Re: [PATCH net-next] netdevsim: correctly check return value of debugfs_create_dir

[David Miller <davem@davemloft.net>]

From: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Date: Fri,  8 Dec 2017 09:52:50 +0900

> Return value is now checked with IS_ERROR_OR_NULL because
> debugfs_create_dir doesn't return error value. It either returns
> NULL or a valid pointer.
> 
> Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
> ---
>  drivers/net/netdevsim/netdev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
> index eb8c679fca9f..88d8ee2c89da 100644
> --- a/drivers/net/netdevsim/netdev.c
> +++ b/drivers/net/netdevsim/netdev.c
> @@ -469,7 +469,7 @@ static int __init nsim_module_init(void)
>  	int err;
>  
>  	nsim_ddir = debugfs_create_dir(DRV_NAME, NULL);
> -	if (IS_ERR(nsim_ddir))
> +	if (IS_ERR_OR_NULL(nsim_ddir))
>  		return PTR_ERR(nsim_ddir);

debugfs_create_dir() should really be fixed, either it uses error pointers
consistently and therefore always provides a suitable error code to return
or it always uses NULL.

This in-between behavior makes using it as an interface painful because
no clear meaning is given to NULL.

So please do the work necessary to make debugfs_create_dir()'s return
semantics clearer and more useful.

Thank you.