linux-kernel - Re: [for-next][PATCH 7/7] tracing: Have mkdir and rmdir be part of tracefs

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Date:	Mon, 9 Feb 2015 15:07:22 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [for-next][PATCH 7/7] tracing: Have mkdir and rmdir be part of
 tracefs

On Wed, Feb 04, 2015 at 09:34:27AM -0500, Steven Rostedt wrote:
> +static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
> +{
> +	char *name;
> +	int ret;
> +
> +	name = get_dname(dentry);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	/*
> +	 * The mkdir call can call the generic functions that create

	   The mkdir can call ... ?


> +	 * the files within the tracefs system. It is up to the individual
> +	 * mkdir routine to handle races.
> +	 */
> +	mutex_unlock(&inode->i_mutex);
> +	ret = tracefs_ops.mkdir(name);
> +	mutex_lock(&inode->i_mutex);
> +
> +	kfree(name);
> +
> +	return ret;
> +}
> +
> +static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
> +{
> +	char *name;
> +	int ret;
> +
> +	name = get_dname(dentry);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	/*
> +	 * The rmdir call can call the generic functions that create

Ditto.


> +	 * the files within the tracefs system. It is up to the individual
> +	 * rmdir routine to handle races.
> +	 * This time we need to unlock not only the parent (inode) but
> +	 * also the directory that is being deleted.
> +	 */
> +	mutex_unlock(&inode->i_mutex);
> +	mutex_unlock(&dentry->d_inode->i_mutex);
> +
> +	ret = tracefs_ops.rmdir(name);
> +
> +	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
> +	mutex_lock(&dentry->d_inode->i_mutex);
> +
> +	kfree(name);
> +
> +	return ret;
> +}
> +

[SNIP]
> +/**
> + * tracefs_create_instance_dir - create the tracing instances directory
> + * @name: The name of the instances directory to create
> + * @parent: The parent directory that the instances directory will exist
> + * @mkdir: The function to call when a mkdir is performed.
> + * @rmdir: The function to call when a rmdir is performed.
> + *
> + * Only one instances directory is allowed.
> + *
> + * The instances directory is special as it allows for mkdir and rmdir to
> + * to be done by userspace. When a mkdir or rmdir is performed, the inode
> + * locks are released and the methhods passed in (@mkdir and @rmdir) are

s/methhods/methods/

Thanks,
Namhyung


> + * called without locks and with the name of the directory being created
> + * within the instances directory.
> + *
> + * Returns the dentry of the instances directory.
> + */
> +struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
> +					  int (*mkdir)(const char *name),
> +					  int (*rmdir)(const char *name))
> +{
> +	struct dentry *dentry;
> +
> +	/* Only allow one instance of the instances directory. */
> +	if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
>  		return NULL;
>  
> -	inode = tracefs_get_inode(dentry->d_sb);
> -	if (unlikely(!inode))
> -		return failed_creating(dentry);
> +	dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
> +	if (!dentry)
> +		return NULL;
>  
> -	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
> -	inode->i_op = &simple_dir_inode_operations;
> -	inode->i_fop = &simple_dir_operations;
> +	tracefs_ops.mkdir = mkdir;
> +	tracefs_ops.rmdir = rmdir;
>  
> -	/* directory inodes start off with i_nlink == 2 (for "." entry) */
> -	inc_nlink(inode);
> -	d_instantiate(dentry, inode);
> -	inc_nlink(dentry->d_parent->d_inode);
> -	fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
> -	return end_creating(dentry);
> +	return dentry;
>  }
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