Re: [PATCH v2] net/mlx5e: Use refcount_t for refcount

From: Leon Romanovsky
Date: Sun Aug 04 2019 - 08:59:08 EST


On Sat, Aug 03, 2019 at 12:48:28AM +0800, Chuhong Yuan wrote:
> refcount_t is better for reference counters since its
> implementation can prevent overflows.
> So convert atomic_t ref counters to refcount_t.

I'm not thrilled to see those automatic conversion patches, especially
for flows which can't overflow. There is nothing wrong in using atomic_t
type of variable, do you have in mind flow which will cause to overflow?

Thanks
>
> Signed-off-by: Chuhong Yuan <hslester96@xxxxxxxxx>
> ---
> Changes in v2:
> - Add #include.
>
> drivers/net/ethernet/mellanox/mlx5/core/lib/vxlan.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/vxlan.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/vxlan.c
> index b9d4f4e19ff9..148b55c3db7a 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/lib/vxlan.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/vxlan.c
> @@ -32,6 +32,7 @@
>
> #include <linux/kernel.h>
> #include <linux/module.h>
> +#include <linux/refcount.h>
> #include <linux/mlx5/driver.h>
> #include <net/vxlan.h>
> #include "mlx5_core.h"
> @@ -48,7 +49,7 @@ struct mlx5_vxlan {
>
> struct mlx5_vxlan_port {
> struct hlist_node hlist;
> - atomic_t refcount;
> + refcount_t refcount;
> u16 udp_port;
> };
>
> @@ -113,7 +114,7 @@ int mlx5_vxlan_add_port(struct mlx5_vxlan *vxlan, u16 port)
>
> vxlanp = mlx5_vxlan_lookup_port(vxlan, port);
> if (vxlanp) {
> - atomic_inc(&vxlanp->refcount);
> + refcount_inc(&vxlanp->refcount);
> return 0;
> }
>
> @@ -137,7 +138,7 @@ int mlx5_vxlan_add_port(struct mlx5_vxlan *vxlan, u16 port)
> }
>
> vxlanp->udp_port = port;
> - atomic_set(&vxlanp->refcount, 1);
> + refcount_set(&vxlanp->refcount, 1);
>
> spin_lock_bh(&vxlan->lock);
> hash_add(vxlan->htable, &vxlanp->hlist, port);
> @@ -170,7 +171,7 @@ int mlx5_vxlan_del_port(struct mlx5_vxlan *vxlan, u16 port)
> goto out_unlock;
> }
>
> - if (atomic_dec_and_test(&vxlanp->refcount)) {
> + if (refcount_dec_and_test(&vxlanp->refcount)) {
> hash_del(&vxlanp->hlist);
> remove = true;
> }
> --
> 2.20.1
>