RDS: IB: Change the proxy qp's path_mtu to IB_MTU_256

The path_mtu of proxy qp of RDS is currently set to IB_MTU_4096, but it
doesn't have much relevance, since the proxy qp is used only for
registration and invalidation of MRs. For the proxy qp to work in most
environments, this patch changes the path_mtu to IB_MTU_256.

Orabug: 26864694

Signed-off-by: Avinash Repaka <[email protected]>

Reviewed-by: Wei Lin Guay <[email protected]>
Reviewed-by: Håkon Bugge <[email protected]>

Suggested-by: Parav Pandit <[email protected]>

Orabug: 27364391

(cherry picked from commit cf9b99b)
cherry-pick-repo=linux-uek.git

Signed-off-by: Gerd Rausch <[email protected]>
Signed-off-by: Somasundaram Krishnasamy <[email protected]>

Author: Avinash Repaka

net/rds/ib_cm.c

@@ -1570,7 +1570,7 @@ int rds_ib_setup_fastreg(struct rds_ib_device *rds_ibdev)
 	/* Use modify_qp verb to change the state from INIT to RTR */
 	memset(&qp_attr, 0, sizeof(qp_attr));
 	qp_attr.qp_state	= IB_QPS_RTR;
-	qp_attr.path_mtu	= IB_MTU_4096;
+	qp_attr.path_mtu	= IB_MTU_256;
 	qp_attr.dest_qp_num	= rds_ibdev->fastreg_qp->qp_num;
 	qp_attr.rq_psn		= 1;
 	qp_attr.ah_attr.ah_flags	= IB_AH_GRH;