Re: RDMA (smbdirect) testing

[Tom Talpey <tom@talpey.com>]

On 5/24/2022 1:49 PM, Steve French wrote:
> Or alternatively - the "query network interfaces" ioctl - wonder if
> additional flags that could be added (beyond what is defined in
> MS-SMB2 2.2.32.5

Huh? I see no reason to expose this over the wire, it's entirely a local
device API question. Zero impact on the far side of the connection.

> On Tue, May 24, 2022 at 4:16 AM David Howells <dhowells@redhat.com> wrote:
>>
>> Is there some way for cifs to ask the RDMA layer what it supports?

Yes, and in fact the client and server already fetch it. It's a
standard verbs device attibute.

client fs/cifs/smbdirect.c:

> 	if (info->id->device->attrs.max_send_sge < SMBDIRECT_MAX_SGE) {
> 		log_rdma_event(ERR,
> 			"warning: device max_send_sge = %d too small\n",
> 			info->id->device->attrs.max_send_sge);
> 		log_rdma_event(ERR, "Queue Pair creation may fail\n");
> 	}
> 	if (info->id->device->attrs.max_recv_sge < SMBDIRECT_MAX_SGE) {
> 		log_rdma_event(ERR,
> 			"warning: device max_recv_sge = %d too small\n",
> 			info->id->device->attrs.max_recv_sge);
> 		log_rdma_event(ERR, "Queue Pair creation may fail\n");
> 	}

server fs/ksmbd/transport_rdma.c:

> 
> 	if (device->attrs.max_send_sge < SMB_DIRECT_MAX_SEND_SGES) {
> 		pr_err("warning: device max_send_sge = %d too small\n",
> 		       device->attrs.max_send_sge);
> 		return -EINVAL;
> 	}
> 	if (device->attrs.max_recv_sge < SMB_DIRECT_MAX_RECV_SGES) {
> 		pr_err("warning: device max_recv_sge = %d too small\n",
> 		       device->attrs.max_recv_sge);
> 		return -EINVAL;
> 	}

Tom.