【dma mr verbs question】

[oulijun <oulijun@xxxxxxxxxx>]

Hi, Christoph Hellwig & Jason
  I found a question about IB core recently. We need to call get_dma_mr verbs and don't enable the mr_access_flags for IB_ACCESS_REMOTE_ATOMIC.
  Why? Is it not supported? What should we do if we need to call get_dma_mr for allowing incoming RDMA Atomic in mr?
  Still only local write operation when dma mr?
  The code from the newest linux maintain as follows:

      struct ib_pd *__ib_alloc_pd(struct ib_device *device, unsigned int flags,
		const char *caller)
{
	struct ib_pd *pd;
	int mr_access_flags = 0;

	pd = device->alloc_pd(device, NULL, NULL);
	if (IS_ERR(pd))
		return pd;

	pd->device = device;
	pd->uobject = NULL;
	pd->__internal_mr = NULL;
	atomic_set(&pd->usecnt, 0);
	pd->flags = flags;

	if (device->attrs.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY)
		pd->local_dma_lkey = device->local_dma_lkey;
	else
		mr_access_flags |= IB_ACCESS_LOCAL_WRITE;

	if (flags & IB_PD_UNSAFE_GLOBAL_RKEY) {
		pr_warn("%s: enabling unsafe global rkey\n", caller);
		mr_access_flags |= IB_ACCESS_REMOTE_READ | IB_ACCESS_REMOTE_WRITE;
	}

	pd->res.type = RDMA_RESTRACK_PD;
	rdma_restrack_set_task(&pd->res, caller);
	rdma_restrack_add(&pd->res);

	if (mr_access_flags) {
		struct ib_mr *mr;

		mr = pd->device->get_dma_mr(pd, mr_access_flags);
		if (IS_ERR(mr)) {
			ib_dealloc_pd(pd);
			return ERR_CAST(mr);
		}

		mr->device	= pd->device;
		mr->pd		= pd;
		mr->uobject	= NULL;
		mr->need_inval	= false;

		pd->__internal_mr = mr;

		if (!(device->attrs.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY))
			pd->local_dma_lkey = pd->__internal_mr->lkey;

		if (flags & IB_PD_UNSAFE_GLOBAL_RKEY)
			pd->unsafe_global_rkey = pd->__internal_mr->rkey;
	}

	return pd;
}

Thanks
Lijun Ou