Patch "IB/{qib, hfi1}: Avoid flow control testing for RDMA write operation" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

IB/{qib, hfi1}: Avoid flow control testing for RDMA write operation

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-qib-hfi1-avoid-flow-control-testing-for-rdma-write-operation.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mike Marciniszyn <[email protected]>
Date: Mon, 21 Aug 2017 18:26:20 -0700
Subject: IB/{qib, hfi1}: Avoid flow control testing for RDMA write operation

From: Mike Marciniszyn <[email protected]>

commit 5b0ef650bd0f820e922fcc42f1985d4621ae19cf upstream.

Section 9.7.7.2.5 of the 1.3 IBTA spec clearly says that receive credits should never apply to RDMA write.

qib and hfi1 were doing that. The following situation will result in a QP hang:
- A prior SEND or RDMA_WRITE with immmediate consumed the last credit for a QP using RC receive buffer credits
- The prior op is acked so there are no more acks
- The peer ULP fails to post receive for some reason
- An RDMA write sees that the credits are exhausted and waits
- The peer ULP posts receive buffers
- The ULP posts a send or RDMA write that will be hung

The fix is to avoid the credit test for the RDMA write operation.

---
 drivers/infiniband/hw/hfi1/rc.c    |    3 ++-
 drivers/infiniband/hw/qib/qib_rc.c |    4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

@@ -551,7 +551,7 @@ int hfi1_make_rc_req(struct rvt_qp *qp,
 		case IB_WR_RDMA_WRITE:
 			if (newreq && !(qp->s_flags & RVT_S_UNLIMITED_CREDIT))
 				qp->s_lsn++;
-			/* FALLTHROUGH */
+			goto no_flow_control;
 		case IB_WR_RDMA_WRITE_WITH_IMM:
 			/* If no credit, return. */
 			if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT) &&

@@ -559,6 +559,7 @@ int hfi1_make_rc_req(struct rvt_qp *qp,
 				qp->s_flags |= RVT_S_WAIT_SSN_CREDIT;
 				goto bail;
 			}
+no_flow_control:
 			put_ib_reth_vaddr(
 				wqe->rdma_wr.remote_addr,
 				&ohdr->u.rc.reth);

@@ -357,7 +357,7 @@ int qib_make_rc_req(struct rvt_qp *qp, u
 		case IB_WR_RDMA_WRITE:
 			if (newreq && !(qp->s_flags & RVT_S_UNLIMITED_CREDIT))
 				qp->s_lsn++;
-			/* FALLTHROUGH */
+			goto no_flow_control;
 		case IB_WR_RDMA_WRITE_WITH_IMM:
 			/* If no credit, return. */
 			if (!(qp->s_flags & RVT_S_UNLIMITED_CREDIT) &&

@@ -365,7 +365,7 @@ int qib_make_rc_req(struct rvt_qp *qp, u
 				qp->s_flags |= RVT_S_WAIT_SSN_CREDIT;
 				goto bail;
 			}
-
+no_flow_control:
 			ohdr->u.rc.reth.vaddr =
 				cpu_to_be64(wqe->rdma_wr.remote_addr);
 			ohdr->u.rc.reth.rkey =

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ib-qib-hfi1-avoid-flow-control-testing-for-rdma-write-operation.patch