cgroup: four misc fixes

index e2f46ba..364aeb22 100644
@@ -1566,10 +1566,10 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 		mutex_lock(&cgroup_mutex);
 		mutex_lock(&cgroup_root_mutex);
 
-		root_cgrp->id = idr_alloc(&root->cgroup_idr, root_cgrp,
-					   0, 1, GFP_KERNEL);
-		if (root_cgrp->id < 0)
+		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;

index 364aeb22..2e9f12a 100644
@@ -4158,7 +4158,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	struct cgroup *cgrp;
 	struct cgroup_name *name;
 	struct cgroupfs_root *root = parent->root;
-	int ssid, err = 0;
+	int ssid, err;
 	struct cgroup_subsys *ss;
 	struct super_block *sb = root->sb;
 

@@ -4168,8 +4168,10 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 		return -ENOMEM;
 
 	name = cgroup_alloc_name(dentry);
-	if (!name)
+	if (!name) {
+		err = -ENOMEM;
 		goto err_free_cgrp;
+	}
 	rcu_assign_pointer(cgrp->name, name);
 
 	/*

@@ -4177,8 +4179,10 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 	 * a half-baked cgroup.
 	 */
 	cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);
-	if (cgrp->id < 0)
+	if (cgrp->id < 0) {
+		err = -ENOMEM;
 		goto err_free_name;
+	}
 
 	/*
 	 * Only live parents can have children.  Note that the liveliness

index 2e9f12a..b0e030f 100644
@@ -2763,10 +2763,7 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
 	 */
 	update_before = cgroup_serial_nr_next;
 
-	mutex_unlock(&cgroup_mutex);
-
 	/* add/rm files for all cgroups created before */
-	rcu_read_lock();
 	css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
 		struct cgroup *cgrp = css->cgroup;
 

@@ -2775,23 +2772,19 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
 
 		inode = cgrp->dentry->d_inode;
 		dget(cgrp->dentry);
-		rcu_read_unlock();
-
 		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(&cgroup_mutex);
 		mutex_unlock(&inode->i_mutex);
-
-		rcu_read_lock();
 		if (ret)
 			break;
 	}
-	rcu_read_unlock();
+	mutex_unlock(&cgroup_mutex);
 	dput(prev);
 	deactivate_super(sb);
 	return ret;

index b0e030f..5c8fe40 100644
@@ -1265,10 +1265,10 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 		return -EINVAL;
 
 	/*
-	 * We either have to specify by name or by subsystems. (So all
-	 * empty hierarchies must have a name).
+	 * We either have to specify by name or by subsystems.  All empty
+	 * hierarchies must have a name and also "none" option specified.
 	 */
-	if (!opts->subsys_mask && !opts->name)
+	if (!opts->subsys_mask && (!opts->name || !opts->none))
 		return -EINVAL;
 
 	return 0;

@@ -1417,12 +1417,9 @@ 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;
-
 	root = kzalloc(sizeof(*root), GFP_KERNEL);
 	if (!root)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	init_cgroup_root(root);
 

@@ -1461,10 +1458,6 @@ static int cgroup_set_super(struct super_block *sb, void *data)
 	int ret;
 	struct cgroup_sb_opts *opts = data;
 
-	/* If we don't have a new root, we can't set up a new sb */
-	if (!opts->new_root)
-		return -EINVAL;
-
 	BUG_ON(!opts->subsys_mask && !opts->none);
 
 	ret = set_anon_super(sb, NULL);

@@ -1532,8 +1525,8 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 	 * reusing an existing hierarchy.
 	 */
 	new_root = cgroup_root_from_opts(&opts);
-	if (IS_ERR(new_root)) {
-		ret = PTR_ERR(new_root);
+	if (!new_root) {
+		ret = -ENOMEM;
 		goto out_err;
 	}
 	opts.new_root = new_root;