Re: [PATCH 12/12] IB/srp: Make CM timeout dependent on subnet timeout

[Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 4/30/2015 12:02 PM, Bart Van Assche wrote:
> In large networks the subnet timeout may have been set to a value
> above 20. In small networks it can be safe to reduce the subnet
> timeout below 20. The CM timeout should be proportional to the
> subnet timeout. Hence make the CM timeout dependent on the subnet
> timeout. Since the default subnet timeout used by OpenSM is 18
> this patch does not change the CM timeout if the default OpenSM
> subnet timeout is used.
>
> Signed-off-by: Bart Van Assche <bart.vanassche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
> Cc: Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> Cc: Sebastian Parschauer <sebastian.riemer-EIkl63zCoXaH+58JC4qpiA@public.gmane.org>
> ---
>   drivers/infiniband/ulp/srp/ib_srp.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
> index 27d3a64..a18a2ae 100644
> --- a/drivers/infiniband/ulp/srp/ib_srp.c
> +++ b/drivers/infiniband/ulp/srp/ib_srp.c
> @@ -704,6 +704,19 @@ static int srp_lookup_path(struct srp_rdma_ch *ch)
>   	return ch->status;
>   }
>
> +static u8 srp_get_subnet_timeout(struct srp_host *host)
> +{
> +	struct ib_port_attr attr;
> +	int ret;
> +	u8 subnet_timeout = 18;
> +
> +	ret = ib_query_port(host->srp_dev->dev, host->port, &attr);
> +	if (ret == 0)
> +		subnet_timeout = attr.subnet_timeout;
> +
> +	return subnet_timeout;
> +}
> +
>   static int srp_send_req(struct srp_rdma_ch *ch, bool multich)
>   {
>   	struct srp_target_port *target = ch->target;
> @@ -711,8 +724,11 @@ static int srp_send_req(struct srp_rdma_ch *ch, bool multich)
>   		struct ib_cm_req_param param;
>   		struct srp_login_req   priv;
>   	} *req = NULL;
> +	u8 subnet_timeout;
>   	int status;
>
> +	subnet_timeout = srp_get_subnet_timeout(target->srp_host);

Is this really something that srp initiator should look at?
I'd say that this needs to be a ib_cm code in case the input timeout
values are not set (e.g. zero).
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