Re: [PATCH RFC 18/38] proc: don't WARN about a name that is already registered

[Alexey Dobriyan <adobriyan@gmail.com>]

> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -401,9 +401,10 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
>  	write_lock(&proc_subdir_lock);
>  	dp->parent = dir;
>  	if (pde_subdir_insert(dir, dp) == false) {
> -		WARN(1, "proc_dir_entry '%s/%s' already registered\n",
> -		     dir->name, dp->name);
>  		write_unlock(&proc_subdir_lock);
> +		pr_warn("proc_dir_entry '%s/%s' already registered\n",
> +			dir->name, dp->name);
> +		dump_stack();
>  		goto out_free_inum;
>  	}
>  	write_unlock(&proc_subdir_lock);

I don't like this patch.

WARN is there to make bugs noticeable, /proc entries aren't supposed to be
created randomly unlike regular files so deleting non-existent name or
registering twice is probably a bug.

Now, some names do come from userspace but it is up to subsystems to
find duplicates and return errors (and sanitize for dots/slashes!).

In userspace mkdir;mkdir returns error second time, as well as
unlink;unlink. In kernel error is BUG/WARN (like it is now) and it is up
to subsystem to evade it.

	/proc/alexey