[PATCH v7 1/5] configfs: Allow dynamic group (un)registration

[Daniel Baluta <daniel.baluta-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

We don't want to hardcode default groups at subsystem
creation time. Thus, we export:
	* configfs_register_group
	* configfs_unregister_group
that allows drivers to programatically create/destroy groups.

Signed-off-by: Daniel Baluta <daniel.baluta-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
I am not sure about the locking scheme here, Joel can you help? :)

 fs/configfs/dir.c        | 39 +++++++++++++++++++++++++++++++++++++--
 include/linux/configfs.h |  4 ++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index c81ce7f..dde3251 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -651,7 +651,8 @@ static void detach_groups(struct config_group *group)
  * try using vfs_mkdir.  Just a thought.
  */
 static int create_default_group(struct config_group *parent_group,
-				struct config_group *group)
+				struct config_group *group,
+				struct dentry **dentry)
 {
 	int ret;
 	struct configfs_dirent *sd;
@@ -671,6 +672,8 @@ static int create_default_group(struct config_group *parent_group,
 		if (!ret) {
 			sd = child->d_fsdata;
 			sd->s_type |= CONFIGFS_USET_DEFAULT;
+			if (dentry)
+				*dentry = child;
 		} else {
 			BUG_ON(d_inode(child));
 			d_drop(child);
@@ -691,7 +694,7 @@ static int populate_groups(struct config_group *group)
 		for (i = 0; group->default_groups[i]; i++) {
 			new_group = group->default_groups[i];
 
-			ret = create_default_group(group, new_group);
+			ret = create_default_group(group, new_group, NULL);
 			if (ret) {
 				detach_groups(group);
 				break;
@@ -1636,6 +1639,38 @@ const struct file_operations configfs_dir_operations = {
 	.iterate	= configfs_readdir,
 };
 
+int configfs_register_group(struct config_group *parent_group,
+	struct config_group *group)
+{
+	struct dentry *dentry;
+	int ret;
+
+	link_group(parent_group, group);
+
+	ret = create_default_group(parent_group, group, &dentry);
+	if (ret == 0)
+		configfs_dir_set_ready(dentry->d_fsdata);
+
+	return ret;
+}
+EXPORT_SYMBOL(configfs_register_group);
+
+void configfs_unregister_group(struct config_group *group)
+{
+	struct dentry *dentry = group->cg_item.ci_dentry;
+
+	mutex_lock(&d_inode(dentry)->i_mutex);
+	configfs_detach_group(&group->cg_item);
+	d_inode(dentry)->i_flags |= S_DEAD;
+	dont_mount(dentry);
+	mutex_unlock(&d_inode(dentry)->i_mutex);
+
+	d_delete(dentry);
+	dput(dentry);
+	unlink_group(group);
+}
+EXPORT_SYMBOL(configfs_unregister_group);
+
 int configfs_register_subsystem(struct configfs_subsystem *subsys)
 {
 	int err;
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index c9e5c57..726980e 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -251,6 +251,10 @@ static inline struct configfs_subsystem *to_configfs_subsystem(struct config_gro
 int configfs_register_subsystem(struct configfs_subsystem *subsys);
 void configfs_unregister_subsystem(struct configfs_subsystem *subsys);
 
+int configfs_register_group(struct config_group *parent_group,
+			    struct config_group *group);
+void configfs_unregister_group(struct config_group *group);
+
 /* These functions can sleep and can alloc with GFP_KERNEL */
 /* WARNING: These cannot be called underneath configfs callbacks!! */
 int configfs_depend_item(struct configfs_subsystem *subsys, struct config_item *target);
-- 
2.1.4