[PATCH 4.14 052/138] net/mlx5: Fix race for multiple RoCE enable

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Jurgens <dani...@mellanox.com>


[ Upstream commit 734dc065fc41f6143ff88225aa5d335cb1e0f6aa ]

There are two potential problems with the existing implementation.

1. Enable and disable can race after the atomic operations.
2. If a command fails the refcount is left in an inconsistent state.

Introduce a lock and perform error checking.

Fixes: a6f7d2aff623 ("net/mlx5: Add support for multiple RoCE enable")
Signed-off-by: Daniel Jurgens <dani...@mellanox.com>
Reviewed-by: Parav Pandit <pa...@mellanox.com>
Signed-off-by: Leon Romanovsky <l...@kernel.org>
Signed-off-by: Jason Gunthorpe <j...@mellanox.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/vport.c |   33 +++++++++++++++++++-----
 include/linux/mlx5/driver.h                     |    2 -
 2 files changed, 28 insertions(+), 7 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/vport.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/vport.c
@@ -36,6 +36,9 @@
 #include <linux/mlx5/vport.h>
 #include "mlx5_core.h"
 
+/* Mutex to hold while enabling or disabling RoCE */
+static DEFINE_MUTEX(mlx5_roce_en_lock);
+
 static int _mlx5_query_vport_state(struct mlx5_core_dev *mdev, u8 opmod,
                                   u16 vport, u32 *out, int outlen)
 {
@@ -998,17 +1001,35 @@ static int mlx5_nic_vport_update_roce_st
 
 int mlx5_nic_vport_enable_roce(struct mlx5_core_dev *mdev)
 {
-       if (atomic_inc_return(&mdev->roce.roce_en) != 1)
-               return 0;
-       return mlx5_nic_vport_update_roce_state(mdev, MLX5_VPORT_ROCE_ENABLED);
+       int err = 0;
+
+       mutex_lock(&mlx5_roce_en_lock);
+       if (!mdev->roce.roce_en)
+               err = mlx5_nic_vport_update_roce_state(mdev, 
MLX5_VPORT_ROCE_ENABLED);
+
+       if (!err)
+               mdev->roce.roce_en++;
+       mutex_unlock(&mlx5_roce_en_lock);
+
+       return err;
 }
 EXPORT_SYMBOL_GPL(mlx5_nic_vport_enable_roce);
 
 int mlx5_nic_vport_disable_roce(struct mlx5_core_dev *mdev)
 {
-       if (atomic_dec_return(&mdev->roce.roce_en) != 0)
-               return 0;
-       return mlx5_nic_vport_update_roce_state(mdev, MLX5_VPORT_ROCE_DISABLED);
+       int err = 0;
+
+       mutex_lock(&mlx5_roce_en_lock);
+       if (mdev->roce.roce_en) {
+               mdev->roce.roce_en--;
+               if (mdev->roce.roce_en == 0)
+                       err = mlx5_nic_vport_update_roce_state(mdev, 
MLX5_VPORT_ROCE_DISABLED);
+
+               if (err)
+                       mdev->roce.roce_en++;
+       }
+       mutex_unlock(&mlx5_roce_en_lock);
+       return err;
 }
 EXPORT_SYMBOL_GPL(mlx5_nic_vport_disable_roce);
 
--- a/include/linux/mlx5/driver.h
+++ b/include/linux/mlx5/driver.h
@@ -794,7 +794,7 @@ struct mlx5_core_dev {
        struct mlx5e_resources  mlx5e_res;
        struct {
                struct mlx5_rsvd_gids   reserved_gids;
-               atomic_t                roce_en;
+               u32                     roce_en;
        } roce;
 #ifdef CONFIG_MLX5_FPGA
        struct mlx5_fpga_device *fpga;