Re: [PATCH] ref_tracker: use %ld format specifier for PTR_ERR() during directory creation failure

[Nathan Chancellor <nathan@kernel.org>]

Hi Qasim,

On Sat, Apr 12, 2025 at 11:27:44PM +0100, Qasim Ijaz wrote:
> PTR_ERR yields type long, so use %ld format specifier in pr_warn.
> 
> Fixes: ada5a12aae58 ("ref_tracker: add a top level debugfs directory for ref_tracker")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202504130520.rX5EVbVq-lkp@intel.com/ 
> Signed-off-by: Qasim Ijaz <qasdev00@gmail.com> 
> ---
>  lib/ref_tracker.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
> index 4064154252a6..02e9f0c3dd82 100644
> --- a/lib/ref_tracker.c
> +++ b/lib/ref_tracker.c
> @@ -283,7 +283,7 @@ static int __init ref_tracker_debug_init(void)
>  {
>  	ref_tracker_debug_dir = debugfs_create_dir("ref_tracker", NULL);
>  	if (IS_ERR(ref_tracker_debug_dir)) {
> -		pr_warn("ref_tracker: unable to create ref_tracker debugfs directory: %d\n",
> +		pr_warn("ref_tracker: unable to create ref_tracker debugfs directory: %ld\n",

While there is nothing wrong with doing this to resolve the warning, I
think this would be a good opportunity to use the '%pe' format specifier
[1] instead of '%ld', as that will print the symbolic error name (such
as -EINVAL instead of just -22) and make it easier for people to
decipher what has gone wrong.

  pr_warn("ref_tracker: unable to create ref_tracker debugfs directory: %pe\n",
          ref_tracker_debug_dir);

[1]: From the "error pointers" section in Documentation/core-api/printk-formats.rst

Cheers,
Nathan

>  			PTR_ERR(ref_tracker_debug_dir));
>  		ref_tracker_debug_dir = NULL;
>  	}
> -- 
> 2.39.5
> 
>