linux-kernel - Re: [PATCH net v1] bna:Fix error checking for debugfs_create

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Date:   Wed, 12 Jul 2023 22:50:12 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Wang Ming <machel@...o.com>, Rasesh Mody <rmody@...vell.com>,
        Sudarsana Kalluru <skalluru@...vell.com>,
        GR-Linux-NIC-Dev@...vell.com,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Krishna Gudipati <kgudipat@...cade.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com
Subject: Re: [PATCH net v1] bna:Fix error checking for debugfs_create_dir()

Hi--

On 7/12/23 22:38, Wang Ming wrote:
> The debugfs_create_dir() function returns error pointers,
> it never returns NULL. Most incorrect error checks were fixed,
> but the one in bnad_debugfs_init() was forgotten.
> 
> Fix the remaining error check.
> 
> Signed-off-by: Wang Ming <machel@...o.com>
> 
> Fixes: 7afc5dbde091 ("bna: Add debugfs interface.")

Comment from fs/debugfs/inode.c:

 * NOTE: it's expected that most callers should _ignore_ the errors returned
 * by this function. Other debugfs functions handle the fact that the "dentry"
 * passed to them could be an error and they don't crash in that case.
 * Drivers should generally work fine even if debugfs fails to init anyway.

so no, drivers should not usually care about debugfs function call results.
Is there some special case here?

> ---
>  drivers/net/ethernet/brocade/bna/bnad_debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
> index 04ad0f2b9677..678a3668a041 100644
> --- a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
> +++ b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
> @@ -512,7 +512,7 @@ bnad_debugfs_init(struct bnad *bnad)
>  	if (!bnad->port_debugfs_root) {
>  		bnad->port_debugfs_root =
>  			debugfs_create_dir(name, bna_debugfs_root);
> -		if (!bnad->port_debugfs_root) {
> +		if (IS_ERR(bnad->port_debugfs_root)) {
>  			netdev_warn(bnad->netdev,
>  				    "debugfs root dir creation failed\n");
>  			return;

-- 
~Randy