From: Chuck Lever <chuck.lever@oracle.com>
Date: Mon, 16 Oct 2017 15:01:39 -0400
Subject: xprtrdma: Decode credits field in rpcrdma_reply_handler
Patch-mainline: v4.15-rc1
Git-commit: be798f9082aa54524b209fac2c8164c81cd28f77
References: bsc#1103992 FATE#326009

We need to decode and save the incoming rdma_credits field _after_
we know that the direction of the message is "forward direction
Reply". Otherwise, the credits value in reverse direction Calls is
also used to update the forward direction credits.

It is safe to decode the rdma_credits field in rpcrdma_reply_handler
now that rpcrdma_reply_handler is single-threaded. Receives complete
in the same order as they were sent on the NFS server.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sunrpc/xprtrdma/rpc_rdma.c  |   14 ++++++++++++--
 net/sunrpc/xprtrdma/verbs.c     |   25 +------------------------
 net/sunrpc/xprtrdma/xprt_rdma.h |    2 +-
 3 files changed, 14 insertions(+), 27 deletions(-)

--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -1244,7 +1244,7 @@ void rpcrdma_complete_rqst(struct rpcrdm
 out:
 	spin_lock(&xprt->recv_lock);
 	cwnd = xprt->cwnd;
-	xprt->cwnd = atomic_read(&r_xprt->rx_buf.rb_credits) << RPC_CWNDSHIFT;
+	xprt->cwnd = r_xprt->rx_buf.rb_credits << RPC_CWNDSHIFT;
 	if (xprt->cwnd > cwnd)
 		xprt_release_rqst_cong(rqst->rq_task);
 
@@ -1297,8 +1297,10 @@ void rpcrdma_reply_handler(struct rpcrdm
 {
 	struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
 	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
 	struct rpcrdma_req *req;
 	struct rpc_rqst *rqst;
+	u32 credits;
 	__be32 *p;
 
 	dprintk("RPC:       %s: incoming rep %p\n", __func__, rep);
@@ -1315,7 +1317,7 @@ void rpcrdma_reply_handler(struct rpcrdm
 		goto out_shortreply;
 	rep->rr_xid = *p++;
 	rep->rr_vers = *p++;
-	p++;	/* credits */
+	credits = be32_to_cpu(*p++);
 	rep->rr_proc = *p++;
 
 	if (rep->rr_vers != rpcrdma_version)
@@ -1332,7 +1334,15 @@ void rpcrdma_reply_handler(struct rpcrdm
 	if (!rqst)
 		goto out_norqst;
 	xprt_pin_rqst(rqst);
+
+	if (credits == 0)
+		credits = 1;	/* don't deadlock */
+	else if (credits > buf->rb_max_requests)
+		credits = buf->rb_max_requests;
+	buf->rb_credits = credits;
+
 	spin_unlock(&xprt->recv_lock);
+
 	req = rpcr_to_rdmar(rqst);
 	req->rl_reply = rep;
 	rep->rr_rqst = rqst;
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -133,25 +133,6 @@ rpcrdma_wc_send(struct ib_cq *cq, struct
 		       wc->status, wc->vendor_err);
 }
 
-/* Perform basic sanity checking to avoid using garbage
- * to update the credit grant value.
- */
-static void
-rpcrdma_update_granted_credits(struct rpcrdma_rep *rep)
-{
-	struct rpcrdma_buffer *buffer = &rep->rr_rxprt->rx_buf;
-	__be32 *p = rep->rr_rdmabuf->rg_base;
-	u32 credits;
-
-	credits = be32_to_cpup(p + 2);
-	if (credits == 0)
-		credits = 1;	/* don't deadlock */
-	else if (credits > buffer->rb_max_requests)
-		credits = buffer->rb_max_requests;
-
-	atomic_set(&buffer->rb_credits, credits);
-}
-
 /**
  * rpcrdma_wc_receive - Invoked by RDMA provider for each polled Receive WC
  * @cq:	completion queue (ignored)
@@ -181,9 +162,6 @@ rpcrdma_wc_receive(struct ib_cq *cq, str
 				   rdmab_addr(rep->rr_rdmabuf),
 				   wc->byte_len, DMA_FROM_DEVICE);
 
-	if (wc->byte_len >= RPCRDMA_HDRLEN_ERR)
-		rpcrdma_update_granted_credits(rep);
-
 out_schedule:
 	rpcrdma_reply_handler(rep);
 	return;
@@ -295,7 +273,7 @@ rpcrdma_conn_upcall(struct rdma_cm_id *i
 	case RDMA_CM_EVENT_DISCONNECTED:
 		connstate = -ECONNABORTED;
 connected:
-		atomic_set(&xprt->rx_buf.rb_credits, 1);
+		xprt->rx_buf.rb_credits = 1;
 		ep->rep_connected = connstate;
 		rpcrdma_conn_func(ep);
 		wake_up_all(&ep->rep_connect_wait);
@@ -995,7 +973,6 @@ rpcrdma_buffer_create(struct rpcrdma_xpr
 
 	buf->rb_max_requests = r_xprt->rx_data.max_requests;
 	buf->rb_bc_srv_max_requests = 0;
-	atomic_set(&buf->rb_credits, 1);
 	spin_lock_init(&buf->rb_mwlock);
 	spin_lock_init(&buf->rb_lock);
 	spin_lock_init(&buf->rb_recovery_lock);
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -407,7 +407,7 @@ struct rpcrdma_buffer {
 	struct list_head	rb_send_bufs;
 	struct list_head	rb_recv_bufs;
 	u32			rb_max_requests;
-	atomic_t		rb_credits;	/* most recent credit grant */
+	u32			rb_credits;	/* most recent credit grant */
 
 	u32			rb_bc_srv_max_requests;
 	spinlock_t		rb_reqslock;	/* protect rb_allreqs */