Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags

[Haggai Eran <haggaie@mellanox.com>]

On 07/07/2015 17:17, Steve Wise wrote:
> 
> 
>> -----Original Message-----
>> From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-owner@vger.kernel.org] On Behalf Of Haggai Eran
>> Sent: Monday, July 06, 2015 2:09 AM
>> To: Steve Wise; dledford@redhat.com
>> Cc: sagig@mellanox.com; ogerlitz@mellanox.com; roid@mellanox.com; linux-rdma@vger.kernel.org; eli@mellanox.com; target-
>> devel@vger.kernel.org; linux-nfs@vger.kernel.org; trond.myklebust@primarydata.com; bfields@fieldses.org
>> Subject: Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
>>
>> On 06/07/2015 02:22, Steve Wise wrote:
>>> +int rdma_device_access_flags(struct ib_pd *pd, int roles, int attrs)
>>> +{
>>> +	int access_flags = attrs;
>>> +
>>> +	if (roles & RDMA_MRR_RECV)
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE;
>>> +
>>> +	if (roles & RDMA_MRR_WRITE_DEST)
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_WRITE;
>>> +
>>> +	if (roles & RDMA_MRR_READ_DEST) {
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE;
>>> +		if (rdma_protocol_iwarp(pd->device,
>>> +					rdma_start_port(pd->device)))
>>> +			access_flags |= IB_ACCESS_REMOTE_WRITE;
>>> +	}
>>> +
>>> +	if (roles & RDMA_MRR_READ_SOURCE)
>>> +		access_flags |= IB_ACCESS_REMOTE_READ;
>>> +
>>> +	if (roles & RDMA_MRR_ATOMIC_DEST)
>>> +		access_flags |= IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_ATOMIC;
>>
>> I think you need LOCAL_WRITE for ATOMIC_SOURCE in order to receive the
>> results of the atomic operation.
>>
> 
> Where/how are the results returned?  In a recv completion?  If so, then that MR would need RDMA_MRR_RECV, not RDMA_MRR_ATOMIC_SOURCE.

They are returned in the scatter list provided in ib_send_wr.sg_list,
similarly to how RDMA read results are returned.