netdev - [net-next 01/15] mlx5: reduce stack usage in mlx5_setup

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Date:   Tue,  7 Feb 2023 16:36:58 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Saeed Mahameed <saeedm@...dia.com>, netdev@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        Jacob Keller <jacob.e.keller@...el.com>
Subject: [net-next 01/15] mlx5: reduce stack usage in mlx5_setup_tc

From: Arnd Bergmann <arnd@...db.de>

Clang warns about excessive stack usage on 32-bit targets:

drivers/net/ethernet/mellanox/mlx5/core/en_main.c:3597:12: error: stack frame size (1184) exceeds limit (1024) in 'mlx5e_setup_tc' [-Werror,-Wframe-larger-than]
static int mlx5e_setup_tc(struct net_device *dev, enum tc_setup_type type,

It turns out that both the mlx5e_setup_tc_mqprio_dcb() function and
the mlx5e_safe_switch_params() function it calls have a copy of
'struct mlx5e_params' on the stack, and this structure is fairly
large.

Use dynamic allocation for the inner one.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
---
 .../net/ethernet/mellanox/mlx5/core/en_main.c   | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 3973d86905e8..6b9267c19e00 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3002,32 +3002,37 @@ int mlx5e_safe_switch_params(struct mlx5e_priv *priv,
 			     mlx5e_fp_preactivate preactivate,
 			     void *context, bool reset)
 {
-	struct mlx5e_channels new_chs = {};
+	struct mlx5e_channels *new_chs;
 	int err;
 
 	reset &= test_bit(MLX5E_STATE_OPENED, &priv->state);
 	if (!reset)
 		return mlx5e_switch_priv_params(priv, params, preactivate, context);
 
-	new_chs.params = *params;
+	new_chs = kzalloc(sizeof(*new_chs), GFP_KERNEL);
+	if (!new_chs)
+		return -ENOMEM;
+	new_chs->params = *params;
 
-	mlx5e_selq_prepare_params(&priv->selq, &new_chs.params);
+	mlx5e_selq_prepare_params(&priv->selq, &new_chs->params);
 
-	err = mlx5e_open_channels(priv, &new_chs);
+	err = mlx5e_open_channels(priv, new_chs);
 	if (err)
 		goto err_cancel_selq;
 
-	err = mlx5e_switch_priv_channels(priv, &new_chs, preactivate, context);
+	err = mlx5e_switch_priv_channels(priv, new_chs, preactivate, context);
 	if (err)
 		goto err_close;
 
+	kfree(new_chs);
 	return 0;
 
 err_close:
-	mlx5e_close_channels(&new_chs);
+	mlx5e_close_channels(new_chs);
 
 err_cancel_selq:
 	mlx5e_selq_cancel(&priv->selq);
+	kfree(new_chs);
 	return err;
 }
 
-- 
2.39.1