)
@@ -5338,23 +4464,30 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
 {
 	struct cgrp_cset_link *link;
 	struct css_set *cset;
+	char *name_buf;
+
+	name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+	if (!name_buf)
+		return -ENOMEM;
 
-	read_lock(&css_set_lock);
+	down_read(&css_set_rwsem);
 	rcu_read_lock();
 	cset = rcu_dereference(current->cgroups);
 	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
 		struct cgroup *c = link->cgrp;
-		const char *name;
+		const char *name = "?";
+
+		if (c != cgroup_dummy_top) {
+			cgroup_name(c, name_buf, NAME_MAX + 1);
+			name = name_buf;
+		}
 
-		if (c->dentry)
-			name = c->dentry->d_name.name;
-		else
-			name = "?";
 		seq_printf(seq, "Root %d group %s\n",
 			   c->root->hierarchy_id, name);
 	}
 	rcu_read_unlock();
-	read_unlock(&css_set_lock);
+	up_read(&css_set_rwsem);
+	kfree(name_buf);
 	return 0;
 }
 
@@ -5364,7 +4497,7 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
 	struct cgroup_subsys_state *css = seq_css(seq);
 	struct cgrp_cset_link *link;
 
-	read_lock(&css_set_lock);
+	down_read(&css_set_rwsem);
 	list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
 		struct css_set *cset = link->cset;
 		struct task_struct *task;
@@ -5380,7 +4513,7 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
 			}
 		}
 	}
-	read_unlock(&css_set_lock);
+	up_read(&css_set_rwsem);
 	return 0;
 }
 
@@ -5423,11 +4556,9 @@ static struct cftype debug_files[] =  {
 	{ }	/* terminate */
 };
 
-struct cgroup_subsys debug_subsys = {
-	.name = "debug",
+struct cgroup_subsys debug_cgrp_subsys = {
 	.css_alloc = debug_css_alloc,
 	.css_free = debug_css_free,
-	.subsys_id = debug_subsys_id,
 	.base_cftypes = debug_files,
 };
 #endif /* CONFIG_CGROUP_DEBUG */
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 6c3154e477f6..7201a637c405 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -52,7 +52,7 @@ static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
 
 static inline struct freezer *task_freezer(struct task_struct *task)
 {
-	return css_freezer(task_css(task, freezer_subsys_id));
+	return css_freezer(task_css(task, freezer_cgrp_id));
 }
 
 static struct freezer *parent_freezer(struct freezer *freezer)
@@ -84,8 +84,6 @@ static const char *freezer_state_strs(unsigned int state)
 	return "THAWED";
 };
 
-struct cgroup_subsys freezer_subsys;
-
 static struct cgroup_subsys_state *
 freezer_css_alloc(struct cgroup_subsys_state *parent_css)
 {
@@ -189,7 +187,7 @@ static void freezer_attach(struct cgroup_subsys_state *new_css,
 	 * current state before executing the following - !frozen tasks may
 	 * be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
 	 */
-	cgroup_taskset_for_each(task, new_css, tset) {
+	cgroup_taskset_for_each(task, tset) {
 		if (!(freezer->state & CGROUP_FREEZING)) {
 			__thaw_task(task);
 		} else {
@@ -473,13 +471,11 @@ static struct cftype files[] = {
 	{ }	/* terminate */
 };
 
-struct cgroup_subsys freezer_subsys = {
-	.name		= "freezer",
+struct cgroup_subsys freezer_cgrp_subsys = {
 	.css_alloc	= freezer_css_alloc,
 	.css_online	= freezer_css_online,
 	.css_offline	= freezer_css_offline,
 	.css_free	= freezer_css_free,
-	.subsys_id	= freezer_subsys_id,
 	.attach		= freezer_attach,
 	.fork		= freezer_fork,
 	.base_cftypes	= files,
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 4410ac6a55f1..d8bec21d7a11 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -119,7 +119,7 @@ static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
 /* Retrieve the cpuset for a task */
 static inline struct cpuset *task_cs(struct task_struct *task)
 {
-	return css_cs(task_css(task, cpuset_subsys_id));
+	return css_cs(task_css(task, cpuset_cgrp_id));
 }
 
 static inline struct cpuset *parent_cs(struct cpuset *cs)
@@ -467,7 +467,7 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
 	 * be changed to have empty cpus_allowed or mems_allowed.
 	 */
 	ret = -ENOSPC;
-	if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress)) {
+	if ((cgroup_has_tasks(cur->css.cgroup) || cur->attach_in_progress)) {
 		if (!cpumask_empty(cur->cpus_allowed) &&
 		    cpumask_empty(trial->cpus_allowed))
 			goto out;
@@ -829,55 +829,36 @@ static struct cpuset *effective_nodemask_cpuset(struct cpuset *cs)
 }
 
 /**
- * cpuset_change_cpumask - make a task's cpus_allowed the same as its cpuset's
- * @tsk: task to test
- * @data: cpuset to @tsk belongs to
- *
- * Called by css_scan_tasks() for each task in a cgroup whose cpus_allowed
- * mask needs to be changed.
- *
- * We don't need to re-check for the cgroup/cpuset membership, since we're
- * holding cpuset_mutex at this point.
- */
-static void cpuset_change_cpumask(struct task_struct *tsk, void *data)
-{
-	struct cpuset *cs = data;
-	struct cpuset *cpus_cs = effective_cpumask_cpuset(cs);
-
-	set_cpus_allowed_ptr(tsk, cpus_cs->cpus_allowed);
-}
-
-/**
  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
- * @heap: if NULL, defer allocating heap memory to css_scan_tasks()
  *
- * Called with cpuset_mutex held
- *
- * The css_scan_tasks() function will scan all the tasks in a cgroup,
- * calling callback functions for each.
- *
- * No return value. It's guaranteed that css_scan_tasks() always returns 0
- * if @heap != NULL.
+ * Iterate through each task of @cs updating its cpus_allowed to the
+ * effective cpuset's.  As this function is called with cpuset_mutex held,
+ * cpuset membership stays stable.
  */
-static void update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
+static void update_tasks_cpumask(struct cpuset *cs)
 {
-	css_scan_tasks(&cs->css, NULL, cpuset_change_cpumask, cs, heap);
+	struct cpuset *cpus_cs = effective_cpumask_cpuset(cs);
+	struct css_task_iter it;
+	struct task_struct *task;
+
+	css_task_iter_start(&cs->css, &it);
+	while ((task = css_task_iter_next(&it)))
+		set_cpus_allowed_ptr(task, cpus_cs->cpus_allowed);
+	css_task_iter_end(&it);
 }
 
 /*
  * update_tasks_cpumask_hier - Update the cpumasks of tasks in the hierarchy.
  * @root_cs: the root cpuset of the hierarchy
  * @update_root: update root cpuset or not?
- * @heap: the heap used by css_scan_tasks()
  *
  * This will update cpumasks of tasks in @root_cs and all other empty cpusets
  * which take on cpumask of @root_cs.
  *
  * Called with cpuset_mutex held
  */
-static void update_tasks_cpumask_hier(struct cpuset *root_cs,
-				      bool update_root, struct ptr_heap *heap)
+static void update_tasks_cpumask_hier(struct cpuset *root_cs, bool update_root)
 {
 	struct cpuset *cp;
 	struct cgroup_subsys_state *pos_css;
@@ -898,7 +879,7 @@ static void update_tasks_cpumask_hier(struct cpuset *root_cs,
 			continue;
 		rcu_read_unlock();
 
-		update_tasks_cpumask(cp, heap);
+		update_tasks_cpumask(cp);
 
 		rcu_read_lock();
 		css_put(&cp->css);
@@ -914,7 +895,6 @@ static void update_tasks_cpumask_hier(struct cpuset *root_cs,
 static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 			  const char *buf)
 {
-	struct ptr_heap heap;
 	int retval;
 	int is_load_balanced;
 
@@ -947,19 +927,13 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 	if (retval < 0)
 		return retval;
 
-	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
-	if (retval)
-		return retval;
-
 	is_load_balanced = is_sched_load_balance(trialcs);
 
 	mutex_lock(&callback_mutex);
 	cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
 	mutex_unlock(&callback_mutex);
 
-	update_tasks_cpumask_hier(cs, true, &heap);
-
-	heap_free(&heap);
+	update_tasks_cpumask_hier(cs, true);
 
 	if (is_load_balanced)
 		rebuild_sched_domains_locked();
@@ -1052,53 +1026,22 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk,
 	task_unlock(tsk);
 }
 
-struct cpuset_change_nodemask_arg {
-	struct cpuset		*cs;
-	nodemask_t		*newmems;
-};
-
-/*
- * Update task's mems_allowed and rebind its mempolicy and vmas' mempolicy
- * of it to cpuset's new mems_allowed, and migrate pages to new nodes if
- * memory_migrate flag is set. Called with cpuset_mutex held.
- */
-static void cpuset_change_nodemask(struct task_struct *p, void *data)
-{
-	struct cpuset_change_nodemask_arg *arg = data;
-	struct cpuset *cs = arg->cs;
-	struct mm_struct *mm;
-	int migrate;
-
-	cpuset_change_task_nodemask(p, arg->newmems);
-
-	mm = get_task_mm(p);
-	if (!mm)
-		return;
-
-	migrate = is_memory_migrate(cs);
-
-	mpol_rebind_mm(mm, &cs->mems_allowed);
-	if (migrate)
-		cpuset_migrate_mm(mm, &cs->old_mems_allowed, arg->newmems);
-	mmput(mm);
-}
-
 static void *cpuset_being_rebound;
 
 /**
  * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
  * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
- * @heap: if NULL, defer allocating heap memory to css_scan_tasks()
  *
- * Called with cpuset_mutex held.  No return value. It's guaranteed that
- * css_scan_tasks() always returns 0 if @heap != NULL.
+ * Iterate through each task of @cs updating its mems_allowed to the
+ * effective cpuset's.  As this function is called with cpuset_mutex held,
+ * cpuset membership stays stable.
  */
-static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
+static void update_tasks_nodemask(struct cpuset *cs)
 {
 	static nodemask_t newmems;	/* protected by cpuset_mutex */
 	struct cpuset *mems_cs = effective_nodemask_cpuset(cs);
-	struct cpuset_change_nodemask_arg arg = { .cs = cs,
-						  .newmems = &newmems };
+	struct css_task_iter it;
+	struct task_struct *task;
 
 	cpuset_being_rebound = cs;		/* causes mpol_dup() rebind */
 
@@ -1114,7 +1057,25 @@ static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
 	 * It's ok if we rebind the same mm twice; mpol_rebind_mm()
 	 * is idempotent.  Also migrate pages in each mm to new nodes.
 	 */
-	css_scan_tasks(&cs->css, NULL, cpuset_change_nodemask, &arg, heap);
+	css_task_iter_start(&cs->css, &it);
+	while ((task = css_task_iter_next(&it))) {
+		struct mm_struct *mm;
+		bool migrate;
+
+		cpuset_change_task_nodemask(task, &newmems);
+
+		mm = get_task_mm(task);
+		if (!mm)
+			continue;
+
+		migrate = is_memory_migrate(cs);
+
+		mpol_rebind_mm(mm, &cs->mems_allowed);
+		if (migrate)
+			cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
+		mmput(mm);
+	}
+	css_task_iter_end(&it);
 
 	/*
 	 * All the tasks' nodemasks have been updated, update
@@ -1130,15 +1091,13 @@ static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
  * update_tasks_nodemask_hier - Update the nodemasks of tasks in the hierarchy.
  * @cs: the root cpuset of the hierarchy
  * @update_root: update the root cpuset or not?
- * @heap: the heap used by css_scan_tasks()
  *
  * This will update nodemasks of tasks in @root_cs and all other empty cpusets
  * which take on nodemask of @root_cs.
  *
  * Called with cpuset_mutex held
  */
-static void update_tasks_nodemask_hier(struct cpuset *root_cs,
-				       bool update_root, struct ptr_heap *heap)
+static void update_tasks_nodemask_hier(struct cpuset *root_cs, bool update_root)
 {
 	struct cpuset *cp;
 	struct cgroup_subsys_state *pos_css;
@@ -1159,7 +1118,7 @@ static void update_tasks_nodemask_hier(struct cpuset *root_cs,
 			continue;
 		rcu_read_unlock();
 
-		update_tasks_nodemask(cp, heap);
+		update_tasks_nodemask(cp);
 
 		rcu_read_lock();
 		css_put(&cp->css);
@@ -1184,7 +1143,6 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
 			   const char *buf)
 {
 	int retval;
-	struct ptr_heap heap;
 
 	/*
 	 * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
@@ -1223,17 +1181,11 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
 	if (retval < 0)
 		goto done;
 
-	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
-	if (retval < 0)
-		goto done;
-
 	mutex_lock(&callback_mutex);
 	cs->mems_allowed = trialcs->mems_allowed;
 	mutex_unlock(&callback_mutex);
 
-	update_tasks_nodemask_hier(cs, true, &heap);
-
-	heap_free(&heap);
+	update_tasks_nodemask_hier(cs, true);
 done:
 	return retval;
 }
@@ -1261,38 +1213,22 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val)
 }
 
 /**
- * cpuset_change_flag - make a task's spread flags the same as its cpuset's
- * @tsk: task to be updated
- * @data: cpuset to @tsk belongs to
- *
- * Called by css_scan_tasks() for each task in a cgroup.
- *
- * We don't need to re-check for the cgroup/cpuset membership, since we're
- * holding cpuset_mutex at this point.
- */
-static void cpuset_change_flag(struct task_struct *tsk, void *data)
-{
-	struct cpuset *cs = data;
-
-	cpuset_update_task_spread_flag(cs, tsk);
-}
-
-/**
  * update_tasks_flags - update the spread flags of tasks in the cpuset.
  * @cs: the cpuset in which each task's spread flags needs to be changed
- * @heap: if NULL, defer allocating heap memory to css_scan_tasks()
- *
- * Called with cpuset_mutex held
- *
- * The css_scan_tasks() function will scan all the tasks in a cgroup,
- * calling callback functions for each.
  *
- * No return value. It's guaranteed that css_scan_tasks() always returns 0
- * if @heap != NULL.
+ * Iterate through each task of @cs updating its spread flags.  As this
+ * function is called with cpuset_mutex held, cpuset membership stays
+ * stable.
  */
-static void update_tasks_flags(struct cpuset *cs, struct ptr_heap *heap)
+static void update_tasks_flags(struct cpuset *cs)
 {
-	css_scan_tasks(&cs->css, NULL, cpuset_change_flag, cs, heap);
+	struct css_task_iter it;
+	struct task_struct *task;
+
+	css_task_iter_start(&cs->css, &it);
+	while ((task = css_task_iter_next(&it)))
+		cpuset_update_task_spread_flag(cs, task);
+	css_task_iter_end(&it);
 }
 
 /*
@@ -1310,7 +1246,6 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
 	struct cpuset *trialcs;
 	int balance_flag_changed;
 	int spread_flag_changed;
-	struct ptr_heap heap;
 	int err;
 
 	trialcs = alloc_trial_cpuset(cs);
@@ -1326,10 +1261,6 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
 	if (err < 0)
 		goto out;
 
-	err = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
-	if (err < 0)
-		goto out;
-
 	balance_flag_changed = (is_sched_load_balance(cs) !=
 				is_sched_load_balance(trialcs));
 
@@ -1344,8 +1275,7 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
 		rebuild_sched_domains_locked();
 
 	if (spread_flag_changed)
-		update_tasks_flags(cs, &heap);
-	heap_free(&heap);
+		update_tasks_flags(cs);
 out:
 	free_trial_cpuset(trialcs);
 	return err;
@@ -1449,6 +1379,8 @@ static int fmeter_getrate(struct fmeter *fmp)
 	return val;
 }
 
+static struct cpuset *cpuset_attach_old_cs;
+
 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
 static int cpuset_can_attach(struct cgroup_subsys_state *css,
 			     struct cgroup_taskset *tset)
@@ -1457,6 +1389,9 @@ static int cpuset_can_attach(struct cgroup_subsys_state *css,
 	struct task_struct *task;
 	int ret;
 
+	/* used later by cpuset_attach() */
+	cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset));
+
 	mutex_lock(&cpuset_mutex);
 
 	/*
@@ -1468,7 +1403,7 @@ static int cpuset_can_attach(struct cgroup_subsys_state *css,
 	    (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
 		goto out_unlock;
 
-	cgroup_taskset_for_each(task, css, tset) {
+	cgroup_taskset_for_each(task, tset) {
 		/*
 		 * Kthreads which disallow setaffinity shouldn't be moved
 		 * to a new cpuset; we don't want to change their cpu
@@ -1520,10 +1455,8 @@ static void cpuset_attach(struct cgroup_subsys_state *css,
 	struct mm_struct *mm;
 	struct task_struct *task;
 	struct task_struct *leader = cgroup_taskset_first(tset);
-	struct cgroup_subsys_state *oldcss = cgroup_taskset_cur_css(tset,
-							cpuset_subsys_id);
 	struct cpuset *cs = css_cs(css);
-	struct cpuset *oldcs = css_cs(oldcss);
+	struct cpuset *oldcs = cpuset_attach_old_cs;
 	struct cpuset *cpus_cs = effective_cpumask_cpuset(cs);
 	struct cpuset *mems_cs = effective_nodemask_cpuset(cs);
 
@@ -1537,7 +1470,7 @@ static void cpuset_attach(struct cgroup_subsys_state *css,
 
 	guarantee_online_mems(mems_cs, &cpuset_attach_nodemask_to);
 
-	cgroup_taskset_for_each(task, css, tset) {
+	cgroup_taskset_for_each(task, tset) {
 		/*
 		 * can_attach beforehand should guarantee that this doesn't
 		 * fail.  TODO: have a better way to handle failure here
@@ -2024,8 +1957,7 @@ static void cpuset_css_free(struct cgroup_subsys_state *css)
 	kfree(cs);
 }
 
-struct cgroup_subsys cpuset_subsys = {
-	.name = "cpuset",
+struct cgroup_subsys cpuset_cgrp_subsys = {
 	.css_alloc = cpuset_css_alloc,
 	.css_online = cpuset_css_online,
 	.css_offline = cpuset_css_offline,
@@ -2033,7 +1965,6 @@ struct cgroup_subsys cpuset_subsys = {
 	.can_attach = cpuset_can_attach,
 	.cancel_attach = cpuset_cancel_attach,
 	.attach = cpuset_attach,
-	.subsys_id = cpuset_subsys_id,
 	.base_cftypes = files,
 	.early_init = 1,
 };
@@ -2090,10 +2021,9 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
 		parent = parent_cs(parent);
 
 	if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
-		rcu_read_lock();
-		printk(KERN_ERR "cpuset: failed to transfer tasks out of empty cpuset %s\n",
-		       cgroup_name(cs->css.cgroup));
-		rcu_read_unlock();
+		printk(KERN_ERR "cpuset: failed to transfer tasks out of empty cpuset ");
+		pr_cont_cgroup_name(cs->css.cgroup);
+		pr_cont("\n");
 	}
 }
 
@@ -2141,7 +2071,7 @@ retry:
 	 */
 	if ((sane && cpumask_empty(cs->cpus_allowed)) ||
 	    (!cpumask_empty(&off_cpus) && !cpumask_empty(cs->cpus_allowed)))
-		update_tasks_cpumask(cs, NULL);
+		update_tasks_cpumask(cs);
 
 	mutex_lock(&callback_mutex);
 	nodes_andnot(cs->mems_allowed, cs->mems_allowed, off_mems);
@@ -2155,7 +2085,7 @@ retry:
 	 */
 	if ((sane && nodes_empty(cs->mems_allowed)) ||
 	    (!nodes_empty(off_mems) && !nodes_empty(cs->mems_allowed)))
-		update_tasks_nodemask(cs, NULL);
+		update_tasks_nodemask(cs);
 
 	is_empty = cpumask_empty(cs->cpus_allowed) ||
 		nodes_empty(cs->mems_allowed);
@@ -2217,7 +2147,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
 		mutex_lock(&callback_mutex);
 		top_cpuset.mems_allowed = new_mems;
 		mutex_unlock(&callback_mutex);
-		update_tasks_nodemask(&top_cpuset, NULL);
+		update_tasks_nodemask(&top_cpuset);
 	}
 
 	mutex_unlock(&cpuset_mutex);
@@ -2621,19 +2551,17 @@ void cpuset_print_task_mems_allowed(struct task_struct *tsk)
 	 /* Statically allocated to prevent using excess stack. */
 	static char cpuset_nodelist[CPUSET_NODELIST_LEN];
 	static DEFINE_SPINLOCK(cpuset_buffer_lock);
-
 	struct cgroup *cgrp = task_cs(tsk)->css.cgroup;
 
-	rcu_read_lock();
 	spin_lock(&cpuset_buffer_lock);
 
 	nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN,
 			   tsk->mems_allowed);
-	printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n",
-	       tsk->comm, cgroup_name(cgrp), cpuset_nodelist);
+	printk(KERN_INFO "%s cpuset=", tsk->comm);
+	pr_cont_cgroup_name(cgrp);
+	pr_cont(" mems_allowed=%s\n", cpuset_nodelist);
 
 	spin_unlock(&cpuset_buffer_lock);
-	rcu_read_unlock();
 }
 
 /*
@@ -2683,12 +2611,12 @@ int proc_cpuset_show(struct seq_file *m, void *unused_v)
 {
 	struct pid *pid;
 	struct task_struct *tsk;
-	char *buf;
+	char *buf, *p;
 	struct cgroup_subsys_state *css;
 	int retval;
 
 	retval = -ENOMEM;
-	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	buf = kmalloc(PATH_MAX, GFP_KERNEL);
 	if (!buf)
 		goto out;
 
@@ -2698,14 +2626,16 @@ int proc_cpuset_show(struct seq_file *m, void *unused_v)
 	if (!tsk)
 		goto out_free;
 
+	retval = -ENAMETOOLONG;
 	rcu_read_lock();
-	css = task_css(tsk, cpuset_subsys_id);
-	retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
+	css = task_css(tsk, cpuset_cgrp_id);
+	p = cgroup_path(css->cgroup, buf, PATH_MAX);
 	rcu_read_unlock();
-	if (retval < 0)
+	if (!p)
 		goto out_put_task;
-	seq_puts(m, buf);
+	seq_puts(m, p);
 	seq_putc(m, '\n');
+	retval = 0;
 out_put_task:
 	put_task_struct(tsk);
 out_free:
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 45e5543e2a1e..1bc932a8a263 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -361,7 +361,7 @@ struct perf_cgroup {
 static inline struct perf_cgroup *
 perf_cgroup_from_task(struct task_struct *task)
 {
-	return container_of(task_css(task, perf_subsys_id),
+	return container_of(task_css(task, perf_event_cgrp_id),
 			    struct perf_cgroup, css);
 }
 
@@ -389,11 +389,6 @@ perf_cgroup_match(struct perf_event *event)
 				    event->cgrp->css.cgroup);
 }
 
-static inline bool perf_tryget_cgroup(struct perf_event *event)
-{
-	return css_tryget(&event->cgrp->css);
-}
-
 static inline void perf_put_cgroup(struct perf_event *event)
 {
 	css_put(&event->cgrp->css);
@@ -612,9 +607,7 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 	if (!f.file)
 		return -EBADF;
 
-	rcu_read_lock();
-
-	css = css_from_dir(f.file->f_dentry, &perf_subsys);
+	css = css_tryget_from_dir(f.file->f_dentry, &perf_event_cgrp_subsys);
 	if (IS_ERR(css)) {
 		ret = PTR_ERR(css);
 		goto out;
@@ -623,13 +616,6 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 	cgrp = container_of(css, struct perf_cgroup, css);
 	event->cgrp = cgrp;
 
-	/* must be done before we fput() the file */
-	if (!perf_tryget_cgroup(event)) {
-		event->cgrp = NULL;
-		ret = -ENOENT;
-		goto out;
-	}
-
 	/*
 	 * all events in a group must monitor
 	 * the same cgroup because a task belongs
@@ -640,7 +626,6 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 		ret = -EINVAL;
 	}
 out:
-	rcu_read_unlock();
 	fdput(f);
 	return ret;
 }
@@ -8055,7 +8040,7 @@ static void perf_cgroup_attach(struct cgroup_subsys_state *css,
 {
 	struct task_struct *task;
 
-	cgroup_taskset_for_each(task, css, tset)
+	cgroup_taskset_for_each(task, tset)
 		task_function_call(task, __perf_cgroup_move, task);
 }
 
@@ -8074,9 +8059,7 @@ static void perf_cgroup_exit(struct cgroup_subsys_state *css,
 	task_function_call(task, __perf_cgroup_move, task);
 }
 
-struct cgroup_subsys perf_subsys = {
-	.name		= "perf_event",
-	.subsys_id	= perf_subsys_id,
+struct cgroup_subsys perf_event_cgrp_subsys = {
 	.css_alloc	= perf_cgroup_css_alloc,
 	.css_free	= perf_cgroup_css_free,
 	.exit		= perf_cgroup_exit,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 633d0456868c..9684848f3bf2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7214,7 +7214,7 @@ void sched_move_task(struct task_struct *tsk)
 	if (unlikely(running))
 		tsk->sched_class->put_prev_task(rq, tsk);
 
-	tg = container_of(task_css_check(tsk, cpu_cgroup_subsys_id,
+	tg = container_of(task_css_check(tsk, cpu_cgrp_id,
 				lockdep_is_held(&tsk->sighand->siglock)),
 			  struct task_group, css);
 	tg = autogroup_task_group(tsk, tg);
@@ -7641,7 +7641,7 @@ static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css,
 {
 	struct task_struct *task;
 
-	cgroup_taskset_for_each(task, css, tset) {
+	cgroup_taskset_for_each(task, tset) {
 #ifdef CONFIG_RT_GROUP_SCHED
 		if (!sched_rt_can_attach(css_tg(css), task))
 			return -EINVAL;
@@ -7659,7 +7659,7 @@ static void cpu_cgroup_attach(struct cgroup_subsys_state *css,
 {
 	struct task_struct *task;
 
-	cgroup_taskset_for_each(task, css, tset)
+	cgroup_taskset_for_each(task, tset)
 		sched_move_task(task);
 }
 
@@ -7998,8 +7998,7 @@ static struct cftype cpu_files[] = {
 	{ }	/* terminate */
 };
 
-struct cgroup_subsys cpu_cgroup_subsys = {
-	.name		= "cpu",
+struct cgroup_subsys cpu_cgrp_subsys = {
 	.css_alloc	= cpu_cgroup_css_alloc,
 	.css_free	= cpu_cgroup_css_free,
 	.css_online	= cpu_cgroup_css_online,
@@ -8007,7 +8006,6 @@ struct cgroup_subsys cpu_cgroup_subsys = {
 	.can_attach	= cpu_cgroup_can_attach,
 	.attach		= cpu_cgroup_attach,
 	.exit		= cpu_cgroup_exit,
-	.subsys_id	= cpu_cgroup_subsys_id,
 	.base_cftypes	= cpu_files,
 	.early_init	= 1,
 };
diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 622e0818f905..c143ee380e3a 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -41,7 +41,7 @@ static inline struct cpuacct *css_ca(struct cgroup_subsys_state *css)
 /* return cpu accounting group to which this task belongs */
 static inline struct cpuacct *task_ca(struct task_struct *tsk)
 {
-	return css_ca(task_css(tsk, cpuacct_subsys_id));
+	return css_ca(task_css(tsk, cpuacct_cgrp_id));
 }
 
 static inline struct cpuacct *parent_ca(struct cpuacct *ca)
@@ -275,11 +275,9 @@ void cpuacct_account_field(struct task_struct *p, int index, u64 val)
 	rcu_read_unlock();
 }
 
-struct cgroup_subsys cpuacct_subsys = {
-	.name		= "cpuacct",
+struct cgroup_subsys cpuacct_cgrp_subsys = {
 	.css_alloc	= cpuacct_css_alloc,
 	.css_free	= cpuacct_css_free,
-	.subsys_id	= cpuacct_subsys_id,
 	.base_cftypes	= files,
 	.early_init	= 1,
 };
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index f3344c31632a..695f9773bb60 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -111,8 +111,7 @@ static char *task_group_path(struct task_group *tg)
 	if (autogroup_path(tg, group_path, PATH_MAX))
 		return group_path;
 
-	cgroup_path(tg->css.cgroup, group_path, PATH_MAX);
-	return group_path;
+	return cgroup_path(tg->css.cgroup, group_path, PATH_MAX);
 }
 #endif
 
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index cb00829bb466..b135853e68f3 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -30,7 +30,6 @@ struct hugetlb_cgroup {
 #define MEMFILE_IDX(val)	(((val) >> 16) & 0xffff)
 #define MEMFILE_ATTR(val)	((val) & 0xffff)
 
-struct cgroup_subsys hugetlb_subsys __read_mostly;
 static struct hugetlb_cgroup *root_h_cgroup __read_mostly;
 
 static inline
@@ -42,7 +41,7 @@ struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
 static inline
 struct hugetlb_cgroup *hugetlb_cgroup_from_task(struct task_struct *task)
 {
-	return hugetlb_cgroup_from_css(task_css(task, hugetlb_subsys_id));
+	return hugetlb_cgroup_from_css(task_css(task, hugetlb_cgrp_id));
 }
 
 static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg)
@@ -358,7 +357,7 @@ static void __init __hugetlb_cgroup_file_init(int idx)
 	cft = &h->cgroup_files[4];
 	memset(cft, 0, sizeof(*cft));
 
-	WARN_ON(cgroup_add_cftypes(&hugetlb_subsys, h->cgroup_files));
+	WARN_ON(cgroup_add_cftypes(&hugetlb_cgrp_subsys, h->cgroup_files));
 
 	return;
 }
@@ -402,10 +401,8 @@ void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
 	return;
 }
 
-struct cgroup_subsys hugetlb_subsys = {
-	.name = "hugetlb",
+struct cgroup_subsys hugetlb_cgrp_subsys = {
 	.css_alloc	= hugetlb_cgroup_css_alloc,
 	.css_offline	= hugetlb_cgroup_css_offline,
 	.css_free	= hugetlb_cgroup_css_free,
-	.subsys_id	= hugetlb_subsys_id,
 };
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 53385cd4e6f0..d9c6ac1532e6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -66,8 +66,8 @@
 
 #include <trace/events/vmscan.h>
 
-struct cgroup_subsys mem_cgroup_subsys __read_mostly;
-EXPORT_SYMBOL(mem_cgroup_subsys);
+struct cgroup_subsys memory_cgrp_subsys __read_mostly;
+EXPORT_SYMBOL(memory_cgrp_subsys);
 
 #define MEM_CGROUP_RECLAIM_RETRIES	5
 static struct mem_cgroup *root_mem_cgroup __read_mostly;
@@ -538,7 +538,7 @@ static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
 {
 	struct cgroup_subsys_state *css;
 
-	css = css_from_id(id - 1, &mem_cgroup_subsys);
+	css = css_from_id(id - 1, &memory_cgrp_subsys);
 	return mem_cgroup_from_css(css);
 }
 
@@ -1072,7 +1072,7 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
 	if (unlikely(!p))
 		return NULL;
 
-	return mem_cgroup_from_css(task_css(p, mem_cgroup_subsys_id));
+	return mem_cgroup_from_css(task_css(p, memory_cgrp_id));
 }
 
 struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
@@ -1683,15 +1683,8 @@ static void move_unlock_mem_cgroup(struct mem_cgroup *memcg,
  */
 void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 {
-	/*
-	 * protects memcg_name and makes sure that parallel ooms do not
-	 * interleave
-	 */
+	/* oom_info_lock ensures that parallel ooms do not interleave */
 	static DEFINE_SPINLOCK(oom_info_lock);
-	struct cgroup *task_cgrp;
-	struct cgroup *mem_cgrp;
-	static char memcg_name[PATH_MAX];
-	int ret;
 	struct mem_cgroup *iter;
 	unsigned int i;
 
@@ -1701,36 +1694,14 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 	spin_lock(&oom_info_lock);
 	rcu_read_lock();
 
-	mem_cgrp = memcg->css.cgroup;
-	task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);
-
-	ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
-	if (ret < 0) {
-		/*
-		 * Unfortunately, we are unable to convert to a useful name
-		 * But we'll still print out the usage information
-		 */
-		rcu_read_unlock();
-		goto done;
-	}
-	rcu_read_unlock();
-
-	pr_info("Task in %s killed", memcg_name);
+	pr_info("Task in ");
+	pr_cont_cgroup_path(task_cgroup(p, memory_cgrp_id));
+	pr_info(" killed as a result of limit of ");
+	pr_cont_cgroup_path(memcg->css.cgroup);
+	pr_info("\n");
 
-	rcu_read_lock();
-	ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
-	if (ret < 0) {
-		rcu_read_unlock();
-		goto done;
-	}
 	rcu_read_unlock();
 
-	/*
-	 * Continues from above, so we don't need an KERN_ level
-	 */
-	pr_cont(" as a result of limit of %s\n", memcg_name);
-done:
-
 	pr_info("memory: usage %llukB, limit %llukB, failcnt %llu\n",
 		res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
 		res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
@@ -1745,13 +1716,8 @@ done:
 		res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
 
 	for_each_mem_cgroup_tree(iter, memcg) {
-		pr_info("Memory cgroup stats");
-
-		rcu_read_lock();
-		ret = cgroup_path(iter->css.cgroup, memcg_name, PATH_MAX);
-		if (!ret)
-			pr_cont(" for %s", memcg_name);
-		rcu_read_unlock();
+		pr_info("Memory cgroup stats for ");
+		pr_cont_cgroup_path(iter->css.cgroup);
 		pr_cont(":");
 
 		for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
@@ -3401,7 +3367,7 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 						  struct kmem_cache *s)
 {
 	struct kmem_cache *new = NULL;
-	static char *tmp_name = NULL;
+	static char *tmp_path = NULL, *tmp_name = NULL;
 	static DEFINE_MUTEX(mutex);	/* protects tmp_name */
 
 	BUG_ON(!memcg_can_account_kmem(memcg));
@@ -3413,18 +3379,20 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 	 * This static temporary buffer is used to prevent from
 	 * pointless shortliving allocation.
 	 */
-	if (!tmp_name) {
-		tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!tmp_path || !tmp_name) {
+		if (!tmp_path)
+			tmp_path = kmalloc(PATH_MAX, GFP_KERNEL);
 		if (!tmp_name)
+			tmp_name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+		if (!tmp_path || !tmp_name)
 			goto out;
 	}
 
-	rcu_read_lock();
-	snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
-			 memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
-	rcu_read_unlock();
+	cgroup_name(memcg->css.cgroup, tmp_name, NAME_MAX + 1);
+	snprintf(tmp_path, PATH_MAX, "%s(%d:%s)", s->name,
+		 memcg_cache_id(memcg), tmp_name);
 
-	new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
+	new = kmem_cache_create_memcg(memcg, tmp_path, s->object_size, s->align,
 				      (s->flags & ~SLAB_PANIC), s->ctor, s);
 	if (new)
 		new->allocflags |= __GFP_KMEMCG;
@@ -4990,7 +4958,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
 	struct cgroup *cgrp = memcg->css.cgroup;
 
 	/* returns EBUSY if there is a task or if we come here twice. */
-	if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
+	if (cgroup_has_tasks(cgrp) || !list_empty(&cgrp->children))
 		return -EBUSY;
 
 	/* we call try-to-free pages for make this cgroup empty */
@@ -5172,7 +5140,7 @@ static int __memcg_activate_kmem(struct mem_cgroup *memcg,
 	 * of course permitted.
 	 */
 	mutex_lock(&memcg_create_mutex);
-	if (cgroup_task_count(memcg->css.cgroup) || memcg_has_children(memcg))
+	if (cgroup_has_tasks(memcg->css.cgroup) || memcg_has_children(memcg))
 		err = -EBUSY;
 	mutex_unlock(&memcg_create_mutex);
 	if (err)
@@ -6183,17 +6151,15 @@ static int memcg_write_event_control(struct cgroup_subsys_state *css,
 	 * automatically removed on cgroup destruction but the removal is
 	 * asynchronous, so take an extra ref on @css.
 	 */
-	rcu_read_lock();
-
+	cfile_css = css_tryget_from_dir(cfile.file->f_dentry->d_parent,
+					&memory_cgrp_subsys);
 	ret = -EINVAL;
-	cfile_css = css_from_dir(cfile.file->f_dentry->d_parent,
-				 &mem_cgroup_subsys);
-	if (cfile_css == css && css_tryget(css))
-		ret = 0;
-
-	rcu_read_unlock();
-	if (ret)
+	if (IS_ERR(cfile_css))
+		goto out_put_cfile;
+	if (cfile_css != css) {
+		css_put(cfile_css);
 		goto out_put_cfile;
+	}
 
 	ret = event->register_event(memcg, event->eventfd, buffer);
 	if (ret)
@@ -6566,11 +6532,11 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
 		 * unfortunate state in our controller.
 		 */
 		if (parent != root_mem_cgroup)
-			mem_cgroup_subsys.broken_hierarchy = true;
+			memory_cgrp_subsys.broken_hierarchy = true;
 	}
 	mutex_unlock(&memcg_create_mutex);
 
-	return memcg_init_kmem(memcg, &mem_cgroup_subsys);
+	return memcg_init_kmem(memcg, &memory_cgrp_subsys);
 }
 
 /*
@@ -7264,9 +7230,7 @@ static void mem_cgroup_bind(struct cgroup_subsys_state *root_css)
 		mem_cgroup_from_css(root_css)->use_hierarchy = true;
 }
 
-struct cgroup_subsys mem_cgroup_subsys = {
-	.name = "memory",
-	.subsys_id = mem_cgroup_subsys_id,
+struct cgroup_subsys memory_cgrp_subsys = {
 	.css_alloc = mem_cgroup_css_alloc,
 	.css_online = mem_cgroup_css_online,
 	.css_offline = mem_cgroup_css_offline,
@@ -7292,7 +7256,7 @@ __setup("swapaccount=", enable_swap_account);
 
 static void __init memsw_file_init(void)
 {
-	WARN_ON(cgroup_add_cftypes(&mem_cgroup_subsys, memsw_cgroup_files));
+	WARN_ON(cgroup_add_cftypes(&memory_cgrp_subsys, memsw_cgroup_files));
 }
 
 static void __init enable_swap_cgroup(void)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 2f2f34a4e77d..566f7af6527a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -145,14 +145,10 @@ static int hwpoison_filter_task(struct page *p)
 		return -EINVAL;
 
 	css = mem_cgroup_css(mem);
-	/* root_mem_cgroup has NULL dentries */
-	if (!css->cgroup->dentry)
-		return -EINVAL;
-
-	ino = css->cgroup->dentry->d_inode->i_ino;
+	ino = cgroup_ino(css->cgroup);
 	css_put(css);
 
-	if (ino != hwpoison_filter_memcg)
+	if (!ino || ino != hwpoison_filter_memcg)
 		return -EINVAL;
 
 	return 0;
diff --git a/net/Kconfig b/net/Kconfig
index e411046a62e3..a83bc4cc45a4 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -239,7 +239,7 @@ config XPS
 	default y
 
 config CGROUP_NET_PRIO
-	tristate "Network priority cgroup"
+	bool "Network priority cgroup"
 	depends on CGROUPS
 	---help---
 	  Cgroup subsystem for use in assigning processes to network priorities on
diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c
index 719efd541668..22931e1b99b4 100644
--- a/net/core/netclassid_cgroup.c
+++ b/net/core/netclassid_cgroup.c
@@ -23,7 +23,7 @@ static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state
 
 struct cgroup_cls_state *task_cls_state(struct task_struct *p)
 {
-	return css_cls_state(task_css(p, net_cls_subsys_id));
+	return css_cls_state(task_css(p, net_cls_cgrp_id));
 }
 EXPORT_SYMBOL_GPL(task_cls_state);
 
@@ -73,7 +73,7 @@ static void cgrp_attach(struct cgroup_subsys_state *css,
 	void *v = (void *)(unsigned long)cs->classid;
 	struct task_struct *p;
 
-	cgroup_taskset_for_each(p, css, tset) {
+	cgroup_taskset_for_each(p, tset) {
 		task_lock(p);
 		iterate_fd(p->files, 0, update_classid, v);
 		task_unlock(p);
@@ -102,19 +102,10 @@ static struct cftype ss_files[] = {
 	{ }	/* terminate */
 };
 
-struct cgroup_subsys net_cls_subsys = {
-	.name			= "net_cls",
+struct cgroup_subsys net_cls_cgrp_subsys = {
 	.css_alloc		= cgrp_css_alloc,
 	.css_online		= cgrp_css_online,
 	.css_free		= cgrp_css_free,
 	.attach			= cgrp_attach,
-	.subsys_id		= net_cls_subsys_id,
 	.base_cftypes		= ss_files,
-	.module			= THIS_MODULE,
 };
-
-static int __init init_netclassid_cgroup(void)
-{
-	return cgroup_load_subsys(&net_cls_subsys);
-}
-__initcall(init_netclassid_cgroup);
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 9043caedcd08..f9f3a40d3350 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -224,7 +224,7 @@ static void net_prio_attach(struct cgroup_subsys_state *css,
 	struct task_struct *p;
 	void *v = (void *)(unsigned long)css->cgroup->id;
 
-	cgroup_taskset_for_each(p, css, tset) {
+	cgroup_taskset_for_each(p, tset) {
 		task_lock(p);
 		iterate_fd(p->files, 0, update_netprio, v);
 		task_unlock(p);
@@ -244,15 +244,12 @@ static struct cftype ss_files[] = {
 	{ }	/* terminate */
 };
 
-struct cgroup_subsys net_prio_subsys = {
-	.name		= "net_prio",
+struct cgroup_subsys net_prio_cgrp_subsys = {
 	.css_alloc	= cgrp_css_alloc,
 	.css_online	= cgrp_css_online,
 	.css_free	= cgrp_css_free,
 	.attach		= net_prio_attach,
-	.subsys_id	= net_prio_subsys_id,
 	.base_cftypes	= ss_files,
-	.module		= THIS_MODULE,
 };
 
 static int netprio_device_event(struct notifier_block *unused,
@@ -283,37 +280,9 @@ static struct notifier_block netprio_device_notifier = {
 
 static int __init init_cgroup_netprio(void)
 {
-	int ret;
-
-	ret = cgroup_load_subsys(&net_prio_subsys);
-	if (ret)
-		goto out;
-
 	register_netdevice_notifier(&netprio_device_notifier);
-
-out:
-	return ret;
-}
-
-static void __exit exit_cgroup_netprio(void)
-{
-	struct netprio_map *old;
-	struct net_device *dev;
-
-	unregister_netdevice_notifier(&netprio_device_notifier);
-
-	cgroup_unload_subsys(&net_prio_subsys);
-
-	rtnl_lock();
-	for_each_netdev(&init_net, dev) {
-		old = rtnl_dereference(dev->priomap);
-		RCU_INIT_POINTER(dev->priomap, NULL);
-		if (old)
-			kfree_rcu(old, rcu);
-	}
-	rtnl_unlock();
+	return 0;
 }
 
-module_init(init_cgroup_netprio);
-module_exit(exit_cgroup_netprio);
+subsys_initcall(init_cgroup_netprio);
 MODULE_LICENSE("GPL v2");
diff --git a/net/ipv4/tcp_memcontrol.c b/net/ipv4/tcp_memcontrol.c
index f7e522c558ba..20a0aca9131e 100644
--- a/net/ipv4/tcp_memcontrol.c
+++ b/net/ipv4/tcp_memcontrol.c
@@ -219,7 +219,7 @@ static struct cftype tcp_files[] = {
 
 static int __init tcp_memcontrol_init(void)
 {
-	WARN_ON(cgroup_add_cftypes(&mem_cgroup_subsys, tcp_files));
+	WARN_ON(cgroup_add_cftypes(&memory_cgrp_subsys, tcp_files));
 	return 0;
 }
 __initcall(tcp_memcontrol_init);
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index d3b6d2cd3a06..7f88bcde7c61 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -58,11 +58,9 @@ static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
 
 static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
 {
-	return css_to_devcgroup(task_css(task, devices_subsys_id));
+	return css_to_devcgroup(task_css(task, devices_cgrp_id));
 }
 
-struct cgroup_subsys devices_subsys;
-
 /*
  * called under devcgroup_mutex
  */
@@ -684,13 +682,11 @@ static struct cftype dev_cgroup_files[] = {
 	{ }	/* terminate */
 };
 
-struct cgroup_subsys devices_subsys = {
-	.name = "devices",
+struct cgroup_subsys devices_cgrp_subsys = {
 	.css_alloc = devcgroup_css_alloc,
 	.css_free = devcgroup_css_free,
 	.css_online = devcgroup_online,
 	.css_offline = devcgroup_offline,
-	.subsys_id = devices_subsys_id,
 	.base_cftypes = dev_cgroup_files,
 };