Re: [PATCH v10 1/5] configfs: Allow dynamic group creation

[Christoph Hellwig <hch@lst.de>]

Andrew,

is this simple addition something you could still send on to Linus
for this merge window?  I would make my life easier to have it in
so I could start using it in patches for various trees in the next
merge window.

Thanks,
	Christoph

On Fri, Oct 23, 2015 at 06:33:27PM +0300, Daniel Baluta wrote:
> 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>
> ---
>  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
---end quoted text---