netdev - Re: [PATCH net] net/mlx5: Don't fail driver on failure to create debugfs

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Message-ID: <20200602192724.GA672@Ryzen-9-3900X.localdomain>
Date:   Tue, 2 Jun 2020 12:27:24 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Leon Romanovsky <leonro@...lanox.com>,
        clang-built-linux@...glegroups.com, linux-rdma@...r.kernel.org,
        netdev@...r.kernel.org, Saeed Mahameed <saeedm@...lanox.com>,
        Vu Pham <vuhuong@...lanox.com>
Subject: Re: [PATCH net] net/mlx5: Don't fail driver on failure to create
 debugfs

On Tue, Jun 02, 2020 at 03:28:37PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...lanox.com>
> 
> Clang warns:
> 
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1278:6: warning: variable
> 'err' is used uninitialized whenever 'if' condition is true
> [-Wsometimes-uninitialized]
>         if (!priv->dbg_root) {
>             ^~~~~~~~~~~~~~~
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1303:9: note:
> uninitialized use occurs here
>         return err;
>                ^~~
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1278:2: note: remove the
> 'if' if its condition is always false
>         if (!priv->dbg_root) {
>         ^~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/mellanox/mlx5/core/main.c:1259:9: note: initialize
> the variable 'err' to silence this warning
>         int err;
>                ^
>                 = 0
> 1 warning generated.
> 
> The check of returned value of debugfs_create_dir() is wrong because
> by the design debugfs failures should never fail the driver and the
> check itself was wrong too. The kernel compiled without CONFIG_DEBUG_FS
> will return ERR_PTR(-ENODEV) and not NULL as expected.
> 
> Fixes: 11f3b84d7068 ("net/mlx5: Split mdev init and pci init")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1042
> Reported-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Leon Romanovsky <leonro@...lanox.com>

Thanks! That's what I figured it should be.

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
> Original discussion:
> https://lore.kernel.org/lkml/20200530055447.1028004-1-natechancellor@gmail.com
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/main.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> index df46b1fce3a7..110e8d277d15 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> @@ -1275,11 +1275,6 @@ static int mlx5_mdev_init(struct mlx5_core_dev *dev, int profile_idx)
> 
>  	priv->dbg_root = debugfs_create_dir(dev_name(dev->device),
>  					    mlx5_debugfs_root);
> -	if (!priv->dbg_root) {
> -		dev_err(dev->device, "mlx5_core: error, Cannot create debugfs dir, aborting\n");
> -		goto err_dbg_root;
> -	}
> -
>  	err = mlx5_health_init(dev);
>  	if (err)
>  		goto err_health_init;
> --
> 2.26.2
>