Re: [PATCH] fs/configfs: allow to create groups on demand

[Joel Becker]

On Thu, Nov 29, 2012 at 05:41:23PM +0100, Sebastian Andrzej Siewior wrote:
> This patch adds a function add a group to an existing one and its
> counterart. The newly created group behaves as it would be created via
> default_groups[] which means the user can't rmdir it.
> This should be used by the upcomming USB gadget interface in order to
> add the currently available UDCs as a child of the UDC node. The UDC
> itself will appear once the hardware driver is loaded and can appear
> later.

I've now responded to the original thread.  Sorry I didn't notice last
week.  Please see my thoughts there and comment.

Joel

> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
>  fs/configfs/dir.c        |   63 ++++++++++++++++++++++++++++++++++------------
>  include/linux/configfs.h |    4 +++
>  2 files changed, 51 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index 7414ae2..50ee2bd 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -1663,19 +1663,13 @@ const struct file_operations configfs_dir_operations = {
>  	.readdir	= configfs_readdir,
>  };
>  
> -int configfs_register_subsystem(struct configfs_subsystem *subsys)
> +static int __create_group(struct config_group *group, struct dentry *root)
>  {
>  	int err;
> -	struct config_group *group = &subsys->su_group;
>  	struct qstr name;
>  	struct dentry *dentry;
> -	struct dentry *root;
>  	struct configfs_dirent *sd;
>  
> -	root = configfs_pin_fs();
> -	if (IS_ERR(root))
> -		return PTR_ERR(root);
> -
>  	if (!group->cg_item.ci_name)
>  		group->cg_item.ci_name = group->cg_item.ci_namebuf;
>  
> @@ -1708,25 +1702,48 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
>  
>  	mutex_unlock(&root->d_inode->i_mutex);
>  
> -	if (err) {
> +	if (err)
>  		unlink_group(group);
> -		configfs_release_fs();
> +
> +	return err;
> +}
> +
> +int configfs_create_group(struct config_group *parent, struct config_group *new)
> +{
> +	int ret;
> +
> +	ret = __create_group(new, parent->cg_item.ci_dentry);
> +	if (!ret) {
> +		struct configfs_dirent *sd = new->cg_item.ci_dentry->d_fsdata;
> +
> +		sd->s_type |= CONFIGFS_USET_DEFAULT;
>  	}
>  
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(configfs_create_group);
> +
> +int configfs_register_subsystem(struct configfs_subsystem *subsys)
> +{
> +	int err;
> +	struct dentry *root;
> +
> +	root = configfs_pin_fs();
> +	if (IS_ERR(root))
> +		return PTR_ERR(root);
> +
> +	err = __create_group(&subsys->su_group, root);
> +	if (err)
> +		configfs_release_fs();
> +
>  	return err;
>  }
>  
> -void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
> +void configfs_remove_group(struct config_group *group)
>  {
> -	struct config_group *group = &subsys->su_group;
>  	struct dentry *dentry = group->cg_item.ci_dentry;
>  	struct dentry *root = dentry->d_sb->s_root;
>  
> -	if (dentry->d_parent != root) {
> -		printk(KERN_ERR "configfs: Tried to unregister non-subsystem!\n");
> -		return;
> -	}
> -
>  	mutex_lock_nested(&root->d_inode->i_mutex,
>  			  I_MUTEX_PARENT);
>  	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
> @@ -1749,6 +1766,20 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
>  	dput(dentry);
>  
>  	unlink_group(group);
> +}
> +EXPORT_SYMBOL_GPL(configfs_remove_group);
> +
> +void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
> +{
> +	struct config_group *group = &subsys->su_group;
> +	struct dentry *dentry = group->cg_item.ci_dentry;
> +	struct dentry *root = dentry->d_sb->s_root;
> +
> +	if (dentry->d_parent != root) {
> +		pr_err("configfs: Tried to unregister non-subsystem!\n");
> +		return;
> +	}
> +	configfs_remove_group(group);
>  	configfs_release_fs();
>  }
>  
> diff --git a/include/linux/configfs.h b/include/linux/configfs.h
> index 34025df..660c25d 100644
> --- a/include/linux/configfs.h
> +++ b/include/linux/configfs.h
> @@ -249,6 +249,10 @@ static inline struct configfs_subsystem *to_configfs_subsystem(struct config_gro
>  		NULL;
>  }
>  
> +int configfs_create_group(struct config_group *parent,
> +		struct config_group *new);
> +void configfs_remove_group(struct config_group *group);
> +
>  int configfs_register_subsystem(struct configfs_subsystem *subsys);
>  void configfs_unregister_subsystem(struct configfs_subsystem *subsys);
>  
> -- 
> 1.7.10.4
> 
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