[PATCH rdma-next v2 01/14] net/mlx5: Fix race for multiple RoCE enable

Leon Romanovsky
2018-01-04T15:25:31Z

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 <danielj-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Reviewed-by: Parav Pandit <parav-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
drivers/net/ethernet/mellanox/mlx5/core/vport.c | 33 ++++++++++++++++++++-----
include/linux/mlx5/driver.h | 2 +-
2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/vport.c b/drivers/net/ethernet/mellanox/mlx5/core/vport.c
index d653b0025b13..916523103f16 100644
--- 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)
{
@@ -988,17 +991,35 @@ static int mlx5_nic_vport_update_roce_state(struct mlx5_core_dev *mdev,

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);

diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
index 0776554f18dc..5b0443c9d337 100644
--- a/include/linux/mlx5/driver.h
+++ b/include/linux/mlx5/driver.h
@@ -835,7 +835,7 @@ 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;