Commit b334eaab authored by Tom Tucker's avatar Tom Tucker Committed by Trond Myklebust
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RPC/RDMA: fix connection IRD/ORD setting 



This logic sets the connection parameter that configures the local device
and informs the remote peer how many concurrent incoming RDMA_READ
requests are supported. The original logic didn't really do what was
intended for two reasons:

- The max number supported by the device is typically smaller than
any one factor in the calculation used, and

- The field in the connection parameter structure where the value is
stored is a u8 and always overflows for the default settings.

So what really happens is the value requested for responder resources
is the left over 8 bits from the "desired value". If the desired value
happened to be a multiple of 256, the result was zero and it wouldn't
connect at all.

Given the above and the fact that max_requests is almost always larger
than the max responder resources supported by the adapter, this patch
simplifies this logic and simply requests the max supported by the device,
subject to a reasonable limit.

This bug was found by Jim Schutt at Sandia.

Signed-off-by: default avatarTom Tucker <tom@opengridcomputing.com>
Acked-by: default avatarTom Talpey <talpey@netapp.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 3197d309

net/sunrpc/xprtrdma/verbs.c

+14 −37
Original line number Diff line number Diff line
@@ -705,30 +705,13 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia, 
	ep->rep_remote_cma.private_data_len = 0;



	/* Client offers RDMA Read but does not initiate */

	switch (ia->ri_memreg_strategy) {

	case RPCRDMA_BOUNCEBUFFERS:

	ep->rep_remote_cma.initiator_depth = 0;

	if (ia->ri_memreg_strategy == RPCRDMA_BOUNCEBUFFERS)

		ep->rep_remote_cma.responder_resources = 0;

		break;

	case RPCRDMA_MTHCAFMR:

	case RPCRDMA_REGISTER:

	case RPCRDMA_FRMR:

		ep->rep_remote_cma.responder_resources = cdata->max_requests *

				(RPCRDMA_MAX_DATA_SEGS / 8);

		break;

	case RPCRDMA_MEMWINDOWS:

	case RPCRDMA_MEMWINDOWS_ASYNC:

#if RPCRDMA_PERSISTENT_REGISTRATION

	case RPCRDMA_ALLPHYSICAL:

#endif

		ep->rep_remote_cma.responder_resources = cdata->max_requests *

				(RPCRDMA_MAX_DATA_SEGS / 2);

		break;

	default:

		break;

	}

	if (ep->rep_remote_cma.responder_resources > devattr.max_qp_rd_atom)

	else if (devattr.max_qp_rd_atom > 32)	/* arbitrary but <= 255 */

		ep->rep_remote_cma.responder_resources = 32;

	else

		ep->rep_remote_cma.responder_resources = devattr.max_qp_rd_atom;

	ep->rep_remote_cma.initiator_depth = 0;



	ep->rep_remote_cma.retry_count = 7;

	ep->rep_remote_cma.flow_control = 0;
@@ -858,14 +841,6 @@ if (strnicmp(ia->ri_id->device->dma_device->bus->name, "pci", 3) == 0) { 
	}

}



	/* Theoretically a client initiator_depth > 0 is not needed,

	 * but many peers fail to complete the connection unless they

	 * == responder_resources! */

	if (ep->rep_remote_cma.initiator_depth !=

				ep->rep_remote_cma.responder_resources)

		ep->rep_remote_cma.initiator_depth =

			ep->rep_remote_cma.responder_resources;



	ep->rep_connected = 0;



	rc = rdma_connect(ia->ri_id, &ep->rep_remote_cma);
@@ -894,14 +869,16 @@ if (strnicmp(ia->ri_id->device->dma_device->bus->name, "pci", 3) == 0) { 
	if (ep->rep_connected <= 0) {

		/* Sometimes, the only way to reliably connect to remote

		 * CMs is to use same nonzero values for ORD and IRD. */

		if (retry_count++ <= RDMA_CONNECT_RETRY_MAX + 1 &&

		    (ep->rep_remote_cma.responder_resources == 0 ||

		     ep->rep_remote_cma.initiator_depth !=

				ep->rep_remote_cma.responder_resources)) {

			if (ep->rep_remote_cma.responder_resources == 0)

				ep->rep_remote_cma.responder_resources = 1;

			ep->rep_remote_cma.initiator_depth =

				ep->rep_remote_cma.responder_resources;

		if (ep->rep_remote_cma.initiator_depth == 0)

			++ep->rep_remote_cma.initiator_depth;

		if (ep->rep_remote_cma.responder_resources == 0)

			++ep->rep_remote_cma.responder_resources;

		if (retry_count++ == 0)

			goto retry;

		}

		rc = ep->rep_connected;

	} else {

		dprintk("RPC:       %s: connected\n", __func__);

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