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Subject[RFC 1/9] configfs: Allow dynamic group creation
Date
From: Daniel Baluta <daniel.baluta@intel.com>

We don't want to hardcode default groups at subsystem
creation time. We export:
* configfs_register_group
* configfs_unregister_group
to allow drivers to programatically create/destroy groups
later, after module init time.

This is needed for IIO configfs support.

Suggested-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Joel Becker <jlbec@evilplan.org>
---
fs/configfs/dir.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/configfs.h | 10 +++++
2 files changed, 120 insertions(+)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index c81ce7f..a7a1b21 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1636,6 +1636,116 @@ const struct file_operations configfs_dir_operations = {
.iterate = configfs_readdir,
};

+/**
+ * configfs_register_group - creates a parent-child relation between two groups
+ * @parent_group: parent group
+ * @group: child group
+ *
+ * link groups, creates dentry for the child and attaches it to the
+ * parent dentry.
+ *
+ * Return: 0 on success, negative errno code on error
+ */
+int configfs_register_group(struct config_group *parent_group,
+ struct config_group *group)
+{
+ struct configfs_subsystem *subsys = parent_group->cg_subsys;
+ struct dentry *parent;
+ int ret;
+
+ mutex_lock(&subsys->su_mutex);
+ link_group(parent_group, group);
+ mutex_unlock(&subsys->su_mutex);
+
+ parent = parent_group->cg_item.ci_dentry;
+
+ mutex_lock_nested(&d_inode(parent)->i_mutex, I_MUTEX_PARENT);
+ ret = create_default_group(parent_group, group);
+ if (!ret) {
+ spin_lock(&configfs_dirent_lock);
+ configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
+ spin_unlock(&configfs_dirent_lock);
+ }
+ mutex_unlock(&d_inode(parent)->i_mutex);
+ return ret;
+}
+EXPORT_SYMBOL(configfs_register_group);
+
+/**
+ * configfs_unregister_group() - unregisters a child group from its parent
+ * @group: parent group to be unregistered
+ *
+ * Undoes configfs_register_group()
+ */
+void configfs_unregister_group(struct config_group *group)
+{
+ struct configfs_subsystem *subsys = group->cg_subsys;
+ struct dentry *dentry = group->cg_item.ci_dentry;
+ struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
+
+ mutex_lock_nested(&d_inode(parent)->i_mutex, I_MUTEX_PARENT);
+ spin_lock(&configfs_dirent_lock);
+ configfs_detach_prep(dentry, NULL);
+ spin_unlock(&configfs_dirent_lock);
+
+ configfs_detach_group(&group->cg_item);
+ d_inode(dentry)->i_flags |= S_DEAD;
+ dont_mount(dentry);
+ d_delete(dentry);
+ mutex_unlock(&d_inode(parent)->i_mutex);
+
+ dput(dentry);
+
+ mutex_lock(&subsys->su_mutex);
+ unlink_group(group);
+ mutex_unlock(&subsys->su_mutex);
+}
+EXPORT_SYMBOL(configfs_unregister_group);
+
+/**
+ * configfs_register_default_group() - allocates and registers a child group
+ * @parent_group: parent group
+ * @name: child group name
+ * @item_type: child item type description
+ *
+ * boilerplate to allocate and register a child group with its parent. We need
+ * kzalloc'ed memory because child's default_group is initially empty.
+ *
+ * Return: allocated config group or ERR_PTR() on error
+ */
+struct config_group *
+configfs_register_default_group(struct config_group *parent_group,
+ const char *name,
+ struct config_item_type *item_type)
+{
+ int ret;
+ struct config_group *group;
+
+ group = kzalloc(sizeof(*group), GFP_KERNEL);
+ if (!group)
+ return ERR_PTR(-ENOMEM);
+ config_group_init_type_name(group, name, item_type);
+
+ ret = configfs_register_group(parent_group, group);
+ if (ret) {
+ kfree(group);
+ return ERR_PTR(ret);
+ }
+ return group;
+}
+EXPORT_SYMBOL(configfs_register_default_group);
+
+/**
+ * configfs_unregister_default_group() - unregisters and frees a child group
+ * @group: the group to act on
+ */
+void configfs_unregister_default_group(struct config_group *group)
+{
+ configfs_unregister_group(group);
+ kfree(group);
+}
+EXPORT_SYMBOL(configfs_unregister_default_group);
+
int configfs_register_subsystem(struct configfs_subsystem *subsys)
{
int err;
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 63a36e8..931ca25 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -252,6 +252,16 @@ 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);
+
+struct config_group *
+configfs_register_default_group(struct config_group *parent_group,
+ const char *name,
+ struct config_item_type *item_type);
+void configfs_unregister_default_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);
--
1.9.1


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