1 files changed, 386 insertions, 368 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f24f724620dd..f34c41bfaa37 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -138,6 +138,9 @@ struct cgroupfs_root {
 	/* Hierarchy-specific flags */
 	unsigned long flags;
 
+	/* IDs for cgroups in this hierarchy */
+	struct ida cgroup_ida;
+
 	/* The path to use for release notifications. */
 	char release_agent_path[PATH_MAX];
 
@@ -171,8 +174,8 @@ struct css_id {
 	 * The css to which this ID points. This pointer is set to valid value
 	 * after cgroup is populated. If cgroup is removed, this will be NULL.
 	 * This pointer is expected to be RCU-safe because destroy()
-	 * is called after synchronize_rcu(). But for safe use, css_is_removed()
-	 * css_tryget() should be used for avoiding race.
+	 * is called after synchronize_rcu(). But for safe use, css_tryget()
+	 * should be used for avoiding race.
 	 */
 	struct cgroup_subsys_state __rcu *css;
 	/*
@@ -242,6 +245,10 @@ static DEFINE_SPINLOCK(hierarchy_id_lock);
  */
 static int need_forkexit_callback __read_mostly;
 
+static int cgroup_destroy_locked(struct cgroup *cgrp);
+static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
+			      struct cftype cfts[], bool is_add);
+
 #ifdef CONFIG_PROVE_LOCKING
 int cgroup_lock_is_held(void)
 {
@@ -294,11 +301,6 @@ static int notify_on_release(const struct cgroup *cgrp)
 	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 }
 
-static int clone_children(const struct cgroup *cgrp)
-{
-	return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
-}
-
 /*
  * for_each_subsys() allows you to iterate on each subsystem attached to
  * an active hierarchy
@@ -782,12 +784,12 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
  *	The task_lock() exception
  *
  * The need for this exception arises from the action of
- * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
+ * cgroup_attach_task(), which overwrites one task's cgroup pointer with
  * another.  It does so using cgroup_mutex, however there are
  * several performance critical places that need to reference
  * task->cgroup without the expense of grabbing a system global
  * mutex.  Therefore except as noted below, when dereferencing or, as
- * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
+ * in cgroup_attach_task(), modifying a task's cgroup pointer we use
  * task_lock(), which acts on a spinlock (task->alloc_lock) already in
  * the task_struct routinely used for such matters.
  *
@@ -854,30 +856,6 @@ static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
 	return inode;
 }
 
-/*
- * Call subsys's pre_destroy handler.
- * This is called before css refcnt check.
- */
-static int cgroup_call_pre_destroy(struct cgroup *cgrp)
-{
-	struct cgroup_subsys *ss;
-	int ret = 0;
-
-	for_each_subsys(cgrp->root, ss) {
-		if (!ss->pre_destroy)
-			continue;
-
-		ret = ss->pre_destroy(cgrp);
-		if (ret) {
-			/* ->pre_destroy() failure is being deprecated */
-			WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs);
-			break;
-		}
-	}
-
-	return ret;
-}
-
 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
 {
 	/* is dentry a directory ? if so, kfree() associated cgroup */
@@ -898,7 +876,7 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
 		 * Release the subsystem state objects.
 		 */
 		for_each_subsys(cgrp->root, ss)
-			ss->destroy(cgrp);
+			ss->css_free(cgrp);
 
 		cgrp->root->number_of_cgroups--;
 		mutex_unlock(&cgroup_mutex);
@@ -917,6 +895,7 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
 
 		simple_xattrs_free(&cgrp->xattrs);
 
+		ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
 		kfree_rcu(cgrp, rcu_head);
 	} else {
 		struct cfent *cfe = __d_cfe(dentry);
@@ -987,7 +966,7 @@ static void cgroup_clear_directory(struct dentry *dir, bool base_files,
 		if (!test_bit(ss->subsys_id, &subsys_mask))
 			continue;
 		list_for_each_entry(set, &ss->cftsets, node)
-			cgroup_rm_file(cgrp, set->cfts);
+			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
 	}
 	if (base_files) {
 		while (!list_empty(&cgrp->files))
@@ -1015,33 +994,6 @@ static void cgroup_d_remove_dir(struct dentry *dentry)
 }
 
 /*
- * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
- * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
- * reference to css->refcnt. In general, this refcnt is expected to goes down
- * to zero, soon.
- *
- * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
- */
-static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
-
-static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
-{
-	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
-		wake_up_all(&cgroup_rmdir_waitq);
-}
-
-void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
-{
-	css_get(css);
-}
-
-void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
-{
-	cgroup_wakeup_rmdir_waiter(css->cgroup);
-	css_put(css);
-}
-
-/*
  * 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.
@@ -1150,7 +1102,7 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",xattr");
 	if (strlen(root->release_agent_path))
 		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
-	if (clone_children(&root->top_cgroup))
+	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);
@@ -1162,7 +1114,7 @@ struct cgroup_sb_opts {
 	unsigned long subsys_mask;
 	unsigned long flags;
 	char *release_agent;
-	bool clone_children;
+	bool cpuset_clone_children;
 	char *name;
 	/* User explicitly requested empty subsystem */
 	bool none;
@@ -1213,7 +1165,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 			continue;
 		}
 		if (!strcmp(token, "clone_children")) {
-			opts->clone_children = true;
+			opts->cpuset_clone_children = true;
 			continue;
 		}
 		if (!strcmp(token, "xattr")) {
@@ -1397,14 +1349,21 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 		goto out_unlock;
 	}
 
+	/*
+	 * Clear out the files of subsystems that should be removed, do
+	 * this before rebind_subsystems, since rebind_subsystems may
+	 * change this hierarchy's subsys_list.
+	 */
+	cgroup_clear_directory(cgrp->dentry, false, removed_mask);
+
 	ret = rebind_subsystems(root, opts.subsys_mask);
 	if (ret) {
+		/* rebind_subsystems failed, re-populate the removed files */
+		cgroup_populate_dir(cgrp, false, removed_mask);
 		drop_parsed_module_refcounts(opts.subsys_mask);
 		goto out_unlock;
 	}
 
-	/* clear out any existing files and repopulate subsystem files */
-	cgroup_clear_directory(cgrp->dentry, false, removed_mask);
 	/* re-populate subsystem files */
 	cgroup_populate_dir(cgrp, false, added_mask);
 
@@ -1432,6 +1391,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
 	INIT_LIST_HEAD(&cgrp->children);
 	INIT_LIST_HEAD(&cgrp->files);
 	INIT_LIST_HEAD(&cgrp->css_sets);
+	INIT_LIST_HEAD(&cgrp->allcg_node);
 	INIT_LIST_HEAD(&cgrp->release_list);
 	INIT_LIST_HEAD(&cgrp->pidlists);
 	mutex_init(&cgrp->pidlist_mutex);
@@ -1450,8 +1410,8 @@ static void init_cgroup_root(struct cgroupfs_root *root)
 	root->number_of_cgroups = 1;
 	cgrp->root = root;
 	cgrp->top_cgroup = cgrp;
-	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
 	init_cgroup_housekeeping(cgrp);
+	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
 }
 
 static bool init_root_id(struct cgroupfs_root *root)
@@ -1518,12 +1478,13 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
 
 	root->subsys_mask = opts->subsys_mask;
 	root->flags = opts->flags;
+	ida_init(&root->cgroup_ida);
 	if (opts->release_agent)
 		strcpy(root->release_agent_path, opts->release_agent);
 	if (opts->name)
 		strcpy(root->name, opts->name);
-	if (opts->clone_children)
-		set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
+	if (opts->cpuset_clone_children)
+		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
 	return root;
 }
 
@@ -1536,6 +1497,7 @@ static void cgroup_drop_root(struct cgroupfs_root *root)
 	spin_lock(&hierarchy_id_lock);
 	ida_remove(&hierarchy_ida, root->hierarchy_id);
 	spin_unlock(&hierarchy_id_lock);
+	ida_destroy(&root->cgroup_ida);
 	kfree(root);
 }
 
@@ -1701,7 +1663,6 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 
 		free_cg_links(&tmp_cg_links);
 
-		BUG_ON(!list_empty(&root_cgrp->sibling));
 		BUG_ON(!list_empty(&root_cgrp->children));
 		BUG_ON(root->number_of_cgroups != 1);
 
@@ -1750,7 +1711,6 @@ static void cgroup_kill_sb(struct super_block *sb) {
 
 	BUG_ON(root->number_of_cgroups != 1);
 	BUG_ON(!list_empty(&cgrp->children));
-	BUG_ON(!list_empty(&cgrp->sibling));
 
 	mutex_lock(&cgroup_mutex);
 	mutex_lock(&cgroup_root_mutex);
@@ -1808,9 +1768,11 @@ static struct kobject *cgroup_kobj;
  */
 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 {
+	struct dentry *dentry = cgrp->dentry;
 	char *start;
-	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
-						      cgroup_lock_is_held());
+
+	rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(),
+			   "cgroup_path() called without proper locking");
 
 	if (!dentry || cgrp == dummytop) {
 		/*
@@ -1821,9 +1783,9 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 		return 0;
 	}
 
-	start = buf + buflen;
+	start = buf + buflen - 1;
 
-	*--start = '\0';
+	*start = '\0';
 	for (;;) {
 		int len = dentry->d_name.len;
 
@@ -1834,8 +1796,7 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 		if (!cgrp)
 			break;
 
-		dentry = rcu_dereference_check(cgrp->dentry,
-					       cgroup_lock_is_held());
+		dentry = cgrp->dentry;
 		if (!cgrp->parent)
 			continue;
 		if (--start < buf)
@@ -1930,9 +1891,7 @@ EXPORT_SYMBOL_GPL(cgroup_taskset_size);
 /*
  * cgroup_task_migrate - move a task from one cgroup to another.
  *
- * 'guarantee' is set if the caller promises that a new css_set for the task
- * will already exist. If not set, this function might sleep, and can fail with
- * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
+ * Must be called with cgroup_mutex and threadgroup locked.
  */
 static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
 				struct task_struct *tsk, struct css_set *newcg)
@@ -2025,12 +1984,6 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 	}
 
 	synchronize_rcu();
-
-	/*
-	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
-	 * is no longer empty.
-	 */
-	cgroup_wakeup_rmdir_waiter(cgrp);
 out:
 	if (retval) {
 		for_each_subsys(root, ss) {
@@ -2200,7 +2153,6 @@ static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
 	 * step 5: success! and cleanup
 	 */
 	synchronize_rcu();
-	cgroup_wakeup_rmdir_waiter(cgrp);
 	retval = 0;
 out_put_css_set_refs:
 	if (retval) {
@@ -2711,10 +2663,17 @@ static int cgroup_create_file(struct dentry *dentry, umode_t mode,
 
 		/* start off with i_nlink == 2 (for "." entry) */
 		inc_nlink(inode);
+		inc_nlink(dentry->d_parent->d_inode);
 
-		/* start with the directory inode held, so that we can
-		 * populate it without racing with another mkdir */
-		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
+		/*
+		 * 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;
@@ -2725,32 +2684,6 @@ static int cgroup_create_file(struct dentry *dentry, umode_t mode,
 	return 0;
 }
 
-/*
- * cgroup_create_dir - create a directory for an object.
- * @cgrp: the cgroup we create the directory for. It must have a valid
- *        ->parent field. And we are going to fill its ->dentry field.
- * @dentry: dentry of the new cgroup
- * @mode: mode to set on new directory.
- */
-static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
-				umode_t mode)
-{
-	struct dentry *parent;
-	int error = 0;
-
-	parent = cgrp->parent->dentry;
-	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
-	if (!error) {
-		dentry->d_fsdata = cgrp;
-		inc_nlink(parent->d_inode);
-		rcu_assign_pointer(cgrp->dentry, dentry);
-		dget(dentry);
-	}
-	dput(dentry);
-
-	return error;
-}
-
 /**
  * cgroup_file_mode - deduce file mode of a control file
  * @cft: the control file in question
@@ -2791,12 +2724,6 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 
 	simple_xattrs_init(&cft->xattrs);
 
-	/* does @cft->flags tell us to skip creation on @cgrp? */
-	if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
-		return 0;
-	if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
-		return 0;
-
 	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
 		strcpy(name, subsys->name);
 		strcat(name, ".");
@@ -2837,6 +2764,12 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 	int err, ret = 0;
 
 	for (cft = cfts; cft->name[0] != '\0'; cft++) {
+		/* does cft->flags tell us to skip this file on @cgrp? */
+		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
+			continue;
+		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
+			continue;
+
 		if (is_add)
 			err = cgroup_add_file(cgrp, subsys, cft);
 		else
@@ -3044,6 +2977,92 @@ static void cgroup_enable_task_cg_lists(void)
 	write_unlock(&css_set_lock);
 }
 
+/**
+ * cgroup_next_descendant_pre - find the next descendant for pre-order walk
+ * @pos: the current position (%NULL to initiate traversal)
+ * @cgroup: cgroup whose descendants to walk
+ *
+ * To be used by cgroup_for_each_descendant_pre().  Find the next
+ * descendant to visit for pre-order traversal of @cgroup's descendants.
+ */
+struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
+					  struct cgroup *cgroup)
+{
+	struct cgroup *next;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	/* if first iteration, pretend we just visited @cgroup */
+	if (!pos) {
+		if (list_empty(&cgroup->children))
+			return NULL;
+		pos = cgroup;
+	}
+
+	/* visit the first child if exists */
+	next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
+	if (next)
+		return next;
+
+	/* no child, visit my or the closest ancestor's next sibling */
+	do {
+		next = list_entry_rcu(pos->sibling.next, struct cgroup,
+				      sibling);
+		if (&next->sibling != &pos->parent->children)
+			return next;
+
+		pos = pos->parent;
+	} while (pos != cgroup);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);
+
+static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
+{
+	struct cgroup *last;
+
+	do {
+		last = pos;
+		pos = list_first_or_null_rcu(&pos->children, struct cgroup,
+					     sibling);
+	} while (pos);
+
+	return last;
+}
+
+/**
+ * cgroup_next_descendant_post - find the next descendant for post-order walk
+ * @pos: the current position (%NULL to initiate traversal)
+ * @cgroup: cgroup whose descendants to walk
+ *
+ * To be used by cgroup_for_each_descendant_post().  Find the next
+ * descendant to visit for post-order traversal of @cgroup's descendants.
+ */
+struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
+					   struct cgroup *cgroup)
+{
+	struct cgroup *next;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	/* if first iteration, visit the leftmost descendant */
+	if (!pos) {
+		next = cgroup_leftmost_descendant(cgroup);
+		return next != cgroup ? next : NULL;
+	}
+
+	/* if there's an unvisited sibling, visit its leftmost descendant */
+	next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
+	if (&next->sibling != &pos->parent->children)
+		return cgroup_leftmost_descendant(next);
+
+	/* no sibling left, visit parent */
+	next = pos->parent;
+	return next != cgroup ? next : NULL;
+}
+EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);
+
 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
 	__acquires(css_set_lock)
 {
@@ -3757,7 +3776,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
 	if (flags & POLLHUP) {
 		__remove_wait_queue(event->wqh, &event->wait);
 		spin_lock(&cgrp->event_list_lock);
-		list_del(&event->list);
+		list_del_init(&event->list);
 		spin_unlock(&cgrp->event_list_lock);
 		/*
 		 * We are in atomic context, but cgroup_event_remove() may
@@ -3894,7 +3913,7 @@ fail:
 static u64 cgroup_clone_children_read(struct cgroup *cgrp,
 				    struct cftype *cft)
 {
-	return clone_children(cgrp);
+	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
 }
 
 static int cgroup_clone_children_write(struct cgroup *cgrp,
@@ -3902,9 +3921,9 @@ static int cgroup_clone_children_write(struct cgroup *cgrp,
 				     u64 val)
 {
 	if (val)
-		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
 	else
-		clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
 	return 0;
 }
 
@@ -4017,19 +4036,57 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
 	css->flags = 0;
 	css->id = NULL;
 	if (cgrp == dummytop)
-		set_bit(CSS_ROOT, &css->flags);
+		css->flags |= CSS_ROOT;
 	BUG_ON(cgrp->subsys[ss->subsys_id]);
 	cgrp->subsys[ss->subsys_id] = css;
 
 	/*
-	 * If !clear_css_refs, css holds an extra ref to @cgrp->dentry
-	 * which is put on the last css_put().  dput() requires process
-	 * context, which css_put() may be called without.  @css->dput_work
-	 * will be used to invoke dput() asynchronously from css_put().
+	 * css holds an extra ref to @cgrp->dentry which is put on the last
+	 * css_put().  dput() requires process context, which css_put() may
+	 * be called without.  @css->dput_work will be used to invoke
+	 * dput() asynchronously from css_put().
 	 */
 	INIT_WORK(&css->dput_work, css_dput_fn);
-	if (ss->__DEPRECATED_clear_css_refs)
-		set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
+}
+
+/* invoke ->post_create() on a new CSS and mark it online if successful */
+static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+{
+	int ret = 0;
+
+	lockdep_assert_held(&cgroup_mutex);
+
+	if (ss->css_online)
+		ret = ss->css_online(cgrp);
+	if (!ret)
+		cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
+	return ret;
+}
+
+/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
+static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
+{
+	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+
+	lockdep_assert_held(&cgroup_mutex);
+
+	if (!(css->flags & CSS_ONLINE))
+		return;
+
+	/*
+	 * css_offline() should be called with cgroup_mutex unlocked.  See
+	 * 3fa59dfbc3 ("cgroup: fix potential deadlock in pre_destroy") for
+	 * details.  This temporary unlocking should go away once
+	 * cgroup_mutex is unexported from controllers.
+	 */
+	if (ss->css_offline) {
+		mutex_unlock(&cgroup_mutex);
+		ss->css_offline(cgrp);
+		mutex_lock(&cgroup_mutex);
+	}
+
+	cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
 }
 
 /*
@@ -4049,10 +4106,27 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	struct cgroup_subsys *ss;
 	struct super_block *sb = root->sb;
 
+	/* allocate the cgroup and its ID, 0 is reserved for the root */
 	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
 	if (!cgrp)
 		return -ENOMEM;
 
+	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
+	if (cgrp->id < 0)
+		goto err_free_cgrp;
+
+	/*
+	 * Only live parents can have children.  Note that the liveliness
+	 * check isn't strictly necessary because cgroup_mkdir() and
+	 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
+	 * anyway so that locking is contained inside cgroup proper and we
+	 * don't get nasty surprises if we ever grow another caller.
+	 */
+	if (!cgroup_lock_live_group(parent)) {
+		err = -ENODEV;
+		goto err_free_id;
+	}
+
 	/* 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
@@ -4060,8 +4134,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	 * fs */
 	atomic_inc(&sb->s_active);
 
-	mutex_lock(&cgroup_mutex);
-
 	init_cgroup_housekeeping(cgrp);
 
 	cgrp->parent = parent;
@@ -4071,26 +4143,51 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	if (notify_on_release(parent))
 		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 
-	if (clone_children(parent))
-		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
+		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
 
 	for_each_subsys(root, ss) {
 		struct cgroup_subsys_state *css;
 
-		css = ss->create(cgrp);
+		css = ss->css_alloc(cgrp);
 		if (IS_ERR(css)) {
 			err = PTR_ERR(css);
-			goto err_destroy;
+			goto err_free_all;
 		}
 		init_cgroup_css(css, ss, cgrp);
 		if (ss->use_id) {
 			err = alloc_css_id(ss, parent, cgrp);
 			if (err)
-				goto err_destroy;
+				goto err_free_all;
 		}
-		/* At error, ->destroy() callback has to free assigned ID. */
-		if (clone_children(parent) && ss->post_clone)
-			ss->post_clone(cgrp);
+	}
+
+	/*
+	 * Create directory.  cgroup_create_file() returns with the new
+	 * directory locked on success so that it can be populated without
+	 * dropping cgroup_mutex.
+	 */
+	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
+	if (err < 0)
+		goto err_free_all;
+	lockdep_assert_held(&dentry->d_inode->i_mutex);
+
+	/* allocation complete, commit to creation */
+	dentry->d_fsdata = cgrp;
+	cgrp->dentry = dentry;
+	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
+	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
+	root->number_of_cgroups++;
+
+	/* each css holds a ref to the cgroup's dentry */
+	for_each_subsys(root, ss)
+		dget(dentry);
+
+	/* creation succeeded, notify subsystems */
+	for_each_subsys(root, ss) {
+		err = online_css(ss, cgrp);
+		if (err)
+			goto err_destroy;
 
 		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
 		    parent->parent) {
@@ -4102,50 +4199,34 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 		}
 	}
 
-	list_add(&cgrp->sibling, &cgrp->parent->children);
-	root->number_of_cgroups++;
-
-	err = cgroup_create_dir(cgrp, dentry, mode);
-	if (err < 0)
-		goto err_remove;
-
-	/* If !clear_css_refs, each css holds a ref to the cgroup's dentry */
-	for_each_subsys(root, ss)
-		if (!ss->__DEPRECATED_clear_css_refs)
-			dget(dentry);
-
-	/* The cgroup directory was pre-locked for us */
-	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
-
-	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
-
 	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
-	/* If err < 0, we have a half-filled directory - oh well ;) */
+	if (err)
+		goto err_destroy;
 
 	mutex_unlock(&cgroup_mutex);
 	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
 
 	return 0;
 
- err_remove:
-
-	list_del(&cgrp->sibling);
-	root->number_of_cgroups--;
-
- err_destroy:
-
+err_free_all:
 	for_each_subsys(root, ss) {
 		if (cgrp->subsys[ss->subsys_id])
-			ss->destroy(cgrp);
+			ss->css_free(cgrp);
 	}
-
 	mutex_unlock(&cgroup_mutex);
-
 	/* Release the reference count that we took on the superblock */
 	deactivate_super(sb);
-
+err_free_id:
+	ida_simple_remove(&root->cgroup_ida, cgrp->id);
+err_free_cgrp:
 	kfree(cgrp);
 	return err;
+
+err_destroy:
+	cgroup_destroy_locked(cgrp);
+	mutex_unlock(&cgroup_mutex);
+	mutex_unlock(&dentry->d_inode->i_mutex);
+	return err;
 }
 
 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
@@ -4197,153 +4278,60 @@ static int cgroup_has_css_refs(struct cgroup *cgrp)
 	return 0;
 }
 
-/*
- * Atomically mark all (or else none) of the cgroup's CSS objects as
- * CSS_REMOVED. Return true on success, or false if the cgroup has
- * busy subsystems. Call with cgroup_mutex held
- *
- * Depending on whether a subsys has __DEPRECATED_clear_css_refs set or
- * not, cgroup removal behaves differently.
- *
- * If clear is set, css refcnt for the subsystem should be zero before
- * cgroup removal can be committed.  This is implemented by
- * CGRP_WAIT_ON_RMDIR and retry logic around ->pre_destroy(), which may be
- * called multiple times until all css refcnts reach zero and is allowed to
- * veto removal on any invocation.  This behavior is deprecated and will be
- * removed as soon as the existing user (memcg) is updated.
- *
- * If clear is not set, each css holds an extra reference to the cgroup's
- * dentry and cgroup removal proceeds regardless of css refs.
- * ->pre_destroy() will be called at least once and is not allowed to fail.
- * On the last put of each css, whenever that may be, the extra dentry ref
- * is put so that dentry destruction happens only after all css's are
- * released.
- */
-static int cgroup_clear_css_refs(struct cgroup *cgrp)
+static int cgroup_destroy_locked(struct cgroup *cgrp)
+	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
 {
+	struct dentry *d = cgrp->dentry;
+	struct cgroup *parent = cgrp->parent;
+	DEFINE_WAIT(wait);
+	struct cgroup_event *event, *tmp;
 	struct cgroup_subsys *ss;
-	unsigned long flags;
-	bool failed = false;
+	LIST_HEAD(tmp_list);
+
+	lockdep_assert_held(&d->d_inode->i_mutex);
+	lockdep_assert_held(&cgroup_mutex);
 
-	local_irq_save(flags);
+	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
+		return -EBUSY;
 
 	/*
-	 * Block new css_tryget() by deactivating refcnt.  If all refcnts
-	 * for subsystems w/ clear_css_refs set were 1 at the moment of
-	 * deactivation, we succeeded.
+	 * Block new css_tryget() by deactivating refcnt and mark @cgrp
+	 * removed.  This makes future css_tryget() and child creation
+	 * attempts fail thus maintaining the removal conditions verified
+	 * above.
 	 */
 	for_each_subsys(cgrp->root, ss) {
 		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
 
 		WARN_ON(atomic_read(&css->refcnt) < 0);
 		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
-
-		if (ss->__DEPRECATED_clear_css_refs)
-			failed |= css_refcnt(css) != 1;
-	}
-
-	/*
-	 * If succeeded, set REMOVED and put all the base refs; otherwise,
-	 * restore refcnts to positive values.  Either way, all in-progress
-	 * css_tryget() will be released.
-	 */
-	for_each_subsys(cgrp->root, ss) {
-		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
-
-		if (!failed) {
-			set_bit(CSS_REMOVED, &css->flags);
-			css_put(css);
-		} else {
-			atomic_sub(CSS_DEACT_BIAS, &css->refcnt);
-		}
 	}
+	set_bit(CGRP_REMOVED, &cgrp->flags);
 
-	local_irq_restore(flags);
-	return !failed;
-}
-
-static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
-{
-	struct cgroup *cgrp = dentry->d_fsdata;
-	struct dentry *d;
-	struct cgroup *parent;
-	DEFINE_WAIT(wait);
-	struct cgroup_event *event, *tmp;
-	int ret;
-
-	/* the vfs holds both inode->i_mutex already */
-again:
-	mutex_lock(&cgroup_mutex);
-	if (atomic_read(&cgrp->count) != 0) {
-		mutex_unlock(&cgroup_mutex);
-		return -EBUSY;
-	}
-	if (!list_empty(&cgrp->children)) {
-		mutex_unlock(&cgroup_mutex);
-		return -EBUSY;
-	}
-	mutex_unlock(&cgroup_mutex);
-
-	/*
-	 * In general, subsystem has no css->refcnt after pre_destroy(). But
-	 * in racy cases, subsystem may have to get css->refcnt after
-	 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
-	 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
-	 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
-	 * and subsystem's reference count handling. Please see css_get/put
-	 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
-	 */
-	set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
+	/* tell subsystems to initate destruction */
+	for_each_subsys(cgrp->root, ss)
+		offline_css(ss, cgrp);
 
 	/*
-	 * Call pre_destroy handlers of subsys. Notify subsystems
-	 * that rmdir() request comes.
+	 * Put all the base refs.  Each css holds an extra reference to the
+	 * cgroup's dentry and cgroup removal proceeds regardless of css
+	 * refs.  On the last put of each css, whenever that may be, the
+	 * extra dentry ref is put so that dentry destruction happens only
+	 * after all css's are released.
 	 */
-	ret = cgroup_call_pre_destroy(cgrp);
-	if (ret) {
-		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
-		return ret;
-	}
-
-	mutex_lock(&cgroup_mutex);
-	parent = cgrp->parent;
-	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
-		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
-		mutex_unlock(&cgroup_mutex);
-		return -EBUSY;
-	}
-	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
-	if (!cgroup_clear_css_refs(cgrp)) {
-		mutex_unlock(&cgroup_mutex);
-		/*
-		 * Because someone may call cgroup_wakeup_rmdir_waiter() before
-		 * prepare_to_wait(), we need to check this flag.
-		 */
-		if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
-			schedule();
-		finish_wait(&cgroup_rmdir_waitq, &wait);
-		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
-		if (signal_pending(current))
-			return -EINTR;
-		goto again;
-	}
-	/* NO css_tryget() can success after here. */
-	finish_wait(&cgroup_rmdir_waitq, &wait);
-	clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
+	for_each_subsys(cgrp->root, ss)
+		css_put(cgrp->subsys[ss->subsys_id]);
 
 	raw_spin_lock(&release_list_lock);
-	set_bit(CGRP_REMOVED, &cgrp->flags);
 	if (!list_empty(&cgrp->release_list))
 		list_del_init(&cgrp->release_list);
 	raw_spin_unlock(&release_list_lock);
 
 	/* delete this cgroup from parent->children */
-	list_del_init(&cgrp->sibling);
-
+	list_del_rcu(&cgrp->sibling);
 	list_del_init(&cgrp->allcg_node);
 
-	d = dget(cgrp->dentry);
-
+	dget(d);
 	cgroup_d_remove_dir(d);
 	dput(d);
 
@@ -4353,21 +4341,35 @@ again:
 	/*
 	 * Unregister events and notify userspace.
 	 * Notify userspace about cgroup removing only after rmdir of cgroup
-	 * directory to avoid race between userspace and kernelspace
+	 * directory to avoid race between userspace and kernelspace. Use
+	 * a temporary list to avoid a deadlock with cgroup_event_wake(). Since
+	 * cgroup_event_wake() is called with the wait queue head locked,
+	 * remove_wait_queue() cannot be called while holding event_list_lock.
 	 */
 	spin_lock(&cgrp->event_list_lock);
-	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
-		list_del(&event->list);
+	list_splice_init(&cgrp->event_list, &tmp_list);
+	spin_unlock(&cgrp->event_list_lock);
+	list_for_each_entry_safe(event, tmp, &tmp_list, list) {
+		list_del_init(&event->list);
 		remove_wait_queue(event->wqh, &event->wait);
 		eventfd_signal(event->eventfd, 1);
 		schedule_work(&event->remove);
 	}
-	spin_unlock(&cgrp->event_list_lock);
 
-	mutex_unlock(&cgroup_mutex);
 	return 0;
 }
 
+static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
+{
+	int ret;
+
+	mutex_lock(&cgroup_mutex);
+	ret = cgroup_destroy_locked(dentry->d_fsdata);
+	mutex_unlock(&cgroup_mutex);
+
+	return ret;
+}
+
 static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
 {
 	INIT_LIST_HEAD(&ss->cftsets);
@@ -4388,13 +4390,15 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 
 	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
 
+	mutex_lock(&cgroup_mutex);
+
 	/* init base cftset */
 	cgroup_init_cftsets(ss);
 
 	/* Create the top cgroup state for this subsystem */
 	list_add(&ss->sibling, &rootnode.subsys_list);
 	ss->root = &rootnode;
-	css = ss->create(dummytop);
+	css = ss->css_alloc(dummytop);
 	/* We don't handle early failures gracefully */
 	BUG_ON(IS_ERR(css));
 	init_cgroup_css(css, ss, dummytop);
@@ -4403,7 +4407,7 @@ 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] = dummytop->subsys[ss->subsys_id];
+	init_css_set.subsys[ss->subsys_id] = css;
 
 	need_forkexit_callback |= ss->fork || ss->exit;
 
@@ -4413,6 +4417,9 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 	BUG_ON(!list_empty(&init_task.tasks));
 
 	ss->active = 1;
+	BUG_ON(online_css(ss, dummytop));
+
+	mutex_unlock(&cgroup_mutex);
 
 	/* this function shouldn't be used with modular subsystems, since they
 	 * need to register a subsys_id, among other things */
@@ -4430,12 +4437,12 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
  */
 int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
 {
-	int i;
 	struct cgroup_subsys_state *css;
+	int i, ret;
 
 	/* check name and function validity */
 	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
-	    ss->create == NULL || ss->destroy == NULL)
+	    ss->css_alloc == NULL || ss->css_free == NULL)
 		return -EINVAL;
 
 	/*
@@ -4464,10 +4471,11 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
 	subsys[ss->subsys_id] = ss;
 
 	/*
-	 * no ss->create seems to need anything important in the ss struct, so
-	 * this can happen first (i.e. before the rootnode attachment).
+	 * no ss->css_alloc seems to need anything important in the ss
+	 * struct, so this can happen first (i.e. before the rootnode
+	 * attachment).
 	 */
-	css = ss->create(dummytop);
+	css = ss->css_alloc(dummytop);
 	if (IS_ERR(css)) {
 		/* failure case - need to deassign the subsys[] slot. */
 		subsys[ss->subsys_id] = NULL;
@@ -4482,14 +4490,9 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
 	init_cgroup_css(css, ss, dummytop);
 	/* init_idr must be after init_cgroup_css because it sets css->id. */
 	if (ss->use_id) {
-		int ret = cgroup_init_idr(ss, css);
-		if (ret) {
-			dummytop->subsys[ss->subsys_id] = NULL;
-			ss->destroy(dummytop);
-			subsys[ss->subsys_id] = NULL;
-			mutex_unlock(&cgroup_mutex);
-			return ret;
-		}
+		ret = cgroup_init_idr(ss, css);
+		if (ret)
+			goto err_unload;
 	}
 
 	/*
@@ -4522,10 +4525,19 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
 	write_unlock(&css_set_lock);
 
 	ss->active = 1;
+	ret = online_css(ss, dummytop);
+	if (ret)
+		goto err_unload;
 
 	/* success! */
 	mutex_unlock(&cgroup_mutex);
 	return 0;
+
+err_unload:
+	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);
 
@@ -4552,6 +4564,15 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
 	BUG_ON(ss->root != &rootnode);
 
 	mutex_lock(&cgroup_mutex);
+
+	offline_css(ss, dummytop);
+	ss->active = 0;
+
+	if (ss->use_id) {
+		idr_remove_all(&ss->idr);
+		idr_destroy(&ss->idr);
+	}
+
 	/* deassign the subsys_id */
 	subsys[ss->subsys_id] = NULL;
 
@@ -4567,7 +4588,6 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
 		struct css_set *cg = link->cg;
 
 		hlist_del(&cg->hlist);
-		BUG_ON(!cg->subsys[ss->subsys_id]);
 		cg->subsys[ss->subsys_id] = NULL;
 		hhead = css_set_hash(cg->subsys);
 		hlist_add_head(&cg->hlist, hhead);
@@ -4575,12 +4595,12 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
 	write_unlock(&css_set_lock);
 
 	/*
-	 * remove subsystem's css from the dummytop and free it - need to free
-	 * before marking as null because ss->destroy needs the cgrp->subsys
-	 * pointer to find their state. note that this also takes care of
-	 * freeing the css_id.
+	 * remove subsystem's css from the dummytop and free it - need to
+	 * free before marking as null because ss->css_free needs the
+	 * cgrp->subsys pointer to find their state. note that this also
+	 * takes care of freeing the css_id.
 	 */
-	ss->destroy(dummytop);
+	ss->css_free(dummytop);
 	dummytop->subsys[ss->subsys_id] = NULL;
 
 	mutex_unlock(&cgroup_mutex);
@@ -4624,8 +4644,8 @@ int __init cgroup_init_early(void)
 
 		BUG_ON(!ss->name);
 		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
-		BUG_ON(!ss->create);
-		BUG_ON(!ss->destroy);
+		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);
@@ -4832,44 +4852,19 @@ void cgroup_fork(struct task_struct *child)
 }
 
 /**
- * cgroup_fork_callbacks - run fork callbacks
- * @child: the new task
- *
- * Called on a new task very soon before adding it to the
- * tasklist. No need to take any locks since no-one can
- * be operating on this task.
- */
-void cgroup_fork_callbacks(struct task_struct *child)
-{
-	if (need_forkexit_callback) {
-		int i;
-		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
-			struct cgroup_subsys *ss = subsys[i];
-
-			/*
-			 * forkexit callbacks are only supported for
-			 * builtin subsystems.
-			 */
-			if (!ss || ss->module)
-				continue;
-
-			if (ss->fork)
-				ss->fork(child);
-		}
-	}
-}
-
-/**
  * cgroup_post_fork - called on a new task after adding it to the task list
  * @child: the task in question
  *
- * Adds the task to the list running through its css_set if necessary.
- * Has to be after the task is visible on the task list in case we race
- * with the first call to cgroup_iter_start() - to guarantee that the
- * new task ends up on its list.
+ * Adds the task to the list running through its css_set if necessary and
+ * call the subsystem fork() callbacks.  Has to be after the task is
+ * visible on the task list in case we race with the first call to
+ * cgroup_iter_start() - to guarantee that the new task ends up on its
+ * list.
  */
 void cgroup_post_fork(struct task_struct *child)
 {
+	int i;
+
 	/*
 	 * use_task_css_set_links is set to 1 before we walk the tasklist
 	 * under the tasklist_lock and we read it here after we added the child
@@ -4889,7 +4884,30 @@ void cgroup_post_fork(struct task_struct *child)
 		task_unlock(child);
 		write_unlock(&css_set_lock);
 	}
+
+	/*
+	 * Call ss->fork().  This must happen after @child is linked on
+	 * css_set; otherwise, @child might change state between ->fork()
+	 * and addition to css_set.
+	 */
+	if (need_forkexit_callback) {
+		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
+			struct cgroup_subsys *ss = subsys[i];
+
+			/*
+			 * fork/exit callbacks are supported only for
+			 * builtin subsystems and we don't need further
+			 * synchronization as they never go away.
+			 */
+			if (!ss || ss->module)
+				continue;
+
+			if (ss->fork)
+				ss->fork(child);
+		}
+	}
 }
+
 /**
  * cgroup_exit - detach cgroup from exiting task
  * @tsk: pointer to task_struct of exiting process
@@ -5022,15 +5040,17 @@ static void check_for_release(struct cgroup *cgrp)
 /* Caller must verify that the css is not for root cgroup */
 bool __css_tryget(struct cgroup_subsys_state *css)
 {
-	do {
-		int v = css_refcnt(css);
+	while (true) {
+		int t, v;
 
-		if (atomic_cmpxchg(&css->refcnt, v, v + 1) == v)
+		v = css_refcnt(css);
+		t = atomic_cmpxchg(&css->refcnt, v, v + 1);
+		if (likely(t == v))
 			return true;
+		else if (t < 0)
+			return false;
 		cpu_relax();
-	} while (!test_bit(CSS_REMOVED, &css->flags));
-
-	return false;
+	}
 }
 EXPORT_SYMBOL_GPL(__css_tryget);
 
@@ -5049,11 +5069,9 @@ void __css_put(struct cgroup_subsys_state *css)
 			set_bit(CGRP_RELEASABLE, &cgrp->flags);
 			check_for_release(cgrp);
 		}
-		cgroup_wakeup_rmdir_waiter(cgrp);
 		break;
 	case 0:
-		if (!test_bit(CSS_CLEAR_CSS_REFS, &css->flags))
-			schedule_work(&css->dput_work);
+		schedule_work(&css->dput_work);
 		break;
 	}
 	rcu_read_unlock();
@@ -5439,7 +5457,7 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
 }
 
 #ifdef CONFIG_CGROUP_DEBUG
-static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
+static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
 {
 	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
 
@@ -5449,7 +5467,7 @@ static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
 	return css;
 }
 
-static void debug_destroy(struct cgroup *cont)
+static void debug_css_free(struct cgroup *cont)
 {
 	kfree(cont->subsys[debug_subsys_id]);
 }
@@ -5578,8 +5596,8 @@ static struct cftype debug_files[] =  {
 
 struct cgroup_subsys debug_subsys = {
 	.name = "debug",
-	.create = debug_create,
-	.destroy = debug_destroy,
+	.css_alloc = debug_css_alloc,
+	.css_free = debug_css_free,
 	.subsys_id = debug_subsys_id,
 	.base_cftypes = debug_files,
 };