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

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Date:   Wed, 3 Jun 2020 11:34:36 -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 12:27:24PM -0700, Nathan Chancellor wrote:
> 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;

Actually, this removes the only use of err_dbg_root, so that should be
removed at the same time.

Cheers,
Nathan

> > -	}
> > -
> >  	err = mlx5_health_init(dev);
> >  	if (err)
> >  		goto err_health_init;
> > --
> > 2.26.2
> >