Re: [PATCH 00/16 v3] tracing: Add new file system tracefs

[Al Viro <viro@ZenIV.linux.org.uk>]

On Mon, Jan 26, 2015 at 03:58:22PM -0500, Steven Rostedt wrote:
> On Mon, 26 Jan 2015 15:44:19 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > Now what I could also do is to only allow this to be called once. And
> > in that case, we can hard code what mkdir and rmdir are. This could
> > work as currently there only exists a single instance of the instances
> > directory.
> > 
> > I might just do that too.
> 
> And just did:
> 
> diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
> index c7eb4c58579e..13e17bf677f4 100644
> --- a/fs/tracefs/inode.c
> +++ b/fs/tracefs/inode.c
> @@ -50,6 +50,11 @@ static const struct file_operations tracefs_file_operations = {
>  	.llseek =	noop_llseek,
>  };
>  
> +struct tracefs_dir_ops {
> +	int (*mkdir)(const char *name);
> +	int (*rmdir)(const char *name);
> +};

Why go through that indirection at all...

> +struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
> +					   int (*mkdir)(const char *name),
> +					   int (*rmdir)(const char *name));

... when there's exactly one caller of that thing, and the values of
mkdir and rmdir callbacks are the same on each call?