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

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Date:	Mon, 31 Aug 2015 18:02:43 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Daniel Baluta <daniel.baluta@...el.com>, jic23@...nel.org,
	jlbec@...lplan.org, linux-iio@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
CC:	knaack.h@....de, linux-kernel@...r.kernel.org,
	octavian.purdila@...el.com, pebolle@...cali.nl,
	patrick.porlan@...el.com, adriana.reus@...el.com,
	constantin.musca@...el.com, marten@...uitiveaerial.com,
	cristina.opriceana@...il.com, pmeerw@...erw.net, hch@....de,
	viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Subject: Re: [PATCH v7 1/5] configfs: Allow dynamic group (un)registration

[...]
> +int configfs_register_group(struct config_group *parent_group,
> +	struct config_group *group)
> +{
> +	struct dentry *dentry;
> +	int ret;
> +
> +	link_group(parent_group, group);

This needs to hold subsys->su_mutex

I think from here to before the return we need to hold the parent dentry
mutex with I_MUTEX_PARENT

> +
> +	ret = create_default_group(parent_group, group, &dentry);
> +	if (ret == 0)
> +		configfs_dir_set_ready(dentry->d_fsdata);

This needs to hold configfs_dirent_lock

> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(configfs_register_group);
> +
> +void configfs_unregister_group(struct config_group *group)
> +{
> +	struct dentry *dentry = group->cg_item.ci_dentry;
> +

We probably need to do the detach_prep stuff somewhere in here.


I think this needs to hold the parent dentry mutex with I_MUTEX_PARENT from
here to ...

> +	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);

 ... here

> +	dput(dentry);
> +	unlink_group(group);

needs subsys->su_mutex

> +}
> +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);
> 

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