Re: [PATCH 1/1] RDMA/cm: Delete two redundant condition branches

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, May 10, 2021 at 05:08:40PM +0800, Zhen Lei wrote:
> The statement of the last "if (xxx)" branch is the same as the "else"
> branch. Delete it to simplify code.
> 
> No functional change.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>  drivers/infiniband/core/cm.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
> index 0ead0d223154011..510beb25f5b8a0b 100644
> --- a/drivers/infiniband/core/cm.c
> +++ b/drivers/infiniband/core/cm.c
> @@ -668,8 +668,6 @@ static struct cm_id_private *cm_insert_listen(struct cm_id_private *cm_id_priv,
>  			link = &(*link)->rb_right;
>  		else if (be64_lt(service_id, cur_cm_id_priv->id.service_id))
>  			link = &(*link)->rb_left;
> -		else if (be64_gt(service_id, cur_cm_id_priv->id.service_id))
> -			link = &(*link)->rb_right;
>  		else
>  			link = &(*link)->rb_right;
>  	}
> @@ -700,8 +698,6 @@ static struct cm_id_private *cm_find_listen(struct ib_device *device,
>  			node = node->rb_right;
>  		else if (be64_lt(service_id, cm_id_priv->id.service_id))
>  			node = node->rb_left;
> -		else if (be64_gt(service_id, cm_id_priv->id.service_id))
> -			node = node->rb_right;
>  		else
>  			node = node->rb_right;
>  	}

I don't like this, if you want to reorganize this function then it
should be written in the normal pattern for this kind of comparision

 if (a < b)
   ..
 else if (a > b)
   ..
 else // a == b
   ..

You can see the a==b clause written explicitly above this if ladder:

		if ((cur_cm_id_priv->id.service_mask & service_id) ==
		    (service_mask & cur_cm_id_priv->id.service_id) &&
		    (cm_id_priv->id.device == cur_cm_id_priv->id.device)) {

Which is why the trailing else is just unexectuable code.

Jason