linux-kernel - Re: [PATCH] staging: unisys: Properly test debugfs_create

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Message-ID: <2030244.KlZ2vcFHjT@leap>
Date:   Tue, 29 Mar 2022 19:00:49 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        dan.carpenter@...cle.com
Cc:     David Kershner <david.kershner@...sys.com>,
        sparmaintainer@...sys.com, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: unisys: Properly test debugfs_create_dir() return values

On martedì 22 marzo 2022 09:38:58 CEST Fabio M. De Francesco wrote:
> debugfs_create_dir() returns a pointers to a dentry objects. On failures
> it returns errors. Currently the values returned to visornic_probe()
> seem to be tested for being equal to NULL in case of failures.
> 
> Properly test with "if (IS_ERR())" and then assign the correct error 
> value to the "err" variable.
> 
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
>  drivers/staging/unisys/visornic/visornic_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/unisys/visornic/visornic_main.c b/drivers/staging/unisys/visornic/visornic_main.c
> index 643432458105..58d03f3d3173 100644
> --- a/drivers/staging/unisys/visornic/visornic_main.c
> +++ b/drivers/staging/unisys/visornic/visornic_main.c
> @@ -1922,11 +1922,11 @@ static int visornic_probe(struct visor_device *dev)
>  	/* create debug/sysfs directories */
>  	devdata->eth_debugfs_dir = debugfs_create_dir(netdev->name,
>  						      visornic_debugfs_dir);
> -	if (!devdata->eth_debugfs_dir) {
> +	if (IS_ERR(devdata->eth_debugfs_dir)) {
>  		dev_err(&dev->device,
>  			"%s debugfs_create_dir %s failed\n",
>  			__func__, netdev->name);
> -		err = -ENOMEM;
> +		err = PTR_ERR(devdata->eth_debugfs_dir);
>  		goto cleanup_register_netdev;
>  	}
>  
> -- 
> 2.34.1
> 
Hi Greg, Dan,

Now I have time to rework this patch but, if I'm not misunderstanding, you 
asked for two contrasting works to do here...

Dan wrote that "[in] this case you can delete the whole devdata->eth_debugfs_dir 
and the related code.".

Greg wrote that "We really shouldn't be checking this value at all.  There's 
no reason to check the return value of a debugfs_* call. Can you fix up the code to
do that instead?".

I'm confused because they look like two incompatible requests. What should I do?

Thanks,

Fabio M. De Francesco